JP2009078268A - Coating method and coating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method and a coating apparatus, which enable coating with a uniform film thickness even when a highly viscous coating liquid is used and the film thickness is relatively large. <P>SOLUTION: The coating method comprises coating the surface of a center core 1 with a coating liquid 2. The coating method and the coating apparatus are characterized by installing beforehand a cyclic body 5 in a freely movable state provided with a hole 6 larger than the external diameter of the cross section of the center core 1 in the coating liquid 2 filled in a cyclic coating tank 7, detecting the position of the cyclic body 5 keeping a desired height so as to prevent the bottom surface of the cyclic body 5 from leaving from the liquid surface of the coating liquid 2 while the cyclic body 5 being uplifted from the liquid surface of the coating liquid 2 because of the center core 1 caused to go through the hole 6 of the cyclic body 5, controlling to reduce the ascent rate of the center core 1 compared with that upon initiation of coating, and ascending the center core 1 relatively from the coating liquid 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coating method, a coating apparatus, and an endless belt obtained by coating a coating liquid having a high viscosity on the surface of a core to form a relatively thick film. In particular, the present invention relates to a coating method and a coating apparatus that can be preferably applied when manufacturing rolls or belt members such as photoreceptors, fixing rolls, charging rolls, transfer rolls, transfer belts, and fixing belts in electrophotographic apparatuses.

  In an electrophotographic apparatus, a rotating body made of metal, various plastics, or rubber is used for a photoreceptor, a charged body, a transfer body, a fixing body, and the like. In order to reduce the size or increase the performance of the apparatus, it is sometimes preferable that the fixing rotating body is deformable as described in JP-A-8-262903 and JP-A-11-13376, for example. A thin resin belt is used. In this case, if there is a seam in the belt, a defect due to the seam occurs in the output image. Therefore, an endless belt without a seam is preferable. As the material, polyimide (hereinafter abbreviated as PI) resin is particularly preferable in terms of strength, dimensional stability, heat resistance, and the like.

  In order to produce an endless belt made of PI resin, for example, as described in JP-A-57-74131, a centrifugal molding method in which a PI precursor solution is applied to the inner surface of a cylindrical body and dried while rotating, As described in JP-A-62-19437, there has been an inner surface coating method in which a PI precursor solution is developed on the inner surface of a cylindrical body. However, in the method of forming a film on these inner surfaces, when the PI precursor is heated and reacted, it is necessary to remove the coating from the cylindrical body and place it on the outer mold, which increases the number of steps.

  As another method for producing an endless belt, for example, as described in JP-A-61-273919, the PI precursor solution is applied to the surface of the core body by a dip coating method, dried, heated, There is also a method of peeling the PI resin film from the core. This method is advantageous because it does not require man-hours for mounting on the outer mold. However, when the PI precursor solution is applied to the surface of the core by the dip coating method, generally, the PI precursor solution has a very high viscosity, so that the coating amount increases and the film thickness becomes too thick. There's a problem.

  Therefore, for example, as disclosed in JP-A-6-23770 and JP-A-7-24859, after a coating liquid containing a resin or a precursor thereof is thickly attached to the surface of the core, a predetermined amount is obtained. There was also a method of scraping off excess coating liquid by passing through an outer mold having an inner diameter of the gap. However, there is a disadvantage that the number of work processes increases.

  In addition, the coating liquid containing the PI precursor can be diluted and dip-coated so that the film thickness does not become too thick, but the dripping at the upper end of the coating increases and the uniformity of the film thickness is greatly impaired. There was a problem.

On the other hand, some photoreceptors, fixing rolls, charging rolls, and transfer rolls have a functional film formed on the surface of a rotating body. As a functional coating, in the case of a fixing roll, a non-adhesive coating that adjusts toner fixability and releasability, and in the case of a charging roll, the discharge characteristics to the photoreceptor, charging properties, charge leakage, etc. are adjusted. In the case of a semiconductive film, a transfer roll, a film that adjusts conductivity, nip, etc., and in the case of a photoreceptor, there are a photosensitive layer or a protective layer. Such a coating is generally desired to have a thickness of 10 to 100 μm. However, when the coating is formed by a dip coating method, there is still a problem that dripping at the upper end of the coating is increased.
JP-A-8-262903 Japanese Patent Application Laid-Open No. 11-133776 JP-A-57-74131 Japanese Patent Laid-Open No. 62-19437 Japanese Patent Laid-Open No. 61-273919 JP-A-6-23770 JP-A-7-24859

An object of the present invention is to solve the conventional problems and achieve the following objects. That is, an object of the present invention is to provide a coating method and a coating apparatus that can apply a film thickness uniformly even when the film thickness is relatively thick using, for example, a coating solution having a high viscosity. .
Further, by using this coating method and coating device, a relatively thick film charge transport layer can be uniformly coated on a support for an electrophotographic photosensitive member, or by using this coating method, a fixing roll, a charging roll Another object is to uniformly coat the functional film of the transfer roll.

The above problem is solved by the following means. That is, the present invention
(1) An application method for applying a coating liquid to the surface of a core body,
After installing the annular body provided with a hole larger than the outer diameter of the cross-section of the core body in a freely movable state in the coating liquid filled in the annular coating tank,
The annular body is lifted from the coating liquid surface through the core body into the hole of the annular body, and the annular body has a desired height so that the bottom surface of the annular body does not leave the coating liquid surface. An application method, wherein the position is detected and control is performed to reduce the rising speed of the core from that at the start of application, and the core is relatively raised from the coating liquid.

  (2) The coating method according to (1), wherein a sinking prevention member for preventing sinking of the annular body into the coating liquid is provided in the annular body or the annular coating tank.

(3) After installing the annular body provided with a circular hole larger than the outer diameter of the cross-section of the core body in a freely movable state in the coating liquid filled in the annular coating tank,
An application method for applying the coating liquid onto the surface of the core body by relatively raising the core body from the coating liquid through the core body in the hole of the annular body,
The core body is provided with an interval adjusting member at the distal end in the ascending direction so that the outer diameter of the distal end portion is larger than the outer diameter of the core body and less than the minimum diameter of the hole of the annular body. A coating method, wherein a gap between the core and the annular body is uniformly matched when the core is raised.

(4) A coating device for applying a coating liquid to the surface of the core body,
An annular coating tank for storing the coating liquid;
While providing a hole larger than the outer diameter of the core section, an annular body installed in the coating liquid in a freely movable state,
Elevating means for relatively raising the core body from the coating liquid through the core body in the hole of the annular body,
Detecting means for detecting the height of the annular body;
Based on the signal from the detection means, the core body is lifted so that the annular body is lifted from the coating surface and the bottom surface of the annular body is at a desired height so as not to be detached from the coating surface. Control means for adjusting the amount to be less than at the start of application,
A coating apparatus comprising:

(5) A coating device for coating a coating liquid on the surface of a core body,
An annular coating tank for filling the coating solution;
While providing a hole larger than the outer diameter of the core section, an annular body installed in the coating liquid in a freely movable state,
Elevating means for relatively raising the core body from the coating liquid through the core body in the hole of the annular body,
With
The core body is provided with a spacing adjustment member at the leading end in the ascending direction so that the outer diameter of the leading edge is larger than the outer diameter of the core body and less than the minimum diameter of the hole of the annular body. A coating apparatus characterized in that a gap between the core body and the annular body is uniformly matched when the core body is raised.

  (6) The coating apparatus according to (5), wherein the annular body or the annular coating tank is provided with a sinking prevention member for preventing the annular body from sinking into the coating liquid.

  By the coating method of the present invention, even if the film thickness is relatively thick, the film thickness can be applied uniformly. By using this coating method, a functional film such as a fixing member, a charging member, or a transfer member can be uniformly applied. Furthermore, according to the present invention, an endless belt having a uniform film thickness can be manufactured.

  Hereinafter, the coating method of the present invention will be described with reference to the drawings. In addition, the coating apparatus of this invention is demonstrated with the coating method of this invention. In addition, components having substantially the same functions are described with the same reference numerals throughout the drawings, and description thereof may be omitted in some cases.

  FIG. 1 is a schematic configuration diagram showing a coating apparatus applied to a coating method of a reference example. However, only the main part of application was shown and the peripheral part was omitted. In the present specification, “apply on the cylindrical core” means that the coating liquid is applied on the surface of the cylindrical core and, if there is a layer on the surface, on the layer. For example, when the cylindrical core is a support for an electrophotographic photosensitive member, the coating on the support includes the case of coating on the layer when the surface has a layer. Further, “rising the cylindrical core” is a relative relationship with the coating liquid surface, and includes a case of “stopping the cylindrical core and lowering the coating liquid surface”. In the present invention, hereinafter, the gap between the smallest inner diameter portion of the hole 6 of the annular body 5 and the cylindrical core body 1 is referred to as a “gap”. Shows the height to the liquid level.

  A coating apparatus shown in FIG. 1 includes a chucking device 20 (elevating means) for immersing a cylindrical core body 1 in a coating liquid 2 with its longitudinal direction vertical, and a coating tank filled with the coating liquid 2. 3. On the coating liquid 2, an annular body 5 provided with a circular hole 6 larger than the outer peripheral outer diameter of the cross section of the cylindrical core body 1 is installed in a freely movable state. The chucking device 20 includes a rotating shaft 21 in which a spiral groove is formed, and an arm 22 that is attached to the rotating shaft 21 while attaching the cylindrical core body 1 with its longitudinal direction vertical. Although not shown in the figure, the connecting portion of the arm 22 with the rotating shaft 21 has a protrusion that engages with the spiral groove of the rotating shaft 21, and the arm 22 moves up and down as the rotating shaft 21 rotates. As shown in FIGS. 1 and 3, the chucking device 20 includes a drive unit 23 that drives the rotating shaft 21, a detector 24 (detection means) that detects the height of the annular body 5, and a detector. And a control unit 25 that controls the rotational speed of the rotary shaft 21 by the drive unit based on information from the control unit 24.

  The dip coating apparatus overflows from the upper part of the coating tank 3 when the cylindrical core 1 is immersed in the coating liquid 2, when necessary, such as a pump. There may be provided an overflow receiving means for receiving the coating liquid, a refeeding means for circulating the overflow coating liquid again to the container, and the like.

  In the coating apparatus shown in FIG. 1, the cylindrical core body 1 is put in the coating liquid 2 in the coating tank 3, the arm 22 is lowered and the cylindrical core body 1 is immersed in the coating liquid 2 by the rotation of the rotating shaft 21, and then the rotating shaft is rotated. By the reverse rotation of the arm 21, the arm 22 is raised and the cylindrical core body 1 is raised and applied, whereby the film forming coating film 4 is formed. At this time, the cylindrical core body 1 is immersed in the coating liquid 2 through the holes 6, and then the cylindrical core body is raised, and the film thickness of the coating film 4 is limited by the gap between the cylindrical core body 1 and the holes 6.

  The material of the annular body 5 is not affected by the coating liquid, and is selected from various metals and plastics. The annular body may have, for example, a hollow structure for weight reduction.

  The gap between the inner diameter of the hole 6 of the annular body 5 and the outer diameter of the cylindrical core body 1 is adjusted in view of the desired film thickness. The dry film thickness is the product of the wet film thickness and the non-volatile concentration of the coating liquid. From this, the desired wet film thickness is obtained, and the gap should be 1 to 2 times the desired wet film thickness. Good. The reason for setting it to 1 to 2 times is that the distance of the gap does not always become a wet film thickness due to the viscosity and / or surface tension of the coating liquid and the contraction of the film.

  As shown in the cross-sectional view of FIG. 1, the shape of the inner wall of the hole 6 provided in the annular body 5 is an oblique linear shape as long as the gap between the core body is wide at the lower part immersed in the coating liquid and the upper part is narrow. In addition to those described above, it may be stepped or curved.

  As shown in FIG. 4A, the annular member 5 includes a component 52 including a minimum inner diameter portion of the hole 6, and another component 53 that can be attached to and detached from the component 52. The structure may be divided in the axial direction. By adopting such a configuration, for example, only the component 52 in which the minimum inner diameter portion size of the hole 6 is changed in accordance with the desired size of the cylindrical core material 1 or the desired thickness of the coating film 4. Can be prepared, the desired annular body 5 can be prepared, and cost reduction can be realized. Further, for example, a material having a specific gravity higher than that of the constituent member 52 including the minimum inner diameter portion of the hole 6 is used, and the other constituent member 53 is manufactured to lower the center of gravity of the annular body and improve the stability at the time of lifting. be able to. As shown in FIG. 4 (b), the annular member 5 includes a component member 52 including a minimum inner diameter portion of the hole 6 and other component members 53 that can be attached to and detached from the component member 52. The structure may be divided in a direction substantially orthogonal to the opening axis direction.

  And the coating method of this invention applies the coating method of a reference example to the coating method shown in FIG. In the coating apparatus applied to the coating method shown in FIG. 2, coating is performed when the coating liquid 2 is placed in the annular coating tank 7 and passed through the cylindrical core body 1 from the lower part to the upper part. A sealing material 8 is attached to the bottom of the annular coating tank 7 so that the coating liquid does not leak. The sealing material is made of a flexible plate material such as polyethylene, silicone rubber, or fluorine resin. The other configuration is the same as that of the coating apparatus shown in FIG.

  The annular coating method using the annular coating tank 7 has an advantage that less coating liquid is required than the dip coating method shown in FIG. The annular body 5 is installed on the coating liquid 2 in a freely movable state as described above.

  Thus, in the coating method of the present invention, the annular body 5 is installed in a freely movable state so that it can move with a slight force on the coating liquid 2. In addition to the method of floating on the liquid, there are a method of supporting the annular body 5 with a roll or a bearing, a method of supporting the annular body 5 with air pressure, and the like. Also, as shown in FIG. 1 or 2, in order to prevent the annular body 5 from sinking, support for preventing the sinking into the coating liquid 2 by supporting the annular body on the outer peripheral surface of the annular body 5 or the coating tank 3. A rod 51 may be provided. When the support rod 51 as a sinking prevention member is provided on the outer peripheral surface of the annular body 5, for example, as shown in FIG. 2, the upper end of the outer wall of the coating tank 3 at a height at which the annular body 5 is immersed in the coating liquid 2 to some extent. When the annular body 5 sinks in the coating liquid 2 to some extent at a predetermined location on the inner wall of the coating tank, for example, as shown in FIG. Provided. The configuration of the sinking prevention member is not limited to the support rod, and any configuration such as a plate shape, a projection shape, or a ring shape may be used as long as the configuration prevents the annular body 5 from sinking.

  In the coating method of the present invention, when the cylindrical core body 1 is raised through the hole 6 of the annular body 5, friction resistance is generated in the gap between the cylindrical core body 1 and the annular body 5 due to the interposition of the coating liquid 2. Ascending force acts on the body 5, and the annular body 5 is lifted.

  When the annular body 5 is lifted in this way, the annular body 5 moves in the horizontal direction so that the frictional resistance with the cylindrical core body 1 is constant in the circumferential direction, and the gap is constant in the circumferential direction. When the annular body 5 is displaced in one direction, the frictional resistance is increased in the portion where the gap is narrowed, and on the opposite side, an unbalanced state in which the gap is widened and the frictional resistance is reduced occurs. Since the annular body 5 moves in the horizontal direction so that the gap becomes smaller, that is, the gap becomes wider, the annular body 5 does not come into contact with the cylindrical core body 1 and a constant gap is always maintained.

  When the cylindrical core body 1 is raised, the annular body 5 follows the cylindrical core body 1 in the horizontal direction even if the cylindrical core body 1 is slightly inclined or the raising means of the cylindrical core body 1 has a flare. Therefore, there is an advantage that the film thickness can be applied uniformly.

  In order for the annular body 5 to act in this way, the annular body 5 must be lifted to some extent. When the height to which the annular body 5 is lifted is low, since the force for restoring the annular body 5 to the center position is weak, the gap is applied while being shifted in the circumferential direction. As shown in FIG. 5, a sine wave undulation occurs. That is, the film thickness of the part with the wide gap is thick, and the film thickness of the opposite part is thin. Here, the film thickness difference between the undulation peaks and valleys is referred to as “film thickness unevenness due to undulation”. The film thickness unevenness due to the undulation is usually required to be 5% or less of the average film thickness, although it depends on the use of the endless belt used.

  As a result of the study by the present inventors to achieve this, the minimum inner diameter portion of the hole 6 of the annular body 5 is lifted from the coating liquid 2 liquid surface, and the bottom surface of the annular body 5 is lifted from the coating liquid 2 liquid surface. It has been found that the cylindrical core body 1 should be relatively raised from the coating liquid 2 through the hole 6 of the annular body 5 so as to have a desired height so as not to be detached. In particular, it has been found that the height at which the minimum inner diameter portion of the hole 6 of the annular body 5 is lifted is 5 mm or more, preferably 5 to 50 mm from the surface of the coating liquid 2.

  The ascending force of the annular body 5 increases as the rising speed of the cylindrical core body 1 increases. However, if the annular body 5 is lifted too much and its bottom surface is separated from the liquid surface, the bottom surface of the annular body 5 enters the coating liquid 2 from the bottom surface. Air is entrained, and there is a problem that air bubbles enter the coating film 4. Further, when the bottom surface of the annular body 5 is separated from the surface of the coating liquid 2, the annular body 5 falls to the surface of the coating liquid 2 at the end of coating, but at that time, bubbles are also involved in the coating liquid 2. Therefore, it is very inconvenient when repeating the coating operation.

  Here, in the present invention, when the annular body 5 is pulled up from the coating liquid 2, the coating liquid 2 has a certain level of viscosity, so that it follows the bottom surface of the annular body 5 and is applied from the bottom edge of the annular body 5. The bottom of the liquid 2 liquid surface is formed, but when this skirt is located outside the bottom edge of the annular body 5, it is considered that “the bottom surface of the annular body 5 does not separate from the liquid surface of the coating liquid 2”. When positioned on the inner side, it is considered that “the bottom surface of the annular body 5 has detached from the surface of the coating liquid 2”. If the bottom of the liquid surface of the coating liquid 2 is positioned on the inner side of the bottom edge of the annular body 5, air is entrained from the bottom, causing a problem that air bubbles enter the coating film 4 as described above. It will be.

  For the above reasons, when the cylindrical core body 1 is raised, the annular body 5 is not too high and not too low, and needs to have a certain range of heights. Therefore, in the present invention, the rising speed of the cylindrical core body 1 is adjusted. That is, when the lifting amount (height) of the annular body 5 is low, the speed is increased, and conversely, when the annular body is excessively raised and the bottom surface is about to be separated from the liquid surface, the increasing speed is decreased. . However, in the present invention, control is performed such that the rising speed of the cylindrical core body 1 is reduced as compared with that at the start of coating.

  For this reason, in the coating method shown in FIG. 1, the detector 24 detects the height of the annular body, and the control unit 25 controls the drive unit 23 accordingly to increase the rotational speed of the rotary shaft 21. For example, the rising speed of the annular body 5 is adjusted. As the detector 24, various mechanical and optical detectors can be used. For example, an optical switch, a laser distance meter, an ultrasonic distance meter, or the like can be used. Further, without using the detector 24, the height of the annular body can be judged visually and the speed can be adjusted manually.

In addition, the height at which the annular body 5 is lifted during application increases as the following conditions.
(1) The gap between the annular body 5 and the cylindrical core body 1 is narrow (that is, the film thickness is thin).
(2) The viscosity of the coating liquid 2 is high.
(3) The mass of the annular body 5 is light.

  Here, the gap between the annular body 5 and the cylindrical core body 1 is an indispensable condition for obtaining a desired film thickness, and the viscosity of the coating liquid 2 cannot be easily changed in many cases. If the desired value is desired, it is convenient to adjust the mass of the annular body 5. In that case, if the annular body 5 has a structure separated as shown in FIG. 4, the constituent member 52 including the minimum inner diameter portion of the hole 6 is left as it is, and the other constituent member 53 is replaced with one having a different weight. That's fine.

  The relationship between the mass of the annular body 5 and the coating speed (the rising speed of the cylindrical core body 1) is such that the speed at which the cylindrical core body 1 is relatively lifted is proportional to the mass of the annular body. For example, when the core has a diameter of 0.366 mφ, the core body is lifted when the core body is lifted after the 2.6 kg annular body is floated on the coating liquid, and the height of the annular body is stabilized at about 20 mm. The speed is 0.67 m / min. Next, after 3.8 kg of the annular body 5 is floated on the coating liquid 2, the core body 1 is raised and the height of the annular body 5 is stabilized to about 20 mm. The core rising speed was 1.0 m / min. In all cases, the mass of the annular body 5 was a coating speed of 0.26 m / min per kg. This relationship is a guideline for the annular body design when it is desired to set the coating speed to a desired value. Furthermore, when the experiment was performed by changing the weight of the annular body 5 twice, the relationship between the mass of the annular body and the coating speed was linearly proportional as shown in the graph of FIG.

  It should be noted that it takes some time until the cylindrical body 1 is raised and the annular body 5 is lifted, the annular body 5 moves in the horizontal direction, and the gap between the annular body 5 and the cylindrical core body 1 becomes uniform. May take. In that case, the uniform area | region of a film thickness will reduce in the upper part of a cylindrical core.

  Therefore, it is preferable to provide an interval adjusting member at the tip end portion of the cylindrical core body 1 in the upward direction so that the outer diameter of the tip portion is larger than the outer diameter of the core body and less than the minimum diameter of the hole of the annular body. Specifically, for example, as shown in FIG. 7, a plate-like gap in which the outer diameter of the tip is approximately equal to the minimum diameter of the hole 6 of the annular body 5 so that the annular body 5 can be aligned. An adjustment member 9 is provided.

  The gap adjusting member 9 is preferably a projection having a tip portion in the rising direction of the cylindrical core body 1 that is substantially equal to or slightly thinner than the gap, and is more preferably plate-shaped. As shown in FIG. 7, the gap adjusting member 9 may be at least at three or more locations. In the case of this plate shape, the upper end portion of the cylindrical core body 1 may be provided over the entire circumference. As shown in FIG. 8, when the hole 6 of the annular body 5 passes through the portion of the cylindrical core body 1 to which the gap adjusting member 9 is attached, the annular body 5 is forcibly aligned and the cylindrical core body 1. Immediately after the rise, the gap with the cylindrical core body 1 becomes uniform. Thus, immediately after the rise of the cylindrical core body 1, the distance from the annular body 5 becomes constant, and the film thickness unevenness due to undulation over the entire cylindrical core body 1 can be reduced. In particular, even if the height at which the annular body 5 is lifted into the coating liquid 2 is less than 5 mm, the film thickness unevenness due to waviness can be reduced. Of course, the height is more preferably 5 mm or more.

  Next, the cylindrical core will be described. In the case of a photoreceptor, the cylindrical core body 1 as an object to be coated is made of a metal such as aluminum or stainless steel, or a plastic imparted with conductivity. When the object to be coated is a charging roll, the cylindrical core 1 is a roll provided with an elastic layer made of a rubber material having excellent heat resistance such as silicone rubber or fluorine rubber around the core metal. When the object to be coated is a charging roll, the cylindrical core 1 is a roll provided with an elastic layer such as urethane rubber or sponge around the cored bar.

Hereinafter, the endless belt produced by the coating method of the present invention will be described.
In order to produce an endless belt by the coating method of the present invention, a coating liquid for film formation is applied to the cylindrical core 1, and then a film is formed by performing any or all of drying, heat curing, and baking, The formed film is peeled off from the core. As described above, since the coating method of the present invention can uniformly apply the film thickness, the endless belt produced thereby has little film thickness unevenness due to waviness, and the waviness of the sine wave component of the film thickness is the average film thickness. 5% or less.

  The cylindrical core for producing the endless belt is preferably aluminum from the viewpoint that it is better to have a high coefficient of thermal expansion for removing the belt. In order to improve the peelability of the film, it is also effective to plate the surface with chromium or nickel, coat the surface with a fluorine resin or a silicone resin, or apply a release agent to the surface.

  Note that when aluminum is heated to 200 ° C. or higher, the strength is reduced and deformation is likely to occur. However, such thermal deformation of aluminum occurs when strain accumulates during cold working to the core shape. Cheap. In order to remove the distortion, there is a method of annealing (annealing) aluminum. However, since thermal deformation can also occur by annealing, it is necessary to process the core body after annealing. The annealing may be performed by heating the aluminum material to 300 to 400 ° C. and naturally cooling in the air.

  Next, the coating liquid 2 will be described. In the present specification, the “coating liquid 2” means liquids such as various solutions and dispersions.

  The coating liquid 2 preferably has a viscosity of 200 mPa · s or more, and more preferably 400 mPa · s or more, in view of lifting the annular body 5 by frictional force. A coating liquid having a viscosity of 200 mPa · s or more has less dripping at the upper end. Therefore, the sagging at the upper end, which has always been a problem in the conventional dip coating method, can be reduced by the method of the present invention.

  When the object to be coated (cylindrical core 1) is an organic photoreceptor, the coating method of the present invention is preferably applied to a charge transport layer having a large film thickness. Since the charge generation layer is generally thin, it can be applied by a conventional dip coating method. However, when a thick charge generation layer is required, the coating method of the present invention can be used.

  A charge transport layer preferable for the coating method of the present invention will be briefly described. The charge transport layer is prepared by mixing a charge transport agent such as a hydrazone compound, stilbene compound, benzidine compound, butadiene compound, or triphenylamine compound with a binder resin such as polycarbonate, polyarylate, polymethyl methacrylate, or polyester. . The higher the molecular weight, the harder it is to wear, and the binder resin is preferable. However, when the molecular weight is large, the viscosity of the coating liquid increases, so that the conventional dip coating method is too thick and difficult to apply. . Further, if the amount of the dilution solvent is increased in order to reduce the viscosity, there is a problem that the nonuniformity of the film thickness due to sagging increases. However, in the coating method of the present invention, since the film thickness can be controlled even when the viscosity of the coating liquid is high, a binder resin having a molecular weight larger than that of the conventional dip coating method can be employed.

  Various solvents are used for the coating liquid 2. As this solvent, aromatic hydrocarbons such as toluene, xylene and monochlorobenzene; chlorinated hydrocarbons such as methylene chloride, chloroform and chlorocene; ketones such as acetone, butanone and cyclohexanone; esters such as ethyl acetate and butyl acetate; Examples include ethers such as tetrahydrofuran and dioxane. These may be used alone or in combination.

  The solid concentration of the coating liquid 2 is preferably about 20 to 50%, and the viscosity is preferably about 200 to 8000 mPa · s, more preferably 400 mPa · s or more. This is a higher concentration and higher viscosity than the coating solution for the charge transport layer applied to the conventional dip coating method. The film thickness of the charge transport layer is generally about 15 to 40 μm, but is particularly preferred in the present invention when a film thickness of 25 μm or more is desired. As a condition for coating, the ascending speed is preferably about 0.1 to 0.8 m / min.

Next, a functional film formed on the surface of the fixing roll will be briefly described. Examples of the functional coating include release layers described in JP-A-9-22212 and JP-A-11-338283. Its coating liquid is mainly composed of fluorocarbon rubber, fluorocarbon resin particles and SiC optionally include a mixture of inorganic particles such as Al2O _3.

  Fluororubber includes vinylidene fluoride (VdF) as a main component, a copolymer of VdF and hexafluoropropylene (HFP), and a ternary of VdF-HFP copolymer and tetrafluoroethylene (TFE). Examples thereof include fluorine-based elastomers such as copolymers and alternating copolymers of TFE and propylene. In addition, a VdF-chlorotrifluoroethylene copolymer or a mixture of, for example, silicone rubber, fluorosilicone rubber and the like, and the above-mentioned fluorine-based elastomer containing VdF as a main component can also be used. These fluororubbers can also be used as the constituent material of the elastic layer. In many cases, the viscosity of the coating liquid mainly composed of fluororubber is 200 mPa · s or more. When such a high-viscosity coating liquid is used, the film thickness becomes too thick in the conventional dip coating method. Application is possible by using the body. The thickness of the release layer is preferably in the range of 5 to 30 μm.

  The functional coating formed on the surface of the charging roll and transfer roll to which the coating method of the present invention is preferably applied will be briefly described.

  The coating liquid 2 used for these functional coatings is a liquid of a binder resin such as nylon, urethane or acrylic alone or in which conductive particles are dispersed. In addition, the coating liquid 2 applied to the hard transfer roll which does not have an elastic layer may be the same as the material of the transfer belt mentioned later.

  In these coating liquids 2, the conductive particles may be the same as those used when the endless belt is used as a charged body or a transfer belt. However, when the conductive particles are generally dispersed in a binder resin solution, the viscosity is 10 to 30. %, And the viscosity may be 200 mPa · s or more. In such a case, the conventional dip coating method could not be applied because the film thickness was too thick, but by using an annular body, the coating could still be performed. The thickness of the coating applied to the charging roll or transfer roll is preferably in the range of 2 to 30 μm.

  When producing an endless belt, the coating liquid 2 contains a resin material and / or a precursor thereof (hereinafter also referred to as “resin material or the like”). Examples of the resin material include polyimide (abbreviated as PI), polyamideimide, polybenzimidazole, phthalic acid polyester, and polycarbonate. Among these, PI is particularly preferable in terms of strength and dimensional stability. The solid content concentration of the coating liquid containing the resin material or the like is preferably about 15 to 50%, the viscosity is 10 to 1000 Pa · s, and the rising speed is about 0.1 to 1.5 m / min. The thickness of the endless belt is preferably in the range of 25 to 200 μm.

In order to produce an endless belt, the cylindrical core body 1 is pulled up from the coating liquid 2 through the hole 6 of the annular body 5 and applied to the surface of the core body. After the coating liquid is dried, when the coating film is heated together with the core at a predetermined temperature, the resin material and the like are cured and a coating film is formed. When the coating liquid hangs down during drying, the coating liquid may be dried while being rotated sideways. The formed film is peeled from the core to obtain an endless belt.
When the residual solvent cannot be completely removed during drying, or when vaporized components such as water generated from the resin during the heating reaction cannot be removed, it is unavoidable that the resin film swells. This is particularly remarkable when the film thickness of the PI resin film exceeds 50 μm.
In that case, it is effective to roughen the surface of the core body to about Ra 0.2 to 2 μm. Thereby, the residual solvent or water vapor generated from the PI resin film can be discharged to the outside through a slight gap formed between the core body and the PI resin film, and swelling can be prevented. For roughening the surface of the core body, there are methods such as blasting, cutting, and sandpaper.

When the endless belt is used as a charged body such as a contact charging film or a transfer belt, conductive particles are dispersed in advance in a resin material or the like as necessary. Examples of the conductive particles include carbon black, carbon-based materials such as carbon beads obtained by granulating carbon black, carbon fiber, and graphite; metals or alloys such as copper, silver, and aluminum; tin oxide, indium oxide, antimony oxide, Examples thereof include conductive metal oxides such as SnO ₂ · In ₂ O ₃ composite oxide; conductive whiskers such as potassium titanate.

  In order to manufacture a fixing belt from an endless belt, it is preferable to form a non-adhesive film on the surface of the endless belt in order to prevent adhesion of toner. Examples of non-adhesive materials include fluorine resins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene / hexafluoropropylene copolymer (FEP). Is preferred. 5-50 micrometers is preferable and, as for the thickness of a fluororesin layer, 10-45 micrometers is more preferable.

  In order to form the fluororesin layer, it is preferable to apply a method in which the aqueous dispersion is applied and baked. As the coating method, a dip coating method as shown in FIG. 9 is preferable in terms of the smoothness of the coating film and the uniformity of the film thickness. For dip coating as shown in FIG. 9, the cylindrical core body 1 on which the coating film 4 for film formation is formed is immersed in the fluororesin dispersion 10 and then raised to form the fluororesin coating film 11. To do.

  At that time, in order to prevent the fluororesin dispersion from being applied to the core surface or the fluororesin dispersion from entering the gap between the core and the coating film, If there is an end portion of the coating film on the lower end side and an exposed portion of the core surface, it is preferable to perform coating treatment with the coating material 12 on that portion.

  When the viscosity of the fluororesin aqueous dispersion is high and the film thickness becomes too thick, the coating method of the present invention using an annular body can also be employed. Moreover, after application | coating, a solvent is dried and a fluororesin is baked. During the firing, the coating film-forming coating film may be subjected to heat treatment at the same time.

  The endless belt obtained by the coating method of the present invention can be used to produce a fixing roll, a charging roll, or a transfer roll whose surface is made of a functional film (for example, a PI resin) by covering the endless belt. That is, when manufacturing a fixing roll, an endless belt is placed on the surface of a roll provided with an elastic layer made of a heat-resistant rubber material such as silicone rubber or fluorine rubber around the core metal. When manufacturing charging rolls and transfer rolls, endless belts in which conductive particles are dispersed on the surface of a metal cylinder or roll provided with an elastic layer such as rubber or sponge with conductivity around the core Cover.

  The durability can be increased by covering the surface of the roll with an endless belt made of PI resin. When covering the endless belt on the surface of the roll, it is preferable to shrink the elastic layer provided on the roll. There is also a method in which the endless belt is placed on the surface of the roll after the base and the elastic layer are cooled and contracted. Further, an adhesive may be interposed in order to prevent the elastic layer and the endless belt from shifting.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention.

(Reference Example 1)
An N-methylpyrrolidone solution of a polyimide precursor (trade name: U Varnish S, manufactured by Ube Industries, Ltd.) was used as a coating solution 2. The solid concentration is about 18%, and the viscosity is 5 Pa · s. This was put into a coating tank having an inner diameter of 80 mm and a height of 500 mm similar to the configuration shown in FIG.

  An aluminum cylinder having an outer diameter of 30 mm and a length of 400 mm was prepared, and the surface was roughened to Ra 0.8 μm by blasting with spherical alumina particles (made by Fuji Seisakusho, particle size 105 to 125 μm). A silicone release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied and baked at 300 ° C. for 1 hour to obtain a core 1.

  On the other hand, a hollow body made of polyacetal resin having a hole 6 having a height of 25 mm, an outer diameter of 60 mm, and an inner diameter of 31.2 mm at the narrowest portion was produced as an annular body. The inner wall is an inclined surface. The mass of the annular body was 0.29 kg.

  The annular body was floated on the coating solution. The height of the annular body from the liquid level was detected visually. First, the annular body was fixed so as not to sink, and the core body was immersed therein at a speed of 1 m / min. Next, the fixation of the annular body was released, and the core body was raised at a speed of 0.7 m / min. As a result, the annular body was immediately lifted by about 20 mm from the liquid surface. Increased. Therefore, when the speed was gradually reduced, the height of the annular body was stabilized at about 20 mm when the core body was raised about 60 mm, so that the rising speed of the core body was made constant. The speed at that time was 0.4 m / min.

  During the ascent of the core body, the annular body did not contact the core body, and after coating, the coating film 4 having a wet film thickness of about 600 μm was formed on the core body. The film thickness was determined by the gap between the hole of the core body and the annular body, and was not affected by the rising speed of the core body.

  Thereafter, the core is dried at 120 ° C. for 60 minutes while the axis of the core is rotated at 20 rpm, and then the resin is reacted by heating the core vertically at 200 ° C. for 30 minutes and 380 ° C. for 1 hour. It was. An endless belt made of polyimide resin could be obtained by removing the film after cooling to room temperature.

  When the film thickness was measured, it was uniform at 70 μm except for 30 mm from the upper end. The film thickness within 30 mm from the upper end part had a thick part and a thin part in the circumferential direction, but this was a little until the annular body moved in the horizontal direction and the gap with the core body was evenly fitted. It is thought that it took time.

  Next, in consideration of productivity, the coating speed was 1 m / min. Therefore, an annular weight was attached to the bottom of the annular body, and the mass was 2.5 times 0.73 kg. The coating speed was 1 m / min. It was able to be min.

(Reference Example 2)
In Reference Example 1, as in the structure shown in FIG. 7, three 0.5 mm-thick polyethylene sheets cut into 5 mm squares are attached to the front end of the core in the upward direction at 120 ° intervals. It was. When the core body was immersed in the coating liquid, the portion was immersed to the position of the minimum inner diameter portion of the annular body. Thereby, the center position of the annular body is adjusted from the beginning of application. Next, the coating operation was performed in the same manner as in Reference Example 1, and the gap adjusting member was removed after drying.

  When the film thickness of the obtained endless belt was measured, the part below 10 mm from the upper end was uniform at 70 μm, and more film thickness uniform parts were obtained than in Reference Example 1.

(Comparative Example 1)
In Reference Example 1, when the coating was applied to the core without using an annular body, the wet film thickness was applied to about 2 mm or more, not only was it too thick, but there was dripping of the liquid from the lower end, and it was dried It was difficult. If the annular body was not used, the film thickness was too thick.

(Comparative Example 2)
In Comparative Example 1, the coating was diluted with a 1: 1 mixed solvent of N-methylpyrrolidone and dioxane, and adjusted to a viscosity of 150 mPa · s and a solid content concentration of about 10%. As a result, a film having a wet film thickness of about 120 μm was formed. However, since the solid content concentration was low, the final film thickness was only 18 μm, and only a film thickness smaller than the initial target film thickness, that is, the film thickness of 70 μm obtained in Reference Example 1 was obtained.

(Comparative Example 3)
In Reference Example 1, when the core body was applied at a constant speed of 0.7 m / min from the beginning, the annular body increased with the core body rising, and the core body passed about 90 mm from the top. Then, the lower part of the annular body was separated from the liquid surface, and reached a height of about 100 mm at the end of coating, and the annular body dropped onto the liquid as the core body was stopped. At that time, many fine bubbles were generated in the coating film, and bubbles were also mixed in the coating liquid. Due to the high viscosity of the coating solution, the bubbles did not disappear easily, hindering the next coating operation.

(Example 3)
An aluminum cylinder having an outer diameter of 68 mm and a length of 400 mm was prepared. This is a tube with an outer diameter of 70 mm and a length of 400 mm heated at 300 ° C. for 10 minutes and cooled, and then the surface was cut to an outer diameter of 68 mm. Next, the surface is roughened to Ra 0.9 μm by blasting with spherical alumina, and then a silicone-based mold release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) is applied to the surface for 30 minutes at 300 ° C. The core was baked.

  An annular sealing material made of soft polyethylene having a thickness of 0.5 mm and having a hole with an inner diameter of 67 mm in the center was attached to an annular coating tank having an inner diameter of 100 mm and a height of 50 mm having the same configuration as that shown in FIG. An intermediate made of polyether resin having an outer diameter of 68 mm and a length of 60 mm was fitted into the hole, and then the same coating liquid 2 as in Reference Example 1 was placed in the coating tank.

  The annular body is an aluminum processed product having a minimum inner diameter of 69.2 mm, a maximum inner diameter of 80 mm, an inner wall having an inclined surface, an outer diameter of 86 mm, and a height of 30 mm. The annular body was placed on the coating solution so that the rod was placed on the upper end of the outer wall of the annular coating tank. The height of the annular body was detected by two optical switches provided in the vicinity of the support rod.

  Application | coating raised the core 1 at a speed | rate of 1 m / min first. When the annular body was raised 30 mm from the liquid level, the upper limit switch was operated to decrease the speed, and the lower limit switch was operated at a height of 20 mm to control and increase the speed. As a result, the speed became approximately 0.5 m / min from the time when the core body rose about 50 mm.

  After the application was completed, a PI precursor coating film having a wet film thickness of about 600 μm was formed on the core. Subsequently, when it was dried at 120 ° C. for 60 minutes while the axis direction was horizontal and rotated at 20 rpm, a PI precursor film having a thickness of about 150 μm was formed. A polyester adhesive tape having a width of 20 mm was applied to the coating on one side of the end portion over the entire circumference to cover the coating and the exposed portion of the core.

  As shown in FIG. 8, a PFA water-based paint (trade name: 710CL, manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd., concentration 60%, viscosity 400 mPa · s, containing ethanol and t-butanol as a solvent in addition to water) It put into the coating tank of inner diameter 90mm and height 480mm. The core was immersed in the core vertically with the coating on the bottom, leaving only 5 mm of the upper PI precursor film. Subsequently, it pulled up at a speed of 0.3 m / min to form a PFA coating film.

  After drying at 80 ° C. for 10 minutes, the coating was removed. Next, it was heat-dried at 150 ° C. for 20 minutes and then at 200 ° C. for 20 minutes. As a result, the solvent was removed from the PI precursor coating, and water was removed from the PFA coating. Thereafter, the PI precursor film was reacted by heating at 380 ° C. for 30 minutes to form a PI resin film, and the PFA coating film was baked. After cooling to room temperature, the film was removed from the core to obtain an endless belt. When the film thickness was measured, the PI resin was 75 μm and the PFA layer was 30 μm except for 30 mm from the upper end. This endless belt was cut into a length of 320 mm to obtain an endless fixing belt. The adhesion between the PI resin and the PFA layer was strong.

(Reference Example 4)
A solution of a PI precursor was prepared by reacting 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride with an equimolar amount of p-phenylenediamine. The concentration was adjusted to 23% by mass and the viscosity was adjusted to about 10 Pa · s. Carbon black (trade name: Special Black 4, manufactured by Degussa Huls) was mixed with the PI precursor solution at a solid content mass ratio of 23%, and then dispersed by a high-pressure jet mill for 2 hours to obtain a coating solution.

  On the other hand, an aluminum cylinder having an outer diameter of 366 mm and a length of 500 mm was prepared, and the surface was treated with a roughening treatment and a silicone-based release agent in the same manner as in Reference Example 1 to obtain a core. As an annular body, a stainless steel hollow ring having an outer diameter of 400 mm, a minimum inner diameter of 367.2 mm, and a height of 30 mm was produced, and the inner wall was an inclined surface. The mass was 2.1 kg.

  Next, the height of the annular body from the liquid surface is measured with a laser distance meter (manufactured by Keyence Corporation), and the ascending speed of the core body is in the range of 0.5 to 1 m / min so that it is always 20 mm. When the coating was carried out with adjustment, the film was stabilized at a speed of 0.55 m / min. Next, drying and heating were performed in the same manner as in Reference Example 1.

By removing the PI resin film after cooling to room temperature, an endless belt made of PI resin could be obtained. The film thickness of this endless belt was 75 μm. When the film thickness distribution was examined in the circumferential direction, a sine wave undulation as shown in FIG. 10 was observed, and the film thickness difference between the peaks and valleys was 3 μm. The ratio of the waviness to the average film thickness was 4%, and the volume resistance was measured to be about 10 ⁹ Ωcm, and could be used as an electrophotographic transfer belt.

(Reference Example 5)
In Reference Example 4, it is more convenient for the coating time to be within 30 seconds for continuous production. Therefore, an annular body having a mass of 4.0 kg was manufactured by changing the outer diameter while keeping the same minimum inner diameter. When this was used for coating, the stable coating speed was 1.1 m / min, and it was possible to apply to a core body having a length of 500 mm within 30 seconds.

(Comparative Example 4)
In Reference Example 4, when the core body was applied at a constant speed of 0.2 m / min from the beginning, the annular body slightly lifted from the liquid level with the rise of the core body. It was about 3 mm. In other cases, an endless belt was prepared in the same manner, and when the film thickness was measured, the average film thickness was 75 μm. However, when the film thickness distribution was examined in the circumferential direction, a sine wave undulation as shown in FIG. 10 was observed. The film thickness difference between the peaks and valleys was 6 μm. The ratio of the waviness to the average film thickness is 8%, and it can be used as a paper conveying belt, but when used as a transfer belt, it causes a color shift of the transfer toner, so it is inferior in quality. .

(Reference Example 6)
In Reference Example 4, as the annular body, the structural member including the minimum inner diameter portion of the hole, which is similar to the structure shown in FIG. 4A, and other structural members that can be attached to and detached from this structural member, When applied in the same manner as in Reference Example 4 except that the one having a structure divided in the direction of the opening axis of the hole was used, an excellent endless belt made of PI resin could be obtained. The annular body used has an outer diameter of 400 mm with an inclined inner wall, a minimum inner diameter of 367.2 mm, and a height of 30 mm. The constituent members including the minimum inner diameter portion are made of aluminum (mass 1.3 kg), and other configurations. A member made of stainless steel (mass 1.5 kg) was used (total mass 2.8 kg).

(Reference Example 7)
Further, as in Reference Example 5, in order to perform continuous production, instead of that in Reference Example 6, the other constituent member described above has a mass of 2.7 kg, and the total mass of the annular body is 4 kg. As in the case of Reference Example 5, the coating speed could be increased.

It is a schematic block diagram for demonstrating the coating method of a reference example. It is a schematic block diagram for demonstrating the coating method of this invention. It is a block diagram which shows the structure of the chucking apparatus used for the coating method of this invention. It is a schematic sectional drawing which shows the annular body used for the coating method of this invention. It is a related figure which shows the wave | undulation of the sine wave seen in the film thickness of an endless belt. It is a relationship figure which shows the relationship between the mass of an annular body, and a coating speed. It is a schematic block diagram which shows the cylindrical core body provided with the gap | interval adjustment member used for the coating method of this invention. It is explanatory drawing for demonstrating a gap | interval adjustment member. It is a schematic block diagram for demonstrating the dip coating method. It is a related figure which shows the wave | undulation of the sine wave seen in the film thickness of the endless belt obtained by the reference example 4 and the comparative example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical core body 2 Coating liquid 3 Coating tank 4 Coating film 5 Ring body 6 Hole 7 Ring coating tank 8 Sealing material 9 Gap adjustment member 10 Fluororesin dispersion 11 Coating film 12 Coating material 20 Chucking device 21 Rotating shaft 22 Arm 23 Drive unit 24 Detector 25 Control unit

Claims (6)

An application method for applying a coating liquid to the core surface,
After installing the annular body provided with a hole larger than the outer diameter of the cross-section of the core body in a freely movable state in the coating liquid filled in the annular coating tank,
The annular body is lifted from the coating liquid surface through the core body into the hole of the annular body, and the annular body has a desired height so that the bottom surface of the annular body does not leave the coating liquid surface. An application method, wherein the position is detected and control is performed to reduce the rising speed of the core from that at the start of application, and the core is relatively raised from the coating liquid.   The coating method according to claim 1, wherein a sinking prevention member for preventing sinking of the annular body into the coating liquid is provided in the annular body or the annular coating tank. After installing an annular body provided with a circular hole larger than the outer diameter of the core section in a coating liquid filled in the annular coating tank in a freely movable state,
An application method for applying the coating liquid onto the surface of the core body by relatively raising the core body from the coating liquid through the core body in the hole of the annular body,
The core body is provided with an interval adjusting member at the distal end in the ascending direction so that the outer diameter of the distal end portion is larger than the outer diameter of the core body and less than the minimum diameter of the hole of the annular body. A coating method, wherein a gap between the core and the annular body is uniformly matched when the core is raised. An application device for applying a coating liquid to the core surface,
An annular coating tank for storing the coating liquid;
While providing a hole larger than the outer diameter of the core section, an annular body installed in the coating liquid in a freely movable state,
Elevating means for relatively raising the core body from the coating liquid through the core body in the hole of the annular body,
Detecting means for detecting the height of the annular body;
Based on the signal from the detection means, the core body is lifted so that the annular body is lifted from the coating surface and the bottom surface of the annular body is at a desired height so as not to be detached from the coating surface. Control means for adjusting the amount to be less than at the start of application,
A coating apparatus comprising: An application device for applying a coating liquid to the core surface,
An annular coating tank for filling the coating solution;
While providing a hole larger than the outer diameter of the core section, an annular body installed in the coating liquid in a freely movable state,
Elevating means for relatively raising the core body from the coating liquid through the core body in the hole of the annular body,
With
The core body is provided with a spacing adjustment member at the leading end in the ascending direction so that the outer diameter of the leading edge is larger than the outer diameter of the core body and less than the minimum diameter of the hole of the annular body. A coating apparatus characterized in that a gap between the core body and the annular body is uniformly matched when the core body is raised.   The coating apparatus according to claim 5, wherein a sinking prevention member for preventing sinking of the annular body into the coating liquid is provided in the annular body or the annular coating tank.