JP2001066903A - Intermediate transfer belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer belt which is excellent in heat resistance and, therefore, can be used for an image forming device in which liquid toner is heated. SOLUTION: This intermediate transfer belt 1 is provided with a substrate 3, a metallic layer 5 and a covering layer 7. The substrate 3 comprises primarily polyimide, polyphenylene sulfide, polyether sulfone or polyether ether ketone. Melting point of the substrate 3 is more than 280 deg.C. The metallic layer 5 consists of copper. Thickness of the metallic layer 5 is more than 0.5 μm and less then 20 μm. The metallic layer 5 is formed by means of sputtering or ion plating. The covering layer 7 comprises primarily heat-resistant fluorinated resin such as fluorinated vinylidene resin, teterafluoroethylene resin and trifluoroethylene resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate transfer belt used for an image forming apparatus such as a copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art When an image is formed by an image forming apparatus using an intermediate transfer belt, an electrostatic latent image is first formed on a photosensitive drum. Next, toner is supplied onto the photosensitive drum to form a toner image. The toner image is temporarily transferred from the photosensitive drum to the outer peripheral surface of the intermediate transfer belt, and further transferred from the intermediate transfer belt to a printing medium such as paper and fixed. For color printing, black, magenta,
4 color toners of cyan and yellow (3 excluding black)
Are transferred to an intermediate transfer belt, and these are transferred to a printing medium. Thus, a desired image is printed. The intermediate transfer belt is mainly made of rubber or synthetic resin, and has a volume resistivity of about 10 ⁶ Ω · cm to 10 ¹² Ω · cm (that is, conductive) in terms of a toner image transfer mechanism.

In recent years, demands for higher density and higher accuracy for images have been increasing. To achieve high image quality, it is preferable that the particle size of the toner is small (for example, 5 μm or less). If the toner collecting device is installed in the image forming apparatus, the scattering is prevented, but the load on the image forming apparatus is increased, which is against the demand for downsizing. For this reason, ordinary toners have an average particle diameter of about 6 μm to 10 μm, and the achievement of high image quality with this toner has reached its limit.

[0004] In order to achieve high image quality, liquid toner is being adopted. This liquid toner is 1% by weight with an organic solvent.
And about 2% by weight of toner particles. Since the toner particle size is as small as about 1 μm, the accuracy of an image can be improved. However, since a large amount of an organic solvent is used in the liquid toner, the organic solvent may adversely affect the human body.

Japanese Patent Application Laid-Open No. 11-167295 discloses a transfer drum type image forming apparatus using a liquid toner in which a large amount of toner particles are dispersed in silicone oil. In this image forming apparatus, the liquid toner transferred to the transfer drum is heated to evaporate and remove volatile components, and after the binder resin is melted, the toner particles are transferred to the printing medium. Since the amount of the organic solvent used in the liquid toner is small, adverse effects on the human body are suppressed.

[0006]

When a method of transferring the heated toner particles to a printing medium is employed in an image forming apparatus of an intermediate transfer belt type, the liquid toner is heated on the intermediate transfer belt. Therefore, it is necessary that the intermediate transfer belt has heat resistance. However, the conventional intermediate transfer belt is not designed on the assumption that it is heated, and does not always have sufficient heat resistance.

The present invention has been made in view of such a problem, and has as its object to provide an intermediate transfer belt which has excellent heat resistance and can be used in an image forming apparatus in which a liquid toner is heated.

[0008]

Means for Solving the Problems An invention made to achieve the above object is to provide a base mainly composed of a synthetic resin having a melting point of 280 ° C. or more, and a thin film formed on the front side of the base. An intermediate transfer belt including a metal layer and a coating layer formed on the front side of the metal layer.

The base of the intermediate transfer belt has a melting point of 280.
Since the main component is a synthetic resin having a temperature of not less than ° C., it can withstand heat during heating of the liquid toner. Further, since the intermediate transfer belt is provided with the metal layer, the intermediate transfer belt is excellent in electrostatic attraction, and easily absorbs liquid toner from the photosensitive drum. Further, since the intermediate transfer belt includes the coating layer, the transfer of the toner particles to the printing medium is performed smoothly.

Examples of the synthetic resin having a melting point of 280 ° C. or higher include polyimide, polyphenylene sulfide, polyether sulfone, polyether ether ketone and the like. When polyimide is used, the thickness of the substrate is preferably 10 μm or more and 100 μm or less from the viewpoint of compatibility between the durability of the intermediate transfer belt and the moldability of the coating layer. When polyphenylene sulfide, polyether sulfone or polyether ether ketone is used, the thickness of the substrate is preferably 50 μm or more and 250 μm or less from the viewpoint of compatibility between the durability of the intermediate transfer belt and the moldability of the coating layer.

[0011] Preferably, the metal layer is made of copper.
Copper does not have magnetism and thus has excellent electrostatic attraction. Also,
Preferably, the thickness of the metal layer is 0.5 μm or more and 20 μm or less.

[0012] Preferably, the metal layer is formed directly on the substrate. Examples of the forming method include sputtering, ion plating, and vacuum deposition. In particular, if the metal layer is formed by sputtering or ion plating on the base, the adhesion between the base and the metal layer is increased by the so-called anchor effect. Further, on the target anchor layer formed by sputtering or ion plating on the base, a metal layer may be formed by sputtering, ion plating, electrodeposition plating, or the like. Is suppressed.

Preferably, the coating layer contains a heat-resistant fluororesin such as vinylidene fluoride resin, tetrafluoroethylene resin, trifluoroethylene resin or the like as a main component. Since these resins are excellent in detachability of toner particles, transfer of the toner particles to a printing medium becomes smooth. Furthermore, these resins can also have a function as a dielectric layer.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A preferred embodiment of the present invention will now be described. FIG. 1 is a perspective view showing an intermediate transfer belt 1 according to one embodiment of the present invention. The overall shape of the intermediate transfer belt 1 is substantially cylindrical (that is, endless). However, the intermediate transfer belt 1 is flexible and can be freely deformed by its own weight or the like. FIG. 1 shows the entire shape (that is, the cross section in the traveling direction is substantially an elliptical shape) assuming that it is stretched between two shafts.

FIG. 2 is a sectional view taken along the line II-II in FIG. The intermediate transfer belt 1 includes a base 3, a metal layer 5, and a coating layer 7. The outer peripheral surface 9 of the intermediate transfer belt 1 is a surface to which the liquid toner adheres. The inner peripheral surface 11 is a surface that directly contacts a drive shaft, a driven shaft, and the like during rotation.

The base 3 is made of a heat-resistant synthetic resin having a melting point of 280 ° C. or higher. Usually, the melting point of the binder resin used for the toner particles is from 150 ° C. to 200 ° C.
C., and the liquid toner on the intermediate transfer belt 1 is heated to a temperature slightly higher than the melting point of the binder resin. Also at this time, since the melting point of the base 3 is 280 ° C. or higher, the base 3 is not melted or deformed. Further, even when the metal layer 5 is formed by sputtering or when the coating layer 7 is fired (the firing temperature is usually about 260 ° C.), the base 3 is melted or deformed as described later. There is no.

Examples of the synthetic resin having a melting point of 280 ° C. or higher include polyimide, polyphenylene sulfide, polyether sulfone, polyether ether ketone, nylon 46, nylon 6T / 6I, polyamide imide, and liquid crystal polyester. In addition to the synthetic resin, various additives may be added to the base 3 as necessary. The common logarithmic value of the volume resistivity of the base 3 is 6 or more and 10 or less (that is, a semiconductive region). When a conductive filler such as carbon black or metal powder is blended into the substrate 3, the common logarithm value falls within the above range.

When polyimide is used, the thickness of the substrate 3 is preferably 10 μm or more and 100 μm or less, and 20 μm or less.
It is particularly preferable that the thickness be at least 50 μm. If the thickness is less than the above range, the strength of the intermediate transfer belt 1 may be insufficient, and it may be difficult to form the coating layer 7. vice versa,
If the thickness exceeds the above range, the rigidity may be too high and the base 3 may be cracked.

When polyphenylene sulfide, polyether sulfone or polyether ether ketone is used, the thickness of the substrate 3 is preferably 50 μm or more and 250 μm or less, particularly preferably 80 μm or more and 200 μm or less.
If the thickness is less than the above range, the strength of the intermediate transfer belt 1 may be insufficient, and it may be difficult to form the coating layer 7. Conversely, if the thickness exceeds the above range, when the intermediate transfer belt 1 rotates while being heated, the smoothness may not be maintained due to bending and stretching on the rotating shaft.

The metal layer 5 is made of copper. Since copper has no magnetism, the electrostatic attraction of the intermediate transfer belt 1 can be enhanced. Here, copper includes not only pure copper but also a copper alloy containing pure copper as a main component. Further, the metal layer 5 may be made of aluminum having no magnetism like copper.

The thickness of the metal layer 5 is 0.5 μm or more and 20 μm
The following is preferable, and 1 to 10 micrometers is especially preferable. If the thickness is less than the above range, the liquid toner may not be uniformly held on the intermediate transfer belt 1 in some cases. Conversely, if the thickness exceeds the above range, the rigidity of the metal layer 5 may be too high to cause a crack or the metal layer 5 to peel off from the base 3 in some cases.

The metal layer 5 is formed directly on the base 3. When the metal film is bonded to the base 3 with an adhesive, the adhesive may melt when the liquid toner is heated. However, such a situation can be avoided if the metal layer 5 is formed directly. Examples of the forming means include sputtering, ion plating, and vacuum deposition. In particular, sputtering or ion plating is preferable because the adhesion between the base 3 and the metal layer 5 is increased by the so-called anchor effect. The peel strength between the substrate 3 and the metal layer 5 is 1 k
g / cm ² or more, which prevents peeling of the substrate 3 and the metal layer 5 having different coefficients of thermal expansion during heating.

A target anchor layer formed by sputtering a metal material or ion plating may be provided between the base 3 and the metal layer 5.
The target anchor layer prevents unreacted products, sulfur components, and the like in the base 3 from coming into direct contact with the metal layer 5 and suppresses corrosion of the metal layer 5. Preferred metals used for the target anchor layer include titanium, palladium and the like. The thickness of the target anchor layer is
It is about 1 angstrom to tens of angstroms.

When a target anchor layer is provided,
The formation of the metal layer 5 on the target anchor layer is not particularly limited, and the metal layer 5 is formed by, for example, sputtering, ion plating, vacuum deposition, electrodeposition plating, or the like. The base 3 and the metal layer 5 are firmly adhered via the target anchor layer.

The coating layer 7 is made of a heat-resistant fluororesin. Suitable heat-resistant fluororesins include vinylidene fluoride-based resins, tetrafluoroethylene-based resins, trifluoroethylene-based resins, and the like, which may be used alone or in combination of two or more. Is also good. The melting point of these resins needs to be higher than the heating temperature of the liquid toner (usually 150 ° C. to 200 ° C.), thereby preventing the coating layer 7 from being melted or deformed during heating. In addition, the melting points of these resins need to be lower than the melting points of the resins constituting the base 3 (for example, 280 ° C.), thereby preventing the base from being melted or deformed when the coating layer 7 is fired. Usually, the baking of the coating layer 7 is performed at about 260 ° C. The vinylidene fluoride resin is a copolymer of vinylidene fluoride as a main monomer and another monomer.
Suitable vinylidene fluoride-based resins include vinylidene fluoride-hexafluoropropylene copolymer because the coating layer 7 is effectively baked and formed at 260 ° C.

The common logarithmic value of the volume resistivity of the coating layer 7 is 11 or more and 14 or less. Thus, the coating layer 7 functions as a dielectric layer, and the liquid toner is adsorbed. Further, the releasability of the toner particles is enhanced by the coating layer 7, and the transfer of the toner particles to the printing medium is facilitated.

The coating layer 7 may be formed from triazine thiol instead of the heat-resistant fluororesin. Since triazine thiol has a lower melting point than vinylidene fluoride-hexafluoropropylene copolymer, the coating layer 7 can be formed at a relatively low temperature.
Can be fired. Therefore, the manufacturing cost of the intermediate transfer belt 1 is reduced. However, the intermediate transfer belt 1 provided with the coating layer 7 of triazine thiol is slightly inferior in durability to the intermediate transfer belt 1 provided with the coating layer 7 of vinylidene fluoride-hexafluoropropylene copolymer.

The thickness of the coating layer 7 is 0.5 μm or more and 50 μm.
The following is preferable, and 3 to 30 micrometers is especially preferable. If the thickness is less than the above range, the coating layer 7 may be worn out during use and the detachability of the toner particles may be poor. Conversely, if the thickness exceeds the above range, it takes time and effort to form the coating layer 7, and the material cost of the intermediate transfer belt 1 may be increased.

The surface roughness Rz of the intermediate transfer belt 1 after the formation of the coating layer 7 is preferably 4 μm or less. Roughness 4
If it exceeds μm, the transferability of the toner particles from the intermediate transfer belt 1 to the printing medium may be deteriorated.

FIG. 3 is a schematic front view showing an image forming apparatus to which the intermediate transfer belt 1 of FIG. 1 is attached. This image forming apparatus includes a drive shaft 13, a first driven shaft 15, a second driven shaft 17, a photosensitive drum 19, a transfer roll 21, a silicone sponge roll 23, and a heater 25. The intermediate transfer belt 1 is stretched around the drive shaft 13, the first driven shaft 15, and the second driven shaft 17. The intermediate transfer belt 1 is rotating in a direction indicated by an arrow A in the figure.

When an image is formed by the image forming apparatus, first, liquid toner is supplied onto the photosensitive drum 19 by a developing roll (not shown) to form a toner image. Next, the toner image is transferred to the intermediate transfer belt 1 passing between the photosensitive drum 19 and the transfer roll 21.
Next, the liquid toner is heated by the heater 25.
By this heating, volatile components of the liquid toner are volatilized to some extent, and the binder resin of the toner particles is melted. Next, the toner image is transferred onto the printing medium 27 supplied between the intermediate transfer belt 1 and the sponge roll 23. This toner image is fixed to form an image. In this figure, one photosensitive drum 19 is shown, but in the case of color printing, four photosensitive drums of black, magenta, cyan and yellow are used.
A photosensitive drum 19 is prepared for each of the color toners. Since the intermediate transfer belt 1 is heat-resistant, the heater 2
5 does not melt or deform when heated.

The liquid toner may be heated by setting the drive shaft 13 at a high temperature without providing the heater 25. In this case, since it is necessary to conduct heat from the drive shaft 13 located on the back side of the intermediate transfer belt 1 to the liquid toner located on the front side, from the viewpoint of thermal efficiency, the intermediate transfer belt 1
Needs to be relatively thin. Specifically, the thickness of the base 3 is preferably 100 μm or less, and particularly preferably 50 μm or less. For such a thin-walled substrate 3, a polyimide, to which a centrifugal molding method or a coating molding method can be applied and a thin wall is easily achieved, is preferable.

[0033]

EXAMPLES Hereinafter, the effects of the present invention will be clarified based on examples, but it is needless to say that the present invention should not be construed as being limited based on the description of the examples.

Example 1 A substrate made of polyimide (trade name “U Varnish-S” of Ube Industries, Ltd.) having a thickness of about 50 μm was formed. Titanium was sputtered on the surface of the substrate to form a target anchor layer having a thickness of about 50 Å. A metal layer made of copper and having a thickness of about 3 μm was formed on the surface of the target anchor layer by electrodeposition plating. On the surface of this metal layer, a resin composition containing vinylidene fluoride-hexafluoropropylene copolymer as a main component (trade name “Dai Latex GLS-213” of Daikin Industries, Ltd.) was applied, and the temperature was 100 ° C.
For 10 minutes, and further cured at a temperature of 260 ° C. for 30 minutes to form a coating layer having a thickness of about 10 μm. Thus, the intermediate transfer belt of Example 1 was obtained. The surface roughness Rz of this intermediate transfer belt was 0.5 μm.

Example 2 An intermediate transfer belt of Example 2 was obtained in the same manner as in Example 1 except that the thickness of the base was about 100 μm and the thickness of the metal layer was about 5 μm. The surface roughness Rz of the intermediate transfer belt was 0.4 μm.

Comparative Example 1 The procedure of Example 1 was repeated except that the thickness of the substrate was about 100 μm and no coating layer was provided.
An intermediate transfer belt of Comparative Example 1 was obtained. The surface roughness Rz of the intermediate transfer belt was 0.3 μm.

Example 3 A substrate made of polyphenylene sulfide (PPS, trade name “Torelina” manufactured by Toray Industries, Inc.) having a thickness of about 150 μm was used, and the thickness of the metal layer was set to about 5 μm.
Other than the above, an intermediate transfer belt of Example 3 was obtained in the same manner as in Example 1. The surface roughness Rz of this intermediate transfer belt is 4 μm.
m.

Comparative Example 2 Polyester elastomer having a melting point of 230 ° C. (trade name “Perprene E45” manufactured by Toyobo Co., Ltd.)
OB) having a thickness of about 200 μm, a metal layer having a thickness of about 5 μm, and a curing temperature of the coating layer of 180 μm.
An intermediate transfer belt of Comparative Example 2 was obtained in the same manner as in Example 1 except that the symbol Δ was used. The surface roughness Rz of the intermediate transfer belt was 5 μm.

Comparative Example 3 A polyester elastomer having a melting point of 160 ° C. (trade name “Perprene P30” manufactured by Toyobo Co., Ltd.)
B)) having a thickness of about 200 μm was used, and titanium was sputtered on the base to form a target anchor layer. As a result, the base was melted and holes were formed. Subsequent steps were stopped.

[Evaluation of Toner Particle Transferability] 170 parts by weight of trimellitic anhydride, 16 parts by weight of phthalic anhydride, 16 parts by weight of adipic acid, 270 parts by weight of neopentyl glycol, and 40 parts by weight of xylene were mixed and nitrogen atmosphere was produced. 20
The mixture was refluxed at 0 ° C. for 2 hours to cause a polymerization reaction to obtain a polyester-melamine resin. Diethylene glycol monobutyl ether 14 is added to this polyester-melamine resin.
After adding 0 parts by weight and cooling to 70 ° C., 160 parts by weight of hexamethoxymethylol melamine was added and reacted at 100 ° C. for 1 hour to crosslink the polyester-melamine resin. A pigment (Chromophthal Red A3B) 3
0 parts by weight, 5 parts by weight of dry silica (trade name “Aerosil A200” of Degussa) and 50 parts by weight of diethylene glycol monobutyl ether are added, and the mixture is stirred with a three-roll mill to disperse the pigment to obtain a magenta liquid toner. Was. The stirring was performed until the average particle diameter of the pigment was 1 μm or less, and 80% or more of all the pigments had a particle diameter of 1 μm or less.

Next, the intermediate transfer belt was stretched around a drive shaft, a first driven shaft and a second driven shaft as shown in FIG. The liquid toner prepared by the above-described method is applied onto the intermediate transfer belt, and the liquid toner is heated by a heater so that the surface temperature of the intermediate transfer belt is from 160 ° C. to 180 ° C., and the transfer pressure is 2.0 kgf. The toner particles were transferred to paper. Then, the transferability was visually confirmed. A sample to which all of the toner particles were transferred was indicated by “○”, a sample in which the remaining toner particles were slightly observed was indicated by “△”, and a sample in which the toner particles remained largely was indicated by “×”. The results are shown in Table 1 below.

[Evaluation of Durability] An intermediate transfer belt is stretched around the above-mentioned drive shaft, first driven shaft and second driven shaft, and the surface temperature of the intermediate transfer belt is adjusted from 160 ° C. to 180 ° C. by a heater. While heating, it was continuously rotated for 250 hours.
The rotation was performed under the condition that the moving speed of the intermediate transfer belt was 0.15 m / s, and the liquid toner and the paper were not supplied during the rotation. Visually observe the intermediate transfer belt after rotation, and if there is no separation between layers or cracks in each layer, mark "○"
And what was seen was marked as "x". The results are shown in Table 1 below.

[0043]

[Table 1]

In Table 1, in the intermediate transfer belt of Comparative Example 1 in which the coating layer was not formed, the transferability of the toner particles was poor. Further, in the intermediate transfer belt of Comparative Example 2, in which the curing temperature of the coating layer had to be lowered due to the low melting point of the base, the coating layer was peeled off during rotation, and thus the transferability of the toner particles was poor. became. From the above evaluation results, the superiority of the present invention was confirmed.

As described above, the intermediate transfer belt of the present invention has been described by taking as an example the case where the intermediate transfer belt is mounted on an image forming apparatus using a liquid toner. It can also be mounted on a forming device.

[0046]

As described above, the intermediate transfer belt of the present invention has excellent heat resistance. By using this intermediate transfer belt in an image forming apparatus, a high quality image can be obtained without adversely affecting the human body.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an intermediate transfer belt according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a schematic front view illustrating the image forming apparatus equipped with the intermediate transfer belt of FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 intermediate transfer belt 3 base 5 metal layer 7 coating layer 9 outer peripheral surface 11 inner peripheral surface 13 drive shaft 15 first driven shaft 17 second driven shaft 19 photosensitive drum 21 transfer roller 23 sponge roller 25 heater 27 paper

Claims (7)

[Claims] 1. A base mainly composed of a synthetic resin having a melting point of 280 ° C. or more, a thin metal layer formed on the front side of the base, and a coating layer formed on the front side of the metal layer. Intermediate transfer belt provided. 2. The intermediate transfer belt according to claim 1, wherein the base is mainly composed of polyimide, and has a thickness of 10 μm or more and 100 μm or less. 3. The method according to claim 1, wherein the substrate is polyphenylene sulfide,
Mainly composed of polyethersulfone or polyetheretherketone, the thickness of which is 50 μm or more and 250 μm
2. The intermediate transfer belt according to claim 1, wherein m is equal to or less than m. 4. A metal constituting the metal layer is copper,
The thickness thereof is 0.5 μm or more and 20 μm or less.
The intermediate transfer belt according to any one of claims 1 to 3. 5. The intermediate transfer belt according to claim 1, wherein the metal layer is formed by sputtering or ion plating on a substrate. 6. A target anchor layer formed between said substrate and said metal layer by sputtering or ion plating on said substrate.
The intermediate transfer belt according to any one of the above items. 7. The intermediate transfer belt according to claim 1, wherein the coating layer contains a heat-resistant fluororesin as a main component.