JPH11174886A - Fixing roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent offset or entangling around a heating roller and to obtain a toner image of high quality at low temp. fixing by coating the surface of a core metal of the roller with a polymer thin film essentially comprising tetrafluoroethylene vinylidene fluoride and polypropylene as a release layer and controlling the peeling strength between the release layer and a toner to a specified range. SOLUTION: The surface of a core metal roller 101 is coated with a release layer 102 of a polymer thin film comprising at least tetrafluoroethylene, vinylidene fluoride and polypropylene. The peeling strength of the release layer 102 for a toner is controlled to between >=0.1 mN/cm<2> and <=5 mN/c<2> . The polymer thin film covering the core metal roller 101 essentially consists of (a) tetrafluoroethylene, (b) vinylidene fluoride and (c) polypropylene, and proportions of these components (a), (b), (c) are preferably 20 to 70% (a), 20 to 50% (b) and 10 to 30% (c).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing roller,
More specifically, a fixing roller for transferring and fixing a toner image obtained by developing an electrostatic latent image formed by an electrophotographic method, an electrostatic recording method, an electrostatic printing method, etc. with a toner onto a transfer material such as paper. It is about.

[0002]

2. Description of the Related Art In general, an electrophotographic method, an electrostatic recording method and the like use a toner supply roller such as a developing sleeve to transfer an electrostatic latent image formed on a latent image carrier made of a photoconductive photoreceptor or a dielectric. Develop a finely-powdered toner image which has been thinned by a blade or the like and appropriately charged, and then, if necessary, or mixed with a carrier and appropriately charged and finely-powdered toner image. After a toner image is transferred to a transfer material such as paper, the toner image is fixed by heating pressure, solvent vapor, or the like to obtain a copy. There are various toner fixing methods applied to these electrophotographic methods and the like, but a heat roller fixing method is widely used because of its high thermal efficiency and high-speed fixing.

When high-speed fixing is performed by such a heat roller fixing method, the toner is required to have good low-temperature fixability (or a low fixing lower limit temperature). Also,
For this reason, if a low softening resin is contained as a binder resin,
At the time of fixing, a part of the toner image adheres to the surface of the heat roller, which is transferred onto the copy paper to cause background contamination, and a so-called winding phenomenon in which the copy paper adheres to the surface of the heat roller and winds (particularly, a heat phenomenon). (Often when the roller temperature is low).

Therefore, as means for preventing the occurrence of these undesirable phenomena, Japanese Patent Laid-Open Publication No.
No. 57-148752, No. 58-97056,
JP-A-60-247250 proposes adding a solid silicone varnish, a higher fatty acid, a higher alcohol, various waxes, and the like as a release agent to the surface layer of the heat roller. Nothing is known that exhibits sufficient resistance to offset and wrap while maintaining.

Specifically, polyolefin waxes such as low molecular weight polyethylene and low molecular weight polypropylene have good offset resistance, but do not have sufficient low-temperature fixability. Vegetable waxes such as carnauba wax and candelilla wax have good offset resistance and low-temperature fixability, but do not have sufficient winding resistance. Solid silicone varnishes, solid silicone oils, amide waxes, higher fatty acids, higher alcohols and montan waxes have good low-temperature fixability, but do not have sufficient offset resistance and winding resistance. Moreover, conventional release materials are
During development, there are many so-called filming and spent in which the release agent is released from the toner and adheres to the photoreceptor and the carrier, and it has been difficult to form a high-quality image stably over a long period of time.

In recent years, energy saving of OA equipment has been avoided, and it has been urgently required to improve a fixing process which accounts for most of power consumption in copying machines and printers. To cope with this, energy saving in the fixing process has been studied by using the above-mentioned technology and a resin having a low softening temperature (such as polyester). However, low-temperature fixing of toner for energy saving is still insufficient. Further, since the fixing roller is used for a long period of time, stability over time of the fixing roller is desired. In a conventional fixing roller, a release layer has been formed on the roller surface by forming a coating film by powder coating or covering a shrinkable tube on a cored bar. However, the fixing roller obtained by these methods has a lot of fine irregularities and polishing scratches on its surface, and toner and paper powder adhere to and remain in those portions due to repeated copying, and the fixing quality over time. Has deteriorated, and in addition, problems such as an offset phenomenon have also been observed. Further, film shaving and adhesion of residual toner due to minute unevenness and unevenness of the material on the surface of the release layer have been a serious problem with respect to durability.

Japanese Patent Application Laid-Open No. Hei 6-167900 discloses PFA as a release material used for the surface of a fixing roller.
It is unknown whether sufficient release properties can be secured on the surface of the fixing roller. In Japanese Patent Application Laid-Open No. 6-167901, a fluororesin tube in which a conductive substance is dispersed is used as a release material. However, there is a possibility that the conductive substance may appear on the outermost surface of the release layer, and there is a problem in durability. Remains. When these fixing rollers are used, the release layer usually has a thickness of 20 to 50 μm, so that the heat efficiency is poor, the initial rise time of a copying machine or the like is long, and the surface temperature of the heat roller is 200 μm. At present, it is necessary to set the temperature around ° C., so that an increase in power consumption cannot be avoided at present.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-quality toner image which can be fixed at a low temperature without causing an offset phenomenon or a winding phenomenon around a heat roller at the time of fixing, and is stable over time. Is provided.

[0009]

According to the present invention, first, the surface of a cored metal roller is coated with a polymer thin film containing tetrafluoroethylene, vinylidene fluoride and polypropylene as main components. A fixing roller having a peel strength from toner of 0.1 to 5 mN / cm ² is provided. Secondly, the first fixing roller is provided, wherein the polymer thin film contains carbon black. Third, the second fixing roller is provided, wherein the carbon black has a primary particle diameter of 50 to 500 °. Fourth, the first, second or third fixing roller is provided, wherein the polymer thin film contains magnesium. Fifthly, there is provided the fixing roller according to any one of the first to fifth aspects, wherein the polymer thin film contains calcium. Sixth, there is provided any one of the first to fifth fixing rollers, wherein the thickness of the polymer thin film is 5 to 30 μm. Seventh, there is provided any one of the first to sixth fixing rollers, wherein the polymer thin film is formed by a vacuum evaporation method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In order to produce a highly durable fixing roller having good releasability, the present invention coats the surface of a cored roller with a polymer thin film composed of at least tetrafluoroethylene, vinylidene fluoride and polypropylene, and the polymer thin film and toner And a peel strength of 0.1 mN / cm ² or more and 5 mN / cm ² or less. Further, the fixing roller contains (a) carbon black for ensuring electrostatic releasability, preferably the primary particle diameter of carbon black is 50 to 500 °, and (b) the film strength is greatly improved. For this reason, the polymer thin film contains magnesium,
(C) calcium is contained to improve the durability of the release layer, (d) a polymer thin film is formed by vacuum evaporation to increase the surface smoothness, and (e) the thickness of the polymer thin film Is set to 5 to 30 [mu] m, thereby making it possible to produce a fixing roller which can perform low-temperature fixing and has high durability and high reliability.

In the present invention, the polymer thin film covering the surface of the cored roller is (a) tetrafluoroethylene,
(B) It is mainly composed of vinylidene fluoride and (c) polypropylene.
The content ratio of (c) is 20-70% in (a) and 2% in (b).
0 to 50% and (c) 10 to 30% are suitable. For the polymer thin film, in addition to these, a polymer material such as (d) chlorotrifluoroethylene, trifluoride ethylene, difluoride ethylene, ethylene, etc. can be used. The amount is kept in the range of 5% or less.

The peel strength between the polymer thin film and the toner is 0.1
The measurement method for adjusting the pressure to ５5 mN / cm ² was performed by the apparatus shown in FIG. FIG. 2 shows an apparatus for measuring the peel strength between the toner and the fixing roller. When the temperature is measured using a thermocouple and the toner reaches the fixing temperature and the fixing strength becomes sufficient, the temperature between the toner and the fixing roller is increased. Peel strength is operated independently of the measurement sample, measured using a force gauge having a gantry that can operate in the vertical direction, the gantry to move in the vertical direction, also moves manually,
An evaluation device that moves at a maximum of 200 mm / sec and outputs a measurement result to paper or the like using a device having an arithmetic function. The configuration of the device includes a peel strength measuring unit, a measurement result calculating unit and an output unit, a movable unit of the peel strength measuring unit,
It consists of a sample support base and a sample temperature measurement unit. Next, each will be described in detail.

[Peeling strength measuring part] The peeling strength measuring part is composed of a force gauge and a member towing metal fitting. As the force gauge, a spring type or a load cell type can be used. Preferably, a load cell type with high accuracy is used. The load cell type force gauge includes a monitor section on which a measurement result is displayed and an operation section capable of changing a mode. The mode can change the unit of the output value to a unit such as N or g. Measurement accuracy is 0.01mN or more and 500mN
The following forces can be measured and are preferably ± 0.1 mN or more. As the member towing member, various shapes can be used, but a hook type member gives a good result in terms of improving the measurement accuracy.

[Measurement Result Calculation Unit and Output Unit] Data is sent from the peel strength measurement unit to the measurement result calculation unit and the output unit using a cable or infrared rays. The data transfer timing can be sent at a speed of 0.1 second or more. The measurement calculation unit calculates the maximum value, minimum value, average,
Calculate the number of data, standard deviation, and all data. The calculated result is output from the output unit to paper or a monitor unit.
When outputting to paper, a dot printer, a thermal printer, an electrophotographic printer, or the like can be used. When outputting to the monitor section, the monitor section includes an LED, L
CD, ELD, CRT can be used. The LED is a light emission diode, the LCD is a liquid crystal display, the ELD is an electroluminescence display, and the CRT is a cathode ray tube monitor. Considering costs and the like, it is preferable to use a dot printer for the output unit.

[Movable Part of Peeling Strength Measuring Unit] The peeling strength measuring unit must be movable to peel off the adhered member from the sample. Therefore, the peel strength measuring unit is fixed on a movable stage. The moving stage can move up and down in the vertical direction or left and right in the horizontal direction. The moving speed is 0 to 100 mm / sec. Moving at a speed of 100 mm / sec or more is not preferable because a problem occurs in measurement accuracy. A belt-type motor drive, a worm gear type, or a rack and pinion type can be used as the moving method, but a worm gear type is preferable in terms of position accuracy and cost.

[Sample support portion] The sample support portion is made of a hot plate so that the temperature can be varied. In addition, a constant temperature layer may be provided in order to heat at ambient temperature. This makes it possible to measure the peel strength at any temperature.

[Sample Temperature Measuring Section] The sample temperature is measured by a thermocouple. Since the thermocouple has a shape that can be applied to various samples, a thin wire is preferable.

In the present invention, the "peeling strength" refers to a value in which the toner temperature is set to the same temperature as that at the time of fixing by applying an appropriate pressure while the toner is sandwiched between the release material applied on the substrate and the paper. It refers to a value measured when the force acting between the toner and the release material is measured in a state where the temperature is raised to a certain extent. This value is 0.1mN
/ Cm ² , there is a problem of measurement sensitivity, and conversely, 5 m
If it is larger than N / cm ² , the releasability of the toner is deteriorated, and a highly durable fixing roller cannot be obtained.

The fixing roller has a phenomenon in which the toner is peeled and discharged when the toner is fixed, and the toner image forming the image may be disturbed due to the discharge. Therefore, in the present invention, the problem can be suppressed by including carbon black or graphite. The carbon black preferably has a primary particle diameter of 50 to 500 ° because it is preferable that the carbon black is uniformly dispersed in the polymer thin film. If it is less than 50 °, the volume resistance of the fixing roller becomes too low, and
If it is more than 00 °, uniform dispersion becomes impossible, and the intended volume resistance control of the fixing roller is impossible.

When forming a polymer thin film, if magnesium and / or calcium are contained, a stronger thin film can be formed. Therefore, magnesium and calcium are preferable as release materials for a fixing roller. It is. Magnesium and calcium contained in the polymer thin film may be used alone, but may be added in the form of compounds such as magnesium oxide, magnesium hydroxide, calcium hydroxide, and calcium carbonate. The content of each of magnesium and calcium in the polymer thin film is 1 to 10%, preferably 2 to
6%, and when both are contained simultaneously, the total content is suitably 2 to 14%.

There are several methods for forming a polymer thin film. In the present invention, a polymer thin film having excellent surface smoothness can be obtained by forming a thin film by a vacuum evaporation method. The thickness of this polymer thin film is 5 μm or more and 30
μm or less is appropriate, and within this range, it is effective to reduce the initial rise and the power consumption during fixing.

[0022]

EXAMPLES Next, examples of the present invention will be described specifically.
The present invention is not limited to these.

Example 1 Each gas of tetrafluoroethylene, propylene and vinylidene fluoride was introduced into a vacuum chamber, and was chemically vapor-deposited on an aluminum hollow roller (40 mmφ, t = 2 mm). At the same time, graphite, magnesium oxide and calcium hydroxide were deposited on a hollow aluminum roller. The obtained chemical vapor deposition film was obtained by mixing magnesium oxide, calcium hydroxide and graphite in a polymer thin film having a composition of tetrafluoroethylene: 50 / propylene: 30 / vinylidene fluoride / 20 (each number is the weight of a monomer). A uniformly dispersed product was obtained (FIG. 1). Graphite has an average particle size of 1
And the peel strength between the polymer thin film and the toner was 0.1.
It was 5 mN / cm ² . The resulting polymer film thickness is 11μ.
m.

Example 2 A fixing roller was prepared in the same manner as in Example 1 except that the calcium hydroxide compound was not deposited. Graphite had an average particle size of 150 °, and the peel strength between the polymer thin film and the toner was 1.2 mN / cm ² . The resulting polymer film thickness was 15 μm.

Example 3 A fixing roller was manufactured in the same manner as in Example 1 except that the magnesium oxide compound was not deposited. Graphite had an average particle size of 250 °, and the peel strength between the polymer thin film and the toner was 3.2 mN / cm ² . The resulting polymer film thickness was 5 μm.

Comparative Example 1 A commercially available film having a film thickness of 3 was formed on the aluminum hollow roller of Example 1.
A 0 μm PFA tube was covered. The peel strength between the polymer thin film and the toner was 5.3 mN / cm ² .

Each of the four types of rollers produced in the above manner was mounted on an electrophotographic copying machine (FT6500) manufactured by Ricoh Co., Ltd., and an image was formed using toner obtained by the following method. Table 1 shows the evaluation results. (Preparation of Toner) After melt-kneading 5 parts by weight of carnauba wax and 5 parts by weight of carbon black into 90 parts by weight of a styrene / butyl acryl copolymer having a weight average molecular weight of 100,000, rolling and cooling, jet pulverization, and classification, 1 part by weight of silica is obtained. The mixture was kneaded (externally added) to obtain a toner. The average particle size of the toner was 8.5 μm.

[0028]

[Table 1] (1) Offset property: The density of toner adhering to the fixing roller was evaluated based on the image density. The case of 1 or less was rated as ◎, the case of 0.2 or less was rated as ○, and the value after 10,000 sheets was 0.5 or greater was rated as x. (2) Releasability: A solid image was copied, and no trace after being scratched by the separation claw installed on the fixing roller was indicated by ◎, slightly observed ○, completely seen Is indicated by x. (3) Durability: ◎ when the durability of 200,000 sheets or more was maintained, ○ when the durability of 100,000 sheets or more was maintained, and × for any of the above characteristic values for 10,000 sheets The thing was made into ×. (4) Surface roughness: expressed by ten-point average roughness (Rz).

[0029]

According to the first aspect of the present invention, it is possible to obtain a fixing roller which can perform low-temperature fixing, is highly durable, and has high rotation speed.
According to the second and third aspects of the present invention, it is possible to obtain a fixing roller in which peeling discharge during toner fixing is suppressed. According to the fourth and fifth aspects of the present invention, a fixing roller on which a strong polymer thin film is formed can be obtained. According to the sixth aspect of the present invention, it is possible to obtain a fixing roller having reduced power consumption during initial startup and fixing. According to the invention of claim 7, a fixing roller having a polymer thin film having excellent surface smoothness can be obtained.

[Brief description of the drawings]

FIG. 1A is a side view of a fixing roller, and FIG.
FIG. 2 is a sectional view taken along line BB ′ of FIG.

FIG. 2 is a diagram of a peel strength measuring device model.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measuring part movable support body 2 Peeling strength measuring part 3 Data transfer part 4 Sample towing fitting 5 Sample support base 6 Movable rail 7 Operation part and output part 8 Pedestal 101 Metal core metal roller 102 Release layer 103 Particles such as magnesium oxide

Claims (7)

[Claims] 1. A surface of a cored metal roller is coated with a polymer thin film containing tetrafluoroethylene, vinylidene fluoride and polypropylene as main components, and the peel strength between the polymer thin film and toner is 0.1 to 5 mN / cm ^2. A fixing roller, characterized in that: 2. The fixing roller according to claim 1, wherein said polymer thin film contains carbon black. 3. The fixing roller according to claim 2, wherein said carbon black has a primary particle diameter of 50 to 500 °. 4. The fixing roller according to claim 1, wherein the polymer thin film contains magnesium. 5. The fixing roller according to claim 1, wherein the polymer thin film contains calcium. 6. The fixing roller according to claim 1, wherein the thickness of the polymer thin film is 5 to 30 μm. 7. The fixing roller according to claim 1, wherein the polymer thin film is formed by a vacuum deposition method.