WO2008143429A1

WO2008143429A1 - Method for producing a coating agent for anti-glare coating, and the coating agent and anti-glare film

Info

Publication number: WO2008143429A1
Application number: PCT/KR2008/002728
Authority: WO
Inventors: Young Hoon Lee; Jong Chul Choi
Original assignee: Hanwha L & C Corp.
Priority date: 2007-05-23
Filing date: 2008-05-16
Publication date: 2008-11-27
Also published as: KR20080103215A; KR100907357B1

Abstract

Disclosed herein is a method of producing a coating agent for antireflection coating, comprising: mixing and stirring an organic solvent, a surfactant, and colloidal silica having a particle size of 2 ~ 50 nm and a concentration of 5 ~ 40% to form a solution including silica reverse micelles having a particle size of 10 ~ 100 nm; mixing and stirring a silane derivative in the solution including silica reverse micelles to surface-treat the silica reverse micelles; and removing the organic solvent and surfactant from the solution including silica reverse micelles to produce porous silica particles having a particle size of 10 ~ 100 nm. The antireflection film produced using the method has high transmissivity, low turbidity, and excellent antireflection.

Description

METHOD FOR PRODUCING A COATING AGENT FOR ANTI-GLARE COATING, AND THE COATING AGENT

AND ANTI-GLARE FILM

Technical Field

[1] The present invention relates to a coating agent for antireflection coating, a method of producing the coating agent, and an antireflection film using the coating agent. Background Art

[2] Recently, in order to prevent visibility of a screen from decreasing and to prevent screen glare, an antireflection film has been increasingly used in the field of displays, such as liquid crystal displays (LCDs), organic light emitting diodes (OLEDs), plasma display panels (PDPs), and the like.

[3] Generally, an antireflection film includes a transparent substrate, a resin layer for imparting hard coatability, and a low refractive coating layer, which is an antireflection layer. Here, the low refractive coating layer is formed using a dry coating method or a wet coating method.

[4] First, the dry coating method may include vacuum deposition, sputtering, chemical vapor deposition (CVD), and the like. This dry coating method is disadvantageous in that, although the low refractive coating layer formed using this dry coating method has high antireflectivity, there is a limitation on producing the low refractive coating layer (antireflection layer) in large quantities, and the production cost thereof is high.

[5] Next, the wet coating method is a method of applying a low refractive coating agent

(an antireflection coating agent) on a film or sheet. This wet coating method is advantageous in that the low refractive coating layer (antireflection layer) can be produced in large quantities, and the production cost thereof is lower than that of the dry coating method. Therefore, recently, the wet coating method has been widely researched. In particular, in the wet coating method, since the antireflectivity of the produced antireflection film depends on the refractive index of the low refractive coating layer, research for improving the antireflectivity of the antireflection film is being actively conducted.

[6] As the wet coating method, Korean Unexamined Patent Publication Nos.

2000-0Q59818 and 20Q5-0083890, and U.S. Pat. Nos. 5,74,537, 4,846,650, 6,773,121 and 6,908,647 disclose methods of impregnating a low refractive coating layer with a fluorine resin having a low refractive index.

[7] These methods are advantageous in that the refractive index of the antireflection film is decreased as the amount of the fluorine resin included in the low refractive coating layer is increased, but are disadvantageous in that there is a limitation on decreasing the refractive index of the antireflection film by increasing the amount of the fluorine resin included in the low refractive coating layer because the inherent refractive index of the fluorine resin is about 1.35-1.40, and in that the adhesivity and hardness of the coating layer are decreased as the amount of the fluorine resin is increased.

[8] In addition, as a method of decreasing the refractive index of a low refractive coating layer, there is a method of adding porous particles to a low refractive coating layer. Since the refractive index of the porous particles is approximately 1, in the method, the refractive index of the low refractive coating layer is decreased by increasing the amount of porous particles included in the low refractive coating layer. For example, U.S. Pat. N). 6,777,069 discloses a method of preparing porous silica particles by forming mixed particles of silica and alumina and then melting the alumina in the mixed particles through acid treatment.

[9] However, this method can be successfully used to prepare porous silica-dispersed particles having a particle size of 100 nm or less, but is problematic in that processes are complicated. Further, this method is problematic in that, since mixed particles of silica and alumina are prepared using precursors of silica and alumina in aqueous solution, alumina is not completely dissolved at the time of dissolving alumina through acid treatment, and thus the remaining high-refractive alumina has a negative influence on transmissivity and refractive index. Disclosure of Invention Technical Problem

[10] Accordingly, the present invention has been made keeping in mind the above problems oxurring in the prior art, and an object of the present invention is to provide porous silica particles having a particle size of 100 nm or less, which do not include metal components, such as alumina, and the like, and are suitable for a low refractive layer, a method of producing the porous silica particles, and an antireflection film using the porous silica particles. Technical Solution

[11] In order to accomplish the above object, the present invention provides a coating agent for antireflection coating, produced using a method comprising: (A) mixing and stirring 100 parts by weight of an organic solvent, 0.5 - 5 parts by weight of a surfactant, and 2 - 10 parts by weight of colloidal silica having a particle size of 2 - 50 nm and a concentration of 5 - 40% to form a solution including silica reverse micelles having a particle size of 10 - 100 nm; (B) mixing and stirring 20 - 300 parts by weight, based on 100 parts by weight of the solid content of the colloidal silica, of a silane derivative in the solution including silica reverse micelles to surface-treat the silica reverse micelles; and (Q removing the organic solvent and surfactant from the solution including the surface-treated silica reverse micelles to produce porous silica particles.

[12] The present invention also provides a method of producing a coating agent for an- tireflection coating, comprising: (A) mixing and stirring an organic solvent, a surfactant, and colloidal silica having a particle size of 2 - 50 nm and a concentration of 5 - 40% to form a solution including silica reverse micelles having a particle size of 10 - 100 nm; (B) mixing and stirring a silane derivative in the solution including silica reverse micelles to surface-treat the silica reverse micelles; and (Q removing the organic solvent and surfactant from the solution including silica reverse micelles to produce porous silica particles having a particle size of 10 - 100 nm.

[13] In the step (A) of the method, an amount of the colloidal silica may be 2 - 10 parts by weight based on 100 parts by weight of the organic solvent, and an amount of the surfactant may be 0.5 - 5 parts by weight based on 100 parts by weight of the organic solvent.

[14] In the step (B) of the method, an amount of the silane derivative may be 20 - 300 parts by weight based on 100 parts by weight of the solid content of the colloidal silica.

[15] The step (B) of the method may comprise: (a) separating silica particles from the solution including silica reverse micelles obtained in the step (B); (b) washing the silica particles obtained in the step (a) and then dispersing them in water or alcohol; and (c) filtering and concentrating the solution obtained in the step (b) to form a silica particle solution having a concentration of 1 - 10%.

[16] The step (B) of the method may comprise: (a) dispersing the solution including silica reverse micelles obtained in the step (B) in alcohol to form a silica-dispersed solution; and (b) filtering and concentrating the silica-dispersed solution obtained in the step (a) to form a silica particle solution having a concentration of 1 - 10%.

[17] Meanwhile, the coating agent may be used for an antireflection film, which is used to prevent light from reflecting from a surface of a display. Advantageous Effects

[18] According to the present invention, a porous coating agent for antireflection coating, having a particle size of 100 nm or less, which does not include metal components, such as alumina, and the like, can be produced.

[19] Further, the antireflection film including the coating agent exhibits high trans- missivity, low turbidity, and an excellent antireflection effect. Best Mode for Carrying Out the Invention

[20] Hereinafter, the present invention will be described in detail.

[21] In order to accomplish the above object, in the present invention, porous silica reverse micelles are formed of silica, and then the silica reverse micelles are surface- treated using a silane derivative such that the pores of the silica reverse micelles are not exposed, thereby producing a coating agent for antireflection coating, that is, pure porous silica particles having a particle size of 100 nm or less, which are suitable for a low refractive coating layer. The method of producing the coating agent according to the present invention will be described in detail below.

[22] [Process of forming silica reverse micelles]

[23] In this process, an organic solvent, a surfactant, and colloidal silica having a particle size of 2 ~ 50 nm and a concentration of 5 ~ 40% are mixed and stirred, thus forming porous silica reverse micelles having a particle size of 10 ~ 100 nm.

[24] Examples of the organic solvent may include pentane, hexane, heptane, octane, nonane, benzene, toluene, xylene, 1,2-dichloroethane, chloroform, and mixtures thereof. Among them, hexane and heptane are suitable from the aspects of solubility in water, toxicity and price.

[25] As the surfactant, an anionic surfactant, a cationic surfactant, and a nonionic surfactant may be used. Among them, it is preferred that the anionic surfactant and nonionic surfactant, which have high solubility in the organic solvent, be used. In particular, a sodium sulfonate anionic surfactant may be used in small quantities, and is suitable from the aspects of solubility in the organic solvent and particle size of the formed reverse micelles. It is preferred that the amount of the surfactant be 0.5 ~ 5 parts by weight based on 100 parts by weight of the organic solvent. When the amount of the surfactant is less than 0.5 parts by weight, it is difficult to form reverse micelles having a particle size of 100 nm or less. In contrast, when the amount of the surfactant is more than 5 parts by weight, the surfactant cannot be completely dissolved in the organic solvent. [26] The colloidal silica may have a particle size of 2 ~ 50 nm and a solid content of 5 ~

40%. When the solid content of the colloidal silica is below 5%, the formed silica reverse micelles have excessively high porosity, so that they do not have good stability, and cannot be easily surface-treated. In contrast, when the solid content of the colloidal silica is above 40%, the porosity of the silica reverse micelles is greatly decreased. Further, it is preferred that the amount of the colloidal silica be 2 ~ 10 parts by weight based on 100 parts by weight of the organic solvent. When the amount of the colloidal silica is below 2 parts by weight, the solid content is excessively low, which is not practical. In contrast, when the amount of the colloidal silica is above 10 parts by weight, the colloidal silica particles are clustered, thus forming macroparticles.

[27] [Process of surface-treating reverse micelles]

[28] In this process, a silane derivative is mixed with the solution including the reverse micelles obtained in the process of forming silica reverse micelles, and then the solution is stirred, thereby surface-treating the reverse micelles. In order to surface- coat the reverse micelles using the silane derivative, ammonia may be used as a coating promoter. Due to the surface coating of the reverse micelles, the pores of the reverse micelles are not externally exposed, so that contaminants do not infiltrate into the pores, thereby preventing the refractive index of the reverse micelles from being influenced by the contaminants.

[29] Examples of the silane derivative may include tetramethoxy silane, tetraethoxysilane, tetrapropoxy silane , trimethoxymethylsilane , trimethoxyethylsilane , trimethoxypropylsilane, triethoxymethylsilane, triethoxyethylsilane, tri- ethoxypropylsilane, tripropoxymethylsilane, tripropoxyethylsilane, tripropoxypropylsilane, dimethoxydimethylsilane, dimethoxydiethylsilane, dimethoxy- dipropylsilane, diethoxydimethylsilane, diethoxydiethylsilane, diethoxydipropylsilane, dipropoxydimethylsilane, dipropoxydiethylsilane, dipropoxydipropylsilane, and the like. It is preferred that the amount of the silane derivative be 20-300% of the solid content of the colloidal silica. When the amount of the silane derivative is below 20%, the reverse micelles cannot be efficiently surface-treated. In contrast, when the amount of the silane derivative is above 300%, an excessive amount of silane is bonded on the surface of the reverse micelles, so that the porosity of the reverse micelles is decreased, with the result that the refractive index reduction effect becomes low.

[30] [Process of removing organic solvent, surfactant, etc from reverse micelle solution]

[31] In this process, an organic solvent, a surfactant, and various impurities are removed from the reverse micelle solution obtained in the process of surface-treating reverse micelles, thus preparing pure porous silica particles having a particle size of 10 ~ 100 nm.

[32] This process may be performed in the following two ways.

[33] First, silica particles are separated from the silica reverse micelle solution obtained in the process of surface-treating reverse micelles, are washed, and are then dispersed in water or alcohol to form a solution, and then the solution is filtered and concentrated to form a silica particle solution having a concentration of 1 ~ 10%.

[34] Second, the silica reverse micelle solution obtained in the process of surface-treating reverse micelles is dispersed in alcohol to form a silica-dispersed solution, and then the silica-dispersed solution is filtered and concentrated to form a silica particle solution having a concentration of 1 ~ 10%.

[35] The silica particle solution may be applied thickly when its concentration is low.

However, when the concentration of the silica particle solution is below 1%, the silica particle solution is excessively diluted, thus decreasing productivity and coating uniformity. In contrast, when the concentration thereof is above 10%, the silica particle solution is excessively concentrated, and thus the thickness of the coating layer cannot be easily controlled.

[36] [Application of antireflection coating agent]

[37] The silica particles, prepared as above, do not include metal salts, such as alumina, etc, and exhibit high transmissivity, low turbidity, and an excellent antireflection effect when they are applied on a film or sheet.

[38] The silica particles may be independently used, or may be used by mixing them with a UV-curing coating material or a thermo-curing coating material. For example, as the UV-curing coating material, a mixed coating material of an acrylic oligomer and a photoinitiator may be used, and as the thermo-curing coating material, a sol solution, formed by treating tetraethoxysilane with nitric acid, may be used. Mode for the Invention

[39] Hereinafter, Examples of the present invention will be described in more detail.

[40] Example 1

[41] 15L (about 9.905 kg) of n-hexane was put into a reactor, and then 257 g of didode- cylsuocinate sodium sulfonate, which is a surfactant, was additionally put into the reactor to form a mixture, and then the mixture was melted. Subsequently, 495g of aqueous colloidal silica solution having a solid content of 15% was added thereto, and was then stirred for 4 hours to prepare reverse micelles. Subsequently, 58.5 g of tri- ethoxysilane, which is a silane derivative, was additionally put into the reactor, and was then further stirred for 20 hours.

[42] Thereafter, 1% of aqueous ammonia was put into the reactor and was then stirred for

3 hours, and then 600 g of acetone was added thereto to form a precipitate. Solids were separated from the precipitate using a centrifugal separation method, and the precipitate, from which the solids were separated, was washed two times using acetone. Subsequently, 6 kg of distilled water was added to the precipitate, and then precipitate particles were dispersed in the distilled water using ultrasonic waves.

[43] Thereafter, the dispersed precipitate particles were filtered using a filter having a particle size of 0.2 μm to form a filtrate, and then the filtrate was concentrated to prepare 1.2 kg of a silica particle solution including silica particles having a porosity of 5% and a particle size of 100 nm or less. The average particle size of the prepared silica particles was 14 nm.

[44] Subsequently, the prepared silica particle solution including silica particles having a particle size of 100 nm or less was applied on a glass substrate having a thickness of 1 mm using a spin-coating method, and was then dried at a temperature of 200⁰C for 10 minutes to form an antireflection layer having a thickness of 100 nm. Subsequently, the physical properties of the formed antireflection layer were measured, and the results thereof are given in Table 1.

[45] Example 2

[46] 1.2 kg of a silica particle solution including silica particles having a porosity of 5% and a particle size of 100 nm or less was prepared using the same method as in Example 1, except that 214.5 g of didodecylsuαinate sodium sulfonate, which is a surfactant, was additionally put into the reactor. The average particle size of the silica particles prepared in Example 2 was 14 nm.

[47] As in Example 1, the prepared silica particle solution including silica particles was applied on a glass substrate having a thickness of 1 mm using a spin-coating method, and was then dried at a temperature of 200⁰C for 10 minutes to form an antireflection layer having a thickness of 100 nm. Subsequently, the physical properties of the formed antireflection layer were measured, and the results thereof are given in Table 1.

[48] Example 3

[49] 15L (about 9.905 kg) of n-hexane was put into a reactor, and then 257 g of didode- cylsuocinate sodium sulfonate was additionally put into the reactor to form a mixture, and then the mixture was melted. Subsequently, 495g of aqueous colloidal silica solution having a solid content of 15% was added thereto, and was then stirred for 4 hours to prepare reverse micelles. Subsequently, 58.5 g of triethoxysilane, which is a silane derivative, was additionally put into the reactor, and was then further stirred for 20 hours. Thereafter, 1% of aqueous ammonia was put into the reactor and was then stirred for 3 hours to form a silica solution. This procedure is the same as that of Example 1 up to this point.

[50] Subsequently, the silica solution was slowly dispersed in hexane and 10 kg of ethylhexyl alcohol to form a mixed solution. The mixed solution was filtered using an ultrafiltration method to remove hexane and a surfactant therefrom, and then the mixed solution, from which the hexane and surfactant were removed, was concentrated to prepare 0.3 kg of a silica particle solution including silica particles having a porosity of 2% and a particle size of 100 nm or less. The average particle size of the prepared silica particles was 25 nm. Here, the amounts of raw materials are the same as in Example 2, but the average particle size of the prepared silica particles was slightly increased compared to that in Example 2.

[51] Subsequently, the prepared silica particle solution including silica particles was applied on a glass substrate having a thickness of 1 mm using a spin-coating method, and was then dried at a temperature of 200⁰C for 10 minutes to form an antireflection layer having a thickness of 100 nm. Subsequently, the physical properties of the formed antireflection layer were measured, and the results thereof are given in Table 1.

[52] Example 4

[53] The silica particle solutions prepared in Examples 1 to 3 were mixed with thermo- curing coating materials such that the mixing ratio of the silica particle solution to the thermo-curing coating material was 1 : 1 by weight, and were then applied on a glass substrate having a thickness of 1 mm using a spin-coating method, and were then dried at a temperature of 200⁰C for 10 minutes to form antireflection layers having a thickness of 100 nm. Subsequently, the physical properties of the respective formed antireflection layers were measured, and the results thereof are given in Table 1. In Table 1, Examples corresponding to Examples 1, 2 and 3 are represented by Examples 4-1, 4-2 and 4-3, respectively.

[54] The thermo-curing coating material was prepared as follows.

[55] That is, 117 g of triethoxymethylsilane was mixed with 177 g of ethanol, and then 81 g of an aqueous 0.1 N nitric acid solution was added thereto to form a mixed solution, and then the mixed solution was stirred for 24 hours. Subsequently, 410 g of ethanol was added to the mixed solution to prepare a thermo-curing coating material having a solid content of 5%. [56] Comparative Example 1 [57] The colloidal silica used in Example was independently applied on a glass substrate having a thickness of 1 mm using a spin-coating method, and was then dried at a temperature of 200⁰C for 10 minutes to form an antireflection layer having a thickness of 100 nm. Subsequently, the physical properties of the formed antireflection layer were measured, and the results thereof are given in Table 1.

[58] Comparative Example 2 [59] The thermo-curing coating material prepared in Example 4 was independently applied on a glass substrate having a thickness of 1 mm using a spin-coating method, and was then dried at a temperature of 200⁰C for 10 minutes to form an antireflection layer having a thickness of 100 nm. Subsequently, the physical properties of the formed antireflection layer were measured, and the results thereof are given in Table 1.

[60] Table 1 [Table 1] [Table ]

[61] As shown in Table 1, it can be seen that the antireflection layers, prepared using the porous silica particles having a particle size of 100 nm or less in Examples 1 to 4, exhibit excellent results from the aspects of turbidity and minimum reflectance, compared to Comparative Examples 1 and 2.

Claims

[1] A coating agent for antireflection coating, produced using a method comprising:

(A) mixing and stirring 100 parts by weight of an organic solvent, 0.5 - 5 parts by weight of a surfactant, and 2 - 10 parts by weight of colloidal silica having a particle size of 2 - 50 nm and a concentration of 5 - 40% to form a solution including silica reverse micelles having a particle size of 10 - 100 nm;

(B) mixing and stirring 20 - 300 parts by weight, based on 100 parts by weight of the solid content of the colloidal silica, of a silane derivative in the solution including silica reverse micelles to surface-treat the silica reverse micelles; and (Q removing the organic solvent and surfactant from the solution including the surface-treated silica reverse micelles to produce porous silica particles.

[2] A method of producing a coating agent for antireflection coating, comprising:

(A) mixing and stirring an organic solvent, a surfactant, and colloidal silica having a particle size of 2 - 50 nm and a concentration of 5 - 40% to form a solution including silica reverse micelles having a particle size of 10 - 100 nm;

(B) mixing and stirring a silane derivative in the solution including silica reverse micelles to surface-treat the silica reverse micelles; and

(Q removing the organic solvent and surfactant from the solution including silica reverse micelles to produce porous silica particles having a particle size of

10 - 100 nm.

[3] The method of producing a coating agent for antireflection coating aαjording to claim 2, wherein, in the step (A), an amount of the colloidal silica is 2 - 10 parts by weight based on 100 parts by weight of the organic solvent.

[4] The method of producing a coating agent for antireflection coating aαjording to claim 2, wherein, in the step (A), an amount of the surfactant is 0.

5 - 5 parts by weight based on 100 parts by weight of the organic solvent. [5] The method of producing a coating agent for antireflection coating aαjording to claim 2, wherein, in the step (B), an amount of the silane derivative is 20 - 300 parts by weight based on 100 parts by weight of the solid content of the colloidal silica.

[6] The method of producing a coating agent for antireflection coating aαjording to claim 2, wherein the step (Q comprises:

(a) separating silica particles from the solution including silica reverse micelles obtained in the step (B); (b) washing the silica particles obtained in the step (a) and then dispersing them in water or alcohol; and

(c) filtering and concentrating the solution obtained in the step (b) to form a silica particle solution having a concentration of 1 ~ 10%.

[7] The method of producing a coating agent for antireflection coating aαjording to claim 2, wherein the step (Q comprises:

(a) dispersing the solution including silica reverse micelles obtained in the step (B) in alcohol to form a silica-dispersed solution; and

(b) filtering and concentrating the silica-dispersed solution obtained in the step (a) to form a silica particle solution having a concentration of 1 ~ 10%.

[8] An antireflection film, which is used to prevent light from reflecting from a surface of a display, coated with the coating agent of claim 7.