US3238859A - Electroluminescent photocopying - Google Patents

Description

March 8, 1966 J. w. MAUCHLY 3,238,859

ELECTROLUMINESGENT PHOTOCOPYING Filed July 5, 1962 2 Sheets-Sheetl VAR/ABLE A. 6'. SOURCE 62 v INVENTOR 60 JOHN m MAUCHU QJPMAZSW ATTORNEY March 8, 1966 J. w. MAUCHLY 3,238,859

ELECTROLUMINESCENT PHOTOCQPYING Filed July 5, 1962 2 Sheets-Sheet 2 INVENTOR.

JOHN W MAUCHLV AMM SW ATTORNEY United States Patent 3 238,859 ELECTROLUMINESCENT PHOTOCOPYING John W. Mauchly, Ambler, Pa., assignor to Mauchly Associates, Inc., Fort Washington, Pa., a corporation of Pennsylvania Filed July 3, 1962, Ser. No. 207,214 2 Claims. (Cl. 95-73) In general, this invention relates to a new and different method of photocopying letters, drawings, printed matter or other .materal. More particularly, it relates to the use of an electroluminescent sheet as a light source for photocopying.

Heretofore, many methods have been devised for making copies of printed matter, drawings, or the like on loose sheets. Some methods call for pressing sheets flat under a glass plate while exposing a photosensitive paper in contact with the material to be copied. Another method would be to place the copy material and the photosensitive paper through rollers following a curved path around a light source. However, these methods are either clumsy and awkward or completely impractical when applied to the copying of pages in a bound book. Even when used for such purpose, it is necessary by reason of the process utilized to bend the binding of the book and thereby injure it. Additionally, it is diificult to photo copy quickly more than one page of the bound book.

In the prior photocopying methods, if it is desired to change for any reason the type of photosensitive paper, i.e. from paper sensitive to one color of light rather than another, it was necessary to place a light filter in front of the light source. This too called for bulky equipment and the necessity of keeping a variety of light filters available.

The present photocopying devices commercially available are extremely bulky and require a permanent installation. Thus, they could not be easily transported by one who had photocopying needs in various places.

It is the general object of this invention to avoid and overcome the foregoing and other diificulties of the prior art by the provision of a new and better photocopying system.

Another object of this invention is to provide a better photocopying system which utilizes a flexible electroluminescent sheet as the light source.

Another object of this invention is to provide a better reflex copying system which can be utilized to photocopy a plurality of pages in a book in one operation.

Another object of this invention is to provide a new and better photocopying device which is lightweight and easy to transport.

Another object of this invention is to provide a simple and better photocopying system in which the light source is variable both in color and in magnitude.

Another object of this invention is to provide a new method of photocopying two adjacent pages in a book in a single operation from a single source of light.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a pictorial view of a flexible laminated electroluminescent lamp utilized in the present invention, the various constitutent layers being delaminated or peeled open at one corner to show the internal construction.

FIGURE 2 is a pictorial view illustrating the first step in photocopying two adjacent pages in a book in accordance with the present invention.

FIGURE 3 is a partial cross section view of the apparatus of FIGURE 2 in the photocopying stage.

may be any flexible electroluminescent light source.

3,238,859 Patented Mar. 8, 1966 FIGURE 4 is a second embodiment of the present invention utilizing a plurality of electroluminescent sheets to photocopy a group of pages in a book simultaneously.

FIGURE 5 is a pictorial view illustrating the first step in copying two papers utilizing apparatus built in accordance with the principles of the present invention.

Referring to the drawings, and more particularly to FIGURE 1, there is shown a flat rectangular electroluminescent sheet 10. This sheet is made up of flexible components laminated together and is entirely sealed in plastic material. The sheet is energized by applying an alternating voltage to the copper screen terminals 12 and 14 projecting laterally from the edge of the plastic envelope.

The electroluminescent sheet 10 shown in FIGURE 1 In the interest of clarity, one sample electroluminescent sheet which might be utilized in the present invention is shown in detail.

The lowermost film and the uppermost film 16 which form respectively the underside and topside of the envelope in the finished lamp consist of sheets of thermoplas- -tic material which fiows under heat and pressure and welds together along the margins. The material selected must be reasonably tough and stable, in addition to being light-transmitting and preferably flexible. Examples of such materials are polyethylene, polytetrafluoroethylene, polystyrene, and fluoride polymers.

A rectangular sheet 28 of low-density polyethylene sheet is placed under a rectangular sheet of conducting micro-fiber glass paper 26 coated with an insulating layer 24 of high dielectric constant material and thereover a light producing layer 22 of electroluminescent phosphor is placed over the lowermost polyethylene sheet 30 leaving a clear margin all-around. A second sheet of conducting micro-fiber glass paper 20 is laid over the coated sheet 26 leaving a narrow margin of coated sheet uncovered all-around. Preferably a thin sheet 18 of low-density polyethylene is placed over the conducting glass paper and conveniently is of the same size as the high-density envelope sheets 16 and 30, and extends to their margins. The first sheet of low-density polyethylene 28 is also of the same size. During the laminating process, the low density polyethylene sheets 18 and 28 are substantially liquified and forced through the porous glass paper 20 and 26. Thus the glass paper sheets 26 and 26 are bound in place being partly embedded in low-density polyethylene sheets and also cemented to the phosphor layer 22. The juxtaposed margins of the thermoplastic sheets 16, 18, 28 and 30 project beyond the edges of the glass paper sheets and are fused or sealed together. The high dielectric constant material coating 24 may be a thin insulating layer of barium titanate dispersed in an organic polymeric matrix. The electroluminescent layer can consist of phosphor such as zinc sulfide-zinc oxide with suitable activators such as copper, manganese, lead or silver likewise dispersed in an organic polymeric matrix. Examples of organic polymeric matrices are cellulose nitrate, polyvinyl chloride, cellulose acetate, andepoxy cements.

The conducting glass paper sheets 20 and 26 consist of commercially available micro-fiber glass paper which is made conducting by dipping in a solution of a metal salt which upon drying and baking at an elevated temperature forms a con-ducting coating. It should be appreciated that when the flat flexible sheet 10 is completed, it is less than .05 inch thick.

In order to energize the electroluminescent sheet, it is necessary to apply an alternating voltage between the conductive layers, that is, to the micro-fiber glass paper sheets 20 and 26. This may conveniently be effected by means (J of flattened flexible copper braids or ribbons 32 and 34, the former being laid over the conductive glass paper 20, that is, between the glass paper and low-density polyethylene sheet 18, and the latter being laid under the micro-fiber glass paper sheet 26 between the glass paper and the low-density polyethylene sheet 28. The copper ribbons 32 and 34 extends substantially to the edge of the polyethylene envelope sheets 16 and 30 at one end and there overlie respectively a pair of laterally projecting copper screens 12 and 14. During the laminating step, the copper ribbons become embedded in the thermoplastic sheets and are at the same time pressed against the glass paper sheets. The ends of the copper ribbons and the copper screens 12 and 14 likewise become embedded in the thermoplastic envelope sheets and are pressed in mutual contact. The ends of the screens projecting beyond the thermoplastic envelope serve as contact terminals. It will be appreciated that when the electroluminescent lamp is lit, the phosphor is energized and lights up to the margin of the conductive glass paper. The band between the margin of the conductive glass paper and the edge of the sheet is not illuminated but is transparent, or at least translucent.

The excitation of the phosphor layer is governed by the strength of the electric field requiring constant thickness in the various layers of the finished electroluminescent lamp. It is to be appreciated that the conducting glass paper may be replaced by a light-transmitting flexible sheet of high-melting point plastic such as Mylar coated with a thin layer of evaporated metal or a semi-conductor such as gold metal or cuprous iodide.

In FIGURE 2, there is shown one preferred embodiment of the present invention. When it is desired to photocopy two adjacent pages 40 and 42 in a book 44, it is only necessary to do the following. The book 44 is Opened to the pages, and therein inserted first a photosensitive sheet 38, the electroluminescent sheet 10 and a photosensitive sheet 36 in place on one page 42. The book 44 is then closed and acts as a press holding the three sheets 36, 10 and 38 flat against the pages 40 and 42 to be copied.

The flexible electroluminescent sheet 10 has its terminals 12 and 14 connected to a variable alternating current source 46. The alternating current source 46may be one such as shown in US. Patent 2,937,298. The alternating current source 46 is capable of varying'its voltage and frequency output.

The color and intensity of light emitted by the electroluminescent sheet depend not only on what phosphors are used in the manufacture of the sheet, but also on the frequency of the electrical voltage used to excite it. As the frequency of the alternating current source goes up, the color of the emitted light from the electroluminsecent sheet shifts towards the colors having shorter wave lengths.

The intensity of the light is somewhat proportional to the magnitude of the applied voltage.

It should be noted, however, that there are other ways of producing all variations of the spectrum using an electroluminescent sheet. One such method is shown in US. Patent 2,925,532. It should be noted that because of the ability to shift the intensity and the color of the light produced by the electroluminescent sheet by simple variation of the AC. source, it is possible to tailor the light produced to the particular sensitivity of the photocopying paper used. In this manner, the electroluminescent sheet has eliminated the need for special filters when a change is made in the type of photocopy paper.

In FIGURE 3, there is shown a cross sectional area of the sheets 36 and 38 described with reference to FIG- URE 2 in place when the book 44 has been closed. Only pages 40 and 42 of the book 44 have been shown for purposes of clarity.

Although the present invention is especially useful in reflex copying, it may also be utilized in contact copying if so desired. Additionally, the process shown in FIG- URE 2 is utilized for copying two adjacent pages of a book. It can easily be seen that if only one page of the book is tobe copied, only one sheet of photosensitive paper is needed.

In FIGURE 2, the electroluminescent sheet 10 is shown sandwiched between two photocopy sheets 36 and 38. Pages 40 and 42 are placed flat against sheets 36 and 38 respectively.

As shown in FIGURE 3, the face of the page 42 to be copied is placed in contact with the support 48 of photocopying sheet 38 which has on its other face a lightsensitive emulsion layer 50. The support 48 has a relatively high transparency; it may consist of a suitable paper, and it contains a non-volatile agent having such characteristics as are indicated below. When the photocopying paper 38 is exposed to light, the emulsion coated surface 50 is directed towards the light source. The incident light which successively passes through the emulsion layer 50 and the support 48 reaches the face to be copied of page 42 and is reflected thereby in proportion of the densities printed on the face of the page.

It should be noted that for purposes of example, the light-sensitive element 38 has been shown with it's emul sion coated surface directed toward the light source. However, it is within the scope of this invention to have a reflex copy process where the emulsion coated surface is in contact with the document to be copied. The arrangement shown in FIGURE 2, wherein the support of the light-sensitive element rather than the emulsion is in contact with the page, makes it possible to obtain directly a non-laterally inverted copy.

The light-senstive element, or photocopy paper 36, also consists of a support 54 and an emulsion layer 52. The emulsion layer 52 is directed toward the light source 10 while the support 54 is adjacent the page 40 to be copied. The light-sensitive emulsion layers 52 and 50 are prefer-. ably made of a usual lgelatino-silver halide emulsion. may be an emulsion of the type giving a negative copy from a positive original. Preferably, a reversal emulsion is used, especially a direct positive emulsion which upon development in a usual black and white developer, directly gives a positive image from a positive original. Thus, using the type of photocopy paper 36 and 38 discussed above, it is possible by means of a single exposure followed by a single development step to obtain a nonlaterally-inverted positive copy of any original.

The book 44 acts as an opaque support so that the printed matter on the back of pages 40 and 42 does not interfere with the copying of the material on the sides adjacent photocopying paper 36 and 38. The book also acts as a press to hold the photocopy paper 36 and 38 and the electroluminescent sheet 10 between the pages 40 and 42 without any undue strain on the binding of the book.

After exposing the photocopy paper 36 and 38 by exciting the electroluminescent sheet 10 from the alternating current source 46 for a given period of time, the photocopy paper is subjected to the usual photographic processing order to develop the latent image. This treatment usually comprises a development step and a subsequent fixing or stabilizing step and, if desired, a washing step. On the other hand, it may be desirable to use rapid processing where required which would only call for a single development and a subsequent stabilization without any washing step.

The supports 54 and 48 are transparentized paper, made such by incorporating a non-volatile transparentizing agent and selecting such transparentizing agent so that it can be eliminated from the support while the exposed element is being processed in one of the photographic baths. By non-volatile, it is meant that the transparentizing agent is not eliminated during storing, whatever the hygrometric conditions may be. One such transparentizing agent is sodium lactate. After exposure, the

transparentizing agent is normally completely eliminated in the development process.

It can be seen that if only one photocopy is desired with a single electroluminescent sheet, it is possible to substitute for one of the conducting layers in the electroluminescent sheet a light-reflective conducting layer so as to direct all light produced by the sheet toward the photocopy paper. However, when the present invention is utilized in photocopying pages of a book, the book itself acts as a light-reflective backing so as to direct all of the light toward the light-sensitive paper and the page to be copied.

In FIGURE 4, there is shown a second embodiment of the presentinvention utilizing a plurality of electroluminescent sheets and photocopy'paper to simultaneously photocopy a portion of a book. Normally, when it became necessary to photocopy pages of a book by standard photocopying processes, it was necessary to individually copy each page in the book. However, by utilizing the present invention, all the pages which are to be copied can be duplicated at one time. As shown in FIGURE 4, all that is necessary is to provide a plurality of electroluminescent sheets connected in parallel with the variable A.C. source. The electroluminescent sheets have been generally designated as 56, 58, 60 and 62. The book 44 is opened to the appropriate pages, photocopy paper is inserted where needed, the electroluminescent sheets are put in place, and the book closed. The book will act as a press, and one application of electrical energy from the source 46 will expose tall the photocopy sheets in the book 44.

The present state of the electroluminescent phosphor art requires the use of a separate alternating current supply capable of high frequencies and high voltages. This is so as it is the only method of obtaining adequate light intensity from the phosphors so that photocopying may be accomplished. The norm-a1 house current 120 volts and 60 cycle AC. is suflicient only t produce a small amount of light in the known electroluminescent sheets. However, simple, light and easily transportable converters may be utilized to increase the voltage and frequency of ordinary house current so that it may be more effectively used in the present invention. By so providing a small alternating current converter, the entire photocopying unit may be stored in as small a place as a persons briefcase. The electroluminescent sheets do not take up much space. The only limitation in ease of transportation would be the amount of photocopy paper which could be carried.

In FIGURE 5, there is shown permanent apparatus for photocopying papers utilizing the principles of the present invention. The photocopying machine in FIGURE 5 is generally designated by the numeral 64 and consists of a base or housing 66 and a movable opaque plate 68. The housing 66 has at the bottom thereof a tray 70 in which the developing process can be completed. A valve 71 at the bottom of the housing 66 is used to drain the developing solution from the tray 70 after it has lost its strength. The opaque plate 68 is used as a press for the photocopying process and is secured to the housing 66 through upright vertically slotted hinges 72 and 74 secured to opposite sides of one end of the housing 66. The top face 76 forms the bottom of the press for the photocopying operation. The top face 76 has a slot 78 therein at the end opposite from the hinges 72 and 74 which cooperates with a locking mechanism 80 on the plate 68. A handle 82 is operative to disengage the hook or latch 80 from the hole 78 when the plate 68 is to be raised.

An electroluminescent sheet such as the sheet shown in FIGURE 1 could be utilized with the apparatus 64 to photocopy the material shown in FIGURE 5. However, in order to obtain more light from a single electroluminescent sheet, the double layer electroluminescent sheet 84 shown in FIGURE 5 was utilized.

The sheet 84 consists of two back-to-back electroluminescent layers 86 and 88 having a common electrically conductive sheet at their mating faces. This electrically conductive sheet (not shown) is connected to a terminal 92. The outer faces of electroluminescent layers 86 and 88 are connected to terminals 90 and 94 respectively. The outer faces of electroluminescent layers 86 and 88 are transparent and could be made of a glass fiber fabric such as was discussed with reference to FIGURE 1. The mating faces of the electrically conductive sheet may be transparent also or, in the alternative, could be manufactured of a light reflective electrically conductive material such as a thin metal foil. By using a thin metal foil, the two electroluminescent layers effectively act as separate electroluminescent lamps whose light transmission is independent one from another.

A photosensitive matrix 96 is then placed over the electroluminescent layer 86 with its photosensitive coating on the side opposite from the layer 86. The photosensitive matrix 96 has a translucent support through which the light emanating from the layer 86 is transmitted to the photosensitive coating on the matrix 96. A paper 98 which is to be copied is placed face downwardly upon the matrix 96 with the photosensitive coating adjacent the object 98 to be copied. A similar matrix 100 is placed under layer 88 with its photosensitive surface contiguous with a paper 102 to be copied. The paper 102 is under the matrix 100.

The electroluminescent lamp 84, photocopy matrix paper 96 and 100, and papers 98 and 102 are then placed between plate 68 and top face 76 in the manner suggested by the pictorial view in FIGURE 5. The plate 68 is heavy and, therefore, when it is latched by means of hook 80 and hole 78, it presses the papers, matrix paper and lamp together. Both the top face 76 and 68 are opaque surfaces. Terminals 90, 92 and 94 are energized from a suitable source of variable AC. voltage (not shown) to excite the matrix paper 96 and 100 and produce a negative image thereon. The matrix paper 96 and 100 is then placed in the developing and fixing bath in tray 70 along with positive copy paper to produce a positive image of the objects to be copied.

If it is desired to use only coherent light, a polarizing filter could be placed over the transparent faces of electroluminescent layers 86 and 88.

It can also be seen that if more than one electroluminescent lamp 84 is available, more than two papers can be copied. That is, the plate 86 can be raised so as to accommodate more electroluminescent lamps, photocopying matrix paper, and pages to be copied.

The present invention may be embodied in other specific forms Without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

I claim:

1. Photocopying apparatus comprising a fiat electroluminescent sheet, converter means adapted to be connected to a source of electrical energy and to convert the electrical energy to excite said electroluminescent sheet, connector means for connecting said electroluminescent sheet to said converter, said electroluminescent sheet being adapted to be juxtaposed to a light-sensitive sheet contiguous with an object to be copied to expose said light sensitive sheet and thereby the object, said converter including output signal frequency varying means operative to vary said converter output signal frequency in accordance with a desired color of light to be produced by the electroluminescent sheet, the color of light produced being dependent upon the light sensitivity of the light-sensitive sheet.

2. Photocopying apparatus comprising a bottom support having a flat rigid opaque surface, a flat rigid opaque press member biased toward contiguous abutment with said surface, an electroluminescent sheet, connecting means for connecting said electroluminescent sheet to a source of alternating current for exciting said electroluminescent sheet, said electroluminescent sheet being adapted to be juxtaposed to said light-sensitive sheet contiguous with an object to be copied between said press member and said surface to said light-sensitive sheet and thereby copy the object, said electroluminescent sheet consisting of two separately excited electroluminescent layers having a reflective coating therebetween, each of the electroluminescent layers being adapted to be juxtaposed to a light-sensitive sheet contiguous with an object to be copied and placed between said press member and said surface to expose said light-sensitive sheets and thereby copy the objects.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 6/ 1954 Australia.

1930 Great Britain. 1/ 1962 Great Britain.

NORMAN G. TORCHIN, Primary Examiner.

Claims (2)

1. PHOTOCOPYING APPARATUS COMPRISING A FLAT ELECTROLUMINESCENT SHEET, CONVERTER MEANS ADAPTED TO BE CONNECTED TO A SOURCE OF ELECTRICAL ENERGY AND TO CONVERT THE ELECTRICAL ENERGY TO EXCITE SAID ELECTROLUMINESCENT SHEET, CONNECTOR MEANS FOR CONNECTING SAID ELECTROLUMINESCENT SHEET TO SAID CONVERTER, SAID ELECTROLUMINESCENT SHEET BEING ADAPTED TO BE JUXTAPOSED TO A LIGHT-SENSITIVE SHEET CONTIGUOUS WITH AN OBJECT TO BE COPIED TO EXPOSE SAID LIGHT SENSITIVE SHEET AND THEREBY THE OBJECT, SAID CONVERTER INCLUDING OUTPUT SIGNAL FREQUENCY VARYING MEANS OPERATIVE STO VARY SAID CONVERTER OUTPUT SIGNAL FREQUENCY IN ACCORDANCE WITH A DESIRED COLOR OF LIGHT TO BE PRODUCED BY THE ELECTROLUMINESCENT SHEET, THE COLOR OF LIGHT PRODUCED BEING DEPENDENT UPON THE LIGHT SENSITIVITY OF THE LIGHT-SENSITIVE SHEET.

2. PHOTOCOPYING APPARATUS COMPRISING A BOTTOM SUPPORT HAVING A FLAT RIGID OPAQUE SURFACE, A FLAT RIGID OPAQUE PRESS MEMBER BIASED TOWARD CONTIGUOUS ABUTMENT WITH SAID SURFACE, AN ELECTROLUMIESCENT SHEET, CONNECTING MEANS FOR CONNECTING SAID ELECTROLUMIESCENT SHEET TO A SOURCE OF ALTERNATING CURRENT FOR EXCITING SAID ELECTROLUMINESCENT SHEET, SAID ELECTROLUMINESCENT SHEET BEING ADAPTED TO BE JUXTAPOSED TO SAID LIGHT-SENSITIVE SHEET CONTIGUOUS WITH AN OBJECT TO BE COPIED BETWEEN SAID PRESS MEMBER AND SAID SURFACE TO SAID LIGHT-SENSITIVE SHEET AND THEREBY COPY THE OBJECT, SAID ELECTROLUMINESCENT SHEET CONSISTING OF TWO SEPARATELY EXCITED ELECTROLUMINESCENT LAYERS HAVING A REFLECTIVE COATING THEREBETWEEN, EACH OF THE ELECTROLUMINESCENT LAYERS BEING ADAPTED TO BE JUXTAPOSED TO A LIGHT-SENSITIVE SHEET CONTIGUOUS WITH AN OBJECT TO BE COPIED AND PLACED BETWEEN SAID PRESS MEMBER AND SAID SURFACE TO EXPOSE SAID LIGHT-SENSITIVE SHEETS AND THEREBY COPY THE OBJECTS.

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