JPH11119449A - Electrophotographic photoreceptor, and image forming method and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrophotographic photoreceptor high in durability not causing image defects, such as striation trouble due to filming in a reversal development process, by incorporating a branched bisphenol-Z-type-polycarbonate in a photosensitive layer having a specified glass transition point or higher. SOLUTION: The photoreceptor is obtained by forming the photosensitive layer and, when needed, a protective layer on a conductive substrate. This photosensitive layer is an organic photoreceptor, preferably, containing a charge generating material and a charge transfer material, and this photosensitive layer contains the branched bisphenol-Z-type-polycarbonate and has a glass transition point of >=65 deg.C, preferably, >=70 deg.C, especially, 73-95 deg.C. The photosensitive layer is preferably 25-35 μm in film thickness. This polycarbonate to be used has a viscosity average molecular weight of 10,000-300,000, especially, 30,000-150,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, an image forming method, and an image forming apparatus, and more particularly, to an electrophotographic photosensitive member having excellent durability, and an image forming method and an image forming apparatus using the photosensitive member. About.

[0002]

2. Description of the Related Art Generally, in order to form an image by electrophotography, a toner image is formed by charging, exposing, and developing a photoreceptor surface, and the toner image is transferred and fixed on a transfer material. Is obtained, and the photoreceptor after the transfer is cleaned and removed of residual toner, and is repeatedly used for a long period of time.

Accordingly, the photoreceptor has not only electrophotographic performance such as charging potential, sensitivity, dark decay and residual potential characteristics, but also
Good physical properties such as printing durability, abrasion resistance, and moisture resistance during repeated use, and resistance to ozone generated during corona discharge and image exposure are also required.

On the other hand, as the electrophotographic photoreceptor, inorganic photoconductive photoreceptors using amorphous silicon, selenium, cadmium sulfide and the like have been widely used, but recently, they are low cost, have no toxicity, and have poor processability. Organic photoconductive photoconductors (hereinafter simply referred to as organic photoconductors), which are excellent and have a high degree of freedom for selection according to the purpose, have become mainstream.

[0005] The fatigue deterioration due to repeated use of the electrophotographic photosensitive member is caused by the steps of transferring and separating a toner image formed on the photosensitive member onto a transfer material and cleaning residual toner on the photosensitive member after the transfer. Are caused by the decomposition and deterioration of the photosensitive layer in each step such as friction and damage on the surface of the photosensitive layer due to the rubbing, and charging, image exposure, and static elimination of the photosensitive member surface.

Therefore, improvement of the surface of the photosensitive layer is an important subject in order to prevent fatigue deterioration of the photosensitive member. In particular, the photosensitive layer of the organic photoreceptor is softer than the inorganic photoreceptor, and since the photoconductive substance is organic, the deterioration of the photoreceptor upon repeated use is large, and the surface of the photosensitive layer is improved. More important.

Hitherto, bisphenol Z type polycarbonate (hereinafter also referred to as BPZ) has been widely used as a binder for electrophotographic photosensitive members because of its excellent abrasion resistance and solvent crack resistance. However,
According to Toriumi et al., A photosensitive layer using bisphenol Z-type polycarbonate has a large contribution of a viscous term and is easily deformed by an external force (Toriumi et al., Japan Hard).
copy '94 Proceedings P233-236 (199
4)) Reported. No specific harm was pointed out in the range of the number of usable OPCs in the conventional OPC.
As the durability level required for C increases,
Problems that have not been seen in the past have become apparent. Especially when using the rubber rubber blade as a cleaning means for a long time,
There is a problem that minute irregularities occur on the surface of the photoreceptor, and that filming of paper powder and toner tends to occur easily.

An image defect such as a streak failure caused by the above filming is a phenomenon particularly noticeable in the reversal development process. This is because the photoreceptor and the toner have the same polarity of charge, which reduces the adhesion and is advantageous for cleaning.On the other hand, the toner also reduces the abrasion by the toner, thus reducing the effect of suppressing adhering substances such as paper dust. Tends to be insufficient. Therefore, it is important to secure a surface state in which adhesion is less likely to occur over a long period of time.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly durable electrophotographic photosensitive member without causing image defects such as streak failure due to filming in a reversal development process. is there.

[0010]

The above objects of the present invention have been attained by the following constitutions.

(1) An electrophotographic photoreceptor comprising a layer having a branched bisphenol Z-type polycarbonate and having a glass transition point of 65 ° C. or higher.

(2) The electrophotographic photosensitive member as described in (1) above, wherein the branched bisphenol Z-type polycarbonate has a viscosity average molecular weight of 30,000 or more.

(3) The electrophotographic photosensitive member as described in (1) or (2) above, wherein the photosensitive layer has a thickness of 25 μm or more.

(4) After transferring the toner image developed on the photoreceptor according to any one of (1) to (3) to a recording material, the toner remaining on the photoreceptor is cleaned with an elastic rubber blade. An image forming method comprising the steps of: reversal development.

(5) The photoreceptor according to any one of (1) to (3), and the toner image reversely developed on the photoreceptor is transferred onto a recording material and remains on the photoreceptor. An image forming apparatus comprising a step of cleaning a toner with an elastic rubber blade.

The present invention will be described in more detail. The electrophotographic photoreceptor of the present invention is constituted by providing a photosensitive layer on a conductive support and, if necessary, a protective layer thereon. The photosensitive layer of the electrophotographic photoreceptor of the present invention may be an inorganic photoreceptor using selenium, amorphous silicon, cadmium sulfide, or the like, but is preferably an organic charge generating material (CGM) and a charge transporting material (CTM). And an organic photoreceptor.
The photosensitive layer contains a branched bisphenol Z-type polycarbonate and has a glass transition point of 65 ° C. or higher. A preferred glass transition point is 70 ° C. or higher, and more preferably 73 to 95 ° C.

The glass transition temperature of the photosensitive layer is determined by differential thermal analysis (D
SC). The measurement conditions are as follows.

Measuring equipment: 7Series Thermo
l Analysis System (manufactured by PerkinElmer) Measurement conditions: rate = 10 ° C./min Measurement range: 0 to 200 ° C. The thickness of the photosensitive layer may be 20 μm or more, but is preferably 25 to 35 μm.

Next, the branched bisphenol Z-type polycarbonate of the present invention will be described. The branched bisphenol Z-type polycarbonate of the present invention is a polymer having a structural unit represented by the following general formula (I) and a branched monomer unit described below.

[0020]

Embedded image

In the formula, R _{1 to} R ₈ each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted carbon atom
Represents an alkyl group, a cycloalkyl group or an aryl group of 10 to 10, Z represents an atom group forming a 4 to 11 saturated or unsaturated carbocyclic ring, R ₉ represents a hydrogen atom, a carbon atom of 1 to 9
Represents an alkyl group or an aryl group.

As the polycarbonate resin having the structural unit of the general formula (I), commercially available products such as BP
Z: poly (4,4'-cyclohexylidenediphenyl)
There is a carbonate, TS-2050: Teijin Limited, Z
-PCR: Mitsubishi Gas Corporation and the like. The branched bisphenol Z-type polycarbonate of the present invention is as described above,
It is obtained by polymerizing a polycarbonate resin having a structural unit of the general formula (I) using a branched monomer in an amount of 2 mol% or less.

Examples of the branched monomer include fluoroglucin, 2,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) 3-heptene, 4,6-dimethyl-2,
4,6-tri (4-hydroxyphenyl) 2-heptene, 1,3,5-tri (2-hydroxyphenyl) benzol, 1,1,1-tri (4-hydroxyphenyl)
Ethane, 2,6-bis (2-hydroxy-5-methylbenzyl) 4-methylphenol, α, α ′, α ″ -tri (4-hydroxyphenyl) 1,3,5-triisopropylbenzene, ichisanbisphenol, 5-chloroitisan, 5,7-dichloroitisan, 5-bromoichisan and the like.

The branched bisphenol Z type polycarbonate of the present invention has a viscosity average molecular weight of 10,000 to 300,
000 resins are used. In particular, the viscosity average molecular weight is
Resins greater than 30,000 and less than 150,000 are preferred.

The viscosity average molecular weight of the sample (branched BPZ)
Prepare 6.0 (g / l) dichloromethane solution and add 20 g
It is obtained from the following formula from ηSP measured at ° C.

ΗSP / C = [η] (1 + K′ηSP) [η] = K (Mv) α C: Polymer concentration (g / l) K ′ = 0.28 K = 1.23 × 10 ⁻³ α = 0.
83 [η]: Intrinsic viscosity Mv: Viscosity average molecular weight As the solvent or dispersion medium of the branched bisphenol Z-type polycarbonate of the present invention, n-butylamine, diethylamine, ethylenediamine, isopropanolamine,
Triethanolamine, triethylenediamine, N, N
-Dimethylformamide, acetone, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1 −
Examples thereof include trichloroethane, trichloroethylene, tetrachloroethane, tetrahydrofuran, dioxane, methanol, ethanol, 2-propanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, and methyl cellosolve. Although the present invention is not limited to these, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone and the like are preferably used. These solvents can be used alone or as a mixture of two or more solvents.

Examples of the organic charge generating substance (CGM) preferably used in the present invention include known phthalocyanine pigments, polycyclic quinone pigments, azo pigments, perylene pigments, and the like.
Indigo pigments, quinacridone pigments, azurenium pigments,
Squarylium dye, cyanine dye, pyrylium dye,
Thiopyrylium dye, xanthene dye, triphenylmethane dye, styryl dye and the like.

Examples of the organic charge transporting substance (CTM) preferably used in the present invention include known oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, and the like.
Imidazole derivatives, imidazolone derivatives, imidazoline derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, benzidine compounds, pyrazoline derivatives, stilbene compounds, amine derivatives, oxazolone derivatives, benzothiazole derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine Derivatives, phenazine derivatives, aminostilbene derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene, and the like.

Examples of the conductive support of the electrophotographic photoreceptor of the present invention include: 1) a metal plate such as an aluminum plate or a stainless plate 2) a metal such as aluminum, palladium, or gold on a support such as paper or a plastic film. A thin layer provided by lamination or vapor deposition 3) A layer provided by applying or vapor-depositing a layer of a conductive compound such as a conductive polymer, indium oxide or tin oxide on a support such as paper or a plastic film. Can be

As a coating method for producing the electrophotographic photoreceptor of the present invention, coating methods such as dip coating, spray coating, and circular amount control type coating are used. For the processing, it is preferable to use a coating processing method such as spray coating or circular amount control type coating in order not to dissolve the lower layer film as much as possible and to achieve uniform coating processing.

In the present invention, an intermediate layer having both a barrier function and an adhesive resin may be provided between the conductive support and the photosensitive layer. Materials for the intermediate layer include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, and phenolic resin polyamides (nylon 6, nylon 66,
Nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide and the like. The thickness of the intermediate layer is 0.1 to 10
μm is preferred, and particularly preferably 0.1 to 5 μm.

The shape of the support may be a drum shape, a sheet shape, or a belt shape, and is preferably an optimum shape for the applied image forming apparatus.

The electrophotographic photosensitive member of the present invention can be applied to general image forming apparatuses such as analog copying machines, digital copying machines, laser printers, LED printers, and liquid crystal shutter printers.

The image forming apparatus of the present invention has an elastic rubber blade cleaning step. The elastic rubber blade is used by pressing against the electrophotographic photosensitive member incorporated in the image forming apparatus of the present invention with a pressing force of 5 to 50 g / cm in the counter direction.

[0035]

EXAMPLES The present invention will be described below in more detail with reference to examples, but embodiments of the present invention are not limited thereto.

<Synthesis of Branched Bisphenol Z-Type Polycarbonate> Bisphenol Z manufactured by Mitsubishi Gas Chemical Company
0.3 mol% of 1,1,1-tri (4-hydroxyphenyl) ethane (branching monomer) was added to (4,4′-cyclohexylidenediphenol) and polymerized, and the viscosity average molecular weight was 22 5,000, 53,000 and 0.5 mol% of a branched monomer were added, and the viscosity average molecular weight was 10
5,000 branched bisphenol Z-type polycarbonates were obtained.

Example 1 <Preparation of Photoreceptor> As a conductive support, a mirror-finished aluminum support having a diameter of 80 mm and a height of 355 mm was used.

The following undercoat layer coating solution was prepared on the support and coated so as to have a dry film thickness of 1.0 μm.

Undercoat Layer Coating Solution Titanium chelate compound (TC-750 manufactured by Matsumoto Pharmaceutical) 30 g Silane coupling agent (KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd.) 17 g 2-propanol 150 ml Was dispersed and prepared and applied so as to have a film thickness of 0.5 μm.

Charge Generating Layer Coating Solution Y-type titanyl phthalocyanine 10 g Silicone resin (KR-5240 manufactured by Shin-Etsu Chemical Co., Ltd.) 10 g-t-butyl acetate 1000 ml A dispersion of the above coating solution using a sand mill for 20 hours.

The following charge transport layer coating solution CTL-1 was prepared on this charge generation layer, applied to a dry film thickness of 30 μm, and dried at 100 ° C. for 1 hour to obtain a photoreceptor.

Charge transport layer coating solution Charge transport substance (T-1) 420 g Branched bisphenol Z-type polycarbonate (Mv = 53,000) 660 g Dichloromethane 2800 ml

[0043]

Embedded image

A KONICA 705 digital copier employing the reversal development method for the photoreceptor produced as described above.
0 (manufactured by Konica Corporation).

Rubber hardness JIS A 70 °, thickness 2
mm, elastic rubber blade with free length 9mm, contact angle 20 °
In the counter direction with respect to the rotation of the photoreceptor with a pressing force of 18 g / cm by a weight-type load method.

In this state, a 100,000 copy actual shooting test was performed to evaluate the quality of the copied image, and the results are shown in Table 1.

Example 2 In Example 1, a branched bisphenol Z-type polycarbonate having a viscosity average molecular weight Mv = 22,000 was used in place of the branched bisphenol Z-type polycarbonate (Mv = 53,000) of the coating solution for the charge transport layer. A photoreceptor was prepared in the same manner as in Example 1 except that
A real copy test of 100,000 copies was performed to evaluate the quality of the copied image, and the results are shown in Table 1.

Example 3 In Example 1, a branched bisphenol Z type polycarbonate having a viscosity average molecular weight Mv = 105,000 was used in place of the branched bisphenol Z type polycarbonate (Mv = 53,000) of the coating solution for the charge transport layer. A photoreceptor was prepared in the same manner as in Example 1 except that the photoreceptor was used, and a 100,000 copy actual photographing test was performed in the same manner as in Example 1 to evaluate the quality of the copied image. The results are shown in Table 1.

Example 4 A photoreceptor was prepared in the same manner as in Example 1 except that the dry film thickness was changed to 22 μm. And the results are shown in Table 1.

Example 5 A photoreceptor was prepared in the same manner as in Example 1 except that the drying conditions were changed to 120 ° C. for 1 hour. The image quality was evaluated and the results are shown in Table 1.

Comparative Example 1 In Example 1, a bisphenol Z-type polycarbonate (TS2050 Mv = 50,0) was used in place of the branched bisphenol Z-type polycarbonate in the charge transport layer coating solution.
00: manufactured by Teijin Chemicals Limited, except that a photoreceptor was produced in the same manner as in Example 1, a 100,000 copy actual photographing test was performed in the same manner as in Example 1, and the quality of the copied image was evaluated. Shown in

Comparative Example 2 A photoreceptor was prepared in the same manner as in Example 1 except that the drying conditions were changed to 80 ° C. for 1 hour. The image quality was evaluated and the results are shown in Table 1.

<Evaluation Conditions> Filming Evaluation Filming conditions were visually evaluated from surface observation of the photoreceptor after image formation at 5 KC in a high temperature and high humidity environment (30 ° C., 80%).

○ good △ slight × multiple occurrences Surface roughness The ten-point average roughness (RZ) of the drum after 100,000 copies was measured.

Image Evaluation The image samples after 100,000 copies were examined for the presence or absence of image defects such as background fog, white stripes and black stripes, and uneven shading in halftone images.

[0056]

[Table 1]

As is evident from Table 1, the electrophotographic photosensitive member of the present invention is a highly durable electrophotographic photosensitive member without filming. In addition, the viscosity average molecular weight is 3
The electrophotographic photoreceptor containing 2,000 or more branched bisphenol Z-type polycarbonates or the electrophotographic photoreceptor of the present invention having a photosensitive layer having a thickness of 25 μm or more has a sufficient surface roughness and 100,000 copies or more. Printing durability.

Claims (5)

[Claims] 1. An electrophotographic photoreceptor comprising a layer containing a branched bisphenol Z-type polycarbonate and having a glass transition point of 65 ° C. or higher. 2. The electrophotographic photosensitive member according to claim 1, wherein the branched bisphenol Z-type polycarbonate has a viscosity average molecular weight of 30,000 or more. 3. The electrophotographic photoreceptor according to claim 1, wherein the thickness of the photosensitive layer is 25 μm or more. 4. After transferring the toner image developed on the photoreceptor according to claim 1 to a recording material, cleaning the toner remaining on the photoreceptor with an elastic rubber blade. An image forming method comprising the steps of: reversal development. 5. The photoreceptor according to claim 1, wherein the toner image reversely developed on the photoreceptor is transferred onto a recording material and remains on the photoreceptor. An image forming apparatus comprising a step of cleaning a toner with an elastic rubber blade.