JPH0973247A - Electrophotographic fixing device and method for fixing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic fixing device and the fixing method suited for the full color image fixing, capable of stably obtaining excellent toner releasing property over a long period. SOLUTION: In the device at least, provided with a fixing roll R1 furnished with a heat resistant elastic body layer on the roll base body while furnished with the outermost layer of fluorinated resin held in contact with the toner on the recording medium, or a fixing belt furnished with the heat resistant elastic body layer on an endless type film base body while furnished with the outermost layer, and an oiler R3 for feeding the releasing oil on a surface of the fixing roll R1 or the fixing belt, the surface roughness of the outermost layer is made <=Ra1μm, and as for the releasing oil, the flow silicone oil whose surface tension is <=20dyn/cm is adopted. In the particularly full color electrophotographic image fixing, offset occurrence is prevented and uneven glossiness is restrained from occurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic fixing device using a fixing roll or a fixing belt and a fixing method, and more particularly to an electrophotographic fixing device suitable for fixing a full-color image and a fixing device for a full-color electrophotographic image. Regarding the fixing method.

[0002]

2. Description of the Related Art Conventionally, in order to fix a toner image obtained by an electrophotographic method on a recording medium, a method of pressing and fusing toner with a fixing roll or a fixing belt is known.
It is commonly used. When obtaining a full-color image, a full-color toner having a low melt viscosity is used in order to improve the uniformity and resolution of the image.

However, such a full-color toner has a narrower softening temperature range near the melting point and a weaker cohesive force at the time of melting as compared with a monochrome toner, so that the toner can be fixed in a temperature range in which the toner can be fixed. Is narrow and tends to cause offset. Therefore, the PF on the substrate, which has been conventionally used in a monochrome image fixing device, is used.
A fluororesin such as A (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), PTFE (polytetrafluoroethylene), FEP (copolymer of tetrafluoroethylene and hexafluoropropylene) was coated as a surface layer material. Fixing roll and fixing belt
When it was used for fixing a full-color image as it was, an offset occurred and a good fixed image could not be obtained.

Further, even if a dimethyl silicone oil, which has been conventionally used as a release oil for offset prevention, is applied to a fixing roll or fixing belt having such a fluororesin as a surface layer material, it is not familiar with the fluororesin. Since it was not sufficient, uniform coating was not possible, and it was difficult to prevent the occurrence of offset. Therefore, especially for fixing a full-color image, by using a fixing roll or a fixing belt having a silicone rubber that is well compatible with dimethyl silicone oil as a surface layer material, and using dimethyl silicone oil as a releasing oil, I was trying to prevent.

[0005]

However, a fixing roll or fixing belt using silicone rubber as a surface layer material has an advantage that dimethyl silicone oil, which is a release oil, can be uniformly applied, and that offset prevention is easy. However, there is a problem that the surface layer material is swelled by dimethyl silicone oil and is likely to be worn or deteriorated, and the dye in the toner penetrates into the surface layer material, so that the releasability is reduced and the service life is shortened. It was

Therefore, the present invention provides an electrophotographic fixing device suitable for fixing a full-color image, and a fixing method suitable for fixing a full-color electrophotographic image, which can stably obtain excellent toner releasability over a long period of time. It was intended.

[0007]

The electrophotographic fixing device of the present invention is a fixing roll provided with a heat-resistant elastic layer on a roll base and an outermost layer of fluororesin which comes into contact with toner on a recording medium, or an endless roll. A heat-resistant elastic layer is provided on the belt substrate and a fixing belt having an outermost layer of fluororesin that contacts the toner on the recording medium, and the release oil is directly or indirectly supplied to the fixing roll or the surface of the fixing belt. The surface roughness of the outermost layer is Ra 1 μm or less, and the built-in release oil is a fluorosilicone oil having a surface tension of 20 dyn / cm or less.

The electrophotographic image fixing method of the present invention further comprises:
A heat-resistant elastic layer is provided on the roll substrate and a fixing roll having an outermost layer of fluororesin that contacts the toner on the recording medium, or a heat-resistant elastic layer is provided on the endless belt substrate and contacts the toner on the recording medium At least a fixing belt having an outermost layer of fluororesin and a coating device for directly or indirectly supplying a releasing oil to the surface of the fixing roll or the fixing belt are provided, and the surface roughness of the outermost layer is Ra1μ.
When fixing an electrophotographic image using a fixing device of m or less, a fluorosilicone oil having a surface tension of 20 dyn / cm or less is used as the releasing oil.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The fixing roll or fixing belt in the electrophotographic fixing device of the present invention preferably has a structure in which a heat resistant elastic body layer is provided on a metallic substrate and a fluororesin layer is provided as the outermost layer. I have. Silicone rubber, fluororubber, or the like can be used as the heat resistant elastic layer, but it is not limited thereto. The thickness of such a heat-resistant elastic layer is preferably 0.2 mm or more in the case of a fixing roll. 0.2mm thick
If it is less than the range, the fusion of the toner tends to be non-uniform, resulting in uneven gloss of the image. Further, if the thickness exceeds 2 mm, the thermal conductivity becomes low, and it takes time for the fixing device to start up and it is easily deteriorated. Therefore, the thickness is preferably 2 mm or less.

In the case of a fixing belt, the thickness of the heat-resistant elastic body layer is preferably 0.07 mm or more, and 0.0
If it is less than 7 mm, there is a problem in that the gloss of the image becomes uneven as in the case of the fixing roll. Further, if the thickness exceeds 1 mm, the thermal conductivity becomes low, so that there is a problem that it takes time to start up the fixing device and it becomes difficult to control the temperature of the fixing belt. Therefore, the thickness is preferably 1 mm or less.

The outermost layer of the fixing roll or the fixing belt can be formed by using PFA, PTFE or the like as the fluororesin. The outermost layer is formed by applying a fluororesin powder or dispersion and then baking it, or by covering the roll with a fluororesin film formed into a tubular shape in advance, and then heating and shrink-adhering it. However, the method for forming the fluororesin layer is not particularly limited as long as it has a uniform thickness and is smooth. The thickness of the fluororesin layer is 2 to 100.
The thickness is preferably in the range of μm, and when it is too thin, the abrasion resistance decreases, and when it is too thick, uneven glossiness occurs in the image.

The outermost layer of the fixing roll or fixing belt in the electrophotographic fixing device of the present invention has a surface roughness Ra of 1 μm.
It must be: When the surface roughness exceeds Ra 1 μm, the releasability from the toner is deteriorated, and it becomes difficult to evenly fuse the toner to cause uneven gloss in the image, which is not preferable.

The coating device for supplying the built-in release oil in the electrophotographic fixing device of the present invention may be one in which the release oil is directly applied to the outermost layer of the fixing roll or the fixing belt, or a relay member such as a pressure roll. A release oil that can be applied indirectly via a pad, a web, a conventionally known coating device including a coating member such as a coating roll, in which the release oil is impregnated and held, or Those stored are preferably used. The release oil used here must be fluorosilicone oil (FSO) having a surface tension of 20 dyn / cm or less. With the dimethyl silicone oil (MSO) conventionally used in this type of fixing device, no one having a surface tension of 20 dyn / cm or less has been obtained, and no silicone oil satisfying the object of the present invention was found. . Further, with a fluorinated oil (FO) or the like, which can be expected to have a low surface tension, a sufficient offset preventing effect cannot be obtained even if the surface tension matches the above value.

[0014]

1 shows a first embodiment of the electrophotographic fixing device of the present invention, in which R ₁ is a hollow cylindrical mandrel made of aluminum having a diameter of 28.3 mm and a silicone having a thickness of 0.8 mm. A fixing roll (roll A) obtained by coating a rubber (SR) and further covering a PFA tube having a thickness of 50 μm, having an outer diameter of 30 mm and a surface roughness Ra of 0.15 μm.

For R ₂ , a core metal made of aluminum having a diameter of 29 mm was coated with a silicone rubber to a thickness of 0.95 mm, and a fluororesin-containing fluororubber was further applied so as to have a thickness of 25 μm. Apply it to 25 μm,
It is a pressure roll having an outer diameter of 31 mm obtained by firing. And
The pressure roll R ₂ is pressed against the fixing roll R ₁ by a spring and adjusted so that the nip width is 3.5 mm.

R ₃ is a release oil coating roll having a diameter of 12 mm
Washi paper is wrapped around the iron cored bar of No. 1, coated with aramid fiber felt, and impregnated with fluorosilicone oil with surface tension of 18.5 dyn / cm (Asahi Glass, FLS507, hereinafter referred to as oil A), and A4 copy paper is applied. In contrast, the coating weight is 2 mg
It has been adjusted so that The release oil coating roll R ₃ is spring-pressed to the fixing roll R ₁ . H ₁ is a heating source provided inside the fixing roll R ₁ , and S ₁ is a temperature sensor for measuring the temperature of the surface of the fixing roll R ₁ . G ₁ is a guide for supporting the copy sheet P carrying the unfixed toner image T.

In the second embodiment of the electrophotographic fixing device of the present invention, instead of the fixing roll (roll A) in the first embodiment, the thickness of the silicone rubber layer is 0.3 mm, and the fluorine resin is contained on the silicone rubber layer. A fluororubber latex (manufactured by Daikin Industries, GLS-213) was applied to form a layer having a thickness of 25 μm, the lower layer being a fluororubber and the outermost layer being an FEP layer, and having a surface roughness Ra of 0.80 μm. The fixing roll (roll B) having the same structure as that of the fixing roll (roll A) and having an outer diameter of 30 mm is used. The pressure roll R _2, a release oil application roll R _3, other members such as is constructed in exactly the same manner as in the first embodiment.

Using the roll type electrophotographic fixing devices of the first and second embodiments, the surface temperature of the fixing roll is 160
Fixing test of unfixed color image created using Fuji Xerox color copying machine (A color 930) under conditions of ℃ and image passing speed of 60 mm / sec (Experiment No. a and b)
I went. As a result, as shown in Table 1, no offset phenomenon occurred, and the fixed image did not have uneven gloss.

For comparison, instead of the fixing roll of the first embodiment, the surface was sandblasted after being prepared in the same manner as the roll A of the first embodiment, and the surface roughness was 30 mm. Having a thickness of Ra 1.5 μm, a PFA having a thickness of 20 μm directly on the aluminum hollow cylindrical core metal without providing a silicone rubber layer.
With resin layer, outer diameter is 30mm and surface roughness is Ra0.2.
0 μm fuser roll (Roll D), and similarly a thickness of 0.
A fixing roll (Roll E) in which a fluororesin-containing fluororubber latex was applied to a thickness of 25 μm on a 15 mm silicone rubber layer as in the roll B of the second embodiment.
To prepare a fixing device (each of which is referred to as a first comparative example, a second comparative example, and a third comparative example). Then, a fixing test (experimental numbers c, d, and e) of an unfixed color image was conducted using these devices under the same conditions as above, and as shown in Table 1 together, all were unsatisfactory. The results were obtained.

Further, instead of the release oil coating roll R ₃ in the fixing device of the first embodiment, the surface tension is 20.3 dyn / cm.
Fluorosilicone oil (oil B) having a surface tension of 21.
A release oil coating roll having the same structure except that dimethyl silicone oil (Oil C) of 0 dyn / cm and fluorinated oil (Oil D) having a surface tension of 18.0 dyn / cm are respectively impregnated as release oils. Were incorporated into the fixing devices of the fourth comparative example, the fifth comparative example, and the sixth comparative example. Furthermore, a fixing device of the seventh comparative example from which the release oil coating roll was removed was added, and a fixing test (experimental numbers f, g, h, and i) of an unfixed color image was conducted under the same conditions as above. As also shown in Table 1, unsatisfactory results were obtained.

[0021]

[Table 1]

Next, FIG. 2 shows a third embodiment of the electrophotographic fixing device of the present invention. Here, R ₄ is an iron core having a diameter of 12 mm and a silicone sponge having a thickness of 4 mm, and has an outer diameter of 2
A fixing roll having a diameter of 0 mm and R ₆ is a heating roll obtained by subjecting an aluminum hollow cylindrical core metal having a diameter of 20 mm to an alumite treatment. A fixing belt B having a peripheral length of 157 mm is stretched between the fixing roll R ₄ and the heating roll R ₆ .
R ₅ is a pressure roll having an outer diameter of 20 mm, which is obtained by coating an iron cored bar having a diameter of 14 mm with a silicone rubber having a thickness of 3 mm,
By pressing the fixing roll R ₄ from below via the fixing belt B, a 4 mm nip portion is formed between the fixing belt B and the pressure roll R ₅ .

The fixing belt B is formed by coating a nickel rubber belt base having a thickness of 40 μm with a silicone rubber having a thickness of 0.15 mm, and further coating a fluororesin-containing fluororubber latex so as to have a thickness of 25 μm. Is an endless belt (belt A) having a surface roughness Ra of 0.75 μm, wherein the intermediate layer is a fluororubber and the outermost layer is an FEP layer.

R ₇ is a release oil coating roll impregnated with fluorosilicone oil (oil A) having a surface tension of 18.5 dyn / cm, similar to that used in the first embodiment. In addition, H
₂ is a heating source provided inside the heating roll R ₆ , and S
₂ is a temperature sensor for measuring the temperature of the surface of the heating roll R ₆ . G ₂ is a guide for supporting the copy sheet P carrying the unfixed toner image T.

The fourth embodiment of the electrophotographic fixing device of the present invention has the same structure except that the thickness of the silicone rubber layer is 0.08 mm instead of the fixing belt (belt A) in the third embodiment. And a fixing belt (belt B) having a surface roughness Ra of 0.70 μm is mounted. The release oil coating roll R ₇ and other members are constructed in exactly the same manner as in the third embodiment.

Using the belt type electrophotographic fixing devices of the third and fourth embodiments, the surface temperature of the heating roll R ₆ is 1
Under the conditions of 60 ° C. and an image passing speed of 60 mm / sec, a fixing test (experimental numbers j and k) was performed on an unfixed color image prepared by using a color copying machine (A color 930) manufactured by Fuji Xerox. As a result, as shown in Table 2, no offset phenomenon occurred, and the fixed image did not have uneven gloss.

Also, for comparison, instead of the fixing belt in the third embodiment, a fixing belt (belt C) having the same structure as the belt A in the third embodiment but having a surface roughness Ra of 1.4 μm. , A PFA resin layer having a thickness of 20 μm was directly provided on a nickel electroconductive belt substrate having a thickness of 40 μm without providing a silicone rubber layer, and the surface roughness was Ra0.
35 μm fixing belt (belt D) and thickness 40 μm
A fixing belt (belt E having a surface roughness Ra of 0.72 μm) having the same structure as that of the belt B of the third embodiment except that a 0.05 mm thick silicone rubber layer is provided on the nickel-electro-alloy belt base body. ) Each, and each
The fixing devices of the comparative example, the ninth comparative example, and the tenth comparative example were prepared. Then, using these devices, under the same conditions as above, a fixing test of unfixed color images (experimental numbers 1, m,
And n), as shown in Table 2 together,
All were unsatisfactory results.

Further, in place of the release oil coating roll R ₇ in the apparatus of the third embodiment, fluorosilicone oil (oil B) having a surface tension of 20.3 dyn / cm, surface tension of 21.0 dy.
A release oil coating roll having exactly the same structure except that n / cm dimethyl silicone oil (oil C) and fluorinated oil (oil D) having a surface tension of 18.0 dyn / cm are impregnated as release oils. Are incorporated into the fixing devices of the 11th comparative example, the 12th comparative example, and the 13th comparative example, respectively. Further, a fixing device of the 14th comparative example from which the release oil coating roll was removed was added, and a fixing test (experimental numbers o, p, q, and r) of the unfixed color image was conducted under the same conditions as above. As shown in Table 2 together, unsatisfactory results were obtained.

[0029]

[Table 2]

[0030]

The electrophotographic fixing device of the present invention is a fixing device suitable for fixing a full-color electrophotographic image, and the outermost layer of the fixing roll or the fixing belt which comes into contact with the unfixed toner image has a surface roughness. Is a fluororesin layer with Ra of 1 μm or less, and has a coating device that incorporates fluorosilicone oil with a surface tension of 20 dyn / cm or less as a release oil. It is a full color image with good image quality without offset or uneven gloss. You can get images, and it's highly reliable,
It has the effect of maintaining quality over a long period of time.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an example of a roll-type fixing device of an electrophotographic fixing device of the present invention.

FIG. 2 is a conceptual diagram of an example of a belt-type fixing device of the electrophotographic fixing device of the present invention.

[Explanation of symbols] R ₁ fixing roll R ₂ pressure roll R ₃ release oil applying roll H ₁ heating source S ₁ temperature sensor G ₁ guide T unfixed toner image P copy sheet B fixing belt R ₄ fixing roll R ₅ addition Pressure roll R ₆ Heating roll R ₇ Release oil coating roll H ₂ heating source S ₂ temperature sensor G ₂ guide

Claims (5)

[Claims] 1. A fixing roll provided with a heat resistant elastic layer on a roll base and an outermost layer of a fluororesin in contact with a toner on a recording medium, and a built-in release oil directly or indirectly on the surface of the fixing roll. At least with a coating device to supply,
An electrophotographic fixing device for full-color image fixing, wherein the outermost layer has a surface roughness Ra of 1 μm or less, and the built-in release oil is a fluorosilicone oil having a surface tension of 20 dyn / cm or less. 2. The electrophotographic fixing device according to claim 1, wherein the heat-resistant elastic layer has a thickness of 0.2 mm or more. 3. A fixing belt provided with a heat resistant elastic body layer on an endless belt substrate and an outermost layer of fluororesin which comes into contact with toner on a recording medium, and a release layer incorporated directly or indirectly on the surface of the fixing belt. At least a coating device for supplying oil is provided, and the surface roughness of the outermost layer is Ra 1 μm or less,
The electrophotographic fixing device for fixing a full-color image, wherein the built-in release oil is a fluorosilicone oil having a surface tension of 20 dyn / cm or less. 4. The electrophotographic fixing device according to claim 3, wherein the heat-resistant elastic body layer has a thickness of 0.07 mm or more. 5. A heat-resistant elastic body layer is provided on a roll base and an outermost layer of a fluororesin which is in contact with toner on a recording medium, or a heat-resistant elastic body layer is provided on an endless belt base. The outermost surface of the outermost layer is provided with at least a fixing belt provided with an outermost layer of a fluororesin in contact with the above toner, and a coating device for directly or indirectly supplying a releasing oil to the fixing roll or the surface of the fixing belt. When fixing an electrophotographic image by using a fixing device having a roughness Ra of 1 μm or less, a fluorosilicone oil having a surface tension of 20 dyn / cm or less is used as the releasing oil, thereby fixing a full-color electrophotographic image. .