JP5434790B2 - Elastic transfer belt and image forming apparatus using the same - Google Patents

Description

  The present invention relates to an elastic transfer belt used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and an image forming apparatus including the elastic transfer belt. More specifically, an electrostatic latent image is formed on an image carrier. The electrostatic latent image formed on the image carrier is visualized as a toner image, and then the toner image is primarily transferred onto an intermediate transfer belt, and the primary transferred toner image is recorded on a recording medium. The present invention relates to an intermediate transfer belt (elastic transfer belt) of an image forming apparatus for secondary transfer, and an image forming apparatus using the intermediate transfer belt.

  In an image forming apparatus using an electrophotographic process, image formation is performed by a charging process, an exposure process, a development process, a transfer process, and a fixing process. In the transfer process, the toner image developed on the photoconductor may be directly transferred to paper. However, in order to support color images, toner images of each color (yellow, magenta, cyan, and black toners are formed on the intermediate transfer belt. After the image is transferred, the toner image on the transfer belt is generally further transferred to paper.

  The intermediate transfer belt is required to have a high strength that can withstand repeated use without causing color misregistration due to deformation during running, and is also required to be flame retardant. Therefore, polyimide or polyamideimide resin is preferably used. It has been. In particular, a polyimide resin is preferably used in terms of creep deformability and durability. However, these resins generally have high hardness. Therefore, for example, in the primary transfer process of the toner image from the photoconductor as the image carrier to the transfer belt and the secondary transfer process of the toner image from the transfer belt to a transfer material such as paper, the toner image ( In particular, the central portion of the character) is subjected to stress concentration, and a transfer failure called a so-called character void phenomenon tends to occur. Such a phenomenon is particularly prominent when the recording medium (transfer material) is an OHP sheet.

  On the other hand, image forming apparatuses often form images on various types of paper, and not only normal smooth paper but also recycled paper and embossed paper from slippery and highly smooth paper such as coated paper Roughly surfaced materials such as Japanese paper and kraft paper are increasingly used. Such followability to papers having different surface properties is important. If the followability is poor, uneven unevenness of color and uneven color tone occur. In addition, the intermediate transfer belt in contact with the sheet requires not only the ability to follow the sheet but also wear resistance.

  In order to improve the above-described character dropout phenomenon and to provide excellent paper compatibility, there are some which form the surface of the intermediate transfer belt with an elastic layer. Rubber materials such as urethane rubber, acrylic rubber, and nitrile rubber are used for the elastic layer. Since the surface of the intermediate transfer belt is actually made elastic, the surface of the intermediate transfer belt can be freely deformed according to the thickness of the toner image, the surface roughness of the transfer material, etc. Concentration is reduced, and transfer defects (letter missing characters) and paper compatibility are improved. Further, pressure is not applied to the toner more than necessary, toner aggregation can be suppressed, and transfer efficiency can be increased.

By the way, since the toner images of the respective colors are superimposed on the intermediate transfer belt incorporated in the full-color image forming apparatus, the intermediate transfer belt is required to have extremely high positional accuracy. Therefore, in order to adjust the position accuracy before or during image formation, a toner patch image for position detection is created on the intermediate transfer belt, and the position of the intermediate transfer belt is adjusted by an optical sensor. There are many cases.
In addition, as the image formation is repeated, the density of the image formed may change due to changes in the characteristics of the photoconductor, developer, and charger. For this reason, it is often performed to create a toner patch for density detection on the intermediate transfer belt, measure the density of the toner patch with an optical sensor, and change the image forming conditions.

Generally, the light used for the optical sensor is near infrared light of 800 to 1000 nm or a wavelength capable of detecting each toner color, but near infrared light capable of detecting density by the same optical sensor is preferably used. Thus, image density detection is performed based on the difference in intensity of reflected light between when there is no toner image and when there is no toner image. For this reason, the intermediate transfer belt itself is required to reflect light used for the optical sensor to some extent.
In the transfer belt whose elastic layer is a rubber-based material, since the surface of the rubber-based material is not smooth compared to a normal resin film such as polyimide, it is easy to diffusely reflect light used for the optical sensor, and the regular reflection component is reduced. There is a problem that it is difficult to perform position control and image density control using the above-described optical sensor.

Therefore, the surface layer of the intermediate transfer belt is a polymer composition (binder resin: UV curable) containing particles (titanium oxide fine particles) having an average particle diameter of 20 nm or less and a refractive index of 2.3 or more with respect to light having a wavelength of 800 nm. An intermediate transfer belt has been proposed in which a surface reflectance is ensured by forming a layer made of an acrylic resin (see, for example, Patent Document 1).
This intermediate transfer belt is generally mixed with carbon as a conductive agent. However, although carbon absorbs light of almost all wavelengths, titanium oxide contains titanium oxide particles because it has a higher refractive index than carbon. If the layer to be positioned is located on the surface, the light is efficiently reflected. However, the ultraviolet curable acrylic resin layer in which the titanium oxide fine particles are dispersed is cracked while the intermediate transfer belt is used, and the image quality is remarkably deteriorated in the image forming apparatus using the intermediate transfer belt. There was a problem. In addition, when an ultraviolet curable acrylic resin layer in which titanium oxide fine particles are dispersed is laminated on the elastic layer, cracks occur earlier and the refractive index of the ultraviolet curable acrylic resin layer in which titanium oxide fine particles are dispersed. Since the refractive index of the titanium oxide fine particles and the refractive index of the ultraviolet curable acrylic resin are synthesized, the surface reflectance itself cannot be sufficiently secured.

In addition, in order to obtain an intermediate transfer body capable of improving transfer efficiency and preventing the occurrence of abnormal images while preventing image polymerization misalignment, the surface layer of the intermediate transfer body is made of organic resin particles (fluororesin particles, silicon It is known to comprise a layer containing resin particles or the like (see, for example, Patent Document 2).
However, the surface layer of this intermediate transfer member contains carbon black and a binder resin. The intermediate transfer belt having the surface layer laminated on the elastic layer is not suitable for performing position control and image density control using an optical sensor.

  The present invention solves the above-described problems of the prior art, and is an elastic transfer belt that has excellent paper compatibility and can control the position and image density, and can form a high-quality image using the elastic transfer belt. An image forming apparatus is provided.

In order to improve the light reflectance of the transfer belt, the present inventors laminated a layer containing titanium oxide fine particles having an average particle diameter of 20 nm or less as described in Patent Document 1 on the elastic layer. As a result, the inventors have found that the reflectivity is considerably improved, although the reflectivity expected by the present inventors has not been reached. However, when this transfer belt was mounted on an image forming apparatus as an intermediate transfer belt, cracks and wrinkles occurred in the titanium oxide fine particle-containing layer when image formation was repeated, and the image quality was greatly deteriorated. Various attempts were made to change the binder resin of the titanium oxide fine particle-containing layer, but satisfactory results were not obtained.
Mechanical properties of the elastic layer and the titanium oxide fine particle-containing layer on the surface are greatly different. The intermediate transfer belt is driven by inserting a plurality of rollers inside the intermediate transfer belt and rotating the rollers. At that time, since the transfer belt was bent to the diameter of the roller, it was found that the titanium oxide fine particle-containing layer could not be attached to the bending of the elastic layer, leading to generation of cracks and wrinkles.

  Therefore, the present inventors changed the way of thinking and did not use the titanium oxide fine particle-containing layer described above, but provided a relatively large 0.5 to 3 μm spherical titanium oxide on the surface of the elastic layer without a binder resin. I tried. Then, the spherical titanium oxide is spread almost uniformly on the elastic layer and is appropriately embedded in the elastic layer, so that even if the transfer belt is bent, only the elastic layer extends on the surface, so no cracks will occur. I found. The present invention has been made based on these findings. That is, the said subject of this invention is achieved by the following.

(1) In an elastic transfer belt in which an elastic layer is laminated on a base layer containing a polyimide resin or a polyamideimide resin, an average particle size of 0.5 to 4 μm having a refractive index at a wavelength of 900 nm larger than that of the elastic layer on the elastic layer It is characterized by being spread with spherical particles.
(2) The elastic transfer belt according to (1), wherein the spherical particles have a refractive index of 2.2 or more at a wavelength of 900 nm.
(3) In the elastic transfer belt according to the above (1) or (2), the spherical particles are such that a region of 60 to 90% of the diameter of the spherical particles exposed on the surface is buried in the elastic layer. Features.
(4) The elastic transfer belt according to any one of (1) to (3), wherein the spherical particles cover 45% or more of the surface area of the elastic layer.
(5) In the elastic transfer belt according to any one of (1) to (4), the spherical particles include titanium oxide, barium titanate, barium sulfide, silicon, zinc oxide, zinc sulfide, strontium titanate, sulfide. It is selected from strontium, germanium, and silicon carbide.
(6) An image in which a plurality of color toner developed images sequentially formed on an image carrier are sequentially superimposed on an intermediate transfer belt to perform primary transfer, and the primary transfer image is collectively transferred to a recording medium. In the forming apparatus, the intermediate transfer belt is the elastic transfer belt according to any one of (1) to (5).
(7) In the image forming apparatus according to (5) or (6), a lubricant application unit for applying a lubricant to the surface of the intermediate transfer belt is provided in the vicinity of the intermediate transfer belt. It is characterized by that.
(8) The image forming apparatus according to (7), wherein the lubricant is a metal soap.
(9) In the image forming apparatus according to any one of (5) to (8), a test pattern toner image is transferred onto the intermediate transfer belt, and the density of the test pattern toner image is optically measured. The image forming conditions are adjusted from the measured density of the toner image.
(10) In the image forming apparatus described in (9) above, the means for optically measuring the density of the toner image of the test pattern measures reflection of near infrared light.

According to the invention described in claim 1, spherical particles having an average particle diameter of 0.5 to 3 μm having a larger refractive index (refractive index at a wavelength of 900 nm) than that of the elastic layer are spread on the elastic layer. As a result, the reflectivity of the elastic transfer belt can be secured and the image density can be detected, so that the image forming conditions can be controlled to an appropriate state, and the paper compatibility is excellent. Can be done.
According to the second aspect of the present invention, since the refractive index of the spherical particles at a wavelength of 900 nm is 2.2 or more, a desired reflectance of the elastic transfer belt can be secured, and the image density can be detected. Therefore, the image forming conditions can be controlled to an appropriate state, and the paper compatibility is excellent, and high-quality image formation can be performed over a long period of time.
According to the invention described in claim 3, since the spherical particles are densely spread on the elastic layer, the reflectance of the intermediate transfer belt can be reliably ensured and the image density can be detected. Further, the image forming conditions can be controlled to an appropriate state, and the paper compatibility is excellent, and high-quality image formation can be performed over a long period of time.
According to the invention described in claim 4, since the spherical particles are securely fixed to the elastic layer and the reflectance of the elastic transfer belt can be ensured, it is excellent in paper compatibility and performs high-quality image formation over a long period of time. be able to.
According to the invention described in claim 5, since the spherical particles are limited to titanium oxide particles, silicon particles, and other specific particles, the desired reflectance of the elastic transfer belt can be ensured, so that the image density is detected. Therefore, the image forming conditions can be controlled to an appropriate state, whereby high-quality image formation can be performed over a long period of time.

According to the invention described in claim 6, since the image forming apparatus incorporates the elastic transfer belt according to any one of claims 1 to 5 as an intermediate transfer belt, the image forming apparatus is not affected by the type of paper. Quality image formation can be performed over a long period of time.
According to the seventh and eighth aspects of the present invention, the lubricant application means for applying the lubricant to the surface of the intermediate transfer belt is provided in the vicinity of the intermediate transfer belt, and the lubricant is applied to the surface of the intermediate transfer belt. Since image formation is performed in a coated state, high-quality image formation can be performed over a long period of time.
According to the ninth and tenth aspects of the present invention, since the image forming conditions can be controlled to an appropriate state, high-quality image formation can be performed over a long period of time.

It is a principal part schematic diagram for demonstrating the seamless belt and apparatus used for the belt structure part of the electrophotographic apparatus which concerns on this invention. FIG. 3 is a schematic diagram of a main part illustrating a configuration example in which a plurality of photosensitive drums are arranged in parallel along one intermediate transfer belt provided in a belt configuration unit of the electrophotographic apparatus according to the present invention. It is a schematic diagram of the state by which the spherical particle is being fixed in the elastic layer. 2 is an SEM image of the surface of an elastic transfer belt produced in Example 1.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
In the elastic transfer belt according to the present invention, an elastic layer is laminated on a base layer containing a polyimide resin or a polyamide-imide resin, and an average particle diameter of 0.5 to larger refractive index at a wavelength of 900 nm than that of the elastic layer is formed on the elastic layer. It consists of a structure in which 4 μm spherical particles are spread.
Here, the layer made of spherical particles as the surface layer may contain some binder resin, but when the content of the binder resin increases, the refractive index of the layer made of spherical particles decreases. Therefore, it is not preferable, and it is particularly preferable that the resin is not formed of a binder resin and is formed only of spherical particles.

In the present invention, “spherical particles having a refractive index at a wavelength of 900 nm larger than that of the elastic layer” means that the relationship between the refractive index η1 of the spherical particles with respect to the light with a wavelength of 900 nm and the refractive index η2 of the elastic layer with respect to the light with a wavelength of 900 nm It means that η1> η2.
The phrase “spherical particles are spread on the elastic layer” means that the spherical particles are fully spread on the elastic layer.

[Spherical particles]
The spherical particles in the present invention have an average particle size of 0.5 to 4 μm, preferably 1 to 3 μm. When the average particle size is less than 0.5 μm, it becomes difficult to spread spherical particles on the elastic layer, and the spherical particles are completely buried in the elastic layer, or conversely, only a part is buried, For this reason, it is not preferable because the spherical particles are easily dropped by bending the transfer sheet. On the other hand, if the average particle diameter of the spherical particles exceeds 4 μm, the surface of the transfer belt is too rough and the image quality is remarkably deteriorated. On the other hand, if the thickness exceeds 4 μm, the surface resistance of the transfer belt increases and the transfer efficiency decreases, which is not preferable. In addition, the average particle diameter here is a number average particle diameter.
The particle size distribution is preferably as uniform as possible because the particles can be spread over the entire elastic layer surface.

Further, the spherical particles of the present invention are required to satisfy the relationship of η1> η2. The refractive index at a wavelength of 900 nm of the rubber component itself of the elastic layer is about 1.6, but if necessary, the elastic layer contains carbon and the carbon has a refractive index of about 2. Therefore, when the carbon content is large, the refractive index of the elastic layer is about 1.7. Since the reflectance is (η1−η2) ² / (η1 + η2) ² , η1−η2 needs to be 0.3 or more, preferably 0.4 or more, more preferably 0.5 or more. If η1−η2 is smaller than 0.3, the reflectance is low, so it is not preferable because it is necessary to increase the intensity of light used for the photosensor or increase the sensitivity of the photosensor.

  Examples of the spherical particles of the spherical particles of the present invention include titanium oxide, barium titanate, barium sulfide, silicon, zinc oxide, zinc sulfide, strontium titanate, strontium sulfide, germanium, silicon carbide and the like. Titanium oxide, zinc sulfide, barium titanate, barium sulfide, silicon, strontium titanate, strontium sulfide, germanium, and silicon carbide are preferred, the refractive index is 2.5 or more, and spherical particles are easily manufactured and economical. From the above aspect, titanium oxide and silicon are particularly preferable.

  In the spherical particles having a refractive index larger than that of the elastic layer covering the surface of the elastic transfer belt of the present invention, it is preferable that a region of 60 to 90% of the diameter of the particles exposed on the surface is buried in the elastic layer. FIG. 3 shows a schematic diagram in which spherical particles are fixed in the elastic layer. When more than half of the particle size of the spherical particles is buried in the elastic layer, the elastic layer rises in the gaps between the spherical particles and fixes the spherical particles. Therefore, when 60% or more of the diameter is embedded in the elastic layer, the spherical particles will not fall out of the elastic layer. If the spherical particles embedded in the elastic layer are smaller than 60% of the diameter of the particles, the spherical particles are likely to fall off, and if the spherical particles are larger than 90% of the diameter of the particles, the reflectance of the elastic transfer belt is decreased. It is preferable that the spherical particles are present only on the surface of the elastic layer, and the spherical particles are completely embedded in the elastic layer, and the spherical particles present thereon have a small retention effect by the elastic layer. It is easy to remove and is not preferable.

In the elastic transfer belt of the present invention, it is preferable that the spherical particles cover 45% or more, preferably 46% or more, more preferably 46 to 52% of the elastic layer. If the ratio of the spherical particles covering the elastic layer is less than 45%, the transfer rate of the elastic transfer belt is lowered and the reflectance of the elastic transfer belt is lowered, which is not preferable.
The ratio of the spherical particles covering the elastic layer can be exemplified by an electron microscope, a method of measuring the surface shape by SPM, and a method of determining the elemental composition of the elastic transfer belt surface by XPS. Among these, the measurement by XPS has good reproducibility. For example, when the spherical particles are titanium oxide (TiO ₂ ), the ratio of At (atomic%) of Ti measured by XPS is At / (100/3) × It can be calculated by 100 (%). Further, when the spherical particles are germanium (Ge) and the Ge ratio measured by XPS is Ag, Ag (%) is obtained. Similarly, in the case of silicon oxide (SiO ₂ ) and the Si ratio measured by XPS, As / (100/3) × 100 (%). The ratio of the spherical particles covered in the examples and comparative examples of the present invention is obtained by performing XPS measurement on the elastic transfer belt surface.

  The “diameter” of the spherical particles means an average value (m1 + m2) / 2 of the longest diameter (m1) and the shortest diameter (m2) of the spherical particles. The average particle diameter can be measured using a laser diffraction / scattering LA-920 (manufactured by Horiba).

[Base layer containing polyimide resin or polyamideimide resin]
In the elastic transfer belt of the present invention, a polyimide resin or a polyamideimide resin, which is a resin with little elongation, is used on the center side (base layer), and a polyimide resin is particularly preferably used in terms of durability.

Polyimide resin as the base layer resin can be any of thermoplastic type, solvent-soluble type, and thermosetting type, but it is necessary to mix various materials, especially resistance adjusting agent for adjusting electric resistance. When there is a need for blending, a thermosetting type one in which a solution (polyimide varnish) containing a polyimide precursor using an organic polar solvent is applied and thermally cured to form is suitable.
The polyimide precursor which is a composition of the coating liquid in the present invention and the polyimide produced by heat treatment (imidization) of the precursor will be described.

<Polyimide>
The polyimide used in the present invention is first obtained via a polyamic acid (polyimide precursor) by reaction of a generally known aromatic polycarboxylic acid anhydride or derivative thereof with an aromatic diamine. That is, polyimide is insoluble in solvents and the like due to its rigid main chain structure and has an infusible property. Therefore, a polyimide precursor that is soluble in an organic solvent from an acid anhydride and an aromatic diamine ( Polyamic acid or polyamic acid) is synthesized, and at this stage, molding is performed by various methods, and then the polyamic acid is subjected to dehydration reaction by heating or a chemical method to be cyclized (imidized) to obtain polyimide. The outline of the reaction is shown in the following chemical reaction formula (I).

(In the formula, Ar ¹ represents a tetravalent aromatic residue containing at least one carbon 6-membered ring, and Ar ² represents a divalent aromatic residue containing at least one carbon 6-membered ring.)

Specific examples of the aromatic polyvalent carboxylic acid anhydride include, for example, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3 '-Benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,2- Bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis ( 3,4-dicarbo Silphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid Dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride Products, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and the like. These may be used alone or in combination of two or more.
In addition, other (non-aromatic) polyvalent carboxylic acid anhydrides such as ethylenetetracarboxylic dianhydride and cyclopentanetetracarboxylic dianhydride are included in a range not impairing the object of the present invention (50 mol%). Can be used in combination.

  Next, specific examples of the aromatic diamine to be reacted with the aromatic polycarboxylic acid anhydride include, for example, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, and p-aminobenzyl. Amine, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, bis (3-aminophenyl) sulfide, (3-aminophenyl) (4-aminophenyl) sulfide, bis (4-aminophenyl) sulfide, bis (3-aminophenyl) sulfide, (3-aminophenyl) (4-aminophenyl) sulfoxide, bis (3-aminophenyl) sulfone, (3-aminophenyl) (4-amino Phenyl) sulfone, bis (4-aminophenyl) sulfur 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, Bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] methane, 1,1-bis [4- (3-aminophenoxy) phenyl] ethane, 1,1- Bis [4- (4-aminophenoxy) phenyl] -ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl Propane, 2,2-bis [4- (3-aminophenoxy) phenyl] butane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexa Fluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,3-bis (3-aminophenoxy) benzene, 1 , 3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (3-aminophenoxy) Biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [ -(3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfoxide, bis [4- (4-aminophenoxy) phenyl Sulfoxide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- ( 4-aminophenoxy) phenyl] ether, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 4,4′- Bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [3- (3-a Minophenoxy) benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α- Dimethylbenzyl) phenoxy] diphenylsulfone, bis [4- {4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- (4-aminophenoxy) phenoxy] -α, α-dimethylbenzyl Benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene and the like. These are used individually or in mixture of 2 or more types.

  A polyimide precursor (polyamic acid) can be obtained by polymerizing the polycarboxylic acid anhydride component and the diamine component in an organic polar solvent using approximately equimolar amounts. Below, the manufacturing method of a polyamic acid is demonstrated concretely.

  Examples of the organic polar solvent used in the polymerization reaction of polyamic acid include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, N , N-dimethylacetamide, N, N-diethylacetamide and other acetamide solvents, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone and other pyrrolidone solvents, phenol, o-, m-, or p- Phenolic solvents such as cresol, xylenol, halogenated phenol, catechol, ether solvents such as tetrahydrofuran, dioxane, dioxolane, alcohol solvents such as methanol, ethanol, butanol, cellosolve such as butyl cellosolve or hex Methyl phosphoramide, .gamma.-butyrolactone, etc. may be mentioned, it is desirable to use them alone or as a mixed solvent. The solvent is not particularly limited as long as it dissolves polyamic acid, but N, N-dimethylacetamide and N-methyl-2-pyrrolidone are particularly preferable.

  As an example for producing a polyimide precursor, first, one or a plurality of diamines are dissolved in the above organic solvent or diffused in a slurry state in an inert gas atmosphere such as argon or nitrogen. When at least one polyvalent carboxylic acid anhydride or derivative thereof is added to this solution (either in a solid state, in a solution state dissolved in an organic solvent, or in a slurry state), it opens with heat generation. A cyclopolyaddition reaction occurs, and the viscosity of the solution is rapidly increased, and a high molecular weight polyamic acid solution is obtained. The reaction temperature at this time is preferably controlled to −20 ° C. to 100 ° C., desirably 60 ° C. or less. The reaction time is about 30 minutes to 12 hours.

  The above is an example. Contrary to the addition procedure in the reaction, the polycarboxylic acid anhydride or derivative thereof may be first dissolved or diffused in an organic solvent, and the diamine may be added to the solution. . The diamine may be added in a solid state, in a solution state dissolved in an organic solvent, or in a slurry state. That is, the mixing order of the acid dianhydride component and the diamine component is not limited. Furthermore, the tetracarboxylic dianhydride and the diamine may be simultaneously added to the organic polar solvent and allowed to react.

As described above, the polyamic acid composition is uniformly mixed in the organic polar solvent by polymerizing the polycarboxylic acid anhydride or derivative thereof and the diamine component in an organic polar solvent in approximately equimolar amounts. A polyimide precursor solution is obtained in a dissolved state.

As the polyimide precursor solution (polyamic acid solution) in the present invention, the one synthesized as described above can be used, but the so-called polyamic acid composition is simply dissolved in an organic solvent. What is marketed as a polyimide varnish can also be obtained and used.
Typical examples include Trenice (manufactured by Toray Industries, Inc.), U-Varnish (manufactured by Ube Industries, Ltd.), Optmer (manufactured by JSR), SE812 (manufactured by Nissan Chemical Industries), CRC8000 (manufactured by Sumitomo Bakelite Co., Ltd.), and the like. It is mentioned as a thing.

  In addition, examples of the thermoplastic type include Aurum (manufactured by Mitsui Chemicals) and Vespel (manufactured by DuPont). Examples of the solvent-soluble type include Rika Coat (manufactured by Nippon Nippon Chemical Co., Ltd.), block copolymerized polyimide (manufactured by PI Engineering Co., Ltd.), GPI (manufactured by Gunei Chemical Industry Co., Ltd.) and the like. These can be used by being added to and mixed with a thermosetting type material as a subcomponent resin within a range not impairing the object of the present invention.

  A coating liquid is prepared by blending a synthesized or obtained polyamic acid solution with a compound as necessary. The coating liquid is applied to a support (molding mold) and then subjected to a treatment such as heating, whereby conversion (imidation) from polyamic acid, which is a polyimide precursor, to polyimide is performed.

  As a method for converting polyamic acid to polyimide, imidization can be performed by a method (1) only by heating or a chemical method (2). The heating only method (1) is a method of converting polyamic acid to polyimide by heat treatment at 200 to 350 ° C., and is a simple and practical method for obtaining polyimide (polyimide resin). On the other hand, the chemical method (2) is a method in which a polyamic acid is reacted with a dehydrating cyclization reagent (such as a mixture of a carboxylic acid anhydride and a tertiary amine) and then heat-treated to completely imidize, (1 The method (1) is often used because it is a complicated and costly method compared to the heating only method.

  However, recently, although it is a kind of the method (2), a method of promoting imidization at the time of drying by incorporating an amine such as imidazole or quinoline in the varnish as a catalyst is often employed. In order to demonstrate the intrinsic performance of polyimide, it is necessary to complete the imidization by heating above the glass transition temperature of the corresponding polyimide, but this promotes imidization at a lower temperature. It is said that mechanical durability is also improved. However, these catalysts are in very small amounts, and some of them decompose and sublime during drying, but some remain as impurities, which is not preferable.

The progress of imidization (degree of imidization) can be evaluated by a usual method for measuring the imidization rate.
As a method for measuring such an imidization rate, for example, nuclear magnetic resonance spectroscopy calculated from an integration ratio of 1H attributed to an amide group in the vicinity of 9 to 11 ppm and 1H attributed to an aromatic ring in the vicinity of 6 to 9 ppm. Various methods are used such as a method (NMR method), Fourier transform infrared spectroscopy (FT-IR method), a method for quantifying moisture accompanying imide ring closure, and a carboxylic acid neutralization titration method. -Lier transformation infrared spectroscopy (FT-IR method) is the most common method.

In Fourier transform infrared spectroscopy (FT-IR method), the imidization rate is defined as follows, for example. That is, assuming that (A) is the number of moles of imide groups at the firing stage (imidation treatment stage) and (B) is the number of moles of imide groups when 100% imidized (theoretical), It is.
Imidization rate = [(A) / (B)] × 100

The number of moles of the imide group in this definition can be determined from the absorbance ratio of the characteristic absorption of the imide group measured by the FT-IR method. For example, as a typical characteristic absorption, the imidization ratio can be evaluated using the following absorbance ratio.
(1) Absorbance ratio between 725 cm ⁻¹ (immobilization vibration band of imide ring C═O group), which is one of characteristic absorptions of imide, and 1,015 cm ⁻¹ of characteristic absorption of benzene ring (2) Characteristics of imide Absorbance ratio between 1,380 cm ⁻¹ (inflection vibration band of imide ring C—N group) which is one of absorption and 1,500 cm ⁻¹ characteristic absorption of benzene ring (3) One of characteristic absorption of imide Absorption ratio between 1,720 cm ⁻¹ (an azimuthal vibration band of the imide ring C═O group) and 1,500 cm ⁻¹ characteristic absorption of the benzene ring (4) 1, which is one of characteristic absorption of imide Absorbance ratio between 720 cm ⁻¹ and amide group characteristic absorption 1,670 cm ⁻¹ (interaction between amide group N—H bending vibration and CN stretching vibration) and amide group over 3000 to 3300 cm ⁻¹ Confirm the disappearance of multiple absorption bands Further more reliable imidization complete if.

In the coating solution for forming the base layer of the present invention, another resin may be used in combination with the polyimide. Various materials for imparting a necessary function as a transfer belt can also be blended.
As a material to be blended, for example, a resistance adjusting agent, a reinforcing material, a leveling agent, a surfactant, a lubricant, an antioxidant, a catalyst, and the like can be blended. Of these, the resistance adjusting agent is particularly important.

Next, the resistance adjusting material will be described. The resistance adjusting material is added when it is necessary to adjust the elastic transfer belt to a predetermined resistance value.
Any resistance control agent can be used as long as it can adjust the resistance value of polyimide. For example, carbon black, graphite, or metals such as copper, tin, aluminum, indium, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, tin oxide doped with antimony, tin doped Fillers such as metal oxide fine powders such as indium oxide, conductive polymer materials such as polyetheramide, polyetheresteramide, polypyrrole, polythiophene, polyaniline, tetraalkylammonium salt, trialkylbenzyl, ammonium Salt, alkyl sulfonate, alkyl benzene sulfonate, alkyl sulfate, glycerol fatty acid ester, sorbitan fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty alcohol ester, alkyl Tyne, may be used an ion-conductive material, such as lithium perchlorate. These can also be used in combination. In addition, the resistance control agent in this invention is not limited to these exemplary compounds.

  Of the above resistance control agents, carbon black is preferably used in the base layer of the present invention. As the carbon black, furnace black, acetylene black, ketjen black, channel black, and the like can be used. Oxidized carbon black obtained by oxidizing these surfaces is preferable.

  Moreover, you may use a dispersing aid as needed. Furthermore, the surface functional group of carbon black and an organic compound having reactivity with the functional group may be surface-treated.

Next, a method for producing a seamless belt using the coating liquid containing the polyimide precursor will be described. For example, it is manufactured by the following process.
A dispersion preparing step for dispersing a resistance adjusting agent in a polyamic acid solution, a coating solution preparing step for adjusting the dispersion obtained by the step to the content of a predetermined resistance adjusting material, and a coating solution prepared by the step The step of applying and casting to (molding mold), the step of removing the solvent in the coating applied and cast on the support by heating, the precursor imide contained in the coating by heating at elevated temperature It is manufactured by releasing the formed thin film from the support and making it a seamless belt.

In the step of dispersing the resistance adjusting agent, there are a method of dispersing and mixing the resistance control agent directly in the polyimide precursor solution or a method of dispersing the resistance control agent in a solvent in advance and then mixing with the polyimide precursor solution.
Here, a method of dispersing carbon black as a resistance control agent will be described as an example. Note that this is an example and the present invention is not limited to this.

N-methyl-2-pyrrolidone is mixed with a small amount of carbon black and a polyimide precursor, and dispersed in a ball mill, paint shaker, bead mill or the like for a predetermined time using zirconia beads. After being dispersed to a certain particle size, the liquid taken out is used as a dispersion. The polyimide precursor solution is mixed with the dispersion to dilute to a predetermined carbon black concentration. As a mixing method at this time, a centrifugal stirrer, a Henschel mixer, a homogenizer, a planetary stirrer, or the like can be used.
If necessary, additives such as a leveling agent and a catalyst can be added at this time.
Further, after stirring, it is preferable to defoam using a vacuum defoamer or the like.

Next, the process of applying the coating solution prepared above will be described.
Examples of the method for forming a base layer on a support (which is removed after the base layer and elastic layer are formed) include centrifugal molding, roll coating, blade coating, ring coating, dipping, spray coating, dispenser coating, and die coating. As a method for forming a polyimide seamless belt, a centrifugal molding method is often used. However, in order to form a film on the inner surface of a support, when a layer is laminated on the surface, after film formation, the mold is once removed from the mold. It is necessary to transfer to a mold and form an elastic layer by another coating method, and the process becomes complicated.
Therefore, in the case of the present invention, roll coating, dispenser coating, ring coating, die coating, and spray coating are preferable as a method for applying the coating on the outer surface of the support and sequentially laminating the base layer and the elastic layer.

  After applying a coating solution containing polyamic acid to a predetermined film thickness on the outer surface of a metal cylindrical support that has been previously coated with a release agent by the above method, the coating film is dried using a hot air dryer, an IH heater, a far infrared heater, or the like. . In drying, first, drying is performed at a temperature of about 80 to 120 ° C. for 10 to 60 minutes, and then the temperature is increased at a temperature rising rate of about 2 to 5 ° C./min, and imidization baking is performed at 300 to 400 ° C. Do. Then, after sufficiently cooling, the elastic layer is applied. The base layer and the elastic layer are not necessarily formed by the same method.

As a film thickness of the base layer formed by this invention, 50-100 micrometers is preferable. If the film thickness is too thin, the strength is insufficient and the durability is inferior, and if it is too thick, the rigidity is too large to be stably driven by a driving roller having a small curvature. The content of carbon black as the resistance adjusting agent, preferably 5-25 wt%, it is preferable that a ¹⁰ 6 ^{to 10 10} [Omega] cm as volume resistivity. If the carbon black content is too small, it is difficult to control the variation in resistance value. If the carbon black content is too large, the film is brittle and inferior in flexibility and inferior in durability. If the resistance value is too low, the toner is scattered in the non-image area at the time of transfer and the sharpness is lowered. On the other hand, if it is too high, the transfer electric field does not work well, which is not preferable in terms of transfer efficiency.

[Elastic layer]
The elastic layer of the transfer belt used in the present invention is not particularly limited as long as it has moderate elasticity, bend resistance, ozone resistance, and flame retardancy. Butyl rubber, fluorine rubber, acrylic rubber, EPDM, NBR, acrylonitrile-butadiene-styrene rubber natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-propylene terpolymer, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, urethane rubber, syndiotactic Tic 1,2-polybutadiene, epichlorohydrin rubber, ricone rubber, fluororubber, polysulfide rubber, polynorbornene rubber, hydrogenated nitrile rubber, thermoplastic elastomer (eg polystyrene, polyolefin, polyvinyl chloride, polyurethane) System, polyamide, polyurea, may be used one kind or two kinds or more selected from the group consisting of polyester, fluorocarbon resin) or the like.

  A resistance value adjusting conductive agent is added to the elastic layer as necessary. The conductive agent for adjusting the resistance value is not particularly limited. For example, carbon black, graphite, metal powder such as aluminum and nickel, tin oxide, titanium oxide, antimony oxide, indium oxide, potassium titanate, antimony oxide-tin oxide Conductive metal oxides such as composite oxide (ATO) and indium oxide-tin oxide composite oxide (ITO), and conductive metal oxide covered with insulating fine particles such as barium sulfate, magnesium silicate, and calcium carbonate. It may be a thing. Among these, carbon black is excellent in the resistance adjusting function and is preferable for enhancing the mechanical strength of the elastic layer.

The elastic layer preferably has a thickness of 50 μm to 1000 μm and an elastic modulus of 0.1 MPa to 10 MPa. If the thickness of the elastic layer is less than 50 μm, when used in an image forming apparatus, the transfer capability for paper with irregularities on the surface is low, which is not preferable because the image quality is deteriorated. When driven by being inserted, a small roller increases the stress on the surface of the intermediate transfer belt, so it is necessary to increase the diameter of the roller inserted into the intermediate transfer belt, and the entire image forming apparatus becomes large. It is not preferable. If the elastic modulus of the elastic layer is less than 0.1 MPa, the elastic layer is too soft, and the transferred image quality deteriorates, which is not preferable. On the other hand, when the pressure is larger than 10 MPa, the elastic layer is too hard, the transfer ability with respect to the paper having unevenness on the surface is low, and the image quality is deteriorated.
Further, the refractive index of the elastic layer at a wavelength of 900 nm is generally 1.6 to 1.7 although it depends on the material constituting the elastic layer. The refractive index of the elastic layer can also be adjusted by adjusting the amount of conductive agent and filler contained in the layer.

  The elastic layer can be formed by a wet method, and examples thereof include a centrifugal molding method, a coating method, a dipping method, a casting method for injecting into an inner mold, and an outer mold.

[Production of transfer belt]
In the transfer belt of the present invention, after applying an elastic layer on a polyimide or polyamideimide layer, the refractive index is applied to the surface of the soft elastic layer in a state where the elastic layer is not completely dried or before vulcanization. A spherical particle having a larger average particle diameter of 0.5 to 4 μm is uniformly sprinkled and pressed with a rubber blade or the like, so that the spherical particle can be bitten into the elastic layer and fixed. Pressure at this time, the thickness of the elastic layer is not determined to unanimously by such ^elasticity, about 10mN / cm ² ~1000mN / cm 2 are suitable.

[Image forming equipment]
Next, the seamless belt used in the belt constituting unit equipped in the electrophotographic apparatus according to the present invention will be described in detail below with reference to a schematic diagram of relevant parts. The schematic diagram is an example, and the present invention is not limited to this.

The schematic diagram of FIG. 1 shows a schematic configuration of the main part of an electrophotographic apparatus equipped with a belt component and the like.
The intermediate transfer unit (500) which is a belt component shown in FIG. 1 includes an intermediate transfer belt (501) which is an intermediate transfer member stretched around a plurality of rollers. Around the intermediate transfer belt (501), there are a secondary transfer bias roller (605) as a secondary transfer charge applying means of the secondary transfer unit (600), and a belt cleaning blade (504) as an intermediate transfer body cleaning means. A lubricant application brush (505), which is a lubricant application member of the lubricant application means, is disposed so as to face each other.

  Further, a position detection mark (not shown) is provided on the outer peripheral surface or inner peripheral surface of the intermediate transfer belt (501). However, on the outer peripheral surface side of the intermediate transfer belt (501), it is necessary to devise a position detection mark that avoids the passing area of the belt cleaning blade (504), which may be difficult to arrange. In this case, a position detection mark may be provided on the inner peripheral surface side of the intermediate transfer belt (501). The optical sensor (514) as a mark detection sensor is provided at a position between the primary transfer bias roller (507) and the belt driving roller (508) on which the intermediate transfer belt (501) is stretched. Position detection is performed by detecting light reflection from the surface of the intermediate transfer belt. Therefore, detection becomes unstable when the glossiness of the surface of the intermediate transfer belt decreases or becomes non-uniform. By using the intermediate transfer belt of the present invention, it is possible to suppress a decrease in surface glossiness and to stabilize detection.

  The intermediate transfer belt (501) includes a primary transfer bias roller (507), a belt driving roller (508), a belt tension roller (509), a secondary transfer counter roller (510), which are primary transfer charge applying means, and a cleaning device. It is stretched between the counter roller (511) and the feedback current detection roller (512). Each roller is made of a conductive material, and each roller other than the primary transfer bias roller (507) is grounded. The primary transfer bias roller (507) is controlled by a primary transfer power source (801) controlled by a constant current or a constant voltage so that the current or voltage is controlled to a predetermined magnitude according to the number of superimposed toner images. A bias is applied.

  The intermediate transfer belt (501) is driven in the direction of the arrow by a belt drive roller (508) that is driven to rotate in the direction of the arrow by a drive motor (not shown). The intermediate transfer belt (501), which is the belt component, is usually a semiconductor or insulator and has a single layer or multilayer structure, but the seamless belt of the present invention is preferably used, thereby improving durability. In addition, excellent image formation can be realized. In addition, the intermediate transfer belt is set to be larger than the maximum sheet passing size in order to superimpose the toner images formed on the photosensitive drum (200).

  A secondary transfer bias roller (605), which is a secondary transfer means, is in contact with / separating means, which will be described later, with respect to the belt outer peripheral surface of a portion of the intermediate transfer belt (501) stretched around the secondary transfer counter roller (510). It is comprised so that contact / separation is possible by the contact / separation mechanism. The secondary transfer bias roller (605) is disposed so as to sandwich the transfer paper P, which is a recording medium, between the portion of the intermediate transfer belt (501) stretched around the secondary transfer counter roller (510). A transfer bias having a predetermined current is applied by a secondary transfer power source (802) controlled at a constant current.

  The registration roller (610) is a transfer sheet as a transfer material at a predetermined timing between the secondary transfer bias roller (605) and the intermediate transfer belt (501) stretched around the secondary transfer counter roller (510). Send (P). Further, a cleaning blade (608) as a cleaning unit is in contact with the secondary transfer bias roller (605). The cleaning blade (608) removes and removes adhering material adhering to the surface of the secondary transfer bias roller (605).

  In the color copying machine having such a configuration, when the image forming cycle is started, the photosensitive drum (200) is rotated in the counterclockwise direction indicated by an arrow by a drive motor (not shown), and a charging charger is used according to each color. After charging by (203) and image exposure by the exposure means (L), Bk (black) toner image formation, C (cyan) toner image formation, M (magenta) toner image formation on the photosensitive drum (200) , Y (yellow) toner image formation is performed. The intermediate transfer belt (501) is rotated clockwise by the belt driving roller (508) as indicated by an arrow. As the intermediate transfer belt (501) rotates, the primary transfer of the Bk toner image, the C toner image, the M toner image, and the Y toner image is performed by the transfer bias by the voltage applied to the primary transfer bias roller (507). Finally, toner images are formed on the intermediate transfer belt (501) in the order of Bk, C, M, and Y.

For example, the Bk toner image formation is performed as follows.
In FIG. 1, a charging charger (203) uniformly charges the surface of the photosensitive drum (200) to a predetermined potential with a negative charge by corona discharge. The timing is determined based on the belt mark detection signal, and raster exposure with laser light is performed based on the Bk color image signal by a writing optical unit (not shown). When this raster image is exposed, the charge proportional to the exposure light amount disappears in the exposed portion of the surface of the photosensitive drum (200) that is initially charged uniformly, and a Bk electrostatic latent image is formed. When the negatively charged Bk toner on the developing roller of the Bk developing machine (231K) comes into contact with this Bk electrostatic latent image, the toner adheres to the portion where the charge of the photosensitive drum (200) remains. In other words, toner is attracted to a portion having no charge, that is, an exposed portion, and a Bk toner image similar to the electrostatic latent image is formed.

  The Bk toner image formed on the photosensitive drum (200) in this way is primary on the belt outer peripheral surface of the intermediate transfer belt (501) rotating at a constant speed while being in contact with the photosensitive drum (200). Transcribed. Some untransferred residual toner remaining on the surface of the photoreceptor drum (200) after the primary transfer is cleaned by the photoreceptor cleaning device (201) in preparation for reuse of the photoreceptor drum (200). Is done. On the photosensitive drum (200) side, the process proceeds to the Y image forming process after the Bk image forming process, and reading of Y image data by a color scanner starts at a predetermined timing. A Y electrostatic latent image is formed on the surface of the body drum (200).

  Then, after the rear end portion of the previous Bk electrostatic latent image passes and before the front end portion of the (T) electrostatic latent image arrives, the revolver developing unit (230) is rotated and Y development is performed. The machine (231Y) is set at the development position, and the Y electrostatic latent image is developed with Y toner. Thereafter, the development of the Y electrostatic latent image area is continued, but when the rear end of the Y electrostatic latent image passes, the revolver developing unit is rotated in the same manner as in the previous Bk developing machine (231K). Then, the next C developing machine (231C) is moved to the developing position. This is also completed before the leading edge of the next C electrostatic latent image reaches the developing position. Note that the C and M image forming steps are the same as the Bk and Y steps described above because the color image data reading, electrostatic latent image forming, and developing operations are the same as those described above.

  The Bk, Y, C, and M toner images sequentially formed on the photosensitive drum (200) in this manner are sequentially aligned on the same surface on the intermediate transfer belt (501) and primarily transferred. As a result, a toner image having a maximum of four colors superimposed on the intermediate transfer belt (501) is formed. On the other hand, at the time when the image forming operation is started, the transfer paper (P) is fed from a paper feed unit such as a transfer paper cassette or a manual feed tray, and is waiting at the nip of the registration roller (610).

  Then, on the intermediate transfer belt (501), the intermediate transfer belt (501) stretched around the secondary transfer counter roller (510) and the secondary transfer bias roller (605) form a nip. When the leading edge of the toner image approaches, the registration roller (610) is driven so that the leading edge of the transfer paper (P) coincides with the leading edge of the toner image, and is transferred along the transfer paper guide plate (601). The paper (P) is conveyed and registration of the transfer paper (P) and the toner image is performed.

  In this way, when the transfer paper (P) passes through the secondary transfer portion, the intermediate transfer belt (501) is transferred by the transfer bias due to the voltage applied to the secondary transfer bias roller (605) by the secondary transfer power source (802). ) The four-color superimposed toner image on the top is transferred onto the transfer paper (P) at once (secondary transfer). Conventionally, plain paper that is relatively smooth has been used as this transfer paper, but in recent years, paper with relatively rough surface properties such as recycled paper has also been used. Furthermore, photographic images are often printed using a wide variety of paper such as coated paper and embossed paper. In particular, when a paper having unevenness and patterns on its surface such as embossed paper is used, there is a problem that the toner image cannot be transferred well due to the unevenness. A conventional intermediate transfer belt made of polyimide cannot follow this uneven shape, and thus toner is not transferred to the concave portion, resulting in uneven transfer. This phenomenon results in an uneven color image having a different color tone on the pattern, particularly in a color portion where two or more colors overlap. By using the intermediate transfer belt of the present invention, it is possible to realize good transfer without causing unevenness due to the unevenness of the paper.

  This transfer paper (P) is conveyed along the transfer paper guide plate (601) and passes through a portion facing the transfer paper neutralization charger (606) comprising a static elimination needle disposed downstream of the secondary transfer portion. After being neutralized by this, the belt is conveyed toward the fixing device (270) by the belt conveying device (210) which is a belt component (see FIG. 1). Then, after the toner image is melted and fixed at the nip portion of the fixing rollers (271) and (272) of the fixing device (270), the transfer paper (P) is sent out of the apparatus main body by a discharge roller (not shown). Stacked face up on a copy tray (not shown). Note that the fixing device (270) may be configured to include a belt component if necessary.

  On the other hand, the surface of the photosensitive drum (200) after the belt transfer is cleaned by the photosensitive member cleaning device (201) and is uniformly discharged by the discharging lamp (202). The residual toner remaining on the outer peripheral surface of the intermediate transfer belt (501) after the toner image is secondarily transferred to the transfer paper (P) is cleaned by the belt cleaning blade (504). The belt cleaning blade (504) is configured to contact and separate at a predetermined timing with respect to the belt outer peripheral surface of the intermediate transfer belt (501) by a cleaning member separating and contacting mechanism (not shown).

  A toner seal member (503) that contacts and separates from the belt outer peripheral surface of the intermediate transfer belt (501) is provided on the upstream side of the belt cleaning blade (504) in the moving direction of the intermediate transfer belt (501). Yes. The toner seal member (503) receives the falling toner dropped from the belt cleaning blade (504) during cleaning of the residual toner, and the falling toner is scattered on the transfer path of the transfer paper (P). It is preventing. The toner seal member (503) is brought into contact with and separated from the belt outer peripheral surface of the intermediate transfer belt (501) together with the belt cleaning blade (504) by the cleaning member separating and contacting mechanism.

  The lubricant (506) scraped by the lubricant application brush (505) is applied to the belt outer peripheral surface of the intermediate transfer belt (501) from which the residual toner has been removed in this way. The lubricant (506) is, for example, a metal soap, and is made of a solid block such as zinc stearate, zinc palmitate, zinc stearate-zinc palmitate mixture, etc., and is in contact with the lubricant application brush (505). It is arranged. This lubricant application mechanism is intended to maintain the transfer performance or cleaning performance in a good condition over the long term, but if this function is not necessary depending on the performance of the intermediate transfer belt, it is not necessary to use this function. Good.

  However, in the intermediate transfer belt having a structure in which spherical particles are spread on the elastic layer as in the present invention, since the metal soap is present on the spherical particles, the adhesion of the toner component is greatly reduced. A high reflectivity can be maintained, which is preferable. The action of applying metal soap also leads to the action of firmly fixing the spherical particles on the elastic intermediate transfer belt, which is particularly preferable.

  The residual charge remaining on the outer peripheral surface of the intermediate transfer belt (501) is removed by a neutralizing bias applied by a belt neutralizing brush (not shown) that is in contact with the outer peripheral surface of the intermediate transfer belt (501). Here, the lubricant application brush (505) and the belt neutralizing brush are brought into and out of contact with the outer peripheral surface of the intermediate transfer belt (501) at a predetermined timing by a contact / separation mechanism (not shown). It has become.

  Here, at the time of repeat copy, the operation of the color scanner and the image formation on the photosensitive drum (200) are performed at a predetermined timing following the image formation process for the fourth color (M) of the first sheet. The process proceeds to the image forming process for the first color (Bk). The intermediate transfer belt (501) has two sheets in the area cleaned by the belt cleaning blade (504) on the outer peripheral surface of the belt following the batch transfer process of the first four-color superimposed toner image to the transfer paper. The Bk toner image of the eye is primarily transferred. After that, the operation is the same as the first sheet. The above is a copy mode for obtaining a four-color full-color copy. In the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and number of times. In the case of the single color copy mode, only the developing device of the predetermined color of the revolver developing unit (230) is set in the developing operation state until the predetermined number of sheets is completed, and the belt cleaning blade (504) is moved to the intermediate transfer belt (501). The copy operation is performed with the touch panel kept in contact.

In the above-described embodiment, the copying machine including only one photosensitive drum 1 has been described. However, the present invention may be configured such that, for example, a plurality of photosensitive drums as illustrated in FIG. 2 are arranged in parallel along one intermediate transfer belt. The present invention can also be applied to the image forming apparatus.
FIG. 2 shows four drums including four photosensitive drums (21BK), (21Y), (21M), and (21C) for forming toner images of four different colors (black, yellow, magenta, and cyan). 1 shows an example of the configuration of a type digital color printer.

  In FIG. 2, the printer body (10) includes an image writing unit (12), an image forming unit (13), and a paper feeding unit (14) for performing color image formation by electrophotography. Based on the image signal, the image processing unit converts the image signal into black (BK), magenta (M), yellow (Y), and cyan (C) color signals for image formation, and the image writing unit (12). Send to. The image writing unit (12) is a laser scanning optical system including, for example, a laser light source, a deflector such as a rotary polygon mirror, a scanning imaging optical system, and a mirror group, and corresponds to each color signal described above. An image document corresponding to each color signal is provided in an image carrier (photosensitive member) (21BK), (21M), (21Y), and (21C) having four writing optical paths and provided for each color of the image forming unit. Doing

  The image forming unit (13) is a photoconductor (21BK), (21M), (21Y) which is an image carrier for black (BK), magenta (M), yellow (Y), and cyan (C). ), (21C). As each photoconductor for each color, an OPC photoconductor is usually used. Around each of the photosensitive members (21BK), (21M), (21Y), and (21C), there are a charging device, a laser beam exposure unit from the writing unit (12), and each color of black, magenta, yellow, and cyan Developing devices (20BK), (20M), (20Y), (20C), primary transfer bias rollers (23BK) as primary transfer means, (23M), (23Y), (23C), cleaning devices ( (Not shown), and a photosensitive member neutralizing device (not shown) are provided. The developing devices (20BK), (20M), (20Y), and (20C) use a two-component magnetic brush developing system. The intermediate transfer belt (22), which is a belt component, includes the photosensitive members (21BK), (21M), (21Y), and (21C) and the primary transfer bias rollers (23BK), (23M), and (23Y). , (23C), and the toner images of the respective colors formed on the respective photoreceptors are sequentially superimposed and transferred.

  On the other hand, the transfer paper (P) is fed from the paper feed section (14) and then carried by the transfer conveyance belt (50), which is a belt constituting section, via the registration rollers (16). When the intermediate transfer belt (22) and the transfer conveying belt (50) come into contact with each other, the toner image transferred onto the intermediate transfer belt (22) is transferred to a secondary transfer bias roller (60) as a secondary transfer unit. ) For secondary transfer (collective transfer). Thereby, a color image is formed on the transfer paper (P). The transfer paper (P) on which the color image is formed is conveyed to the fixing device (15) by the transfer conveying belt (50). After the image transferred by the fixing device (15) is fixed, the transfer paper (P) is removed from the printer main body. To be discharged.

  The residual toner that is not transferred during the secondary transfer and remains on the intermediate transfer belt (22) is removed from the intermediate transfer belt (22) by the belt cleaning device (25). A lubricant application device (not shown) is disposed on the downstream side of the belt cleaning device (25). This lubricant application device includes a solid lubricant and a conductive brush that rubs the intermediate transfer belt (22) to apply the solid lubricant. The conductive brush is always in contact with the intermediate transfer belt (22) and applies a solid lubricant to the intermediate transfer belt (22). The solid lubricant has the effect of improving the cleaning property of the intermediate transfer belt (22), preventing the occurrence of filming and improving the durability, and for maintaining the reflectance and fixing the spherical particles as described above. Is also preferable.

  Further, position detection marks (not shown) are provided on the outer peripheral surface or inner peripheral surface of the intermediate transfer belt (22). However, on the outer peripheral surface side of the intermediate transfer belt (22), it is necessary to devise a position detection mark that avoids the passing area of the belt cleaning device (25), which may be difficult to arrange. In this case, a position detection mark may be provided on the inner peripheral surface side of the intermediate transfer belt (22). The optical sensor (28) as a mark detection sensor is provided at a position between the secondary transfer bias roller (60) and the belt drive roller (24). Position detection is performed by detecting light reflection from the surface of the intermediate transfer belt.

  In addition to position detection, an image density detection mark is provided on the surface of the intermediate transfer belt, the density of the mark is measured with an optical sensor, and it is determined whether the image being formed has an appropriate density. Is not suitable, it is preferable that the toner density in the developer, the developing bias, the charging potential of the photosensitive member, etc. can be adjusted to always form an appropriate image.

  The seamless belt according to the present invention can be preferably applied to an intermediate transfer belt type image forming apparatus equipped with the intermediate transfer belt (501) or (22) as described above, and the intermediate transfer belt (501) or ( The present invention can also be applied to a transfer / conveying belt type image forming apparatus equipped with a transfer / conveying belt instead of 22). Further, in the case of an image forming apparatus using a transfer / conveying belt system, the present invention can be applied to either the 1-photosensitive drum system or the 4-photosensitive drum system.

  Next, the present invention will be specifically described with reference to examples and comparative examples. In addition, a part here is a weight part.

[Example 1]
A metal cylinder having an outer diameter of 1000 mm and a length of 300 mm having a mirror-finished outer surface is used as a mold. While rotating the cylinder mold at 55 rpm (times / min), a polyimide solution in which carbon black is dispersed is applied at 120 ° C. And then heated at 190 ° C. for 20 minutes, stopped rotating, slowly cooled, and then heat treated at 320 ° C. for 60 minutes to produce a polyimide seamless belt having a final film thickness of 70 μm. .
On this polyimide seamless belt, a polyurethane solution in which carbon black was dispersed was applied so that the final film thickness of the polyurethane was 400 μm and dried by touch. Spherical titanium oxide having an average particle diameter of 2.0 μm (refractive index of 2.5 at 900 nm) was uniformly applied to the surface, and a urethane blade was pressed at a pressure of 500 mN / cm ² . The seamless belt was heated at 120 ° C. for 40 minutes to produce an elastic intermediate transfer belt in which spherical titanium oxide was laminated on a polyurethane elastic layer (refractive index 1.7 at 900 nm, elastic modulus 150 N / mm ² ).

  An SEM image of the surface of the produced elastic transfer belt is shown in FIG. The spherical titanium oxide particles were spread on the surface of the polyurethane layer (elastic layer). From the observation result of the cross-sectional SEM, the spherical titanium oxide particles located on the surface of the surface layer have 70 to 82% of the particle diameter embedded in the polyurethane layer, and more than 50% of the surface of the polyurethane layer is spherical titanium oxide particles. It was found to be coated. (In FIG. 4, the spherical titanium oxide particles are finely packed, but the polyurethane appears on the surface as the spherical titanium oxide particles are buried.)

The produced elastic transfer belt is mounted as an intermediate transfer belt on an imagio MP C2500 remodeling machine (manufactured by Ricoh, tandem image forming apparatus, with a mechanism for applying a zinc stearate-zinc palmitate mixture to the intermediate transfer belt). Image formation was performed 10,000 sheets using a commercially available ordinary two-component developer in an environment of 55 ° C. and RH. As a result, the 10,000th image formed image was a high quality image.
This image forming apparatus irradiates an image density detection patch on the intermediate transfer belt with an LED having a light emission center of 950 nm for every 250 image formations when the image forming apparatus is started up, and has a maximum light receiving sensitivity at 800 nm. The image density is detected from the measured value of the reflected light by the sensor, and the image condition is set.

[Comparative Example 1]
In Example 1, a surface layer coating solution consisting of 50 parts of titanium oxide particles (average particle size 20 nm) and 100 parts of ultraviolet curable acrylic resin was applied on the polyurethane layer, and irradiated with ultraviolet rays to form a 20 μm thick titanium oxide. A layer was formed to produce an elastic transfer belt.
The produced elastic transfer belt was mounted as an intermediate transfer belt on the image forming apparatus used in Example 1, and 10,000 sheets of images were formed.
In the 10,000th image formed, a streak-like abnormal image occurred. When the elastic intermediate transfer belt was observed, cracks occurred in the titanium oxide layer of the elastic intermediate transfer belt.

[Comparative Example 2]
In Example 1, an elastic transfer belt was produced in the same manner as in Example 1 except that silicon oxide (average particle diameter 1.8 μm, refractive index 1.6 at a wavelength of 900 nm) was used instead of spherical titanium oxide. In this elastic transfer belt, 48% or more of the surface of the polyurethane layer is coated with silicon oxide particles.
When the produced elastic transfer belt was mounted as an intermediate transfer belt in the image forming apparatus used in Example 1, and the image forming apparatus was turned on, it stopped during the startup of the image forming apparatus.
As a result of examining the cause of the image forming apparatus being stopped, the reflectance of the elastic transfer belt is so low that the intensity of the light received by the optical sensor in the place where the image density detection patch is and where it is not is so low that the image It was found that the concentration could not be detected.

[Example 2]
In Example 1, an elastic transfer belt was produced in the same manner as in Example except that spherical silicon particles (average particle size 2.2 μm, refractive index 4.0 at a wavelength of 900 nm) were used instead of spherical titanium oxide. In this elastic transfer belt, 50% or more of the surface of the polyurethane layer is coated with spherical silicon particles.
The produced elastic transfer belt was mounted as an intermediate transfer belt on the image forming apparatus used in Example 1, and 10,000 sheets of images were formed. Image formation The 10,000th image was a high-quality image.

Example 3
Example 1 is the same as Example 1 except that NBR (nitrile rubber) in which carbon black is dispersed instead of polyurethane (elastic modulus 200 N / mm ^{2 of} elastic layer, refractive index 1.7 at a wavelength of 900 nm) is used as the elastic layer. Similarly, an elastic transfer belt was produced.
The produced elastic transfer belt was mounted as an intermediate transfer belt on the image forming apparatus used in Example 1, and 10,000 sheets of images were formed. Image formation The 10,000th image was a high-quality image.

[Examples 4 to 8 and Comparative Examples 3 to 4]
In Example 1, an elastic transfer belt was produced by setting the particle diameter of the spherical titanium oxide particles and how the spherical titanium oxide particles were embedded in the elastic layer as shown in Table 1. The produced elastic transfer belt was mounted as an intermediate transfer belt in the image forming apparatus used in Example 1, and images on the 1000th and 10000th sheets of image formation were observed and evaluated. The results are shown in Table 1.

Image evaluation result ○: High quality image Δ: Although it is within the allowable range, when the image is magnified with a magnifying glass, an abnormal image is obtained.
X: Image omission occurs as a whole.

Example 9
In the image forming apparatus using the elastic transfer belt produced in Example 6 as an intermediate transfer belt, 10,000 images were formed in an environment of 30 ° C. and 85% RH, and a high-quality image was obtained even on the 10,000th sheet. Obtained. Further, 200,000 sheets of images were formed, and high quality images were obtained even on the 200,000 sheets.

Example 10
In the image forming apparatus using the elastic transfer belt produced in Example 6 as an intermediate transfer belt, image formation was similarly performed without applying the zinc stearate-zinc palmitate mixture to the intermediate transfer belt. A high quality image was also obtained in the eyes. Furthermore, although 200,000 sheets of images were formed, the image was in an allowable range, but when the image was enlarged with a magnifying glass, the image had a place where image blur occurred.

(In Fig. 1)
P Transfer paper 70 Static elimination roller 80 Ground roller 200 Photosensitive drum 201 Photoconductor cleaning device 202 Static elimination lamp 203 Charging charger 204 Potential sensor 205 Toner image density sensor 210 Belt transport device 230 Revolver developing unit 231Y Y developing machine 231K Bk developing machine 231C C Developer 231M M Developer 270 Fixing device 271, 272 Fixing roller 500 Intermediate transfer unit 501 Intermediate transfer belt 503 Toner seal member 504 Belt cleaning blade 505 Lubricant application brush 506 Lubricant 507 Primary transfer bias roller 508 Belt drive roller 509 Belt Tension controller 510 Secondary transfer counter roller 511 Cleaning counter roller 512 Feedback current detection roller 513 Toner image 514 Optical sensor -600 Secondary transfer unit 601 Transfer paper guide plate 605 Secondary transfer bias roller 606 Transfer paper neutralization charger 608 Cleaning blade 610 Registration roller 801 Primary transfer power source 802 Secondary transfer power source (in FIG. 2)
P Transfer paper 10 Printer body 12 Image writing unit 13 Image forming unit 14 Paper feeding unit 15 Fixing device 16 Registration rollers 20BK, 20M, 20Y, 20C Developing devices 21BK, 21M, 21Y, 21C Photoconductor 22 Intermediate transfer belts 23BK, 23M , 23Y, 23C Primary transfer bias roller 25 Belt cleaning device 50 Transfer conveyance belt 60 Secondary transfer bias roller

JP 2007-11311 A Japanese Patent Laid-Open No. 08-202064

Claims (10)

  In a transfer belt in which an elastic layer is laminated on a base layer containing polyimide resin or polyamideimide resin, spherical particles having an average particle size of 0.5 to 4 μm having a refractive index at a wavelength of 900 nm larger than that of the elastic layer are spread on the elastic layer. An elastic transfer belt.   The elastic transfer belt according to claim 1, wherein the spherical particles have a refractive index of 2.2 or more at a wavelength of 900 nm.   3. The elastic transfer belt according to claim 1, wherein a region of 60 to 90% of the diameter of the spherical particle exposed on the surface of the spherical particle is embedded in the elastic layer. 4.   The elastic transfer belt according to claim 1, wherein the spherical particles cover 45% or more of the surface area of the elastic layer.   The spherical particles are selected from titanium oxide, barium titanate, barium sulfide, silicon, zinc oxide, zinc sulfide, strontium titanate, strontium sulfide, germanium, and silicon carbide. The elastic transfer belt described in 1.   In an image forming apparatus for performing primary transfer by sequentially superimposing a plurality of color toner developed images sequentially formed on an image carrier on an intermediate transfer belt, and performing secondary transfer of the primary transfer image collectively to a recording medium An image forming apparatus, wherein the intermediate transfer belt is the elastic transfer belt according to claim 1.   The image forming apparatus according to claim 6, wherein a lubricant application unit for applying a lubricant to the surface of the intermediate transfer belt is provided in the vicinity of the intermediate transfer belt.   The image forming apparatus according to claim 7, wherein the lubricant is a metal soap.   A test pattern toner image is transferred onto the intermediate transfer belt, a density of the test pattern toner image is optically measured, and an image forming condition is adjusted from the measured density of the toner image. The image forming apparatus according to claim 6.   The image forming apparatus according to claim 9, wherein the means for optically measuring the density of the toner image of the test pattern is for measuring reflection of near-infrared light.