DE69026869T2 - Matrix plate for the electrophotographic production of printing plates and printing plates - Google Patents

Description

The invention relates to a matrix plate for electrophotographic plate making and to a printing plate obtained by exposing the matrix plate to radiation and developing it. In particular, it relates to a plate-making matrix plate sensitive to a semiconductor laser and capable of directly making a plate by an electrophotographic process and a printing plate obtained by exposing the matrix plate to radiation and developing it.

Due to technical advances in computer image processing and mass storage, the news has recently supported the proposal to effect a new system of so-called phototelegraphic printing by processing a given image with a computer, obtaining the image information in the form of a digital signal, electrically transmitting the image information by a telephone circuit or a communications satellite, processing the image information reaching the receiver by a scanning device at the receiver side, and exposing this image information with a laser in the manner of a scanner.

The conventional matrix plate for plate making has mainly relied on the method using a photosensitive resin (PS plate method). In the case of the PS plate method, there is a disadvantage that the plate making process requires a bulky apparatus and takes a long time because the plate making is carried out by writing the obtained information into a silver salt film as a preliminary step, pressing the film firmly against a matrix plate and exposing the film to radiation. In addition, most photosensitive materials for the PS plate method utilize a photochemical reaction and therefore require that they be exposed to sufficient radiation and are generally insufficient in of sensitivity. Therefore, the photosensitive materials of the PS plate process have the disadvantage of being unable to produce completely satisfactory image information when exposed to an inexpensive, low-power semiconductor laser.

To solve the above-described problems of the PS plate process, a method using a photosensitive material containing silver halide as a photogenerating matrix plate and a method using the electrophotographic process have been proposed and partly put into practice. Although the former method enjoys highly satisfactory sensitivity, it suffers from the disadvantage that the plate has insufficient resistance to the effects of printing and is unduly expensive. In contrast, the latter method allows direct plate making, enjoys relatively high sensitivity and inexpensiveness, and promises successful production of a printing plate with high resistance to the effects of printing. Therefore, it has been the subject of active studies in recent years.

For the matrix plate for electrophotographic plate making, zinc oxide and organic compounds have been used as photoelectroconductive substances. The plate making matrix plate using zinc oxide generally suffers from disadvantages such as (A) the fact that the produced printing plate tends to be soiled because its non-image forming part has insufficient hydrophilicity, (B) the fact that the produced printing plate is insufficient in resistance to the effects of printing because the photosensitive layer suffers from peeling off under the mechanical pressure applied during printing or due to the penetration of the water used for moistening, and (C) the fact that the produced printing plate does not have a completely satisfactory sensitivity despite being previously sensitized with pigment to impart sensitivity to it in the visible light region. in the range of long wavelengths above 600 nm. This does not allow for simple effective exposure by a semiconductor laser.

In the case of the plate-forming matrix plate using a photoelectroconductive organic compound, plate formation is made possible by dispersing the photoelectroconductive organic compound in a binder resin mainly composed of an alkali-soluble resin, thereby yielding a photosensitive material. This photosensitive material is applied to a roughened surface of a substrate such as an aluminum sheet, a photosensitive layer is applied to the substrate, a toner image is formed on the photosensitive layer by the electrophotographic technique, and the non-image-forming part is dissolved out and removed with an alkaline extractant.

A variety of electrophotographic plate-making matrix plates have been proposed which are provided with a photosensitive layer and in which various photoelectroconductive organic compounds are dispersed in alkali-soluble resin. For example, JP-A-54-134632 (1979), JP-A-55-105254 (1980) and JP-A-55-153948 (1980) disclose such matrix plates using phenol resin as the alkali-soluble resin. However, when phenol resin is used as a binder resin for such photoelectroconductive organic compounds, the film produced has the disadvantage of being brittle and therefore insufficient in resistance to the effects of printing.

JP-A-58-76843 (1983), JP-A-59-147355 (1984), JP-A-60-17752 (1985), JP-A-60-243670 (1985), JP-A-62-198864 (1987) and JP-A-64-23260 (1989) disclose matrix plates using a styrene-maleic acid copolymer as an alkali-soluble resin. However, when a styrene-maleic acid copolymer is used as a binder resin for photoelectroconductive organic compounds, there is a disadvantage that the film produced is so hard that the printing plate tends to crack when it is bent. In many cases, acrylic resins have been used. JP-A-54-89801 (1979) discloses a matrix plate using a aqueous acrylic resin is used as a binder resin and an ε-type crystalline copper phthalocyanine is used as a photoelectroconductive organic compound. These matrix plates have the ability to form an image by an electrophotographic process. However, they suffer from the disadvantage that they cannot be easily etched with an aqueous alkali solution and it is impossible to obtain effective exposure with near infrared irradiation such as a semiconductor laser.

JP-A-56-146145 (1981) discloses a process using as a binder resin such as an acrylic resin such as an acrylic acid/methyl methacrylate/butyl acrylate copolymer and as a photoelectroconductive organic compound a pigment of a condensed polycyclic quinone type and an oxadiazole derivative. Although the matrix plate obtained by this process allows an etching treatment which can be easily effected by an aqueous alkali solution, it has the disadvantage that it does not have completely satisfactory electrophotographic properties and shows poor stability in storage for a long period of time. It also has the disadvantage that it is unsuitable for being effectively exposed to radiation in the near infrared region such as a semiconductor laser. One problem is its poor resistance to the effects of printing, since it is unsuitable for being effectively exposed by irradiation in the near infrared range such as with a semiconductor laser, or if this is somehow adjusted or exposure is achieved in some other way, it does not show fully satisfactory performance in its electrophotographic properties.

JP-A-64-145474 discloses the use of a fluorine-containing phthalocyanine compound as a photoelectroconductive material in media for optical information storage. The object of the invention is therefore to provide a new matrix plate for electrophotographic plate production and a printing plate which is produced by exposing this matrix plate to radiation and then developing it.

Another object of the invention is to provide a matrix plate having electrophotographic plate-making quality using an improved process using a photoelectroconductive organic compound, and a lithographic printing plate.

Another object of the invention is to provide a matrix plate having an electrophotographic plate-making quality and being superior in electrophotographic properties and alkaline extractability, and a lithographic printing plate being superior in printing properties.

Still another object of the invention is to provide a matrix plate having electrophotographic plate-making quality and capable of producing a printing plate excellent in storage stability over an extended period of time and resistance to the effects of printing.

Another object of the invention is to provide a matrix plate having an electrophotographic plate-making quality provided with a photosensitive layer superior in light fastness and weather stability due to the use of a binder resin having highly satisfactory strong adhesiveness to the substrate and satisfactory mechanical strength.

A further object of the invention is to provide a matrix plate which has an electrophotographic plate-making quality and has a high sensitivity even in the near infrared wavelength range and which allows an effective exposure with a semiconductor laser.

The objects described above are achieved by an electrophotographic matrix plate which contains an electroconductive substrate having a photosensitive layer comprising an alkali-soluble binder resin and a photoconductive, fluorinated zinc phthalocyanine compound, the matrix plate being characterized in that the photoconductive compound is an octafluoro zinc phthalocyanine represented by the general formula list:

wherein R is a -SZ group (wherein Z is a phenyl group, an alkyl-substituted phenyl group having 1 to 5 carbon atoms or a naphthyl group) and the binder resin is a copolymer obtainable by polymerizing a monomer mixture of (a) at least one compound selected from the group consisting of hydroxyalkyl acrylates and hydroxyalkyl methacrylates, (b) at least one copolymerizable, unsaturated carboxylic acid, (c) at least one styryl compound and (d) at least one compound selected from acrylic acid esters which do not fall under the hydroxyalkyl acrylates of (a) and optionally (e) at least one methacrylic acid ester which does not fall under the hydroxyalkyl methacrylates of (a).

The objects described above are also achieved by a lithographic printing plate which is prepared by forming a toner image by an electrophotographic process on the electrophotographic plate-forming matrix plate as described above, fixing the toner image and removing the non-image forming parts with an alkaline etching liquid.

Since the electrophotographic process is formed on the electrophotographic plate-forming matrix plate of the present invention as described above, it produces the following effect.

(1) It has excellent electrophotographic properties and is capable of effecting electrophotographic plate making with high efficiency.

(2) It has superior alkaline extractability and allows the required etching to be carried out effectively during the plate making process.

(3) It enables the photosensitive layer to be prepared with a low phthalocyanine content in a thin wall without adversely affecting the highly desirable states of the electrophotographic properties (chargeability and sensitivity).

(4) Since it has highly satisfactory sensitivity even in the long wavelength region, it can be effectively exposed not only by an ordinary light source such as a tungsten lamp, but also by a low-power laser. As a result, it is possible to achieve direct plate formation with a variable light source.

(5) The binder resin has a high affinity for zinc phthalocyanine and has a highly satisfactory dispersibility therein.

(6) The printing plate obtained by the electrophotographic plate-making technique excels in printing properties and allows the production of clear prints even after 100,000 repeated applications. It also excels in stability and can withstand extended storage periods.

The electrophotographic plate-making quality matrix plate according to the present invention is provided on an electroconductive substrate having a photosensitive layer. This photosensitive layer is formed from an alkali-soluble binder resin containing a photoelectroconductive organic compound.

The photoelectroconductive organic compound used in the invention is a zinc phthalocyanine represented by the above-mentioned general formula I. This zinc phthalocyanine excels in its electrophotographic properties even when it is contained in the alkali-soluble binder resin and does not interfere with the alkaline extraction capability.

As concrete examples of the zinc phthalocyanines represented by the above-mentioned general formula (I), the following compounds may be mentioned. A total of eight fluorine atoms is constant in all these compounds, one each of which is present at positions 1, 4, 5, 8, 9, 12, 13 and 16 of the phthalocyanine nucleus represented by the following formula (II). The formulas given in [ ] are abbreviations.

Octafluoro-octakis(phenylthio)-zinc phthalocyanine [F₈(PhS)₈ZnPc],

Octafluoro-octakis(o-tolylthio)-zinc phthalocyanine [F₈(o-MePhS)₈ZnPc],

Octafluoro-octakis(m-tolylthio)-zinc phthalocyanine [F₈(m-MePhS)₈ZnPc],

Octafluoro-octakis(p-tolylthio)-zinc phthalocyanine [F₈(p-MePhS)₈ZnPc],

Octafluoro-octakis(2,4-xylylthio)-zinc phthalocyanine [F₈(2,4-MePhS)₈ZnPc],

Octafluoro-octakis(2,3-xylylthio)-zinc phthalocyanine [F₈(2,3-MePhS)₈ZnPc],

Octafluoro-octakis(o-ethylphenylthio)-zinc phthalocyanine [F₈(o-EtPhS)₈ZnPc],

Octafluoro-octakis(p-ethylphenylthio)-zinc phthalocyanine [F₈(p-EtPhS)₈ZnPc],

Octafluoro-octakis(o-isopropylphenylthio)-zinc phthalocyanine [F₈(o-IPrPhS)₈ZnPc),

Octafluoro-octakis(o-butylphenylthio)-zinc phthalocyanine [F₈(o-BuPhS)₈ZnPc],

Octafluoro-octakis(m-butylpherylthio)-zinc phthalocyanine [F₈(m-BuPhS)₈ZnPc],

Octafluoro-octakis(p-butylphenylthio)-zinc phthalocyanine [F₈(p-BuPhS)₈ZnPc],

Octafluoro-octakis(p-tert-butylphenylthio)-zinc phthalocyanine [F₈(p-t-BuPhS)₈ZnPc], and

Octafluoro-octakis(naphthylthio)-zinc phthalocyanine [F₈(NPhS)₈ZnPc].

The zinc phthalocyanines represented by the general formula (I) can be prepared as described below, for example, from 3,4,5,6-tetrafluorophthalonitrile as a starting material. In an organic solvent such as methanol or acetonitrile, 3,4,5,6-tetrafluorophthalonitrile is allowed to react with RSH, RSNa or RSK, where R is a phenyl group or a naphthyl group, in the presence of a condensing agent such as an alkaline substance (e.g. KF) to produce 3,4,5,6-tetrafluorophthalonitrile substituted by functional groups at positions 4 and 5 where fluorine atoms were previously located. Then the phthalonitrile obtained, which now carries the substituents, and zinc powder or a zinc halide are reacted by heating or by heating in an organic solvent and the above-mentioned zinc phthalocyanine is obtained.

The binder resin used according to the invention is a copolymer obtained by polymerizing a monomer mixture which contains (a) at least one compound selected from the group consisting of hydroxyalkyl acrylates and hydroxyalkyl methacrylates, (b) at least one copolymerizable, unsaturated carboxylic acid, (c) at least one styryl compound and (d) at least one compound selected from acrylic acid esters which do not fall under the hydroxyalkyl acrylates of (a).

The monomer of (a) is at least one compound selected from hydroxyalkyl acrylates and hydroxyalkyl methacrylates having hydroxyalkyl groups of 2 to 10, preferably 2 to 6 carbon atoms (hereinafter, acrylic acid and methacrylic acid are collectively referred to as "(meth)acrylic acid"). In particular, the hydroxyalkyl (meth)acrylates that can be used include, for example, 2-hydroxyethyl (meth)acrylates, 2-hydroxypropyl (meth)acrylates, 3-hydroxypropyl (meth)acrylates, 2-hydroxybutyl (meth)acrylates, glycerin mono(meth)acrylates and trimethylolpropane (meth)acrylates. The use of the monomer (a) results in an improvement in electrophotographic properties and durability as a printing plate. It also helps to produce a uniform and attractive coating. This advantageous effect can be logically explained by considering that the introduction of the hydroxyl group into the binder resin increases the firm adhesion of the binder resin to the electroconductive substrate and at the same time increases the affinity of the binder resin for the phthalocyanine of the present invention so that the dispersibility is improved. It also causes the increase in alkaline etchability and enables a reduction in the amount of the copolymerizable unsaturated carboxylic acid which tends to impair the electrophotographic properties when used in a high amount.

The proportion of the monomer (a) to be used is in the range of 0.5 to 40 wt.%, preferably 2 to 25 wt.%, based on the total amount of the mixed monomer. If the proportion is less than 0.5 wt.% or not is less than 40 wt.%, there is the disadvantage that the electrophotographic properties and the durability of the printing plate are reduced.

The monomer from (b) is at least one copolymerizable, unsaturated carboxylic acid. The copolymerizable, unsaturated carboxylic acids that can be used here include such unsaturated monomers as monocarboxylic acids, represented by (meth)acrylic acids, dicarboxylic acids represented by maleic acid, itaconic acid and citraconic acid and dicarboxylic acid monoesters represented by monoisopropyl maleic acid esters, which have at least one carboxyl group in their molecular unit. Among other unsaturated monomers mentioned above, (meth)acrylic acid and/or itaconic acid are advantageously used. The proportion of the monomer (b) to be used here is in the range of 10 to 40% by weight, preferably 15 to 30% by weight, based on the total amount of the monomer mixture. If this proportion is less than 10% by weight, there follows a disadvantage that the alkali solubility of the copolymer produced is insufficiently low and the etching rate is proportionally low. On the contrary, if the proportion exceeds 40% by weight, the photosensitive layer is insufficient in its strength to be effectively used. In order to obtain highly satisfactory etchability, the copolymer to be used as a binder resin according to the present invention may contain a carboxylic acid to adjust the acid content in the range of 50 to 300 mg KOH/g. By using the copolymerizable carboxylic acid in the specific range mentioned above, the etchability can be improved without impairing the electrophotographic properties.

The monomer of (c) is a styryl compound. The styryl compounds effectively used for this purpose include, for example, styrene and alkylstyrenes such as methylstyrene, ethylstyrene and isopropylstyrene. Among other styryl compounds mentioned above, styrene is particularly preferable. The proportion of the monomer (c) to be used is in the range of 10 to 70 wt. %, preferably 25 to 55 wt.% based on the total amount of the monomer mixture. If this proportion is less than 10 wt.%, there arises a disadvantage that the strength, the affinity (dispersibility) for phthalocyanine and the load-bearing capacity are unduly low. On the contrary, if the proportion exceeds 70 wt.%, there arises a disadvantage that the aforementioned effects due to the use of the monomers (a) and (b) are no longer maintained because the amounts of the monomers (a) and (b) are proportionally reduced.

The monomer (d) is at least one compound selected from the acrylic acid esters which do not fall under the hydroxyalkyl acrylates used for the monomers (a). The acrylic acid esters which can be used effectively for this purpose include alkyl acrylates having alkyl groups of 1 to 12, preferably 2 to 8, carbon atoms and cycloalkyl acrylates having cycloalkyl groups of 5 to 7 carbon atoms. Typical examples of alkyl acrylates and cycloalkyl acrylates are methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate and cycloheptyl acrylate. The proportions of alkyl acrylates or cycloalkyl acrylates which are used for this purpose are in the range of 5 to 50% by weight, preferably 10 to 40% by weight, based on the total amount of the monomer mixture. As long as this proportion is in the above-mentioned range, the added alkyl acrylates or cycloalkyl acrylates increase the oleophiles and the copolymer produced enjoys increased binding forces and improved flexibility. If the proportion exceeds 50% by weight, the disadvantage arises that the above-mentioned effects brought about by the use of the monomers (a), (b) and (c) are no longer stable, since the proportions of the monomers (a), (b) and (c) are proportionally reduced. The monomer (e) which can be used optionally according to the invention is at least one compound selected from methacrylic acid esters which do not belong to the aforementioned hydroxyalkyl methacrylates. In particular, methacrylic acid esters which are alkyl methacrylates with alkyl groups of 1 to 12, preferably 2 to 8 carbon atoms and cycloalkyl methacrylates having cycloalkyl groups of 5 to 7 carbon atoms.

As typical examples of alkyl methacrylates and cycloalkyl methacrylates, there may be mentioned methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate and cycloheptyl methacrylate. The proportion of alkyl methacrylate or cycloalkyl methacrylate to be used is in the range of 0 to 40 wt%, preferably not more than 15 wt%. As long as this proportion is in the above range, the added methacrylate has the effect of increasing the durability. If the proportion exceeds 40 wt%, there is a disadvantage that the dispersibility of the phthalocyanine is impaired.

Of the various monomer mixtures listed above, the typical monomer mixtures (p-1) to (p-10) identified below have the indicated compositions and monomer ratios.

(p-1) 2-hydroxypropyl acrylate/acrylic acid/styrene/butyl acrylate (5/20/35/40) (in weight percent, as stated consistently hereinafter)

(p-2) 2-hydroxyethyl methacrylate/methacrylic acid/styrene/butyl acrylate (2/23/40/35),

(p-3) 2-hydroxybutyl methacrylate/acrylic acid/styrene/isopropyl acrylate (15/25/45/15),

(p-4) 3-hydroxypropyl methacrylate/acrylic acid/styrene/methacrylate/ ethyl methacrylate (5/20/35/25/15),

(p-5) 3-hydroxybutyl acrylate/methacrylic acid/styrene/isobutyl acrylate/ isopropyl methacrylate (20/30/25/20/5),

(p-6) 2-hydroxyethyl methacrylate/methacrylic acid/styrene/propyl acrylate/ ethyl methacrylate (5/25/40/25/5),

(p-7) 2-hydroxybutyl methacrylate/itaconic acid/styrene/butyl acrylate/ Methyl methacrylate (10/15/35/30/10) and

(p-8) 3-Hydroxybutyl acrylate/acrylic acid/styrene/ethyl acrylate/ butyl acrylate/butyl methacrylate (5/20/25/4/10).

No particular method is specified for the polymerization of the above-mentioned monomer mixture. For example, the monomer mixture can be polymerized by any conventional polymerization method such as the bulk polymerization method, the solution polymerization method and the suspension polymerization method in the presence of a radical polymerization initiator such as a peroxide, a hydroperoxide or azobisisobutyronitrile at a temperature in the range of 50° to 100°C, preferably 70° to 90°C. As for the manner of adding the monomer mixture, the method of simultaneous addition, separate addition, continuous addition or a suitable combination thereof can be used.

The number average molecular weight of the copolymer obtained by polymerizing the monomer mixture is in the range of 1,000 to 50,000, preferably 3,000 to 30,000.

The copolymer obtained by polymerizing the monomer mixture and having a number average molecular weight in the above range is soluble in an alkaline substance. The photosensitive layer obtained when this copolymer is used in combination with the above-mentioned photoelectroconductive phthalocyanine compound shows highly satisfactory alkali solubility and excels in etchability.

The electrophotographic plate-making quality matrix plate of the present invention is a product obtained by preparing a coating liquid consisting of the aforementioned photoelectroconductive phthalocyanine compound and the aforementioned copolymer as a binder resin and then this coating liquid is applied to an electroconductive substrate, whereupon a photosensitive layer is formed.

The method for preparing the coating liquid is not particularly restricted . The preparation can be achieved by dissolving or dispersing the binder resin (or the photoelectroconductive phthalocyanine compound) in an appropriate solvent and then dissolving or dispersing the photoelectroconductive compound (or the binder resin) in the resulting solution, or by dissolving or dispersing the binder resin and the photoelectroconductive phthalocyanine compound in different solvents, respectively, and mixing the resulting solutions. The solvents suitable for dissolving or dispersing the binder resin and the photoelectroconductive phthalocyanine compound are organic solvents and include aromatic hydrocarbons such as benzene and toluene, cyclic ethers such as tetrahydrofuran and dioxane, halogen-containing hydrocarbons such as chloroform, dichloromethane and dichloroethane, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate and cellosolves such as methyl cellosolve.

For the production of the above-mentioned coating liquid, the photoelectroconductive phthalocyanine compound is used in a proportion in the range of 3 to 50 wt.%, preferably 5 to 30 wt.%, based on the amount of the binder resin.

The concentrations of the photoelectroconductive phthalocyanine compound and the binder resin dissolved or dispersed in their solvents are both desirably in the range of usually 0.5 to 50 wt%, preferably 5 to 30 wt%.

The thickness of the photosensitive layer is in the range of 2 to 10 µm, preferably 3 to 6 µm. If the wall thickness is greater than the upper limit of this range, there is a disadvantage that the etching treatment tends to form corners at the sides and consequently tends to scratch away fine lines. If the wall thickness is less than the lower limit of the range, there is a disadvantage that the photosensitive layer suffers from reduced loadability.

The coating liquid prepared to form a photosensitive layer of the type used to be positively charged may, in order to improve its electrophotographic properties, additionally contain as a sensitizer at least one compound selected from organic compounds of polybasic acids such as compounds represented by the following general formulas III, IV and V, succinic anhydride and maleic anhydride.

wherein X¹ to X⁵ are the same or different and represent a hydrogen atom, a fluorine atom, a -COOH group or an NO₂ group,

wherein Y¹ and Y⁴ are the same or different and represent a hydrogen atom, a fluorine atom, a -COOH group or a -NO₂ group and

wherein Z¹ and Z² are the same or different and represent a hydrogen atom, a fluorine atom, a -COOH group or a -NO₂ group.

Typical examples of these sensitizers include succinic anhydride, maleic anhydride, phthalic acid, tetrafluorophthalic acid, 4-nitrophthalic acid, phthalic anhydride, tetrafluorophthalic anhydride, 4-nitrophthalic anhydride, trimellitic acid, trimellitic anhydride, benzoic acid, pentafluorobenzoic acid and tetrafluorobenzoic acid. Among other sensitivity improvers mentioned above, succinic anhydride, tetrafluorophthalic anhydride, benzoic acid, pentafluorobenzoic acid and tetrafluorobenzoic acid are preferred and tetrafluorophthalic anhydride, pentafluorobenzoic acid and tetrafluorobenzoic acid are particularly preferred.

It is preferable to use the sensitizer in a proportion in the range of 0.01 to 10 wt.%, preferably less than 2.0 wt.%, based on the amount of the photoelectroconductive phthalocyanine compound.

The coating solution prepared for forming the photosensitive layer, which can be used for charging with negative polarity, may additionally contain an electric charge transfer substance such as an oxazole derivative, an oxadiazole derivative, a pyrazoline derivative, a hydrazone derivative or a triphenylamine derivative and/or an aminotriazine resin to further improve its electrophotographic properties.

It is preferable to use a hydrazone derivative represented by the following general formula VI as an electronic charge transfer substance. wherein R¹ and R² each represent an aryl group or an alkylaryl group and R³ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a benzyl group, an alkoxy group having 1 to 4 carbon atoms, a phenoxy group or a benzyloxy group.

As typical examples of the hydrazine compounds represented by the above general formula, the following compounds are mentioned.

The aminotriazine resins that can be used include, for example, melamine resin, benzoguanamine resin, acetoguanamine resin, CTU guanamine resin (protected product of Ajinomoto Co., Inc.) and cyclohexylguanamine. It is particularly preferable to use cyclohexylcarboguanamine resin among the other aminotriazine resins mentioned above.

The aminotriazine resin is an aminotriazine resin composition, namely the oxymethylated or alkyloxymethylated product of aminotriazine obtained by reacting aminotriazine with formaldehyde and optionally further with an alcohol such as butanol. It is used either in its unmodified form or in a form suitable for condensation by dehydration. It is preferred to use the aforementioned electric charge transfer substance and/or aminotriazine resin in an amount not exceeding 60% by weight and preferably falling within the range of 0.1 to 20% by weight.

The electroconductive substrate used in the present invention is not particularly limited. The electroconductive substrates that can be effectively used include monometallic plates such as aluminum plate and zinc plate, bimetallic plates such as copper-aluminum plate, copper-stainless steel plate and chromium-copper plate, and trimetallic plates such as chromium-copper-aluminum plate, chromium-copper-iron plate and chromium-copper-aluminum plate, all of which have an equally hydrophilic surface and are in general use. The thickness of the electroconductive substrates is desirably in the range of about 0.05 to 0.5 mm.

Particularly in the case of a substrate having an aluminum surface, it is advantageous if it is subjected to a surface treatment such as sanding, immersion in an aqueous solution of sodium silicate or potassium fluorozirconate, or anodic oxidation.

The anodic oxidation treatment can be carried out by placing an aluminum plate in an electrolysis solution formed by dissolving an inorganic acid such as phosphoric acid, chromic acid, sulfuric acid or boric acid, an organic acid such as oxalic acid or amidosulfonic acid or one of the salts of these acids and passing an electric current through the aqueous solution with the aluminum plate as an anode. Furthermore, it is advantageous to provide an intermediate layer made of a resin having a composition within the range of the present invention and having a higher acid value than the binder resin in the sensitive layer between the electroconductive substrate and the electrophotosensitive layer in order to improve the printing quality of the present invention.

The electrophotographic plate-making quality matrix plate of the present invention does not differ due to the method used for its manufacture. This manufacture can be effected by any method heretofore known in the art. In accordance with the conventional electrophotographic technique, for example, a toner image is obtained on a photosensitive layer by first uniformly charging the photosensitive layer in a dark place with a corona charger, exposing the charged photosensitive layer to the reflected image and exposing it using a light source such as a tungsten lamp, a halogen lamp, a xenon lamp or a fluorescent lamp, or exposing the solid contact image through a transparent positive film or scanning exposure with a laser beam such as a He-Ne laser, an argon laser or a semiconductor laser to form a latent electrostatic image, developing this latent image with a toner and thermally fixing the developed toner image.

The toner must be hydrophobic and capable of absorbing ink, sufficiently adhesive to the matrix plate to withstand the effects of printing and resistant to the action of an aqueous alkaline etching liquid used in the course of etching. Since a liquid developer has a powdery developer in resolving power, it is preferable to use the former developer as the electrophotographic developer over the latter developer. In order that the toner can meet the above requirements, the resin containing the toner is preferably, for example, styrene resin, acrylic resin, styrene-acrylic resin, styrene-methacrylic resin, polyester resin or epoxy resin. The dispersing agent for the toner is an organic solvent having a low dielectric constant and a high insulating power. Preferably, for example, an isoparaffin-type hydrocarbon is used. The toner may contain a pigment or dye for the purpose of coloring or an electric charge regulating agent for transferring positive charge or negative charge in an amount which is incapable of exerting an adverse effect on the stability and fixing properties of the toner and yet is suitable for the toner used.

When the plate-forming matrix plate on which the toner image has been formed as described above is immersed in an alkaline solvent liquid, the photosensitive layer in the non-image forming part not masked with the toner image is dissolved and removed to develop the hydrophilic surface of the electroconductive substrate and the image forming portion of the toner image is allowed to remain on the surface of the substrate to form the intended lithographic printing plate.

The alkaline dissolving liquid which can be effectively used for dissolving and removing the photosensitive layer in the non-image forming part includes aqueous alkaline solutions of, for example, inorganic salts such as sodium silicate, sodium phosphate, sodium hydroxide and sodium carbonate, aqueous alkaline solutions of organic amines such as triethanolamine and ethylenediamine, and solutions containing organic solvents such as ethanol, benzyl alcohol, ethylene glycol and glycerin as surfactants. For example, an aqueous alkaline etching liquid having the following composition can be advantageously used.

Edta-4H 4g

Benzyl alcohol 30 g

Monoethanolamine 5 g

Triethanolamine 60 g

NaOH 25g

Water added to dilute the above ingredients to a total volume of 11.

The matrix plate with electrophotographic plate-making quality can, on the other hand, also be used as an electrophotographic sensitive material with laser printer quality (OPC). In a laser printer, the developed toner is transferred to a sheet of paper and fixed thereon.

Now, the present invention will be described hereinafter with reference to Preparation Examples and Working Examples. Wherever "parts" and "percents" are mentioned, they are to be understood as "parts by weight" and "percents by weight" unless otherwise specified.

Preparation Example 1 [Preparation of F₈(PhS)₈ZnPc] (1) Synthesis of the starting material

19.6 g (98 mmol) of 3,4,5,6-tetrafluorophthalonitrile, 21.6 g (196 mmol) of thiophenol, 17.1 g (294 mmol) of potassium fluoride (KF) and 100 ml of acetonitrile are added to a four-necked flask with an internal volume of 200 ml and allowed to react at 50ºC for 12 hours while stirring. The reaction mixture is then cooled to room temperature. The yellow solid that subsequently forms in the mixture is separated by filtration. The filter cake thus obtained is purified by washing first with methanol and then with hot water to obtain 34.5 g of 3,6-difluoro-4,5-bisphenylthiophthalonitrile (yield: 92.5 mol% based on 3,4,5,6-tetrafluoronitrile).

(2) Synthesis of F₈(PhS)₈ZnPc

In a four-necked flask with an internal volume of 100 ml, 10 g (26.2 mmol) of 3,6-difluoro-4,5-bisphenylthiophthalonitrile, 3.14 g (9.8 mmol) of zinc iodide and 50 ml of benzonitrile are added and allowed to react at 175°C for 6 hours with stirring. Then, the reaction mixture is cooled. The green solid thus formed in the reaction mixture is separated by filtration and washed in a Soxhlet extractor with methanol, benzene and acetone sequentially in the order given to obtain F₈(PhS)gZnPc in a yield of 79.4 mol% based on 3,6-difluoro-4,5-bisphenylthiophthalonitrile.

Preparation Example 2 [Preparation of the copolymer]

For example, the copolymer can be prepared as follows. In a separatory funnel equipped with a thermometer, a condenser, a nitrogen inlet tube, a dropping funnel for the monomer mixture and a dropping funnel for a polymerization initiator, 40 parts of isopropanol as a solvent are added, and then nitrogen is introduced through the nitrogen inlet tube to replace the air trapped in the flask with nitrogen. Then, 60 parts of a monomer mixture are added to the dropping funnel for the monomer mixture and 0.1 part of azobisisobutyronitrile is added to the dropping funnel for the polymerization initiator. While the internal temperature of the flask is kept at 80°C, the monomer mixture and the polymerization initiator are dropped into the flask over a period of 2 hours. The mixture in the flask is heated to 80ºC for 2 hours, then to 85º to 95ºC for 2 hours and then cooled.

example 1

In a paint dispersion shaker, 1.5 parts of F8(o-MePhS)8znPc, 0.05 part of pentafluorobenzoic acid, 12.0 parts of a copolymer obtained from the monomer mixture (P-1) and 83 parts of dichloroethane are shaken for 2 hours to disperse. The obtained dispersion is coated on an aluminum plate which has been ground to a thickness of 0.15 mm and then treated by anodic oxidation by a rail coating machine. The coated dispersion layer is dried with hot air at 60°C for 30 minutes and then dehydrated at 100°C under vacuum (1 mmHg) for 2 hours to form a photosensitive layer. The film (photosensitive layer) thus obtained has a thickness of 5 µm.

The monolayer type electrophotographic sensitive material obtained as a matrix plate of electrophotographic plate-making quality as described above is positively charged at +6.0 kV using an electrostatic paper analyzer (manufactured by Kawaguchi Denki K.K. and sold under the product name "SP-428").

The photosensitive material is then held in a dark place for 5 seconds and then exposed to white light (from a tungsten lamp) at an illuminance of 5 lux for 5 seconds to examine the charge properties [surface potential (V0), potential (V5) after 5 seconds of holding in a dark place, and the amount of exposure required to reduce the existing pre-exposure potential by exposure to half (E1/2) (lux x sec)]. It is then exposed to monochromatic light of 780 nm separated by scattering with a spectral filter to 0.5 µw/cm2 to determine the half-life exposure energy sensitivity (µJ/cm2).

Thereafter, the monolayer type electrophotographic sensitive material is immersed in an aqueous 0.5% sodium hydroxide solution and then washed with water to remove the photosensitive layer. In this case, the alkali solution property is determined in terms of the rate of removal of the photosensitive layer.

Then, the same monolayer type electrophotographic sensitive material independently formed on a ground aluminum plate is subjected to plate making by the liquid development process using a TTP laser plate making device manufactured by Toppan Printing Co., Ltd. Corona charging is carried out at +6 kV. The latent electrostatic image is developed with a negatively polarized developer. The developed image is thermally fixed to obtain a toner image.

The toner image thus formed is washed out with an alkaline aqueous etching solution and washed with water to obtain a lithographic printing plate.

The printing plate thus obtained is mounted in an offset printing machine and used to make prints by a conventional process. The prints made initially and the prints made after 100,000 prints are examined for the degree of blistering and the clarity of the print.

The results of the investigation of electrophotographic properties, alkali solution property and printing quality are shown in Table 2.

Examples 2 to 17

Electrophotographic platemaking quality matrix plates are prepared by following the procedure of Example 1, with Difference that various photoelectroconductive phthalocyanine compounds as shown in Table 1, copolymers obtained from various monomer mixtures (P-1) to (P-8) and sensitizers are used in place of F₈(o-MePhS)₈ZnPc and the copolymer of the monomer mixture (P-1). They are evaluated for their electrophotographic properties, alkali solution property and printing quality. The results are shown in Table 2.

The electrophotographically sensitive materials prepared as described above are left in a fluorescent-lighted room for two months and then examined for their electrophotographic properties and print quality. The properties showed practically no difference before and after the two months.

Control examples 1 to 6

Electrophotographic plate-making quality matrix plates are prepared by following the procedure of Example 1 except that various photoelectroconductive phthalocyanine compounds as shown in Fig. 1, copolymers of monomer mixtures (P-1) and (P-8) and monomer mixtures (S-1) to (S-5) as shown below, and sensitizers are prepared in the same manner as in Preparation Example 2. They are tested for electrophotographic properties, alkali solution property and printing quality, respectively. The results are shown in Table 2.

(S-1) Acrylic acid/butyl acrylate/butyl methacrylate (25/20/55),

(S-2) Methacrylic acid/styrene/isopropyl acrylate (30/15/55),

(S-3) Methacrylic acid/methyl acrylate/ethyl methacrylate (15/60/25),

(S-4) Acrylic acid/styrene/ethyl acrylate/methyl methacrylate (25/8/20/47) and

(S-5) Acrylic acid/butyl acrylate/methyl methacrylate/2-hydroxyethyl methacrylate (10/40/40/10). Table 1 Photoelectroconductive phthalocyanine compound Copolymer Sensitizer Type Quantity (parts) Film thickness (µm) Example Control example α-type copper phthalocyanine ε-type copper phthalocyanine α-type TiOPc not used Pentafluorobenzoic acid Succinic anhydride Benzoic acid Phthalic anhydride Tetrafluorophthalic anhydride Tetrafluorobenzoic acid Table 2 Exposure half-value amount (E1/2) Surface potential V₀(V) Potential at a dark spot V₅(V) Exposure with a tungsten lamp (Lux sec) Exposed to light of 780 nm (µJ/cm²) Rate of alkali dosing (sec) Print quality Example Control example No sensitivity Not measured over 30 sec

Surface potential, V₀ (V); Potential at a dark spot, V₅ (V)

Exposure half-value (E1/2)

exposed with a tungsten lamp (lux x sec)

exposed to light of 780 nm (µJ/cm²)

Alkali dissolution speed (sec) Print quality

A: Capable of producing 100,000 very clear prints free from smeared background and lines on it.

B: Capable of producing 100,000 clear prints free from smeared background but not from lines on it.

C: Producing prints that suffer from smeared backgrounds and reduced clarity.

D: Peeling of the plate surface after producing 100,000 prints observed.

E: No toner image obtained and no pressure achieved.

Examples 18 to 27

Electrophotographic plate-making quality matrix plates are prepared by following the procedure of Example 1 except that the various photoelectroconductive phthalocyanine compounds shown in Table 3 and the copolymers obtained from the monomer mixtures (P-1) to (P-8) are used instead of F₈(o-MePhS)₈ZnPc and the copolymer of the monomer mixture (P-1). The electrophotographically sensitive materials of the single layer type obtained as electrophotographic plate-making quality matrix plates as described above are coated with an electrostatic Paper analyzer negatively charged to -6.0 kV. They are examined for their electrophotographic properties, alkali solution property and printing quality in the same manner as in Example 1. The results are shown in Table 4. Table 3 Electroconductive phthalocyanine compound Copolymer Sensitizer Type Quantity (parts) Film thickness (µm) Example Table 2 Exposure half-life amount (E1/2) Surface potential V₀(V) Potential at a dark spot V₅(V) Exposure with a tungsten lamp (Lux sec) Exposed to light of 780 nm (µJ/cm²) Rate of alkali dosing (sec) Print quality Example DBG: oxymethylated benzoguanamine condensate (molecular weight 480) DCHG: oxymethylated cyclohexyl-carboguanamine condensate (molecular weight 780) BG-600: butyl ether-oxymethylated benzoguanamine condensate (molecular weight 600)

Claims (10)

1.Electrophotographic matrix plate comprising an electrically conductive substrate having a photosensitive layer comprising an alkali-soluble binder resin and a photoconductive, fluorinated zinc phthalocyanine compound, characterized in that the photoconductive compound is an octafluoro-zinc phthalocyanine represented by the general formula I: wherein R is a -SZ group in which Z is a phenyl group, a phenyl group substituted with an alkyl group having 1 to 5 carbon atoms, or a naphthyl group, and that the binder resin is a copolymer obtainable by polymerizing a monomer mixture comprising (a) one or more hydroxyalkyl acrylate(s) and/or hydroxyalkyl methacrylate(s), (b) at least one copolymerizable unsaturated carboxylic acid, (c) at least one styryl compound and (d) at least one acrylic acid ester which differs from the hydroxyalkyl acrylate(s) under (a), and optionally (e) at least one methacrylic acid ester which is different from the hydroxyalkyl methacrylate(s) of (a). 2. Matrix plate according to claim 1, characterized in that the binder resin is a copolymer with a number-average molecular weight in the range of 1000 to 50,000, which is obtainable by polymerizing a monomer mixture composed of (a) 0.5 to 40% by weight of one or more hydroxyalkyl acrylate(s) and hydroxyalkyl methacrylate(s) with alkyl groups of 2 to 10 carbon atoms, (b) 10 to 40% by weight of at least one copolymerizable carboxylic acid selected from acrylic acid, methacrylic acid and itaconic acid, (c) 10 to 70% by weight of at least one styryl compound, (d) 5 to 50% by weight of at least one acrylic acid ester selected from alkyl acrylates with alkyl groups of 1 to 12 carbon atoms and cycloalkyl acrylates with cycloalkyl groups of 5 to 7 carbon atoms and optionally (e) up to 40% by weight of at least one methacrylic acid ester selected from the group consisting of alkyl methacrylates having alkyl groups of 1 to 12 carbon atoms and cycloalkyl methacrylates having cycloalkyl groups of 5 to 7 carbon atoms. 3. Matrix plate according to claim 1 or 2, characterized in that the photosensitive layer, if it is to be charged to positive polarity in use, contains a sensitizer. 4. Matrix plate according to claim 3, characterized in that the sensitizer is at least one compound selected from the compounds represented by the following general formulas III, IV and V, as well as from succinic anhydride and maleic anhydride: wherein X¹ to X⁵ are either the same or different and represent a hydrogen atom, a fluorine atom, a -COOH group or a -NO₂- group, wherein Y¹ to Y⁴ are either the same or different and represent a hydrogen atom, a fluorine atom, a -COOH group or a -NO₂- group, and where Z¹ and Z² are either the same or different and represent a hydrogen atom, a fluorine atom, a -COOH group or a -NO₂- group. 5. Matrix plate according to claim 1 or 2, characterized in that the photosensitive layer, when it is to be charged to negative polarity in use, contains at least one charge transfer substance selected from oxazole derivatives, oxadiazole derivatives, pyrazoline derivatives, hydrazone derivatives and triphenylamine derivatives. 6. Matrix plate according to claim 5, characterized in that the charge transfer substance is represented by the following general formula VI: wherein R¹ and R² are each an aryl group or an aralkyl group and R³ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a benzyl group, an alkoxy group having 1 to 4 carbon atoms, a phenoxy group or a benzyloxy group. 7. Matrix plate according to claim 1 or 2, characterized in that the photosensitive layer, when it is to be charged to a negative polarity in use, contains an aminotriazine resin. 8. Matrix plate according to claim 7, characterized in that the aminotriazine resin has at least one composition selected from benzoguanamine resin compositions, cyclohexylcarboguanamine resin compositions, melamine resin compositions and acetoguanamine resin compositions. 9. Matrix plate according to claim 7, characterized in that the aminotriazine resin or a composition thereof is the condensate of oxymethylated aminotriazine or the condensate of alkyl ether oxymethylated aminotriazine. 10. A lithographic printing plate obtainable by forming a toner image on an electrophotographic matrix plate according to any one of claims 1 to 9 by the electrophotographic process, fixing the toner image and then removing the non-image forming part of the toner image with an alkaline etching liquid.