JPH02216160A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance the sensitivity of the photosensitive body for plate making and to lower the residual potential as well as to decrease the development fogging by incorporating leuco malachite green as a sensitizing material into this body. CONSTITUTION:The photosensitive layer of this photosensitive body is formed by dispersing a photoconductive material (A) and the sensitizing material (B) into an alkaline soluble or alcohol soluble binder resin (C). One or more kinds among perylene-, perinone- and anthanthrone pigments are used as the component A and at least the leuco malachite green is usable as the component B. A butyl methacrylate/(meth)acrylic acid copolymer, etc., are usable for the component C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an electrophotographic photoreceptor, and more particularly to a negatively charged electrophotographic photoreceptor used in a plate-making system using an electrophotographic method.

(Prior art) As a plate-making material used for offset printing, a PS plate (Presensitized plate) is prepared by coating a photocurable resin or a photodegradable resin on a base treated to make it hydrophilic (for example, an aluminum plate whose surface has been treated to make it hydrophilic). plat
There is e). PS plates are widely used in offset printing because they allow high-quality plate making and have good printing properties. However, it has the disadvantage that the plate-making process is complicated and the cost of the entire process is high.

On the other hand, direct plate making using an electrophotographic method is available to compensate for the drawbacks of PS plates.

An example of a plate-making material is one in which zinc oxide is dispersed in a binder resin and coated on a base (mainly paper). A printing plate for offset printing is created by directly exposing the original to light reflected from the original and making it visible using a developer. Direct plate making is widely used in the printing market due to its simple plate making process and low running costs. However, there is room for improvement in such direct plate-making materials, such as expanding the range of application of printing conditions (for example, types of printing ink, etchant, and dampening solution).

As a material that expands the applicable range of printing conditions in direct plate-making materials, the elutable photosensitive layer is combined with a hydrophilic base (
For example, there is a plate-making material created by coating on an aluminum plate whose surface has been treated to make it hydrophilic, and it is directly plate-made using an electrophotographic method.

An example of a plate-making process is to apply an alkali-soluble or alcohol-soluble photosensitive layer to a plate-making material prepared by applying an alkali-soluble or alcohol-soluble photosensitive layer onto an aluminum plate whose surface has been made hydrophilic. After charging the plate-making material with a charger, the reflection from the original is applied. Exposure to light forms an electrostatic latent image. The electrostatic latent image formed in this way is developed and fixed using electrophotographic toner that is insoluble in the eluent (alkaline eluent or alcohol eluent), and the image area is resistive to the eluate. Forms a film of

When this plate is eluted with an eluent, only the portions of the photosensitive layer without the toner coating are eluted, exposing the hydrophilic base.

If the toner is lipophilic, it can be used as a printing plate for offset printing. In addition, instead of exposing to light reflected from the original, characters, images, etc. are directly exposed to the plate-making material using electrical signals generated by an electronic circuit using an output device using a laser light source, LED light source, etc. to create a latent image. There is also a way to form.

Eluents used in such plate-making systems include alkaline eluents whose main components are sodium silicate, sodium hydroxide, sodium carbonate, etc., alkaline eluents whose main components are benzyl alcohol, propatool, etc. There are some that are a combination of the two, and the appropriate one is selected depending on the type of binder resin and toner.

The characteristics required for an electrophotographic photoreceptor used as a final plate-making material for plate-making using the method described above include that the photosensitive layer is soluble in the eluent, and the initial potential, sensitivity, dark decay rate, and residual potential rate are It is necessary that the electrophotographic properties such as , etc. are good. In particular, the electrophotographic photoreceptor used for direct plate making has a limited exposure amount due to limitations of the plate making machine, and needs to have high sensitivity. Photoreceptors that are negatively charged and sensitive include electrophotographic photoreceptors in which photoconductive substances such as perylene pigments, perinone pigments, and anthanthrone pigments are dispersed in an alkali-soluble or alcohol-soluble binder resin. However, sufficient sensitivity has not been obtained as an electrophotographic photoreceptor used in direct plate making.

When an electron donating substance (donor agent) is added to the photosensitive layer of this type of electrophotographic photoreceptor, due to the doping effect,
It is known to be sensitized. However, when a donor agent is added, other electrophotographic properties (initial potential, dark decay rate, etc.) deteriorate, and at present, the sensitivity is insufficient for use as an electrophotographic photoreceptor for direct plate making, and for other electrophotographic photoreceptors. A photoreceptor with good characteristics has not been obtained.

Furthermore, when this type of electrophotographic photoreceptor is used with a negative charge, it is known that the addition of an electron transporting agent results in sensitization. However, the current situation is that there is no electron transport agent that exhibits a good electron transport effect, is harmless to the human body, and is relatively inexpensive.

Electrophotographic photoreceptors in which photoconductive substances such as perylene pigments, perinone pigments, and anzanthrone pigments are dispersed in a binder resin generally have a high residual potential, causing fogging over the entire developed image and causing problems with the printing plate. Image quality was insufficient.

(Object of the Invention) An object of the present invention is to provide an electrophotographic photoreceptor for plate-making materials that has high sensitivity as a negatively charged electrophotographic photoreceptor, has a low residual potential, and has little development fog.

(Structure of the Invention) At least one or more perylene pigments, perinone pigments, and anthanthrone pigments as a photoconductive substance and at least leucomalachite green as a sensitizing substance in an alkali-soluble or alcohol-soluble binder resin. The above problem was solved by using an electrophotographic photoreceptor characterized by having a photosensitive layer containing .

The photoconductive substance used in the present invention is preferably a negatively charged, highly sensitive substance with a high electron transport ability, and it has been found that perylene pigments, perinone pigments, anzanthrone pigments, etc. are suitable. In addition, although it is possible to use only one type of these photoconductive substances, if necessary, two or more types may be used in combination, or they may be used in combination with other photoconductive substances. It is also possible.

The perylene pigment used in the present invention is represented by the following general formula.

A perylene pigment with particularly good sensitivity is represented by the following formula.

The perinone pigment used in the present invention is represented by the following general formula.

(R) in the formula represents an alkyl group, an aryl group, an alkoxy group, a benzyl group, a halogen atom, a nitro group, hydrogen, or a composite group thereof.

The anzanthrone pigment used in the present invention is represented by the following general formula.

Leucomalachite green used in the present invention is represented by the following formula.

Anzanthrone pigments with particularly good sensitivity are represented by the following formula.

The alkali-soluble or alcohol-soluble binder resin used in the present invention is appropriately selected depending on electrical resistance, mechanical strength, solubility in eluent, characteristics when used as an electrophotographic photoreceptor, and the like. Examples of alkali-soluble or alcohol-soluble resins include resins having hydroxyl groups, acid anhydride groups, and carboxyl groups. For example, 1. Acrylic acid (or methacrylic acid) and methacrylic esters (e.g. stearyl methacrylate, lauryl methacrylate, alkyl methacrylate, butyl methacrylate, octyl methacrylate, methyl methacrylate, ethyl methacrylate) A copolymer with at least one type of.

2. A homopolymer of vinyl esters (e.g., vinyl acetate, vinyl butyrate, vinyl propionate) or at least one kind of vinyl ester and an unsaturated carboxylic acid (e.g., stearic acid, lauric acid, alkyl acid, butyric acid, Copolymer of octylic acid, methyl acid, ethyl acid, crotonic acid).

3. Copolymer of styrene and maleic acid (or maleic anhydride).

4. Polyvinyl alcohol or a copolymer of polyvinyl alcohol and vinyl acetate.

5. Phenolic resin.

6. The polymer blend product of two or more of the above resins and the support (base) used in the electrophotographic photoreceptor of the present invention must be electrically conductive and have a hydrophilic surface. Examples include metal plates such as aluminum, metal foils, conductive plastic films, films, or materials whose surfaces have been treated to make them hydrophilic, or materials whose surfaces have been coated with hydrophilic substances. . Furthermore, if necessary, an adhesive layer is provided between the base and the photosensitive layer to improve the adhesion between the photosensitive layer and the base, or a barrier layer is provided to improve the electrophotographic characteristics (dark decay rate, initial potential). You can also do that.

In the electrophotographic photoreceptor of the present invention, a solvent is added to adjust the coating liquid to an appropriate viscosity. As a solvent, alcohols (e.g. methanol, ethanol, propatool), aromatic hydrocarbons (e.g. toluene, benzene)
Ketones (e.g., acetone, methyl ethyl ketone), halogenated hydrocarbons (e.g., chloroform, methylene chloride), ethers, cyclic ethers, (e.g., tetrahydrofuran, dioxane), esters (e.g.,
(ethyl acetate, methoxyethanol), etc., and one or more types are used that have good compatibility with the binder resin and good film-forming properties during coating.

In the present invention, by dispersing leucomalachite green in the photosensitive layer of an electrophotographic photoreceptor sensitized with either a donor agent or a charge transport agent, or both, an electrophotographic photoreceptor with even higher sensitivity can be obtained. is obtained. Donor agents or charge transport agents that can be used in the present invention include:
The following substances may be mentioned. For example, hydrazone compounds,
These include oxadeazole compounds and triphenylmethane compounds.

In the electrophotographic photoreceptor for plate-making materials of the present invention, other substances can be added as necessary. For example, substances that improve electrophotographic properties (sensitizers other than leucomalachite green, etc.) substances that improve the dispersibility of photoconductive substances, substances that improve the adhesion between the base and the photosensitive layer (coupling agents, etc.) Examples include.

The method for producing the electrophotographic photoreceptor of the present invention will be described below.

First, photoconductive substances such as perylene pigments, perinone pigments, and anthanthrone pigments, leucomalachite green, and other substances that require addition are dispersed in an alkali-soluble resin or an alcohol-soluble resin to form a photoreceptor. Create a coating solution. At this time, in order to adjust the coating liquid to an appropriate viscosity, a suitable solvent from among the above-mentioned solvents is added. Although simple stirring may be used as a dispersion method, it is preferable to uniformly disperse by mechanical means in order to improve electrophotographic properties and plate-made images. - Examples of the projectile dispersion means include ball mills, vibrating ball mills, and the like.

Next, the uniformly dispersed coating liquid is applied onto the above-mentioned base and dried to form a photosensitive layer.

At this time, a suitable solvent from among the solvents listed above is added to adjust the mixed liquid to a suitable viscosity. As a means of applying,
Examples include doctor blades, roll coaters, wire bars, etc. Regarding the drying conditions, conditions are selected so that the added solvent completely evaporates, a good coating film is formed, and the substances constituting the photoreceptor do not change.

The thickness of the photosensitive layer is preferably 0.5 to 30 μm, more preferably 1 to 10 μm.

The ratio of photoconductive material to binder resin is 1 part by weight of photoconductive material to 0.0 parts by weight of alkali-soluble binder resin. 5～
The amount is preferably 15 parts by weight, and more preferably 1 to 6 parts by weight. Furthermore, the amount of leucomalachite green added to the pigment is 0.01 to 10 parts by weight per 1 part by weight of the pigment.
0% by weight is preferable, more preferably 0.1 to 50% by weight.
Weight%.

The present invention will be explained below with reference to Examples.

Example Topylene pigment (represented by formula 2) 20 parts by weight Alkali-soluble resin (copolymer of butyl methacrylate and methacrylic acid) 60 parts by weight Leucomalachite green 5 parts by weight Methyl ethyl ketone/methoxyethanol mixed solvent 10
0 parts by weight The mixture having the above formulation was placed in a glass ball mill and rotated on a ball mill stand for 48 hours to uniformly disperse the mixture. The prepared photosensitive solution was applied onto an aluminum plate using a wire bar and dried, forming a film with a thickness of 3 μm on the aluminum plate.
An electrophotographic photoreceptor having a photosensitive layer of m was prepared.

The bright attenuation characteristics and dark attenuation characteristics of the electrophotographic photoreceptor created in this way were measured using a paper analyzer 5P-
428 (manufactured by Kawaguchi Denki Co., Ltd.).

As for the measurement conditions, for the dark decay rate, the surface potential 5 seconds after corona charging of an electrophotographic photoreceptor prepared with a charging voltage of -6 KV is (V5), and the surface potential 60 seconds later is (V2).
C) and rl-[(V2C)/(V5)] X1
00J was taken as the dark decay rate DD (%). Regarding bright decay characteristics, the produced electrophotographic photoreceptor was corona charged at a charging voltage of -6 KV, and after being left in a dark place for 5 seconds, the surface potential at this time was taken as the initial potential (5). Thereafter, it was exposed to white light using a tungsten lamp at an exposure dose of 10 Lux. The surface potential after the start of exposure relative to (v5) is 1/2
The exposure amount that decreases to
Expressed in units of ux-sec). Similarly, the exposure amount at which the surface potential after the start of exposure decreases to 1/10 with respect to (V5) is set as 1/10 exposure amount (El/10), and (Lux-s
Expressed in units of e c). Furthermore, after the start of exposure, 15
The surface potential after seconds was measured as residual potential (Vr). The results are shown in Table 1.

Example 2 An electrophotographic photoreceptor was produced and measured in the same process as in Example 1, except that the blending ratio was changed as shown below. The results are shown in Table 1.

- Anzanthrone pigment, 20 parts by weight (represented by formula 5) - Alkali-soluble resin (copolymer of butyl methacrylate and methacrylic acid) 60 parts by weight - Leucomalachite green 5 parts by weight - Methyl ethyl ketone/methoxyethanol mixed solvent
100 parts by weight Example 3 An electrophotographic photoreceptor was prepared and measured in the same process as in Example 1, except that the blending ratio was changed as shown below. The results are shown in Table 1.

- Perinone pigment (represented by formula 3) 20 parts by weight - Alkali-soluble resin (copolymer of butyl methacrylate and methacrylic acid) 60 parts by weight - Leucomalachite green 3 parts by weight - Methyl ethyl ketone/methoxyethanol mixed solvent 10
0 parts by weight Example 4 An electrophotographic photoreceptor was prepared and measured in the same process as in Example 1, except that the blending ratio was changed as shown below. The results are shown in Table 1.

- 20 parts by weight of perylene pigment (represented by formula 2) - 60 parts by weight of alkali-soluble resin (copolymer of butyl methacrylate and acrylic acid) - 3 parts by weight of leucomalachite green - 1 part by weight of methyl ethyl ketone/methoxyethanol mixed solvent
00 parts by weight hydrazone 2
Comparative Example 1 (Parts by weight) An electrophotographic photoreceptor was prepared and measured in the same process as in Example 1 except that the blending ratio was changed as shown below. The results are shown in Table 1.

- 20 parts by weight of perylene pigment (represented by formula 2) - 60 parts by weight of alkali-soluble resin (copolymer of butyl methacrylate and methacrylic acid) - Methyl ethyl ketone/methoxy ethanol mixed solvent
100 parts by weight Comparative Example 2 An electrophotographic photoreceptor was prepared and measured in the same process as in Example 1, except that the blending ratio was changed as shown below. The results are shown in Table 1.

・Anzanthrone pigment, 20 parts by weight (represented by formula 5) ・Alkali-soluble resin (copolymer of butyl methacrylate and methacrylic acid) 60 parts by weight ・Mixed solvent of methyl ethyl ketone and methoxyethanol
100 parts by weight Comparative Example 3 An electrophotographic photoreceptor was prepared and measured in the same process as in Example 1, except that the blending ratio was changed as shown below. The results are shown in Table 1.

・20 parts by weight of perinone pigment (represented by formula 3) ・60 parts by weight of alkali-soluble resin (copolymer of butyl methacrylate and methacrylic acid) ・Mixed solvent of methyl ethyl ketone and methoxyethanol
100 parts by weight Comparative Example 4 An electrophotographic photoreceptor was prepared and measured in the same process as in Example 1, except that the blending ratio was changed as shown below. The results are shown in Table 1.

・20 parts by weight of perylene pigment (represented by formula 2) ・60 parts by weight of alkali-soluble resin (copolymer of butyl methacrylate and acrylic acid) ・Mixed solvent of methyl ethyl ketone and methoxyethanol
100 parts by weight hydrazone
2 parts by weight (hereinafter referred to as margins) Table 1 From the results summarized in Table 1, Examples 1 to 4 in which leucomalachite green was dispersed in the photosensitive layer had high sensitivity;
There is no residual potential. Further, by dispersing leucomalachite green in the photosensitive layer, a good electrophotographic photoreceptor was obtained without deteriorating other electrophotographic properties (initial potential, dark decay rate).

Evaluation Example 1 The electrophotographic photoreceptors prepared in Examples 1 to 3 were plate-made using a direct plate-making machine (IP-701, manufactured by Iwasaki Tsushinki), and the sensitivity as a plate-making material and image quality (development fog, image quality) were evaluated. Toner concentration) was evaluated. Results, Example 1~
The electrophotographic photoreceptors prepared in Example No. 3 each had a sensitivity sufficient for plate making, and there was very little development fog, and good plate-made images were obtained.

Evaluation Example 2 The electrophotographic photoreceptors prepared in Comparative Examples 1 to 3 were plate-made using a direct plate-making machine (IP-701, manufactured by Iwasaki Tsushinki), and the sensitivity as a plate-making material and image quality (development fog, toner on the image) were evaluated. Concentration) was evaluated. Results, Comparative Examples 1 to 3
The electrophotographic photoreceptors prepared in the above had insufficient sensitivity for plate making, and development fog was observed, so that good plate-made images could not be obtained.

Evaluation Example 3 The electrophotographic photoreceptor prepared in Example 4 was plate-made using a direct plate-making machine (IP-701, manufactured by Iwasaki Tsushinki), and the sensitivity as a plate-making material and image quality (development fog, toner density on the image) were evaluated. was evaluated. As a result, the plate had sufficient sensitivity for plate making, and a good plate-made image with extremely little development fog was obtained.

・Evaluation Example 4 The electrophotographic photoreceptor prepared in Comparative Example 4 was plate-made using a direct plate-making machine (IP-701, manufactured by Iwasaki Tsushinki), and the sensitivity as a plate-making material and image quality (development fog, toner density on the image) were evaluated. ) was evaluated. As a result, although the sensitivity was sufficient for plate making, development fog was observed and a good plate-making image could not be obtained.

Evaluation Example 5 Using the coating liquids prepared in Example 1 and Example 4,
As a base, the surface was grained and coated on an anodized aluminum plate to create an electrophotographic photoreceptor, which was then plate-made using a direct plate-making machine (IP-701, manufactured by Iwasaki Tsushinki).
Sensitivity as a plate-making material, and image quality (development fog,
The toner density on the image) was evaluated. It had sufficient sensitivity for plate making, and there was very little development fog, and good plate-made images were obtained. This plate is used to elute the photosensitive layer in the areas where there is no toner coating using an alkaline eluent.
The hydrophilic base was exposed and an offset printing plate was created. Using this plate, offset printing was performed using tap water with a pH of 6.5 as a dampening solution, and as a result, good printed matter was produced.

(Effects of the Invention) The present invention provides at least one type of perylene pigment, perinone pigment, and anzanthrone pigment as a photoconductive substance, and at least leucomalachite green as a sensitizing substance, in an alkali-soluble or alcohol-soluble form. By having a photosensitive layer contained in a soluble binder resin, it has high sensitivity as an electrophotographic photoreceptor for negatively charged plate-making materials, and
It was possible to provide an electrophotographic photoreceptor with low residual potential and low development fog.

Patent applicant: Iwasaki Tsushinki Co., Ltd. Same as Takashi Kitamura Procedural amendment Display of incidents 1999 Patent Application No. 38059 name of invention electrophotographic photoreceptor person who makes corrections Date of amendment order 6. Contents of amendment The contents of the description are amended as follows.

(1) Delete [(e.g. stearic acid, lauric acid, alkyl acid, butyric acid, octylic acid, methyl acid, ethyl acid, crotonic acid)] from lines 7 to 9 on page 11.

(2) Delete [(4° polyvinyl alcohol or copolymer of polyvinyl alcohol and vinyl acetate,)] from lines 12 to 13 on page 11.

(3) Correct [5,] in line 14 of page 1.1 to [4,].

(4) Correct [6,1 on page 11, line 15] to [5,].

(5) In page 15, line 18, [ball mi ni] is corrected to [ball mi ni ko].

Claims (1)

[Claims] 1. Containing at least one or more perylene pigments, perinone pigments, and anzanthrone pigments as a photoconductive substance, and at least leucomalachite green as a sensitizing substance in an alkali-soluble or alcohol-soluble binder resin. An electrophotographic photoreceptor characterized by having a photosensitive layer.