GB2172711A - Images on plain paper - Google Patents

Abstract

Images are formed on plain paper using imaging sheets having a coating containing a chromogenic material and a photosensitive composition with at least the photosensitive composition encapsulated in a layer of rupturable microcapsules as an internal phase by a process which comprises image-wise exposing the imaging sheet to actinic radiation placing the imaging sheet in contact with a sheet of plain paper with the layer of microcapsules adjacent the sheet of plain paper, subjecting the microcapsules to a uniform rupturing force, the steps of subjecting the layer of microcapsules to the rupturing force and placing the imaging sheet in contact with the sheet of plain paper being conducted such that the chromogenic material is image-wise transferred to the sheet of plain paper, and applying a developer material to the surface of the sheet of plain paper to which the chromogenic material is transferred, the developer material thereupon reacting with the chromogenic material and producing a visible image.

Description

1 GB 2 172711 A 1

SPECIFICATION

Method and apparatus for forming images on plain paper Description

The present invention relates to a method for forming images on plain paper.

U.S Patent 4,399,209 to The Mead Corpo- ration describes a transfer imaging system wherein an imaging sheet comprising a support and a layer of microcapsules containing a chromogenic material and a photosensitive composition is image-wise exposed to actinic radiation. The exposed sheet is next assembled with a developer sheet and the two are passed through a calender nip whereupon the microcapsules rupture and the contents of the microcapsules are image-wise transferred to the developer sheet where they react and form a coloured image. Typically, the photo sensitive composition is a photocurable com position containing an ethylenically unsaturated compound and a photoinitiator, the chromo genic material is a substantially colourless electron donating compound, and the devel oper is an electron acceptor such as an aromatic carboxylic acid salt.

Upon image-wise exposing the imaging 95 sheet to actinic radiation, the internal phase of the microcapsules is hardened in the exposed areas. The internal phase in the unexposed ' areas remains liquid and the internal phase in areas receiving ah intermediate level of exposure is hardened to an intermediate degree. Thus, the microcapsules in the unexposed areas are capable of rupturing and releasing the internal phase upon subjecting the ex- posed imaging sheet to a uniform rupturing force. The microcapsules in the underexposed areas may rupture and release the internal phase to an intermediate degree. In this manner, the internal phase of the microcapsules is image-wise transferred to the developer sheet 110 where the image is obtained.

While the transfer imaging system described in U.S. Patent 4,399,209 can be used in numerous formats and be designed to be useful in various applications, the user must purchase two coated paper products to reproduce images, namely, the imaging sheet and the developer sheet. Furthermore, the final image Js obtained on a chemically coated paper which may cause skin irritation and does not have a desirable feel.

As will become apparent from the description which follows, the present invention enables images to be formed on plain paper.

The examples of the method described do not involve wet development processing steps.

The invention can be applied to a photographic process which is useful in forming full colour images on plain paper.

According to a first aspect of the present invention, there is provided a process for forming images using an imaging sheet comprising a support having a chromogenic ma- terial and a layer of microcapsules containing a photo-sensitive composition on the surface thereof, which comprises the steps of: imagewise exposing said imaging sheet to actinic radiation; placing said imaging sheet in contact with a sheet of plain paper with said layer of microcapsules adjacent said sheet of plain paper; subjecting said layer of microcapsules to a uniform rupturing force; said steps of subjecting said layer of microcapsules to said rup- turing force and placing said imaging sheet in contact with said sheet of plain paper being conducted such that said chromogenic material is image- wise transferred to said sheet of plain paper; and applying a developer material to the surface of said sheet of plain paper to which said chromogenic material is trans ferred, said developer material being adapted to react with said chromogenic material and to produce a visible image.

In a second and alterr)ative aspect thereof, the invention provides an apparatus useful in forming images on plain paper utilizing an im aging sheet comprising a support carrying a layer of microcapsules containing a photosen sitive composition and a chromogenic material, said apparatus comprising: means for image wise exposing said imaging sheet to actinic radiation; means for subjecting said layer of microcapsules to a uniform rupturing force; means for assembling said imaging sheet with a sheet of plain paper; means for separating said sheet of plain paper and said imaging sheet; and means for applying a developer material to the surface of said sheet of plain paper.

Preferably the chromogenic material is present in the microcapsules with the photosensitive composition. The microcapsules can be ruptured with the imaging sheet in contact with the plain paper or separately. The former practice is preferred because it simplifies handling and tends to maximize the amount of chromogenic material transferred from the imaging sheet to the plain paper sheet. When the microcapsules are ruptured and the chromogenic material is transferred to the plain paper in separate steps, there is a tendency to lose some of the chromogenic material and, consequently, it is more difficult to obtann good image ddnsity.

The developer can be applied to the paper after transfer of the chromogenic material or simultaneously with its transfer. In one embodiment, the developer material is provided on the surface of the imaging sheets with the microcapsules and the chromogenic material. The developer is preferably provided in admixture with the microcapsules in a single layer on the surface of the imaging sheet, but em- bodiments are also possible in which the de- 2 GB 2 172 711 A 2 veloper is provided in a separate layer overlying or underlying the layer of microcapsules.

When the developer is provided on the surface of the imaging sheet, the developer is optionally encapsulated. In this case, a liquid developer or a developer solution is used. On the other hand, in many cases, solid developers such as developer resins can be directly admixed with the microcapsules and provided in a layer on the support without being separately encapsulated. With the developer present on the surface of the imaging sheet, images are formed by simply image-wise exposing the sheet to actinic radiation, subjecting the sheet to a uniform rupturing force, and effecting transfer to the surface of the plain paper. The developer and the chromogenic material begin to react as they are transferred 'to the surface of the plain paper.

Full colour images can be formed through the use of an imaging sheet carrying microcapsules having distinct sensitivities and respectively containing cyan, magenta, yellow and optionally black colour formers. In this process, a colour image is resolved into its red, green, blue and optionally black components, each of which is then respectively translated into radiation to which the photosensitive composition associated with the comple- mentary colour former is sensitive. The imaging sheet is then sequentially or simultaneously image-wise exposed to the translated radiation. A full colour image is then obtained on the surface of a plain sheet of paper by the process of subjecting the microcapsules to a uniform rupturing force, contacting the sheet of paper with the imaging sheet, and treating the surface of the paper to which the chromogenic material is transferred with a developer 'material as described above.

The invention is hereinafter more particularly described by way of example only, with reference to the accompanying drawings, in which:

Figs. 1-4 schematically illustrate an embodi- ment of imaging process in accordance with the present invention; Fig. 5 is one example of an imaging appafra tus useful in carrying out a process according to the present invention; Fig. 6 is a schematic illustration of one 115 apparatus for applying developer in a process in accordance with the present invention; Fig. 7 is a schematic illustration of an appa ratus for applying developer from a particle bed in another process in accordance with the present invention; and Fig. 8 is a schematic illustration of a magnetic brush useful in applying developer in a yet further process in accordance with the present invention.

The term "microcapsules" as used herein includes both microcapsules having discrete walls and microcapsules within a so-called open phase system consisting of a dispersion of the internal phase in a binder.

The term "photosensitive composition" as used herein means compositions which undergo a change in viscosity upon exposure to actinic radiation, The term "actinic radiation" includes the entire electromagnetic spectrum including ultraviolet and infrared radiation, X-rays, and particle radiation such as ion beam radiation.

The term "plain paper" as used herein re- fers to paper which is not coated with a developer material. It includes bond paper as well as papers which are treated or manufactured using techniques which enhance the quality of the image obtained in accordance with the present invention. It is desirable to use papers in which surface irregularities (roughness) is minimized.

The disclosure of U.S. Patent 4,399,209 is incorporated herein by reference. The patent describes imaging sheets useful in the present invention in detail as well as the mechanism by which the microcapsules selectively release the chromogenic material. The disclosures of British Patent 2113860 and European Patent

Application No 85303484.1 (Publication No: 0164931) are also incorporated herein by reference. These prior patent publications are concerned with imaging sheets useful in forming full colour images as well as methods for exposing the imaging sheets to obtain full colour images.

The present invention is based upon our discovery that an imaging sheet, otherwise useful in forming images by transfer to a col- our developer sheet, can be used to form images on plain paper by effecting a transfer of chromogenic material to paper instead of to a developer sheet and simultaneously or thereafter treating the paper with a developer material. We have found that a transfer of chromogenic material from the imaging sheet to paper can be effected and a sufficient quantity of the chromogenic material remains accessible on the surface of the paper to react with a developer material and form an image.

A typical example of the imaging sheet used in the present invention is shown in Fig. 1. The sheet 10 comprises a support 12 (preferably a thin plastic film) and a layer 14 of microcapsules 16. The microcapsules can be formed with discrete walls or consist of a dispersion of internal phase in a binder. In the former case the microcapsules are formed by processes such as coacervation or polymeriza- tion. Where the microcapsules have discrete walls, they may. be adhered to the support 12 with a binder or, in many instances, the wall forming compounds themselves adhere the microcapsules to the support.

The microcapsules shown in Fig. 1 have a discrete wall 18 and contain an internal phase 20. The internal phase typically consists of the photosensitive composition and the chromogenic material. In some cases, however, the chromogenic material is not in the internal 3 GB 2 172711 A 3 phase. Rather it is associated with the microcapsules in o;her ways, such as by placing the chromogenic material in the capsule wall or in a layer contiguous with the microcap- sules. In the latter case, the internal phase is designed to dissolve the chromogenic material as it is released from the micro-capsules and carry it to the plain paper.

When the developer is present on the sur- face of the imaging sheet with the chromogenic material, the developer must not react with the chromogenic material prior to development. This is typically resolved by encapsulating one or both of the developer and the chromogenic material. On the other hand, if the developer is a solid such as a developer resin, premature reaction can be prevented without encapsulation.

The photosensitive composition can be a photo-hardenable or photosoftenable composition. In the former case, exposure inhibits or prevents chromogenic material from being transferred to the paper sheet. In the latter case, exposure enhances the ability of the chromogenic material to be transferred to the paper sheet. In Fig.1, the internal phase is liquid and represents an unexposed photocurable composition. Typical examples of photosensitive compositions useful in the present invention are described in U.S. Patent No. 4,399,209. A composition containing trimethylol propane triacrylate and a photoinitiator is a representative example of a photohardenable composition.

Exposure of the microcapsules is illustrated schematically in Fig. 2. The exposed and ' unexposed areas are defined by a photomask 24 through which radiation (designated by arrows) from an unshown source selectively passes. Exposure solidifies the internal phase 20A of the exposed microcapsules 16A while the internal phase 20B of the unexposed or underexposed microcapsules 16B remains liquid. The illustration in Fig. 2 is a simplified illustration of exposure and the distribution of exposed and unexposed microcapsules on the surface of the imaging sheet. Depending upon the nature of the photosensitive composition, intermediate degrees of exposure will produce an intermediate degree of hardening of the internal phase resulting in the chromogenic material being transferred to the plain paper in an intermediate amount. In a full colou imaging system, in accordance with one embodiment of the invention, a predetermined area on the surface of the imaging sheet will include a combination of exposed micro-capsules, unexposed microcapsules, and microcapsules exposed to an intermediate degree. The image produced in accordance with the present invention is thus the product of a combination of microcapsules rupturing and releasing their internal phases in accordance with degree of exposure.

Various imaging apparatuses can be used to 130 expose the imaging sheets in the present invention. It is anticipated that the imaging process of the present invention will be used to copy computer generated output and for this purpose certain electronically controlled imaging apparatuses will be used. Typical examples of such electronic imaging apparatuses include light valve imaging apparatuses of the type described in U.S. Patents 4,229,095; 4,367,946; and 4,406,521. Cathode ray tubes and certain laser imaging apparatuses can also be used to image-wise expose the imaging sheet in accordance with the present invention. Of course, photomasks can also be used.

Where fullcolour images are produced, the preferred exposure device will control three or four distinct bands of radiation which may be emitted from a single radiation source or a plurality of sources. For example, a Dunn or matrix camera may be used to produce electronic signals corresponding to the cyan, magenta, and yellow (and optionally black) images that are desired. This output drives the electronic control means for an exposure device which may include a conventional multiplexer logic package and timing means. The exposure device selectively emits radiation to which the microcapsules on the imaging sheet are sensitive and thereby image-wise exposes the imaging sheet.

Following exposure of the imaging sheet, it is usually assembled with a sheet of plain paper 30, as shown in Fig. 3, and the microcap- sules are subjected to a uniform rupturing force. This is conveniently accomplished by passing the paper and imaging sheet in unison through the nip between a pair of pressure rollers. This causes the unexposed and/or un- derexposed microcapsules 16B to rupture and release the internal phase. In contact with paper 30, the internal phase is transferred to the paper where a latent image 34 in the form of unreacted chromogenic material is formed.

Fig. 3 illustrates the most typical approach to rupturing the microcapsules and transferring the chromogenic material to the paper surface wherein the paper is in contact with the image-wise exposed imaging sheet as the cap- sules are ruptured. Images can also be formed by rupturing the microcapsules and transferring the chromogenic material in separate steps. For example, the microcapsules can be ruptured by contacting the imaging sheet with the fibrous outer surface of a developer roll as described in U.S. Patent 4, 448,516 and, thereafter, the imaging sheet can be assembled with the paper sheet with pressure to effect transfer of the chromogenic material and the formation of the latent image in the form of unreacted chromogenic material.

When the developer is not transferred with the chromogenic material, after transfer, the paper is contacted with a developer material and the image is developed through reaction 4 GB2172711A 4 of the chromogenic material and the developer. This procedure is illustrated in Fig. 4 wherein a paper 30 is shown in contact with a rotating developer applicator brush 42. The brush 42 applies developer material 44 on to the surface of paper 30 where it reacts with the chromo-genic material and produces the colourimage 46. The brush 42 can be a brush having a fibrous outer surface as described in U.S. Patent 4,448,516, or it can be a socalled magnetic brush of the type conventionally used in applying xerographic toner.

The developer is preferably a dry material which is dusted upon or otherwise applied to the surface of the paper carrying the chromogenic material. It is envisioned, however, that for certain applications it may be desirable to apply the developer in the form of a solution to accelerate the reaction between the devel- oper and the chromogenic material and to enable the developer to react with chromogenic material which is absorbed by the paper and may not be accessible to a completely dry developer material. If the developer is applied as a liquid, it is desirable to minimize the wetting of the paper and to dry the paper if necessary.

The latent image can be developed by contacting the imaging sheet 30 with a bed of developer material as shown in Fig. 6. This can be accomplished by passing the paper through a trough containing dry developer material. Therein, a tray 144 supports the body of free particles 129 and a cylinder 146 is horizontally mounted above the tray 144 for rotation about an axis 147. The cylinder 146 is located relative to the tray 144 such that a sector 148 of the circumference of the cylinder 146 extends into the body of free par- ticles 129. The free particles can consist of particles of solid developer material or a combination of developer material and a dispersant such as sand. A sheet of plain paper 150 carrying a latent image is secured to the cylin- der 146 such that the surface of the paper 150 is mounted with the latent image facing outwardly. The paper 150 is then processed by rotating the cylinder 146 such that the surface of the paper 150 contacts the body of free particles 129. The operation of the em- bodiment of Fig. 6 may be enhanced by vi brating the tray 144 as the cylinder 146 is rotated, such vibration being indicated by an arrow 152.

Another embodiment of apparatus for per forming development in the presently de scribed system is shown in Fig. 7. In this embodiment, a primary cylindrical drum 154 is mounted for rotation about a horizontal axis 156. A secondary retaining drum 157 is posi tioned concentrically within drum 154 with the paper 153 and developer particles 129 being inserted between drums 153 and 154. The paper 153 is positioned along the interior of the surface of the drum 154 by means of 130 insertion through a slot 160 which is angled in the direction of drum rotation indicated by the arrow 162. The paper 153 is held against the inside surface of drum 154 by the secondary drum 157. Alternatively, paper 153 can be held against the inside of the drum 154 by means of clamping members.

As the drum 154 is rotated, the particles 130 of the body of free particles 129 carrying the developer move over the surface of the paper 153 to develop the latent image thereon. Preferably, the speed of rotation of the primary cylindrical drum 154 is limited such that the particles 129 do not tumble, i.e., the particles are not thrown around in the drum, and are not held against the interior of the drum 154 by centrifigual forces. Rather, the speed is selected such that the particles are carried partially up the interior surface of the drum and then return toward the bottom of the drum in an oscillatory wave- like motion defining a swishing action.

Fig. 8 shows a schematic cross-sectional view of an apparatus for developing the latent image using a magnetic brush in one example of the present process. A magnetic brush 170 includes a fixed shaft 172 having at least one pair of magnets 174 fixed thereto. The shaft 172 is situated within a cylindrical sleeve 176 which is rotated in the clockwise direction in the illustrative embodiment as indicated by an arrow 178. The sleeve 176 engages a body of magnetically attraGtable free particles 180 carrying developer which is held within a sump or trough 182 which is axially aligned with the magnetic brush 170. It is noted that other designs of magnetic brushes maintain an outer sleeve fixed and rotate an inner magnetized member to form a traveling pile on the outer sleeve.

As the sleeve 176 is rotated, the particles 180 stand up in trees or bristle-like formations to form a pile 184 on the outer surface. of the sleeve 176. The pile 184 formed on the sleeve 176 rotates in the clockwise direction with the sleeve 176 as indicated by the arrow. 178 into engagement with a trim blade or doctor blade 186 which is adjusted to define the length of the pile 188 on the section of the magnetic brush 170 which is to engage an imaging sheet. A sheet of plain paper 194 carrying a latent image is passed over the pile 188 on the magnetic brush 170 and is contacted by the pile 188 such that the developer is carried to the surface of the paper where it reacts with the latent image.

The paper may be placed in contact with the pile of the magnetic brush in a variety of ways. In accordance with this embodiment of the present invention, a carrier cylinder 190 is mounted for rotation about an axis 192 parallel to the magnetic brush 170 with the cylinder 190 being sized and positioned such that the pile 188 traveling on the magnetic brush 170 is just slightly greater than the gap be- GB 2 172711 A 5 tween the sleeve 176 and the cylinder 190. The carrier cylinder 190 can be operated in the same or opposite direction as that of the moving pile on the magnetic brush 170. How- ever, it is preferred that paper 194 secured to the outer surface of the cylinder 190 travel in the same direction as the pile 188 on the magnetic brush 170 and the magnetic brush 170 rotate at a higher tangential velocity than cylinder 190 such that the pile 188 sweeps along the surface paper 194 carrying the latent image.

The paper 194 may be secured to the cylinder 190 by sheet stabilizing means comprising clips 196 or preferably by means of vacuum systems well known in the art. The particles 180 are deposited back to the trough 182 as the cylinder 176 is rotated such that the particles 180 are continuously recirculated to form the pile 188 of the brush 170. It may be desirable to provide particle agitation means within the trough 182, such as stirrers 198, as shown.

As a further alternative, the paper sheet can be sprayed or coated with the developer in 90 powder or liquid form using well known tech niques.

It is often desirable to heat the paper to accelerate development and enhance the im age density. This treatment can be carried out as the developer is applied or thereafter de pending upon the mode of its application. The heating conditions are not critical. A treatment at 50-6Q'C for 1-5 seconds is often sufficient.

In accordance with anot her embodiment of the present invention, the imaging sheet shown in Fig. 1 is modified to include a developer material on the surface of the sheet with the microcapsules containing the photosensi- tive composition. The imaging sheet is used in a manner similar to the imaging sheet of Fig. 1 except the step of applying the developer material to the plain paper is carried out at the same time as the chromogenic material is transferred to the surface of the sheet of plain paper.

The developer material may be provided on the surface of the imaging sheet in the same layer as the microcapsules (i.e., layer 14 in Fig. 1) or in a separate layer underlying or overlying the layer of microcapsules. In accordance with one embodiment of the invention, the developer material is directly admixed with the microcapsules and coated on the support.

In one embodiment of the invention, the developer material is encapsulated in microcapsules. If the microcapsules contain a photosensitive composition in addition to the developer, the release and transfer of the developer material is controlled by imagewise exposure of the imaging sheet to actinic radiation.

Where the developer is encapsulated, a liquid developer or a developer solution may be used.

As previously indicated, means other than 130 pressure can be used to rupture the microcapsules. For example, in other embodiments the microcapsules can be ruptured ultrasonically, by abrasion as described in U.S. Patent 4,448,516, or by heating. In the latter case the microcapsules may include an agent which generates a gas upon heating above a predetermined temperature. The latter processes can also be performed separately or with the paper sheet in contact with the surface of the imaging sheet. To obtain the maximum transfer of chromogenic material from the imaging sheet to the paper, it is preferred to rupture the microcapsules in contact with the paper sheet as illustrated in Fig. 3.

The process of the present invention can be carried out using plain bond paper. It will be noted, however, that other papers may be used. Preferred papers will have the property of retaining a sufficient quantity of the chromogenic material on the surface of the paper where it can react with a dry developer material. Papers which are highly absorbent and which draw the chromogenic material into the paper where it is not accessible to the developer are not desirable.

Those skilled in the art will appreciate that various apparatus designs are available for carrying out the process of the present invention. Exposure and development are preferably integrated in a single imaging device although separate devices can be designed for each function.

One example of an apparatus useful in the present invention is shown schematically in Fig. 5. The basic elements of the apparatus are a light valve exposure device 100, an exposure drum 102, a pressure roller 108, a transfer roll 109, a carrier drum 110, and a developer applicator 112. The operation of light valve exposure device 100 is described in more detail in U.S. Patent 4,229,095. The light valve exposure device 100 exposes the imaging sheet 10 as it is scrolled past the device on the exposure drum 102. The light valve exposure device includes a radiation source 104, a light valve array 106, and lens means 108 for focusing the array output of to a strip 11 of the imaging sheet 10. The radia- tion source 104 and the array 106 are electronically controlled by means not shown here.

In forming full colour images, the radiation source 104 must emit radiation to which each set of the microcapsules on the imaging sheet is sensitive. This is usually accomplished by using a radiatic;n source which emits radiation over a fairly broad range of wavelengths in combination with filters which are synchro- nized with the operation of light valve array 106.

After exposure, drum 102 rotates the imaging sheet 10 into contact with plain paper 30 which is fed into contact with the drum at the nip between drum 102 and pressure roller 6 GB 2 172 711 A 6 108. Roller 108 applies sufficient pressure to the combination of imaging sheet 10 and paper 30 to rupture the microcapsules on sheet 10 and effect an image-wise transfer of the chromogenic material contained or otherwise associated with the microcapsules on sheet 10 to the paper 30. A latent image is thus formed as shown in Fig. 3 above.

Paper 30 is stripped from drum 102 by conventional means such as a stripping gate (not shown) and conveyed around pressure roller 108 and transferred via roll 109 to car rier drum 110 to which the paper isattached via a vacuum or other means.

As the drum 110 is rotated, paper 30 is 80 contacted with a developer brush 112 which carries a dry developer material from sump 114 to the surface of sheet 30 where it reacts with the chromogenic material on the surface of paper sheet 30 and produces a cofour image. Drum 110 may be heated to accelerate development.

The rate with which the image is developed on paper 30 is a function of the amount of chromogenic material transferred to the sur face of paper 30, as well as the amount of developer material applied to the surface of the sheet and the temperature of the sheet. In most cases, several revolutions of the paper on carrier roll 108 in contact with developer roll 112 will be required to produce the visible image.

Using one developer roll as shown in Figs.

4 and 5, development can require about one minute. One means of reducing the develop ment time is to use a plurality of developer rolls in tandem to apply the developer to the surface of the imaging sheet. With the addi tion of each developer roll, the development time is reduced proportionately.

As indicated initially, the imaging sheet de scribed in U.S. Patent 4,399,209 is suitable for use in the present invention. Certain modi fications of the imaging sheet may, however, be desirable to facilitate plain paper copying. 110 In particular, it appears to be desirable to use a higher amount of chromogenic material in the internal phase of the microcapsules in or der to deliver more chromogenic material to the surface of the paper. This can be accom- 115 plished by using a higher concentration of chromogenic material in the microcapsules or using a larger microcapsule containing more internal phase. Typically, the internal phase of the microcapsules used in the present inven- 120 tion contains about 0.5 to 208 by weight of the chromogenic material.

The developer used in the present invention can be selected from among those materials 60- conventionally used for the purpose in the carbonless paper art. One of the most advan tageous features of the present invention is that it may function as a totally dry photogra phic process. One of the preferred developers is a resin grind containing an aromatic car- 130 boxylic acid or salt thereof prepared according to the teachings in U.S. Patent 3,864,146 to Oda et al and, more particularly, a resin grind containing 3,5-di(a-methylbenzyl)salicylate.

Other developers that can be used in the present invention include acid clay, active clay, acid polymers such as phenol-formaldehyde resins, phenols such as p-cresol and p-octyphenol, aromatic carboxylic acids such as 3,5- di-tert-butylsalicylic acid and salts thereof, and the like. Developers can also be applied in liquid form in accordance with certain embodiments of the invention although this may necessitate additional processing steps.

Claims (23)

1. A process for forming images using an imaging sheet comprising a support having a chromogenic material and a layer of microcap- sules containing a photosensitive composition on the surface thereof, which comprises the steps of: image-wise exposing said imaging sheet to actinic radiation; placing said imaging sheet in contact with a sheet of plain paper with said layer of microcapsules adjacent said sheet of plain paper; subjecting said layer of microcapsules to a uniform rupturing force; said steps of subjecting said layer of microcapsules to said rupturing force and placing said imaging sheet in contact with said sheet of plain paper being conducted such that said chromogenic material is image-wise transferred to said sheet of plain paper; and applying a developer material to the surface of said sheet of plain paper to which said chromogenic material is transferred, said developer material being adapted to react with said chromogenic material and to produce a visible image.

2. A process according to Claim 1, wherein said imaging sheet is placed in contact with said sheet of plain paper prior to subjecting said layer of microcapsules to said uniform rupturing force.

3. A Process'according to Claim 2, wherein the steps of subjecting said layer of microcapsules to said uniform rupturing force comprises passing said imaging sheet in contact with said sheet of plain paper through a pressure nip on a calender press.

4. A process according to any preceding claim, wherein said step of imagewise exposing said imaging sheet comprises image-wise exposing said sheet using an electronic imaging device.

5. A process according to Claim 4, wherein said electronic imaging device is a light valve imaging device.

6. A process according to any preceding claim, wherein said photosensitive composition is a photohardenable composition and said chromogenic material is encapsulated with said photohardenable composition in microcapsules. having a discrete wall.

7. A process according to Claim 6, wherein sa chromogenic material is a substantially 7 G132 17271 1A 7 colourless electron donating compound and said developer material is an electron accept ing compound.

8. A process according to any preceding claim, wherein said developer material is a dry 70 electron accepting compound.

9. A process according to Claim 8, wherein said developer material is a resin grind.

10. A process according to any preceding claim, wherein said step of applying said de veloper material comprises contacting the sur face of said sheet of plain paper carrying said transferred chromogenic material with a fibrous roller carrying said developer material.

11. A process according to any of Claims 1 80 to 9, wherein said developer material is ap plied to the surface of said sheet of plain paper by passing said sheet of plain paper carrying said chromogenic material through a body of particles containing the said developer material.

12. A process according to any of Claims 1 to 9, wherein said developer material is applied to said sheet of plain paper with a mag- netic brush.

13. A process according to Claims 6 or 7, wherein said developer material is a liquid developer material which is encapsulated and is co-present on the surface of said imaging sheet with said microcapsules containing said photosensitive composition, and said developer material is applied to the surface of said sheet of said plain paper by transfer from said imaging sheet with said chromogenic material. 35

14. A process according to Claim 13, wherein said developer is encapsulated in microcapsules having a discrete wall.

15. A process according to Claim 14, wherein said microcapsules containing said de- veloper additionally contain a photohardenable composition.

16. A process according to Claims 6 or 7, wherein said developer material is a developer resin which is co-present on the surface of said imaging sheet, and said developer material is applied to the surface of said sheet of plain paper by transfer from said imaging sheet with said chromogenic material.

17. A process according to Claims 6 or 7, wherein said developer is co-present on the surface of said imaging sheet with said microcapsules containing said photosensitive composition, and said developer is applied to the surface of said sheet of said plain paper by transfer from said imaging sheet with said chromogenic material.

18. A process according to any preceding claim, wherein said paper retains a sufficient quantity of said transferred chromogenic ma- terial on the surface of said paper to react with said developer material and form a visible image.

19. A process according to any preceding claim, wherein said process comprises the ad- ditional step of heating said paper to acceler- ate the reaction of said chromogenic material and said developer material.

20. An apparatus useful in forming images on plain paper utilizing an imaging sheet comprising a support carrying a layer of microcapsules containing a photosensitive composition and a chromogenic material, said apparatus comprising: means for image-wise exposing said imaging sheet to actinic radiation; means for subjecting said layer of microcapsules to a uniform rupturing force; means for assembling said imaging wheet with a sheet of plain paper; means for separating said sheet of plain paper and said imaging sheet; and means for applying a developer material to the surface of said sheet of plain paper.

21. Substantially as hereinbefore described with reference to and as shown in the accompanying drawings, an apparatus useful in form- ing images on plain paper utilizing an imaging sheet comprising a support carrying a layer of microcapsules containing a photosensitive composition and a chromogenic material.

22. Substantially as hereinbefore described with reference to the accompanying drawings, a process for forming images using an imaging sheet comprising a support having a chromogenic material and a layer of microcapsules containing a photosensitive composition on the surface thereof.

23. A plain paper sheet bearing an image produced by a process according to any of Claims 1 to 19 or 22.

Printed in the United Kingdom for Her Majesty's Stationery Office, Dd 8818935, 1986, 4235. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained-