JP2010513978A - Intermediate transfer belt and manufacturing method thereof - Google Patents

Abstract

An intermediate transfer belt used in laser printers, facsimiles, copiers, etc., which uses a polyimide compound and has a surface resistance between the inner and outer peripheral surfaces without any subsequent surface treatment such as antistatic coating. An intermediate transfer belt having a constant thickness is disclosed in which the difference in the above is reduced to improve the operation characteristics of the intermediate transfer belt, and the thickness deviation is minimized without seams. A method for producing the intermediate transfer belt is also provided.

Description

  The present invention relates to an intermediate transfer belt used for laser printers, facsimiles, copiers, and the like and a method for manufacturing the intermediate transfer belt.

In general, in order to be used as an intermediate transfer belt for laser printers, facsimiles, copiers, etc., heat dissipation properties, water repellency, oil repellency, stain resistance, heat resistance, elastic modulus, paper releasability, static elimination, It must have excellent durability and antistatic properties.
Polyimide compounds have many advantages such as excellent thermal stability, mechanical properties, electrical properties, etc., so research to use them as intermediate transfer belts has been conducted. It is very sensitive, and undesirably, the reliability of the electrical insulation decreases with time, and the processing is very difficult due to the high glass transition temperature and has the property of being easily charged.

Further, the intermediate transfer belt is required to have a characteristic having an appropriate volume resistance value for transferring the toner, and when it is lower or higher than the required volume resistance value, these antistatic characteristics, transferability, image The physical properties such as characteristics, releasability and stain resistance may be deteriorated, which may cause a fatal defect of image defect.
On the other hand, when the difference in surface resistance between the inner and outer peripheral surfaces of the intermediate transfer belt is large, it is difficult to adjust the resistance of the region required for the intermediate transfer belt, and the volume resistance differs depending on which part is measured. The operation of the intermediate transfer belt is uncertain. Therefore, as a conventional method, in order to reduce the difference in surface resistance, there is a method in which an antistatic coating is applied to the inner peripheral surface or the outer peripheral surface, or a surface resistance is prepared by polishing or the like. The method has a problem that it is complicated.

In particular, in the case of an additional antistatic coating, the manufacturing method is complicated and the manufacturing cost is increased. Further, in the product, the layer is separated between the antistatic coating layer and the belt, and the coating layer is scratched. Which can adversely affect the quality of the resulting image.
Intermediate transfer belts such as laser printers, facsimiles, and copiers serve to transfer toner and must be manufactured without seams.

  Therefore, in order to make an intermediate transfer belt without a seam, there is a method of applying a polyamic acid solution to the inner peripheral surface or outer peripheral surface of a mold (mold) using a dispenser. It is inferior in that it is difficult to apply uniformly, and the viscosity of the solution must be high. Furthermore, when a polyamic acid solution is applied to the outer peripheral surface of the mold using a dispenser and heat is applied from the outside, the solvent cannot evaporate and the defect occurrence rate increases.

  Further, there is a washing tub method in which centrifugal molding is performed by high-speed rotation in order to make an intermediate transfer belt without a seam. However, such a method can only be used when the solution viscosity is low. Further, if the rotation shaft is inclined, an intermediate transfer belt having a predetermined thickness cannot be manufactured. In addition, when the rotation axis of the tank is arranged vertically, there is a limit to the high-speed rotation, so that there is a disadvantage that a deviation occurs in thickness.

Accordingly, the present invention provides an intermediate transfer belt manufactured from a polyimide compound and having a small difference in surface resistance between the inner peripheral surface and the outer peripheral surface, thereby improving the operating characteristics of the belt, and a method for manufacturing the intermediate transfer belt.
The present invention also provides an intermediate transfer belt having no seam and a uniform thickness, and a method for manufacturing the intermediate transfer belt.

According to a preferred first aspect of the present invention, the present invention is not subjected to additional surface treatment, and the surface resistance ratio of the surface resistance of the outer peripheral surface to the surface resistance of the inner peripheral surface is 10 ⁻² to 10 ² . A polyimide based intermediate transfer belt is provided.
The intermediate transfer belt according to the first aspect may have a thickness deviation of 7% or less, a volume resistance value of 10 ⁵ to 10 ¹² Ωcm, and an elastic modulus (Modulus) of 3.0 to 7.0 GPa.

According to a second preferred embodiment of the present invention, the present invention provides a polyimide comprising: a step of applying a polyamic acid solution to the outer peripheral surface of a mold with a roller; and a step of imidizing the applied polyamic acid solution by heat treatment A method for producing a system intermediate transfer belt is provided.
In the second aspect, two or more rollers can be used.
In the second aspect, the polyamic acid solution may contain 0.5 to 20% by weight of an electrically conductive filler with respect to the total amount of solute.

  In the second aspect, the heat treatment in the imidization step can be performed at 60 to 450 ° C.

As described above, the present invention is manufactured from a polyimide compound, and the difference in surface resistance between the inner peripheral surface and the outer peripheral surface is small and the operation characteristics are improved without additional processing such as antistatic coating. An intermediate transfer belt and a manufacturing method thereof can be provided.
In addition, the present invention can provide an intermediate transfer belt having no seam and having a uniform thickness by minimizing thickness deviation, and a method for manufacturing the intermediate transfer belt.

FIG. 1 is a perspective view schematically showing an example of an intermediate transfer belt manufacturing method of the present invention.

Hereinafter, the present invention will be described in more detail.
The polyimide resin useful for the intermediate transfer belt of the present invention is prepared by dissolving a dianhydride, a diamine and an electrically conductive filler in a solvent to produce a polyamic acid solution, and then applying this to the outer peripheral surface of the mold with a roller. Then, it is obtained by heat treatment and imidization.
When the intermediate transfer belt is measured without being subjected to surface treatment such as antistatic coating after molding, the surface resistance ratio is preferably in the range of 10 ⁻² to 10 ² . The ratio of surface resistance can be calculated by the following formula 1.

(Formula 1)
Ratio of surface resistance = | Surface resistance value of outer peripheral surface / Surface resistance value of inner peripheral surface |
If the ratio of the surface resistance is more than 10 ^2, it is difficult to adjust the resistance of the desired area of the intermediate transfer belt, since the change volume resistivity, resulting in the belt becomes difficult operation during the image embodied . On the other hand, when the surface resistance ratio is less than 10 ^−2, the outer peripheral surface of the belt has a low resistance with respect to the applied voltage, and the developing filler such as toner does not fix well.

The intermediate transfer belt satisfying the surface resistance ratio in the above range is not only a monomer for producing the polyimide resin constituting the intermediate transfer belt, but also an electrically conductive filler that has a great influence on the electrical conductivity. To be distributed. As a result, when applied to a printer or a copier, an intermediate transfer belt having excellent developability can be realized.
A diamine component useful for producing a polyimide resin that can provide an intermediate transfer belt having such a surface resistance ratio is not particularly limited as long as it is typically used in the production of a polyimide resin. Oxydianiline (4,4′-Oxydianline, ODA), para-phenylenediamine (para-phenylenediamine, pPDA), meta-phenylenediamine (meta-phenylenediamine, mPDA), para-methylenediamine (para-methylene). Diamin, pMDA), para-methylenediamine (mMDA), and the like can be used.

  On the other hand, the dianhydride is not particularly limited as long as it is used in the production of a polyimide resin, and 1,2,4,5-benzenetetracarboxylic dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride). , Pyromellitic acid dianhydride (PMDA)), benzophenone tetracarboxylic dianhydride (3,3,4,4-Benzophenonetetracarboxylic dianhydride, BTDA), biphenyltetracarboxylic dianhydride (3,3,3) 4,4-Biphenyltetracarboxylic dianhydride (BPDA), oxydiphthal dianhydride (4,4-Oxydiphthalic dianhydrr) ide) or the like.

The diamine for producing the polyimide resin and the dianhydride are used in equimolar amounts.
The solvent can be selected from aprotic superpolar solvents such as N, N-dimethylformamide (DMF), dimethylacetamide (DMAc) and N-methylpyrrolidinone (NMP).

  Further, an electrically conductive filler having a function of adjusting the volume resistance value of the intermediate transfer belt is added during the production of the polyamic acid solution. Examples of the electrically conductive filler include ketjen black, acetylene black, funace black, a metal such as aluminum or nickel, a metal oxide such as tin oxide, or titanium. Conductive or semiconductive powder such as potassium acid, or one or a mixture of two or more selected from conductive polymers such as polyaniline or polyacetylene with respect to the total amount of solute It is preferable to use it in an amount of 0.5 to 35% by weight in order to obtain the desired electrical conductivity. The metal filler can be further contained in an amount of 0.1 to 5% by weight based on the total amount of the solute.

The dispersion method of the electrically conductive filler is not particularly limited, and it is preferable to use an ultrasonic disperser capable of efficient dispersion.
The dispersion stabilizer used in the present invention is a polymer dispersant, and examples thereof include poly-N-vinylformamide, poly-N-vinylacetamide (poly-N-vinylacetamide). ), Poly-N-vinyl pyrrolidone, and poly-N-vinyl caprolactam can be used, and the dispersant varies depending on the type of dispersion. Things can be used.

The reaction temperature for producing the polyamic acid solution for producing the polyimide resin is preferably 0 to 60 ° C., and the reaction time is preferably 0.5 to 12 hours.
After the produced polyamic acid solution is applied to the outer peripheral surface of the mold with a roller, it is heat-treated and imidized to obtain a polyimide-based intermediate transfer belt.
In the present invention, two or more rollers are used in order to manufacture an intermediate transfer belt having the above-described surface resistance ratio. This will be described in more detail based on the accompanying drawings.

FIG. 1 is a perspective view schematically showing an example of an intermediate transfer belt manufacturing method of the present invention.
In the present invention, the polyamic acid solution 4 is applied to the outer peripheral surface of the mold 3 with the rollers 1 and 2 and then heat treated to imidize to produce an intermediate transfer belt.
The rollers 1 and 2 are positioned in parallel with the mold 3, and the two rollers 1 and 2 and the mold 3 are engaged with each other and rotated.

  Specifically, when the first roller 1 rotates in the clockwise direction, the second roller 2 rotates in the counterclockwise direction, and the die 3 rotates in the clockwise direction. At this time, since the first roller 1 is in contact with the polyamic acid solution 4, the polyamic acid solution 4 is applied to the first roller 1 as the first roller 1 rotates, and the applied solution 4 is subsequently It is applied to the second roller 2 that rotates in contact with the first roller 1. Next, the solution 4 is applied to the outer peripheral surface of the mold 3 that rotates in contact with the second roller 2. In this way, the polyamic acid solution 4 is applied to the mold 3 via the plurality of rollers 1 and 2, whereby the coating amount and the coating thickness of the polyamic acid solution 4 are adjusted. When the polyamic acid solution 4 is heat-treated with the mold 3 to produce an intermediate transfer belt, the polyamic acid solution 4 is applied to be 40 to 200 μm, and the thickness deviation is preferably 7% or less. When the thickness deviation exceeds 7%, after the polyamic acid solution 4 is imidized, the thickness deviation of the film becomes large and the developability of the intermediate transfer belt is lowered.

When the rollers 1 and 2 and the mold 3 are not parallel to each other, the solution 4 concentrates at a large interval in the gap between the first roller 1 and the second roller 2 and between the second roller 2 and the mold 3. This results in a significant imbalance of the coating thickness and it is difficult for the roller and the mold to rotate normally with respect to each other. Therefore, it is important to position the roller and the mold parallel to each other.
When the rotation speed and rotation time of the rollers 1 and 2 and the mold 3 are not adjusted, the polyamic acid solution 4 is concentrated and applied between the first roller 1 and the second roller 2, and as a result, is not applied to the mold 3. The thickness deviation may be large. Therefore, care must be taken in adjusting the rotation speed and rotation time. Considering such points, the rotation speeds of the rollers 1 and 2 and the mold 3 are set to 50 to 200 rpm, and the rotation time is set to 1 to 4 hours.

As the mold 3, alumina, stainless steel, Teflon, or the like can be used, and the size is not particularly limited, but is preferably 200 to 300 mm in length and 100 to 150 mm in inner diameter.
The polyamic acid solution 4 applied to the mold 3 is heat-treated stepwise and then removed from the mold 3, thereby producing a polyimide-based intermediate transfer belt. The stepwise heat treatment can be performed with an IR heater, an electric furnace, a hot air oven, or the like. Pre-baking is performed in a temperature range of 50 to 100 ° C., and solvent and moisture remaining on the belt surface. Is preliminarily removed. After the above pretreatment, the solvent remaining at the surface and inside of the intermediate transfer belt is finally post-cured at 350 to 400 ° C. at a heating rate of 2 to 10 ° C./min. In addition, by completely removing the moisture, the imidization proceeds and is completed, and the solid phase film is completed. Alternatively, if necessary, after pre-baking, the belt can be removed from the mold and turned over, fitted into a slightly smaller mold, and post-cured.

When the intermediate transfer belt is manufactured by such a manufacturing method, the thickness deviation can be reduced by minimizing the rotation of the mold 3 for adjusting the thickness of the intermediate transfer belt, and the manufactured intermediate transfer belt can be reduced. The difference in surface resistance between the outer peripheral surface and the inner peripheral surface can be reduced.
After molding of the polyamic acid solution 4 applied to the mold 3, followed ratio of surface resistance of the surface resistance and the inner peripheral surface of the outer peripheral surface with no surface treatment was performed, such as antistatic coating is 10 ^-2 to 10 ² When the thickness deviation is 7% or less, an intermediate transfer belt exhibiting excellent insulation and developability can be realized.

Although the preferred embodiments of the present invention have been disclosed for the purpose of explanation based on the drawings, those skilled in the art can make various modifications, loads, and substitutions without departing from the technical idea of the present invention. You will understand that.
The manufactured intermediate transfer belt has a volume resistance value of 10 ⁵ to 10 ¹² Ωcm, which is classified as an intermediate resistance value, thereby improving the antistatic property and the printability of the semiconductive laser printer, facsimile machine and copy. An intermediate transfer belt for machine is obtained.

  The transfer belt of the present invention has an elastic modulus of 3.0 to 7.0 GPa, preferably 3.2 to 5.0 GPa. When the elastic modulus is low, the intermediate transfer belt may be mechanically deformed during long-term use. When the elastic modulus is high, the intermediate transfer belt is rigid and difficult to be molded.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but these are for the purpose of illustration and do not limit the scope of the present invention.
<Example 1>
While introducing nitrogen into a four-necked flask equipped with a mechanical stirrer, reflux concentrator and nitrogen inlet, 3.36 g of Ketjen black was added to 1007 g of DMF and dispersed with an ultrasonic disperser. 118 g and 80 g of ODA were added and continuously dispersed with an ultrasonic disperser. By reacting the dispersion at room temperature, a polyamic acid solution containing a conductive filler was produced. The viscosity of this solution was 1950 poise at 23 ° C.

  Thereafter, as shown in FIG. 1, after applying the polyamic acid solution to the outer peripheral surface of the cylindrical mold, pre-baking is performed at a temperature of 80 ° C. to primarily remove the solvent and moisture remaining on the belt surface. After that, post-curing is finally performed at 350 ° C. at a temperature rising rate of 5 ° C./min, thereby completely removing the solvent and moisture remaining on the surface and the inside thereof. Thus, a polyimide intermediate transfer belt containing a conductive filler was produced. At this time, the thickness of the manufactured belt was 65 μm.

<Example 2>
A polyamic acid solution was produced in the same manner as in Example 1, and after applying the solution to the mold, it was pre-baked. The resulting belt was removed from the mold and turned over, and then the inner diameter of the mold used in Example 1 was larger. After mounting the belt on a 4% smaller mold, post-curing was performed to produce a polyimide intermediate transfer belt. At this time, the thickness of the manufactured belt was 63 μm.

<Comparative Example 1>
While flowing nitrogen into a four-necked flask equipped with a mechanical stirrer, reflux concentrator and nitrogen inlet, 3.36 g of ketjen black was added to 1007 g of DMF, and dispersed with an ultrasonic disperser. 118 g and 80 g of ODA were added and dispersed with an ultrasonic disperser. By reacting the obtained dispersion at room temperature, a polyamic acid solution containing a conductive filler was produced. The viscosity of this solution was 1840 poise at 24 ° C.

Thereafter, the polyamic acid solution was applied to the inner peripheral surface of a cylindrical cylinder having an inner diameter of 120 mm and a length of 250 mm, rotated at 1200 rpm for 20 minutes, treated under the same conditions as in Example 1 to remove the solvent, and post-cured. As a result, a polyimide intermediate transfer belt was manufactured. At this time, the thickness of the manufactured belt was 71 μm.
<Comparative example 2>
After the polyamic acid solution was produced in the same manner as in Comparative Example 1, the polyamic acid solution was put into a double-layered cylindrical Teflon mold having an outer cylinder and an inner cylinder, and prebaked at a temperature of 80 ° C. Then, after preliminarily removing the solvent and moisture remaining on the belt surface, the inner cylinder was separated from the outer cylinder.

Thereafter, final post-curing was performed at 350 ° C. at a rate of temperature increase of 5 ° C./min to produce a polyimide intermediate transfer belt. The thickness of the manufactured belt was 68 μm.
The physical properties of the intermediate transfer belts produced in the examples and comparative examples were evaluated by the following methods. The results are shown in Table 1.
(1) Ratio of surface resistance It measured by applying a voltage to a sample continuously using a resistance measuring machine (HIRESTA UP) available from Mitsubishi Chemical. At this time, the voltage applied to the sample was 100V. In addition, in order to measure the surface resistance, a sample is placed on a substrate formed of a fluorinated polymer having high insulating properties, and the inner surface resistance and outer surface resistance of the sample are separately separated at intervals of 10 seconds. It was measured. At this time, a ring-shaped probe was used. The size of the sample used for the surface resistance measurement was 20 × 20 cm, and the measurement was performed 10 times on the corresponding surface to obtain an average value. The obtained value was substituted into the following formula 1 to calculate the surface resistance ratio.

(Formula 1)
Ratio of surface resistance = | Surface resistance value of outer peripheral surface / Surface resistance value of inner peripheral surface |
(2) Volume resistance value It measured by applying a voltage to a sample continuously using the resistance measuring machine (HIRESTA UP) available from Mitsubishi Chemical. At this time, the voltage applied to the sample was 100V. Further, in order to measure the volume resistance, a sample was placed on a metal substrate, and the volume resistance was measured using a ring-shaped probe at intervals of 10 seconds. The size of the sample used for measuring the volume resistance was 20 × 20 cm, and the measurement was performed 10 times to obtain an average value.

(3) Modulus
Measurements were made according to ASTM D882 using a Universal Testing Machine Model 1000 available from Instron.
(4) Thickness and thickness deviation After the sample was dried at 100 ° C. for 1 hour, its thickness was measured using a micrometer (Anritus, electric micrometer). The thickness of the sample was obtained by averaging the measured values other than the maximum value and the minimum value after measuring 50 times. The thickness deviation was calculated by a general formula for calculating the thickness deviation and expressed in%.

(5) Developability The intermediate transfer belt manufactured in Examples and Comparative Examples was applied to a transfer unit and connected to a color laser printer, and the same image was transferred repeatedly. The image state of the developed paper was determined by checking the number of defects. Very good when developed 1000 times and the number of defects is less than 10 times, good when over 10 times and under 30 times, good when over 30 times and under 50 times, usually over 50 times and under 100 times In the case of, the evaluation was bad, and in the case of exceeding 100 times, the evaluation was very bad.

  As a result of measuring the physical properties, the intermediate transfer belts of the examples manufactured by the manufacturing method of the present invention had a surface resistance ratio of 4.23 and 2.17, respectively, and the difference in surface resistance between the outer peripheral surface and the inner peripheral surface was Since it was very small, it was confirmed that the filler was uniformly dispersed. Further, since the thickness deviation is 7% or less, the intermediate transfer belt of the present invention has a relatively uniform thickness, and as a result, exhibits a very good developability.

On the other hand, the intermediate transfer belt of the comparative example, the surface resistivity ratio of 10 ² or more, since the difference in surface resistance between the inner and outer peripheral surfaces is large, thickness variation exceeds 7%, the lower developability It was.

1: First roller 2: Second roller 3: Mold
4: Polyamic acid solution

Claims (8)

This is a polyimide-based intermediate transfer belt that is not subjected to additional surface treatment, and the ratio of the surface resistance of the outer peripheral surface and the surface resistance of the inner peripheral surface calculated by the following formula 1 is 10 ⁻² to 10 ² . A polyimide intermediate transfer belt.
(Formula 1)
Ratio of surface resistance = | Surface resistance value of outer peripheral surface / Surface resistance value of inner peripheral surface |   2. The polyimide intermediate transfer belt according to claim 1, wherein a thickness deviation is 7% or less. 2. The polyimide-based intermediate transfer belt according to claim 1, wherein the volume resistance value is 10 ⁵ to 10 ¹² Ωcm.   The polyimide-based intermediate transfer belt according to claim 1, wherein an elastic modulus is 3.0 to 7.0 GPa. A method for producing a polyimide-based intermediate transfer belt, comprising: a step of applying a polyamic acid solution to a peripheral surface of a mold with a roller; and a step of heat-treating the applied polyamic acid solution to imidize.   The method for producing a polyimide-based intermediate transfer belt according to claim 5, wherein the number of the rollers is two or more.   6. The method for producing a polyimide-based intermediate transfer belt according to claim 5, wherein the polyamic acid solution contains 0.5 to 35% by weight of an electrically conductive filler with respect to the total amount of solute.   The method for producing a polyimide intermediate transfer belt according to claim 5, wherein the heat treatment in the imidization step is performed at 50 to 400 ° C. 6.