JPH02115858A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain potential characteristics stable against changes of environment, such as temperature and humidity, by providing an interlayer containing a polymer of a polyether polyol compound and an isocyanate compound in a specified isocyanate to hydroxyl molar ratio in the starting composition of the polymer. CONSTITUTION:A photosensitive layer is laminated on the interlayer 2 formed on a conductive substrate 1, and the photosensitive layer may be a laminated structure functionally separated into a charge generating layer 3 and a charge transfer layer 4 or a single layer 5 having both functions. The interlayer 2 contains the polymer obtained by condensing the polyether polyol compound with the isocyanate compound in an isocyanate/hydroxyl (NCO/OH) molar ratio of 1.0-2.0, thus permitting deterioration of potential in the dark due to deterioration of barrier function under high temperature and high humidity, rise of potential in the light due to increase of resistance under low temperature and low humidity, and the like to be prevented, and stability against environmental conditions to be enhanced.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and more specifically, an electrophotographic photoreceptor in which an intermediate layer having functions as an adhesive layer and a barrier layer is provided on a conductive support. Regarding the body.

[Conventional technology]

Generally, Carlson type electrophotographic photoreceptors are charged with
In order to form images with constant image density and no background smearing when exposure is repeated, the stability of the dark area potential and the bright area potential is important.

For this reason, it functions as a barrier layer between the photosensitive layer and the conductive support, and provides adhesion between the photosensitive layer and the conductive support to cover defects, dirt, deposits, scratches, etc. on the surface of the support. It is known to provide an intermediate layer that functions as a layer.

Such an intermediate layer is made of polyamide (Japanese Patent Application Laid-open No.
47344, JP-A-52-25638), polyester (described in JP-A-52-20836, JP-A-54-26738), polyurethane (described in JP-A-53-89435), Casein (described in JP-A-55-103556), polypeptide (described in JP-A-53-48532), polyvinyl alcohol (described in JP-A-52-100240), polyvinylpyrrolidone (described in JP-A-48-30936) (stated in the publication),
Vinyl acetate-ethylene copolymer (JP-A-48-2614
1), maleic anhydride ester polymer (described in JP-A-52-10138), ethyl cellulose (
JP-A-55-143564), polyvinyl butyral (JP-A-57-90639, JP-A-58)
-106549), quaternary ammonium salt-containing polymers (JP-A-51-126149, JP-A-56
It is known to use resins such as (described in Japanese Patent No. 60448).

However, in photoreceptors using these materials as intermediate layers, the potential tends to change due to the influence of temperature and humidity environments, and the barrier function deteriorates under high temperature and humidity, and the dark area potential decreases due to carrier injection from the support side, making it difficult to copy. There was a drawback that the image density was low.

Further, when such a photoreceptor is used in an electrophotographic printer that performs reversal development, there is a problem in that images are fogged under high temperature and high humidity conditions.

In particular, in a laminated electrophotographic photoreceptor in which the photosensitive layer is a charge generation layer and a charge transport layer laminated in sequence, the charge generation layer containing a high concentration of charge generation substance is located in contact with the intermediate layer, so carriers from the support side are Potential drop due to increased injection is more likely to occur (fogging was more likely to occur in printers using reversal development method even if the barrier function of the intermediate layer was slightly reduced).

Furthermore, when photoreceptors using conventional materials for the intermediate layer are used repeatedly, the potential in the bright area tends to increase and the potential in the dark area tends to fluctuate. Due to the residual charge, the bright area potential increases significantly, and it has the disadvantage that copies with a constant image quality cannot be obtained when used continuously.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an electrophotographic photoreceptor that can provide a stable dark potential against changes in temperature and humidity environments.

Another object of the present invention is to provide an electrophotographic photoreceptor that suppresses increases in bright area potential and fluctuations in dark area potential even after repeated use.

[Means for solving problems]

That is, the present invention provides an electrophotographic photoreceptor having a photosensitive layer on a conductive support via an intermediate layer, wherein the intermediate layer contains a polymer of a polyether polyol compound and an isocyanate compound, and The molar ratio of isocyanate group to hydroxyl group is 1.0 ≦NCO group/OH group ≦2
．． This is an electrophotographic photoreceptor characterized in that:

The present invention will be explained in detail below.

Regarding the appropriate molar ratio of isocyanate groups (CNCO groups) and hydroxyl groups (OH groups) in raw materials when producing polyurethane, which is a polymer of a polyol compound and an isocyanate compound, it is disclosed in JP-A-53-89435. , 0.5≦NCO group/OH group<1.0.

Initially, we thought that this value would hold for all polyol compounds. However, as we continued to study various polyol compounds, we found that when the polyol compound is a polyether polyol compound, the appropriate molar ratio is 1.0 ≦NCO group/OH group ≦, contrary to the content disclosed in the above publication. It was found that it is 260.

With a molar ratio within this range, there is no decrease in dark area potential due to a decrease in barrier function under high temperature and high humidity conditions, and there is no increase in light area potential due to increased resistance under low temperature and low humidity conditions (thereby, the product has excellent environmental stability).

If this molar ratio is lower than 1.0, the sensitivity of the photoreceptor deteriorates, and at the same time, the barrier properties of the intermediate layer decrease under high temperature and high humidity conditions, resulting in a decrease in dark area potential. Moreover, the solvent resistance and hardness of the coating film are also reduced. On the other hand, if the molar ratio is greater than 2.0, the adhesion of the coating film will decrease.

Therefore, the range of molar ratios disclosed in the above publication seems to be limited only to cases where the polyol compound is a polyester polyol compound, judging from the examples in the specification.

Polyether polyol compounds used as raw materials for the intermediate layer of the present invention include poly(oxypropylene) glycol, poly(oxypropylene) poly(oxyethylene) glycol, poly(oxybutylene) glycol, poly(oxytetramethylene) Poly(oxyalkylene) glycols such as glycol, poly(oxyalkylene) triols such as poly(oxypropyne) triol, poly(oxypropyne) poly(oxyethylene) triol, poly(oxybutylene) triol, ethylene diamine, pentaerythritol, sorbitol,
Examples include poly(oxyalkylene) polyols such as poly(oxypropylene) polyols and poly(oxypropylene) poly(oxyethylene) polyols using sucrose, starch, etc. as initiators.

The isocyanate compound used as a raw material for the intermediate layer is tolylene diisocyanate.

Aromatic isocyanate compounds such as metaxylylene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenylisocyanate, hydrogenated products of the above isocyanates, aliphatic isocyanate compounds such as hexamethylene diisocyanate, and the isocyanate groups of these isocyanate compounds are converted to phenol and ketoxime.

Aromatic secondary amines, tertiary alcohols, amides.

Examples include blocked isocyanate compounds blocked with lactams, heterocyclic compounds, sulfites, and the like.

In addition, naphthenic acid salts such as magnesium naphthenate and cobalt naphthenate, and dibutyltin dilaurate are used as catalysts to promote the production of polymers.

Dimethyltin dilaurate, tin compounds such as stannous chloride, triethylenediamine, N-methylmorpholine,
Amine compounds such as N, N, N', N'-tetramethylpolymethylene diamine, etc. may be added. The amount of catalyst added is 0.05 to 5% by weight based on the polymer.

The intermediate layer of the present invention may be formed by dissolving a polymer of a polyol compound and an isocyanate compound in a suitable solvent, coating and drying the mixture, or by forming a mixture of an unreacted polyol compound and an isocyanate compound or a partially reacted mixture of a polyol compound and an isocyanate compound. It may also be formed by diluting a prepolymer of a polyol compound and an isocyanate compound with a suitable solvent, coating it, and then reaction-curing it.

Further, the intermediate layer can be applied by methods such as dip coating, spray coating, and roll coating. The film thickness is preferably 0.11 μm to 10 μm, particularly 0.5 μm to 5 μm.

FIG. 1 shows the layer structure of the electrophotographic photoreceptor of the present invention.

In the present invention, the photosensitive layer may be of a laminated structure type in which the charge generation layer 3 and charge transport layer 4 are functionally separated, or may be a single layer 5 containing a charge generation substance and a charge transport substance in the same layer.

The charge generation layer 3 is made of azo pigments such as Sudan Red and Diane Plugienus Green B, algol yellow, quinone pigments such as pyrenequinone and indanthrene brilliant violet RRP, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, and indigo pigments such as indigo and thioindigo. Charge generating substances such as bisbenzimidazole pigments such as orange toner, phthalocyanine pigments such as copper phthalocyanine, and quinacridone pigments are combined with charge generating substances such as polyvinyl butyral, polystyrene, polyvinyl chloride, polyvinyl acetate, acrylic resin, polyvinylpyrrolidone, methyl cellulose, hydroxypropyl methyl cellulose, etc. The dispersion liquid is dispersed in a binder resin, and the dispersion liquid is added to the intermediate layer 2 of the present invention.
It can be formed by coating on top of. The thickness of such a charge generation layer is 5 μm or less, preferably 0.01 μm.
m to 2 μm is appropriate.

The charge transport layer 4 provided on the charge generation layer 3 has a main chain or a side chain containing a polycyclic aromatic compound such as anthracene, pyrene, phenanthrene, coronene, or indole, carbazole, oxazole, isoxazole, thiazole,
It is formed using a coating liquid in which charge transport substances such as nitrogen-containing cyclic compounds such as imidazole, pyrazole, oxadiazole, pyrazoline, thiadiazole, and triazole, hydrazone compounds, and styryl compounds are dissolved in a resin that has film-forming properties. Ru. This is because the charge transport material generally has a low molecular weight and has poor film-forming properties by itself.

Such resins include polyester, polysulfone,
Examples include polycarbonate, polymethacrylates, polystyrene, and the like.

The thickness of the charge transport layer 4 is 5 μm to 40 μm, preferably 1
It is 0 μm to 25 μm.

Further, the charge generation layer 3 may be laminated on the charge transport layer 4.

Furthermore, in addition to the above-mentioned photosensitive layers used in the present invention, organic photoconductive polymer layers such as poly-N-vinylcarbazole and polyvinylanthracene, selenium vapor-deposited layers,
Examples include a selenium-tellurium vapor deposited layer and an amorphous silicon layer.

The conductive support l used in the present invention may be any material as long as it has conductivity, and may be formed of metal such as aluminum, copper, molybdenum, chromium, nickel, or brass into a drum or sheet shape. metal foil such as aluminum or copper laminated to a plastic film, aluminum, indium oxide, tin oxide, etc. deposited on a plastic film, or a conductive layer coated with a conductive substance together with a suitable binder resin. Examples include the aforementioned metals, plastic films, and paper.

The conductive substances used in this conductive layer include metal powders such as aluminum, nickel, copper, and silver, metal foils and short metal fibers, conductive metal oxides such as antimony oxide, tin oxide, and indium oxide, polypyrrole, Examples include polymer conductive materials such as polyaniline and polymer electrolytes, carbon fiber, carbon black, graphite powder, organic and inorganic electrolytes, and powders whose surfaces are coated with these conductive substances.

In addition, examples of the binder resin for the conductive layer include polyvinyl alcohol, polyvinyl alkyl ether, poly-N-vinylimidazole, alkyl cellulose, nitrocellulose, polyacrylic ester, casein, gelatin, polyester, polyamide, polyethylene oxide, polypropylene oxide, Amino acid ester, polyvinyl acetate, polycarbonate, polyvinylpyrrolidone, chloroprene rubber, nitrile rubber, polymethacrylate ester, polypeptide, polymaleic anhydride, polyacrylamide, polyvinyl formal, polyvinylpyridine, polyethylene gelcol, polypropylene gelcol, polyvinyl Examples include thermoplastic resins such as butyral, chlorosulfonated polyethylene, and thermoplastic polyurethane, and thermosetting resins such as thermosetting polyurethane, phenol resin, and epoxy resin.

The mixing ratio of the conductive material and the binder resin is 5:1~! =
It is about 5. This ratio is determined by considering the resistance, surface properties, coating suitability, etc. of the conductive layer.

When the conductive substance is a powder, a mixture is prepared by a conventional method using a ball mill, roll mill, sand mill, attritor, or the like.

In addition, other additives include surfactants, silane coupling agents, titanate coupling agents, silicone oil,
A silicone lebbing agent or the like may also be added.

The conductive layer is applied by dip coating, spray coating, roll coating, etc., and the film thickness is approximately 0.5 μm to 30 μm, which is determined by taking into account the degree of defects and scratches on the support and the electrophotographic characteristics. It will be done.

The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers, CRT printers,
It can be used in electrophotographic plate making systems, etc.

The present invention will be explained in more detail with reference to specific examples below.

Examples 1 to 5 and Comparative Examples 1 to 4 50 parts of titanium oxide powder coated with tin oxide containing lO% antimony oxide, 25 parts of resol type phenolic resin, 20 parts of methyl cellosolve, 5 parts of methanol, silicone oil (dimethyl Polysiloxane polyoxyalkylene copolymer, average molecular ffi: 3500) 0.002
The mixture was dispersed for 1 hour in a sand mill using 1φ glass beads to prepare a coating material for a conductive layer.

The above paint was applied by dip coating onto an aluminum cylinder measuring 30 mmφ x 260 mm, and dried at 140° C. for 30 minutes to form a conductive layer with a thickness of 20 μm.

Next, poly(oxypropylene) triol (hydroxyl value:
115 mgKOH/g) and 0.02 part of dibutyltin dilauret were dissolved in 80 parts of methyl ethyl ketone. To this, a ketoxime block of hexamethylene diisocyanate (effective NCO: 11.6% by weight) 2.6 to 8
．． By adding 9 parts, the molar ratio of NCO group/OH group was 0.7.
0.9. 1.0. 1.2. 1.5. 1.8°2.0. Intermediate layer paints were prepared so that the values were 2.2 and 2.4. Each of these solutions was applied onto the conductive layer by dip coating, dried and cured at 180°C for 40 minutes, and the film thickness was 1.0.
An intermediate layer of .mu.m was formed.

Next, 60 parts of xanone with the following structural formula was dispersed for 5 hours in a sand mill using 0.5φ glass beads, and then 12 parts of methyl ethyl ketone was dispersed.
A dispersion liquid was prepared by adding 0 part of the dispersion liquid and dried at 80° C. for 20 minutes to form a charge generation layer with a coating weight of 0.15 g/rrr.

Next, 10 parts of trisazo pigment of the following structural formula, polymethyl methacrylate (
average molecular weight = 11000), and 8 parts of styryl compound to cyclo and polycarbonate (average molecular weight fi
: 8000) 10 parts and 40 parts of dichloromethane.

Monochlorobenzene was dissolved in a mixed liquid medium of 20 parts, and this solution was dip-coated onto the charge generation layer, and then heated at 120°C for 50 minutes.
It was dried for a minute to form a charge transport layer with a thickness of 20 μm.

Regarding the photoconductor produced as described above, the NCO group/OH group molar ratio in the intermediate layer raw material was 1.0. 1.2゜1.
5. 1.8 and 2.0 respectively in Examples 1゜2, 3. 4 and 5. Also, the molar ratio is 0.7
Those of 0.9, 2.2 and 2.4 were designated as Comparative Examples 1, 2.3 and 4, respectively.

These photoconductors are printed on a Canon Laser Printer LB.
Attach it to P-3X and store it at room temperature and humidity (22°C, 155%).
RH) and high temperature and high humidity (32° C., 985% RH). Evaluation of electrophotographic properties and image evaluation were performed. These results are shown in Table 1.

The molar ratio in the intermediate layer raw material is 1.0≦NCO group/OH group≦2
．． In the case of 0, the sensitivity is good, and the difference between the dark potential (Vd) and the bright potential (Vjl) is large (sufficient potential contrast is obtained, and the dark potential (Vd) is stable even under high temperature and high humidity.
The image quality was stable and good images without black spots or fog were obtained.

On the other hand, when the molar ratio of NCO group/OH group is less than 1.0, the sensitivity of the obtained photoreceptor deteriorates and the bright area potential (vg is high (sufficient potential contra).

In addition, under high temperature and high humidity conditions, the dark area potential (Vd) decreased significantly, causing fog in the image.

In addition, when the molar ratio of NCO group/OH group exceeds 2.0, the adhesion of the intermediate layer was poor, and the coating film was easily peeled off using cellophane tape or the like.

Example 6 Poly(oxypropylene) triol (hydroxyl value 170
mgKOH/g) 10 parts, tolylene diisocyanate 3
and 0.15 parts of triethylenediamine were dissolved in 100 parts of methyl ethyl ketone to prepare an intermediate layer paint (NCO group/
OH group molar ratio: 1.14) was prepared.

The above paint for the intermediate layer was applied by dip coating onto an aluminum silcedar having a diameter of 30 mm and a diameter of 260 mm as a conductive support, and dried at 120° C. for 30 minutes to form an intermediate layer having a thickness of 0.6 μm.

Next, 10 parts of a disazo pigment having the following structural formula, 6 parts of cellulose acetate butyrate resin (average molecular fi 24000) and 6 parts of cyclohexanone were added.
0 parts was dispersed for 5 hours using a sand mill device using lφ glass beads.

100 parts of methyl ethyl ketone was added to this dispersion, which was applied onto the intermediate layer by dip coating, and dried by heating at 100° C. for 10 minutes to form a charge generation layer with a coating weight of 0.15 g/rrr.

Next, 10 parts of a hydrazone compound having the following structural formula and 15 parts of styrene-methyl methacrylate copolymer (styrene/methyl methacrylate = 8/2, average molecular weight 35,000) were added to 8 parts of toluene.
Dissolved in 0 parts. This liquid was dip-coated onto the charge generation layer and dried with hot air at 100° C. for 1 hour to form a charge transport layer with a thickness of 18 μm.

The electrophotographic photoreceptor produced in this way was used in a small copying machine (FC-
5. Attach it to the Canon product and store it at room temperature and humidity (21℃,
60% RH) and high temperature and high humidity (33°C, 185% RH)
), the electrophotographic properties were evaluated, and good images were obtained with no fluctuation in dark area potential even under high temperature and high humidity conditions.The results are shown in Table 2.

Comparative Example 5 Poly(ethylene adipate) triol (hydroxyl value: 19), which is a polyester triol, was used as a paint for the intermediate layer.
Paint (NCO group/
A photoreceptor was produced in the same manner as in Example 6 except that OH group molar ratio: 1.14) was used. The evaluation results are shown in Table 2.

Under high temperature and high humidity conditions, the dark area potential decreased due to increased carrier injection from the conductive support, resulting in a decrease in image density.

Table 2 Example 7 As a paint for the charge generation layer, 10 parts of a disazo pigment having the following structural formula, 5 parts of polyvinyl butyral (number average molecule i24.ooo) and 5 parts of cyclohexanone were used.
The intermediate layer and charge transport layer were the same as in Example 6, except that a charge generation layer was formed using a paint prepared by dispersing 0 parts in a sand mill using lφ glass beads for 3 hours, and then adding 80 parts of methyl ethyl ketone. An electrophotographic photoreceptor was fabricated.

When the electrophotographic photoreceptor thus prepared was attached to a laser printer (LBP-ST, manufactured by Canon) and 1,000 images were continuously printed at low temperature and low humidity (10°C, 10% RH), an increase in bright area potential was observed. (A very stable image was obtained.

The results are shown in Table 3.

Example 8 As a paint for the intermediate layer, 5 parts of poly(oxypropylene) polyol (hydroxyl value 400 mgKOH/g) using polypentaerythritol as an initiator, 5 parts of metaxylene diisocyanate, 0.3 parts of triethylene diamine, and 100 parts of isobutyl acetate were used. An electrophotographic photoreceptor was prepared in the same manner as in Example 7, except that a paint dissolved in the above was used, and evaluated in the same manner.

The results are shown in Table 3.

Example 9 Poly(
oxypropylene) polyol (hydroxyl value: 500mg
Electrophotographic exposure was carried out in the same manner as in Example 7, except that a paint containing 6.2 parts of KOH/g), 5.8 parts of hexamethylene diisocyanate, and 0.02 parts of dibutyltin dilaure dissolved in 100 parts of methyl ethyl ketone was used. A body was prepared and evaluated in the same manner.

The results are shown in Table 3.

Comparative Example 6 Poly(ethylene adipate) triol (hydroxyl value: 280), which is a polyester triol, was used as a paint for the intermediate layer.
mgKOH/g) 7.87 parts, hexamethylene diisocyanate 4.13 parts, dibutyltin dilaurate 0.0
An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 7, except that 2 parts of the sample were dissolved in 100 parts of methyl ethyl ketone.

The results are shown in Table 3.

〔Effect of the invention〕

As described above, according to the electrophotographic photoreceptor of the present invention, it is possible to always obtain stable potential characteristics and good images against changes in temperature and humidity environment.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the layer structure of an electrophotographic photoreceptor.

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor having a photosensitive layer on a conductive support via an intermediate layer, the intermediate layer contains a polymer of a polyether polyol compound and an isocyanate compound,
An electrophotographic photoreceptor characterized in that the molar ratio of isocyanate groups to hydroxyl groups in the polymer raw material is 1.0≦NCO groups/OH groups≦2.0.