JPH0650404B2 - Image holding member - Google Patents

Description

The present invention relates to an improvement of an image holding member for holding an electrostatic image or a toner image.

[Conventional technology]

Electrostatic or toner images are formed by various electrophotographic processes. As the image holding member that holds the formed image, there are an image holding member having a photoconductive layer called an electrophotographic photoreceptor and an image holding member having no photoconductive layer.

The electrophotographic photosensitive member has various configurations depending on the type of electrophotographic process applied. A typical electrophotographic photosensitive member is a photosensitive member having a photoconductive layer formed on a support and a photosensitive member provided with a laminate of a photoconductive layer and its insulating layer as an image holding layer, which are widely used. ing.

The electrophotographic photosensitive member is applied to a predetermined electrophotographic process to form an electrostatic image, and the electrostatic image is developed and visualized. However, the surface layer of such an image holding member is subjected to various treatments in the electrophotographic process, such as charging, exposure,
It is subjected to electromechanical processing such as development, transfer and cleaning. Therefore, in order to repeatedly use the photoconductor, it is important that the surface layer has strong durability against these treatments. Under the present circumstances, it is difficult to obtain a surface layer that satisfies durability especially in an environment of high humidity. Specifically, paper powder etc. of transfer paper adheres to the surface layer by repeated use, and the interaction between moisture under high humidity and ozone generated during corona discharge causes a thin film of low resistance material to be deposited on the surface layer. A layer is formed. When the electrostatic image formed in such a state is visualized, the obtained image has a phenomenon (hereinafter referred to as image deletion) in which it seems that only the portion where the low resistance material layer is formed flows.

In order to improve the durability under such high humidity, it is effective to make the surface layer hydrophobic. As a means therefor, there is a method of dispersing a general coating film surface modifier such as a fluorine-based oligomer or a fluorine-based surfactant, or a powder such as Teflon.

However, since the general surface modifiers have poor compatibility with the components of the coating liquid to be added, they migrate to the surface layer or ooze out during long-term use, which causes a problem in the sustainability of the effect. was there. Also, when the surface layer itself forms a photoconductive layer, the surface modifier has poor compatibility with the photoconductive substance, and moreover tends to become a trap for the movement of carriers due to photogeneration, and the repeated electrophotographic process The residual charge tended to increase. On the other hand, the surface layer in which Teflon powder or the like is dispersed has problems such as poor dispersibility, reduced transparency, and carrier trapping.

[Problems to be solved by the invention]

An object of the present invention is to solve the above problems and to provide an image holding member having a transparent and hydrophobic surface layer.

Another object of the present invention is to provide an image holding member capable of always obtaining a high-quality image without accumulating residual charges in a repeated electrophotographic process.

[Means for solving problems]

That is, in the present invention, in an image holding member having a surface layer holding an electrostatic image or a toner image, the surface layer has a polymerizable monomer having a fluorine atom in a side chain and a polymerizable monomer at one end of the molecular chain. It contains a fluorine-type comb-type graft polymer having a functional group having a heavy bond and obtained by copolymerizing the polymerizable monomer and a macromonomer having an affinity with the binder resin for forming the surface layer after polymerization ( However, the image holding member is characterized by containing a polycarbonate resin at the same time).

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. A graft polymer having a polymerizable monomer having a fluorine atom as a side chain, which is used as a constituent component of a surface layer of an image holding member according to the present invention as a constituent component (hereinafter referred to as a fluorine-based comb type graft). Polymer) is a polymerizable monomer having a fluorine atom as a side chain (hereinafter referred to as a fluorine-based polymerizable monomer) having a macromonomer, for example, a functional group having a polymerizable double bond at one end of each molecular chain. It is obtained by copolymerizing a macromonomer consisting of a relatively low molecular weight polymer having a molecular weight of about 1000 to 10000, and has a structure in which the macromonomer polymer is branched in the trunk of the fluoropolymer. ing.

The macromonomer is selected from those having an affinity with the main material (for example, a binder resin) that constitutes the surface layer in which the fluorine-based graft polymer is blended. For example, acrylic acid esters, methacrylic acid esters or A polymer such as a styrene compound or a copolymer is used.

On the other hand, as the fluorine-based polymerizable monomer, one or more of the following polymerizable monomers having a fluorine atom in the side chain is used, but the fluorine-based polymerizable monomer is not limited thereto.

[In the formula, R ₁ represents a hydrogen atom or a methyl group. R ₂ represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group or a nitrile group, and a combination of several kinds thereof may be used. n represents an integer of 1 or more, m represents an integer of 1 to 5, k represents an integer of 0 to 4, and m + k = 5. The content of the fluorine-based monomer residue in the fluorine-type comb-type graft polymer is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, in the fluorine-type comb-type graft polymer. Fluorine monomer residue content is 5% by weight
If it is less than the above, the effect of modifying hydrophobicity cannot be sufficiently exerted,
If the content of the fluorine-based monomer residue exceeds 90% by weight, the solubility with the macromonomer becomes poor.

Since the fluorine-based comb-type graft polymer in the present invention has such a structure, it has excellent compatibility with a coating liquid containing a binder resin for forming a surface layer, and thus the resulting coating film has good transparency. It has a long-lasting effect without migrating or bleeding out onto the surface layer like a conventional surface modifier, and the fluorine-containing branch portion has an excellent interfacial migration property. Therefore, the surface modification is achieved by adding a small amount. Furthermore, even if this additive is contained in the surface layer, stable charge characteristics can be obtained without accumulation of residual charges due to repeated electrophotographic processes. This is because the graft polymer does not substantially exist in the bulk of the photoconductive layer due to the interfacial migration property of the fluorine-based comb polymer as described above, and the transport of the photocarrier is not hindered at all. Moreover, no trap is formed. The amount of the fluorine-type comb-type graft polymer added is appropriately 0.01 to 10% by weight, and particularly preferably 0.05 to 5% by weight, based on the solid content of the surface layer. If the amount added is less than 0.01% by weight, a sufficient surface-modifying effect cannot be obtained, while if it exceeds 10% by weight, the graft polymer will be present not only on the surface of the coating film but also in the surface of the palk. Due to the problem of compatibility with the resin, which is the main component, and the photoconductive substance, whitening is caused, and residual charge is accumulated when the electrophotographic process is repeated.

The form of the surface layer containing a fluorine-type comb polymer (1) when the surface layer itself is a photoconductive layer coating a photoconductive polymer or photoconductive powder dispersed or dissolved in a binder resin It is formed by applying and drying a liquid; and (2) when the surface layer is formed on the photoconductive layer, (a) the surface layer is a relatively thin film (about 0.0 to 10 μm) and image formation is performed. The process is the same as the above (1), and (b) the surface layer is a relatively thick film (about 10 to 50 μm) and the image forming process is different from the above (1);
And so on. In any of the above cases, the composition used for forming the surface layer is dispersed or dissolved in a solvent and the fluorine-based comb-type graft polymer is added to the solution, and the obtained coating solution is applied onto a suitable substrate or An image holding member is obtained by coating on the photoconductive layer and drying. Here, as the binder resin and the photoconductive substance contained in the composition for forming the surface layer, known ones usually used in this field can be used.

〔Example〕

 The present invention will be further described below with reference to examples.

Example 1 100 parts of zinc oxide powder for electrophotography (parts by weight, the same applies hereinafter), 0.5 parts of rose bengal as a dye, 5 parts of methanol, and 100 parts of toluene were well dispersed in a ball mill, and then the solvent was removed by absorption. Excluded. Butyral resin (trade name BM) as a binder for zinc oxide sensitized in this way
-1, Sekisui Chemical Co., Ltd.) 20 parts, blocked isocyanate 20
Parts, 0.4 parts of triethanolamine as a curing agent, 50 parts of methyl ethyl ketone as a solvent, and 20 parts of ethanol were added, and well dispersed by a ball mill again to obtain a photoconductive coating. This was dip-coated in an aluminum cylinder of 80φ × 300 mm that had been subjected to an undercoating treatment, and was cured by heating at 120 ° C. for 30 minutes to form a 25 μm photosensitive layer.

Next, 100 parts of conductive TiO ₂ (product name ECT-62 titanium industry) was well dispersed with a ball mill in a liquid prepared by dissolving 100 parts of acrylic modified silicone resin (product name KR-3093, Shin-Etsu Silicone) in 1500 parts of toluene. A coating solution for protective layer was obtained. Furthermore, the trunk of this coating solution is polyfluoroacrylate (CH ₂ = C
HCOOCH ₂ CH ₂ C _n F _{2n + 1} polymer n = 8, 10, 12, ₁₄ )), a branch consisting of polymethylmethacrylate having a molecular weight of 5000, a molecular weight of 80,000, and a fluoroacrylate having a fluoroacrylate content of 50% by weight. 4 parts of the type graft polymer was added as a solid content. This solution is coated on the photosensitive layer,
It was dried with hot air at 100 ° C. for 20 minutes to form a 2 μ protective layer. This is designated as Sample 1.

For comparison, a sample was prepared in the same manner as in Sample 1, except that the fluorine-type comb polymer was not added.

This is designated as Sample 2.

For these samples, −5.5 kV corona charging, image exposure,
Durability was evaluated by an electrophotographic process consisting of dry toner development, toner transfer to plain paper, and cleaning with a urethane rubber blade. The results are shown in Table 1. The evaluation environment is 32.5 ° C. and RH 90%.

Example 2 100 parts of CdS powder (parts by weight, the same applies hereinafter), 15 parts of diallyl phthalate resin (trade name, Daiso Dup, manufactured by Osaka Soda Co., Ltd.) as a binder, and 0.5 parts of benzoyl peroxide.
Part was dissolved in MEK and mixed well with a roll mill device to obtain a photoconductive coating. This is applied to an 80 × 300 mm Al cylinder by a dipping method, cured at 110 ° C. for 10 minutes, and 40 μm
It was a thick photoconductive layer. Then on top of this benzoyl peroxide 3
A diallyl phthalate resin (same as above) liquid containing 10 wt% was applied and cured at 110 ° C. for 10 minutes to form a resin layer having a thickness of 10 μm.

Next, urethane acrylate resin (trade name: Sonne,
(Manufactured by Kansai Paint Co., Ltd.) was applied and cured by irradiation with ultraviolet rays to form a layer having a thickness of 10 μm.

In addition, polysulfone resin (trade name Udel P-1700UCC
10 parts by weight) was dissolved in 50 parts of monochlorobenzene and 20 parts of MEK, and the trunk was made of polyfluoroacrylate (CH ₂
= CHCOOCH ₂ CH ₂ C _n F _{2n + 1} polymer n = 8, 10, 12, ₁₄
As a solid content, 0.2 part of a fluorine-type comb-type graft polymer having a molecular weight of 120,000 and a fluoroacrylate content of 30% by weight. This solution was applied onto the above layer and dried at 100 ° C. for 20 minutes to form a surface layer of 5 μm. This is designated as Sample 3. For comparison, a sample was prepared in the same manner as in Sample 3 except that the fluorine-type comb polymer was not added. This is designated as Sample 4.

For the sample thus obtained, primary + 6kV corona charging,
The durability was evaluated by an electrophotographic process consisting of secondary AC corona charging, simultaneous image exposure, overall light irradiation, dry toner development, transfer to plain paper, and cleaning with a urethane rubber blade. The results are shown in Table 2. The evaluation environment is 32.5 ° C. and RH 90%.

Example 3 10 parts (weight part, the same applies hereinafter) of New Zealand lactic casein was measured and dispersed in 90 parts of water, and then 1 part of ammonia water was added and dissolved. On the other hand, hydroxypropyl methylcellulose resin (trade name: Metroses 60
SH50, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in 20 parts of water, and then both were mixed to prepare a coating solution for the undercoat layer.

This solution was applied to an Al cylinder of 80φ × 300 mm by a dipping method and dried at 80 ° C. for 10 minutes to form a 2 μ thick undercoat layer.

Next, 10 parts of a disazo pigment having the following structural formula is used. 1 part of 6 parts of cellulose acetate butyrate resin (trade name: CAB-381; manufactured by Eastman Chemical) and 60 parts of cyclohexanone
It was dispersed for 20 hours by a sand mill device using glass beads. To this dispersion, 100 parts of methyl ethyl ketone was added, dip-coated on the undercoat layer, and dried by heating at 100 ° C. for 10 minutes to give a charge generation layer having a coating amount of 0.1 g / m ² .

Then, 10 parts of a hydrazone compound having the following structural formula And 10 parts of methylmethacrylate-styrene copolymer resin (trade name MS-600, manufactured by Nippon Steel Chemical Co., Ltd.) were dissolved in 55 parts of monochlorobenzene. To this solution, 0.1 part of the fluorine-type comb-type graft polymer used in Example 1 was added. This was applied onto the charge generation layer and dried in hot air at 100 ° C. for 1 hour to form a charge transport layer having a thickness of 16 μm. This is designated as Sample 5. For comparison, a sample without the fluorine-based comb-type graft polymer was prepared in the same manner, and this is designated as sample 6.

The sample thus obtained was subjected to durability evaluation by an electrophotographic process consisting of -5.6 kV corona charging, image exposure, dry toner development, toner transfer to plain paper, and cleaning with a urethane rubber blade. The results are shown in Table 3.
The evaluation environment is 32.5 ° C RH 90%.

Example 4 10 parts (part by weight, the same applies hereinafter) of New Zealand lactic casein was weighed and dispersed in 90 parts of water, and then 1 part of ammonia water was added and dissolved. On the other hand, hydroxypropyl methylcellulose resin (trade name: Metroses 60
SH50, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in 20 parts of water, and then both were mixed to prepare a coating solution for the undercoat layer.

This solution was applied to an aluminum cylinder of 80φ × 300 mm by a dipping method and dried at 80 ° C. for 10 minutes to form a 10 μ thick undercoat layer.

Next, 12 parts of a pyrazoline compound having the following structural formula, polysulfone resin 10 parts (trade name: made by Udel P-1700UCC) was dissolved in 52 parts of monochlorobenzene. This solution was applied onto the undercoat layer by dip coating and dried at 100 ° C. for 1 hour to form a charge transport layer having a thickness of 16 μm.

Next, 10 parts of a bisazo pigment having the following structural formula is used. Polyvinyl butyral resin (Product name: S-REC BM-S
30 parts of Sekisui Chemical Co., Ltd.) and 30 parts of butyl acetate were dispersed for 20 hours in a sand mill using 1φ glass beads. To this dispersion, 0.4 part of the fluorine-type comb-type graft polymer used in Example 2 was added. This was applied onto the above charge transport layer and dried at 80 ° C. for 20 minutes to form a 2 μ charge generation layer. This is designated as Sample 7.

For comparison, a sample without the fluorine-type comb-type graft polymer was prepared in the same manner as Sample 7. This is designated as Sample 8.

The sample thus obtained was evaluated for durability by an electrophotographic process consisting of +5.6 kV corona charging, image exposure, dry toner development, toner transfer to plain paper, and cleaning with a urethane rubber blade. The results are shown in Table 4.
The evaluation environment is 32.5 ° C. and RH 90%.

On the other hand, in order to investigate the water repellency of the surface layer of the above sample, the contact angle with water was measured.

The measurement conditions for the contact angle are 10 to 30 ° C and 20 to 20 ° C.
An air atmosphere of 80% RH is standard.

Here, the contact angle is about 0.001 of pure water on the surface of the image holding member.
ml is placed, and a tangent line is drawn to the surface of the water drop from the contact point of the water drop formed at this time, the surface and the air, and the angle formed by this tangent line and the surface is meant. In the present invention, a Kyowa contact angle meter CA-DS type manufactured by Kyowa Kagaku Co., Ltd. is used for 10 to 30.
Approximately with a droplet adjuster in an air atmosphere at 20 ° C to 80% RH
0.001 ml of pure water was gently placed on the sample surface and the contact angle was measured after 30 seconds.

The results are shown in Table 5.

[Effects of the Invention] As is apparent from the above, according to the present invention, by incorporating a specific fluorine-based comb-type graft polymer as a component constituting the surface layer, excellent water repellency that has never been obtained, high temperature and high humidity can be obtained. It is possible to provide an image holding member that can stably obtain a high-quality image even in an environment.

Claims (4)

[Claims] 1. An image holding member having a surface layer for holding an electrostatic image or a toner image, wherein the surface layer comprises a polymerizable monomer having a fluorine atom in a side chain and a polymerizable double chain at one end of the molecular chain. It contains a fluorine-type comb-type graft polymer having a functional group having a bond and obtained by copolymerizing the polymerizable monomer and a macromonomer having an affinity with the binder resin for forming the surface layer after polymerization (provided that ,
(Excluding the simultaneous inclusion of polycarbonate resin)
An image holding member characterized by the above. 2. The image holding member according to claim 1, wherein the graft polymer is 0.01 to 10% by weight based on the solid content of the surface layer. 3. The image holding member according to claim 1, wherein the surface layer is formed on the photoconductive layer. 4. The image holding member according to claim 1 or 2, wherein the surface layer is a photoconductive layer.