JP2007057706A - Pressure roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure roller which is hardly soiled by preventing adhesion of toner without providing a resin layer on the outermost surface of an elastic layer. <P>SOLUTION: The pressure roller is equipped with a rubber layer on the outermost layer. Then, phenyl oil is dispersed and arranged all over the circumference inside the surface layer part of the rubber layer, and exudes to the surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pressure roller set in a fixing unit in an image forming apparatus such as an electrophotographic or electrostatic recording type copying machine, a facsimile machine, or a laser beam printer, and in particular, eliminates a surface layer made of an expensive resin layer. However, the toner hardly adheres to reduce the occurrence of contamination.

Conventionally, in this type of image forming apparatus, generally, a charging process for charging a photosensitive drum → an exposure process for forming an electrostatic latent image on the photosensitive drum → a toner (developer) is attached to the electrostatic latent image. An image is formed on the sheet through a developing process for forming a toner image → a transfer process for transferring the toner image on the photosensitive drum to the sheet → a fixing process for fixing the unfixed toner image on the sheet.
Various units such as a sheet conveying roller, a charging roller, a transfer roller, a fixing roller, and a pressure roller are arranged in each part of the image forming apparatus, and the required functions in each process are shared.

In the fixing process, a fixing unit is set, and a fixing roller and a pressure roller are arranged to face each other to form a nip portion as required, and a sheet is introduced into the nip portion and is nipped and conveyed to hold the unfixed image on the sheet. It is fixed on the top.
The pressure roller needs moderate flexibility and low thermal conductivity in order to press the sheet against the fixing roller.

  However, when a foamed rubber layer is used to reduce hardness and thermal conductivity, the rubber material blended with a foaming agent is foamed during thermal vulcanization, resulting in variations in the degree of foaming in the longitudinal and circumferential directions of the roller. There is a problem that it is difficult to make the hardness distribution uniform in the rubber layer. In an image forming apparatus, when a roller having a variation in hardness and thermal conductivity is used in a rubber layer, problems such as fixing property, paper feeding property, transfer property, and charging property occur.

In order to solve the above problem, the present applicant, in JP 2000-230541 A (Patent Document 1), instead of foaming with a foaming agent, a rubber layer containing a resin microballoon is formed on a roller base material, A rubber-covered roller including a pressure roller having an outermost layer made of a fluororesin or a polyimide resin as an outermost layer is provided.
Japanese Patent Application Laid-Open No. 2002-148988 (Patent Document 2) also provides a pressure roller having the same configuration as that of Patent Document 1. The pressure roller also includes a rubber layer dispersedly containing voids formed by resin microballoons, and is made of fluororesin and fluororubber as described in claim 12, embodiment and examples. The outermost layer is provided.

  As described above, since any pressure roller of Patent Documents 1 and 2 forms a rubber layer having voids using a resin microballoon, a foaming agent is blended with a rubber material and foamed during vulcanization. In comparison, it has an advantage that variation in hardness distribution can be suppressed. In addition, since the outermost layer is provided with a coating layer made of fluororesin or the like, the toner transferred to the fixing roller or the sheet is prevented from adhering to the exposed gap or recess of the pressure roller, and the pressure roller using the toner There is an advantage that does not cause dirt.

As described above, in order to prevent adhesion of toner and make the roller difficult to get dirty, there is an advantage of providing the outermost resin layer made of a fluororesin or the like on the surface of the rubber layer, but there are also the following problems.
That is, as a method of providing a coating layer such as a fluororesin on the outermost layer, three methods have been conventionally employed.
(1) Forming a rubber layer such as silicone rubber on an aluminum core, and covering the rubber layer with a fluororesin tube and heat shrinking the coating:
(2) A method of forming a fluororesin layer by forming a rubber layer such as silicone rubber on an aluminum core, applying a liquid fluororesin paint on the rubber layer, and baking it.
(3) Applying a liquid fluororesin paint to the inner surface of the cylinder wall of the mold, drying and firing to form a cylindrical cured thin film of fluororesin on the inner surface of the cylinder wall, and then etching the inner surface of the cured thin film After the application, a roller cored bar is inserted into the axial center of the cylindrical wall, a liquid silicone rubber containing a resin microballoon is pressed between the cured thin film and the cored bar, and the silicone rubber is thermally vulcanized. .

The method (1) has a problem that the surface of the fluororesin tube is wavy when the fluororesin tube is heated and contracted, the smoothness is impaired, and the thickness of the fluororesin layer cannot be reduced.
In the method (2), since the firing temperature of the high melting point fluororesin exceeds the heat resistance temperature of the rubber layer, the rubber layer is likely to deteriorate, and the adhesion between the rubber layer and the fluororesin layer is not sufficient. There's a problem.
In the method (3), in order to sufficiently secure the adhesion between the resin layer and the rubber layer, an adhesive is applied in advance to the inner surface of the resin layer to be in close contact with the rubber layer, or the inner surface of the resin layer is activated. It is preferable to arrange an intermediate layer. In that case, there is a problem that the number of processes increases and the cost increases. Further, there is a problem that it is difficult to completely eliminate a problem that a part of a thin resin layer is torn or wrinkles are generated and the surface smoothness is easily impaired at the time of releasing from the mold.
Furthermore, in any case, when the resin layer is provided as the outermost layer of the elastic layer, the flexibility of the roller surface is lowered and the sheet conveying force tends to be weakened. The rollers are required to have sufficient flexibility in order to cope with recent high-speed copying and full-color images. However, it is impossible to sufficiently meet the requirements.

Japanese Patent Laid-Open No. 2000-230541 JP 2002-148988

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a pressure roller in which toner is not easily attached and is not easily soiled even when a rubber layer is exposed on the surface without providing a resin layer as an outermost layer. It is said.
Furthermore, an object of the present invention is to provide a pressure roller having a rubber layer that is flexible and has small variations in hardness and thermal conductivity, and is excellent in flexibility, heat resistance, surface smoothness, durability, and the like. .

In order to solve the above problems, the present invention is a pressure roller mounted in an image forming apparatus,
Provided is a pressure roller comprising a rubber layer as an outermost layer, wherein phenyl oil is distributed over the entire circumference of a surface layer portion of the rubber layer, and the phenyl oil can be oozed on the surface. ing.

That is, in the present invention, instead of the outermost resin layer made of fluororesin or the like provided to prevent the toner from adhering to the surface of the rubber layer or entering the voids of the rubber layer, the toner adheres in the present invention. In addition to dispersing the difficult-to-perform phenyl oil in the rubber layer, it is formed so as to overflow on the surface of the rubber layer, and the phenyl oil reduces and prevents toner adhesion.
By eliminating the fluororesin film for preventing toner adhesion formed on the outermost layer as described above, the above-mentioned problems can be solved, and the cost can be reduced and the manufacturing process can be reduced.

  The rubber layer is mixed with a resin microballoon in the rubber layer and heated to form a shell of the resin microballoon, as in Japanese Patent Application Laid-Open No. 2000-230541 related to the prior application of the present applicant. It breaks to form voids in the rubber layer in which phenyl oil is blended. Therefore, the rubber layer containing phenyl oil has a structure in which the shell of the resin microballoon remains between the rubber component and the gap.

As described above, by forming a rubber layer using a rubber component containing a resin microballoon, flexibility equivalent to foamed rubber can be imparted and hardness variation can be reduced.
Preferably, the resin microballoon surrounds the hollow portion with a shell made of a thermoplastic resin. The resin microballoon that forms voids in the rubber layer preferably has an average particle size of 5 μm to 200 μm.

The rubber component used for the rubber layer is preferably silicone rubber, fluororubber, or a mixture thereof.
The rubber layer has a thickness of 100 μm to 5 mm, preferably 0.1 to 3 mm.
The voids in the elastic layer are preferably 10 to 50% by volume.

The rubber layer has an Asker C hardness of 55 degrees or less, more preferably 50 degrees or less, and 5 degrees or more, preferably 10 degrees or more.
The thermal conductivity is 0.5 × 10 ⁻³ cal / cm · sec · ° C. or less, more preferably 1 × 10 ⁻⁴ cal / cm · sec · ° C. or less, and 0.1 × 10 ⁻⁴ cal / cm · ° C. It is about sec · ° C. or higher.
Furthermore, the surface roughness (Ra) is preferably 3 μm or less.

  The rubber layer is preferably provided on a roller base material made of a core metal or a metal tube, and the thickness of the rubber layer is preferably 100 μm to 5 mm.

  The pressure roller is formed by mixing a resin microballoon with liquid silicone rubber compounded with phenyl oil and then heating to break the shell of the resin microballoon to form voids in the rubber layer compounded with phenyl oil. Yes.

  The resin microballoon to be mixed with the liquid silicone rubber is preferably heated and expanded in advance. The average particle diameter of the heat-expanded resin microballoon is preferably 5 to 200 μm.

  Specifically, a fluororesin film is formed on the inner peripheral surface of the cylindrical mold, the roller base material is inserted into the center of the hollow portion of the mold, and then between the roller base material and the inner peripheral surface of the mold. The heated and expanded resin microballoon is mixed with a liquid silicone rubber material containing phenyl oil, and then heated at a required temperature to heat and cure the liquid silicone rubber and destroy the shell of the resin microballoon. Yes.

In the above-described pressure roller of the present invention, the fluororesin layer is not provided on the outermost surface of the rubber layer forming the elastic layer, and only the rubber layer is used. Therefore, labor can be saved and the cost can be reduced.
Also, instead of providing a fluororesin layer, phenyl oil is dispersed and filled in the rubber layer so that the phenyl oil can overflow to the surface, so that toner adhesion can be reduced and prevented, and toner contamination is less likely to occur. be able to.
And since the fluororesin is not provided, the surface flexibility can be enhanced and the above-mentioned problems in manufacturing can be solved.
Further, since the rubber layer is provided with a void by the resin microballoon, the hardness variation in the axial direction and the circumferential direction of the roller can be reduced.

  1A and 1B show a pressure roller 1 according to a first embodiment used in an image forming apparatus of the present invention, and an elastic layer made of a rubber layer 3 is provided on a roller base 2. The surface 3a of the rubber layer 3 is not provided with a resin layer, and the surface 3a of the rubber layer 3 is the outermost layer. Inside the rubber layer 3 and on the surface layer are provided with voids 5 formed by resin microballoons 8 shown in FIG. 2, and phenyl oil 6 is dispersed and blended in the rubber layer 3. The voids 5 are continuous with each other and are also exposed on the surface 3a of the elastic layer 3, so that the phenyl oil 6 can overflow to the surface.

  As shown in FIG. 2, the resin microballoon 8 has a shape in which a hollow portion is surrounded by a resin shell 10. The resin microballoon 8 is expanded by heating and uniformly mixed in the liquid silicone rubber, and the liquid silicone rubber mixed with the resin microballoon 8 is heated and vulcanized to cure the liquid silicone rubber, and The void 5 is provided by breaking the shell 10 of the resin microballoon 8. Therefore, the resin microballoon shell 10 remains in the rubber layer 3 between the silicone rubber 7 and the gap 5.

As described above, silicone rubber is used as the rubber component containing the resin microballoon 8, but fluororubber and a mixture thereof are also heat resistant enough to withstand continuous use at the fixing temperature when used as a pressure roller. Any material having the property can be used.
Specifically, as the rubber material, silicone rubber such as dimethyl silicone rubber, fluorosilicone rubber, methylphenyl silicone rubber, vinyl silicone rubber; vinylidene fluoride rubber, tetrafluoroethylene-propylene rubber, tetrafluoroethylene-perfluoromethyl And fluorine rubbers such as vinyl ether rubber, phosphazene fluorine rubber, and fluoropolyether. Among these, liquid silicone rubber that can be easily injected into a mold is preferably used.

Since the resin microballoon 8 is dispersed and blended in the rubber layer 3 to form the gap 5, the rubber layer 3 can be provided with required flexibility and heat insulation.
The spherical shell 10 of the resin microballoon used in the present invention is made of, for example, a thermoplastic resin such as polyvinylidene chloride or polystyrene, or an organic polymer material such as rubber.
The resin microballoon 8 has a size of several μm to several hundreds of μm, and has a size of about 5 to 200 μm when heated and expanded.

  The ratio of the resin microballoon 8 in the rubber component (liquid silicone rubber) is 5 to 60% by volume, preferably 10 to 50% by volume, and more preferably 15 to 45% by volume. Resin microballoons are spherical and have a small ratio of surface area to volume. Therefore, even if the rubber material is highly filled, fluidity can be maintained well and evenly dispersed. If the proportion of the resin microballoon is too small, it is difficult to sufficiently impart flexibility and / or heat insulation to the rubber layer. If the proportion is too large, the viscosity of the rubber material becomes too high, or the strength of the rubber layer is low. There is a risk of decline.

  The void 5 formed by breaking the shell 10 of the resin microballoon 8 mixed in the rubber material is 5 to 60% by volume, preferably 10 to 50% by volume, more preferably 15 to 45% in the rubber layer. Volume%.

  If desired, the rubber component may contain an inorganic filler such as carbon black, mica, and titanium oxide, or an organic filler such as a natural resin. The blending ratio of the filler is usually 100 parts by weight or less, preferably 80 parts by weight or less with respect to 100 parts by weight of rubber.

In the present embodiment, the rubber layer 3 has an Asker C hardness of 50 degrees or less and 10 degrees or more from the viewpoint of flexibility. Further, when the pressure roller takes heat from the transfer material, the toner is not sufficiently melted and the fixing property is lowered, so that it is desired to have excellent heat insulation properties. In the form, it is 0.5 × 10 ⁻³ cal / cm · sec · ° C. or lower, and 0.1 × 10 ⁻⁴ cal / cm · sec · ° C. or higher. The hardness and thermal conductivity of the rubber layer 3 are adjusted by the blending ratio of the resin microballoons and the type of rubber material.
The rubber layer 3 has a surface roughness (Ra) of 3 μm or less.

  The thickness of the rubber layer 3 is appropriately set within the above range from the application, the structure of the machine device to be installed, the target elasticity, the hardness of the material used, etc., but is about 100 μm to 5 mm, preferably about 0.1 to 3 mm. is there.

  The roller base 2 is made of a metal having a good thermal conductivity, such as aluminum, aluminum alloy, iron, stainless steel or the like, or a metal core made of ceramics such as alumina or silicon carbide, or iron, nickel, alloys thereof, or ferrite. A metal tube made of stainless steel is used.

The pressure roller 1 is manufactured at the center of the hollow portion of the cylindrical mold by the roller base 2.
Then, the resin microballoon 8 is mixed and injected into the liquid silicone rubber into the gap between the roller base 2 and the inner surface of the mold, and then vulcanized at the required temperature. Liquid silicone rubber is cured. Thereafter, the shell 10 is heated at a temperature at which the shell 10 of the resin microballoon 8 is broken, so that the shell 10 is broken to form the gap 5.
Thereafter, the pressure roller 1 having the rubber layer 3 formed on the roller base material 33 is extracted from the mold.

An adhesive may be applied to the surface of the roller base 2.
The resin microballoon 8 is heated and expanded before mixing with the liquid silicone rubber, but it is not always necessary to expand it in advance.

The cylindrical mold is preferably made of metal such as iron, stainless steel, and aluminum, but is not limited as long as it has heat resistance capable of withstanding the heat treatment temperature.
In addition, in order to facilitate removal of the roller base material from the cylindrical mold together with the vulcanized rubber layer in the final process, the inner surface of the cylindrical mold is subjected to plating treatment and fluorine coating so that the surface roughness (Rz) is 1 μm or less. It is preferable to keep it. Thereby, the rubber layer which has no unevenness | corrugation on the surface and has smoothness can be obtained.

[Example]
The inner surface of an aluminum cylindrical mold having an inner diameter of 24 mmφ and a length of 300 mm was coated with a primer and baked after coating with a primer, and then the fluororesin was baked to form a fluororesin film on the inner surface of the mold.
A silicone-based adhesive was applied to the surface of an aluminum cored bar having an outer diameter of 20 mmφ and a length of 300 mm and dried, and then inserted into the hollow of the cylindrical mold so that the axes of both coincided.
In the gap between the inner surface of the cylindrical mold and the cored bar, liquid silicone rubber (manufactured by Shin-Etsu Chemical Co., KE1380) is mixed with phenyl oil, and 20% by volume of micron spheres made of resin microball (made by Dow) The blended rubber material was poured.
Subsequently, the rubber was heat vulcanized by heating at 160 ° C. for 15 minutes. Subsequently, the resin microballoon shell was broken by heating at 240 ° C. for 360 minutes to form voids.
Thereafter, the mold was removed to obtain a roller.

The obtained roller had no wrinkles or tears on the surface, and no waviness or unevenness on the surface. Further, the phenyl oil can overflow from the surface of the rubber. Further, the hardness of the rubber layer of the roller was 16 degrees in Asker C, and the thermal conductivity was 0.5 × 10 ⁻³ cal / cm · sec · ° C.

The roller thus obtained was set as a pressure roller in the fixing unit.
A roller member in which a silicone rubber layer having a thickness of 2 mm and a fluororesin layer having a thickness of 20 μm were laminated in this order on an aluminum cored bar was used as the fixing roller disposed to face the pressure roller. The temperature was raised with a halogen lamp heater so that the surface temperature of the fluororesin layer of the fixing roller was 180 ° C. Using a Canon laser printer, the copy paper on which an unfixed image was formed with monochrome toner was passed through the fixing unit and pressed with a nip width of 3 mm to continuously fix 10,000 sheets. As a result, a good fixed image without offset was obtained. It was.

(A) is a schematic sectional drawing which shows the pressure roller of 1st Embodiment of this invention, (B) is a partially expanded view of (A). It is a schematic sectional drawing of the resin microballoon used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressure roller 2 Roller base material 3 Rubber layer 5 Cavity 6 Phenyl oil 7 Silicone rubber 8 Resin microballoon shell 10 Shell

Claims (6)

A pressure roller mounted in the image forming apparatus,
A pressure roller comprising a rubber layer as an outermost layer, phenyl oil dispersed and disposed in the entire surface portion of the rubber layer, and the phenyl oil being allowed to exude on the surface.   The rubber layer has a void, and the void is formed by breaking a shell of a resin microballoon blended with a rubber component, and the shell of the resin microballoon remains between the rubber component and the void. The pressure roller according to claim 1.   The pressure roller according to claim 2, wherein the rubber component used in the rubber layer is silicone rubber, fluororubber, or a mixture thereof.   The pressure roller according to claim 2 or 3, wherein the gap in the rubber layer is 5 to 60% by volume. The rubber layer has a hardness of 55 degrees or less in Asker C, a thermal conductivity of 0.5 × 10 ⁻³ cal / cm · sec · ° C. or less, and a surface roughness (Ra) of 3 μm or less. Item 5. The pressure roller according to any one of items 4 to 6.   The said rubber layer is provided on the roller base material which consists of a metal core or a metal tube, and the thickness of this rubber layer is 100 micrometers-5 mm, The addition of any one of Claims 1 thru | or 5 Pressure roller.

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