Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording-members for original recording by exposure, e.g. to light, to heat or to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
  • G03G5/0664—Dyes
  • G03G5/0675—Azo dyes
  • G03G5/0679—Disazo dyes
  • G03G5/0681—Disazo dyes containing hetero rings in the part of the molecule between the azo-groups
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording-members for original recording by exposure, e.g. to light, to heat or to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
  • G03G5/0664—Dyes
  • G03G5/0675—Azo dyes
  • G03G5/0679—Disazo dyes

Definitions

• the present invention relates to a litho­graphic printing plate and in particular to a litho­graphic printing plate made by electrophotography.
• Lithographic printing plate materials of electrophotographic type having photoconductive materials are relatively high in sensitivity and can afford inexpensive printing materials of high printing endurance and have intensively been studied.
• Printing plates of this type are made by forming a photo­conductive layer on a support and forming electrophoto­graphically a toner image and hydrophilizing or dissolving away non-image portion.
• a photoconductive layer comprising a binder containing zinc oxide as a photoconductive material and a sensitizer
• non-image portion is hydrophilized with potassium ferrocyanide to make a lithographic printing plate, but hydrophilicity of the non-image portion is poor and so print is apt to be stained and printing endurance is low.
• photoconductive layer contains zinc oxide in a large amount and hence dissolution is difficult and the hydrophilic aluminum surface cannot be sufficiently utilized.
• a photoconductive layer comprising a binder soluble in an aqueous alkali or alcohol solution to which a large amount of oxadiazole organic photoconductor and a small amount of sensitizing dye are added is coated on an aluminum sheet.
• Another example is to use a photoconductive layer comprising a binder soluble in aqueous alkali or alcohol solution in which organic photoconductive pigment is dispersed.
• the object of the present invention is to provide a lithographic printing plate material which is free from the above defects, improved in pre-exposure properties, has high sensitivity, easy in dissolving away of non-image portion, less in printing stain and high in printing endurance.
• the above object can be attained by printing plate made by forming a toner image by electrophotographic method on a printing plate material comprising an electrically conductive and hydrophilic base and, provided thereon, a photoconductive layer and thereafter dissolving away non-image portion other than the toner image portion with a solution mainly composed of an alkali and/or alcohol, characterized in that said photoconductive layer contains an alkali and/or alcohol soluble resin binder, an azo compound heat treated in an organic solvent excluding alcohol solvent and represented by the following formula (I):
• A represents a divalent residue which bonds through its C atom to N atoms which constitute azo
• Cp1 and Cp2 are identical or different and at least Cp1 is a group represented by the formula: (wherein Z represents a group of atoms necessary to form a substituted or unsubstituted carbocyclic aromatic ring, a substituted or unsubstit
• the first component which constitutes the photoconductive layer of the electrophotographic lithographic printing plate of the present invention is a resin binder soluble in alkali and/or alcohol.
• resin binder soluble in alkali and/or alcohol.
• these resin binders there have been known, for example, phenolic resin, alcohol-soluble nylon resin, styrene-maleic anhydride copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-maleic anhydride copolymer, and bipolymers or terpolymers of acrylic acid, methacrylic acid, crotonic acid or itaconic acid with styrene, acrylic acid ester or methacrylic acid ester.
• the second component of the photoconductive layer of the present invention is an azo compound (pigment) represented by the formula (I) and heat treated in an organic solvent.
• A represents a divalent residue which bonds through its C atom to N atoms which constitute azo
• Cp1 and Cp2 are identical or different and at least Cp1 is a group represented by the formula: (wherein Z represents a group of atoms necessary to form a substituted or unsubstituted carbocyclic aromatic ring, a substituted or unsubstituted heterocyclic aromatic ring, or an unsubstituted monocyclic hydrocarbon ring and R represents an aryl group having one or two CF3 groups)].
• Cp2 can be selected from the following formulas (a)-(f):
• Z1 and Z2 each represents a group of atoms necessary to form a substituted or unsubstituted aromatic hydrocarbon ring or a substituted or unsubstituted heterocyclic ring
• R1 and R2 each represents a substituted or unsubstituted alkyl, aralkyl, aryl or heterocyclic group
• R3 represents an alkyl group or a carboxyl group or an ester thereof
• R4 and R6 each represents a substituted or unsubstituted aryl or heterocyclic group
• R5 represents a hydrogen atom or a substituted or unsubstituted alkyl, aralkyl, aryl or heterocyclic group
• Y1 and Y2 each represents -NR7R8, -OR9
• -NHN CH-R10 or -NHNR11R12
• Nonlimiting examples of azo compounds represented by the formula (I) and useful in the present invention are shown below.
• the azo compounds used in the present inven­tion where Cp1 and Cp2 are different are also synthe­sized by conventional method in two stages of coupling with the first coupling component and that with the second coupling component.
• the azo compound of the above formula (I) shows substantially no photosensitivity when it is dispersed as it is in a polymer and a photoconductive layer is formed therefrom, but shows high photo­sensitivity when a carrier transport material referred to hereinafter is added thereto.
• Content of the azo compound in photoconductive layer is not critical, but suitably is 30% by weight or less and preferably 5-30% by weight for obtaining good dissolving-away properties in practical use.
• organic solvents used for heating and stirring treatment in the present invention mention may be made of, for example, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, aromatic solvents such as toluene and xylene, ester solvents such as ethyl acetate and n-butyl acetate, halogenated hydrocarbon solvents such as chlorobenzene and dichloromethane, ether solvents such as tetrahydrofuran and dioxane, and dimethylformamide and dimethylacetamide. Especially preferred are ester solvents.
• ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone
• aromatic solvents such as toluene and xylene
• ester solvents such as ethyl acetate and n-butyl acetate
• halogenated hydrocarbon solvents such as chlorobenz
• Conditions such as temperature and time for the heating and stirring treatment are determined considering characteristics as electrophotographic photoreceptor and dissolving-away properties of the photosensitive layer and preferably are 30-60 minutes at 40-80°C. When heat treatment for a long time at high temperature is conducted, sometimes electrophotographic characteristics or dissolving-away properties of photosensitive layer are adversely affected.
• the azo compound may be used at dry state by evaporation of solvent, but preferably is used at wet state.
• the heat treatment of azo compound with organic solvent in the present invention means trans­formation of crystal of the azo compound, but does not merely mean enhancement of sensitivity of photosensitive layer, but also improves dissolving-away properties of photosensitive layer.
• the third component in the present invention is the carrier transport material.
• the carrier transport material When the azo compound alone is dispersed in a binder to form a photo­sensitive layer, such layer is very low in photosensi­tivity.
• amount of the carrier transport material insoluble in the dissolu­tion solution including the azo compound should be as small as possible. Under such circumstances, a carrier transport material which is effective in a small amount is necessary.
• carrier transport materials can be used in the present invention.
• a long time is required before toner development and thus dark decay of surface potential of the photosensitive layer is desired to be as small as possible.
• dark decay is great.
• carrier transport materials of diarylalkanes and triphenylmethanes represented by the following formulas are preferred for the azo compounds used in the present invention.
• R1, R2, R3 and R4 which may be identical or different each represents a hydrogen atom, a methyl group, an ethyl group, a benzyl group or a benzyl group having substituent
• R5 and R6 which may be identical or different each represents a hydrogen atom or an alkyl group
• R7 and R8 which may be identical or different each represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom
• R1, R2, R3 and R4 which may be identical or different each represents a hydrogen atom, a methyl group, an ethyl group, a benzyl group or a benzyl group having substituent
• R5 represents a hydrogen atom or an alkyl group
• R6, R7 and R8 which may be identical or different each represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom
• Nonlimiting examples of the carrier transport materials are enumerated below.
• the above carrier transport materials normally act as hole transport materials and are added in a large amount in binder, but in the present invention, they exhibit the effect to increase photosensitivity in a smaller amount than the azo compound. It is assumed that in the present invention, the carrier transport material interacts on -CF3 group on the surface of azo compound to reduce the surface barrier high to promote migration of photocarrier to outside and thus photosensitivity is enhanced.
• addition amount of the carrier transport material may be smaller than that of the azo compound in the preset invention. If it is added in a large amount, there occur problems such as reduction of charged potential and increase of dark decay. There­fore, it is preferred to use the carrier transport material in an amount of 5-80% by weight of the azo compound.
• the printing plates according to the present invention is made by toner developing a printing plate material comprising an electrically conductive and hydrophilic base and, provided thereon, a photo­conductive layer comprising the above-mentioned three components by electrophotographic process to form images, and washing away non-image portion other than the toner images by dissolving-out method.
• the base for printing plate materials of the present invention there may be used all of the known bases of printing plate materials, for example, metal sheets such as aluminum sheet, zinc sheet, magnesium sheet and copper sheet; films and synthetic papers such as polyester, cellulose acetate, poly­styrene, polycarbonate, polyamide and polypropylene; and coated papers such as resin-coated papers.
• metal sheets such as aluminum sheet, zinc sheet, magnesium sheet and copper sheet
• films and synthetic papers such as polyester, cellulose acetate, poly­styrene, polycarbonate, polyamide and polypropylene
• coated papers such as resin-coated papers.
• bases having hydrophobic surface must be previously subjected to hydrophilic treatment.
• Metal sheets, especially aluminum sheets are most suitable and preferably they are subjected to surface treatments such as sand blasting treatment, alkali treatment, acid treatment and anodization treatment.
• films it is preferred that they are coated with polymers of relatively high hydrophilicity, followed by crosslinking treatment or they are subjected to vapor deposition with a metal or laminated with a metal.
• a metal or laminated with a metal it is preferred to subject the surface of the base to electroconductive treatment.
• the printing plate material of the present invention is made by adding the above three components to a solvent and dispersing them by a suitable known dispersing machine, for example, sand mill, colloid mill, homogenizer, and ultrasonic dispersing machine to prepare a coating liquid and coating this coating liquid at a thickness of 1-10 ⁇ on the above support and drying the coat.
• a suitable known dispersing machine for example, sand mill, colloid mill, homogenizer, and ultrasonic dispersing machine to prepare a coating liquid and coating this coating liquid at a thickness of 1-10 ⁇ on the above support and drying the coat.
• the coating can be performed by known coating methods such as dip coating, bead coating, wire bar coating, blade coating, roller coating, curtain coating and extrusion coating.
• the solvents usable here includes all organic solvents which can dissolve the binder and can dissolve or disperse the photoconductive compound.
• solvents such as methanol, ethanol, propanol, butanol and hexyl alcohol
• cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve
• aromatics such as benzene, toluene and xylene
• cyclic ethers such as dioxane and tetrahydrofuran
• esters such as ethyl acetate, butyl acetate and amyl acetate
• ketones such as acetone, methyl isobutyl ketone and methyl ethyl ketone, dimethylformamide, dimethyl­sulfoxide and halogenated hydrocarbons.
• the resulting printing plate material is subjected to image formation by electrophotographic process and non-image portion is dissolved away to make a printing plate.
• Either of dry toner or wet toner may be used as toner for formation of image, but use of wet toner according to liquid developing is much preferred for obtaining print of excellent resolving power.
• the toner is required to be hydrophobic and ink-receptive and has adhesion high enough to stand printing and besides, to have resistivity against alkalis and alcohols when the non-­image portion is dissolved away by alkali or alcohol.
• Toners which satisfy these requirements are dry toner comprising a mixture of iron powder with fine powder of a resin such as styrene resin, acrylic resin, polyester resin, epoxy resin or vinyl acetate resin and wet toner prepared by adding a charge control agent to a disper­sion of the above resin in an electrically insulating isoparaffinic solvent or to a fine particle formed by polymerization of monomers of the above resin in an isoparaffinic solvent.
• the toner contains a pigment or dye for coloration in such amount as having no adverse effect on safety or fixability.
• aqueous solutions of inorganic or organic various alkalis and/or alcohols include, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium phosphate, potassium phosphate, and ammonia and organic alkalis include, for example, amino alcohols such as monoethanolamine, diethanolamine and triethanolamine.
• Alcohols include, for example, lower alcohols and aromatic alcohols such as methanol, ethanol, propanol and benzyl alcohol, and ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol and cellosolves.
• Dissolvability of dissolution solution is selected depending on solubility of the photosensitive layer and degree of resistivity of the toner and designed considering dissolution rate, resolving power, image reproducibility and running processability. Generally, a small amount of surfactant is added to raise dissolution rate. After the non-image portion has been dissolved away, the plate can be subjected to wash­ing with water, treatment with dilute aqueous acid solution or gumming treatment with aqueous solution of gum arabic to obtain advantageous effect to inhibit stain in background in printing or reproducibility of print image.
• Electrophotographic characteristics of this printing plate material were measured under the condi­tions of a corona voltage of -6.0 KV and tungsten lamp 10 lux using an electrostatic field measuring apparatus SP428 (manufactured by Kawaguchi Electric Co.).
• Printing plate material was made in the same manner as in Example 1 except that heat treatment of the azo compound was not carried out and electrophotographic characteristics were measured as in Example 1.
• Printing plate material was made in the same manner as in Example 1 except that methanol was used as the solvent for heat treatment and electrophotographic characteristics of the material were measured as in Example 1.
• Printing plate material was made in the same manner as in Example 2 except that the following comparative azo compound (A) was used as the azo compound and electrophotographic characteristics thereof were measured as in Example 1.
• Printing plate material was made in the same manner as in Comparative Example 3 except that heat treatment of the azo compound was not carried out and electrophotographic characteristics thereof were measured as in Example 1.
• the printing plate materials of the preset invention had high sensitivity.
• Examples 1 and 2 the printing plate materials of the present invention (Examples 1 and 2) and those of Comparative Examples were set in commercially available plate making machine of electrophotographic type and were subjected to toner development and non-image portion was dissolved away with eightfold diluted solution of DP-4 (aqueous alkali solution manufactured by Fuji Photo Film Co., Ltd.), followed by water-washing and gumming to obtain lithographic printing plates.
• DP-4 aqueous alkali solution manufactured by Fuji Photo Film Co., Ltd.
• the printing plate materials of Comparative Examples 3 and 4 were low in sensitivity and much fogging occurred in the exposed portion and dissolution of non-image portion was inferior.
• pigment remained after dissolving away of non-image portion to cause staining of printed copies.
• line image became thin to cause defect of image.
• the printing plate materials of the present invention are high in sensitivity and are improved in dissolution of non-image portion and thus can provide electro­ photographic lithographic printing plates of high printing endurance and causing less stain of printed copies.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Photoreceptors In Electrophotography (AREA)

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• 1989
  • 1989-04-05 JP JP8765789A patent/JPH02264963A/ja active Pending
• 1990
  • 1990-04-04 EP EP19900106400 patent/EP0391371A3/de not_active Ceased

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