KR101151437B1 - High brightness diffusion film - Google Patents

Abstract

The present invention relates to a diffusion film, and more particularly, to a diffusion film composed of a surface layer and a base layer, wherein the surface layer includes a plurality of unit structures protruding embossed and positioned on an upper surface of the base layer, wherein the unit structure has a polygonal pyramidal shape. It provides a high brightness diffuser film, characterized in that the corner of the protruding portion is rounded in a curve.

Diffusion film, round, polygonal pyramid, square pyramid, high brightness

Description

High brightness diffusion film

The present invention relates to a high brightness diffuser film, and more particularly, to a high brightness diffuser film formed by applying an embossed protrusion to a light diffusion 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 plates (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. Currently, the most widely used method is a cold cathode fluorescent lamp (LFT) having a light guiding panel (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 problems described above, it is desired to develop a diffusion film having excellent luminance characteristics and a wide viewing angle.

In order to solve the above problems, the present invention is to provide a high brightness diffusion film having a high light condensing effect and a wide viewing angle while serving as a diffusion film.

Another object of the present invention is to provide a high brightness diffuser film having improved physical properties as a diffuser film such as brightness, transparency, and blur.

In order to solve the above problems, the present invention provides a diffusion film composed of a surface layer and a base layer, wherein the surface layer includes a plurality of unit structures protruding embossed and positioned on an upper surface of the base layer, wherein the unit structures protrude as a polygonal pyramidal shape. It provides a high brightness diffuser film, characterized in that the corners of the corners are rounded.

In another aspect, the present invention provides a high brightness diffuser film further comprises a rounded upper portion of the unit structure.

In another aspect, the present invention provides a high-brightness diffusion film characterized in that it further comprises a backing layer located on the bottom of the base layer.

In another aspect, the present invention provides a high brightness diffuser film, characterized in that the polygonal pyramid shape.

In another aspect, the present invention provides a high brightness diffusion film, characterized in that the length (L) of the bottom surface of the unit structure is 40 to 200㎛.

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

In another aspect, the present invention provides a high brightness diffusion film, characterized in that the plurality of unit structures are the same shape.

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

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

In the present invention, the base layer is methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydride Monomer selected from oxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, metalolacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate and 2-ethylhexyl acrylate It provides a high brightness diffuser film further comprising one or more selected light diffusing particles consisting of beads and silicone-based spherical particles made of a homopolymer, copolymer or terpolymer, polyethylene, polystyrene, polypropylene, acryl and olefin copolymer. .

The high brightness diffuser film according to the present invention has a high light condensing effect and a wide viewing angle while serving as a diffuser film.

In addition, the high brightness diffusion film according to the present invention has the effect of improving the physical properties as a diffusion film, such as brightness, transparency, blurring.

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.

As used herein, the terms “about”, “substantially”, and the like, are used at, or in close proximity to, numerical values when manufacturing and material tolerances inherent in the meanings indicated are intended to aid the understanding of the invention. Accurate or absolute figures are used to assist in the prevention of unfair use by unscrupulous infringers.

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 a diffusion film consisting of a surface layer and a base layer, the surface layer comprises a plurality of unit structures protruding embossed located on the upper surface of the base layer, the unit structure is a polygonal pyramid shape in the corner of the protruding portion curved It is rounded and the top of the unit structure is characterized in that the rounded curve.

In addition, a back layer made of a material different from the base layer may be optionally located on the bottom surface of the base layer.

The present invention is described by way of example in the form of a square pyramid protruding in a polygonal pyramid shape with respect to the unit structure, but is not limited thereto, the unit structure may be applied without limitation, such as triangular pyramid, pentagonal pyramid and polygonal pyramid or more.

1 shows a perspective view of a diffusion 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, and FIG. 3 is a cross-sectional view of the unit structure protruding in relief.

In FIG. 1, the protrusion of the unit structure forms a square pyramid shape, the corners of which are rounded by a curve, and the top of the unit structure is rounded by a curve. However, the corners forming the base do not have rounded corners. That is, the bottom surface of the protrusion of the unit structure forms a square having four rounded corners, preferably four rounded squares. That is, the cross section in the horizontal direction in the quadrangular pyramid shape is a rectangular shape 113 with four rounded corners (see FIG. 3), and the longitudinal section (see FIG. 2) has a triangular shape 111 with a rounded upper portion. But the diffusion effect is excellent.

The protruding unit structure serves to diffuse and condense the incoming light, and the light condensed or diffused by the unit structure moves toward the liquid crystal display panel, and the reflected light is reflected back through the base layer. Condensed or diffused through the unit structure.

In addition, if the unit structure has a triangular pyramid shape and rounded corners and tops are curved, the bottom surface of the protrusion of the unit structure is triangular in three angles, and the vertical cross section of the unit structure in the vertical direction is rounded. If it is a true triangular shape, in the case of other polygonal pyramid shape, the angle forming the base will be a rounded polygonal shape.

On the other hand, when four angles are rounded in the transverse cross section (see FIGS. 2 and 3), the curvature has a predetermined curvature. Preferably, all four radii of curvature shown in FIG. 3 are the same. In addition, even when the upper portion is rounded in the triangular shape 111 in the longitudinal cross section (see FIG. 2), it is a matter of course that has a predetermined radius of curvature.

Next, when the length of the bottom of the unit structure is determined, the maximum length in the figure representing the bottom of the protrusion is the length "L" of the bottom of the unit structure, the line connecting the diagonal line in the case of Figure 4 will be the maximum length The length L of the bottom surface of the unit structure is preferably 40 to 200 μm.

In addition, the height of the unit structure according to an embodiment of the present invention can be represented by the height (H) of the triangular shape 111 rounded in FIG. 2, the height (H) of the unit structure is 10 to 150㎛ desirable.

In addition, in the diffusion film 100, the unit structure has a plurality, it is preferable that the unit structure has 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 length L of the bottom surface of the unit structure. For example, when the length of the bottom surface is 100㎛, it is preferable that the separation distance of the unit structure is formed to 50㎛ or less.

On the other hand, the polymer resin of the surface layer 110 in the diffusion film may be a polycarbonate, a non-limiting example is preferably an aromatic polycarbonate and more preferably bisphenol-A [2,2-bis (4-hydroxyphenyl) ) Propane] may be a polycarbonate. 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 benzophenone, benzoxazinone, and benzotriazole.

In addition, the back layer 130 may be selectively positioned on a lower surface of the base layer with a material different from the base layer (see FIG. 5). The back layer 130 may function to prevent yellowing due to ultraviolet rays generated from a lamp. It may be made of the same material as the surface layer 110.

In addition, the material of the polymer resin of the base layer 120 may be prepared as a blend or a composition in a specific ratio of copolyester and polycarbonate, and specifically, may include 10 to 90% by weight of copolyester and 10 to 90% by weight of polycarbonate. have. 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.

Meanwhile, the base layer 120 may further include light diffusing particles. 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 may be used. In this case, inorganic particles having a refractive index of 1.50-1.80 can 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 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 base layer resin. 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.

As described above, the material of the base layer 120 has a property of lowering the glass transition temperature of the polycarbonate and the copolyester as a blend or a composition, compared to the surface layer 110 made of the polycarbonate, and the glass transition temperature of the base layer 120 Lower than the surface layer 110, the dimensional stability is improved.

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

Example  One

As the resin of the surface layer, a polycarbonate resin containing bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] was used, and 2- (2'-hydroxy-5-methylphenyl), a benzotriazole-based material) Benzotriazole was added.

As the resin of the base layer, a polycarbonate-based resin containing a polyester-based resin mainly composed of 1,4-cyclohexanedicarboxylic acid and bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] It was mix | blended in the ratio of 1: 1.

The unit structure was formed in the shape of a square pyramid of the protruding portion, the corner and the top of the unit structure in a rounded shape, the length (L) of the bottom surface of the unit structure is 100㎛, the height (H) is 35㎛ The separation distance of the unit structure was located in close contact with 0㎛ and a diffusion film was prepared in a plurality of the same shape.

Example  2

In the same manner as in Example 1, the base layer was blended with 15 parts by weight of ethyl methacrylate as a light diffusing agent based on 100 parts by weight of the resin of the base layer, the length (L) of the bottom of the unit structure is 140㎛, The height (H) is 50㎛ to form a unit structure consisting of a plurality of the same shape to produce a diffusion film.

Example  3 and 4

Example 1 and 2 were carried out in the same manner, but the back layer was made of the same material as the surface layer and placed on the lower surface of the support layer to produce a diffusion film.

Comparative example  One

A diffusion film was prepared in the same manner as in Example 1, without forming a unit structure on the surface layer.

Comparative example  2

A diffusion film was prepared in the same manner as in Example 1 except that the unit structure had a hemispherical lens shape having a diameter of 50 μm and the separation distance between the unit structures was 5 μm.

Comparative example  3 and 4

Comparative Examples 1 and 2 were carried out in the same manner, but the back layer was made of the same material as the surface layer and placed on the lower surface of the support layer to produce a diffusion film.

* Test Methods

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

2. Luminance: Measure the film on the stage equipped with TOPCON BM-7 under the conditions of 16.5V and Dimming value of 2.8V with CCFL voltage on the backlight unit (diffusion plate-diffusion film-prism-diffusion film). .

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

division Haze (%) Brightness (cd / m 2) Example 1 91.7 10100 Example 2 92.6 10030 Example 3 91.2 10050 Example 4 91.3 10060 Comparative Example 1 91.3 9340 Comparative Example 2 91.4 9730 Comparative Example 3 91.7 9260 Comparative Example 4 91.5 9770

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 a diffusion 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 cross-sectional view as a transverse direction of the unit structure protruding embossed in the diffusion film according to an embodiment of the present invention.

Figure 4 shows the shape of the bottom surface of the unit structure in the diffusion film according to an embodiment of the present invention.

Figure 5 shows a cross-sectional view of the diffusion film according to another embodiment of the present invention.

Claims (11)

In the diffusion film consisting of a surface layer and a base layer, The surface layer includes a plurality of unit structures located on the upper surface of the base layer and protruding embossed, The unit structure has a rectangular pyramid shape and rounded corners of the protruding portion are curved. The rounded portion is a high brightness diffusion film, characterized in that having the same radius of curvature.  The method of claim 1, The high brightness diffusion film further comprises a rounded upper portion of the unit structure. The method according to claim 1 or 2, High brightness film, characterized in that it further comprises a back layer located on the bottom surface of the base layer. delete The method according to claim 1 or 2, Length (L) of the bottom surface of the unit structure is characterized in that the high brightness diffuser film. The method according to claim 1 or 2, The height (H) of the unit structure is a high brightness diffusion film, characterized in that 10 to 150㎛. The method according to claim 1 or 2, The plurality of unit structures are high brightness diffusion film, characterized in that the same shape. The method according to claim 1 or 2, The separation distance of each unit structure in the plurality of unit structures is a high brightness diffusion film, characterized in that 0 to 100㎛. The method of claim 3, The surface layer and the back layer is a high brightness diffusion film, characterized in that the polycarbonate containing bisphenol-A [2,2-bis (4-hydroxyphenyl) propane]. The method according to claim 1 or 2, The base layer is a high brightness diffusion 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 base layer 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 latex, hydroxyethyl acrylate, acrylamide, metarollacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate and 2-ethylhexyl acrylate, A high brightness diffuser film further comprising at least one light diffusing particle comprising a bead and a silicon-based spherical particle made of a copolymer or terpolymer, polyethylene, polystyrene, polypropylene, acryl and olefin copolymer.

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