KR20090030196A - Antireflection film - Google Patents

Abstract

An anti-reflection film is provided to implement anti-reflection effect economically by making the anti-reflection film of a single coating layer type with a simple coating process. An anti-reflection film includes a step for coating a silica sol, an inorganic silica precursor and a cationic surface active agent on a heat resistance transparent film and a step for forming a pore of a micelle type. The inorganic silica precursor has an alkoxy group more than 3 on the heat resistance transparent film. The silica precursor is tetramethyl orthosilicate, tetraethyl othosilicate, tetrapropyl orthosilicate or tetrabuthyl orthosilicate.

Description

Antireflection Film {antireflection film}

The present invention relates to an antireflective film, and more particularly to a transparent antireflective film that imparts an antireflective effect that can be used in the front panel of a display.

When watching TV in the sun, it's common to see the screen invisible due to sunlight reflections. This is because glass used for glasses and displays does not show 100% transmittance and has a reflectance of about 4.5%. For example, in the case of using glasses, the reflected light is captured by the reflection so that it is obstructed to see a clear object, and in the case of TV, the external light is reflected on the surface glass to interfere with the screen. In order to reduce such reflection of transparent materials, antireflection (AR) technology by multilayer coating is widely employed. To prevent glare caused by reflection or the invisibility of the screen, this technique that lowers the reflectance of light in the visible region is collectively referred to as AR coating technology. Experience. This is because glass used for glasses and displays does not show 100% transmittance and has a reflectance of about 4.5%. For example, in the case of using glasses, the reflected light is captured by the reflection so that it is obstructed to see a clear object, and in the case of TV, the external light is reflected on the surface glass to interfere with the screen.

Since 1940, Geffken has applied for a three-layer AR coating patent, four-layer AR coating technology has been used for a long time. U.S. Patent 5856018 discloses a four-layer coating technique of SiO2 / TiO2 / SiO2 / TiO2 applied on a polymethyl methacrylate as a substrate. Korean Patent Application No. 10-1994-0036298 discloses a reflection reducing coating in which a high refractive index layer, a low refractive index layer and an uneven low refractive index layer are sequentially stacked. As such, the conventional antireflective coating consists of at least two to four layers of multilayer coatings such as TiO2 / SiO2, SiO2 / TiO2 / SiO2, TiO2 / SiO2 / TiO2 / SiO2, or is applied directly to a substrate such as a glass substrate. The process is complex and difficult to apply to large areas. In particular, the TiO2 layer has a stacking thickness of 15 nm to 30 nm, which is applied as a very thin layer, and is very sensitive to moisture, resulting in many defect rates.

The present invention is to provide a product that implements the anti-reflective effect at a low cost by a simple coating process consisting of a single coating layer.

It is also an object of the present invention to provide an antireflection film that can be easily applied to a large screen and can be economically produced.

According to the present invention, an inorganic silica precursor or oil having three or more alkoxy groups on a heat resistant transparent film, an inorganic hybrid silica precursor, a cationic surfactant in a ratio of 0.0001 to 0.1 mole per mole of the silica precursor, a lower alcohol having 1 to 5 carbon atoms, A silica sol consisting of an acid concentration controlling acid and a residual amount of water was coated on the heat-resistant transparent film, baked at 80 ° C. to 150 ° C., and then removed from the surfactant and dried to reflect micelle-shaped pores formed by the surfactant. The prevention film is provided.

Such anti-reflective film may be used to attach to the front plate of a substrate such as an LCD or a PDP to impart an anti-reflection effect to the screen. In addition, by adding a transparent adhesive layer on the back of the heat-resistant transparent film can be easily attached to the front plate of the display. Outside the adhesive layer may further include a release paper to protect the adhesive layer. In addition, the transparent film that provides an anti-reflection effect may further include a protective paper that is weakly coupled by physical force, such as electrostatic or vacuum adsorption force to protect it.

The silica precursor refers to a substance which forms a silica network structure by hydrogen substitution of an alkoxy group and subsequent dehydration reaction. It is an inorganic silica precursor selected from the group which consists of an alkoxy alkylsilane, an alkoxy alkenylsilane, an alkoxy aryl silane, and an alkoxy aralkyl silane, or an oil and inorganic hybrid silica precursor. The alkyl is preferably C1 to C5 alkyl and the alkoxy group is preferably C1 to C5 substituted or unsubstituted alkoxy and most preferably C1 to C4 unsubstituted alkoxy, for example methoxy or Ethoxy. Said alkanes or alkylenes are each substituted or unsubstituted alkanes or alkylenes of C1 to C5, respectively, preferably unsubstituted alkanes or alkylenes of C1 to C3, respectively, for example ethane or ethylene, respectively. The silica precursor is most preferably tetramethyl orthosilicate, TEOS (tetraethyl orthosilicate), tetrapropyl orthosilicate or tetrabutyl orthosilicate.

The cationic surfactant is preferably a surfactant defined by the following formula (1).

Equation 1

In which R ₁ Is alkyl having 12 to 18 carbon atoms and R ₂ , R ₃ and R ₄ are each hydrogen or alkyl having 1 to 8 carbon atoms and X is Br, Cl or I.

As the cationic surfactant, for example, DTAB (dodecyltrimethylammonium bromide), TRAB (trimethyltridecylammonium bromide), TTAB (tetradecyltrimethylammonium bromide), CTAB (cetyltrimethylammonium bromide), CTAC (cetyltrimethylammonium) Chloride), CDEAB (cetyldimethylammonium bromide), HPAB (haptadecyltrimethylammonium bromide) or OTAB (octadecyltrimethylammonium bromide) is used. Such cationic surfactants are used in a ratio of 0.0001 to 0.1 mol per mol of the silica precursor.

The lower alcohol having 1 to 5 carbon atoms is, for example, ethyl alcohol or propyl alcohol, and preferably 10 to 80 molar ratio is used. The acid concentration adjusting acid is preferably hydrochloric acid in which an inorganic acid or acetic acid is used. The amount of acid for adjusting acid concentration is used in an amount of approximately 0.0001 to 0.1 molar ratio.

The heat resistant transparent film used in the present invention is, for example, polyester, polycarbonate or polyimide, preferably a polyester (PET) film. The baking temperature can be varied from 80 degrees to 150 degrees depending on the choice of silica spheres and transparent films. The baking or drying method is not particularly limited but may be a hot stove or an infrared heating method. The surfactant is well soluble in weakly acidic or alcoholic aqueous solutions and thus is removed in these aqueous solutions.

As an adhesive used for the back surface of the antireflection film of this invention, an epoxy, an acryl, a polyurethane, or a silicone adhesive is used as a transparent material, for example. Such an adhesive is preferably thermosetting, including a crosslinkable component.

The surfactant forms micelles in the sol component including the silica precursor, remains in the baking process, and exits the removal process to form pores. In the case of the silica sol be an anti-reflective coating of the present invention thereto, but are not limited to single layer coating will be described the theoretical background as shown press null equation (Fresnel`s equation ) Being

When the refractive index of the substrate is n _t = 1.52, if n ₁ = 1.23 and the thickness is 1/4 of the desired wavelength, a value having a reflectance of 0% can be obtained as shown in the graph below.

In order to convert a coating layer with a refractive index of 1.52 to a material of 1.23 (the material with a coating layer of 1.23 has not been found so far), pores must be made using the following equation:

In the above formula

는 기공물질 계수

는 기공물질 밀도

Is the pore material coefficient

Is the pore density

는 비기공물질 계수

는 비기공물질 밀도

Is the non-porous material coefficient

Is the nonporous material density

Therefore, if there is a material with a refractive index of 1.52, a porosity of 60% is given to the refractive index of 1.23. Here, if the pore size is similar to the wavelength of light, the coating layer becomes opaque, so the pore size should be several hundred nanometers or less smaller than the wavelength of light (Mihai D. Morariu: University of Groningen, the Netherlands 9th July, 2004). .

For large area such as 40-inch or larger PDP, it is very disadvantageous in terms of cost and efficiency when multi-layer coating is applied directly to the front glass, but the monolayer antireflection film of the present invention is inexpensive and can be easily attached to the glass surface through an adhesive layer. Economical and effective antireflection effect.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are only to illustrate the present invention and should not be construed as limiting the present invention.

Example 1

Place the reaction vessel in a silicon oil bath with the temperature set to 80 ° C on a hot plate, add water, hydrochloric acid, and a surfactant of 16 carbon atoms (CTAB) to ethanol for 1 hour, and then add TEOS and react for 3 hours. Make The molar ratio of TEOS: EtOH: H ₂ O: HCl: surfactant carbon number 16 (CTAB) is 1: 55: 5: 0.004: 0.03. After the sol was spin-coated at 1000 rpm on a PET film, the surfactant was removed according to the time (30 sec, 60 sec, 90 sec, 120 sec) after heat treatment at 100 ° C. for 20 minutes. Table 1 shows the reaction conditions. FT-IR (SINCO NICOLET 380) analysis graph before and after removal is shown in FIG. In the FT-IR graph before removal, peaks appear between 2800 and 3000 nm, and therefore, surfactants containing 16 carbon atoms are included, and after removal, the peaks between 2800 and 3000 nm disappear in the FT-IR graph. It can be seen that it is removed. The graph is shown below as shown in FIG.

Examples 2-7

A silica sol was prepared in the same manner as in Example 1, but a silica sol was prepared by adding 0.03 mol of a surfactant having a different carbon number from the main chain, and the sol was spin-coated at 1000 rpm, 1500 rpm and 2000 rpm on a PET film. Table 2 shows the reaction conditions. The coated PET film was heat-treated at 100 ° C. for 5 minutes in a dry oven, and the surfactant was removed for 1 minute, and then heat-treated at 100 ° C. for 5 minutes in a dry oven. The reflectance of the 800 nm region (visible light region) is examined and the results are shown in Figs.

Examples 8-13

A silica sol was prepared in the same manner as in Example 1, but the concentration was changed with respect to the surfactant (OTAB; octadecyltrimethylammonium bromide) having a good reflectance in the 350 to 800 nm region (the pseudo light region). The prepared sol is spin-coated at 1000 rpm, 1500 rpm, 2000 rpm and 2500 rpm on a PET film. Table 3 shows the reaction conditions. The transmittance and reflectance of visible light 550 nm according to the molar concentration of the surfactant OTAB based on a 1000 rpm spin coating were measured using a UV-VIS S-3100 instrument (SINCO). The result is shown in FIG. 0.045 mol of OTAB was the best in transmittance and reflectance.

Table 1

TEOS EtOH water HCl 16 carbon number of surfactant rpm Removal time Example 1 One 55 5 0.004 0.03 1000 30, 60, 90, 120 sec

Table 2

TEOS EtOH water HCl Surfactant main chain carbon number (0.03 mol) rpm Example 2 One 55 5 0.004 C12 1000, 1500, 2000 Example 3 One 55 5 0.004 C13 1000, 1500, 2000 Example 4 One 55 5 0.004 C14 1000, 1500, 2000 Example 5 One 55 5 0.004 C16 1000, 1500, 2000 Example 6 One 55 5 0.004 C17 1000, 1500, 2000 Example 7 One 55 5 0.004 C18 1000, 1500, 2000

Table 3

TEOS EtOH water HCl Surfactant (18 main chain carbon) concentration rpm Example 8 One 55 5 0.004 0.013 1000, 1500, 2000, 2500 Example 9 One 55 5 0.004 0.026 1000, 1500, 2000, 2500 Example 10 One 55 5 0.004 0.035 1000, 1500, 2000, 2500 Example 11 One 55 5 0.004 0.04 1000, 1500, 2000, 2500 Example 12 One 55 5 0.004 0.045 1000, 1500, 2000, 2500 Example 13 One 55 5 0.004 0.05 1000, 1500, 2000, 2500

1 is a graph of FT-IR before and after surfactant removal of Example 1

2 to 7 are reflectance graphs in the visible light region of Examples 2 to 7, respectively.

8 is a graph showing transmittance and reflectance according to the surfactant concentration at 550 nm of visible light of Examples 8 to 13;

Claims (5)

Inorganic silica precursor or oil, inorganic hybrid silica precursor having three or more alkoxy groups on the heat-resistant transparent film, cationic surfactant at a ratio of 0.0001 to 0.1 mole per mole of the silica precursor, lower alcohols having 1 to 5 carbon atoms, acid and remaining amount for acid concentration adjustment The anti-reflection film having the micelle-shaped pores formed by the surfactant prepared by coating a silica sol made of water on the heat-resistant transparent film, baking at 80 ° C. to 150 ° C., and then removing and drying the surfactant. The antireflection film according to claim 1, wherein the silica precursor is tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate or tetrabutyl orthosilicate. The antireflection film according to claim 1, wherein the transparent film is a polyester film. The antireflection film according to claim 1, wherein the surfactant is defined by Formula 1 below. Equation 1

Wherein R ₁ is alkyl having 12 to 18 carbon atoms and R ₂ , R ₃ and R ₄ are each hydrogen or alkyl having 1 to 8 carbon atoms and X is Br, Cl or I. The antireflection film as described in any one of Claims 1-4 which has a transparent adhesive layer on the back surface of the said transparent film, and adheres to a base material.

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