JPH0627951B2 - Electrophotographic planographic printing plate material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to an electrophotographic lithographic printing plate material.
More specifically, the present invention relates to an electrophotographic lithographic printing plate material in a developing system using a wet developing solution, which is free from deterioration of the developing solution with time due to the support of the printing plate material.

[Conventional technology]

In recent years, due to the development of small offset printing machines and the development of automatic printing machines, the mainstream of light printing is shifting to offset printing.

Many researches and developments have been made on such offset printing plate materials, and various materials have been put to practical use. Among these materials, the electrophotographic lithographic printing plate material having a photoconductive photosensitive layer containing zinc oxide as a main component is inexpensive and the plate making process is simple, so that it is considered to be the mainstream of light printing plate materials. It has become. The electrophotographic lithographic printing plate is usually subjected to corona charging, exposure, development and fixing processes in a desired pattern on the photoconductive photosensitive layer of the printing plate material by using a plate making machine, whereby the photoconductive photosensitive layer is obtained. It is obtained by forming a visible image of a desired pattern.

In the developing step in the above printing plate preparation, a dry developing method using a mixture of a toner and a carrier such as iron powder,
Either a wet development method using a developer in which toner is dispersed in an organic solvent such as Isopar is used.

When a plate is made using the wet development method, the resulting printing plate has good reproducibility of half-tone (mild tone) images, has excellent resolution, and has a short plate-making time and correction. It is advantageous in that it does not require the use of the electrophotographic lithographic printing plate, which is widely used in Japan.

The electrophotographic lithographic printing plate material is required to have various characteristics required as a lithographic printing plate material in addition to the image characteristics generally required as an electrophotographic copying material. For example, in a printing plate that has undergone a development process, the non-image area needs to be desensitized. Further, as a plate material for offset printing, it is possible to make the non-image area hydrophilic by treating the surface of the photoconductive layer with an etchant. It must have excellent water resistance to water. Therefore, in order to improve the water resistance of the printing plate,
Attempts have been made to improve the water resistance of the support and to form a water resistant intermediate layer between the photoconductive photosensitive layer and the support.

The support is based on paper, but the printing plate support is required to have water resistance higher than the level of water resistance required for general printing paper.

The paper substrate is porous and has a property of absorbing liquid. In order to use such a paper substrate as a support for an electrophotographic lithographic printing plate material, a treatment for filling voids on the surface or inside of the paper substrate with a water-resistant colloid to prevent liquid infiltration and strengthen the paper substrate. is necessary. This treatment is sizing, and the colloid used for this treatment is size or sizing agent. There are various types of colloids used as sizing agents, and the following two types are usually used for the sizing method. One of them is to apply glue, starch, carboxymethyl cellulose, and / or polyvinyl alcohol to the surface of paper obtained by papermaking drying or to the surface of paper in a paper machine. It is called a method.

The other one is called rosin size, plant size or engine size. In this method, rosin was previously saponified, mixed with paper stock, and a sulfuric acid band was added to the resulting papermaking slurry to release rosin again, which was then bound to pulp fiber and prepared in this way. Papermaking is performed from the prepared papermaking slurry, and such a sizing method is called an internal addition size method.

When the electrophotographic lithographic printing plate is subjected to printing, a large amount of dampening water is supplied to the plate surface in the printing machine during printing, and therefore the support must have sufficient water resistance. Therefore, it is generally necessary to use both the internally added size and the surface size together with the paper substrate. As an internal sizing agent, a rosin sizing agent is most widely used because it is inexpensive and easy to handle. However, since the rosin sizing agent has a low degree of fixing to the paper substrate, it is necessary to increase the amount of rosin sizing agent added to the paper substrate in order to obtain higher sizing properties. Further, it is necessary to make paper with acidity in order to increase the fixing rate of rosin.

In order to overcome these problems of rosin sizing agents, it has been attempted to use a so-called wax sizing agent in which paraffin, vegetable wax, polyethylene or the like is mixed with an emulsifier such as rosin or stearic acid and the mixture is emulsified. . The wax sizing agent has a relatively high sizing property as compared with the rosin sizing agent, but it is difficult to handle, and when the addition amount is increased, the paper strength of the obtained paper decreases remarkably and the stiffness of the paper decreases. There is a problem of doing. For this reason, the practical use of wax sizing agents has not reached widespread use.

When making electrophotographic lithographic printing plate material using paper manufactured by acidic papermaking as a support and applying wet development with liquid toner (dispersed in Isopar), use wet developing solution for a long time If so, there arises a problem that the obtained image density decreases with time.

Therefore, it has been strongly desired to solve the problems of deterioration of the wet developing solution caused by the support of the printing plate material and accompanying decrease of the image density with time.

[Problems to be Solved by the Invention]

The present invention is a conventional electrophotographic lithographic printing plate containing a water-resistant support, when a wet developer is used for a long period of time,
It is an object of the present invention to solve the problem that the wet toner deteriorates with time due to the support of the printing plate material, and the density of the resulting image decreases accordingly.

[Means for Solving the Problems]

The electrophotographic lithographic printing plate material of the present invention has a support having a paper base and a photoconductive photosensitive layer formed on one surface side of the support, and the paper base of the support is an alkyl ketene. It is characterized in that it is internally sized by a sizing agent containing a neutral sizing agent as a main component and containing at least one selected from dimer, alkenyl succinic anhydride and stearic anhydride. It is a thing.

[Action]

As described above, a printing plate material comprising a conventional acidic papermaking base paper-sized support sized with a rosin-sulfuric acid band mixture undergoes a rosin-sulfuric acid band composite when subjected to a wet development step. Are gradually extracted into the toner dispersion medium of the developer, that is, Isopar. Then, the electric resistance value of the developing solution is gradually lowered, and thus the electrophoretic property of the toner is gradually lowered, and as a result, the density of the obtained image is lowered with time.

In order to eliminate the drawbacks of conventional printing plate materials as described above,
In the printing plate material of the present invention, at least one selected from the group consisting of alkyl ketene dimer, alkenyl succinic anhydride, and stearic anhydride on a paper substrate as a support.
A neutral sizing agent containing a neutral sizing compound as a main component and subjected to internal sizing treatment is used.

In the present invention, the base paper used as the support paper substrate may be one produced from any one of hardwood pulp, softwood pulp and hardwood softwood mixed pulp, and is usually kraft pulp, sulfite pulp, soda pulp or the like. Any of the above pulps may be produced, and if necessary, synthetic pulp and / or synthetic fibers may be mixed with the pulp.

The internally added neutral sizing agent used in the present invention contains a specific neutral sizing agent compound as a main component. Neutral sizing compounds useful in the present invention include alkyl ketene dimers, Alkenyl succinic anhydride, And stearic anhydride Chosen from.

Unlike non-reactive sizing agents such as rosin and wax, alkyl ketene dimers react with the cellulose units on the surface of pulp particles and change their hydroxyl groups into water-repellent hydrophobic groups. The effect is permanent and the size effect is not degraded by acid or alkali.

The reaction between the ketene dimer and the cellulose pulp does not occur in the presence of water, but when the paper substrate impregnated with the ketene dimer-containing sizing agent is dried, the above substitution reaction occurs. As the drying conditions, heating at a temperature of 82 to 100 ° C. for 1 to 5 minutes is sufficient.

When alkenyl succinic anhydride is used as a cationic emulsion for sizing treatment, alkenyl succinic anhydride is efficiently fixed on the surface of pulp fiber, and when it is dried, it reacts with hydroxyl groups of cellulose to exert a permanent size effect.

Generally, the alkenyl group of the alkenyl succinic anhydride is preferably selected from an isooctadecenyl group, an n-hexadecenyl group, a dodecenyl group, a triisobutenyl group and the like.

Stearic anhydride is used as an aqueous emulsion and can be used in combination with cationized starch to enhance the fixability of the pulp fiber surface. The stearic anhydride fixed on the pulp fibers reacts with the hydroxyl groups of the cellulose upon drying and exhibits a permanent size effect.

In order to further improve the fixability of the neutral sizing agent used in the present invention to pulp fibers, the combined use of cationized starch is effective. Particularly, in the sizing treatment with alkenyl succinic anhydride, it is preferable to use a cationized starch in combination and emulsify it evenly just before papermaking.

The size used in the present invention preferably comprises at least 20% by weight of neutral size. In order to improve the size yield of the neutral sizing agent, the neutral sizing agent used in the present invention is 100% by weight or less, preferably 20 to 90%.
It may contain wt% cationic additives. As the cationic additive, cationic starch, aluminum chloride, long-chain aliphatic amine, amine group-containing polymer and the like are used.

In order to produce the support of the present invention, the sizing agent containing the specific neutral sizing agent compound as a main component may be applied to the paper substrate by the internal addition sizing method.

Even when the specific neutral sizing agent of the present invention is applied to the paper substrate by the surface sizing method, it is possible to sufficiently prevent the deterioration of the toner in the wet developer of the electrophotographic lithographic printing plate with time and the resulting reduction in the image density. I can't.

In the support composed of the paper base thus sized, the content of the neutral sizing agent is based on the total weight of the support.
It is preferably in the range of 0.2 to 3.0%.

In addition to the above-mentioned sizing agent, the paper substrate contains usual additives such as paper strengthening agent, wet strength agent, retention improver and filler at a normal content of 1 to 10% by weight. It may be contained at the content rate.

Generally, in the printing plate material of the present invention, a photoconductive photosensitive layer is formed on one surface side of the support, and it is preferable that an intermediate layer is formed between the support and the photoconductive photosensitive layer. .

The characteristics required for such an intermediate layer are as follows.

1) It has excellent adhesiveness to both the support and the photoconductive photosensitive layer.

2) It has an excellent barrier property so that it can be prevented from penetrating into the support when the photoconductive photosensitive layer-forming coating material is applied.

3) Do not leave it in the solvent of the coating for forming the photoconductive photosensitive layer.

4) It has excellent water resistance and can prevent peeling of the photoconductive photosensitive layer for image reception from the support even when it comes into contact with water.

5) It has appropriate conductivity so that it does not cause a contrast defect due to a decrease in image density or an increase in fog during image formation.

Various types of interlayers have been proposed to meet the above requirements.

As the component constituting the intermediate layer, a mixture of an inorganic pigment, a water-soluble polymer compound, a water-proofing agent and the like is used, and a synthetic resin as a binder may be further contained.

As the water-soluble polymer compound, starch or its derivative, cellulose derivative, casein, polyvinyl alcohol, styrene maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer and the like can be used.

Inorganic pigments include carbonates such as Ca, Ba, Pb Zn, Ti, S
Oxides such as i and Pb, hydroxides such as Al and Zn Zn, Ca and Ba
And the like, silicates of Si and Al, sulfides such as Ba, Ca and Zn, and muscovite powder. As the waterproofing agent, aldehyde compound dialdehyde starch such as aminoplast initial condensate glyoxal or dimethylurea, polyamide, epoxidized polyamide epoxy compound, and silane coupling agent can be used.

Generally, synthetic resin in the binder of the intermediate layer is 20 to 40% by weight.
(Dry weight), the aqueous polymer compound is preferably contained in an amount of 5 to 15% by weight, and the waterproofing agent is preferably contained in an amount of 1 to 5% by weight.

When synthetic resins are used as the binder for forming the intermediate layer, these synthetic resins include, for example, acrylic ester copolymer resins, polyurethane resins, acrylic acid-
It is selected from acrylonitrile copolymer resin, styrene-butadiene copolymer resin and the like. Generally, when forming the intermediate layer, the binder synthetic resin is mixed in the intermediate layer-forming coating material as an aqueous emulsion or an aqueous latex.

In the printing plate material of the present invention, the photoconductive photosensitive layer is formed on one surface side of the support, preferably with an intermediate layer interposed therebetween.

The photoconductive photosensitive layer is formed by applying a paint comprising a photoconductive pigment such as zinc oxide or titanium oxide, an insulating binder, a sensitizing agent, and a solvent on the intermediate layer and drying. It is formed.

As the insulating binder for the photoconductive photosensitive layer, acrylic acid ester copolymers, methacrylic acid ester copolymers, vinyl acetate copolymers, silicone resins, butyral resins and the like are generally used. These binder resins include
Functional (hydrophilic) monomers such as acrylic acid, methacrylic acid, and maleic acid are usually copolymerized for the purpose of improving image quality, coating properties, and mechanical strength of the coating film. Such a resin has good hydrophilicity and is effective in preventing the occurrence of background stains on the printed matter obtained during printing.

In the printing plate material of the present invention, it is preferable that a conductive layer is formed on the back surface of the photoconductive layer.

It is generally preferred that the conductive layer comprises 80-85 wt% conductive material and 20-15 wt% (dry) binder.

The conductive material as a constituent of the conductive layer includes, for example, quaternary ammonium salt type polymer compounds such as polydiallyldimethylammonium chloride and polyvinyldimethylammonium chloride, sodium polyacrylate, sodium polystyrene sulfonate, and polystyrene sulfone. It preferably contains at least one polymer electrolyte selected from ammonium acid salts and the like.
As the binder for the photosensitive layer, polyvinyl alcohol, polyvinyl acetate resin, polyacrylic ester resin, styrene-butadiene resin, etc. can be used.

The weight of the conductive layer is preferably in the range of 5 to 15 g / m ² .

In order to produce the printing plate material of the present invention, one surface of a support is coated with an intermediate layer coating material, which optionally contains the required components and a solvent, and then dried, and a photoconductive pigment containing a photoconductive pigment is then applied. The paint may be applied and dried. In order to form the conductive layer, a coating material containing a conductive material and a binder may be applied on the opposite surface of the support and dried and solidified.

〔Example〕

 The present invention will be further described below with reference to examples.

Example 1 An electrophotographic lithographic printing plate material was prepared by the steps (1) to (6) described below, and the printing plate material was further processed in the step (7).
A printing plate was produced by the method described above, and its characteristics, particularly the image density, were measured, and its temporal stability was evaluated.

(1) Paper having a basis weight of 100 g / m ^{2 was made} from a papermaking mixture having the following composition.

Pulp (blending weight ratio: LBKP / NBKP = 70/30, beaten to 400 ml Canadian Standard Freeness) 100 parts Alkyl ketene dimer ^{* 1} 0.40 parts Cationized starch ^{* 2} 0.60 parts Polyamide epichlorohydrin ^{* 3} 0.25 parts PH = with baking soda Papermaking was performed by adjusting to 8.0.

[Note] * 1-Trademark: SPK-902, Arakawa Chemical Co., Ltd. * 2-Trademark: Cato F, Oji National Co., Ltd. * 3-Trademark: Arafix-100, Arakawa Chemical Co., Ltd. (2) Size the barrier
It was formed by press treatment so as to have a weight of 2 g / m ² (dry coating amount).

Polyvinyl alcohol 80 parts (solid content weight) Sodium polyacrylate 20 parts (solid content weight) (3) The above size press-processed base paper (thickness 110μ
An intermediate layer paint having the following composition was applied to the surface of the barrier layer of m) and dried to form an intermediate layer having a dry coating amount of 10 g / m ² .

Muscovite ^{* 4} 40 parts (weight) Polyurethane aqueous dispersion ^{* 5} 40 parts (weight) Casein 10% aqueous solution 10 parts (weight) Silane coupling ^{* 6} 10 parts (weight) [Note] * 4-Trademark: A- 21, made by Yamaguchi Mica, average particle size 20μ
m * 5-Trademark: Iserax S-1071, Hodogaya Chemical Co., Ltd. * 6-Trademark: SH6040, Toray Silicone (4) A photoconductive layer coating composition having the following composition is applied to the surface of the intermediate layer, dried, and dried. A photoconductive layer having a work amount of 25 g / m ² was formed.

Photoconductive zinc oxide ^{* 7} 100 parts (weight) Silicone resin ^{* 8} 30 parts (weight) Rose Bengal 0.1 part (weight) Toluene 150 parts (weight) [Note] * 7-Trademark: SAZEX200, Sakai Chemical * 8- Trademark: KR-211, manufactured by Shin-Etsu Chemical (5) A conductive layer coating material having the following composition is applied to the back surface of the laminate produced as described above, dried, and a dry coating amount of 8 g /
A conductive layer of m ² was formed.

Polyvinyl alcohol ^{* 9} 30 parts (weight) Vinyl acetate resin ^{* 10} 50 parts (weight) Quaternary ammonium type polymer conductive agent ^{* 11} 20 parts (weight) [Note] * 9-Trademark: T-330, Nippon Synthetic Chemical * 10-Trademark: Sebian A-522, Daicel * 11-Trademark: Chemistat 5500, Sanyo Kasei (6) The obtained printing plate material was acclimated for 24 hours in a dark room atmosphere of 50% RH and 25 ° C. .

(7) A printing plate having a predetermined pattern was prepared from this printing plate material using an AP-30X (Iwasaki Tsushinki) electronic plate making machine. In order to examine the toner deterioration due to the long-term use of the wet developing solution due to the size of the support (paper), 50 B-4 size printing plate materials were placed in AP-3DX toner (3) at room temperature for 17 days. After the immersion, the printing plate material was removed, and this toner was put into the developing section of the AP-3DX plate making machine to prepare a printing plate having a predetermined pattern on the printing plate material whose humidity was adjusted in (6) above. The image density measurement results are shown in Table 1.

Example 2 A printing plate was produced by the same steps as in Example 1. However, the papermaking conditions for the base paper were changed as follows, and a base paper having a basis weight of 100 g / m ² was made. Further, alkenyl succinic anhydride (trademark: Fibran, manufactured by Oji National Co., Ltd.) is used as a neutral sizing agent, and cationized starch (trademark: Cato F, manufactured by Oji National Co., Ltd.) is added thereto just before paper making After the alkenyl succinic anhydride / cationized starch was added at a weight ratio of 40/60, the mixture was stirred using a homogenizer to prepare a uniform emulsion and added to the papermaking raw material.

Pulp (blending weight ratio: LBKP / NBKP = 70/30, beaten to 400 ml Canadian Standard Freeness) 100 parts Alkenyl succinic anhydride / cationized starch emulsion 1 part Polyamide epichlorohydrin (*) ₃ 0.25 parts Papermaking was performed by adjusting to 8.0.

Using this base paper as a support, a printing plate was prepared in the same manner as in Example 1, and the image density was measured. The results are shown in Table 1.

Example 3 A printing plate was produced by the same steps as in Example 1. However, the papermaking conditions for the base paper were changed as follows, and a base paper having a basis weight of 100 g / m ² was made.

Pulp (blending weight ratio: LBKP / NBKP = 70/30, beaten to 400 ml Canadian Standard Freeness) 100 parts Stearic anhydride emulsion (trademark: NS-815, manufactured by Modern Chemical Co., Ltd.) 0.4 parts Cationized starch (*) ₂ 0.6 parts Polyamide epichlorohydrin (*) ₃ 0.25 parts Papermaking was carried out by adjusting the pH to 8.0 with sodium bicarbonate.

Using this base paper as a support, a printing plate was prepared in the same manner as in Example 1, and the image density was measured. The results are shown in Table 1.

Comparative Example 1 A printing plate was prepared by the same steps as in Example 1. However, the papermaking conditions for the base paper were as follows.

Basis weight 100g Pulp (blending weight ratio: LBKP / NBKP = 70/30, beaten to 400 ml Canadian Standard Freeness) 100 parts SPOA (Rosin size agent, Arakawa Chemical Co., Ltd.) 1.0 part Sulfate band 1.2 parts Colamine P1000 (urea formalin) Resin, manufactured by Mitsui Toatsu) 1.0 part Paper was made with PH = 4.5.

A printing plate material is prepared by using this base paper as a support, and this printing plate material, B-4 size, 50 sheets is immersed in AP-3DX- (3) at room temperature for 17 days, and then the printing plate material is removed. This toner
The printing plate was placed in the developing section of the AP-30X plate making machine to prepare a printing plate having a printing pattern. The image density measurement results are shown in Table 1.

Comparative Example 2 The step (1) of Example 1 was performed. However, no alkyl ketene dimer was added to the pulp formulation.

Next, the base paper obtained in the above step (1) was subjected to the step (2) of Example 1. However, in a mixture of 80 parts polyvinyl alcohol and 20 parts sodium polyacrylate, 0.
40 parts of alkyl ketene dimer was mixed to prepare a surface size / pressing agent for the intermediate layer (barrier layer).

The above-mentioned surface-sized pressed base paper was subjected to the step (3) of Example 1. However, the surface size-pressed base paper showed strong water repellency, many spots were generated in the applied intermediate layer paint, and this could not be applied uniformly. Therefore, the subsequent steps were stopped.

Comparative Example 3 A printing plate was prepared by the same steps as in Example 1. However, the papermaking conditions for the base paper were changed as follows, and a base paper having a basis weight of 100 g / m ² was made.

Pulp (blending weight ratio: LBKP / NBKP = 70/30, beaten to 400 ml Canadian Standard Freeness) 100 parts Self-fixing neutral sizing agent (cationized gum, trademark: Pearl Gum CS, manufactured by Seikou Sangyo) 0.4 parts Polyamide epichlorohydrin (*) ₃ 0.25 parts Papermaking was carried out by adjusting the pH to 8.0 with baking soda.

Using this raw paper as a support, a printing plate material was prepared in the same manner as in Example 1. This printing plate material, B-4 plate, 50
After soaking the sheets in AP-3DX toner (3) at room temperature for 17 days, remove the printing plate material and put this toner into the developing section of AP-3DX electronic plate making machine to make a printing plate with a predetermined pattern. did. The image density measurement results are shown in Table 1.

As is clear from Table 1, when the self-fixing neutral sizing agent of Comparative Example 3 was used, the image density was higher than when the neutral sizing agent of the present invention was used (Examples 1 to 3). The decrease was large.

〔The invention's effect〕

In the present invention, a sizing agent containing a specific neutral sizing compound as a main component is used as an internally added sizing agent for the paper substrate, which is the main component of the support, to prevent deterioration of the wet developer over time. As a result, it is possible to prevent the density of the obtained image from decreasing with time and obtain a printing plate of stable quality.

Claims (9)

[Claims] 1. A support having a paper base, and a photoconductive photosensitive layer formed on one surface side of the support, wherein the support paper base is an alkyl ketene dimer or an alkenyl anhydrous amber. Electrophotographic lithographic printing, characterized by being subjected to internal sizing treatment with a sizing agent containing a neutral sizing agent containing at least one selected from acid and stearic anhydride as a main component. Plate material. 2. Material according to claim 1, wherein the amount of neutral sizing agent in the support is in the range of 0 to 3.0%, based on the total weight of the support. 3. The material according to claim 1, wherein in the alkenyl succinic anhydride, the alkenyl group is selected from an isooctadecenyl group, an n-hexadecenyl group, a dodecenyl group, and a triisobutenyl group. 4. A material according to claim 1 wherein said sizing agent comprises a cationic additive added to said neutral sizing agent. 5. The method according to claim 4, wherein the cationic additive is selected from cationic starch, aluminum chloride, long-chain fatty acid amine, and amine group-containing polymer.
Material described in the item. 6. The neutral sizing agent content in the sizing agent is 20.
The material according to claim 1, which is at least wt%. 7. The material according to claim 4, wherein the content of the cationic additive in the sizing agent is 20 to 90% by weight. 8. The material according to claim 1, wherein an intermediate layer is formed between the support and the photoconductive photosensitive layer. 9. The material according to claim 1, wherein a conductive layer is formed on the other surface of the support.