JPS62266174A - Coating method - Google Patents

Abstract

PURPOSE:To enhance the uniformity of leveling and a film thickness by eliminating liquid dripping, by forming a film under such a coating condition that the value calculated from the viscosity of a coating solution, the thickness of the wet film after coating and a coating pitch enters a specific range using a spiral coating device. CONSTITUTION:If a ball screw 10 is rotated at predetermined rotational frequency when a substrate 1 rotates at predetermined rotational frequency, a coating head 4 moves in parallel to a rotary shaft 3 and, therefore, if a coating solution is supplied to the coating head 4, spiral coating is performed. In this case, when the viscosity of the coating solution is set to 7(CP), the thickness of a wet film to hw(cm) and a coating pitch to lambda(cm), it is necessary that a coating condition satisfies formula I and the thickness hw of the wet film is 0.1-40mum on a dry basis.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coating method, and more particularly to an improvement in a spiral coating method that eliminates unevenness in film thickness such as pitch unevenness and liquid dripping.

[Background of the Invention] Conventionally, dip coating methods and spiral coating methods are known as coating means for forming a coating film of about 15 pLm. However, the dip coating method has problems such as poor production efficiency and non-uniform coating at both ends (top and bottom) of the photoreceptor, so attempts have been made to develop a spiral coating method that does not have these drawbacks.

Traditionally, the spiral coating method was disclosed in Japanese Patent Application Laid-Open No. 52-11965.
It is known from No. 1 and No. 60-150053,
Various studies have been conducted on how to smoothen the surface of the coating film and eliminate unevenness in film thickness. However, all of these conventional methods only propose a general method for spiral coating and do not propose specific and appropriate coating conditions, so when they are actually implemented, the film thickness unevenness does not improve as much as the above publications say. It turned out that this was not the case. The present invention is a technology that proposes specific and appropriate coating conditions that have not been proposed by conventional methods.

Generally, the following leveling formula is known as a formula for ensuring the smoothness of the coating film surface.

4η/γhW4 where lj4 is the time required for the amplitude of the unevenness to become tsubo, the coating pitch η is the coating liquid viscosity γ, the surface tension is a constant for the wet film thickness.

” - As is clear from the text, leveling is achieved by reducing the value, and in order to reduce tXA,
It is thought that it is sufficient to reduce the input and η and increase h-.

However, in order to improve the productivity of coating, it is necessary to increase the input, and when the input is increased, the tread becomes larger and leveling becomes difficult.

Therefore, it is conceivable to reduce η and increase hW. However, reducing η tends to cause liquid dripping, and increasing ht+ also causes liquid blurring.

Therefore, trying to increase input in order to improve productivity goes against the grain from a leveling perspective, and it is therefore extremely difficult to find conditions that simultaneously satisfy productivity and leveling.

On the other hand, in the production of electrophotographic photoreceptors, the development of functionally separated photoreceptors has recently progressed, and a charge generation layer (hereinafter referred to as CGL) is placed on a charge transport layer (hereinafter referred to as CTL), or CTI, CGL-L, etc. It is formed by coating.

The film thickness of CGL is 0.1 to 5 m, and the film thickness of CTL is 5 to 40/7. m is appropriate.

If the thickness of the CGL or CTL is non-uniform, the charging potential and sensitivity will be non-uniform, resulting in uneven images when used in a copying machine or the like.

Therefore, in order to obtain a photoreceptor with good characteristics, CGL, C
Eliminating uneven coating of TI is an extremely important issue.

Therefore, it is an object of the present invention to provide a coating method that performs coating under coating conditions that do not cause unevenness in film thickness even when the coating pitch is increased.

[Means for Solving the Problems J] The inventors of the present invention have conducted intensive studies to achieve the above objects and have arrived at the present invention.

That is, in the coating method of the present invention, a substrate having an endlessly formed continuous peripheral surface is rotated at a constant speed, and a coating head provided close to the surface of the substrate is rotated at a predetermined position relative to the rotation axis direction of the substrate. In a coating method in which the coating liquid is applied spirally to the substrate surface by moving at a coating pitch, the viscosity of the coating liquid is η (cp), the wet film thickness after coating is hH (am), and the coating pitch is λ (cm) and S
.

It is characterized by coating under the following conditions [I] and [11].

[1] I XIO3≦in4η / hW'≦I
X] (17[11]h, is 0.1~ in dry conversion
40 gm, preferably lO to 30 lm.

Hereinafter, an apparatus for carrying out the present invention will be explained based on the accompanying drawings.

FIG. 1 is a plan view showing an example of a spiral coating device, and in the same figure, l is a base body having an endless continuous circumferential surface, and in this embodiment, a roll-shaped base body is used. When the substrate 1 is used as an electrophotographic photoreceptor, aluminum is used as the material, for example.

The base 1 is fixed to a rotating shaft 3 that can be rotated by a driving motor 2.

Reference numeral 4 denotes a coating head provided close to the surface of the substrate 1 (particularly preferably in the -1 direction), and is fixed to a mounting member 4A of a coating machine (not shown). The coating liquid stored in the coating liquid tank 5 is pumped by a pump 6 (for example, a metering pump such as a gear pump).
is supplied to the coating head 4 with or without filter 7.

The positional relationship between the coating head 4 and the substrate 1 is as shown in FIG.
Streamline direction X of the coating liquid flowing out from the coating head 4 and the substrate 1
It is preferable that the angle θ formed between the second coating liquid contact point P and the tangent Y to the rotation direction satisfies 90°≦θ≦1800.

Although the means for relatively moving the coating head 4 in the direction of the rotation axis of the base 1 is not particularly limited, for example, a pole screw type moving mechanism 8 is used. The moving mechanism 8 includes a drive motor 9
A pole screw 10 connected to is provided parallel to the rotating shaft 3 of the base body, a mounting member 11 of the coating head is screwably fixed to the screw 8, and a coating head 4 is fixed to the handle 1 member 11. It consists of Takeaway 1 member 11 is usually a pole screw l
A guide rod 12 provided parallel to O is provided and fixed. Since the tip of the coating head 4 has a degree of freedom, it is in contact with the surface of the substrate l.

Adjustment of θ can be performed by providing a mechanism having a degree of freedom such as a Z-shaped disk stand at the attachment location of the coating head attachment member 11, but is not limited thereto.

Since the configuration is as described below, when the base l is rotating at a predetermined rotation speed, if the pole screw 10 is rotated at a predetermined rotation speed, the coating head will be aligned parallel to the rotation axis 3. Since it moves, spiral coating is performed when the coating liquid is supplied to the coating head.

In the above embodiments, the substrate 1 may be in the form of a sheet other than a roll, and does not need to be seamless as it only needs to be endless. Furthermore, since the base 1 and the coating head 4 only need to move relative to each other, the base 1 may also move.

Next, the coating conditions of the present invention will be explained.

The coating conditions in the present invention are as follows: Coating liquid viscosity: η (cp) Wet film thickness: hy (Cm) Coating pitch: On (cm) The following conditions [I] and [IT] are satisfied.

[I] I X105≦In 4η / hw'≦IX
107[11]hga is 0.1 to 40I in dry conversion
i, ffl, preferably 10 to 30 JLID.

In the present invention, λ4η/hw'<I XIO3
In this case, the viscosity of the coating liquid is too low, causing liquid sway, or the coating head is too small to pass over the drying wet film over and over again. Causes streaks. Other input 4η /
When hw'> lX107, no liquid drips, but leveling becomes insufficient and the film thickness becomes non-uniform depending on the pitch.

In the present invention, the coating liquid viscosity refers to a value measured at a coating liquid temperature of 25° C. using a B-type viscometer manufactured by Tokyo Keiki Co., Ltd.

Further, the wet film thickness is the film thickness in a wet state before drying, and is the value obtained by dividing the amount of coating liquid supplied by the coating area. Furthermore, the coating pitch refers to the distance that the coating head moves in the axial direction during one rotation of the base.

Although the coating method of the present invention is applicable to coating various substrates,
Preferably, it is applied to CTL coating. C.T.L.
is formed by dissolving a charge transport material and a binder in a suitable solvent and applying a coating solution.

For example, 1 as a charge transport substance (Japanese Patent Publication No. 34-5467
), oxazole derivatives (e.g. No. 35-1125), oxadiazole derivatives (e.g. No. 34-5466),
), pyrazoline derivatives (e.g. No. 34-10366), imidazole derivatives (e.g. No. 35-11215, No. 37-16096), fluorenone derivatives (Japanese Patent Laid-open Nos. 128373-1983 and 110837-1983),
Examples include carbazole derivatives (for example, No. 54-59142), as well as substances described in No. 58-134642, No. 58-65440, and the like.

As a binder, it has high compatibility with charge transport substances,
Furthermore, materials with high transparency and insulation properties are preferred, and all materials commonly used in electrophotographic photoreceptors can be used. For example, polyester resins, polyethylene resins, polyamide resins, polycarbonate resins, epoxy resins,
Examples include polyvinyl butyral resin and polymethyl methacrylate resin.

As a suitable solvent, one with a boiling point (bp) of 80°C to 150°C is preferable, and more preferably one with a boiling point (bp) of 80°C to 150°C, because if the temperature is too low, leveling will likely be insufficient, and if it is too high, it will take too long for the coating film to solidify. ℃~120℃. Specifically, l,2-dichloroethane (bp=
83.5°C), 1,1.2-)dichloroethane (bp
= +13.5°C), 1,4-dioxane (bp = 10
1.3°C), benzene (bp=80.1'C), toluene (bp=110.8°C), o,m,p,-xylene (bp=138-1440C), and the like. Further, even a solvent whose boiling point is not 80 to 150°C can be used by adjusting the boiling point by making a mixed solvent.

The coating liquid used in the present invention may contain other substances in addition to those mentioned above. For example, the inclusion of a siloxane compound has the effect of smoothing the coating surface.

Examples of the siloxane compounds include dimethylpolysiloxane, methylphenylpolysiloxane, and the like.

The additive layer preferably has an amount of 1 to 110,000 ppn+, more preferably 10 to 1,000 ppn+, based on the total amount of the coating solution.

The temperature of the coating liquid used in the present invention is preferably 10 to 30°C, more preferably 15 to 25°C.

The coating method of the present invention explained above applies not only to photoreceptors but also to
It is also applicable to coating insulating layers (NP), recording layers for electrostatic recording, magnetic recording materials, etc.

[Effects of the Invention] According to the present invention, even if the coating pitch is increased, coating can be performed under coating conditions with no unevenness in film thickness.

[Example] EXAMPLES The present invention will be described in more detail below with reference to Examples.

Example 1 A coating solution having the following composition was prepared. The viscosity was +2 cp.

Dichloroethane 5oII1 Sentence 1.1
．． 2-Trichloroethane 50m polycarbonate) (L-1250, manufactured by Kijin Kasei Co., Ltd.) g 1.1-bis(4-N, N-dibenzylamino-2-
Methylphenyl) normal butane 5g then the first
Coating was carried out in the following manner using the apparatus shown in the figure.

An aluminum cylinder of 100n++oφX 350mm was used as a substrate. While rotating this substrate at 1100 rpm, a gear pump was used in the coating head to
Pour the above coating liquid at a rate of 8mJ1/min,
The coating head was moved at a speed of 10ff110ff1. A coating head with a rll of 15 mm was used. The coating pitch (on) was 6 mm.

The coating head contacts the substrate at θ=135° via the coating liquid, and performs spiral coating with the coating liquid supplied from the coating head to the substrate, forming a coating film with a wet film thickness of 202 m. did.

This coating was leveling on the substrate. Next, after drying the base for about 10 minutes at room temperature while rotating, the base was removed from the shaft and dried in an oven kept at 100°C for about 3 minutes.
Dry for 0 minutes.

When the film thickness was measured, a uniform coating film of 15 gm was obtained.

What is the value of 4η/bW4 in the above coating method? 1.
3Xl06.

Example 2 In Example 1, the coating conditions were changed to coating pitch (on) of 3.6.
Coating was carried out in the same manner except that λ4η/hW 4 =1.2X106 was used as (2). As a result, the wet film was also leveled, and the dry coating had a uniform thickness of 15 μm.

Example 3 A coating liquid having the following composition was prepared. The viscosity was 13.5 cp.

Dichloroethane 50m sentence 1.1.2
-Trichloroethane 50II 1-mon polycarbonate) (L-1250, manufactured by Kijin Kasei Co., Ltd.) g 1.1-bis(4-N, N-dibenzylamino-2-
Methylphenyl) normal butane (6 g) Coating was carried out under the same conditions as in Example 1 using the above coating solution.

As a result, the wet film thickness was 20 Bgm, and the dry film thickness was 18 Bgm.
It was μm.

In addition, input 4η/hw' = L? It was 5×106.

As a result of the second application, leveling occurred when wet as in Example 1, and a uniform coating film was obtained when dry.

Example 4 A small amount of methylphenylpolysiloxane was added to the coating solution used in Example 1.

When this coating liquid was applied in exactly the same manner as in Example 1, the wet film leveled in Example 1 was further smoothed, and a coating film without orange skin was obtained.

Comparative example 1 A coating solution having the following composition was prepared. The viscosity was 6 cp.

Dichloroethane 50m sentence 1.1.2
-) Dichloroethane 50m polycarbonate) (L-1250, manufactured by Ondai Kasei Co., Ltd.) 2.5 g 1.1-bis(4-N, N-dibenzylamino-2-
2.5 g of (methylphenyl) normal butane, then
Coating was carried out in the same manner as in Example 1 except for the following conditions.

Amount of coating liquid supplied to the coating head: 37 m/lin Moving speed of the coating head: 5 mm/sec Coating pitch (
) Wet film thickness 3 under conditions of 3 mm or more
Although a coating film of No. 93 ILm was obtained, liquid blurring occurred and it could not be applied successfully.

In addition, at the time of this application, input 4η / hw '=
It was 2.0×104.

Comparative Example 2 A coating liquid having the following composition was prepared. The viscosity was 45 cp.

Dichloroethane 5011 sentence 1.1.
2-) Dichloroethane 50Il! 1-bis(4-N, N-dibenzylamino-2-
(methylphenyl) normal butane (10 g) Then, coating was carried out in the same manner as in Example 1 except for the following conditions.

Amount of coating liquid supplied to the coating head 21 ttr sentences/win
Coating head moving speed 10 mm/sec Coating pitch (λ) A coating film with a wet film thickness of 111 pLm was obtained under conditions of 6 mm or more, but the coating pitch was 6+*
At m, unevenness in film thickness occurred in the coating film.

[Brief explanation of drawings]

Figure 1 is a plan view showing an example of a spiral coating device, and Figure 2 is an enlarged view of the main part showing the angle θ between the coating liquid supply direction from the coating head and the tangent to the coating liquid flow direction on the substrate. FIG. 1... Base 2... Drive motor 3... Rotating shaft 4... Coating head 5... Coating liquid tank 6... Pump 7... Filter 8... Pole screw type moving mechanism 9 ...Drive motor lO...Pole screw 11...Mounting member 12...Guide rod

Claims (1)

[Claims] A base body having an endlessly formed continuous peripheral surface is rotated at a constant speed, and a coating head provided close to the base surface is applied at a predetermined coating pitch relative to the rotation axis direction of the base body. In the coating method in which the coating liquid is applied to the surface of the substrate in a spiral manner, the viscosity of the coating liquid is set to η(cp
), the wet film thickness after coating is h_w (Cll), and the coating pitch is λ (cm), the following [I] and [
II]. [I] 1×10^5≦λ^4η/h_w^4≦1×1
0^7 [II] h_w is 0.1 to 40 μm in dry terms.