JP5314373B2 - Endless belt for electrophotographic equipment - Google Patents

Description

  The present invention relates to an endless belt for electrophotographic equipment, and more particularly, an endless belt for electrophotographic equipment used as an intermediate transfer belt and a transport belt for electrophotographic equipment such as an electrophotographic copying machine, a printer, and a facsimile machine.

In general, in electrophotographic equipment adopting electrophotographic technology such as full color LBP (laser beam printer) and full color PPC (plain paper copier), for applications such as toner image transfer, paper transfer conveyance, and photoreceptor substrate, Endless belts (seamless belts) are frequently used. As such an endless belt, for example, a single layer belt such as polyimide resin, polycarbonate resin, polyvinylidene fluoride (PVDF) resin, or a belt provided with a surface layer has been proposed (for example, Patent Documents 1 to 3). 3).
JP 2001-162691 A Japanese Patent Laid-Open No. 10-10880 JP 2000-355432 A

  However, in the case of a single-layer belt, since the material design focuses on ensuring strength and stabilizing resistance, it is difficult to incorporate a function for toner transferability. That is, during toner cleaning, the toner is clogged between the cleaning blade or cleaning brush and the belt, but the toner contains a hard external additive, which can cause streaks on the surface of the soft belt, and transfer There are problems such as circumferential streaks in objects. Also, depending on the dispersion state of the conductive agent such as carbon, there is a problem that abnormal discharge occurs and the image deteriorates (white spot image or the like).

  Also, in the case of a belt provided with a surface layer, the adhesion at the interface between the base layer and the surface layer is inferior, so problems such as peeling or scraping of the surface layer occur. ) Occurs. Furthermore, depending on the material of the surface layer, there are problems such as poor toner transferability, poor toner adhesion, and image defects.

  The present invention has been made in view of such circumstances, and its object is to provide an endless belt for an electrophotographic apparatus that is excellent in adhesion and durability at the interface between the base layer and the surface layer and can obtain an excellent image. To do.

In order to achieve the above object, an endless belt for electrophotographic equipment of the present invention is an endless belt for electrophotographic equipment in which a surface layer is formed on the outer peripheral surface of a base layer, and the base layer comprises the following (A): -(C) component, and it consists of the hardening body of the resin composition by which the NCO index was set to the range of 90-95, and the said surface layer contains the following (D) and (E) component, NCO, It takes the structure that it consists of the hardening body of the resin composition set to the range of the index of 125-500.
(A) Aromatic diisocyanate.
(B) An aromatic polycarboxylic acid anhydride.
(C) Diol or dicarboxylic acid.
(D) Isocyanate compound.
(E) A fluororesin having a functional group that reacts with the isocyanate group of the component (D).

  That is, the present inventors have made extensive studies in order to obtain an endless belt for electrophotographic equipment that is excellent in adhesion and durability at the interface between the base layer and the surface layer and can obtain an excellent image. An endless belt for electrophotographic equipment having a two-layer structure in which a surface layer is formed on the outer peripheral surface of the base layer, the base layer being an aromatic diisocyanate (component A) and an anhydride of an aromatic polyvalent carboxylic acid (B component) and a diol or a dicarboxylic acid (C component), and a cured product of a resin composition having an NCO index in the range of 90 to 95, and the surface layer comprises an isocyanate compound (D component) and And a resin-made electrophotographic apparatus comprising a cured resin composition containing a fluororesin (E component) having a functional group that reacts with the isocyanate group of component D and having an NCO index in the range of 125 to 500 It was found that the intended purpose can be achieved by the endless belt, and the present invention has been achieved. In the present invention, the isocyanate compound (D component), which is a surface layer material, and the fluororesin (E component) having a functional group that reacts with the isocyanate group of the D component are cured and crosslinked, and the isocyanate compound (D The remaining isocyanate group which is not cross-linked with the component) is bonded to the hydroxyl group of the diol (C component) or the carboxyl group of the dicarboxylic acid (C component) in the base layer material, whereby the base layer and the surface layer are in close contact with each other. That is, the NCO index of the resin composition containing the components A to C that forms the base layer is set in the range of 90 to 95, and the resin composition containing the components D and E that forms the surface layer. By setting the NCO index in the range of 125 to 500, the adhesiveness at the interface between the base layer and the surface layer can be improved for the above reasons, and the decrease in the base layer strength can be suppressed, and the durability of the endless belt is excellent. It is possible to obtain an excellent image having no white spot image or the like.

  Thus, the endless belt for an electrophotographic apparatus of the present invention is cured by the surface layer material, an isocyanate compound (D component), and a fluororesin (E component) having a functional group that reacts with the isocyanate group of this D component. The remaining isocyanate groups that are not crosslinked by the isocyanate compound (D component) are bonded to the hydroxyl groups of the diol (C component) or the carboxyl groups of the dicarboxylic acid (C component) in the base layer material. The base layer and the surface layer come into close contact with each other. That is, the NCO index of the resin composition containing the components A to C that forms the base layer is set in the range of 90 to 95, and the resin composition containing the components D and E that forms the surface layer. By setting the NCO index in the range of 125 to 500, it is possible to suppress a decrease in the base layer strength, and it is possible to obtain an excellent image having excellent durability of the endless belt and no white spot image.

  When the diol (component C) is 1,8-octanediol, adhesion, durability, and image are further improved.

  Further, when the dicarboxylic acid (component C) is sebacic acid, the adhesion, durability, and image are further improved.

  Furthermore, when the specific fluororesin (E component) is at least one of an acrylic-modified fluororesin and a hydroxyl-modified fluororesin, adhesion, durability, and images are further improved.

  Next, embodiments of the present invention will be described in detail.

  The endless belt for an electrophotographic apparatus of the present invention has a two-layer structure in which a surface layer 2 is directly formed on the outer peripheral surface of a base layer (base layer) 1 as shown in FIG.

  The base layer 1 of the endless belt for electrophotographic equipment of the present invention comprises an aromatic diisocyanate (component A), an aromatic polycarboxylic acid anhydride (component B), and a diol or dicarboxylic acid (component C). It contains a modified polyamideimide (PAI) resin obtained by polymerization (reaction). As the material for forming the base layer 1 (base layer material), the resin composition containing the above-described components A to C is used.

  In the present invention, the NCO index of the resin composition containing the components A to C is in the range of 90 to 95, preferably in the range of 91 to 94. That is, when the NCO index is too small, the durability of the endless belt is deteriorated. On the other hand, when the NCO index is too large, the adhesion at the interface between the base layer 1 and the surface layer 2 is deteriorated.

  Here, in the present invention, the NCO index is a value obtained by dividing the total number of isocyanate groups in the isocyanate by the total number of hydroxyl groups and carboxyl groups such as polyols, and the number of active hydrogens that react with the isocyanate groups, If the isocyanate group is stoichiometrically equal, the NCO index is 100.

  As the aromatic diisocyanate (component A), a compound having an aromatic ring in the molecular structure is used. For example, diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), tolidine diisocyanate (TODI), xylylene diisocyanate (XDI). ), Lysine diisocyanate (LDI), naphthalene diisocyanate (NDI), paraphenylene diisocyanate (PPDI), tetramethylxylene diisocyanate (TMXDI) and the like. These may be used alone or in combination of two or more. Among these, MDI and TODI are preferably used in terms of reactivity, cost, and product physical properties.

  The aromatic polyvalent carboxylic acid anhydride (component B) has an aromatic ring in the molecular structure and undergoes a condensation reaction with the aromatic diisocyanate (component A). In addition to trimellitic anhydride (trimellitic anhydride), naphthalene-1,2,4-tricarboxylic anhydride, benzene-1,2,4,5-tetracarboxylic acid (pyromellitic acid), benzophenone -3,3 ', 4,4'-tetracarboxylic acid, diphenyl ether-3,3', 4,4'-tetracarboxylic acid, benzene-1,2,3,4-tetracarboxylic acid, biphenyl-3,3 ', 4,4'-tetracarboxylic acid, biphenyl-2,2', 3,3'-tetracarboxylic acid, naphthalene-2,3,6,7-tetracarboxylic acid, naphthalene-1,2,4,5 -Tetracarbo Acid, naphthalene-1,4,5,8-tetracarboxylic acid, decahydronaphthalene-1,4,5,8-tetracarboxylic acid, 4,8-dimethyl-1,2,3,5,6,7- Hexahydronaphthalene-1,2,5,6-tetracarboxylic acid, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid, 2,7-dichloronaphthalene-1,4,5,8- Tetracarboxylic acid, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid, phenanthrene-1,3,9,10-tetracarboxylic acid, perylene-3,4,9, 10-tetracarboxylic acid, bis (2,3-dicarboxyphenyl) methane, bis (3,4-dicarboxyphenyl) methane, 1,1-bis (2,3-dicarboxyphenyl) ethane, 1,1- Screw (3,4- Carboxyphenyl) ethane, 2,2-bis (2,3-dicarboxyphenyl) propane, 2,3-bis (3,4-dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) sulfone, bis And dianhydrides of aromatic polycarboxylic acids such as (3,4-dicarboxyphenyl) ether, ethylene glycol bis (anhydrotrimellitate), propylene glycol bis (anhydrotrimellitate), and the like. . These may be used alone or in combination of two or more. Among these, trimellitic anhydride (trimellitic anhydride) is preferably used in terms of reactivity, cost, product physical properties, and the like. In the present invention, an aromatic polyvalent carboxylic acid that is not an anhydride may be used in combination with the aromatic polyvalent carboxylic acid anhydride (component B).

  Here, the total number of moles of the isocyanate group of the aromatic diisocyanate (component A) and the total number of moles of the anhydride group of the aromatic polyvalent carboxylic acid (component B) and the carboxyl group. The molar mixing ratio with (b) is preferably in the range of (a) / (b) = 90/100 to 130/100, particularly preferably in the range of (a) / (b) = 100/100 to 120/100. It is. That is, if the value of (a) / (b) is out of the above range, it is difficult to increase the molecular weight of the polyamideimide resin, and the durability tends to deteriorate.

  Next, examples of the diol (component C) used together with the aromatic diisocyanate (component A) and the aromatic polycarboxylic acid anhydride (component B) include 1,8-octanediol, 1,4, and the like. -Butanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol and the like. These may be used alone or in combination of two or more. Among these, 1,8-octanediol is preferable in terms of strength and elastic modulus.

  In addition, the compounding quantity of the said diol (C component) is adjusted so that an NCO index may be in the range of 90-95 as mentioned above.

  Examples of the dicarboxylic acid (C component) used together with the aromatic diisocyanate (component A) and the aromatic polycarboxylic acid anhydride (component B) include, for example, sebacic acid, adipic acid, pimelic acid, and suberin. Acid, azelaic acid, maleic acid, fumaric acid, dicarboxylic acid ester and the like. These may be used alone or in combination of two or more. Among these, sebacic acid is preferable in terms of elastic modulus and strength.

  In addition, the compounding quantity of the said dicarboxylic acid (C component) is adjusted so that an NCO index may be in the range of 90-95 as mentioned above.

  Next, the modified PAI resin obtained by copolymerizing the components A to C can be prepared, for example, as follows. That is, a reaction vessel equipped with a stirrer, a nitrogen introduction tube, a thermometer, and a cooling tube was prepared, and the aromatic diisocyanate (component A) and an anhydride of an aromatic polycarboxylic acid such as trimellitic anhydride ( B component) and a predetermined amount of diol or dicarboxylic acid (C component) are blended, and N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAC) A polar solvent such as γ-butyrolactone is charged, and the temperature is raised to a predetermined temperature (preferably 130 to 150 ° C.) over a predetermined time (preferably 1 to 3 hours) with stirring in a nitrogen stream. Next, the modified PAI resin can be prepared by reacting at a predetermined temperature (preferably 130 to 150 ° C.) for a predetermined time (preferably about 3 to 5 hours) and then stopping the reaction.

  The modified PAI resin thus obtained preferably has a number average molecular weight (Mn) in the range of 10,000 to 100,000, particularly preferably Mn in the range of 30,000 to 70,000. That is, if the Mn of the modified PAI resin is too small, the tear strength is lowered and the durability is deteriorated. Conversely, if the Mn of the modified PAI resin is too large, the solution viscosity is increased and the workability tends to be deteriorated. It is. The number average molecular weight (Mn) can be measured by a gel permeation chromatograph (GPC) method.

  In addition to the above-mentioned components A to C, an organic solvent such as a conductive agent, DMF, DMAC, toluene, acetone, NMP, or a filler may be used as the base layer material.

Examples of the conductive agent include conductive powders such as carbon black and graphite, metal powders such as aluminum powder and stainless steel powder, conductive zinc oxide (c-ZnO), conductive titanium oxide (c-TiO ₂ ), conductive Conductive metal oxides such as conductive iron oxide (c-Fe ₃ O ₄ ) and conductive tin oxide (c-SnO ₂ ), quaternary ammonium salts, phosphate esters, sulfonates, aliphatic polyhydric alcohols, Examples thereof include ionic conductive agents such as aliphatic alcohol sulfate salts. These may be used alone or in combination of two or more.

  For example, the base layer material is appropriately mixed with a conductive agent, an organic solvent, a filler, and the like together with the components A to C, mixed with a stirring blade, and then used with a ring mill, a ball mill, a sand mill, or the like. It can be prepared by dispersing.

  Next, the surface layer 2 formed on the outer peripheral surface of the base layer 1 is a reaction product (cured) of an isocyanate compound (D component) and a fluororesin (E component) having a functional group that reacts with the isocyanate group of the D component. Body). As a material for forming the surface layer 2 (surface layer material), a resin composition containing the D component and the E component is used.

  In the present invention, the NCO index of the resin composition containing the D component and the E component is in the range of 125 to 500, and preferably in the range of 250 to 400. That is, if the NCO index is too small, the remaining isocyanate groups that are not cross-linked with the specific fluororesin (E component) in the isocyanate compound (D component) are reduced, resulting in the diol (C component) in the base layer material. This is because the bonding between the hydroxyl group or the carboxyl group of the dicarboxylic acid (component C) is insufficient and the adhesion at the interface between the base layer 1 and the surface layer 2 is deteriorated. On the other hand, if the NCO index is too large, the isocyanate group becomes excessive, the toner cleaning property is deteriorated, and the durability is also deteriorated.

  As said isocyanate compound (D component), the isocyanate generally used as a raw material of a polyurethane is used suitably, for example, aromatic isocyanate, aliphatic isocyanate, alicyclic isocyanate etc. are mention | raise | lifted. Among these, aliphatic isocyanates and alicyclic isocyanates are preferable in that a reaction product having a high elongation rate can be obtained. Specifically as said aliphatic isocyanate, hexamethylene diisocyanate (HDI), its modified body, etc. are preferable. Specifically as said alicyclic isocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate (MDI), etc. are preferable.

  Next, what has a functional group which reacts with the isocyanate group of the said isocyanate compound (D component) is used as a specific fluororesin (E component) used with the said isocyanate compound (D component). Examples of the functional group include functional groups having active hydrogen such as a hydroxyl group, an amino group, a carboxyl group, and a sulfonic acid group.

  As said specific fluororesin (E component), what modified | denatured the fluororesin by modified resins, such as an acrylic resin, a urethane resin, an epoxy resin, a phenol resin, is used, for example. These may be used alone or in combination of two or more. Among these specific fluororesins (component E), acrylic-modified fluororesins, hydroxyl-modified fluororesins, and urethane-modified fluororesins are preferable from the viewpoint of reactivity with isocyanate.

  Examples of the fluororesin modified with the above-described modified resin such as acrylic resin include tetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene resin (FEP), and tetrafluoroethylene-perfluoro. Alkoxyethylene resin (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), trifluorochloroethylene resin (CTFE), ethylene-trifluorotrifluoroethylene resin (ECTFE), vinyl fluoride resin (PVF), etc. Can be given.

  The hydroxyl value (OHV) of the specific fluororesin (E component) is preferably in the range of 5 to 120, particularly preferably in the range of 6.5 to 72, as the solid content.

  The solid content of the specific fluororesin (component E) is preferably in the range of 20 to 50%, particularly preferably in the range of 31 to 50%.

  Here, as described above, the mixing ratio (weight ratio) between the isocyanate compound (D component) and the specific fluororesin (E component) is such that the NCO index of the resin composition as the surface layer material is 125 to 500. Specifically, the range of D component / E component = 1/99 to 60/40 is preferable, and D component / E component = 1.9 / 98.1 is particularly preferable. It is the range of -47.6 / 52.4.

  In addition to the isocyanate compound (D component) and the specific fluororesin (E component), the surface layer material includes a conductive agent, an organic solvent, a filler, a flame retardant, an antifoaming agent, a dispersant, a release agent. An agent or the like may be appropriately blended as necessary.

Examples of the conductive agent include conductive powders such as carbon black and graphite, metal powders such as aluminum powder and stainless steel powder, conductive zinc oxide (c-ZnO), conductive titanium oxide (c-TiO ₂ ), conductive Conductive metal oxides such as conductive iron oxide (c-Fe ₃ O ₄ ) and conductive tin oxide (c-SnO ₂ ), quaternary ammonium salts, phosphate esters, sulfonates, aliphatic polyhydric alcohols, Examples thereof include ionic conductive agents such as aliphatic alcohol sulfate salts. These may be used alone or in combination of two or more.

  Moreover, the compounding quantity of the said electrically conductive agent is the range of 5-60 parts with respect to a total of 100 weight part (henceforth "part") of the said isocyanate compound (D component) and specific fluororesin (E component). Is preferable, and the range of 10 to 20 parts is particularly preferable.

  The surface layer material is, for example, an isocyanate compound (D component) and a specific fluororesin (E component), if necessary, appropriately blended with a conductive agent and the like, and mixed with a stirring blade, then a ring mill, a ball mill It can be prepared by dispersing using a sand mill or the like.

  Next, a method for producing an endless belt for electrophotographic equipment according to the present invention will be specifically described. That is, first, the base layer material and the surface layer material are respectively prepared in the same manner as described above. Then, a mold (cylindrical base body) is prepared, and the base layer material is roll-coated on the surface to form the base layer 1 on the surface of the mold. This is heated and heated for a predetermined time (preferably 2 hours) from room temperature (25 ° C.) to 250 ° C. Next, the surface layer material is dip coated (dipped) on the surface of the base layer 1 and dried at 150 to 300 ° C. (preferably 150 ° C.) for 1 to 6 hours (preferably 1 hour). 2 is formed. Thereafter, the endless belt having a two-layer structure in which the cylindrical base is extracted by blowing air between the base layer 1 and the mold (cylindrical base) and the surface layer 2 is formed on the outer peripheral surface of the base layer 1 (FIG. 1). For example). In addition, the formation method of the said surface layer 2 is not limited to the said dip coating, For example, you may form by spray coating etc.

  The thickness of each layer of the endless belt for electrophotographic equipment of the present invention is appropriately set according to the use of the belt, but the thickness of the base layer 1 is preferably in the range of 30 to 300 μm, particularly preferably in the range of 50 to 200 μm. It is. The thickness of the surface layer 2 is preferably in the range of 0.1 to 30 μm, particularly preferably in the range of 0.5 to 20 μm. The endless belt for an electrophotographic apparatus of the present invention preferably has an inner peripheral length of 500 to 2500 mm and a width of about 150 to 600 mm. That is, if the size is set within the above range, the size is appropriate for use in an electrophotographic copying machine.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples.

  First, prior to the examples and comparative examples, the following materials were prepared.

(1) Base layer material [MDI (component A)]
Millionate MT (Mn: 250.06), manufactured by Nippon Polyurethane Industry

[TODI (A component)]
Nippon Soda Co., Ltd., TODI / R203 (Mn: 264.29)

[Trimellitic anhydride (component B)]
Trimellitic anhydride (Mitsubishi Gas Chemical Co., Ltd.)

[Dicarboxylic acid (component C)]
Sebacic acid (manufactured by Toyokuni Oil)

[Diol (component C)]
1,8-octanediol (Wako Pure Chemical Industries, OHV: 768)

〔Carbon black〕
Cabot Japan, Show Black N220

(2) Surface layer material [isocyanate compound (component D)]
Nippon Polyurethane Industry Co., Ltd. Coronate L (NCO in solid content: 13.2%, solid content: 75%)

[Modified fluororesin A (component E)]
Hydroxyl-modified fluororesin (manufactured by DIC, Fluonate K-700, OHV (as solid content): 48 mg / KOH, solid content: 50%)
[Modified fluororesin B (component E)]
Hydroxyl group-modified fluororesin (manufactured by DIC, Fluoronate K-707, OHV (as solid content): 72 mg / KOH, solid content: 50%)
[Modified fluororesin C (E component)]
Acrylic modified fluororesin (manufactured by DIC, Defensor TR310, OHV (as solid content): 6.5 mg / KOH, solid content: 31%)
[Modified fluororesin D (component E)]
Acrylic modified fluororesin (manufactured by DIC, Defensor TR330, OHV (as solid content): 19.5 mg / KOH, solid content: 31%)
[Modified fluororesin E (E component)]
Hydroxyl-modified fluororesin (manufactured by Central Glass Co., Ltd., Cefal Coat CC-04, OHV (as solid content): 28 mg / KOH, solid content: 31%)

[Fluorine resin]
PVDF (manufactured by Arkema, Kyner SL, OHV (as solid content): 0 mg / KOH, solid content: 100%)

[Conductive agent]
Ketjen Black (Ketjen Black International)

  Next, an endless belt was produced using the base layer material and the surface layer material.

[Example 1]
(Preparation of base layer material)
In a reaction vessel equipped with a stirrer, nitrogen introducing tube, thermometer, and cooling tube, 7.5 parts of MDI, 18.5 parts of TODI, 18 parts of trimellitic anhydride, 3 parts of sebacic acid, and 247 parts of NMP solvent The mixture was heated to 130 ° C. over 1 hour with stirring in a nitrogen stream, reacted for about 5 hours at 130 ° C., and then the reaction was stopped to prepare a PAI-NMP solution (PAI: 20% by weight). . Next, 10 parts of carbon black was added to this PAI-NMP solution, mixed with a stirring blade, and then dispersed with a ball mill to prepare a base layer material.

(Preparation of surface layer material)
18.5 parts of isocyanate compound, 81.5 parts of modified fluororesin A, and 10 parts of a conductive agent were blended and mixed with a stirring blade to prepare a surface layer material.

(Production of endless belt)
First, a mold (cylindrical base) was prepared, and the base layer material was roll-coated on the surface to form a base layer on the surface of the mold. This was heated and heated for 2 hours from normal temperature (25 ° C.) to 250 ° C. Next, the surface layer material was dip coated on the surface of the base layer, and this was heat-treated at 150 ° C. for 1 hour. Thereafter, air is blown between the base layer and the mold (cylindrical base body) to extract the cylindrical base body and to form a surface layer (thickness: 1 μm) on the outer peripheral surface of the base layer (thickness: 80 μm). An endless belt having a structure (see FIG. 1) was produced.

[Examples 2 to 10, Comparative Examples 1 to 6]
A surface layer (thickness: 1 μm) is formed on the outer peripheral surface of the base layer (thickness: 80 μm) in the same manner as in Example 1 except that the base layer material and the surface layer material shown in Table 1 and Table 2 below are used. An endless belt having a two-layer structure (see FIG. 1) was produced.

  Using the endless belts of Examples and Comparative Examples thus obtained, each characteristic was evaluated according to the following criteria. These results are shown in Tables 1 and 2 above.

[Adhesion (base layer / surface layer)]
Using each endless belt, a cut of 10 squares × 10 squares (1 square dimension: 2 mm × 2 mm) was made in the surface layer, and a cross cut test was performed. In the evaluation, the case where there was at least one separation at the interface between the base layer and the surface layer was evaluated as x, and the case where there was no separation was evaluated as ◯.

[White spot image]
Each endless belt was incorporated into a color printer (Ricoh Co., SPC810), a halftone image was printed, and a white spot image was visually observed. In the evaluation, “X” indicates that there is a white dot image, and “◯” indicates that there is no white point image.

[Image after endurance test]
Each endless belt was incorporated into a color printer (RPC, SPC810), 20,000 halftone images were printed, and a white spot image was visually observed. In the evaluation, a case where the white spot image deteriorated, or an image unevenness due to belt creep or an image unevenness due to toner adhesion was evaluated as x, and a case where the white spot image deteriorated or no image unevenness was evaluated as ◯.

  From the results shown in Tables 1 and 2, all of the examples were excellent in adhesion at the interface between the base layer and the surface layer, had no white spot image, and the image after the durability test was also good.

  On the other hand, since the product of Comparative Example 1 is a single layer belt that does not form a surface layer made of a specific material, a white spot image is observed and an image after the durability test is inferior. Since the product of Comparative Example 2 used a surface layer material that did not contain an isocyanate compound and a modified fluororesin, the adhesion between the base layer and the surface layer was inferior, and the image after the durability test was also inferior. The product of Comparative Example 3 was inferior in the image after the durability test because the NCO index of the base layer material was too small. Since the NCO index of the base layer material of the comparative example 4 product was too large, the adhesion between the base layer and the surface layer was poor, the surface layer was peeled off after the durability test, a defect occurred, and an abnormal image was generated. Since the NCO index of the surface layer material was too small, the comparative example 5 product was inferior in adhesion between the base layer and the surface layer, and surface layer peeling occurred after the durability test. Since the NCO index of the surface layer material was too large, the comparative example 6 product was inferior in the toner cleaning property (because the tack property increased and the toner adhered), and an abnormal image was generated after the durability test.

  The endless belt for an electrophotographic apparatus of the present invention is used as an intermediate transfer belt, a conveying belt, or the like in an electrophotographic apparatus such as an electrophotographic copying machine, a printer, or a facsimile.

It is a fragmentary sectional view which shows an example of the endless belt for electrophotographic apparatuses of this invention.

Explanation of symbols

1 base layer 2 surface layer

Claims (4)

An endless belt for an electrophotographic apparatus in which a surface layer is formed on the outer peripheral surface of a base layer, wherein the base layer contains the following components (A) to (C), and an NCO index is set in a range of 90 to 95: And a cured product of the resin composition in which the surface layer contains the following components (D) and (E) and the NCO index is set in the range of 125 to 500: An endless belt for electrophotographic equipment.
(A) Aromatic diisocyanate.
(B) An aromatic polycarboxylic acid anhydride.
(C) Diol or dicarboxylic acid.
(D) Isocyanate compound.
(E) A fluororesin having a functional group that reacts with the isocyanate group of the component (D).   The endless belt for an electrophotographic apparatus according to claim 1, wherein the diol of the component (C) is 1,8-octanediol.   The endless belt for an electrophotographic apparatus according to claim 1 or 2, wherein the dicarboxylic acid as the component (C) is sebacic acid.   The endless belt for an electrophotographic apparatus according to any one of claims 1 to 3, wherein the fluororesin of the component (E) is at least one of an acrylic modified fluororesin and a hydroxyl group modified fluororesin.

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