JP6424670B2 - Intermediate transfer body, image forming apparatus provided with the same, and method of manufacturing the intermediate transfer body - Google Patents

Description

  The present invention relates to an intermediate transfer member, an image forming apparatus provided with the same, and a method of manufacturing the intermediate transfer member.

  In an electrophotographic image forming apparatus, for example, a latent image formed on an electrostatic latent image carrier (also referred to as a photosensitive member) is developed with toner, and the obtained toner image is The toner image on the intermediate transfer member is transferred onto a recording material such as paper by temporarily holding the toner image on an intermediate transfer belt.

  Here, the intermediate transfer member can be made elastic by laminating the elastic layer on the resin base material layer constituting the intermediate transfer member. As a result, the surface of the intermediate transfer member can follow the uneven paper or the like, so that improvement of the transferability (transfer rate) is expected.

  However, the elastic layer has low strength and durability due to its soft surface and high friction. For this reason, when the surface of the elastic layer is scraped by paper, a photosensitive member or the like due to the use of the intermediate transfer member, the image quality and the transferability deteriorate with time. Therefore, in order to provide a surface coat having high durability to the elastic layer, it is considered to form a layer (surface layer) covering the surface of the elastic layer with a polyimide resin having a hard surface and low friction. (For example, Unexamined-Japanese-Patent No. 2010-217777 (patent document 1)).

JP, 2010-217777, A

  However, common polyimide resins are only soluble in high boiling aprotic polar solvents (eg, N-methyl-2-pyrrolidone, boiling point: 202 ° C.). When a solution in which a polyimide resin is dissolved is applied to such a high boiling point solvent to form a surface layer, heating to a high temperature (for example, 200 ° C. or more) is necessary to evaporate the solvent. When heated to a high temperature, the elastic layer deteriorates and hardens, which causes a problem that the transferability is deteriorated. Further, the solvent having a high boiling point tends to dissolve the elastic body, and there is also a problem that when the elastic body dissolves, the surface layer can not be formed.

  The present invention has been made in view of such a situation, and an object thereof is to provide an intermediate transfer member having high durability while having excellent transferability, and an image provided with the same. It is to provide a forming device.

  The present inventors diligently studied to solve the above problems, and it was found that a specific polyimide having a structural unit represented by the following chemical formula (1) was dissolved in a solvent having a low boiling point (for example, less than 150 ° C.) The present invention has been completed by finding out and conducting further studies. As described above, according to the present invention, by providing the surface layer made of a specific polyimide resin on the elastic layer, it is possible to provide an intermediate transfer belt having high durability while having excellent transferability. It is.

  That is, the intermediate transfer member of the present invention is an image in which the toner image carried on the electrostatic latent image carrier is primarily transferred to the intermediate transfer member, and then the toner image is secondarily transferred from the intermediate transfer member to the recording material. It is used in a forming apparatus and has an endless belt shape, and at least a resin base layer, an elastic layer laminated on the outer side of the resin base layer, and an outer side of the elastic layer. And a laminated surface layer, wherein the surface layer is made of a polyimide resin containing a specific polyimide having a structural unit represented by the chemical formula (1) as a main component. In Chemical Formula (1), X represents a divalent group containing 7 or more and 25 or less carbons.

  Further, the present invention is used in an image forming apparatus in which a toner image carried on an electrostatic latent image carrier is primarily transferred to an intermediate transfer member, and then the toner image is secondarily transferred from the intermediate transfer member to a recording material. The intermediate transfer member, wherein the intermediate transfer member has an endless belt-like shape, and a resin base layer containing at least an elastic material, and a surface layer laminated on the outside of the resin base layer The present invention also relates to an intermediate transfer member comprising a polyimide resin containing as a main component a specific polyimide having the structural unit represented by the chemical formula (1).

Here, it is preferable that said X is a bivalent group containing 2 or more and 4 or less phenylene group.
Further, X is more preferably a divalent group represented by the chemical formula (2). In Chemical Formula (2), Y represents a divalent group or a single bond.

  Here, Y is selected from the group consisting of an alkylene group having 2 to 4 carbon atoms which may have a branch, an oxylene group, a phenylene group which may have a substituent, a carbonyl group, and a sulfonyl group. It is preferred to include at least one group.

  Moreover, it is more preferable that said Y is a bivalent group shown by Chemical formula (3)-Chemical formula (7).

  The specific polyimide is preferably one synthesized from 2,3,3 ', 4'-oxydiphthalic anhydride represented by the chemical formula (8) and oxyaniline represented by the chemical formula (9). In Chemical Formula (9), Ar represents a phenylene group, and X represents a divalent group containing 7 or more and 25 or less carbons.

  In the above intermediate transfer member, the thickness of the surface layer is preferably 0.5 μm or more and 5.0 μm or less.

  The present invention also relates to an image forming apparatus provided with any of the above-described intermediate transfer members.

  Further, the present invention is the method for producing an intermediate transfer member according to any one of the above, wherein a solution obtained by dissolving the specific polyimide in a solvent having a boiling point of less than 150 ° C. is applied, and the temperature is less than 150 ° C. The present invention also relates to a manufacturing method, which comprises the step of forming the surface layer by heating the above to evaporate the solvent.

  The intermediate transfer member of the present invention has excellent transferability because it can suppress curing and dissolution of the elastic layer by having a surface layer formed using a polyimide resin soluble in a solvent having a low boiling point. However, it exhibits an excellent effect of having high durability.

FIG. 2 is a schematic cross-sectional view showing a part of the intermediate transfer member of Embodiment 1. FIG. 1 is a schematic view showing an example of an image forming apparatus of the present invention.

  Hereinafter, embodiments according to the present invention will be described in more detail. In addition, when demonstrating using a drawing in the following embodiment, what attached | subjected the same referential mark has shown the identical part or the equivalent part.

Embodiment 1
<Intermediate transfer body>
The intermediate transfer member according to the present embodiment (hereinafter simply referred to as “the present embodiment”) firstly transfers the toner image carried on the electrostatic latent image carrier to the intermediate transfer member, and then transfers the toner image to the intermediate transfer member. It is used in an image forming apparatus for secondary transfer from an intermediate transfer body to a recording material. The details of such an image forming apparatus will be described later.

  Such an intermediate transfer member 21 has an endless belt shape (see FIG. 2). Here, the endless belt-like shape is one having this literally shape and, for example, conceptually (geometrically) formed by joining both ends of a sheet of a long sheet It is preferable to have a seamless belt-like or cylindrical shape in practice.

  Further, the intermediate transfer body 21 includes at least a resin base layer 21a, an elastic layer 21b and a surface layer 21c in order from the inside (see FIG. 1). Note that FIG. 1 shows a part of the intermediate transfer member 21 cut out, and the entire shape is not shown, but the lower side of FIG. 1 corresponds to the inside of the intermediate transfer member (intermediate transfer belt).

  And, such an intermediate transfer member can include any other configuration as long as it includes at least a resin base layer, an elastic layer and a surface layer. An adhesive layer, a reinforcement layer, an intermediate layer etc. can be mentioned as such other composition.

  Such an intermediate transfer member preferably has high durability as well as securing electrical and physical performance by the synergistic action of the resin base layer and the surface layer.

The respective components constituting the intermediate transfer member will be described below.
<Resin base material layer>
The resin base material layer contained in the intermediate transfer member of the present embodiment can be used without particular limitation on conventionally known materials used for this type of application. For example, such a resin substrate layer may be made of polyimide (PI), polyamide imide (PAI), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polycarbonate, polyvinylidene fluoride, polyalkylene terephthalate (polyethylene terephthalate, poly It can be composed of resin materials such as butylene terephthalate etc., polyether, polyether ketone, ethylene tetrafluoroethylene copolymer, polyamide and the like. Among these, super ene engineering plastics having strength and durability such as polyimide, polyamide imide, polyphenylene sulfide, polyether ether ketone and the like are preferable.

  It is preferable that such a resin base material layer has a Young's modulus measured by nanoindentation method exceeding 5.0 GPa, and the thickness is preferably 50 to 200 μm.

  Although it is possible to use a material obtained by blending the above resin material and an elastic material as a material of such a resin base layer, the intermediate transfer body of this embodiment has an elastic layer described later. In particular, it is not necessary to blend elastic materials. As an elastic material, the elastic material used as a material of the elastic-body layer mentioned later can be used, for example.

Such a resin base material layer is a seamless belt in which an electrical resistance value (volume resistivity) is adjusted to 10 ⁵ Ω · cm to 10 ¹¹ Ω · cm by adding a conductive substance (conductive filler) to a resin material. And drums are preferred.

  As such a conductive substance, carbon black, carbon nanotubes and the like can be used. As carbon black, neutral or acidic carbon black can be used. The amount of conductive material used varies depending on the type of conductive material used, but it may be added so that the volume resistance value and surface resistance value of the intermediate transfer member fall within a predetermined range, and generally 100 parts by volume of resin material To 10 parts by volume, preferably 10 parts by volume to 16 parts by volume.

  In addition, in order to make the dispersibility in resin material of such a conductive substance favorable, it is also possible to add a dispersing agent. A nylon compound etc. can be mentioned as such a dispersing agent.

  The resin base layer can be produced by a conventionally known general method. For example, a resin as a material is melted by an extruder, and formed into a cylindrical shape by an inflation method using an annular die, and then it is cut into circular rings, whereby an annular endless belt-shaped resin base layer can be produced.

<Elastic layer>
The elastic layer contained in the intermediate transfer member of the present embodiment is formed on the resin base layer (outside of the resin base layer). The elastic layer is not limited to the case of being formed in direct contact with the resin base layer, and may be formed, for example, on another layer formed on the resin base layer.

  The elastic layer is made of an elastic material. As an elastic material, a thermosetting elastomer is mentioned, for example. As a thermosetting elastomer, rubber | gum, a thermosetting resin type elastomer, etc. are mentioned. Examples of the rubber include chloroprene rubber, nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), ethylene / propylene / diene rubber (EPDM), butyl rubber, silicone rubber and the like. Examples of the thermosetting resin elastomer include hydrogenated polybutadiene, polyurethane, chlorinated polyisoprene and the like. These may be used alone or in combination of two or more. The elastic material preferably contains chloroprene rubber or HNBR, particularly in view of hardness, durability and the like.

  The effect of the intermediate transfer member of the present embodiment is particularly effective when the elastic layer deteriorates and solidifies at a high temperature (for example, 150 ° C. or more).

  The thickness of such an elastic layer is not particularly limited, but is preferably 100 to 500 μm in consideration of mechanical strength, image quality, manufacturing cost and the like.

<Surface layer>
The surface layer included in the intermediate transfer member of the present embodiment is formed on the elastic layer (outside of the elastic layer). The surface layer is not limited to the case of being formed in direct contact with the elastic layer, and may be formed, for example, on another layer formed on the elastic layer.

  Here, the surface layer is preferably formed to cover the entire surface of the elastic layer. In this case, the surface of the elastic layer means the surface on which the toner image is transferred (formed). However, even if a part of the surface of the elastic layer is not covered by the surface layer, it does not deviate from the present embodiment as long as the above-mentioned effects are exhibited.

  Such a surface layer is made of a polyimide resin containing a specific polyimide as a main component, and the specific polyimide has a structural unit (repeating unit) represented by the chemical formula (1).

  In the above chemical formula (1), X represents a divalent group containing 7 or more and 25 or less carbons. The carbon number contained in X is preferably 12 or more and 19 or less.

  Note that at both ends of the chemical formula (1), a bond (a straight line) having nothing attached to one side indicates that it becomes a bond with a similar structural unit or another structural unit. Also, it is shown that the bond between the oxygen atom on both sides of X and the benzene ring adjacent thereto bonds to any carbon of the benzene ring, and two substituents (bonds) in these benzene rings Means that the position of is either ortho, meta or para.

  In the present specification, the “main component” is a component contained most in the material, preferably a component having a content of more than 50% by weight, and more preferably a component having a content of 70% by weight or more. More preferably, it is a component having a content of 90% by weight or more. The main component may be 100% by weight (the polyimide resin may be composed only of the above-mentioned specific polyimide).

  The polyimide resin constituting the surface layer may contain specific polyimides different in molecular weight (degree of polymerization), and the weight average molecular weight of the specific polyimide is preferably 10,000 to 100,000, more preferably 2 It is 10,000 to 70,000, and more preferably 30,000 to 50,000. When the mass average molecular weight is less than 10,000, the hardness of the surface layer may be insufficient, and when the mass average molecular weight is more than 100,000, it may be difficult to dissolve in a low boiling point solvent.

  It is inferred that the specific polyimide contained in the polyimide resin constituting the surface layer exhibits the following function by having such a configuration. That is, when the constituent unit represented by the chemical formula (1) in the polyimide has a chain of a predetermined length in the portion of X in the chemical formula (1), molecules of the solvent easily enter the steric structure of the polyimide It is presumed that it becomes soluble in a low boiling point solvent because it has become.

  The intermediate transfer member of the present embodiment can suppress the curing and dissolution of the elastic layer by having a surface layer formed of such a specific polyimide resin soluble in a solvent having a low boiling point. Thus, both excellent transferability (followability to irregularities of paper and the like) and high durability (abrasion resistance) are realized.

  Moreover, the surface layer of this embodiment is flexible because the structural unit represented by the chemical formula (1) of the specific polyimide has a chain of a predetermined length in the portion of X of the chemical formula (1). It is considered that the flexibility is improved and the transferability is improved because the property is imparted.

  In addition, although "polyimide" is a general term for a polymer having an imide bond in a constituent unit (repeating unit), the aromatic compound in the specific polyimide containing the constituent unit represented by the chemical formula (1) is an imide bond directly It is an aromatic polyimide connected by

  Moreover, it is preferable that X of Chemical formula (1) is a bivalent group containing 2 or more and 4 or less phenylene group. The number of phenylene groups contained in X is more preferably 2 or more and 3 or less. In this case, the above effects become particularly remarkable. Incidentally, “a divalent group containing two or more phenylene groups” means not only a divalent group represented by the chemical formula (2) described later, but also both end sides of two phenylene groups of the chemical formula (2) (Y At least one of the opposite sides) may further contain a divalent group.

  X in the chemical formula (1) is preferably a divalent group represented by the chemical formula (2).

  In Chemical Formula (2), Y represents a divalent group or a single bond. When Y is a single bond, the bivalent group represented by the chemical formula (2) is a biphenylene group, but this biphenylene group is also included in the above-mentioned “divalent group containing two or more phenylene groups”. Be

  In the above chemical formula (2), Y is a group consisting of an alkylene group having 2 to 4 carbon atoms which may have a branch, an oxylene group, a phenylene group which may have a substituent, a carbonyl group, and a sulfonyl group. It is preferable to include at least one group selected from the group consisting of

  In the above chemical formula (2), Y is, for example, a divalent group represented by chemical formula (3) to chemical formula (7).

  A specific polyimide containing a constitutional unit represented by the above chemical formula (1) is a 2,3,3 ', 4'-oxydiphthalic anhydride represented by the chemical formula (8) and an oxyaniline represented by the chemical formula (9) And can be synthesized from

  In Chemical Formula (9), Ar represents a phenylene group, and X represents a divalent group containing 7 or more and 25 or less carbons. The carbon number contained in X is preferably 12 or more and 19 or less.

  As a synthesis method of a specific polyimide having a structural unit represented by the above chemical formula (1), a conventionally known method can be adopted without any particular limitation, but, for example, chemical imidization reaction (for example, patent 5495464) And synthetic methods using a thermal imidization reaction.

  In addition, the specific polyimide used by this embodiment is not restricted to what contains only the structural unit shown by Chemical formula (1), and the copolymer containing another structural unit may be sufficient. When it is a copolymer, it is preferable that the ratio of the structural unit shown by Chemical formula (1) with respect to the whole polymer is 80 mass% or more.

  Moreover, when a specific polyimide contains another structural unit, examples of the other structural unit include (meth) acrylic acid derivatives, aromatic vinyl monomers, olefin hydrocarbon monomers, and vinyl ester monomers. And structural units derived from vinyl halide monomers, vinyl ether monomers and the like. In addition, such other structural units are not limited to one type, and may be two or more types.

  The thickness of the surface layer in the present embodiment is preferably 0.5 to 5.0 μm. If the thickness of the surface layer is too thick, the effect of improving the transferability by the elasticity of the elastic layer can not be sufficiently exhibited. On the other hand, when the thickness of the surface layer is too thin, the effect of improving the durability by the surface layer can not be sufficiently exhibited.

  Such a surface layer may be, for example, an endless belt-like resin base having a solution (coating solution for forming a surface layer) in which a component of a polyimide resin (surface layer) containing the specific polyimide described above as a main component is dissolved in a solvent. It can form by apply | coating on the outer peripheral surface of the elastic-body layer formed on the material layer.

  Specifically, for example, a coating solution for forming a surface layer is applied onto the outer peripheral surface by a dip coating method using a coating device. The coating conditions are adjusted, for example, such that the thickness of the surface layer after drying is 0.5 to 5.0 μm. Thereafter, the coating film is heated to evaporate the solvent in the coating film and to cure the polyimide resin, whereby a surface layer can be formed. In addition, heating of a coating film can be performed by electromagnetic induction heating, for example.

  As a solvent (solvent) of the coating liquid for surface layer formation, a proton type polar solvent is mentioned, for example. As the protic polar solvent, for example, tetrahydrofuran (boiling point: 66 ° C.), methyl isobutyl ketone (boiling point: 116 ° C.) and the like can be suitably used.

  The boiling point of the solvent is preferably less than 150 ° C., more preferably 100 ° C. or less, still more preferably 90 ° C. or less. When the boiling point of the solvent is less than 150 ° C., the heating temperature may be low (less than 150 ° C.) when the surface layer is formed by evaporating the solvent from the coating solution for forming the surface layer. Curing can be suppressed. In general, the elastic layer tends to deteriorate and harden when heated at a temperature of 150 ° C. or higher.

  In addition, since the solvent having a low boiling point hardly dissolves the elastic layer, the surface layer can be formed on the elastic layer using the coating solution for forming the surface layer. Furthermore, since the solvent having a low boiling point generally has a low viscosity, the viscosity of the coating liquid for forming a surface layer is reduced, which is advantageous in that the operability of coating is improved.

<Additives>
The resin base layer, the elastic layer, the surface layer, and the other layers described above can each contain an additive. As such additives, photo-curing initiators, conductive particles (conductive fillers), various fillers (mainly for the purpose of improving strength), various modifiers (graft copolymer etc.), organic solvents, Light stabilizers, UV absorbers, catalysts, colorants, antistatic agents, lubricants, leveling agents, antifoaming agents, polymerization accelerators, antioxidants, flame retardants, infrared absorbers, surfactants, surface modifiers Etc. can be mentioned.

<Image forming apparatus>
The image forming apparatus according to the present embodiment is provided with the above-described intermediate transfer member, and as long as such an intermediate transfer member is provided, the other configuration should be adopted without particular limitation to the conventionally known configuration. Can.

  Hereinafter, the image forming apparatus of the present embodiment will be described based on FIG. FIG. 2 is a schematic view showing an example of the image forming apparatus of the present embodiment.

  The image forming apparatus 1 of FIG. 2 forms an image on a recording material by a known electrophotographic method, and includes an image processing unit 10, a transfer unit 20, a paper supply unit 30, a fixing unit 40, and a control unit. 45, and selectively executes color and monochrome printing based on print jobs received from an external terminal device (not shown) via a network (for example, a LAN).

  The image processing unit 10 includes image forming units 10Y, 10M, 10C, and 10K corresponding to development colors of yellow (Y), magenta (M), cyan (C), and black (K). The image forming unit 10Y includes a photosensitive drum 11, which is an electrostatic latent image carrier, and a charger 12, an exposure unit 13, a developing unit 14, a primary transfer roller 15, and a cleaner 16 disposed around the photosensitive drum. . The charger 12 charges the circumferential surface of the photosensitive drum 11 rotating in the direction indicated by the arrow A.

  The exposure unit 13 exposes and scans the charged photosensitive drum 11 with laser light to form an electrostatic latent image on the photosensitive drum 11. The developing unit 14 contains a developer containing toner inside, develops the electrostatic latent image on the photosensitive drum 11 with the toner, and thereby forms a toner image of Y color on the photosensitive drum 11 . That is, thereby, the toner image is carried on the electrostatic latent image carrier.

  The primary transfer roller 15 electrostatically transfers the Y-color toner image on the photosensitive drum 11 onto the intermediate transfer member 21. That is, the toner image described above is primarily transferred to the intermediate transfer member. The cleaner 16 cleans the residual toner remaining on the photosensitive drum 11 after transfer. The other imaging units 10M to 10K have the same configuration as that of the imaging unit 10Y, and the reference numerals are omitted in FIG. The transfer unit 20 further includes an intermediate transfer member 21 stretched between the driving roller 24 and the driven roller 25 and circulated and driven in the arrow direction. The intermediate transfer body 21 has a seamless belt shape (that is, an endless belt shape), and is a cylindrical shape obtained by injection molding or centrifugally molding a resin material so as to have a desired circumferential length determined by design.

  When color printing (color mode) is performed, toner of the corresponding color is formed on the photosensitive drum 11 for each of the image forming units 10M to 10K, and each of the formed toner images is The image is transferred onto the intermediate transfer body 21. The image forming operation for each of the colors Y to K is performed with timing shifted from the upstream side to the downstream side so that the toner images of the respective colors are transferred overlappingly on the same position of the traveling intermediate transfer member 21. Ru.

  The sheet feeding unit 30 feeds the sheets S serving as the recording material one by one from the sheet feeding cassette in accordance with the above-described image formation timing, and directs the fed sheet S onto the secondary transfer roller 22 on the conveyance path 31. Transport. When the sheet S conveyed to the secondary transfer roller 22 passes between the secondary transfer roller 22 and the intermediate transfer member 21, each color toner image formed on the intermediate transfer member 21 is of the secondary transfer roller 22. The secondary transfer is collectively performed on the sheet S by electrostatic action. That is, the toner image is secondarily transferred from the intermediate transfer member to the recording material.

  The sheet S on which each color toner image has been secondarily transferred is conveyed to the fixing unit 40, and is heated and pressed in the fixing unit 40, whereby the toner on the surface is fused to the surface of the sheet S and fixed. Then, the sheet is discharged onto the sheet discharge tray 33 by the sheet discharge roller 32. Thus, an image corresponding to the toner image is formed on the recording material.

  In the above, the operation in the case of executing the color mode has been described, but in the case of executing printing of monochrome, for example, black (monochrome mode), only the image forming unit 10K for black is driven. By the same operation as in the above, the black image formation (printing) is executed on the sheet S through the steps of charging, exposure, development, transfer, and fixing for black.

  The toner and toner pattern which can not be transferred to the sheet S on the intermediate transfer member 21 are removed by a cleaning blade 26 disposed at a position facing the driven roller 25 with the intermediate transfer member 21 interposed therebetween. Further, on the downstream side of the traveling direction of the intermediate transfer member 21 of the image forming unit 10K, for example, a density detection sensor 23 composed of a reflection type photoelectric sensor is disposed. Detect the concentration.

  The control unit 45 controls each unit based on print job data received from an external terminal device via a network to execute a smooth printing operation. The operation panel 35 is disposed on the front side and the upper side of the main body of the image forming apparatus 1 and at a position where the user can easily operate. The operation panel 35 includes a button for receiving various instructions from the user, a touch panel liquid crystal display unit, and the like, and can transmit the received instruction contents to the control unit 45.

  As such an image forming apparatus, an electrophotographic image forming apparatus such as a copying machine, a printer, a digital printing machine, a simple printing machine and the like can be mentioned, and it may be either dry type or wet type but it is a dry type image It is preferable to use a forming apparatus.

  Such an image forming apparatus provided with the intermediate transfer member of the present embodiment exhibits an excellent effect that an image of high image quality can be formed over a long period of time.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

Example 1
(1) Formation of Elastic Layer A mixture of chloroprene rubber (elastic material) and carbon black (conductive filler) was dissolved in toluene to prepare a coating solution for forming an elastic layer. An elastic body having a film thickness of 200 μm formed by dipping on the outer peripheral surface of a resin base layer (a polyimide belt generally used for an intermediate transfer member of an image forming apparatus) by using the coating solution for forming an elastic layer. The layers were made.

(2) Formation of surface layer 310 g (1 mol) of 2,3,3 ', 4'-oxydiphthalic acid in a 5000 mL round-bottom four-necked flask equipped with a mechanical shaker, thermometer and nitrogen gas inlet tube Anhydride (a compound represented by the chemical formula (8)), 200 g of an oxyaniline represented by the chemical formula (9) (wherein X in the chemical formula (9) is a divalent group represented by the following chemical formula (10) And 2200 mL of DMAC (dimethyl acetamide) were added and reacted for 4 hours to prepare a polyimidic acid solution.

  Next, imidization is completed by adding 1050 g of acetic anhydride, 260 g of triethylamine, and 220 g of toluene and reacting for 1 hour, filtering out the polyimide powder, and subsequently, 3 mg of the powder with 1000 mL of acetone. After washing twice, filtration, drying for 2 hours, and heat treatment at 220 to 280 ° C. for 2 to 5 hours, 426.6 g of polyimide powder was prepared.

  In addition, the obtained polyimide is corresponded to the specific polyimide which has a structural unit which is a bivalent group shown by said Chemical formula (10) in Chemical formula (1). Moreover, the number average molecular weight (Mn) of the obtained polyimide powder was 33000, and the weight average molecular weight (Mw) was 65000.

  The polyimide powder was dissolved in tetrahydrofuran (THF, boiling point: 66 ° C.) which is a protic polar solvent to prepare a THF solution (coating solution for forming a surface layer) containing 15% by mass of the specific polyimide.

  A coating film was formed on the outer peripheral surface of the elastic layer by applying a coating solution for forming a surface layer by dipping to a dry film thickness of 0.6 μm.

  The coated film was heated at a temperature of 100 ° C. by electromagnetic induction heating to evaporate the solvent to cure the coated film, thereby forming a surface layer. Thus, an intermediate transfer member was obtained.

<Examples 2 and 3>
Intermediate transfer bodies of Examples 2 and 3 and Comparative Examples 1 to 4 were produced in the same manner as the intermediate transfer body of Example 1 except that the thickness of the surface layer was changed as shown in Table 1.

<Comparative Examples 1 to 3>
In Comparative Examples 1 to 3, instead of the oxyaniline represented by the above Chemical Formula (9) used in Examples 1 to 3, an oxyaniline represented by the above Chemical Formula (9) (here, X in Chemical Formula (9) Is a phenyl group) was used. Moreover, the thickness of each surface layer of Comparative Examples 1 to 3 was set to the thickness shown in Table 1. The intermediate transfer members of Comparative Examples 1 to 3 were produced in the same manner as in Examples 1 to 3 except for that point.

Comparative Example 4
In the oxyaniline represented by the above chemical formula (9), the intermediate transfer body of Comparative Example 4 is the same as the intermediate transfer member of Comparative Example 2 except that X in Chemical Formula (9) is changed to n-hexylene group. A transcript was produced.

[Evaluation]
The following evaluations 1 to 3 were performed on the intermediate transfer members of Examples 1 to 3 and Comparative Examples 1 to 4 prepared above.

<Evaluation 1: THF solubility>
To 80 g of tetrahydrofuran (THF), 20 g of various polyimide powders used to form the surface layers of the intermediate transfer members of Examples and Comparative Examples were added, and the solution state of the THF solution after overnight stirring was confirmed. And THF solubility was evaluated on the following reference | standard. The results are shown in Table 1 ("THF solubility" section).
A: colorless and clear.
B: There is no sediment but the solution is cloudy.
C: There is a sediment.

<Evaluation 2: Transferability>
Set each of the intermediate transfer members of the examples and comparative examples in a full-color digital printing system (trade name: “bizhub PRESS C 8000”, manufactured by Konica Minolta Business Technologies, Inc.) to optimize the exposure amount, etc., 20 ° C., 50% RH Then, 10 sheets were printed on a blue solid image (two-color superposition of cyan and magenta) and printer paper (embossed paper) as a recording material (trade name: Rezac 66 302 g, manufactured by Tokushu Tokai Paper Co., Ltd.).

  The mass of toner on the intermediate transfer belt before transfer to paper (amount of toner before transfer) and the mass of image toner remaining on the intermediate transfer belt after transfer onto paper (amount of residual toner) are measured by weighing. The transfer rate was calculated by Equation (1) of

Transfer ratio (%) = [(pre-transfer toner amount) − (remaining toner amount)] / (pre-transfer toner amount)
... Equation (1)

And the following criteria evaluated transferability. The results are shown in Table 1 (“transferability”).
S: The transfer rate is 95 to 100%.
A: The transcription rate is 93-95%.
B: The transfer rate is 90-93%.
C: The transfer rate is 90% or less.

  The full color digital printing system described above employs a laser exposure and a reversal development method, and primarily transfers the toner image carried on the electrostatic latent image carrier to an intermediate transfer member, and then transfers the toner image. An image forming apparatus for performing secondary transfer from the intermediate transfer body to a recording material, which is schematically shown in FIG.

<Evaluation 3: Rz (durability)>
A printing endurance test of 600 k (600,000) sheets was performed on the intermediate transfer members of Examples 1 to 3 and Comparative Examples 1 to 4. Then, Rz (average roughness) of the surface of the intermediate transfer member (intermediate transfer belt) after the initial (before the endurance test) and after the endurance test was measured.

  In the measurement of Rz, when the intermediate transfer belt is formed into a circular tubular shape, four places in the axial direction (width direction) of the intermediate transfer belt in each of four directions of 90.degree. The absolute value of the elevation from the mean line of the roughness curve on the surface of the surface layer was measured for a total of 16 points), and Rz was determined as the average value of those measured values.

Then, Rz was evaluated based on the following criteria. The results are shown in Table 1 ("Rz (durability)" section).
A: Rz is less than 1 μm.
B: Rz is 1 μm or more and less than 2 μm.
C: Rz is 2 μm or more.

  As apparent from Table 1, while the polyimide used for the surface layer of the intermediate transfer member of the comparative example is not soluble in a low boiling point solvent (THF, boiling point: 66 ° C.), the intermediate transfer member of the example is It is found that certain polyimides used in the surface layer of are soluble in low boiling point solvents (THF). Then, it was confirmed that the intermediate transfer member of the example had high durability while having excellent transferability as compared with the intermediate transfer member of the comparative example. That is, it is apparent that the intermediate transfer member of the present invention exhibits the excellent effect of having high durability while having excellent transferability by having the constitution of the present invention.

  Although the embodiments and examples of the present invention have been described as above, it is also originally intended to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all the modifications within the meaning and scope equivalent to the claims.

  Reference Signs List 1 image forming apparatus, 10 image processing unit, 11 photosensitive drum, 12 chargers, 13 exposure units, 14 developing units, 15 primary transfer rollers, 16 cleaners, 20 transfer units, 21 intermediate transfer members, 21a resin base layer , 21b elastic layer, 21c surface layer, 22 secondary transfer roller, 23 density detection sensor, 24 drive roller, 25 driven roller, 26 cleaning blade, 30 paper feed unit, 31 conveyance path, 32 paper discharge roller, 33 paper discharge Tray, 35 operation panel, 40 fixing unit, 45 control unit.

Claims (10)

The intermediate transfer member is used in an image forming apparatus for performing secondary transfer of the toner image from the intermediate transfer member to the recording material after primary transfer of the toner image carried on the electrostatic latent image carrier onto the intermediate transfer member. ,
The intermediate transfer body has an endless belt shape and is laminated on at least a resin base layer, an elastic layer laminated on the outer side of the resin base layer, and an outer side of the elastic layer. Including a surface layer,
The intermediate transfer member, wherein the surface layer is made of a polyimide resin containing, as a main component, a specific polyimide having a structural unit represented by the chemical formula (1).

[In chemical formula (1), X represents a divalent group containing 7 or more and 25 or less carbons. ] The intermediate transfer member is used in an image forming apparatus for performing secondary transfer of the toner image from the intermediate transfer member to the recording material after primary transfer of the toner image carried on the electrostatic latent image carrier onto the intermediate transfer member. ,
The intermediate transfer body has an endless belt-like shape, and includes a resin base layer containing at least an elastic material, and a surface layer laminated on the outside of the resin base layer,
The intermediate transfer member, wherein the surface layer is made of a polyimide resin containing, as a main component, a specific polyimide having a structural unit represented by the chemical formula (1).

[In chemical formula (1), X represents a divalent group containing 7 or more and 25 or less carbons. ]   The intermediate transfer member according to claim 1 or 2, wherein X is a divalent group containing 2 or more and 4 or less phenylene groups. The intermediate transfer member according to claim 3, wherein X is a divalent group represented by the chemical formula (2).

[In chemical formula (2), Y shows a bivalent group or a single bond. ]   At least one selected from the group consisting of an alkylene group having 2 to 4 carbon atoms which may have a branch, an oxylene group, a phenylene group which may have a substituent, a carbonyl group, and a sulfonyl group; The intermediate transfer body according to claim 4, which comprises two groups. The intermediate transfer member according to claim 4, wherein Y is a divalent group represented by Chemical Formula (3) to Chemical Formula (7).

The specific polyimide is synthesized from 2,3,3 ', 4'-oxydiphthalic anhydride represented by the chemical formula (8) and oxyaniline represented by the chemical formula (9). Intermediate transfer body as described.

[In the chemical formula (9), Ar represents a phenylene group, and X represents a divalent group containing 7 or more and 25 or less carbons. ]   The intermediate transfer member according to any one of claims 1 to 7, wherein the thickness of the surface layer is 0.5 μm or more and 5.0 μm or less.   An image forming apparatus comprising the intermediate transfer member according to any one of claims 1 to 8. A method of manufacturing an intermediate transfer member according to any one of claims 1 to 8,
A method of forming a surface layer by applying a solution in which the specific polyimide is dissolved in a solvent having a boiling point of less than 150 ° C., and heating the temperature at less than 150 ° C. to evaporate the solvent. .

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