JP2001301083A - Durable polyimide film, method for manufacturing the film, and use of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a durable polyimide film especially improved in abrasion resistance and corona discharge resistance or the like. SOLUTION: The durable polyimide film is formed by coating the surface of a polyimide film (which may be semiconductive or may have a rubber elastic layer) with a transparent membrane layer comprising alkaline earth metal fluoride. For example, the membrane layer is manufactured by using alkaline earth metal fluoride as a target by sputtering the same on the surface of the polyimide film. When the obtained film is a semiconductive tubular film, it is used as a paper feeding or transfer and thermal fixing belt of a toner copier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide film having better durability and the like, a method for producing the same, and use thereof. In the case where the film is a semiconductive tubular film using polyamideimide, thermoplastic polyimide, or thermosetting polyimide as a matrix resin, it is used as a belt for conveying a sheet of a toner (multicolor) copying machine or for intermediate transfer and heat fixing. Used effectively.

[0002]

2. Description of the Related Art For example, a thermosetting polyimide tubular film excels in heat resistance, chemical resistance, and various physical properties.
Use as a functional member, for example, a belt for intermediate transfer (and heat fixing) of a (color) toner copying machine is effective, and many patent applications have been filed for this. One technique often found in patent applications is a means for improving the transfer of image toner to copy paper. The basic idea is to impart releasability to the film, and specifically, for example, kneading a fluorine-based resin or spray coating a resin purge liquid to form a surface release layer. (Japanese Unexamined Patent Publication No. 61-95361, Japanese Unexamined Patent Publication No. Hei 7-246671, etc.), or a method in which a tubular film of the resin is fitted to form a surface release layer (Japanese Unexamined Patent Publication No. 10-2).
No. 96826), and a method of coating the tubular film with a porous fluororesin impregnated with a liquid fluoropolymer (Japanese Patent Application Laid-Open No. 10-31371). Second, in order to impart appropriate chargeability and static elimination to the film, a conductive member, for example, conductive carbon black is mixed and dispersed to impart semiconductivity.

On the other hand, on the other hand, the characteristics required in the market have become more severe with the progress of color copying technology, and in fact, the above-mentioned means are no longer satisfactory. The requirements are more appropriate charge retention ability (charging property) and its charge removal and releasability, as well as prevention of surface deterioration due to corona discharge (corona resistance), higher abrasion resistance, belt driving torque. (Excellent in static friction). In particular, prevention of the surface deterioration (coloring, etc.) is important for photoelectrically controlling the glossiness of the hard copy to be always constant and for controlling the image quality. For this reason, the surface coat layer is more transparent. Something is needed.

[0004]

However, as for the above-mentioned new requirements, not only the above-mentioned prior art but also any patent applications which have been found thereafter have not been found to be sufficiently solved. The present invention has been made as a result of various intensive studies in order to find a solution that can sufficiently satisfy the above requirements.
The solution is as follows.

[0005]

That is, according to the present invention, first, a transparent thin film layer made of an alkaline earth fluoride according to claims 1 and 2 is coated on the surface of a polyimide film or a surface rubber elastic layer. And a durable polyimide film. In a preferred embodiment of the present invention, there is provided a method for forming a transparent thin film layer by sputtering the above alkaline earth fluoride salt as a target on the surface of a polyimide film. Further, as a preferred use of the film, claims 11 and 12 also provide use as a belt for conveying a sheet of a toner copying machine and for intermediate transfer and heat fixing.

[0006] The inventions according to claims 3 to 9 are also provided, which are provided as preferred embodiments depending on claim 1 or 2. Hereinafter, the present invention will be described in detail with reference to the following embodiments.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a polyimide film as a substrate will be described. This is made of a generally known polyamideimide (hereinafter referred to as PAI), thermoplastic polyimide (hereinafter referred to as tPI) or thermosetting polyimide (hereinafter referred to as tsPI) as a matrix resin which is formed into a web-like material by an appropriate method. (Film) or a tubular film. Therefore, there is no restriction on the method for producing the matrix resin or the molding method, and the matrix resin can be obtained by a method generally found in patent applications and the like.

The PAI is formed, for example, by adding an aromatic tricarboxylic acid anhydride such as trimellitic acid anhydride to 3,
3'-diaminobenzophenone, P-phenylenediamine, 4,4'-diaminodiphenyl, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, bis [4- {3- (4-aminophenoxy) benzoyldiphenyl] ether, 4,4'-bis (3-
Using one or two kinds of aromatic diamines such as aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] sulfone, and 2,2′-bis [4- (3-aminophenoxy) phenyl] propane as a raw material, An equimolar amount thereof is obtained by polycondensation reaction in an aprotic polar organic solvent such as dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone and the like. Here, since PAI itself dissolves in the solvent, it can be obtained after the imidization has been completely completed together with the reaction.

The tPI is, for example, pyromellitic acid 2
Anhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, bis (2,3-dicarboxyphenyl) methane Aromatic tetracarboxylic acid dianhydride such as dianhydride and bis [4- @ 3- (4-aminophenoxy)
Benzoyldiphenyl] ether, 4,4'-bis (3
Using one or two aromatic diamines such as -aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] sulfone, and 2,2'-bis [4- (3-aminophenoxy) phenyl] propane as a raw material; And an equimolar amount thereof are subjected to a polycondensation reaction in the aprotic organic solvent. Here, since tPI itself dissolves in the solvent, it can be obtained after the imidation has been completed at the same time as the reaction, but the solubility is 2 to 3 in the polymer main chain.
Number of _{-O -, - SO 2 -,} - CO-, an alkylene group (C
3 or more), etc., and became thermoplastic.

TsPI is the above-mentioned aromatic tetracarboxylic dianhydride, 3,3'-diaminobenzophenone,
An equimolar amount with an aromatic organic diamine such as P-phenylenediamine or 4,4'-diaminodiphenyl ether is obtained by a polycondensation reaction in the aprotic organic solvent, but tsPI itself is not used. Since it is insoluble in the solvent, the reaction
It must be performed at a low temperature of 0 ° C. or less, and stopped at the stage of the precursor polyamic acid. Therefore, molding (mold) into film
In the first step, the solvent is removed at the stage of polyamic acid, the substantial shaping as a film is completed, and thereafter, the imidization is carried out together with the removal of the remaining solvent.

The above-mentioned PAI, tPI and tsPI are generally used alone, but may be a blended polyimide system in which these are appropriately blended. The choice depends on the intended use. For example, a belt for intermediate transfer and heat fixing of a toner copying machine, which will be described later, has higher heat resistance and mechanical properties.
Is preferably used.

[0012] In general, each film is formed from the above-mentioned polyimide-based organic solvent solution as a raw material (stock solution). Here, when it is desired to impart certain characteristics to the film,
An additive for that purpose is added to the stock solution. For example, when it is desired to provide electrical resistance, a conductive agent such as conductive carbon black (hereinafter simply referred to as CB), a thermal conductive agent such as BN for thermal conductivity, and a flame retardant such as Ca (OH) ₂ for flame retarding. , the mechanical strength improving the reinforcing agent such as _{9Al 2 O 3 · 2B 2 O} 3, piezoelectric piezoelectric agents such as BaTiO _3, light scattering and reflecting the light reflecting agent such as TiO _2, Suridosei the MoS ₂ And the like.

As an example of the case where the above-mentioned additive is added, when the film is used as an intermediate transfer and heat fixing belt of a toner copying machine, it is preferable that the film has proper chargeability and static elimination. Therefore, an appropriate electric resistance is provided. The properties are preferably imparted by the addition of CB. Further, when it is desired to impart thermal conductivity thereto, the above-mentioned thermal conductive agent is also used. Wherein application of electrical resistance, for example, carried out preferably within the range of about 10 ² ~10 ¹⁴ Ω · cm in terms of the volume resistivity, which volume resistivity is 10 ⁰ Omega
-It is performed by using CB powder of about cm and changing the addition amount so as to be within the above range.

The film is formed (molded) by, for example, the following means. First, in the case of web film,
A method in which each of the stock solutions is cast and cast on a heated metal belt or metal drum, extruded and cast, and the organic solvent is evaporated to solidify into a film. On the other hand, in the case of a tubular film, a method of cutting the web film to a predetermined length and joining both ends, and a method of coating and heating using an outer peripheral surface or an inner peripheral surface of a rotating metal drum can be exemplified.

Whether the web film or the tubular film is used depends on the purpose of use. For example, when used as a belt member for conveying a toner in a copying machine or as a belt member for intermediate transfer and heating and fixing, the tubular film is used. Although there are three examples of the molding means as described above, the belt has no seam (endless)
Further, since it is required that the surface and the thickness accuracy are excellent, a molding method of coating and heating the inner peripheral surface of the rotating metal drum, that is, a centrifugal molding method is preferable. This centrifugal molding method also includes molding under centrifugal force and molding under substantially no centrifugal force. The difference between the two appears especially in the case of a polyimide solution containing an additive. That is, under the centrifugal force, the additive is dispersed in the entire surface layer in a state of being inclined in the whole, and conversely, under the non-centrifugal force, the endless film is obtained in the state of being uniformly dispersed throughout. Accordingly, the characteristics of the obtained endless tubular film are different. For example, regarding the electrical resistance provided by CB, the difference between the volume resistance and the surface resistance under a centrifugal force is large, and under a non-centrifugal force, the difference tends to be small.

The conditions (concentration of undiluted solution, heating method and temperature, presence or absence of centrifugal force, etc.) in each of the above molding (mold) methods are determined by prior checks, respectively. It is preferable to complete in two steps without limitation. Rather than continuing heating until all the organic solvent has been removed by evaporation in the metal drum, the two steps are finished by leaving the solvent to a certain extent, and then removing the drum from the apparatus and leaving it unattended. It is put into a separately provided hot-air dryer. Alternatively, the molded film obtained by the evaporation is once peeled off from the drum, taken out, inserted into a separately provided substantially identical cylindrical mold, and put into the dryer or the like, and gradually heated at a higher temperature. This is two steps of heating. By adopting any of these methods, the residual solvent can be more quickly, smoothly, and completely removed, and imidization can be performed more quickly, smoothly, and completely, particularly with the tsPI amide acid. As a result, it is possible to obtain a tubular tsPI film having a smoother surface condition and good quality.

A transparent thin film layer of an alkaline earth fluoride is formed on the entire surface of the polyimide film obtained as described above. For example, a rubber elastic layer is provided on the film in advance, and the polyimide thin film layer is formed thereon. A thin film layer may be provided. This will be described below.

First, the transparent thin film layer is made of calcium fluoride (CaF ₂ ), barium fluoride (BaF ₂ ), magnesium fluoride (MgF ₂ ), strontium fluoride (SrF ₂ ), beryllium fluoride (BeF ₂ ). Formed by any of the alkaline earth fluorides. As a result, the surface of the base film is completely protected, and at the same time, the abrasion resistance, the releasability, etc. are imparted together with the corona resistance. This effect can be obtained almost equally in these alkaline earth fluoride salts, and among them, better adhesion (to the surface of the base film), abrasion resistance (high surface hardness), and transparency (for example, total light transmittance) The former three are preferred from the viewpoint of 90% or more).

The thickness of the transparent dielectric layer is specified as a thin film. The term “thin film” here largely differs from the thick film category obtained by coating with a solution in general, and is based on the concept of an extremely thin film thickness category. When numerically illustrated, 5000 $ or less,
Furthermore, it means thinness of less than 3000 mm,
The lower limit is preferably about 100 °. This is because if it is too thin, the desired improvement effect is not sufficient, particularly in terms of wear resistance and corona resistance. The upper limit is described above, but more preferably 2000 °. This is because in the thicker direction, the bending resistance and the transparency tend to deteriorate, and the risk of delamination increases. Further, for example, when the substrate film is provided with fine irregularities and the thin film is formed thereon, if the film is too thick, the fine irregularities may disappear. In other words, the thin film thickness in numerical terms is 100 to 20 according to claim 5.
00 ° can be exemplified as a preferable range.

The transparent thin film layer is preferably formed by a physical thin film forming means generally found in a vacuum deposition (resistance heating evaporation, EB evaporation) method, an ion plating (ARE, RF) method or a sputtering method. Among them, a method that can be performed efficiently at lower temperature is a sputtering method. The conditions for forming the thin film layer by this sputtering method are roughly as follows.

Prior to sputtering, at least the surface of the base film is degreased and washed (water, solvent).
It is desirable to perform a pre-treatment by plasma and / or corona. This is for further improving the adhesion of the thin film layer. In some cases, fine irregularities are positively formed on the film surface to form a film substrate. This is because, for example, when used as a belt, it is effective to further improve abrasion resistance and to reduce static friction and the like caused by contact rotation. The shaping means, shape, size, and the like of the fine irregularities are not specified because they may be determined sequentially by experimental means in relation to the effect.

The pretreated polyimide-based film substrate (web, tubular strip film or film with a rubber elastic layer) is rolled in a web film or belt-shaped in a tubular film and placed in a sputtering chamber of a sputtering apparatus. Is placed. Then, an alkaline earth fluoride is placed in a planar shape (target) so as to face the film substrate surface. Next to and the chamber interior to a vacuum, and finally to replace the air with an inert gas such as argon 10 ⁰
The gas atmosphere is changed to 10 ⁻² Pa. Next, using the target and the film substrate as both poles, for example, a frequency of 13.65 MHz and an input power of 5 to 10 W /
A high frequency (hereinafter abbreviated as RF) voltage is applied in cm ² . The thickness of the transparent dielectric thin film layer is determined by the intensity of the output, the sputtering speed (feeding speed of the film), the number of times of sputtering, and the like. The formed thin film layer also has excellent releasability,
It has a Mohs hardness of about 4 to 6 and is sufficiently adhered. In addition, in the film substrate having a fine uneven surface, the film thickness is formed to the same detail in the details except for the uneven shape. This effect is a disadvantage of the coating layer formed by the general solution coating method, that is, bubbles are apt to enter, lack denseness, insufficient adhesion, and insufficient film thickness accuracy. It can be said that there is a large difference between the depth of the irregularities and the fact that the shape changes.

When a rubber elastic layer is provided, the rubber elastic layer is preferably formed of a generally known silicone resin having a rubber elasticity, a fluororesin or a fluorosilicone resin obtained by suitably combining the two. A thickness that does not cause loss of rubber elasticity is required. On the other hand, it is too thick to lower the elastic recovery, or the toner image may be deformed. From such a viewpoint, it is preferable to use 20 to 100.
μm. The hardness (Shore A hardness) of the rubber resin itself is preferably about 30 to 80. The formation of the layer
Generally, the precursor liquid of the resin is coated and post-cured. In particular, in the case of a tubular film substrate, it is also formed by fitting a separately molded tubular film in advance to the substrate.

The effect of the present invention, particularly by the alkaline earth fluoride and by the formation of the layer in the form of a transparent thin film, is that the layer itself is formed very densely (no bubbles or surface irregularities at all) and hard. This is considered to be due to the high surface tension and extraordinary strength and hardness.

The thus-obtained durable polyimide film is used for various applications because of its excellent various properties. For example, the case of a tubular film is as follows. For kneading rollers for kneading and mixing inks, adhesives, two or more components at room temperature or under heating. For casting belts for casting film formation. A belt for conveying a sheet or a belt for intermediate transfer and heating and fixing of a toner copying machine according to claims 11 and 12.

Unlike the belt for intermediate transfer and heating and fixing, which will be described later, the belt for transporting the paper (meaning the object to be copied, not limited to paper) of the toner copying machine transports the paper under the standby photosensitive drum. There, a belt for transferring the toner image on the drum directly to paper and delivering it to a heat fixing device provided as a subsequent process.

For reference, an example of the above device is shown in FIG. 1 with a four-color tandem engine type. In the figure, first, the belt 1 is
It is firmly stretched by two stretching rollers 2, 2a. And four photosensitive drums 3 (K-black, Y-yellow,
M-red, C-blue) lies substantially adjacent to the belt. Four corotron chargers 4 are disposed on the back side of the belt 1 so as to face the respective drums. This assists the transfer of the visualized image on the photosensitive drum 3 to the sheet (electrostatic action) by charging the belt, but is mainly used for charging the sheet to convey it while electrostatically attracting the sheet to the belt surface. Used as Therefore, a corotron charger 8 provided opposite to the stretching roll 2 is also provided to convey at least the sheet 5 to the photosensitive drum K while electrostatically adsorbing the same. The sheet 5 that has passed through the last photosensitive drum C is discharged by the charge remover 6 and conveyed to the heating and fixing device 7, where the image is fixed while being sandwiched between the heating roller 7a and the receiving roller 7b, and becomes a copy sheet.

In a preferred form of the above-mentioned paper transport belt, higher heat resistance is not required, but since it is sometimes stretched on a stretch roll having a smaller diameter, it is desirable that the belt be more flexibly bent. In addition, it has proper electric resistance (at least necessary for the sheet to be effectively electrostatically attracted to the belt) and has a large surface area. Of course, it is also necessary to have excellent wear resistance and surface non-deterioration.

From the above points, when specifically selected,
First, a semiconductive tubular PAI or tubular tPI film is preferred. It is preferable that the semiconductivity is given by a conductive agent such as CB. However, the semiconductivity is 10% by volume resistance in order to effectively perform the above-mentioned electrostatic adsorption (the charging life is long even at a low applied voltage). It is preferable that an electric resistance of about ¹⁰ to 10 ¹⁴ Ω · cm (surface resistance of about 10 ⁹ to 10 ¹³ Ω / □) is applied. Further, it is preferable that the film surface has fine irregularities rather than smoothness and has a large surface area, and it is also preferable that this surface is a rubber elastic layer surface.

On the other hand, the intermediate transfer and heat fixing belt is a copy copier that employs an indirect copying method in which a toner image formed on a photosensitive drum is temporarily transferred to a belt, and then transferred to paper and heat-fixed at the same time. The belt member is particularly effective as a belt employing a tandem engine type multicolor copying system in which a multiplex image is formed on the belt, and the resulting image is transferred onto a sheet at a stroke and heat-fixed.

FIG. 2 shows an outline of the above method for reference. First, the belt 9 is firmly stretched by the stretching rollers 10 and 10a and the stretching and heating roller 11a. The four photosensitive drums 12 (K
(Black, Y-yellow, M-red, C-blue), and four corotron chargers 13 are arranged on the back side of the belt so as to face each of the drums. This is for charging the belt and positively transferring a visible image on the photosensitive drum 12 to the belt. A density sensor (light) 14 checks a change in the glossiness of the belt surface. The toner image 15 transferred in the order of KYMC is sent to the heat fixing device 11 and heated by the heating roller 11a, and is pressed and transferred onto the sheet 16 by the receiving roller 11b. After the transfer, the belt is neutralized by a static eliminator 17 to remove the remaining charge, and the surface is cleaned through a cleaner 18 to complete one cycle.

It is needless to say that the preferred form of the belt as described above is such that the base itself rotates smoothly, first of all, it is more heat resistant (at least 200 mm).
° C), and there is no expansion, contraction, surface abrasion, corona resistance (deterioration, coloring, etc.) even when used at this temperature for a long period (for example, continuous use for one month or more). The transfer (large surface area) and transfer (large surface releasability) of the toner image are easily and reliably performed, and furthermore, there is appropriate electric resistance for good charging and slow charging, and particularly, poor transfer. Must have the required gloss and transparency (total light transmittance of 80% or more) when photoelectrically checking. Furthermore, the static friction between the photosensitive drum and the belt acting during rotation is small (a large amount tends to cause blurring of rotation at start-up, resulting in color misregistration).

From the above points, when specifically selected,
As the durable polyimide film, a tubular tsPI film, and an electrical resistance is given by a conductive agent such as CB,
And the resistance has a volume resistance value of 10 ⁷ to 10 ¹¹ Ω · cm.
And the surface resistance is in the range of about 10 ⁸ to 10 ¹² Ω / □, and more preferably, the difference between the two resistances is within one digit. The difference between these two resistance values is generally 2-3
A film having an order of magnitude difference is selected, but in the case of the film approaching within one order, for example, the dependence on the applied voltage is small (the resistance does not change even if the applied voltage changes during copying), This is because the effect of saying that the resistance does not change with time under application of a voltage is greater. Further, it is preferable that the surface of the film has fine irregularities rather than smoothness, and it is more preferable that the film is a rubber elastic layer.

[0034]

EXAMPLES Hereinafter, reference examples and examples will be described in more detail together with comparative examples. In this example, the volume resistance value (Rv) and the surface resistance value (Rs) are values measured after a lapse of 30 seconds by applying 500 V with a resistance meter Hiresta IP / HR probe manufactured by Mitsubishi Chemical Corporation. Rz) is a sample length of 2.5 using a surface roughness meter manufactured by Tokyo Seimitsu Co., Ltd.
mm, the static friction coefficient (μs) (Muse) obtained by measuring at a cutoff value of 0.8 mm is a HEIDON Tribogear Muse meter (μs type) manufactured by Shinto Chemical Co., Ltd.
The surface tension (°) and the contact angle with respect to standard water measured by CA-S Micro 2 manufactured by Kyowa Interface Science Co., Ltd. are shown.

(Reference Example 1) (Production Example of Polyamic Acid of stPI as Matrix Resin) Equimolar amount of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether was determined as N-methylpyrrolidone. A polycondensation reaction was carried out at 20 ° C. in a solvent to obtain 15 kg of an aromatic polyamic acid solution having a solid content of 16% by weight (solution viscosity: 4.2 Pa · s) (hereinafter, PA stock solution).

(Reference Example 2) (Production example of tPI as matrix resin) 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride and bis [4- {3- (4-aminophenoxy)
An equimolar amount of benzoyl [phenyl] ether was subjected to a polycondensation reaction in a dimethylacetamide solvent at 35 ° C. to obtain 15 kg of a solution having a solid content of 18% by weight. When a part of this was collected and subjected to IR analysis, substantially only the absorption derived from the imide bond was observed, and no absorption derived from the amide bond was confirmed. The viscosity of the liquid is 1.9 Pa · s.
Called PI stock solution.

Reference Example 3 (Production Example of PAI as Matrix Resin) An equimolar amount of trimellitic acid monoanhydride and 4,4'-diaminodiphenylmethane was mixed at 30 ° C. in an N-methylpyrrolidone solvent. 22% by weight (solid content) after condensation reaction
15 kg of an aromatic PAI solution was obtained. The viscosity of the liquid is 2P
a · s, which is hereinafter referred to as a PAI stock solution. In addition, IR analysis of a part of the solution showed that the amide group and most of the amide group (although there was a slight absorption due to unclosed amide acid) were based on the imide group.

(Reference Example 4) (Example of molding semi-conductive tsPI endless tubular film) 5 kg of the stock solution of PA of Reference Example 1 was collected, and 100 g of CB powder (10 ^-1 Ω · cm) was added thereto (solids). After the preliminary mixing, the mixture was fully mixed and dispersed by a ball mill, and the resulting mixture was used as a semiconductive tsPI endless tubular film in a molding apparatus having the following structure and molding conditions. Molded into.

As a molding device, a metal molding drum having an inner mirror surface finish (chromium plating finish, R _Z = 0.6 μm) with a width of both sides of 500 mm and an inner diameter of 350 mm is mounted on two rotating rollers. The drum is heated by providing a far-infrared heater on the outer upper surface of the drum and the heater (auxiliary heating) on the roller. A supply nozzle for supplying the stock polymer solution into the drum and a supply / discharge nozzle for positively removing the evaporating organic solvent out of the system are integrated, and a mechanism capable of being inserted into and removed from the drum is provided. Is provided. The stock solution supplied to the drum is formed into an endless film while being rotated and heated by the rotation of the roller.

The molding conditions are as follows. First, the molding drum is slowly rotated at room temperature at an angular velocity of 6 rad / s, and the CB mixture is horizontally moved 2.5 × 10 ⁵ from a 50 mm wide supply nozzle (slit). Injection was started at a pressure of Pa toward the inner surface of the drum. The nozzle was moved from right to left in synchronization with the rotation, and the injection was stopped when the predetermined coating thickness was reached. Then, while maintaining the same angular velocity, heating with the far-infrared heater is started, and when the temperature reaches 120 ° C. (the temperature in the drum), heating is performed at that temperature for 90 minutes, and then the temperature is raised to 150 ° C. and the temperature is increased for 60 minutes. Heated. During this heating, the evaporating solvent was positively discharged and removed from the system using the suction / discharge nozzle. Finally, when the heating was stopped and the temperature was cooled to room temperature, the rotation was stopped and the molded body was separated from the drum and taken out. The molded article was a semiconductive endless tubular film of polyamic acid containing some organic solvent.

Next, the polyamic acid tubular film was inserted into a cylindrical metal mold having an outer diameter of 340 mm and a width of 420 mm, and was put into a hot air dryer. The heating temperature and time here were 300 ° C. for 30 minutes, followed by heating at 450 ° C. for 30 minutes, and when finished, cooled and fitted out of the mold. The resulting film was completely desolvated and turned into an imidized tsPI semiconductive endless tubular film. The thickness of the film is 65 .mu.m, an inner diameter of 340 mm, width 400 mm (cut finish), _{R Z} is 0.5 [mu] m, Rv
Is 5 × 10 ¹⁰ Ω · cm, Rs is 5 × 10 ¹¹ Ω / □,
The coefficient of static friction was 0.29. Under the same conditions, another one of the same tubular films was molded into two.

(Reference Example 5) (Example of molding a semiconductive PAI endless tubular film) 4 kg of the PAI stock solution of Reference Example 3 was collected, and 120 g of this was taken.
CB powder (10 ^-1 Ω · cm) was added (12% by weight based on the solid content), and after preliminary mixing, the mixture was fully mixed and dispersed by a ball mill, and the molding apparatus of Reference Example 4 was used. And molded into a semiconductive PAI endless tubular film under the same molding conditions. However, the finish of the inner surface of the molding drum in this case was Rz = 3.8 μm. Then, the drum is removed from the apparatus, and is directly introduced into a hot-air dryer.
Heat and dry for minutes. After cooling, the film was peeled from the drum to obtain the desired PAI semiconductive endless tubular film. The thickness of the film is 100 μm, inner diameter 339.5 mm, width 400 mm (cut finish) R _Z = 2.2 μm, Rv =
It was 2 × 10 ¹² Ω · cm and the coefficient of static friction was 0.34.
Under the same conditions, another one of the same tubular films was molded,
There were two.

(Reference Example 6) (Example of Forming Non-semiconductive tPI Endless Tubular Film) The tPI stock solution obtained in Reference Example 2 was centrifugally cast under the following conditions by the molding apparatus in Reference Example 5 described above. First, the unheated forming drum is slowly rotated at room temperature at an angular velocity of 6 rad / s, and liquid is started to be discharged from a supply nozzle (slit) having a width of 50 mm, which horizontally moves the stock solution, and the nozzle is synchronized with the rotation. Then, the nozzle was moved from right to left, and the supply was stopped when a predetermined coating thickness was reached. Then, the heating of the drum is started, and the rotation is gradually accelerated so that the angular velocity becomes 10
When the temperature reached 0 rad / s and the temperature reached 130 ° C., heating was performed for 90 minutes in that state, and then the temperature was raised to 170 ° C. and heating was performed for 60 minutes in that state. During this heating, the evaporating solvent was positively discharged and removed from the system using the suction / discharge nozzle. Finally, when the heating was stopped and the temperature was cooled to room temperature, the rotation was stopped and the molded body was separated from the drum and taken out.

Next, the molded body was 340 mm in outer diameter and 4 mm in width.
This was inserted into a 20 mm cylindrical metal mold, and this was put into a hot air drier and dried by heating at 260 ° C. for 80 minutes. Then, it was cooled and fitted out of the mold. The obtained film was completely desolvated and was an endless tubular film of tPI. The thickness of the film is 73 μm, inner diameter 340 mm, width 400 mm
(Cut finish), _{R Z} was 2.0μm.

(Reference Example 7) (Example in which rubber elastic layer is provided in Reference Example 4) One semiconductive tsPI endless tubular film obtained in Reference Example 4 is stretched over two rotating rolls, and Confrontation
A gravure roll is provided in contact therewith, and a one-component silicone rubber liquid (manufactured by Shin-Etsu Chemical Co., Ltd., product no.
-3418) while rotating, and finally 10
While heating to 0 ° C., the mixture was heated and cured for 60 minutes to form a silicone rubber layer. The thickness of the resulting the layer 60 [mu] m, the hardness (A) is about 40, _{R Z} was 0.4 .mu.m.

(Reference Example 8) (Example in which a rubber elastic layer is provided in Reference Example 5) One semiconductive PAI endless tubular film obtained in Reference Example 5 is inserted into a rotating metal cylinder having an outer diameter of 339.5 mm. hand,
After spraying a fluoro rubber latex (product number GLS-213 manufactured by Daikin Industries, Ltd.) from a spray gun to coat, the coating was finally heated to 200 ° C. and cured by heating for 90 minutes to change to a fluoro rubber layer. The thickness of the resulting the layer 20 [mu] m, the hardness (A) is about 70, _{R Z} was 2.8 .mu.m.

(Example 1) (Corresponding Example of Claim 1) The surface of the non-semiconductive tPI endless tubular film obtained in Reference Example 6 was sufficiently degreased and washed, and this surface was subjected to RF sputtering under the following conditions. A corresponding transparent thin film layer was formed. First, the tubular film is stretched on three rotating rolls provided in an inverted regular triangle shape, and this is placed in a sputtering chamber of the apparatus.
To face the F 2 _(target) (distance between the film 5
0 mm). Then, the sputtering chamber was evacuated and replaced with argon gas, and the degree of vacuum was 10 ^-1 to 10 ^-2 P
a. Then, the roll was rotated at a speed of 1 m / min, an RF voltage was applied at an output of 6.4 W / cm ² for 20 minutes, and the sputtering was stopped. When the obtained film was taken out and the surface was viewed, the transparent CaF ₂ film was strongly adhered with high gloss. The adhesion was determined by stretching the film over two rubber rolls having a diameter of 20 mm and continuously rotating the film at 100 rpm at a speed of 60 rpm for 10 days to confirm whether or not the layer was peeled off. Of course, no change was observed in the gloss. Film thickness, coefficient of static friction, surface roughness and surface tension (contact angle) of the obtained layer
Are summarized in Table 1 together with Reference Example 6.

[0048]

[Table 1]

Example 2 The same conditions as in Example 1 except that a flat MgF ₂ was used as a target on the surface of the elastic layer of the semiconductive tsPI endless tubular film having a rubber elastic layer obtained in Reference Example 7 RF sputtering. Take out the obtained film, and see the transparent Mg
F ₂ film with a high gloss, were firmly adhered.
Note that this adhesion is the result of a test performed in the same manner as in Example 1 and confirmed. Of course, no change was observed in the gloss. The film thickness, static friction coefficient, surface roughness, and surface tension (contact angle) of the obtained layer are summarized in Table 1 together with Reference Example 7.

Example 3 The same conditions as in Example 1 were used except that a flat BaF ₂ was used as a target on the surface of the elastic layer of the semiconductive PAI endless tubular film having a rubber elastic layer obtained in Reference Example 8. RF sputtering. Take out the obtained film, and see the transparent BaF
_{The two} films had high gloss and were firmly adhered. still,
This adhesion is the result of a test performed in the same manner as in Example 1 and confirmed. Of course, no change was observed in the gloss. The film thickness, static friction coefficient, surface roughness and surface tension (contact angle) of the obtained layer are summarized in Table 1 together with Reference Example 8.

Example 4 (Usage Example Corresponding to Claim 12) The endless tubular film (semiconductive tsPI endless tubular film + silicone rubber elastic layer + MgF ₂ transparent thin film layer) obtained in Example 2 is cut to a width of 300 mm. This is shown in FIG.
Attached to the intermediate transfer and heat fixing belt 9 of the color toner copying machine, a copy test was performed under the following conditions, and the surface gloss (gloss) was
The coefficient of static friction and the change over time in the driving torque and image quality of the belt with respect to this were checked. The results are shown in Table 2. The gloss and image quality were obtained by comparing the difference (solid density, ghost, white spots) with the 1000th sheet by visual observation, and the driving torque was determined by the belt 11a.
A torque meter was attached to the rotating roll 10 on which was stretched, and the current value was measured and compared. ◎ Copied manuscript: 40 mm wide and 150 long on B5 coated paper
solid image prepared in the order of black, yellow, red, and blue with a strip of mm. ◎ Temperature of the heating roller 11a: 230 ° C. (surface temperature of the belt is 200 ° C.) ◎ Number of copies: 1,000 to 100,000 sheets ◎ Copy speed: 25 sheets / min The test results are shown in Table 2.

[0052]

[Table 2]

(Comparative Example 1) The endless tubular film (semiconductive tsPI endless tubular film + silicone rubber elastic layer) obtained in Reference Example 7 was cut into a width of 300 mm, and this was cut into FIG.
Intermediate transfer and heat fixing belt 9 of the four-color toner copying machine shown in FIG.
, And a copy test was performed under the same conditions as in Example 4. Similarly, the surface gloss, the coefficient of static friction, and the change over time in the driving torque and image quality of the belt with respect to this were checked. The results are shown in Table 2.

As is clear from Table 2, in comparison with Example 4, in Comparative Example 1, gloss was already lacking from the beginning, and 5
Coloring starts around the tenth sheet, and the image quality is worsened accordingly. This is presumably because corona charging caused a change in toner transfer and transferability due to surface deterioration.
Further, the static friction coefficient and the driving torque do not change with time in both cases, but it is well understood that the difference between the inherent static friction and the driving torque due to the static friction coefficient appears.

[0055]

As described above, the present invention has the following advantages.

First, since the abrasion resistance of the surface of the polyimide film was remarkably improved, the service life (durability) for various continuous uses was greatly improved.

When used in a charged state, surface deterioration (blood adhesion, change in surface tension, etc.) caused by corona discharge (electrochemical action) did not occur, and the durability was greatly improved.

When rotating while contacting an object in a belt state, the motor can be rotated very smoothly with low driving torque without abnormal rotation such as rotational blur (this is because the static friction on the surface is small). Because of that.)

In a film having fine irregularities provided in order to increase the contact area with a certain thing, the shape of the film is not changed at all by the formation of the transparent thin film layer of the alkaline earth fluoride. lost. Therefore, there is no difference in the function and effect based on this before and after use, and production and quality control are facilitated.

Various uses have become even more effective. For example, the use as a belt member for paper conveyance or intermediate transfer and heat fixing in a color copying machine has been performed for a long period of time due to remarkable improvements in various points including non-deterioration as well as abrasion resistance of the surface. It is now possible to copy in stable high-quality colors over a wide range.

[Brief description of the drawings]

FIG. 1 is a main schematic diagram of a color copying machine using a paper transport belt.

FIG. 2 is a main schematic diagram of a color copying machine using a belt for intermediate transfer and heat fixing.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 paper transport belt 3, 12 (for 4 colors) photosensitive drum 4, 8, 13 corotron charger 5, 16 paper 6, 17 static eliminator 7, 11 heat fixing device 9 intermediate transfer and heat fixing belt

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/04 C08K 3/04 4F071 C08L 79/08 C08L 79/08 Z 4F100 C23C 14/06 C23C 14/06 G 4J002 G03G 15/16 G03G 15/16 4K029 15/20 101 15/20 101 15/24 15/24 F term (reference) 2H032 BA09 BA18 2H033 BA11 BE09 2H078 AA13 AA21 CC06 3F049 BA11 LA02 LB03 4F006 AA39 AB19 AB39 AB39 BA11 CA01 DA01 DA04 4F071 AA60 AB03 AF37 AH16 AH17 BA02 BB02 BC01 4F100 AA06A AA37C AD11C AK17B AK49C AK52B AN00B AN02B BA03 BA07 BA10A BA10C EH66A GB90 JA20 JB13C JB16C JG01C JG04C JK07B JK09 JK16 JM02A JN01A YY00C 4J002 CM041 DA036 FD116 FD130 FD200 GM01 4K029 AA11 AA25 AA27 BA42 BC08 BD03 CA05 DC05 EA01

Claims (12)

[Claims] 1. A durable polyimide film, wherein a transparent thin film layer made of an alkaline earth fluoride salt is coated on the surface of the polyimide film. 2. A durable polyimide film, wherein said transparent thin film layer is coated with a polyimide film having a surface rubber elastic layer. 3. The durable polyimide film according to claim 1, wherein the surface rubber elastic layer is formed of one of silicone rubber and fluorine rubber. 4. A durable polyimide film according to claim 1, wherein said alkaline earth fluoride salt is any of barium fluoride, calcium fluoride and magnesium fluoride. 5. The transparent thin film layer has a thickness of 100 to 200.
The durable polyimide film according to any one of claims 1 to 4, wherein the angle is 0 °. 6. The durable polyimide film according to claim 1, wherein said polyimide film is a semiconductive polyimide film provided by containing conductive carbon black. 7. The durable polyimide film according to claim 6, which is a tubular film made of semiconductive polyamide-imide having a volume resistance value of 10 ¹⁰ to 10 ¹⁴ Ω · cm. 8. The durable polyimide film according to claim 6, which is a tubular film made of a semiconductive thermoplastic polyimide having a volume resistance value of 10 ¹⁰ to 10 ¹⁴ Ω · cm. 9. A volume resistivity of 10 ⁷ to 10 ¹¹ Ω · cm,
7. A durable polyimide film according to claim 6, which is a tubular film made of semiconductive thermosetting polyimide having a surface resistance value of 10 ⁸ to 10 ¹² Ω / □ and a difference between the two within one digit. . 10. A transparent thin film layer is formed by sputtering the alkaline earth fluoride as a target on the surface of a polyimide film. A method for producing a durable polyimide film. 11. The use of the durable polyimide film according to claim 7 as a paper transport belt for a toner copying machine. 12. Use of the durable polyimide film according to claim 9 as a belt for intermediate transfer and heat fixing of a toner copying machine.