JPH04324450A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a sensitive body having high sensitivity, causing no image defect even at high temp. and humidity, hardly undergoing a potential change even at low temp. and humidity and giving a satisfactory image in any environment by incorporating oxytitanium phthalocyanine into a photosensitive layer and using specified polyamide resin in a middle layer. CONSTITUTION:This sensitive body has a photosensitive layer contg. oxytitanium phthalocyanine (TiOPc) and a middle layer of polyamide resin having ion species concn. of 0.001-0.02wt.% an electric conductive substrate. This substrate may be made of any electric conductive material such as A, stainless steel or other metal, plastic or paper with an electric conductive layer. In the case where image input is carried out with laser light, an electric conductive layer for preventing the occurrence of interference fringes due to scattering is preferably formed. The middle layer is formed on the substrate and coated with a coating liq. prepd. by dispersing TiOPc in a resin binder dissolved in a solvent and the coating liq. is dried to form an electric charge generating layer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor that can be widely used in electrophotographic applications such as electrophotographic copying machines, laser beam printers, and plain paper FAX machines, and to an electrophotographic apparatus using the same.

0002

[Prior Art] Electrophotography is described in US Pat. No. 2,297,691.
As shown in the above publication, a photoconductive material is used whose electrical resistance changes depending on the amount of radiation received during image exposure, and which is made of a support coated with an insulating substance in the dark. The basic characteristics required of an electrophotographic photoreceptor using this photoconductive material are (1) the ability to be charged to an appropriate potential in a dark place; (2) Less charge dissipation in the dark. (3) The ability to quickly dissipate charges by light irradiation.

Conventionally, selenium,
Inorganic photoreceptors having a photosensitive layer mainly composed of an inorganic photoconductive compound such as zinc oxide or cadmium sulfide have been widely used. However, although these satisfy the conditions (1) to (3) above, they do not necessarily satisfy conditions such as thermal stability, moisture resistance, durability, and productivity. For example, when selenium crystallizes, its properties as a photoreceptor deteriorate, making it difficult to manufacture, and heat, fingerprints, and the like cause crystallization, which deteriorates its performance as a photoreceptor. In addition, cadmium sulfide has moisture resistance and durability, while zinc oxide has smoothness, hardness,
There is a problem with abrasion resistance. Furthermore, most inorganic photoreceptors have a limited sensitivity wavelength range. For example, the wavelength range to which selenium is sensitive is the blue region, and it has almost no sensitivity to the red region.

[0004] For this reason, various methods have been proposed to extend the photosensitivity to a long wavelength range, but there are many restrictions on the selection of the sensitive wavelength range. Even when zinc oxide or cadmium sulfide is used as a photoreceptor, its sensitive wavelength range is narrow and it is necessary to add various sensitizers.

In order to overcome the drawbacks of these inorganic photoreceptors, electrophotographic photoreceptors containing various organic photoconductive compounds as main components have been actively developed in recent years. For example, US Pat. No. 3,837,851 discloses a photoreceptor having a charge transport layer containing triallylpyrazoline, and US Pat.
No. 871,882 discloses a photoreceptor comprising a charge generation layer made of a perylene pigment derivative and a charge transport layer made of a condensate of 3-propylene and formaldehyde.

[0006] Furthermore, a photoreceptor using a bisazo pigment or a trisazo pigment as a charge generating substance was disclosed in Japanese Patent Application Laid-Open No. 59-3.
3445, JP-A-56-46237, JP-A-60-111249, etc. are known.

[0007] Furthermore, the organic photoconductive compound allows the sensitivity wavelength range of the electrophotographic photoreceptor to be freely selected depending on the compound. For example, regarding azo organic pigments, JP-A No. 61-272754, JP-A No. 56-16
The substance disclosed in Japanese Patent Publication No. 7759 has high sensitivity in the visible region, and the substances disclosed in Japanese Patent Application Laid-open Nos. 57-195767 and 61-228453 have high sensitivity in the infrared region. It has also been shown that the sensitivity is up to

Among these materials, materials sensitive to the infrared region can be used in laser beam printers, which have made remarkable progress in recent years.
It is used in products such as LBP (hereinafter abbreviated as LBP) and LED printers, and its demand is increasing.

In particular, in recent years, oxytitanium phthalocyanine (hereinafter referred to as TiOPc) has become a material with high sensitivity in the infrared region.
) is attracting attention. TiOPc is known to take many crystal forms, for example,
The crystal form is shown in Publication No. 6 and Japanese Patent Application No. 1-319934.

[0010] Electrophotographic photoreceptors using TiOPc in the charge generation layer have extremely high sensitivity and are sensitive even in the infrared region, but due to the high sensitivity, defects such as chlorides in the conductive support Holes are easily injected from dirt, etc., which can easily cause defects on images.

[0011] As a method for preventing such injection from the substrate, it has been proposed to provide an intermediate layer between the charge generation layer and the support, which functions as a barrier layer and an adhesive layer. Until now, the layer provided between the charge generation layer and the support was made of polyamide (Japanese Patent Laid-Open No. 46-473
44, JP-A-52-25638), polyester (JP-A-52-20836), polyurethane (JP-A-49-10044), and the like.

0012

[Problems to be Solved by the Invention] However, polyester, polyurethane, etc. vary greatly with changes in temperature and humidity, and it is difficult to obtain stable image quality in all environments, from low temperature and low humidity to high temperature and high humidity.

Polyamide is a material that can provide a certain degree of image quality even in all environments, but polyamide has the disadvantage that its resistance decreases and its barrier properties decrease under high temperature and high humidity conditions.

In particular, in the so-called reversal development system that develops the potential of the exposed area, which is often used in LBP, etc., a completely white image (
When taking pictures of solid white images (hereinafter referred to as "solid white"), a phenomenon in which many black spots occur on the image (hereinafter referred to as "image black spots") tends to occur, and even if polyamide is used, high resolution cannot be obtained.

[0015] Accordingly, an object of the present invention is to provide an electrophotographic photoreceptor in which dark spots are less likely to occur in images without impairing the excellent characteristics of an electrophotographic photoreceptor using TiOPc.

[0016]

[Means for Solving the Problems] According to the present invention, in an electrophotographic photoreceptor having a photosensitive layer on a conductive support via an intermediate layer, the photosensitive layer contains oxytitanium phthalocyanine, and the intermediate layer contains ions. An electrophotographic photoreceptor is provided, characterized in that it is made of a polyamide resin having a seed concentration of 0.001% by weight or more and 0.02% by weight or less.

The present invention will be explained in detail below.

[0018] By washing polyamide resin such as alcohol-soluble nylon with hot water that easily dissolves ionic species to lower the concentration of ionic species contained therein, and then using it as an intermediate layer, black spots on images can be eliminated under all environments. Can be done. The effect is difficult to recognize with low-sensitivity pigments such as conventional azo pigments and ε-type copper phthalocyanine, but the effect is particularly remarkable in the case of high-sensitivity pigments such as TiOPc. In the case of TiOPc, the very high sensitivity means that many carriers are generated and carriers are easily injected into the charge transport layer. Therefore, if holes are injected from the support side, image defects will immediately occur because the charge generation layer itself has no barrier properties.

In order to prevent this and maintain the conventional characteristics, it has been found that polyamide containing ion species in a specific concentration range can be used for the intermediate layer. In other words, if the concentration of the ionic species exceeds 0.02% by weight, in the case of TiOPc, the injectability from the support side is promoted, and a large amount of black spots are generated in the image, especially under high temperature and high humidity conditions. Conversely, the concentration of ionic species is 0.00
If it is less than 1% by weight, the resistance will increase significantly under low temperature and low humidity conditions, causing a decrease in sensitivity, making it unusable. Therefore, by using a polyamide in which the concentration of ionic species is in the range of 0.02% by weight to 0.001% by weight as an intermediate layer, an electrophotographic photoreceptor without image defects can be obtained.

Next, the present invention will be explained according to an actual configuration. Examples of the conductive support include metals such as aluminum and stainless steel, or metals provided with a conductive layer, plastics, and paper, as long as they have conductivity. Examples of the conductive support include cylindrical or film shapes. .

[0021] When the image input is laser light, such as in LBP, it is preferable to provide a conductive layer for the purpose of preventing interference fringes due to scattering. This can be formed by dispersing conductive powder such as carbon black or metal particles in a binder resin. The thickness of the conductive layer is 5 to 40 μm, preferably 1
It is 0 to 30 μm.

An intermediate layer made of polyamide is provided thereon. The thickness of the intermediate layer is 0.2 to 5 μm, preferably 0.5 μm.
~1 μm.

A coating solution in which TiOPc is dissolved in a solvent and dispersed in a binder resin is applied onto the intermediate layer and dried to form a charge generation layer.

Examples of the binder resin used here include polyester resin, polyacrylic resin, polyvinylcarbazole resin, phenoxy resin, polycarbonate resin, polystyrene resin, polyvinyl acetate resin, polysulfone resin, polyarylate resin, and vinylidene chloride/acrylonitrillocopolymer resin. , polyvinylbenzal resin, etc. are mainly used. The ratio of binder resin to pigment is preferably 1/5 to 5/1, more preferably 1/2 to 3/1.

The charge transport layer is mainly formed by applying and drying a paint in which a charge transport substance and a binder resin are dissolved in a solvent. Examples of the charge transport substance used include various triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, triallylmethane compounds, and thiazole compounds. As the binder resin, the same resin as that used for the charge generation layer can be used.

As a coating method for these photosensitive layers, a dipping method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, etc. can be used.

FIG. 1 shows a schematic diagram of a general transfer type electrophotographic apparatus using the electrophotographic photoreceptor of the present invention.

In the figure, reference numeral 1 denotes a drum-type photoreceptor of the present invention as an image carrier, which is rotated at a predetermined circumferential speed in the direction of the arrow around a shaft 1a. During the rotation process, the photoreceptor 1 is uniformly charged to a predetermined positive or negative potential on its circumferential surface by the charging means 2, and then subjected to light image exposure L (slit exposure/ laser beam scanning exposure, etc.). As a result, electrostatic latent images corresponding to the exposed images are sequentially formed on the circumferential surface of the photoreceptor.

The electrostatic latent image is then developed with toner by a developing means 4, and the toner developed image is transferred by a transfer means 5 from a paper feed section (not shown) between the photoreceptor 1 and the transfer means 5 as the photoreceptor 1 rotates. The images are sequentially transferred onto the surface of the transfer material P that is synchronously taken out and fed.

The transfer material P that has undergone the image transfer is separated from the photoreceptor surface and introduced into the image fixing means 8, where the image is fixed and printed out as a copy to the outside of the machine.

After the image has been transferred, the surface of the photoreceptor 1 is cleaned by cleaning means 6 to remove residual toner, and is further subjected to charge removal treatment by pre-exposure means 7 and used repeatedly for image formation.

As the uniform charging means 2 for the photoreceptor 1, a corona charging device is generally widely used. Also, the transfer device 5
Corona transfer means are also commonly used. An electrophotographic apparatus is constructed by combining a plurality of components such as the above-mentioned photoreceptor, developing means, and cleaning means into an apparatus unit, and this unit is configured to be detachable from the apparatus main body. It's okay. For example, photoreceptor 1
The cleaning means 6 and the cleaning means 6 may be integrated into one apparatus unit, and may be configured to be detachable using a guide means such as a rail of the apparatus main body. At this time, the above-mentioned device unit may include a charging means and/or a developing means.

When the electrophotographic apparatus is used as a copying machine or a printer, the light image exposure L converts reflected light or transmitted light from a document, or reads the document into a signal, and uses this signal to scan a laser beam and control the LED array. This is done by driving a liquid crystal shutter array or by driving a liquid crystal shutter array.

When used as a facsimile printer, the optical image exposure L is exposure for printing received data. FIG. 2 is a block diagram showing an example of this case.

The controller 11 controls the image reading section 10 and the printer 19. The entire controller 11 is CP
It is controlled by U17. The read data from the image reading section 10 is transmitted to the partner station through the transmitting circuit 13. Data received from the partner station is sent to the printer 19 through the receiving circuit 12. Predetermined image data is stored in the image memory 16. A printer controller 18 controls a printer 19. 14 is a telephone.

Image information received from the line 15 (image information from a remote terminal connected via the line) is demodulated by the receiving circuit 12, decoded by the CPU 17, and sequentially stored in the image memory 16. Stored. Then, when at least one page of image information is stored in the memory 16, the image of that page is recorded. The CPU 17 reads one page of image information from the memory 16 and sends the decoded one page of image information to the printer controller 18. When the printer controller 18 receives one page of image information from the CPU 17, it controls the printer 19 to record the image information of that page.

Note that the CPU 17 is receiving the next page while the printer 19 is recording.

[0038] Images are received and recorded in the manner described above.

The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser beam printers, C
RT printer, LED printer, LCD printer,
It can also be widely used in electrophotographic applications such as laser engraving.

Next, an example of manufacturing TiOPc used in the present invention will be shown.

[Production Example 1] α-chloronaphthalene 100
g, o-phthalodinitrile 5.0g, titanium tetrachloride 2
．． 0g was heated and stirred at 200°C for 3 hours, cooled to 50°C, and the precipitated crystals were filtered off to obtain a paste of dichlorotitanium phthalocyanine. Next, this was stirred and washed with 100 ml of N,N'-dimethylformamide heated to 100°C, and then washed with 100 ml of methanol at 60°C.
The mixture was washed twice and filtered. Further, the resulting paste was stirred in 100 ml of deionized water at 80° C. for 1 hour and filtered to obtain blue TiOPc crystals. Yield: 4.3g.

The elemental analysis values of this compound were as follows.

Elemental analysis value (C32H16N8 TiO)
C
H N
Cl calculated value (%) 66.68 2.8
0 19.44 0.00 Actual value (%
) 66.50 2.99 19.42
0.47 Next, the crystals were dissolved in 30 ml of concentrated sulfuric acid and added dropwise to 300 ml of deionized water at 20°C under stirring to re-precipitate, filter, and thoroughly wash with water to form amorphous TiOPc.
I got it. 4.0 g of this amorphous TiOPc was suspended and stirred in 100 ml of methanol at room temperature (22° C.) for 8 hours, filtered, and dried under reduced pressure to obtain low-crystalline TiOPc. Further, 40 ml of n-butyl ether was added to 2.0 g of low-crystalline TiOPc, and milling treatment was performed at room temperature (22° C.) for 20 hours with 1 mmφ glass beads. The solid content was taken out from this dispersion, thoroughly washed with methanol and water, and dried. Yield: 1.8g.

Diffraction angle 2θ± in X-ray diffraction of this crystal
0.2° is 9.0°, 14.2°, 23.9°, 27.
It had a strong peak at 1°.

[Production Example 2] According to the production example disclosed in JP-A No. 61-239248 (USP 4,728,592), crystalline T, so-called α type, was prepared.
iOPc was obtained.

[0046]

[Example] The following is an explanation based on an example. [Example 1] <Sample No. Creation of 1 > 30φ, 260mm A1
Using a cylinder as a base, a paint composed of the following materials was applied onto the base by a dipping method, and was thermally cured at 140°C for 30 minutes to form a conductive layer of 18 μm. Conductive pigment: titanium oxide coated with tin oxide
...10 parts (by weight, same hereinafter) Pigment for resistance adjustment: Titanium oxide...
10 parts Binder resin: Phenol resin
…10 copies
Leveling agent: silicone oil
...0.001 part
Solvent: methanol/methyl cellosolve = 1/1
...20 parts Next, a solution of 3 parts of N-methoxymethylated nylon and 3 parts of copolymerized nylon dissolved in 65 parts of methanol and 30 parts of n-butanol was coated on top of this by a dipping method to form a layer of 1.0 μm. An intermediate layer was formed.

The nylon used here was purified by the following purification method. 1 g of nylon was dissolved in 1 liter of methanol and added dropwise to 20 liters of methyl ethyl ketone with stirring. After the dropwise addition was completed, the mixture was decanted, washed twice with methyl ethyl ketone, and then filtered and dried. The dried nylon was washed four times with 4 liters of deionized water at 20° C. for 30 minutes each time, filtered, and dried under reduced pressure.

[0048] This solution was applied on aluminum in the same manner to form an intermediate layer, and then peeled off and the amount of ions was measured.
Sodium, calcium, phosphorus, and chloride ions were detected and their concentration was 0.020% by weight.

Next, 3 parts of the pigment prepared in Production Example 1, 2 parts of polyvinyl butyral (trade name: Eslec BM-2, manufactured by Sekisui Chemical Co., Ltd.), and 80 parts of cyclohexanone were dispersed for 4 hours using a sand mill device using φ1 mm glass beads. 115 parts of methyl ethyl ketone was added to obtain a charge generation layer dispersion. This was applied onto the intermediate layer using a dipping method, and 0.2
A charge generation layer of .mu.m was formed.

Next, 10 parts of a compound having the following structural formula

005
1]

[Chemical formula 1] 10 parts of bisphenol Z polycarbonate resin (viscosity average molecular weight 22,000), 50 parts of monochlorobenzene,
It was dissolved in 10 parts of dichloromethane. This paint was applied onto the charge generation layer described above by dipping and dried at 110°C for 1 hour to form a charge transport layer of 20 μm. Photoconductor No. 1 was prepared.

Image evaluation was performed on the obtained photoreceptor. For evaluation, Canon LBP (trade name "Laser Shot") was used. The environment was 35°C and 85% RH. For evaluation of image black spots, the images were ranked according to the number of black spots in an image area of 5 x 5 cm2 as shown in Table 1.

After forming an image at 35° C. and 85% RH, it was aged for 2 days at 15° C. and 15% RH, and the residual potential was measured. Further, after measuring the residual potential, a continuous image printing durability test was conducted for 2,000 sheets, and the potential immediately after that was measured to determine how much the residual potential had increased. The results are shown in Table 2.

[Example 2] Samples having the following ion content values were prepared by changing the time and number of times the nylon was washed with water. No. 2
3 4 5 6
7 Nylon content 0.0
15 0.013 0.010 0.0
08 0.005 0.001
(% by weight) A photoreceptor was prepared in the same manner as in Example 1 except that the nylon of the intermediate layer was changed. The same evaluation as in Example 1 was performed and the results are shown in Table 2.

[Comparative Example 1] Sample No. In sample No. 8, unpurified nylon was used. Samples No. 9 to No. 12 were prepared by changing the nylon washing time and the number of washings to produce samples having the following ion content values.

No. 8
9 10 11
12 Nylon content 0.078
0.042 0.023 0
．． 0008 0.0006 (
(% by weight) A photoreceptor was prepared in the same manner as in Example 1 except that the nylon of the intermediate layer was changed. The same evaluation as in Example 1 was performed and the results are shown in Table 2.

[0057]

[Table 1]

[0058]

[Table 2] [Example 3] Sample No. 1 of Examples 1 and 2 except that the pigment prepared in Production Example 2 was used. Sample No. 1 to 7 were prepared in exactly the same manner. Photoreceptors Nos. 13 to 19 were prepared. The same evaluation as in Example 1 was performed and the results are shown in Table 3.

[Comparative Example 2] Sample No. 1 of Comparative Example 1 was used except that the pigment prepared in Production Example 2 was used. 8~
Sample No. 12 was prepared in exactly the same manner as Sample No. 12. 20 to 24 photoreceptors were made. The same evaluation as in Example 1 was performed and the results are shown in Table 3.

[0060]

[Table 3] [Comparative Example 3] Sample No. 1 of Examples 1 and 2 and Comparative Example 1 except that ε-type copper phthalocyanine was used as the pigment.
Sample No. 1 to 12 were prepared in exactly the same manner. 25 to 36 photoreceptors were made. The same evaluation as in Example 1 was performed and the results are shown in Table 4.

[0061]

[Table 4] [Comparative Example 4] A pigment with the following structural formula was used.

006
2]

Sample No. 1 of Examples 1 and 2 and Comparative Example 1 except that the dispersion time was 60 hours. Sample No. 1 to 12 were prepared in exactly the same manner. No. 37 to 48 photoreceptors were prepared. The same evaluation as in Example 1 was performed and the results are shown in Table 5.

[0063]

[Table 5] As shown in Examples and Comparative Examples 1 and 2 above, TiOPc
is used as the charge generating substance, and the concentration of ionic species in the alcohol-soluble nylon of the intermediate layer is 0.001% by weight or more and 0.0
By using 2% by weight or less, it is possible to produce an electrophotographic photoreceptor that is highly sensitive, has no image defects (black spots on the image) even under high temperature and high humidity conditions, and has little potential fluctuation even under low temperature and low humidity conditions. Especially for TiOPc, the diffraction angle 2θ±0.2° in the X-ray diffraction spectrum is 9.0° and 14.2°.
The effect is particularly remarkable when there are strong peaks at , 23.9°, and 27.1°.

Furthermore, as shown in Comparative Examples 3 and 4, it is clear that azo pigments and ε-type copper phthalocyanine do not have the same effect as TiOPc on potential fluctuations and image characteristics depending on the concentration of ionic species.

[0065]

Effects of the Invention The electrophotographic photoreceptor of the present invention can suppress image defects, particularly black spots in images under high temperature and high humidity, without impairing its excellent electrophotographic properties, and can obtain stable images in all environments. It became possible.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a general transfer type electrophotographic apparatus.

FIG. 2 is a block diagram of a facsimile machine using an electrophotographic device as a printer.

[Explanation of symbols]

1 Photoreceptor 2 Charging means 3 Exposure section 4. Phenomenon means 5 Transfer means 6 Cleaning means 7 Pre-exposure means 8 Image fixing means

Claims (6)

[Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support via an intermediate layer, wherein the photosensitive layer contains oxytitanium phthalocyanine, and the intermediate layer has an ionic species concentration of 0.001 wt. % to 0.02% by weight of a polyamide resin. 2. The oxytitanium phthalocyanine has a diffraction angle of 2θ±0.2 in CuKα characteristic X-ray diffraction.
2. The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor has strong peaks at angles of 9.0°, 14.2°, 23.9°, and 27.1°. 3. The electrophotographic photoreceptor according to claim 1, wherein the intermediate layer is made of alcohol-soluble nylon. 4. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a charge generation layer and a charge transport layer, and the charge generation layer contains the oxytitanium phthalocyanine. 5. An electrophotographic apparatus comprising the electrophotographic photoreceptor according to claim 1. 6. A facsimile machine comprising the electrophotographic photoreceptor according to any one of claims 1 to 4, and receiving means for receiving image information from a remote terminal.