JP2007111628A - Coating apparatus, and method of manufacturing endless belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating apparatus which enables efficient supply of high viscosity coating liquid to a coating bath without changing a liquid state in coating the relatively high viscosity liquid dispersed with a pigment on the surface of a cylindrical core body, and a method of manufacturing endless belt using the same. <P>SOLUTION: The coating apparatus has a coating bath for storing the coating liquid, a coating liquid supply means for supplying the coating liquid to the coating bath, and a holding means for movably holding the cylindrical core body with its axial direction vertical, wherein the cylindrical core body relatively rises with respect to the liquid surface from the coating liquid stored in the coating bath, thereby forming a coating film on the surface of the cylindrical body. The coating supply means has a liquid mixing part joining first and second liquid supply passages to form a mixing channel. The coating liquid, which is formed by mixing a resin solution with a pigment dispersion liquid separately injected from the first and second supply passages in the mixing channel, is directly supplied into the coating bath. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coating apparatus capable of uniformly coating a highly viscous coating liquid on the surface of a cylindrical core and a method for producing an endless belt using the coating apparatus. In particular, the present invention relates to a coating apparatus that can be preferably applied when manufacturing belt members such as a photoreceptor, a transfer belt, and a fixing belt in an electrophotographic apparatus, and an endless belt obtained thereby.

  In an image forming apparatus using an electrophotographic process, a rotating body made of metal, plastic, or rubber is used for a photosensitive member, a charging unit, a transfer unit, and a fixing unit. For this reason, it may be preferable that these rotating bodies be deformable, and for this, a belt made of a plastic film having a small thickness is used. In this case, if the belt has a seam, a defect due to the seam occurs in the output image. Therefore, an endless belt without a seam is preferably used. Materials for the endless belt include polyimide resin, polyamideimide resin and polycarbonate resin in terms of strength, dimensional stability, heat resistance, etc. (hereinafter, polyimide is “PI”, polyamideimide is “PAI”, and polycarbonate is “PC”. Are sometimes used preferably).

  As a method for producing an endless belt, for example, a cylindrical core body whose axial direction is perpendicular to a coating liquid for film formation stored in an annular coating tank is passed through and applied to the surface of the cylindrical core body. There is a method of drawing a resin film from a cylindrical core after heating to form a resin film (see, for example, Patent Document 1).

  In this method, the same cylindrical core body is used consistently from the coating film forming process to the film forming process for heating reaction, but there is an advantage that less coating liquid is required for coating than the dip coating method. is there.

  However, a film-forming resin solution such as a PI resin precursor solution has a very high viscosity at room temperature, and a special dispersion method is required to disperse a pigment such as carbon black as required (for example, , Refer to Patent Document 2) and the like. In addition, when a film is prepared with a coating liquid with insufficient dispersion, problems such as unstable resistance are likely to occur.

  On the other hand, in recent years, there is a method in which a solution is caused to flow through a fine channel called a microreactor or a micromixer to cause reaction or mixing of the solution (for example, see Patent Document 3). In this method, a plurality of solutions can be mixed by introducing a plurality of fluids into the mixing space through a plurality of microchannels. Therefore, by this method, there is a possibility that the resin solution having a high viscosity and the carbon black dispersion can be mixed.

However, even if a coating liquid in which carbon black is dispersed by the above method is obtained, the state of the coating liquid is unstable, so that carbon black agglomerates and settles before being poured into the coating tank after preparation of the coating liquid. Therefore, it was impossible to use the liquid without changing the liquid state from the preparation of the coating liquid by the micromixer to the coating.
JP 2004-275824 A JP 2004-279531 A JP 2003-210959A

The object of the present invention is to solve the above-mentioned problems of the prior art.
That is, the present invention efficiently supplies a high-viscosity coating liquid to a coating tank without changing the liquid state when applying a relatively high-viscosity coating liquid in which a pigment is dispersed on the surface of a cylindrical core. It is an object of the present invention to provide a coating apparatus that can perform the process and a method of manufacturing an endless belt using the same.

The above-mentioned subject is achieved by the following present invention. That is, the present invention
<1> A coating tank for storing the coating liquid, a coating liquid supply means for supplying the coating liquid to the coating tank, and a holding means for holding the cylindrical core body movably with its axial direction vertical, the cylinder A coating device that forms a coating film on the surface of a cylindrical core by raising the core relative to the liquid surface from the coating liquid stored in the coating tank,
The coating liquid supply means includes a liquid mixing unit that forms a mixing flow path by combining the first liquid supply path and the second liquid supply path, and separately from the first liquid supply path and the second liquid supply path. In the coating apparatus, a coating liquid obtained by mixing the injected resin solution and the pigment dispersion liquid in the mixing channel is directly supplied into the coating tank.

  As a coating liquid supply means, a micromixer (liquid mixing section) is provided, and the coating liquid is directly supplied from the micromixer to the coating tank, so that a highly viscous coating liquid with good pigment dispersibility is efficiently produced. In addition, it is possible to perform stable coating with minimal changes in liquid properties due to pigment aggregation and sedimentation.

<2> The coating tank is an annular coating tank having an annular sealing material at the bottom, and the cylindrical core body is passed through the annular coating tank while being inserted into the sealing material in a fitted state. It is a coating device as described in <1> which forms a coating film in this.

  In order to maintain the coating liquid stability during the coating, it is advantageous that the amount of liquid in the liquid storage part is small and the replacement rate of the coating liquid in continuous coating is higher. The configuration of the device is preferred.

<3> The coating apparatus according to <2>, wherein the liquid mixing unit is provided inside an outer peripheral portion of the annular coating tank.

  In order to supply the coating liquid produced by the micromixer (liquid mixing section) directly into the coating tank, it is advantageous that the micromixer is in the vicinity of the liquid storage section. By being incorporated in the unit, it is possible to save the space of the entire apparatus.

<4> An endless belt manufacturing method including a step of forming a coating film on a surface of a cylindrical core body by a coating apparatus, heating the coating film to form a resin film, and then removing the resin film from the cylindrical core body. And
It is a manufacturing method of an endless belt using the coating device according to any one of <1> to <3> as the coating device.

  According to the present invention, when applying a relatively high viscosity coating liquid in which a pigment is dispersed on the surface of a cylindrical core, the high viscosity coating liquid is efficiently supplied to the coating tank without changing the liquid state. Can be provided, and an endless belt manufacturing method using the same.

Hereinafter, the present invention will be described in detail.
<Coating device>
The coating apparatus of the present invention has a coating tank for storing the coating liquid, a coating liquid supply means for supplying the coating liquid to the coating tank, and an elevating means for moving the cylindrical core body with its axial direction vertical. A coating apparatus for forming a coating film on the surface of a cylindrical core by raising the cylindrical core relative to the liquid surface from the coating liquid stored in the coating tank, wherein the coating liquid supply means A liquid mixing unit that forms a mixing flow path by combining the first liquid supply path and the second liquid supply path, and a resin solution separately injected from the first liquid supply path and the second liquid supply path; A coating liquid obtained by mixing a pigment dispersion in the mixing channel is directly supplied into the coating tank.

  As described above, when preparing a coating liquid in which a pigment such as carbon black is dispersed using a resin solution having a relatively high viscosity (1 Pa · s or more), it is difficult to disperse carbon black. The dispersion state tends to vary from dispersion to dispersion. However, even if it is difficult to disperse a pigment such as carbon black in a resin solution having a high viscosity, it is not necessary to use a special disperser if only a solvent or a resin solution having a relatively low viscosity is dispersed. Is possible.

  Therefore, by preparing a pigment dispersion using only the above-mentioned solvent or a low-viscosity resin solution, and mixing this with a high-viscosity resin solution, a high-viscosity coating solution with good dispersibility can be obtained. it can. The mixing of the pigment dispersion and the resin solution may be performed, for example, by adding the resin solution while stirring the pigment dispersion, or by using the above-described micromixer.

  However, as a result of the study by the present inventors, even if the coating liquid is prepared as described above, the dispersion stability of the pigment in the coating liquid is not sufficient, and if the coating liquid is left for a certain period of time, pigment aggregation or sedimentation occurs. It was found that the dispersion state and the pigment concentration in the coating liquid changed. In this case, not only when the coating liquid left after preparation is stored in the coating tank, but also when adding the coating liquid in the middle of coating, the coating liquid immediately after the preparation of the coating liquid and at the time of actual coating The dispersion state is different, which greatly affects the stability of product characteristics such as the endless belt finally obtained and the maintenance of the yield rate.

  Therefore, in the present invention, a pigment is dispersed in advance in a solvent alone or a resin solution having a relatively low viscosity, and the pigment dispersion and the resin solution for forming a high-viscosity film are combined to provide a mixing channel. It was found that the above problem can be solved by directly injecting the coating liquid into the two narrow tubes forming the liquid and supplying it directly to the coating tank in the coating apparatus.

  That is, a liquid mixing unit configured as a micromixer is provided as a part of the coating liquid supply unit of the coating apparatus, and the coating liquid prepared in the liquid mixing unit using the pigment dispersion and the resin solution is directly By supplying it to the coating tank, not only a coating liquid with good dispersibility can be efficiently obtained, but also the coating liquid can be used for coating while maintaining the dispersibility. In particular, even in the follow-up liquid during coating, a coating liquid having the same dispersibility and concentration as the initial one is always added, so that a stable coated product and a film with stable characteristics can be obtained even in continuous coating. Can do.

  In addition, since the coating liquid can be used immediately after preparation, if the coating is performed for a short time, the liquid state is likely to change (for example, the liquid composition is likely to deteriorate, or the two liquids to be mixed are separated. It can be applied even if it is a coating liquid that is easy to precipitate or has a large specific gravity of the pigment and is very easy to settle. In particular, it is not preferable to store the dispersion in a tank or the like because the metal or metal oxide dispersed as a conductive substance in the coating liquid described later has a high specific gravity and the sedimentation is relatively fast. In addition, there is no problem if it is immediately supplied to the application tank and applied.

  In the present invention, the term “direct supply into the coating tank” means that the coating liquid that has passed through the mixing channel in the liquid mixing section described later is supplied to the coating tank as it is without being stored inside or outside the liquid mixing section. Specifically, it means that the coating liquid is supplied to the coating tank within a second after passing through the mixing channel.

  The coating apparatus of the present invention has a coating liquid supply means having a liquid mixing section as described later, and can be applied by raising the cylindrical core relative to the liquid surface from the coating liquid. There is no particular limitation. Therefore, the coating apparatus of the present invention may be provided with a coating tank used for normal dip coating, or may be provided with the following annular coating tank. Since a shorter residence time is more advantageous for the stability of the coating liquid, it is preferable that the coating apparatus includes an annular coating tank.

Hereinafter, a coating apparatus having an annular coating tank as an example of the coating apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of an example of a coating apparatus according to the present invention (including a cylindrical core coated in the drawing), and FIG. 2 is a view of the coating apparatus shown in FIG. . The annular coating tank 10 includes an outer peripheral part 7 and a liquid storage part 30, and in the figure, the first liquid supply path 22 and the second liquid supply path 24, both of which are thin tubes, are united inside the outer peripheral part 7. A liquid mixing unit (micromixer) 20 composed of a mixing channel 26 is incorporated.

  Then, the resin solution is supplied to the first liquid supply path 22 and the pigment dispersion liquid is supplied to the second liquid supply path 24, and they are merged and mixed in the mixing flow path 26 to become a coating liquid, and then the mixing flow path 26. The coating liquid 2 is supplied to the liquid storage unit 30 from the discharge port D on the liquid storage unit 30 side. Next, the cylindrical core body 1 passes through the stored coating liquid 2 from the lower side in the drawing and coating is performed. An annular sealing material 6 for preventing leakage of liquid is attached to the bottom of the annular coating tank 10, and the cylindrical core body 1 passes through the sealing material 6 in a fitted state. Is preferably elliptical. Reference numeral 5 denotes an annular body described later.

Both the inner diameters of the first liquid supply path 22 and the second liquid supply path 24 in the liquid mixing unit 20 are preferably in the range of 0.1 to 2 mm, and the first liquid supply path 22 through which a highly viscous resin solution is supplied. Are connected to the horizontal mixing channel 26 at point A at an angle of 20 to 90 °. On the other hand, the second liquid supply passage 24 to which the pigment dispersion is supplied is connected to the horizontal mixing passage 26 at point A at an angle of 20 to 90 °. As a result, at the point A, the first liquid supply path 22 and the second liquid supply path 24 are united to form the mixing flow path 26.
The length of the first liquid supply path 22 and the length of the second liquid supply path 24 are preferably in the range of 2 to 15 mm.

  The internal diameter of the mixing channel 26 is preferably in the range of 0.1 to 2 mm, and the length is preferably in the range of 5 to 20 mm. The mixing channel 26 may be linear as shown in FIG. 1, or may be a zigzag mixing channel 27 as shown in the enlarged sectional view of FIG. 4 in order to promote mixing.

As shown in FIG. 2, a large number of liquid mixing portions 20 composed of such thin tubes are provided radially on the outer peripheral portion 7 of the annular coating tank, and the intervals are evenly spaced from the viewpoint of uniform liquid supply. To preferred. In this case, the number of the liquid mixing units 20 is, for example, 24 if the interval is 15 °, 36 if the interval is 10 °, and 72 if the interval is 5 °. It is determined by the amount of liquid required.
In this embodiment, the branch of the thin tube of the liquid mixing unit 20 is perpendicular to the coating liquid surface. However, if there is no problem in space, the branch of the thin tube may be parallel to the liquid surface. .

  In the present embodiment, the configuration in which the liquid mixing unit 20 is provided inside the outer peripheral portion 7 of the annular coating tank 10 is shown. However, in the present invention, the liquid mixing unit 20 is not necessarily provided inside the coating tank such as the outer peripheral portion. It does not need to be provided and may be provided outside the coating tank. Alternatively, only the mixing channel 26 in the liquid mixing unit 20 may be provided inside the coating tank outer peripheral portion, and the first liquid supply path 22 and the second liquid supply path 24 may be provided outside the coating tank.

  The position at which the liquid mixing unit is provided in the present invention is not particularly limited as described above, but at least the discharge port D of the mixing flow channel 26 is provided in the vicinity of the bottom surface side of the liquid storage unit 30 such as additional liquid. In this case, it is preferable from the viewpoint of the mixing property to the entire coating liquid 2 and the like, and the aspect in which the entire liquid mixing unit 20 as shown in FIG. This is more preferable from the viewpoint of space.

Next, the coating liquid supply in the coating apparatus having the above configuration will be described.
A resin solution for forming a highly viscous film is supplied to the supply port B of the first liquid supply path 22, and a pigment dispersion is supplied to the supply port C of the second liquid supply path 24. However, these may be reversed.

The liquid supply may be performed by connecting a liquid supply pipe to each of the supply ports B and C of the plurality of liquid mixing units 20 and supplying a resin solution and a pigment dispersion liquid via a liquid feed pump. The supply ports B and the plurality of supply ports C are connected to form flow passages along the outer peripheral portion 7, and the resin solution and the pigment dispersion are respectively supplied to these flow passages through the flow passages. Alternatively, all of the first liquid supply path 22 and the second liquid supply path 24 may be supplied.
The circumferential flow path may be provided inside the annular coating tank or may be provided outside. The inner diameter of the flow passage is preferably in the range of 3 to 15 mm.

The pressure of the solution supplied to each supply port is preferably about 0.5 to 10 MPa. In this case, the supply pressure to the supply port B may be equal to the supply pressure to the supply port C, but the supply pressure to the supply port B (supply pressure of the pigment dispersion) P1 is applied to the supply port C. It is preferable to make the pressure higher than the supply pressure (resin solution supply pressure) P2 for uniform mixing.
Specifically, the supply pressure ratio P1 / P2 is preferably in the range of 1/1 to 5/1.

The liquid flow rate in the first liquid supply path 22 and the second liquid supply path 24 is preferably in the range of 0.3 to 15 ml per minute. As in the case of the supply pressure, the liquid flow rate F1 from the first liquid supply path 22 is preferably larger than the liquid flow rate F2 from the second liquid supply path 24.
Specifically, the liquid flow ratio F1 / F2 is preferably in the range of 1/1 to 5/1.

The discharge amount of the mixed liquid (coating liquid) that has passed through the mixing channel 26 from the discharge port D is in the range of 1 to 20 ml per minute per liquid mixing unit.
The characteristics of the discharged coating liquid are basically determined by the characteristics of the liquid supplied from the first liquid supply path and the second liquid supply path and the liquid flow rate, but the coating liquid produced by the liquid mixing unit 20 in the present invention is used. The number average particle diameter of the pigment in the liquid is preferably in the range of 20 to 1000 nm, the viscosity of the coating liquid is preferably 0.2 to 50 Pa · s, and the concentration of the coating liquid is preferably in the range of 10 to 25% by mass.

In addition, the number average particle diameter of a pigment can be measured using the dynamic light scattering type | mold measuring device PAR-III made from Otsuka Electronics. The measurement conditions are: clock rate: 100 μs, accumulate time: 10 times, correlate ch: 128, temperature: 20 ° C., solvent: N-methylpyrrolodon. The same applies to the following particle sizes.
The viscosity of the coating liquid is 25 ° C., 55 ° C. under conditions of 5 rpm using a conical plate type viscometer (manufactured by Toki Sangyo Co., Ltd., model RE80U) using a rotor: 3 ° × R14. It was measured under the measurement environment of% RH. The same applies to the following viscosities.

  The pigment dispersion used in the present invention is obtained by dispersing a pigment only in a solvent or a resin solution having a low viscosity. For this, a dispersant such as a surfactant may be used in combination. When the pigment is dispersed in the low viscosity resin solution, the concentration of the resin solution is arbitrary, but the mass ratio of the resin to the pigment is preferably about 1:10 to 1: 1.

  The dispersion of the pigment can be carried out by various methods used for ordinary coating preparation, for example, a method using a ball mill, a sand mill, a paint shaker or the like. The total concentration after dispersion is preferably as high as possible, and more preferably in the range of 5 to 30% by mass. The viscosity of the pigment dispersion is preferably in the range of 0.1 to 1 Pa · s.

  On the other hand, a resin solution having a viscosity higher than that of the pigment dispersion is usually used. The resin concentration is preferably in the range of 10 to 30% by mass, and the liquid viscosity is preferably in the range of 1 to 100 Pa · s. As the solvent, the same solvent as that usually used for the pigment dispersion is used, but the composition of the solvent of the pigment dispersion can be slightly different for the purpose of improving the pigment dispersibility.

  In the micromixer, the pigment dispersion and the film forming resin solution are supplied and mixed, and the pigment content in the mixed coating liquid is 15 to 35 parts by mass with respect to 100 parts by mass of the resin. A range of about is preferable.

Below, the other structure of the coating device of this invention is demonstrated easily using FIG. 1, FIG. In the following, an example using an annular body will be described.
As shown in FIG. 1, in this coating apparatus, an annular body 5 having a hole larger than the outer diameter of the cylindrical core body 1 is freely moved to the coating liquid surface in the coating liquid 2 filled in the liquid reservoir 30. The cylindrical core body 1 floated (installed) in a possible state and immersed in the coating liquid 2 is passed through the hole of the annular body 5 from the coating liquid side (from the lower side in the drawing), and then the cylindrical core body 1 is A coating film is formed on the surface of the cylindrical core body 1 by being raised relative to the liquid surface.

  In the present invention, the above-mentioned "form a coating film on the surface of the cylindrical core" means that the coating liquid is applied to the surface of the cylindrical core 1 and, if the surface has a layer, the surface of the layer. . Further, “relatively rising with respect to the liquid level” means a relative relationship with the coating liquid level, and includes the case of “stopping the cylindrical core and lowering the coating liquid level”.

  An annular sealing material 6 having a hole slightly smaller than the outer diameter of the cylindrical core body 1 is provided at the bottom of the annular coating tank 10 (application tank), and the cylindrical core body 1 is inserted through the center of the sealing material 6. The coating liquid 2 is stored in the annular coating tank 10. Thereby, the coating liquid 2 is prevented from leaking. As the sealing material 6, a flexible plate material such as polyethylene, silicone rubber, or fluororesin is used. Further, the annular body 5 is installed on the surface of the coating liquid 2 in a freely movable state.

As shown in FIG. 3, the cylindrical core body 1 is sequentially lifted up by a holding means (not shown) from the lower part to the upper part of the annular coating tank 10 in the drawing, and the coating material 4 is formed on the surface by inserting the sealing material 6. Is done. An intermediate body 1 </ b> A that can be fitted to the cylindrical core body 1 may be attached below the cylindrical core body 1. In addition, you may have a 1st moving means for moving the said holding means to an up-down direction, and / or a 2nd moving means to move the cyclic | annular application tank 10 to an up-down direction.
In the coating apparatus having such an annular coating tank, the annular coating tank 10 can be made smaller than a normal dip coating tank, so that there is an advantage that the required amount of the solution can be reduced.

  The annular body 5 is configured to float on the surface of the coating liquid, and any material can be used as long as it is not affected by the coating liquid 2. For example, the annular body 5 is selected from various metals and plastics. Moreover, in order to reduce weight so that it may float easily, for example, a hollow structure may be sufficient.

Although it does not restrict | limit especially as the cylindrical core 1, Metals, such as aluminum and stainless steel, the plastics which provided electroconductivity, etc. are used.
In addition, as a cylindrical core in this invention, a cylindrical thing is included as mentioned above.

<Method for producing endless belt>
Next, a method for manufacturing an endless belt using the coating apparatus of the present invention will be described.
The endless belt is manufactured by applying the coating liquid onto the surface of the cylindrical core body with the above-mentioned coating apparatus to form a coating film, heating the coating film to form a resin film, and then removing the resin film from the core body. The

  The cylindrical core is preferably a metal cylinder such as aluminum, stainless steel, nickel, copper, etc., and its length is 10 to 40% of the length of the target endless belt in order to secure a margin for the ineffective area generated at the end. Desirably long. The outer diameter of the cylindrical core body is adjusted to the diameter of the endless belt, and the wall thickness is set so that the strength as the core body can be maintained.

  In order to prevent the film from adhering to the surface of the cylindrical core, it is preferable to coat the surface of the core with a fluororesin or silicone resin, or to apply a release agent to the surface.

  Depending on the type of film-forming resin, there are solvent volatiles during heating and gas generated during reaction, and the resin film after heating may partially swell due to the gas. This is particularly noticeable when the film thickness exceeds 50 μm in the PI resin film.

  In order to prevent the swelling, it is preferable that the surface of the cylindrical core body is roughened to an arithmetic average roughness Ra of about 0.2 to 2 μm as disclosed in JP-A-2002-160239. Examples of the roughening method include blasting, cutting, sandpaper peeling, and the like. Thereby, the gas generated from the PI resin can go out through a slight gap formed between the core body and the PI resin film, and does not swell.

The film-forming resin is not particularly limited, but the above-described PI resin, PAI resin, and PC resin are preferably used from the viewpoints of film strength, shape stability, and the like.
As the PI precursor or PAI resin, various known ones can be used. These solvents are aprotic polar solvents such as N-methylpyrrolidone (NMP), N, N-dimethylacetamide (DMAC), and acetamide, and have low volatility at room temperature. In addition, although the density | concentration of a coating liquid used for application | coating, a viscosity, etc. are selected suitably, the solid content concentration of a preferable solution is 10-40 mass%, and a viscosity is 1-100 Pa.s.

  The PC resin is described in JP-B-2-57300 and JP-B-5-3584, which is more soluble in solvents than general-purpose bisphenol A-type resins. The copolymer thereof, the alkyl-modified product described in JP-B-8-20739, the phenyl-substituted product described in JP-A-60-184251, and the like are preferable. Examples of these solvents include cyclohexanone, dioxane, tetrahydrofuran, toluene, xylene, monochlorobenzene, etc. The preferable solid content concentration of the coating liquid used for coating is 10 to 40% by mass, and the viscosity is 1 to 100 Pa · s. .

When an endless belt is used as a transfer belt or a charging belt, it is necessary to disperse a pigment made of a conductive material in the coating liquid to make the film semiconductive. Examples of the conductive material include carbon-based materials such as carbon black, carbon fiber, carbon nanotube, and graphite, metals or alloys such as copper, silver, and aluminum, tin oxide, indium oxide, antimony oxide, SnO ₂ —In ₂ O. ₃ Conductive metal oxides such as complex oxides.

Although it is difficult to disperse these in a resin solution having a relatively high viscosity of 1 to 100 Pa · s, a resin solution having a relatively low viscosity of less than 1 Pa · s is generally used for ball mills, sand mills, dyno mills, and the like. Even a disperser can be easily dispersed. Therefore, a pigment dispersion is prepared by dispersing the pigment in a low-viscosity solvent or resin solution, and the preferred coating liquid is prepared by using this and the high-viscosity resin solution by the liquid mixing unit in the coating apparatus of the present invention. Obtainable.
The content of the pigment with respect to 100 parts by mass of the resin after mixing is preferably about 15 to 35 parts by mass.

  The cylindrical core body 1 is inserted into the annular coating tank 10 in FIG. 1, and the coating liquid is filled in the liquid storage unit 30 through the liquid mixing unit 20 using the pigment dispersion and the resin solution prepared as described above. The height of the coating liquid 2 is preferably about 2 to 10 cm.

  Next, as shown in FIG. 3, another cylindrical core body 1 </ b> A or an intermediate body that may be shorter than the core body is attached to the lower part of the cylindrical core body 1, and the cylindrical core body 1 is raised from the bottom to the top. A film 4 is formed and application is performed. The supply of the coating liquid may be stopped during the application or may continue to be supplied.

  In this case, since the viscosity of the coating liquid 2 is as high as 1 to 100 Pa · s, the film thickness of the coating film 4 is usually too thick. Therefore, it is preferable that an annular body 5 having a circular hole larger than the outer diameter of the cylindrical core body 1 is installed on the solution 2 and the cylindrical core body 1 is pulled up and applied through the circular hole as shown in the figure. An arm or a leg may be attached to the annular body 5 in order to support the annular body when stopped.

  At the time of application, the film thickness of the coating film 4 is determined by the gap between the outer diameter of the cylindrical core body 1 and the inner diameter of the circular hole. Therefore, the inner diameter of the circular hole is adjusted by a desired film thickness. The inner wall surface of the annular body 5 may be stepped or curved as well as a linear inclined surface as shown in FIG. 3 as long as the lower part immersed in the solution is wide and the upper part is narrow. In order to process the roundness high, there may be a portion parallel to the cylindrical core body 1 at the upper part of the inner wall surface of the circular hole.

The pulling speed of the cylindrical core body 1 at the time of application is preferably about 0.1 to 1.5 m / min. When the cylindrical core body 1 is pulled up, the annular body 5 is installed in a floating state, so that it is lifted by the frictional resistance due to the viscosity of the solution. Since the annular body 5 is freely movable, the annular body 5 moves so that the frictional resistance between the cylindrical core body 1 and the annular body 5 is constant in the circumferential direction, that is, the gap is uniform. A coating film 4 having a uniform film thickness is formed. Thus, since a film thickness is controlled by the annular body 5, a highly viscous solution can be applied with a uniform film thickness.
The thickness of the coating film is preferably in the range of 100 to 800 μm.

  After coating, the cylindrical core body 1 is put into a heat drying apparatus, and the solvent is dried. When the coating film drips during drying, the cylindrical core body is leveled and dried while rotating. The rotation speed is preferably about 1 to 60 rpm.

The heating conditions are preferably 90 to 170 ° C. and 20 to 60 minutes. At that time, the higher the temperature, the shorter the heating time, and the temperature may be raised stepwise or at a constant rate.
When the film forming resin is a PAI resin or PC resin, the film can be obtained only by drying the solvent.

In the case where the coating solution is a solution containing a PI precursor, if the solvent is removed too much from the coating film, the coating film does not yet maintain strength, and thus cracking is likely to occur. Therefore, it is preferable to leave the solvent to some extent (15 to 45% by mass in the PI precursor film).
Thereafter, a PI resin film is formed by heating the PI precursor film at 250 to 450 ° C., preferably around 300 to 350 ° C., for 20 to 60 minutes to cause a condensation reaction. At that time, the temperature may be increased stepwise. In this step, since the film is fixed, the core body may be oriented in any direction, and may not be rotated during heating.

  After cooling, the formed film is peeled from the cylindrical core to obtain an endless belt. The endless belt may be further subjected to drilling or ribbing as necessary. A preferred endless belt has a thickness of about 30 to 150 μm.

  In the endless belt manufacturing method of the present invention, the pigment dispersion is dispersed directly into the coating tank while the pigment dispersion and the resin solution are mixed with a micromixer using a thin tube, so that the pigment is dispersed in the high-viscosity resin solution. There is no need to do it. In addition, when an annular coating tank is used, the coating liquid mixed in the narrow tube is immediately consumed for coating, so that it is not necessary to manage the stability of the coating liquid against aggregation and sedimentation. On the other hand, since the dispersion before being injected into the narrow tube has a low viscosity, it is easy to stir. If sedimentation is eliminated, even if there is agglomeration, it is re-dispersed in the narrow tube, and thus management is easy. In addition, the solution placed in the coating tank is uniform without stirring, and the film thickness and resistance value are uniform by passing through a cylindrical core body with the axial direction vertical and applying to the core body surface. Endless belts can be manufactured.

Hereinafter, the present invention will be specifically described by way of examples.
Example 1
A PI precursor solution (trade name: U Varnish A, manufactured by Ube Industries, Ltd., solid content concentration: 18% by mass, viscosity: 50 Pa · s) was prepared as a resin solution for film formation.
On the other hand, a PI precursor solution (trade name: U varnish A, manufactured by Ube Industries, Ltd., solid content concentration: 18% by mass, viscosity: 5 Pa · s) is also prepared for the pigment dispersion, and this is diluted with DMAC. When the solid content concentration was 8% by mass, the viscosity was 0.4 Pa · s. Carbon black (trade name: Special Black 4, manufactured by Degussa Huls Co., Ltd.) is mixed with resin three times as much as the solid content, and a surfactant (trade name: Disparon LS009, manufactured by Enomoto Kasei Co., Ltd.) is added as a solid content. 0.5% of the resin content was added by mass ratio, and then dispersed for 2 hours with a Dynomill disperser (manufactured by Shinmaru Enterprise, KDL type) to obtain a pigment dispersion. The viscosity of this pigment dispersion was 0.8 Pa · s, and the number average particle diameter of carbon black was 500 nm.

  On the other hand, a hole with an inner diameter of 386 mm is formed in the bottom surface of the annular coating tank 10 having the liquid reservoir 30 having an inner diameter of 500 mm and an inner height of 80 mm as shown in FIG. An annular sealing material 6 made of ultrahigh molecular weight polyethylene resin having a thickness of 0.5 mm was attached.

  Further, the outer peripheral portion 7 having a width of 16 mm of the annular coating tank 10 has a first liquid supply path 22 having an inner diameter of 1.0 mm and a length of 4 mm, and a second liquid supply having an inner diameter of 0.5 mm and a length of 8 mm. The liquid mixing unit 20 that forms a mixing channel 26 with an inner diameter of 0.8 mm and a length of 10 mm is formed 20 mm from the bottom of the liquid storage unit. The position was set to be the discharge port D. It should be noted that 36 liquid mixing portions 20 were installed radially along the entire circumference of the outer peripheral portion 7 at intervals of 10 °.

  Further, although not shown, a flow passage having an inner diameter of 8 mm is provided in the liquid supply port B of the first liquid supply passage, and a flow passage having an inner diameter of 5 mm is provided in the liquid supply port C of the second liquid supply passage. Provided four supply ports in the circumferential direction so that the solution could be supplied from the outside.

  As the annular body 5, an aluminum body having an outer diameter of 420 mm, an inner diameter of 367.1 mm at the smallest part of the circular hole, and a height of 50 mm was prepared. The inner wall was linearly inclined, and the inclination angle with respect to the vertical line was 7 °. The upper end was formed with a 2 mm portion parallel to the core.

  An aluminum cylinder having an outer diameter of 366 mm, a wall thickness of 10 mm, and a length of 450 mm was prepared, and the surface was roughened to an arithmetic average roughness Ra of 1.0 μm by blasting with spherical alumina particles. A silicone release agent (trade name: Sepacoat, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface of the cylinder to form a cylindrical core.

  After the cylindrical core body 1 was passed through the center of the annular coating tank 10 and the annular body 5 was disposed, the solution was supplied using two MONO pumps (NE type, manufactured by Hyojin Equipment Co., Ltd.). Specifically, the resin solution is supplied from four supply ports to the flow passage connected to the liquid supply port B, and the pigment dispersion is supplied from four supply ports to the flow passage connected to the liquid supply port C. did. At this time, the resin solution has a pressure of about 3 MPa and a total flow rate of 90.7 ml / min, and the pigment dispersion has a pressure of about 4 MPa and a total flow rate of 26.0 ml / min. Injected into.

  Thereby, the coating liquid in which carbon black was mixed at a ratio of 28 parts by mass with respect to 100 parts by mass of the resin solid content was discharged from the discharge port D at a total of about 117 ml / min. In about 30 minutes, since the height of the coating liquid 2 became 5 cm, the injection of each solution was stopped. In addition, the viscosity of the coating liquid 2 in the liquid storage part 30 of the annular coating tank 10 was about 25 Pa · s.

  Next, another cylindrical core body having the same shape was placed under the cylindrical core body 1 and pushed up at 0.8 m / min for application. At that time, the annular body 5 was lifted by about 20 mm. Thereby, the PI precursor coating film 4 having a wet film thickness of about 500 μm was formed on the surface of the cylindrical core body 1.

After coating, a stainless steel shaft having a diameter of 20 mm is passed through the center of the cylindrical core body 1, placed on a turntable and leveled, and heated at 80 ° C. for 20 minutes and at 130 ° C. for 30 minutes while rotating at 6 rpm. The body coating was dried. As a result, a PI precursor film having a thickness of about 150 μm was obtained.
Next, the cylindrical core body 1 was made vertical, the shaft was removed, and it was placed on a table, and placed in a heating device, and heated and reacted at 200 ° C. for 30 minutes and 320 ° C. for 30 minutes to form a PI resin film.

  After cooling to room temperature, the film was extracted from the core while blowing air between the cylindrical core and the film to obtain an endless belt. The film thickness of the endless belt was 75 μm and uniform. The endless belt was cut from each end by about 35 mm to obtain an endless belt having a length of 360 mm.

  On the other hand, the coating solution was injected into the liquid storage part 10 of the annular coating tank 10 where the first coating was applied over the course of about 4 minutes in the same manner as described above, and the second coating was performed in the same manner. . This operation was repeated to apply a total of 100 coatings to obtain 100 endless belts.

The appearance of the 100 endless belts obtained was visually observed for every 10 in the coating order, and it was confirmed that there was no foreign matter adhering or coating unevenness, but there was no problem with all endless belts.
Further, for each of the obtained endless belts, the volume resistivity of 90 points in total of 5 points in the width direction and 18 points in the peripheral direction was measured for every 10 pieces in the coating order, and about 10 ¹⁰ Ωcm at any measurement position. It was found that it has uniform semiconductivity and can be used as an electrophotographic transfer belt. The volume resistivity was measured using a HI probe manufactured by Mitsubishi Yuka Co., Ltd., and 100 V was applied to the electrode at 24 ° C. and 50% RH according to JIS K6911, and after 30 seconds. The value obtained from the current value.

(Comparative Example 1)
90.7 parts by mass of the resin solution in Example 1 and 26 parts by mass of the pigment dispersion were prepared, and the resin solution was gradually added to and mixed with stirring the pigment dispersion in a container. In order to prepare a coating liquid having the same characteristics, it was necessary to disperse with a counter collision type disperser (PY type jet mill manufactured by Genus).

  As the coating apparatus, as shown in the configuration cross-sectional view of FIG. 5, in the coating apparatus shown in FIG. 1, the liquid supply means is supplied from the supply tank 40 to the liquid reservoir 30 of the annular coating tank 10 through the supply pipe 42. The same thing was used except having used it. The coating liquid supply rate from the supply pipe 42 was about 117 ml / min.

  The prepared coating liquid 2 was put in a supply tank 40, and the coating liquid was supplied to the liquid storage unit 30 in the same manner over about 30 minutes by a pump through a supply pipe 42, and the first application was performed in the same manner. . Next, a reduced amount of coating solution was injected from the supply tank 40 over about 4 minutes, and the second coating was performed in the same manner. This operation was repeated to apply a total of 100 coatings. These coating films were dried and heated in the same manner as in Example 1 to obtain 100 endless belts.

  For these endless belts, the appearance and volume resistivity were measured in the same manner as in Example 1. As a result, an equivalent endless belt could be obtained. However, it has the disadvantage of requiring a lot of man-hours.

  From this result, even when continuously applied by using the coating apparatus of the present invention, it is possible to perform coating with the same liquid characteristics, and to always stably obtain a uniform endless belt. You can see that

It is schematic structure sectional drawing which shows an example of the coating device of this invention. It is the figure which looked at the coating device of the present invention from the coating direction. It is schematic structure sectional drawing which shows the state of the coating device of this invention during application | coating. It is an expanded sectional view which shows the other aspect of a liquid mixing part. It is schematic structure sectional drawing of the coating device used for the comparison.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A Cylindrical core body 2 Coating liquid 4 Coating film 5 Ring body 6 Sealing material 7 Outer peripheral part 10 Annular application tank 20 Liquid mixing part 22 1st liquid supply pipe 24 2nd liquid supply pipe 26, 27 Mixing flow path 30 Liquid storage Section 40 Supply tank 42 Supply pipe

Claims (4)

A coating tank for storing the coating liquid, a coating liquid supply means for supplying the coating liquid to the coating tank, and a holding means for holding the cylindrical core body so that the cylindrical core body can be moved vertically. A coating apparatus that forms a coating film on the surface of the cylindrical core body by raising the liquid surface relative to the liquid surface stored in the coating tank,
The coating liquid supply means includes a liquid mixing unit that forms a mixing flow path by combining the first liquid supply path and the second liquid supply path, and separately from the first liquid supply path and the second liquid supply path. A coating apparatus, wherein a coating liquid obtained by mixing an injected resin solution and a pigment dispersion liquid in the mixing flow path is directly supplied into the coating tank.   The coating tank is an annular coating tank having an annular sealing material at the bottom, and a cylindrical core is passed through the annular coating tank while being inserted into the sealing material in a fitted state, and a coating film is formed on the surface of the cylindrical core. The coating apparatus according to claim 1, wherein the coating apparatus is formed.   The coating apparatus according to claim 2, wherein the liquid mixing unit is provided inside an outer peripheral portion of the annular coating tank. A method for producing an endless belt including a step of forming a coating film on a surface of a cylindrical core body by a coating apparatus, heating the coating film to form a resin film, and then removing the resin film from the cylindrical core body,
The manufacturing method of the endless belt characterized by using the coating device of any one of Claims 1-3 as said coating device.

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