JPH04195079A - Fixing device - Google Patents

Abstract

PURPOSE:To arbitrarily select and fix an image on a transfer body to be glossy or non-glossy by providing a non-gloss mode cooling a heating belt after heating it to a fixed temperature and a gloss mode cooling after heating to a still higher temperature. CONSTITUTION:When the non-gloss mode is selected by a selection means, control temperature of a heater H is changed over to the low temperature side by a control part, and periphery temperature of the heating belt 454 is set to be the fixing temperature TL which is higher than glass transition point Tg but lower than melting temperature TH. Next, toner forming the image on the transfer paper is fixed as the non-glossy image being cooled after having the fixing temperature TL reached by the heat of heating belt 454. On the other hand, when the gloss mode is selected, the periphery temperature of the heating belt 454 is set to TH. Then when the fixing temperature TH is reached by the toner being heated by the heating belt 454, the toner is cooled to below the glass transition point Tg while being pressurized by a pressing belt 458 from the high temperature state, and the toner is fixed as a glossy image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device that can selectively fix a toner image on a transfer member to be glossy or non-glossy.

[Background of the invention]

Conventionally, image forming apparatuses such as electrophotographic copying machines have been equipped with means to monitor the toner concentration of the developer and automatically replenish toner, or to measure the average density of the document and change development conditions according to the results. Devices are known which are designed to obtain copies that are as faithful to the original as possible or that are easy to read. However, an apparatus capable of reproducing even the glossiness of an original image has not yet been realized.

[Problem to be solved by the invention]

On the other hand, when looking at images recorded on transparent array sheets used in Overherad projectors, etc., by giving the image surface a gloss, diffuse reflection of transmitted light is prevented and a clear projected image can be obtained. There is a demand for transferred images with high gloss.

Also, regarding images transferred onto recording paper, if the original is a photograph or the like, a glossy copy is preferable, as this also improves the quality of the image.

In order to meet such demands, the present invention aims to provide a fixing device that can arbitrarily select and fix an image on a transfer member to be glossy or non-glossy.

[Failure to solve the problem]

The above object is to provide a fixing device that performs fixing by bringing a toner image-bearing image into contact with a heating belt, a non-glossy mode in which the heating setting temperature of the heating belt is variable, and the heating belt is heated to the fixing temperature and then cooled; This is achieved by a fixing device that is capable of selectively controlling a gloss mode in which the image is heated to a high temperature and then cooled.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 to 4.

FIG. 1 shows the detailed structure of a fixing device 45 showing an embodiment of the present invention. In the figure, 451 is a heating roller with a built-in heater H, which is driven and rotated clockwise in a fixed position by the power of the main body of the device. .

A driven roller 452 is located on the downstream side in the conveying direction of the transfer paper P, and is rotatably supported by a rotation support shaft 453 that engages with the elongated hole 45A.

454 is a heating belt that is passed around the heating roller 451 and the driven roller 452, and a compression spring 455 is held between the rotation support shaft 453 of the driven roller 452 and the protrusion 45B.
It is conveyed in the direction of the arrow under appropriate tension by the urging force. The toner on the transfer material is transferred to a heating roller 451 and a heating belt 4.
54, after being sufficiently fixed, it is cooled during the conveyance process (cooled down to the glass region shown in FIG. 4 shown later) and then stably separated without offset.

On the other hand, 456 is a pressure roller rotated counterclockwise through a gear (not shown) by the heating roller 451, 457 is a driven roller installed corresponding to the driven roller 452, and 458 is the pressure roller The heating belt 4 is connected to the roller 456 and the driven roller 457 by a pressure-bonding belt.
54 and is conveyed in the direction of the arrow.

The temperature of the heating belt 454 at the pressure contact section is directly or indirectly measured by the sensor S, and the measured value is input to the control section. The control unit stores in advance the fixing temperature values in two stages, high and low, as voltage values, and the voltage values corresponding to the fixing temperature values of high temperature for glossy fixing and low temperature for non-glossy fixing are called out. The value measured by the sensor S is compared, and the heater H is controlled to turn on and off, thereby maintaining the fixing temperature at a high or low temperature.

The fixing device R45 described above exhibits its effects when used, for example, in a color image forming apparatus shown in FIG.

The color image forming apparatus includes an image reading system A that reads and scans a document image, and an apparatus main body that houses a laser writing system B and an image forming section C.

In the image reading system A, a document placed on the document placement section 11 is divided into a first mirror unit 12 having an exposure lamp 14 and a mirror 15, and mirrors 16 and 17.
Upon receiving the exposure scan of the second mirror unit 13 comprising
The image is formed on the color CCD 23 via the main lens 20.

The image data of each color obtained by the color CCD 23 is subjected to image processing as an image signal under the control of a control section, and is sequentially outputted to the laser writing system B as an image signal for each color.

In the laser writing system B, the polygon mirror 32 is rotated by the driving of the drive motor 31, and a laser beam corresponding to a yellow image is first projected onto the photosensitive drum 30, which has been charged by the charger 35, and is electrostatically charged. A latent image is formed. This electrostatic latent image is developed in a non-contact manner by a developing device 36Y containing yellow developer into a yellow visible image.

The photosensitive drum 30 on which this yellow visible image has been formed is removed by the cleaning device 39 where the blade 39A is retracted.
Further, charging by a charger 35 and laser beam writing corresponding to a magenta image are performed, and a visible magenta image is superimposed by a developing device 36M containing magenta developer.

Similarly, writing is performed sequentially with a laser beam, and the cyan and black visible images are superimposed by the developing devices 36G and 36BK, respectively, to form a multicolor toner image on the photoreceptor drum 30.

In parallel with this, the transfer paper PA or PB is carried out from the paper feed cassette 40A or 40B, and the photosensitive drum 30
The paper is fed via a timing roller 42 in synchronization with the toner image above.

The toner image on the photosensitive drum 30 is transferred to the fed transfer paper FA or PB by the action of the transfer device 37.
After being separated from the photosensitive drum 30 by the separator 38, it is conveyed via the conveyor belt 44 to the fixing device 45 of the present invention.

Prior to the start of copying by the color image forming apparatus, a process for making the transferred image glossy or non-glossy is selected by one of the selection means Sl, S2, and S3 shown in the control circuit of FIG. .

In the case of using the selection means S1, selection buttons for glossy mode and non-glossy mode are provided on the operation panel (not shown) of the device,
When the user presses one of the selection buttons, the corresponding fixing control is performed.

When the selection means S2 is used, preliminary scanning is performed by the image reading system A to determine whether the image is a glossy image or a non-glossy image. That is, the incident angle of the exposure lamp 14 with respect to the document attached to the first mirror unit is changed periodically during preliminary scanning, and images are discriminated from the output fluctuations. Repeatedly moving between
This shows a state in which an image is discriminated as a glossy original or a non-glossy original based on the difference in reflectance of the original.

Furthermore, when using the selection means S3, the paper feeding power center 40A is loaded with plain paper, while the paper feeding cassette 40B is loaded with
The transparent range sheet for HP is stored, and the operation panel is equipped with selection buttons for plain paper and transparent range sheets, and when feeding plain paper using the selection buttons, you can select between non-glossy mode/glossy mode and transparent range. When feeding sheets, each gloss mode is controlled to be automatically selected.

When the non-glossy mode is selected by any of these selection means, in the fixing device 45, the control temperature of the heater H by the control section is switched to the low temperature side, and the peripheral surface temperature of the heating belt 454 is changed to the glass temperature. The fixing temperature TL is set and controlled to be higher than the transposition temperature Tg and lower than the melting temperature TH.

As a result, the toner forming the image on the transfer paper reaches the fixing temperature TL due to heating by the heating belt 454, and I
: Later, it is cooled and fixed as a non-glossy image.

The heating belt 454 is made of, for example, an endless thin plate of stainless steel or phosphor bronze with a thickness of about 50 μm, and a Teflon or silicone rubber layer with a thickness of about 0.1 to 1 mm adhered to the outer peripheral surface thereof. On the other hand, in contrast to the heating belt 454, the pressure belt 458 is used in combination with an elastic belt molded from silicone rubber or Teflon.

On the other hand, when the gloss mode is selected by any of the selection means described above, the control temperature of the heater H by the control section in the fixing device 45 is switched to the high temperature side, and the peripheral surface temperature of the heating belt 454 is changed to the previous temperature. The fixing temperature TH is set to be higher than the fixing temperature TL, for example by +20 to 50°C. This temperature TH heats the toner above the hot portion of the rubbery region, or more preferably above the melting temperature TH, into the flow zone.

As a result, the toner forming the image on the transfer paper reaches the fixing temperature TH due to heating by the heating belt 454.
Tg while receiving pressure from the crimping belt 458 from a high temperature state.
The image is then cooled until it is fixed as a sufficiently smooth and glossy image.

As a toner for use in such an image which is fixed by freely switching between glossy and non-glossy, toners having a wide viscoelastic range as described below are preferably used.

These toners are mainly made of high molecular weight polymers.
It has a dynamic elastic modulus corresponding to the temperature as shown in Figure 4. At low temperatures, the toner is in a solid state in which the molecular arrangement, also called a glass region, is arranged in an amorphous manner, and as the toner temperature increases, the glass transition point Tg When passing through, the molecules become free to move and become a viscoelastic region with reduced viscoelasticity.

In addition, for high molecular weight polymers with a weight average molecular weight of approximately 100,000 or more, the molecular arrangement that has become able to move freely takes a spiral shape, and has a rubber-like region with stable viscoelasticity. As the temperature rises further, it becomes a liquid melting region with fluidity.

It is possible to obtain a glossy image by heating the toner above the melting temperature TH to the flow range, then cooling and separating it, but if the toner is not sufficiently cooled before separation, an offset phenomenon tends to occur.

When such a toner is fixed using a heating belt or roller, the temperature conditions for fixing without causing an offset phenomenon are required to be within the temperature range of the rubber-like region.

In addition, in order to obtain a glossy toner image, after being fixed in the high temperature region of the viscoelastic region or the fluid region, the toner must be pressed by the smooth surface of a belt or roller during the cooling process after passing through the glass transition point Tg. It is necessary for the glass transition point Tg to be passed through the above-mentioned glass transition point Tg in this state.

In the present invention, the heating temperature conditions when performing heat fixing under a constant pressure are made variable. At high temperatures, the toner softens and the surface becomes smooth due to pressure, and in this state, it is cooled to obtain gloss. On the other hand, at low temperatures, the toner softens insufficiently, and even under the same pressing conditions, the surface will not be smooth and will become non-glossy, resulting in a glossy or non-glossy copy image. became.

Further, in this embodiment, the heating temperature condition is configured to be switched in two stages, but it is also possible to add an intermediate heating temperature condition to achieve multistage switching.

[Effects of the Invention] According to the present invention, a fixing device capable of fixing a transferred toner image by arbitrarily switching to a glossy image or a non-glossy image is realized, and as a result, diffused reflection of the image and decrease in saturation are prevented. Thus, a fixing device for a color image forming apparatus has been provided which can obtain high image quality and a low-grade transfer image that is close to the original image.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram of a fixing device of the present invention, FIG. 2 is a cross-sectional configuration diagram of a color image forming apparatus equipped with the fixing device, FIG. 3 is a control circuit diagram thereof, and FIG. 4 is a toner used in the device. FIG. 5 is an explanatory diagram showing the case of glossiness detection by preliminary scanning. 30... Photosensitive drum 35... Charger 36Y, 3
6M, 36C, 36BK...Developer 37...Transfer device 4OA, 40B...Paper cassette 44...
・Transport belt 45...Fixing device 46...Discharge roller 451...Heating roller 452, 457...Followed roller 454...Heating belt 456...Pressure roller 458...Pressure belt H・··heater

Claims (1)

[Scope of Claims] A fixing device that performs fixing by bringing a recording material having a toner image into contact with a heating belt, the heating belt having a non-glossy mode in which the heating setting temperature of the heating belt is variable and the heating belt is heated to the fixing temperature and then cooled. , and a gloss mode in which the fixing device is heated to a high temperature and then cooled down.