JPH0754414B2 - Electrophotography method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic method using a specific electrophotographic photosensitive member, and more specifically, a combination of a specific electrophotographic photosensitive member and an exposure light source for the photosensitive member, The present invention relates to an electrophotographic method capable of clearly reproducing a red portion of a document.

[Conventional technology]

In the electrophotographic method, the surface of the electrophotographic photosensitive member is usually charged by a corona charger, image exposure is performed, the formed latent image is toner-developed, and the toner image is transferred and fixed on a transfer paper to make a copy. It is a process to obtain, the photoconductor is neutralized as necessary,
After the processing such as cleaning is performed, the next copying cycle is started.

[Problems to be solved by the invention]

When making a copy image with an electronic copying machine that executes such a copying process, it may be desirable to clearly reproduce not only the black portion of the document but also the red portion.

In order to make a clear copy of the red portion, the red color may be treated as black, and for this purpose, the original may be exposed by irradiating the original with green light which is the complementary color of red.

On the other hand, in order to expose the photoconductor to green light, it is necessary to use a photoconductor that absorbs green light well. To that end, it is convenient for the photoreceptor to be a color that absorbs green well, ie red. Therefore, it is preferable to use a photosensitive layer containing a red pigment as the photoreceptor.

By the way, in an electronic copying machine, when the electrophotographic process described above is repeated and the photoconductor is continuously used, deterioration of an image may be caused due to a decrease in charging property or sensitivity or an increase in residual potential. This phenomenon may occur, and this phenomenon is particularly likely to occur when the photosensitive layer is a photoreceptor in which the charge generation layer and the charge transport layer are functionally separated. Upon investigating the cause of this, as one of the causes, it was found that the function of the charge generation layer is likely to deteriorate when the charge generation layer is irradiated with light other than that absorbed by the layer. It is considered that the deterioration of the function of the charge generation layer is due to a decrease in the photocharge injection property, a photo-fatigue phenomenon due to an increase in the carrier trap, and a change in the repeated charging characteristics.

In view of the above circumstances, it is preferable to use a light source that does not include light having a wavelength other than green as the light source of the copying machine.

Therefore, the present invention optimizes the light of the light source to
An object of the present invention is to provide an electrophotographic method in which the reproducibility of a red original is improved and the deterioration of the function of the photoconductor is prevented. Another object of the present invention is to provide an electrophotographic method capable of reducing the size of a light source, reducing its weight, lowering its cost, extending its life, and preventing heat generation.

[Means for solving problems]

The present invention relates to an electrophotographic method which uses a photoreceptor having a photosensitive layer formed on a substrate and uses a green light source in at least the image exposure step of the image exposure step, the erase step, the charge removal step and the like for the photoreceptor. Provided is an electrophotographic method, wherein the photoreceptor uses brominated anthanthrone as a red pigment, and the green light source is a green light emitting diode.

A light emitting diode is known as a light source that is small and lightweight, emits light with low power without generating heat. Generally, green and red light emitting diodes are widely used, but in the present invention, green ones are used.

As the green light emitting diode, a gallium-phosphorus-nitrogen semiconductor diode is generally known. The emission wavelength is about
It is about 565 nm. Since the light of the light emitting diode contains only this wavelength component, harmful light is not included in the photoconductor, which is extremely convenient as a light source for achieving the object of the present invention.

FIG. 1 shows a schematic sectional view of an optical system for carrying out the method of the present invention. The original 2 is irradiated with the light from the light emitting diode 1, and the photoconductor 4 is exposed through the lens system 3.

In order to use the insulated light emitting diode as a light source, it is sufficient to use an array in which a large number of elements are arranged by the length of the original or the photosensitive member. Since the intensity of light changes or unevenness of the light amount occurs depending on the distribution density, it is preferable that the density be optimized.

In the present invention, a green light emitting diode may be used as a light source for image exposure, but since the photoconductor is red, the green light emitting diode may be used in an exposure process other than image exposure. Such a step is, for example, an erasing step of erasing the surface potential after development or transfer, a removing step of uniformly removing the surface potential after cleaning the photoconductor, or a pre-exposure step.

The photosensitive layer in the photoreceptor used in the present invention contains brominated anthanthrone. The brominated anthanthrone pigment may be dispersed in a suitable binder resin to form a photosensitive layer, but when the charge retention is poor, the brominated anthanthrone dispersion layer is used as the charge generation layer, and the pigment-free charge generation layer is used. It is effective to use a function-separated photosensitive layer in combination with a charge transport layer that only transports.

Examples of the charge transport material used in the charge transport layer include amine compounds, diamine compounds, hydrazone compounds, pyrazoline compounds, oxazole compounds, oxadiazole compounds, stilbene compounds, carbazole compounds, and other hole transport materials, and trinitrofluorenone. , Electron-transporting substances such as dinitroanthracene, dinitroacridine, tetracyanopyrene, dinitroanthraquinone and the like.

As the binder resin used in the charge generation layer, polycarbonate, polystyrene, polyester, polyvinyl butyral, methacrylic acid ester polymer or copolymer,
Usual resins such as vinyl acetate polymer or copolymer, cellulose ester or ether, polybutadiene, polyurethane, epoxy or phenoxy can be mentioned. If necessary, a film-forming resin such as polycarbonate, polyarylate, polyester, polystyrene, styrene-acrylonitrile copolymer, polysulfone, polymethacrylic acid esters, or styrene-methacrylic acid ester copolymer is used for the charge transport layer. Among these, the following structural formula Polycarbonate Z shown by means that the melting point and glass transition point are high, so that there are few characteristic fluctuations at around room temperature, that mechanical strength is high, and that the crystallinity of the molecule is low, so solution stability is high. preferable.

The method for producing the photoreceptor of the present invention will be described in more detail. First, in the charge generation layer, the above-mentioned pigment is dispersed in a solution of a binder resin. The dispersion method is carried out by a usual method using a ball mill, a roll mill, a sand mill, an attritor or the like. The mixing ratio of the pigment and the resin is 40: 1 to 1: 4, preferably 20:
It is about 1 to 1: 2.

If the blending amount of the pigment is too large, the stability of the coating composition is lowered, and if it is too small, the sensitivity is lowered. As the solvent for the resin, any solvent can be used as long as it has solubility, but a solvent having good pigment dispersibility is selected. You may mix and use two or more.

The charge transport layer is applied by dissolving the charge transport material and the resin for film formation in a solvent that dissolves both. The compounding ratio of the former and the latter is 5: 1 to 1: 5, preferably about 3: 1 to 1: 3. If the former is too large, the mechanical strength of the charge transport layer is lowered, and if it is too small, the sensitivity is lowered.

As the layer structure of the present invention, for example, as shown in FIG. 2 (a), the charge transport layer 6 is provided on the charge generation layer 5 on the substrate 7, or as shown in FIG. 2 (b). In some cases, the charge generation layer 5 is provided on the charge transport layer 6 on the substrate 7.

The charge generation layer has a thickness of 0.05 to 5 μm and the charge transport layer has a thickness of 5
It is about 5 μ.

On the other hand, a barrier layer may be provided between the photosensitive layer and the substrate.
The barrier layer is effective for preventing unnecessary charge injection from the substrate, and can enhance the chargeability of the photosensitive layer. Further, the adhesiveness between the photosensitive layer and the substrate can be improved. Materials for the barrier layer include polyvinyl alcohol, polyvinylpyrrolidone, polyvinylpyridine, cellulose ethers, cellulose esters, polyamide, polyurethane, casein, gelatin, polyglutamic acid, starch, starch acetate, amine starch, polyacrylic acid chloride, polyacrylamide, etc. Is mentioned. The resistivity of the material is preferably about 10 ⁵ to 10 ¹⁴ Ωcm.
The thickness of the barrier layer is about 0.05 to 2 μ.

Although the electrophotographic method of the present invention is effectively applied to an electrophotographic copying machine, it is also applicable to various printers (especially light emitting diode printers), microfilm readers, electrophotographic plate making systems, etc. to which the Xerographic technique is applied. Applicable.

〔Example〕

Example 1 First, preparation of a photoreceptor using brominated anthanthrone as a pigment for a photosensitive layer will be described.

4 g of a polyester resin (trade name: Adhesive 49000, manufactured by Dupont) was dissolved in 80 g of cyclohexanone, 16 g of brominated anthanthrone was mixed therein, and then dispersed by a sand grinder for 2 hours. To 60 g of the taken-out dispersion liquid, 40 g of methyl ethyl ketone was added to prepare a coating liquid,
Coating was performed on the surface of an aluminum pipe of 84φ × 338 mm with a ring color coating machine described in JP-A-53-22544. It was dried at 100 ° C. for 10 minutes to form a 0.4 μ thick charge generation layer.

Next, as a charge transport material, the following structural formula 10 g of the compound represented by and 11 g of polycarbonate Z resin (molecular weight 40,000 to 50,000) are dissolved in 45 g of monochlorobenzene and 45 g of methylene chloride to prepare a coating solution, which is applied onto the charge generation layer by a ring color coating machine. . After drying at 110 ° C. for 30 minutes, a 17 μ thick charge transport layer was formed.

Using the photoconductor thus prepared, an optical system as shown in FIG. 1, that is, a green light emitting diode array 1,
With the original 2 having black and red characters and the self-locking lens 3, the exposure amount of the photoconductor to the white part of the original is 8e.
It was used under the condition of rgs / cm ² .

When the photoconductor is charged to -800V, the electric potential of the white part is -180
The electric potentials of V and black were -780V, and the electric potential of red was -700V, and the two images were reproduced well even in the copied image.

Comparative Example 1 The same optical system as in Example 1 was used except that a gallium-arsenic-phosphorus (GaAHs _0.6 P _0.4 ) red light emitting diode array having an emission wavelength of about 650 nm was used instead of the green emitting diode. The amount of exposure and the expected charging potential of
An original copy test was conducted in the same manner as in. The white part has a potential of −480V, the black part has a potential of −780V, and the red part has a potential of −52V.
It was 0V, and the copy image was inferior because of a lot of fog.

Comparative Example 2 A photoconductor was produced in the same manner as in Example 1 except that the pigment of Example 1 (brominated anthoanthrone) was replaced by a perylene pigment which is also a red pigment, and the optical system and the exposure amount of the photoconductor were measured. The original charge potential was the same as in Example 1 and a copy test of the original was conducted. The potential of the white part is -250V, the potential of the black part is-
The potential of 780 V and the red portion was −600 V, and the reproducibility of the red portion in the copied image was inferior to the result of Example 1.

Example 2 The same photoreceptor as in Example 1 was used. A green light emitting diode array, which is provided with a density of six green light emitting diodes per 1 mm, is placed close to the photoconductor at a distance of 50 μm without a self-ox lens, and the light emitting points are modulated according to the image signal. Used for light emitting diode printer.
When the photoconductor is charged to -800V, a potential of -780V is obtained in the image part (the part where the light emitting diode is not emitting light) and -200V in the white part (issued part), and the printout image is of good quality. It was.

In addition, the light source that deteriorates the photoreceptor (wavelength 450 nm
Since the following light) is not contained at all, the characteristics of the photoconductor are stable, and the quality is not deteriorated even after printing 5,000 sheets.

Example 3 0.5 g of brominated anthanthrone was added to a solution consisting of 10 g of polycarbonate Z resin (same as in Example 1), 40 g of tetrahydrofuran, and 30 g of monochlorobenzene, and dispersed by a paint shaker. In addition, as a charge transport material,
The following formula 5g of the compound of the structure 3 g of the compound having the structure of was added. This solution was applied to the same aluminum pipe as in Example 1 and dried at 110 ° C. for 30 minutes to form a photosensitive layer having a thickness of 19 μm (a photosensitive layer having a red pigment dispersed in a charge transport layer).

The photoconductor thus prepared was charged to +800 V and subjected to a copy test in the same manner as in Examples 1 and 2, and similarly good copies could be obtained.

〔The invention's effect〕

The present invention provides an electrophotographic method in which an electrophotographic photoreceptor having a photosensitive layer containing a red pigment formed on a substrate is used, and exposure is performed using a green light emitting diode in a part or all of the exposure step. The red part of the original can be clearly reproduced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an optical system in an electrophotographic apparatus for carrying out the electrophotographic method of the present invention, and FIGS. 2 (a) and 2 (b) are sectional views of a function-separated photosensitive layer. Symbols in the figure: 1 ... Green light emitting diode array; 2 ... Original document; 3 ... Lens system; 4 ... Photoconductor; 5 ... Charge generation layer; 6 ... Charge transport layer; 7
…… Substrate; 8 …… Red pigment.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 21/08 (56) References JP-A-60-158468 (JP, A) JP-A-59- 109070 (JP, A) JP 56-31270 (JP, A) JP 54-116936 (JP, A) JP 56-91256 (JP, A) JP 60-97337 (JP, A) JP-A-57-70535 (JP, A) JP-A-57-67933 (JP, A) JP-A-55-126254 (JP, A) JP-A-55-17105 (JP, A)

Claims (3)

[Claims] 1. An electrophotographic method which uses a photoreceptor having a photosensitive layer formed on a substrate, and uses a green light source in at least the image exposure step of the image exposure step, the erase step, the charge removal step and the like of the photoreceptor. 2. An electrophotographic method, wherein the photoconductor uses brominated anthanthrone as a red pigment, and the green light source is a green light emitting diode. 2. The electrophotographic method according to claim 1, wherein an electrophotographic photosensitive member in which the photosensitive layer containing a brominated anthanthrone pigment is a charge generating layer is used. 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer containing the brominated anthanthrone pigment is a photosensitive layer in which brominated anthanthrone is dispersed in a charge transport layer. Electrophotographic method.