JPS61228481A - Fixing device for electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To prevent staining of a heating roll and offset of a toner at the time of fixing by providing a means for feeding a positively triboelectrifiable agent to the heating roll. CONSTITUTION:The means for feeding the positively triboelectrifiable agent is provided with a rotary feed roll rotating in pressed contact with the heating roll 21, and the outer circumference of the feed roll is provided with a means for attaching said agent. It is preferred to construct the feed roll composed of a flexible material, such as felt or sponge, contg. said agent. The positively triboelectrifiable agent may be of a liquid or solid type, and the powder type is embodied by silica or the like metal oxide particles having particle diameters of 0.1-10mum surface treated with a silane coupling agent having amino groups, such as H2NCH2CH2CH2Si(OCH3)3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device for contact heating and fixing a toner image on the surface of a support supporting the toner image in a copying machine.

2. Description of the Related Art Conventionally, a method is known in which a toner image is formed on a support by electrophotography or the like, and this toner image is fixed on the surface of the support as required. The toner used here is generally a mixture of a thermoplastic resin and a coloring agent such as carbon black, which is an electroscopic fine particle of about 0°1 to 50 μm, and this toner is applied to a support by various developing methods. A toner image is formed on. Further, this toner image is permanently fixed on the support by being melted or dissolved by heat, pressure, solvent vapor, or the like.

Although fixing using the above-mentioned solvent vapor is more efficient than heat fixing, the solvent vapor scatters, causing many odor and hygienic problems.

In addition, fixing using pressure, called pressure fixing, requires less energy and enables quick start and high speed, but the fixing performance is worse than other fixing methods, and pressure-sensitive toner has a complicated manufacturing method. However, it has the disadvantage of being expensive and is not widely put into practical use.

As another method, an oil-less donor is known in which the release property between the toner and the heating roll is not determined by the addition of oil such as silicone, but in which the toner itself contains a release agent.

However, heat fixing is generally widely used for fixing toner images. Conventionally, heat fixing is known in which fixing is performed by applying a constant pressure between a pair of rolls, at least one of which is heated, and passing the unfixed toner image through a support. Compared to a fixing device, it has advantages such as lower power consumption and less risk of fire due to paper jams in the fixing section. The heating roll of this fixing device (hereinafter referred to as the first roll) is one whose surface is coated with a heat-resistant release material such as tetrafluoroethylene (trade name: Deflon), ITV silicone rubber, RTV silicone rubber, etc. One of the pressure rolls (hereinafter referred to as the second roll) is made of a heat-resistant elastic material such as silicone rubber or fluororubber in order to have a certain contact width (hereinafter referred to as the nip) when it comes into pressure contact with the first roll. The one consisting of is used. When the support supporting the toner image passes through the nip of the contact heating fixing device using the first roll and the second roll, the toner is softened by heat transfer from the surface of the first roll, and the toners coalesce. When paper is used as a support, it penetrates into the fibers of the paper and is then solidified by cooling to form a permanently fixed image.

In the fixing device described above, since the heating surface of the first roll comes into direct contact with the toner image, a phenomenon occurs in which sticky substances such as toner adhere to the surface of the first roll (hereinafter referred to as offset). In order to prevent this, an oil supply device is required to continuously apply a mold release agent such as silicone oil, for example, dimethylbolysiloxylene oil having a viscosity of 100 CP.

When the S layer of dimeryl polysiloxane oil is applied to the surface of the first roll, it forms an interface between the roll surface and the toner image supported on the support.

This interfacial low surface energy layer is imparted to the toner as it passes through the nip and prevents the toner from offsetting onto the first roll.

FIG. 5 shows a fixing device equipped with a general oil supply device. Oil 10 is always uniformly supplied to the first mill 1 through a wick 7.

In addition to wicks, rolls are also commonly used. Blade 8 to control the oil supply within a certain range.
Some use .

However, despite the supply of silicone oil, an invisible offset, ie, an offset of particulate toner, occurs. This toner offset gradually contaminates the oil supply system, and eventually it becomes impossible to supply even oil, which causes the offset to increase rapidly, staining the copy, and causing oil stains on the copy. appear.

Conventionally, attempts have been made to overcome this particulate offset by using various cleaning members. As the cleaning member, a cleaning blade 9 and a cleaning roll 11 shown in FIG. 1 are often used.

The cleaning blade 9 and the cleaning roll 11
Although it has become possible to clean offset toner by using It has the disadvantage that it has to be done.

It has been known that the amount of toner offset varies greatly depending on the surface temperature of the first roll. In other words, if the roll surface is insufficiently heated, the toner particles do not fuse together and remain particulate, and the toner only near the roll surface melts and becomes sticky, resulting in a large amount of toner offset. It is said that it will. Furthermore, if the roll surface is heated too much, the cohesive force that holds the group of fused viscous toner becomes smaller than the adhesion force that offsets the toner to the roll surface, causing the toner to break up and cause a large amount of toner offset. It is being said. Although the temperature of many contact heating fixing devices is set within the above-mentioned temperature range, invisible particulate toner offset still occurs.

It is important to minimize the toner offset described above in order to reduce the burden on the cleaning device and the burden on maintenance.

It is known that toner offset varies depending on many parameters such as toner resin, roll material, roll surface temperature, pressure in the nip, oil supply amount, and nip passage time. It is said that this is caused by the adhesion force and the cohesive force of the toner.

An outline of a conventional contact heating fixing device will be explained based on FIG. 1 in the figure is the first roll, which is made of Teflon or HTV silicone rubber or RT to prevent toner offset.
Aj cocoa is coated with a heat-resistant mold release material 2 such as V silicone rubber. A second roll 4 has a metal core 6 coated with a heat-resistant elastic material such as silicone rubber 5, and works together with the first roll 1 to fix a toner image 16, which is a material to be fixed, under heat and pressure. 7 to 10 are oil supply devices and cleaning devices to the first roll, 7 is a wick for oil supply, and oil 10 is always supplied by capillary action.
is supplied to the first roll 1 in a constant amount, and the amount is controlled by the blade 8. A cleaning blade 9 scrapes off the offset toner. The cleaning of the second roll 4 is performed by a cleaning roll 11.
An infrared Kortz lamp 12 is installed inside the roll 1, and a sensor 13 for temperature control and a claw 14 for peeling the support from the first roll are also installed. When the support 15 carrying the toner image 16 passes through the nip area between the first roll 1 and the second roll 4, a negative charge is generated on the surfaces of both rolls 1.4 due to frictional charging, and the support A positive charge is generated in the body 15. Generally, most of the materials coated on the first roll 1 and the second roll 4 are Teflon or silicone, and the polarity of the charge generated when it comes into contact with the support can be determined by examining the charge series of the roll material and the support. It becomes clear.

The surface potential of the first roll reaches minus several hundred volts - minus 1000 volts, minus several thousand volts to minus tens of thousands of volts for the second roll, and plus several hundred volts to plus several thousand volts for the support. It is known that electric potential affects the offset phenomenon.

Therefore, in Japanese Patent Application Laid-open No. 55-55374, by appropriately changing the roll surface and the polarity and charge amount of the toner, the offset toner itself is reduced and maintenance of the offset cleaning device is facilitated and simplified. A fixing method that does not require a feeding device or a cleaning device is described. This is achieved by making the polarity of the first roll surface and the toner the same or non-polar.
This can also be achieved by making the surface of the second roll and the toner polarities different from each other or non-polar. In other words, by applying electrostatic repulsive force between the first roll and the toner, the second roll
Offset toner is reduced by applying electrostatic attraction between the roll and the toner.

Problems to be Solved by the Invention However, with such a conventional fixing device, sufficient releasability could be obtained for negatively charged toner (for example, Japanese Patent Application Laid-Open No. 1983-1999) No. 55374), when a positively charged toner was used, a new problem occurred in that the releasability between the toner and the heating roll was poor, resulting in offset of the toner and staining of the heating roll. This is due to the fact that the heating roll is made of Teflon or silicon, which exhibits strong negative chargeability.

Generally, when negatively charged toner is used, frictional electrification with a heating roll made of Teflon or silicone is reduced by JP-A-55.
This does not become a big problem because of the technique disclosed in No. 55374. However, when trying to solve the problem with simpler means or using positively charged toner, the toner is charged by rg friction with the Teflon coating material for the heating roll, and the heating roll becomes negatively charged with a large charge gap. do. For this reason,
Positively charged toner electrostatically adheres to the heating roll, and even if the toner has excellent rheological release properties, the toner adheres to the heating roll, staining the roll surface and generating offset toner.

The present invention has been made to solve these problems, and it ensures sufficient mold releasability for positively charged toner, prevents staining of the heating roll, and prevents offset toner during fixing. The purpose is to prevent this from occurring.

Means for Solving the Problems In order to solve the problems of the prior art, the fixing device for an electrophotographic copying machine of the present invention includes a heating roll equipped with a heating heater inside, and a heating roll that rotates in pressure contact with the heating roll. It consists of a heating roll and a pressure roll that rotate under pressure to fix the positively charged toner image formed on the paper sandwiched between both rolls, and also to apply a positively charged substance to the heating roll. It is configured by providing means for supplying it.

Preferred embodiments of the present invention include: (1) The positively chargeable substance supplying means is provided with a supply roll that rotates while being pressed into contact with the heating roll, and the positively chargeable substance is attached to the outer peripheral surface of the supply roll. (ii) The positively charged substance supply means is provided with a supply blade for supplying the positively charged substance in the vicinity of the heating roll; (iii) The O- of the heating roll. (iv) A powder material is used as the positively chargeable material, and the means for supplying the powder material to the heating roll includes a storage tray for storing the powder material and a means for supplying the powder material to the heating roll. Examples include means for attaching powdered material stored in a storage tray to a pressure roll. Further, in the embodiment shown in (i) above, it is more preferable that the supply roll is made of a flexible material such as felt or sponge, and that the flexible material contains a positively chargeable substance.

A liquid or powder material is used as the positively charged substance, and examples of the powder material include H2NCH2CH2C)f2Si(OCH3)3H
2NCH2CH2CH2S1 (OC2H5)3H2NC
oNHCH2CH2CH2Si(OC2H5)3H2N
(CH2CH2NH)2CH2CH2CH2s1(OC
H3) Silane coupling agent having an amino group such as 3,
Or, (CH3)2C=NCH2CH2CH2Si(OCH3
)3(CH3)2C=NCH2CH2CH2Si(OC
2H5)3CH3-C= NCH2CH2CH25i(
OCH3)372H5 CH3-C= NCH2CH2CH25i(OC2H5
)3H3 [Yes] CH=NCH2CH2cH2s1 (OC2H5)
3 [phase] CH= NCI(2CH2CH2Si(OCH
3) 3 children NCH2CH2CH251 (OCH3) 3÷N
A silane coupling agent having an imino group such as CH2CH2CH25i(OC2H5)3, or a silane coupling agent having the general formula (wherein R1 is hydrogen, an alkyl group, an aryl group, or an alkoxy group, R2 is an alkylene group, a phenylene group, and R3 is an alkylene group, a phenylene group). silicone oil represented by the general formula (where R1 is hydrogen, an alkyl group, an aryl group, or an alkoxy group, R2 is an alkylene group, a phenylene group,
is a silicone oil having an amine represented by hydrogen alkyl group, aryl group, alkylene group, phenylene M),
Particle size: 0.1 m/, (m ~ 10 μm) Surface treated with metal oxides (e.g. silicon dioxide, aluminum oxide, iron oxide, titanium oxide, copper oxide, nickel oxide), sulfides, nitrides, etc. In this case, the surface treatment consists of metal oxide, sulfide or nitride.
Powder of μTrL ~ 10 μm is placed in a container,
Stir while heating to 200°C, add the above coupling agent,
This can be done by spraying a treatment agent such as silicone oil as it is or diluting it with a solvent. The amount of the processing agent added is approximately 0.1 to 30 wt% based on the powder material.

Examples of liquid positively charged substances include KF859.
(-General formula % formula % R is OH or OCH3; amino modified silicone oil; manufactured by Shin-Etsu Chemical ■), or silicone oil having an amino group represented by the general formula, ■, or general formula % formula % A silicone oil having an imino group shown in is used.

The basic configuration of the fixing device is a real IM as shown in Figure 1.
To explain this in detail, FIG. 1 is a schematic vertical cross-sectional view of an actual embodiment in which both the heating roll and the pressure roll are equipped with heating heaters. The heating roll 21 has a Teflon coating layer 2 with a thickness of 36 μm on the surface of a sleeve 22 made of A material with an outer diameter of 50 JIl+ and an inner thickness of 8 M.
3, and a halogen lamp 24 of, for example, 900 W is housed inside the sleeve 22 as a heater for heating the roll surface. A thermistor 25 as a temperature sensor is lightly in contact with a part of the Teflon coat 1123 on the surface of the roll, and the thermistor 25 detects the heating roll surface temperature and sends a detected temperature signal to a control circuit (not shown).

The pressure roll 26 includes a sleeve (core) 27 made of Fe with an outer diameter of 36 mm and a wall thickness of 5 mm, and a tubular rubber 2 with a wall thickness of 8 mm on the outer periphery of the sleeve (core) 27.
The tubular rubber 28 in this case is made of silicone rubber with approximately 50 wt% of silica (SiO□) added, and its thermal conductivity is approximately 15 x 10-'
The hardness is approximately 60 degrees at cal/3-sec-'C. A 360W halogen lamp 29 is housed inside the core 27 as a heater that heats the entire pressure roller, and a thermistor 30 as a temperature sensor is installed on the surface of the tubular rubber 28 to detect the surface temperature. It is provided in light contact with the surface of the tubular rubber 28.

The heating roll 21 and the pressure roll 26 rotate in the directions shown by arrows A and B in FIG. The paper is removed from the heating roll 21 by the paper peeling claw 31 so that the ejected paper does not get wrapped around the heating roll 21.
I'm trying to peel it off.

In the actual Y/A mode shown in FIG. 1, heaters are provided inside both the heating roll and the pressure roll.
In the present invention, it is sufficient that at least the heating roll is provided with a heating heater, and the heating roller does not need to be provided inside the pressurizing roller. Further, although the surface layer of the heating roll shown in FIG. 1 is made of Teflon and the surface layer of the pressure roll is made of silicone rubber, the materials of the surface layers of both rolls are not limited in the present invention.

Examples of the present invention will be described below, and the results of experiments in which a fixing operation was performed by supplying the positive polarity and highly chargeable powder material or liquid to a heating roll will also be explained in the explanation of each example. I will discuss it later.

Example 1 Positively chargeable powder treated with silicon dioxide fine powder (10 mμ) on the surface (a) was used, and this was made of Teflon with a diameter of 30 μm.
ll: It was attached to a heating roll with a width of 300 m and/or a pressure roll made of silicone rubber with a diameter of 25 m and a width of 300 #ll11. As shown in FIG. 2, the appropriate initial amount of charged powder to be deposited is 0.1 to 100 q per roll (see a in FIGS. 2 and 3). If it is less than 0.1q, there is no effect, and if it is more than 100q, the heat transfer characteristics to the toner change and offset toner occurs. According to experiments, if offset toner does not occur for the first 3,000 to 5,000 copies, there is only a very small amount of toner attached, and until the end of the heating roll's lifespan, U-ru dirt and offset toner will not occur. It has become clear that this does not occur.

The means for adhering the charged powder include: 1) a means of pressing a supply roll to which the powder has been adhered to a fixing roll; 2) a means of containing the above-mentioned powder in a soft material such as felt or sponge; and 3) a means of pressing the powder against a fixing roll. There is a method in which the powder is supplied in contact with the fixing roll using a dish-shaped container containing powder.4) A method using a powder supply blade, but sufficient effects were obtained with either method.

Example 2 Positively chargeable powder (b) in which the surface of silicon dioxide fine powder (10 mμ) was treated with H2NCH2CH2CH251(OCH3)3 was used, and this was made of Teflon with a diameter of 30rn11 and a width of 3
It was attached by the means described in Example 1 to a 00 m heating roll and/or a pressure roll made of silicone rubber and having a diameter of 25 m and a width of 300 m.

As shown in FIG. 2, 0.1q to 1100It is appropriate for the initial material llff1 of the charged powder (see b in FIGS. 2 and 3). There is no effect below 0.1a9,
At 100 #j or more, the heat transfer characteristics to the toner changed and offset toner occurred. According to experiments, if offset toner does not occur for the first 3,000 to 5,000 copies, there is only a very small amount of toner adhering to it, and roll stains and offset will continue until the end of the heating roll's lifespan. It became clear that there was no.

Example 3 Positively chargeable powder treated with H2NCH2CH2CH2-51 (OCH3)3 on the surface of aluminum oxide fine powder (50 mμ) (C) was heated in a Teflon tube of 30 in diameter and 300 in width. Example 1 was applied to a pressure roll made of roll and/or silicone rubber with a diameter of 25 am and a width of 300 m.
It was attached using the method described in . As shown in Figure 2, the initial amount of charged powder deposited is 0.1.9 to 100 II.
! F is appropriate (see C in Figures 2 and 3). 0.1
■There is no effect below 100#l! At F or higher, the heat transfer characteristics to the toner changed and offset toner was generated. According to experiments, if offset toner does not occur for the first 3,000 to 5,000 copies, there is only a very small amount of toner adhering to it, and roll stains and offset will continue until the end of the heating roll's lifespan. It became clear that there was no.

In Examples 1 to 3 above, each powder (a), (b), (
When C) was subjected to TRIBO weight measurement using a blow-off band R amount measuring device, the heating roll was contaminated with a distribution as shown in Figure 4, and all powders had positive charging characteristics, indicating only positive charging characteristics. It is important that it is a powder that has only . In addition, Figure 2 shows the amount of dirt on the heating roll when powder is attached to the heating roll, and Figure 3 shows the number of days the heating roll is soiled when powder is attached to the pressure roll, but these are not shown. Total NO on heating roll and pressure roll
, 1Rg to 110OR, the amount of staining on the heating roll was also sufficiently low.

Example 4 KF859 (amine modified silicone oil whose general formula R is CH or OCH3; Shin-Etsu Chemical Co., Ltd.) was used as a positively charged liquid, and this was heated to a diameter 30 mm made of Teflon.
The film was supplied to a heated roll having a diameter of 300 m and a width of 300 m, or a pressure roll made of silicone and having a diameter of 25 sr and a width of 300 #III. The adhesion amount of chargeable liquid is from 0.1@J to 110O
R was appropriate, and both roll dirt and toner offset were significantly improved. In this case, as a means for attaching the chargeable liquid, 1) a method of direct dropping, 2) a method of infiltrating a soft material such as felt or sponge with the above-mentioned liquid and pressing it against a roll, etc. could be used. As the chargeable liquid, it was also possible to use a silicone oil having an amino group represented by the general formula % or a silicone oil having an imino group represented by -Si-0-.

Example 5 Pressure was applied to supply the charged powder to the heating roll by kneading 1 to 3 Q wt% of the positively chargeable powder (a) used in Example 1 into the silicone rubber constituting the pressure roll.
1-Rule was created. In this case as well, as in Example 1, toner offset and heating roll staining were significantly improved.

Example 6 By impregnating 1 to iowt% of the positively charged liquid KF859 (manufactured by Shin-Etsu Chemical Co., Ltd.) used in Example 4 into the silicone rubber constituting the pressure roll, the charged liquid is supplied to the heating roll. A pressure roll was created. In this case as well, toner offset and heating roll stain were improved as in Example 4.

Example 7 A heating roll of the present invention was prepared by incorporating 1 to 30 wt % of the positively chargeable powder (a) used in Example 1 into the Teflon coating material of the heating roll. In this case as well, toner offset and roll staining were similarly improved.

Effects of the Invention According to the present invention, when fixing a positively charged toner image to be transferred onto a sheet of paper, a charged substance that is easily charged to a positive polarity is supplied to the heating roll, so that the apparatus is simple. Despite this, it is possible to reduce the amount of toner staining on the heating roll, and also to prevent the occurrence of offset toner, thereby achieving even better fixing action.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of an embodiment of the present invention, Figure 2 is a graph showing the relationship between the amount of positively charged powder applied to the heating roll and dirt on the heating roll, and Figure 3. Figure 4 is a graph showing the relationship between the adhesion layer of positively charged powder supplied to the pressure roll and dirt on the heating roll. FIG. 5 is a schematic sectional view showing a conventional example. 21: Heating roll 22 Sleeve 23: Teflon coat layer 24: Halogen lamp (heater) 26: Pressure roll 27; Sleeve 28: Tubular rubber

Claims (7)

[Claims] (1) Consists of a heating roll equipped with a heating heater inside, and a pressure roll that rotates in pressure contact with the heating roll, and forms on the paper sandwiched between the heating roll and the pressure roll while rotating in pressure contact with the heating roll. A fixing device for an electrophotographic copying machine for fixing a positively charged toner image, characterized in that the fixing device for an electrophotographic copying machine is provided with means for supplying a strongly positively charged substance to a heating roll. . (2) The positively chargeable substance supply means is characterized in that a supply roll that rotates while being pressed into contact with the heating roll is attached, and means for attaching the positively chargeable substance to the outer peripheral surface of the supply roll is provided. A fixing device for an electrophotographic copying machine according to claim 1. (3) The electrophotographic copying according to claim 2, wherein the supply roll is made of a flexible material such as felt or sponge, and the flexible material contains a positively chargeable substance. Fixing device of the machine. (4) The electrophotographic copying machine according to claim 1, wherein the positively chargeable substance supplying means includes a supply blade for supplying the positively chargeable substance near the heating roll. Fusing device. (5) The fixing device for an electrophotographic copying machine according to claim 1, wherein the heating roll contains a positively chargeable substance in its surface layer. (6) The fixing device for an electrophotographic copying machine according to any one of claims 1 to 5, wherein the positively chargeable substance is made of a liquid or a powder material. (7) A powder material is used as the positively charged substance, and the means for supplying the powder material to the heating roll includes a storage tray for storing the powder material, and a pressure roll for attaching the powder material stored in the storage tray. 2. A fixing device for an electrophotographic copying machine according to claim 1, further comprising means for: