JP2006022227A - Polyurethane and belt for electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyurethane which excels in the property of carrying toner images, has follow-up properties to the irregularities of rough paper and the like and can prevent the belt from curling after being left to stand in the state wound on a pulley having a small diameter for a long rest, and an electrophotographic device obtained by using the polyurethane. <P>SOLUTION: The polyurethane has a peak temperature of the major dispersion of tan δ, obtained from the temperature dispersion of the kinematic viscoelasticity measured at a dynamic strain of 0.1% and a frequency of 10 Hz, of being present at 100-200°C, exists in the region of glass at 25°C, and has a transition of the storage modulus E' obtained under the same conditions in the range of -55 to -20°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a polyurethane and a belt for an electrophotographic apparatus.

Conventionally, as an intermediate transfer belt or transfer / conveying belt for an electrophotographic apparatus, a resin film such as a polyimide resin film or a polycarbonate resin film is generally used. However, a belt using such a resin film has a hard surface, insufficient toner image retention, and poor followability to the irregularities on the paper surface. Therefore, it has been required to give a certain degree of elasticity to the belt surface.

A belt for an electrophotographic apparatus in which an elastic layer is laminated on a resin film has been proposed as one that improves the image quality by imparting elasticity to the belt surface. However, since it is necessary to form an adhesive layer between the film and the elastic layer, the process is complicated, and the difference in shrinkage is large in the laminated structure of different materials, so that the belt is warped. Etc. have the following problems. For this reason, in recent years, a belt for an electrophotographic apparatus has been proposed in which an elastic layer of low-hardness polyurethane is provided on a high-hardness (that is, polyurethane) core layer.

Patent Document 1 discloses an elastic layer having a JIS A hardness of 30 to 95 degrees obtained by curing liquid thermosetting polyurethane and a core having a JIS D hardness of 75 to 90 degrees obtained by curing liquid thermosetting polyurethane or thermosetting polyurea. An electrophotographic belt having a two-layer structure with a body layer is disclosed.

Patent Document 2 discloses at least a two-layer structure including a core layer and an elastic layer made of polyurethane formed from a polyol, a low molecular weight aromatic amine, and an aliphatic isocyanate having a bifunctional group and a trifunctional group. A belt for an electrophotographic apparatus is disclosed.

Patent Document 3 discloses a polyurethane constituted by a reaction of a polyol compound, a low-molecular aromatic amine compound having a chlorine group and two or more amino groups on the same aromatic ring, and a bifunctional and trifunctional aliphatic isocyanate. A belt for an electrophotographic apparatus having a core layer containing a resin and an elastic layer containing polyurethane formed by a reaction between a polyol compound having an average functional group number of 2 to 3 and an isocyanate compound is disclosed.

These electrophotographic belts disclosed in Patent Documents 1 to 3 do not require an adhesive layer between the core layer and the elastic layer, and both the core layer and the elastic layer are made of polyurethane. The belt does not have a problem of warping.

However, in recent years, from the viewpoints of miniaturization, cost reduction, and high image quality of electrophotographic apparatuses, belt units tend to be compact and pulley diameters tend to become smaller, and belts to prevent curling There is also a tendency that a mechanism for loosening the belt tension is not provided in the apparatus when the apparatus is transported in a unit state or when images are not output. Furthermore, in order to correct the color misregistration of the belt, a device has been devised such as irradiating a laser on the belt surface and providing a sensor for preventing color misregistration by the reflected light.

In the case where a belt separating / connecting mechanism is not provided, the belt is driven after being rested for a long time while being wound around a small-diameter pulley. For this reason, if the belt curl is large, it will move to the straight part between the pulleys with the curl on the pulley attached, and it will take time to achieve smooth rotation. The sensor that prevents the malfunction causes a problem that a high-quality image cannot be obtained.

Accordingly, there is a demand for a core body having a smaller curl than the conventional core body, but the core body in the electrophotographic belt disclosed in Patent Documents 1 to 3 described above sufficiently prevents curl. I couldn't.

Patent Document 4 discloses a conductive member for an electrophotographic apparatus having at least one base material made of polyurethane in which a specific polyether polyol having high hydrophobicity is a polyol component. However, the electroconductive member for electrophotographic apparatus disclosed here is disclosed as a belt dimension that does not expand and contract even under environmental changes and long-term use, and cannot sufficiently prevent curling. Met.
JP 2001-34078 A JP 2001-142311 A JP 2001-356612 A JP 2002-148949 A

In view of the present situation, the present invention is excellent in toner image carrying ability, has followability to unevenness such as rough paper, and after resting for a long time while the belt is wound around a small-diameter pulley, etc. An object of the present invention is to provide a polyurethane capable of preventing the occurrence of curling wrinkles and a belt for an electrophotographic apparatus obtained by using the polyurethane.

In the present invention, the peak temperature of the main dispersion of tan δ determined from the temperature dispersion of dynamic viscoelasticity measured under the conditions of dynamic strain of 0.1% and frequency of 10 Hz exists in the range of 100 to 200 ° C. The polyurethane is characterized by having a transition in a region where the storage elastic modulus E ′ obtained from the same conditions is −55 to −20 ° C.

The polyol component forming the polyurethane is preferably a polycarbonate polyol having a portion containing a carbonate bond and a linear portion having 5 to 12 carbon atoms.

The straight chain portion preferably has 8 to 9 carbon atoms and has a side chain and / or includes an isomer.
The linear portion is preferably derived from 1,9-nonanediol and methyloctanediol.

The curing agent component that forms the polyurethane is an aromatic diamine, and the isocyanate component is preferably a bifunctional or trifunctional aliphatic isocyanate.

The present invention also provides a belt for an electrophotographic apparatus, wherein a conductive filler is dispersedly contained in the polyurethane and formed into a thin cylindrical shape.
It is preferable that an elastic surface layer having a JIS-A hardness of 30 to 80 degrees is further laminated on the outer periphery of the thin cylindrical belt base material.

It is preferable that the elastic surface layer and the belt base material are both integrally formed by centrifugal molding without using an adhesive.
The electrophotographic belt is preferably an intermediate transfer belt or a transfer conveyance belt.
Hereinafter, the present invention will be described in detail.

The belt for an electrophotographic apparatus obtained by using the polyurethane of the present invention is one in which the occurrence of curling is prevented. For this reason, for example, after the belt for an electrophotographic apparatus obtained by using the polyurethane is rested for a long time while being wound around a small-diameter pulley, the occurrence of curling can be reduced. Accordingly, even when such an electrophotographic belt is wound for a long time in a state where it is wound around a small-diameter pulley and then driven, the malfunction of the color shift sensor can be sufficiently prevented. A high-quality image can be obtained.

Since the belt for an electrophotographic apparatus is always used with a tension of 1 to several tens kg, it is important that the belt does not stretch with this tension. That is, at least in the operating temperature range of the apparatus, it is necessary that the polyurethane used for the belt for an electrophotographic apparatus exhibits a glass state (below the glass transition point) (generally 5 to 50 ° C.).

When used as a core of a belt for an electrophotographic apparatus, particularly rigid physical properties are required, and it is necessary to increase the hard segment content. In other words, the conventional polyurethane-based elastomer generally has a sea-island structure in which the soft segment composed of the polyol component is the sea and the hard segment composed of the low molecular weight extender and the polyisocyanate is the island. By increasing the hard segment content, a polyurethane having a structure opposite to the conventional one, that is, a polyurethane in which the hard segment is the sea and the polyol is the island is preferably used. In this case, in the obtained polyurethane, the storage elastic modulus (E ′) obtained from the temperature dispersion of dynamic viscoelasticity measured under the conditions of 0.1% dynamic strain and frequency of 10 Hz shows a high temperature region where the main dispersion temperature of tan δ ( Usually, the transition region disappears up to 100-200 ° C.

It is presumed that curling which occurs when the belt for an electrophotographic apparatus is rested for a long time while being wound around a small-diameter pulley is likely to occur because the polymer is in a glass state. For this reason, in the present invention, by slightly securing the molecular mobility of the polyol component forming the island, a slight rubber state is introduced into the glass region, and as a result, the occurrence of curling can be prevented. . The polyurethane of the present invention has a main dispersion peak temperature of tan δ determined from temperature dispersion of dynamic viscoelasticity measured under the conditions of dynamic strain 0.1% and frequency 10 Hz. It is not only a region, but also has a transition in a region where the storage elastic modulus E ′ determined from the same conditions is −55 to −20 ° C. Polyurethanes having such high rigidity characteristics and rubber-like characteristics have a low elongation with respect to tension at a temperature of about 5 to 50 ° C. and are excellent in recovery from deformation.

In order to set the peak temperature of the main dispersion of tan δ to a high temperature range such as 100 to 200 ° C., and to have a storage elastic modulus E ′ having a transition at −55 to −20 ° C., for example, a polycarbonate is added to the polyol component. The portion containing the bond is arranged at an appropriate interval with a linear portion having 5 to 12 carbon atoms, and the molecular weight is set to 800 to 2000, and at the same time, the cohesive force of the hard segment is increased to increase the number. Control the physical properties. If the peak temperature of tan δ is less than 100 ° C., it may be insufficient to suppress the temperature dimensional change due to heat. If it exceeds 200 ° C., it becomes too hard and cracking is likely to occur due to bending.

The polyurethane is a glass region at 25 ° C. The belt for an electrophotographic apparatus obtained by using such a polyurethane prevents the elastic modulus from changing suddenly in the operating temperature range of an in-machine temperature of 50 ° C. (0 to 60 ° C.), and affects the elongation rate of the belt. Can be prevented.

The polyurethane has a transition in the region where the storage elastic modulus E ′ obtained from the temperature dispersion of dynamic viscoelasticity measured under conditions of dynamic strain 0.1% and frequency 10 Hz is −55 to −20 ° C. . By using a material having a transition in such a region, a rubber region can be introduced into the glass region, and as a result, curling of the belt for an electrophotographic apparatus can be prevented. If the transition is higher than −20 ° C., the molecular mobility is poor and the curl may not be improved. Since this transition is based on the movement of the polyol, the lower the temperature, the better. However, the transition in the cryogenic temperature lower than −55 ° C. is usually not obtained, and is −55 to −20 ° C.

The polyol component forming the polyurethane preferably has a portion containing a carbonate bond and a linear portion having 5 to 12 carbon atoms. By having a carbonate bond, it can be made more hydrophobic than an ester bond, and the influence of moisture absorption can be eliminated. Further, by using a polyol having such a carbonate-containing portion and a straight chain portion having 5 to 12 carbon atoms, there is a transition in a region where the storage elastic modulus E ′ is −55 to −20 ° C. A polyurethane can be obtained. If the straight chain portion has less than 5 carbon atoms, the E ′ transition may not exist in the region of −55 to −20 ° C. When it exceeds 12, there is a possibility that the carbonate bond becomes too small and the physical properties are not sufficiently developed. More preferably, it is 6-9. Note that the linear _portion, -CH ₂ -CH ₂ -CH ₂ - is a linear portion indicated by like.

The polyol component forming the polyurethane is referred to as polycarbonate polyol, and preferably has a part containing a carbonate bond and a hydrocarbon chain part derived from a diol having 9 carbon atoms. By using a polycarbonate polyol having a hydrocarbon chain portion derived from a diol having 9 carbon atoms, a polyurethane having a transition in a region where the storage elastic modulus E ′ is −55 to −20 ° C. can be obtained. When the obtained belt for an electrophotographic apparatus is wound on a small-diameter pulley for a long time while being wound, the occurrence of curling can be reduced. The hydrocarbon chain part includes a side chain.

The hydrocarbon chain portion derived from a diol having 9 carbon atoms of the polycarbonate polyol preferably has a side chain and / or contains an isomer (the carbon number of the straight chain portion is 8). By having a hydrocarbon chain portion derived from a diol having a side chain, the crystallinity at a low temperature can be lowered and the molecular mobility of the polyurethane can be secured. There can be a transition in the region of 55 to -20 ° C. And the belt for an electrophotographic apparatus obtained by using such a polyurethane is less likely to cause curling.

When the said hydrocarbon chain part has a side chain, it is preferable that content of the hydrocarbon chain which has the said side chain is 30 to 90% among the hydrocarbon chain parts derived from the said C9 diol. If it is less than 30%, the effect of preventing the occurrence of curling may not be exhibited, and if it exceeds 90%, it may crystallize at a low temperature and molecular mobility may not be ensured. More preferably, it is 35 to 85%.

The hydrocarbon chain portion derived from a diol having 9 carbon atoms is preferably a hydrocarbon chain derived from 1,9-nonanediol and methyloctanediol.

Examples of the commercially available polycarbonate polyol having a hydrocarbon chain portion derived from a diol having 9 carbon atoms include, for example, Kurapol C-1065N (manufactured by Kuraray Co., Ltd., hydroxyl value 114.8 KOHmg / g, 1,9-nonanediol / methyloctane). Diol mass ratio 65/35), Kurapol C-2065N (manufactured by Kuraray Co., Ltd., hydroxyl value 58.1 KOH mg / g, 1,9-nonanediol / methyloctanediol mass ratio 65/35), Kurapol C-1015N (manufactured by Kuraray Co., Ltd.) , Hydroxyl value 112KOHmg / g, 1,9-nonanediol / methyloctanediol mass ratio 15/85), and the like.

The number average molecular weight of the polycarbonate polyol is preferably 800 to 2000. If it is less than 800, elasticity at low temperatures may be lost. If it exceeds 2000, the molecular mobility becomes too high, and there is a possibility that the tensile elastic modulus necessary for the belt cannot be secured. More preferably, it is 1000-1800.

The polyol component that forms the polyurethane is preferably the polycarbonate polyol, but may contain other polyol components as necessary. Examples of other polyols include polyolefin polyols, adipates of adipate esters partially using trifunctional alcohol, polypropylene glycol, polycaprolactone ester bifunctional and polyfunctional blends, and the like. . These may be used alone or in combination of two or more.

In the polyurethane formation, an aromatic diamine is used as an active hydrogen-containing compound other than the polyol to react with an isocyanate component to introduce a urea bond having a cohesive force stronger than a urethane bond into the hard segment, and the soft segment and the hard segment are combined. Separate the islands to make the sea-island structure clearer and to ensure soft segment mobility.

Examples of the aromatic diamine include 4-chloro-3,5-diaminobenzoic acid isobutyl ester, 3,3′-dichloro-4,4′-diaminodiphenylmethane, dimethylthiotoluenediamine, diethyltoluenediamine, 4, Examples include 4'-diamino-3,3'-diethyl-diphenylmethane, 2,2 ', 3,3'-tetrachloro-4,4'-diaminodiphenylmethane, trimethylenebis-4-aminobenzoate and the like. These may be used alone or in combination of two or more.

Among the above aromatic diamines, an aromatic amine compound having a chlorine group and two amino groups in one aromatic ring is particularly preferable. Thereby, reactivity and rigidity can be improved more. When there is no chlorine group, the reaction between the isocyanate group and the amino group is fast, and not only the pot life but also the reaction difference with the polyol component forming the soft segment component is large, and the pot life is fast but the demolding property is inferior. There is a risk that this will occur. Further, in the case of an amine compound having a structure with two aromatic rings, the belt itself becomes too hard due to a rigid aromatic ring, which may result in poor flex resistance.

As the aromatic amine compound having a chlorine group and two amino groups in one aromatic ring, for example, 4-chloro-3,5-diaminobenzoic acid isobutyl ester is preferable. Examples of commercially available products include Vitec 1604 (manufactured by Sumika Bayer Urethane Co., Ltd.), CDAB (YSS Two Co., Ltd.), and the like.

The aromatic diamine preferably has a molecular weight of 200 to 1,000 because a hard segment having an aromatic ring can be formed.

In the formation of the polyurethane, the blending amount of the aromatic diamine is preferably not less than the equivalent and not more than 10 times the OH group present in the polycarbonate polyol. If it is less than the equivalent, the necessary elastic modulus may not be obtained. If it exceeds 10 times, since there are too many hard segments, the transition of the storage elastic modulus (E ′) in the region of −55 to 20 ° C. disappears and the elongation is remarkably lowered, which may make it brittle. More preferably, it is 3 to 10 times.

As an isocyanate component which forms the said polyurethane, 2-3 trifunctional aliphatic isocyanate is preferable. The reaction with the aromatic diamine is slower than that of the aromatic isocyanate, the pot life of the mixed solution is moderately long, and the injection work into the centrifugal mold becomes easy. Furthermore, in consideration of bending resistance, curl resistance, and tension stability, the component that forms the hard segment is more cohesive when introducing a urea bond obtained by the reaction of an amino group and an isocyanate group than a urethane bond. It is effective from the viewpoint. If it is formed only with urethane bonds, it is excellent in bending resistance, but the necessary tension for the belt cannot be obtained, and the belt may be stretched, and may not be used.

Examples of the bifunctional aliphatic isocyanate include hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, dimer acid diisocyanate, lysine diisocyanate, and norbornane diisocyanate. Of these, isophorone diisocyanate and norbornane diisocyanate are particularly preferred from the viewpoints of hygiene, reactivity, and hard segment aggregation. These may be used alone or in combination of two or more. As a commercial item of the said bifunctional aliphatic isocyanate, Cosmonate NBDI (made by Mitsui Takeda Chemical Company), Death Module I (made by Sumika Bayer Urethane Co., Ltd.), etc. can be mentioned, for example.

Examples of the trifunctional aliphatic isocyanate include, for example, hexamethylene diisocyanate and isophorone diisocyanate isocyanurate, biuret, and adduct modification. From the viewpoint of heat resistance, isocyanurate is preferred. Of these, a modified product of hexamethylene diisocyanate is particularly preferable from the viewpoint of viscosity and compatibility with a bifunctional aliphatic isocyanate compound. Here, the modified product of hexamethylene diisocyanate refers to one in which one isocyanate group is nurate-modified, burette-modified, prepolymer-modified, or the like. As a commercial item of the said trifunctional aliphatic isocyanate, Sumidur N3300, Sumidur N3200, Desmodur TP LS 2010/1 (above, Sumika Bayer Urethane Co., Ltd. product) etc. can be mentioned. These may be used alone or in combination of two or more.

By adding not only the above-mentioned bifunctional aliphatic isocyanate but also the above trifunctional aliphatic isocyanate, an appropriate crosslinking point is formed in the structure of the polyurethane, and the balance of the bending resistance, curl and tension of the belt. Can be taken.

When the bifunctional aliphatic isocyanate and the trifunctional aliphatic isocyanate are used, the mixing ratio (mass ratio) of the bifunctional aliphatic isocyanate and the trifunctional aliphatic isocyanate is the average functionality of the isocyanate. It is preferable to mix so that it may become 2.01-2.30 in base number. If it is less than 2.01, the effect of introducing the crosslinking hardly appears, and if it exceeds 2.30, the chemical crosslinking becomes dominant, the cohesive force of the hard segment is reduced, and the phase separation between the hard segment and the soft segment is caused. There is a possibility that the transition region in the low temperature region of E ′ may not be generated due to insufficient progress. The average functional group number is more preferably 2.05 to 2.25. From the viewpoint of preventing curling, the polyurethane of the present invention comprises polycarbonate polyol, 4-chloro-3,5-diaminobenzoic acid isobutyl ester, norbornane diisocyanate, which contains 1,9-nonanediol and methyloctanediol as polyol components. It is particularly preferable to have an isocyanurate form of hexamethylene diisocyanate as a forming component.

The belt for an electrophotographic apparatus of the present invention is formed by forming a polyurethane having a conductive filler such as carbon black dispersed therein in a thin cylindrical shape. Even in the case of driving, curling is prevented, so that the color misregistration sensor does not malfunction and a high-quality image can be obtained.

As a method for dispersing the conductive filler in the polyurethane, for example, it is preferable to prepare a master batch in which the polyol component is kneaded with a conductive filler such as carbon black with a three-roll or the like and uniformly dispersed.

The belt for an electrophotographic apparatus is formed by forming a thin-walled cylindrical polyurethane in which the above-mentioned conductive filler is dispersed. In addition to a single layer, the belt is further provided on the outer periphery of the belt base material and has a JIS-A hardness of 30. It includes those formed in two or more multilayers in which an elastic surface layer of ˜80 degrees is laminated. If the hardness of the elastic surface layer is less than 30 degrees, the elastic surface layer may be tacked or the toner retainability may be too good, leading to a decrease in transfer efficiency. If it exceeds 80 degrees, the ability to follow the unevenness of the paper will be reduced, and a sharp image may not be obtained. In order to make the elastic surface layer have a JIS-A hardness of 30 to 80 degrees, the kind of polyol component or isocyanate component is changed, or the molar ratio of [NCO] / [OH] is adjusted.

In the belt for an electrophotographic apparatus in which the belt base material and the elastic surface layer are laminated, the belt base material is preferably as thin as possible from the viewpoint of maintaining the tension as the belt and stably running the belt. The belt base material preferably has a lower limit of 0.05 mm and an upper limit of 0.3 mm. If it is less than 0.05 mm, the strength of the base material is insufficient and the durability may be poor. If it exceeds 0.3 mm, the substrate becomes difficult to bend, and there is a possibility that it cannot be wound around a small-diameter pulley. More preferably, it is 0.08-0.25 mm.

The elastic surface layer preferably has a lower limit of 0.05 mm and an upper limit of 1.0 mm. If it is less than 0.05 mm, the effect of the elastic surface layer may not be sufficiently exhibited. If it exceeds 1.0 mm, the belt becomes too thick and color misalignment tends to occur. More preferably, it is 0.1 mm to 0.9 mm.

The laminated belt for an electrophotographic apparatus can be formed by centrifugal molding in the order of the elastic surface layer and then the belt base material. That is, the raw material liquid constituting the elastic surface layer is poured into a centrifugal molding machine, heated while being subjected to centrifugal force and semi-cured, and then the raw material liquid constituting the belt base material is formed by the previous centrifugal molding machine. It can be produced by pouring onto the surface layer (inside) and heat-curing together. Since both the elastic surface layer and the resin constituting the belt base material are polyurethane, the two layers can be bonded and integrated without an adhesive, and are not repeatedly peeled and delaminated. Further, since the elastic surface layer and the belt base material layer are made of the same type of polyurethane, there is no great difference in shrinkage rate, and warpage and bending are not easily generated in the obtained belt.

The belt for an electrophotographic apparatus of the present invention in which the belt core layer and the elastic surface layer are laminated may further have a surface coating layer outside the elastic surface layer. The surface coating layer can be formed, for example, by coating with a resin paint containing a fluorine-based component. By forming the surface coating layer, it is possible to improve the releasability from the toner, cleaning properties, and the like.

Hereinafter, an electrophotographic apparatus belt (FIGS. 1, 2, and 3) obtained by using the polyurethane of the present invention, and an electrophotographic apparatus (FIGS. 4 and 5) using the belt as an intermediate transfer belt and a transfer conveyance belt will be described. This will be described with reference to the drawings.

FIG. 1 is a perspective view of the belt 1 for an electrophotographic apparatus of the present invention, and is composed of a single layer formed in a thin cylindrical shape. FIG. 2 shows a belt having a two-layer structure in which an elastic surface layer 3 is provided outside the belt substrate 2. FIG. 3 shows a three-layer belt having a surface coating layer 4 outside the elastic surface layer 3.

FIG. 4 is a side view of the periphery of the photoreceptor 11 of the electrophotographic apparatus using the electrophotographic apparatus belt of the present invention as the intermediate transfer belt 16. The photoconductor 11 is uniformly charged by a charging unit, and exposed by a laser beam or reflected light in an exposure unit to form an electrostatic latent image. The photoreceptor 11 rotates in the direction of the arrow, contacts the first developing roller (developing unit 14), and the yellow component is developed. The photoconductor 11 moves without contacting the second to fourth developing rollers, and contacts the intermediate transfer belt 16. The intermediate transfer belt 16 is stretched around the pulleys 12 and 13 and moves in the direction of the arrow, and the yellow image on the photoconductor 11 is transferred to the intermediate transfer belt 16. The photoreceptor 11 is neutralized by removing the remaining yellow toner with a cleaning blade.

Similarly to the above, the charging → exposure → developing unit and the photosensitive member 11 rotate and contact only the magenta color developing roller, and a magenta toner image is formed on the photosensitive member 11 and moves to the transfer unit as it is. The toner image is transferred to the intermediate transfer belt 16 and superimposed on the yellow image.

Similarly, a cyan toner image is formed on the photoreceptor 11 and is superimposed on the intermediate transfer belt 16. Finally, a black toner image is formed on the photoconductor 11 and is superimposed on the intermediate transfer belt 16 to form a color image on the intermediate transfer belt 16. The color image on the intermediate transfer belt 16 is transferred onto a sheet member, for example, paper, supplied between the roller 15 and the pulley 13 and fixed by a fixing device. The intermediate transfer belt 16 transfers the color image onto the paper, and then the remaining toner is removed by the cleaning blade.

FIG. 5 is a side view of the periphery of the photoreceptor 11 of the electrophotographic apparatus using the electrophotographic apparatus belt of the present invention as the transfer / conveying belt 16 '. Similar to FIG. 4, the photoconductor 11 rotates and moves with the charging unit, the exposure unit, and the development unit 14 to form and carry a black toner image, and comes into contact with the paper sent on the transfer conveyance belt 16 ′. Then, the toner image is transferred onto a sheet of paper, and is transferred to the fixing unit by the transfer / conveying belt 16 'as it is to be fixed. The transfer conveyance belt 16 ′ is stretched around the pulleys 12 and 13 and moves in the direction of the arrow. As in FIG. 4, the photoconductor 11 is discharged by removing the toner remaining with the cleaning blade.

4 and 5, the intermediate transfer belt and the transfer conveyance belt are rested or stored for a long time while being wound around a small-diameter roller pulley having an outer diameter of 10 to 20 mm. Be seen.

The polyurethane of the present invention has improved curling while maintaining the necessary elastic modulus as a belt by specializing the configuration of polyol, soft segment and hard segment, and chemical bond. In addition, the toner image is excellent in carrying ability and followability to unevenness. Therefore, for example, it can be suitably used as an intermediate transfer belt or a transfer conveyance belt.

EXAMPLES Hereinafter, although an Example is hung up and demonstrated in more detail, this invention is not limited only to these Examples. In the examples, “parts” and “%” mean “parts by mass” and “% by mass” unless otherwise specified.

Examples 1-4
(Preparation of elastic surface layer forming liquid)
Three polyester polyols having an average functional group number of 2.3, Nippon Polycarbonate 4032 (manufactured by Nippon Polyurethane Industry Co., Ltd., hydroxyl value = 60 KOHmg / g), previously added with Ketjen Black, which is conductive carbon, to 1 mass%. A conductive material-containing polyol was obtained by kneading and dispersing with a roll. After dehydrating under reduced pressure at 100 ° C. for 12 hours, 9.8 parts of tolylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., “Coronate T-80”) was mixed with 100 parts to prepare an elastic surface layer forming liquid. The hardness was adjusted by changing the [NCO] / [OH] molar ratio and the isocyanate species.

(Preparation of belt substrate forming liquid)
Polycarbonate diol having a hydrocarbon chain part having 9 carbon atoms and a methyl group as a side chain, “Kurapol C-1065N” (manufactured by Kuraray Co., Ltd., hydroxyl value = 14.8 KOHmg / g, 1,9-nonanediol / methyloctanediol) Mass ratio 65/35), “Kurapol C-2065N (Kuraray Co., Ltd., hydroxyl value = 58.1 KOH mg / g, 1,9-nonanediol / methyloctanediol mass ratio 65/35),“ Kurapol C-1015N ”( Kuraray Co., Ltd., hydroxyl value = 112 KOH mg / g, 1,9-nonanediol / methyloctanediol mass ratio = 15/85) was used.

As the aromatic diamine, “Vitec 1604” (molecular weight = 242 manufactured by Sumika Bayer Urethane Co., Ltd.) was used as 4-chloro-3,5-diaminobenzoic acid isobutyl ester.

As the isocyanate, norbornane diisocyanate (manufactured by Mitsui Takeda Chemical Co., “Cosmonate NBDI”, NCO = 40.8%) was used as the bifunctional aliphatic isocyanate. As the trifunctional isocyanate, an isocyanurate of hexamethylene diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., “Sumidule N3300”, NCO = 21.8%) was used. By mixing these materials in the proportions shown in Table 1, a belt base material forming liquid was obtained. In addition, 1% of ketjen black, which is conductive carbon, was contained in the polyol in the same manner as the elastic surface layer.

(Seamless belt molding)
Using a centrifugal molding machine, with a mold having a mold diameter of 180 mm and a width of 350 mm, first, the elastic surface layer forming liquid was introduced at a mold rotation speed of 500 rpm, and immediately shifted to a high-speed rotation of 2500 rpm for 10 minutes. Thereafter, the number of revolutions was reduced to 500 rpm, and after half-curing at 125 ° C. for 2 minutes, the belt base material forming solution was charged under the same conditions as the elastic surface layer with the formulation shown in Table 1 to obtain a belt. In Examples 1 to 3, a belt having no elastic surface layer was manufactured.

Comparative Examples 1-3
(Preparation of belt substrate forming liquid)
As an aromatic polyester polyol, a polyol “Kuraray polyol P1020” (manufactured by Kuraray Co., Ltd., hydroxyl value = 113.9 KOHmg / g) composed of 3-methyl-1,5-pentanediol and terephthalic acid, 3-methyl-1, A polyol composed of 5-pentanediol and isophthalic acid “Kuraray Polyol P1030” (manufactured by Kuraray Co., Ltd., hydroxyl value = 113.6 KOH mg / g), polycarbonate polyol composed of 1,4-cyclohexanedimethanol, “UC-CARB100” ( Ube Industries, Ltd., hydroxyl value = 110.8 KOHmg / g) was used. The same aromatic diamine and aliphatic isocyanate as in Example 1 were used in the formulation shown in Table 2.

(Seamless belt molding)
A belt was produced in the same manner as the belt forming method of the example.

〔Evaluation methods〕
The curl was evaluated using sample belts cut to a width of 30 mm from the thin cylindrical belts obtained in the above Examples and Comparative Examples, and the results are shown in Tables 1 and 2. Further, the temperature dispersion data of the storage elastic modulus E ′ measured under the conditions of the dynamic strain of the belt base material (polyurethane) 0.1% and the frequency 10 Hz obtained in the above examples and comparative examples are shown in FIGS. Indicated.

(Evaluation of rolls)
As shown in the measuring apparatus of FIG. 8, the sample belt 41 (length 550 mm × width 30 mm) is wound around two pulleys (an outer diameter of 20 mm) of a fixed pulley 46 and a slide pulley 47, and a weight (1 kg) is wound around the belt. Tension was applied and kept for 24 hours. The belt removed after the holding was cut into a length of about 100 mm centering on the portion around the pulley and placed on a surface plate as shown in FIG. 9, and the apex height t was measured with a height gauge. The measured apex height t (mm) is shown in Tables 1 and 2 as a curl.

As a result, it can be seen that the belt obtained in the example is improved to about 1/2 of the curl compared with the belt obtained in the comparative example. From FIG. 6 and FIG. 7, the polyurethane used in the examples uses a polycarbonate polyol having a hydrocarbon chain portion having a predetermined number of carbon atoms and a carbonate bond portion as a polyol, and introduces a urea bond having a large cohesive force using an aromatic diamine. The conventional polyurethanes of Comparative Examples 1 to 3 in which the storage elastic modulus E ′ has a transition in the range of −55 to −20 ° C. and the peak temperature of tan δ is 100 to 200 ° C. are not possible. It turns out that it has the characteristic that it had.

The polyurethane of the present invention can be used for an electrophotographic apparatus belt, and the electrophotographic apparatus belt obtained by using the polyurethane is preferably used as an intermediate transfer belt or a transfer conveyance belt, for example. It is something that can be done.

It is an example of the perspective view of the belt 1 for electrophotographic apparatuses of this invention. It is an example of the perspective view of the belt 1 for electrophotographic apparatuses of this invention. It is an example of the perspective view of the belt 1 for electrophotographic apparatuses of this invention. 1 is an example of a side view of the periphery of a photoreceptor 11 of an electrophotographic apparatus using the belt for an electrophotographic apparatus of the present invention as an intermediate transfer belt 16. FIG. 3 is an example of a side view of the periphery of a photoreceptor 11 of an electrophotographic apparatus using the belt for an electrophotographic apparatus of the present invention as a transfer conveyance belt 16 ′. It is the figure which showed the data of the temperature dispersion | variation of the storage elastic modulus E 'of the polyurethane used in the Example. It is the figure which showed the data of the temperature dispersion | variation of the storage elastic modulus E 'of the polyurethane used by the comparative example. It is the schematic of the apparatus used for generation | occurrence | production of a curl. It is the schematic of the measuring apparatus of the vertex height which is a curl.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrophotographic belt 2 Belt base material 3 Elastic surface layer 4 Surface coating layer 11 Photoconductor 12, 13 Pulley 14 Developing unit 15 Transfer roller 16 Intermediate transfer belt 16 'Transfer conveyance belt 41 Belt 42 Weight 43 Dial gauge 44 Surface plate 45 Height gauge 46 Fixed pulley 47 Slide pulley 48 Slide bearing

Claims (9)

The peak temperature of the main dispersion of tan δ determined from the temperature dispersion of dynamic viscoelasticity measured under the conditions of dynamic strain 0.1% and frequency 10 Hz exists in 100 to 200 ° C., and is a glass region at 25 ° C., and A polyurethane characterized by having a transition in a region where the storage elastic modulus E ′ obtained from the same conditions is −55 to −20 ° C. The polyurethane according to claim 1, wherein the polyol component forming the polyurethane is a polycarbonate polyol having a portion containing a carbonate bond and a linear portion having 5 to 12 carbon atoms. The polyurethane according to claim 2, wherein the straight chain portion includes a side chain having 8 to 9 carbon atoms and / or an isomer. The polyurethane according to claim 2, wherein the linear portion is derived from 1,9-nonanediol and methyloctanediol. The polyurethane according to claim 1, 2, 3 or 4, wherein the curing agent component forming the polyurethane is an aromatic diamine, and the isocyanate component is a bifunctional or trifunctional aliphatic isocyanate. A belt for an electrophotographic apparatus, comprising a conductive filler dispersed in the polyurethane according to claim 1, 2, 3, 4 or 5, and formed into a thin cylindrical shape. 7. The belt for an electrophotographic apparatus according to claim 6, wherein an elastic surface layer having a JIS-A hardness of 30 to 80 degrees is further laminated on the outer periphery of the thin cylindrical belt base material. 8. The belt for an electrophotographic apparatus according to claim 7, wherein both the elastic surface layer and the belt base material are integrally laminated by a centrifugal molding method without using an adhesive. 9. The electrophotographic apparatus belt according to claim 6, 7 or 8, wherein the electrophotographic apparatus belt is an intermediate transfer belt or a transfer conveyance belt.

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