JPS5882249A - Electrophotographic receptor for laser printer - Google Patents

Abstract

PURPOSE:To prevent the generation of uneven density in a solid picture, by forming an electric charge transfer layer on an electric charge generating layer of which the transmittance to the laser light used is smaller than a specific value thereby eliminating the interference between the reflected light on the substrate surface and the reflected light on the surface of the charge transfer layer. CONSTITUTION:An electric charge generating layer 2 of which the transmittance to the laser light used is <=10% is formed on a substrate of Al or the like to d2 thickness by coating paint contg. epsilon type copper phthalocyanine and a butyral resin at the same pts.wt. in the case of, for example, a Ga-Al-As semiconductor layer (780nm wavelength of emitted light). For the thickness d2, alpha d2 is made larger than 2.3 so that the I/I0 expressed by the equation (I is transmittance, I0 is incident light, alpha is a coefft. of absorption of the layer 2). To attain the specified alpha, the paek of the spectral absorption of the layer 2 is made near the emission wavelength of the laser or coloring matter absorbing the laser light used for this purpose is mixed. Thus, excellent pictures are obtained by suppressing the interference between the reflected light 5 from the surface of the layer 3 and the reflected light 6 from the substrate surface 1 and eliminating the unevenness of the solid pictures.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor for a laser printer. More specifically, no interference fringe-like density unevenness appears,
The present invention relates to an electrophotographic photoreceptor for laser printers that can reproduce solid images well.

Conventionally, as a photoreceptor for an electrophotographic printer using a laser as a light source, selenium, a selenium-based alloy, a cadmium sulfide resin dispersion system, a charge transfer complex with polyvinyl carboxyfluorenone, and the like have been used. In addition, gas lasers such as helium-cadmium, argon, and helium-neon lasers have been used as a substitute for lasers, and semiconductor lasers, which are small, low cost, and can be directly modulated, have also come into use.

As for photoreceptors, a laminated photoreceptor including a charge transfer layer and a charge generation layer is attracting attention in order to obtain sufficient sensitivity and charging characteristics depending on the wavelength of the laser beam used.

Compared to a photoconductor that uses a single photoconductive layer, in a laminated photoconductor the photosensitivity can depend only on the charge generation layer, so it is important to compare photoconductive materials that are sensitive to the wavelength of the laser light used. You can choose freely.

The charge generation layer of the laminated photoreceptor has the role of absorbing light and generating free charges, and its thickness is usually as thin as Q, 1 to 5 μm. The charge transfer layer has the role of accepting static charges and transporting free charges, and absorbs almost no self-forming light, and its thickness is usually 5 to 30 .mu.m.

By the way, when using such a laminated photoreceptor and outputting an image by scanning a line of laser light with a laser printer, there is no problem with line images such as characters, but in the case of solid images, interference fringe-like density may occur. Unevenness appears.

The cause of this is thought to be interference between the light reflected on the surface of the charge transfer layer and the light reflected on the surface of the substrate such as metal. That is, the laminated electrophotographic photoreceptor has a structure in which a charge generation layer 2 and a charge transfer layer 3 are laminated on one substrate 1, as shown in FIG. When laser light 4 (emission wavelength is approximately 0.8 μm for semiconductor lasers and 0.63 μm for helium-neon lasers) is incident on this laminated photoreceptor, as shown in FIG. Interference occurs between the reflected light 5 on the surface of the charge transfer layer 30 and the light 6 reflected on the surface of the substrate 10 and emerging from the surface of the charge transfer layer 3. If the refractive index of the laminated layer of the charge generation layer 2 and the charge transfer layer 3 is n, the thickness is di, and the wavelength of the laser beam is λ, then when ndl is an integral multiple of λ/2, the intensity of the reflected light is maximum; In other words, when the intensity of the light entering the charge transfer layer 3 is minimum (according to the law of conservation of energy), and nd is an odd multiple of λ/4, the reflected light is minimum, that is, the light entering the inside is maximum. Become. Incidentally, due to manufacturing reasons, s'l has an unavoidable local unevenness of about 1 μm. Since laser light has good monochromaticity and is coherent, the above-mentioned interference conditions change in response to unevenness in the area of the laser beam, causing unevenness in the amount of laser light absorbed by the charge generation layer 2, which causes the solid image to become uneven. It is thought that this appears as interference fringe-like unevenness in density. Note that in a normal copying machine, the light source emits monochromatic light, so the width of the density unevenness in the form of interference fringes changes depending on the wavelength, and is averaged out so that it cannot be seen.

The main object of the present invention is to provide a laminated photoreceptor that does not cause density unevenness due to interference when used in a laser printer.

The electrophotographic photoreceptor for laser printers according to the present invention has a charge transfer layer and a transmittance of 10 to the laser beam used.
% or less. That is, by setting the transmittance of the charge generation layer to laser light to be 10 or less, interference of the laser light can be prevented and a photoreceptor can be provided which can provide a solid image with uniform density.

The electrophotographic photoreceptor for laser printers of the present invention has a structure in which a charge generation layer 2 and a charge transfer layer 3 are laminated on a base 1 as shown in FIG. The transmittance is 10% or less. Transmittance is 10
In the following cases, the incident laser light passes through the charge transfer layer 3
, is absorbed by the charge generation layer 2, reflected by the surface of the substrate 10, absorbed again by the '-charge generation layer, and is absorbed back and forth before returning to the surface of the charge transfer layer 3. 1! Attenuates below X. The value of the transmittance of ION or less means that, as a result of various experimental studies, a solid image with a uniform density to the extent that there is no problem in practical use can be obtained. It is thought that this is occurring, although it is small.

Note that 5X or less is particularly preferable.

As shown in FIG. 2, if the thickness of the charge generation layer 2 that absorbs the loser light is does, and the absorption coefficient of the charge generation layer 2 with respect to the laser light is α-1, then the incident light Io and the transmittance The relationship with ■ is given by the following equation.

I = Io exp (-αd) To make the transmittance less than 10%, that is, I /Io less than 0.1, αd! may be made larger than 2.3. αd
, the thickness d! of the charge generation layer 2 must be increased. or increase the absorption coefficient α.Increasing α increases the emission wavelength of the laser used, approaches the charge generation layer 20 wavelength light absorption peak, and also increases the wavelength of the laser beam applied to the charge generation layer 2. There are methods such as mixing absorbing dyes.

Suitable substrates for the photoreceptor according to the present invention include metals such as aluminum, stainless steel, brass, and metals, or a thin layer of these metals adhered to a plastic sheet or glass with an adhesive. Alternatively, it may be formed by vapor deposition. The charge generation layer of the laminated photoreceptor used in the present invention is formed by using a charge generation substance alone or by mixing it with a polymer. Examples of charge-generating substances include organic substances such as -eyy7Yu@□-disazo pigments, quinocyanine pigments, -perylene pigments, phthalocyanine pigments, squaric acid derivative dyes, biryllium dyes, and charge transfer complexes of polyvinylcarpansulfate and trinitrofluorenone. used. Also amorphous selenium.

Inorganic materials such as selenium alloys, cadmium sulfide, and amorphous silicon are also used. The charge transfer layer generally has a transmittance of 80 or more for laser light, and is formed using a charge transfer substance alone or in a mixture with a polymer. Charge transfer substances include polyvinylcarbabel and pyrazoline derivatives.

Hydrazone derivatives, oxadiazole derivatives.

Triphenylmethane derivatives, triphenylamine, trinitrofluorenone, etc. are used.

As the dye that absorbs laser light, carbon and various dyes corresponding to the emission wavelength of each laser are effective, and cyanine dyes are particularly effective for semiconductor lasers with wavelengths of 750 mμ or more.

Cyanine dyes are also called polymethine dyes because they have a long chain of methine groups (-0H=OH-), and each time one methine group becomes longer, the resonance wavelength shifts to a longer wavelength by about 1007 Lm.

The present invention will be explained below with reference to Examples. ◎ Example 1 - (Epsilon) 1 part by weight of shaped steel phthalocyanine (manufactured by Toyo Ink Co., Ltd., trade name: Lionol Blue BS) and butyral resin (manufactured by Tanezu Kagaku Co., Ltd., trade name: ESLETSUKU BM-2)
1 part by weight and 15 parts by weight of isopropyl alcohol were placed in a ball mill and dispersed for 4 hours to prepare a charge generating substance coating liquid.

This coating liquid was applied with a wire bar onto an aluminum foil having a thickness of 10 μm which was laminated to a polyester film having a thickness of 757 Im, and was dried to form a charge generation layer. The thickness of the charge generation layer is approximately 0.7 μm. Next, 1 part by weight of a pyrazoline derivative having the following structural formula, 1 part by weight of polysulfone resin (manufactured by Union Carbide, trade name: P1700), and 6 parts by weight of monochlorobenzene were mixed, stirred and dissolved using a magnetic stirrer, and charged. It was used as a moving substance coating liquid. This coating liquid was applied onto the charge generation layer using a wire bar and dried to form a charge transfer layer. The film thickness is approximately 10 μm. This laminated photoreceptor was used in an experimental laser printer (charged with negative polarity) equipped with a galium-aluminum arsenide semiconductor laser (emission wavelength 780 nm, output 5 m).

Developed with negative toner) to create an image. As a result, an image with uniform density in the peta image area and sharp line images was obtained.

A charge generation layer of the same thickness was formed on glass using the same charge generation material coating solution as in step 9 using photosensitive isolation lIK, and the spectral transmittance was measured, and the transmittance was 4X at 780 nm. . A charge transfer layer with the same thickness was formed on glass using the same charge transfer substance coating liquid used to prepare the photoreceptor, and the spectral transmittance was measured.
The transmittance was 90% or more in the range of m to 850 nm.

Comparative Example I A charge generation layer was formed in the same manner as in Example 1 using a charge generation material coating liquid having a composition of 1 part by weight of C-shaped steel phthalocyanine, 1 part by weight of butyral resin, and 30 parts by weight of isopropyl alcohol.

The film thickness is approximately 0.3 μm. A charge transfer layer similar to that in Example 1 was formed on this charge generation layer. When this laminated photoreceptor was attached to the same experimental laser printer as in Example 1 and an image was produced, there was no problem with the line image, but density unevenness in the form of interference fringes appeared in the solid image area.

A charge generation layer of the same thickness was formed on glass using the same charge generation substance coating liquid used to prepare the photoreceptor, and the spectral transmittance was measured.The transmittance at 780 nm was 2.
It was 5%.

Comparative Example 2 Example 1 was prepared using a charge-generating substance coating liquid having a composition of 1 part by weight of β-type copper phthalocyanine (manufactured by Toyo Ink Co., Ltd., Lionol Blue GLA'), 1 part by weight of butyral resin, and 15 parts by weight of isopropyl alcohol. A charge generation layer was formed in the same manner as described above. The film thickness is approximately 0.7 μm. A charge transfer layer similar to that in Example 1 was formed on this charge generation layer. When this laminated photoreceptor was attached to the same experimental laser printer as in Example 1 and an image was produced, there was no problem with the line image, but density unevenness in the form of interference fringes appeared in the solid image area.

A charge generation layer of the same thickness was formed on glass using the same charge generation substance coating liquid used to produce the photoreceptor, and the spectral transmittance was measured.The transmittance was 1 at 780 nm.
It was 8N.

The e-shaped steel phthalocyanine of Example 1 has a higher β value than that of Comparative Example 2.
The absorption peak was at a longer wavelength than that of copper phthalocyanine.

Example 2 1 part by weight of e-shaped steel phthalocyanine (manufactured by Toyo Ink Co., Ltd., trade name: Lionol Blue ES) and a cyanine dye having the following structural formula (Japan Photosensitive Pigment Research New Exhibition).

0.1 part by weight of (trade name: NK-123), 1 part by weight of butyral resin (manufactured by Tanesui Kagaku Co., Ltd., trade name: Eslec BM-2), and 20 parts by weight of isopropyl alcohol were placed in a ball mill and dispersed for 4 hours to charge. It was used as a generation layer coating liquid. Apply this coating solution to aluminum and laminated polyester film.
Apply it to the surface with a wire bar, dry it, and use it as a charge generation layer. The film thickness is approximately 0.6 μm. Next, a charge transfer layer similar to that in Example 1 was formed.

Next, 1 part by weight of the same pyrazoline derivative as in Example 1 and polysulfone resin (manufactured by Union Carbide, trade name: P
1700) and 6 parts by weight of monochlorobenzene were mixed and stirred and dissolved using a magnetic stirrer to obtain a charge transfer substance coating liquid. This coating liquid was applied onto the charge generation layer using a wire bar and dried to form a charge transfer layer. The film thickness is approximately 11 μm. This laminated photoreceptor was attached to an experimental laser printer (charged with negative polarity, developed with negative toner) equipped with a galium-aluminum arsenide semiconductor laser (emission wavelength: 820 nm, output: 10 mW) to produce an image. As a result, a solid image with uniform density and sharp line images was obtained.

A charge generation layer of the same thickness was formed on glass using the same charge generation substance coating liquid used to produce the photoreceptor, and the spectral transmittance was measured; the transmittance was 7% at 820 nm. there were.

Example 3 Fried amorphous silicon was deposited to a thickness of 2 μm on a mirror-finished aluminum cylinder by a capacitively coupled high-frequency glow discharge method to form a charge generation layer. The deposition conditions were silane gas flow rate of 10 rx” for 7 minutes;
Gas pressure 6.5 Pa, frequency 13.56 MHz, high frequency/power 100W, substrate temperature 250°C, deposition rate 1μ
m/hour, 71 parts by weight of zero-order trinitrofluoreno, and saturated polyester resin (manufactured by Toyobo Co., Ltd., Byron 2).
00) 1 weight part of IM and 6 parts by weight of monochlorobenzene were mixed and dissolved by stirring with a stirrer to prepare a charge transfer substance coating liquid. This coating liquid was applied onto the charge generation layer by a dipping method and dried to form a charge transfer layer. The film thickness is approximately 12 μm. This laminated photosensitive drum was attached to an experimental laser printer (charged with positive polarity) equipped with a He-Ne laser (emission wavelength: 633 nm, output IQ mW) to produce an image. As a result, a solid image with uniform density and sharp line images was obtained. In addition, the same laminated photosensitive drum was used with a semiconductor laser (emission wavelength 780 nm,
Laser printer experimental machine (output 5 mW)
When the image was produced by charging it to a positive polarity (developing with positive toner), interference fringe-like density unevenness appeared in the peta image area.

Amorphous silicon was deposited to the same thickness on glass under the same deposition conditions as when producing the photosensitive drum, and the spectral transmittance was measured.The transmittance was 2% at 633 nm and 180 nm.
The transmittance was 45X at nm.

[Brief explanation of the drawing]

FIG. DESCRIPTION OF SYMBOLS 1...Substrate, 2...No charge generation, 3...Charge transfer layer, 4...Incoming laser light, 5...Reflected light on the surface of charge transfer layer, 6...Surface of substrate The light that is reflected by the surface of the charge transfer layer and returns to the surface of the charge transfer layer. Figure 1 2nd position

Claims (3)

[Claims] (1) An electrophotographic photoreceptor for a laser printer, comprising a charge transfer layer and a charge generation layer having a transmittance of IOX or less to the laser beam used. (2) The electrophotographic photoreceptor for a laser printer according to claim 1, wherein the laser is a semiconductor laser. (3) The electrophotographic photoreceptor for a laser printer according to claim 1, wherein the charge generation layer contains a phthalocyanine pigment.