JPH02222962A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide a high sensitivity and a excellent copying characteristic of a red original by incorporating an N type pigment and P type pigment at a specific weight ratio into a charge generating layer. CONSTITUTION:This electrophotographic sensitive body is constituted by laminating a charge transfer layer and the charge generating layer in this order on a conductive base material. The N type pigment and the P type pigment are incorporated into the charge generating layer at such a ratio at which the weight ratio (N type pigment/the P type pigment) thereof attains 40/60 to 90/100. As a result, the heat holes existing in the P type pigment are implanted into the charge transfer layer and negative space charge is generated in the charge generating layer if the photosensitive body is electrostatically charged positive by a corona discharge, etc. This negative space charge intensifies the electric field of the photocarriers in the charge generating layer and enhances the generation efficiency of the photocarriers in the subsequent exposing process. The images are formed with the good sensitivity and the excellent copying characteristic of the red original in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrophotographic photoreceptor suitably used in image forming apparatuses such as copying machines, and more specifically, to an electrophotographic photoreceptor having high sensitivity and
The present invention relates to an electrophotographic photoreceptor that has excellent copyability for red originals.

<Prior art and problems to be solved by the invention> In recent years, as electrophotographic photoreceptors, photoreceptors with a high degree of freedom in functional design, especially charge-generating materials that generate charges (positive charges and negative charges) when irradiated with light, have been developed. A charge generation layer (CG L) containing;
A positively charged electrophotographic photoreceptor comprising a charge transport layer (CTL) containing a charge transport material that transports generated positive charges has been proposed.

In such a laminated photoreceptor, in order to form an electrostatic latent image, positive charges photogenerated on the surface layer of the charge generation layer must
It must travel through the charge generation layer to the interface with the charge transport layer and be injected into the charge transport layer.

By the way, as a charge-generating substance, a red condensed polycyclic organic pigment (
For example, Ansunthrone type, PEIJ Ren type, Azo type, etc.)
is often used.

However, since all of these pigments are N-type pigments (electron-accepting pigments), they have poor positive charge transportability. Therefore, during exposure to light, some of the positive charges do not move to the interface between the charge generation layer and the charge transport layer, but remain in the charge generation layer, resulting in a decrease in sensitivity.

The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-mentioned problems and provide a positively charged electrophotographic photoreceptor that has high sensitivity and excellent copyability for red originals. shall be.

Means and Effects for Solving the Problems> The electrophotographic photoreceptor of the present invention has a charge transport layer and a charge generation layer laminated in this order on a conductive base material, the charge generation layer comprising: N-type pigment and P-type pigment are determined by their weight ratio (N-type pigment/P
type pigment) in a ratio of 40/60 to 90/10.

The photoreceptor of the present invention configured as described above has the following effects.

When the photoreceptor is positively charged by corona discharge or the like, thermal holes present in the P-type pigment are injected into the charge transport layer, generating negative space charges in the charge generation layer.

This negative space charge enhances the electric field of photocarriers in the charge generation layer, increasing the efficiency of photocarrier generation in the subsequent exposure process.

When this photoreceptor is exposed to light, the absorption edge of light is 550 to 600.
Both positive and negative charges are generated by the N-type pigment, which is ns. Of these, positive charges are transported through the charge generation layer to the interface between the charge generation layer and the charge transport layer by the P-type pigment having hole transport properties, and then injected into the charge transport layer. On the other hand, the negative charge neutralizes the positive charge induced on the surface layer of the photoreceptor during charging, thereby forming an electrostatic latent image on the exposed portion.

The present invention will be explained in detail below.

The photoreceptor of the present invention contains two types of pigments, N-type and P-type, in the charge generation layer. The reason why the P-type pigment is included is to enhance the sensitivity by emphasizing the electric field for generating photocarriers and improving the hole transportability in the charge generation layer, as described above.

Furthermore, the photoreceptor of the present invention has a weight ratio of both pigments (N-type pigment/
P-type pigment (hereinafter referred to as rN/P ratio J) is 40/6
The range is 0 to 90/10.

In this way, the weight ratio is specified because the N/P ratio is 90.
/ If it exceeds 1.0, the content of P-type pigment in the layer will be relatively small, which will weaken the electric field enhancement and hole transport properties, resulting in poor sensitivity, and the N/P ratio will decrease. is 4
If it is less than 0/6'0, the content of the N-type pigment will be relatively small, resulting in poor sensitivity and poor copyability of red originals.

As the N-type pigment and P-type pigment that can be used in the present invention, various conventionally known pigments can be used.

For example, examples of N-type pigments include perylene compounds, anthanthrone compounds, azo compounds, methane, diphenylmethane, xanthine, and acridine, which have an amino group or a derivative thereof as a substituent. Among these, anthanthrone compounds are preferred because they have high photocarrier generation efficiency.

Examples of P-type pigments include various pigments having a sulfonic group or carboxyl group, such as ab, anthraquinone, triphenylmethane, nitro, xanthine, azine, and quinoline, and phthalocyanine compounds. Among these, it is preferable to use phthalocyanine compounds, particularly oxotitanylphthalocyanine, which are non-toxic and have excellent processability.

Examples of the charge transport substance forming the charge transport layer include fluorenone compounds such as tetracyanoethylene, 2,4.7-) dinitro-9-fluorenone, and nitro compounds such as 2,4.8-) linitrothioxanthone and dinitroanthracene. oxadiazole compounds such as succinic anhydride, maleic anhydride, dibromomaleic anhydride, 2,5-di(4-dimethylaminophenyl)-13,4-oxadiazole, 9-(4-diethylamino styryl compounds such as anthracene, carbazole compounds such as polyvinylcarbazole, 1-phenyl-3-(p-
Pyrazoline compounds such as dimethylaminophenyl)birazoline, 4.4',4'-1lis(N,N-diphenylamino)triphenylamine, 4.4'-bis[N-phenyl-N-(3-methylphenyl) ) Amine derivatives such as aminocodiphenyl, conjugated unsaturated compounds such as 1,1-bis(4-diethylaminophenyl)-4,4-diphenyl-1,3-butadiene, 4-(N,N-diethylamino)benzaldehyde- Nitrogen-containing cyclic compounds such as hydrazone compounds such as N,N-diphenylhydrazone, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds compounds, fused polycyclic compounds, and the like. These charge transport materials may be used alone or in combination of two or more.

Examples of the binder resin used in the charge generation layer and the charge transport layer include styrene polymers, acrylic polymers, styrene-acrylic copolymers, polyethylene,
Ethylene-vinyl acetate copolymer, chlorinated polyethylene,
Olefin polymers such as polypropylene and ionomers, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers,
Polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin, phenol resin, melamine resin, benzoguanamine resin, epoxy acrylate, Examples include photocurable resins such as urethane acrylate and polyester acrylate. These binder resins may be used alone or in combination of two or more. Among the charge transport materials, photoconductive polymers such as poly-N-vinylcarbazole can also be used as a binder resin.

The charge transport layer and the charge generation layer may contain sensitizers such as terphenyl, halonaph I/quinones, acenaphthylene, antioxidants, ultraviolet absorbers, plasticizers, and the like.

Note that a surface protective layer made of silicone resin or the like may be provided on the surface of the charge generation layer in order to improve the abrasion resistance of the surface of the charge generation layer. This surface protective layer may contain an ultraviolet absorber, an antioxidant, a conductivity imparting agent, etc., as necessary.

To form a positively charged laminated photosensitive layer, first, a charge transport layer is formed on a conductive substrate using a charge transport layer coating solution containing a charge transport substance, a binder resin, and if necessary a solvent. After that, a charge generation layer coating liquid containing a charge generation substance, a binder resin, and if necessary a solvent is applied onto the charge transport layer to form a charge generation layer.

When forming the charge transport layer, the ratio of the charge transport substance and the binder resin may be appropriately selected. Typically, charge transport material 10
30 to 500 parts by weight of the binder resin or the like is used relative to 0 parts by weight. The charge transport layer may be formed to have an appropriate thickness.

It is usually formed to about 10 to 30/7ffi.

In addition, when forming the charge generation layer, a binder resin may be used in combination, or a charge generation substance may be directly formed on the charge transport layer using a film forming method such as vapor deposition or sputtering without using a binder resin. You may.

When forming a charge generation layer using a binder resin, the binder resin is usually used in an amount of 1 to 300 parts by weight per 100 parts by weight of the charge generating substance. The charge generation layer usually has a film thickness of 0.3 to 1
It is formed to a μ-degree size.

For mixing and preparing each coating solution for forming the charge generation layer and the charge transport layer, conventional methods such as mixer ball mill, paint shaker sand mill,
Various conventional mixing means such as an attritor and an ultrasonic disperser can be used. The coating solution may be applied onto the photosensitive layer using conventional coating methods such as dip coating (immersion method), spray coating, spin coating, roller coating, blade coating, curtain coating, bar coating, etc. This can be done using various methods.

Further, the conductive base material on which the photoreceptor is laminated may be in the form of a conductive sheet or a drum.
Various conductive materials such as aluminum, aluminum alloy, copper, tin, platinum, gold, silver, vanadium,
molybdenum, chromium, cadmium, titanium, nickel,
Examples include simple metals such as palladium, indium, stainless steel, and brass, and plastic materials and glass on which conductive layers of the above metals, indium oxide, tin oxide, etc. are formed by means such as vapor deposition. In order to improve the adhesion with the photosensitive layer, one of the above conductive base materials having an oxide surface,
In particular, alumite-treated aluminum, in particular, the thickness of the alumite-treated layer is 5 to 12-1, and the surface roughness is 1.
Anodized aluminum of 5S or less is preferred. Note that in order to further improve the adhesion between the conductive base material and the photosensitive layer, the conductive base material may be treated with a surface treatment agent such as a silane coupling agent or a titanium coupling agent.

<Example> Hereinafter, the present invention will be explained in more detail based on Examples.

Examples 1 to 5 Preparation of coating liquid for charge generation layer The amounts N and P of the N-type pigment and P-type pigment were determined in each example as shown in Table 1 at an N/P ratio of 40/60 to 9.
Coating liquids for a charge generation layer having the following compositions were prepared by changing the ratio within a range of 0/10.

(Ingredients) (Parts by weight) N-type pigment
N (dibromoanthanthrone) P-type pigment P (metal-free phthalocyanine) Polyvinyl butyral 100 (manufactured by Tanezu Chemical Industry Co., Ltd., trade name "S-LEC BM-2J") Isopropyl alcohol 2000 Preparation of coating liquid for charge transport layer Charge transport with the following composition A layer coating solution was prepared.

(Hereinafter, blank space) (Ingredients) (Parts by weight) p-diethylaminobenzaldehyde diphenylhydrazone 100 Polyarylate 100 (manufactured by Unitika, trade name rU-100J) dichloromethane
Preparation of 900 Photoreceptor A charge transport layer coating solution was dip coated onto an aluminum conductive substrate and dried at a temperature of 90° C. for 30 minutes to prepare a charge transport layer. Next, the charge generation layer coating solution was applied by dip coating onto this charge transport layer, and dried at a temperature of 110° C. for 30 minutes to form a charge generation layer, thereby producing a photoreceptor.

Comparative Examples 1 to 5 As shown in Table 1, Example 1 except that the N/P ratio was less than 40/60 or more than 90/10.
A photoreceptor was produced in the same manner as in Steps 5 to 5.

Examples 6 to 1O Electrophotographic photoreceptors were produced in the same manner as Examples 1 to 5, except that a perylene compound represented by the following formula was used as the N-type pigment in place of dibromoanthanthrone.

Comparative Examples 6 to 10 As shown in Table 2, Example 6 except that the N/P ratio was less than 40/60 or more than 90/10.
A photoreceptor was produced in the same manner as in Steps 1 to 10.

Examples 11 to 15 Example 1 except that an azo compound represented by the following formula was used instead of dibromoanthanthrone as the N-type pigment.
Comparative Examples 11 to 15 Comparative Examples 11 to 15 were prepared in the same manner as in Example 1 to 5, except that a material with an N/P ratio of less than 40/60 or more than 90/10 was used, as shown in Table 3.
Photoreceptors were produced in the same manner as in Examples 1 to 15.

Examples 16-20 Examples 1-4 except that copper phthalocyanine was used as the P-type pigment instead of metal-free phthalocyanine.
A photoreceptor was produced in the same manner as described above.

Comparative Examples 16-20 As shown in Table 4, Example 1 except that the N/P ratio was less than 40/60 or more than 90/10.
Photoreceptors were produced in the same manner as in Examples 6 to 20.

Example 21 Except for using oxotitanyl phthalocyanine instead of metal-free phthalocyanine as the P-type pigment,
Photoreceptors were produced in the same manner as in Examples 1 to 4.

Example 22 A photoconductor was produced in the same manner as in Examples 1 to 4, except that oxotitanyl phthalocyanine was used as the P-type pigment instead of metal-free phthalocyanine, and n-butanol was used as the solvent for the charge generation layer coating solution. was created.

Evaluation Test In order to examine the charging characteristics of the electrophotographic photoreceptors obtained in each Example and Comparative Example, each photoreceptor was positively charged and its surface potential (V) was measured.

Further, each photoreceptor was charged to 700V, and exposed to light using a halogen lamp at an illuminance of 77 lux through a 465-600 nm bus filter, and the time until the surface potential was reduced to 1/2 was determined. The half-reduction exposure amount was calculated.

Further, when a red original with a reflection density of 0.7 was copied, the reflection density of the copy was measured, and the value was taken as an evaluation value indicating the quality of the copyability of the red original.

Tables 1 to 4 show the surface potential, half-decreased exposure amount, and evaluation values for copyability of red originals determined as described above.

From Table 1, in the photoreceptors of Examples 1 to 5 in which the N/P ratio is within the range of 40/60 to 90/10,
While both the half-life exposure amount and the copyability of red originals show values that can be used practically, the photoreceptors of Comparative Examples 1 to 5, whose N/P ratios are outside the above range, have a half-life exposure amount and copyability of red originals. It can be seen that at least one of the copyability of the red original is inferior. That is, Comparative Examples 1 to 3 are inferior in both the half-life exposure amount and the copyability of red originals, while Comparative Examples 4 and 5 are excellent in the copyability of red originals, but the half-life exposure amount is poor. many.

Moreover, from Tables 2 to 4, it can be seen that even if the N-type and P-type pigments and the solvent of the coating liquid for the charge generation layer were changed, the same results as above were obtained.

<Effects of the Invention> As described above, the electrophotographic photoreceptor of the present invention has the advantage of being able to form images with good sensitivity and excellent copyability for red originals.

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor in which a charge transport layer and a charge generation layer are laminated in this order on a conductive base material, the charge generation layer carries an N-type pigment and a P-type pigment by weight. An electrophotographic photoreceptor characterized in that the ratio (N-type pigment/P-type pigment) is contained in a ratio of 40/60 to 90/10. 2.Claim 1, wherein the N-type pigment is an anthanthrone compound.
The electrophotographic photoreceptor described above. 3.Claim 1, wherein the P-type pigment is a phthalocyanine compound.
The electrophotographic photoreceptor described above. 4. The electrophotographic photoreceptor according to claim 3, wherein the phthalocyanine compound is oxotitanyl phthalocyanine.