KR20110072348A - High brightness optical film - Google Patents

Abstract

PURPOSE: A high brightness optical film is provided to enhance optical diffusion efficiency by using a different kind or size of optical diffusion particle. CONSTITUTION: An optical film(100) includes a plurality of unit structures. The unit structures have an inverted conic shape. The vertex of the conic shape of the unit structure is rounded. A diameter of the bottom plane of the unit structure is 40 to 250 micrometer. A height of the unit structure is 10 to 150 micrometer.

Description

High brightness optical film

The present invention relates to a high brightness optical film, and more particularly, to a high brightness optical film formed by applying an intaglio pattern to an optical film for a backlight unit.

Recently, various flat panel display devices have been developed. These flat panel display devices include liquid crystal displays (LCDs), plasma display panels (PDPs), and field emission displays (FEDs). In addition, studies are being actively conducted to improve the display quality of such flat panel displays.

Among them, LCD is a device that injects liquid crystal between two sheets of glass and applies power to the electrodes installed on the upper and lower glass plates to change the arrangement of liquid crystal molecules and display images in each pixel. Such an LCD display device is usually composed of an LCD panel unit, a driver, and a backlight unit. The LCD panel does not emit light by itself and has only a function of transmitting light on the rear surface. Therefore, in the absence of light, that is, at night or indoors, it is a structure that can not display images without the help of backlight. The backlight unit refers to a system for implementing the backlight of such an LCD.

The backlight unit is largely composed of a lamp, sheets, a mechanism part, and a driving circuit. Since the lamp alone cannot produce uniform light over the entire area, the light guide plate, diffuser plate, reflector plate, prism, frame, etc., sheets and mechanisms are provided.

There are various methods for the backlight unit, and the most widely used method is a cold cathode fluorescent lamp (CCFT) having a light guiding plate (LGP) printed with a reflection pattern in the center by side light method. The cold cathode fluorescent lamp is placed on the edge. At this time, the reflective pattern printed on the light guide plate is printed in a structure to reduce the phenomenon that the brightness difference occurs depending on the position of the lamp is located at the edge of the panel. Although the method of printing the reflective pattern on the light guide plate is high in productivity, the light loss caused by the printing pattern material itself is inferior in efficiency, and the larger the LCD, the worse the uniformity of the overall brightness.

Since the light guide plate method does not provide sufficient brightness, a direct method in which a plurality of lamps are arranged at regular intervals under the diffuser plate is used. In this method, several fluorescent lamps are arranged in a row on the rear surface of the diffusion sheet to improve luminance and improve uniformity than the photometric type. In order to display a bright screen, the backlight light source must be very bright. This is because the light from the light source goes through several steps before reaching the LCD, and loses its original brightness in the process. In addition, the uniformity of light throughout the screen is lost because of the scattering effect.

One way to overcome this problem is to increase the size of the light source, but this is expensive installation cost, high power consumption, and also has a problem of increasing the weight a lot. Thus, several attempts have been made to improve the light source brightness without loss as much as possible during the transmission process.

In flat panel display devices such as LCDs and projection TVs, a diffuser is an optical element that plays an important role in reaching light from the light source to the viewer's eyes. The diffuser plate uniformly distributes the light from the light source and plays an important role in the direct type than in the case of LCD. Structural metering is a structure where light guided by a light guide can be uniformly distributed throughout the screen, but in the case of a direct type, several light sources are distributed below the screen, so that the point just above the light source and the point between the light source and the light source Because there is a difference in the light intensity, you have to offset it.

The most important optical properties of the optical film used to improve visibility in the backlight unit are light transmittance and haze, which require a total amount of light of 60% or more and 85% or more of light for visible light. In order to satisfy these characteristics, a light diffusion film generally includes a surface diffusion method of refraction or dispersion in a number of directions using surface roughness and a bulk diffusion film method having an inherent light dispersion element.

The surface diffusion type diffusion film uses a rough surface exposed to air to maximize the difference in refractive index between the material of the diffusion film and the surrounding medium as much as possible to spread the incident light at the largest angle. For example, light diffusivity is imparted by forming irregularities on the film surface. There is a light diffusing film in which the unevenness is formed on the surface of the transparent resin made of a polyester resin, a polymethyl methacrylate resin or a polycarbonate resin. However, it is difficult to simultaneously obtain excellent light transmittance and light diffusivity only by imparting irregularities to the surface by embossing or sand blasting. In addition, the temperature in the backlight unit generally rises from 80 ° C to 90 ° C, and when the humidity is high, shape deformation may occur severely, so that a material having excellent optical properties while having high heat resistance and low moisture absorption rate is used.

The bulk diffusion film is a light diffusing agent such as fine particles dispersed within the film, and is usually made of a transparent resin made of a resin such as polymethyl methacrylate, polycarbonate, etc., calcium carbonate, titanium dioxide, glass beads, silica particles, polystyrene There are light diffusing plates in which particles, silicone resin particles, crosslinked polymer particles and the like are dispersed.

Korean Patent Laid-Open Publication No. 2004-0024725 relates to an optical film, a method of manufacturing the same, and a backlight unit for a liquid crystal display device using the same, wherein a plurality of square pyramidal shaped protrusions, which are prism patterns, are formed on a substrate of the optical film, and the protrusions are spaced apart from each other. It is disclosed that the arrangement is arranged without repeating adjacent to or spaced apart from each other, the invention can obtain a high brightness characteristics in the shape of a protruding square pyramid, but there was a problem that the viewing angle is narrowed.

Due to the above problems, it is desired to develop an optical film having excellent luminance characteristics and a wide viewing angle.

In order to solve the above problems, an object of the present invention is to provide a high brightness optical film having a high light condensing effect and a wide viewing angle when serving as an optical film.

Another object of the present invention is to provide a high brightness optical film having improved physical properties as an optical film such as haze and luminance.

In order to solve the above problems, the present invention provides a high-brightness optical film, characterized in that in the optical film comprising a plurality of unit structures formed in the inverted conical shape.

In another aspect, the present invention provides a high-brightness optical film, characterized in that the vertex portion is rounded in a conical shape of the unit structure.

In another aspect, the present invention provides a high brightness optical film, characterized in that the diameter of the bottom surface of the unit structure is 40 to 250㎛.

In another aspect, the present invention provides a high brightness optical film, characterized in that the height (H) of the unit structure is 10 to 150㎛.

The present invention also provides a high brightness optical film, characterized in that the plurality of unit structures are the same shape.

In another aspect, the present invention provides a high brightness optical film, characterized in that the separation distance of each unit structure in the plurality of unit structures is 0 to 100㎛.

In another aspect, the present invention provides a high-brightness optical film containing 10 to 90% by weight of copolyester and 10 to 90% by weight of polycarbonate as a blend or composition of the copolyester and polycarbonate.

In addition, the present invention is the optical film methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, Selected from hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, metalolacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate and 2-ethylhexyl acrylate It provides a high-brightness optical film further comprising at least one light diffusing particle consisting of beads and silicone-based spherical particles made of monomer homopolymer, copolymer or terpolymer, polyethylene, polystyrene, polypropylene, acrylic and olefin copolymer. do.

In another aspect, the present invention provides a high-brightness optical film characterized in that it further comprises a back layer on the lower surface of the optical film.

In another aspect, the present invention provides a high-brightness optical film, characterized in that the back layer is a polycarbonate containing bisphenol-A [2,2-bis (4-hydroxyphenyl) propane].

The high brightness optical film according to the present invention has a high light condensing effect and a wide viewing angle when it serves as an optical film.

In addition, the high-brightness optical film according to the present invention has an effect of improving physical properties as an optical film such as haze and luminance.

As used herein, the term "film" is used to mean both films, sheets, and plates having a predetermined width and thickness.

The present invention is an optical film including a unit structure formed of a plurality of intaglio, wherein the unit structure is characterized in that the inverted cone shape.

1 shows a perspective view of an optical film according to an embodiment of the present invention. 2 is a cross-sectional view taken along the line X and X 'of FIG. 1 according to an embodiment of the present invention, Figure 3 is a longitudinal cross-sectional view of the optical film according to another embodiment of the present invention.

In Figure 1 the unit structure forms an inverted cone shape. That is, the cross section in the horizontal direction of the unit structure is circular, and the cross section in the vertical direction (see FIG. 2) has a triangular shape that forms three angles. In the shape as described above, as well as the characteristics of high brightness, the diffusion effect is excellent, there is a feature that improves visibility.

The unit structure serves to diffuse, condense, or reflect the incoming light. The light collected or diffused by the unit structure moves in the direction of the liquid crystal display panel, and the reflected light is reflected back through the reflective sheet. Condensed or diffused through the unit structure.

In addition, the vertex portion of the conical shape of the unit structure may optionally be rounded without an angle, Figure 3 shows a longitudinal cross-sectional view of the optical film according to another embodiment of the present invention. Therefore, when the vertex portion of the triangular shape of the unit structure in the longitudinal cross section (Fig. 3) is rounded, it has a predetermined radius of curvature (R).

Next, the length of the bottom of the unit structure, the length of the bottom represents a circle in the conical shape formed on the surface of the optical film, if the diameter of the bottom is "L", the diameter of the bottom (L) is It is preferable that it is 40-250 micrometers.

In addition, the height of the unit structure according to an embodiment of the present invention can represent the vertical distance from the vertex to the bottom in Figure 2 as the height (H), the height (H) of the unit structure is 10 to 150㎛ desirable.

In addition, in the optical film 100, the unit structure has a plurality, but the unit structure preferably forms the same shape.

In addition, the plurality of unit structures may be formed at an arbitrary distance or in close contact with each other. It is preferable that the separation distance of each unit structure is 0-100 micrometers. However, the separation distance is preferably less than 1/2 times the diameter (L) of the bottom surface of the unit structure. For example, when the diameter of the bottom surface is 100㎛, it is preferable that the separation distance of the unit structure is formed to 50㎛ or less.

Meanwhile, the polymer resin material of the optical film 100 may be prepared as a blend or a composition in a specific ratio of copolyester and polycarbonate, and specifically, may include 10 to 90 wt% of copolyester and 10 to 90 wt% of polycarbonate. Can be. However, the present specification is described as the material, but is not limited thereto.

The copolyester may be terephthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid or a mixture thereof as the acid component, and ethylene glycol and 1,4-cyclohexanedimethanol (CHDM) may be used as the glycol component. . Non-limiting examples of suitable copolyesters include poly (1,4-cyclohexylenedimethylene terephthalate) (PCT), poly (1,4-cyclohexylenedimethylene naphthalenedicarboxylate) (PCN), poly (1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) (PCC) can be used.

The material has a feature that the process moisture content is relatively low to maintain shape stability even at high humidity.

In addition, the optical film may further include light diffusing particles, and since the light diffusing particles should be compatible with a binder (resin) containing particles, organic particles having a similar refractive index to materials and spherical silicon particles having a low refractive index It was used to examine the material, the refractive index of the material between 1.50-1.80 inorganic particles can also be used. Particularly, the particle selection used is advantageous to solve the problem such as showing the bright line due to the spherical particles having the refractive index difference of 0.1 to 0.2 from the material to improve the shielding, and to maximize the diffusion effect with a relatively small particle amount. It is very advantageous.

The refractive index of the diffusing agent particles used increases the light diffusion effect as the difference between the material and the refractive index is larger, but when the refractive index difference is too large, it is disadvantageous in terms of increasing the brightness, so that the proper refractive index difference is obtained and sometimes similar to the material. It is preferable to use the particle | grains with a big difference.

Non-limiting examples of light diffusing particles that can be used in the present invention include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, Hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, metalolacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate and 2 Homopolymers, copolymers or terpolymers of monomers selected from ethylhexyl acrylate, beads made from copolymers of polyethylene, polystyrene, polypropylene, acrylics and olefins, and silicone-based spherical particles may be used. Preferably, the material is spherical particles between 1 micron and 10 microns having a refractive index difference of about 0.1 to about 0.2. Spherical organic particles having such a difference in refractive index can be easily dispersed in the resin because they have densities similar to those of the material used in the present invention (about 1.10 to 1.30 g / cm 3).

The light diffusing particles used in the present invention may use different ones in type and / or size. For example, light diffusion efficiency can be enhanced by mixing two or more kinds of particles having a difference in refractive index rather than a single type. In addition, light diffusing efficiency may be increased by using particles having similar refractive indices and different sizes, and by applying porous particles, the brightness may be increased while maximizing light diffusing efficiency after assembling the backlight unit.

Using particles of uniform particle size requires a large amount of particles to produce a predetermined light diffusing effect, which results in not only economic inefficiency, but also lowering the overall light transmittance. According to one embodiment of the present invention, the size of the light diffusing particles can be used to increase the light diffusion effect while reducing the particle content by using two kinds of particles of size 20 to 30 microns and 1 to 15 microns.

The light diffusing particles may be used at 0.5 to 20% by weight, preferably 1 to 10% by weight based on the total weight of the optical film. When the light diffusing particles are 0.5 wt% or less, a predetermined light diffusing effect cannot be obtained, and when the light diffusing particles is more than 20 wt%, the light transmittance is lowered, and the dispersibility of the particles is reduced and uniform. Particle dispersion cannot be obtained.

On the other hand, the lower surface of the optical film 100 may optionally further include a back layer 200 as a material different from the optical film (see FIG. 4), wherein the back layer 200 prevents yellowing due to ultraviolet rays generated from a lamp. can do.

The polymer resin of the backing layer 200 may be polycarbonate-based, and as a non-limiting example, preferably an aromatic polycarbonate and more preferably bisphenol-A [2,2-bis (4-hydroxyphenyl) propane]. It may be a polycarbonate containing. A material having a benzoyl group may be added to the polycarbonate to prevent yellowing due to ultraviolet rays. Non-limiting examples of the benzoyl group include a benzophenone series, benzoxazinone series, and benzotriazole series.

Hereinafter, embodiments of the present invention will be described in detail.

Example  One

Polycarbonate-based resin containing a polyester-based resin mainly composed of 1,4-cyclohexanedicarboxylic acid and bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] as a polymer resin of an optical film Was mixed in a 1: 1 ratio and blended by mixing 15 parts by weight of ethyl methacrylate as a light diffusing agent with respect to 100 parts by weight of the resin of the base layer.

The unit structure was manufactured in an inverted cone shape. The bottom surface of the unit structure had a diameter (L) of 120 μm and a height (H) of 50 μm, and the distance between the unit structures was 0 μm. An optical film was prepared.

Example  2

In the same manner as in Example 1, but the diameter (L) of the bottom surface of the unit structure is 100㎛, the height (H) is 40㎛ to form a unit structure consisting of a plurality of the same shape to prepare an optical film.

Example  3 and 4

Examples 1 and 2 were carried out in the same manner, but the optical film was prepared by rounding the corners of the vertex in the inverted conical shape of the unit structure.

Example  5 and 6

In the same manner as in Examples 1 and 2, but the lower surface of the optical film included a back layer, the back layer comprising bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] A polycarbonate resin was used and 2- (2'-hydroxy-5-methylphenyl) benzotriazole, a benzotriazole-based material, was added.

Comparative example  One

In the same manner as in Example 1, an optical film was prepared without forming a unit structure.

Comparative example  2

In the same manner as in Example 1, the intaglio unit structure is formed in a lenticular hemispherical shape, the diameter is 80㎛, the unit structure spacing was 5㎛ to prepare an optical film.

Comparative example  3 and 4

In the same manner as in Comparative Examples 1 and 2, the lower surface of the optical film included a back layer, the back layer comprising bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] A polycarbonate resin was used and 2- (2'-hydroxy-5-methylphenyl) benzotriazole, a benzotriazole-based material, was added.

* Test Methods

1.Haze: Measured by ASTM D1003 method using NIPPON DENSHOKU 300A analytical equipment in Japan.

2. Luminance: Measured on a stage equipped with a film produced in the backlight unit, TOPCON BM-7 with CCFL voltage of 16.5V, Dimming value 2.8V.

Table 1 shows the results of testing the optical properties of the haze and the brightness of the prepared optical film for each of Examples and Comparative Examples.

division Haze (%) Luminance (cd / ㎡) Example 1 91.3 10100 Example 2 91.4 10070 Example 3 91.5 10090 Example 4 91.8 10130 Example 5 92.3 10020 Example 6 92.5 10030 Comparative Example 1 91.5 9510 Comparative Example 2 91.3 9840 Comparative Example 3 91.6 9480 Comparative Example 4 91.7 9720

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. It will be clear to those who have knowledge of.

1 shows a perspective view of an optical film according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line X and X ′ of FIG. 1.

Figure 3 shows a longitudinal cross-sectional view of an optical film according to another embodiment of the present invention.

Figure 4 shows a cross-sectional view of an optical film according to another embodiment of the present invention.

Claims (10)

In the optical film including a unit structure formed of a plurality of intaglio, The unit structure is a high brightness optical film, characterized in that the inverted cone shape.  The method of claim 1, The conical shape of the unit structure is a high brightness optical film, characterized in that the vertex portion rounded to a curve. The method according to claim 1 or 2, A high brightness optical film, characterized in that the diameter of the bottom surface of the unit structure is 40 to 250㎛. The method according to claim 1 or 2, The height (H) of the unit structure is a high brightness optical film, characterized in that 10 to 150㎛. The method according to claim 1 or 2, The plurality of unit structures are high brightness optical film, characterized in that the same shape. The method according to claim 1 or 2, High brightness optical film, characterized in that the separation distance of each unit structure in the plurality of unit structures is 0 to 100㎛. The method according to claim 1 or 2, The optical film is a high brightness optical film containing 10 to 90% by weight of copolyester and 10 to 90% by weight of polycarbonate as a blend or composition of copolyester and polycarbonate. The method according to claim 1 or 2, The optical film is methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate Homopolymers of monomers selected from acrylate, hydroxyethyl acrylate, acrylamide, metarolacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate and 2-ethylhexyl acrylate The high brightness optical film further comprising at least one light diffusing particle made of a copolymer or a terpolymer, polyethylene, polystyrene, polypropylene, acryl and olefin-based beads and silicon-based spherical particles. The method according to claim 1 or 2, High brightness optical film, characterized in that it further comprises a back layer on the lower surface of the optical film. 10. The method of claim 9, The back layer is a high brightness optical film, characterized in that the polycarbonate containing bisphenol-A [2,2-bis (4-hydroxyphenyl) propane].

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