JP2002212420A - Polyimide resin composition and semiconductive belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide resin composition having high mechanical characteristics and small variations of electrical resistance, reduced in deterioration in resistance with the lapse of time caused by electrical loads and the like and exhibiting semiconductive properties, and a semiconductive belt composed of the polyimide resin composition. SOLUTION: The polyimide resin composition is composed mainly of a polyimide resin comprising a carbon black, has a residual radical amount per unit weight of at most 2×1018 spin/g and a surface resistivity in terms of the common logarithm of 8-14 logΩ/(square). The semiconductive belt is composed of the polyimide resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a semiconductive property,
The present invention relates to a polyimide resin composition having a low resistance and a semiconductive belt formed using the polyimide resin composition.

[0002]

2. Description of the Related Art In a recording apparatus for forming an image by an electrophotographic method such as a copying machine, a laser printer, and a facsimile, an image formed on an image carrier such as a photosensitive drum via a recording agent such as a toner is directly recorded on a recording sheet. A transfer method that can avoid the fixing method has been studied. One is a method using an intermediate transfer belt, in which the charged toner on the image carrier is temporarily transferred to the intermediate transfer belt by applying a voltage with a transfer roll or the like facing an image carrier such as a photoconductor. (Primary transfer step), and then transfer the charged toner held on the intermediate transfer belt onto a recording sheet supplied together with the intermediate transfer belt by applying a voltage using another transfer roll or the like (second transfer step). Next transfer step).

[0003] The other is a system using a transfer / conveying belt, and by applying a voltage with a transfer roll or the like facing the image carrier, a recording sheet supplied with the transfer / conveyor belt is placed on the image carrier. After the charged toner is directly transferred and held (transfer step), the recording sheet is conveyed to the fixing device side by a transfer convey belt (convey step). Further, for the purpose of downsizing the apparatus, a transfer and fixing method in which these steps and a fixing step are further performed on one belt has been studied.

There are various transfer methods which differ in whether or not the belt is energized, and in the form of charging / discharging of the belt. The intermediate transfer belt, the transfer / transport belt or the transfer / fixing belt used for the transfer method is different. In order to appropriately balance insulation, antistatic properties, and static elimination properties, semiconductive belts having appropriate conductivity have been used.

As such a semiconductive belt, a semiconductive belt using a film made of polyvinylidene fluoride, an ethylene / tetrafluoroethylene copolymer, polycarbonate or the like (JP-A-5-200904, JP-A-5-200904) -345368, JP-A-6-95521, etc.) are known. However, in recent years, the belt has been required to have a high function such as high speed, and it is difficult to obtain a belt that can withstand practical use in mechanical strength, surface accuracy, and resistance control. In order to improve this, a conductive filler is blended into the polyimide film to make the volume resistivity 1 to 10 ¹³ Ω.
Cm, the maximum value of which is in the range of 1 to 10 times the minimum value (JP-A-5-77252) is known.

However, the semiconductive belt made of polyimide using ordinary carbon black as the conductive filler as described above has some improvement in the initial resistance value variation as compared with the conventional belt, Resistance area (common logarithmic value of surface resistivity is 8 to 14 log Ω /
In the case of □), higher precision resistance control was required, and a belt having a dispersion state that was satisfactory for practical use could not be obtained. Further, since the voltage dependence of the resistance value is large, there is a problem that the electric resistance value is reduced by an electric load such as voltage concentration applied to the transfer unit. Since such a decrease in the electric resistance value causes an excessive current to flow through the belt during transfer, when the belt is used as an intermediate transfer belt,
Problems such as retransfer of toner once transferred occur on the image. Such a decrease in resistance leads to shortening of the life of the semiconductive belt in the electrophotographic image forming apparatus, resulting in an increase in labor and maintenance costs such as belt replacement and the like.

On the other hand, as another means of improvement, a method of applying carbon black obtained by grafting a hydrophobic oligomer (styrene, methyl methacrylate, etc.) onto the surface of carbon black as a conductive material (Japanese Patent Laid-Open No. 10-108)
No. 80) is also conceivable. However, it was found that when the grafted carbon black used here was to be dispersed in a polyimide precursor solution or a polymerization solvent, the affinity for the solvent was poor, and aggregation and non-uniform dispersion of the carbon black occurred. Further, a belt using such a precursor solution becomes a belt having a large variation in electric resistance value when used in an electrophotographic image forming apparatus, and has a problem that an unclear image is formed.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a semiconductive polyimide resin composition having high mechanical properties, a small variation in electric resistance, and a small decrease in resistance over time due to an electric load or the like. And a semiconductive belt comprising the polyimide resin composition.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and found that they have a semiconductivity in a high resistance region (common logarithmic value of surface resistivity is 8 to 14 log Ω / □). With respect to the polyimide resin composition, by setting the amount of residual radicals per unit weight to 2 × 10 ¹⁸ spin / g or less, a decrease in the resistance value over time due to an electrical load or the like is small. The inventors have found that the present invention can be obtained, and have completed the present invention.

That is, the present invention relates to a polyimide resin composition containing a polyimide resin containing carbon black as a main component, wherein the residual radical amount per unit weight is 2 × 10 ¹⁸ spin / g or less, The present invention also relates to a polyimide resin composition characterized by a common logarithmic value of surface resistivity of 8 to 14 log Ω / □.

[0011] The polyimide resin composition may further contain a polymer dispersant. Further, in the polyimide resin composition, the carbon black contained therein may be subjected to a radical attenuation treatment.

Further, the present invention relates to a semiconductive belt comprising the polyimide resin composition.

[0013] The semiconductive belt of the present invention may be subjected to a radical attenuation treatment after the belt is formed. Further, in the semiconductive belt of the present invention, the difference between the surface resistivity before the discharge deterioration test and the surface resistivity after the discharge deterioration test is preferably 1.5 logΩ / □ or less as a common logarithmic value.

[0014]

Embodiments of the present invention will be described below in more detail.

The polyimide resin composition of the present invention is mainly composed of a polyimide resin containing carbon black as a conductive substance, and has a residual radical amount per unit weight of 2 × 10 ¹⁸ spin / g or less, preferably 1 × 10 ¹⁸ spin / g or less. 10 ¹⁸ spin / g or less. When the residual radical concentration of the polyimide resin composition in which carbon black is dispersed exceeds this, when the polyimide resin composition is used as a functional belt in an electrophotographic image forming apparatus, the resistance due to an electrical load such as a transfer voltage is reduced. The decrease is significant. The reason for this is not clear, but the discharge voltage applied or generated in the transfer process is due to the synergistic effect of the radicals remaining in the carbon black itself or the pyrolytically modified products such as polymer dispersants, unreacted monomers and polymers. Due to this, it is considered that the non-uniform polyimide polymer portion or the polymer dispersant component is deteriorated, and the electrical resistance of the resin composition or the entire belt is reduced because the conductive path is easily formed due to conductivity. .

[0016] radical of the carbon black itself, so as to satisfy the remaining radical of conditions can be selected appropriately according to the content of carbon black in the polyimide resin composition is usually 1.0 × 10 ²⁰ Spin / g or less, preferably 5.0 × 10 ¹⁹ spin / g or less.
Further, the radical amount of the carbon black itself can be set to a desired value by a radical decay treatment described later.

The amount of radicals and the amount of residual radicals of carbon black itself can be measured by various methods.
In the present invention, the electron spin resonance analysis (ES
R) is based on the value measured.

The carbon black used in the present invention includes, for example, channel black, furnace black and the like. Specifically, as a channel black, "Color Black FW" manufactured by Degussa Huls Co., Ltd.
200 "," Color Black FW2 "," C
color Black FW2V "," Color B
black FW1 ”,“ Color Black FW ”
18 "," Special Black 6 "," Co
lor Black S170 "," ColorBla
ck S160 "," Special Black "
5 "," Special Black 4 "," Spe
Cial Black 4A "," Printex 1
50T ”,“ Printex U ”,“ Printex ”
V "," Printex 140U "," Print
ex 140V ", Furnace Black" Special Black 55 "manufactured by Degussa Huls.
0 "," Special Black 350 "," S
special Black250 "," Special
Black 100 "," Printex 35 ",
"Printex 25", "MA" manufactured by Mitsubishi Chemical Corporation
7 "," MA 77 "," MA 8 "," MA 1 "
1 "," MA 100 "," MA 100R "," MA
220 "," MA 230 ", manufactured by Cabot Corporation," M
ONARCH 1300 ”,“ MONARCH 110 ”
0 "," MONARCH 1000 "," MONARC "
H 900 "," MONARCH 880 "," MON
ARCH 800 "," MONARCH 700 ",
"MOGUL L", "REGAL 400R", "V
ULCAN XC-72R "and the like, and a single kind or plural kinds of carbon blacks may be used in combination.

In the present invention, in order to keep the amount of residual radicals of the polyimide resin composition in which carbon black is dispersed and the semiconductive belt to the value of the present invention or less, the carbon black to be added may be subjected to a radical attenuation treatment. Examples of the radical attenuating treatment here include aging (processing in a warehouse, a constant temperature room, or the like), heat treatment (heat treatment with a roll-type heating device, an oven, or the like), and electron beam irradiation. it can. Since the addition amount of carbon black is appropriately determined based on a resistance value required as a final article made of a polyimide resin composition such as a seamless belt, carbon black is preferably subjected to a radical attenuation treatment as necessary. .

In the polyimide resin composition of the present invention, the content of carbon black is preferably as small as possible in order to improve the resistance reduction due to an electric load or the like as long as the resistance value does not vary. However, for practical use, the content of carbon black depends on the resistance value required for the finally obtained polyimide resin composition. The amount is preferably about 10 to 50% by weight, more preferably 12 to 30% by weight, based on the weight of the polyimide resin. 1
If the amount is less than 0% by weight, the uniformity of the electrical resistance tends to decrease. On the other hand, if the amount exceeds 50% by weight, a desired resistance value is hardly obtained, and the high mechanical strength derived from the polyimide resin composition decreases. Or the amount of apparent residual radicals contained in the resin composition increases, and the surface shape tends to deteriorate.

Since the polyimide resin composition of the present invention is applied to an intermediate transfer belt, a transfer conveyance belt and the like, a common logarithm of the surface resistivity is 8 to 14 log Ω.
/ □, preferably 9 to 13 logΩ / □,
13 log Ω / □ is more preferable.

The surface resistivity is a value measured by the method shown in the examples.

The polyimide resin composition of the present invention may further contain a polymer dispersant for improving the dispersibility of the carbon black used in the present invention. Specific examples of the polymer dispersant include poly (N-vinyl-2-pyrrolidone), poly (N, N′-diethylacrylazide), poly (N-vinylformamide), and poly (N-vinylacetamide). , Poly (N-vinylphthalamide), poly (N-vinylsuccinamide), poly (N-vinylphthalamide)
Vinyl urea), poly (N-vinyl piperidone), poly (N-vinyl caprolactam), poly (N-vinyl oxazoline) and the like, and a single or a plurality of polymer dispersants can be combined.

The content of the polymer dispersing agent is usually 2 to the carbon black in the polyimide resin composition from the viewpoint of increasing the dispersibility of the carbon black and not impairing the mechanical strength of the polyimide resin composition. ~ 30% by weight
And preferably 5 to 25% by weight.

The polyimide resin in the present invention can be obtained by polymerizing an acid dianhydride component and a diamine component.

The acid dianhydride is preferably a tetracarboxylic dianhydride or a derivative thereof. Examples thereof include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride and the like Is mentioned.

Examples of diamines include 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane,
3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenylsulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3′-dimethyl-4, 4'-biphenyldiamine, benzidine, 3,
3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 4,4′-diaminophenylsulfone, 4,
4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylpropane and the like.

As the dispersion solvent, an organic polar solvent capable of causing a polymerization reaction of an acid dianhydride, which is a raw material of polyimide, and a diamine component is preferable, and N, N-dialkylamides are preferable. Specifically, N, N-dimethylformamide,
N, N-dimethylacetamide, N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide,
Hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine, dimethylsulfoxide, tetramethylenesulfone, dimethyltetramethylenesulfone and the like can be mentioned, and a single solvent or a plurality of solvents can be used in combination.

In addition to the above materials, in the present invention, the above-mentioned polymer dispersant can be added in order to enhance the dispersibility of carbon black. In addition, a silicone-based or fluorine-based organic compound, a coupling agent, a lubricant, an antioxidant, and other additives may be added to the extent that physical properties are not impaired.

To prepare a polyimide resin composition using these materials, first, a polyimide precursor solution is prepared. As this method, carbon black is previously dispersed in a dispersion medium, and an acid anhydride component and a diamine component are dissolved and polymerized in the dispersion medium to obtain a carbon black-dispersed polyimide precursor solution. Known methods such as a method in which an anhydride component and a diamine component are dissolved and polymerized to prepare a polyimide precursor solution, and carbon black is added to the solution, and the like can be applied as appropriate. At this time, a known dispersion method can be applied, and the dispersion operation is appropriately performed by a method such as a ball mill, a sand mill, and an ultrasonic dispersion.

The monomer concentration (the concentration of the acid anhydride and the diamine in the solvent) in the polyimide precursor solution of the present invention is set according to various conditions, but is preferably 5 to 30% by weight. The reaction temperature is preferably set at 80 ° C. or lower, particularly preferably 5 to 50 ° C., and the reaction time is 5 to 10 hours. The polymer component of the polyimide precursor solution may be a copolymer or a blend of the above-mentioned acid dianhydride and diamine component as long as the object of the present invention can be achieved.

When the solvent of the polyimide precursor solution is removed by heating or the like, the dehydration ring-closing water is removed, and the imide conversion reaction is completed, the polyimide resin composition of the present invention can be obtained.

Further, the semiconductive belt of the present invention can be obtained by molding using the polyimide resin composition.

The semiconductive belt according to the present invention is characterized in that the polyimide precursor solution is applied to the outer surface of the core material by dip coating or applied to the inner surface of a cylindrical mold, and then the ring mold, the centrifugal force, and the bullet traveling body are used. A film can be obtained as a seamless belt by forming a coating film by molding or the like, drying and removing the solvent and ring-closing water, imidation, and the like.

The semiconductive belt of the present invention is an electrophotographic type.
When used as a functional belt in image forming apparatuses, etc.
From the viewpoint, the amount of residual radicals per unit weight is 2 ×
10 ¹⁸Spin / g or less, preferably 1 × 10¹⁸spin/
g or less.

The semiconductive belt of the present invention may be subjected to a radical attenuation treatment after molding so as to have a desired residual radical amount. The radical decay treatment can be performed by a method such as heat treatment (heating treatment with a roll-type heating device, an oven, or the like), electron beam irradiation, or the like.

The semiconductive belt of the present invention can be selected from electrical resistance values that appropriately balance the insulation properties, antistatic properties, static elimination properties, etc., according to the application and the system, so that the electric resistance value suitable for each is selected. Can be obtained. Generally, semiconductive belts such as an intermediate transfer belt and a transfer conveyance belt used in an electrophotographic image forming apparatus have a common logarithmic value of surface resistivity of 8 to 14 log Ω / □, preferably 9 to 13 log Ω / □. Yes, more preferably 10
13 log Ω / □.

In the semiconductive belt of the present invention, the difference between the surface resistivity before the discharge deterioration test and the surface resistivity after the discharge deterioration test is preferably 1.5 log Ω / □ or less as a common logarithmic value.
More preferably, it is 1.0 logΩ / □ or less, and further preferably, 0.8 logΩ / □ or less.

Here, the discharge deterioration test is performed by performing a discharge treatment under the apparatus and conditions shown in the examples. The discharge treatment reduces the surface resistivity of the semiconductive belt.

Before and after the discharge deterioration test, the surface resistivity of the semiconductive belt was measured, and the difference between the obtained values was the amount of decrease in surface resistivity (Δρ). Ask.

In the semiconductive belt of the present invention that satisfies the above conditions, the resistance is hardly reduced by an electric load such as a transfer voltage, and the resistance is reduced with time when used as a transfer belt or an intermediate transfer belt. It becomes a seamless belt that is difficult to do.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below.

Example 1 A radical amount of 1.6 × 10 ¹⁹ spin / g in 1800 g of N-methyl-2-pyrrolidone
Was mixed with a ball mill at room temperature for 8 hours. Add 3 to this carbon black dispersion
294 g of 3 ', 4,4'-biphenyltetracarboxylic dianhydride and 108 g of p-phenylenediamine were dissolved and polymerized with stirring under a nitrogen atmosphere at room temperature for 5 hours to obtain a polyimide precursor solution containing carbon black. . After applying this polyimide precursor solution to the inner surface of the cylindrical mold, the film thickness is made uniform using a bullet-shaped traveling body.
While rotating at 00 rpm, hot air of 60 ° C. was applied from the outside of the mold to dry and solidify the belt itself by removing the solvent and the like until the belt itself could be supported. Release this belt from the cylindrical mold, then replace it with an aluminum pipe,
5 ° C / 200 ° C to 350 ° C in order to remove the residual solvent, remove the dehydrated ring-closing water, and complete the imide conversion reaction.
After heating at a heating rate of 1 minute and cooling to room temperature, a seamless belt having a thickness of 75 μm (23% by weight of carbon black based on polyimide resin) was obtained.

Comparative Example 1 294 g of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 108 g of p-phenylenediamine were dissolved in 1464 g of N-methyl-2-pyrrolidone, and the mixture was dissolved in a nitrogen atmosphere. The reaction was carried out while stirring at room temperature for 5 hours to obtain a polyimide precursor solution.
This polyimide precursor solution was used in the same manner as in Example 1 to obtain a seamless belt.

[Comparative Example 2] A polyimide semiconductive material was prepared in the same manner as in Example 1, except that the carbon black having a radical amount of 7.8 × 10 ¹⁹ spin / g was used as the carbon black dispersion in Example 1. A conductive belt (23% by weight of carbon black based on polyimide resin) was prepared.

Example 2 The carbon black used in Comparative Example 2 was subjected to a radical decay treatment by leaving it to stand in a drying oven at 200 ° C. for 48 hours, and the residual radical amount of the carbon black after the treatment was measured. However, 1.2 × 10
¹⁹ spin / g. This carbon black was dispersed in N-methyl-2-pyrrolidone to prepare a carbon black dispersion. Using this carbon black dispersion,
A semiconductive belt was produced in the same manner as in Example 1.

Example 3 The semiconductive belt obtained in Comparative Example 2 was subjected to a radical attenuation treatment by electron beam irradiation under the following conditions.

An electron beam irradiation device (CB / 1, manufactured by Iwasaki Electric Co., Ltd.)
75/15 / 180L), the sample was previously replaced with nitrogen gas as an inert gas in the treatment layer, and the sample transfer speed was 5 m.
The electron beam was irradiated at an acceleration voltage of 165 kV and a current of 4.6 mA / min. The absorbed dose at this time was 200 kGy.

(Evaluation)-Radical amount or residual radical amount-The radical amount or the residual radical amount was measured using an electron spin resonance analyzer (JES-EF1XG manufactured by JEOL Ltd.) at a temperature of 23 to 24 ° C and a resonance frequency microwave output. 0.5-2m
W, measurement magnetic field 0.3280 ± 0.010T, modulation magnetic field 1
Under a condition of 00 kHz and 0.0001 T, a manganese marker was used as an internal standard, and a sample was measured by putting carbon black or a strip obtained by cutting a belt into a measuring cell. The method of quantitatively calculating the amount of radicals or the amount of residual radicals is based on Mn ²⁺ / MgO as a reference standard for calibration, and using a benzene solution of DPPH (1,1-diphenyl-2-picrylhydrazyl) of known concentration as a standard sample for determination. Was performed from each area ratio. The sample weight was set to 1 to 50 mg. When the radical concentration was too high and exceeded the measurement range, the measurement was performed by appropriately reducing the sample weight.

-Surface resistivity- Hiresta UP, MCP-HTP16 (manufactured by Mitsubishi Chemical Corporation,
Probe: UR-100) applied voltage 500 V, 10
sec. Thereafter, measurement was performed under measurement conditions of 25 ° C./60% RH environment, and the logarithmic value was obtained.

-Discharge Degradation Treatment (Corona Discharge Treatment)-By performing corona discharge treatment on the semiconductive seamless belt to cause discharge deterioration, the same effect as reduction in surface resistivity due to voltage concentration can be obtained. Each of the seamless belts obtained in Examples and Comparative Examples was subjected to voltage: 70 V, current: 3 A, electrode length: 0.3 m, using a corona discharge tester shown in FIG.
Electrode-sheet distance: 3 mm, sample moving speed: 0.
45 m / min. The surface resistivity before and after the treatment was measured to determine the decrease in surface resistivity (Δρ).

[0052]

[Table 1]

According to the polyimide resin composition of the present invention having a defined residual radical amount, not only can a member having a uniform and stable resistivity be obtained, but also it is possible to obtain a member with a lapse of time even under an electrical load such as a transfer voltage. The resistance decreases little and the initial resistivity can be maintained. Further, the semiconductive belt molded from the polyimide resin composition of the present invention is a belt for an image forming apparatus such as an electrophotographic intermediate transfer belt, a transfer conveyance belt, and a transfer fixing belt due to the above-mentioned effects of the polyimide resin composition. As a result, initial characteristics such as surface resistivity can be maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic view of a discharge deterioration tester.

[Explanation of symbols]

 1 Roll 2 Sample transport direction 3 Discharge electrode

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08K 3/04 C08K 3/04 5G301 9/00 9/00 G03G 15/16 G03G 15/16 15/20 101 15/20 101 H01B 1/24 H01B 1/24 Z (72) Inventor Toshihiko Tomita 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Inside Nitto Denko Corporation (72) Inventor Masahiro Uebayashi 1-chome Shimohozumi, Ibaraki-shi, Osaka No. 1-2 F-term in Nitto Denko Corporation (reference) 2H033 BA08 BA12 BE09 2H200 GB40 JB06 JB45 JB46 JC03 JC15 JC16 MA02 MA06 MA17 MB02 MB05 4F071 AA60 AB03 AE15 AF37 AH17 BA02 BB02 BB03 BC01 4A0731 A0104 CM041 DA036 FB016 FB066 FD116 GM01 5G301 DA18 DA51 DD10

Claims (6)

[Claims] 1. A polyimide resin composition comprising a polyimide resin containing carbon black as a main component, wherein the amount of residual radicals per unit weight is 2 × 10 ¹⁸ spin / g or less, and the surface resistivity is The common logarithm of
Polyimide resin composition characterized by being 14 log Ω / □. 2. The polyimide resin composition according to claim 1, further comprising a polymer dispersant. 3. The polyimide resin composition according to claim 1, wherein the carbon black has been subjected to a radical attenuation treatment. 4. A semiconductive belt comprising the polyimide resin composition according to claim 1. 5. The semiconductive belt according to claim 4, wherein a radical attenuation treatment is performed after the belt is formed. 6. The semiconductive belt according to claim 4, wherein the difference between the surface resistivity before the discharge deterioration test and the surface resistivity after the discharge deterioration test is 1.5 log Ω / □ or less as a common logarithmic value.