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
2001-01-30
2003-05-27
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
C430S281100, C430S288100, C430S306000, C430S325000, C430S919000, C430S920000, C430S921000, C430S925000, C430S926000, C430S944000, C522S026000, C522S027000, C522S028000, C522S030000, C522S052000, C522S057000, C522S059000, C522S060000, C522S061000, C522S063000, C522S065000, C522S067000, C522S068000, C522S151000, C522S153000, C522S154000, C522S167000, C522S168000, C522S178000, C522S180000
Reexamination Certificate
active
06569603
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a light-sensitive composition and a method for forming a relief image utilizing the light-sensitive composition. More specifically, it relates to a light-sensitive composition which is capable of forming an image by using a scanning exposure device such as laser, etc. Also, it relates to a light-sensitive composition suitable for forming a lithographic printing plate, a resist for forming a printed circuit, a color filter or a phosphor pattern.
2. Prior Art
In a light-sensitive composition, its molecular structure causes chemical changes by a photoreaction, and as a result, changes occur in physical properties. As the chemical changes due to light, there are cross-linking, polymerization, decomposition, depolymerization, exchange in functional groups, etc., whereby various changes such as changes in solubility, adhesive property, refractive index, substance permeability, phase transfer, etc. occur. Such a light-sensitive composition has been practically used in various fields including a printing plate, resist, paint, coating agent, color filter, etc. Moreover, it has been used in the field of a photoresist using a photomechanical process (photolithography), and developed. The photoresist is a technique utilizing change in solubility by a photoreaction, and an accurate material design has been desired more and more due to the demand of high resolution.
A widely used type of lithographic printing plate has a light-sensitive coating film coated on an aluminum support. This coating film cures by exposure to light and the portion not exposed is dissolved by a developing treatment. This type of a plate is called to as a negative type printing plate. A lithographic printing plate utilizes surface properties of a pattern formed on the surface of the lithographic printing plate and a background portion having lipophilic property and hydrophilic property, respectively. When conducting lithographic printing, ink and damping water are simultaneously applied onto the printing surface of a printing press, and the ink is selectively transferred onto the pattern having lipophilic property. The ink transferred onto the pattern is then transferred to an intermediate material called to as a blanket and further transferred to a printing paper whereby printing is carried out.
Many researches have been conventionally done about light-sensitive composition for forming a relief image utilizing change in solubility by the photoreaction as mentioned above, and practically applicable materials have been provided. For example, in Japanese Patent Publications No. 34041/1974 and No. 105353/1994 and U.S. Pat. No. 5,153,095, etc., a light-sensitive composition mainly comprising a polymer having an ethylenically unsaturated bond at the side chain, a cross-linking agent and a photopolymerization initiator has been disclosed. Such a composition has a light-sensitive property to light having a short wavelength mainly at a ultraviolet rays region of 400 nm or shorter.
On the other hand, in recent years, it has been desired to develop a light-sensitive material having high sensitivity to visible rays accompanying with the progress of image forming techniques. For example, researches have been actively carried out on a light-sensitive material and a light-sensitive lithographic printing plate corresponding to an output machine using argon laser, helium-neon laser, red-color LED, etc.
Moreover, accompanying with the marked progress in semi-conductor laser, a near infrared laser light source having 700 nm to 1300 nm can be easily used whereby a light-sensitive material and a light-sensitive lithographic printing plate corresponding to said laser light has attracted attention.
As a photopolymerizable composition having a light-sensitive property at the above-mentioned visible rays to near infrared rays, there are disclosed a lithographic printing plate containing a radical polymerizable compound having an ethylenically unsaturated bond, a photosensitizing dye having an absorption peak at 400 to 500 nm and a polymerization initiator in Japanese Provisional Patent Publication No. 134007/1997; a combination of an organic boron anion and a dye in Japanese Provisional Patent Publications No. 143044/1987, No. 150242/1987, No. 5988/1993, No. 194619/1993, No. 197069/1997 and No. 2000-98603; a combination of a dye and an s-triazine compound in Japanese Provisional Patent Publications No. 31863/1992 and No. 43633/1994; a combination of a resol resin, a novolac resin, an infrared rays absorber and a photo-acid generator in Japanese Provisional Patent Publications No. 20629/1995 and No. 271029/1995; and a combination of a specific polymer, a photo-acid generator and a near infrared sensitizing dye in Japanese Provisional Patent Publications No. 212252/1999 and No. 231535/1999.
However, in the above-mentioned polymerizable compositions using the photopolymerization initiator or the photo-acid generator, it is difficult to provide sufficiently high light-sensitivity at the visible rays to near infrared region, and light-sensitivity was particularly insufficient for applying them to scanning exposure using various kinds of laser beams.
Also, in the above-mentioned polymerizable compositions, there is a problem that a latent image is regressed after exposure. That is, a portion exposed to light shall form an image after development. However, depending on a lapse of time from exposure to developing treatment, there is a problem that an image cannot sufficiently be formed, i.e., fading of a latent image. This phenomenon occurs between several ten minutes and several hours after exposure depending on the conditions of temperature and humidity as well as an exposed dose, etc.
Moreover, in the above-mentioned light-sensitive compositions, there is a problem that it is difficult to ensure stability and long-term preservability of sensitivity, etc. Thus, it has generally been carried out to provide an overcoating layer comprising polyvinyl alcohol, etc. on the light-sensitive layer for the purpose of heightening oxygen barrier property and preventing from causing flaws at the surface of the material. According to the presence of such an overcoating layer, there are problems of lowering image quality due to light scattering at the time of laser beam exposure, requiring to effect a pre-washing step for removing the overcoating layer prior to alkali development, and requiring to provide a step of further coating an overcoat layer after coating the light-sensitive layer for manufacture the material. Furthermore, in the polymerization using a photopolymerization initiator or a photo-acid generator, polymerization does not proceed sufficiently only by exposure to light in many cases so that it is necessary to effect a heat treatment after exposure or a developing treatment to progress and complete the polymerization. In particular, in the case of a light-sensitive lithographic printing plate material to which a light-sensitive property is provided at the wavelength region from visible rays to infrared rays, a heat treatment is an important preparation step. However, the heat treatment is not only lowering production efficiency but also contains a factor which makes product quality unstable. For example, it is difficult to maintain the difference in solubility between the exposed portion/unexposed portion constantly. Thus, when insufficient heating is carried out, there is a problem that the exposed portion is also dissolved by a developer, or else, when heating temperature is too high, there is a problem that the unexposed portion is partially insolubilized whereby development cannot sufficiently be carried out.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a light-sensitive composition having high sensitivity, in particular, to provide a light-sensitive composition having sufficiently high sensitivity with a wide range from visible rays to infrared rays. Another object of the present invention is to provide a light-sensitive composition
Baxter Janet
Lee Sin J.
Manelli Denison & Selter PLLC
Mitsubishi Paper Mills Limited
White, Jr. Paul E.
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