KR101171827B1 - Optical polyester adhesive film having antireflection layer - Google Patents

Abstract

The present invention relates to an optical polyester-based easy adhesive film with improved brightness. The present invention provides a polyester-based adhesive film comprising a polyester film substrate, a polymer easily adhesive layer formed on one surface of the substrate, and a low refractive index anti-reflection layer formed on the other surface of the substrate.

The optical polyester-based adhesive film of the present invention has excellent adhesion between the base film and the easy-adhesive layer or the base film and the anti-reflection layer, and has excellent light transmittance but low turbidity, so that the base film or backlight for prism sheet used in LCD It can be widely used as a base film for hard coating, anti-reflective base film and CRT protective film.

Optical film, polyester film, easily bonding layer, antireflection layer.

Description

Optical polyester adhesive film containing an antireflection layer {OPTICAL POLYESTER ADHESIVE FILM HAVING ANTIREFLECTION LAYER}

The present invention relates to an optical polyester-based adhesive film having an improved brightness including an antireflection layer, and more specifically, to one surface of a polyester-based film substrate, acrylic, polyester, or poly generally used in industry. An easy adhesive layer including a urethane-based binder and inorganic nanoparticles is formed, and a low refractive index anti-reflective layer including fluorine, acrylic or silicone resins and inorganic nanoparticles is formed on the other side of the polyester film substrate. The present invention relates to an optical polyester-based easy adhesive film which is effective in synergy.

Conventionally, an easy-adhesive layer was introduced to impart adhesion between the resin forming the prism acid and the polyester-based substrate, and the roughness was improved by using inorganic particles or the like to impart slip property to the substrate. However, in accordance with ever-increasing demand for brightness enhancement, the use of large inorganic particles that impede brightness enhancement is not desirable. Therefore, inorganic particles in nano units are used in the adhesive layer without using inorganic particles in the substrate. . In addition, anti-reflective coating technology has been introduced to the adhesive layer as a method to maximize the utilization of light incident on the prism sheet. Originally, the anti-reflection film technology is used for an optical filter of a polarizing plate or a PDP of LCD and is a technology for preventing the incident light from being reflected through the lamination of the high and low refractive layers. Therefore, in order to improve the brightness, a structure capable of reducing the loss of light through controlling the refractive index of the anti-reflection layer that contacts the air layer without being post-processed is required.

Korean Patent Publication No. 10-0611460 proposes a method of improving luminance based on the above principle in various structures. In fact, having such structures will have various functions, but the number of post-processing will increase by the number of coating layers, thereby reducing economic efficiency. In addition, even the simplest single-layer coatings require a post-processing process, resulting in higher costs. In the above patent, the anti-reflective function is given to the urethane adhesive layer treated film. However, if it is possible to implement such an antireflective low refractive layer through in-line coating during film formation, there is no additional post-processing cost, and thus it is economically significant. .

Typically, the PET film has a refractive index of 1.65, and the refractive index of the polymer coating applied to the inline coating is usually about 1.5 to 1.6, but when using a fluorine-based or silicon-based polymer material, the refractive index may be lowered to 1.4 or less. Accordingly, the present inventors confirmed that by reducing the refractive index of the coating layer on the non-post-processed surface of the polyester-based film to reduce light loss, the vertical luminance value can be increased after the post-processing such as a prism lens or hard coating. The present invention has been reached.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical poly with an easy adhesive layer on one surface of a polyester film, which is used as a diffusion plate of a conventional LCD, and a low refractive index anti-reflection layer on the other surface, thereby reducing the loss of light. It is to provide an ester adhesive film.

Optical film of the present invention for achieving the above object is a polyester film substrate having a thickness of 50 to 500㎛; An adhesive layer formed on one surface of the substrate and composed of at least one polymer binder and inorganic nanoparticles selected from the group consisting of acrylic resins, urethane resins and polyester resins; And a low refractive index anti-reflection layer formed on the other side of the substrate and composed of one or more polymer binders and inorganic nanoparticles selected from the group consisting of fluorine, acrylic and silicone resins.

At this time, the thickness of the easily adhesive layer is preferably 0.01 to 3.00㎛, in the case of the antireflection layer, the refractive index is preferably 1.2 to 1.45, the thickness is preferably 80 to 120nm.

On the other hand, the optical film of the present invention is produced by a method of uniaxially stretching the substrate and then water-based coating both sides of the film using a gravure coating or Meyer bar coating method, and then drying and curing both layers simultaneously with lateral stretching. can do.

In the optical film of the present invention, the adhesion between the base film and the easy-adhesive layer or the base film and the anti-reflection layer is maintained at 100% after 96 hours moisture resistance test at 65 ℃, 95% relative humidity conditions see. In addition, the surface of the film on which the easily adhesive layer and the antireflection layer were formed had a total light transmittance of 90% or more and a haze value (haze value) of 2% or less. As a result, the optical film of the present invention can be used throughout the various optical members because of its excellent synergistic effect during post-processing such as prism lens processing, hard coat processing, antireflection processing and the like. In particular, the optical film may be widely used as a prism sheet base film or backlight base film, hard coat processing or antireflection base film, CRT protective film, and the like.

The optical film of this invention is a polyester film base material; A polymer adhesive layer formed on one surface of the substrate and composed of at least one polymer binder and inorganic particles selected from the group consisting of acrylic resins, urethane resins, and polyester resins; And a low refractive index anti-reflection layer formed on the other side of the substrate.

It is preferable that the polyester film base material which concerns on this invention is 50-500 micrometers in thickness. On the other hand, polyester-based resin which forms a polyester film base material is sufficient as it is polyester-based resin used for a normal optical film. Specifically, a polyester resin having a dicarboxylic acid component and a branched glycol component as a component may be used.

Branched glycol components include, for example, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2 -Methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-hexyl-1,3-propanediol, 2,2-di Ethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-hexyl-1,3-propanediol, 2,2-di-butyl-1,3 -Propanediol, 2-butyl-2-propyl-1,3-propanediol, 2,2-di-hexyl-1,3-propanediol, and the like. It is preferable to contain the branched glycol component at a rate of 10 mol% or more in the total glycol component, particularly preferably at least 20 mol%. Moreover, it is preferable to contain the branched glycol component in a ratio of 80 mol% or less in the total glycol component. If it is less than 10 mol%, there exists a tendency for adhesiveness with a biaxially-oriented polyester film to become inadequate. As glycol components other than the said compound, ethylene glycol is the most preferable. As small amount, diethylene glycol, propylene glycol, butanediol, hexanediol or 1,4-cyclohexanedimethanol may be used.

As the dicarboxylic acid component contained as a constituent of the polyester resin, terephthalic acid and isophthalic acid are most preferred. If small amount, other dicarboxylic acid, especially diphenylcarboxylic acid and aromatic dicarboxylic acid of 2, 6- naphthalenedicarboxylic acid, may be added and copolymerized.

In addition to the dicarboxylic acid component, in order to impart water dispersibility, it is preferable to use 5-sulfoisophthalic acid in the range of 1 to 10 mol%, in addition, sulfoterephthalic acid and 4-sulfonaphthalene isophthalic acid-2 , 7-dicarboxylic acid or 5- (4-sulfophenoxy) isophthalic acid and salts thereof may be used in the same ratio.

One or more polymer materials selected from the group consisting of water-dispersible acrylic resins, urethane resins and polyester resins are used as the polymer binder for the adhesive layer formed on one surface of the substrate. At this time, the said acrylic resin is 1 or more in 1 molecule and 1 or more of the monomer and the prepolymer of 3 or more, More preferably, 4 or more, More preferably, 5 or more (meth) acryloyloxy group in 1 molecule. The main constituent is a mixture consisting of at least one of monomers having ˜2 ethylenically unsaturated double bonds. More specific examples include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth ) Acrylate, dipentaerythritol hexa (meth) acrylate, trimetholpropane tri (meth) acrylate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer , Pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer and the like can be used. These monomers and the prepolymer can be used 1 type or in mixture of 2 or more types. Especially the polyfunctional acrylate compound which has one or more hydroxyl groups among these is especially preferable because an adhesive of a base film can be improved when an epoxy type hardening | curing agent is used together. On the other hand, the urethane resin may be used a variety of solvent type, solvent-free or aqueous coating agent. As resin containing a block type isocyanate group, the thermally reactive water-soluble urethane resin which blocked the terminal isocyanate group by the hydrophilic group is mentioned, for example. Examples of the blocking agent for the isocyanate group include phenols, lactams, oximes, alcohols and active methylene compounds containing sulfonic acid groups and bisulfites. The polyester resin is a generic term for polymers having ester bonds as the main bond chains of the main chain, and preferred polyesters include ethylene terephthalate, propylene terephthalate, ethylene-2,6-naphthalate, butylene terephthalate, and propylene-. 2,6-naphthalate, ethylene-α, β-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylate, ethylene-α, β-bis (phenoxy) ethane-4,4 ' It is possible to use at least one constituent selected from dicarboxylate and the like as the main constituent. Although these components may be used alone or in combination of two or more, it is preferable to use polyesters having ethylene terephthalate as the main component, in view of overall quality, economy and the like. Moreover, a part of another dicarboxylic acid component and a diol component may be copolymerized in these polyester preferably 20 mol% or less.

The easy adhesive layer should be improved in durability by using a curing agent such as melamine or epoxy. As a hardening | curing agent used for this use, HMMA, Bisphenol A epoxy, etc. are used in the ratio of 0.1%-50%.

In addition, the polymer easily adhesive layer includes inorganic nanoparticles for the purpose of preventing blocking. As the inorganic nanoparticles for this purpose, silica, alumina, titanium dioxide and the like can be used alone or in combination, and in particular, inexpensive silica and low refractive index are preferable. The size of the inorganic nanoparticles used as the utilization is preferably 50nm to 500nm.

The thickness of the polymer adhesive layer should be 0.01 to 5.00 μm, preferably 0.05 to 3.00 μm. When the thickness of the coating is thinner than 0.01 μm, the transparency becomes good but the adhesion is poor.

Surfactants may be used for use in the water-soluble coating solution of the polyester film according to the present invention. In order to increase the wettability of the base film and to uniformly apply the coating liquid, it is preferable to apply to the base film by using a known amount of anionic or nonionic surfactant.

The antireflective layer coating used in the present invention is prepared using silica nanoparticles based on the dispersed fluorine, acrylic, and silicone polymers. If necessary, it can be used with melamine or epoxy curing agent. The antireflective coating agent functions to form a transparent coating film having a lower refractive index than usual and to increase the transmittance of the incident light in the visible light region through the constructive interference at the interface.

At this time, ethylene tetrafluoroethylene, 2,2,2-trifluoroethyl methacrylate, and the like are used as the water-dispersed fluorine-based polymer, and polyisobutyl methacrylate, poly2-methoxyethyl acrylate, etc. are used as the acrylic polymer. Polymethylhydrosiloxane, polydimethylsiloxane, and the like may be used as the silicone-based polymer. Each polymer resin will account for about 50 to 95% of the total coating after curing, and the remainder may be a surfactant, a curing agent, organic or inorganic particles, and the like. Using the polymer as described above can obtain the low refractive index necessary for the anti-reflective layer production and there is no problem to use as an in-line coating solution in the PET film forming process because it is an aqueous coating liquid. If necessary, drying and curing of the coating may be performed in the secondary stretching process during film formation using a thermosetting resin. The low refractive index coating layer thus obtained serves as an antireflection layer when it has a precisely controlled thickness.

On the other hand, in addition to the polymer binder resin, inorganic nanoparticles are added to the easily adhesive layer and the antireflection layer for the purpose of imparting antiblocking properties. As the inorganic nanoparticles, silica, alumina, titanium dioxide and the like can be used alone or in combination, and in particular, silica is preferred. Silica particles have an antiblocking function, and silica particles having a size of 50 nm to 500 nm are used. If it is more than 500nm, it is too large to fall off compared to the inline coating, and if it is less than 50nm, it is hard to expect anti-blocking function by being buried in the inline coating. Meanwhile, a siloxane compound may be coated on the surface of the silica particles for the purpose of increasing adhesion between the silica particles and the substrate or the silica particles.

The optical film according to the present invention is obtained by uniaxially stretching the substrate, and then coating both sides of the film by water-based coating using gravure coating or Meyer bar coating method, and then drying and curing both layers simultaneously with transverse stretching. Can be.

First, a pellet of a polyester resin used as a substrate is melt-extruded into a sheet using a conventional method and rapidly cooled on a metal roll to obtain a casting film having a thickness of about 2000 μm. The casting film is heated with a heated roll group and an infrared heater, and then stretched in the longitudinal direction to a roll group having a circumferential speed difference to obtain a uniaxially oriented film, which is used as a substrate.

Next, the easily-adhesive coating liquid and the anti-reflective coating liquid of the composition mentioned above are apply | coated to the polyester film both surfaces by the reverse roll method, respectively, and are dried. In particular, the antireflective coating is coated so as to have a thickness of 100 nm after drying and curing, according to the formula described below. Then, the film is gripped at the end with a clip, introduced into the hot air region, and dried.

Finally, the film is stretched at a high draw ratio in the transverse direction at a high temperature, and then heated and fixed again by raising the temperature, and then undergoes a process of lateral relaxation. In this manner, a biaxially oriented PET film coated with an easily adhesive layer and an antireflection layer can be finally obtained.

It is preferable that the refractive index of the low refractive layer formed by the above composition and the manufacturing method is 1.20-1.45, and its thickness is 80-120 nm. The antireflective coating must satisfy the following two equations.

[Equation 1]

nd = λ / 4 (n: refractive index of coating, d: thickness of coating, λ: wavelength of incident light)

&Quot; (2) "

n ² = n _s * n _a (n: refractive index of the coating, n _s : refractive index of the substrate, n _a : external refractive index)

In general, n _a is 1 when no further treatment is applied to the anti-reflective coating, and when the refractive index of the polyester-based resin is 1.65, the preferred refractive index of the anti-reflective coating is 1.28. Further processing requires adjustment of the refractive index. If the refractive index is 1.2 or less, the reflectance increases, and if it exceeds 1.4, the reflectance also increases, which is not good.

In addition, since the wavelength range of the human eye is the most sensitive is 550 nm, the preferred coating thickness by Equation 1 is 107 nm. The thickness of the antireflective layer should be exactly as designed, and control of such nano units is not easy, but is the most important item in the present invention. If the thickness of the coating does not reach 80 nm, the low reflectance band shifts from 550 nm to the short wavelength to increase the total reflectivity. If the coating exceeds 120 nm, the low reflectance band shifts to the long wavelength and the total reflectance increases, which is undesirable.

In the optical film according to the present invention, the adhesive force between the base film and the easy-adhesive layer or the base film and the anti-reflection layer shows 90% or more after a 96-hour humidity resistance test at 65 ° C and 95% relative humidity. . Further, the surface of the film on which the polymer adhesive layer and the antireflection layer are formed has a total light transmittance of 90% or more and a haze (haze value) of 2% or less.

Hereinafter, the present invention will be described in more detail with reference to Examples. This is for explaining the present invention more specifically, but the scope of the present invention is not limited to these Examples.

<Examples>

In this embodiment, the adhesive coating liquid

Water --- 73.9% by weight

30% by weight of aqueous dispersion of acrylic resin dispersed in water --- 20.0% by weight,

Water dispersion containing 30% by weight of melamine curing agent --- 5.0% by weight, water dispersion containing 10% by weight of anionic surfactant --- 1.0% by weight,

Aqueous dispersion containing 70% by weight of colloidal silica particles --- 0.1% by weight

Using to prepare an easily adhesive layer coating coating liquid of 7.7% by weight of solids.

In addition, the antireflective coating liquid

Water --- 73.9% by weight

Aqueous dispersion containing 30% by weight of fluorine-containing siloxane resin --- 20.0% by weight,

Aqueous dispersion containing 30% by weight of melamine curing agent --- 5.0% by weight,

Aqueous dispersion containing 10% by weight of anionic surfactant --- 1.0% by weight,

Aqueous dispersion containing 70% by weight of colloidal silica particles --- 0.1% by weight

Using to prepare a fluorine-containing siloxane-based coating liquid to a solid content of 7.7% by weight.

In the embodiment, the polyethylene terephthalate resin pellets were dried under reduced pressure (1.3 hPa) at 135 ° C. for 6 hours, fed to an extruder, and then melt-extruded into a sheet at about 280 ° C., and maintained at a surface temperature of 20 ° C. It was quenched in phase to obtain a casting film having a thickness of 1925 µm. Next, the cast film is heated to a heated roll group and an infrared heater to 100 ° C., and then stretched 3.2 times in the longitudinal direction to a roll group having a circumferential speed difference to obtain a uniaxially oriented PET film, which is used as a substrate. It was.

The adhesive coating liquid and the anti-reflective coating liquid prepared above were applied to one side of the uniaxially oriented PET film by the reverse roll method on both sides, respectively, and dried. In particular, the antireflective coating was coated to have a thickness of 100 nm after drying and curing. Then, the film was gripped at the end with a clip, introduced into the hot air region, and dried.

Thereafter, the film was stretched at a stretch ratio of 3.2 times in the transverse direction at 130 ° C, heat-set at 240 ° C, and laterally relaxed at 3 ° C at 200 ° C. In this manner, a biaxially oriented PET film coated with an adhesive layer and an antireflection layer was finally obtained.

&Lt; Comparative Example 1 &

The easily-adhesive coating solution was prepared in the same manner as in Example, and the anti-reflective coating solution was also prepared in the same manner as in Example. A film was obtained in the same manner as in Example, except that the coating was dried to have a thickness of 40 nm after curing and curing of the antireflective coating.

&Lt; Comparative Example 2 &

The easily-adhesive coating solution was prepared in the same manner as in Example, except that the anti-reflective coating solution was prepared separately, except that the easily-adhesive coating solution was used to obtain a film in the same manner as in Example.

Comparative Example 3

The easily-adhesive coating solution was prepared in the same manner as in Example, and the anti-reflective coating solution was used without preparing an anti-reflective coating solution. A film was obtained in the same manner as in Example, except that the coating was dried to have a thickness of 40 nm after curing and curing of the antireflective coating.

1. Measurement of turbidity and permeability

After the thermosetting was applied to the PET film of 188㎛ with the coating liquid made in the above Examples and Comparative Examples and measured the average reflectance in the 300 ~ 800nm range with a Shimadzu spectrophotometer, NIPPON DENSHOKU The turbidity and transmittance were measured using a haze meter manufactured by the company.

2. Luminance Measurement

After coating and thermosetting a 188 ㎛ PET film using the coating solution prepared in Examples and Comparative Examples, the prism acid was formed using UV resin, and each luminance value was measured by BM7 manufactured by TOPCON. (Compared with Comparative Example 1, the luminance value was 5000cd and 100%, and the relative luminance value was compared and tested).

The results according to Examples and Comparative Examples 1 to 3 are shown in Table 1 below.

[Table 1]

Item High Temperature & Humidity Adhesion (Surface / Rear)
65 ℃ 95% RH, 96hr (%) Average reflectance
(%) Turbidity (%) Transmittance
(%) Luminance
(%) Slip Example 100/100 7 0.7 93 102 ○ Comparative Example 1 100/100 9 0.6 92 101 ○ Comparative Example 2 100/100 10 0.6 93 101 ○ Comparative Example 3 100/100 12 0.5 92 100 ○

O: no slip

The prism fabric and prism sheet produced through the embodiment as described above can be seen that the average reflectance is lower than 20% and the brightness is also improved compared to the sheet produced by the conventional method. Moreover, sufficient physical properties are shown by the high temperature, high humidity adhesive force which evaluates the slip property and stability required for winding up.

While the invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (14)

Polyester film substrates; A polymer adhesive layer formed on one surface of the substrate and composed of an acrylic resin binder and inorganic nanoparticles; And And an anti-reflection layer formed on the other side of the substrate and composed of one or more polymer binders and inorganic nanoparticles selected from the group consisting of fluorine, acrylic and silicone resins. The adhesive force between the base film and the easily adhesive layer or the base film and the antireflection layer is maintained at a temperature of 65 ° C. and 95% relative humidity for 96 hours after the moisture resistance test, and maintains 90% or more of the adhesive force before the moisture resistance test. Polyester-based easy adhesive film for optics. The polyester-based easy-adhesive film for optics according to claim 1, wherein the polyester film base material has a thickness of 50 to 500 µm. According to claim 1, wherein the content of the polymer binder of the polymer adhesive layer is the optical polyester-based adhesive film, characterized in that 90% by weight to 99.9% by weight. The optical polyester-based adhesive film of claim 1, wherein the polymer adhesive layer has a thickness of 0.01 to 5.00 µm. According to claim 1, wherein the content of the polymeric binder of the anti-reflection layer is the optical polyester-based easy adhesive film, characterized in that 90% by weight to 99.9% by weight. The optical polyester-based easy-adhesive film according to claim 1, wherein the inorganic nanoparticles of the easy-adhesive layer or the anti-reflection layer are at least one selected from the group consisting of silica, alumina and titanium dioxide. The method of claim 1, wherein the inorganic nanoparticles have a size of 50 nm to 500 nm; The optical polyester-based easy-adhesive film, characterized in that the content is 0.1% by weight to 10% by weight. The method of claim 1, wherein the anti-reflection layer has a refractive index of 1.2 to 1.45; The optical polyester-based easy-adhesive film, characterized in that the thickness is 80 to 120nm. The optical polyester-based easy-adhesive film of claim 1, wherein the refractive index and thickness of the anti-reflection layer satisfy the following Equations 1 and 2. [Equation 1] nd = λ / 4 (n: refractive index of coating, d: thickness of coating, λ: wavelength of incident light) &Quot; (2) &quot; n ² = n _s * n _a (n: refractive index of the coating, n _s : refractive index of the substrate, n _a : external refractive index). delete The optical polyester-based easy-adhesive film according to claim 1, wherein the surface of the film on which the polymer easily adhesive layer and the anti-reflection layer are formed has a total light transmittance of 90% or more and a haze (haze value) of 2% or less. delete delete delete