WO2005068206A1

WO2005068206A1 - Porous imaging material

Info

Publication number: WO2005068206A1
Application number: PCT/EP2004/014014
Authority: WO
Inventors: Walter Von Wirth; Catalin Ghimboasa
Original assignee: Sihl Group Ag
Priority date: 2003-12-15
Filing date: 2004-12-09
Publication date: 2005-07-28

Abstract

A self-destructive porous imaging system having a base substrate, an optional barrier layer and a method for making the self-destructive porous imaging system is provided. The ink receptive layer is a two-part emulsion of polymeric spheres in a polymeric matrix or the ink receptive layer comprises substantially about 100 % wt. % cellulose nitrate, a printed image having enhanced ink capacity and reduced ink migration. The barrier layer between the base substrate and the ink receptive layer prevents the ink from bleeding into the paper base substrate.

Description

POROUS IMAGING MATERIAL

BACKGROUND OF THE INVENTION [001] 1. Field of the Invention

[002] This invention relates generally to inkjet printing technology. In particular, this invention relates to a self-destructive porous imaging system suitable for non-aqueous inks, particularly solvent-base inks and aqueous-base inks containing some amount of organic solvents.

[003] 2. Description of the Related Art

[004] Inkjet printing technology has gained considerable popularity as a printing method in recent years, especially in the areas of color graphics and color pictures, in addition to printed text. Ink droplets are forced through a nozzle onto an inkjet recording material, such as paper. The recording material absorbs the droplets, thereby forming an image. Examples of inkjet processes are disclosed in U.S. Pat. No. 5,958,168 and U.S. Pat. App. No. 2003/0099816 A1. Recent advances in inkjet technology have resulted in the ability to produce high-quality, photographic images. Image quality depends on certain critical performance parameters such as inkjet recording material characteristics, image formation speed, image glossiness, ink layer integrity (propensity for cracking, etc.), ink viscosity, ink migration, ink capacity, and resistance to moisture or sun damage.

[005] Recording materials typically include a base paper substrate with a coating. The coating usually contains high levels of silica particles and a water- soluble polymeric binder. An example of this technology is disclosed in U.S. Pat. No. 4,4788,910. Problems associated with silica coatings include high binder demand, low image glossiness, and limited ink dot size. Hence, various other polymers have been developed for the coating process.

[006] Early attempts to create a viable polymeric coating for inkjet recording materials resulted in the development of addition-polymerizable vinyl monomer salts colloidally dispersed in a coating medium. Later advances included aqueous dispersions of co-polymers combined with a binder or sizing agent and a filler. Other attempts included coating a paper substrate with a latex polymer, developing a coating layer containing a film forming polymer that included micro cracks therein, and creating a coating layer containing co-polymers having differing transition temperatures in using this coating layer in combination with a temperature-controlled print process in an attempt to improve image glossiness. Such processes are disclosed, for example, in U.S. Pat. Nos. 4,481 ,244; 4,425,405; 4,371 ,582; 4,496,629; 5,215,812. Despite the advances made by these attempts, problems associated with ink capacity, ink migration, and image glossiness remained.

[007] To overcome these persisting problems, various emulsions of polymers and particulates were developed. For example, U.S. Pat. No. 5,405,678 discusses an inkjet recording sheet comprised of a base substrate coated with a hydrophobic polymeric latex in emulsion with 30 to 65 weight percent silica solids. Although this reference discloses the coating as providing advantages over the prior art due to voids formed in the ink receptive layer by the silica solids, the problems associated with silica solids were namely low ink capacity, increased ink migration, and reduced glossiness. Problems associated with non-aqueous inks also persisted.

[008] U.S. Pat. App. No. 2002/0057323 discloses an inkjet recording material comprised of a base layer coated with an ink receptive layer that has a continuous pore ratio from 20 to 100 percent. Pore formation occurs from foaming reactions in the ink receptive layer wherein organic particles are held in emulsion with synthetic resin polymers or copolymers. While this application seeks to avoid the problems associated with silica particulates in the ink receptive layer, the use of the disclosed recording material is also limited to aqueous-base ink applications. Further, the disclosed technology only addresses open voids where the continuous void ratio is a function of the ratio of continuous voids and air passing rates of a coated paper versus a non-coated paper. In addition to only addressing aqueous-base inks and open voids, the disclosed technology does not address or solve the problems of low ink capacity, high ink migration, and unsuitable ink viscosity for inkjet recording material.

[009] Non-aqueous inks have relatively lower viscosity and surface tension than aqueous-base inks. Thus, use of non-aqueous inks in inkjets is desired, particularly when printing larger images, because higher speed imaging, with increased accuracy, is possible. The formulation use of non-aqueous inks for use in inkjet applications is discussed in Japanese Pat. Nos. JP-A-57-10660; JP- A-57-10661; JP-A-5-202324; and JP-A-5-331397.

[0010] EP Pat. No. 1216839 discloses an inkjet printing medium having a barrier layer between a base paper and an ink receptive layer where a binder in the barrier layer is a post-cross-linking polyacrylate dispersion. While this reference discloses non-aqueous inks, it focuses on the use of a polymer/particulate emulsion in the barrier layer between the base paper and the ink receptive layer. Hence, it fails to address the aforementioned non-aqueous ink problems, including ink capacity, ink migration, and ink viscosity.

[0011] Thus, despite advances made in inkjet recording, there continues to be a need for an inkjet recording material that provides high speed imaging in which optimal image glossiness and image integrity are maintained with controlled ink viscosity, ink migration, and ink capacity.

[0012] More specifically, there needs to be a printing surface, useable with vibrant, non-aqueous inks, that combines the benefits of porous and non-porous surfaces. Porous surfaces provide good ink absorption, thorough drying, smear resistance, and controllable ink capacity. However, porous surfaces are prone to low glossiness, poor definition, and high ink migration (bleeding), especially when printing with low viscosity inks. Non-porous surfaces provide excellent definition, high ink density, and high glossiness, but suffer from low smear resistance, poor absorption, and poor ink capacity control. SUMMARY OF THE INVENTION

[0013] The present invention provides inkjet technology and an inkjet recording process that meets the aforementioned needs. One aspect of the present invention provides a self-destructive porous imaging system that includes a base substrate, a barrier layer, an optional anti-curl layer, and an ink receptive layer upon which an image may be formed with non-aqueous inks. Unlike the conventional art, the ink receptive layer utilizes phase transition principles to achieve a uniform film at the image layer via the various polymeric interactions between the ink receptive layer and the non-aqueous ink. Moreover, control of the weight percentages of polymers present in the ink receptive layer allows the inkjet recording material and method to be optimally used on a variety of machines with varying ink capacities.

[0014] The present invention is a two-part system, wherein the solubility of polymers selected for the polymeric matrix differs from the solubility of the polymers selected for the polymeric spheres. The polymers selected for the polymeric spheres may be more soluble in the non-aqueous ink system than those selected for the polymeric matrix. Hence, the polymeric spheres will dissolve more quickly upon impact with non-aqueous inks allowing the ink to be trapped in the pores, or spaces, previously occupied by the polymeric spheres. Further, the overall viscosity of the resulting film is increased when the polymeric spheres are dissolved in the non-aqueous ink. The result is decreased ink migration and image bleeding and an overall increase in image quality.

[0015] One embodiment of the present invention provides a self-destructive porous imaging system having an ink receptive layer that comprises an emulsion of polymeric spheres and a polymeric matrix. Preferably, the polymeric spheres range from about 80 wt.% to about 93 wt.% of the emulsion. The polymeric spheres are selected from the group consisting of acrylates, esters of acrylates, polystyrenes, and polyamides. Preferably, the polymeric matrix ranges from about 20 wt.% to about 7 wt.% of the emulsion. The polymeric matrix is selected from the group consisting of acrylates, esters of acrylates, polyvinylacetates, ethylacetates, polyvinylchlorides, polyvinyl alcohols and polystyrenes. [0016] In a second embodiment of the present invention, the polymeric matrix comprises 100% of the ink receptive layer. The polymeric matrix may be comprised of cellulose nitrate for use in solvent-base systems. When the cellulose nitrate is mixed with solvents, such as ethyl acetate and isomeric xylene, and coated onto a conventional size pressed paper, the resulting ink receptive layer contains open pores as the solvents evaporate. The advantage of open pores in this embodiment is increased porosity as the polymers in the ink receptive layer are solved resulting in enhanced image quality via reduction in ink migration and image bleed for solvent-base systems.

[0017] In a third embodiment of the present invention, the ink receptive layer comprises an emulsion of polymeric spheres and a polymeric matrix having the following ranges. The polymeric spheres preferably range from about 15 wt.% to about 40 wt.% of the emulsion while the polymeric matrix comprises from about 85 wt.% to about 60 wt.% of the emulsion. The polymeric spheres are selected from the group consisting of acrylates, esters of acrylates, polystyrenes, and polyamides; and the polymeric matrix is selected from the group consisting of acrylates, esters of acrylates, polyvinylacetates, ethylacetates, polyvinylchlorides, polyvinyl alcohols and polystyrenes.

[0018] In an alternative embodiment, the polymer or polymers within the polymeric matrix may be cross-linked. Cross-linking of polymers, or joining two or more polymers via covalent bonding, is commonly known by those skilled in the art. Cross-linking of the polymer or polymers may occur before the polymeric matrix is mixed with the polymeric spheres. Alternatively, the polymer or polymers may be post-cross linked, or cross-linked after being mixed with the polymeric spheres. One of the advantages of cross-linking or post-cross linking the polymeric matrix of the present invention is increased solubility of the polymeric spheres when contacted with non-aqueous inks. As previously mentioned, the overall viscosity of the ink film is increased when the polymeric spheres are dissolved in non-aqueous inks resulting in less image bleed and image migration. Because of this, another advantage of cross-linking or post- cross linking the polymeric matrix of the present invention is increased image glossiness.

[0019] The final uniform ink receptive layer traps pigments in the non- aqueous ink mixture, thereby reducing ink migration speed and controlling image bleeding. In addition, varying phases in the ink receptive layer helps to control overall image quality and integrity by creating more uniform densities of primary colors and solid areas. For example, the polymeric spheres may be solid polymeric spheres or polymer shells filled with an inert gas, such as nitrogen. In an alternative embodiment, the polymeric matrix may contain open pores consisting of air. In both embodiments, overall image quality is enhanced while controlling image bleeding and reducing ink migration.

[0020] Another aspect of the present invention provides a self-destructive porous imaging system comprising an ink receptive layer including an emulsion of polymeric spheres and a polymeric matrix, wherein the polymeric matrix may comprise a homopolymer or a co-polymer blend represented as X + Y. X and Y may be selected from a group consisting of acrylates, esters of acrylates, polyvinylacetates, ethylacetates, polyvinylchlorides, polyvinyl alcohols, and polystyrenes. X may range from 85 wt.% to 100 wt.% and Y may range from about 15 wt.% to about 0 wt.% of the total weight of the polymeric matrix. The polymeric matrix may consist of cellulose nitrate dissolved in isomeric xylene and ethylacetate for solvent-based systems. Alternatively, the polymeric matrix may consist of two or more reactive polymers that react to form a co-polymer.

[0021] Another aspect of the present invention provides an ink receptive layer including an emulsion of polymeric spheres and a polymeric matrix, wherein the polymeric spheres may also be a homo-polymer or a co-polymer blend, wherein the polymer or polymers are selected from a group consisting of acrylates, esters of acrylates, polystyrenes, and polyamides. One embodiment of the polymeric spheres is a combination of acrylates and polystyrenes while the polymeric matrix comprises an aery late. [0022] Still another aspect of the invention is a method of producing a self- destructive porous imaging system. The first step of this method is depositing a non-aqueous ink image onto an ink receptive layer of a self-destructive porous imaging system in accordance with the present invention. The self-destructive porous imaging system has a base substrate, an ink receptive layer, and an optional barrier layer between the substrate and the ink receptive layer. The purpose of the barrier layer is to prevent ink, or any other liquid, from penetrating the top two layers of the self-destructive porous imaging system and seeping into the base substrate to prevent undesirable swelling of the base substrate. The ink receptive layer, however, may itself operate as a barrier layer when used with conventional inkjet technology. A single coating of the ink receptive layer of the present invention on conventional size pressed coated paper will yield enhanced print quality for typical printed images. A double coating of the ink receptive layer of the present invention on conventional size pressed coated paper will yield enhanced print quality for high gloss and photo-grade images. The purpose of the ink receptive layer is to achieve optimal image formation speed, image glossiness, image integrity, ink viscosity, ink migration, and ink capacity. The second step includes applying a non-aqueous ink layer onto the ink receptive layer to produce an inkjet image. The third step involves creating a uniform film via interactions between polymers in the ink receptive layer and compounds present in the non-aqueous ink to create a final inkjet image.

[0023] The aforementioned objects and resulting advantages will become apparent from the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Fig. 1 is a perspective view of a self-destructive porous imaging system in accordance with the present invention illustrating details of the constituent elements. [0025] Fig. 2 is a graphic representation of polymeric spheres in emulsion with a polymeric matrix to form the ink receptive layer in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0026] Referring now to Figure 1 , there is shown a self-destructive porous imaging system 10 of the present invention. The self-destructive porous imaging system 10 generally comprises a base substrate 12, an optional barrier layer 14, and an ink receptive layer 16. An anti-curl layer 18 may be optionally provided.

[0027] The base substrate 12 provides the foundation for the self-destructive porous imaging system 10 and method of this invention. The base substrate 12 may be any sheet material possessing suitable flexibility, dimensional stability and adherence properties to the barrier layer. Examples of acceptable materials include paper, cloth, fabrics, plastic films, glass, and sheet metals. In accordance with one embodiment of the present invention, the base substrate 12 is short-fiber wood pulp, bleached hardwood pulp or eucalyptus wood pulp. Pigments may be added to the wood pulp to vary the color of the base substrate 12. The addition of other additives to the wood pulp, such as de-aerators, defoamers and amphoteric sizing agents, is commonly known to those skilled in the art. In addition, an anti-curl layer 18 may be applied to the back side of the base substrate 12 as it is being created on a paper machine. The base substrate 12 is produced in a conventional paper machine utilizing conventional techniques widely known in the art. The base paper 12 of the present invention generally has a basis weight of 100 to 300 grams per square meter. One can cast with a range of from 60 to 600 grams per square meter with the only limit being what the printer will accept. The preferred basis weight range is 140 to 220 grams per square meter for optimal image quality and formation speed.

[0028] The base substrate 12 may be optionally coated with a barrier layer 14 as it is being created on a paper machine. The barrier layer 14 may be applied to one side of the base substrate 12. If the base substrate 12 includes a coating, such as an anti-curl layer 18, on one side, the barrier layer 14 is generally applied to the opposite, non-coated side of the base substrate 12. The barrier layer 14 between the base substrate 12 and the ink receptive layer 16 prevents the ink from bleeding into the paper base substrate 12.

[0029] The barrier layer 14 is an optional pre-coating important for use in inkjet printing materials for high gloss of photo quality images. The optional, pre- coated barrier layer 14 preferably consists of a mixture of calcium carbonate, polystyrene particles, a post-cross linking polyacrylate emulsion, hydrous sodium hydroxide, defoamer, wetting agent, flow control agent, and an optional biocide as is well known in the art. After the base substrate 12 is produced using known techniques, the substrate 12 is dried until it contains less than 2 wt.% water. The barrier layer 14 may then be applied, allowing the base substrate 12 to absorb some of the water in the barrier layer 14. The barrier layer 14 is applied onto the base substrate 12 pursuant to techniques widely known in the art. The barrier layer is beneficial to achieve gloss but it is not essential to achieve good print quality and is, therefore, optional. The barrier layer 14 may be coated on conventional photo-based paper or size pressed coated paper depending on the desired use of the self-destructive porous imaging system 10. The optional separate barrier layer 14 coated on conventional paper is advantageous for photo-grade or high gloss images. However, the ink receptive layer in the present invention may operate as the barrier layer when coated onto conventional size pressed coated paper. A single coating of the ink receptive layer of the present invention on conventional size pressed coated paper will yield enhanced print quality for typical printed images. A double coating of the ink receptive layer of the present invention on conventional size pressed coated paper will yield enhanced print quality for high gloss and photo-grade images.

[0030] The ink receptive layer 16 may be applied over the optional barrier layer 14 or may be applied directly over size pressed coated paper. Optionally, the base substrate 12 and barrier layer 14 may be calendared prior to the application of the ink receptive layer 16. While calendaring may provide a certain level of control over formation of a foam structure within the polymeric matrix 24, the present invention does not require the calendar step within the preferred weight percent ranges for the components within the ink receptive layer 16 as discussed below. The ink receptive layer 16 is applied utilizing a coating machine. Solvents present in non-aqueous inks will solve or swallow the polymers chosen for the ink receptive layer 16 and form a uniform film for the final image layer 20. The uniform film at the image layer 20 is beneficial for trapping pigments in the non-aqueous ink mixture, thereby reducing ink migration speed and controlling image bleeding. In addition, varying phases in the ink receptive layer 16 helps control overall image quality and integrity by creating more uniform densities of primary colors and solid areas. The uniform film formation also enhances half-toning in the final image layer 20.

[0031] The ink receptive layer 16 is an emulsion comprising a first polymer selected from the group consisting of acrylates, esters of acrylates, polystyrenes, and polyamides and a second homo-polymer or co-polymer selected from the group consisting of acrylates, esters of acrylates, polyvinylacetates, ethylacetates, polyvinylchlorides, polyvinyl alcohols and polystyrenes.

[0032] Referring now to Figure 2, the first polymer is represented as polymeric spheres 22 that act to control the overall porosity of the ink receptive layer 16 such that ink migration, image density and gloss may be optimized. The second polymer comprises a polymer matrix 24 that is largely responsible for the overall adhesion of the ink receptive layer 16 to the barrier layer 14 or directly to the size pressed coated paper.

[0033] In one embodiment of the present invention, the polymeric spheres 22 preferably range from about 80 wt.% to about 93 wt.% of the emulsion. The polymeric spheres 22 are selected from the group consisting of polyacrylic esters, polystyrenes, and polyamides. The polymeric matrix 24 preferably ranges from about 20 wt.% to about 7 wt.% of the emulsion and is selected from the group consisting of acrylates, esters of acrylates, polyvinylacetates, ethyl acetates, polyvinylchlorides, polyvinyl alcohols and polystyrenes. [0034] In a second embodiment of the present invention, the polymeric matrix comprises 100% of the ink receptive layer 16. The polymeric matrix 24 may be comprised of cellulose nitrate for use in solvent-base systems, When the cellulose nitrate is mixed with solvents, such as ethyl acetate and isomeric xylene, and coated onto a conventional size pressed paper, the resulting ink receptive layer 16 contains open pores as the solvents evaporate. The advantage of open pores in this embodiment is increased porosity as the polymers in the ink receptive layer 16 are solved resulting in enhanced image quality via reduction in ink migration and image bleed for solvent-base systems.

[0035] In a third embodiment of the present invention, the ink receptive layer 16 comprises an emulsion of polymeric spheres 22 and a polymeric matrix 24 having the following ranges. The polymeric spheres 22 preferably range from about 15 wt.% to about 40 wt.% of the emulsion while the polymeric matrix 24 comprises from about 85 wt.% to about 60 wt.% of the emulsion. The polymeric spheres 22 are selected from the group consisting of acrylates, esters of acrylates, polystyrenes, and polyamides; and the polymeric matrix 24 is selected from the group consisting of acrylates, esters of acrylates, polyvinylacetates, ethylacetates, polyvinylchlorides, polyvinyl alcohols and polystyrenes.

[0036] The ranges of polymeric spheres 22 and polymeric matrix 24 stated above will achieve an ink receptive layer 16 having proper adhesion while optimizing ink capacity.

[0037] The final uniform film forming the inkjet image layer 20 is beneficial for trapping pigments in the non-aqueous ink mixture, thereby reducing ink migration speed and controlling image bleeding. Varying phases in the ink receptive layer 16 help control overall image quality and integrity by creating more uniform densities of primary colors and solid areas. Thus, in an alternative embodiment of the present invention, the polymeric spheres 22 may be solid polymeric spheres 22 or polymer shells filled with air, inert gas, or polymer gas. In yet an alternative embodiment, the spheres 22 may simply be air. [0038] By controlling the ratio of the polymer selected for the polymeric spheres 22 to the polymer selected for the polymeric matrix 24 , the present invention may be adjusted for use with a variety of different inks and ink volumes provided from different machines. In general, the present invention is designed for the use of non-aqueous inks. However, aqueous-base inks having some portion of organic solvents or glycol are well-suited for use with the present invention.

[0039] In one embodiment of the present invention, a co-polymer mixture may be used in the polymeric matrix 24. The polymeric matrix 24 may comprise a homopolymer or a co-polymer blend represented as X + Y, wherein both X and Y are selected from a group consisting of acrylates, esters of acrylates, polyvinylacetates, ethylacetates, polyvinylchlorides, polyvinyl alcohols, and polystyrenes. X may range from 85 wt.% to 100 wt.% and Y may range from about 15 wt.% to about 0 wt.% of the total weight of the polymeric matrix 24 blend. The preferred composition for the polymeric matrix 24 is anacrlyate.

[0040] In yet another embodiment of the present invention the polymeric spheres 22 may also be a homo-polymer or a co-polymer blend, wherein the polymer or polymers are selected from a group consisting of acrylates, esters of acrylates, polystyrenes, and polyamides. One preferred embodiment of the polymeric spheres 22 is a combination of acrylates and polystyrenes while the polymeric matrix 24 comprises anacrylate.

[0041] In another embodiment of the present invention, the solubility of the first polymer is different than the solubility of the second polymer. The first polymer forms well-defined solid spheres 22 having a relatively uniform size. The structural integrity of the spheres 22 controls ink migration. In order to achieve appropriate adhesion of the ink receptive layer 16 to the barrier layer 14, the emulsion of the polymeric matrix 24 and the polymeric spheres 22 must be sintered or passed through a calendar. Under optimal conditions, the result of sintering or passing through the calendar is a foam structure in the ink receptive layer 16. [0042] Yet another embodiment of the present invention utilizes spheres 22 containing air or gas-filled polymeric spheres 22. The gas used may be air, nitrogen or other inert gases. Use of these gas-filled spheres 22 in conjunction with non-aqueous ink systems is beneficial from a production standpoint because air can be readily suspended in such systems when mixing at high shear rates. Processes involving a non-aqueous polymeric matrix 24 and suspended air bubbles may be difficult to control for consistent quality. Thus, a polymer in gas phase may be used instead of air and partially precipitated during the drying step. Selecting non-aqueous ink containing two solvents with varying solubility and boiling points may then control image quality.

[0043] Another embodiment of the present invention also utilizes polymeric spheres 22 filled with gas or air that are sintered or passed through a calendaring machine using known techniques in order to achieve suitable adhesion of the ink receptive layer 16 to the barrier layer 12. The result of this process is an internal/external foam structure whereby there are pores outside 26 the polymeric spheres 22 and pores inside 28 the polymeric spheres 22.

[0044] Another embodiment of the present invention includes an emulsion of solid polymeric spheres 22 and a polymeric matrix 24, which is either sintered or passed through a calendar machine. Doing so introduces additional air pockets into the ink receptive layer 16. Controlling the ratio of the polymeric matrix 24 to the polymeric spheres 22 controls the pore to polymer ratio of the emulsion. The structure and particle size of the polymeric spheres 22 is controlled in order to enhance control of ink migration and image bleed, as the solubility of the polymer used in the polymeric spheres 22 is different than the solubility of the polymer used in the polymeric matrix 24. Hence, the solvents in the non- aqueous ink will solve or swallow the first and second polymers at different rates. The variability in solubility coupled with the varying phase transitions introduced via the pores outside 26 the polymeric spheres 22 and via the solid polymeric spheres 22 themselves, facilitates optimal control of film formation during the imaging process. [0045] In yet another embodiment of the present invention, an emulsion of gas or air- filled polymeric spheres 22 and a polymeric matrix 24 is comprised of homo-polymers or co-polymers. This emulsion creates similar advantages for film formation during the imaging process as those discussed in the previous embodiment due to the varying phases present in the emulsion. The pore space outside 26 of the polymer spheres 22 is controlled by the ratio of the first polymer to the second polymer in the polymeric matrix 24. The pore space inside 28 the polymeric spheres 22 is controlled by the selection of the polymer for the shell 30 of the polymer spheres 22. Again, control of these parameters is critical in controlling ink migration and image bleed during the imaging process.

[0046] The present invention may optionally include a nano-sized particle additive to prevent sticking during long-term storage of the finished product. The additive comprises about 10 dry wt.% of the ink receptive layer.

[0047] In all of the foregoing embodiments, the preferred coat weight for the ink receptive layer 16 ranges from 2 grams per square meter to 12 grams per square meter.

[0048] The advantageous, unexpected and surprising properties of the present invention can be observed by reference to the following examples which illustrate, but are not intended to limit, the invention. In the following examples, the base substrate 12 to be coated was paper. The coating thickness varied from 10 grams to 12 grams per square meter. A variety of polymers were tested for the polymeric spheres 22 including polyacrylic esters, polystyrene, polyamide and xylene. Tested polymeric matrixes 24 included acrylesters, polyvinylacetate, ethylacetate, polyvinylchloride and polystyrene. A pure solvent ink system was tested and is discussed in Example 9. In addition, aqueous-base inks were tested and is discussed in Example 10.

EXAMPLES

[0049] The following ten material combinations were developed and tested.

The results of these ten examples are summarized in the following table, Table 1, with explanations of the materials and processes immediately following the table. After depositing inkjet images onto the ink receptive layers, some of the samples exhibited good print quality and others exhibited excellent print quality. The term "good print quality" as used herein means the final image exhibited one or more of the following characteristics smooth tonal transitions, less short term color drift, more resistance to gas fading, better water fastness, crisper image appearance, higher ink capacity, reduced ink migration, better image gloss. The term "excellent print quality" as used herein means the final image exhibited a higher degree of improvement in the aforementioned characteristics. In addition, adhesion was also observed. Good adhesion is the ability of the ink receptive layer to properly adhere to the base substrate substantially without gaps.

TABLE 1

Mixtures Example 1 400g of styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) were mixed with 30g of modified acrylate MAKROVIL® D 7438 (Indulor, Germany) using a low shear stirring unit. The mixture was then coated onto size pressed coated 110g paper to a coat weight of 10g. The coating had a pore volume of 11.3 vol.%, where 7.1 vol.% was provided from closed pores and 4.2 vol.% was provided from open pores. The result was a glossy coating that showed excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). The material had good print quality and good adhesion. Example 2

400g of styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) were mixed with 60g of modified acrylate MAKROVIL® D 7438 (Indulor, Germany) using a low shear stirring unit. The mixture was then coated onto size pressed coated 110g paper to a coat weight of 10g. The coating had a pore volume of 7%, where 6.8% of the volume was provided from closed pores and 0.2% of the volume was provided from open pores. The result was a glossy coating with excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). The material had good print quality with good ink capacity, good adhesion and a high printing gloss. Example 3

400g of styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) were mixed with 70g of styrene/acrylate copolymer Jetsize™ AE65 (Akzo Chemicals, Germany) using a low shear stirring unit. The mixture was then coated onto size pressed coated 110g paper to a coat weight of 10g. The coating had a pore volume of 11.2%, where 6.6% of the volume was closed pores and 4.6% of the volume was open pores. The result was a glossy coating with excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). The material had good print quality with an ink capacity and adhesion similar to Example 1. Example 4

400g of styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) were mixed with 64g of polyvinylacetate Mowilith™ DM 104 (Wacker Chemie, Germany) using a low shear stirring unit. The mixture was coated onto size pressed coated 110g paper to a coat weight of 10g. The coating had a pore volume of 11.4%, 6.7% of which were closed pores and 4.7% open pores. The result was a glossy coating with excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). The material had lower ink capacity but better adhesion than the material of Example 1.

Pure Open Pores

Example 5

400g of modified acrylate Mowilith™ LDM 7530 (Wacker Chemie, Germany) were mixed with 60 g of modified acrylate MAKROVIL® D 7438 (Indulor, Germany). The mixture was coated to a coat weight of 10g onto size pressed coated 110g paper. The coating had a pore volume of 4.1% by volume, all of which were open pores because the spheres formed were solid. The result was a glossy coating with excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). The material had a lower ink capacity but better adhesion than the material of Example 1. Example 6

293g of modified polystyrene DPP 3740 DOW Plastic Pigment (DOW Chemical Company, Corp., USA) were mixed with 60g of modified acrylate MAKROVIL® D 7438 (Indulor, Germany). The mixture was coated onto size pressed coated 110g paper to a coat weight of 10g. The coating had a pore volume of 4.6% by volume, all of which were open pores because the spheres formed were solid. The result was a glossy coating that showed excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). The material had a lower ink capacity but better adhesion than the material of Example 1. Example 7

300g of polyamide Orgasol® 2001 EXD was stirred with 750g of aqueous solution of polyvinyl alcohol Mowiol® 4-88 (8% solids) (Kuraray Specialities Europe, Germany). After stirring for 30 min, 50g of polyvinylacetate Mowilith™ DM 104 (Wacker Chemie, Germany) were added and stirred for an additional 15 min. The mixture was then coated onto size pressed coated 110g paper to a coat of weight 10g. The coating had a pore volume of 3.9% by volume, all of which were open pores because the spheres formed were solid. The result was a matte coating that showed good print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). Example 8

35g of cellulose nitrate E 375 (Wolff Walsrode, Germany) were dissolved in 50g of ethyl acetate and stirred using a low shear stirring device. 40g of xylene isomeric composition were added to the ethyl acetate solution and stirred for an additional 15 min. The mixture was then coated, at 12 g per m^2, onto a size pressed treated paper. The coating had a pore volume of 9.5% by volume, all of which were open pores. The result was a glossy coating that showed excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan).

Example 9

400g of styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) were mixed with 30g of modified acrylate MAKROVIL® D 7438 (Indulor, Germany) using a low shear stirring unit. The mixture was then coated onto size pressed coated 110g paper to a coat weight of 10g. The coating had a pore volume of 11.3 vol.%, where 7.1 vol.% was provided from closed pores and 4.2 vol.% was provided from open pores. The material was printed on an Epson Stylus 9600 and showed good print quality.

Pure Polymeric Spheres

Example 10

Styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) was coated onto size pressed coated 110g paper to a coat weight of 10g. A small amount of the styrene/acrylate copolymer in liquid form was mixed with the polymeric spheres so that the copolymer blend could be applied to the size pressed coated paper without precipitation of the polymeric spheres. The resulting coating was a fine, powdery layer of styrene/acrylate copolymer on the size pressed coated paper. The coating had a pore volume of 21.7 vol.%, where 7.6 vol.% was provided from closed pores and 14.1 vol.% was provided from open pores. The result was a glossy coating that showed good print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). While this sample exhibited good print quality for the final printed image, it exhibited poor adhesion of the styrene/acrylate copolymer to the size pressed coated paper at the preprint stage and for any non-print areas remaining after the print stage.

Example 11

Modified acrylate, Mowilith™ LDM 7530 (Wacker Chemie, Germany), was coated to a coat weight of 10g onto size pressed coated 110g paper. Again, a small amount of the modified acrylate in liquid form was mixed with the polymeric spheres so that the modified acrylate spheres could be applied to the size pressed coated paper without precipitation of the polymeric spheres. The resulting coating was a fine, powdery layer of modified acrylate on the size pressed coated paper. Because Mowilith™ LDM 7530 forms solid spheres, there were only open pores at 6.1 vol.%. The result was a satin coating that showed good print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). As noted in Example 11 , this sample exhibited good print quality for the final printed image. However, exhibited poor adhesion of the modified acrylate to the size pressed coated paper at the pre-print stage and for any non- print areas remaining after the print stage.

Pure Closed Pores

Example 12

300g of styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) were mixed with 545g of modified acrylate MAKROVIL® D 7438 (Indulor, Germany) using a low shear stirring unit. The mixture was then coated onto size pressed coated 110g paper to a coat weight of 14g. The coating had a pore volume of 1.9 vol.%, all of which were closed pores. This sample exhibited a glossy coating that showed excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan) and good adhesion to the base substrate.

Example 13

120g of styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) were mixed with 168g of modified acrylate MAKROVIL® D 7438 (Indulor, Germany) using a low shear stirring unit. The mixture was then coated onto size pressed coated 110g paper to a coat weight of 14g. The coating had a pore volume of 2.3 vol.%, all of which were closed pores. The result was a glossy coating that showed excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). This sample exhibited comparable ink capacity and better adhesion than Examples 10 and 11.

Example 14

180g of styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) were mixed with 162g of modified acrylate MAKROVIL® D 7438 (Indulor, Germany) using a low shear stirring unit. The mixture was then coated onto size pressed coated 110g paper to a coat weight of 14g. The coating had a pore volume of 3 vol.%, all of which were closed pores. This sample exhibited a glossy coating with excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). The material exhibited comparable ink capacity and better adhesion than Examples 10 and 11.

Example 15

21 Og of styrene/acrylate copolymer Ropaque™ HP-543P (Rohm & Haas, USA) were mixed with 714g of modified acrylate MAKROVIL® D 7438 (Indulor, Germany) using a low shear stirring unit. The mixture was then coated onto size pressed coated 110g paper to a coat weight of 14g. The coating had a pore volume of 1.2 vol.%, all of which were closed pores. This material had a glossy coating with excellent print quality on a Mimaki™ JV3 printer (Mimaki Engineering Co., Ltd., Japan). The material exhibited lower ink capacity and better adhesion than Examples 10 and 11.

Claims

1. A self-destructive porous imaging system comprising; a. a base substrate; and b. a two-part ink receptive layer comprising an emulsion of about 80 wt.% to about 93 wt.% polymeric spheres and about 20 wt.% to about 7 wt.% polymeric matrix.

2. The self-destructive porous imaging system of claim 1 further comprising a barrier layer interposed between the base substrate and the ink receptive layer.

3. The ink receptive layer of claim 1 wherein the polymeric spheres comprise about 87 wt.% of the emulsion.

4. The ink receptive layer of claim 1 wherein the polymeric matrix comprises about 13 wt.% of the emulsion.

5. The ink receptive layer of claim 1 wherein the polymeric spheres are selected from the group consisting of acrylates, polystyrenes, and polyamides.

6. The ink receptive layer of claim 1 wherein the polymeric matrix is selected from the group consisting of acrylates, polyvinylacetates, polyvinyl alcohols and polystyrenes.

The ink receptive layer of claim 1 further comprising polymeric spheres comprising a co-polymer blend of polystyrenes and acrylates.

8. The ink receptive layer of claim 1 further comprising a polymeric matrix comprising an acrylate.

9. The ink receptive layer of claim 1 further comprising a volume percentage of pores comprising open pores and closed pores.

10. The ink receptive layer of claim 9 wherein the pores range from about 3.9 vol.% to about 11.4 vol.% of the ink receptive layer.

11. The ink receptive layer of claim 9 wherein the open pores are about 0.2 vol.% of the ink receptive layer and the closed pores are about 6.8 vol.% of the ink receptive layer.

12. A self-destructive porous imaging system comprising; a. a base substrate; and b. a two-part ink receptive layer comprising an emulsion of about 15 wt.% to about 40 wt.% polymeric spheres and about 85 wt.% to about 60 wt.% polymeric matrix.

13. The self-destructive porous imaging system of claim 12 further comprising a barrier layer interposed between the base substrate and the ink receptive layer.

14. The ink receptive layer of claim 12 wherein the polymeric spheres comprise about 25 wt.% of the emulsion.

15. The ink receptive layer of claim 12 wherein the polymeric matrix comprises about 75 wt.% of the emulsion.

16. The ink receptive layer of claim 12 wherein the polymeric spheres are selected from the group consisting of acrylates, polystyrenes, and polyamides.

17. The ink receptive layer of claim 12 wherein the polymeric matrix is selected from the group consisting of acrylates, polyvinylacetates, polyvinyl alcohols and polystyrenes.

18. The ink receptive layer of claim 12 further comprising polymeric spheres comprising a co-polymer blend of polystyrenes and acrylates.

19. The ink receptive layer of claim 12 further comprising a polymeric matrix comprising an acrylate.

20. The ink receptive layer of claim 12 further comprising a volume percentage of pores comprising open pores and closed pores.

21. The ink receptive layer of claim 20 wherein the pores range from about 1.2 vol.% to about 3 vol.% of the ink receptive layer.

22. The ink receptive layer of claim 20 wherein the open pores are about 0 vol.% of the ink receptive layer and the closed pores are about 1.9 vol.% of the ink receptive layer.

23. A self-destructive porous imaging system having an ink receptive layer, the ink receptive layer comprising substantially about 100 wt.% cellulose nitrate.

24. The ink receptive layer of claim 23 wherein the pore volume comprises 9.5 vol.% of the ink receptive layer.

25. The ink receptive layer of claim 24 wherein the pore volume comprises 9.5 vol.% open pores.

26. A method of preparing a self-destructive porous imaging system comprising: a. providing a base substrate; and b. providing a two-part ink receptive layer comprising an emulsion of about 80 wt.% to about 93 wt.% polymeric spheres and about 20 wt.% to about 7 wt.% polymeric matrix.

27. The method of claim 26 wherein preparing the self-destructive porous imaging system comprises interposing a barrier layer between the base substrate and the ink receptive layer.

28. The method of claim 26 wherein preparing the emulsion comprises providing polymeric spheres in an amount equal to about 87 wt.% of the emulsion.

29. The method of claim 26 wherein preparing the emulsion comprises providing a polymeric matrix in an amount equal to about 13 wt.% of the emulsion.

30. The method of claim 26 wherein preparing the ink receptive layer comprises selecting the polymeric spheres from the group consisting of acrylates, polystyrenes, and polyamides.

31. The method of claim 26 wherein preparing the ink receptive layer comprises selecting the polymeric matrix from the group consisting of acrylates, polyvinylacetates, polyvinyl alcohols and polystyrenes.

32. The method of claim 26 further comprising preparing an ink receptive layer wherein the polymeric spheres are a co-polymer blend of polystyrenes and acrylates.

33. The method of claim 26 further comprising preparing an ink receptive layer wherein the polymeric matrix is an acrylate.

34. The method of claim 26 wherein preparing the ink receptive layer comprises including some volume percentage of pores in the ink receptive layer comprising open pores and closed pores.

35. The method of claim 34 wherein preparing the ink receptive layer comprises including about 3.9 vol.% to about 11.4 vol.% pores in the ink receptive layer.

36. The method of claim 34 wherein preparing the ink receptive layer comprises including about 0.2 vol.% open pores and about 6.8 vol.% closed pores in the ink receptive layer.

37. A method of preparing a self-destructive porous imaging system comprising: a. providing a base substrate; and b. providing a two-part ink receptive layer comprising an emulsion of about 15 wt.% to about 40 wt.% polymeric spheres and about 85 wt.% to about 60 wt.% polymeric matrix.

38. The method of claim 37 wherein preparing the self-destructive porous imaging system comprises interposing a barrier layer between the base substrate and the ink receptive layer.

39. The method of claim 37 wherein preparing the emulsion comprises providing polymeric spheres in an amount equal to about 25 wt.% of the emulsion.

40. The method of claim 37 wherein preparing the emulsion comprises providing a polymeric matrix in an amount equal to about 75 wt.% of the emulsion.

41. The method of claim 37 wherein preparing the ink receptive layer comprises selecting the polymeric spheres from the group consisting of acrylates, polystyrenes, and polyamides.

42. The method of claim 37 wherein preparing the ink receptive layer comprises selecting the polymeric matrix from the group consisting of acrylates, polyvinylacetates, polyvinyl alcohols and polystyrenes.

43. The method of claim 37 further comprising preparing an ink receptive layer wherein the polymeric spheres are a co-polymer blend of polystyrenes and acrylates.

44. The method of claim 37 further comprising preparing an ink receptive layer wherein the polymeric matrix is an acrylate.

45. The method of claim 37 wherein preparing the ink receptive layer comprises including some volume percentage of pores in the ink receptive layer comprising open pores and closed pores.

46. The method of claim 45 wherein preparing the ink receptive layer comprises including about 1.2 vol.% to about 3 vol.% pores in the ink receptive layer.

47. The method of claim 45 wherein preparing the ink receptive layer comprises including about 0 vol.% open pores and about 1.9 vol.% closed pores in the ink receptive layer.