JPS63136055A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sharpness and gradation of the image to be formed by using metal-free phthalocyanine particles having a crystal form of a gamma-type, gamma'-type, eta-type, or eta'-type, as an electric charge generating material, and specifying a longer axis diameter to shorter axis diameter ratio, and the shorter axis diameters of said particles. CONSTITUTION:The charge generating material is the metal-free phthalocyanine particles having the crystal form of a gamma-type, gamma'-type, eta-type, or eta'-type, and a longer axis diameter to shorter axis diameter ratio of 1.5-10, and the shorter axis diameters regulated to <=0.35mum confirmed by the centrifugal precipitation type particle size determination method using the scanning type electron microscope, and the particle size distribution is obtained by dispersing the phthalocyanine particles into a solvent, such as tetrahydrofuran, and measuring the average particle diameter. This photosensitive body is constituted by successively laminating on a conductive substrate an undercoat layer, the charge generating layer, and a charge transfer layer, or omitting the undercoat layer from the other layers, thus permitting deterioration of sharpness and gradation of the image to be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an electrophotographic photoreceptor, and more specifically, the present invention relates to an electrophotographic photoreceptor that has high sensitivity, stable repeatability over a long period of time, and 2.
This invention relates to an electrophotographic photoreceptor with good gradation.

(Conventional technology) Conventionally, electrophotographic photoreceptors are made of selenium or selenium alloys.

Those using inorganic photoconductors such as zinc oxide, cadmium sulfide and titanium oxide have mainly been used.

In recent years, the development of semiconductor lasers has been remarkable, and small and stable laser oscillators have become available at low cost and are beginning to be used as light sources for electrophotography.

However, using semiconductor lasers that emit short-wavelength light in these devices has many problems in terms of lifespan, output, etc., so semiconductor lasers that emit long-wavelength light, which do not have these problems, are now being used. according to the long wavelength region (78
There is now a need to develop photoconductive materials that have high sensitivity in the wavelength range (0 nm or more). Recently, laminated photoreceptors using organic materials, especially phthalocyanine, which is sensitive in the long wavelength region, are being developed.
P research is being actively conducted.

The present inventors have already found an arotropic phthalocyanine having crystal forms of the τ, τ′η and η′ types that are sensitive to wavelengths above 780 nm. Electrophotographic photoreceptors using these metal-free phthalocyanines have flexibility,
Although it has excellent processability and hygiene, and good sensitivity to long wavelength light, it has been found that there are problems with image quality, resolution, and stability during repeated use.

(Problems to be Solved by the Invention) The objects of the present invention are to be able to form a uniform and smooth charge generation layer, to have high sensitivity and stable repeating characteristics over a long period of time, and to have two image clarity and two gradation levels. The object of the present invention is to obtain an electrophotographic photoreceptor with good properties.

(Means for solving problems) The present invention provides a charge generating material on a conductive support.

In an electrophotographic photoreceptor formed of a layer containing a charge transfer substance, the charge generation substance is metal-free phthalocyanine particles having a crystal form selected from τ type, τ′ type, η type, and η′ type, The particles are electrophotographic, characterized in that the ratio of major axis diameter/minor axis diameter (hereinafter referred to as L/S ratio) is in the range of 1.5 to 10, and the minor axis diameter is 0.35 μm or less. It is a photoreceptor.

Used in the present invention. τ-type metal-free, genus phthalocyanine is described in JP-A-58-18263982639; type gold-paste phthalocyanine is described in JP-A-58-183758; τ'-type and η'-type metal-free phthalocyanine is described in JP-A-60-19153. They are described in the respective publications, and are made by kneading α-type metal-free phthalocyanine or α-type metal-free phthalocyanine and phthalocyanine derivative as raw materials together with a grinding aid, a solvent, etc. using various dispersers.

Crystal transition can be carried out into metal-free phthalocyanine particles having a predetermined crystal type.

The gold-free redundant phthalocyanine having the above-mentioned crystal form usually has a rod-like crystal form, but in the present invention, phthalocyanine particles having a specific L/S ratio and a particularly small minor axis diameter are electrophotographed. Excellent photosensitivity.

Such fine crystal particles can be obtained by appropriately selecting conditions such as transition time, transition temperature, ratio of dispersion media to raw materials, ratio of grinding aid to raw materials, and solvent during crystal transition. .

The crystalline metal-free phthalocyanine particles obtained in the present invention have an L/S ratio in the range of 1.5 to 10, and particularly have a minor axis length of 0.35 μm or less, preferably 0°25 μm.
The thickness is more preferably 0.15 μm or less. Since the particles are as fine as the metal-free phthalocyanine obtained in the present invention, the particles are well dispersed in the coating liquid, and a uniform charge generation layer can be formed in the coating. When the minor axis diameter of the metal-free phthalocyanine particles becomes larger than 0.35 μm, the dispersion of the coating liquid deteriorates and the smoothness of the surface of the charge generation layer decreases, which affects the electrostatic image and, as a result, reduces the image resolution. and tonality decreases.

On the other hand, the L/S ratio of one particle is preferably in the range of 1.5 to 10; if the L/S ratio is too small, the coating liquid in which the phthalocyanine particles are dispersed tends to aggregate, decreasing the stability over time and increasing thixotropy. As a result, a uniform coating film is formed (
As a result, sensitivity increases as crystal defects increase.

The repeatability will deteriorate.

The minor axis diameter of the phthalocyanine particles can be confirmed by a centrifugal sedimentation type particle size distribution measurement method and a scanning electron microscope (SEM). In the particle size distribution measurement method, phthalocyanine particles are dispersed in a solvent such as tetrahydrofuran, and the average particle diameter is measured under conditions of two revolutions of about 5000 revolutions/minute.

In this case, it is assumed that the phthalocyanine particles are spherical, so it is necessary to be quick with the obtained values, but the average particle diameter thus obtained and the value based on the observed image by SEM almost match. The particle diameter measured by SEM is determined by sandwiching the particle between two parallel lines for a certain observed particle image.

The minimum distance between these two lines is defined as the minor axis diameter (S).

The distance when the particle is sandwiched between two parallel lines perpendicular to this is defined as the major axis diameter (L).

A preferable layer structure of the photoreceptor in the present invention is one in which an undercoat layer, a charge generation layer, and a charge transfer layer are laminated in this order on a conductive substrate, or one in which the above layers are formed except for the undercoat layer. be.

Each layer is preferably formed by dispersing and coating a charge generating agent and a charge transfer agent with a suitable binder resin.

The above-mentioned binder resin includes silicone resin, ketone resin,
Insulating resins include, but are not limited to, polyvinyl chloride resin, acrylic resin, polyester resin, polycarbonate resin, and polyvinyl butyral resin.

The charge generation layer is formed by applying a coating solution containing at least 40% by weight of the metal-free phthalocyanine compound of the present invention and a solvent for the above resin using a spin coater, an applicator, a spray coater, a bar coater, or a dry coater. The film thickness after drying using coating equipment such as M coater, doctor blade, roller coater, curtain coater, bead coater, etc. is 5 to 5.
It is formed to have a thickness of 50 μm, preferably 10 to 20 μm.

The charge transfer layer has a dry film thickness of 0.1 to 5 μm, preferably 0.3 to 1 μm, of a single layer of a charge transfer agent or a coating liquid in which a charge transfer agent is dissolved and dispersed in a binder resin solution. It was formed by As the charge transfer substance, either an electron transfer substance or a hole transfer substance can be used. Preferred charge transfer agents include oxazole derivatives and carbazole derivatives.

hydrazone derivatives, styryl dyes, cyanine dyes,
Oxadiazole derivatives, pyrazoline derivatives.

There are hole transfer substances such as triphenylmethane compounds, triphenylamine compounds, and nitrofluorenones.

Nylon 610. copolymerized nylon,
Alcohol-soluble polyamides such as alkoxymethylated nylon, casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymers, gelatin, polyurethane, polyvinyl butyral and metal oxides such as aluminum oxide, preferably 0.1 to 20 μm, preferably 0.1 It is formed to have a thickness of ~1 μm.

Further, conductive and dielectric particles such as metal oxides such as zinc oxide and titanium oxide, silicon nitride, silicon carbide, and carbon black can be included in the resin for adjustment.

As the conductive support on which each of the above layers is to be formed.

Aluminum, alloys of aluminum and other metals.

In addition to metals such as steel, iron, copper, and nickel, conductive plastics and plastics, paper, glass, etc. that have been imparted with conductivity can be used.

In addition to lasers, digital light sources for printers include L
ED can also be used. LEDs in the visible light range are also used, but those that are generally in practical use are those with wavelengths of 65 Qnm or more,
It typically has an oscillation wavelength of 660 parts m. Also,
Since the metal-free phthalocyanine compound has an absorption peak around 650 parts m, it can be used as an effective material for LEDs.

Two embodiments of the present invention will be described below. In the examples, part means 1 part by weight.

(Examples) Reference Example 1 (Production of α-type metal-free phthalocyanine) 14.5 parts of aminoiminoisoindolenine was heated at 200° C. for 2 hours in 50 parts of trichlorobenzene.

After the reaction, the solvent was removed by steam distillation and a 2% aqueous hydrochloric acid solution was obtained.

After subsequent purification with a 2% aqueous sodium hydroxide solution.

After thorough washing with water, 8.8 parts of metal-free phthalocyanine (yield 70%) was obtained by drying. The metal-free phthalocyanine thus obtained has a β-type crystal form. The transition from β type to α type is produced by the following operation. 10
“1 part of β-type metal-free phthalocyanine was dissolved little by little in 10 parts of 98% sulfuric acid of C or less.

The mixture is stirred for about 2 hours while maintaining the temperature below 5°C. Subsequently, the sulfuric acid solution is poured into 200 parts of ice water, and the precipitated crystals are filtered. The crystals are washed with distilled water until no acid remains and are dried to obtain 0.95 parts of α-type metal-free phthalocyanine.

Reference Example 2 (Production of τ-type gold-free phthalocyanine) 10 parts of α-type metal phthalocyanine was mixed with 30 parts of common salt.

Put 8 parts of polyethylene glycol into a kneader and heat at 80°C.
After kneading for 7 to 15 hours, sampling, and confirming the transition to the τ type using an X-ray diffraction pattern.

It was taken out from the kneader, and after washing and removing the grinding aid and solvent with water and methanol, it was stirred and purified in a 2% dilute sulfuric acid aqueous solution, filtered, washed with water, and dried to obtain blue crystals with a clear hue. These crystals were also confirmed to be τ-type gold-free phthalocyanine by measurement of infrared absorption spectra.

The size of the phthalocyanine particles thus obtained was determined by measuring the particle size distribution using a centrifugal sedimentation method (rotation speed: 500 rpm) and using a scanning electron microscope! I just acknowledged it.

The minor axis diameter was 0.13 μm, and the major axis diameter was 0.70 μm (major axis diameter/minor axis diameter ratio 5.38).

Reference Example 3 (Production of τ”-type metal-free phthalocyanine) 10 parts of α-type metal-free phthalocyanine, 300 parts of common salt.

Place 300 parts of ethylene glycol in a sand mill.

Milling was carried out at 100°C for 20 hours. sample and
After confirming the transition to the τ'' type (modified τ type) using an X-ray diffraction diagram, the mixture was taken out from the kneader and the same procedure as in Reference Example 2 was carried out to obtain blue crystals. This crystal was also confirmed to be a τ' type gold mud phthalocyanine by measurement of infrared absorption spectrum.

When the size of these phthalocyanine particles was measured in the same manner as in Reference Example 2, the short axis diameter was 0.13 μm and the long axis diameter was 0.7 μm.
It was 0 μm (ratio of major axis diameter/minor axis diameter 5.38).

Reference Example 4 (Production of η-type non-metallectal phthalocyanine) 100 parts of hot metal phthalocyanine, diethylaminomethyl phthalocyanine (diethylaminoethyl groups average 1.1 +
10 parts (containing 1I) were dissolved in water-cooled 98% sulfuric acid, this solution was poured into water, and the precipitate was filtered.

A homogeneous mixture was obtained by washing with water and drying.

100 parts of this mixture, 300 parts of ground salt and 80 parts of polyethylene glycol were placed in a kneader, and heated at 90°C for 7 hours.
Kneaded for ~20 hours. After sampling and confirming that it had transitioned to the η type using an X-ray diffraction diagram.

Take out from the kneader, wash and remove the grinding aid and solvent with water and methanol, and stir in a 2% dilute sulfuric acid aqueous solution 1↑.
It was purified in the same manner as in Reference Example 2 to obtain blue crystals. This crystal was also confirmed to be an η band thermometal phthalocyanine by measurement of infrared absorption spectrum.

When the size of these phthalocyanine particles was measured in the same manner as in Reference Example 2, the short axis diameter was 0.13 μm and the long axis diameter was 0.7 μm.
01 parts m (ratio of major axis diameter/minor axis diameter 5.38).

Reference Example 5 (Production of η'-type metal-free redundant phthalocyanine) 100 parts of α-type metal-free phthalocyanine, phthalocyanine derivative Pc-→C0CHYN Hc, H, ), I (PC
represents a metal-free phthalocyanine residue. ) 15 parts.

300 parts of ground salt and 80 parts of polyethylene glycol were placed in a kneader, and kneaded at 100°C for 8 hours. After sampling, the X-ray diffraction pattern shows η′ type (modified τ type)
After confirming that the crystals had transformed into , the crystals were taken out from the kneader, and blue crystals were obtained in the same manner as in Reference Example 2. This crystal was also confirmed to be an η' type gold metal phthalocyanine by measurement of infrared absorption spectrum.

When the size of these phthalocyanine particles was measured in the same manner as in Reference Example 2, the short axis diameter was 0.13 μm and the long axis diameter was 0.7 μm.
It was 0 μm (ratio of major axis diameter/minor axis diameter 5.38).

Example 1 10 parts of polyvinyl alcohol (saponification degree 86-89%) was mixed on the aluminum surface of an aluminum-deposited polyethylene terephthalate sheet (75 μm), 500 parts of ethanol was added, and the coating liquid was dispersed in a ball mill for 3 hours using a wire bar. , and heat-dried at 70℃ for 3 hours.
A subbing layer having a thickness of 0.5 μm was formed.

Next, 3 τ-type metal-free phthalocyanine obtained in Reference Example 1
and 3 parts of vinyl chloride-vinyl acetate copolymer resin (trade name VMCH, manufactured by Union Carbide) were dispersed together with 94 parts of tetrahydrofuran for 2 hours in a ball mill. This dispersion was applied onto the undercoat layer and dried at 100°C for 2 hours.
．． A charge generation layer of 35 μm was formed.

Next, as a charge generating agent, 1-benzyl-1,2°3.4
-Tetrahydroquinoline-6-carpoxyaldehyde 1',1'-diphenylhydrazone 10 parts, polyester resin (trade name: Vylon 200, manufactured by Toyobo Co., Ltd.) 10 parts
100 parts by weight of methylene chloride was applied onto the charge generation layer and dried to form a charge transfer layer with a thickness of 15 μm.

The electrophotographic photoreceptor prepared above was corona charged at -5.4 KV using an electrostatic copying paper tester 5P-428 manufactured by Kawaguchi Electric, and the amount of charge was reduced to 1/2 by irradiating it with a surface potential of 1 and white light of 5 lux. The white light half-reduction exposure sensitivity (EV2) was investigated from the time it takes for the light to decrease to . In addition, the repetition characteristics were evaluated by charging under the conditions of -5.4 KV and a corona linear velocity of 20 m/min, leaving it in the dark for 2 seconds, and exposing it to 5 1 LIX for 3 seconds. 2 Surface potential, residual potential, and sensitivity. Deterioration was measured. Note that the residual potential is the potential after 3 seconds of light irradiation.

Next, this photoreceptor was attached to the drum of an electrophotographic copying machine having a corona charger, an exposure section, a transfer charging section, a static eliminating exposure section, and a cleaner. The dark potential of this copier was set to -650V, the light potential to -130V, and 5000V was set.
After the repeated durability test of the sheets, the two images were compared and evaluated in five stages according to the following criteria.

◎...Very good O...Good△...Normal
After corona charging at 5.4 KV, the sample was irradiated with monochromatic light using a monochromator using a 500 W xenon lamp as a light source, and the light attenuation during charging exposure was measured.

The results are shown in Table 1.

Examples 2 to 4 Electrophotographic photoreceptors were prepared using the crystalline metal-free phthalocyanines obtained in Reference Examples 3 to 5 in the same manner as in Example 1, and the electrophotographic properties and images were evaluated. The results are shown in Table 1.

Examples 5 to 8 In Reference Examples 2 to 5, the amount of the grinding aid was changed as shown below to obtain metal-free phthalocyanine particles having the minor axis diameter (S) and L/S ratio of various crystal types.

Example 52 25 parts τ 0.20μ 6.06
3250 copies '0.21μ 5.774250 copies
η 0.20μ 6.085250 parts η'0.2
0 μ 6.0 Electrophotographic photoreceptors were prepared using each of the crystalline metal-free phthalocyanines obtained above in the same manner as in Example 1, and the electrophotographic properties and images were evaluated. The results are shown in Table 2.

Examples 9 to 12 In Reference Examples 2 to 5, the amount of the grinding aid was changed as shown below to obtain metal-free phthalocyanine particles having various crystal types with short axis diameters (S) and L/S ratios.

Example 92 20 copies τ 0.31μ 4.21
03200 copies τ'0.30μ 4.3114200
part η 0.30μ 4.3125200 parts η'0
．． 31μ 4.2 Using each of the crystalline metal-free phthalonanine obtained above, electrophotographic photoreceptors were prepared in the same manner as in Example 1, and the electrophotographic properties and images were evaluated.

The results are shown in Table 3.

Examples 13 to 16 In Reference Examples 2 to 5, the amount of the grinding aid was changed as shown below to obtain metal-free phthalocyanine particles having various crystal types with short axis diameters (S) and L/S ratios.

Table 1 Table 2 Reference example Grinding aid Crystal type S L/S Example 132 50 parts τ 0.13μ 2.814
3500 parts '0.35μ 2.7154500 parts η 0.36μ 2.6165500 parts η'
0.36μ 2.6 Using each of the crystalline metal-free phthalocyanines obtained above, electrophotographic photoreceptors were prepared in the same manner as in Example 1, and the electrophotographic properties and images were evaluated. The results are shown in Table 4.

Comparative Examples 1 to 4 In Reference Examples 2 to 5, the amount of the grinding aid was changed as shown below to obtain metal-free phthalocyanine particles having the minor axis diameter (S) and L/S ratio of various crystal types. The major axis diameter of the metal-free phthalocyanine particles was in the range of 1.5 to 2.0 μm.

Comparative example 12 15 parts τ 0,55μ23150
Parts τ'0.61μ 34150 parts η 0.58μ 45150 parts η'0.59μ Using each crystal type metal-free phthalocyanine obtained above, an electrophotographic photoreceptor was prepared in the same manner as in Example 1. The electrophotographic characteristics and images were evaluated. The results are shown in Table 5.

Table 5 (Effects of the Invention) The metal-free phthalocyanine particles of the present invention have a specific LZS ratio and have a relatively small short axis diameter.

It is possible to form a uniform and smooth charge ordering layer,
While maintaining sensitivity to long wavelength light around 800 nm, which is a characteristic of these crystal types, high-quality images can be obtained with stable repeat characteristics over a long period of time. The images produced by the electrophotographic photoreceptor using the phthalocyanine particles in the present invention have excellent effects in that the single gradation property and sharpness hardly deteriorate even after repeated use several thousand times.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the major axis diameter (L) and minor axis diameter (S) of the gold-free phthalocyanine particles of the present invention. FIG. 2 is a scanning electron micrograph showing the structure of the τ-type phthalocyanine particles of Example 5. The distance between the white lines in the diagram is 5μ
It is m.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a layer containing a charge-generating substance and a charge-transfer substance formed on a conductive support, wherein the charge-generating substance is τ-type, τ′-type, metal-free phthalocyanine particles having a crystal form selected from η type and η type,
An electrophotographic photoreceptor characterized in that the particles have a ratio of major axis diameter/minor axis diameter in the range of 1.5 to 10, and a minor axis diameter of 0.35 μm or less. 2. The minor axis diameter of metal-free phthalocyanine particles is 0.25 μm
An electrophotographic photoreceptor according to claim 1, which is as follows. 3. The minor axis diameter of metal-free phthalocyanine particles is 0.15 μm
An electrophotographic photoreceptor according to claim 1, which is as follows. 4. Claim 1 in which the major axis diameter is 1.0 μm or less
The electrophotographic photoreceptor described in .