Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2001-05-21
2003-09-30
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S302000, C430S944000, C430S138000
Reexamination Certificate
active
06627380
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lithographic printing plate used in the field of offset printing, and more particularly to an original plate for lithographic printing which can be used in a so-called computer-to-plate (CTP) method and which is applicable to direct plate making based on digital signals from a computer or the like, a method for producing images on the original plate, and a photosenstitive composition preferably used for producing such original plates for lithographic printing.
2. Description of the Related Art
With the progress of the computer image processing technology, there has been recently developed a method for inscribing an image directly on a photosensitive layer by means of photoirradiation based on digital signals. A computer-to-plate (CTP) system, which utilizes this method for lithographic printing to form an image directly on the printing plate without outputting the image to a silver halide mask film, has attracted much attention. The CTP system using high power lasers having maximum strength in a near infrared or infrared region as a light source for photoirradiation has various advantages. For example, compact and high power lasers can be easily obtained, a high resolution image can be produced with a short period of exposure, and the printing plate material used for this method may be handled in a lighted room.
As the printing plate material which is used in the above-described system and which does not require heating before development of latent images, Japanese Unexamined Patent Application, First Publication No. Hei 9-171249 and Japanese Unexamined Patent Application, First Publication No. Hei 11-268225 disclose a manufacturing method for an original plate for lithographic printing using an image forming material including hydrophobic fine resin particles and an alkali soluble resin or a hydrophilic binder.
However, when the weight ratio of hydrophobic fine resin particles included in the image forming material is high relative to the total weight of the hydrophobic fine resin particles and the alkali soluble resin or the hydrophilic binder, the above-described manufacturing method has a problem in that printed material was marred, because the image forming material cannot be completely dissolved in a developer, and thereby, a non-image area cannot be completely removed.
When the weight ratio of the alkali soluble resin or the hydrophilic binder included in the image forming material is high relative to the total weight of the hydrophobic fine resin particles and the alkali soluble resin or the hydrophilic binder, the above-described manufacturing method has a problem in that an image area is removed together with a non-image area during developing, the loss of images occurs, and the development property of the original plate, when stored for long periods under high temperature and high humidity, is decreased.
Moreover, Japanese Unexamined Patent Application, First Publication No. Hei 11-271962 discloses a manufacturing method of an original plate for lithographic printing including a first layer made of an alkali soluble resin and a second layer which is made of fine particles of a heat melting resin and is disposed on the first layer.
However, when a non-image area is removed by using an alkali developer, the manufacturing method has a problem in that the loss of images occurs, because the alkali developer penetrates into the first layer disposed under the second layer including an image area, the alkali soluble resin is dissolved into the alkali developer, and then, the image area is also removed together with the non-image area.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a useful original plate for lithographic printing, an image-producing method therefor, and a photosenstitive composition preferably used to produce the original plate for lithographic printing, which permits image inscription by laser beam, reduces the image loss, and has a high resolving power, an improved development property which results in reducing blurs in the non-image area, and a high sensitivity, and of which development property is not decreased by storage under the high temperature and high humidity.
A second object of the present invention is to provide a useful original plate for lithographic printing which is used in the computer-to-plate (CTP) system, fulfills the first object mentioned above, and can be applicable to direct plate making based on digital signals from a computer or the like, and in which heat processing is not required prior to developing a latent image.
As a result of extensive research aimed at realizing the above objects, the inventors of the present invention discovered that by using a photosenstitive composition comprising an aqueous resin composition including fine particles of a resin having anionic groups in which some or all of the anionic groups are neutralized, and a water soluble resin having anionic groups in which some or all of the anionic groups are neutralized, an original plate for lithographic printing using the photosenstitive composition can form satisfactory images, which are prevented from generating the loss of images in an image area, and can show satisfactory development properties, and which prevents the generation of blurring in non-image areas. Moreover, by regulating the quantity of the water soluble resin added into the aqueous resin composition, a more useful photosenstitive composition, in which the development property is not reduced even when the photosensitive composition is stored under high temperature and high humidity coditions, can be obtained.
The inventors of the present invention also discovered that by neutralizing some or all of the anionic groups included in the fine particles of the resin with a basic compound, a water soluble resin can be produced, and by controlling the quantity of the basic compound used for the neutralization, the amount of water soluble resin produced can be easily regulated, so that a photosenstitive composition having satisfactory storage stability can be obtained.
The inventors of the present invention also discovered that by forming a photosensitive layer using the photosenstitive composition onto a hydrophilic surface of a support, a useful original plate for lithographic printing can be obtained. As a result, the present invention has been completed.
That is, the present invention provides a photosenstitive composition comprising an aqueous resin composition including fine particles (a) of a resin having at least one neutralized anionic group and having a heat fusion property, and a water soluble resin (b) having at least one neutralized anionic group, wherein the water soluble resin (b) is included in a range of 1 to 30% by weight, relative to the total weight of the aqueous resin composition; and a substance (c) which absorbs light and generates thermal energy.
The aqueous resin composition may be produced by adding a basic compound to fine particles (a′) of a resin having at least one anionic group and having a heat fusion property. The fine particles (a′) of the resin having at least one anionic group and having a heat fusion property may be produced by an emulsion polymerization.
The glass-transition temperature of the resin showing a heat fusion property may be in a range of 50 to 150° C. The resin forming the fine particles (a) or the fine particles (a′) may have 35 to 530 millimoles of anionic groups per 100 g of resin solid content. The fine particles (a) may be crosslinked with each other.
The present invention also provides an original plate for lithographic printing comprising a support having a hydrophilic surface; and a photosensitive layer which includes the photosenstitive composition according to the present invention and is disposed on the hydrophilic surface.
The present invention also provides an image-producing method comprising the steps of inscribing images by using a laser beam on the original plate for lithographic printing accord
Hayakawa Eiji
Kojima Yasuhiko
Oe Koji
Saito Naohito
Watanabe Yasuyuki
Baxter Janet
Dainippon Ink and Chemicals Inc.
Walke Amanda C
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