JP5551014B2 - Immersion coating method - Google Patents

Description

  The present invention relates to a dip coating method, and more particularly to a dip coating method suitable for forming a coating film (coating) such as a primer film or a hard film on a plastic lens by a dip treatment.

  Here, a case where a hard film or a primer film is dip-coated (dipped) on a plastic lens as a lens will be described as an example, but the present invention is not limited to this.

  The dip coating method of the present invention can be applied to optical parts such as the above-described lens, and further to electric / electronic parts such as a printed board, a liquid crystal substrate, and a wafer.

  Examples of the optical components include optical lenses such as eyeglass lenses and camera lenses, and front glass or front filters of various displays, reflecting mirrors, optical prisms, and the like.

  In recent years, organic glass lenses (plastic lenses) that are lighter and harder to break than inorganic glass lenses have become popular as spectacle lenses. However, in general, a plastic lens has much lower scratch resistance than an inorganic glass lens. Therefore, normally, a hard film is formed on the surface of the organic glass lens substrate. Since the hard film usually has poor adhesion to the plastic lens base, it also serves to improve impact resistance, and a thermoplastic elastomer (TPE) or the like is used as a base between the lens base 11 and the hard film 13. In many cases, a primer film 15 is formed (see FIG. 2B).

  The coating films (coating films) such as the hard film 13 and the primer film 15 are formed by dip coating (dip coating: dip coating) using a coating liquid (processing liquid) that forms them. This is from the viewpoint of functionalization and mass productivity on both sides.

  However, it was common knowledge to those skilled in the art that dip coating cannot avoid the occurrence of film thickness unevenness due to sagging of the uncured coating film. Further, in the case of a substrate such as an optical lens (especially a spectacle lens) having a significantly different thickness between the peripheral part and the central part, film thickness unevenness is more likely to occur. Due to this unevenness in film thickness, variations in durability quality are likely to occur. In particular, this tendency becomes more prominent for lenses with a high power and high-curve lenses.

  Accordingly, there has been a demand for the emergence of a technique that hardly causes film thickness unevenness of an optical lens as much as possible.

  However, in the field of optical lenses, the present inventors do not know in detail about a technique that hardly causes film thickness unevenness in a coating film by dip coating.

  In the method of forming a photoreceptor layer on the surface of a drum substrate (cylindrical body) for a photoreceptor in an electronic copying machine, the speed of pulling up from the viewpoint of reducing the occurrence of film thickness unevenness due to coating sagging. Patent Documents 1 to 3 propose an invention (technical idea) in which the value is changed between the beginning and the end (the beginning is made early and the end is made late).

  However, it has been found that even if the technical idea of the photosensitive drum is applied to an optical lens as it is, it is insufficient to reduce the occurrence of film thickness unevenness.

  Further, although not affecting the patentability of the present invention, Patent Document 4 proposes a method for manufacturing an aspherical body having the following configuration in the field of optical lenses.

  “In a member having an aspheric surface (including a spherical surface) such as an optical lens, a coating layer (coating film) such as an organopolysiloxane resin or an ultraviolet curable resin is applied to the member by dip coating with a controlled pulling speed. By providing, the aspherical shape of the member is controlled. ”

JP-A-57-5058 (Claims etc.) JP 59-46171 (Claims) JP 2008-62131 A (Claims etc.) JP-A-61-33267 (Claims etc.)

  In the optical lens or the like, the reason why the above-mentioned Patent Documents 1 to 3 are insufficient to reduce the occurrence of film thickness unevenness is the difference in form between the optical lens and the photosensitive drum. As a result of considering and paying attention to the following, the following knowledge was reached.

  “In the case of an optical lens (for example, a concave lens), when the refracting surface is pulled up horizontally with respect to the paint liquid surface, air or paint liquid is accumulated on the lens concave surface side. A technique is employed in which the optical lens is pulled up in a vertical state.

  When the optical lens is dip-coated by the conventional technology in the photosensitive drum described above, the cross section of the object to be coated parallel to the liquid surface of the coating liquid, such as an optical lens, is horizontal with respect to an object that is not circular. Unevenness in film thickness cannot be reduced.

On the other hand, in the case of applying a dip coating method to an optical lens to form a coating film, in order to prevent foreign matter from being mixed into the coating film, the object to be coated is washed (e.g., ultrapure water, ultrasonic cleaning), and then undergoes a heating and drying step (e.g., 80 ° C. × 15min) (see Fig. 3). For this reason, the object to be coated has a temperature much higher than room temperature (for example, 60 to 80 ° C.).

  In the case of continuously laminating the composite coating film, the object to be coated has a temperature much higher than room temperature immediately before the coating of the second and subsequent layers is applied by the drying process of the first layer ( For example, 60-80 degreeC).

  Furthermore, the coating liquid (coating liquid) is usually controlled at a temperature lower than room temperature (for example, 10 ° C.) in order to suppress solvent volatilization and reaction rate.

  For the above reason, when there is a large temperature difference (for example, 50 ° C. or more) between the object to be coated and the coating liquid, the difference between the outer periphery and the thin part is locally faster and the temperature of the coating liquid becomes smaller. The thicker portion has a large temperature difference, that is, temperature unevenness occurs temporarily. In particular, in the case of an organic glass lens, this temperature unevenness is easily maintained because of low thermal conductivity. In general liquids, the higher the temperature, the lower the viscosity. Therefore, the higher the temperature, the higher the flow rate of the dripping, and the thinner the film. "

  Based on the above knowledge, the present inventors have found that even when a non-cylindrical object such as an optical lens is to be coated, it is possible to reduce the occurrence of film thickness unevenness, and have come up with a dip coating method having the following configuration.

An immersion coating method using an optical lens as an object to be coated,
After washing, the object to be coated that has been subjected to the heating and drying process is immersed in a coating liquid that is controlled at a temperature lower than room temperature, and then the object to be coated is relatively lifted from the coating liquid and applied to the surface of the object to be coated. In the dip coating method to form
The temperature of the object to be coated is adjusted with a cooling medium equal to or less than −10 ° C. of the liquid temperature so that the temperature difference between the object to be coated and the coating liquid is as small as possible. When the film is soaked in and pulled up, the speed of the pulling is changed between the beginning and the end to reduce the occurrence of film thickness unevenness due to sagging of the coating film.

It is a model figure which shows an example of the mechanism used for the dip coating method of this invention. It is the top view (A) and the same sectional view (B) which show the film thickness position of an optical lens. It is a flowchart in the case of immersing the optical lens of an Example group or a comparative example group. It is a relationship diagram of pulling speed / elapsed time in Examples 1 and 3 and Comparative Examples 1-2 and 3-2. It is a relationship diagram of the raising speed / elapsed time in Comparative Examples 1-1, 1-3, 3-1, 3-3. It is a relationship diagram of pulling speed / elapsed time in Examples 2 and 4 and Comparative Examples 2-2 and 4-2. It is a relationship diagram of the raising speed / elapsed time in Comparative Examples 2-1, 2-3, 4-1, and 4-3. It is each graph figure (A) and (B) which shows the state of the up-down direction film thickness in Example 1, and the left-right direction film thickness. It is each similar graph figure (A) in comparative example 1-1, and (B). It is each similar graph figure (A) in comparative example 1-2, and (B). It is each similar graph figure (A) and (B) in comparative example 1-3. It is each graph figure (A) and (B) similar in Example 2. FIG. It is each similar graph figure (A) and (B) in comparative example 2-1. It is each similar graph figure (A) in comparative example 2-2, and (B). It is each similar graph figure (A) and (B) in comparative example 2-3. It is each similar graph figure (A) in Example 3 (B). It is each similar graph figure (A) and (B) in comparative example 3-1. It is each similar graph figure (A) in comparative example 3-2, and (B). It is each similar graph figure (A) and (B) in comparative example 3-3. It is each similar graph figure (A) in Example 4, (B). It is each similar graph figure (A) in comparative example 4-1, and (B). It is each similar graph figure (A) and (B) in comparative example 4-2. It is each similar graph figure (A) in comparative example 4-3, and (B).

  Hereinafter, an embodiment of the present invention will be described in detail. Here, the case where the primer film 15 to the hard film 13 are formed on the base material (object to be coated) 11 of the optical lens (concave lens for spectacles) using the pulling mechanism as shown in FIG. 1 as shown in FIG. Take an example and explain.

  That is, the optical lens substrate 11 is set on a lifting means (elevating means) 21 connected to a lifting drive unit 19 controlled by the arithmetic unit 17, and the optical lens substrate 11 is coated with a paint liquid 23. After being immersed in the liquid tank 25, it is pulled up. At this time, the immersion time is 5 to 40 seconds.

  FIG. 3 shows an example of a flowchart for immersion coating.

  Here, the organic glass substrate is composed of polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene, polyvinyl chloride, polyethylene terephthalate, polyurethane, aliphatic allyl carbonate, aromatic allyl carbonate, polythiourethane, etc. Can be mentioned.

Examples of the inorganic glass substrate include crown glass (n _d = 1.52 to 1.72), flint glass (n _d = 1.53 to 1.88), and the like.

  Then, the lens substrate (object to be coated) is subjected to the temperature adjustment process so that the temperature difference from the coating liquid is as small as possible, and then the relative lifting is performed. That is, the coating liquid tank 25 may be raised and lowered without raising and lowering the lens substrate.

  In the present invention, the temperature of the lens base material (object to be coated) is as close as possible to the temperature of the coating liquid (immersion liquid) before the lens base dipping / pulling process, as in the examples described later. The biggest feature is to adjust the tone.

  For example, when the lens substrate is heated in a drying furnace, the lens substrate is cooled with cold air (cooling medium) at the same temperature as the coating liquid or slightly lower (within −10 ° C., preferably within −5 ° C.). Cooling. The cooling medium may be liquid (water) or vapor, but if the liquid (water) is not pure (eg, pure water) that does not contain any contaminants, it will be contaminated with water, and the lens base that has been cleaned at an angle will be used. This is undesirable because the material can be contaminated. On the other hand, if the temperature of the cooling medium such as cold air is too low than the coating liquid, it is excessively cooled and the lens substrate may be subjected to thermal shock, which is not desirable. Note that the time until the temperature of the object to be coated and the coating liquid becomes the same depends on the temperature of the cold air, the thickness of the object to be coated, the thermal conductivity of the object to be coated, and the like, and is set from the experimental results.

  The coating liquid for forming the hard film 13 is usually a silicone-based one.

  For example, a catalyst and metal oxide fine particles (including composite fine particles) are added to a hydrolyzate of an organoalkoxysilane, and the viscosity is adjusted to allow coating with a diluting solvent. Furthermore, a surfactant, an ultraviolet absorber, and the like can be appropriately added to the hard film coating liquid.

  The thickness of the hard film 13 is 0.5 to 50 μm, preferably 1 to 10 μm. Here, if it is thin, it is difficult to obtain scratch resistance, and if it is thick, it is difficult to obtain surface accuracy (leveling property). Therefore, the film thickness of the hard film is appropriately set from the balance of both characteristics.

  As the coating liquid for forming the primer film 15, for example, it is desirable to use a TPE coating liquid.

  For example, TPEE, TPU, etc. can be mentioned as TPE.

  The primer film coating liquid (primer composition) preferably contains metal oxide fine particles (including composite fine particles) for the purpose of adjusting the refractive index and improving the strength.

  The primer film has a thickness of 0.2 to 10 μm, preferably 0.5 to 5 μm. If it is thin, it is difficult to obtain impact resistance, and if it is thick, it is difficult to obtain surface accuracy. Therefore, the thickness of the primer film is appropriately set from the balance of both characteristics.

  Thus, before forming each coating film (primer film, hard film), by adjusting the temperature so that the base material is as close as possible to the temperature of the coating liquid, the center part, the peripheral edge and the thin part of the lens In addition, the temperature influence on the coating liquid as in the conventional case is small between the thick-walled portion and the liquid dripping property of the coating film before drying becomes uniform for each part.

  Therefore, even if the shape of the object to be coated parallel to the liquid surface of the coating liquid is not cylindrical or the cross section is other than non-circular, the film thickness unevenness of the coating film due to the temperature difference can be reduced.

  Furthermore, by changing the pulling speed (from the start of pulling to the completion of pulling) according to a conventionally known method, the film thickness unevenness in the vertical direction can be reduced, and the effect of reducing the film thickness unevenness in the entire lens plane can be obtained.

The relative pulling speed (V) at this time is normally reduced linearly represented by the following formula. This is because a straight line is easier to control. In the following formulas, V ₀ = 1.0~5mms ^-1 (preferably ^{1.5~3.5mms -1), a = 0.005~0.02mms -2} ( preferably 0.01~0.015mms ^-1) and.

V (mms ⁻¹ ) = V ₀ −at
V ₀ : initial speed (mms ⁻¹ ), a: coefficient (mms ⁻² ), t: elapsed time (s).

  The relative pulling speed may be changed exponentially with e as the bottom as shown in the following formula described in Patent Document 2.

V (mms ⁻¹ ) = V ₀ exp (−At)
However, A: coefficient (s ^-1), V ₀ is the same city as the, A = 0.001~0.02s ^-1 (preferably 0.002~0.01s ^-1) and.

  As described above, an optical lens (concave lens) has been described as an example of the object to be coated. However, the present invention is also applicable to other inorganic / organic glass optical parts, printed circuit boards, liquid crystal boards, wafers, and other electrical / electronic parts. The present invention can be applied without being limited to a non-cylindrical shape.

  Here, the optical components include optical lenses such as eyeglass lenses and camera lenses, as well as front glass or front filters of various displays, reflecting mirrors, optical prisms, and the like.

  Examples carried out to confirm the effects of the present invention will be described below together with comparative examples.

  (1) The lens substrate which is the object to be coated was used with the following specifications.

Lens I: Allyl plastic lens with a refractive index of 1.50 with a diameter of 75 mm, outer peripheral thickness of 8 mm, and a central thickness of 2 mm Lens II: Thiourethane with a refractive index of 1.74 with a diameter of 75 mm, an outer peripheral thickness of 8 mm, and a central thickness of 1 mm Plastic lens

(2) The dip coating pretreatment was performed according to the flow shown in FIG.
That is, each Example and Comparative Example was ultrasonically cleaned with ultrapure water and dried in a hot air drying furnace at 80 ° C. for 15 minutes. Thereafter, it was cooled in a 10 ° C. (or 30 ° C.) cold air oven for 15 minutes.

  (3) The following primer film coating liquid or hard film coating liquid having a liquid temperature of 10 ° C. was used as the coating liquid.

    Primer film paint liquid: TPEE paint having a viscosity of 2.2 cPs (mPas) and a refractive index of 1.60 when used as a coating film.

    Hard film paint solution: An organosilicone paint with a viscosity of 3.3 cPs (mPas) and a refractive index of 1.60.

<Example 1>
The primer film coating liquid was applied to the lens I that had been cooled with cold air (10 ° C.) shown in FIG. 3 by a dip coating method.

  After immersing the lens substrate for 10 seconds, as shown in FIG. Then, it dried for 30 minutes in a 100 degreeC hot-air drying furnace.

  The film thickness state of the coating film (primer film) thus prepared is shown in FIG. The standard deviation (σ) was 0.02 (upper and lower) and 0.00 (left and right), and a very uniform film was obtained.

<Comparative Example 1-1>
In Example 1, the temperature of cold air cooling was set to 30 ° C., and the pulling rate was kept constant as shown in FIG. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.07 up and down: 0.04 right and left: 0.04.

<Comparative Example 1-2>
In Example 1, the temperature of cold air cooling was 30 ° C. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.06 up and down: 0.05 and left and right: 0.05.

<Comparative Example 1-3>
In Example 1, the pulling-up was performed while keeping the pulling speed constant as shown in FIG. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was up and down: 0.05, left and right: 0.01, and uneven film thickness was observed in the top and bottom.

<Example 2>
In Example 1, a hard film coating liquid was used instead of the primer film coating liquid, and coating was performed by a dip coating method.

  At that time, as shown in FIG. 6, the pulling-up speed was initially high and gradually slowed. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.12 up and down: 0.02 and left and right: a substantially uniform film was obtained.

<Comparative Example 2-1>
In Example 2, the temperature of cold air cooling was set to 30 ° C., and the pulling rate was kept constant as shown in FIG. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.33 up and down: 0.20 left and right.

<Comparative Example 2-2>
In Example 2, the temperature of cold air cooling was 30 ° C. The other conditions were the same. The film thickness state of the coating film thus prepared is shown in FIG.

  The standard deviation was 0.31: up and down: left and right: 0.25.

<Comparative Example 2-3>
In Example 2, the pulling-up was performed while keeping the pulling speed constant as shown in FIG. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.24 up and down: 0.03 and left and right: 0.03.

<Example 3>
In Example 1, the lens I is the lens II. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.03 in the vertical direction and 0.00 in the horizontal direction, and a substantially uniform film was obtained.

<Comparative Example 3-1>
In Example 3, the temperature of cold air cooling was set to 30 ° C., and the pulling rate was kept constant as shown in FIG. The other conditions were the same. The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.08 up and down: 0.05 and left and right: 0.05.

<Comparative Example 3-2>
In Example 3, the temperature of cold air cooling was 30 ° C. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.07 up and down: 0.07 right and left: 0.06.

<Comparative Example 3-3>
In Example 3, the lifting was performed while keeping the lifting speed constant as shown in FIG. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.06 up and down: 0.06 and left and right: 0.01, and film thickness unevenness was observed at the top and bottom.

<Example 4>
In Example 2, the lens I was a lens II. The other conditions were the same. The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.14 up and down: 0.04 and left and right, and a substantially uniform film was obtained.

<Comparative Example 4-1>
In Example 4, the temperature of cold air cooling was set to 30 ° C., and the pulling rate was kept constant as shown in FIG. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.39 up and down: 0.23 left and right, and film thickness unevenness was seen both up and down and left and right.

<Comparative Example 4-2>
In Example 4, the temperature of cold air cooling was 30 ° C. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.37 up and down: 0.27 left and right: 0.29.

<Comparative Example 4-3>
In Example 4, the lifting was performed while keeping the lifting speed constant as shown in FIG. The other conditions were the same.

  The film thickness state of the coating film thus prepared is shown in FIG. The standard deviation was 0.29 up and down: 0.03 and left and right: 0.03.

  Table 1 summarizes the processing conditions and results of each of the above examples and comparative examples.

  The technical idea of the dip coating method of the present invention is not limited to the coating method, and can also be applied to a dip treatment method such as chemical conversion treatment. The configuration in that case is as follows.

In the immersion surface treatment method in which the object to be treated is immersed in a treatment liquid, and then the object to be treated is lifted relatively vertically from the treatment liquid.
The relative pulling is performed after the temperature difference between the object to be processed and the processing liquid is made as small as possible.

11 Organic Glass Base Material 14 Hard Film 15 Primer Film

Claims (3)

An immersion coating method using an optical lens as an object to be coated,
After washing, the object to be coated that has been subjected to the heating and drying process is immersed in a coating liquid that is controlled at a temperature lower than room temperature, and then the object to be coated is relatively lifted from the coating liquid and applied to the surface of the object to be coated. In the dip coating method to form
The temperature of the object to be coated is adjusted with a cooling medium equal to or less than −10 ° C. of the liquid temperature so that the temperature difference between the object to be coated and the coating liquid is as small as possible. When dipping in and pulling up, the speed of the pulling is changed between the beginning and the end, reducing the occurrence of film thickness unevenness due to coating sagging,
A dip coating method characterized by that.   2. The immersion coating method according to claim 1, wherein the object to be coated is non-cylindrical. The dip coating method according to claim 2, wherein the coating film has a thickness of 0.1 to 50 μm.

Images