JPH0318856A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a photosensitive body having diffusion stability and adhesiveness, freed of occurrence of black stops and the like, and superior in image quality by using tau-type and/or X-type phthalocyanine as a carrier generating material and an aliphatic cellulose ester as a binder. CONSTITUTION:The electrophotographic sensitive body is obtained by successively laminating on a conductive substrate 1 an interlayer 7, a carrier generating layer 6, and a carrier transfer layer 4. The carrier generating layer 6 is obtained by dissolving the tau-type and/or X-type phthalocyanine as the carrier generating material and the aliphatic cellulose ester as a binder in an ester type, ketone type, or ether-type solvent or a mixture of them, and coating and drying it, thus permitting the obtained electrophotographic sensitive body to be superior in dispersion stability and interlayer adhesiveness, and to prevent occurrence of defective image quality, such as black spots.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor that has good interlayer adhesion and improved sensitivity, image quality, etc.

[Prior Art] Photoconductors using organic photoconductive materials have advantages such as non-pollution and high productivity compared to photoconductors using inorganic photoconductive materials such as selenium and cadmium sulfide. However, its low sensitivity made it difficult to put it into practical use. For this reason, several sensitization methods have been proposed, but it is known that an effective method is to use a functionally separated photoreceptor in which the photosensitive layer is divided into a carrier generation layer and a carrier transport layer, which are laminated. ing.

This allows the carrier generation function and the carrier transport function to be assigned to different substances, making it easy to control electrophotographic characteristics such as sensitivity and charging characteristics, resulting in a highly sensitive and durable photoreceptor. It is expected that this will be obtained. However, in order to improve electrostatic properties and image properties, the carrier generation layer generally needs to be uniform, extremely thin, and smooth. Generally, the carrier generation layer is an extremely thin layer of about 0.5 μm, so the slightest defects, dirt, deposits, scratches, etc. on the substrate surface will affect the uniformity of the carrier generation layer's film thickness. If the thickness of the generation layer is non-uniform, uneven sensitivity will occur on the photoreceptor. Therefore, it is required to make the thickness of the carrier generation layer as uniform as possible. For this reason, it has been proposed to provide an intermediate layer having a barrier layer function between the carrier generation layer and the conductive layer. This intermediate layer must also have the function of an adhesive layer. That is, poor adhesion causes peeling of the photosensitive layer, making effective charge injection difficult and causing a decrease in sensitivity.

Furthermore, in order to stably obtain a thin layer, the dispersibility and dispersion stability of the dispersion liquid itself become important issues.

Additionally, τ-type phthalocyanine or X-type phthalocyanine is known as a carrier-generating substance effective for the carrier-generating layer of such a functionally separated photoreceptor. However,
A carrier generation layer coating solution using τ-type phthalocyanine or X-type phthalocyanine has poor dispersion stability, resulting in decreased sensitivity and image quality. In order to improve dispersion stability, resin selection becomes an important issue. That is, in photoreceptors using τ-type phthalocyanine or X-type phthalocyanine as a carrier-generating substance, silicone resin or the like has been used as a binder for the carrier-generating layer. However, the adhesiveness, sensitivity and image quality were not satisfactory. For example, JP-A-60-19147 describes an example in which τ-type phthalocyanine is used as a carrier-generating substance and silicone resin is used as a binder in the carrier-generating layer.
Although the sensitivity and image quality have been improved, the adhesion is poor.

[Problem to be solved by the invention] That is, as described above, a photoreceptor using τ-type phthalocyanine or At present, a photoreceptor with excellent image quality without such defects has not yet been obtained.

[Means for Solving the Problems] The above object of the present invention is to provide an electrophotographic photoreceptor comprising at least an intermediate layer, a carrier generation layer, and a carrier transport layer laminated on a conductive support, in which the carrier generation layer is a carrier. This is achieved by an electrophotographic photoreceptor characterized by containing τ-type phthalocyanine and/or X-type phthalocyanine as a generating substance and containing fatty acid cellulose ester as a binder.

The present invention will be explained in more detail below.

In the present invention, as a carrier generating substance,
Type phthalocyanine (Japanese Patent Publication No. 49-4338) is used.

Fatty acid cellulose ester is used as the binder for the carrier generation layer constituting the electrophotographic photoreceptor of the present invention. Examples of fatty acid cellulose esters include cellulose acetate, cellulose propionate, cellulose butyrate,
Triesters such as cellulose valerate, cellulose caproate, cellulose enanthate, cellulose caprylate, cellulose caprate, cellulose laurate, cellulose myristate, cellulose valmitate, or mixed esters such as cellulose acetate propionate and cellulose acetate butyrate. It is preferable to use cellulose acetate, cellulose butyrate, cellulose propionate, cellulose laurate, cellulose acetate butyrate, or cellulose acetate propionate.

The molecular weight of the fatty tt=lulose ester used in the present invention is generally from 5,000 to 200,000, preferably from io,ooo to 100,000.

The fatty acid cellulose ester used in the present invention is synthesized by a known method. Further, as commercial products, cellulose acetate rLT-35J, rL-70J (manufactured by Daicel Chemical Co., Ltd.), cellulose acetate butyrate rcABJ (manufactured by Eastman Chemical Co., Ltd.), etc. can also be obtained.

These fatty acid cellulose esters are ester solvents such as methyl acetate and ethyl acetate, ketone solvents such as acetone, methyl ethyl ketone (MEK), and cyclohexanone, or ether solvents such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether.
Or, since it is soluble in these mixed solvents, ester, ketone, or ether solvents are used as the carrier generation layer coating solution, and fatty acid cellulose esters are used as the carrier transport layer coating solution. It is preferable to use an insoluble hydrocarbon solvent or a halogenated hydrocarbon solvent.

The carrier generation layer includes τ-type phthalocyanine and/or
After dispersing this solution, it is obtained by coating and drying by a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a wire bar coating method, a blade coating method, a roller coating method, a curtain coating method, etc.

The carrier generation layer preferably has a thickness of 0.1 to 5 μm.

In the carrier generation layer, the content n of the carrier generation substance is preferably such that the value of carrier generation substance/fatty acid cellulose ester is 175 to 3/1, particularly 173 to 2.
/1 is preferable.

In the present invention, other general binders can also be used in combination with the fatty acid cellulose ester.

The present invention also includes other general carrier-generating substances such as
Phthalocyanine pigments, azo pigments, polycyclic quinone pigments, perylene pigments, indigoid pigments, etc. can also be used in combination.

The photoreceptor of the present invention has the structure shown in FIG. 1, for example.

In this photoreceptor, on the conductive support (substrate) 1,
A carrier generation layer 6 is provided through the intermediate layer 7 described above, and a carrier transport layer 4 is provided on this carrier generation layer 6. 8 indicates a photosensitive layer. Therefore, since the intermediate layer 7 is provided between the carrier generation layer 6 and the support 1,
While non-uniform hole injection from the support side shown in FIG. 3 is effectively prevented, electrons, which are photocarriers, can be efficiently transported to the support side during light irradiation.

The photoreceptor of the present invention may have a layer structure (for positive charging) in which the carrier generation Ei6 and the carrier transport m4 are upside down, as shown in FIG.

Further, in the photoreceptor of the present invention, a protective layer (protective film) may be formed on the surface of the photoreceptor in order to improve printing durability, for example, a synthetic resin film may be coated.

In the present invention, an intermediate layer is provided between the conductive support and the photosensitive layer. The binder contained in the intermediate 1 includes polyurethane, polyamide, polyvinyl alcohol, epoxy, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, casein, methyl cellulose,
Examples include nitrocellulose and phenol resin.

In particular, when an ethylene copolymer is used as a binder in the intermediate layer in the present invention, the potential characteristics are good and the effect of significantly improving the prevention of black spots during reversal development is exhibited.

Wm coating method using a solution of one or more of these binders dissolved in an alcohol solution such as methanol, ethanol or butanol, or a solvent such as toluene;
It can be obtained by coating on a substrate using a coating method such as a roll coating method, a spray coating method, a wire bar coating method, a bead coating method, or a curtain coating method. The film thickness is 0.1
~5μ- is - boat fishing, preferably 0.5-3μm. The binder used is 1-5% by weight based on the solvent.
It is preferable that

The carrier transport layer can be formed by applying and drying a carrier transport substance dissolved or dispersed in a suitable solvent or dispersion medium alone or together with a binder resin. Solvents or dispersion media used include n-butylamine, diethylamine ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, NN-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene,
Examples include xylene, chloroform, 1,2-dichloroethane, dichloromethane, tetrahydrofuran dioxane, methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, and dimethyl sulfoxide.

There are no particular limitations on carrier transport substances that can be used in the present invention, but examples include carbazole derivatives, oxazole inducers,
11 oxadiazoles, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidasilone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline derivatives, oxacilone derivatives, benzothiazole derivatives, benzimidazole derivatives, Quinazoline M conductor, benzofuran derivative, acridine derivative,
Phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, poly-N-vinylcarbazole, poly-1
- One or more types selected from vinylpyrene, poly-9-vinylanthracene, etc.

Specific examples of such carrier transport substances include
It is described in January 1985-5085.

The carrier transporting material used in the present invention is preferably one that has an excellent ability to transport holes generated during light irradiation to the support side and is suitable for combination with a charge generating material.

Preferred carrier transport substances include styryl compounds represented by the following general formula [Vl] or [■].

General formula [■]: (However, in this general formula, R+1, R42 represents an i-substituted or unsubstituted alkyl group, an aryl group, and substituents include an alkyl group, an alkoxy group, a substituted amino L hydroxyl group, a halogen atom, Use an aryl group.

Ar5, Ar6: li represents a substituted or unsubstituted aryl group, and as a substituent, an alkyl group, an alkoxy group, a substituted amino group, a hydroxyl group, a halogen atom, or an aryl group is used.

RI9, R1→: Represents a substituted or unsubstituted 7-aryl group or a hydrogen atom, and as a substituent, an alkyl group, an alkoxy group, a substituted amino group, a hydroxyl group, a halogen atom, or an aryl group is used. ) Compounds represented by the above general formula [Vl] are disclosed in, for example, JP-A Nos. 58-65440, 58-198425, 58-198043, 60-93445, 60
-98437 etc.

General formula [■]: Rls (However, in this general formula, Rls: substituted or unsubstituted aryl group, R16: hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, alkoxy group, amiLL-substituted amino group, water m group, RI7: l! represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group) The above compounds are described, for example, in JP-A-57-148750.

Furthermore, a hydrazone compound represented by the following general formula [rX] or [XI] can also be used as a carrier transport substance.

General formula [■]: (However, in this general formula, R18 and R19: each a hydrogen atom or a halogen atom, R2O and R21: each a substituted or unsubstituted aryl group, A r ?: a substituted or unsubstituted arylene group) ) The above compound is described, for example, in JP-A-57-72148.

General formula [XI]: (However, in this general formula, R3': substituted or unsubstituted aryl group or substituted or unsubstituted heterocyclic group, R35: hydrogen atom, substituted or unsubstituted aralkyl group, or substituted or unsubstituted heterocyclic group) (Unsubstituted aryl group, Q: hydrogen atom, halogen atom, alkyl group, substituted amino group, alkoxy group, or cyam L S: represents an integer of 0 or 1.) In addition, as a carrier transport substance, the following general formula [XI ] Pyrazoline compounds can also be used.

Examples of the above compounds include JP-A-58-134642 and JP-A No. 58-134642;
8-166354M etc.

Other useful carrier transport materials include, for example, JP-A-57-64244, JP-A-59-15252, and JP-A-57-1989.
No. 67940, No. 55-2285, No. 57-1952
54, No. 56-4148, and the like.

The thickness of the carrier transport layer is preferably 10 μm or more.

The thickness of the entire photosensitive layer is preferably within the range of 10 to 40 μm, more preferably within the range of 15 to 30 μm. If the film thickness is smaller than the above range, the charging potential will be low due to the thinness, and the printing durability will also tend to decrease.

Moreover, if the film thickness is larger than the above range, the residual potential will increase on the contrary, and the same problem as described above will occur when the carrier generation layer is too thick, making it difficult to obtain sufficient transport performance. Therefore, the residual potential tends to increase during repeated use.

Further, in the carrier transport layer, the carrier transport substance preferably has excellent compatibility with the binder substance.

As a result, even if the amount of the binder substance is increased, it does not become cloudy or opaque, so the mixing ratio with the binder substance can be set at a very wide range. is uniform and stable, resulting in better sensitivity and charging characteristics, and it is possible to obtain a photoreceptor that can form clear images with higher sensitivity. However, it is preferable that the base of the carrier transport substance used is 40 to 70% by weight based on the binder of the carrier transport layer.

Furthermore, especially when used in repeated transfer type electrophotography, it is possible to achieve the effect that fatigue deterioration is less likely to occur.

Conventionally known antioxidants, electron-accepting substances, surface modifiers, ultraviolet absorbers, and the like are used in the carrier transport layer and the carrier generation layer.

The binder of the protective layer provided as necessary has a volume resistance of 108Ω・ci+ or more, preferably 1010Ω・
A transparent resin having a resistance of 1013 Ω·cm or more, preferably 10 13 Ω·cm or more is used.

Further, the binder may be a resin that is cured by light or heat, and the resin that is cured by light or heat includes:
For example, thermosetting acrylic resin, epoxy resin, urethane resin, urea resin, polyester resin, alkyd resin,
Examples include melamine resins, photocurable cinnamic acid resins, and copolymer or synthetic resins thereof, as well as all other photo- or thermosetting resins used in electrophotographic materials.

In addition, the protective layer contains improvements in processability and physical properties (crack prevention,
If necessary, a thermoplastic resin may be contained in an amount of less than 50 wt% for the purpose of imparting flexibility, etc.). Examples of such thermoplastic resins include polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polycarbonate resin, or copolymer resins thereof, polymeric organic semiconductors such as poly-N-vinylcarbazole, and others. All of the thermoplastic resins available for electrophotographic materials are utilized.

The conductive support can be prepared by applying, vapor depositing, laminating, or the like a conductive thin layer made of a metal plate, a metal drum, or a conductive polymer, a conductive compound such as indium oxide, or a metal such as aluminum, palladium, or gold. Those provided on a substrate such as paper or plastic film are used.

[Example] Hereinafter, the present invention will be explained in more detail with reference to M examples.
The present invention is not limited thereby, and of course includes other embodiments with various modifications.

Examples 1-3. Comparative Examples 1 to 3 First, photoreceptors 1 to 3 of Examples 1 to 3 and photoreceptors 1 to 3 of Comparative Examples 1 to 3 were manufactured in the following manner. The manufacturing procedure for each photoreceptor is common as follows.

First, add 60 g of resin a or b shown below to 200 g of toluene.
0 mN and was completely dissolved while heating to 50° C. to prepare a coating solution for an intermediate layer.

a) L-Pax 4260 (Dupont Mitsui Chemicals If) Ethylene-vinyl acetate-methacrylic acid copolymer Vinyl acetate content N 28 wt%, M F R6! J/10
m1nb) Dumilan D-2513 (manufactured by Narita Pharmaceutical Industries, Ltd.) Ethylene-vinyl acetate to vinyl alcohol copolymer
M F R14o/10m1n diameter 80mm, length 3
An aluminum cylinder with a mirror-finished surface, measuring 55 ml and 111 m thick, was immersed in the above-mentioned intermediate layer coating solution, and dip coating was performed at a pulling rate (coating speed) of 300 ml/5 h.

After coating, dry at 40°C for 30 minutes, and apply 0.5 μn of I
! An intermediate layer of I thickness was provided. 7 for the lower sliding door used here
Liquid No. 11 was filtered through a 0.6 μl filter.

Next, as a carrier generating substance (CGM), 40 g of each phthalocyanine shown in Table 1 was added to 2.00 g of a solution of 40 g of the binder shown in the table dissolved in each solvent (JTF) and dispersed for 4 hours using a sand grinder. A coating solution for a carrier generation layer was prepared.

For bisazo pigments, add 15 g to 100 ml of methyl ethyl ketone solution (hρ) containing 59 resins,
A coating solution was prepared in the same manner by dispersing in a ball mill for 12 hours.

The cylinder having the above intermediate layer is immersed in this liquid, and 7
Dip coating was performed at a coating speed of 20 mm/min, and a carrier generation layer (CGL) with a thickness of 0.5 μI was applied.
) was obtained.

In addition, carrier transport items 14 (CTM
) 200Q and polycarbonate resin [Kneepilon Z-
200J (Mitsubishi Gas Chemical) 4oog was dissolved in 2000d of 1,2-dichloroethane, and the cylinder coated with the intermediate layer and carrier generation layer was immersed in the resulting solution, and the cylinder with the intermediate layer and carrier generation layer was immersed at a pulling rate of 90++++/mi- ( coating speed)
The carrier transport layer (CTL) with a film thickness of 20 g was formed by pulling it up and applying a dip coating, and drying it at 85°C for 1 hour.
) to prepare photoreceptors 1 to 3 according to the present invention and photoreceptors 1 to 3 of comparative examples.

Next, measurements were performed on each photoreceptor.

However, the dispersion stability of the charge generation layer coating liquid was measured by the following method. That is, regarding dispersion stability,
Dispersibility was evaluated by the degree of sedimentation when the dispersion was allowed to stand for one week. Those evaluation criteria are shown below.

(Evaluation Criteria) Each of the photoreceptors 1 to 3 according to the present invention and the photoreceptors 1 to 3 of the comparative example was mounted on a modified rU-Bix 1550 J (manufactured by Nipo Rikisha (equipped with semiconductor laser beam 11N)), V
Adjust the grid voltage so that ++ is -700 ± 10 [V], set the potential of the exposed surface at the time of irradiation of 0.71 W to VL, perform reversal development with the phenomenon bias -GOO [V], and make the copy image The black spots on the white background were evaluated (yH500
0 and yL5000 are potentials after 5000 copies, respectively).

The evaluation of black spots was performed using an image analysis device "Omnicon 300".
The particle size and number of black spots were measured using a "shape" (manufactured by Shimadzu Corporation), and one black spot with a diameter of 0.05 mm or more was determined.
Judgment was made based on how many pieces there are per CO2.

The criteria for black spot evaluation are as shown in the figure below.

In addition, if the result of black spot determination is 010, it will be practical, but
Δ may not be suitable for practical use, and × may not be suitable for practical use.

The adhesion between the intermediate layer and the photosensitive aperture was evaluated by a base grain test. In other words, the distance between adjacent gaps is 11
Using the cutter guide No. 01, make 11 parallel scratches vertically and horizontally on the conductive support with a cutter, making 100 squares (
form the basal orders). After pasting cellophane tape with a width of 2411 I on top of it, peel it off from one end. The number of squares that peeled off at that time was counted and expressed as the number of squares remaining out of 100.

As a guideline for adhesion, 100/100 is considered good adhesion, and Q/100 is considered poor.

Table 1 does not show the evaluation results of Examples and Comparative Examples.

Book 4) CTM: [A[ [B] As is clear from Table 1, photoreceptors 1 to 3 of the present invention had excellent dispersion stability and no black spots occurred compared to the comparative photoreceptors. It was also found that the adhesive properties were excellent.

[Effects of the Invention] As explained in detail above, according to the present invention, the coating liquid for the carrier generation layer has excellent dispersibility and dispersion stability, and is also excellent in edge adhesion and electric potential characteristics, and is free from black spot formation. It was possible to provide an electrophotographic photoreceptor that does not cause image quality defects such as the above.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views of the layer structure of the electrophotographic photoreceptor. 1... Conductive support (substrate)

Claims (3)

[Claims] (1) In an electrophotographic photoreceptor comprising at least an intermediate layer, a carrier generation layer, and a carrier transport layer laminated on a conductive support, the carrier generation layer contains τ-type phthalocyanine and/or X-type phthalocyanine as a carrier generation substance. An electrophotographic photoreceptor comprising a fatty acid cellulose ester as a binder. (2) The fatty acid cellulose ester is characterized in that it contains at least one selected from the group consisting of cellulose acetate, cellulose butyrate, cellulose propionate, cellulose laurate, cellulose acetate butyrate, and cellulose acetate propionate. The electrophotographic photoreceptor according to claim 1. (3) The weight ratio of the carrier-generating substance and fatty acid cellulose ester in the carrier-generating layer is 1/5 to 3/1.
The electrophotographic photoreceptor according to claim 1 or 2, characterized in that: