JP2007190789A - Correction fluid for lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a correction fluid which can simply erase a flaw of an unnecessary image defining line part or non-image defining line part, a stain due to the flaw in a lithographic printing plate with the non-image defining line part of a hydrophilic polymer produced by a new CTP (computer to plate) system technique, without passing through complicated processes such as etching, and a correction method. <P>SOLUTION: This correction fluid for the lithographic printing plate contains a water-soluble polymer and a water dispersible hydrophobic polymer in the mass ratio of 10:90 to 90:10. Also the correction method using this correction fluid is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lithographic printing plate, particularly a lithographic printing plate for forming an image area using a hydrophilic / hydrophobic phase change, ink jet, or the like, and a correction liquid for correcting an unnecessary image area or scratch, The present invention relates to a correction method using a correction liquid.

In recent years, so-called CTP (Computer To Plate), in which digital data is directly written on a printing plate by scanning a laser on the printing plate, has become widespread, and at the same time, a technique for easily and inexpensively creating a lithographic printing plate is required. It is coming.
Under the circumstances as described above, a method for preparing a lithographic printing plate using a laser, a thermal head, an ink jet or the like has been proposed. For example, Patent Document 1 and Patent Document 2 propose a technique in which a hydrophilic resin photosensitive layer containing a crosslinked hydrophilic polymer is provided on a support and the hydrophilicity is changed to lipophilicity by laser exposure.
Further, Patent Document 3 and Patent Document 4 propose a technique for producing a lithographic printing plate by supplying hot-melt ink such as wax or fatty acid ester to a hydrophilic printing substrate as an image line portion by an inkjet method. .

Here, when creating an lithographic printing plate by the above method, if an unnecessary image line is formed due to an error in plate making, or if the plate surface is damaged due to an error in handling, etc., the non-image line Correction processing is required to restore the part. As a correction liquid for performing this correction process, for example, Patent Document 5 proposes a correction liquid made of a composition containing a hydrophilic polymer and a solvent. However, this correction liquid has a problem that the hydrophilic polymer is dissolved in the fountain solution used during printing and the effect is not maintained. A correction liquid composed of inorganic fine particles having sol-gel reactivity has also been proposed in Patent Document 6, but this correction liquid is strongly fixed on the surface of the printing plate composed of an inorganic substance, so that the effect is maintained. Since the adhesiveness with the surface of the printing plate containing as a main component is poor, the effect is not maintained, and the end portion of the fixed correction liquid tends to be stepped, which may cause new stains.
Thus, a correction liquid of the type that is applied and fixed on the plate surface and suitable for a lithographic printing plate made of a new type of hydrophilic polymer has not been put into practical use, and development is desired.
International Publication No. 01/83234 Pamphlet JP 2005-14523 A Japanese Patent Laid-Open No. 11-21485 Japanese Patent Laid-Open No. 11-100573 JP 2001-329191 A JP 2001-350274 A

  An object of the present invention is to provide a correction liquid for lithographic printing, which can eliminate unnecessary image areas and scratches on a lithographic printing plate made of a hydrophilic polymer produced by a novel CTP system technology and can be easily corrected. It is to provide.

  The present applicant has made extensive studies in order to solve the above-mentioned problems, and as a correction liquid, found that a mixture of a water-soluble polymer and a water-dispersed hydrophobic polymer in a specific ratio is extremely effective, and the present invention has been developed. completed.

  That is, the present invention is a lithographic printing plate correction solution comprising a water-soluble polymer and a water-dispersed hydrophobic polymer in a mass ratio of 10:90 to 90:10.

  The correction liquid for a lithographic printing plate of the present invention can be easily corrected without going through a complicated process by coating on the printing plate surface to be corrected and drying, and is extremely industrially valuable.

  The correction liquid for a lithographic printing plate of the present invention contains a water-soluble polymer and a water-dispersed hydrophobic polymer, and the ratio of the water-soluble polymer to the water-dispersed hydrophobic polymer is 10:90 to 90:10 mass ratio. It is a feature. Here, the mass ratio in the present invention is the ratio of the number of parts by weight of the non-volatile content remaining after the solvent such as water is completely evaporated from the water-soluble polymer solution and the water-dispersed hydrophobic polymer solution.

  By using the correction liquid containing the water-soluble polymer and the water-dispersed hydrophobic polymer, the correction portion can be given sufficient hydrophilicity and at the same time has good adhesion to the printing plate surface. The correction effect is sustained.

  The water-soluble polymer in the present invention is a polymer having a hydrophilic substituent and showing water solubility. Examples of the hydrophilic substituent include a hydroxyl group, an amide group, a sulfonamide group, an amino group, an oxymethylene group, and oxyethylene. Examples thereof include acidic groups such as carboxyl groups, sulfonic acid groups, and phosphonic acid groups, and alkali metal salts and ammonium salts of these acidic groups. The water-soluble polymer specifically has a solubility in water of preferably 20% by mass or more, more preferably 50% by mass or more, and more preferably 80% by mass or more in water at 25 ° C. Is even more preferable.

  Examples of the water-soluble polymer that can be used in the present invention include natural polymers such as gelatin and starch, semi-synthetic polymers such as carboxymethyl cellulose, and synthetic polymers such as polyvinyl alcohol. It is particularly preferable because of the magnitude of the degree. Examples of the synthetic polymer include, in addition to polyvinyl alcohol, a polymer or copolymer of the above-mentioned vinyl monomer having a hydrophilic substituent, and for example, selected from substituted or unsubstituted (meth) acrylamide and N-vinylpyrrolidone. In addition to polymers mainly composed of one or two or more monomers, polymers such as polyethylene glycol can be mentioned, and it is particularly preferable to use polyvinyl alcohol, polyacrylamide, polyvinyl pyrrolidone or the like.

  The molecular weight of the water-soluble polymer is not particularly limited, but is preferably 1,000 to 1,000,000, particularly 10,000 to 500,000 so that the shape of the film is maintained after coating and drying. A degree is preferred.

The Among the water-soluble polymer can be exemplified by Mitsui Chemicals Co., Ltd. polyacrylamide "Hopuron ^TM" series and Kuraray Co., Ltd. polyvinyl alcohol Commercial examples available "Kuraray Poval ^TM" series and the like. These water-soluble polymers can be used singly or in appropriate combination of two or more.

  The water-dispersed hydrophobic polymer used in the present invention preferably has a property that the hydrophobic polymers dispersed in water are fused together by heat. As used herein, the term “fusion” refers to a phenomenon in which adjacent particulate polymers are united when heated. The use of water-dispersed hydrophobic polymer fine particles having the above properties is preferable because a macro-insolubilized region is formed when the correction liquid is applied and dried.

  More preferably, the water-dispersed hydrophobic polymer has a film-forming property so that the correction liquid application region is formed into one film. The lower the film forming temperature of the polymer fine particles, the easier it is to form a film. Therefore, the minimum film forming temperature of the water-dispersed hydrophobic polymer used in the present invention is 50 ° C. or lower, more preferably 30 ° C. or lower. The use of a water-dispersed hydrophobic polymer having the above properties is preferable because a water-insoluble film is quickly formed on the plate surface when the correction liquid is applied and dried on the plate surface.

  The minimum film-forming temperature in the present invention refers to the minimum temperature at which adjacent particulate polymers are united (fused) to form a film (film-forming) when the dispersion solvent evaporates. The minimum film-forming temperature can be measured by a method based on ISO 2115, and for example, a film-forming temperature (MFT) test apparatus manufactured by Imoto Seisakusho Co., Ltd. can be used.

The particle size of the water-dispersed hydrophobic polymer is not particularly limited, but the smaller the particle size, the easier it is to form a film and the minimum minimum filming temperature can be lowered. Is preferably 500 nm or less, particularly preferably in the range of 10 nm to 150 nm.
The molecular weight of the water-dispersed hydrophobic polymer is not particularly limited, but is 1,000 to 1,000,000, particularly 10,000 to 500,000 as the number average molecular weight so that the shape is maintained as a film after coating and drying. About 000 is preferable.

Examples of the water-dispersed hydrophobic polymer used in the present invention include those obtained by emulsifying a polymer that does not dissolve in water with a surfactant or the like, or water that is partially emulsified by introducing a hydrophilic functional group into the polymer chain. There is no particular limitation as long as it is a dispersed hydrophobic polymer, and any polymer may be used.
The synthetic polymer is mostly hydrophobic and may be any polymer such as a vinyl monomer polymer, polyester, polyurethane, etc., but in particular, it can be obtained as fine particles, and a thermoplastic polymer is preferred. Polyester and the like can be suitably used.

Commercial examples that can be used out of the water dispersed hydrophobic polymer, manufactured by Mitsui Chemicals Co., Ltd. "I Star ^TM" series, manufactured by Toyobo Co., Ltd. "Vylonal ^TM" series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. "Superflex ^TM" A series etc. can be illustrated. The hydrophobic polymer can be used alone or in combination of two or more.

  The correction liquid for lithographic printing according to the present invention needs to contain the water-soluble polymer and the water-dispersed hydrophobic polymer in a ratio of 10:90 to 90:10. Preferably, it is 30: 70-80: 20 mass ratio. In a correction liquid that does not contain a water-soluble polymer that is outside the above range or contains only a small amount, the hydrophilicity of the correction portion is insufficient, and ink adheres and stains occur. On the other hand, a correction liquid that does not contain a water-dispersed hydrophobic polymer or contains only a small amount dissolves in dampening water during printing, so that the correction effect does not last.

  The correction liquid of the present invention can be obtained by mixing the water-soluble polymer and the water-dispersed hydrophobic polymer at a predetermined mass ratio and stirring the mixture at a rotational speed of about 500 to 1500 rpm for about 1 minute. There is no restriction | limiting in particular about the stirrer to be used, A well-known stirrer can be used, For example, a homodisper, a clear mix, a three-one motor etc. can be illustrated as a usable stirrer.

  In the present invention, it is also possible to add water in order to adjust the nonvolatile content of the correction fluid. The amount of water added at this time is preferably added so that the nonvolatile content of the entire correction liquid is in the range of 2 to 50%, more preferably the nonvolatile content is in the range of 10 to 30%. By adding water within the above range, scratches and streaks can be eliminated without excessive non-volatile content causing the polymer to swell in the correction area and reducing image quality, or excessive dilution to reduce the correction effect. This is preferable because it can be erased. Moreover, when adding water, in order to disperse | distribute uniformly, adding during said stirring is preferable.

  In addition to the water-soluble polymer and the water-dispersed hydrophobic polymer, the correction liquid of the present invention is intended to improve the curing speed at the time of coating, to improve the insolubility of the correction portion in water and to maintain the correction effect, etc. It is also preferable to further contain a crosslinking agent. The crosslinking agent may be self-crosslinking or non-self-crosslinking, but it is preferable to use a crosslinking agent having self-crosslinking properties in order to shorten the curing time. As a preferable crosslinking agent having the self-crosslinking property, for example, a compound containing melamine or epoxy can be exemplified.

Of the above-mentioned cross-linking agent, as commercially available examples that can be used, Japan Cytec Industries Co., Ltd. of melamine resin "Cymel ^TM" series, "My coat ^TM" series, Nagase Chemtex Co., Ltd. of the epoxy compound "Denacol ^TM" series Etc. can be illustrated. In addition, said crosslinking agent can be used individually or in combination of 2 or more types.

  If the crosslinking agent is added excessively, the correction liquid may be cured in the container before coating. Therefore, the addition amount of the crosslinking agent is preferably 60 parts by weight or less, more preferably 50 parts by weight or less, when the total amount of the water-soluble polymer and the water-dispersed hydrophobic polymer is 100 parts by weight. In addition, the weight part in the present invention is the number of parts by weight of the nonvolatile content remaining after the solvent is completely volatilized.

The correction liquid of the present invention can contain a surfactant for the purpose of improving hydrophilicity and wettability with respect to the plate surface. As the surfactant, an anionic surfactant, a cationic surfactant, a nonionic surfactant, a leveling agent, a repellency inhibitor, or the like can be used. Examples of commercially available surface-active agents which can be used, made in Japan emulsifier Co., Ltd. "New call ^TM" series, Dai-ichi Kogyo Seiyaku Co., Ltd. "NOIGEN ^TM" series, "NEOCOL ^TM" series, "Epan ^TM" series, " can be exemplified plies surf ^TM "series, manufactured by air Products Japan, Inc." Surfynol ^TM "series, the Seimi Chemical Co., Ltd." Sarfron ^TM "series and the like. The above surfactants can be used alone or in combination of two or more.

  If the above surfactant is added in excess, the drying time of the correction liquid during application will be long, or the correction portion will be easily eluted in the dampening water, and the correction effect will not be sustained. Therefore, the amount of the surfactant to be added is preferably within the range of 0.001 to 7.5 parts by weight when the total amount of the water-soluble polymer and the water-dispersed hydrophobic polymer is 100 parts by weight.

  The correction liquid of the present invention is effective for any planographic printing plate other than the conventional PS plate, for example, a lithographic printing plate in which an image area is formed by a hydrophilic / hydrophobic phase change, an ink jet method or the like. This is effective for correction of a lithographic printing plate formed from a composition as described in Kaikai 2005-14523.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.
[Modified performance evaluation method]
As the printing plate, the plate described in Example 1 of JP-A-2005-14523 was used. The non-image area of this plate is scratched with a cutter in advance. Next, the prepared correction liquid was applied to a part of the image area and the scratch using a brush and dried with a dryer for 1 minute. This corrected plate is set on a sprint 26 manufactured by Komori Corporation, an offset printing machine, and a 2% aqueous solution of H liquid astromark 3 from Nikken Chemical Research Co., Ltd. as a dampening solution, and Dainippon Ink & Chemicals, Inc. as ink. use varius ^G TM -M manufactured by (Corporation) were printed 1,000 sheets at a printing speed 8000Rph.

Example 1
Correction fluid 1 having the following composition was prepared.
Polyvinyl alcohol (Kuraray Co., Ltd., “Kuraray Poval ^™ ” 20% aqueous solution of PVA117) 67 parts Water-dispersed urethane resin (Mitsui Chemicals Co., Ltd., Olester ^™ UD350: minimum film forming temperature 0 ° C. or lower: solid content 40 %: Average particle size 35 nm) 33 parts When the above evaluation method was carried out using correction liquid 1, the image area and scratches were completely erased on the 1000th sheet.

Example 2
Evaluation was conducted in the same manner as in Example 1 except that the water-soluble polymer in Example 1 was replaced with polyacrylamide (Maiho Chemical Co., Ltd., HOPRON ^™ 520B: 20% aqueous solution). Had been erased. On the 1000th sheet, ink was slightly attached to the image area, but the scratches were completely erased.

Example 3
Evaluation was conducted in the same manner as in Example 1 except that the water-soluble polymer of Example 1 was replaced with polyvinyl pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd., 20% aqueous solution of K30). Had been erased. On the 1000th sheet, ink was slightly attached to the image area, but the scratches were completely erased.

Example 4
Evaluation was performed in the same manner as in Example 3 except that the blending ratio of Example 3 was changed to polyacrylamide: water-dispersed urethane resin = 50 parts: 50 parts, and the image area and scratches were completely erased on the 1000th sheet. .

Example 5
Correction fluid 5 having the following composition was prepared.
30 parts of polyacrylamide (Mitsui Chemicals, Hoplon ^TM 520B: 20% aqueous solution) Water-dispersed polyester resin (Toyobo Co., Ltd., Vylonal ^TM MD1480: minimum film-forming temperature 20 ° C .: solid content 25%: average grain (Diameter 90 nm) 70 parts When the correction liquid 5 was used and the same operation as in Example 3, the image area and scratches were completely erased on the 1000th sheet.

Example 6
Correction fluid 6 having the following composition was prepared.
Polyacrylamide (Mitsui Chemicals Co., Ltd., Hoplon ^TM 520B: solid content 20%) 53 parts water-dispersed urethane resin (Mitsui Chemicals Co., Ltd., Olester ^™ UD350: Minimum film forming temperature 0 ° C. or less: Solid content 40% : Average particle size 35 nm) 47 parts melamine resin (Cymel ^TM 385 manufactured by Nippon Cytec Industries, Ltd., 33 parts solids) 33 parts Evaluation was performed using the above-mentioned evaluation method, and the image area and scratches were observed on the 1000th sheet. It was completely erased, and the image area and scratches were completely erased even at the 5000th sheet.

Comparative Example 1
Evaluation was performed in the same manner as in Example 1 except that the water-dispersed urethane resin of Example 1 was not used. As a result, the ink was slightly attached to the image area on the 100th sheet, and the image area and scratches were clearly visible on the 200th sheet. Ink adhered.

Comparative Example 2
When the evaluation was performed in the same manner as in Example 1 except that the polyvinyl alcohol of Example 1 was not used, the entire portion where the correction liquid was applied was soiled.

Comparative Example 3
Evaluation was conducted in the same manner as in Example 3 except that the blending ratio of Example 3 was changed to polyacrylamide: water-dispersed urethane resin = 5 parts: 95 parts, and the ink was attached to the image area at the first sheet. The ink adhered to the edge of the portion where the correction liquid was applied, and the ink was clearly adhered to the image area and the scratches on the 200th sheet.

Comparative Example 4
Evaluation was performed in the same manner as in Example 3 except that the blending ratio of Example 3 was changed to polyacrylamide: water-dispersed urethane resin = 95 parts: 5 parts. As a result, the image area and scratches were completely erased on the first sheet. However, in the 100th sheet, the ink was slightly adhered to the image line portion, and in the 200th sheet, the image line portion and the scratch were clearly adhered.

○: No ink adheres to the corrected area. Δ: Lightly adheres to the corrected area. X: The ink clearly adheres to the corrected area.

  The correction of the present invention can erase scratches on the image area and non-image area for a lithographic printing plate in which the non-image area where a valid correction solution has not existed is made of a hydrophilic polymer. However, a complicated process such as an etching process is not required, and the efficiency of the correction work can be improved.

Claims (5)

A lithographic solution for correction by coating and fixing on a lithographic printing plate surface, wherein the correction solution contains a water-soluble polymer and a water-dispersed hydrophobic polymer in a ratio of 10:90 to 90:10. Correction fluid for printing plates. The correction liquid for lithographic printing plates according to claim 1, wherein the water-dispersed hydrophobic polymer is polymer fine particles that are fused by heat. The correction liquid for lithographic printing plates according to claim 1 or 2, wherein the minimum film-forming temperature of the water-dispersed hydrophobic polymer is 50 ° C or lower. The lithographic printing plate correction liquid according to any one of claims 1 to 3, wherein the correction liquid further contains a crosslinking agent. A correction method for a lithographic printing plate, wherein the correction liquid according to claim 1 is used.