JP2001329191A - Correcting agent for lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a correcting agent which is used for lithographic printing plates, can hydrophilize unnecessary images due to scratches formed on a daily work and stains produced on the non-image portions of the printing plate without deteriorating the printing characteristics of the printing plate, simplifies a correction work, and has high durability on a printing work, and to provide a method for the correction. SOLUTION: A correcting agent useful for correcting images or wounds wrongly formed on the lithographic printing plate, especially wounds formed on the lithographic printing plate in a printing process or in a process for handling the printing plate, wherein image portions are formed on the lithographic printing plate by a UV light- cross-linking method, a printing method using laser beams or an electrophotographic method. The correcting agent comprises a hydrophilic polymer and a solvent as main components, and if necessary, fine hydrophilic inorganic particles. The method for correcting the lithographic printing plate comprises using the correcting agent. Thereby, the wounds and scratches on the printing plate are covered with this composition comprising the hydrophilic polymer and the solvent by the simple treating method comprising coating and then drying, thus giving an image-correcting performance having high printing durability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a lithographic printing plate in which an image portion is formed by an image or a scratch formed on the printing plate by mistake, in particular, an ultraviolet crosslinking system, a laser printing system, and an electrophotographic system. In a printing plate, the present invention relates to a correcting agent for a defective portion generated on a printing plate in a printing process and a handling process of the printing plate.

[0002]

2. Description of the Related Art In general, a correction in printing is caused by an unnecessary image formed on a printing plate due to a mistake in plate making, or by scratching or scraping the plate surface by mistake during handling. In addition, it means that a defective portion on the printing plate, which occurs as a stain during printing due to sensitization of those portions, is hydrophilized with a correcting agent to restore a normal non-image.
In the printing field, this restoring work may be referred to as "erase" or "modification" in addition to "correction". However, the present inventors collectively call it "correction" hereinafter.

Defects on a printing plate requiring correction of an image portion generally include an unnecessary image due to an error in the original at the corrected portion, and a photoengraving method using a film, which is contaminated by foreign matter or exposed due to overlapping of the original. Unnecessary oil-sensitive components caused by the shadow of the image, and residual image components due to poor liquid conditions and scratches generated during handling in a system including a developing step. Therefore, it is necessary to perform an operation of hydrophilizing an unnecessary image or a scratch caused by some reason and originally caused by a portion which should be a non-image portion to become non-image portion with a correcting agent to correct the non-image portion to a normal non-image portion.

[0004] Conventionally, a photosensitive layer having a photosensitive layer on a support which has been subjected to a graining treatment by chemically treating the surface of an aluminum plate mechanically roughened and then electrochemically roughening the surface is used. As a lithographic printing plate modifier obtained by subjecting the lithographic printing plate to image exposure and development processing, forcibly dissolving the three-dimensionally crosslinked or insolubilized image component, hydrofluoric acid, highly soluble A modifier containing an organic solvent and an alkali compound as main components is disclosed. (JP-A-57-97534, JP-A-60-179743, JP-A-2-8855, JP-A-3-192363)

In an offset printing plate produced by a photoengraving method using a silver image as an ink receptivity, a bromide compound or an iodide compound is added to a compound having a mercapto group or a thione group, or cationized guar gum is added. A method of exposing a lower non-image portion by wiping a silver image is disclosed. Further, it is disclosed that addition of inorganic fine particles as an abrasive promotes removal of unnecessary image areas. (JP-A-4-311961, JP-A-7-1
56671) In the electro-toner type photoengraving, although the solvent having a strong dissolving power as described above is not used, the image component is also dissolved by using the solvent and wiped off to expose the non-image expression layer under the non-image expression layer. A method of restoring performance (Japanese Patent Laid-Open No. 6-124007) is disclosed.

However, these methods for dissolving and removing defective portions on a printing plate require time and effort for wiping the plate so that oil-sensitive components do not remain on the plate after dissolving. Further, the organic solvent used for dissolution has a problem that the odor due to the vapor and the influence on the human body when absorbed into the human body must be considered. On the other hand, in the same electronic toner type photoengraving, as an alternative to the dissolution removal method,
A correction method for covering a defective portion on a printing plate with a hydrophilic substance has been proposed.

In JP-A-2-249693, a stannous chelate compound is dissolved in an acidic aqueous solution, applied to the image of the printing plate, and then used to change the pH of the solution during drying. A method of reproducing a non-image portion by depositing and fixing the first chelate compound on an image portion to be imaged is disclosed. Further, Japanese Patent Application Laid-Open No. 8-282145
Discloses a modifier using a combination of zinc oxide, an acrylate-based binder resin and an organic solvent.

[0008] These so-called coating methods have the advantage of eliminating the need for wiping and improving the working efficiency as compared with the above-mentioned dissolving and removing methods, but they still use an organic solvent and an acidic solution, so that environmental problems still remain. Is left. When zinc oxide is used, it is necessary to perform a correction process prior to an etching step performed after an image is formed on a printing plate. This means that it is necessary to perform a correction operation between the printing step and the etching step. As a result, it is difficult to perform both steps continuously, which is inefficient. In addition, when the correction unit newly discovered during printing is processed by stopping the printing press, it is necessary to etch the correction part before restarting printing after correction.
The work becomes complicated. Further, the zinc oxide used has a particle diameter of at least 0.1 micron or 1 micron in average particle diameter.
Micron-sized particles are used, and in order to cover the corrected portion of the toner image using such hydrophilic particles having a coarse particle size, the amount of zinc oxide must be 40% by weight or more based on the total solid content of the correcting agent. The amount is needed. If the weight ratio of the hydrophilic particles is large, uniform dispersion in an organic solvent or a small amount of a binder resin becomes difficult.
Even if the particles are temporarily dispersed, sedimentation of the hydrophilic particles cannot be avoided. In order to stabilize the dispersibility, it is also possible to use an organic solvent or a surfactant according to the characteristics of the hydrophilic particles to be used. There are problems such as impairing the environment. In addition, in the conventional method, since the large hydrophilic particles cover the repaired portion thickly, they are easily peeled off by abrasion during printing, and the printing durability is not satisfactory.

Further, in recent years, digitization of information has been advanced, and in the printing industry, digitalization of manuscripts and simplicity of the conventional complicated plate-making work can be simplified. Computer tow plates (CTP) have begun to be put into practical use. Infrared lasers are used to print the image area. Unlike plate materials that require a conventional development process, instead of exposing the aluminum surface that has been hydrophilized, a plate material composition consisting of an organic compound and an inorganic compound is used. Are plate materials constituting an image portion and a non-image portion, respectively. For example, Japanese Patent Application Laid-Open No. 7-1849 discloses a hydrophilicity containing a microencapsulated lipophilic component, which converts the non-image part into an image part by the heat of an infrared laser irradiated to the non-image part of the plate in the printing process. A phase-change type thermal printing plate comprising a hydrophilic layer made of a binder polymer and a support is disclosed. However, when a conventional correction agent was used for these plate materials, the surface layer composed of the organic compound and the inorganic compound was peeled off, or no correction effect was observed. At present, there is no modification agent suitable for this new type of plate material, and there is a demand for the development of the CTP plate material modification agent which is expected to become mainstream in the future.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to remove unnecessary images due to scratches generated in daily work and to remove non-image portions on a printing plate by printing without impairing printing characteristics. An object of the present invention is to provide a lithographic printing plate modifier which can be made hydrophilic, can be easily modified, and has high durability in printing.

[0011]

Means for Solving the Problems In order to achieve the above object, the present inventors have proposed a method for modifying a solution comprising a composition containing a hydrophilic polymer capable of exhibiting non-image properties and a solvent, or an image portion or a printing plate of a printing plate. By applying it on the wound and drying it, it is possible to easily and easily correct it with high durability. Furthermore, by combining hydrophilic inorganic fine particles with the hydrophilic polymer, their synergistic effects make it a performance agent as a modifier. It has been found that the present invention can be further improved, and the present invention has been accomplished.

The hydrophilic polymer used in the present invention includes poly (meth) acrylates, polyoxyalkylenes,
Polyurethane, epoxy ring-opening addition polymerization, poly (meth) acrylic acid, poly (meth) acrylamide polyester, polyamide, polyamine, polyvinyl, polysaccharide or their composites Carbon containing one or more hydrophilic functional groups such as a carboxyl group, a phosphoric acid group, a sulfonic acid group, an amino group or salts thereof, a hydroxyl group, an amide group, and a polyoxyethylene group.
-A polymer composed of a carbon bond, a polymer composed of a carbon atom or a carbon-carbon bond bonded with at least one or more hetero atoms composed of oxygen, nitrogen, sulfur, and phosphorus, or a carboxyl group or phosphorus Acid group, sulfonic acid group, amino group or a salt thereof, hydroxyl group, amide group, a polymer containing one or more hydrophilic functional groups consisting of polyoxyethylene groups, when directly applied to the printing plate, Non-image areas can be exhibited during printing. Among these, acrylic acid, acrylamide, vinyl sulfonate, allylamine-based polymers and metal chlorides thereof, which have particularly high hydrophilicity, are preferable, and among them, polyacrylic acid is more preferable.
It is a copolymer of polyacrylamide, acrylic acid, and acrylamide, and a metal chloride thereof. These may be used alone or in any mixture.

As the hydrophilic polymer, combinations of different molecular weights and types can be used for adjusting the viscosity. The average molecular weight is 1,000 to 200,000, preferably 10,000 to 100,000 in number average molecular weight. Is suitable. 2
If it exceeds 100,000, the durability will be high, but it will be unfavorable because it will be thickly applied to the correction portion to lower the print quality, and the viscosity of the solution will increase to lower the handleability. Conversely, when the degree of polymerization is low, the durability decreases.

The solid content concentration is preferably in a range where the viscosity of the modifying agent becomes appropriate. Depending on the type and molecular weight of the binder polymer used, 1 to 20% by weight, based on the total modifier, is suitable, preferably 3 to 10% by weight. If the content is 20% by weight or more, the durability is increased, but the coating is applied thickly to lower the print quality, and the viscosity of the solution is increased to lower the handleability, which is not preferable. Conversely, if it is less than 1% by weight, the durability will be reduced. In erasing the image of the present invention, as will be described later, the durability is further improved by mixing hydrophilic inorganic fine particles with the hydrophilic polymer.

The solvent used in the present invention is mainly water, but lower alcohols, ketones, ethers, etc. may be used depending on the solubility of the hydrophilic polymer and the dispersing performance of the hydrophilic inorganic fine particles described later. it can. Water takes a longer time to dry after the correction treatment, but has a practically usable drying time in normal work, and is the best solvent in terms of safety and working environment. When a volatile solvent such as a lower alcohol is used, the drying time can be shortened.

In the modifier of the present invention, hydrophilic inorganic fine particles can be added for the purpose of improving durability during printing. Silica-based inorganic particles, alumina-based inorganic particles, tin-based inorganic particles, natural or artificially synthesized mica-based particles, and the like can be used as the hydrophilic inorganic-based fine particles. The smaller the particle size, the larger the surface area and the higher the hydrogen bonding force between particles, so that the durability can be increased. The practical particle size is from 1 nm to 100 nm, but is preferably 20 nm or less.

The ratio of the hydrophilic inorganic fine particles to the total amount of the solid content is sufficiently 50% by weight or less because the polymer constituting the solid content itself has sufficient hydrophilicity as a modifier. In particular, from 20 weight percent to 5
A range of 0 weight percent is preferred. Even if less than 20% by weight, the modifying effect can be exhibited, but the durability is reduced.
On the other hand, if it exceeds 50% by weight, the dispersibility of the hydrophilic inorganic fine particles in the modifier is remarkably reduced, and the coating treatment becomes difficult, which is not practical.

In using these modifying agents,
It is possible to add a modifying agent, such as a pigment, an organic or inorganic pigment, for coloring, but this is not an essential requirement to achieve the object of the present invention. The correction treatment of the present invention is performed by applying a hydrophilic polymer solution or a mixed solution or dispersion solution of a hydrophilic polymer and hydrophilic inorganic fine particles to the correction portion and drying. No conventional wiping or finish wiping after application is required. Specifically, the adjusted corrector is directly applied to unnecessary images and scratches by brushing and air-dried. The coating liquid coats the processed part and forms a thin film. Printing can be performed if the solvent is no longer visually observed. When printing is started, usually, a pre-hydrophilic treatment, so-called etching treatment, is unnecessary, and printing can be started as it is. Originally, a plate material that does not develop a non-image unless printing is started after etching, such as a printing plate manufactured by a photoengraving method using a silver image as an ink receptive or an electronic toner type photoengraving method The printing plate can be modified before and after the etching step. Performing the correction after the etching step makes the plate making work more efficient, but even if the correction is performed before the etching step, the etching treatment does not cause a chemical change of the correcting agent of the present invention, so that the non-image property is obtained. Has no effect.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to examples, but these examples do not limit the present invention. [Synthesis of hydrophilic polymer (1)] A mixed solution of 30 g of acrylic acid and 270 g of water was heated to 70 ° C in a reactor, and 1 g of AIBN was added thereto as a polymerization initiator and reacted for 5 hours to obtain a hydrophilic binder. Polymer (1) (number average molecular weight by GPC: 5 × 10 ⁴ ) was obtained. [Synthesis of hydrophilic polymer (2)] acrylamide 32
g, 3.5 g of acrylic acid and 315 g of water were heated to 70 ° C. in a reactor, and AIB was used as a polymerization initiator.
1 g of N and reacted for 5 hours to obtain a hydrophilic binder polymer (2) (number average molecular weight by GPC: 1.5 × 1).
0 ⁵ ) was obtained.

[Evaluation Method of Correction Performance] A printing plate on which an image portion having a defective portion is formed is prepared. A part of the non-image area is previously scratched with a cutter blade. next,
The prepared correcting agent is applied to the image defect portion and the place where the image is scratched using a brush, and is allowed to air-dry at room temperature for about 1 to 2 minutes. The plate material thus treated is mounted on a printing press and printing is performed without etching. The correction performance of the processed part, specifically, the presence or absence of an image line generated on a printed matter due to a defective image portion and a scratch is visually evaluated. That is, in the printed matter, the printing result of the image defect portion of the printing plate and the portion corresponding to the scratch in the non-image portion are visually observed, and as the printing is continued, the image due to the image defect portion and the scratch is recognized in the printed material. The number of copies to be printed was recorded. As a comprehensive judgment criterion, at the stage where 10,000 copies were printed, when no image derived from the defective image portion and the scratch portion was found in the printed matter, ◎, one or both images were 3,000 copies or more, 1
If the image was recognized at the stage of printing less than 10,000 copies, ○, if one or both images were recognized at the stage of printing more than 500 copies and less than 3,000 copies, Δ, if either or both images were one copy When it was recognized from the eyes, it was evaluated as x. Depending on the material, the heat-sensitive layer on the plate material surface may be swollen and peeled off by the solvent constituting the modifying agent, and may not be worthy of evaluation. Also, due to the difference in elevation in the processing part due to the viscosity and dispersibility of the modifying agent, if dirt occurs at the boundary between the processing part and the untreated part, it is described as `` dirt '',
The evaluation was x.

[0021]

Example 1 A hydrophilic polymer (1) was used as a modifying agent-1,
Next, the phase-change-type thermal offset printing plate described in Example 1 of JP-A-11-311861 was used to apply 830 nm.
An image was formed with an infrared laser, and a non-image area was intentionally scratched with a cutter. The corrective agent 1 was applied to the image area and the wound area with a thin brush and air-dried. The printing plate obtained in this manner was used as an offset printing machine (G
TO-52 type) and printed 10,000 sheets. The printing room was at 24 ° C. and the humidity was 60%. The printing materials are commercial printing ink (Magenta of Sakata Ink's MS-M) and dampening solution (Astromark 3 of Niken Kagaku Kenkyusho).
2% aqueous solution) and coated paper. The corrected performance results are shown in Table 1.

[0022]

Example 2 Using the hydrophilic polymer (2) as the modifier-2, the printing plate was modified and its modification performance was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0023]

Example 3 5 g of a liquid obtained by uniformly dispersing colloidal silica having a fine particle diameter of 4 to 6 nm (trade name: Snowtex ST-XS (Nissan Chemical Industries)) at 10% by weight in purified water was used. Modifier-3 was prepared by mixing 10 g of the hydrophilic polymer solution of No.1. The solid content in the modifier was 10% by weight, and the colloidal silica concentration in the solid content was 33% by weight. Next, JP-A-11-31
An image was formed on the phase-change-type thermal offset printing plate described in Example 1 of the specification of Example 1861 by an infrared laser of 830 nm, and a non-image portion was scratched by a intentional cutter. A thin brush was applied to the image part and the wound part and air-dried. The printing plate thus obtained was mounted on an offset printing machine (Model GTO-52) manufactured by Heidelberg Co., Ltd., and 10,000 sheets were printed. The printing room was at 24 ° C. and the humidity was 60%. The printing material used was a commercial printing ink, fountain solution and coated paper. Table 1 shows the corrected performance results
It was shown to.

[0024]

Example 4 The polyacrylic acid of Example 3 (AC10M
P) with polyacrylamide (number average molecular weight: 1 × 1)
Except that instead of 0 ⁵⁾ fixes a printing plate and fixes performance evaluation using the modified agent -4 were prepared in the same manner as in Example 3. The results are shown in Table 1.

[0025]

Example 5 A similar formulation was used except that tin oxide fine particles having an average particle diameter of 4 nm (trade name: stannic oxide sol (Yamanaka Chemical)) were used instead of the colloidal silica having a fine particle diameter of Example 3. A modifier was prepared (Modifier-5) and the same experiment was performed. The results are shown in Table 1.

[0026]

Comparative Example 1 A hydrophilic silica powder having an average particle diameter of 1.4 μm (trade name: Siloid 150 (Fuji Silysia Chemical Ltd.) was uniformly dispersed at 40% by weight in purified water, and 10 g of a liquid was used. Was mixed with 2 g of a hydrophilic polymer solution of the formula (I) to prepare a corrective agent 6. The solid content of the corrective agent was 35% by weight, and the concentration of colloidal silica in the solid content was 95% by weight. Thereafter, a modifying agent was prepared according to the same formulation as in Example 3 (Correcting Agent-6), and the same experiment was performed, and the results are shown in Table 1.

[0027]

COMPARATIVE EXAMPLE 2 Instead of modifying agent 1 of Example 1, commercially available P
Japanese Patent Application Laid-Open No. Heisei 1 using a modified pen for S plate (Kesilon Safety, sold by SK Liquid Manufacturing Co., Ltd.)
An image was formed on the phase-change-type thermal offset printing plate described in Example 1 of the specification of 1-311861 by an infrared laser of 830 nm, and a non-image portion was scratched by a deliberate cutter. A coating process was performed. The results are shown in Table 1.

[0028]

Comparative Example 3 Commercially available P was used in place of the modifying agent 1 of Example 1.
Retouch pen for S plate (Erasing stick manufactured by Fuji Film Photo Co., Ltd.)
(Correcting agent-8), and processed in the same manner, and the same printing experiment was performed. The results are shown in Table 1.

[0029]

[Comparative Example 4] Instead of modifying agent 1 of Example 1, a commercially available pen for silver master (manufactured by Niken Chemical Laboratory Co., Ltd.)
(Correcting Agent-9) using the same formula, and the same printing experiment was performed. Table 1 shows the results.
It was shown to.

[0030]

Comparative Example 5 Instead of the corrective agent 1 of Example 1, a commercially available corrective pen for pink master (Master Kesilon, manufactured and sold by Esk Liquid Co., Ltd.) was used (corrective agent-10) and treated with the same formulation. Printing experiment was performed. The results are shown in Table 1.

[0031]

[Table 1]

[0032]

According to the lithographic printing modifier of the present invention, there is provided an image and a non-image scratch for a lithographic printing plate in which a non-image portion is composed of an organic compound and an inorganic compound. The correction agent is effective, and these corrections can be processed by a simple method of coating and drying without etching treatment, thereby improving the efficiency of the printing plate correction operation. In addition, since no toxic organic solvent is used as a solvent, corrective work can be performed without a problem of working environment such as a bad smell.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C09D 201/00 C09D 201/00 F term (reference) 2H114 AA04 AA14 AA22 AA24 BA01 BA03 BA06 BA10 DA15 DA53 DA75 DA79 EA02 EA04 EA06 EA08 FA16 GA28 4J038 BA011 CG031 CG171 CJ131 CR071 DB001 DD001 DF021 DG001 DH001 DJ011 EA011 GA02 GA03 GA06 GA09 GA13 GA14 GA16 HA156 KA06 KA08 KA20 MA08 MA10 MA12 NA06 PB11 PB12

Claims (6)

[Claims] 1. A lithographic printing plate modifier comprising a composition comprising a hydrophilic polymer and a solvent. 2. The lithographic printing plate modifier according to claim 1, which contains hydrophilic inorganic fine particles. 3. The hydrophilic polymer according to claim 1, wherein the hydrophilic polymer contains at least one hydrophilic polymer selected from the group consisting of polyacrylic acid, polyacrylamide, a copolymer of acrylic acid and acrylamide, and metal chlorides thereof. The lithographic printing plate modifier of claim 2. 4. The lithographic printing plate modifier according to claim 1, wherein the solvent is water. 5. The hydrophilic inorganic fine particles have a particle diameter of 20 n.
m or less, and the ratio of the amount of the hydrophilic inorganic fine particles to the total solid content of the hydrophilic polymer and the hydrophilic inorganic fine particles is 20% by weight to 50% by weight. Modifier for lithographic printing plates. 6. A method for correcting a lithographic printing plate using the correcting agent according to claim 1, 2, 3, 4, or 5.