JP2988841B2 - Lithographic printing plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic printing original plate, and more particularly to a lithographic printing original plate which is free from wrinkling of a printing original plate and has good automatic feeding and discharging properties in a printing press.

[0002]

2. Description of the Related Art In recent years, with the development of small offset printing machines and automatic printing machines, offset printing has become the mainstream in the field of light printing. As a lithographic printing plate precursor used for such offset printing, an electrophotograph in which a photoconductive fine powder such as zinc oxide is applied on a support together with an electrically insulating binder to form a photoconductive layer as a recording layer. A lithographic printing plate is well known, and such a printing plate is used as an offset printing plate by forming an oleophilic image on the surface of a recording layer by an electrophotographic method. Also, an electrophotographic image created separately can be transferred to an image receiving layer containing an inorganic pigment and a binder on a support, that is, a lithographic printing original plate on which a recording layer is formed, using oil-based ink or type printing. A method for forming an image directly on an image receiving layer by using a direct drawing offset printing plate, and a lithographic printing original plate such as one using a photosensitive resin or a silver halide photosensitive material as a recording layer. Those used are known.

When offset printing is performed using the lithographic printing plate precursor as described above, non-image portions on the plate surface are subjected to a hydrophilizing treatment with a desensitizing solution to prevent ink from adhering, and wet printing is performed during printing. The water is subjected to a hydrophilizing treatment with water (usually, a desensitizing solution is diluted with water). Since such a treatment liquid is mainly composed of water, there is a problem in that the original plate generates wrinkles due to water absorption during printing, thereby causing stains on printed matter. This problem is particularly noticeable when paper is used for the support. In order to prevent the generation of such wrinkles, the printing original plate is provided with an under layer on the recording layer side of the surface to impart water resistance, and the surface of the support on which the recording layer is not formed, that is, from the back side. Measures such as providing a water-resistant back layer to suppress water absorption and using a water-resistant plastic film as a support have been implemented.

[0004] However, the processing liquid that is excessively attached to the printing plate during the above-mentioned hydrophilic treatment is not absorbed by the printing plate and scatters inside and outside the printing press, thereby contaminating the printing press and printing paper. Having. In addition, when used in a printing press having an automatic plate feeding / discharging function, if the processing liquid is excessively attached to the back side surface of the printing plate, the plate feeding / discharging property is reduced, and a problem of poor mounting of the printing plate occurs. Furthermore, when a plastic film is used as a support, in addition to the above-described problems of dirt and plate feeding / discharging properties, in a printing machine having an automatic plate feeding / discharging function, mounting failure or processing of a printing original plate due to deterioration of plate feeding / discharging properties due to static electricity or the like. There are problems such as performance, cost, and disposal. In addition, when the printing original plate is stored in a roll or sheet form, the recording layer surface and the back layer surface of the printing original plate are superimposed on each other, so that a resin or a water-proofing agent contained in the back layer is formed. The hydrophobic substance is transferred to the surface of the recording layer to cause stains during printing, which causes a problem of so-called stain stains.

As a measure against printing wrinkles, Japanese Patent Laid-Open Publication No.
No. 36, the outermost layer containing a hydrophilic polymer as a backing layer of a printing plate and a water absorption of 45 g / 45 min.
It has been proposed to provide an inner layer of m ² or less. However, although such a technical means was effective in preventing wrinkles and stains, it does not take into account any processing liquid that is excessively attached to the printing plate during plate making or the like. There was a problem of deterioration in the supply / discharge properties and contamination due to scattering.

[0006]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a lithographic printing plate precursor which is free of wrinkles at the time of printing, has good print quality free of stains, and has excellent automatic plate feeding and discharging properties. Is provided.

[0007]

According to the present invention, in a lithographic printing plate precursor having a recording layer on one side of a support, the Cobb water absorbency of the surface on the side where the recording layer is not formed is 0.1 in 20 seconds. 02 to 5 g / m ² and the value at 45 minutes is 0.02.
A lithographic printing original plate characterized by a weight of 〜15 g / m ² .

That is, the present invention simultaneously solves the above contradictory problems and achieves excellent printability by providing a surface of a support on which a recording layer is not formed (hereinafter referred to as a back surface). ) Was focused on the water absorbency of Cobb in order to appropriately control the water absorbency. That is, as the ease of absorbing the attached water, that is, the water absorption in a short time, the Cobb water absorption is 0.02 to 5 g / m ² in 20 seconds,
In addition, water absorption (penetration) rate and absorption amount are kept below a certain level, that is, 0.02 to 15 g in 45 minutes as long time
It has been found that it is effective to have a Cobb water absorption of / m ² on the back surface of the support.

In the present invention, the Cobb water absorption on the side where the recording layer is not formed, that is, on the back side surface is as described above.
0.02 to 5 g / m ² for 20 seconds, 0.02 for 45 minutes
１５15 g / m ² , but preferably 0.0
Is 0.5 to 10 g / m ² in 5~0.2g / m ^2, 45 minutes value. Such Cobb water absorption is measured according to JIS P8140 “Testing method for water absorption of paper and paperboard”. Instead of water, ELP-E2 (desensitizing agent) manufactured by Fuji Photo Film Co., Ltd. and water are used. A solution mixed at a ratio of 1: 5 is used. For the measurement of the water absorption, one having a measurement accuracy of 0.0001 g is used.

In the present invention, as a method of adjusting the Cobb water absorption of the back side surface to the above-mentioned range, for example, a back layer having a composition in which the types and ratios of binders and pigments are appropriately selected is formed on a support. A high water-resistant barrier layer is provided on a support, and a water-absorbing back layer is provided on the barrier layer, and a support whose water absorption is adjusted by impregnation with a binder, a pigment, or the like is used. But,
It is not limited to these.

The above method will be specifically described. A hydrophobic resin and a hydrophilic resin described below are mixed and used as the back layer, and the ratio of the hydrophilic resin in the resin component is 10 to 70.
% By weight, preferably 20 to 50% by weight. In addition, the following pigment was added to the resin as a back layer, and the ratio of resin: pigment = 1:
A composition dispersed in a ratio of 0.8 to 2.5, preferably 1: 1 to 1.7 may be provided, or the back layer may have good wettability, for example, a low resistance such as a surfactant or a quaternary ammonium salt. By incorporating an agent, colloidal silica or the like, the Cobb's water absorption can be adjusted to the range specified in the present invention. Further, when the support is impregnated, the distribution ratio of the hydrophilic resin and the pigment can be appropriately controlled similarly to the composition of the back layer.

Examples of the hydrophobic resin include acrylic resin, vinyl chloride resin, styrene resin, styrene-butadiene resin, styrene-acrylic resin, urethane resin, vinylidene chloride resin, vinyl acetate resin and the like. Examples of the hydrophilic resin include a polyvinyl alcohol-based resin, a cellulose-based derivative, starch and its derivatives, a polyacrylamide-based resin, and a styrene-maleic anhydride-based copolymer. Examples of the pigment include clay, kaolin, talc, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide, mica and the like.

The Cobb water absorption of the back side surface of the lithographic printing plate precursor according to the present invention is adjusted to 0.02 g / m ² or more for a value of 20 seconds and 15 g / m ² or less for a value of 45 minutes as described above. However, if the value of 20 seconds is less than 0.02 g / m ² , the moisture (desensitizing solution or dampening solution) attached to the printing original plate scatters inside and outside the printing machine or plate making machine, and There is a problem in that the printing paper (printed matter) is stained and plate feeding / discharging properties are deteriorated. On the other hand, the value of 20 seconds is 5 g /
If the value is larger than m ² or the 45-minute value exceeds 15 g / m ² , the water absorption is so good that wrinkles are likely to occur as the number of prints increases, and the number of printings of the printing original plate decreases. Cause problems. The 45-minute value is 0.
In the case of less than 5 g / m ^2, it becomes difficult to absorb the extra fountain solution as the number of prints increases, as in the case where the 20-second value is less than 0.02 g / m ^2. This may cause the problem of dirt and poor plate feeding / discharging properties.

The lithographic printing plate precursor of the present invention is characterized in that the Cobb's water absorption on the back side surface is adjusted to a specific range as described above. The sheet itself may be a sheet having a composition having the above-mentioned properties, or the support may be impregnated with a resin or a pigment as described above. Further, a back layer having the composition as described above may be provided on the support by lamination by coating or lamination, and the back layer may have a single-layer structure or a laminated structure of two or more layers, particularly It is not limited. The thickness of the back layer can be appropriately set depending on the composition and the like, but is usually about 1 to 15 μm.

On the other hand, on the side of the support on which the recording layer is formed,
At least a recording layer is provided on the support,
If necessary, an under layer may be provided between the support and the recording layer in order to impart water resistance and improve the adhesiveness of the recording layer.

In the lithographic printing plate precursor of the present invention having the above-mentioned layer constitution, as the support, for example, wood pulp paper, synthetic pulp paper, mixed paper of wood pulp and synthetic pulp,
A nonwoven fabric, a plastic film, a cloth, a metal sheet, a composite sheet thereof, or the like can be used as appropriate. The support may be impregnated with a low-resistance substance, and may be subjected to a conductive treatment by coating, vapor deposition, or the like. Further, as described above, a hydrophobic resin, a hydrophilic resin, or a hydrophilic resin may be used to adjust the Cobb water supply degree on the back surface. Impregnating with a coating liquid composed of a conductive resin, a pigment or the like. In the present invention, particularly remarkable functions and effects are obtained and effective particularly in the case of a paper or a mixed paper made of wood pulp, which is liable to undergo dimensional change due to water absorption.

As the recording layer, any known recording layer according to the method of preparing a printing original plate can be used. For example, a photoconductive layer of an electrophotographic system, a recording layer for direct printing, a photosensitive resin or silver A recording layer using a salt material is applied. In the present invention, in particular, in a lithographic printing plate used in an automatic plate feeding type printing press, since excess adhesion moisture can be reduced, deterioration in plate feeding / discharging properties (for example, slipping on a plate feeding roll) does not easily occur, and it is excellent. Such a lithographic printing original plate is effective because it has good printability, and examples thereof include an electrophotographic lithographic printing original plate.

The photoconductive layer of the electrophotographic lithographic printing plate precursor contains at least a photoconductive agent and a binder. Examples of the photoconductive agent include zinc oxide, cadmium sulfide, titanium oxide, selenium, and selenium. Inorganic materials such as tellurium alloys, and organic pigments such as cyanine-based pigments, quinoline-based pigments, and phthalocyanine-based pigments having photoconductive properties, and organic materials such as triphenylamine derivatives, anthracene, pyrazoline derivatives, perylene, tetracene, and carbazole Is mentioned. Acrylic resin as a binder,
Various resins such as a styrene resin, a vinyl acetate resin, a vinyl chloride resin, a silicon resin, and a butyral resin can be used.

As the under layer, a hydrophobic resin and a hydrophilic resin which can be used for the above-mentioned back layer are appropriately used. In the electrophotographic lithographic printing plate precursor, it is preferable to smooth the underlayer surface by calendering or the like in order to improve the recording characteristics.
Furthermore, the under layer and the back layer may contain a water-resistant agent such as a melamine resin, a melamine formaldehyde resin, a polyamide resin, a polyamide-epichlorohydrin resin, a glyoxal, and a chromium ban to improve water resistance. It is effective in preventing the occurrence of.

[0020]

Next, the present invention will be described with reference to examples. In addition, the number of parts representing the combination indicates parts by weight. Example 1 A high-quality paper having a basis weight of 120 g / m ² was used as a support, and a B1 paint having the following composition was first used as an inner layer on one surface of the support using a Meyer bar so that the dry coating amount was 6 g / m ^2. After coating and drying, a B2 paint having the following composition was applied as an outer layer on the inner layer by a Meyer bar so that the dry coating amount was 4 g / m ^2, and dried to form a two-layer back layer. B1 paint (inner layer) ・ Kaolin (50% aqueous dispersion) 120 parts ・ Polyvinyl alcohol 10% aqueous solution 60 parts ・ SBR latex 100 parts (solid content 48%, SN-307 manufactured by Sumitomo Nogatack) ・ Melamine resin precondensate 10 parts (solid content 80%, Sumiretz Resin SR-613) B2 paint (outer layer) ・ Kaolin (50% aqueous dispersion) 200 parts ・ Polyvinyl alcohol 10% aqueous solution 60 parts ・ SBR latex (solid content 49%) 100 parts・ Melamine resin precondensate 3 parts (solid content 80%, Sumiretz Resin SR-613)

Next, the following coating material for the under layer was applied to the other surface of the support using a Meyer bar at a dry coating amount of 15 g / m 2.
² become as coating, after drying, provided the under layer by calendering treatment. Next, the following coating material for a recording layer was applied using a Mayer bar so as to have a dry coating amount of 25 g / m ² , dried to form a recording layer, and then seasoned at 20 ° C. and 60% RH for 16 hours. Thus, a lithographic printing original plate of the present invention was prepared. Underlayer paint ・ Kaolin (50% aqueous dispersion) 200 parts ・ Oxidized starch (20% aqueous solution) 30 parts ・ SBR latex (solid content 49%) 150 parts ・ Melamine resin precondensate 10 parts (solid content 80%, Sumiretz Resin SR-613) Recording layer coating ・ Photoconductive zinc oxide (Sasex # 2000, Sakai Chemical Co., Ltd.) 100 parts ・ Acrylic resin (LR018, Mitsubishi Rayon Co., Ltd.) 20 parts ・ Rose Bengal 0.1 parts ・ Fluoresce 0.2 parts of methanol 10 parts of methanol 150 parts of toluene

Example 2 The procedure of Example 1 was repeated, except that a polyethylene terephthalate film (surface corona-treated product) having a thickness of 125 μm was used as a support and the inner layer of the back layer was not provided. A lithographic printing plate precursor was prepared. Comparative Example 1 A lithographic printing original plate for comparison was prepared in exactly the same manner as in Example 1 except that only the inner layer was provided without providing the outer layer as the back layer.

Comparative Example 2 In Example 1, only the inner layer was provided without the outer layer as the back layer, and the inner layer was dried at a coating weight of 10 g / m ^2.
A lithographic printing plate precursor for comparison was produced in exactly the same manner as in Example 1 except that the above conditions were used. Comparative Example 3 In Example 1, only the outer layer was provided without providing the inner layer as the back layer, and the outer layer had a dry coating amount of 10 g / m ^2.
A lithographic printing plate precursor for comparison was produced in exactly the same manner as in Example 1 except that the above conditions were used.

Comparative Example 4 A high-quality paper of 85 g / m ² was used as a support, and on one side of the support, a B3 paint having the following composition was first applied as an inner layer using a Meyer bar so that the dry coating film became 7 μm. After working and drying, a B4 paint having the following composition was applied as an outer layer on the inner layer using a Meyer bar so that the dried coating film became 3 μm, and dried to form a two-layer back layer. B3 paint ・ Clay (50% aqueous dispersion) 90 parts ・ SBR latex (solid content 49%) 51 parts ・ Melamine crosslinking agent (solid content 80%) 4.1 parts ・ Water 99 parts B4 paint ・ Clay (50% water) (Dispersion liquid) 116 parts ・ Polyacrylic acid ester 76 parts (solid content 45%, Bonron S282 manufactured by Mitsui Toatsu Chemicals, Inc.) ・ Polyvinyl alcohol 10% aqueous solution 90 parts ・ Melamine crosslinking agent (solid content 80%) 5.4 parts ・Next, an under layer and a recording layer were provided on the other surface of the support in exactly the same manner as in Example 1 to prepare a lithographic printing plate precursor for comparison. Comparative Example 5 A polyethylene terephthalate film (surface corona treated product) having a thickness of 125 μm was used as a support, and an under layer and a recording layer were provided on one surface of the support in the same manner as in Example 1 for comparison lithographic printing. A master was made.

The Cobb water absorption of the lithographic printing plate precursors of Examples 1-2 and Comparative Examples 1-5 prepared above was measured by the above-described method. In addition, printing wrinkles, scattering of a processing solution, and plate supply / discharge properties were evaluated as printability. The evaluation was performed using an electrophotographic plate making machine ELP-404V manufactured by Fuji Photo Film Co., Ltd.
00 PFA automatic printing machine, ink is F gloss (black ink) manufactured by Dainippon Ink and Chemicals, Ltd., desensitizing solution is ELP-E2 manufactured by Fuji Photo Film Co., Ltd., dampening solution is the same desensitizing solution ELP Printing was performed using a solution obtained by diluting 1 part of E2 with 5 parts of water, and the number of sheets that could be printed before the occurrence of wrinkles was examined. In addition, the state of scattering of the processing solution when the automatic plate feeding and automatic plate discharging were repeated 50 times under the above conditions was visually inspected, and those with little scattering and good were marked with ○, those with considerable scattering were marked with Δ, and the scattering was severe. Those that do not withstand practical use were marked with x. Further, as the plate feeding / discharging property, the number of occurrences of mounting failure in the repetition of the 50 plates was examined. Regarding the plate making properties of the above plate making machines, the planographic printing plate precursors of Examples and Comparative Examples both had good image characteristics.

[0026]

[Table 1]

The evaluation results are as shown in Table 1. The lithographic printing plate precursor of the present invention has no printing wrinkles, has no problem of contamination of the printing press due to scattering of the processing solution, and has good automatic feeding and discharging properties. It was confirmed that the composition had excellent printability. On the other hand, in the printing masters of Comparative Examples 1, 2, 4, and 5, scattering of the processing liquid was observed because the Cobb water absorption was low for 20 seconds, and the printing masters of Comparative Example 5 also had a problem in the supply / discharge properties. Had. In addition, the printing original plate of Comparative Example 3 had a problem in that printing wrinkles due to water absorption were generated on 1,000 sheets because the Cobb water absorption was large at 45 minutes.

[0028]

According to the lithographic printing plate precursor of the present invention, there is no generation of printing wrinkles and no scattering of the processing liquid, so that a good printed matter can be obtained, the number of printings can be improved, and the plate feeding / discharging property of the printing press can be improved. And has a remarkable effect of preventing the printing press from being stained by the scattering of the processing liquid and causing no trouble in the printing press.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takao Nakayama, Fuji Photo Film Co., Ltd., 4000 Kawajiri, Yoshida-cho, Haibara-gun, Shizuoka Prefecture (72) Inventor Masayuki Dan 4000, Kawarijiri, Yoshida-cho, Haibara-gun, Shizuoka Fuji Photo Film Co., Ltd. Examiner Toshihiko Nakazawa (56) Reference JP-A-49-127706 (JP, A) JP-A-52-143101 (JP, A) JP-A-58-5293 (JP, A) JP-A-59-58443 (JP) JP, A) JP-A-5-6018 (JP, A) JP-A-5-6036 (JP, A) JP-A-8-87139 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , (DB name) B41N 1/14 G03G 5/14 G03G 5/10 G03G 13/28

Claims (2)

(57) [Claims] 1. A lithographic printing plate precursor having a recording layer on one surface of a support, wherein the Cobb water absorption on the surface on which the recording layer is not formed is 0.02 to 5 g / m ² in 20 seconds. And a lithographic printing plate precursor having a 45-minute value of 0.02 to 15 g / m ² . 2. The water absorption of the Cobb is 0.05 at a value of 20 seconds.
０．２0.2 g / m ² , and the value at 45 minutes is 0.5〜１０10 g / m ^2.
The lithographic printing plate precursor according to claim 1, characterized in that the g / m ^2.