JPH067265B2 - Electrophotographic recording material base material coating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic recording material in which a coating solution is simultaneously and uniformly applied in a superposition of two or more layers on the outer surface of a base material having an endless continuous surface. The present invention relates to a coating device for substrates and the like.

BACKGROUND OF THE INVENTION Various methods such as a spray coating method, a dip coating method, a blade coating method and a roll coating method have been studied for uniform coating with a thin film on the outer surface of a base material having an endless continuous surface. There is. In particular, thin film uniform coating such as electrophotographic photosensitive drum is being studied to develop a coating device having excellent productivity. However, the conventional apparatus for coating a base material having an endless continuous surface has drawbacks that a uniform coating film cannot be obtained and productivity is poor.

In the spray coating method, the solvent evaporates by the time the coating droplets ejected from the spray gun reach the outer peripheral surface of the base material having the endlessly formed continuous surface, so that the solid content concentration of the coating droplets increases. When the droplets reach the surface due to the increase in viscosity of the applied droplets, the droplets do not spread sufficiently on the surface, or the dried and solidified particles adhere to the surface. The smoothness of the coated surface cannot be obtained. Further, since the arrival rate of droplets to the base material having the continuous surface is not 100% and is partially uneven, it is very difficult to control the film thickness. Further, since a polymer solution or the like may cause stringing, there are restrictions on the solvent and resin used. The blade coating method and the roll coating method include, for example, arranging a blade or a roll in the length direction of a cylindrical base material, rotating the cylindrical base material in the circumferential direction to perform coating, and rotating the cylindrical base material once, and then the blade. Alternatively, the roll is retracted. However, when the blade or roll is retracted, there is a drawback in that a part of the coating film thickness is thicker than other parts due to the viscosity of the coating liquid, and a uniform coating film cannot be obtained. JP-A-54-87229, JP-A-54-128740, the blade in the blade coating is connected to the change of the direction of movement of the piston in the tank or cylinder that can switch between vacuum and atmosphere,
By switching to the vacuum side when the blade is retracted, the excess coating liquid is absorbed to obtain a uniform coating film. However, in order to obtain a uniform coating film, it is necessary to set the suction timing and precisely control the amount of the coating liquid to be sucked, but there are drawbacks such that this control is complicated and difficult.

The dip coating method (see Japanese Patent Application Laid-Open No. 49-130736) is improved in that the surface smoothness of the coating film and the uniformity of the coating film are poor. However, the control of the coating film thickness is governed by the physical properties of the coating liquid (viscosity, surface tension, density) and the coating speed, and adjustment of the physical properties of the coating liquid is very important. Also, the coating speed is limited to a low level, resulting in poor productivity. There is a drawback of.

JP-A-56-15864, JP-A-56-15865, JP-A-SHO
56-15866 discloses that the film thickness to be formed by moving a scraping blade arranged with a clearance around the circumference of a cylindrical base material to determine the coating thickness is determined by the clearance between the scraping blade and the cylindrical base material. The film thickness is about 1/2 of the clearance, and in order to obtain a uniform film thickness, we have proposed a method of rotating the cylindrical substrate and holding the scraping blade to keep the clearance constant. Furthermore, when changing the coating thickness, the coating thickness will be about 1/2 of the clearance, so it is necessary to prepare and replace a scraping blade that has a clearance according to the required coating thickness. Every time the film thickness is changed, the worker is forced to perform complicated work. Further, since the setting accuracy of the scraping blade is the film thickness accuracy immediately, there is no play (variability) in accuracy, and it is very difficult to finely adjust the coating film thickness.

The present applicant has filed a patent application first to solve the above-mentioned drawbacks.
Proposed as No. 57-74030. According to the coating device of the previously proposed technology, it is possible to obtain a uniform film thickness on a base material having a continuous surface formed endlessly, and it is possible to perform high-precision film thickness control quickly and easily. It is a coating device that can However, in the coating apparatus, only one coating film can be coated on the substrate in one coating step, and two or more coating liquids cannot be simultaneously coated in a superposition of two or more layers. Therefore, in the case of overlapping coating on the base material, it was necessary to dry each layer in the coating step and repeat the coating step, and the operation was extremely complicated.

[Object of the Invention] The present invention has been made to solve the above-mentioned drawbacks, and two or more coating liquids of two or more layers are simultaneously applied to a base material having a continuous surface formed endlessly in one application step. SUMMARY OF THE INVENTION The present invention provides a coating apparatus capable of coating multiple layers, and other and related objects of the present invention will be made clear by the following description of the present specification.

[Means for Solving the Problems] A coating method of the present invention for achieving the above-mentioned object has a continuous peripheral surface formed endlessly and has the same shape from one end to the other end like an electrophotographic photoreceptor substrate. In a fixed bead coating apparatus for coating a liquid while continuously moving a columnar or tubular base material having an upward direction, an endless hopper edge surrounds the base material peripheral surface and the base material peripheral surface. A hopper device is arranged so as to maintain a gap capable of cross-linking a bead composed of two or more superposed coating liquid layers over the entire circumference of the base material, and the hopper device comprises the endless hopper edge. At the end of the liquid slide curved slope that is configured as an endless structure in which the entire circumference gradually converges toward the hopper edge and is inclined downward, and the liquid slide curved slope is endlessly formed. Two or more coating liquid outlets formed, and an endless coating liquid that flows down the liquid slide curved surface from the coating liquid outlet to supply the coating liquid to each of the overlapping layers of the coating liquid beads in a superposed relationship. And a distribution chamber.

Incidentally, JP-A-49-42343 and JP-A-54-124039 describe a coating method in the case where the base material to be coated is in the form of a sheet instead of endless. The invention of the present application for applying a columnar or tubular base material having the above is a technology in a different field having completely different configurations, problems, and objects. This is because in the technique of applying in a sheet shape, the liquid slide surface is a mere flat surface, and the coating liquid flowing on the liquid slide surface remains in the state of being pushed out from the liquid outlet, that is, on the flat surface with substantially the same width. It flows down and is applied flat on a flat base material while maintaining its width.However, in the case of a columnar or tubular base material, the surface on which the coating solution flows down is an endless curved slope. The point that the coating liquid flowing down is endless without side edges, and the coating liquid is
This is because it has a completely different configuration, problem, or object in that the entire circumference flows down from a coating liquid outlet toward a substrate on a curved slope that gradually converges.

[Specific Configuration of the Invention] A coating apparatus according to the present invention coats a liquid on the outer surface of a columnar or tubular base material having a continuous peripheral surface formed endlessly and having the same shape from one end to the other end. In the apparatus, two or more coating liquid distribution chambers and coating liquid distribution slits connected to the coating liquid distribution chambers are continuous, and a coating liquid supply means for supplying the coating liquid to each coating liquid distribution chamber is a coating liquid distribution chamber. The coating liquid outlets of the coating liquid distribution slits gradually converge toward the hopper edge so that the coating liquid outlet of each coating liquid distribution slit terminates at the endless hopper edge, and the liquid slide curved inclined surface inclines downward. The endless hopper edge formed at the end of the liquid slide curved slope is 0.05 to 1 mm larger than the outer dimension of the base material, and the length extending downward from the liquid slide curved slope end is 0.1 to 10 m.
m, preferably 0.5 to 4 mm. Further, the hopper edge is inclined vertically downward from the end of the slanted slope and up to 30 degrees from the end, and is more preferably inclined vertically downward and 20 degrees from the base.
It extends with an inclination within a range of up to degrees.

When the inclination of the hopper edge exceeds 30 degrees, the cross-linking of the coating solution becomes short, the bead becomes unstable, and it becomes difficult to obtain a good coating film. Further, the coating liquid supplied to the coating device is once stored in each coating liquid distribution chamber, and the coating liquid is evenly distributed to each of the coating liquid distribution slits connected thereto.
The pressure loss ratio of the coating liquid distribution chamber to the coating liquid distribution slit is set so that the coating liquid can be uniformly distributed to the slits and the coating liquid distributed to the slits can be uniformly coated on the substrate surface. Is 40 or more, and more preferably 40 to 100,000. If the pressure loss is less than 40, it will be difficult to evenly distribute and apply each coating liquid, and if it exceeds 100,000, it will be necessary to enlarge each coating liquid distribution chamber or to lengthen each slit, which is a structural problem of the device. Cause

A coating film obtained by coating two or more superposed coating liquid layers in the coating apparatus of the present invention is formed by coating liquid beads. In other words, the layer of the coating liquid leaving the coating device is not directly applied to the base material in a layer having the same thickness as when the coating liquid leaves the coating device, but is transferred to the base material once it forms a liquid pool (bead). is there. Therefore, the coating formed by this coating solution bead is not actually formed directly from the coating apparatus to the substrate, but the coating apparatus simply maintains the coating solution bead and the substrate is coated from the bead. In coating with this bead, the thickness of the coating applied on the substrate that moves across and across the bead is determined by the action of the bead and the rate at which the substrate moves, the feed rate of the coating liquid, It changes depending on the efficiency of the hopper structure.

In the coating apparatus of the present invention, when the base material having a continuous peripheral surface formed endlessly to be coated has a cylindrical shape, the hopper edge has a diameter slightly larger than the cylindrical base material diameter (0.
The liquid slide curved slope that becomes a circular end portion (diameter of 05 to 1 mm larger) and ends at the hopper edge is a conical slope, that is, a so-called mortar shape, and the coating formed on the liquid slide curved slope. The liquid distribution slit is also circular.

The coating by the coating device of the present invention is performed as follows. That is, in the case of applying a columnar or tubular base material having a continuous peripheral surface formed endlessly and having the same shape from one end to the other end as in an electrophotographic photoreceptor,
A hopper is provided so as to surround the peripheral surface of the base material and to maintain a gap between the peripheral surface of the base material and the peripheral surface of the base material. A coating solution bead for cross-linking and is formed all around, and one coating solution layer is continuously and simultaneously supplied to the bead together with another coating solution layer so that each individual layer is distinct. The base material is continuously moved upward so that the peripheral surface of the base material intersects and contacts the coating liquid bead, and the peripheral surface of the base material is a superposed layer of the coating liquid bead. The bonding layers are simultaneously drawn out by simultaneously engaging with the outer ends of the layers, and are applied simultaneously.

EXAMPLES Examples of the present invention will be described below in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

FIG. 1 is a partial sectional perspective view showing a coating apparatus according to the present invention,
FIG. 2 is a cross-sectional view showing a coating state on a base material.

In each drawing, 1 is a coating apparatus main body, and 2 is a hopper apparatus for coating a coating liquid. 3A and 3B are coating liquid distribution chambers, and supply pipes 4A and 4B for supplying different coating liquids S1 and S2 are connected to the distribution chambers 3A and 3B. 5A,
5B is a coating liquid distribution slit, which is continuously formed so as not to have an end portion and to surround the outer periphery of the base material. 6A and 6B are coating solution outlets, 7 is a liquid slide curved slope, 8 is a hopper edge, and 9 is a coating solution bead.

A different amount of the different coating liquids S1 and S2 are distributed through the pipes 4A and 4B by a pump (not shown) to the distribution chambers 3 respectively.
It is supplied to A and 3B. Therefore, the coating liquids S1 and S2 are distributed in the circumferential direction of the cylindrical drum, and the distribution slits 5A and 5
Slide portion 7 from coating liquid outlets 6A and 6B via B
Flowing out uniformly in the circumferential direction upward, and while flowing down the liquid slide curved slope 7, the coating liquid S1 and S2 are formed into two layers,
A bead is formed by bridging from the hopper edge 8 to the entire outer peripheral surface 11 of the cylindrical base material 10 through the liquid slide curved surface 7 to form a two-layered layer on the outer peripheral surface 11 of the base material. L1 and L2 are applied.

In a preferred embodiment of the present invention, the difference between the hopper edge diameter and the cylindrical substrate outer diameter is in the range of 0.05 to 1 mm, preferably 0.1 to 0.6 mm. Moreover, the inclination angle of the liquid slide curved slope is in the range of 10 to 70 ° with respect to the horizontal, and more preferably in the range of 20 to 45 °.

The viscosity of the coating liquid applied in this device is 0.5 to 700 cp.
In the range of 1 to 500 cp. The coating film applied in this apparatus has a seamless distribution chamber distribution slit and a slide portion arranged in the circumferential direction of the cylindrical substrate, and thus the applied coating film is seamless and uniform. Further, the coating film thickness can be easily controlled because it is determined by the supply amount of the coating liquid and the moving speed of the cylindrical shape, and at the same time, the coating speed can be much faster than that of the dipping method. Further, a plurality of the hopper devices may be provided according to different kinds of coating liquids.

In the figure, the parts designated by the same reference numerals as those in FIGS. 1 and 2 are the same as the members designated by the corresponding reference numerals in FIGS. 1 and 2.

As the coating liquid supply means for supplying the coating liquid to the coating liquid distribution chamber, it is preferable to use a pipe as shown in the above-mentioned embodiment, and a plurality of pipes of two or more are provided although not shown for the stability and uniformity of the coating liquid. You may use the pipe of this.

In the coating apparatus of the present invention, when coating with a film thickness less than the film thickness range determined by the viscosity of the coating liquid, when the coating liquid viscosity is too high, or when the coating speed is too high, the cylindrical base When the liquid applied on the circumference of the material at the hopper edge is carried away, the viscosity of the liquid strongly acts to lift the liquid of the bead upward, forming between the cylindrical base material and the hopper edge. The bead may not be able to exist stably, and in order to prevent this, as shown in FIG. 3, the bead of the coating liquid formed between the hopper edge 8 and the base material 10 having a continuous surface. A decompression chamber 12 that cooperates with the bead and the cylindrical substrate 10 is provided in the lower part of the decompression chamber, and a gas discharge pipe 13 that communicates with the decompression chamber 12 is provided to reduce the pressure inside the decompression chamber 12 to a negative pressure below the atmospheric pressure. A coating device that is designed to perform coating is also preferable. It can be used for.

If this device is used, air is discharged from the inside of the decompression chamber 12 including the bead and a part of the surface of the cylindrical substrate 10 as a part of the wall below the bead, and the internal pressure of the decompression chamber 12 becomes negative than the atmospheric pressure ( Desirably, the coating pressure is controlled to be kept lower than the atmospheric pressure in the range of 1 mm water column to 300 mm water column). Therefore, it is possible to prevent uneven coating due to fluctuations in the coating speed, fluctuations in the gap between the cylindrical substrate and the hopper edge, and the like.

As described above, in the embodiments of the present invention, the case where the two coating liquids are simultaneously applied in a superimposed manner has been described, but three or more coating liquids can be applied simultaneously in an overlapping manner.

This device is a thin electrophotographic photosensitive drum that requires a uniform coating film, manufacturing of electrostatic recording media, coating on the roller surface,
It is used for forming a coating film on the outer peripheral surface of an endless strip or the like, and is not limited thereto. That is, it is used as a simultaneous superposition coating device on the outer surface of a columnar or tubular base material having an endless continuous peripheral surface and the same shape from one end to the other.

In this device, the hopper edge and the cylindrical base material are arranged with a certain gap, so the base material (cylindrical drum)
Not hurt.

In addition, the coating solution used in this device can be supplied in an amount necessary for coating, so only a small amount is required. Which is advantageous.

[Experimental Example] An experimental example of the present invention will be described below.

The substrate to be coated is a drum made of aluminum having an outer diameter of 100 mm, and the drum has a charge generation layer (CGL) as a lower layer.
Was coated with a charge transport layer (CTL). The composition of each coating solution and the coating conditions are described below.

CGL coating liquid composition 25 parts by weight of monoazo pigment and 25 parts by weight of polycarbonate were pulverized and mixed, and then 850 parts by weight of 1,2-dichloroethane was added,
It was dispersed in a beer mill for 24 hours to obtain a coating liquid. The viscosity of the coating solution was 100 cp (B-type viscometer NO.2 rotor 60 rpm).

Composition of CTL coating liquid 100 parts by weight of polycarbonate, 75 parts by weight of polyvinylcarbazole (PVK), and 1045 parts by weight of 1,2-dichloroethane were dissolved by stirring to obtain a coating liquid. The viscosity of the coating solution is 200 cp
Met.

Experimental Example 1 CGL under the following coating conditions using the coating apparatus shown in FIG.
The CTL coating liquid was supplied from the supply port 4B connected to the distribution chamber 3B so that the coating liquid is on the lower side, and the CTL coating liquid was supplied from the supply port 4A connected to the distribution chamber 3A by a pump to apply the liquid, and immediately after the application, it was dried with a dryer. As a result, a uniform coating film was obtained.

Coating conditions Coating speed (drum rise speed) = 2m / min CGL supply rate = 12.6cc / min (film thickness after drying = 1μm, film thickness before drying = 20μm) CTL supply rate = 107cc / min (film thickness after drying = (Corresponding to 25 μm, film thickness before drying = 170 μm) Coating device inner diameter = 100.5 mm Comparative Example 1 A coating solution having the above composition was coated by the dip coating method described in JP-A-49-130736.

After the coating liquid of the above composition was filled in the coating tank, the drum was dipped, and then the drum was pulled up and dried with a dryer.

As a result, at the coating speed of 2.0 m / min, the CGL coating liquid became too thick and dripping occurred on the entire circumference of the drum. In order to obtain a film thickness of 1 μm after drying, it was necessary to reduce the coating speed to 0.9 m / min.

Also, the CTL coating liquid is similar to the CGL coating liquid in coating speed
At 2.0 m / min, the film became too thick and dripping occurred, and a uniform coating film could not be obtained. In order to obtain a uniform coating film, it was necessary to reduce the coating speed to 0.24 m / min.

From the above results, in the dip coating method of Comparative Example 1, in order to obtain a uniform coating film, the coating speed was set to Experimental Example 1 (the present invention).
Compared to CGL, CY
The productivity is extremely low because each L must be applied separately for each layer.

Comparative Example 2 First, CGL was prepared by the coating method described in JP-A-56-15864.
The coating liquid was applied, and then the CTL coating liquid was applied.

Application of CGL The film thickness after scraping by this coating method is about half the clearance between the scraping blade and the drum, so the film thickness before drying = 20
In order to obtain μm, the following inner diameter of the blade was 100.08 mm, the scraping blade moving speed was 2 m / min, and the drum rotation speed was 400 rpm.

The resulting coating film had spiral-shaped unevenness of light and shade with a pitch of about 5 mm. Since the CGL coating liquid is a pigment dispersion liquid, it exhibits pseudoplasticity, and has the property of rapidly increasing viscosity when the shearing force acting on the liquid is removed, and the film thickness before drying is 20μ.
It is thought that unevenness in shade occurred because it was not leveled because it was as thin as m. The conditions under which the drum rotation speed was increased and the leveling effect was easily obtained were examined, but 100 rpm was the limit for application. At this time, although the pitch-like unevenness in the shape of a spiral was reduced, it remained, and a uniform coating film could not be obtained.

Application of CTL Application of CTL was performed in the same manner as application of CGL except that the inner diameter of the scraping blade was 100.6 mm.

The obtained coating film was uniform in appearance, unlike CGL, but when the film thickness was measured, there was a film thickness variation of 3 μm at about 5 mm. It is considered that 1,2-dichloroethane was not leveled because the viscosity increased during the drying process because the evaporation was relatively fast.

From the above results, it is not necessary to significantly slow down the coating speed in the coating method of Comparative Example 2 as in the dip coating method of Comparative Example 1, but it is difficult to obtain a uniform coating film.

[Effects of the Invention] As described above, the coating apparatus of the present invention is capable of coating two or more coating liquids having different properties at one time without damaging the continuous peripheral surface of a columnar or tubular base material formed endlessly. It is possible to apply two or more layers simultaneously in the process so that a uniform film thickness can be obtained, and it is easy to control the film thickness. Combined with the structure of continuous coating while continuously moving, it has high productivity in a quick manner. In particular, when the present invention is used for producing a recording body such as an electrophotographic photoreceptor, an undercoat layer, a charge generation layer, a charge transport layer, etc. (JP-A-51-90827, 57-67934,
See 57-179857. ) Can be applied at the same time.

[Brief description of drawings]

FIG. 1 is a partial sectional perspective view showing a coating apparatus according to the present invention,
FIG. 2 is a cross-sectional view showing a coating state on a base material having an endless continuous surface, and FIG. 3 is a cross-sectional view showing another embodiment. In the figure, 1 is a coating device main body, 2 is a hopper device,
3A and 3B are coating liquid distributors, 4A and 4B are pipes, 5
A and 5B are coating liquid distribution slits, 6A and 6B are coating liquid outlets, 7 is a liquid slide curved slope, 8 is a hopper edge, and 9 is a hopper edge.
Is a coating liquid bead, 10 is a base material, 11 is an outer peripheral surface of the base material, 12 is a decompression chamber, and 13 is a discharge pipe.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Yamamoto 1 Sakura-cho, Hino-shi, Tokyo Within Konishi Roku Photo Industry Co., Ltd. (56) Reference JP-A-49-42343 (JP, A) JP-A-54- 124039 (JP, A) JP 56-15864 (JP, A) JP 49-107040 (JP, A) JP 53-2768 (JP, A) JP 58-189061 (JP, A)

Claims (1)

[Claims] 1. A columnar or tubular base material having an endless continuous peripheral surface and having the same shape from one end to the other end, such as an electrophotographic photosensitive base material, is continuously moved upward. Meanwhile, in a fixed bead coating device for coating a liquid, a bead composed of two or more overlapping coating liquid layers is formed on the entire base material such that an endless hopper edge surrounds the peripheral surface of the base material and the peripheral surface of the base material. A hopper device is arranged to maintain a bridging gap around the circumference, the hopper device gradually converging around the entire circumference toward the hopper edge so as to terminate at the endless hopper edge. And a slanted liquid slide curved surface which is inclined endlessly, two or more coating liquid outlets which are endlessly formed on the liquid slide curved slope, and the liquid sludge is provided from the coating liquid outlet. And an endless coating liquid distribution chamber for supplying the coating liquid to each of the superposed layers of the coating liquid beads in a superposed relationship by flowing down the curved slope. Applicator for etc.