GB2213950A

GB2213950A - A method of image formation and an image-forming material

Info

Publication number: GB2213950A
Application number: GB8730328A
Authority: GB
Inventors: Masaaki Matsuo; Masujiro Sumita; Isao Hosoi; Hirohumi Aoki; Masaru Ohta
Original assignee: Toyo Ink Mfg Co Ltd
Current assignee: Toyo Ink Mfg Co Ltd
Priority date: 1987-09-17
Filing date: 1987-12-31
Publication date: 1989-08-23
Anticipated expiration: 2007-12-31
Also published as: DE3800768A1; GB8730328D0; DE3800768C2; GB2213950B

Description

A METHOD OF IMAGE FORMATION AND AN IMAGE-FORMING MATERIAL This invention

relates to image formation More specifically, it relates to a method of image formation by a mono-color or overlaps of multi-colors using a difference of adhesion between an exposed portion and non-exposed portion in light sensitive layer, which can give a transferred matter similar to a printed matter, for pre-press proof or off-press of color(s).

In the field of printing industry, it is conventionally known to use pre-press proof as means to check, prior to printi;, the finish, color tone, etc, of final printed matter 'or this pre-press proof, there are overlay method and surprint method, and these methods are used in order to check final image quality and steps of plate making and printing.

In the overlay method, a light sensitive layer for a separated color of an image is provided in each of transparent base films, and one of the films obtained by active beam irradiation and development steps is overlaid on another with registering an image of a separated color by eye-examination, etc This method is very simple, however, has defects that an image obtained by this method is affected by reflected lights from overlaid films, and differs from the texture of an actual printed matter to a great extent.

In the surprint method, as disclosed, e g, in U.S Patents 3,060,023, 3,060,024, and 3,060,025, several light sensitive layers are contacted onto a single substrate one after another to consecutively form an image by separated colors As to coloring, there is a method of simple transferring or using powder color toners The transfer method has an advantage of being simple in operation.

Meanwhile, the method of using powder cblor toners makes it necessary to consider operational environments due to scatter of the powder It is a purpose of pre-press proof to obtain a duplicate very similar to a printed matter, however, it cannot be said that a duplicate obtained by transfer is similar to a printed matter in gloss, dot reproducibility, etc And in the method using powder color toners, since its operation is quite apart from printing, it is difficult to make its resulting duplicate similar to an actual printed matter.

Further, U S Patent 3,060,023 discloses a transfer method in which a light sensitive layer and an image receptor are flatly contacted to each other under pressure, heated and then separated However, said method has disadvantage of lacking stable image reproduction and rapidness required of pre-press proof It also has a defect in operation that adjustment of a speed, direction and strength in separation after the contact under pressure is difficult Namely, when a light sensitive layer and an image receptor are separated after the flat contact under pressure, a picking easily takes place if the operational conditions are not rigidly adjusted.

Further, It is difficult to control the conditions of speed, direction, etc, so that reproduction of transferred images is rendered unstable, nonuniformity of reflection density of a transferred image and minute periodic patterns are caused, and further minute directionally repetitive patterns are caused; Accuracy in color reproduction is markedly reduced.

U.S Patent 1,097,945 discloses a method in which a sheet is formed by coating a substrate with a layer sensitive to UV light and a layer of diazo sensitized material, said layers are transferred to a single substrate by using pressure, then, the exposure is effected through a half-tone negative to form an image and thereafter, the image is subjected to a development This procedure is consecutively repeated on the same substrate to form an image This method is also a consecutive formation of an image of separated colors the same substrate, however, since a step of development by a solvent is necessary, there are defects of not only a problem of operational envioronment due to a solvent but fragility of a film of the resulting image.

Japanese Laid-Open Patent Publications 97140/84 and 188537/86 disclose a proofing system usable both in the overlay method and surprint method In this proofing system; 3 ( 1) A color sheet is prepared by consecutively laminating a release layer, coloring light sensitive layer and protection layer on a polyester substrate; and an image receptor film is prepared by laminating an image receptor layer and protection layer on a polyester substrate; ( 2) the chemically treated surface of the color sheet and a half-tone negative are intimately contacted to form an image, and a non-exposed portion is eluted with a sodium carbonate/butylcellosolve/water mixture liquid with regard to black, cyan, magenta and yellow The obtained image each after dried is effective also for overlay type proofing; ( 3) in proofing as surprint system, the image of black formed on the above color sheet is transferred to an image receptor at a temperature of 110 'C, under a pressure of 2 bars and at a speed of 60 cm/minute and then, the receptor film is registered by eye-examination or punching, and an image of cyan is transferred in the same procedure as in the image of black The same procedure is repeated also with regard to magenta and yellow.

( 4) then, the color image is transferred to a receptor to obtain a normal image, and thereafter, the receptor is covered with a film which has been subjected to matting treatment to reduce reflection gloss of a transfer layer and coloring layer to obtain a proofing sheet.

This method has a characteristic in the point where a release layer is provided between a colored light sensitive layer and a substrate and this release layer prevents degradation of a transferred image quality under conditions of high temperature and humidity, and therefore, this method can give a texture more similar to a printed matter.

However, in the above Japanese Laid-Open Patent Publication No 97140/84, since an image once transferred faces reversely to a printed article, another transfer step is necessary to obtain a normal image Or if it is attempted to obtain a normal image by one transfer, accuracy in the resulting image decreases, that is, there is a defect that a sharp image cannot be obtained In an ordinary image formation using a proofing sheet by two transfer steps in the above method, for example, a polyethylene terephthalate film on one surface of which is formed a layer of original image is laid on a proofing sheet composed of a cover sheet (polyethylene film), light sensitive layer and substrate such that the layer of original image contacts the cover sheet, and exposed to light After the exposure, the cover sheet is detached, and the proofing sheet is contacted to an image receptor under pressure to form an image Hence, an image formed on the light sensitive layer is reverse, and another transfer step is necessary to obtain a normal image In this case, since only a cover sheet is present between the layer of original image and the light sensitive layer, the thickness is not so large and light diffusion due to the exposure (reducing accuracy of an image) is relatively small Since, however, the surface state of a polyethylene film as a cover sheet is, in general, coarse, it cannot always be said that a highly accurate image is formed.

In the case of obtaining a normal image by one transfer step, a polyethylene terephthalate film on one surface of which is formed a layer of original image is laid on a cover sheet such that said surface of the film contacts the cover sheet, and exposed to light In this case, a normal image is obtained by detaching the cover sheet However, since the cover sheet and polyethylene terephthalate film are present between the layer of original image and the light sensitive layer, the total thickness is rendered considerably large, light diffusion due to the exposure therefore becomes large and the image quality is degraded.

As transfer method, methods by flat transfer and relief proof printing machine are known The method by flat transfer has various defects as mentioned above Further, in the transfer by a proof printing machine, an image-forming material exposed to light is fixed to a branket cylinder and the branket cylinder is rotated to transfer an image to an image receptor held on a paper-holding bed Since an apparatus used in this method by a proof-printing machine is, in general, large and heavy, the method is not only disadvantageous placewise and costwise but also it is difficult to stabilize the heating in the transfer and the temperature after the heating And further, it is difficult to form a uniform image and it takes time for the job preparation in many cases Further, the method by a proof printing machine requires another device for the exposure to light, and it is difficult to effect the exposure and transfer successively.

In any method that can prepare a pre-press proof sheet, the method includes a substantial development step.

Hence, the preparation step is complicated and the obtained image differs from that of an actual printed matter obtained by an actual printing machine The pre-press proof sheet is used in many cases to check steps from color preparation to printing Although t e pre-press proof sheet is used as substitute for an actual printed matter, it has been regarded as being different qualitywise.

For this reason, there has been a desire to develop a method and material capable of forming an image which has a constant reflection density and fineness.

It is an object of this invention to provide a method of image formation and a material which can form an image quality equal to that obtained by an actual printing machine.

It is another object of this invention to provide a method of image formation and a material which can reproduce an image rapidly and stably.

It is still another object of this invention to provide a method of image formation and a material which produce a transferred image having a uniform reflection density and no minute directionally repetitive patterns.

It is yet another object of this invention to provide a method of image formation and a material which do not cause a picking at the time of separating an image-forming material and an image receptor such as paper.

6 It is another object of this invention to provide a method of image formation and a material which are excellent in color reproduction.

It is, further, another object of this invention to provide a method of image formation and a material which obviate the need of two transfer steps.

It is, still further, another object of this invention to provide a method of image formation and a material which can form an image at low cost and simply.

It is, furthermore, another object of this invention to provide a method of image formation and a material which make it possible to effect the exposure and transfer succesively.

It is another object of this invention to provide a method of image formation and a materip 1 which are suitable for use in the surprint method.

It is another object of this invention to provide a method of image formation and a material which can give an image quality equal to that of a printed matter by a proof printing machine and can therefore omit the proof by a proof printing machine.

This invention provides a method of image formation which comprises image-exposing to light an image-forming material comprising a substrate and, on said substrate, a light sensitive layer containing dye and/or pigment and an optically porymerizable compound, producing, by said exposure, a difference in adhesion between an exposed portion and a nonexposed portion in the light sensitive layer and transferring an image to an image receptor, characterized in that the exposed light sensitive layer of the image-forming material and the image receptor are, facing each other, directed in between rollers to transfer the image formed in said light sensitive layer to the image' receptor by means of nip pressure between the rollers and that said image-forming material and said image receptor are separated immediately after the nip portion is passed through.

Further, this invention provides an image-forming 7 material, for use in the above method of an image formation, which is characterized in that the internal cohesive strength of a light sensitive layer to be transferred to an image receptor is smaller than the boundary adhesive strength between said light sensitive layer and the substrate and the boundary adhesive strength between said light sensitive layer and-the image receptor.

Figure 1 is a schematic view showing a state of contact, transfer and separation in the method of an image formation in this invention.

In this invention, it is possible, in the surprint method, to obtain a color proof sheet, which has a texture equal to that of an actual printed matter, simply, rapidly and stably The method of this invention is also applicable to the overlay method That is, according to this invention, it is possible to obtain a proof sheet having nearly equal texture to an actual printed matter, and further, it is possible tc obtain a color proof sheet having stable quality by the dry development method, i,e, by development by separation.

In this invention, no crawling (minute periodic patterns and minute directionally repetitive patterns) is not caused in a transferred image, and it is possible to effect the transfer directly to art paper which is an ink receptor in an actual printing machine, and that it is possible to obtain a duplicated matter very similar to an actual printed matter since a light sensitive layer is transferred in the same state as in the printing by a printing machine Further, a fine image can be also transferred stably.

The image-forming material of this invention is usually comprised of a substrate, a color light sensitive layer and a protection film Examples thereof are given hereinbelow.

A material stable against heat, chemical and light, and permeable to active beam is preferable as a substrate.

a Examples of the substrate include cellulose acetate, polystyrene, polyvinyl chloride, polyethylene terephthalate, polycarbonate, polyimide, polypropylene, etc A polyethylene terephthalate film is especially preferable in aspect of transparency, thermal stability and dimensional stability, etc.

Further, each substrate of the above examples may be used as such, and it is also possible to pretreat these substrates with an oil repellent substance for release A silicon resin, fluorine resin, etc, can be cited as the oil repellent substance.

Examples of the protection film include a polyethylene film, polyethylene terephthalate film, acetate film, etc, however, are not limited thereto.

The light sensitive layer of this invention is composed of:

(a) an optically polymerizable compound and colorant, or (b) an optically polymerizabl compound, thermo- plastic resin and colorant, and, usually, a polymerization initiator and thermal polymerization inhibitor are used in combination.

As the optically polymerizable compound, at least one selected from monomer, oligomer and prepolymer is used.

Further, other additive can be used in combination.

There is no special limitation in the optically polymerizable compound, however, preferable is a compound which can plasticize a thermoplastic resin at a room temperature.

The light sensitive layer is formed on a substrate and a protection film is further provided onto the light sensitive layer The protection film is to protect the light sensitive layer against dirt caused by contact to an exposure device, etc, at the time of exposure for an image formation from the substrate side A polyethylene film is, preferably, used However, any film meeting the above-mentioned performance can be used besides a polyethylene film.

9 The light sensitive layer, which is optically polymerizable, has advantages that it is made possible to form a reproduced fine image since its cured portion by exposure to light loses adhesive strength to an image receptor layer and also its nonexposed portion has a suitable internal cohesive strength, and that it is made easy by release by breakaway within the light sensitive layer to transfer an image onto an image receptor Said "suitable internal cohesive strength" means that the transfer of the entire light sensitive layer does not take place to form an image on an image receptor.

Namely, the release takes place by breakaway within the light sensitive layer.

The sui gable internal cohesive strength of the light sensitive layer in this invention can be selected in various degrees depending upon kind and/or incorporation ratio of each of an optically polymerizable compound, dye and pigment which are used in the light sensitive layer The internal cohesive strength also varies depending upon what the image receptor or substrate is.

A color proof work, etc, as application of this invention requires highly accurate reproduction of an image by a color separation film, etc, as a mask At the same time, it is also required to shorten time in the color proof work.

In order to meet these requirements and secure quality of stable finish of an image, the following technical elements have to be cleared.

The main technical element with regard to the highly accurate reproduction of an image is to make thin the film (coat) thickness of an image to be formed The other main technical element with regard to the shortening of time is to obviate the need to develop an image to be formed In order to meet these requirements and achieve these technical elements, it is the best solution to produce a breakaway release strength within a light sensitive layer by imparting a suitable internal cohesive strength to a film (coat) of an image to be formed, and omit a development step.

The optically polymerizable compound usable in this I O invention is an ethylenically unsaturated compound, and examples of said compound include low-molecular-weight optically polymeric compounds such as (meth)acrylic acid, methyl(meth)acrylate, butyl(meth)acrylate, cyclohexyl(meth)acrylate, dimethylaminoethyl(meth)acrylate, benzyl(meth)- acrylate, carbitol(meth)acrylate, 2-ethylhexyl (math)acrylate, lauryl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2- hydroxypropyl(meth)acrylate, glycidyl(meth)acrylate, (meth)- acrylamide, N-methylol(meth)acrylamide, styrene, acrylonitrile, N-vinyl pyrolidone, ethyleneglycoldiacrylate, diethleneglycoldiacrylate, triethyleneglycoldiacrylate, polyethyleneglycoldi(meth)acrylate, polypropyleneglycoldi- (meth)acrylate, butyleneglycoldi(meth)acrylate, neopentylglycoldi(meth)acrylate, 1,4-butanedioldiacrylate, 1,6-hexanedioldi(meth)acrylate, pentaerythritoldiacrylate, pentaerythritoldi acrylate, pentaerythritoltriacrylate, trimethylolpropanetriacrylate, dipentaerythritolhexaacrylate, phenoxyethylacrylate, nonylphenoxyacrylate, tetrahydrofurfuryloxyacrylate, caprolactone-modified tetrahydrofurfurylacrylate, ethylene oxide (EC 1-modified methacrylate, phenoxydiethyleneglycolacrylate, EO-modified phthalic acid acrylate, (meth)acrylate of alkylen oxide-added phenol, caprolactone-modified hydroxypivalic acid neopentylglycoldiacrylate, dicyclopentanyldiacrylate, etc, or high-molecular-weight optically polymeric compounds such as epoxyacrylate, urethane acrylate, polyester acrylate, alkyd acrylate, modified acrylate of petroleum resin, etc These compounds may be used alone or in combination.

The thermoplastic resin (organic polymer binder) usable is a polymer which is thermoplastic, excellent in compatibility with an optically polymerizable compound and without optically polymeric property Examples of this resin include polyvinyl chloride, poly(meth)acrylic acid, poly(meth)acrylic acid ester, polyvinyl ether, polyvinyl acetal, urethane resin, epoxy resin, polyamide, polyester, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-vinyl acetate copolymer, ethylene-vinyl acetate t copolymer, cellulose derivative (e g, methylcellulose, ethylcellulose and cellulose acetate), polyolefin (e g, chlorinated polyethylene), synthetic rubber such as butadieneacrylonitrile copolymer, diallylphthalate resin (e g, diallylisophthalate polymer, diallylorthophthalate polymer and hydrogen-addition product of these), etc.

It is also possible to obtain the desired physical property by adding a polymer other than the above thermoplastic substances That is, adhesion to a substrate and adhesion to a receptor at the time of the transfer can be improved Examples of suitable polymer substance that is not thermoplastic include phenol resin, malamine-formaldehyde resin, urethane resin, etc Beside these, the light sensitive layer may contain, as a component, a small amount of a filler, examples of which include silica, mica, bentonite, etc, and a suitable amount of the filler may be present depending upon a quality required.

The optical polymerization initiator having small absorption in the visible ray portion is preferable as such.

Examples of the initiator include benzophenone, 4,4-bis (diethylamino) benzophenone, 4-methoxy-4-dimethylaminobenzo- phenone, 2-ethyl-anthraquinone, phenanthraquinone, enzoin, benzoinmethyl ether, benzoinphenyl ether, isobutylbenzoin ether, benzoinethyl ether, isobutylbenzoin ether, isopropyl- benzoin ether, benzoinethyl ether, 2,2-diethoxyacetophenone, 2-hydroxy-2-methylpropiophenone, 4 '-isopropyl-2-hydroxy-2- methylpropiophenone, p-tert butyltrichloroacetophenone, Michler's ketone, benzyldimethylketal, 2,2-dimethoxy-2- phenylacetophenone, hydroxycyclohexylphenyl ketone, benzophenone, azobisisobutylnitrile, 2-chlorothioxanthone, 2methylthioxanthone, 2-ethylthioxanthone, 2-isopropylthio- xanthone, etc These addition polymerization initiators may be used alone or in combination When at least two initiators are used, influence on free radicals to be generated respectively by light absorption should be taken into consideration Further, various sensitizers may be added in order to improve the addition polymerization Conventionally known optical polymerization initiators may be used alone or in combination.

As thermalpolymerization inhibitor, there may be used p-methoxyphenol, hydroquinone, t-butylcatechol, pyrogallol, pyridine, allylphosphite, etc.

The film thickness of the light sensitive layer may be about 0 5 to 5 gm The suitable amount of the optically polymerizable compound to be applied varies according to dye and/or pigment to be contained, however, the amount is from 0.5 g/m 2 to 10 g/m 2, and it is preferably from 1 0 g/m 2 to 5 g/m 2 In this invention, the application to a substrate is carried out by the use of a bar coater and a spin coater, and the other coaters similar thereto also may be used.

As thermoplastic substance effective especially in this invention, the other materials than the above-mentioned ones can also be cited However, in view of a combination with a suitable ethylenically unsaturated compound, polyacrylate-type high-molecular-weight substance and diallylisophthalate polymer are suitable The suitable proportion of the thermoplastic substance and ethylenically unsaturated compound varies depending upon what are used as said substance and compound In general, if the proportion of the thermoplastic substance and ethylenically unsaturated compound is between 40: 60 and 90: 10, it is possible to achieve a state in which the surface of the light sensitive layer has no adhesion property at room temperature If there is a residual adhesion in the light sensitive layer, the registration is rendered difficult, and further, environmental dust, etc, are adhered onto the surface of the light sensitive layer to degrade the quality of an image as color proof A small amount of a thermal polymerization inhibitor may further be added to prevent a dark reaction from taking place with the passage of time.

As dye and/or pigment to be contained in the light sensitive layer, conventionally known dye and pigment may be used Dye and/or pigment having a hue identical to these of four colors, yellow, magenta, cyan and black are necessary, 3 and in addition, metal powder, white pigment, fluorescent pigment, etc, may also be used As for color proof for which yellow, crimson, indigo and black are used, any pigment or dye agreeing with the hues thereof may be selected.

The following are some examples of the dye and organic pigment of az 't type, phthalocyanine type, quinacridon type, anthraquinone type, indigo type, methine type, etc, or inorganic pigments etc, that is, Lionol Yellow GRO (C.

121090), No 1201 Lionol Yellow, No 1206 Lionol Yellow, Lionol Yellow No 1208, No 1305 Lionol Yellow (C 121100), No 1306 Lionol Yellow, No,1307 Lionol Yellow, Lionol Yellow FG 1310, Lionol Yellow FGN-T (C 121105), No 7100 Lionol Yellow (C.

121096), Lionol Yellow-NBR (C 121108), Brilliant Carmine 6 BA (C 115850: 1), Lionol Red 6 B 4201, Lionol Red 7 B 4401, Brilliant Carmine 8 BA, Lionol Blue FG 7330 (C 174160), Lionol Blue FG 7351, Lionol Blue GX-1 (the above items are all manufactured by Toyo Ink Manufacturing Co, Ltd), Mitsubishi Carbon Black MA-7, Mitsubishi Carbon Black MA-100, etc These items are suitably used As colorant, these items may be used alone or in combination with another.

These dyes and pigments can be easily incorporated into a light sensitive layer through suitable means.

The suitable amount of the dye and/or pigment incorporated into a light sensitive layer is 5 to 50 % by weight based on the entire solids If it is not more than 5 % by weight, too large an amount of a coat (film) is required to obtain a necessary strength of color, and a transferred image tends to be bad If it is not less than 50 % by weight, sufficient active beam does not permeate, and a stain is caused.

In exposure to light, there are two methods therefor; one is an exposure by, in general, directly contacting a protection film of a light'sensitive layer and a mask, and the other is an exposure from a substrate side In the method of exposing an image to light by directly contacting a protection film of a light sensitive layer and a mask, the amount of a light sensitive layer film may be 10 ( 4 f g/m 2, however, the resulting image faces reversely, and an image including characters or letters is very difficult to observe.

In addition, a light sensitive layer subjected to suitable matting treatment is effective to obtain a good texture as required.

On the other hand, in the case of exposing an image to light from the substrate side, the resulting image becomes normal, however, if the amount of a light sensitive layer film is more than 10 g/m 2, the transferred image tends to be not clear.

Further, a protection film is laid on a light sensitive layer As described in Japanese Laid-Open Patent Publication No 31323/73, a polyethylene film, which has a weaker adhesion to a light sensitive layer than a base substrate of a polyethylene terephthalate film, is preferable.

And in an optical polymerization system, it is known that the polymerization speed varies depending upon oxygen in the air.

This variation is prevented by means of either a protection film formed by coating a polyvinyl alcohol on a color light sensitive layer or a protection film laminated thereon These two means are both effective, and the means of a protection film laminated is more preferable.

In this invention, a method of exposing an image from the substrate (transparent in nearly all the cases) side is preferable This method makes it possible to improve the positional relation of an image such as a direction in which an image faces, and provide a method which obviates the need of a special intermediate image receptor to correct the facing of an image.

In this invention, when an image-forming material having a protection film is used, the transparent substrate means one which is contacted to an image receptor under pressure and then separated, and the exposure is effected from this transparent substrate side.

The protection film optionally used prevents a gleasing caused by adhesion of a light sensitive layer to an -14 exposure device, etc, when the exposure to form an image is effected from the substrate side, and reducesan influence of oxygen on a light sensitive layer.

Color proof work etc, to which this invention is applied, requires highly accurate reproduction of an image by a color separation film as a mask At the same time, it is required to shorten a time in color proof work In order to meet these requirements and secure the stable finish quality, it is necessary to provide a step of simple work for accurate positionirv of a reproduced image and correspondence of the front and reverse of an image, and for this reason, it is preferable to effect the exposure from the transparent substrate side.

The following is an explanation of each of the steps in the case of using this invention, for example, as an image- forming material for color proofing.

( 1) Holes for register pins are made in a mask of color separation image and an image-forming material.

Further, if the image receptor is a paper, etc, the image receptor is also holed for register pins.

( 2) An image is exposed to light That is, a light sensitive layer is exposed to light sufficient to harden the image-forming material by the use of an active ray such as ultra violet ray through an image of the color separation mask.

( 3) Then, a protection film on the image-forming material is detached, and the image receptor and the surface of a color light sensitive layer are positioned such that these two members face each other, and directed in between rollers Contact and transfer are effected in a nip portion of the rollers, and the above two members are detached immediately after they have passed the nip portion.

Usually, the transfer is effected under heat as required By separating these two members, an image formed on the light sensitive layer is retained on the image receptor by a half of the film thickness of the image or a suitable amount owing to a predetermined internal cohesive strength, and as a 16 result, a transferred image is formed.

( 4) A post-exposure is effected to the entire image in order to secure the firm adhesion thereof and disipate the viscous property of the transferred image.

The above steps 1 to 4 are repeated, for example, 4 times (yellow, magenta, cyan, black) to obtain a reproduced image of the four colors for color proofing.

As examples of the above receptor, there are art papers, coat papers, etc, which are materials generally used in proof printing, however, these examples do not limit this invention.

This invention mainly has its features in the above step ( 3), and makes it possible to effect the contact, transfer and separation rapidly and proceed with these operations stably as compared with the case of planar contact under pressure Further, nonuniformity of temperature at the time of heating is also small as compared with the case of planar contact under pressure.

Figure 1 shows a schematic cross sectional view of the contact between rollers, transfer and separation in this invention Numeral 1 indecates a platen roller (rubber), 2 indicates a heating roller (metal), 3 indicates a substrate, 4 indicates a light sensitive layer, and 5 indicates an image receptor The contact and transfer between the light sensitive layer and the image receptor between the rollers are usually carried out under pressure and heat, however, may be done under only pressure In the case of heating, it is preferable to heat to an extent that an image receptor used does not expand or contract to a great extent It improves the transfer speed and the reproduction accuracy of a fine image to effect the heating such that the surface temperature of a roller becomes 50 to 150 C, preferably 70 to 110 'C.

That is, it is made possible to effect the transfer well without causing problems of crawling, picking, etc.

Further, a thermal difference may be provided between the surface of one roller and the surface of the other For example, one roller may be heated and the other roller may be cooled.

The diameter of each of the rollers is preferably 30 to 500 mm, and the diameter may be the same or different from one roller to the other When the rollers have different diamters, it is usual that the roller on the image receptor side has a larger diameter In addition, When the rollers have diameters in the above-mentioned range, the smaller the diameters are, the earlier the separation takes place, and the separation can be effected at temperatures at the vicinity of those of the rollers Therefore, the smaller diameters are preferable In the case when the diameters are smaller than the lower limit of the above range, wrinkle takes place and a good image quality cannot be obtained.

In Figure 1, a light sensitive layer and an image receptor are directed in between rollers while the light sensitive layer and receptor are not substantially contacted to each other, then contacted to transfer an image in the nip portion of the rollers, and separated immediately after they have passed through the nip portion By this method, the good transfer is effetively carried out without causing problems of crawling, picking, etc, due to heat or drop in temperature.

Namely, the processing between rollers makes it possible to carry out the processing at high speed.

As a device to carry out the transfer between rollers, a conventional laminater may be used to carry out the transfer and separation of this invention.

The most simplest constitution of only two rollers may be sufficient for the transfer between rollers in this invention In that case, for example, the heating procedure is made easy, the space for the device is made small, and the preperation for operation is made simple Further, an exposure device may be incorporated in addition to the two rollers, whereby the operation from the exposure to the transfer can be carried out in series.

Adjustment of the pressure between rollers is easy, since there are only two rollers, and the pressure can be also adjusted simply to any neccessary pressure Further, there is -t 7- an advantage that the uniform pressurization makes the operation easy and the resulting image is made uniform without a skilled worker This advantage meets the actual demand in the case when a proof printing is carried out by forming a plurality of sheets of an image from one original, and is useful.

This invention obviates the need for heating before the transfer and complicated separation procedure required of the conventional method, and an image having a texture very similar to a printed matter is reproduced on an image receptor such as paper, etc, by a simple work.

The following Examples illustrate this invention.

"part" stands for "part by weight" and "%" stands for "% by weight" hereinbelow.

EXAMPLE 1

A liquid for a light sensitive layer consisting of the following formulation was prepared.

Diallylisophthalate prepolymer(Daiso Isodap, Osaka Soda Co, Ltd,): 21 23 parts Dipentaerythritolhexaacrylate DPHA(Nippon Kayaku K.K): 7 08 parts Addition polymerization initiator Benzophenone: 0 5 parts 4,4 bis-diethylaminobenzophenone(EAB, Hodogaya Chemical Co, Ltd): 0 17 parts Hydroquinone: 0 001 parts Carbonblack(MA-7, Mitsubishi Chemical Ind): 5 0 parts Toluene: 38 0 parts Methylethyl ketone: 40 0 parts This liquid for a light sensitive layer was coated on a biaxially stretched polyethylene terephthalate film (film thickness = 1 2 Wm) such that a dried coat thickness became 2.4 Vm, and a polyethylene film was applied onto the coated surface thereof to prepare an image-forming material.

This image-forming material is image-exposed to light from the polyethylene terephthalate film (substrate) -18 ( Iq side, then a protection film of polyethylene was separated, and an image receptor of art paper and the light sensitive layer were contacted to effect the transfer and separated as shown in Figure 1 Then, post-exposure was effected to give a finish of an image utterly equal to a usual printed matter obtained by a usual printing machine.

In the above procedures, the feed rate was 50 cm/minutes, the nip pressure between the rollers was 4 kg/cm', and the temperatures were 50 C at the upper roller and 1000 C at the lower roller And, the diameter of each of the upper and lower rollers was 150 mm, the Shore hardness A of the upper roller was 70, and the lower roller was of metal The original transferred had a width of 260 mm, and the distance while the image-receptor and the image-forming material were contacted was 10 mm.

Further, the same original was used four times to form images, and the resultant images were compared to show that these images were uniform and indistinguishable from one to another.

COMPARATIVE EXAMPLE 1 Similarly to Example 1, an identical image-forming material was image-exposed, a protection film was separated and the image-forming material was laid on an image receptor of art paper Then, by the use of a flat-bed transfering machine (Naoprinter Mini, manufactured by Naomoto Industry Co., Ltd), the flat-transfer was effected under the conditions that the temperature was 100 O C, the pressure was 1 kg/cm 2 and the transfer time was 1 minute When the image- forming material and the receptor were separated from each other at room temperature, a picking was caused in a non- exposed portion, and it was impossible to obtain a uniform image.

COMPARATIVE EXAMPLE 2 Comparative Example 1 was repeated except that the pressure was changed to 4 kg/cm 2 As a result, however, a picking took place similarly.

COMPARATIVE EXAMPLE 3 Similarly to Example 1, an identical image-forming material was image-exposed and a protection film was separated Then, by the use of a flat-bed proofing machine having a heating device on its paper-fixing bed, the image- forming material was fixed around a branket cylinder, and the branket cylinder was rotated such that an image receptor of art paper was contacted to the image-forming material to transfer an image under the conditions that the temperature was 100 XC, the pressure was 4 kg/cm 2 and the transfer time was 1 minute.

However, phenomena of nonuniformity in solid portions, crawling in dots, etc, were observed in the resultant image, and it was difficult to say that the resultant image was always satisfactory It had a clear difference from an image of a printed matter obtained by a usual printing machine.

The image formation was effected four times, and the images obtained were compared to show that all of these images had nonuniformity.

The transferring device used in this Comparative Example 3 required a space about three times the space for the transferring device used in Example 1 in order to obtain transferred matters of the same size.

COMPARATIVE EXAMPL 4 Similarly to Example 1, an identical image-forming material was image-exposed, a protection film was separated, and an image receptor of art paper and the image-forming material was contacted to effect the transfer as shown in Figure 1 These two members were separated 5 minutes after they passed through a nip portion (instead of separating these two members immidiately after they passed therethrough) The result was that a picking took place.

EXAMPLE 2

Example 1 was repeated except that the conditions of the transfer between rollers and the separation were changed as follows.

The feed rate was 40 cm/minute, the nip pressure -20 2 A\ between rollers was 2 kg/cm 2, the temperature of an upper roller was 50 'C, and the temperature of a lower roller was 90 C.

Then, the results nearly identical to those of Example 1 were obtained.

EXAMPLE 3

Example 1 was repeated except that the conditions of the-transfer between rollers and the separation were changed as follows.

The feed rate was 40 cm/minute, the nip pressure between rollers was 4 kg/cm 2, the temperature of an upper rollers was 50 'C and the temperature of a lower roller was C.

Then the resu' I nearly identical to those of Example 1 were obtained According to this invention, the transfer between rollers and the subsequent separation can be well and effectively carried out.

EXAMPLE 4

Example 1 was repeated except that Lionol Yellow FG 1310, Carmine 7 BFG 4412 and Lionol Blue FG 7330 were used respectively in place of carbon black to prepare liquids for light sensitive layers, and then image-forming materials were obtained as in Example 1.

The transfer was repeated by contacting each of the above image-forming materials to the image receptor of Example 1 to form a color image.

That is, the same procedure as in Example 1 was repeated with regard to the above three colors respectively to give a color proof image formed with black, cyan, magenta and yellow in this order.

The preparation of the above color proof image was repeated four times to show that all four color proof images were uniform.

EXAMPLE 5

A liquid for a light sensitive layer consisting of the following materials was prepared.

Polyester (Vylon 300, Toyobo Co, Ltd) as a polymer, tetraethyleneglycoldiacrylate (A-4 EG, New Nakamura Chemical Co, Ltd) and trimethylolpropane triacrylate (ATMPT, by the latter company) as monomers, and 2-hydroxy-2-methyl- propiophenone (Darocur, Merck Co, Ltd) as an initiator.

Further, as pigments, the following were used.

Lionol Yellow FG 1310 (Toyo Ink Manufacturing Co, Ltd) for yellow, Lionol Red 7 BFG 4412 (Toyo Ink Manufacturing Co., Ltd) for magenta, Lionol Blue FG 7330 (Toyo Ink Manufacturing Co, Ltd) for cyan and Mitsubishi Carbon MA 7 for black.

In order to dissolve the polymer in MEK (methylethylketone) in a polymer-to-solvent ratio of 3 parts to 7 parts, a mixture of these two components was subjected to a shaking in a warm bath for 48 hours to give a solution of dissolved polymer.

Then, the monomers of 1 part of A-4 EG and 3 parts of ATMPT were mixed with the solution of dissolved polymer, and further 3 %, based on the entire solids, of the above initiator was added to obtain a liquid for a light sensitive layer In order to incorporate pigments into the aboveobtained liquid for a light sensitive layer, the shaking in a warm bath by a red devil was repeated five times In general, it is preferable to add a solvent, etc, in order to maintain suitable fluidity.

As for color proofing material for printing, pigments were incorporated into the liquid for a light sensitive layer in amounts, based on the entire solids of the liquid, of 18 % for yellow, 18 % for magenta, 18 % for cyan and 9 % for black After the materials were milled by a red devil, light sensitive materials were coated on biaxially stretched polyethleneterephtalate films ( 25 pm thick) respectively, and the coated films were subjected to irradiation by an infrared lamp ( 3 KW) for 30 seconds and dried to give a positive-type colored light sensitive layers The coat (film) thickness (dried) was 5 ptm.

A polyethylene film as a protection film was laminated onto each of the dried light sensitive layers to give image-forming materials The above image-forming material for yellow and the corresponding color separation positive film were contacted, and subjected to an image- exposure by a 1 5 kw ultra-high pressure mercury lamp for 30 seconds (equal to 100 m J/cm 2) Then, the polyethylene film was detached, and the transfer was carreid out between rollers such that the light sensitive layer was intimately contacted to a white paper and detached therefrom in the same way as in Example 1 The post-exposure was effected to give an image.

There was obtained a reproduced image of 20 lines/mm fidelity corresponding to an image on the color sedration positive film In the above procedure in this Example, about 3/4 of the light sensitive layer was transferred.

Thereafter, the same procedure was carried out, by accurately registering with register pins, with regard to the remaining three colors in the order of magenta, cyan and black, and an image each was formed on the same image receptor to give an image having texture very similar to a usual printed matter.

EXAMPLE 6

A liquid for a light sensitive layer consisting of the following components was prepared.

Diallylphthalate (DAPL, Osaka Sanso Co, Ltd) as a polymer, Oligoester acrylate (M-7100, Toa Gosei Co, Ltd) as a monomer, and benzophenone/ethyl ketone f(benzophenone (Daiichi Kasei Co, Ltd)/ EAB (Hodogaya Chemical Co, Ltd)l as an initiator.

As pigments, there were used Lionol Yellow FG 1310 (Toyo Ink Manufacturing Co, Ltd) for yellow, Carmine BFG 4412 (Toyo Ink Manufacturing Co, Ltd) for magenta, Lionol Blue FG 7330 (Toyo Ink Manufacturing Co, Ltd) and Mitsubishi Carbon MA-7 for black.

Twelve parts of the above polymer was dissolved in parts of MEK, and 12 parts of the above monomer was mixed therewith The initiator was added in an amount, based on the entire solids of the above liquid, of 2 5 to 4 % Further, the pigments were added in amounts, based on the entire solids 23 - ( of the liquid, of 9 to 18 % as in Example 5 to obtain liquids for light sensitive layers.

In the same way as in Example 5, the above-obtained liquids for light sensitive layers were coated on substrates to prepare image-forming materials, and transfered onto a white paper to give an image having a texture very similar to a printed matter About 1/2 of the light sensitive layers were transferred in this Example, and a reproduced image of 50lines/mm fidelity was obtained.

According to this invention, the following effects have been ascertained.

In this invention, it is possible to form a good, stable image effectively by means of the transfer between rollers and by the use of a material to produce a breakaway separation within a light sensitive layer Further, it is clearly seen in the following Tables that the performance of images obtained according to this invention improves as compared, in a nearly identical coat thickness, with those obtained by the separation and transfer of entire materials, owing to the method of an image formation using an internal cohesive strength within a light sensitive layer.

Quality of printing elements were totally evaluated in terms of resolving power, dot form, presence or absence and size of void, uniformity of density and presence or absence of crawling which were observed by means of 17 5-power magnifier In the following Table, A, B and C stand for "good", " fair" and "poor" respectively.

Table 1

Example 1

Example 2

Example 5

Example 6

Comparative Example 3

Resolving Power (lines/mm) Quality of Printing elements A A A A B-C Furthermore, the coat thickness each of the images reproduced on image receptors of paper, etc, are as shown in the following Table When the image-forming materials of this invention are used as color-proofing materials, it is possible to provide a texture very similar to that of printed matter, and any trouble due to a texture difference is not caused.

Surface state was determined by means of a 195-power microphotograph.

Table 2

Film thickness on image receptor (Em) Surface State Example 4

Example 5

Comparative Example 3 common printig ink slightly coarse coarse 3.5 0.6-1 9 coarse 0 8-1 2 slightly coarse Comparative Example 3 shows that is nonuniform and unstable.

the coat thickness I

Claims

C L A I M S

1 A method of image formation which comprises imagewise exposing to light an image-formimg material comprising a substrate bearing a light sensitive layer containing dye and/or pigment and an optically polymerisable compound, producing, by said exposure, a difference in adhesion between an exposed portion and a nonexposed portion in the light sensitive layer, transferring an image to an image receptor by directing the exposed light sensitive layer of the image-forming material and the image receptor, in face to face contact, into a nip portion between rollers to transfer the image formed in said light sensitive layer to the image receptor by means of a nip pressure between the rollers and separating said image-forming material and said image receptor immediately after they have passed through the nip portion.

2 A method according to claim 1, wherein the substrate is transparent.

3 A method according to claim 1 or 2, wherein the image-forming material further comprises a protective film.

4 A method according to claim 1, 2 or 3, wherein the imagewise exposure is effected from the substrate side.

A method according to any one of the preceding claims, wherein the light sensitive layer of the image-forming material and the image receptor are not contacted with each other before they are directed into the nip portion between the rollers.

6 A method according to any one of the preceding claims, wherein at least one of the rollers has a surface temperature of from room temperature ( 20 C) to 1500 C.

7 A method according to claim 6, wherein the transfer and separation are carried out under heat.

V -27-

8 A method according to claim 6 or 7, wherein at least one of the rollers has a surface temperature of from 50 to 1500 C.

9 A method according to any one of the preceding claims, wherein an image comprising only a part of the thickness of the light sensitive layer is transferred to the image receptor.

A method according to any one of the preceding claims, wherein the diameters of the rollers are in the range from 30 to 500 mm.

11 A method according to any one of the preceding claims, where the nip pressure between the rollers is adjustable.

12 A method according to any one of the preceding claims, wherein the transferred image is transferred to another image receptor to form an image.

13 A method according to claim 1, substantially as hereinbefore described.

14 An image-forming material for use in the method of claim 1 comprising a substrate bearing a light sensitive layer containing dye and/or pigment and an optically polymerisable compound, wherein the internal cohesive strength of the light sensitive layer to be transferred to the image receptor is smaller than the boundary adhesive strength between the light sensitive layer and the substrate and the boundary adhesive strength between the light sensitive layer and the image receptor.

An image-forming material according to claim 14, wherein the substrate is transparent.

16 An image-forming material according to claim 14 or 15, wherein the image-forming material further comprises a protective film.

17 An image-forming material according to claim 14, 15 or 16, wherein the light sensitive layer contains an optically polymerisable compound and, further, an organic polymer binder which is not optically polymerisable.

18 An image-forming material according to claim 17, wherein the optically polymerisable compound is an ethylenically unsaturated compound.

19 An image-forming material according to claim 17 or 18, wherein the organic polymer binder is a thermoplastic resin.

An image-forming material according to claim 17, 18 or 19, wherein the weight ratio of thermoplastic resin to the ethylenically unsaturated compound is from 40:60 to 90:10.

21 An image-forming material according to any one of claims 17 to 20, wherein the organic polymer binder is a diallyphthalate resin.

22 An image-forming material according to any one of claims 17 to 21, wherein the light sensitive layer further contains an optical polymerisation initiator.

23 An image-forming material according to any one of claims 17 to 22, wherein the light sensitive layer further contains an optical polymerisation inhibitor.

24 An image-forming material according to any one of claims 13 to 23, wherein the light sensitive layer is from 0.5 to 5 pm thick.

An image-forming material according to claim 13, substantially as described herein.

Published 1988 at The Patent Office State House 6671 High Holborn London WC 1 R 4 TP Further copies may be obtained from The Patent Office.

Sales Branch, St Mazy Cray Orpington, Kent BR 5 3RD Printed by Multiplex techniques ltd St Mary Cray Kent Con 1 '87.

24 An image-forming material according to any one of claims 14 to 23, wherein the proportion of the dye and/or pigment is in the range of 5 to 50 % by weight based on the entire solids in the light sensitive layer.

An image-forming material according to any one of claims 14 to 24, wherein the light sensitive layer is from 0 5 to 5)um thick.

26 An image-forming material according to claim 14, substantially as described herein.

( I 1 q - Amendments to the claims have been filed as follows 1 A method Qf image formation which comprises imagewise exposing to light an image-forming material comprising a substrate bearing a light sensitive layer containing dye and/or pigment and an optically polymerisable compound, producing, by said exposure, a difference in adhesion between an exposed portion and a nonexposed portion in the light sensitive layer, transferring an image comprising only a part of the thickness of the light sensitive layer to an image receptor by directing the exposed light sensitive layer of the image-forming material and the image receptor, in face to face contact, into a nip portion between rollers to transfer the image formed in said light sensitive layer to the image receptor by means of a nip pressure between the rollers and separating said image-forming material and said image receptor immediately after they have passed through the nip portion.

2 A method according to claim 1, wherein the substrate is transparent.

A method according to any one of the preceding claims, wherein the light sensitive layer of the image-forming material and the image receptor are not - contacted with each other before they are directed into the nip portion between the rollers.

6 A method according to any one of the preceding claims, wherein at least one of the rollers has a surface temperature of from room temperature ( 20 'C) to 1500 C.

9 A method according to any one of the preceding claims, wherein the diameters of the rollers are in the range from 30 to 500 mm.

A method according to any one of the preceding claims, where the nip pressure between the rollers is adjustable.

11 A method according to any one of the preceding claims, wherein the transferred image is transferred to another image receptor to form an image.

12 A method according to claim 1, substantially as hereinbefore described.

13 An image-forming material for use in the method of claim 1 comprising a substrate bearing a light sensitive layer containing dye and/or pigment and an optically polymerisable compound, wherein the internal cohesive strength of the light sensitive layer to be transferred to i N 31 - the image receptor is smaller than the boundary adhesive strength between the light sensitive layer and the substrate and the boundary adhesive strength between the light sensitive layer and image receptor.

14 A image-forming material according to claim 13, wherein the substrate is transparent.

An image-forming material according to claim 13 or 14, wherein the image-forming material further comprises a proctective film.

16 A image-forming material according to claim 13, 14 or 15, wherein the light sensitive layer contains an optically polymerisable compound and, further, an organic polymer binder which is not optically polymerisable.

17 An image-forming material according to claim 16, wherein the optically polymerisable compound is an ethylenically unsaturated compound.

18 An image-forming material according to claim 16 or 17, wherein the organic polymer binder is a thermoplastic resin.

19 An image-forming material according to claim 16, 17 or 18, wherein the weight ratio of thermoplastic resin to the ethylenically unsaturated compound is from 40:60 to 90:10, An image-forming material according to any one of claims 16 to 19, wherein the organic polymer binder is a diallyphthalate resin.

_ 92 21 An image-forming material according to any one of claims 16 to 20, wherein the light sensitive layer further contains an optical polymerisation initiator.

22 An image-forming material according to any one of claims 16 to 21, wherein the light sensitive layer further contains an optical polymerisation inhibitor.

23 An image-forming material according to any one of claims 13 to 22, wherein the proportion of the dye and/or pigment is in the range of 5 to 50 % by weight based on the entire solids in the light sensitive layer.