JP2013245322A - Thermosetting solution, tubular body, method for manufacturing the same, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosetting solution capable of providing a molded product reduced in fluctuations in volume resistivity due to a difference in storage time.SOLUTION: A thermosetting solution includes: a polyimide precursor in which 70% or more of all terminal groups are amino group; a carbon black having a content to the polyimide precursor of 15 mass% or more and 30 mass% or less and a pH of 3 or more and 4 or less; and a solvent.

Description

  The present embodiment relates to a thermosetting solution, a tubular body, a manufacturing method thereof, and an image forming apparatus.

  An endless belt used in an electrophotographic image forming apparatus or the like may be required to have strength and dimensional stability. In addition, it is known that the endless belt includes a conductive agent in order to be applied to various apparatuses using an electrophotographic system.

Patent Document 1 proposes a seamless belt containing polyimide resin or conductive powder.
Patent Document 2 proposes an intermediate transfer belt made of a thermosetting polyimide resin in which a conductive metal oxide is dispersed.
In Patent Document 3, a semiconductive polyamic acid solution containing polyamic acid, carbon black powder, and an organic solvent is supplied to the inner surface of a metal drum and heated to produce a polyamic acid endless tubular film. It has been proposed.
Patent Document 4 proposes an endless semiconductive belt having a layer containing oxidized carbon black and polyimide resin as a conductive agent.

  In Patent Document 5, carbon black is dispersed in a resin solution having a viscosity in the range of 1 to 20 Pa · s to prepare a carbon black dispersion, and the prepared carbon black dispersion and a viscosity adjusting solution having a viscosity higher than that of the resin solution are disclosed. It has been proposed to produce a semiconductive member by preparing a semiconductive paint by mixing with and applying the semiconductive paint to form a semiconductive member.

JP-A-5-77252 Japanese Patent Laid-Open No. 10-63115 JP 2002-86465 A JP 2004-287383 A JP 2007-86492 A

  The subject of this invention is providing the thermosetting solution from which the molded object by which the fluctuation | variation of the volume resistivity by the difference in storage time was suppressed was obtained.

The above problems are solved by the present invention described below. That is,
The invention according to claim 1
A polyimide precursor in which 70% or more of all terminal groups are amino groups;
A conductive material having a content of 15% by mass to 30% by mass with respect to the polyimide precursor, a pH of 3 to 4 and having an acidic group;
A solvent,
Is a thermosetting solution.

The invention according to claim 2
The thermosetting solution according to claim 1, wherein the conductive material is carbon black.

The invention according to claim 3
A tubular body having a cured layer of the thermosetting solution according to claim 1.

The invention according to claim 4
Forming a coating film of the thermosetting solution according to claim 1 or 2,
Heat-curing the coating film;
It is a manufacturing method of the tubular body which has this.

The invention according to claim 5
An image carrier,
Charging means for charging the surface of the image carrier;
Latent image forming means for forming a latent image on the surface of the charged image carrier;
Developing means for developing a latent image on the surface of the image carrier with toner to form a toner image;
An intermediate transfer member to which the toner image formed on the surface of the image holding member is transferred, the intermediate transfer member comprising the tubular member according to claim 3,
Primary transfer means for primarily transferring the toner image formed on the surface of the image carrier to the surface of the intermediate transfer member;
Secondary transfer means for secondary transfer of the toner image transferred to the surface of the intermediate transfer member to a transfer medium;
Fixing means for fixing the toner image transferred to the recording medium;
An image forming apparatus.

  According to the first and second aspects of the invention, a polyimide precursor in which 70% or more of all terminal groups are amino groups, and a content with respect to the polyimide precursor is 15% by mass or more and 30% by mass or less, and a pH is 3 or more. It is possible to provide a thermosetting solution capable of obtaining a molded body in which the variation in volume resistivity due to the difference in holding time is suppressed as compared with the case where the conductive material having an acidic group of 4 or less is not combined.

  According to the invention of claim 3, the polyimide precursor in which 70% or more of all terminal groups are amino groups, the content with respect to the polyimide precursor is 15% by mass to 30% by mass, and the pH is 3 or more and 4%. Provided is a tubular body in which the volume resistivity fluctuation due to the difference in storage time of the thermosetting solution is suppressed as compared with the case where a thermosetting solution that is not combined with a conductive material having an acidic group is applied. it can.

  According to the invention of claim 4, the polyimide precursor in which 70% or more of all terminal groups are amino groups, the content with respect to the polyimide precursor is 15% by mass or more and 30% by mass or less, and the pH is 3 or more and 4%. The tubular structure in which the volume resistivity variation of the tubular body due to the difference in the storage time of the thermosetting solution is suppressed as compared with the case where a thermosetting solution that is not combined with the conductive material having an acidic group is applied. The manufacturing method of the tubular body which implement | achieved manufacture of the body can be provided.

  According to the fifth aspect of the present invention, compared to the case without the intermediate transfer body in this configuration, image quality fluctuation due to the change in volume resistivity of the intermediate transfer body due to the difference in the storage time of the thermosetting solution is suppressed. An image forming apparatus can be provided.

It is a schematic diagram which shows an example of the film-forming apparatus used for the manufacturing method of the tubular body (endless belt) in this Embodiment. It is a schematic diagram which shows an example of the film-forming apparatus used for the manufacturing method of the tubular body (endless belt) in this Embodiment. It is a schematic diagram which shows the state by which the coating film or the tubular body (endless belt) was formed in the core. It is a schematic diagram which shows an example of the volume resistivity measuring apparatus which measures the volume resistivity of an endless belt, (B) is a top view, (A) is A-A 'sectional drawing of (B). 1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment.

  Embodiments that are examples of the present invention will be described below.

(Thermosetting solution)
The thermosetting solution according to the present embodiment has a polyimide precursor in which 70% or more of all terminal groups are amino groups, a content of 15% by mass to 30% by mass with respect to the polyimide precursor, and a pH of 3 or more. The conductive material is 4 or less and has an acidic group (hereinafter referred to as “acidic conductive material”) and a solvent.

The thermosetting solution which concerns on this embodiment can obtain the molded object by which the fluctuation | variation of the volume resistivity by the difference in the storage time was suppressed by the said composition.
The reason for this is not clear, but is thought to be due to the following reasons.

The terminal of the molecular chain of the polyimide precursor (polyamic acid) is mainly an amino group or a carboxy group. Specifically, a polyimide precursor is a molecule in which both ends are amino groups, a molecule in which both ends are carboxy groups (including a terminal anhydrous carboxy group in which two carboxy groups have been dehydrated), or one end is an amino group. The other end is a carboxy group (including a terminal anhydrous carboxy group in which two carboxy groups are dehydrated).
Here, it is considered that the terminal amino group of the polyimide precursor forms a hydrogen bond with the acidic conductive material (the acidic group on the surface), thereby causing an interaction. When this interaction occurs, it is considered that the dispersibility of the acidic conductive material increases.

  However, the polyimide precursor may undergo a dissociation reaction over time. When the dissociation reaction occurs, the molecular ends of the polyimide precursor increase, and accordingly, the number of terminal amine groups increases. As the number of terminal amine groups increases, the number of groups that interact with the acidic conductive material (the acidic groups on the surface) increases, and the dispersion state of the acidic conductive material is considered to vary.

  In particular, when an acidic conductive material having a pH in the above range is blended with the polyimide precursor in the above range, it is considered that the dispersibility of the acidic conductive material is likely to vary greatly. This is because when the acidic conductive material is blended in the above range, the acidic conductive material is dispersed in the polyimide precursor to such an extent that it does not become overcrowded while forming a conductive path, resulting in fluctuations in interaction with an increase in the number of terminal amine groups. On the other hand, the dispersibility of the acidic conductive material is considered to be excessively affected. In addition, since the acidic conductive material having a pH in the above range is not excessively acidic, the acidic conductive material is dispersed in the polyimide precursor without excessively interacting with the terminal amine group. This is because the dispersibility of the acidic conductive material is considered to be excessively affected by the variation in the interaction accompanying the increase in the number of amine groups.

On the other hand, when a polyimide precursor in which 70% or more of all terminal groups are amino groups is applied and the terminal amine groups of the polyimide precursor are excessively increased, the dissociation reaction of the polyimide precursor over time occurs. Even if the number of terminal amino groups increases, it is considered that the increase rate with respect to the total terminal amino groups can be minimized.
In other words, if the terminal amine group of the polyimide precursor is excessively increased and the state of interaction with the acidic conductive material is increased from the initial stage of production, the interaction with the increase in the number of terminal amine groups over time It is considered that the dispersibility of the acidic conductive material becomes less susceptible to fluctuations.
For this reason, even if the number of terminal amino groups of the polyimide precursor increases with time, it is considered that the dispersion state of the acidic conductive material hardly changes.

From the above, the thermosetting solution according to the present embodiment provides a molded body in which the variation in volume resistivity due to the difference in storage time is suppressed.
Then, when a tubular body is manufactured as a molded body using the thermosetting solution according to the present embodiment, a change in volume resistivity caused by a difference in storage time of the thermosetting solution (for example, volume resistivity between production lots). The production of the tubular body can be realized.
Further, when this tubular body is applied to an image forming apparatus as an intermediate transfer body, image quality fluctuations caused by fluctuations in the volume resistivity of the intermediate transfer body caused by differences in the storage time of the thermosetting solution are suppressed.

  Hereinafter, each component of the thermosetting solution according to the present embodiment will be described.

-Polyimide precursor-
In the polyimide precursor, 70% or more of all terminal groups are amino groups. The ratio of this terminal amino group to all terminal groups is preferably 70% or more and 90% or less. If this proportion is less than 70%, the dispersion of the dispersibility of the carbon black with time will occur. On the other hand, if this ratio is too high, the stability as a polyimide precursor is poor, and the lot life may be shortened, and the above range is desirable.

The ratio of terminal amino groups to all terminal groups is determined as follows.
First, a polyimide precursor to be measured is dropped into a large amount of methanol to reprecipitate the polyimide precursor, followed by washing, filtration and drying. While obtaining the number average molecular weight of the obtained polyimide precursor by gel permeation chromatography, the obtained polyimide precursor is dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a solution having a known concentration, An equivalent amount of trifluoro acid anhydride diluted with acetonitrile is added and reacted at room temperature (25 ° C.), followed by reprecipitation to obtain a terminal amino group trifluoro acid anhydride derivatized polyimide precursor.
By analyzing the spectrum peak area value of derivatization by 19F-nuclear magnetic resonance analysis, the terminal amino group strength is obtained. By dividing the terminal amino group strength by the number average molecular weight obtained by the gel permeation chromatography method, the average number of terminal amino groups indicating the number of amino groups per molecule of the polyimide precursor is calculated.
If the average number of terminal amino groups determined by fluorine intensity analysis is “0”, both ends of the polyimide precursor are carboxylic acid groups derived from tetracarboxylic dianhydride (terminal anhydrous carboxy dehydrated by two carboxy groups). Group), that is, the ratio of terminal amino groups to all terminal groups is 0%, and if it is “2”, both ends of the polyimide precursor are amine groups derived from diamine components, that is, all terminal amino groups The ratio with respect to the terminal group is 100%. Therefore, the average number of terminal amino groups of the polyimide precursor in which 70% or more of all terminal groups are amino groups is 1.4 or more.
Based on this, the ratio of terminal amino groups to all terminal groups is calculated.

  A polyimide precursor is a tetracarboxylic dianhydride, a diamine compound, and a polymer, for example. Although it does not restrict | limit especially as a kind of polyimide precursor, The aromatic polyimide precursor which is a polymer of an aromatic tetracarboxylic dianhydride and an aromatic diamine compound is desirable from the point of the intensity | strength of the molded object obtained.

Typical examples of the aromatic tetracarboxylic acid include the following, for example, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2,3,4,4'-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1, 2,5,6-naphthalenetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) ether dianhydride, tetracarboxylic acid esters thereof, or mixtures of the above tetracarboxylic acids Is mentioned.
On the other hand, as aromatic diamine components, paraphenylenediamine, metaphenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminophenylmethane, benzidine, 3,3′-dimethoxybenzidine, 4,4′- Examples include diaminodiphenylpropane and 2,2-bis [4- (4-aminophenoxy) phenyl] propane.

  Here, in the polyimide precursor, in order to set the ratio of terminal amino groups to all terminal groups within the above range, 1) the molar ratio of the diamine component to tetracarboxylic dianhydride is adjusted beforehand (specifically, For example, a method in which the molar ratio of the diamine component to the tetracarboxylic dianhydride is adjusted to be excessive), and 2) the reaction of tetracarboxylic dianhydride and diamine component is 1: 1. There is a method in which the reaction is carried out at a molar ratio and the reaction is allowed to proceed until the desired viscosity is reached, and then the necessary amount of the diamine component is added to react.

-Acid conductive material-
The acidic conductive material has a pH of 3 or more and 4 or less. When the pH is less than 3, when the number of terminal amino groups of the polyimide precursor increases with time, the dispersion state of the acidic conductive material may easily change. When the pH is greater than 4, the dispersibility in the polyimide precursor solution However, many conductive paths are formed, and the volume resistivity of the molded body may not be a target value of about 9 log Ω · cm or more and 13 log Ω · cm or less. From this viewpoint, the above range is preferable.
The pH of the acidic conductive material is determined by adjusting an aqueous suspension of carbon black and measuring with a glass electrode. In addition, the pH of the acidic carbon black is adjusted by conditions such as the treatment temperature and treatment time in the oxidation treatment step.

  Examples of the acidic conductive material include carbon-based substances having an acid group (carbon black, carbon fiber, carbon nanotube, graphite, etc.), whisker having an acid group (tin oxide, indium oxide, antimony oxide, etc.) Product; potassium titanate, etc.). Among these, it is desirable to use carbon black.

  Examples of the acid group that the acidic conductive material has include a carboxyl group, a quinone group, a lactone group, and a hydroxyl group. When the conductive material has an acid group, it is considered that the dispersibility in the solution is improved and the dispersion stability is obtained.

  The acidic conductive material can be obtained, for example, by oxidizing the conductive materials listed above. As a method for oxidizing the conductive material, an air oxidation method in which the reaction is performed by contacting with air at a high temperature (for example, 800 ° C. or higher), for example, a reaction with nitrogen oxide or ozone at a normal temperature (for example, 30 ° C.). Examples thereof include a method, a method in which ozone is oxidized at a high temperature and then ozone oxidation at a low temperature (for example, 20 ° C. or lower), a contact method, and the like. Examples of the contact method include a channel method and a gas black method.

  The acidic conductive material may be manufactured by, for example, a furnace black method using gas or oil as a raw material. Furthermore, if necessary, after performing these treatments, a liquid phase oxidation treatment with nitric acid or the like may be performed.

  Specific examples of the acidic conductive material include “Special Black 350” (pH 3.5, volatile matter 2.2%) and “Special Black 100” (pH 3.3, volatile matter 2.2%) manufactured by Degussa. ), "Special Black 250" (pH 3.1, volatile content 2.0%), "Special Black 5" (pH 3.0, volatile content 15.0%), "Special Black 4" (pH 3.0) , Volatile content 14.0%), "Special Black 4A" (pH 3.0, volatile content 14.0%), "Printex 150T" (pH 4.0, volatile content 10%), "REGAL400R" manufactured by Cabot Corporation. (PH 4.0, volatile matter 3.5%) and the like.

  The content of the acidic conductive material is 15% by mass to 30% by mass with respect to the polyimide precursor, preferably 16% by mass to 28% by mass, and more preferably 18% by mass to 26% by mass. It is. Note that. When the content of the acidic conductive material is not within this range, characteristics such as volume resistivity of the molded body may not be the target value, so the above range is also preferable from this viewpoint.

-Solvent-
Examples of the solvent include organic polar solvents. Specifically, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; N, Acetamide solvents such as N-dimethylacetamide and N, N-diethylacetamide; Pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; Phenol, o-, m-, or p-cresol Phenol solvents such as xylenol, halogenated phenol and catechol; ether solvents such as tetrahydrofuran, dioxane and dioxolane; alcohol solvents such as methanol, ethanol and butanol; cellosolv systems such as butyl cellosolve; and hexamethylphosphor De, and the like and γ- butyrolactone.
Among these, pyrrolidone solvents are preferable, and N-methyl-2-pyrrolidone (NMP) is more preferable.
A solvent may use only 1 type or may use 2 or more types together.

  The content of the solvent is preferably 70% by mass or more and 80% by mass or less, and more preferably 76% by mass or more and 78% by mass or less with respect to the total amount of the thermosetting solution, from the viewpoint of dispersibility of the acidic conductive material. preferable.

  In addition, the said organic polar solvent is used also as a polymerization solvent used when a tetracarboxylic dianhydride and a diamine compound are made to synthesize | combine a polyimide precursor, The said organic polar solvent is used individually or in mixture. Is preferred. As the polymerization solvent, aromatic hydrocarbons such as xylene and toluene may be further used. The polymerization solvent for the polyimide precursor is not particularly limited as long as it dissolves the polyimide precursor.

-Other additives-
The thermosetting solution according to the present embodiment may include other additives, for example.
Examples of other additives include a dispersant. As the dispersant, for example, a low molecular weight or a high molecular weight may be used, and any type of dispersant selected from cationic, anionic and nonionic may be used. It is preferable to use a nonionic polymer as a dispersant.

Nonionic polymers include poly (N-vinyl-2-pyrrolidone), poly (N, N′-diethylacrylazide), poly (N-vinylformamide), poly (N-vinylacetamide), poly (N -Vinylphthalamide), poly (N-vinylsuccinamide), poly (N-vinylurea), poly (N-vinylpiperidone), poly (N-vinylcaprolactam), poly (N-vinyloxazoline) and the like.
These nonionic polymers may be used alone or in combination of two or more. Of these, poly (N-vinyl-2-pyrrolidone) is preferable.
The compounding amount of the nonionic polymer in the thermosetting solution is preferably 0.2% by mass or more and 3% by mass or less with respect to the polyimide precursor.

-Preparation of thermosetting solution-
The thermosetting solution according to the present embodiment may be prepared by, for example, dissolving a polyimide precursor in a solution in which an acidic conductive material is dispersed in a solvent, or a solution in which a polyimide precursor is dissolved in a solvent. Alternatively, it may be prepared by dispersing an acidic conductive material. Moreover, the thermosetting solution which concerns on this embodiment may prepare the thermosetting solution from which the density | concentration of an acidic electrically conductive material differs previously, and may mix this.
Examples of the method for dispersing the acidic conductive material include a ball mill, a sand mill, a bead mill, and a jet mill (counter collision type disperser).
Regardless of which dispersion method is used, from the viewpoint of improving dispersibility, the viscosity of the solution during dispersion (a solution containing an acidic conductive material and a polyimide precursor) may be 1 Pa · s or more and 50 Pa · s or less. desirable.

In the case where the polyimide precursor is dissolved in the solution in which the acidic conductive material is dispersed, the viscosity is preferably maintained. For example, there is a method of adjusting the temperature of the solution at the time of dispersion. Specifically, at the time of dispersion, for example, it is desirable to adjust the temperature of the solution to be 50 ° C. or higher.
In addition, for the heating of the solution at the time of dispersion, for example, heat generated by mechanical energy at the time of dispersion may be used, or heat may be applied to a container used at the time of dispersion.

  For example, when the acidic conductive material is dispersed in a solution in which the polyimide precursor is dissolved, the concentration of the acidic conductive material at the time of dispersion is desirably 50% by mass or more and 200% by mass or less with respect to the solid content mass of the solution. . This is because it may take time for the conductive agent to disperse, and it is considered more efficient to reduce the amount of liquid and disperse the conductive agent at a high concentration.

-Application-
The thermosetting solution which concerns on this embodiment is utilized for manufacture of molded objects, such as a conductive or semiconductive film (conductive or semiconductive sheet) and a tubular body, for example.

(Tubular body and manufacturing method thereof)
The tubular body according to this embodiment (hereinafter referred to as “endless belt”) is a tubular body having a cured layer (hereinafter referred to as “polyimide layer”) of a thermosetting solution according to this embodiment. That is, the endless belt according to the present embodiment is an endless belt having a polyimide layer obtained by converting the polyimide precursor of the thermosetting solution according to the present embodiment to imide by heating.
The endless belt according to the present embodiment may be composed of a polyimide layer alone, for example, a laminate of a plurality of polyimide layers or a polyimide layer as a base layer, and at least an inner peripheral surface and an outer peripheral surface thereof. A laminate in which a functional layer (for example, a release layer or an elastic layer) is laminated on one side may be used.

Hereinafter, the endless belt according to the present embodiment will be described together with the manufacturing method thereof.
The endless belt manufacturing method according to the present embodiment includes a step of forming a coating film of a thermosetting solution (hereinafter simply referred to as “thermosetting solution”) according to the present embodiment (hereinafter referred to as “coating layer forming step”). And a step of heat-curing the coating film (hereinafter referred to as “heat-curing step”).

-Coating film formation process-
In the coating film forming step, for example, a thermosetting solution is applied to the core body to form a coating film of the thermosetting solution. Examples of the material of the core include metal (aluminum, stainless steel, etc.), fluororesin, silicone resin, or metal whose surface is covered with these resins. When metal is used as the core material, the endless belt formed on the core body can be easily removed from the core body by, for example, plating the surface with chromium or nickel in advance, or applying a release agent. May be.

  Examples of the desirable shape of the core include a cylindrical shape and a columnar shape.

  The method for applying the thermosetting solution to the core is not particularly limited. For example, the outer surface coating method described in JP-A-6-23770, etc., the dip coating method described in JP-A-3-180309, etc., the spiral coating method described in JP-A-9-85756, etc. Also, a spin coating method can be cited, and it is selected according to the shape and size of the core.

  Hereinafter, the method of applying the thermosetting solution will be described by taking as an example the case of using the spiral coating method.

  As shown in FIGS. 1 and 2, in the film forming apparatus 40, the thermosetting solution 20A is applied to the outer surface of the core body 34 while rotating the cylindrical core body 34 in the circumferential direction, and this is applied to the core. Application is performed while leveling with a blade 29 arranged in contact with the outer surface of the body 34.

  In the film forming apparatus 40, the thermosetting solution 20 </ b> A stored in the storage unit 20 is supplied to the outer surface of the core body 34 rotated in the direction of arrow A by the pump 24 through the supply pipe 22 and the nozzle 26. To do.

  The thermosetting solution 20 </ b> A applied in a streak pattern on the outer surface of the core body 34 is smoothed by the blade 29. For this reason, 10 A of coating films are formed on the core body 34, suppressing that the spiral stripe | line by the thermosetting solution 20A remains. Examples of the rotational speed of the core 34 at the time of application include 20 rpm to 300 rpm, and the relative movement speed between the nozzle 26 and the core 34 is, for example, 0.1 m / min to 2.0 m / min. Is mentioned.

  The film forming apparatus 40 and the core body 34 are relatively moved from one end side in the longitudinal direction of the core body 34 toward the other end side (see the arrow B direction in FIG. 1). As a result, a coating film 10A made of the thermosetting solution 20A is formed on the core body 34 (see FIG. 3).

  In the film forming apparatus 40, the thermosetting solution 20A stored in the storage unit 20 and the thermosetting solution 20A flowing through the supply pipe 22, the pump 24, and the nozzle 26 are maintained at a target temperature. A temperature maintaining device 32 is provided. The temperature maintaining device 32 is configured to maintain the thermosetting solution 20A stored in the storage unit 20 and the thermosetting solution 20A flowing through the supply pipe 22, the pump 24, and the nozzle 26 at a target temperature. If it is.

For example, the temperature maintaining device 32 includes a configuration including the heat retaining member 28, the temperature adjusting device 30, the temperature measuring device 36, and the control unit 38.
The heat retaining member 28 is a member having a heat retaining function, and is provided so as to cover the storage unit 20, the supply pipe 22, the pump 24, and the nozzle 26. As the heat retaining member 28, a known member having a heat retaining function may be used. The temperature adjusting device 30 is a device that maintains the temperature inside the heat retaining member 28 (that is, inside the storage unit 20, the supply pipe 22, the pump 24, and the nozzle 26) at a target temperature. As the temperature adjusting device 30, a known device having a function of adjusting the temperature (heating or cooling function) may be used. The inside of the heat retaining member 28 is cooled by the temperature adjusting device 30, so that the reservoir 20, the supply pipe 22, the pump 24, and the thermosetting solution 20 </ b> A in the nozzle 26 exist inside the heat retaining member 28. The target temperature is maintained by the device 30.

The temperature measuring device 36 is provided in the storage unit 20 (for example, the bottom inside the storage unit 20), and measures the temperature of the thermosetting solution 20A stored in the storage unit 20.
The control unit 38 is electrically connected to the temperature measuring device 36 and the temperature adjusting device 30, and based on the temperature information received from the temperature measuring device 36, the inside of the heat retaining member 28 maintains the target temperature. Next, the temperature adjusting device 30 is controlled.

-Heat curing process-
Next, the coating film 10A formed by the above-described coating film forming process is heat-cured (heat-curing process). However, it is desirable that the coating film 10A be dried or semi-cured before this step.
Here, “drying” refers to heating to evaporate the solvent contained in the thermosetting solution constituting the coating film 10A. In practice, for example, the time is about 100 ° C. or more and 200 ° C. or less. It is set (for example, 30 minutes or more and 60 minutes or less). “Semi-cured” refers to a state in which the polyimide precursor contained in the thermosetting solution is partially imidized to such an extent that the imidization reaction of the polyimide precursor does not proceed. Actually, for example, when a time according to the purpose is set at about 120 ° C. or more and 250 ° C. or less, the coating film 10A becomes a semi-cured state, and the strength is increased as compared with the dried state.

  These drying or semi-curing is carried out by setting the temperature and time depending on the polyimide precursor and the solvent type, but if the solvent completely evaporates from the coating film 10A, the coating film 10A may easily crack. Therefore, it is desirable to leave a certain amount of solvent (for example, about 5% by mass or more and 40% by mass or less at the beginning).

  The drying time may be shorter as the temperature is higher. It is also desirable to apply hot air during drying. The temperature may be increased stepwise or at a constant rate.

  In order to prevent the coating film 10 </ b> A from dripping, it is desirable that the drying be performed while rotating the axial direction of the core body 34 along the horizontal direction and at a rotational speed of 5 rpm to 60 rpm. In the next heat curing step, it is desirable to heat cure in a state where the axial direction of the core body 34 is along the vertical direction.

  In the heat curing step, the coating film 10A dried or semi-cured as described above is heated to imidize the polyimide precursor contained in the coating film 10A to form a polyimide layer, thereby obtaining the endless belt 10. (See FIG. 3).

  For example, imidization is performed by heating to 250 ° C. or higher and 450 ° C. or lower (desirably, 300 ° C. or higher and 400 ° C. or lower), whereby the polyimide precursor is cured to become a polyimide resin. Examples of the heating time include 30 minutes or more and 180 minutes or less.

  In this heat curing step, the higher the heating temperature, the shorter the time. It is also desirable to apply hot air during heating or irradiate infrared energy. The heating temperature may be increased stepwise or at a constant rate.

  Thus, a polyimide layer is formed on the core body 34, and the endless belt 10 is obtained (see FIG. 3). And the endless belt 10 is isolate | separated from the core body 34, and a post-process is given as needed.

  As thickness of the endless belt 10 which concerns on this embodiment, the range of 30 micrometers or more and 150 micrometers or less is mentioned, for example.

  The endless belt 10 according to the present embodiment is suitably used for an intermediate transfer belt, a paper conveyance transfer belt, a paper conveyance belt, a fixing belt, and the like of an image forming apparatus using an electrophotographic system such as a copying machine or a printer.

(Image forming device)
The image forming apparatus according to the present embodiment includes, for example, an image holding member, a charging unit that charges the surface of the image holding member, a latent image forming unit that forms a latent image on the surface of the charged image holding member, and an image holding unit. A developing means for developing a latent image on the surface of the body with toner to form a toner image, an intermediate transfer body to which the toner image formed on the surface of the image holding body is transferred, and a surface of the image holding body. Primary transfer means for primary transfer of the toner image onto the surface of the intermediate transfer member, secondary transfer means for secondary transfer of the toner image transferred onto the surface of the intermediate transfer member to the transfer medium, and transfer to the recording medium. And an endless belt according to the present embodiment is applied as an intermediate transfer member.

  Note that the image forming apparatus according to the present embodiment includes the endless belt according to the present embodiment as, for example, a sheet conveying transfer belt, a sheet conveying belt, and a fixing belt in addition to the intermediate transfer belt of the image forming apparatus. Also good.

  Details of the image forming apparatus according to the present embodiment will be described below with reference to FIG. FIG. 5 is a schematic configuration diagram illustrating the image forming apparatus according to the present embodiment.

  The image forming apparatus 100 according to the present embodiment is a so-called tandem system, and is an embodiment in which the endless belt according to the present embodiment is applied as an intermediate transfer belt.

  As shown in FIG. 5, the image forming apparatus 100 according to the present embodiment sequentially includes charging devices 102 a to 102 d around the four image holding bodies 101 a to 101 d made of an electrophotographic photosensitive member along the rotation direction. Exposure devices 114a to 114d, developing devices 103a to 103d, primary transfer devices (primary transfer rolls) 105a to 105d, and image carrier cleaning devices 104a to 104d are arranged. Note that a static eliminator may be provided in order to remove residual potential remaining on the surfaces of the image carriers 101a to 101d after transfer.

  Further, an intermediate transfer belt 107 is stretched around tension rolls 106a to 106d, a drive roll 111, and a backup roll 108 to constitute a transfer unit. By these tension rolls 106a to 106d, the drive roll 111, and the backup roll 108, the intermediate transfer belt 107 is in contact with the surfaces of the image carriers 101a to 101d, and the image carriers 101a to 101d and the primary transfer rolls 105a to 105a. It moves in the direction of arrow A between 105d. A portion where the primary transfer rolls 105a to 105d come into contact with the image carriers 101a to 101d via the intermediate transfer belt 107 becomes a primary transfer portion, and a contact portion between the image carriers 101a to 101d and the primary transfer rollers 105a to 105d. A primary transfer voltage is applied to.

  Further, as a secondary transfer device, a backup roll 108 and a secondary transfer roll 109 are arranged to face each other with an intermediate transfer belt 107 interposed therebetween. The transfer medium 115 such as paper moves in the direction of arrow B between the intermediate transfer belt 107 and the secondary transfer roll 109 while contacting the surface of the intermediate transfer belt 107, and then passes through the fixing device 110. A portion where the secondary transfer roll 109 comes into contact with the backup roll 108 via the intermediate transfer belt 107 becomes a secondary transfer portion, and a secondary transfer voltage is applied to a contact portion between the secondary transfer roll 109 and the backup roll 108. . Further, intermediate transfer belt cleaning devices 112 and 113 are arranged so as to come into contact with the intermediate transfer belt 107 after transfer.

  In the image forming apparatus 100 having this configuration, the image carrier 101a rotates in the direction of arrow C, and the surface thereof is uniformly charged by the charging device 102a, and then the first color is exposed by the exposure device 114a such as laser light. An electrostatic latent image is formed. The formed electrostatic latent image is developed (visualized) with toner by a developing device 103a containing toner corresponding to the color to form a toner image. The developing devices 103a to 103d contain toners (for example, yellow, magenta, cyan, and black) corresponding to the electrostatic latent images of the respective colors.

  The toner image formed on the image carrier 101a is electrostatically transferred (primary transfer) onto the intermediate transfer belt 107 by the primary transfer roll 105a when passing through the primary transfer portion. Thereafter, the primary transfer rollers 105b to 105d perform primary transfer so that the second color, third color, and fourth color toner images are sequentially superimposed on the intermediate transfer belt 107 that holds the first color toner image. Finally, a color multiple toner image is obtained.

  The multiple toner images formed on the intermediate transfer belt 107 are electrostatically collectively transferred to the transfer medium 115 when passing through the secondary transfer portion. The transfer medium 115 onto which the toner image has been transferred is conveyed to the fixing device 110, subjected to fixing processing by at least one of heating and pressing, and then discharged outside the apparatus.

  Residual toner is removed from the image carriers 101a to 101d after the primary transfer by the image carrier cleaning devices 104a to 104d. On the other hand, the residual toner is removed from the intermediate transfer belt 107 after the secondary transfer by the intermediate transfer belt cleaning devices 112 and 113 to prepare for the next image forming process.

-Image carrier-
As the image carriers 101a to 101d, known electrophotographic photosensitive members are widely applied. As the electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer made of an inorganic material, an organic photoreceptor having a photosensitive layer made of an organic material, or the like is used. In the organic photoconductor, a function-separated type organic photoconductor in which a charge generation layer that generates charges upon exposure and a charge transport layer that transports charges are stacked, and a function that generates charges and a function that transports charges are the same. A single layer type organic photoreceptor fulfilled by the layer is preferably used. In addition, as the inorganic photoconductor, a photoconductive layer composed of amorphous silicon is preferably used.

  The shape of the image carrier is not particularly limited, and a known shape such as a cylindrical drum shape, a sheet shape, or a plate shape is employed.

-Charging device-
The charging devices 102a to 102d are not particularly limited, and are, for example, conductive (here, “conductive” means, for example, a volume resistivity of less than 10 ⁷ Ω · cm. In this specification, special mention is made. The same is true unless otherwise specified.) Or semiconductive (here, “semiconductive” means, for example, a volume resistivity of 10 ⁷ to 10 ¹³ Ωcm. In this specification, the same applies unless otherwise specified. .) Widely used are known chargers such as contact chargers using rollers, brushes, films or rubber blades, scorotron chargers using corona discharge, and corotron chargers. Among these, a contact charger that generates less ozone and performs efficient charging is preferable.

  The charging devices 102a to 102d normally apply a direct current to the image carriers 101a to 101d, but an alternating current may be further superimposed and applied.

-Exposure device-
The exposure devices 114a to 114d are not particularly limited, and for example, on the surfaces of the image carriers 101a to 101d, light sources such as semiconductor laser light, LED light, or liquid crystal shutter light, or from these light sources through a polygon mirror. A well-known exposure apparatus such as an optical system apparatus that exposes a desired image is widely applied.

-Developer-
The developing devices 103a to 103d are selected according to the purpose. For example, a known developing device that develops a one-component developer or a two-component developer in contact or non-contact with a brush, a roller, or the like can be used.

  The toner (developer) is not particularly limited, and includes, for example, a binder resin and a colorant.

-Primary transfer roll-
The primary transfer rolls 105a to 105d may be either a single layer or a multilayer. For example, in the case of a single layer structure, it is composed of a roll in which an appropriate amount of conductive particles such as carbon black is blended in foamed or non-foamed silicone rubber, urethane rubber, ethylene-propylene-diene rubber (EPDM), or the like. The resistance value is preferably in the range of 10 ⁵ Ω to 10 ¹⁰ Ω. A voltage of 1.0 kV to 5.5 kV is applied to the primary transfer rolls 105a to 105d, and the toner is transferred by an electric field generated between the image carriers 101a to 101d.

-Image carrier cleaning device-
The image carrier cleaning devices 104a to 104d are for removing residual toner adhering to the surfaces of the image carriers 101a to 101d after the primary transfer process. In addition to the cleaning blade, brush cleaning, roll cleaning, or the like Is used. Among these, it is preferable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

-Secondary transfer roll-
The layer structure of the secondary transfer roll 109 is not particularly limited. For example, in the case of a three-layer structure, the layer structure includes a core layer, an intermediate layer, and a coating layer covering the surface. The core layer is a foamed material such as silicone rubber, urethane rubber or EPDM in which conductive particles are dispersed, and the intermediate layer is composed of these non-foamed materials. Examples of the material for the coating layer include tetrafluoroethylene-hexafluoropropylene copolymer and perfluoroalkoxy resin. The volume resistivity of the secondary transfer roll 109 is preferably 10 ⁷ Ωcm or less. A two-layer structure excluding the intermediate layer is also possible.

−Backup roll−
The backup roll 108 forms a counter electrode of the secondary transfer roll 109. The layer structure of the backup roll 108 may be either a single layer or a multilayer. For example, in the case of a single layer structure, it is composed of a roll in which a suitable amount of conductive particles such as carbon black is blended in silicone rubber, urethane rubber, EPDM or the like. In the case of a two-layer structure, it is composed of a roll in which the outer peripheral surface of the elastic layer composed of the rubber material as described above is covered with a high resistance layer. The surface resistivity of the backup roll 108 is preferably in the range of 10 ⁷ Ω / □ to 10 ¹¹ Ω / □.

  A voltage of 1 kV to 6 kV is normally applied between the shafts of the backup roll 108 and the secondary transfer roll 109. Further, instead of applying a voltage to the shaft of the backup roll 108, a voltage may be applied between the electrically conductive electrode member brought into contact with the backup roll 108 and the secondary transfer roll 109. Examples of the electrode member include a metal roll, a conductive rubber roll, a conductive brush, a metal plate, or a conductive resin plate.

-Fixing device-
As the fixing device 110, for example, a known fixing device such as a heat roller fixing device, a pressure roller fixing device, or a flash fixing device is widely applied.

-Intermediate transfer belt cleaning device-
As the intermediate transfer belt cleaning devices 112 and 113, in addition to a cleaning blade, brush cleaning, roll cleaning, and the like can be used. Among these, it is preferable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

  In the above-described embodiment, a so-called tandem image forming apparatus including a plurality of image carriers has been described. However, the present invention is not limited to this. For example, one image carrier is used and intermediate transfer is performed for the number of colors. A well-known apparatus such as a so-called multi-cycle type (for example, four-cycle type) image forming apparatus in which the belt rotates and forms an image can be applied.

  Hereinafter, the present embodiment will be described more specifically by way of examples. However, the present embodiment is not limited to these examples. In the examples, “part” represents “part by mass”.

Example 1
The endless belt 10 was manufactured through the following steps.
First, a polyimide precursor solution composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (solid content concentration 18%, solvent is N-methylpyrrolidone, 25 ° C. The viscosity was 10 Pa · s, and the ratio of terminal amino groups to all terminal groups was 90% (average terminal amine group number 1.8). Then, carbon black (trade name: Special Black 4, manufactured by Evonik Degussa, carbon black having hydroxyl groups and carboxyl groups as acid groups) is added to the polyimide precursor solution as a conductive agent having acid groups. The mixture was mixed by 80% in mass ratio, and then dispersed by a counter collision type disperser (Geanus PY, manufactured by Genus Co., Ltd.). During dispersion, the temperature of the cooling water was adjusted to maintain the solution temperature at 50 ° C., and the collision operation was repeated 5 times for dispersion. Thereby, a dispersion A having a viscosity at 50 ° C. of 4 Pa · s and a viscosity at 25 ° C. of 20 Pa · s was prepared.

  Next, a polyimide precursor solution having an amount of carbon black of 20 parts in the dispersion A (trade name: solid content concentration: 18%, solvent: N-methylpyrrolidone, viscosity at 25 ° C., 100 Pa · s, terminal amino group) 90% of the total terminal groups (average number of terminal amine groups 1.8)) was added and mixed and stirred by a planetary type stirring apparatus (manufactured by Aikosha Seisakusho Co., Ltd.) to prepare a polyimide precursor solution.

  In order to produce an endless belt, a cylindrical member made of SUS304 having an outer diameter of 366 mm, a wall thickness of 6 mm, and a length of 900 mm was separately prepared, and the surface was roughened to Ra 0.4 μm by blasting with spherical alumina particles. Further, as the holding plate for holding the cylindrical member, a disc having a thickness of 8 mm, an outer diameter that fits into the opening of the cylindrical member, and four vent holes having a diameter of 100 mm is provided. It produced with the material, and it fitted and welded to the opening part (width direction both end surface) of the said cylindrical member. On the surface of the cylindrical member, a silicone release agent (trade name: Sepacoat, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied and baked at 300 ° C. for 1 hour. In this way, a core body 34 to which a thermosetting solution was applied was produced.

  Next, a thermosetting solution was applied onto the produced core body 34 using the film forming apparatus 40 shown in FIGS. 1 and 2. The thermosetting solution prepared in this example was placed in the storage unit 20 of the film forming apparatus shown in FIGS. 1 and 2 and stored at 20 ° C. for 3 days by the temperature maintaining device 32.

  In addition, this film-forming apparatus 40 connects the mono-pump 24 to the reservoir 20 containing the thermosetting solution (see 20A in FIG. 1) prepared in this example, and 20 ml per minute from the nozzle 26. It discharged and performed from the position of 40 mm from the one end part of the prepared core body 34 to the position of 40 mm from the other end part (coating film formation process). As described above, as the thermosetting solution 20A, during the period from dispersion to application to the core body 34 (period from the end of dispersion to application to the core body), the solution is kept at 20 ° C. Stored for 3 days. As the blade 29, a stainless steel plate having a thickness of 0.2 mm processed to a width of 20 mm and a length of 50 mm was used.

Then, the core body 34 is rotated in the rotation direction A at 60 rpm, and after the discharged solution 20A adheres to the core body 34, the blade 29 is pressed against the surface thereof, and the axial direction of the core body 34 (arrow in FIG. 1) B)) at a speed of 210 mm / min. Thereby, the spiral streaks on the surface of the coating film 10A disappeared. At the end of the coating film 10A, the blade 29 was retracted 50 mm so as not to contact the surface of the core body 34 directly. Thereby, the coating film 10A having a film thickness of 500 μm was formed (coating film forming step). This thickness corresponds to a film thickness of 80 μm of the endless belt 10 after passing through the following heat curing step. Thereafter, the core body 34 was placed in a drying apparatus at 170 ° C. while being rotated at 10 rpm, and dried for 20 minutes. Thereby, the amount of residual solvent became 40 mass%, and the coating film 10A of the state which does not droop even if it stopped the rotation of the core body 34 and was lengthened was obtained.
Thereafter, the core 34 is lowered from the turntable and placed in a heating furnace in a vertical direction (rotating axis direction is vertical), and heated at 200 ° C. for 30 minutes and at 300 ° C. for 30 minutes, and the remaining solvent is dried and imidized. Were performed simultaneously (heat curing step). After cooling to room temperature (25 ° C.), the coating film 10A (endless belt 10) that had been heat-cured from the core body 34 was extracted.
Furthermore, the center of this heat-cured coating film 10A (endless belt 10) was cut, and unnecessary portions were cut from both ends to obtain two endless belts 10 having a width of 360 mm. When the film thickness of the endless belt 10 was measured with a dial gauge, it was 80 μm.

  Similarly, an endless belt 10 was produced under the same conditions and the same materials as described above except that the period from the preparation of the thermosetting solution to the application to the core 34 was stored at 20 ° C. for 10 days. In the same manner, an endless belt 10 was produced under the same conditions and the same materials as described above except that the period from the preparation of the thermosetting solution to the application to the core 34 was stored at 20 ° C. for 20 days.

(Example 2)
In Example 2, as a polyimide precursor solution for preparing dispersion A, a polyimide precursor solution (trade name: solid content concentration 18%, solvent is N-methylpyrrolidone, viscosity at 25 ° C., 10 Pa · s, terminal A ratio of 80% of amino groups to all terminal groups (average number of terminal amine groups: 1.6)) was used.
Further, as a polyimide precursor solution for adjusting the concentration of carbon black in dispersion A, a polyimide precursor solution (solid content concentration: 18%, solvent: N-methylpyrrolidone, viscosity at 25 ° C., 100 Pa · s, terminal amino group) 80% of all terminal groups (average number of terminal amine groups 1.6) was used.
Other than these, under the same conditions as in Example 1, three types of endless belts 10 (thermosetting solutions stored at 20 ° C. for 3 days, stored at 20 ° C. for 10 days, and stored at 20 ° C. for 20 days) 1) was produced.

(Example 3)
In Example 3, as a polyimide precursor solution for preparing dispersion A, a polyimide precursor solution (solid content concentration 18%, solvent is N-methylpyrrolidone, viscosity at 25 ° C., 10 Pa · s, terminal amino group) A ratio of 70% based on the total terminal groups (average terminal amine group number 1.4) was used.
Further, as a polyimide precursor solution for adjusting the concentration of carbon black in dispersion A, a polyimide precursor solution (solid content concentration: 18%, solvent: N-methylpyrrolidone, viscosity at 25 ° C., 100 Pa · s, terminal amino group) 70% of the total terminal groups (average number of terminal amine groups 1.4).
Other than these, under the same conditions as in Example 1, three types of endless belts 10 (thermosetting solutions stored at 20 ° C. for 3 days, stored at 20 ° C. for 10 days, and stored at 20 ° C. for 20 days) 1) was produced.

(Comparative Example 1)
In Comparative Example 1, as a polyimide precursor solution for preparing dispersion A, a polyimide precursor solution (solid content concentration 18%, solvent is N-methylpyrrolidone, viscosity at 25 ° C., 10 Pa · s, terminal amino group) A ratio of 65% with respect to all terminal groups (average number of terminal amine groups: 1.3)) was used.
Further, as a polyimide precursor solution for adjusting the concentration of carbon black in dispersion A, a polyimide precursor solution (trade name: Uimide, manufactured by Unitika Ltd., solid content concentration: 18%, solvent: N-methylpyrrolidone, 25 ° C. The viscosity was 100 Pa · s, and the ratio of terminal amino groups to all terminal groups was 65% (average number of terminal amine groups: 1.3).
Other than these, under the same conditions as in Example 1, three types of endless belts 10 (thermosetting solutions stored at 20 ° C. for 3 days, stored at 20 ° C. for 10 days, and stored at 20 ° C. for 20 days) 1) was produced.

(Comparative Example 2)
In Comparative Example 2, as a polyimide precursor solution for preparing dispersion A, a polyimide precursor solution (trade name: solid content concentration: 18%, solvent: N-methylpyrrolidone, viscosity at 25 ° C., 10 Pa · s, terminal A ratio of 55% of amino groups to all terminal groups (average number of terminal amine groups 1.1) was used.
Further, as a polyimide precursor solution for adjusting the concentration of carbon black in dispersion A, a polyimide precursor solution (solid content concentration: 18%, solvent: N-methylpyrrolidone, viscosity at 25 ° C., 100 Pa · s, terminal amino group) Was 55% of the total terminal groups (average number of terminal amine groups 1.1).
Other than these, under the same conditions as in Example 1, three types of endless belts 10 (thermosetting solutions stored at 20 ° C. for 3 days, stored at 20 ° C. for 10 days, and stored at 20 ° C. for 20 days) 1) was produced.

(Comparative Example 3)
In Comparative Example 3, as a polyimide precursor solution for preparing dispersion A, a polyimide precursor solution (solid content concentration 18%, solvent is N-methylpyrrolidone, viscosity at 25 ° C., 50 Pa · s, terminal amino group) A ratio of 45% with respect to all terminal groups (average number of terminal amine groups 0.9) was used.
Further, as a polyimide precursor solution for adjusting the concentration of carbon black in dispersion A, a polyimide precursor solution (solid content concentration: 18%, solvent: N-methylpyrrolidone, viscosity at 25 ° C., 100 Pa · s, terminal amino group) Of 45% of all terminal groups (average number of terminal amine groups 0.9).
Other than these, under the same conditions as in Example 1, three types of endless belts 10 (thermosetting solutions stored at 20 ° C. for 3 days, stored at 20 ° C. for 10 days, and stored at 20 ° C. for 20 days) 1) was produced.

(Examples 4-5, Comparative Examples 4-7)
According to Table 1, three types of endless belts 10 (thermosetting solution at 20 ° C. under the same conditions as in Example 1) except that the ratio of terminal amino groups of the polyimide precursor, the type of carbon black, and the content were changed. 3 days, 20 days at 20 ° C. and 20 days at 20 ° C.).

<Evaluation of volume resistivity variation due to difference in solution storage time>
For the endless belts prepared in the above examples and comparative examples, the volume resistivity of the endless belt prepared by storing the thermosetting solution for 3 days and the volume resistance of the endless belt prepared by storing the thermosetting solution for 10 days The ratio and the volume resistivity of an endless belt prepared by storing the thermosetting solution for 20 days were measured by the following measuring methods, and the measurement results are shown in Table 1. The difference between the volume resistivity of the endless belt prepared by storing the solution for 3 days and the common logarithm of the volume resistivity of the endless belt prepared by storing the thermosetting solution for 20 days is obtained, and the fluctuation of the volume resistivity is calculated. evaluated.
The evaluation criteria were as follows.

―Evaluation of volume resistivity variation―
G1: When the difference in the common logarithm of the volume resistivity of the produced endless belt is less than 0.3 when the solution is stored for 3 days and when stored for 20 days.
G2: When the difference in the common logarithm of the volume resistivity of the produced endless belt is 0.3 or more and 0.8 or less when the solution is stored for 3 days and when it is stored for 20 days.
G3: When the difference in common logarithm of volume resistivity of the produced endless belt is greater than 0.8 when the solution is stored for 3 days and when stored for 20 days.

  The volume resistivity of the endless belt was measured by the following measuring method.

  When measuring the volume resistivity, the endless belt 10 is cut in the width direction to form a flat plate, the flat endless belt 10 is sandwiched between the circular electrode 52 and the counter electrode 54, and a voltage is applied between both electrodes. Was applied to measure the volume resistivity.

(Measurement of volume resistivity)
The volume resistivity of the endless belt was measured using a volume resistivity measuring device 50 shown in FIG. 4 according to JIS K6911. Specifically, as shown in FIG. 4, the volume resistivity measuring device 50 includes a circular electrode 52 and a flat counter electrode 54. The circular electrode 52 has a cylindrical electrode portion 56 and a cylindrical cylindrical electrode portion 58 having an inner diameter larger than the outer diameter of the cylindrical electrode portion 56 and surrounding the cylindrical electrode portion 56 with a certain interval. And. The counter electrode 54 is an electrode arranged to face the circular electrode 52 through the endless belt 10 to be measured.

  Examples of the circular electrode 52 include a UR-100 probe manufactured by Mitsubishi Analytech Co., Ltd., Hirestar UP. Moreover, as the counter electrode 54, the flat electrode made from SUS304 is mentioned, for example. Examples of the current measuring device include an R8340A digital ultrahigh resistance / microammeter (manufactured by Advantest Corporation).

  The volume resistivity measuring device 50 in this example uses a UR-100 probe (manufactured by Mitsubishi Analytech) having a double ring electrode structure as the circular electrode 52, and is made of stainless steel (SUS304) and has a thickness of 5 mm as the counter electrode 54. The plate-shaped member (80 mm × 500 mm) was used.

  When measuring the volume resistivity, the endless belt 10 is sandwiched between the cylindrical electrode portion 56 of the circular electrode 52 and the counter electrode 54, and a weight of mass 2.0 kg ± 0.1 kg is placed on the circular electrode 52. Thus, a uniform load is applied to the endless belt 10. Then, the digital ultrahigh resistance / microammeter was electrically connected to the circular electrode 52, and the measurement conditions were a charge time of 10 sec, a discharge time of 1 sec, and an applied voltage of 500V.

At this time, the volume resistivity of the endless belt 10 to be measured is ρv, the thickness t (μm) of the endless belt 10, the reading of the R8340A digital ultrahigh resistance / microammeter is R, and the volume resistivity of the circular electrode 52 is corrected. Let the coefficient be RCF (V). In addition, when the UR-100 probe of Hiresta UP manufactured by Mitsubishi Analytech Co., Ltd. is used as the circular electrode 52, RCF (V) = 19.635 according to the “Insulator series” catalog of Dia Instruments. It is. For this reason, the volume resistivity of the endless belt 10 is calculated by the following formula (1).
Formula (1): ρv [Ω · cm] = R × RCF (V) × (10000 / t) = R × 19.635 × (10000 / t)

According to the above measurement method, the endless belt prepared by storing the thermosetting solution for 3 days, the endless belt prepared by storing the tube for 10 days, and the endless belt prepared by storing for 20 days were prepared in each Example and Comparative Example. For each of the endless belts, the volume resistivity when a voltage of 500 V was applied under the condition of 22 ° C. and 55% RH was measured. The measurement results are shown in Table 2, and the common logarithm of the volume resistivity is shown. The difference of (logΩ / □) is shown in Table 2.
In addition, the common logarithm value A of the volume resistivity of the endless belt produced by storing the thermosetting solution for 3 days and the common logarithm value B of the volume resistivity of the endless belt produced by storing the thermosetting solution for 20 days. Table 2 shows the absolute value of the difference between the two values (indicated as | A−B | in the table).

  Hereinafter, Table 1 shows details of each example, and Table 2 shows the results of the evaluation.

  From the above results, it can be seen that in this example, fluctuations are suppressed by the intended volume resistivity of the endless belt due to the difference in the storage time of the thermosetting solution compared to the comparative example.

100 Image forming apparatus 101Y, 101M, 101C, 101BK Photosensitive drum 102 Intermediate transfer belt 105 to 108 Developer 200 Image forming apparatus 200Y, 200M, 200C, 200Bk Image forming unit 206 Transfer conveyance belt

Claims (5)

A polyimide precursor in which 70% or more of all terminal groups are amino groups;
A conductive material having a content of 15% by mass to 30% by mass with respect to the polyimide precursor, a pH of 3 to 4 and having an acidic group;
A solvent,
A thermosetting solution.   The thermosetting solution according to claim 1, wherein the conductive material is carbon black.   A tubular body having a cured layer of the thermosetting solution according to claim 1. Forming a coating film of the thermosetting solution according to claim 1 or 2,
Heat-curing the coating film;
The manufacturing method of the tubular body which has this. An image carrier,
Charging means for charging the surface of the image carrier;
Latent image forming means for forming a latent image on the surface of the charged image carrier;
Developing means for developing a latent image on the surface of the image carrier with toner to form a toner image;
An intermediate transfer member to which the toner image formed on the surface of the image holding member is transferred, the intermediate transfer member comprising the tubular member according to claim 3,
Primary transfer means for primarily transferring the toner image formed on the surface of the image carrier to the surface of the intermediate transfer member;
Secondary transfer means for secondary transfer of the toner image transferred to the surface of the intermediate transfer member to a transfer medium;
Fixing means for fixing the toner image transferred to the recording medium;
An image forming apparatus.