JP2014015493A - Coating liquid for polycarbonate substrate coating and method of coating polycarbonate substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating liquid capable of forming a coating for polycarbonate, especially excellent in scratch resistance and also having sufficient transparency and chemical resistance, which can be dried at room temperature after direct coating on the polycarbonate substance, and to provide a method of coating the polycarbonate substance to get the coated polycarbonate substance by using the coating liquid.SOLUTION: A coating liquid contains 45 to 65 wt.% of a curable liquid organopolysiloxane (base compound), 7.0 to 10.0 wt.% of an amino group-containing silane coupling agent, 10.0 to 20.0 wt.% of 2-propanol, 10.0 to 25.0 wt.% of ethanol and/or 1-butanol, 1.0 to 20.0 wt.% of 4-hydroxy-4-methylpentanone and/or 4-methyl-2-pentanone, 1.0 to 5.0 wt.% of ethyl acetate.

Description

  The present invention relates to a coating solution for forming a film on a substrate, and a method for forming a film on a transparent polycarbonate substrate using the coating solution.

  In the information age, portable information terminals such as tablet terminals represented by smartphones have been developed with remarkable progress. In a tablet terminal, an operation on a display screen with a touch panel is generally used.

  Currently, highly transparent glass having high elastic modulus and rigidity is used for a display substrate capable of touch panel operation. On the other hand, however, glass is fragile and breaks when subjected to impacts. It also has the disadvantage that it is heavy and difficult to design variously.

  Therefore, resin-based transparent materials that are light and easy to process instead of glass are being studied as substrates for touch panels. Of these, polycarbonate is considered the most prominent. Polycarbonate has a visible light transmittance of 80 to 90% and has the same transparency as glass, but is resistant to impacts and high and low temperatures, and has the characteristics of being hard to break among transparent resin materials. On the other hand, since polycarbonate is a high-hardness material, it is easily scratched (abrasion resistance) and has a characteristic that it is weak against solvents (chemical resistance), so it cannot be used as it is as a substitute for glass. In particular, high scratch resistance is required for use as a substrate for a touch panel display in which the display part is frequently touched with a finger.

  As a solution to this, a method of forming a film that improves the scratch resistance and chemical resistance on the surface of the polycarbonate is conceivable. Such a technique is called a polycarbonate (PC) glazing technique, and has been studied from various angles, centering on a glass replacement technique for automobile windows.

  Among PC glazing techniques, a method of curing a liquid organopolysiloxane to form an organopolysiloxane-based cured film having high scratch resistance and high chemical resistance on the surface of a polycarbonate resin is considered promising.

  On the other hand, polycarbonate has low chemical resistance and also has a problem in adhesion to an organopolysiloxane thermoplastic resin. When the liquid organopolysiloxane is dissolved in a solvent and applied for curing to form a coating, if the solvent is used incorrectly, the polycarbonate becomes cloudy or the coating begins to peel off after prolonged use.

  As means for solving this problem, various contrivances have been made in the technique for forming a film by curing liquid organopolysiloxane. For example, there are a method of ultraviolet curing, a method of curing by high temperature drying, a method of curing by room temperature drying, but a method that requires about 15 days to complete curing.

  For example, in Patent Document 1, hydrolyzed condensate (liquid organopolysiloxane) of a silane compound having an alkoxy group, organic polymer fine particles comprising a copolymer containing a monomer unit having an ultraviolet absorbing group, colloidal silica, anion or A coating liquid containing a nonionic, alcohol-dispersible cerium oxide dispersion, a curing catalyst, a dispersion stabilizer and a dispersion medium is applied to a polycarbonate substrate with a bar coater, preferably at 100 to 140 ° C. A method is described in which a transparent cured film having desired properties is obtained by heat-curing for minutes to 3 hours.

  However, in order to use these curing methods in the mass production stage, initial investment is required due to the introduction of dedicated manufacturing equipment and the like, and this is a method that is particularly difficult for small and medium-sized enterprises that do not have sufficient funds. Further, even the organopolysiloxane cured resin film obtained by these methods has not yet been sufficient with respect to scratch resistance, which is a particularly important characteristic for a touch panel substrate.

JP 2009-185196 A

  In view of the above-mentioned problems, the problem to be solved by the present invention is that a coating film for polycarbonate that is particularly excellent in scratch resistance and also sufficiently satisfactory in transparency and chemical resistance is directly applied to a polycarbonate substrate, and then at room temperature. A coating solution that can be formed by drying, and a method for coating a polycarbonate substrate to obtain a coated polycarbonate substrate using the coating solution.

In order to solve the above problems, the coating liquid for coating a polycarbonate substrate of the present invention is:
Contains the main agent, silane coupling agent and solvent,
The main agent contains a curable liquid organopolysiloxane, the blending ratio with respect to the total amount of the coating liquid is 45 to 65 wt%,
The silane coupling agent has an amino group in its functional group, and the blending ratio with respect to the total amount of the coating liquid is 7.0 to 10.0% by weight,
The solvent includes 2-propanol, alcohol solvent, ketone solvent, ethyl acetate as its components,
The alcohol solvent is ethanol, 1-butanol or a mixture thereof;
The ketone solvent is 4-hydroxy-4-methylpentanone, 4-methyl-2-pentanone or a mixture thereof;
The blending ratio of the solvent components to the total coating liquid
2-propanol 10.0-20.0% by weight,
Alcohol-based solvent 10.0 to 25.0% by weight,
Ketone solvent 1.0 to 20.0% by weight,
Ethyl acetate 1.0-5.0% by weight
It is the most important feature.

  Since the coating liquid of the present invention uses a solvent having a formulation that is very compatible with polycarbonate, the polycarbonate substrate formed by using this solvent has excellent scratch resistance as well as transparency of transparent polycarbonate. Without loss, it has high adhesion to the polycarbonate substrate, and also has excellent chemical resistance to organic solvents.

  Furthermore, in the method for coating a polycarbonate substrate using the coating solution of the present invention, an excellent effect can be obtained by simply coating the polycarbonate substrate of the present invention, which is a one-component type, directly on a polycarbonate substrate and drying at room temperature. Since the film is formed, there is an advantage that it is not necessary to spend expensive equipment.

  Such a coated polycarbonate substrate is highly expected as a weight-reduced glass substitute material. However, the coated polycarbonate substrate of the present invention has a design property that was originally impossible to mold with glass. Thus, it is possible to design freely without any restrictions.

(Coating solution)
The coating liquid of the present invention can form a film having excellent scratch resistance, chemical resistance and adhesion on the surface of a transparent polycarbonate substrate. The components include a main agent that forms a film, a silane coupling agent that cures the main agent, and a solvent that dissolves the main agent and the silane coupling agent and enables application to the polycarbonate substrate surface.

(Main agent)
The main agent used in the present invention contains a curable liquid organopolysiloxane. The curable liquid organopolysiloxane starts condensation at the stage of film formation by a hydrolysis reaction with a silane coupling agent and cures at room temperature. This action forms a silicon dioxide (SiO ₂ ) polymer film on the polycarbonate surface.

  Specific examples of commercially available curable liquid organopolysiloxanes that can be used in the present invention include “Permeate” (manufactured by D & D Co., Ltd.), “Ceraton” (manufactured by Suzuki Sangyo Co., Ltd.), “ Super B "(manufactured by Noguchi Shoji Co., Ltd.)," Type F "(manufactured by Supremo Technica Co., Ltd.), (manufactured by Sarco Co., Ltd.)," Mega Coat "(Sakai Shoten Co., Ltd.), etc. It is not limited.

  The blending ratio of the main agent is 45 to 65% by weight with respect to the total amount of the coating liquid. If it is too much or too little from this range, the adhesion between the coating and the polycarbonate will be poor.

The coating liquid of the present invention includes silane coupling for curing the main agent. As the type of silane coupling agent, one having an amino group in its functional group is used. Specifically, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane (H ₂ NC ₂ H ₄ NHC ₃ H ₆ CH ₃ Si (OCH ₃ ) ₂ ), N-2- (aminoethyl) _{-3-aminopropyltrimethoxysilane: DAMO (H 2 NC 2 H} 4 NHC 3 H 6 Si (OCH 3) 3), N-2- ( aminoethyl) -3-aminopropyltriethoxysilane (H ₂ NC _{2 H 4 NHC 3 H 6 Si (} OC 2 H 5) 3), 3- _{aminopropyltrimethoxysilane: AMMO (H 2 NC 3 H} 6 -Si (OCH 3) 3), 3- aminopropyltriethoxysilane: AMEO (H ₂ NC ₃ H ₆ -Si (OC ₂ H ₅ ) ₃ ), bis (3-triethoxysilylpropyl) amine ( ₃ (C ₂ H ₅ O) SiC ₃ H ₆ -NH-C ₃ H ₆ Si ( OC ₂ H ₅ ) ₃ ), bis (3-trimethoxysilylpropyl) amine ( ₃ (H ₃ CO) SiC ₃ H ₆ -NH-C ₃ H ₆ Si (OCH ₃ ) ₃ ), 3-triethoxysilyl- N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-amino Propyl methyl diethoxy silane, N-(n-butyl) -3-like aminopropyltrimethoxysilane may be mentioned.

  The blending ratio of the silane coupling agent to the total coating liquid is 7.0 to 10.0% by weight. The required amount of the silane coupling agent is determined in relation to the main agent.

(solvent)
The solvent used in the present invention includes the following components. Moreover, each component is mix | blended in the ratio range shown next with respect to coating liquid whole quantity.
2-propanol 10.0-20.0% by weight,
Alcohol-based solvent 10.0 to 25.0% by weight,
Ketone solvent 1.0 to 20.0% by weight,
Ethyl acetate 1.0-5.0% by weight

  Here, the alcohol solvent is ethanol, 1-butanol or a mixture of both, and the ketone solvent is 4-hydroxy-4-methylpentanone, 4-methyl-2-pentanone or a mixture of both. It is.

  As long as each component does not deviate from the said range, another organic solvent can also be further mix | blended with a solvent.

(Film formation method)
The method of applying is not particularly limited, and an appropriate method such as dip coating, spin coating, dip spin coating, bar coating, spray coater, slit coater, brush, spray, etc. can be used.
The blending ratio of the solvent component of the coating liquid of the present invention is preferably changed by the coating method within the above blending range. For example, in the case of dip coating, it is preferable to increase the amount of alcohol solvent.

(Drying method)
This solution can be naturally dried at room temperature with oxygen and moisture by a sol-gel method. However, the curing time is not constant depending on the season. Therefore, when it is necessary to carry out production in a certain period of time for industrial use and mass production, it is possible to carry out heat drying at 50 to 100 ° C. for about 30 to 120 minutes. Since the deformation temperature of polycarbonate is around 135 ° C, heat drying at a high temperature exceeding 100 ° C is not preferable.

  The thickness of the coating is not particularly limited, but the preferred thickness varies depending on the coating method. For example, 0.5 to 5 μm is preferable for gravure printing, 10 to 100 μm for brush printing, 5 to 100 μm for spraying, and about 1 to 20 μm for dipping.

(Plasma treatment)
Prior to the coating step, it is preferable to plasma-treat the surface of the polycarbonate substrate on the coating side. This plasma treatment further improves the adhesion of the coating.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restricted only to the aspect shown in the Example.

Example 1
[Preparation of coating solution]
As a curable liquid organopolysiloxane as a main agent, 2.00 g of a trade name “Permeate” (Suzuki Sangyo Co., Ltd.) and 0.30 g of 3-aminopropyltrimethoxysilane as a silane coupling agent were prepared.

As the solvent, the following components were mixed in the following amounts to prepare 3.4 g of the solvent used in Example 1.
2-propanol (IPA) 0.50g
1-butanol 0.20g
4-Methyl-2-pentanone (MIBK) 0.10g
Ethanol 0.20g
Ethyl acetate 0.10g

  The main agent was added to the mixed solvent, mixed and stirred. Next, the silane coupling agent was further added and stirred to obtain the coating liquid of Example 1. The amount of each component is shown in Table 1. Table 3 shows the weight ratio of each component to the total amount of the coating liquid obtained in Example 1.

[Production of film-formed polycarbonate substrate]
The surface of a 50 mm × 50 mm polycarbonate substrate (“Asahi Glass Co., Ltd.”) is coated with the coating solution of Example 1 by rubbing in the following manner, and then dried to obtain a film-formed polycarbonate substrate of Example 1. It was.

[Coating by rubbing]
The cross paper was folded into a 2 cm square, and the coating liquid of Example 1 of Example 1 was impregnated. The cloth paper was brought into contact with a polycarbonate substrate and applied so as to be stretched lightly in one direction.

(Examples 2-5, Comparative Examples 1-4)
For Examples 2-5, the coating liquid and film-forming polycarbonate of each Example and Comparative Example were prepared in the same manner as in Example 1 using the components described in Table 1 and Comparative Examples 1 to 4 in Table 2. A substrate was obtained. Moreover, the weight ratio of each component with respect to the coating liquid whole quantity of the obtained Example and the comparative example is shown in Table 3 about Examples 2-5, and is shown in Table 4 about Comparative Examples 1-4.

[Evaluation]
The film-formed polyborate substrate obtained in the above Examples and Comparative Examples was evaluated for scratch resistance, transparency, followability and chemical resistance by the methods described below.

(Abrasion resistance)
In the following procedures (1) to (4), scratch resistance was evaluated using pencil hardness as an index.
(1) A film-formed polyborate substrate is placed horizontally. Check the level with a level.
(2) Slide a distance of 7mm or more with the pencil HB to 5H pencil.
(3) Evaluation: Start with a 5H pencil. If there is a scratch or indentation, soften the pencil and look for a pencil scale with no scar. Conversely, if there is no scratch or indentation, make the pencil harder than 5H and look for a pencil scale with a scar.
(4) Definition of pencil hardness: The measurement is continued until the same result is obtained twice on the hardest pencil scale with no scar.

(transparency)
The film-formed polyborated boronate substrate was visually observed and the transparency was evaluated according to the following criteria.
○ Transparent and smooth film △ Transparent × Cloudy

(Adhesion)
The film-formed polyborate substrate was left at room temperature for 48 hours after coating. After that, the both ends of the substrate were held and bent to 5 mm, and the adhesion between the polyborate substrate and the coating was confirmed by the presence or absence of peeling of the ceramic. Judgment criteria are as follows.
○ No cracking, no peeling △ Cracking No peeling × Cracking With peeling

(chemical resistance)
On the coating surface of the film-forming polyborate substrate obtained in the above Examples and Comparative Examples, the coating surface was rubbed 50 times with waste paper soaked with xylene to evaluate chemical resistance. The evaluation criteria are as follows.
○ No deterioration discoloration △ Peeling × Discoloration deterioration

  Table 5 summarizes the above evaluations in each example and comparative example.

The coated polycarbonate substrate obtained by the coating solution of the present invention greatly expands the possibilities for glass replacement applications. For example, in the fields of automobiles, home appliances, construction base materials, etc., there is a possibility that they can be used for applications that require further strength and light weight instead of glass. In particular, it is expected to be applied to a display unit that can operate a touch panel of a portable information terminal such as a smartphone because of its high scratch resistance.

Claims (3)

A coating liquid for coating a polycarbonate substrate containing a main agent, a silane coupling agent and a solvent,
The main agent contains a curable liquid organopolysiloxane, the blending ratio with respect to the total amount of the coating liquid is 45 to 65 wt%,
The silane coupling agent has an amino group in its functional group, and the blending ratio with respect to the total amount of the coating liquid is 7.0 to 10.0% by weight,
The solvent contains 2-propanol, alcohol solvent, ketone solvent and ethyl acetate as its components,
The alcohol solvent is ethanol, 1-butanol or a mixture thereof;
The ketone solvent is 4-hydroxy-4-methylpentanone, 4-methyl-2-pentanone or a mixture thereof;
The blending ratio of the solvent components to the total coating liquid
2-propanol 10.0-20.0% by weight,
Alcohol-based solvent 10.0 to 25.0% by weight,
Ketone solvent 1.0 to 20.0% by weight,
Ethyl acetate 1.0-5.0% by weight
A coating liquid characterized by   A method for coating a polycarbonate substrate, wherein the coating liquid according to claim 1 is directly coated on a polycarbonate substrate and dried at a temperature of 100 ° C. or lower to obtain a coated polycarbonate substrate. 3. The coating method according to claim 2, wherein the coating surface of the polycarbonate substrate is subjected to plasma treatment prior to coating with the coating liquid.