JPH11305475A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which sufficient lubricant performance is obtained, where a supply mechanism is simplified and which can be made small in size by using the composite material of low molecular weight polytetrafluoroethylene (low molecular weight PTFE) with other material as lubricant supplied to the surface of an image carrier. SOLUTION: This device is provided with the lubricant supply mechanism 12 for supplying the lubricant 22 to the surface of a photoreceptor 2 and the lubricant 22 is the composite material of the low molecular weight PTFE with at least one or more kinds of other material. In such a case, it is desirable to use fluororesin as other material, and it is desirable to use the fluororesin being the PTFE having different molecular weight from the low molecular weight PTFE used in this device. Thus, the friction reducing characteristic of the low molecular weight PTFE is obtained as a molded body. The lowering of photoreceptive characteristic or transfer characteristic caused by the shaving of the photoreceptor 2 is restrained. The supply mechanism can directly come in contact with the photoreceptor 2 owing to the frictional characteristic of the low molecular weight PTFE, so that the device can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and the like.
The present invention relates to an image forming apparatus having a function of supplying a lubricant to a surface of an image carrier.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, and a facsimile, a charging roller and an exposure unit are arranged around a photoreceptor, and charging, exposure, development, and transfer are performed as the photoreceptor rotates. Each image forming process such as cleaning, static elimination and the like is executed. Some of the image forming units or members arranged around the photoreceptor are in direct contact with the photoreceptor, and when the photosensitive layer of the photoreceptor is scraped by a certain amount due to contact friction, the photosensitive characteristics change, The predetermined image forming process cannot be performed. That is, the wear of the photosensitive layer leads to a reduction in the life of the photosensitive member.

[0003] Among the members that come into contact with the surface of the photoreceptor, the cleaning blade is the most problematic, and wear due to contact with other members substantially affects the reduction in the life of the photoreceptor. Absent. The reason the cleaning blade is problematic is that it contacts mechanically, i.e., scrapes off, to remove residual toner on the photoreceptor. The wear caused by the cleaning blade is mainly divided into the following two forms. Abrasion caused by shearing force generated between the photoconductor and the cleaning blade Toner acts like a grindstone when the toner is sandwiched between the cleaning blade and the photoconductor, and the abrasion caused by the abrasive action causes such abrasion. Factors to be determined include the mechanical strength of the photoreceptor, the contact pressure of the cleaning blade against the photoreceptor, the composition of the toner particles, and the surface friction coefficient of the photoreceptor.

In order to suppress the abrasion of the photosensitive member surface due to the contact of the cleaning blade, for example, Japanese Patent Laid-Open No.
As disclosed in JP-A-324603 and JP-A-6-324604, a lubricant is conventionally supplied to the surface of a photoreceptor. By supplying the lubricant to the surface of the photoconductor, the frictional force between the cleaning blade and the photoconductor is reduced, and the shaving of the photoconductive layer is suppressed. As the lubricant, a solid lubricant such as zinc stearate is used.

[0005]

As described above, a solid lubricant such as zinc stearate is conventionally used, but its lubricating performance is not sufficiently satisfactory, and the lubricating material is not easily used. Therefore, the supply mechanism cannot be simplified by directly contacting the surface of an image carrier such as a photoreceptor, and the apparatus cannot be reduced in size.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of obtaining sufficient lubricating performance and capable of reducing the size of the apparatus.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention focuses on the friction characteristics of PTFE, further improves its general characteristics to enhance lubricity, and at the same time, improves moldability and mechanical properties. We decided to secure the strength. More specifically, according to the first aspect of the present invention, in the image forming apparatus having a function of supplying a lubricant to the surface of the image bearing member, the lubricant is a low molecular weight polytetrafluoroethylene (hereinafter, referred to as “low molecular weight PTFE”). ") And a composite material with at least one or more other materials.

[0008] According to a second aspect of the present invention, in the configuration of the first aspect, the other material is a fluororesin,
The configuration is adopted.

[0009] In a third aspect of the present invention, in the constitution of the second aspect, the fluorine-based resin is a low-molecular-weight PT.
FE is a polytetrafluoroethylene (hereinafter referred to as “PTFE”) having a different molecular weight.

According to a fourth aspect of the present invention, in the second aspect, the fluorine-based resin is a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (hereinafter, referred to as "PFA"). I am taking it.

According to a fifth aspect of the present invention, in the constitution of the second aspect, the fluorine-based resin is a tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter, referred to as a tetrafluoroethylene-hexafluoropropylene copolymer).
It is called "FEP". ).

According to the invention of claim 6, in claim 4 or 5,
In the described configuration, the ratio of the low-molecular-weight PTFE to the whole is about 30% or less.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a main part of an image forming apparatus according to the present embodiment. As shown in FIG. 1, a charging roller 4, an exposure unit 6, a developing unit 8, a transfer unit 10, a lubricant supply mechanism 1 are provided around a photoreceptor 2 as an image carrier.
2, a cleaning blade 14, a static eliminator 16, and the like are arranged.
Each image forming process such as exposure, development, transfer, cleaning, and static elimination is performed. The exposure by the exposure unit 6 forms an electrostatic latent image of the target image on the photoconductor 2, and the electrostatic latent image is visualized into a toner image by the developing unit 8. Thereafter, the transfer unit 10 transfers the toner image to the sheet P fed at a predetermined timing by the pair of registration rollers 18. The sheet P to which the toner image has been transferred is sent to a fixing device (not shown), where the toner image is fixed as a permanent image on the sheet P by heat and pressure. The toner remaining on the photoreceptor 2 is scraped off by the cleaning blade 14, and the residual charge is removed by the charge remover 16.

The lubricant supply mechanism 12 includes a case 20 fixed to the main body of the apparatus, a lubricant 22 movably housed in the case 20, and a lubricant 22 in contact with the lubricant 22.
And a supply brush 26 for removing the lubricant 22 attached to the supply roller 24 and supplying the lubricant 22 to the surface of the photoconductor 2. The lubricant 22 is formed in a rectangular parallelepiped shape, and the supply roller 24 and the supply brush 26 have a shape extending in the axial direction of the photoconductor 2. The lubricating material 22 is used almost completely.
The supply roller 24 is urged by a spring 28. The lubricating material 22 is a consumable and its thickness decreases with time. However, since the lubricating material 22 is pressed by the spring 28, the lubricating material 22 always contacts the supply roller 24.

The supply of the lubricant 22 is not limited to the configuration shown in FIG. 1, but may be a configuration in which the supply roller 24 is omitted as shown in FIG. Further, the image carrier which is the member to be supplied with the lubricant is not limited to the photoconductor 2 but may be an intermediate transfer belt. This example is shown in FIG. FIG. 3 shows a full-color image forming apparatus. Four developing units 32, 34, 36, and 38 of different colors are provided around the photoreceptor 30, and the toner images of each color are superimposed and transferred onto an intermediate transfer belt 40 as an image carrier. The transfer belt 44 collectively transfers the sheet P to the sheet P fed at a predetermined timing by the pair of registration rollers 42. Although not shown, a cleaning blade for cleaning the toner remaining on the intermediate transfer belt 40 is provided, and a similar problem due to abrasion also occurs in such a configuration. To cope with this, a lubricant supply mechanism is provided.

Here, the level of the coefficient of static friction of the image bearing member (photoreceptor 2) aimed at by the present invention will be described with reference to data measured by an Euler belt method. in this case,
A medium-thick high-quality paper is stretched around the drum 1/4 of the photoreceptor 2 in such a manner that the paper gap is in the longitudinal direction, a load of, for example, 100 gr is applied to one of the belts, and a force gauge is installed to the other. Then, the force gauge is pulled, and the load at the time when the belt is moved is read and calculated by the following equation. μs = 2 / π × 1n (F / w) where μs: coefficient of static friction, F: measured value, w: load The coefficient of static friction of the surface of the photoreceptor 2 is based on the Euler belt method from the viewpoint of its wear. It was found that the effect was obtained at 0.4 or less. Therefore, in the present invention, the goal is to reduce the static friction coefficient of the photoreceptor 2 to 0.4 or less, and an example of the realization is the configuration of the lubricant supply mechanism 2. However, when the wear amount is controlled to a certain level in addition to always maintaining the value of 0.4 or less, the purpose may be such that the value may temporarily exceed 0.4 for an arbitrary time. Further, it can be controlled to 0.3 to 0.1 as a region having a higher effect on abrasion. In this case, it has been experimentally confirmed that the wear amount is further reduced. It has been experimentally confirmed that an image defect occurs when the static friction coefficient is 0.08 or less due to the influence of ionized adhered substances and the like, and it is desirable that the static friction coefficient does not decrease to 0.08 or less. . However, these values vary depending on environmental conditions and the like, so that 0.08 or less is not always defective. Therefore, the lower limit value of the coefficient of static friction may be arbitrarily set according to the environmental conditions and the like.

The lubricant 22 used in each of the above structures is a composite material containing low molecular weight PTFE. Where P
The features of TFE and low molecular weight PTFE will be described. Speaking of general PTFE molding / processing and materials, PT
FE has a very high melt viscosity, and it is difficult to use a molding method such as injection and extrusion used for general thermoplastic plastic materials. For this reason, as a method of molding PTFE, a powder resin is preliminarily molded (mainly at room temperature), and the particles are subjected to a sinter molding process (firing process) in which the powder resin is heated to 350 ° C. to 400 ° C., which is higher than the melting point. A method of solid molding is generally used. Examples of the processing method include a compression molding method, a ram extrusion molding method, and a paste extrusion molding method. PTFE materials used for such molding are roughly classified into two types: molding powders and fine powders. Generally, molding powder is used for compression molding and ram extrusion, and fine powder is used for paste extrusion.

The molding powder is obtained by pulverizing the raw powder obtained by the suspension polymerization to a size of several tens to several hundreds of μm, and then granulating, pulverizing, and preheating according to the usage. It is a general term for powders generated after such processing. Fine powder is obtained by coagulating and drying a latex obtained by emulsion polymerization to adjust the particle size to about 300 to 600 μm.

Low-molecular-weight PTFE is generally used in molding powders and fine powders of 500 or less.
While it has a number average molecular weight of ６００6,000,000 or more, it generally refers to PTFE having a molecular weight of several thousand to several hundred thousand. Such low molecular weight PTFE is used by being added to a resin material other than PTFE, oil, ink, paint and the like. However, the low-molecular-weight PTFE in this example (the present invention) means, in addition to the general theory of the low-molecular-weight PTFE, the molecular weight is controlled and manufactured by a polymerization method, a radiolysis method, a thermal decomposition method, and the like, and is generally used as a molding material. Molecular weight material (approximately 500
As described above, it refers to a material whose average molecular weight is kept low.

Next, a specific example of a method for producing low-molecular-weight PTFE will be described. First, the production of low molecular weight PTFE by the thermal decomposition method will be described. PTFE is a substance that is very stable among resins in terms of heat. At normal molding temperatures there is hardly any weight loss. The molding temperature is generally about 400 ° C. or less. However, above its general molding temperature, its weight gradually decreases. This is due to the thermal decomposition of PTFE.
It has been experimentally confirmed that this decomposition proceeds more rapidly at around 500 ° C. Therefore, by setting the thermal conditions, the molecular weight of PTFE can be reduced.

Next, low molecular weight PTF by radiolysis
The generation of E will be described. PTFE is a radiation-decomposable polymer, and has a particularly high sensitivity to γ-rays, electron beams, and the like as compared with other polymers. In the irradiated PTFE, the decomposition proceeds, and the molecular weight is reduced.

Next, a method for measuring the molecular weight used for defining the molecular weight will be described. However, these are merely examples, and there is no problem in measurement by another method. Since generally known PTFE is hardly dissolved in almost all solvents and has a very high melt viscosity, it is very difficult to determine the molecular weight by a general measuring method. However, as an alternative, the molecular weight can be known from the values obtained by the following direct / indirect measurement methods. First, what is most frequently used as a measure of practical molecular weight is the specific gravity of a molded product produced under a constant molding and heat treatment condition. In this case, the lower the specific gravity, the higher the molecular weight. This can be understood that, in the cooling process after the melting of the molded product, the higher the molecular weight of the PTFE, the lower the mobility, the less the crystallization, the more difficult it is to crystallize, and the more easily the amorphous portion is formed, the lower the specific gravity. . Further, as a means for knowing the molecular weight of a PTFE sample without preparing a molded article, there is a method of measuring the heat of crystallization of a PTFE sample using a differential scanning calorimeter and knowing the molecular weight therefrom.

Next, the friction characteristics of PTFE and the characteristics of PTFE as a lubricant will be described. As shown in FIGS. 4 and 5 (cross section), the molecular structure of PTFE is a completely symmetric linear polymer having a chemical structure in which CF ₂ units simply repeat. In addition, it is a nonpolar polymer having extremely high molecular symmetry, and has very weak intermolecular cohesion. Further, the molecular chain surface is very smooth. It is generally described that the friction coefficient of PTFE is low due to the small intermolecular cohesion and the small unevenness of the molecular chain surface. Here, a case is considered where the mating member to be contacted is a different material.
PTFE is a very soft substance, and has a small cohesive force between molecules and easily slips between molecules.
Worn PTFE is supplied to the mating member of friction.
The "FE transfer" phenomenon occurs easily. Due to this phenomenon, a PTFE layer is formed on the surface of the mating member, and the friction generated there is replaced by the friction between the PTFE, thereby lowering the friction coefficient. This is known as one factor of low frictional resistance between many materials and PTFE in the sliding state. The above-mentioned property of PTFE against friction is one of the reasons for using PTFE as a lubricant in the present invention.

As described above, the wear of the photosensitive member 2 is mainly caused by the friction between the photosensitive member 2 and the cleaning blade 14. Therefore, the lubricant 22 is supplied to the surface of the photoreceptor 2. To simplify the lubricant supply mechanism 12, it is desirable that the lubricant 22 be brought into direct contact with the photoreceptor 2. In this case, there is a problem as to whether or not the lubricant easily transfers to the photoconductor 2. PTFE is suitable as a lubricant for a rotating / driving member such as the photosensitive member 2 because PTFE is easily transferred to a sliding member due to its characteristics. In FIG. 1, the lubricant supply mechanism 12 is an indirect type via a supply roller 24 and a supply brush 26, but the lubricant 22 containing PTFE is used.
In the case of (1), a configuration in which the photosensitive member 2 is brought into direct contact with the photosensitive member 2 may be adopted for the above reason. Further, after the transfer of the PTFE, that is, after the friction between the PTFE becomes dominant, the wear of the PTFE decreases. This is PTFE
This is because the coefficient of friction between the two members is extremely small, so that the shear force generated there is reduced and wear is reduced. For this reason, PTF
When the lubricating material 22 containing E or PTFE is brought into direct contact with the photoreceptor 2 to obtain the lubricating effect, the supply amount of the PTFE is automatically limited after the transfer of the PTFE. Therefore, useless supply is suppressed.

Further, collapse between molecules of PTFE can occur even after the PTFE is transferred to a counterpart member. Due to this property, the PTFE adhered on the photoreceptor 2 is repeatedly adhered and removed (moved) at a certain ratio. The removal is performed by, for example, the cleaning blade 14, the developing unit 8, the transfer paper, and the like. Normally, foreign substances, for example, ionized substances (NOx, SOx, etc.) that cause image blur are attached to the surface of the photoconductor 2. When the lubricant is not supplied, these foreign substances have been removed at the same time as the surface layer of the photoreceptor is abraded in a cleaning section or the like. If the surface of the photoreceptor is reduced by supplying the lubricant, these foreign substances cannot be removed, and an image defect may occur. However, in the case of a lubricant that is repeatedly attached and removed, such as PTFE, these foreign substances are also repeatedly attached and removed, whereby image defects on the surface of the photoconductor 2 can be reduced.

Next, the wear characteristics (mechanical characteristics) of PTFE
The characteristics and effects of low molecular weight PTFE will also be described. The abrasion characteristics of PTFE are greatly affected by the molecular weight of PTFE. The mechanical strength such as general wear of a polymer is affected by its intermolecular cohesion. This is PTF
This also applies to E. If the intermolecular cohesive force is small, slip between molecules is likely to occur, and wear is likely to occur. In addition, the mechanical strength other than wear is also reduced when the intermolecular cohesion is small. As described above, the intermolecular cohesion of PTFE is extremely small. Therefore, PTFE has the property of being easily worn. For this reason, in order to maintain the wear performance and the mechanical performance, means for increasing the molecular weight in PTFE of the molded body is taken. This is because the PTFE molecular chains having a large molecular weight are entangled with each other in the molded article, thereby having an effect of maintaining the mechanical strength.

[0027] In molding PTFE, those which have been put into practical use in order to obtain the strength of molded articles include those having a molecular weight of 50%.
Often from 0 to 10 million are used. Low molecular weight PTFE, etc. is difficult to mold itself due to its molecular weight. In general, PTFE molded products intended for use as mechanical parts are developed to improve the wear characteristics. The use of low molecular weight PTFE as a molding material is rare. Theoretically, the higher the molecular weight, the better the mechanical properties. However, when the molecular weight is higher than the moldable molecular weight, the influence of the difference in molecular weight on the strength becomes smaller,
Rather, the effects of crystallinity and voids, which depend on molding conditions, are greater. That is, once a certain amount of molecular weight is obtained, optimizing the molding conditions can improve the mechanical strength rather than increasing the molecular weight. Generally, the molecular weight at which the mechanical strength is stable is 500.
It is said to be over 6 million. However, since the value may be influenced by conditions such as a filler, the value is a general theory.

In addition to increasing the molecular weight and optimizing the molding conditions, there is also a method for improving the mechanical strength by adding a filler. As the type of the filler, glass fiber, graphite, carbon fiber, and the like are known. For example, particulate fillers such as carbon black, silica, calcium carbonate, clay, titanium oxide, magnesium carbonate, glass beads, and talc, or fibrous fillers such as glass fiber, carbon fiber, aramid fiber, wollastonite, and calcium sulfate Agents, plate-like fillers such as mica, graphite, kaolin, glass flake, and ferrite. Other than these, as a white filler, alumina, kaolin clay, finely divided silica, calcium silicate, magnesium oxide, titanium oxide, magnesium hydroxide, aluminum hydroxide, quartz powder, calcium carbonate, magnesium carbonate, feldspar powder, baryte, white Sing, pyroxene clay, gypsum (anhydrous) and the like, and a single or two or more kinds may be used.

On the other hand, low-molecular-weight PTFE may be added to a bearing member or the like. However, the conventional use of low-molecular-weight PTFE is used only to improve the PTFE-containing substance and lubricity of an object. It is not used for the purpose of reducing the friction between the object and the contact member other than the PTFE-containing substance, and the lubricant 22 between the photoreceptor 2 and the cleaning blade 14 is used as in this embodiment.
Will not be used as.

In the above, general molding of PTFE has been described, including the characteristics of low molecular weight PTFE. Regarding friction, regardless of its molecular weight, PTFE
It can be understood as a whole feature. However,
Regarding abrasion, it can be said that low molecular weight PTFE is a material inferior in performance to a polymer material. However, from the viewpoint of lubricant supply, low-molecular-weight PTFE has low molecular entanglement and low mechanical strength, that is, slippage between molecules is easy to occur. Is likely to peel off and the PT
It can be said that FE supply is an excellent material that can be provided by low shearing force.

This characteristic is that when the lubricant supply mechanism 12 is of a direct contact type, the lubricant can be supplied to the photoconductor 2 even when the lubricant 22 is brought into contact with the photoconductor 2 with a small contact pressure. Is shown. Considering that the supply amount is controlled by changing the contact pressure, it can be said that the condition can be set in a wider range. Thus, by using the low molecular weight PTFE, the lubricant supply mechanism 12
And the lubricating properties of PTFE itself can be obtained. Further, in the case of the direct contact method, suppressing the contact pressure of the lubricant 22 to the photoconductor 2 has an effect of suppressing generation of heat at the contact portion, and can reduce deterioration of the photoconductor 2 due to heat. it can. Further, the stress on the residual toner on the photoconductor 2 at the contact portion of the lubricant 22 can be reduced. In this case, when the contact pressure is high, problems such as toner sticking to the photoconductor 2 occur,
This may cause image defects, and the use of low-molecular-weight PTFE can solve this problem.

Next, processing of a composite material of low molecular weight PTFE and another material will be described. Since low-molecular-weight PTFE itself has low intermolecular cohesion, it is difficult to mold it alone. In order to solve this, the present invention is characterized in that it is molded as a composite material with at least one or more other types of substances (materials). Even as a composite material, PTFE itself is a very stable substance, and since it has a higher melting point than other resins, it is easy to process it so that its physical properties are not lost during composite processing. . In the case of the direct contact method, if the low molecular weight PTFE contained in the composite material is configured to contact the photosensitive member 2 at the contact surface of the lubricant 22 with the photosensitive member 2,
It has been confirmed that the transfer of the PTFE to the photoreceptor 2 occurs and exerts a lubricating effect. In other words, the presence of PTFE on the contact surface with the photoconductor 2 can be said to be a condition for forming and processing the composite material.

Next, a method for producing a composite material will be described. However, these are only given as examples and are not limited to these methods. First,
There is a method of forming by a resin molding method. These are PT
A compression molding method, a ram extrusion molding method, a paste extrusion molding method, or the like, which is a molding method specific to the FE resin, may be used. Also,
You may use injection molding which is a usual resin molding method. These may be properly used depending on the type and ratio of the composite material. In addition to the resin molding method, a substance serving as a binder (for example, a resin material) and a low-molecular-weight PTFE
Is dispersed and applied to an arbitrary member to evaporate the solution. In addition, PT
There is also a method of hardening the FE resin. There is also a method of impregnating and applying a low-molecular-weight PTFE to a porous substance or another substance having an arbitrary form by a disversion process or the like. As the mating material of the composite, there are synthetic resins (for example, engineering plastics such as polycarbonate and polyacetal, fluororesins, adhesive materials, rubber materials) or other rubber materials, adhesive materials, pigments, etc. Can be arbitrarily selected according to the function.

As described above, if the composite material with low molecular weight PTFE is used as a lubricant, the characteristics of PTFE and the characteristics of low molecular weight PTFE described above can be obtained. Also, by solidifying as a molded product, it is easy to install it in the apparatus, and it is possible to improve workability such as replacement and assembly.

[Specific Example 1] The lubricating material 22 is made of low molecular weight PT.
A composite material of FE and a fluororesin was used. Generally, a fluororesin is a synthetic polymer containing a fluorine atom in a molecule, and is usually polytetrafluoroethylene (tetrafluoroethylene resin: PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether. Copolymer (tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin: PFA), tetrafluoroethylene-hexafluoropropylene copolymer (tetrafluoroethylene / 6-fluoropropylene copolymer resin: FE)
P), tetrafluoroethylene-ethylene copolymer (ethylene tetrafluoride / ethylene copolymer resin: E / TFE),
Polyvinylidene fluoride (vinylidene fluoride resin:
PVDF), polychlorotrifluoroethylene (ethylene trifluoride chloride resin: PCTFE), chlorotrifluoroethylene-ethylene copolymer (ethylene trifluoride / ethylene copolymer resin: E / CTFE), tetrafluoroethylene -Perfluorodimethyldioxol copolymer resin (abbreviation: TFE / PDD) and polyvinyl fluoride (vinyl fluoride resin: abbreviation: PVF).

As a characteristic of the fluororesin, the resin itself has lubricity due to the influence of fluorine molecules. Therefore, the fluororesin itself functions as a lubricant. This is considered to be because the intermolecular cohesive energy of the fluorine compound is low due to the small polarizability of the fluorine molecule, the molecular chain surface is structurally smooth, and the frictional resistance is relaxed by the orientation. When the composite material is used as a lubricant, the composite material other than the low-molecular-weight PTFE may come into contact with the photoreceptor 2 and have an effect. Here, if the composite material is a fluororesin, lubricity which is a characteristic of the fluororesin is added to the photoreceptor 2 together with the low molecular weight PTFE, and the lubricity is improved.

[Specific Example 2] The lubricating material 22 is made of a low molecular weight PT.
A composite material of FE and PTFE having different molecular weights was used.
Specifically, one having a higher molecular weight is selected. The reason is that it is difficult to mold low molecular weight PTFE by itself, whereas in the case of high molecular weight PTFE, sufficient mechanical strength can be obtained due to entanglement of molecular chains and the like, so molding can be performed. That's why. The properties of PTFE are as described above, and the lubricating properties are excellent regardless of the molecular weight. However, low molecular weight PTFE is excellent in supply performance. However, even a polymer is transferred to the photoreceptor 2 and contributes to imparting lubricity. Thereby, not only the effect of the low molecular weight PTFE but also the high molecular weight P
The effect of TFE can be added, and more excellent lubricity can be obtained. Further, by dispersing the low molecule in the polymer, the strength of the polymer itself is degraded, and the effect of increasing the supply capacity of the polymer itself is generated.

Next, a specific method of forming a composite material of low molecular weight PTFE and PTFE having different molecular weights will be described. However, the molding method shown here is merely an example, and the present invention is not limited to this. Here, a compression molding method will be described as a molding method. In the compression molding method (eg, free baking method), raw material powders (high molecular weight PTFE and low molecular weight PT
FE mixed powder) is uniformly filled, pressed at room temperature and compressed. At this point, the molded article is relatively brittle. This preform (usually called preform)
Is placed in a high-temperature furnace, heated to a firing temperature, maintained at an arbitrary temperature until firing is completed as a whole, and then cooled at a constant speed to complete molding. In this case, no binding force acts on the member during firing. Therefore, the dimensional accuracy of the molded product is not so excellent, and secondary processing is required when dimensional accuracy is required. For example, when a lubricating material is used as a sheet material or the like, it is processed from a fired block by a cutting process called skiving.

In these molding processes, it should be noted that low molecular weight PTFE is more likely to be decomposed by heat than high molecular weight PTFE. When decomposed, a decomposed gas is generated, bubbles are generated inside the block, and cracks and the like are generated from the decomposed gas, so that molding may not be performed properly.
Therefore, in the case of a low-molecular-weight PTFE composite material, it is necessary to devise a method in which the temperature is set lower than the firing temperature of a single polymer, and the firing time and cooling conditions are adjusted as compared with those of a normal polymer. Also, it is necessary to change the set values for the press conditions before the preform is created.

Conventionally, since the lubricating properties of PTFE are high, there has been no use form in which the mechanical strength is reduced by compounding with PTFE of low molecular weight.

[Specific Example 3] The lubricant 22 was made of low molecular weight PT.
A composite material of FE and PFA was used. PFA is a random copolymer of tetrafluoroethylene (TFE) and perfluoro (alkyl vinyl ether) (FVE). Its melting point is in the range of 305-310 ° C, and PT
Slightly lower than FE. Other properties are close to PTFE, and have lubrication properties equivalent to PTFE. PTF
The difference from E is that the melt viscosity is smaller than that of PTFE (higher than that of general resin). Therefore, P
It becomes possible to use an injection molding method and an extrusion molding method which cannot be performed by TFE. For this reason, even when preparing a composite material, an injection molding method can be used, and the productivity can be improved. However, if the ratio of low molecular weight PTFE in the material becomes too large,
In some cases, the melt viscosity increases, and these molding methods cannot be used. Therefore, it is necessary to suppress the ratio of the low molecular weight PTFE to a certain range, and it is preferable to suppress the ratio to approximately 30% or less. Also, in the case of stretching (for example, inflation), the molding is performed at the melting temperature of PFA, so the low-molecular-weight PTFE may not be melted, and the low-molecular-weight PTFE may break without being able to withstand stretching. Therefore, proper adjustment of the content is required. Since the lubricating performance of PFA is almost equal to PTFE (however, PTFE is relatively superior), it can be used as an excellent lubricating material.

The low-molecular-weight PTFE can be supplied to an injection molding apparatus or the like in the form of being dispersed in molded pellets to perform molding. Further, since the melting point of PFA is slightly lower than that of PTFE, the thermal decomposition of low-molecular-weight PTFE during molding is somewhat improved. As described above, by using PFA as the composite material, lubricity can be improved in a form in which lubricity of PFA is added to lubricity of low molecular weight PTFE. Further, since the injection molding method or the like is made possible, the productivity can be improved, which can contribute to a reduction in the production cost of the product and a reduction in the cost of the apparatus.

[Specific Example 4] The lubricant 22 was made of low molecular weight PT.
A composite material of FE and FEP was used. FEP is PTFE
On the other hand, it is a resin in which a trifluoromethyl group is introduced as a side chain to lower the crystallinity and enable melt processing. Its melting point is in the range of 255-265 ° C., which is lower than that of PTFE. However, if the ratio of the low-molecular-weight PTFE in the material is too large, the melt viscosity increases, and it may be impossible to use these molding methods. Therefore, it is necessary to suppress the ratio of the low molecular weight PTFE to a certain range, and it is preferable to suppress the ratio to approximately 30% or less. In the case of stretching (for example, inflation), molding is performed at the melting temperature of FEP, so that low-molecular-weight PTFE may not be melted, and low-molecular-weight P
It may break at the TFE part without being able to withstand stretching,
It is necessary to adjust the content appropriately. Other properties are almost similar to PTFE, and lubricity is excellent as well as PTFE. The low melting point allows room for thermal decomposition of low molecular weight PTFE at the time of molding a composite material, and can prevent functional deterioration due to decomposition.

The low-molecular-weight PTFE can be supplied to an injection molding apparatus or the like in the form of being dispersed in molded pellets to perform molding. As described above, by using PFA as a composite material, the lubricating properties of low molecular weight PTFE can be improved by FE.
The lubricity can be improved in a form in which the lubricity of P is added. Further, since the injection molding method or the like is made possible, the productivity can be improved, which can contribute to a reduction in the production cost of the product and a reduction in the cost of the apparatus.

[0045]

According to the first aspect of the present invention, since the lubricant is a composite material of low molecular weight PTFE and at least one or more other materials, friction reduction of low molecular weight PTFE higher than PTFE is achieved. The characteristics can be obtained as a molded product, and the deterioration of the photosensitive characteristics or the transfer characteristics due to the scraping of the image carrier can be suppressed. In addition, since the low-molecular-weight PTFE can be configured to be in direct contact with the image bearing member due to its wear characteristics, the size of the apparatus can be reduced.

According to the second aspect of the present invention, the lubricant is
Since the composite material of the low molecular weight PTFE and the fluororesin is used, the lubrication characteristics of the fluororesin can be obtained in addition to the lubrication characteristics of the low molecular weight PTFE, and the lubrication characteristics of the entire lubricant can be improved.

According to the third aspect of the present invention, the lubricant is
Since a low molecular weight PTFE and a composite material of PTFE having different molecular weights are used, the lubricating properties of PTFE can be obtained in accordance with the lubricating properties of low molecular weight PTFE, and the lubricating properties of the entire lubricant can be improved. Mechanical strength can be improved.

According to the fourth aspect of the invention, the lubricant is
Because it was a composite material of low molecular weight PTFE and PFA,
The lubrication characteristics of PFA can be obtained in addition to the lubrication characteristics of low molecular weight PTFE, and the lubrication characteristics of the entire lubricant can be improved. In addition, the productivity can be improved as compared with the case of compounding with PTFE, and the problem due to thermal decomposition can be suppressed.

According to the fifth aspect of the present invention, the lubricant is
As a composite material of low molecular weight PTFE and FEP,
The lubrication characteristics of FEP can be obtained in addition to the lubrication characteristics of low-molecular-weight PTFE, and the lubrication characteristics of the entire lubricant can be improved. In addition, the productivity can be improved as compared with the case of compounding with PTFE, and the problem due to thermal decomposition can be suppressed.

According to the invention of claim 6, the low molecular weight P
Since the ratio of TFE to the whole was set to about 30% or less,
The range of choice of the molding method can be widened, and the productivity can be more reliably improved as compared with the case of compounding with PTFE.

[Brief description of the drawings]

FIG. 1 is a main part side view showing one embodiment of the present invention.

FIG. 2 is a side view showing a modification of the configuration of the lubricant supply mechanism.

FIG. 3 is a side view when the image carrier is an intermediate transfer belt.

FIG. 4 is a diagram showing a molecular structure of PTFE.

FIG. 5 is a diagram showing a cross section of the molecular structure of PTFE.

[Explanation of symbols]

 2 Photoconductor 22 as Image Carrier 22 Lubricant 40 Intermediate Transfer Belt as Image Carrier

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10N 40:00 (72) Inventor Yota Sakon 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Invention Akiyo Nakajima 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd.

Claims (6)

[Claims] 1. An image forming apparatus having a function of supplying a lubricant to the surface of an image bearing member, wherein the lubricant is a low molecular weight polytetrafluoroethylene (hereinafter, referred to as “low molecular weight PTFE”) and at least other components. An image forming apparatus comprising a composite material with one or more materials. 2. An image forming apparatus according to claim 1, wherein said other material is a fluorine resin. 3. The image forming apparatus according to claim 2, wherein said fluororesin is polytetrafluoroethylene having a different molecular weight from said low molecular weight PTFE. 4. An image forming apparatus according to claim 2, wherein said fluororesin is a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer. 5. An image forming apparatus according to claim 2, wherein said fluororesin is a tetrafluoroethylene-hexafluoropropylene copolymer. 6. The image forming apparatus according to claim 4, wherein a ratio of the low molecular weight PTFE to the whole is about 30% or less.