JPH09218510A - Image forming material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid defects in image reproducibility, in particular defects in image reproducibility caused in the area of low area rate of dots by forming an active ray reflection layer on a protective film. SOLUTION: A photosensitive layer 31 is formed on a substrate 30, and a protective film prepared by successively forming an adhesive layer 35, active ray reflection layer 32 and film 36 on a film 34 is laminated so that the photosensitive layer 31 and the film 36 face each other. The protective film is prepared by laminating at least two kinds of films having different kinds and thickness with an adhesive layer is used. This is because to obtain both of dimensional stability and release property for the photosensitive layer. For example, a polyethylene terephthalate film is laminated with a biaxially oriented polypropylene film with an adhesive layer is used. In this method, the film 34 is properly selected from various resin films such as polyesters, acryls, polyolefins by considering the strength and dimensional stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming material used in an image forming method utilizing a thermal transfer system. More specifically, the present invention relates to an image forming material which has a practically satisfactory image exposure sensitivity, eliminates image formation defects that occur during image exposure, and obtains a clear transferred image.

[0002]

2. Description of the Related Art Recently, an image forming material in which a photosensitive layer is coated on one surface of a support is imagewise exposed, and then the image formed on the photosensitive layer is heated at a temperature of about 100.degree. BACKGROUND ART Single-color or multicolor prepress proofs suitable for proof printing, etc., which are transferred to image receivers such as the above, have come to be produced. The image forming material comprises a support, a photosensitive layer formed on one surface of the support, and a protective film. As the support and the protective film, thin films or sheets made of materials such as cellulose acetate, polystyrene, polyvinyl chloride, polyethylene terephthalate, polyethylene and polypropylene are used. The thickness of the support is generally 10 to 30 μm, and the thickness of the protective film is generally 50 to 1
75 μm. As the image receptor, an appropriately selected printing material such as paper or film is adopted.

The above-mentioned prepress proof is generally produced through the following processes. a. On the support A photosensitive layer containing a dye and / or a pigment and a photopolymerizable compound is provided on the support, and a protective film is attached to the photosensitive layer to produce an image forming material. b. A positive film on which an original image (dot image, character image, etc.) is formed is brought into close contact with the side of the support of the image forming material, through which actinic rays, generally ultraviolet rays, are irradiated to perform image exposure and An image is formed on the functional layer. c. The image-wise exposed image forming material is attached to the impression cylinder of the transfer device, and the image receptor is attached to the transfer cylinder. When the image forming material is attached to the pressure copper, the protrusion is formed on the surface of the impression cylinder, that is, the pin bar is fitted into the hole provided in advance on the upper side (holding side) of the material to prevent the attachment position from being displaced. After the material is attached to the impression cylinder, the protective film is peeled off. d. By rotating the impression cylinder and / or the transfer cylinder so that the photosensitive layer and the image receptor are opposed to each other, the both cylinders are brought into contact and pressure, and the image formed on the photosensitive layer is transferred to the nip between the cylinders. Transfer to image receptor. e. When creating a multicolor prepress proof,
The above operations a to d are repeated for one image receptor. For example, in the case of four-color printing, the above operation is repeated four times using four-color image forming materials. When an image receptor such as paper is heated in advance and the photosensitive layer of the above-mentioned image forming material is pressure-bonded thereto and the image formed on the photosensitive layer is transferred to the paper, the image transfer proceeds smoothly. A beautiful transfer image can be obtained. For this reason, it is usual to provide a heating means inside the transfer cylinder to which the image receptor is attached, which can appropriately heat the surface of the transfer cylinder to, for example, about 100 degrees. The image forming method to which the image forming material of the present invention is applied is such that the image forming material image-formed on the photosensitive layer by image exposure as described above is attached to the surface of the impression cylinder, and then the protective film is peeled off to expose. In this method, the photosensitive layer is pressure-bonded to the image receptor attached to the surface of the transfer cylinder, and the image is transferred to the image receptor. As a result of various studies on the image forming method, the present inventors have found that the reproducibility of the transferred image may be poor. As a result of further study, it was found that the reproducibility of the image was particularly poor in a portion having a low halftone dot area ratio such as a skin portion in a human image.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming material which can solve the problem of poor image reproducibility, especially the problem of image reproducibility which occurs at a low dot area ratio.

[0005]

The present invention is directed to imagewise exposure of an image-forming material obtained by forming a photosensitive layer containing a dye and / or a pigment and a photopolymerizable compound on a support and further laminating a protective film thereon. After peeling off the protective film, the photosensitive layer of the image-forming material and the image receptor are introduced into the nip between rollers so as to face each other and pressure-bonded,
In an image forming material used in an image forming method for obtaining a duplicate image through a transfer process of selectively transferring a part of a photosensitive layer of the image forming material to the image receptor, an actinic ray reflecting layer is provided on a protective film. An image forming material is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An image transfer method using a thermal transfer system used in the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of an image transfer apparatus including an impression cylinder to which an image forming material suitable for use in the method of the present invention is attached, and a transfer cylinder to which an image receptor such as paper is attached. The structure of the transfer cylinder 1 will be described with reference to FIG. A partial cutout 2 is provided on the surface of the transfer cylinder 1, and inside the partial cutout, a nail 3 and a nail seat 4 which are upper side (holding side) attachment means of an image receptor (not shown) such as paper. And a clamp composed of a claw 5 and a claw seat 6 which are lower side (holding side) attachment means. To attach the image receptor, after gripping the upper side with the clamp on the gripper side, rotate the transfer cylinder 1 in the direction of the arrow to wind the image receptor around the transfer cylinder 1, and then grip the lower side of the image receptor with the clamp on the gripper side. By doing. The claw 3 and the claw 5 are provided with a drive shaft 7 capable of driving the claw by a driving means such as manual or electric, and the claw 3 is opened and closed by rotation of the drive shaft. An image receptor that can be inserted into the notch between the gripper side clamps 5, 6 and the direction of the arrow of the clamp, that is, movable in the radial direction of the transfer cylinder 1. A pressing bar (not shown) may be installed. The pressing bar is used together with the tray to attach or discharge the image receptor to the transfer cylinder without touching the heated transfer cylinder.

The structure of the impression cylinder 8 will be described with reference to FIG. The impression cylinder 8 is partially provided with a notch 9, and the blanket 10 wound around the surface of the impression cylinder 8 is fixed by the blanket fixing means 11 in the notch. An inclined portion 12 is provided between the partial cutout portion 9 and the impression cylinder surface (circumferential surface), and the pin bar 13 is installed on the inclined portion. Installation of the pin bar 13
It is carried out by pressing the pin bar against the surface of the impression cylinder with a blanket having holes at positions corresponding to the pins of the pin bar. The height of the tip of the pin bar 13 is not outside the circumferential surface of the impression cylinder 8. This is because the surface of the pin bar 13 or the transfer cylinder 1 is not damaged when the impression cylinder 8 and the transfer cylinder 1 rotate. In the vicinity of the inclined portion 12 provided with the pin bar 13 on the surface of the impression cylinder and another inclined portion 12 of the partially cutout portion
Adhesive tape 15 is provided on the surface of the impression cylinder in the vicinity. A magnet sheet 14 may be provided to ensure that the image forming material is held by the pin bar 13. Magnet sheet 1
4 is when tilted in the direction opposite to the arrow described on the impression cylinder 8,
The width is not enough to reach the adhesive tape 15, but is wide enough to cover the pin bar 13.

Above the transfer cylinder 1 and the impression cylinder 8, it is preferable to install a tray which can be rotated around a fulcrum 19 so that the tray tips 20 and 21 can come close to the transfer cylinder surface and the impression cylinder surface, respectively. . The image receptor or the image forming material is placed on the tray to facilitate the work of attaching or discharging the image receptor or the image forming material. Periphery of the transfer cylinder 1 and the impression cylinder 8 may be provided with squeezing rollers 22 and 23 which are respectively in contact with the surfaces of the transfer cylinder 1 and the impression cylinder 8. The ironing rollers 22 and 23 transfer the image receptor and the image forming material to the transfer cylinder 1.
Also, it is advantageous in improving the adhesion of the image receptor and the image forming material to the transfer cylinder 1 and the impression cylinder 8 when it is attached to the impression cylinder 8. The improvement in adhesion is effective in eliminating wrinkles, sagging, and the like that occur when the image receptor and the image-forming material are attached.

The operation of the image transfer method used in the present invention will be described below. The upper side (holding side) of the image receptor (not shown) is gripped by a clamp including a claw 3 and a claw seat 4 provided in the partially cutout 2 of the transfer cylinder 1. Since the image receptor is preheated on the transfer drum 1 before the image transfer operation, the surface temperature of the transfer drum 1 is 10
It is preferable to provide a heating means (not shown) inside so that the temperature is around 0 ° C. After grasping the upper side of the image receptor by the clamp on the holding side, the transfer cylinder 1 is transferred to the transfer cylinder 1.
Rotate in the direction indicated by the arrow. At this time, the ironing roller is brought into contact with the surface of the image receptor and rotated so that the image receptor comes into close contact with the surface of the transfer cylinder 1. The image receptor is then gripped by a clamp consisting of the grippers 5 and 6 on the butt side. By the above operation, the attachment of the image receptor to the transfer cylinder 1 is completed.

The image forming material (not shown) is attached to the impression cylinder 8 by the following procedure. The holes corresponding to the pin bars 13 are provided on the upper side of the image forming material, and these holes are formed in the pin bars 13.
Insert it into the pin. Then, if necessary, the magnetic sheet 14 suppresses the floating of the image forming material around the pins. Then, the ironing roller 23 is brought into contact with the surface of the protective film of the image forming material and rotated, and the impression cylinder 8 is rotated while the image forming material is brought into close contact with the impression cylinder 8 to wind the image forming material around the impression cylinder 8. At this time, the upper and lower sides of the image forming material are fixed to the surface of the impression cylinder with the adhesive tape 15. After the image forming material is attached to the impression cylinder, the protective film is peeled and removed to expose the photosensitive layer. Then, the transfer cylinder 1 and the impression cylinder 8 are synchronously rotated, and the photosensitive layer of the image forming material and the image receptor are introduced into the nip between the rollers formed by the both cylinders so as to face each other, and pressure is applied to the photosensitive drum to form a photosensitive layer. A portion of the layer is selectively transferred to the image receptor and a duplicate image is obtained on the image receptor. When a multi-color prepress proof is created, for example, a positive film having an original image of each color created by color separation into cyan, magenta, yellow, and black is used to form an image of each corresponding color. The material is imagewise exposed and the above operation is repeated for one image receptor.

The present inventors have made various studies on the above-mentioned image transfer method, but have found that the exposure sensitivity in image exposure may be lowered depending on the color of the image forming material. Here, the exposure sensitivity corresponds to the rate of progress of the polymerization reaction of the photopolymerizable compound in the photosensitive layer. If the exposure sensitivity is low, more exposure time is required, which sometimes adversely affects the productivity of the prepress proof. The inventors presumed that the cause of the decrease in exposure sensitivity was that actinic rays were absorbed and attenuated by the dye or pigment in the photosensitive layer. Furthermore, the present inventors have found that the transferred image may be inferior in image reproducibility. Upon further detailed examination, it was found that the image reproducibility was deteriorated particularly in the portion where the halftone dot area ratio was low. As a result of investigating the cause, the inventors presumed that, when the image forming material was imagewise exposed, the actinic ray passing through the photosensitive layer hits the protective film and is reflected and scattered. The present invention improves the image exposure sensitivity by providing an actinic ray reflective layer on the protective film and irradiating the actinic ray that has passed through the photosensitive layer to the photosensitive layer again, and at the same time, reproduces the image by scattering the reflected actinic ray. The feature is that the distance between the photosensitive layer and the actinic ray-reflecting layer is controlled in order to minimize deterioration of the property.

The actinic ray reflection layer is formed by applying a paint containing a pigment that reflects actinic rays to the protective film. Examples of actinic rays include X-rays, ultraviolet rays, visible rays, and electron rays. Examples of pigments that reflect active rays include titanium oxide and aluminum oxide. When the actinic ray reflective layer is in contact with the photosensitive layer, the actinic ray reflective layer preferably has an appropriate releasability in order to facilitate separation from the photosensitive layer. Examples of the releasability imparting agent include silicone resin, fluororesin, polyolefin resin, and aliphatic surfactant. In order to prevent the actinic ray reflection layer from being attacked by the reactive components in the photosensitivity, a reaction-curable type is preferably used as the coating material for the actinic ray reflection layer. Examples of such paints include epoxy paints, polyurethane paints, acrylic paints and the like. Even when the actinic ray-reflecting layer is not directly contacted with the photosensitive layer but is contacted through a transparent film, the above-mentioned releasing agent is added in order to facilitate the peeling of the transparent film from the photosensitive layer. It may be applied on the side of the transparent film which comes into contact with the photosensitive layer. A film having releasability may be used as the transparent film. Examples of the releasable film include polyethylene, polypropylene, polyethylene-vinyl acetate copolymer, polyethylene-vinyl alcohol copolymer, polyvinyl chloride and the like.

As another method of forming the actinic ray reflection layer, a method of laminating a metal foil on the protective film, vapor depositing a metal on the surface of the protective film, and the like are exemplified. The metal used at that time is generally aluminum. Also in these cases, it is preferable to provide an appropriate releasability so as to facilitate the peeling of the protective film from the photosensitive layer. As a method of imparting releasability, a transparent coating material containing a releasability-imparting agent as described above is applied to the surface of the protective film in contact with the photosensitive layer, and a thin film having releasability is laminated. , Etc. are exemplified. Further, as the adhesive used in the adhesive layer when the protective film is a laminate, a two-component reactive adhesive obtained by mixing an isocyanate curing agent with a polyester-based, urethane-modified polyester-based, or polyether-based main agent. Often used.

2 to 3 are schematic cross-sectional views illustrating the constitution of the image forming material of the present invention used in the image forming method described above. In FIG. 2, a photosensitive layer 31 containing a pigment and / or a dye, a photopolymerizable compound, a photopolymerization initiator and the like is provided on a support 30, and a protective film 33 provided with an actinic ray reflection layer 32 is provided as an active layer with the photosensitive layer. An example of the image-forming material laminated with the light-reflecting layer facing each other will be shown. In FIG. 3, the photosensitive layer 31 is provided on the support 30, and the film 3
4, an adhesive layer 35, an actinic ray reflection layer 32, a film 36
An example of an image-forming material is shown in which a protective film sequentially provided with is laminated so that the photosensitive layer 31 and the film 36 face each other. As shown in FIG. 3, as the protective film, a film in which at least two types of films having different types and thicknesses are laminated via an adhesive layer is also used. The reason is to simultaneously achieve performances such as dimensional stability and releasability from the photosensitive layer.
For example, a polyethylene terephthalate film laminated with a biaxially oriented polypropylene film via an adhesive layer is used. In this case, the film 34 is appropriately selected from films of various resins such as polyester, acryl, and polyolefin in consideration of strength and dimensional stability and the film 36, such as easy peeling and smoothness from the photosensitive layer. The film 36 must not be too thick in order to prevent reflection and scattering of the active rays that have passed through the photosensitive layer and prevent deterioration of image reproducibility due to the reflected active rays. A transparent film having a thickness of preferably 30 μm or less, more preferably 20 μm or less, still more preferably 10 μm or less is used.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. In each example, parts and% mean parts by weight and% by weight, unless otherwise specified. A liquid for a photosensitive layer having the following composition was prepared. Diallyl isophthalate prepolymer (Daiso Isodap manufactured by Osaka Soda Co., Ltd.) 16.60 parts Dipentaerythritol acrylate (DPHA manufactured by Nippon Kayaku Co., Ltd.) 8.90 parts Benzophenone ... 0.05 parts 4,4 bis Diethylamino benzophenone (EAB manufactured by Hodogaya Chemical Co., Ltd.) 0.17 parts Hydroquinone 0.001 part Pigment (Carmine 7BFG4412 manufactured by Toyo Ink Mfg. Co., Ltd.) 5.00 parts Toluene 32.00 parts Methyl ethyl ketone 40.00 Department

Example 1 A protective film A having an actinic ray reflecting layer was produced by the following method. 100 μm thick P with aluminum deposited on one side
On the aluminum-deposited surface of the ET film, a polyurethane / isocyanate two-component mixed adhesive was applied and dried so that the dry film thickness was 5 μm, and then an 8-μm thick OPP film was laminated.

Example 2 A protective film B having an actinic ray reflecting layer was produced by the following method. On a PET film (transparent) with a thickness of 100 μm,
A polyurethane / isocyanate two-component mixed type adhesive was applied and dried so that the dry film thickness was 5 μm, and then an aluminum vapor-deposited surface of a polyethylene-vinyl alcohol copolymer film having a thickness of 8 μm and having aluminum vapor-deposited on one surface was bonded.

Comparative Example 1 A protective film C having an actinic ray reflecting layer was manufactured by the following method. 100 μm thick P with aluminum deposited on one side
8 μm thick OPP after applying and drying a polyurethane / isocyanate two-liquid mixed adhesive to the surface of ET film not aluminum-deposited so that the dry film thickness becomes 5 μm.
The films were laminated together.

Comparative Example 2 A protective film D having no active ray reflecting layer was produced by the following method. A 100 μm-thick PET film (transparent) was coated with a polyurethane / isocyanate two-component mixed adhesive so that the dry film thickness was 5 μm, and dried, and then an 8 μm-thick OPP film was laminated.

An image forming material was manufactured by the following method using the above-mentioned protective film. A PET film having a thickness of 12 μm was used as a support, and the above-mentioned photosensitive layer coating liquid was applied and dried thereon to a dry film thickness of 2.4 μm, and then the results are shown in Examples or Comparative Examples. The protective films A to D were laminated so that the OPP or polyethylene-vinyl alcohol copolymer surface was in contact with the photosensitive layer. These are protective films A to
Image forming materials A to D corresponding to D.

An original positive film having a halftone image formed thereon is superposed on the support surfaces of the image forming materials A to D, and after image exposure with ultraviolet rays, the image forming materials are attached to an impression cylinder of a transfer device, The protective film was peeled off, and the photosensitive layer was pressed against the image receptor in the roller nip of the transfer device to obtain a transferred image. Table 1 shows the image exposure amount, the relative sensitivity and the evaluation result of the transferred image required at this time. However, the relative sensitivity shall be proportional to the reciprocal of the required image exposure,
The result of the image forming material D was calculated as 1.00. The unit of the image exposure amount is mJ / cm ² .

Table 1 Image forming material Image exposure amount Relative sensitivity Reproduction of minute halftone dot image Reproduction of fine line A 9.2 3.6 2% (175 L / I) 10 μm B 9.2 3.6 2% (175 L / I) 10 μm C 10.2 3.3 8% (175 L / I) 20 μm D 33.4 1.0 5% (175 L / I) 15 μm

As described above, the image forming materials A, B and C having the actinic ray reflecting layer are the image forming materials D not having the same.
It was confirmed that the image exposure sensitivity was improved as compared with. Further, in the image forming material C in which the distance between the photosensitive layer and the actinic ray reflective layer was 100 μm or more, deterioration was observed in the reproduction of minute halftone dots and fine lines.

[0024]

According to the present invention, an image forming material having an image exposure sensitivity that is practically satisfactory is provided. Further, according to the present invention, there is provided a thermal transfer type image forming material excellent in image reproducibility even in an image having a low dot area ratio of 20% or less.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an image transfer device.

FIG. 2 is a schematic sectional view of an image forming material of the present invention.

FIG. 3 is a schematic sectional view of an image forming material of the present invention.

[Explanation of symbols]

 1 Transfer Cylinder 8 Impression Cylinder 30 Support for Image-Forming Material 31 Photosensitive Layer 32 Actinic Ray Reflecting Layer 33 Protective Film 34 Film 36 Film

Claims (4)

[Claims] 1. An image forming material comprising a support and a photosensitive layer containing a dye and / or a pigment and a photopolymerizable compound formed thereon, and a protective film attached to the support, wherein the protective film is provided with an actinic ray reflecting layer. An image forming material characterized by the above. 2. The image forming material according to claim 1, wherein
An image-forming material comprising an actinic ray-reflecting layer provided on the surface of the protective film which is in contact with the photosensitive layer. 3. The image forming material according to claim 1, wherein
An image-forming material comprising a layer that transmits actinic rays between an actinic ray reflective layer and a photosensitive layer. 4. The image forming material according to claim 3,
An image forming material, wherein the thickness of the actinic ray transmitting layer between the actinic ray reflecting layer and the photosensitive layer is 30 μm or less.