JPS61255352A - Photosensitive body - Google Patents

Abstract

PURPOSE:To increase the resistance of a photosensitive body to wear and scratch by a blade and to prolong the life by forming a protective surface layer of diamondlike carbon on the surface of the photosensitive body. CONSTITUTION:Carbon in a crucible 1 is evaporated by heating the crucible 1 to >=4,200 deg.C with an electron gun. Positive voltage is applied to an ionization electrode 4 placed above the crucible 1 from a voltage source 5 to convert the evaporated carbon particle into ionized particles having positive charge by contact with the electrode 4. A DC electric field is formed between a photosensitive drum 7 having negative voltage applied from a voltage source 8 and the electrode 4 having the applied positive voltage, and the ionized carbon is accelerated toward the drum 7 by the DC electric field and deposits on the surface of the drum 7. A heater 9 may be placed close to the surface of the drum 7 so as to facilitate the growth of a thin carbon film by heating. The drum 7 is rotated with a motor 12 for driving so that uniform deposition is carried out on the whole surface.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a photoreceptor, particularly a photoreceptor having a layer of a diamond-like carbon thin film on its surface, and a method for manufacturing the same.

BACKGROUND ART It has been proposed to use a diamond-like carbon thin film as a multilayer interference film for optical devices such as interference filters, mirrors, and lenses (Japanese Patent Publication No. 41163/1983). This is a method in which a diamond-like carbon layer is provided on a transparent substrate (quartz, diethylene carbonate resin, etc.) using an ion beam sputtering deposition method or a sputtering ion gun, and the purpose is to obtain an interference film.

On the other hand, the provision of a diamond-like carbon layer as a surface protective layer of a photoreceptor has not been proposed at all.

Problems to be Solved by the Invention Photoconductors, especially photoconductor drums, are susceptible to surface abrasion and scratches due to rubbing against paper and cleaning blades during the transfer process, cleaning process, etc., and this often dominates the life of the photoconductor. . In particular, in a photoreceptor having a photosensitive layer in which photoconductive material particles are dispersed in a binder made of an insulating polymer material, the surface of the photosensitive layer is made of resin, so the wear resistance and blade scratch resistance are low. Its life is said to be about 20,000 sheets at most, and usually about 15,000 sheets.

In order to solve the above problem, it is possible to provide a highly hard surface protective layer on the surface of these photoreceptors, but it is not always necessary to select a material that has excellent light transmittance and does not impair the characteristics of the photoreceptor. However, there was also the difficult problem of how to bring this material into close contact with the surface of the photoreceptor. In particular, it was necessary to solve the difficult problem of adhering an inorganic layer to the surface of an organic material, which has completely different properties, without peeling it off.

In addition, the resulting surface layer must be smooth enough to allow easy removal of toner during cleaning.

Means for Solving the Problems The present invention provides a photoreceptor having a surface protective layer of diamond-like carbon on the surface of the photoreceptor.

Examples of the photoreceptor include an inorganic thin film photoreceptor in which a thin film of amorphous selenium or an amorphous selenium group is formed on a substrate, and a resin film type photoreceptor in which photoconductive material particles are bound on a metal drum using a polymeric material.

Although the present invention can be applied to any of the photoreceptors,
It is particularly preferable to apply the present invention to resin model photoreceptors that particularly require a surface protective layer. The applicable resin model photoreceptor is not particularly limited. For example, as a photoconductive material, phthalocyanine pigments (e.g., body phthalonanine, metal-free phthalocyanine, halogen-substituted phthalocyanine, etc.), organic photoconductive materials such as polyvinyl carbazole, and inorganic photoconductive materials such as zinc oxide and cadmium sulfide are used. It may be either. In addition, examples of the resin binder for binding these photoconductive materials include acrylic resin, styrene resin, saturated polyester resin, polyamide resin, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, polycarbonate resin, Epoxy resin,
Examples include, but are not limited to, urethane resins, silicone resins, phenol resins, melamine resins, alkyd resins, and poly-N-vinylcarbazole.

Resins particularly suitable for forming diamond-like carbon thin films include acrylic resins and polycarbonate resins.

Of course, the photosensitive layer itself may have a multilayer structure.

A diamond-like carbon layer is provided on the outermost surface of the photoreceptor. The carbon layer thickness is 0.05 to 1.0 μm, especially 0.1
~0.5 μm is preferred. Diamond is the hardest substance on the Moss scale, but it is brittle when made into a thin film.

In particular, when this is provided on the surface of a resin model photoreceptor, the difference in hardness between the resin model photoreceptor and the photosensitive layer is extremely large, so that peeling and cracking are likely to occur due to stress.

Therefore, the present invention also provides a technique for making the diamond-like carbon layer adhere well to the photosensitive layer and making it difficult for peeling and cracking to occur.

That is, the present invention provides a method for manufacturing an electrophotographic photoreceptor in which an ionizing electrode and a thermionic radiation are provided near the carbon evaporation source, and ionized carbon is accelerated by a DC electric field and adhered to the surface of the photoreceptor. The present invention relates to a method for manufacturing a photoreceptor having a surface protective layer of diamond-like carbon, which is characterized by gradually increasing the electric field strength between it and an ionizing electrode.

The above manufacturing method will be explained based on FIG. Figure 1 shows
This is an ion blating device for forming a carbon layer on the surface of a photoreceptor. (1) is a crucible (made of copper, for example) containing carbon (target) (2). When this crucible (1) is heated (4200° C. or higher) with an electron gun (3), carbon evaporates. An ionization electrode (4) is provided above the crucible, and when a positive voltage is applied to it from a voltage source (5), the evaporated carbon particles come into contact with the ionization electrode and become positively charged ion particles. At this time, the thermionic emission electrode (
6) When a tungsten filament (for example, a tungsten filament) is placed, ionization is promoted by thermionic electrons generated from the filament.

On the other hand, a negative voltage is applied to the photoreceptor drum (7) by a voltage source (8), and a DC electric field is formed between it and the ionization electrode (4) to which a positive charge is applied.

The ionized carbon is accelerated toward the photoreceptor drum (7) by this DC electric field and adheres to the surface of the photoreceptor. If necessary, a heater (9) may be placed near the surface of the photoreceptor to heat the surface of the photoreceptor and assist in the growth of the carbon thin film. Note that the ion blating is preferably carried out in a vacuum container (10) (10-' Torr or less). If necessary, a gas introduction line (ll) may be provided in the vacuum container and used when it is necessary to cause a chemical reaction between the introduced gas and the evaporated particles on the surface of the photoreceptor to form a film. The photosensitive drum (7) is rotated by a driving motor (12) so that the coating is uniform over the entire surface.

In the above method, the carbon thin film structure can be changed by changing the ionization rate or the distance between the target and the ionization electrode, which are the setting conditions for ion prehetting. The ionization rate can be adjusted by changing the ionization voltage and ionization current. If the ionization rate is small or the distance is long, the carbon layer will have an amorphous structure, and vice versa, it will approach a diamond-like carbon layer.

Since amorphous carbon is relatively flexible and has excellent binding properties with resin, it is possible to improve peeling and cracking resistance by interposing a diamond-like carbon layer in between, rather than directly forming a diamond-like carbon layer on the surface of the photoreceptor. can be significantly improved.

The amorphous carbon layer has a thickness of 0.02 to 0.2 μm1, especially 04
The thickness is preferably 1 μm or less. If it is thinner than 0.02 μm, the effect of the amorphous carbon layer will be insufficient;
The thicker the layer, the lower the transparency. After forming the amorphous carbon layer, the ionization rate is gradually increased or the distance between the target and the ionization electrode is shortened to form a diamond-like carbon layer. The thickness of the diamond-like carbon layer is 0
．． 05-1.0μm, more preferably 0.1-0.5μm
It is m. When the thickness of the surface protective layer is made larger than 0.5 μm, the residual potential on the surface of the photoreceptor increases.

In order to form an amorphous carbon layer, the ionization voltage is 2 when the distance between the target and the ionization electrode is 80 mm.
0 to 30 V, ionization current of 50 to 15 (set to 1+A, thickness of 0.01 to 0.02) tm: 0.5
Brate for ~1 minute.

The ionization voltage and ionization current are gradually increased (eg, over 1 to 2 minutes) to reach an ionization rate at which a diamond-like carbon layer is formed. If a diamond-like carbon layer is suddenly formed from an amorphous carbon layer, peeling tends to occur.

In order to form a diamond-like carbon layer, the ionization voltage is preferably 50V or more, preferably 60 to 70V, and the ionization current is 10A or more, preferably 2
It is 0-30A.

Since the boiling point of carbon is extremely high (4200° C.), an electron gun for vaporizing carbon also requires a considerable amount of current (for example, about 600 mA). When the electron beam generated from the electron gun is applied to the -i location of the carbon target (2), the target evaporates quickly and holes are formed rapidly, and the electron beam reaches the crucible, making vapor deposition difficult. To solve this problem, it is preferable to perform vapor deposition while rotating the carbon target (disc) (2) in the copper crucible (1) as shown in FIG. In this method, the spot position (13) of the electron beam is fixed, but since the crucible (1) is rotating, the electron beam hits along the broken line in the figure, and the carbon is gradually evaporated. becomes possible.

In order to evaporate carbon, the ionization electrode is preferably installed within 100 mm, preferably within 60 to 80 mm, from carbon. Since there is a large amount of carbon vapor in this vicinity (1 to 0.1 torr), a discharge occurs between the ionization electrode and the evaporation source. Since this discharge occurs in a localized area, the generation of ultraviolet light harmful to the photoreceptor, especially the organic photoreceptor, is slight.

A schematic cross-sectional view of the photoreceptor obtained in this manner is shown in FIG. In the figure, (14) is a conductive substrate, (15) is a photoconductive layer, (16a) is an amorphous carbon layer, (16b) is a graphite layer, and (16c) is a diamond-like carbon layer.

The present invention will be explained below with reference to Examples.

Kanmu ■ (1') Preparation of photoconductive paint; Dissolve 50 parts by weight of body phthalocyanine and 0.2 parts by weight of tetranitro body phthalocyanine in 500 parts by weight of 98% a sulfuric acid with thorough stirring, and dissolve this in 3000 parts by weight of water. After depositing a photoconductive material composition of a phthalocyanine body and a tetranitro phthalocyanine body, it is filtered and washed with water.
It was dried at 120°C under reduced pressure.

10 parts by weight of the obtained composition was mixed with thermosetting acrylic resin (Acridic A405: manufactured by Dainippon Ink Co., Ltd.) 22.
5 parts by weight, melamine resin (Super Beckamine J820
: 7.5 parts by weight of Dainippon Ink Co., Ltd., 15 parts by weight of hydrazone compound (1) and methyl isobutyl ketone:
The mixture was placed in a ball mill pot with 70 parts by weight of cellosolve acetate (l:1) and kneaded for 48 hours to prepare a photoconductive paint.

(2) Formation of photoconductive layer The above coating material was coated on an aluminum substrate to a thickness of about 15 μm. This was dried and cured at 150° C. to form a photoconductive layer.

(3) Formation of carbon layer The photoreceptor obtained above was placed in the apparatus shown in FIG.

The carbon layer forming conditions are as follows.

Distance between target and photoreceptor surface: 1000 mm Distance between target and ionization electrode: 80 ml Distance between target and thermionic emission electrode: 20 mm (tungsten filament 12 hm) Vacuum vessel internal pressure:
~l O”-5Torr electron beam:
600mA photoreceptor voltage:
-500V photoreceptor surface temperature: 100
°C Thermionic emission electrode voltage (current): 9V (60A) Under the above conditions, first ionization voltage (current) 30V (2A)
) for 1 minute to form an amorphous carbon layer on the photoreceptor. Next, the ionization voltage (current) was increased to 90 V (30 A) over 1 minute to form a graphite layer.

Next, brating was performed for 2 minutes under these conditions to form a diamond-like carbon layer.

The obtained carbon layer had a thickness of 0.2 μm.

(4) Photoreceptor evaluation test The photoreceptor obtained above was installed in an electrophotographic copying machine (manufactured by Minolta Camera Co., Ltd.: EP-300RE), and the basic characteristics, cleaning performance, and durability of the photoreceptor were evaluated. The results are shown in Table-1. In Table-1, Vo is DC voltage +7.
The initial surface potential when 5KV is applied, DDR, is the decay rate of the potential when left in the dark for 1 second after charging, and El
/2 indicates the amount of exposure required until the initial surface potential becomes 1/2.

"Scratch occurrence" refers to the number of copies that can be made without scratches on the surface of the photoreceptor, cleanability refers to the amount of black spots that appear on the copy paper, and change over time refers to changes in the surface condition of the photoreceptor. Surface potential force (the number of printing sheets that changes by +1OOV or more, and all tests are conducted at 20°C/
The test was carried out at 40% RH.

The results are shown in Table-1. For comparison, the test results of the photoreceptor before providing the carbon layer are shown.

Table 1 Effects of the Invention The photoreceptor of the present invention has significantly improved printing durability, is less likely to cause blade scratches or wear, and has improved removal of toner adhering to the surface of the photoreceptor, that is, cleaning performance.

Furthermore, by using the method of the present invention, it is possible to provide an amorphous carbon layer that is compatible with the photoconductive layer, and gradually form a diamond-like carbon layer, thereby making it possible to prevent peeling and cracking. .

[Brief explanation of the drawing]

FIG. 1 shows an ion blasting apparatus for forming the diamond-like carbon layer of the photoreceptor of the present invention, FIG. 2 shows a rotating crucible and target, and FIG. 3 shows the photoreceptor of the invention. (1) Crucible, (2) Carbon target, (
3) Electron gun, (4) Ionization electrode, (6) Thermionic emission electrode, (7) Photoreceptor drum, (9) Heater, (l
O) Vacuum vessel, (13) Electron beam spot, (14
) substrate, (15) photoconductive layer, (16) carbon layer. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A photoreceptor with a diamond-like carbon protective layer on its outermost surface.