KR101192257B1 - Condensing film having lamp concealing property - Google Patents

Abstract

The present invention is formed on a base portion, an upper surface of the base portion, and comprises a lenticular lens portion for condensing light and a light diffusion pattern portion for maintaining a uniform brightness distribution of the light, the light diffusion pattern portion of the light diffusion pattern Provided is a light collecting film, characterized in that the distribution density becomes smaller as the distance from the lamp increases.

The light collecting film of the present invention is a composite functional optical film that performs both a light collecting function and a light source concealment function, and when used, the optical film used in the backlight unit can be reduced.

Backlight Unit, Condensing Film, Lenticular Lens

Description

Condensing film excellent in light source concealment performance {CONDENSING FILM HAVING LAMP CONCEALING PROPERTY}

The present invention relates to a light collecting film for a backlight unit, and more particularly, to a light collecting film for a backlight unit in which a light diffusion pattern having a distribution density varies according to a distance from a light source so as to perform a light source hiding function.

In general, an LCD (Liquid Crystal Display) is a liquid crystal material that is injected between an upper substrate on which a common electrode and a color filter are formed, and a lower substrate on which a thin film transistor and a pixel electrode are formed. By applying different potentials to the common electrode to form an electric field to change the arrangement of the liquid crystal molecules, and through this to control the transmittance of light refers to the device to represent the image.

LCDs have the advantages of miniaturization, light weight, and low power consumption, and thus have been attracting attention as an alternative image display means that can overcome the disadvantages of the conventional brown, and have recently been used in almost all image display devices.

Since the LCD is a passive element that does not emit light by itself, a backlight unit for providing light under the panel should be provided. The backlight unit is divided into an edge type backlight unit in which a light source is positioned near an edge of the liquid crystal panel, and a direct type backlight unit in which light sources are positioned at regular intervals below the liquid crystal panel. In general, an edge type backlight unit is mainly used for a small LCD such as a notebook, and a direct type backlight unit is used for a large LCD.

FIG. 1 is a view illustrating a general direct type backlight unit. As shown in FIG. 1, a direct type backlight unit includes a light source unit 1 including lamps arranged at regular intervals, and is positioned above the light source unit. A diffuser plate 2 for supporting and evenly spreading the light emitted from the light source, a light collecting film 3 for improving the luminance of light in the visible and blue range, and a diffuser for increasing the brightness uniformity of the screen and smoothing the luminance distribution. Film 4 or the like.

Meanwhile, in the LCD field, efforts have been made to reduce the thickness of LCDs for handling, ease of use, and design. In particular, there are attempts to achieve this by reducing the thickness of the backlight unit. 2 shows a configuration of a direct type backlight unit having a reduced thickness. The direct backlight unit having such a thickness does not sufficiently diffuse light because the distance between the light source lamp and the optical films is very close. As shown in FIG. 3, the luminance distribution of the light is high according to the distance to the lamp. The lamp mura phenomenon where the lower part is repeated regularly occurs. In the related art, this problem was solved by using a plurality of diffusion films.

However, in the conventional case, there is a problem in that the thickness of the backlight unit is not only limited, but also the manufacturing cost of the backlight unit is increased.

Accordingly, an object of the present invention is to provide a light collecting film developed to perform a light collecting function and a light source hiding function at the same time, including a light diffusion pattern in which a distribution density varies depending on a distance from a lamp. Furthermore, an object of the present invention is to reduce the number of optical films used in the backlight unit, to facilitate the slimming of the backlight unit, and to reduce the manufacturing cost of the backlight unit by using a light collecting film that performs a composite function. It is done.

To this end, the present invention is formed on the base portion, the upper surface of the base portion, and comprises a lenticular lens portion for condensing light and a light diffusion pattern portion for uniforming the brightness distribution of the light, wherein the pattern of the light diffusion pattern portion Provided is a light collecting film, characterized in that the distribution density becomes smaller as the distance from the lamp increases.

In this case, the light diffusion pattern portion may be formed on an interface between the substrate portion and the lenticular lens portion or a lower surface of the substrate portion, and a protective layer may be further provided to protect the light diffusion pattern portion.

In addition, the light diffusion pattern of the present invention may be formed in a fine dot shape, preferably may be formed in a fine dot shape of 70 to 150㎛ diameter.

The light diffusion pattern may be formed using an ink having a light transmittance of 50 to 80%. In this case, the ink may include 100 parts by weight of the binder resin and 10 to 100 parts by weight of a transparent material that transmits light, and optionally, 0 to 10 parts by weight of a reflective material for diffusing light.

In this case, the binder resin may be used alone or in combination of two or more kinds of urethane acrylate, epoxy acrylate, ester acrylate, ether acrylate or a radical generating monomer, the binder resin has a refractive index of 1.50 to 1.54 after curing It is preferable that it is about degree.

On the other hand, the transmissive material is preferably a refractive index difference of 0.04 or less with the binder resin, silica, polymer beads or a mixture thereof may be used, wherein the silica and polymer beads have a diameter of about 0.1㎛ to 5㎛ It is preferable.

Meanwhile, the reflective material has a refractive index difference of 0.8 from that of the binder resin. To 1.3, preferably TiO ₂ or ZnO.

The present invention forms a light diffusion pattern in which the distribution density decreases as the distance from the lamp decreases on the condensing film, so that a portion near the lamp is more diffused, and a portion far from the lamp is less diffused. Thus, the lamp mura phenomenon can be suppressed.

In addition, the present invention allows the light collecting film to perform a light source concealment function together with the light collecting function, thereby reducing the optical film used in the backlight unit, making the backlight unit slim, and reducing the manufacturing cost of the backlight unit.

Hereinafter, the present invention will be described more specifically.

4 illustrates an embodiment of the light collecting film of the present invention. As shown in FIG. 4, the light collecting film of the present invention includes a substrate portion 10, a lenticular lens portion 20, and a light diffusion pattern portion 30.

The base portion 10 of the present invention is for supporting a light collecting film, and generally polymer films used in the art, for example, polyester films, polyvinyl chloride films, polycarbonate films, and polymethylmethacryl It may be made of a latex film, a polystyrene film, a polyester sulfone film, a polybutadiene film, a polyether ketone film, a polyurethane film and the like.

Next, the lenticular lens unit 20 is positioned on an upper surface of the base unit 10 (in this case, the upper surface means a surface facing the liquid crystal display panel), and the light emitted from the light source is viewed in a viewing range. To condense into.

The lenticular lens unit 20 is formed by continuously arranging lenticular lenses extending in one direction, the cross-sectional shape of which is formed in a hemispherical, triangular or aspherical lens shape.

Meanwhile, the method of forming the lenticular lens portion is well known in the art, and the lenticular lens portion of the present invention can be manufactured using such a conventional manufacturing method. For example, the lenticular lens portion 20 of the present invention may be formed by flowing a curable resin solution between the mold and the base portion 10 in which a desired shape (lenticular lens shape) is engraved and cured. At this time, by adjusting the shape, height or pitch engraved in the mold, it is possible to form the lenticular lens unit 20 of the desired shape.

In this case, as the curable resin, urethane acrylate, epoxy acrylate, ester acrylate or radical generating monomer may be used, and these may be used alone or in combination.

In addition, the light collecting film of the present invention is characterized by having a light diffusion pattern portion 30 together with the base portion 10 and the lenticular lens portion 20. The light diffusion pattern unit 30 improves a phenomenon in which the brightness of light periodically changes according to a distance from a lamp of the backlight unit (see FIG. 3, hereinafter referred to as a lamp mura phenomenon), and improves the brightness of light. For the purpose of uniformity, the distribution density of the light diffusion pattern 35 is different from the distance of the lamp of the backlight unit.

More specifically, the light diffusion pattern portion 30 of the present invention has a density of the light diffusion pattern 35 in a portion close to the lamp 50, that is, a portion corresponding to the portion directly above the lamp, as shown in FIG. 4. The brightness of the light is lowered by increasing the amount of light diffused by increasing the amount of light, and the density of the light diffusion pattern 35 is lowered between a part far from the lamp 50, that is, between the lamp and the lamp, so that the amount of light diffused relatively. To decrease the brightness of the light.

Meanwhile, as illustrated in FIG. 4, the light diffusion pattern 35 may have a fine dot shape. The shape of the dot is not particularly limited, and may be circular as shown in FIG. 4, or may be rectangular or other polygonal shapes.

On the other hand, the distribution density of the pattern can be adjusted by adjusting the distance between the dots or dots, or by adjusting the size of the dots. In other words, when the distance from the lamp is increased, the distribution density of the dots can be adjusted by increasing the distance between the dots or keeping the distance between the dots constant and decreasing the size of the dot as the distance from the lamp increases.

At this time, the fine dot is preferably about 70 to 150㎛ diameter. If the diameter of the fine dots is less than 70 μm, the production of the fine dots may be difficult to adhere to each other at the time of pattern printing. This is because the visibility of the pattern is increased.

As shown in FIG. 4, the light diffusion pattern part 30 may be formed on the lower surface of the substrate part 10 (in this case, the lower surface means a surface facing the light source). It may be formed on the interface between the portion 10 and the lenticular lens portion 20.

In addition, the light collecting film of the present invention may further include a protective layer 40 for protecting the light diffusion pattern, if necessary. The protective layer serves to protect the light diffusion pattern, and may be formed by injecting a curable resin between the film and the flat roll or the intaglio embossing roll.

In this case, as the curable resin used for forming the protective layer, urethane acrylate, epoxy acrylate, ester acrylate or radical generating monomer may be used alone or in combination.

On the other hand, the light diffusion pattern portion 30 of the present invention can be simply implemented by printing a pattern using the ink on the upper or lower surface of the base portion 10. On the other hand, in the present invention, it is preferable to use an ink having a light transmittance of about 50 to 80% for printing the light diffusion pattern. This is to prevent occurrence of luminance unevenness due to the light diffusion pattern.

When the light diffusion pattern is formed on the light collecting film, the lamp mura phenomenon may be improved to some extent, but when the light diffusion pattern is formed using a conventional reflective ink having a high light reflectance, luminance unevenness may occur due to the light diffusion pattern itself. There is a problem that can be. Therefore, in the present invention, by using a special ink manufactured to reflect some of the incident light, diffusely transmit some, and diffusely reflect another part, the luminance unevenness due to the light diffusion pattern is avoided.

The light diffusion pattern forming ink used in the present invention comprises 100 parts by weight of a binder resin and 10 to 100 parts by weight of a transparent material that transmits light, and may further include 0 to 10 parts by weight of a reflective material that selectively diffuses light. Can be. The transmissive material may be used within a relatively wide range as long as it can secure an area that can transmit light, but when the reflective material exceeds 10 parts by weight, it causes unnecessary diffusion by inhibiting the efficient use of light. It is preferably used as.

In the present invention, a general binder resin used in the art may be used as the binder resin, but is not limited thereto. For example, Urethane acrylate, Epoxy acrylate, ester acrylate, ether acrylate, a radical generation type monomer, etc. can be used individually or in mixture of 2 or more types. In particular, the binder resin preferably has a refractive index of about 1.50 to about 1.54 after curing.

Meanwhile, as the permeable material, polymer beads made of silica, PMMA (polymethyl methacrylate), or a mixture thereof may be used, and these have a size of about 5 μm, preferably about 0.1 to 5 μm. Do.

The silica and the polymer beads may be used separately, or may be used in combination, and when used in combination, the physical properties (eg, refractive index, etc.) of the transmission material may be adjusted by adjusting the mixing ratio.

In addition, the transmissive material is preferably a material having a refractive index difference of 0.04 or less with the binder resin, that is, a material having a refractive index in the range of approximately 1.46 to 1.58. If the refractive index difference is greater than 0.04, it is preferable to limit the refractive index difference to within 0.04 because the diffusion transmission characteristic of the light is not transmitted directly to the front and pass while being refracted.

Next, as the reflective material, TiO ₂ having excellent reflectance, ZnO having excellent light resistance, or the like can be used. The reflective material has a refractive index difference of at least 0.8 and preferably 0.8 to 1.3. This is because when the refractive index difference is less than 0.8, the transmission characteristics are stronger than the reflection characteristics, and when it is 1.3 or more, the economic efficiency is inferior.

Meanwhile, the ink used in the present invention may further include an oil, an inorganic additive, a solvent, and the like, in addition to the components, that is, the binder resin, the permeable material, and the reflective material, depending on process conditions or needs.

At this time, the oil, inorganic additives, solvents, etc. include oils, inorganic additives and solvents generally used in the art. For example, the oil and inorganic additives usable in the present invention include surfactants, silicone derivatives, fluorine derivatives, and the like. Ester solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; Methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, methyl ethyl ketone (mek), methyl isobutyl ketone (mibk), acetone ( Alcohol solvents such as Acetone); And one or more cellosolve solvents such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve.

Example

Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example 1

An ink having a transmittance of 50 to 80% was prepared by mixing 25 parts by weight of silica with 100 parts by weight of a binder resin mixed with polyester acrylate and epoxy acrylate 3: 7.

On the upper surface of the PET film (substrate) having a thickness of 188 µm, a light-diffusion pattern having a circular dot shape having a diameter of 100 µm was formed by a silk screen printing method. In this case, the light diffusion pattern was formed to have the dot distribution shown in FIGS. 5A and 5B. 5A and 5B are for illustrating the light diffusion pattern of the present embodiment, and FIGS. 5A and 5B show the same light diffusion pattern, except that the expression methods are different. FIG. 5A is a graph showing a light diffusion pattern as a position (y value) of dots (represented as points on a graph), in which lamps are positioned at both ends of the y-axis. 5B is a graph showing the light diffusion pattern as a distance (y value) between neighboring dots (represented by dots on a graph). In Figs. 5A and 5B, the x axis represents the number of the dot.

As shown in Figs. 5A and 5B, the light diffusion pattern portion of the present embodiment is formed so that the interval of dots becomes wider toward the center portion away from the lamp.

Then, an epoxy acrylate was injected between the upper surface of the base portion on which the light diffusion pattern was formed and the mold in which the shape of the lenticular lens portion was engraved, and then cured to form a lenticular lens portion.

Example 2

Epoxy acrylate is injected between the upper surface of the PET film (substrate part) having a thickness of 188 μm and cured to form a lenticular lens part, and then the silk is formed on the lower part of the base part using the ink prepared in Example 1 above. A light diffusion pattern was formed by screen printing. In this case, the light diffusion pattern was formed to have the dot distribution shown in FIG. 5.

Experimental Example

The light collecting film manufactured by the method of Example 2 was mounted on a diffusion plate of a direct type backlight unit (manufacturer: LG Electronics), and then a lamp mura phenomenon appearing on the surface of the film was photographed. The picture is shown in FIG. 6.

On the other hand, for comparison, the lamp mura phenomenon which appears on the surface of the film when the diffusion plate is mounted on the same backlight unit and when the conventional lenticular lens film (manufacturer, product name) is mounted together with the diffusion plate is photographed. 8 is shown.

As shown in FIG. 6, when the light collecting film of the present invention is mounted, it can be seen that the lamp mura phenomenon hardly appears on the film surface. On the contrary, when the light collecting film is not attached to FIG. 7 and the conventional light collecting film, it is understood that the lamp mura phenomenon still appears in FIG. 8.

1 is a view showing a conventional direct type backlight unit.

2 is a view showing a conventional slimming direct type backlight unit.

FIG. 3 is a view illustrating a lamp mura phenomenon occurring in the direct type backlight unit of FIG. 2.

4 is a view showing an embodiment of a light collecting film of the present invention.

5A and 5B are diagrams showing distribution densities of light diffusion patterns in an embodiment of the present invention.

6 is a photograph of the film surface after the diffusion plate and the light collecting film of the present invention are attached to the backlight unit.

7 is a photograph of the film surface when only the diffusion plate is mounted on the backlight unit.

8 is a photograph of the film surface after attaching the diffusion plate and the conventional light collecting film to the backlight unit.

* Drawing major code *

1: light source unit 2: diffuser plate

3: condensing film 4: diffusion film

10: substrate portion 20: lenticular lens portion

30: light diffusion pattern portion 35: light diffusion pattern

50: lamp

Claims (16)

Equipment, A lenticular lens unit formed on an upper surface of the base unit to collect light; It comprises a light diffusion pattern portion for making the brightness distribution of light constant, The light diffusing pattern portion uses an ink having a light transmittance of 50 to 80%, and the light distribution film is characterized in that the pattern distribution density decreases as the distance from the lamp increases. The method of claim 1, The light diffusing pattern portion is formed on the interface between the substrate portion and the lenticular lens portion. The method of claim 1, The light diffusing pattern portion is formed on a lower surface of the base portion. The method of claim 3, Condensing film further comprises a protective layer for protecting the light diffusion pattern on the lower surface of the light diffusion pattern portion. 5. The method according to any one of claims 1 to 4, The light diffusing pattern is a light collecting film, characterized in that formed in a fine dot shape. 5. The method according to any one of claims 1 to 4, The light diffusing pattern is a light collecting film, characterized in that formed in a fine dot shape having a diameter of 70 to 150㎛. delete The method of claim 1, The ink is 100 parts by weight of the binder resin and Condensing film, comprising 10 to 100 parts by weight of a transparent material that transmits light. 9. The method of claim 8, The ink is a light collecting film, characterized in that it further comprises 10 parts by weight or less of the reflective material for diffusing light. 9. The method of claim 8, The binder resin is a light collecting film, characterized in that selected from the group consisting of urethane acrylate, epoxy acrylate, ester acrylate, ether acrylate, radical generating monomer and a combination of two or more thereof. 9. The method of claim 8, The binder resin has a refractive index of 1.50 to 1.54 after curing, the light condensing film. 9. The method of claim 8, The light-transmitting film of the said transmissive material is 0.04 or less in refractive index difference with binder resin. The method of claim 12, The transmissive material is a light collecting film, characterized in that selected from the group consisting of silica, polymer beads and mixtures thereof. 14. The method of claim 13, Condensing film, characterized in that the diameter of the silica and polymer beads is 0.1 to 5㎛. 10. The method of claim 9, The reflective material is a light collecting film, characterized in that the difference in refractive index with the binder resin is 0.8 to 1.3. 16. The method of claim 15, The reflective material is a light collecting film, characterized in that the TiO ₂ or ZnO.

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