KR101158313B1 - Optical film improving visibility - Google Patents

Abstract

The present invention relates to an optical film having improved visibility. More particularly, in an optical film including a plurality of embossed lens shapes, a plurality of polygonal pyramidal shapes are formed on the lens shape. to provide.

Description

Optical film improving visibility}

The present invention relates to an optical film having improved visibility, and more particularly, to an optical film having improved visibility by imparting a lens shape 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 generally comprises an LCD panel unit, a driving unit, 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.

In addition, another method for improving visibility is a method of imparting a predetermined shape to the optical film. In this way, many optical films having various shapes such as pyramids, shapes, and lens shapes formed on the optical films have been manufactured. However, the optical film thus formed also has a limit in improving the luminance with visibility.

Accordingly, it is desired to develop an optical film having improved visibility while improving luminance.

In order to solve the above problems, the present invention has an object to provide an optical film with improved visibility while performing a role as an optical film.

Another object of the present invention is to provide an 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 an optical film having improved visibility, wherein a plurality of polygonal pyramid shapes are formed on the lens shape in the optical film including a plurality of embossed lens shapes.

In another aspect, the present invention provides an optical film with improved visibility, characterized in that the polygonal pyramid shape is a square pyramid shape.

In another aspect, the present invention provides an optical film with improved visibility, characterized in that the average length of one side in the polygonal pyramid shape is 20 to 50㎛.

In another aspect, the present invention provides an optical film with improved visibility, characterized in that the lens shape is in close contact with the same size uniformly arranged and the diameter of the lens shape is 200 to 500㎛.

In another aspect, the present invention provides an optical film with improved visibility, characterized in that the interval between the plurality of lens shape is 0 to 100㎛.

In another aspect, the present invention provides an optical film with improved visibility, characterized in that a flat space between the lens shape and the lens shape is formed with a plurality of polygonal pyramid shape.

In another aspect, the present invention provides an optical film with improved visibility, wherein the optical film is a blend or composition of copolyester and polycarbonate includes 10 to 90% by weight of copolyester and 10 to 90% by weight of 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 Improved visibility optical film further comprises one or more selected light diffusing particles consisting of beads and silicone-based spherical particles made of a homopolymer, copolymer or terpolymer of monomer, polyethylene, polystyrene, polypropylene, acrylic and olefin copolymer To provide.

In another aspect, the present invention provides an optical film with improved visibility, characterized in that it further comprises a back layer on the lower surface of the optical film.

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

The optical film according to the present invention has an effect of improving visibility by wider viewing angle while serving as an optical film.

In addition, the optical film having improved visibility according to the present invention has an effect of improving physical properties as an optical film such as haze and luminance.

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

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. First, it should be noted that, in the drawings, the same components or parts have the same reference numerals as much as possible. In describing the present invention, detailed descriptions of related well-known functions or configurations are omitted in order not to obscure the subject matter of the present invention.

The terms " about ", " substantially ", etc. used to the extent that they are used herein are intended to be taken to mean an approximation to or in the numerical value of the manufacturing and material tolerances inherent in the meanings mentioned, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

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 characterized in that in the optical film comprising a plurality of embossed lens shape, a plurality of polygonal pyramid shape is formed on the lens 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.

In a plurality of polygonal pyramidal shapes formed on the lens shape, the rectangular pyramid shape is described as an example, but is not limited thereto. The unit structure may be applied to triangular pyramids, pentagonal pyramids, and polygonal pyramids more than pentagonal pyramids.

Referring to FIG. 1, the optical film having a lens shape has a square pyramid shape on the lens shape. Such a shape has a characteristic of improving visibility as well as a property of increasing luminance and improving visibility. That is, the lens shape has the effect of condensing light, and the square pyramid shape formed on the lens shape diffuses, condenses, or reflects the incoming light so that the light collected or diffused by the square pyramid moves toward the liquid crystal display panel. The reflected light is reflected back through a reflective sheet or the like to be focused or diffused through the unit structure.

In the case of simply applying a lens shape to the film, the light collecting property may be excellent, but the diffusion effect may not be excellent, and thus there may be a problem in visibility. However, the present invention can improve visibility by forming a plurality of small square pyramids on the lens shape.

It is preferable that the diameter of the lens shape is 200 to 500 mu m and the height is 50 to 80 mu m, and the average length of one side of the square pyramid is preferably 20 to 50 mu m. In this range, the light condensing and diffusing effects are particularly excellent.

In addition, the lens shape may be arranged closely and spaced apart from each other, it is preferable that the interval between the lens shape is 0 to 100㎛.

In addition, the flat space remaining between the lens shape and the lens shape may be filled with a quadrangular pyramid shape (not shown). The quadrangular pyramid shape may be filled in the flat space, which may be more effective in improving visibility.

Figure 3 shows the position of the lens shape in the optical film according to an embodiment of the present invention, the plurality of the lens shape is the same size, the plurality of lenses in close contact and uniformly arranged, the lens shape arrangement is When connecting the origin of the round shape, it is preferable to be arranged evenly while forming an angle of 60 ° in the form of an equilateral triangle.

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 to be used is advantageous for solving the problem such as showing the bright line due to the spherical particles whose refractive index difference is 0.1 to 0.2 from the material to increase the shielding ability, and can 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 μm and 10 μm 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 having a size of 20 to 30 ㎛ and 1 to 15 ㎛.

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, optionally, the lower surface of the optical film 100 may further include a back layer 200 as a different material from the optical film, Figure 4 shows a cross-sectional view of an optical film including a back layer according to another embodiment of the present invention will be.

The back layer 200 may function to prevent yellowing due to ultraviolet rays generated from the lamp. The polymer resin of the back layer 200 may be polycarbonate-based, and as a non-limiting example, preferably an aromatic polycarbonate, 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 Were mixed in a 1: 1 ratio, and blended by mixing 1 part by weight of ethyl methacrylate as 100 parts by weight of the resin as a light diffusing agent.

The lens shape was 400 μm in diameter, the height was 70 μm, and the interval between lens shapes was 10 μm. An optical film having a plurality of square pyramids having one side length of 30 μm was formed on the lens shape.

Example  2

In the same manner as in Example 1, the lens shape was 500㎛ in diameter, the height was 100㎛ to prepare an optical film.

Example  3 and 4

Examples 1 and 2 were carried out in the same manner, but a plurality of square pyramids were formed on the lens shape to form an optical film having a length of 40 μm.

Example  5 and 6

Examples 1 and 2 were carried out in the same manner, but a flat space between the lens shape and the lens shape to form a plurality of square pyramid shape to prepare an optical film.

Comparative example  1 and 2

In the same manner as in Example 1 and Example 2, an optical film was prepared without forming a square pyramid.

Comparative example  3

It carried out in the same manner as in Example 1, but was formed in a lens-like hemispherical shape with a diameter of 50 ㎛ to prepare an optical film.

* Test Methods

1. Viewing angle measurement: EZcontrast88 is used as the viewing angle measuring instrument.

After combining the film on the top of the backlight unit, the light receiving part of EZcontrast88 was measured to be close to 1mm of the top film.

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 below 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 Viewing angle (degrees) Brightness (cd / m 2) Example 1 38 10250 Example 2 40 10340 Example 3 41 10240 Example 4 39 10360 Example 5 40 10320 Example 6 42 10410 Comparative Example 1 34 9340 Comparative Example 2 32 9420 Comparative Example 3 33 9520

Experimental results When comparing the Example and the Comparative Example, the Examples can see that the viewing angle is about 5 degrees higher than the comparative example, the visibility is improved, and also the luminance is about 10% higher than the Comparative Examples. Could.

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.

Claims (10)

In the optical film comprising a plurality of embossed lens shapes,
The flat space between the lens shape and between the lens shape and the lens shape is characterized in that a plurality of polygonal pyramid shape is formed, the optical film with improved visibility. The method of claim 1,
The polygonal pyramid shape is an optical film with improved visibility, characterized in that the square pyramid shape. The method of claim 1,
The optical film with improved visibility, characterized in that the average length of one side in the polygonal pyramid shape is 20 to 50㎛. The method of claim 1,
The lens shape is in close contact with the same size uniformly arranged and the diameter of the lens shape is 200 to 500㎛ improved optical film, characterized in that. The method of claim 1,
The interval between the plurality of lens shapes is an optical film with improved visibility, characterized in that 0 to 100㎛. delete The method of claim 1,
The optical film is a blend or composition of the copolyester and polycarbonate optical film containing 10 to 90% by weight of copolyester and 10 to 90% by weight of polycarbonate. The method of claim 1,
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 optical film with improved visibility 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 of claim 1,
Optical film with improved visibility, 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 an optical film with improved visibility, characterized in that the polycarbonate containing bisphenol-A [2,2-bis (4-hydroxyphenyl) propane].

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