JPH0743533B2 - Positive photosensitive lithographic printing plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a positive-working photosensitive lithographic printing plate, and more specifically, to a positive-working photosensitive aluminum support which has been previously roughened and anodized. Formed by coating a layer of the composition,
The present invention relates to a positive-working photosensitive lithographic printing plate having faithful halftone dot reproducibility with respect to an original image film, that is, having a small dot reduction effect.

[Prior Art] A positive photosensitive lithographic printing plate (hereinafter referred to as a "positive PS plate") in which a layer of a positive photosensitive resin composition is provided on an aluminum support that has been grained in advance and anodized. When exposed through a positive transparent original image, the solubility in a developing solution in the exposed portion increases, and when this is treated with a developing solution of a positive photosensitive resin composition, the exposed portion of the photosensitive layer is removed and It is known that the hydrophilic surface of the is exposed, thus forming a positive image. When the lithographic printing plate thus obtained is used, printing causes thickening of halftone dots. In order to prevent this, at the time of plate making, the exposure is sufficiently performed to make the halftone dots on the plate thin, and the center line surface roughness as disclosed in Japanese Patent Publication No. 59-26479 is used. (Ha) is 0.6-1.2μ, surface reflectance is
I used to use aluminum support which is more than 50%. However, in recent years, in the production of an original film, the use of a scanner has made it possible to reduce the dot area on the film, and it is no longer necessary to reduce the dot area. Further, in a lith film having a low solid density, the minimum halftone dot disappears when the dots are reduced. Further, when the exposure amount is reduced to produce the minimum halftone dot, light is scattered at the edge portion of the film, so an unnecessary image of that portion is formed on the plate, and after development,
It becomes necessary to erase with an erasing liquid. For this reason, conventionally, a plate with a large reduction in the number of dots has been desired, but in recent years, a plate with more faithful halftone dot reproducibility has been desired.

Japanese Unexamined Patent Publication (Kokai) No. 57-118238 discloses a method in which a compound of the general formula [I] is added to a photosensitive layer to enhance sensitivity and faithfully reproduce tone, and this compound is added. In the method, the effect of making the tone reproducibility faithful is not so great, and further, there is a drawback that the development acceptability is deteriorated.

General formula [I] (In the general formula _{[I], R 1, R 2, R} 3 are each a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a substituted aryl group, an acyl group, a halogen group, .R ₃ showing a nitro group or a hydroxyl group, Can be the same or different.) U.S. Pat. No. 3,891,516 is obtained by graining an aluminum plate with a moist abrasive such as a pumice slurry and then immediately anodizing in sulfuric acid. A positive PS plate using an aluminum support with a dark steel gray shaded surface has been proposed. However, since the surface of the aluminum support of this positive PS plate has a low reflectance from the ultraviolet region to the visible light region, it is difficult to see the print-out image obtained during image exposure, and it is formed after development. The contrast between the oil-sensitive image thus formed and the surface of the support is low, so-called plate inspection is inferior, and there is a problem in that correction work such as erasing and writing is hindered.

On the other hand, a negative photosensitive lithographic printing plate (hereinafter referred to as "negative PS plate") in which a layer of a negative photosensitive resin composition is provided on a support having a hydrophilic surface is a negative transparent original image. When exposed through, the photosensitive layer is cured in the exposed portion, or the adhesive force with the support is changed, and when this is treated with a developer of a negative photosensitive resin composition, the unexposed portion of the photosensitive layer is removed. It is known that the hydrophilic surface of the support is exposed, thus forming an oil-sensitive positive image composed of the cured negative photosensitive resin composition on the support. In this negative PS plate, increasing the exposure time depends on changes in development processing conditions (for example, development time) because the exposed portion of the photosensitive layer is hardened more and the adhesive force with the support is further improved. This is advantageous in that the change in image strength is reduced, a stable image is secured, and the strength of the image is increased, so that a lithographic printing plate having high printing durability can be obtained. On the other hand, however, increasing the exposure time has the serious drawback that the effects of halation and irritation appear, the images become fat, the resolution decreases, and printed matter with good tone reproduction cannot be obtained. . Such drawbacks are particularly noticeable when a support that scatters light well, such as a roughened aluminum support or paper support, is used.
It has been known that this tendency becomes even greater when anodized aluminum plate is further roughened.

As a negative PS plate that eliminates such drawbacks, for example, in the above-mentioned U.S. Pat.No. 3,891,516, an aluminum plate is grained with a wet abrasive such as a slurry of pumice, and then immediately anodized in sulfuric acid. A negative PS plate has been proposed which uses an aluminum support having a dark steel gray shaded surface obtained thereby. However, as with the case of the positive PS plate, the surface of the aluminum support of this negative PS plate also has a low reflectance from the ultraviolet region to the visible light region, so that it can be obtained during image exposure. In addition to making the printed-out image difficult to see, the contrast between the oil-sensitive image formed after development and the surface of the support is low, resulting in poor so-called plate inspection performance, and a new problem of hindering the correction work such as erasing and writing. There was a drawback that caused.

On the other hand, U.S. Pat.No. 3,458,311 discloses a negative PS plate having a photosensitive layer made of a photopolymerizable composition on an aluminum support undercoated with a dibasic acid dye after roughening and hydrophilizing treatment. However, the negative PS plate in which a negative photosensitive resin composition containing a photosensitive diazo resin is provided on the aluminum support, the sensitivity is significantly lowered on the surface of the aluminum support, and It was found that it could not be put to practical use at all due to the insufficient binding force of.

Further, in U.S. Pat.No. 3,280,734, an aluminum plate is anodized, and immediately thereafter, it is described on U.S. Pat. Thus, a negative PS plate provided with a diazo resin is disclosed, further U.S. Pat.No. 4,277,555 anodizes an aluminum plate, and then treats it with an aqueous sodium silicate solution,
Although a negative PS plate provided with a diazo resin on an aluminum support colored with a basic dye is disclosed, all of these negative PS plates are for the purpose of visualizing an oil-sensitive image obtained after development. The surface of the support is colored,
It is not intended to improve tone reproducibility as described above. This means that the photosensitive layer is composed of diazo resin only, and the coating amount is extremely thin, about 10 to 30 mg / m ^2, and in the case of such a thin photosensitive layer, halation and irradiation are substantially eliminated. It is also supported by the fact that the problem of deterioration in tone reproducibility because it does not occur is essentially not inherent. Further, a negative type photosensitive resin composition containing a diazo resin is provided on an aluminum support colored an aluminum plate hydrophilically treated with a moldant dye or a basic dye specifically exemplified in these patents. It has been found that the PS plate of the type has a serious drawback that, when it is subjected to a plate making process after being stored for a long time, a residual color due to a dye is apt to be generated in a non-image area and a background stain is generated on a printed matter.

As described above, many attempts have been made to improve tone reproducibility in the negative PS version, but all have serious drawbacks.

Further, in the positive PS plate, an attempt to faithfully reproduce the tone reproducibility has been made by the above-mentioned JP-A-57-118238 and U.S. Pat.
Nothing has been done other than 3,891,516.

[Object of the Invention]

Therefore, an object of the present invention is to provide a positive PS plate in which tone reproduction is faithful and reproduction of minimum halftone dots is good.

Another object of the present invention is to provide a positive PS plate in which tone reproducibility is faithful and film edge marks are less likely to occur.

[Structure of Invention]

The present inventors have completed the present invention as a result of various studies in order to achieve the above object.

According to the present invention, an aluminum plate surface which has been roughened and then anodized has an absorption intensity at 400 nm of 1 after exposure.
A positive-working photosensitive lithographic printing plate comprising a positive-working photosensitive composition layer coated so as to have a thickness of 0.06 to 0.29 per μm.

The positive photosensitive composition usually contains an o-quinonediazide compound. The photosensitive absorption band of this o-quinonediazide compound is 350 to 450 nm, and photodecomposition is efficient at 400 nm in particular. Therefore, increasing the absorption intensity at 400 nm lowers the sensitivity of the photosensitive composition. However,
The positive PS plate of the present invention using a photosensitive composition having an absorption intensity of 0.06 or more per 1 μm after exposure at 400 nm is the same plate as the conventional positive PS plate, although the sensitivity is lower than that of the conventional positive PS plate. When the exposure amount is adjusted so as to have the upper halftone dot area, film edge marks are generated in the conventional PS plate, whereas film edge marks are not generated in the PS plate of the present invention. When the exposure amount is adjusted so that film edge marks are not generated, the PS plate of the present invention exhibits more faithful tone reproduction than the conventional PS plate.

Hereinafter, the method for producing the planographic printing plate according to the invention will be described in detail in order.

Aluminum plates used in the present invention include pure aluminum and aluminum alloy plates. Various aluminum alloys can be used, such as silicon,
Alloys of aluminum with metals such as copper, manganese, magnesium, chromium, zinc, lead, bismuth, and nickel are used. These compositions include some iron and titanium, as well as other negligible amounts of impurities.

Prior to graining the aluminum plate, if necessary, the surface rolling oil may be removed and a surface of the aluminum plate may be pretreated in order to expose a clean aluminum surface. For the former, solvents such as trichlene and surfactants are used. For the latter, a method using an alkali etching agent such as sodium hydroxide or potassium hydroxide is widely used.

As the graining method that can be used in the present invention, any of mechanical, chemical and electrochemical methods is effective. Mechanical methods include a ball polishing method, a blast polishing method, and a brush polishing method in which a water-dispersed slurry of an abrasive such as pumice is rubbed with a nylon brush.A chemical method includes JP-A-55-31187. A method of immersing in a saturated aqueous solution of an aluminum salt of a mineral acid as described in the publication is suitable, and an electrochemical method is a method of alternating current electrolysis in an acidic electrolytic solution such as hydrochloric acid, nitric acid or a combination thereof. Is preferred. Among such roughening methods, the method disclosed in
The surface-roughening method combining mechanical surface-roughening and electrochemical surface-roughening as described in JP-A-55-137993 is preferable because the adhesion of the oil-sensitive image to the support is strong.

The graining by the above-mentioned method is preferably performed in such a range that the center line surface roughness (Ha) of the surface of the aluminum plate is 0.3 to 1.0 μ.

The grained aluminum plate is washed with water and chemically etched as required.

The etching treatment liquid used in the present invention is usually selected from an aqueous solution of a base or an acid which dissolves aluminum.
In this case, the etched surface must not form a coating different from aluminum derived from the etching solution component. Examples of preferable etching agents include sodium hydroxide, potassium hydroxide, trisodium phosphate, disodium phosphate, tripotassium phosphate, dipotassium phosphate as basic substances; sulfuric acid, persulfuric acid as acidic substances. , Phosphoric acid, hydrochloric acid, and salts thereof, but salts having a lower ionization tendency than aluminum, for example, salts of zinc, chromium, cobalt, nickel, copper, etc. are not preferable because they form an unnecessary film on the etched surface.

Most preferably, these etching agents are used so that the dissolution rate of the aluminum or alloy to be used will be 0.3 to 40 g / m ² per 1 minute of immersion time when the working concentration and temperature are set. It may be above or below.

Etching is carried out by immersing an aluminum plate in the above etching solution, applying an etching solution to the aluminum plate, or the like, and preferably treated so that the etching amount is in the range of 0.5 to 10 g / m ² .

As the above-mentioned etching agent, it is desirable to use an aqueous solution of a base because of its high etching rate. In this case, smut is generated, and thus desmutting is usually performed. As the acid used in the desmutting treatment, nitric acid, sulfuric acid, phosphoric acid, chromic acid, hydrofluoric acid, hydrofluoric acid or the like is used.

The etched aluminum plate is optionally washed with water and then anodized. Anodization can be performed by a method conventionally used in this field.
Specifically, when a direct current or an alternating current is applied to aluminum in sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, etc., or an aqueous solution or a non-aqueous solution containing a combination of two or more thereof, the aluminum support An anodized film can be formed on the body surface.

The treatment conditions for anodization cannot be unconditionally determined because they vary depending on the electrolyte used, but generally the concentration of the electrolyte is 1 to 80% by weight, the liquid temperature is 5 to 70 ° C, and the current density is 0.5 to 6
A range of 0 amperes / dm ² , a voltage of 1 to 100 V and an electrolysis time of 30 seconds to 50 minutes is suitable.

Among these anodizing treatments, British Patent No. 1,41
The method of anodic oxidation at high current density in sulfuric acid described in US Pat. No. 2,768 and the method of anodizing phosphoric acid as an electrolytic bath described in US Pat. No. 3,511,661 are preferable.

The aluminum plate that has been roughened as described above and further anodized may be subjected to a hydrophilic treatment if necessary, and preferred examples thereof are U.S. Patents 2,714,066 and 3,18.
Alkali metal silicates such as those disclosed in 1,461, such as aqueous sodium silicate or JP-B-36-22063.
There is a method of treatment with potassium fluorozirconate disclosed in U.S. Pat. No. 4,096,037 and polyvinylphosphonic acid as disclosed in U.S. Pat. No. 4,153,461.

A layer of the positive working photosensitive composition is provided on the thus treated aluminum support. The positive photosensitive composition used in the present invention is preferably a composition comprising an o-quinonediazide compound and a phenolic resin.

The o-quinonediazide compound used in the present invention is a compound having at least one o-quinonediazide group, which increases the alkali solubility by active irradiation, and examples of such compounds include compounds having extremely various structures. be able to. An example of such an o-quinonediazide compound is "Light-Sensitive Systems" by J. Coser (John Wheelie & Sons: Joh).
n Wiley & Sons, Inc.) pages 339-352. Particularly preferred are sulfonic acid esters or sulfonamides of o-quinonediazide reacted with various aromatic polyhydroxy compounds or amines. Among such o-quinonediazide compounds, an ester of benzoquinone (1,2) -diazide sulfonic acid chloride and polyhydroxyphenyl or naphthoquinone- (1,2) as described in JP-B-43-28403. Most preferred is etching of) -diazide sulfonic acid chloride with pyrogallol-acetone resin. Other suitable o-quinonediazide compounds include benzoquinone- (1,2) -diazidosulfonic acid chloride or naphthoquinone- (1,2) described in U.S. Pat.Nos. 3,046,120 and 3,188,210. There are esters of diazide sulfonic acid chloride and phenol formaldehyde resins.
Other useful o-quinonediazide compounds for use in the present invention include those reported and known in numerous patents. For example, JP-A-47-5303, JP-A-48-63802, JP-A-48-63803, JP-A-48-96575, and JP-A-48-96575.
49-38701, 48-3354, 41-11222, 45
-9610, Sho 49-17481, U.S. Pat.No. 2,797,213
No. 3, No. 3,454,400, No. 3,544,323, No. 3,573,91
No. 7, No. 3,674,495, No. 3,785,825, British Patent No.
1,227,602, 1,251,345, 1,267,005, 1,329,888, 1,330,932, German Patent 854,89
Those described in each specification such as No. 0 can be mentioned.

The phenol resin used in the present invention refers to a novolak resin and a polyvinyl compound having a phenolic hydroxyl group, and the novolak resin is obtained by condensing phenols and formaldehydes in the presence of an acidic catalyst, and other xylenes. Also includes those modified with mesitylene. Typical examples of such novolac resin include phenol-formaldehyde resin, cresol-formaldehyde resin, p-tert-butylphenol-formaldehyde resin, and phenol-modified xylene resin.

Examples of polyvinyl compounds having a phenolic hydroxyl group include polyhydroxystyrene polymers and copolymers thereof, halogenated polyhydroxystyrene polymers and copolymers.

The amount of o-quinonediazide compound in the total photosensitive composition was 10
-50% by weight, more preferably 20-40% by weight. And the compounding amount of the phenolic resin is 45 in the total photosensitive composition.
˜79 wt%, preferably 50-70 wt%.

The positive-working photosensitive composition used in the present invention contains 40
A compound is added so that the absorption intensity at 0 nm is 0.06 to 0.29, preferably 0.08 to 0.29, and more preferably 0.10 to 0.29 per 1 μm. Such compounds have absorption bands in the UV range of especially o-quinonediazide of 350-4.
Any ultraviolet absorber having an absorption at 50 nm may be used. For example, yellow oil-soluble dye Aizen Spilon Yellow GRH [Hodogaya Chemical Co., Ltd.] Diaresin Yellow
F [Mitsubishi Kasei Kogyo Co., Ltd.], Orient Oil Yellow (Orient Oil Yellow) 3G [Orient Chemical Co., Ltd.], Bali Fast Yellow (Vali Fast Yell)
ow) # 3104 [Orient Chemical Industry Co., Ltd.], Vali Fast Yellow # 3105 [Orient Chemical Industry Co., Ltd.], Soldan Yel
low) GRN (Chugai Kasei Co., Ltd.), Primoflavine 8G (Sumitomo Chemical Co., Ltd.) as a yellow basic dye, Aizen Auramine 0-
125 [Hodogaya Chemical Co., Ltd.], Eisen Catillon
Yellow (Aizen Cathilon Yellow) 3GLH (Hodogaya Chemical Co., Ltd.), Aizen Cathilon Brilliant Yellow 5GLH (Hodogaya Chemical Co., Ltd.), Aizen Cathilon Yellow (Aizen Cathilon Yellow) ) GLH [Hodogaya Chemical Co., Ltd.], Sumiacryl Yello
w) 3R [Sumitomo Chemical Co., Ltd.], Diacryl Supra Brilliant Yellow
Yellow) 2GL (Mitsubishi Kasei Co., Ltd.), diacryl
Diacryl Supra Yellow 5RL [Mitsubishi Kasei Kogyo Co., Ltd., Aizen Catillon Yellow (Aize
n Cathilon Yellow) 3RLH [Hodogaya Chemical Co., Ltd.] and the like. The amount of such an ultraviolet absorber used is such that the absorption intensity at 400 nm after exposure is 0.06 to 0.29, and generally 0.3 to 15% by weight in the total photosensitive composition is suitable.

Further, a combination of compounds having a low absorption intensity before exposure and an increased absorption intensity at 400 nm after exposure, for example, o-naphthoquinonediazide-4-sulfonic acid halogenide described in JP-A-50-36209, Trihalomethyl-2-pyrone and trihalomethyltriazine described in JP-A-53-36223, various o-naphthoquinonediazide compounds described in JP-A-55-62444, and JP-A-55-77742. 2-trihalomethyl-5-aryl-1,3,4
A combination of a compound such as an oxadiazole compound that generates an acidic substance upon exposure to light and a PH indicator or dye that interacts with the acidic substance to increase absorption at 400 nm can also be used. An example of this is one that turns yellow on the acidic side, such as bromophenol
Examples thereof include blue (Bromophenol Blue), tetrabromophenol blue (Tetorabromophenol Blue), bromochlorophenol blue (Bromochlorophenol Blue), and bromocresol green (Bromocresol Green).

In any of the above methods, the absorption intensity at 400 nm is 0.06 to 0.2 per 1 μm after the exposure, that is, at the exposure amount higher than the minimum exposure amount at which the non-image area is eluted with the developing solution.
It should be in the range of 9, preferably 0.08 to 0.2.
9, more preferably 0.10 to 0.29. Generally, a photosensitive layer having an exposure amount required to obtain a desired absorption intensity up to about 3 times the minimum exposure amount is useful, and a smaller exposure amount required to obtain a desired absorption intensity is more preferable. It is preferable because it gives faithful tone reproducibility.

In the present specification, "absorption strength" means that a transparent support having a thickness of 100 µm is coated with a photosensitive composition in a dry weight of 2.5 g / m ² and dried, and then an exposure amount of at least 10 times the minimum exposure amount is given. After
4 shows the absorption intensity at 400 nm measured with a transparent support on which a photosensitive composition was not applied as a control. The thickness of the photosensitive composition was measured as 1 μm = 1 g / m ² for convenience.

The positive photosensitive composition used in the present invention includes a dye for image identification, for example, crystal violet, methyl violet, malachite green, fuchsin, parafuchsin, Victoria Blue BH (Hodogaya Chemical Co., Ltd.).
], Victoria Pure Blue BOH [Hodogaya Chemical Co., Ltd.], Oil Blue # 603 [Orient Chemical Co., Ltd.], Oil Pink # 312 [Orient Chemical Co., Ltd.], Oil Red 5B (manufactured by Orient Chemical Industry Co., Ltd.), oil green # 502 (manufactured by Orient Chemical Industry Co., Ltd.), etc. are used in an amount of 0.3 to 1 for all photosensitive compositions.
You may add about 5% by weight. Furthermore, compounds which interact with these dyes to generate photodecomposition products that change the color tone, such as o-naphthoquinonediazide-4-sulfonic acid halogenide described in JP-A-50-36209,
JP-A-53-36223, trihalomethyl-2-pyrone and trihalomethyltriazine, various o-naphthoquinonediazide compounds described in JP-A-55-62444, JP-A-55
The 2-trihalomethyl-5-aryl-1,3,4-oxadiazole compound described in JP-A-77742 can be added. These compounds can be used alone or as a mixture, and the addition amount is preferably 0.3 to 15% by weight.

The acid anhydride compound described in JP-A-55-80022 can be added to the composition of the present invention to increase the sensitivity. Others In the composition of the present invention, a filler, for improving the coating properties, for example, cellulose alkyl ethers, ethylene oxide-based surfactants (3M FC-430, FC-431),
Various additives such as dibutyl phthalate, butyl glycolate, tricresyl phosphate, dioctyl adipate, and other plasticizers may be added to improve the physical properties of the coating film according to various purposes. By adding a filler, not only the physical properties of the coating film can be further improved, but also the surface of the photosensitive layer can be matted, the vacuum adhesion during image printing is improved, and so-called blurring is prevented. can do. Examples of such fillers include talc powder, glass powder, clay, starch, wheat flour, corn flour, and Teflon powder.

The photosensitive composition is dissolved or dispersed in a solvent that dissolves or disperses the above components, and is applied onto a support. Examples of the solvent used here include ethylene dichloride, cyclohexanone, methyl ethyl ketone, methyl cellosolve acetate, propylene glycol monomethyl ether acetate, n-butyl propionate, 3,3-dimethylbutyl acetate, 2-ethoxytetrahydropyran, ethylene glycol monomono. -T-butyl ether,
Solvents that dissolve or disperse the photosensitive composition, such as toluene, ethyl acetate, 2-heptanone, and 2,4-pentanedione, can be used alone or in combination.

And, the concentration of the solid content in the coating liquid is appropriately 2 to 50% by weight. In addition, the coating amount is generally solid
A suitable amount is 0.5 to 3.0 g / m ² . As the coating amount decreases, the photosensitivity increases, but the physical properties of the photosensitive film such as mechanical strength, chemical strength, development tolerance, and oil sensitivity deteriorate.

Examples of the developer for the positive photosensitive composition of the present invention include sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium triphosphate, dibasic sodium phosphate, and tertiary phosphorus. Aqueous solutions of inorganic alkaline agents such as ammonium acid phosphate, dibasic ammonium phosphate, sodium metasilicate, sodium bicarbonate, aqueous ammonia, etc. and organic alkaline agents such as monoethanolamine or diethanolamine are suitable, and their concentrations are 0.1-10% by weight, preferably 0.5-5
It is added so as to become the weight%.

If necessary, an organic solvent such as a surfactant or alcohol can be added to the alkaline aqueous solution.

〔Example〕

Next, the present invention will be described in more detail with reference to examples.
In addition, all "%" in the following examples are% by weight unless otherwise specified.

Examples 1 to 4 and Comparative Examples A and B An aluminum plate (material 1050) having a thickness of 0.3 mm was washed with trichlene and degreased, and then its surface was grained using a nylon brush and a 400 mesh pumisu water suspension. Washed well with water. This plate is immersed in a 25% aqueous solution of sodium hydroxide at 45 ° C for 9 seconds for etching and washing with water.
It was immersed in 20% nitric acid for 20 seconds and washed with water. At this time, the etching amount of the grained surface was about 8 g / m ² . Next, this plate was provided with a DC anodic oxide coating of 3 g / m ² at a current density of 15 A / dm ² using 7% sulfuric acid as an electrolytic solution, and then washed with water and dried. The following positive type photosensitive solution was applied to this aluminum plate and dried to obtain positive type planographic printing plates (Examples) 1 to 4 and (Comparative example), respectively.
A and B were obtained. The coating amount of the photosensitive layer after drying is 2.5 g / m
^{Was 2} .

Photosensitive solution Ester compound of naphthoquinone-1,2-diazide-5-sulfonyl chloride and pyrogallol-acetate resin (Note) ………… 0.90g Cresol-formaldehyde resin ………… 2.00g t-butylphenol-formaldehyde resin (note)
…………… 0.05g Aizen Spilon Yello
w) GRH [Hodogaya Chemical Co., Ltd.] …………… (Note)
Naphthoquinone-1,2-diazide-4-sulfonic acid chloride ………… 0.03g Oil Blue # 603 (Orient Chemical Industry Co., Ltd.) ……
………… 0.05 g Methyl ethyl ketone ……………… 8 g Methyl cellosolve acetate ……………… 15 g Note US Pat. No. 3,635,709, described in Example 1 Note US Patent No. 4,123,279 What is described Note Example 1 …………… 0.04g 2 ……………… 0.08g 3 ………… 0.12g 4 ……… 0.16g Comparative Example A …………… No addition B ……………… 0.02g After exposing these positive type photosensitive printing plates with a 3KW metal halide lamp from a distance of 70cm, DP-8 (trade name: manufactured by Fuji Photo Film Co., Ltd.) was diluted 8 times. According to the above, automatic development (800 U: by Fuji Photo Film Co., Ltd. automatic developing machine) was performed at 25 ° C. for 40 seconds. There are two types of suitable exposure dose at this time,
That is, the exposure amount at which the film edge mark disappears completely (at this time, the gray scale with a density difference of 0.15 (made by Fuji Photo Film Co., Ltd.) makes 5 steps completely clear), and the exposure when the tone reproduction is combined. The amount (that is, the point at which the K value (line width: μm) of the fogler film reproduces 15). The lower the K value is reproduced, the more faithful the tone reproducibility is. Also, after coating and drying each photosensitive composition on a 100 μm-thick transparent support, give a sufficient exposure amount (the point where 7 steps are completely clear in gray scale), and then use the Hitachi's own spectrophotometric value. Absorption intensity at 400 nm was measured with a total of 340 type using a transparent support on which the photosensitive composition was not applied as a control.

The results are shown in Table 1.

As can be seen from Table 1, in Examples 1 to 4 in which the absorption intensity after exposure is 0.06 or more, compared with the conventional positive PS plate comparative example A (absorption intensity 0.04), in the exposure amount at which the film edge mark does not occur. , Showing more faithful tone reproduction. That is, a thinner K value is reproduced. Further, since the K value is reproduced even after sufficient exposure, it is possible to completely prevent the occurrence of film edge marks even in the case of a film in which film edge marks are more likely to occur than the film used in this experiment. On the other hand, in Comparative Example B in which the ultraviolet absorber was added in the same manner, the absorption intensity after exposure was 0.05.
Since it is 5, the result is insufficient.

Example 5 In Examples 1 to 4, Orient Oil Yellow (Orient Oil Yellow) 3G (manufactured by Orient Chemical Co., Ltd.) (0.08 g) was used instead of Aizen Spilon Yellow GHR. However, the absorption intensity after exposure was 0.07. The result is that the tone reproduction of this positive PS version is also faithful.

Example 6 In Examples 1 to 4, the Aizen Spilon Yellow GRH was changed to Aizen Cathilon Yellow GLH [Hodogaya Chemical Co., Ltd.] (0.04 g). The absorption intensity after exposure was 0.08, and the tone reproducibility was faithful and good results were obtained.

〔The invention's effect〕

The positive-working photosensitive lithographic printing plate of the present invention has an excellent effect that it has faithful tone reproducibility and is less likely to cause film edge marks.

Claims (1)

[Claims] 1. An aluminum plate surface which has been roughened and then anodized has an absorption intensity of 400 nm after exposure.
A positive-working photosensitive lithographic printing plate comprising a positive-working photosensitive composition layer coated so as to have a thickness of 0.06 to 0.29 per 1 μm.