Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making printing plates
Reexamination Certificate
2000-12-21
2003-09-30
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making printing plates
C430S315000, C430S325000, C430S413000
Reexamination Certificate
active
06627386
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming method to be applied with a negative type image forming material suitable for so-called direct plate making, wherein a printing plate can be directly made by infrared laser scanning based on a digital signal of a computer or the like.
2. Description of the Related Art
Conventionally, the following systems have been proposed for directly making a printing plate from digital data of a computer; (1) an electrophotography method; (2) photopolymerization by exposure using a laser that emits blue or green light; (3) a silver salt laminated on a photosensitive resin; (4) a silver salt scattering transfer method; and the like.
However, problems are involved in that (1) the electrophotography method requires complicated image forming processes including charging, exposure, and development. Thus, an apparatus is complicated and bulky. (2) The photopolymerization method requires a printing plate highly sensitive to blue or green light. Thus, handling in an illuminated room is difficult. And methods (3) and (4) require complicated processes because of the use of the silver salt, such as development. Moreover, silver is contained in processing waste liquid.
In contrast, development in the field of lasers has been significant recently. In particular, solid lasers and semiconductor lasers that emit infrared ray of a 760 nm to 1,200 nm wavelength and that have a high output and a small size are now easily obtainable. As a recording light source at a time of directly making a printing plate from digital data of a computer or the like, such lasers are extremely useful. However, since most photosensitive recording materials in practical use have an exposing wavelength of 760 nm or less in the visible light range, these infrared lasers cannot be used for forming an image thereon. Therefore, a material recordable with an infrared laser is called for.
As such an image recording material recordable with an infrared laser, U.S. Pat. No. 4,708,925 discloses a recording material containing an onium salt, a phenol resin, and a spectral sensitizer. The image recording material is a positive type image recording material that utilizes a dissolution restraining effect with respect to a developer, which effect is caused by the onium salt and the phenol resin. Thus, the material is not of a negative type, unlike the material of the present invention. In contrast, U.S. Pat. No. 5,340,699 discloses a negative type image recording material containing an infrared ray absorbing agent, an acid generating agent, a resol resin and a novolak resin. In such a negative type image recording material, in general, an image is formed by developing with an alkaline aqueous solution after laser exposure of the image. In this developing process, an automatic developing machine is generally used
For example, Japanese Patent Application Laid-Open (JP-A) No. 8-108621 discloses a negative type image forming material using a photopolymerizable composition, wherein a strong alkaline aqueous solution containing potassium silicate and having a pH value of more than 12 or the like is used for development. Such a developer having a high pH value involves a problem in that the developer absorbs carbon dioxide from air in the automatic developing machine, and a degree of activity of the developer deteriorates with aging.
Further, Japanese Patent Application Publication (JP-B) No. 7-103171 discloses a recording material that does not need a heat treatment after image exposure, containing a cyanine dye having a specific structure, an iodonium salt, and an addition polymerizable compound having an ethylenically unsaturated double bond. This image recording material is developed with a weak alkaline aqueous solution using a carbonate as an alkaline agent. A developer that uses a carbonate is preferable because such a developer does not absorb carbon dioxide in the air, but this developer has a problem in that it has poor solubility with respect to the image recording material. Thus, the photosensitive layer cannot be eliminated completely and fouling may occur in a non-image portion during printing.
In order to improve the solubility of the developer that uses the carbonate with respect to the image recording material, a technique of adding an organic solvent such as benzil alcohol was studied. However, when this solvent is included, although the solubility of the photosensitive layer is improved, there is a problem in that an image portion is also influenced, which reduces printing durability.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an image forming method for application to a negative type image forming material that can be directly recorded with digital data from a computer, by recording with a solid laser or semiconductor laser that emits infrared radiation. Due to the method, image forming properties are excellent and characteristics of a developer do not cause an aging-related reduction in a developing property or a reduction in printing durability.
As a result of in-depth study by the present inventor of physical properties of the negative type image forming material and the developer, it was discovered that the above-mentioned problems can be solved by improving permeability at a non-image portion of a photosensitive layer and utilizing characteristics of a developer containing a carbonate. Thus, the present invention could be achieved.
That is, a first aspect of the present invention is an image forming method which includes the steps of: preparing a negative type image forming material including a supporting member and at least one photosensitive layer which has sensitivity to an infrared laser; exposing the negative type image forming material image-wise by an infrared laser; and developing the negative type image forming material with a weak alkaline aqueous solution having a pH value in a range from 7 to 12 and containing a carbonate and a surfactant.
A second aspect of the present invention is an image forming method which includes the steps of: preparing a negative type image forming material including a supporting member and at least one photosensitive layer containing (A) an infrared ray absorbing agent, (B) a radical generating agent, (C) a radically polymerizable compound, and (D) a binder polymer; exposing the negative type image forming material image-wise by an infrared laser; and developing the negative type image forming material with a weak alkaline aqueous solution having a pH value in a range from 7 to 12 and containing a carbonate and a surfactant.
Although not defined, the reasons for the excellent effects of the present invention are considered as follows. Due to use of a surfactant in an alkaline developer containing a carbonate, development failure caused by deterioration of the developing property, which is caused by absorption of carbon dioxide, can be improved, and the permeability of the developer with respect to the non-image portion of the photosensitive layer can be improved. Further, due to controlling a pH value to within a 7 to 12 weak alkaline range, damage of the image portion of the photosensitive layer is improved, and adverse effects on the printing durability can be prevented.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter the present invention will be explained in detail.
An image forming method according to the present invention is characterized by an alkaline aqueous solution used in development.
As a base for a developer and for a replenisher, which are used in an image forming method of the present invention, a weak alkaline aqueous solution in a 7 to 12 pH range, which solution contains a carbonate and a surfactant, is used.
The weak alkaline aqueous solution used in a developing step of the image forming method of the present invention is required to be in a 7 to 12 pH range, and preferably in an 8 to 11 pH range. In the present invention, pH values refer to values measured at 25° C.
Examples of carbonates preferably used in the met
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Walke Amanda C.
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