JPH0619597B2 - Original plate for printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an improvement of an electrophotographic printing original plate in which a photoconductor layer in a non-image area is removed by an alkaline solution after toner image formation. , And more specifically, the improvement of the image quality.

(Prior Art) Conventionally, as an original plate for printing using the principle of electrophotography, for example, Japanese Patent Publications No. 47-47610, No. 48-40002, No. 48-183.
No. 25, No. 51-15766, No. 51-25761 and the like zinc oxide-resin dispersion type offset printing original plate is known, such an offset printing original plate, using the electrophotographic method. To form a toner image, and then a non-image portion other than the toner image portion is subjected to a non-resining treatment to be used as a printing plate. However, in this type of printing plate, since the image portion is formed only by toner particles, the printing durability is poor, and the number of sheets printed by this original plate is limited to about 5,000 to 10,000 sheets, and more than this number. Is not suitable for printing.

Furthermore, since it is necessary to use an acidic solution such as an alkali metal ferrocyanide salt to perform the desensitizing treatment, there are problems in terms of pollution control and occupational health. In addition, Japanese Patent Publication No. 37-17162, No. 38-7758, No. 46-39405
No. 52-2437, No. 57-161863, No. 58-2854,
No. 58-28760, No. 58-118658 and other publications describe a printing original plate provided with a photoconductor layer in which an organic photoconductive substance is held in a resin on a grained aluminum plate. In these printing plates, after the toner image is formed, the photoconductor layer in the non-image area is removed to form an image. Therefore, the image area is formed from the toner particles and the photoconductor layer, so that the printing durability is excellent, but an organic solvent such as ethylene glycol, glycerin, isopropyl alcohol, and benzyl alcohol is required to remove the non-image area. However, these also have industrial hygiene problems in terms of pollution control.

In contrast to the printing plate precursors described in these publications, a printing plate precursor capable of removing a non-image portion after toner image formation with an alkaline aqueous solution containing no organic solvent is disclosed in JP-A-54-134632 and JP-A-5-134632.
No. 105254, No. 59-12452, and No. 59-49555.

The printing plate precursors described in these publications have a photoconductive layer composed of a photoconductive pigment such as copper phthalocyanine and an alkali-soluble resin such as phenol resin as main constituents after graining and anodization. Although it is provided on a treated aluminum plate, it has color sensitivity over the entire visible range, and as described above, the photoconductor layer can be removed by an alkaline aqueous solution containing no organic solvent. In addition, it has the advantages that it has excellent printing durability and storage stability, and that it can be handled in a bright room.

However, the printing original plates described in these publications still have problems that need to be solved.

That is, the following three methods are mainly known as the form of imagewise exposure of the printing original plate.

(1) The original is exposed on the plate surface by a camera.

(2) The film is stretched and exposed on the plate surface by a projector.

(3) Perform scanning exposure on the plate surface by using a laser.

Of these, particularly when the imagewise exposure is performed in the exposure modes of (1) and (2), the image becomes in a high contrast, small dots easily fly, the shadow part is easily crushed, and the sharpness of the image is also increased. There is a problem in image quality that it is inferior. Therefore,
The present inventors arrived at the present invention as a result of intensive studies to solve the above problems in image quality.

(Object of the Invention) That is, an object of the present invention is to provide a printing original plate satisfying the following items (1), (2), (3) and (4).

(1) A printing original plate that gives an image with excellent gradation.

(2) A printing original plate capable of removing the photoconductor layer with an alkaline aqueous solution containing no organic solvent.

(3) A printing original plate having excellent printability.

(4) An original plate for printing that has excellent storage stability and can be handled in a bright room.

Other objects of the present invention will be apparent from the following description.

The above-mentioned object of the present invention is that the photoconductor layer provided on the support is substantially composed of a photoconductive pigment and an alkali-soluble resin, and after the toner image is formed, the non-image portion is formed by an alkaline solution. In the printing plate for removing the photoconductive layer, the amount of the photoconductive pigment is less than 1/6 by weight ratio of the photoconductive pigment and the alkali-soluble resin, and the support is Is grained by electrolytic polishing in a nitric acid bath, and the roughness of the grain is Ra in the range of 0.2 to 1.0. Ra above is a German standard DIN
It is specified in 4768.

In the achievement of the above object of the present invention, in order to obtain a printing original plate having more excellent gradation reproducibility that further reduces the skipping of small dots and at the same time reduces the collapse of the shadow portion, β-type as a photoconductive substance. It is preferable to mainly use copper phthalocyanine.

Examples of the photoconductive pigment that can be used in the present invention include JP-A-47-3
Nos. 0330 and 56-5552, perylene pigments, quinacridone pigments described in JP-A-47-30331, bisbenzimidazole pigments described in JP-A-47-18543 and the like, Aromatic polycondensed ring compounds described in JP-A-47-18544, JP-A-55-98754, JP-A-55-126254 and JP-A-55-163543, JP-B-44-16474, JP-A-48-30513, JP-A-48-30513 56-32165
Azo pigments described in Japanese Patent Publication No. 50-7434, JP-A No.
7-37543, 55-11715, 56-1944, 56-9752
No. 56-2352, No. 56-80050, etc., disazo pigments, JP-B-44-12671, No. 40-2780, No. 52-1667
No. 46-30035, No. 49-17535, JP-A-49-11136,
No. 49-99142, phthalocyanine pigments described in the same 57-148745, etc., also there is an inorganic photoconductive pigment such as ZnO can be used alone or in combination of two or more, sensitivity Further, it is more preferable to mainly use β-type copper phthalocyanine in terms of balance of gradation reproducibility. Specifically, the proportion of copper phthalocyanine in the photoconductive pigment is preferably at least 50% by weight.

β-type copper phthalocyanine is an X-ray diffraction angle (2θ) of 6,8,8.7,139,15.5,20.5,23.
6, 26.0, 28.0, and is a copper phthalocyanine having a spectrum near 30.0 Å, which is described in U.S. Pat.No. 3,816,118, JP-B-48-34189, 49-4338, etc., and is commercially available. Resino Blue-F, Resino-Blue-P, Resino Blue-T manufactured by Resino Color Co., Chromophtal Blue-4GN manufactured by Ciba-Geigy Co., Ltd., Toyo Ink Co., Ltd.
Lionol Blue-SGPC etc.

Examples of the alkali-soluble resin that can be used in the present invention include phenol resins and / or acrylic acid resins, crotonic acid resins, phthalic acid resins, maleic acid resins and the like described in JP-A-54-134632 and JP-A-55-105254. Although there are acid group-containing resins, other resins can be used in combination so long as they do not hinder the removal of the photoconductor layer due to the alkaline aqueous solution. These resins include polystyrene, hydrocarbon polymers such as styrene-butadiene copolymer polyisobutylene; polyvinyl chloride,
Vinyl resins such as chlorinated polyethylene, polyvinyl acetate, polyvinyl acetal, polyvinyl butyral, and polyvinyl ether; silicone resins; polyamide resins; polyurethane resins; urea resins; melamine resins; polycarbonate; modified or unmodified rosin, balsam, and other natural resins There is.

To prepare the printing original plate of the present invention, first, an alkali-soluble resin is dissolved in a solvent, and if necessary, after passing, a predetermined amount of photoconductive pigment is added, and then a ball mill, glass beads, sand mill, colloid mill, etc. are known. According to the above method, the dispersion is carried out to homogenize the photosensitive solution. The photosensitive solution obtained here is uniformly applied on a conductive support by a wire bar, a roll coater, an applicator or the like, and dried. There is no particular limitation on the thickness of the photoconductor layer, and the normal range (2 to 10 μm)
It's good).

Further, in the present invention, a known sensitizer may be used in combination for the purpose of adjusting the sensitivity or the photosensitive wavelength range. These sensitizers include JP-A-47-30330, 47-30331, 47-30332, and
55-161250 and other electron-donating substances described in JP-A-47-
30330, 55-153948 and the like electron-accepting substance described,
Xanthene dyes such as rose bengal, eosin S, fluorescein and phloxine; bromphenol blue, bromcresol purple, chlorophenol red and other phenolsulfophthalein dyes; alphazurin 2G, pontasil brilliand blue FCF, acid violet Triphenylmethane dyes such as 6B;
There are various dyes such as diphenylmethane dyes such as auramine; acridine dyes such as acridine yellow and acridine orange; rhodamine dyes such as sulfordamine B and acid eosin G. Of these, organic compounds such as benzoic acid, phthalic acid, maleic acid, and fumaric acid are particularly effective in that they can be effectively sensitized, and at the same time, they do not hinder or accelerate the removal of the photoconductor layer by an alkaline solution. Carboxylic acids and their anhydrides are particularly preferred.

In the present invention, "the photoconductive layer is substantially composed of a photoconductive pigment and an alkali-soluble resin" means that components other than these, for example, other than the alkali-soluble resin as described above, are used as long as the effects of the present invention are not lost. It is meant that the present invention includes the resin, the sensitizer and the like.

If the weight ratio of the photoconductive pigment to the alkali-soluble resin in the photoconductor layer of the present invention is 1/6 or more, the removability deteriorates when the photoconductor layer in the non-image area is removed with an alkaline solution. On the other hand, if it is less than 1/40, the sensitivity becomes insufficient. The lower limit is preferably 1/10. If it is 1/10 or less, the sensitivity tends to be insufficient, so it is desirable to use a sensitizer together.

In the printing original plate of the present invention, as a support, an aluminum plate whose surface on which the photoconductor layer is to be provided is grained by electrolytic polishing in a nitric acid bath and the roughness of the grain is Ra in the range of 0.2 to 1.0. Used. Examples of the method for forming such a surface shape include a mechanical method and a method of etching by electrolysis.

Examples of mechanical methods include a ball polishing method, a brush polishing method, a liquid honing method, and a puff polishing method. Examples of the electrolytic etching method include a method of using a solution containing phosphoric acid, sulfuric acid, perchloric acid, hydrochloric acid, nitric acid, pyrophosphoric acid, hydrofluoric acid, or the like. In the present invention, an aluminum plate which has been subjected to a hydrophilizing treatment such as anodic oxidation after the graining treatment and further immersed in an aqueous solution of a silicate, a phosphate or a fluorinated zirconic acid and subjected to a sealing treatment is preferable.

An aluminum plate that has been electrolytically polished in a nitric acid bath is thought to improve sharpness because the grained shape of the surface is denser than that in other baths (usually hydrochloric acid). Then, the removability of the photoconductor layer by the alkaline aqueous solution tends to deteriorate.

Since the photoconductor layer according to the present invention has a better removability with an aqueous alkaline solution than the conventional photoconductor layer, it does not cause the problem of poor removability.

(Examples) Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the embodiments of the present invention are not limited thereto.

Example 1 Preparation of coating liquid for photoconductor layer Phenolic resin having the following structural formula Was dissolved in 30 parts by weight of ethylene glycol monoethyl ether, and then copper phthalocyanine Lionol Blue-made by Toyo Ink Co., Ltd.
ER (ε-type copper phthalocyanine) was added, glass beads were dispersed for 30 minutes, and the obtained dispersion was used as a coating liquid for the photoconductor layer. Here, the amounts of the above-mentioned phenol resin and copper phthalocyanine are as shown in Table 1, and the five types (No. 1 to No. 5) of photoconductors in which the weight ratio of the phenol resin and copper phthalocyanine are changed to 5 types A layer coating solution was prepared.

Preparation of Support A surface of an aluminum plate having a thickness of 0.3 mm was immersed in a 1% sodium hydroxide aqueous solution at 50 ° C. for 10 seconds, degreased, and then washed with water. This aluminum plate was subjected to alternating current electrolytic etching at a current density of 50 A / dm ^{2 at} a temperature of 30 ° C. in a 0.4 mol / nitric acid aqueous solution (nitric acid electropolishing) or hydrogen chloride 17 g / aqueous solution (hydrochloric acid electropolishing) at 30 ° C.

After that, desmutting treatment was performed in a 5% aqueous sodium hydroxide solution at 60 ° C. for 10 seconds, followed by neutralization and washing with water. Furthermore, after anodizing at a current density of 3 A / dm ² at 20 ° C for 1 minute in a 20% sulfuric acid bath, sealing treatment was performed with hot water at 90 ° C, and 10 types of grain roughness and electrolytic polishing bath were changed. A support was prepared.

The photoconductor layer coating solution and the support are combined as shown in Table 2, and the photoconductor layer coating solution is applied onto the support so that the dry film thickness is 6 μm, dried, and printed. An original plate sample was prepared.

With respect to these printing plate precursors, the halftone dot reproducibility, sharpness, and photoconductor layer removability (pigment remaining) were measured by the following methods.
And the water retention (print stain) were evaluated.

A toner image was formed on the printing original plate by a camera exposure type electrophotographic plate making machine, and the non-image portion was removed with an alkaline aqueous solution. The obtained images were evaluated as follows.

1) Halftone dot reproducibility The halftone dot area ratio range in which halftone dots are reproduced well in a chart of 100 lines / inch halftone dots.

2) Sharpness: Horizontal edge break of 8th grade Mincho ◎ Unevenness is less than 3 μm ○ Unevenness is less than 5 μm △ Unevenness is less than 10 μm × Unevenness is 10 μm or more 3) Photoconductor layer removal method (pigment remains) Non-image after elution The number of remaining images (pieces / mm ² ) observed when observing 10 parts with a loupe 4) Water retention (print stain) A No stain B Slight stain C Stain occurrence The above results are shown in Table 2. In each column of Table 2, 1) is the dot reproducibility (%), 2) is the sharpness, 3) is the removability of the photoconductor layer (remaining pigment), and 4) is the water retention (print stain) evaluation. The result. In the above experiment, when the weight ratio of the photoconductive pigment and the alkali-soluble resin was 1/50, the sensitivity was remarkably low and an image could not be obtained.

In Table 2 and the following tables, the P / B ratio is the weight ratio of (photoconductive pigment / alkali-soluble resin).

Example 2 In the same manner as in Example 1 except that 1 part by weight of Resino-Blue-F (β-type copper phthalocyanine) manufactured by Resino Color Co. was used instead of Lionol-Blue-ER (ε-type copper phthalocyanine). An original plate for printing was obtained and evaluated in the same manner as in Example 1. As a result, the dot reproducibility was slightly improved, except that Example 1 was used.
Similar results were obtained.

Comparative Example 1 8 parts by weight of phenolic resin having the following structural formula Is dissolved in 30 parts by weight of ethylene glycol monoethyl ether, and then copper phthalocyanine Lionol Blue-ER manufactured by Toyo Ink Co., Ltd.
1 part by weight of (ε-type copper phthalocyanine) was added, and glass beads were dispersed for 30 minutes. This dispersion was grained in a hydrochloric acid solution by electropolishing, further anodized to impart hydrophilicity, and coated on an aluminum plate sealed with hot water to a dry film thickness of 6 μm. After drying, a printing original plate of Comparative Example 1 was obtained.

Comparative Example 2 A printing original plate of Comparative Example 2 was obtained in the same manner as Comparative Example 1 except that the amount of the phenol resin was changed to 4 parts by weight.

Comparative Example 3 Comparative Example 3 was carried out in the same manner as Comparative Example 1 except that 1 part by weight of Resino-Blue-F (β-type copper phthalocyanine) manufactured by Resino Color Co. was used instead of Lionol-Blue-ER (ε-type copper phthalocyanine). An original plate for printing was obtained.

Comparative Example 4 A printing original plate of Comparative Example 4 was obtained in the same manner as Comparative Example 1 except that 1 part by weight of Resino-Blue-F was used instead of Lionol-Blue-ER.

Example 3 The same procedure as in Example 1 was carried out except that an aluminum plate, which was grained by electrolytic polishing in nitric acid solution, was anodized to form a hydrophilic layer, and was sealed with hot water, was used as a support. A printing original plate of Example 3 was obtained.

Comparative Example 5 A printing original plate of Comparative Example 5 was obtained in the same manner as Comparative Example 2 except that the support used in Example 3 was used as the support.

Example 4 A printing original plate of Example 4 was obtained in the same manner as in Example 3 except that the support used in Example 3 was used as the support.

Comparative Example 6 An original plate for printing of Comparative Example 6 was obtained in the same manner as Comparative Example 4 except that the support used in Example 3 was used as the support.

For the printing plates of Examples 3 and 4 and Comparative Examples 1 to 6, the halftone dot reproducibility, the sheepness and the removability of the photoconductor layer in the non-image area (pigment remaining) were evaluated in the same manner as in Example 1. did. The results are shown in Table 3.

Further, a graph showing the dot reproducibility of the printing original plate is
Shown in the figure. In FIG. 1, the horizontal axis represents the halftone dot percentage of the original halftone dot chart, and the vertical axis represents the halftone dot percentage reproduced on the plate after elution of the non-image area, where 1 is Comparative Example 3
And Examples 4 and 2 show the results obtained in Comparative Example 1 and Examples 3 and 3 and Comparative Examples 4 and 4, respectively.

EFFECT OF THE INVENTION The printing plate precursor of the present invention can remove the photoconductor layer with an alkaline aqueous solution containing no organic solvent, and the method for removing the photoconductor layer in the non-image area, sharpness, gradation and printing durability. It also has excellent storage stability and can be handled in a bright room.

Note that the following will be additionally described with respect to the effects of the present invention.

(1) If the weight ratio of the photoconductive pigment to the weight ratio of the photoconductive pigment to the alkali-soluble resin is 1: 6 or less, the slope of the light decay curve in the electrophotographic characteristics of the plate material becomes moderately moderate, which is a good level. Tonal reproducibility can be obtained. As another effect, the removability of the photoconductor layer due to the alkaline aqueous solution is improved. With these improvements, storage stability and handleability under a bright room are not impaired.

(2) By mainly using β-type copper phthalocyanine as the photoconductive pigment, the bright decay curve is linearly attenuated, and more excellent gradation reproducibility can be provided.

(3) It is considered that the sharpness of the image is improved because the grain shape of the surface of the aluminum plate grained by electrolytic polishing in a nitric acid bath as the support becomes fine.
At this time, in this support, the removability of the photoconductive layer due to the alkaline solution usually tends to deteriorate, but the photoconductive layer according to the present invention has a good removability, so that the elution property of the non-image area is poor. Does not cause.

[Brief description of drawings]

FIG. 1 is a graph showing halftone dot reproducibility obtained in Examples of the present invention and Comparative Examples. 1 ... Comparative Example 3 and Example 4 2 ... Comparative Example 1 and Example 3 3 ... Comparative Example 4 4 ... Comparative Example 2

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-56-29250 (JP, A) JP-A-55-153948 (JP, A) JP-A-56-19063 (JP, A) JP-A-59- 121058 (JP, A)

Claims (1)

[Claims] 1. A photoconductive layer provided on a support is substantially composed of a photoconductive pigment and an alkali-soluble resin, and after the toner image is formed, the photoconductive layer in the non-image area is removed by an alkaline solution. In the printing plate for printing, the amount of the photoconductive pigment is less than 1/6 by weight ratio of the photoconductive pigment and the alkali-soluble resin, and the support is electrolyzed in a nitric acid bath. Grained by polishing, the roughness of the grain is Ra
An original plate for printing, which is an aluminum plate having a range of 0.2 to 1.0.