JPH0679186B2 - Fixing device - Google Patents

Description

The present invention relates to an image forming apparatus such as an electrophotographic or electrostatic recording apparatus for heating and fixing an unfixed toner image formed on an image support such as a transfer paper. And a fixing device suitable for obtaining full-color and multi-color images.

[Conventional technology]

Conventionally, there is USP 3578797 as a fixing device installed in this type of image forming apparatus.

This fixing device uses a pressure roller that is rotationally driven while being pressed against a heating body, and turns the image support body onto the heating body via a fixing medium such as a fixing film that moves at the same speed as the transfer material conveyance speed. It comprises a step of heating and melting the unfixed toner image on the image support by bringing them into close contact, and a cooling separation step of cooling the melted toner image to a soft point or lower and then performing curvature separation of the fixing film and the transfer material. Has been done.

[Problems to be Solved by the Invention]

However, in this type of fixing device, the surface roughness of the fixing film is set to a certain value, so that not only black and white copy images but also offset tones and gravure tones, which are often found in full-color originals, are adjusted accordingly. It was not possible to obtain with a single fixing device, and it was always possible to obtain a fixed copy image with the same tone.

Particularly in full-color copy images, the surface roughness shape has a great influence on the glossiness, density, and color reproducibility of the surface. Control was important, but these controls were not.

Therefore, in obtaining a multicolor image, it is not possible to arbitrarily obtain two or more different fixed copy images such as an offset tone and a gravure tone with one apparatus.

An object of the present invention is to provide a fixing device capable of obtaining not only a black-and-white copy image but also a full-color original document faithfully and optionally an image quality.

[Means for Solving the Problems]

A fixing device for achieving the object of the present invention comprises a heating unit for heating at least a heat-meltable toner image carried on an image carrier to a softening point temperature or higher through a fixing medium, and heating by the heating unit. While pressing the image carrier that has undergone the steps to the fixing medium, press-contact means for press-contacting and conveying the toner image until the temperature of the toner image becomes equal to or lower than the softening point temperature. The fixing medium is characterized in that it has two or more types of surface roughness of the contact surface with the toner image.

[Work]

In the fixing device achieved as described above, by selecting the surface roughness of the fixing medium, the toner image is heated and melted with the selected surface roughness, and then the toner image is brought into close contact until it is cooled and solidified. A fixed image having an image surface with a roughness corresponding to the roughness is formed.

〔Example〕

Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

Embodiment 1 FIG. 1 is a schematic diagram showing Embodiment 1 of a fixing device according to the present invention. This fixing device is equipped with respective developing devices accommodating toners of yellow, magenta, cyan, and black, and a full-color image. Equipped with an electrophotographic copying machine capable of producing a full-color image.

In this embodiment, a heating roller 1 having a built-in heating source 3 such as an electric heater and a pressure roller 2 having a built-in heating source 4 such as an electric heater are pressed against each other and rotated at the same speed in the directions of arrows a and b, respectively. In addition, the fixing film 5 with an end is attached to the pressure contact portion of both rollers.
Through the upper separation roller 10 in the direction of the arrow e, and from the delivery roller 8 to the take-up roller 9,
The transfer material 6 carrying the unfixed toner image 7 on the surface is indicated by an arrow g.
While moving on the transfer material guide member 13 in the direction, the unfixed toner image 7 is passed through the pressure contact portion of both rollers so as to be in close contact with the fixing film 5.

Further, an endless backup conveyor belt 12 that rotates in the direction of arrow f is stretched between the lower separation roller 11 that is in pressure contact with the upper separation roller 10 and the pressure roller 2 to form a pair of separation rollers.
A pressure region for sandwiching and conveying the transfer material 6 is formed between the fixing film 5 and the conveyor belt 12 between the heating rollers 10, 1 and the heating and pressure rollers 1, 2, and the conveyor belt 12 is required in the pressure area. Accordingly, the pressure plate (not shown) is pressed toward the fixing film.

For the heating roller 1 and the pressure roller 2, for example, a 3 mm thick RTV silicone rubber layer is provided on the surface of a hollow aluminum tube, the width of the pressure contact portion is set to 5 mm, and the fixing temperature is set to 170 ° C.

The fixing film 5 is made of polyimide as a base material, and the surface of the fixing film 5 is subjected to a release treatment if necessary. For example, the thickness is 10 μm and the width is
The surface roughness on the contact surface with the unfixed toner image is 300 mm, and the surface roughness is formed in three areas that are different in the moving direction. The width of each area in the moving direction can cover the maximum size of the transfer paper used. Is set to length,
For example, as shown in FIG. 2, the widths of the three areas A, B, and C are set to 3
50 mm, the surface roughness (Ra) of the A area is 0.10 μm, the surface roughness (Ra) of the B area is 0.20 μm, the surface roughness (Ra) of the C area
Is set to 0.35 μm and the moving speed is set to 100 mm / sec. The transfer material 6 has a width of 296 mm, a length of 210 mm, and a separation roller 1
0 and 11 are hollow tubes having an outer diameter of 10 mm, and the conveyor belt 12 is made of, for example, polyimide having a thickness of 100 μm.

When the surface roughness selection button (not shown) is pressed, the fixing film 5 sent from the sending roller 8 to the take-up roller 9 is transferred to the desired area A to C and the transfer material 6 by a controller (not shown) including a microcomputer. At the same time, and are brought into the pressure contact portion between the heating roller 1 and the pressure roller 2, and the pressure area is moved as it is. As a control method, for example, a transfer material guide member
The fact that the transfer material 6 has entered 13 is detected by a transfer material detection means such as a microswitch or an optical sensor, and the time until the transfer material enters the pressure contact portions of the rollers 1 and 2 is counted, and the fixing film The feed roller 8 and the take-up roller 9 are operated so that the tip of the predetermined surface roughness region of 5 coincides with the tip of the transfer material and the fixing film 5 and the transport belt 12 move at substantially the same speed. Let

In the color image forming apparatus equipped with the fixing device of the present embodiment configured as described above, when the surface roughness area is set and the copy button is pressed, an unfixed color toner image is carried on the transfer material and fixed. It is transported toward the device. At this time, the fixing film 5 of the fixing device drives the fixing film drive system by the control device, and the selected region among the three types of surface roughness regions is the pressure contact portion of the heating roller 1 and the pressure roller 2. Waiting for a transfer material detection signal from the transfer material detecting means, and driving so that the tip of the transfer material and the tip of the selected surface roughness region coincide with each other. The toner image is heated and melted through the fixing film 5 as shown in step 1 of FIG. In the conventional fixing device, since the toner image heated and melted at this time is separated from the heating roller, the unevenness of the surface becomes large as shown in step 2 of FIG. 3, but in the present embodiment, the fixing film 5 is used. Conveyor belt 1 to separating rollers 10 and 11 with the toner image fused by
It is nipped and conveyed via 2, and is cooled sufficiently during that time to reach the softening point temperature or lower. The separation roller 10 separates the toner image on the transfer material from the fixing film 5, and the transfer material 6 is discharged to the left side in FIG. 1 to obtain a fixed image having a smooth surface in step 3 of FIG. . In this case, as the fixing film 5, the area A of FIG. 2 having the surface roughness (Ra) of 0.10 μm was selected, and when the area B having the surface roughness (Ra) of 0.20 μm was selected, The fixed image shown in step 3'of FIG. 3 is obtained.

On the other hand, the hand-worn film 5 taken up by the take-up roller 9
During the non-fixing after the fixing step, is moved in the direction opposite to the arrow e direction and is rewound by the sending roller 8 to be used for the next fixing.

As described above, the surface of the toner image after fixing can have a surface shape that follows the surface roughness of the fixing film.

The quality of the image thus obtained was good, and especially in the case of a multicolor image, the color mixture was also good and a high-quality image was obtained. When fixing with the surface roughness Ra = 0.10 μm of the fixing film 5, GLoss (60 °) = 70% gives a high gloss gravure image, and when using the fixing film Ra = 0.35 μm, GLoss (60 °) = 15%, resulting in a low gloss image. The image density and color reproducibility also improved with the increase in gloss, and a gravure-like high-quality image could be obtained.

Further, by using the flexible polymer film as the fixing film 5, the durability of the fixing medium is improved as compared with the case where the conventional elastic rubber is used as the fixing medium.

Further, the general fixability was also improved, and the fix offset and the variation in the fixability at the leading end and the trailing end of the transfer material in the transporting direction in a multicolor image having a large toner layer thickness were improved. This is because the image surface configuration is forcibly determined by cooling in the pressure area, and even if the temperature during melting slightly varies, the surface shape is stabilized in the next cooling step. is there.

Embodiment 2 FIG. 4 shows that the fixing belt 14 is made endless and stretched over the roller 9 ′, the conveying roller 15, the separating roller 10 and the heating roller 1, and the other constitution is the same as that of the above-mentioned Embodiment 1. The surface of the fixing belt 14 has areas of surface roughness A, B,
C is set, and it rotates in the direction of arrow h.

In each of the above-described embodiments, the heater is also provided in the pressure roller 2, but heating from the toner image side, that is, the fixing roller 1 is performed.
It is not always necessary if the heating from is sufficient.

Further, the fixing films 5 and 14 have not only a single-layer structure as shown in FIG. 2, but also a heat-resistant polymer sheet 16 provided with a polymer material 17 having good peelability as shown in FIG. 5, for example. It may have a multilayer structure.

Further, although a film-shaped fixing medium is shown, the invention is not limited to the film structure.

Further, in this embodiment, the case where the surface roughness of the fixing film is three types is shown, but the present invention is not limited to this, and the numerical values of the dimensions and the roughness can be set arbitrarily.

Further, although the fixing unit has the heat roller structure, other structures may be used.

〔The invention's effect〕

As described above, according to the present invention, the surface of the heat-melted toner image is brought into close contact with the fixing medium until it is cooled and solidified, and the surface of the fixing medium has two or more types of roughness. Therefore, by selecting the surface roughness of the fixing medium, multiple image qualities due to the difference in gloss of the fixed toner image can be set with one fixing device. Especially in the case of full-color images, a high-quality image faithful to the original document can be obtained. I was able to get it.

[Brief description of drawings]

1 is a schematic view of Embodiment 1, FIGS. 2 and 5 are sectional views of a fixing film, FIG. 3 is a schematic view showing a fixing state of a toner image, and FIG. 4 is a schematic view of Embodiment 2. is there. 1 ... Heating roller, 2 ... Pressure roller, 3 ... Heater, 4 ... Heater, 5 ... Fixing film, 6 ... Transfer material, 7 ... Toner, 8 ... Take-up roller, 9 ... Feed roller, 10 ...... Separation roller 11 …… Separation lower roller, 12 …… Transfer material transport belt 13 …… Guide member, 14 …… Endless belt 15 …… Transmission roller 16 …… Heat-resistant polymer material 17 …… Releasable polymer material

Claims (1)

[Claims] 1. A heating means for heating at least a heat-meltable toner image carried on an image bearing body to above a softening point temperature via a fixing medium, and the image bearing body which has undergone a heating step by the heating means. A pressure contact means that presses and conveys the toner image while keeping it in close contact with the fixing medium until the toner image becomes a softening point temperature or lower
Separation means for separating the direction of the sheet surface member in the direction away from the toner image surface at the conveying end portion of the pressure contact means, and the fixing medium has two or more types of surface roughness of the contact surface with the toner image. A fixing device characterized by the above.