JP2008062131A - Dip coating method, dip coating device, and electrophotography photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dip coating method which prevents the occurrence of film sagging (a thin film part generated at a coated upper end part) at a coating starting end to form a coating film of uniform thickness on a base material to be coated. <P>SOLUTION: In the dip coating method, a drum as a cylindrical base body is dipped in a coating liquid in a coating tank, and then a coating body to be coated is raised from the coating liquid to form a coating film on the base body to be coated. In this case, a raising speed of the upper end part of the drum decreases as a drum-raising distance increases. As a speed-decreasing mode, it is preferable that the raising speed acceleratively decreases according to an exponential function. Further, when an speed-decreasing operation is finished, a process transits to the raising of the lower part of the drum except its upper part, and in this process, the drum-raising speed is kept to be constant. Accordingly, an electrophotograpy photoreceptor, whose film thickness is uniform over the whole length of the drum, can be manufactured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a dip coating method and apparatus, and an electrophotographic photosensitive member, and more specifically, when a coating solution is applied to a substrate to be coated, little or no film sagging occurs. (Length of film sagging along the pulling direction of the substrate to be coated) The present invention relates to a dip coating method and apparatus relating to a dip coating method and apparatus.

A method of immersing a substrate to be coated in a coating liquid, and then pulling it perpendicular to the liquid surface of the coating liquid and applying it is known as a dip coating method. This dip coating method is also used as a typical method for producing an electrophotographic photosensitive member. However, in the upper part of the coating film applied by the dip coating method, there may be a part (film sagging) where the film thickness becomes thinner than the stable film thickness below it. Since this part does not satisfy the standard for the characteristics as an electrophotographic photosensitive member, various methods for shortening the film sagging (in the case of a cylindrical substrate, shortening the dimension in the axial direction) have been studied.
In recent years, there has been a trend toward a variety of small quantities of photoconductors in terms of diameter and length. In particular, compared to conventional methods, uniformity of film thickness is required up to a portion very close to the axial end of the photoconductor. Have been

For example, in the invention of Patent Document 1, a method is employed in which the pulling speed is changed so that the substrate to be coated is pulled up quickly at the beginning and at the end, but the effect of shortening the film sagging is sufficient. In addition, undulation of the film thickness is likely to occur.
In Patent Document 1, as an example, in a dip coating method in which a cylindrical substrate is immersed in a coating liquid in a container and then the coating container is lowered, an initial speed of 13 mm / s (seconds), and thereafter It describes what lowers the coating container while decreasing the speed by 0.15 mm / s per second.

  Further, in Patent Document 2, the substrate to be coated is immersed in a coating solution in a coating tank, and then the upper end of the substrate to be coated is once pulled up so as to be exposed to the air on the liquid surface for a predetermined time, and then restarted. Although a method of forming a coating film on the substrate to be coated by dipping and then pulling the substrate to be coated again from the coating solution has been adopted, undulation of the film thickness is likely to occur.

  Further, in the inventions disclosed in Patent Document 3, Patent Document 4 and Patent Document 5, a method of reducing the solvent vapor concentration in the coating tank or in the vicinity of the coating liquid surface during the coating process is employed. When air is exhausted or exhausted, air flow unevenness is likely to occur, and the coating substrate circumferential direction unevenness tends to occur.

Further, in the inventions described in Patent Document 6, Patent Document 7 and Patent Document 8, a method of applying while generating a uniform air flow in the circumferential direction is adopted, but there is a limit to the effect of shortening the film sagging. .
Furthermore, in the invention described in Patent Document 9, a negative pressure is generated around the coating liquid surface by applying an upward air flow to the coating film on the surface of the object to be coated, and the outside air is circulated around the liquid surface based on this negative pressure. However, there remains a problem in the complexity of the coating apparatus and the compatibility with the simultaneous dip coating method.

  In addition, as one of the methods for shortening film sagging, a method is known in which an air supply means is provided in an object holding jig used for dip coating, and gas is supplied from this air supply means. However, even when coating is performed by this method, if there is air supply air flow unevenness, uneven film thickness in the circumferential direction occurs on the coating film, resulting in a defective product.

  In recent years, the use of halogen-based solvents has been restricted or prohibited in response to environmental problems. However, if the halogen-based solvent currently used in the coating liquid is changed to a non-halogen-based solvent, There is a problem that a thin part (film sagging) occurs at the upper end of the coating film for reasons such as an increase in boiling point. Furthermore, in a copying machine, printer, or facsimile using an electrophotographic photosensitive member, the photosensitive member coating is worn and thin with repeated use of the electrophotographic photosensitive member, which determines the life of the photosensitive member. It may be.

  In response to this problem, in order to make the electrophotographic photoreceptor highly durable, the resin component constituting the photoreceptor coating film is changed to a polymer compound having excellent wear resistance, or the charge transport agent is polymerized. Attempts have been made to provide wear resistance. If this method is used as a high durability method for electrophotographic photoreceptors, the viscosity of the coating solution will increase at the same solid content concentration as the conventional coating solution formulation. In this case, however, there is a problem that film sagging near the upper end of the coating film increases during coating.

JP-A-57-5048 JP 2002-82454 A JP 59-1227049 A JP 59-174844 A JP-A-2-4470 JP 59-227771 A JP 60-227261 A JP-A-5-111656 JP-A-4-219169

  Accordingly, the first problem of the present invention is to solve such a problem and prevent the occurrence of film sagging at the coating start end (thin film portion formed at the upper end of the coating), thereby coating the coating film with a uniform film thickness. An object of the present invention is to provide a dip coating method and a dip coating apparatus that can be formed on a coating substrate, and in particular to provide the dip coating method and dip coating apparatus suitable for manufacturing an electrophotographic photosensitive member. .

  Moreover, the 2nd subject of this invention is providing the dip coating method and dip coating apparatus which can suppress the film dripping generate | occur | produced when using a non-halogen-type solvent as a solvent of a coating liquid. is there.

  The third object of the present invention is to provide a coating solution for an electrophotographic photoreceptor containing a polymer compound having excellent wear resistance, or an electrophotographic photoreceptor containing a polymer charge transport agent as a charge transport agent. An object of the present invention is to provide a dip coating method and a dip coating apparatus that can suppress film sagging that occurs when a coating liquid is applied.

  The invention according to claim 1 is a dip coating in which a substrate to be coated is immersed in a coating solution in a coating tank, and then the substrate to be coated is pulled up from the coating solution to form a coating film on the substrate to be coated. In the method, the dip coating method is characterized in that the pulling speed of the upper end portion of the substrate to be coated is decelerated as the pulling distance increases.

Examples of the mode of deceleration include the following.
(1) As shown in FIG. 6 to be described later, the pulling speed is sequentially decreased (linearly) while maintaining a first-order proportional relationship with the increase in the pulling distance. In this case, the deceleration rate with respect to the increase in the pulling distance is constant and corresponds to a gradient of a linear function.
(2) As shown in FIG. 7, which will be described later, the pulling speed is reduced with an increase in the pulling distance. In this deceleration mode, the deceleration rate with respect to the increase in the pulling distance gradually decreases. A specific example is deceleration according to an exponential function. In this case, the vehicle decelerates suddenly immediately after the start of the pulling, and when the pulling distance increases, the degree of deceleration becomes moderate and the deceleration operation ends. Then, the pulling up of the upper end portion of the substrate to be coated is completed, and then the process proceeds to the pulling process at the lower portion of the substrate to be coated.

The invention according to claim 2 is characterized in that, in claim 1, the pulling-up speed of the upper end portion of the substrate to be coated with respect to the coating pulling distance is reduced according to an exponential function.
As an example of this exponential function, let X be a deceleration distance (coating distance to be applied by a reduction ratio from the start of coating: this corresponds to “upper end pulling distance” in FIG. 7), and Y is a reduction ratio. When doing the following formula Y = 1.2903 * X ^-0.0792
(Where * is a multiplication symbol).

The invention according to claim 3 is characterized in that, following the pulling of the upper end portion of the substrate to be coated, the pulling operation of the lower portion of the substrate to be coated excluding the upper end portion of the substrate to be coated is performed at a constant pulling speed Vc. A dip coating method according to claim 1 or 2.
The reason why the pulling operation of the lower portion of the substrate to be coated except the upper end portion of the substrate to be coated is performed at a constant pulling speed Vc is to make the coating film thickness uniform in this portion.

In the invention according to claim 4, when the pulling speed Vt is decelerated as the coating pulling distance increases with respect to the upper end portion of the substrate to be coated, this reduction ratio is defined as a ratio of Vt to Vc: Vt / Vc. When
The length La (the coating distance of the deceleration coating, see FIGS. 6 and 7) at which the reduction ratio is 1.15 or more and 1.25 or less and the pulling speed is decelerated. ) Is 25 mm or more and 50 mm or less, The dip coating method according to claim 3. Further, it is particularly preferable that the reduction ratio is 1.20 and its immediate vicinity, and that the length La is 25 mm and slightly longer than this.
Due to the above numerical limitation, dripping of the coating liquid can be suppressed, and a more uniform film thickness can be stably obtained.

  The invention according to claim 5 is the dip coating method according to any one of claims 1 to 4, wherein the solvent of the coating solution is a non-halogen solvent.

  The invention according to claim 6 is the dip coating method according to claim 5, wherein the coating liquid (coating liquid) is a coating liquid for producing an electrophotographic photosensitive member.

The invention according to claim 7 is an electrophotographic photosensitive member-forming coating solution,
(1) Coating liquid comprising polymer compound, low molecular charge transport agent and solvent, (2) Coating liquid comprising polymer charge transport agent and solvent, (3) Polymer compound, polymer charge transport agent and solvent 6. The dip coating method according to claim 5, wherein the coating liquid comprises: (4) a coating liquid comprising a polymer compound, a low molecular charge transport agent, a polymer charge transport agent and a solvent. is there.

  The invention according to claim 8 is the dip coating method according to claim 7, wherein the polymer compound is a polymer compound having wear resistance.

  In the invention according to claim 9, the substrate to be coated is immersed in the coating solution in the coating tank by the substrate-to-be-coated holding means, and then the substrate to be coated is pulled up from the coating solution and placed on the substrate to be coated. In the dip coating apparatus for forming a coating film, the coated substrate holding means includes a pulling speed adjusting mechanism for decelerating the pulling speed of the upper end portion of the coated substrate with an increase in the coating pulling distance. It is a dip coating apparatus characterized by having.

  The invention according to claim 10 is characterized in that the coated substrate holding means performs an operation of decelerating the lifting speed of the upper end portion of the coated substrate with respect to the coating lifting distance according to an exponential function. This is a dip coating apparatus.

  According to an eleventh aspect of the present invention, there is provided a method for producing an electrophotographic photosensitive member, wherein a photosensitive drum substrate is processed by the dip coating method according to any one of the first to eighth aspects.

  The invention according to claim 12 is an electrophotographic photosensitive member obtained by the manufacturing method according to claim 9.

In the above, a dip coating method in which the substrate to be coated is immersed in a coating solution in a coating tank, and then the substrate to be coated is pulled up from the coating solution to form a coating film on the substrate to be coated; Although the apparatus is used, in the present invention, the upper and lower positions of the substrate to be coated can be fixed and the coating tank can be moved up and down, whereby the substrate to be coated can be immersed and pulled up with respect to the coating liquid. Therefore, in the dip coating apparatus of the present invention, by providing a raising / lowering speed adjusting mechanism of the coating tank instead of the pulling speed adjusting mechanism of the coated base, the upper end portion of the coated base with respect to the coating tank is provided. The “relative pulling speed” may be configured to decelerate as the pulling distance increases.
Moreover, in this invention, about the upper end part of a to-be-coated base | substrate, it can also comprise so that the pulling speed with respect to a coating tank may be decelerated with progress of pulling time.

According to the dip coating method and apparatus according to the present invention, it is possible to prevent the occurrence of film sagging at the coating start end (a thin film portion generated at the upper end of the coating) and to form a coating film having a uniform thickness on the substrate to be coated. Can be formed.
In particular, when a non-halogen solvent is used as a solvent for the coating solution, or when a coating solution for forming an electrophotographic photosensitive member is used as the coating solution, film sagging at the coating start end (at the upper end of the coating) Generation of the resulting thin film portion) can be prevented, and a coating film having a uniform film thickness can be formed on the substrate to be coated.
That is, starting the upper end of the substrate to be coated at a high speed, and changing the pulling speed so that the speed decreases sequentially, film dripping at the coating start end (thin film portion generated at the upper end of the coating) Is prevented.
In the invention according to claim 2, by performing an operation of decelerating the pulling speed of the upper end portion of the substrate to be coated with respect to the coating pulling distance according to an exponential function, the effect of preventing the thin film portion generated at the upper end portion of the coating is particularly increased. A highly uniform coating film can be formed over the entire coated substrate.

  According to the present invention, even when a non-halogen solvent (Claim 4) is used as a solvent for the coating solution, it is possible to prevent a thin portion (film sagging) from occurring at the upper end of the coating film. Since it is possible, it can contribute to environmental protection.

  In the dip coating apparatus according to the ninth aspect, the dip coating method according to any one of the first to fourth aspects can be carried out by appropriately setting the operation mode of the pulling speed adjusting mechanism.

  The electrophotographic photosensitive member according to claim 12 can constitute a high-performance developing device. According to the electrophotographic image forming apparatus in which the electrophotographic photosensitive member according to claim 12 is set, the length of the electrophotographic photosensitive member is increased. An image having a uniform density can be stably formed over the entire length.

Embodiments of the present invention will be described below with reference to the drawings as necessary.
In the present invention, the pulling speed of the upper end portion of the substrate to be coated is faster than the constant pulling speed when the deceleration operation is finished and becomes a constant pulling speed. Although it is possible to decelerate according to a linear function with respect to the pulling distance (coating pulling distance) (the rate of deceleration is proportional to the coating pulling distance = constant rate of deceleration with increasing pulling distance), the degree of deceleration is increased. Decreasing with increasing distance, that is, the pulling speed decreases rapidly immediately after the start of pulling, but it is preferable that the pulling speed gradually decreases with increasing pulling distance, and specific examples follow the exponential function described above. Deceleration is preferred.

FIG. 1 is a schematic diagram showing the overall configuration of a dip coating apparatus (hereinafter sometimes referred to as a coating apparatus) according to an embodiment of the present invention.
First, FIG. 1 will be described. This coating apparatus includes a cylindrical coating tank 10 for storing a coating liquid (coating liquid) 2, an overflow liquid receiver (overflow tank) 9 for receiving a coating liquid overflowed from the upper end of the coating tank, A coating liquid tank (circulation tank) 5 is provided that collects the overflow liquid via the return pipe 3 and prepares the coating liquid by making the recovered coating liquid uniform in viscosity and the like. The coating liquid tank 5 is connected to the bottom of the coating tank 10 via a coating liquid supply pipe 6. The coating liquid supply pipe 6 is provided with a liquid feeding pump 7 for returning the coating liquid in the coating liquid tank 5 to the coating tank 10 and a filter 11 for removing foreign matters in the coating liquid from the liquid feeding pump. ing. The coating liquid tank 5 is provided with a stirrer 4 for stirring the coating liquid.

  In the vicinity of the coating tank 10, a drum lifting / lowering device 8 is installed as a holding means for the drum 1 that is a cylindrical substrate to be coated. The elevating device 8 is for holding the drum 1 and immersing it in the coating liquid 2 in the coating tank 10 and then pulling up the drum from the coating liquid. The upper end of the drum 1 with respect to the coating lifting distance of the drum 1 The pulling speed is decelerated according to an exponential function. In this exponential function, the pulling speed decreases at an accelerated rate as the coating pulling distance increases.

  For this purpose, the lifting device 8 includes a ball screw mechanism 8b, a drive mechanism 8a including a motor for driving the ball screw mechanism, a lifting arm 8c attached to the ball screw mechanism 8b, and a drum provided at a lower portion of the arm. 1 supporting member 8d for supporting. The drive mechanism 8a is provided with a motor control mechanism (not shown) for adjusting the rotational speed of the motor so as to control the lifting / lowering speed of the lifting / lowering arm 8c, such as a decelerating operation of the pulling speed of the upper end of the drum 1. Has been. As described above, the drum 1 is moved up and down by the lifting arm 8c.

  FIG. 2 is an explanation showing a drum pulling process in the dip coating apparatus of FIG. 1, and shows a state at the start of the pulling. FIG. 3 is an explanatory diagram showing a state at the moment when the pulling is started from the state of FIG. 2 and the pulling of the upper end of the drum is finished. FIG. 4 is an explanatory diagram showing a state at the moment when the pulling of the portion other than the drum upper end (drum lower portion) is started from the state of FIG. 3 and the pulling of the drum lower portion is finished.

In the dip coating apparatus, as shown in FIG. 2, the upper end of the drum 1 is supported by a support member 8 d, and the entire drum 1 is once immersed in the coating liquid 2 in the coating tank 10 by the lifting device 8. Next, as shown in FIG. 3, the pulling up operation of the upper end portion of the drum 1 is started. The pulling speed in this case is as described above. Furthermore, as shown in FIG. 4, the lowering part (parts other than the upper end part) of the drum 1 is pulled up at a uniform pulling speed. Thus, the coating liquid adhering to the drum 1 is exposed to the atmosphere on the coating liquid surface of the coating tank 10, whereby the solvent in the coating liquid is volatilized and the viscosity increases. A coating film having a uniform film thickness is formed over the entire length of the drum.
The wet film attached to the drum surface by pulling up (coating) can be uniformly leveled by dripping until the solvent evaporates due to gravity and does not sag due to gravity (improves film thickness uniformity). ).

In the present invention, examples of the non-halogen solvent used as a solvent for the coating solution include aromatic hydrocarbon solvents such as toluene, ether solvents such as 1,4-dioxane and tetrahydrofuran, and ketone solvents such as methyl ethyl ketone. Can be mentioned. The coating liquid for forming an electrophotographic photoreceptor includes a coating liquid comprising a polymer compound, a low molecular charge transport agent and a solvent, a coating liquid comprising a polymer charge transport agent and a solvent, and a polymer compound and polymer charge transport. Examples thereof include a coating solution comprising an agent and a solvent, or a coating solution comprising a polymer compound, a low molecular charge transport agent, a polymer charge transport agent and a solvent.
In the present invention, the viscosity of the coating solution is preferably 380 to 500 mPa · s. In the present invention, particularly preferable results are obtained when the substrate to be coated has a diameter of 30 to 100 mm and a length of 242 to 485 m.

  The polymer compound used in the electrophotographic photoreceptor forming coating solution is preferably a polymer compound having excellent wear resistance, and examples thereof include bisphenol A type polycarbonate and bisphenol Z type polycarbonate. May include halogen solvents such as methylene chloride, aromatic solvents such as toluene, and cyclic ether solvents such as tetrahydrofuran and dioxane. According to the dip coating method of the present invention, in particular, a coating solution for an electrophotographic photosensitive member containing a polymer compound having excellent wear resistance, or an electrophotographic photosensitive material containing a polymer charge transporting agent as a charge transporting agent. Even in the case of applying the body coating liquid, it is possible to suppress the occurrence of film sagging and to form a photoreceptor coating film having a uniform film thickness on the substrate to be coated.

The drum pulling method according to the present invention will be described in comparison with the conventional method. FIG. 5 is a graph for explaining a pulling mode of a substrate to be coated according to the prior art. In this case, the drum pulling speed V does not change with respect to the drum pulling distance (coating pulling distance) and is a constant value, and this value is equal to the pulling speed for the portion excluding the upper end.
FIG. 6 is a graph for explaining a pulling mode of a substrate to be coated according to an embodiment of the present invention. In this case, the drum pulling speed V decreases linearly with respect to the drum pulling distance (coating pulling distance) (Va → Vc), and the lower limit value is equal to the pulling speed for the portion excluding the upper end (FIG. 3, (See FIG. 4). That is, FIG. 6 shows that when the pulling speed at the start of pulling is Va and the pulling speed (constant value) excluding the upper end (lower part) is Vc, the upper end pulling speed Vt is set in the pulling operation of the upper end. The voltage is decreased from Va to Vc at a constant rate. In this case, the upper end pulling speed Vt linearly decreases with respect to the pulling distance on the graph.

  FIG. 7 is a graph for explaining a pulling mode of a substrate to be coated according to another embodiment of the present invention. In this figure, the drum pulling speed V decreases exponentially with respect to the drum pulling distance (coating pulling distance), and the lower limit value is equal to the pulling speed for the portion excluding the upper end (see FIGS. 3 and 4). reference). That is, in FIG. 7, when the pulling speed at the start of pulling is Va and the pulling speed (constant value) excluding the upper end (lower part) is Vc, the upper end pulling speed Vt is set in the pulling operation of the upper end. It decreases exponentially from Va to Vc. In this case, the slope of the tangent to the curve indicating the change in the pulling speed Vt gradually decreases.

  According to the present invention as described above, as a result of the film thickness of the film sagging portion being compensated, the occurrence of film sagging at the coating start end (thin film portion formed at the upper end of the coating) is prevented, and the film at the coating start end Occurrence of sagging (thin film portion formed at the upper end of the coating) is reliably prevented. The pulling operation according to FIG. 6 can provide a good result to some extent. However, the pulling operation according to FIG. 7 provides a particularly excellent result, and the coating film having a highly uniform film thickness in the entire pulling direction of the drum 1. Can be formed. In addition, according to the present invention, since it is not necessary to use a high-viscosity coating solution in order to obtain a thick film, there is an effect that the pulling rate is reduced and the production efficiency is not lowered.

Examples of the present invention and comparative examples will be specifically described below.
[Conditions common to Examples 1 to 9 and Comparative Example 1]
A 5 wt% methanol solution of soluble nylon (Alamine CM-8000, manufactured by Toray Industries, Inc.) is dip-coated on an aluminum cylindrical substrate having an outer diameter of 30 mm and a length of 250 mm, and dried at 100 ° C. for 10 minutes to a thickness of 0.3 μm. A subbing layer was formed.
Next, 10 parts by weight of a charge generating agent, 7 parts by weight of polyvinyl butyral, and 145 parts by weight of tetrahydrofuran are placed in a ball mill, milled for 72 hours, added with 200 parts by weight of cyclohexanone, dispersed for 1 hour, and further diluted with cyclohexanone. The generation layer coating solution was dip-coated on the aluminum cylindrical substrate having the undercoat layer and dried at 100 ° C. for 10 minutes to form a charge generation layer having a thickness of about 0.1 μm.

Next, 7 parts by weight of the charge transport agent and 10 parts by weight of polycarbonate (Panlite C-1400, manufactured by Teijin Ltd.) were dissolved in 83 parts by weight of tetrahydrofuran to prepare a charge transport layer coating solution.
This charge transport layer coating liquid is put into the coating tank 10 and the coating liquid tank 5 of the dip coating apparatus shown in FIG. 1, and the aluminum cylindrical substrate (drum 1) on which the charge generation layer is formed is lifted and lowered. It was held at 8 and lowered into the coating solution and immersed. Next, the drum was pulled up from the coating solution to form a coating film on the drum 1.
In this case, the viscosity of the coating solution was 450 mPa · s. Further, the reduction ratio Y at the time of the pulling-up operation is the above-mentioned formula Y = 1.903 * X ^-0.0792
(However, X: 0 to 25 mm, Y: 1 to 1.20).
Further, the sag of the coating solution was measured by an optical interference film thickness meter (Otsuka Electronics MPDC-1100), and the coating surface was measured by a surface shape measuring device (Tokyo Seimitsu surface shape measuring device Suefcom 1200).

[Example 1]
When the drum 1 was pulled up from the coating solution, the charge transport layer was formed by reducing the pulling speed at the upper end as shown in FIG. The uniformity was good. Thereafter, this drum was put in a dryer and dried at 120 ° C. for 30 minutes to obtain an aluminum cylindrical substrate on which a charge transport layer was formed. The reduction ratio when pulling up while decelerating was 1.20, and the coating distance for decelerating was 25 mm.

[Comparative Example 1]
When the drum 1 is pulled up from the coating solution, the charge transport layer is formed in the same manner as in Example 1 except that the pulling speed of the upper end is constant as shown in FIG. Formed. As a result, the film sagging of the film thickness at the upper end was increased.

[Example 2]
When the drum 1 was pulled up from the coating solution, the same procedure as in Example 1 was performed except that the charge transport layer was formed by pulling up while lowering the pulling speed of the upper end as shown in FIG. The film sagging was small and the uniformity of the coating film was very good.

[Example 3, Example 4]
When the drum 1 is pulled up from the coating liquid, coating is performed while reducing the pulling speed at the upper end as shown in FIG. 6 and the reduction ratios are 1.15 (Example 3-1), 1.20 ( The charge transport layer was formed by shaking to Example 3-2) and 1.25 (Example 3-3). As a result, the film sagging at the upper end was small and the uniformity of the coating film was good.
When the drum 1 is pulled up from the coating solution, coating is performed while reducing the pulling speed at the upper end as shown in FIG. 7, and the reduction ratios are 1.15 (Example 4-1), 1.20 ( The charge transport layer was formed by shaking to Example 4-2) and 1.25 (Example 4-3). As a result, film dripping at the upper end was very small, and the uniformity of the coating film was very good.

[Example 5]
When the drum 1 was pulled up from the coating solution, coating was performed while reducing the pulling speed at the upper end as shown in FIG. 7, and a charge transport layer was formed with a reduction ratio of 1.10. As a result, there was little film dripping at the upper end, and the uniformity of the coating film was as good as in Example 3.

[Example 6]
When the drum 1 is pulled up from the coating solution, coating is performed while reducing the pulling speed at the upper end as shown in FIG. 6, and the charge transport layer is formed by changing the reduction ratio to 1.30 and 1.35. did. As a result, the film thickness at the upper end could be prevented from sagging, but the uniformity of the film thickness distribution was lower than in Example 3.

[Example 7]
When the drum 1 was pulled up from the coating liquid, the charge transport layer was formed by decelerating as shown in FIG. 7 and changing the pulled coating distance to be decelerated to 25 mm and 50 mm. As a result, film dripping at the upper end was very small, and the uniformity of the coating film was very good.

[Example 8]
When the drum 1 was pulled up from the coating solution, the charge transport layer was formed by decelerating as shown in FIG. 6 and changing the pulled coating distance to 15 mm and 20 mm. As a result, the film thickness at the upper end could be prevented from sagging, but the uniformity of the film thickness distribution was not so high.

[Example 9]
When the drum 1 was pulled up from the coating solution, the charge transport layer was formed by decelerating as shown in FIG. 6 and changing the pulled coating distance to be decelerated to 55 mm and 65 mm. As a result, the film thickness at the upper end could be prevented from sagging, but the uniformity of the film thickness distribution was not so high.

  As described above, according to the dip coating method and dip coating apparatus of the present invention, it is possible to prevent the occurrence of film sagging at the coating start end (thin film portion formed at the upper end portion of the coating) and to apply a uniform film thickness. A film can be formed on the substrate to be coated. In addition, according to the dip coating method and apparatus of the present invention, an electrophotographic photosensitive member containing a polymer compound excellent in abrasion resistance when a coating solution using a non-halogen solvent as a solvent is applied. Film sagging at the coating start end (thin film portion formed at the upper end of the coating) when applying a coating liquid for electrophotography or a coating liquid for an electrophotographic photoreceptor containing a polymer charge transporting agent as a charge transporting agent Thus, a coating film and a photosensitive layer having a uniform film thickness can be formed on the substrate to be coated.

It is the schematic which shows the whole structure of the dip coating apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the drum pulling-up process in the dip coating apparatus of FIG. 1, Comprising: The state at the time of a pulling start is shown. FIG. 3 is an explanatory diagram showing a state at the moment when the pulling is started from the state of FIG. 2 and the pulling of the drum upper end is finished. FIG. 4 is an explanatory diagram showing a state at the moment when the pulling of the portion other than the drum upper end portion (drum lower portion) is started from the state of FIG. 3 and the pulling of the drum lower portion is finished. It is a graph explaining the pulling aspect of the to-be-coated base based on a prior art. It is a graph explaining the pulling aspect of the to-be-coated substrate which concerns on one Embodiment of this invention. It is a graph explaining the pulling aspect of the to-be-coated base | substrate which concerns on another embodiment of this invention.

Explanation of symbols

1 drum (cylindrical base)
2 Coating liquid (coating liquid)
DESCRIPTION OF SYMBOLS 3 Return piping 4 Stirrer 5 Coating liquid tank 6 Coating liquid supply piping 7 Liquid feed pump 8 (Drum) lifting device 8a Drive mechanism 8b Ball screw mechanism 8c Lifting arm 8d Support member 9 Overflow liquid receptacle (overflow tank)
10 Coating tank 11 Filter

Claims (12)

  In the dip coating method, wherein the substrate to be coated is immersed in a coating solution in a coating tank, and then the substrate to be coated is pulled up from the coating solution to form a coating film on the substrate to be coated. A dip coating method characterized in that the pulling speed of the upper end portion of the substrate is decelerated as the coating pulling distance increases.   2. The dip coating method according to claim 1, wherein the operation of decelerating the pulling speed of the upper end portion of the substrate to be coated with respect to the coating pulling distance is performed according to an exponential function.   The pulling operation of the lower part of the substrate to be coated excluding the upper end of the substrate to be coated is performed at a constant pulling speed Vc following the pulling of the upper end of the substrate to be coated. Immersion coating method. When the pulling speed Vt is decelerated as the coating pulling distance increases with respect to the upper end portion of the substrate to be coated, when this reduction ratio is defined as the ratio of Vt to Vc: Vt / Vc,
The reduction ratio is set to 1.15 or more and 1.25 or less, and the length of the upper end portion of the substrate to be coated for performing the speed reduction operation (coating distance for deceleration coating) is set to 25 mm or more and 50 mm or less. The dip coating method according to claim 3.   The dip coating method according to any one of claims 1 to 4, wherein the solvent of the coating solution is a non-halogen solvent.   6. The dip coating method according to claim 5, wherein the coating solution is a coating solution for producing an electrophotographic photosensitive member. The electrophotographic photoreceptor forming coating solution is
(1) Coating liquid comprising polymer compound, low molecular charge transport agent and solvent, (2) Coating liquid comprising polymer charge transport agent and solvent, (3) Polymer compound, polymer charge transport agent and solvent The dip coating method according to claim 6, wherein the coating liquid comprises: (4) a coating liquid comprising a polymer compound, a low molecular charge transport agent, a polymer charge transport agent, and a solvent.   The dip coating method according to claim 7, wherein the polymer compound is a polymer compound having wear resistance.   Immersion coating in which the substrate to be coated is immersed in the coating solution in the coating tank by the substrate-to-be-coated holding means, and then the substrate to be coated is pulled up from the coating solution to form a coating film on the substrate to be coated. In the apparatus, the coated substrate holding means includes a pulling speed adjusting mechanism for decelerating the pulling speed of the upper end portion of the coated substrate with an increase in the coating pulling distance. Coating equipment.   10. The dip coating apparatus according to claim 9, wherein the coated substrate holding means performs an operation of decelerating the pulling speed of the upper end portion of the coated substrate with respect to the coating pulling distance according to an exponential function.   A method for producing an electrophotographic photosensitive member, comprising treating a photosensitive drum substrate as the substrate to be coated by the dip coating method according to claim 1.   An electrophotographic photosensitive member obtained by the production method according to claim 11.

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