JPH0331260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor for laser printers.

[Prior art]

Up until now, electrophotographic printers that use line scanning with a laser beam have used gas lasers with relatively short wavelengths, such as helium-cadmium lasers, argon lasers, and helium-neon lasers. The body is a CdS-binder based photosensitive layer that forms a thick photosensitive layer, and a charge transfer complex (IBM).
Journal of the Research and Development,
(January 1971, P.75-P.89) was used, so the laser beam did not undergo multiple reflections within the photosensitive layer, and therefore, in practice, an image with interference fringes appeared during image formation. I was bored.

However, in recent years, semiconductor lasers have come to be used in place of the aforementioned gas lasers in order to design devices that are more compact and cost-effective. This semiconductor laser generally has an oscillation wavelength in the long wavelength region of 750 nm or more, and therefore an electrophotographic photoreceptor with high sensitivity characteristics in the long wavelength region is required. has been developed.

Previously known long wavelength light (e.g. 600nm)
Examples of the photoreceptor having photosensitivity to the above) include a laminated electrophotographic photoreceptor having a laminated structure of a charge generation layer and a charge transport layer containing a phthalocyanine pigment such as copper phthalocyanine or aluminum chloride phthalocyanine, or a selenium-tellurium film. An electrophotographic photoreceptor using .

When a photoreceptor sensitive to such long wavelength light is attached to a laser beam scanning type electrophotographic printer and exposed to laser beam light, an interference fringe pattern appears in the formed toner image, making it difficult to obtain a good image. It had the disadvantage that a reproduced image could not be formed. One of the reasons for this is that, for example, a long wavelength laser is not completely absorbed within the photosensitive layer, and its transmitted light is specularly reflected on the substrate surface, resulting in multiple reflections of the laser beam within the photosensitive layer. This is thought to be caused by interference between the light and the light reflected from the surface of the photosensitive layer.

Methods to overcome this drawback include roughening the surface of the conductive substrate conventionally used in electrophotographic photoreceptors by anodizing or sandblasting, or adding a light-absorbing layer between the photosensitive layer and the substrate. It has been proposed to eliminate multiple reflections that occur within the photosensitive layer by using an anti-reflection layer, but as a practical matter, it is not possible to completely eliminate the interference fringe pattern that appears during image formation. Nakatsuta. In particular, in the method of roughening the surface of a conductive substrate by sandblasting, it is difficult to form a rough surface with a uniform roughness sufficient to completely eliminate the interference fringe pattern that appears during image formation; In some cases, relatively large roughness areas may be formed. For this reason, this large roughness area acts as a carrier injection area into the photosensitive layer, causing white spots (or black spots when a reversal development method is used) during image formation. Nakatsuta. Furthermore, it is difficult to produce conductive substrates with uniform roughness within the same manufacturing lot, and there are many points that need to be improved. Further, methods using a light absorption layer or an antireflection layer have drawbacks such as not being able to sufficiently eliminate interference fringes and increasing manufacturing costs.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor and a method for manufacturing the same, which eliminates the drawbacks of the prior art described above.

Another object of the present invention is to provide an electrophotographic photoreceptor for laser printers that prevents the occurrence of density unevenness in the form of interference fringes, and a method for manufacturing the same.

The above purpose is achieved by the following improvement: A mixture obtained by mixing two mutually incompatible resin liquids is applied onto a conductive support to form a microphase-separated coating film. One of the seed resins is dissolved and removed, and the remaining resin is used to form a subbing layer on the light diffusing and reflecting surface having an average surface roughness equal to or more than a half wavelength of the light source for image exposure, and a photosensitive layer is formed on top of the subbing layer. This is achieved by an electrophotographic photoreceptor having the following characteristics.

That is, by setting the average surface roughness of the undercoat layer to λ/2 or more, specifically, 0.5 μm or more,
It is effective to provide a phase difference to the incident light, which also prevents the occurrence of interference fringes in electrophotography after image exposure and development, and eliminates all of the drawbacks of the prior art described above.

The "average surface roughness" described in this specification refers to a value measured using a universal surface profile measuring instrument "SE-3C" manufactured by Kosaka Institute.

[Embodiment]

FIG. 1 and FIG. 2 schematically represent a state in which an electrophotographic photoreceptor is irradiated with a laser beam as interference light. FIG. 1 shows an example using a conventional electrophotographic photoreceptor, and FIG. 2 shows an example using the electrophotographic photoreceptor of the present invention.

In FIG. 1, when the photosensitive layer 3 of the electrophotographic photoreceptor is irradiated with a laser beam I ₁ , reflected light R ₁ is generated on the surface of the photosensitive layer 3 , and the laser beam I ₁ is a laser beam that passes through the inside of the photosensitive layer 3 . The beam I ₂ reaches the surface of the conductive support 1 and produces reflected light R ₂ here. At this time, interference occurred between R ₁ and R ₂ , and moreover, the reflected light R ₂ caused multiple reflections inside the photosensitive layer 3, so that an interference fringe pattern appeared during image formation.

In contrast, in the embodiment of the present invention shown in FIG. 2, an undercoat layer 2 is formed between the conductive support 1 and the photosensitive layer 3, but the surface of the undercoat layer 2 is roughened. A rough surface 4 is formed by processing. That is, the light ray I ₁ incident upon image exposure produces reflected light R ₁ on the surface of the photosensitive layer 3 , while it becomes transmitted light I ₂ inside the photosensitive layer 3 and diffusely reflected light R on the surface of the rough surface 4 . ₃
occurs. This diffusely reflected light R ₃ includes transmitted light I ₂ that further passes through the undercoat layer 2 and is reflected on the surface of the conductive support 1, and the reflected light again includes diffused light generated on the rough surface 4. It is. This diffuse reflected light R ₃ is
50% or more, preferably 60% relative to the intensity of the incident light I ₁
% or more, to suppress interference between reflected light R ₂ and diffuse reflected light R ₃ to such an extent that interference fringe patterns that appear during image formation can be eliminated. Can be done.

50% or more relative to the intensity of the incident light I ₁ , preferably
In order to produce diffusely reflected light R ₃ with an intensity of 60% or more, the rough surface 4 of the undercoat layer 2 should have an average surface roughness of λ/2 (λ: wavelength of the incident light I ₁ ) or more. Sade
It is necessary to set the surface roughness to 0.5 μm or more, preferably in the range of 0.6 μm to 30 μm.

The ratio of the intensity of the diffusely reflected light R ₃ to the incident light I ₁ is
If it is less than 50%, interference fringes that appear during image formation cannot be sufficiently eliminated.

Also, if the average surface roughness of the rough surface 4 is over 30 μm,
Particularly during image formation after repeated use, white spots or black spots tend to appear, resulting in the problem that it becomes difficult to obtain high-quality copy images.

In a preferred embodiment of the present invention, the rough surface 4 formed on the undercoat layer 2 preferably utilizes the so-called micro phase separation phenomenon, and specifically, the rough surface 4 formed on the undercoat layer 2 preferably utilizes the so-called micro phase separation phenomenon. By mixing two resin liquids, coating them on a conductive support, drying them, and dissolving them with a solvent that selectively dissolves one of the resins, a desired size and density can be formed on the conductive support. Undercoat layer 12 having surface irregularities
can be layered. According to this method, the size of the unevenness constituting the rough surface 16, the thickness of the coating film, and the density can be controlled by the mixing ratio of the two types of resin liquids, and it is also advantageous in terms of cost. .

The combination of resins constituting the undercoat layer 2 having a rough surface 4 requires (1) low compatibility; (2) Good adhesion of the remaining resin to the conductive support. (3) Photosensitive layer 1
5. The remaining resin should have good solvent resistance against the solvent in the upper coating layer. (4) The electrical resistance of the remaining resin is approximately 10 ¹³ Ω·cm or less in terms of volume resistivity.

Specific resin combinations that satisfy the above conditions include a combination of phenolic resin and polyamide resin, and a combination of epoxy resin and cellulose resin. Although it varies depending on the density, the ratio of the resin to be dissolved and removed relative to the remaining resin is preferably about 5% to 30%, and the film thickness is suitably about 0.3 μm to 10 μm.

The undercoat layer 2 having a light-diffusing and reflective rough surface 4 is made of a phenolic resin, a polyamide resin, an epoxy resin, a cellulose resin, etc. having a volume resistance of 10 ¹³ Ω·cm or less in order to maintain electrical conductivity with the substrate. The layer is formed by the formation method described above. That is, for example, when a phenolic resin and a polyamide resin are dissolved in an alcoholic solvent and mixed, a resin liquid in which the polyamide resin liquid is dispersed as droplets with a diameter of about 1 to 3 μm in the phenolic resin solution is obtained, and this resin liquid is made conductive. When it is coated on the support 1, dried and cured, and then immersed in a hot alcoholic solvent, only the polyamide resin is dissolved and removed, leaving a cured phenolic resin coated on the conductive support 1 with irregularities of approximately 1 μm. A membrane is obtained. In this way, the surface 4 of the undercoat layer 2 is made to have a surface roughness of λ/2 or more of the laser.

Further, in the present invention, another subbing layer (not shown) may be provided between the subbing layer 2 and the photosensitive layer 3, such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide ( nylon 6, nylon 66, nylon 610,
It can be formed from copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, etc. The appropriate thickness of this layer is 0.1 μm to 5 μm, preferably 0.5 μm to 3 μm.

In a preferred embodiment of the present invention, the photosensitive layer 3 may have a laminated structure consisting of a charge generation layer and a charge transport layer.

The charge generation layer in the present invention includes azo pigments such as Sudan Red, Diane Blue, and Jenas Green B, Algol Yellow, Pyrenequinone,
Indanthrene Brilliant Violet RRP
Quinone pigments such as quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, bisbenzimidazole pigments such as India First Orange Toner, phthalocyanine pigments such as copper phthalocyanine and aluminol-phthalocyanine, quinacridone pigments and -165263, is dispersed in a binder resin such as polyester, polystyrene, polyvinyl butyral, polyvinylpyrrolidone, methylcellulose, polyacrylic acid esters, or cellulose ester. Ru. Its thickness is 0.01~1μm, preferably 0.05~
It is about 0.5μm.

In addition, the charge transport layer may contain polycyclic aromatic compounds such as anthracene, pyrene, phenanthrene, coronene, indole, carbazole, etc. in the main chain or side chain.
Oxazole, isoxazole, thiazole,
imidazole, pyrazole, oxadiazole,
It is formed by dissolving a hole-transporting substance such as a compound having a nitrogen-containing cyclic compound such as pyrazoline, thiadiazole, or triazole, or a hydrazone compound in a resin that has film-forming properties. This is because the charge transporting substance generally has a low molecular weight and has poor film-forming properties by itself. Examples of such resins include polycarbonates, polymethacrylates, polyarylates, polystyrene, polyesters, polysulfones, styrene-acrylonitrile copolymers, styrene-methyl methacrylate copolymers, and the like.

The thickness of the charge transport layer is 5 to 20 μm. Further, the photosensitive layer 3 may have a structure in which the charge generation layer described above is laminated on a charge transport layer.

Further, the photosensitive layer 3 is not limited to the type described above, and for example, the photosensitive layer 3 described above is
Research and Development, January 1971,
Charge transfer complex consisting of polyvinylcarbazole and trinitrofluorenone disclosed on P.75 to P.89, U.S. Patent No. 4315983, U.S. Patent No.
A photosensitive layer using a pyrylium compound described in Publication No. 4327169, or a photosensitive layer containing well-known inorganic photoconductive substances such as zinc oxide or cadmium sulfide dispersed in a resin, selenium, selenium-tellurium, etc. It is also possible to use vapor deposited films such as.

As the conductive support 11, aluminum,
Metals such as copper and stainless steel, or plastics coated with metals are suitable.

The electrophotographic photoreceptor of the present invention can be used in an electrophotographic printer using a semiconductor laser with a relatively long wavelength (for example, 750 nm or more).
It is also suitable for electrophotographic printers using other laser beams, such as helium-neon lasers, helium-cadmium lasers, and argon lasers. The present invention can completely eliminate the interference fringe pattern that appears in image formation when coherent light such as a laser beam is used as a light source, and also can eliminate black spots ( It has the advantage of being able to effectively eliminate black spots.

That is, in general, an electrophotographic printer using a laser beam charges an electrophotographic photoreceptor and then applies a positive image-like scan exposure (image scan exposure) to the laser beam according to an image signal to form an electrostatic latent image on a back image. is formed, and then a developer containing toner of the same polarity as that of this electrostatic latent image is applied to the surface of the electrostatic latent image, thereby depositing toner on the image-scanned positive image-like exposed area. Although the method is adopted,
In the case of this reversal development method, unnecessary toner adhesion in the form of black spots occurred in the formed image. This is because, as mentioned above, on a rough surface formed by sandblasting, the distribution between small and large protrusions is large, and a uniform rough surface is not formed. Carriers are injected into the charge generation layer from the large protrusions, and during charging, the carriers injected from the protrusions are electrostatically neutralized with the charged charges, and the image is already exposed electrically, and when the toner is developed, the toner is causing the adhesion of
This is the cause of the formation of black spots.

On the other hand, in the electrophotographic photoreceptor of the present invention, as described above, the undercoat layer having the rough surface has no carrier injection portion, and no black spots appear even if the above-mentioned reflective development method is adopted. . This point will be explained in detail in the examples below. Of course, the present invention is not limited to the above-mentioned reversal development method, and various development methods such as a cascade development method, a magnetic brush development method, a powder cloud development method, a jumping development method, and a liquid development method can also be employed.

Hereinafter, the present invention will be explained according to examples.

Example 1 Phenol resin methanol solution (solid content 60%:
100 parts by weight of a copolymerized polyamide resin methanol solution (solid content 10%: Amilan CM-8000 manufactured by Toray Industries, Inc.), p-toluenesulfonic acid methanol solution (solid Add 12 parts by weight (50%) and mix thoroughly.
Stirred. Then, apply this mixture onto a 60φ x 258mm aluminum cylinder using the dipping method.
It was dried and cured at 100°C for 20 minutes to form a coating film with a thickness of 5μ. When this cylinder is immersed in methanol heated to 50℃ for 5 minutes, the polyamide component in the coating is dissolved and removed, leaving only the phenolic resin coated surface with irregularities with an average surface roughness of about 1 μm on the cylinder. , an undercoat layer was formed. When the reflection characteristics of this cylinder were measured, the total light diffuse reflectance was 66%. At this time, the average surface roughness is measured using a versatile surface profile measuring instrument "SE-" manufactured by Kosaka Laboratory.
3C", and the ratio of the intensity of total diffuse reflected light to the intensity of incident light (total diffuse reflectance) was measured using "Uvidec-505" manufactured by JASCO Corporation.

Next, low-fat casein (from New Zealand)
An aqueous solution was also applied by dip coating to provide a 1 μm thick casein resin layer.

Next, ε-type copper phthalocyanine (manufactured by Toyo Ink Co., Ltd.)
100 parts by weight, butyral resin (manufactured by Sekisui Chemical Co., Ltd.) 50
Part by weight and 1350 parts by weight of cyclohexanone in 1φ
Dispersion was carried out for 20 hours using a sand mill device using glass beads. 2,700 parts by weight of methyl ethyl ketone was added to this dispersion, and the mixture was applied onto the polyamide resin layer by dip coating and dried by heating at 50° C. for 10 minutes to form a charge generation layer with a coating weight of 0.15 g/m ² .

Next, add 10 parts of a hydrazone compound having the following structural formula. and 15 parts of a styrene-methyl methacrylate copolymer resin (trade name: MS200; manufactured by Steel Chemical Co., Ltd.) were dissolved in 80 parts of toluene. This solution was coated on the charge generation layer and dried with hot air at 100℃ for 1 hour to form a layer of 16 μm.
A thick charge transport layer was formed.

An electrophotographic printer using a reversal development method using the electrophotographic photoreceptor produced in this manner and equipped with a semiconductor laser with an oscillation wavelength of 778 nm [Product name: Canon Laser Beam Printer LBP-CX (manufactured by Canon Inc.)]
After the toner was loaded, a line scan was performed on the entire surface to form an image in which the entire surface was a black toner image, and no interference fringe pattern appeared in this all-black image.

Next, the laser beam was line-scanned according to the character signal to form characters as an image.The operation was repeated 2000 times at a temperature of 15°C and a relative humidity of 10%, and the 2000th copy character image was extracted. . When the number of black spots (black spots) with a diameter of 0.2 mm or more in this copied character image was measured, no black spots were found at all.

Comparative Example 1 As a comparative experiment, an electrophotographic photoreceptor was created in exactly the same manner as in Example 1 above, except that the use of the phenol resin layer used when creating the electrophotographic photoreceptor in Example 1 was omitted. did.

When this comparative electrophotographic photoreceptor was attached to the laser beam printer used in Example 1 and the same measurements were performed, clear interference fringes were formed in the entire black image.

Comparative Example 2 The surface of an aluminum cylinder similar to that used in Example 1 was roughened by sandblasting. Next, the phenol resin layer used in Example 1 was omitted and a 1 μm thick casein layer was directly provided on the surface of this roughened aluminum cylinder. This surface was measured using the Kosaka Institute's universal surface profile measuring instrument (SE).
-3C), the average surface roughness at this time
It was about 2 μm. Next, when the total light diffuse reflectance with respect to the intensity of incident light was measured using "Uvidec-505" manufactured by JASCO Corporation, it was 46%.

A comparative electrophotographic photoreceptor having a photosensitive layer similar to that of Example 1 on top of this casein layer was attached to the laser beam printer used in Example 1, and similar measurements were performed. Clear interference fringes were formed.

Comparative Example 3 An aluminum cylinder similar to that used in Example 1 was prepared, and its surface was
Sandblasted to a thickness of 32 μm, and omitted the phenol resin layer used in Example 1,
A 1 μm casein layer was directly applied. The total light diffuse reflectance of this surface for incident light was measured in the same manner as in Example 1, and was found to be 68%.

A comparative electrophotographic photoreceptor having a photosensitive layer similar to that in Example 1 on top of this casein layer was attached to the laser beam printer used in Example 1, and similar measurements were performed. Although no interference fringes were observed, approximately 30 black spots with a diameter of 0.2 mm or more were formed per 10 cm ² in the 2000th copied character image, making the image extremely difficult to see.

Example 2 Fine particle zinc oxide [Product name: Sazex2000 (Sakai Chemical Co., Ltd.)
Co., Ltd.) 10g, acrylic resin [Product name: Dianal LR009 (Mitsubishi Rayon Co., Ltd.)] 4g, toluene
A coating solution for a photosensitive layer was prepared by sufficiently mixing 10 g of the azulenium compound and 10 mg of an azulenium compound having the following structural formula in a ball mill.

Azulenium compound (described in Japanese Patent Application No. 165263/1983) This photosensitive layer coating solution was provided in place of the photosensitive layer having a laminated structure consisting of a charge generation layer and a charge transport layer used in Example 1 so that the film thickness after drying was 21 μm. An electrophotographic photoreceptor was prepared in a similar manner.

When this electronic photoreceptor was attached to the laser beam printer used in Example 1 (however, the charger and toner were changed so that the charge was of positive polarity) and similar measurements were performed, the entire surface became black. There were no interference fringes in the image, and no black spots with a diameter of 0.2 mm or more were found in the 2000th copy of the text, indicating that it was an extremely good image.

Example 3 Of the mixed solution of the phenolic resin methanol solution and the copolyamide resin methanol solution used in Example 1, the phenolic resin methanol solution was 50 parts by weight, and the copolymer polyamide resin methanol solution was
A phenol resin layer was formed in the same manner as in Example 1, except that the amount was 150 parts by weight.

The average surface roughness of this surface was measured in the same manner as in Example 1 and was found to be 8 μm. Furthermore, when the total light diffuse reflectance of incident light was measured in the same manner as in Example 1, it was 78%.

Furthermore, an electrophotographic photoreceptor was prepared by providing a casein layer and a photosensitive layer similar to those in Example 1 on the phenolic resin layer described above, and measurements were made in the same manner as in Example 1. No interference fringe pattern appeared in the image. Also, 2000
When the second character image was taken out and observed for the presence or absence of black spots, it was found that there were no black spots at all in the character image.

〔Effect of the invention〕

According to the electrophotographic photoreceptor of the present invention, clear electrophotographs can be obtained without causing density unevenness in the form of interference fringes after image exposure and development. Such an effect is particularly remarkable when coherent light, especially a laser, is used as a light source for image exposure, and it is extremely advantageously applied as an electrophotographic photoreceptor for laser printers.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional electrophotographic photoreceptor. FIG. 2 is an explanatory diagram showing the optical path of light incident on the electrophotographic photoreceptor of the present invention. DESCRIPTION OF SYMBOLS 1... Conductive support, 2... Subbing layer, 3... Photosensitive layer, 4... Rough surface.

Claims (1)

[Scope of Claims] 1. A mixture obtained by mixing two mutually incompatible resin liquids is applied onto a conductive support to form a microphase-separated coating film. One of the seed resins is dissolved and removed, and the remaining resin is used to
1. An electrophotographic photoreceptor comprising a light-diffusing and reflective surface undercoating layer having an average surface roughness equal to or more than a half wavelength of a light source for image exposure, and having a photosensitive layer thereon. 2. The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer causes light diffuse reflection at an intensity of 50% or more of the intensity of the light source from the image exposure light source. 3. The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer causes light diffuse reflection at an intensity of 65% or more of the intensity of the light beam from the image exposure light source. 4. The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer has an average surface roughness of 0.5 μm or more.