JPH0690545B2 - Electrophotographic lithographic printing plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic lithographic printing plate precursor prepared by an electrophotographic method, and more particularly to a binder for forming a photoconductive layer of the lithographic printing plate precursor. Regarding improvement of resin.

(Prior Art) At present, various kinds of offset original plates for direct plate making have been proposed and put into practical use. Among them, photoconductive particles such as zinc oxide and a binder resin are mainly contained on a conductive support. A photoconductor provided with a photoconductive layer is subjected to a normal electrophotographic process to form a highly lipophilic toner image on the surface of the photoconductor, and then the surface is treated with a desensitizing solution called an etchant to form a non-image portion. A technique for obtaining an offset original plate by selectively hydrophilizing is widely used.

In order to obtain a good printed matter, first, the original image is faithfully copied to the offset original plate, the surface of the photoconductor is easily compatible with the desensitizing solution, and the non-image area is sufficiently hydrophilized, while at the same time being water resistant. In addition, in printing, the photoconductive layer having an image does not separate and is well compatible with fountain solution, and even if the number of printed sheets is large, the hydrophilicity of the non-image area is sufficient so that stains do not occur. It is necessary to have performance such as being retained.

It is already known that these performances are affected by the ratio of zinc oxide to the binder resin in the photoconductive layer. For example, if the ratio of the binder resin to the zinc oxide particles of the photoconductive layer is reduced, the desensitizing property of the surface of the photoconductive layer is improved and scumming is reduced, while the internal cohesive force of the photoconductive layer itself is reduced. Drop,
Printing durability is reduced due to insufficient mechanical strength. On the contrary, if the ratio of the binder resin is increased, the printing durability is improved, but the background stain is increased. Needless to say, especially, the background stain is a phenomenon related to the quality of the desensitizing property of the surface of the photoconductive layer.
It is clear that the desensitizing property of the surface of the photoconductive layer does not depend only on the ratio of zinc oxide and the binder resin in the photoconductive layer, but also largely depends on the type of binder resin. It is becoming popular.

Known resins have long been known, for example, silicone resin (Japanese Patent Publication No. 34-6670) and styrene-butadiene resin (Japanese Patent Publication No. 35-35).
1960), alkyd resin, maleic acid resin, polyamide (Japanese Patent Publication 35-11219), vinyl acetate resin (Japanese Patent Publication 41-2)
No. 425), vinyl acetate copolymer (Japanese Patent Publication No. 41-2426), acrylic resin (Japanese Patent Publication No. 35-11216), acrylate copolymer (eg Japanese Patent Publication No. 35-11219, Japanese Patent Publication No. 36-8510).
No., Japanese Patent Publication No. 41-13946, etc.) are known. However, in electrophotographic photosensitive materials using these resins, 1)
Low photoconductive layer chargeability 2) Poor image quality (especially halftone dot reproducibility / resolution) of copied image 3) Low exposure sensitivity 4) Desensitization treatment for use as an offset master However, desensitization is not sufficiently performed, and therefore, when offset printing is performed, the printed matter is stained.
5) The film strength of the photosensitive layer is not sufficient, and when the offset printing is performed, the photosensitive layer is detached and the number of printed sheets cannot be increased.
6) There is any problem that the image quality is easily influenced by the environment (for example, high temperature and high humidity) at the time of creating the copied image.

In particular, as an offset original plate, as described above, the occurrence of background stain due to insufficient desensitizing property is a big problem, and in order to improve this, various development of zinc oxide binder resin for improving desensitizing property is studied. Has been done.

For example, in Japanese Examined Patent Publication (Kokoku) No. 50-31011, a (meth) acrylate-based monomer copolymerized with another monomer in the presence of fumaric acid has a resin of w1.8 to 10 × 10 ⁴ and Tg of 10 to 80 ° C.
A combination of an acrylate monomer and a copolymer of a monomer other than fumaric acid, and JP-A-53-540
No. 27 uses a terpolymer containing a (meth) acrylic acid ester having a substituent having a carboxylic acid group separated from the ester bond by at least 7 atoms, and JP-A-54
-20735 and JP-A-57-202544 use a quaternary or quaternary copolymer containing acrylic acid and hydroxyether (meth) acrylate, and JP-A-58-68046 has 6 to 12 carbon atoms. It is described that the one using a terpolymer containing a (meth) acrylic acid ester having an alkyl group as a substituent and a carboxylic acid-containing vinyl monomer is effective for improving the desensitizing property of the photoconductive layer. ing.

(Problems to be Solved by the Invention) However, even the above-mentioned resins that are said to be effective in improving the desensitizing property are still unsatisfactory in the background stain and the printing durability when actually evaluated. It was

The present invention solves the above-mentioned problems of the conventional electrophotographic lithographic printing plate precursor.

The object of the present invention is to reproduce a copy image faithful to the original image, and as an offset original plate, a lithographic printing original plate excellent in desensitizing property which does not generate spot stains as well as uniform background stains on the entire surface. Is to provide.

Another object of the present invention is to provide a lithographic printing plate having high printing durability in which the hydrophilicity of the non-image area is sufficiently maintained and the background stain does not occur even when the number of printed sheets is increased. .

Another object of the present invention is to provide a lithographic printing plate which has a clear and high-quality image even when the environment changes during the plate-making process, such as low temperature and low humidity or high temperature and high humidity, and does not cause background stain.

A further object of the present invention is to provide a lithographic printing plate having excellent preservability of the photographic material before processing.

(Means for Solving the Problems) The above-mentioned objects are to provide an electrophotographic photosensitive member comprising a conductive support and a photoconductive layer comprising at least one layer of photoconductive zinc oxide and a binder resin. In the lithographic printing plate precursor using the body, at least a resin containing at least one functional group having at least two hydroxyl groups in sterically close positions at the same time protected with one protecting group is used. It has been found to be achieved by an electrophotographic lithographic printing plate precursor which is characterized by containing one kind.

Examples of the functional group having at least two hydroxyl groups in sterically close positions in one protected form in the present invention include those represented by the following general formulas (I), (II) and (III). Can be mentioned.

General formula (I) In formula (I), R ₁ and R _{2, which} may be the same or different, each represents a hydrogen atom, a hydrocarbon group or —O—R ′ (R ′ represents a hydrocarbon group), and Z represents It represents a carbon-carbon bond which may be through a hetero atom (provided that the number of atoms between oxygen atoms is within 5).

General formula (II) In formula (II), Z is as defined above.

General formula (III) In formula (III), R ₁ , R ₂ and Z are as defined above.

The functional group will be described in more detail below.

In formula (I), R ₁ and R ₂ may be the same as or different from each other, and preferably a hydrogen atom or an optionally substituted alkyl group having 1 to 12 carbon atoms (for example, a methyl group, an ethyl group, Propyl group, butyl group, hexyl group, 2-methoxyethyl group, octyl group, etc., and aralkyl group having 7 to 9 carbon atoms which may be substituted (eg, benzyl group, phenol group, methylbenzyl group, methoxybenzyl group, chloro group). Benzyl group), an alicyclic group having 5 to 7 carbon atoms (eg, cyclopentyl group, cyclohexyl group, etc.), or an optionally substituted aryl group (eg, phenyl group, chlorophenyl group, methoxyphenyl group, methylphenyl group, Cyanophenyl group) or —O—R ′ (R ′ has the same meaning as the hydrocarbon group for R ₁ and R ₂ ).

Z represents a carbon-carbon bond which may pass through a hetero atom, and the number of atoms between oxygen atoms is 5 or less.

The resin containing at least one functional group used in the present invention has a form in which the hydroxyl groups contained in the polymer in the sterically close positions as described above are protected by a protecting group by a polymer reaction. Produced by a method, or a method of polymerizing by a polymerization reaction with a monomer containing at least two hydroxyl groups in a form previously protected by a protecting group or a polymerization reaction of the monomer and another monomer copolymerizable therewith To be done.

As the former method for producing a polymer reaction, for example, a polymer component which has at least two hydroxyl groups in close proximity to each other as shown below as specific examples or which can have close proximity after polymerization (R ″ is a substituent such as H or CH ₃ ) In a form in which at least two hydroxyl groups of interest are simultaneously protected with one protecting group by reacting a polymer containing a carbonyl compound, an orthoester compound, a halogen-substituted formic acid ester, a dihalogen-substituted silyl and the like. It is possible to form a functional group having. Specifically, edited by The Chemical Society of Japan, “New Experimental Chemistry Course, Vol. 14, Synthesis and Reaction of Organic Compounds [V] page 2505 (published by Maruzen Co., Ltd.), JFWMc. Omie,“ Protective groups in Organic.
Chemistry ”, Chapters 3 and 4 (published by Plenum.Press), etc. In the latter method, a monomer in which at least two hydroxyl groups have been protected in advance is synthesized by a known method cited in the above-mentioned reviews and the like, and if necessary, another monomer which can be copolymerized with the monomer is synthesized. A homopolymer or a multi-component copolymer can be produced by coexisting a monomer and polymerizing by a usual polymerization method.

The resin of the present invention has a molecular weight of 10 ³ to 10 ⁶ , preferably 5 × 10 ^3.
~ 10 ⁵ .

Further, the polymer component containing the functional group in the resin is 0.1 to 100
% By weight, preferably 0.5 to 100% by weight.

More specifically, examples of the polymer component containing the functional group are as follows. However, the scope of the present invention is not limited to the following.

Conventionally known resins can be used in combination with the resin used in the present invention. Examples thereof include silicone resins, alkyd resins, vinyl acetate resins, polyester resins, styrene-butadiene resins, acrylic resins and the like as described above. Specifically, Ryuji Kurita, Jiro Ishiwatari, High Polymer Vol. 17, p. 278 (1968) ), Harumiya Miyamoto, Hidehiko Takei, Imaging 1973 (NO8), page 9, etc.

The resin used in the present invention and a known resin can be mixed in any ratio, but the content of the functional group is 1 to 80% by weight, preferably 3 to 30% by weight based on the total amount of the resin used. %,
Need to occupy.

When the content of the functional group-containing component in the total amount of resin is less than 1% by weight, the resulting lithographic printing plate precursor has sufficient hydrophilicity caused by desensitizing treatment with a desensitizing solution / fountain solution. There is no stain when printing. On the other hand, if it is more than 80% by weight, the image formability at the time of copying becomes poor, or the coating strength of the photoconductive layer at the time of printing becomes weak and the mechanical durability deteriorates.

The resin containing at least one functional group according to the present invention is a resin which is hydrolyzed or hydrogenolytically decomposed by a desensitizing solution or a fountain solution used during printing to generate a hydroxyl group.

Therefore, when the resin is used as the binder resin of the lithographic printing plate precursor, the hydrophilicity of the non-image area which is hydrophilized by the desensitizing liquid is further enhanced by the hydroxyl group generated in the resin. Therefore, the lipophilicity of the image area and the hydrophilicity of the non-image area become clear, and printing ink is prevented from adhering to the non-image area during printing. As a result, it becomes possible to print a large number of clear printed matter having no background stain and having a clear image quality as compared with the conventional lithographic original plate using a resin.

When the conventional resin containing the hydroxyl group itself is used from the beginning, the viscosity of the dispersion of zinc oxide and the binder resin becomes high, and even if it is applied, the smoothness of the photoconductive layer is significantly deteriorated and the film strength is increased. Was not sufficient, and the electrophotographic characteristics were not satisfied. Even if an original plate having sufficient smoothness could be produced, stains were generated during printing. Furthermore, even if a hydroxyl group in the resin is adjusted to produce an original plate with good image quality of the copied image and the image quality of the printed matter, the environment at the time of producing the copied image (plate making process) is low temperature / low humidity or high temperature / high humidity. In the case of grazing (especially in high temperature and high humidity), the image quality of the copied image deteriorated due to the occurrence of background fog, a decrease in density of the image portion, occurrence of fine lines / character skips and the like.

Because these things have strong interaction between the hydroxyl groups in the binder resin and the photoconductive zinc oxide particle surface, the amount of resin adhesion on the particle surface increases, resulting in easy compatibility with the desensitizing solution or fountain solution. Even if the hydroxyl groups in the binder resin are adjusted appropriately for the zinc oxide particles, the hydrophilic atmosphere at the interface between the hydroxyl groups in the resin and the zinc oxide particles may be low temperature / low humidity or It is presumed that when exposed to high temperature and high humidity, the electrophotographic characteristics such as surface potential and dark decay after charging are deteriorated because of a large change.

The lithographic printing plate precursor of the present invention is used at a ratio of 10 to 60 parts by weight, preferably 15 to 30 parts by weight, of the binder resin described above with respect to 100 parts by weight of photoconductive zinc, and if necessary, Various conventionally known additives for electrophotographic photosensitive layers such as sensitizing dyes such as xanthene dyes and cyanine dyes (for example, rose bengal) or chemical sensitizers such as acid anhydrides can be used in combination ( For example, known materials in review articles such as Harumi Miyamoto, Hidehiko Takei, Imaging 1973 (NO8) page 12). The addition amount is not particularly limited, but the photoconductor
It is 0.0005 to 2.0 parts by weight with respect to 100 parts by weight.

The photoconductive layer according to the present invention can be provided on a conventionally known support. Generally speaking, the support of the electrophotographic photosensitive layer is preferably conductive, and as the conductive support, just as in the conventional case, for example, a metal, iron, a plastic sheet or the like having a low resistance substance on a substrate is used. Those which have been subjected to a conductive treatment such as impregnation, those which are coated with at least one layer for the purpose of imparting conductivity to the back surface of the substrate (the surface opposite to the surface on which the photosensitive layer is provided) and further preventing curling, A substrate having a water-resistant adhesive layer on the surface thereof, a substrate having at least one precoat layer provided on the surface layer of the substrate as necessary, a substrate conductive plasticized aluminum vapor-deposited paper, etc. A laminated product can be used.

Specifically, as an example of a conductive substrate or a conductive material,
Yukio Sakamoto, Electronic photography., (NO1), P2 ~ 11 (1975), Hiroyuki Moriga. "Introduction to Special Paper Chemistry" Polymer Publishing Association (1975), MFH
oovev, J. Macvomol. Sci. Chem. A-4 (6), P1327 to 1417
(1970) etc. can be used.

(Examples) The embodiments of the present invention will be illustrated below, but the contents of the present invention are not limited thereto.

Example 1 and Comparative Examples A to C 36 g of n-butyl methacrylate, 5 ethyl methacrylate
4 g, a mixed solution of 10 g of a monomer corresponding to the copolymerization component shown in the specific example (15) and 200 g of toluene under a nitrogen stream at a temperature of 7
After heating to 0 ° C, azobisisobutyronitrile (AIB
N) 1.0 g was added and reacted for 8 hours. The weight average molecular weight of the obtained copolymer was 56,000.

Subsequently, 30 g of the solid content of this copolymer and 10 g of [butyl methacrylate / acrylic acid (98/2) weight ratio] copolymer (weight average molecular weight 45000), zinc oxide 200 g, rose bengal 0.05 g, phthalic anhydride 0.01 A mixture of g and toluene (300 g) was dispersed in a ball mill for 2 hours to prepare a photosensitive layer forming liquid, which was coated on a conductive-treated paper with a wire bar so that the dry adhesion amount was 25 g / m ^2, and the temperature was 110 ° C. for 1 hour. An electrophotographic light-sensitive material was prepared by drying for one minute and then leaving it in the dark at 20 ° C. and 65% RH for 24 hours.

In the above Production Examples, three kinds of comparative photosensitive materials A, B and C were prepared by replacing the photosensitive layer forming material with the following copolymers.

Comparative photosensitive material A; n-butyl methacrylate 40 g, ethyl methacrylate 6
A copolymer was synthesized under the same conditions as in Example 1 except that 0 g and 200 g of toluene were mixed. The weight average molecular weight of the obtained copolymer was 65,000.

A light-sensitive material was prepared in the same manner as in Example 1.

Comparative photosensitive material B; n-butyl methacrylate 36 g, ethyl methacrylate 5
A copolymer was synthesized in the same manner as in Example 1 except that a mixed solution of 4 g, 2-hydroxyethyl methacrylate 10 g and toluene 200 g was prepared. The weight average molecular weight of the obtained copolymer was 6300.
It was 0.

A photosensitive material was prepared in the same manner as in Example 1.

Comparative photosensitive material C; n-butyl methacrylate 30 g, ethyl methacrylate 4
A mixed solution of 5 g, 25 g of 2-hydroxyethyl methacrylate and 200 g of toluene was prepared, and a copolymer was synthesized in the same manner as in Example 1. The weight average molecular weight of the obtained copolymer was 6100.
It was 0.

A light-sensitive material was prepared in the same manner as in Example 1.

The film properties (surface smoothness), electrostatic properties, desensitizing property of the photoconductive layer (expressed by the contact angle of water of the photoconductive layer after desensitizing treatment) and printability of these photosensitive materials were examined. It was Printability is fully automatic plate-making machine ELP404V (Fuji Photo Film Co., Ltd.)
Manufactured by ELP-T, and then exposed and developed,
An image was formed and examined using a lithographic printing plate obtained by etching with an etching processor using the desensitizing liquid ELP-E. (Note that the printing machine is Hamada Star Co., Ltd. 800SX type was used).

The above results are summarized in Table-1.

Embodiments of the evaluation items shown in Table 1 are as follows.

Note 1) Smoothness of photoconductive layer: The smoothness (sec / cc) of the obtained photosensitive material was measured using a Bek smoothness tester (manufactured by Kumagai Riko Co., Ltd.) under an air volume of 1 cc. did.

Note 2) Electrostatic characteristics: Paper analyzer (Paper Analyzer SP manufactured by Kawaguchi Electric Co., Ltd.) on each photosensitive material in a dark room at a temperature of 20 ° C and 65% RH.
-428 type) was used for corona discharge for 20 seconds at -6 KV, then left for 10 seconds, the surface potential Vo at this time was measured, and then the photoconductive layer surface was irradiated with visible light with an illuminance of 2.0 lux,
The exposure time E1 / 10 (lux · sec) is calculated from the time required for the surface potential and Vo to decay to 1/10.

Note 3) Contact angle with water: Each photo-sensitive material was passed through an etching processor once using a desensitizing solution ELP-E (manufactured by Fuji Photo Film Co., Ltd.) to desensitize the photoconductive layer surface. After the treatment, a drop of distilled water (2 μl) is placed on this, and the contact angle with the water formed is measured with a goniometer.

Note 4) Image quality of copied image Each photosensitive material and fully automatic plate-making machine ELP404V (manufactured by Fuji Photo Film Co., Ltd.) are left at room temperature and normal humidity (20 ° C, 65%) for a day and night, and then plate-made to make a copied image. And an image (fog, image quality) of the obtained copy original plate is visually observed (this is referred to as I). The image quality II of the copied image is tested by the same method as I except that the platemaking is performed at high temperature and high humidity (30 ° C., 80%).

Note 5) Background stain of printed matter Each photosensitive material is made into a plate with a fully automatic plate-making machine ELP404V (manufactured by Fuji Photo Film Co., Ltd.) to form a toner image, and desensitized under the same conditions as (Note 3) above. Using this as an offset master, it is applied to an offset printing machine (Hamaduster 800SX type manufactured by Hamada Star Co., Ltd.) to print 500 sheets on high-quality paper, and the background stain of all prints is visually determined. This is designated as background stain I.

For the background stain II of the printed matter, the desensitizing solution is diluted 5 times,
In addition, the test is performed in the same manner as the background stain I, except that the dampening water at the time of printing is diluted twice.

The case of II corresponds to printing under a stricter condition than I.

The copied images obtained using the light-sensitive materials of the present invention and Comparative Examples A and B were both clear image quality, but those of Comparative Example C had a significantly deteriorated smoothness of the photoconductive layer surface and There was a lot of fog in the image area, and the image quality was not clear. Further, in Comparative Examples B and C in which the respective light-sensitive materials were made under the environment of (30 ° C., 80%), the copied images were remarkably deteriorated (ground fog occurred and the image density was 0.6 or less). ).

Furthermore, the contact angle of each desensitized photosensitive material with water with a desensitizing solution was as small as 15 ° C. or less for the materials of the present invention and Comparative Example B, indicating that they were sufficiently hydrophilized. Indicated.

Further, when these were printed as offset master plates, only the plates of the present invention and Comparative Example B were the good ones which did not cause background stains in the non-image area.
Further, even if 10,000 prints were made on both of these plates, the image quality of the printed matter was good and no scumming occurred. However, the plates of Comparative Examples A and C caused scumming.

From the above facts, only the light-sensitive material of the present invention was able to form a clear copy image at all times even when the plate was made under changing environmental conditions, and it was possible to obtain 10,000 or more prints without background stains. .

Further, after leaving this light-sensitive material for 1 year, the same processing as the above was carried out, but there was no change from that before the passage of time.

Example 2 Benzyl methacrylate 30 g, ethyl methacrylate 45
g, a mixed solution of 25 g of a monomer corresponding to the copolymer component shown in Example (23) and 200 g of toluene under a nitrogen stream at a temperature of 7
After heating to 5 ° C., 1.0 g of AIBN was added and reacted for 8 hours.

The weight average molecular weight of the obtained copolymer was 43,000.

The following procedure was repeated under the same conditions as in Example 1 to prepare a light-sensitive material. This is a fully automatic plate making machine as in Example 1.
After making a plate with ELP404V, the density of the obtained master plate for offset printing was 1.2 or more, and the image quality was clear.
Further, when the etching treatment was performed and printing was performed by a printing machine, the printed matter after printing 10,000 sheets had no fog in the non-image area and the image was clear.

Further, this photosensitive material was allowed to stand for one year and then subjected to the same treatment as above, but there was no change from that before the passage of time.

Example 3 Styrene 16 g, ethyl methacrylate 64 g, compound example (2
A mixed solution of 20 g of a monomer corresponding to the copolymer component shown in 2), 0.2 g of acrylic acid and 200 g of tolue was heated under a nitrogen stream at a temperature of 75 g.
After heating to ℃, AIBN 1.0g was added and reacted for 8 hours.
The obtained copolymer had a molecular weight of 55,000.

Example 1 except that 40 g of the solid content of this copolymer was taken
A mixture of the same zinc oxide, rose bengal, phthalic anhydride, and tolue was prepared in the same manner as in Example 1 to prepare a light-sensitive material. When a plate was prepared using the same apparatus as in Example 1, the density of the obtained offset printing master plate was 1.0 or more, and the image quality was clear. Furthermore, after etching treatment and printing with a printing machine, the printed matter after printing 10,000 sheets had a clear image quality without fog.

Further, this photosensitive material was allowed to stand for one year and then subjected to the same processing as above, but it was completely the same as before the passage of time.

Example 4 A mixed solution of 40 g of butyl vinyl ether, 10 g of 4-methylene-1,3-dioxolane and 100 g of ether was added under a nitrogen stream.
The temperature was cooled to −78 ° C., 5 g of BF ₃ -ether solution was added with stirring, and the reaction was carried out for 60 hours. Thereafter, a methanol solution of ammonia was added to terminate the polymerization, and the polymer thus precipitated was separated from the solvent by decantation, washed with n-hexane, and dried under reduced pressure.

Then, 20 g of this copolymer and [butyl methacrylate / acrylic acid (99/1) weight ratio] copolymer (weight average molecular weight 65000) 20 g, zinc oxide 200 g, rose bengal 0.05 g,
The mixture was 0.01 g of phthalic anhydride and 300 g of toluene.
The following operations were performed in the same manner as in Example 1 to prepare a light-sensitive material. When the plate was made using the same apparatus as in Example 1,
The density of the obtained master plate for offset printing is 1.
The image quality was clear at 0 or more. Furthermore, after etching treatment and printing with a printing machine, the printed matter after printing 10,000 sheets had a clear image quality without fog.

Further, this photosensitive material was allowed to stand for one year and then subjected to the same processing as above, but it was completely the same as before the passage of time.

(Effects of the Invention) From the above results, the lithographic printing plate precursor according to the present invention reproduces a copy image faithful to the original image, and since the non-image area has good hydrophilicity, scumming does not occur, and photoconductive It can be seen that the layer has good smoothness and electrostatic properties, and further has excellent printing durability.

Furthermore, the original plate for this planographic printing plate is not affected by the environment during plate making,
Further, the storability of the light-sensitive material before processing is excellent.

Claims (1)

[Claims] 1. A lithographic printing plate precursor utilizing an electrophotographic photosensitive member comprising a photoconductive layer comprising at least one layer of photoconductive zinc oxide and a binder resin on a conductive support. The resin comprises at least one resin containing at least one functional group having at least two hydroxyl groups sterically close to each other simultaneously protected by one protecting group. An original plate for electrophotographic lithographic printing.