KR101363929B1 - Light-reflecting composition and condensing film having lamp concealing property using thereof - Google Patents

Abstract

The present invention relates to a light reflecting composition and a light collecting film having excellent light source hiding performance using the same, and more particularly, to a light reflecting composition including 100 parts by weight of a binder resin and 5 to 50 parts by weight of a light reflecting material, and a diffuser plate using the same. A portion having a large light output with respect to the amount of light emitted has a large density distribution, and a portion having a small light output has a light condensing dot layer including a plurality of light reflection dots formed therein in a pattern having a small density distribution. It is about a film.
By using the light reflecting composition of the present invention, a plurality of light reflecting dots are formed inside the condensing film so that a portion having a large light output has a large density distribution and a portion having a small light output has a small density distribution. It is possible to obtain a uniformity of brightness by improving the lamp mura at a low manufacturing cost while maintaining a thin thickness of the backlight without a film or an additional light source, thus producing a light collecting film with excellent light source concealment performance.

Description

Light-reflecting composition and condensing film having lamp concealing property using

The present invention relates to a light reflecting composition and a light collecting film for a backlight unit, and more particularly, to a light reflecting composition used for forming a light reflecting dot pattern whose distribution density varies depending on light transmittance so as to perform a light source hiding function. The light condensing film for a backlight unit containing the light reflection dot layer formed using the light reflection composition.

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 must 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 the light source is positioned at regular intervals below the liquid crystal panel, and a direct type backlight is mainly used for a large LCD backlight.

FIG. 1 illustrates a configuration of a general direct type backlight unit. As shown in FIGS. 1A and 1B, a direct backlight includes a CCFL disposed at regular intervals on a reflector 1 for recycling light. The same plurality of light sources 2 are arranged, and a diffusion plate 3 is used on the upper part of the light source to even the brightness of the entire screen and serve as a support for the optical films. In addition, at least one condensing film 5, 5 'for condensing the light emitted from the light source to the effective viewing range and improving the brightness of the light, and at least one diffusing film for increasing the uniformity of the screen brightness and smoothing the latitude distribution. (4) and the like. Generally, the light collecting film includes a prism film 5, a lenticular film 5 ′, a MLA film, or the like.

Conventionally, many cold cathode fluorescent lamps (CCFLs) have been used as backlight sources, but recently, LED lamps are more pollutant-free and emit better than CCFLs, which contain environmental pollutants such as mercury for environmental regulation and energy saving. The trend is replacing light sources. The light source of FIG. 1 (b) shows the configuration of the direct type LED backlight in a rough cross section.

On the other hand, in the case of large-sized monitors of LCD or TV, a thinner direct type backlight is required for handling, ease of use, and design. In order to manufacture a slim backlight, a method of reducing the distance between the light source and the diffuser plate is mainly used, but when the distance between the light source and the diffuser plate decreases, light diffusion does not occur sufficiently so that the upper part of the lamp is bright and the lamp is dark between the lamps. This happens and the brightness of the screen becomes uneven. Repeating the light and dark areas according to the arrangement of the light source is called lamp mura, and in order to alleviate this, the LED interval is narrowed to increase the overlapping of the emitted light or to apply diffusion by using a plurality of optical films. Consider increasing the method.

However, this conventional approach not only has a limitation in slimming down the thickness of the backlight unit, but also has a problem in that the manufacturing cost of the backlight unit increases due to the use of a plurality of optical films.

Therefore, in manufacturing the direct type backlight using the LED, a light condensing film that can reduce the manufacturing cost of the backlight and improve the lamp mura by securing the uniformity of brightness without using an additional diffuser film or an additional LED. Is required.

Accordingly, one aspect of the present invention is to provide a light reflecting composition for use in forming a layer for correcting uneven light transmittance in a light collecting film.

Another aspect of the present invention is to improve the lamp mura by forming a layer for correcting the non-uniform light transmittance in the light collecting film to secure the uniformity of brightness of the light collecting film without using a plurality of diffusion films or a plurality of light sources.

According to one aspect of the invention there is provided a light reflection composition comprising 100 parts by weight of the binder resin and 5 to 50 parts by weight of the light reflecting material.

According to another aspect of the present invention, a portion having a large light output with respect to the light output amount of the diffusion plate has a large density distribution and a portion having a small light output includes a plurality of light reflection dots formed in a pattern having a small density distribution. There is provided a light collecting film including a light reflection dot layer therein.

The diameter of the dot is preferably 20 μm to 100 μm.

It is preferable that the said several dot has the same diameter.

The dot layer is preferably formed on the interface between the lens portion and the substrate portion of the light collecting film.

The dot layer is preferably formed on the interface between the base portion and the rear portion of the light collecting film.

The light reflection dot is preferably formed using a light reflection composition comprising 100 parts by weight of the binder resin and 5 to 50 parts by weight of the light reflection material.

It is preferable that the said light reflection composition has a reflectance of 10% or more and 50% or less.

The binder resin is preferably at least one selected from the group consisting of urethane acrylate, epoxy acrylate, polyester acrylate, ether acrylate and radical generating type monomer.

The binder resin preferably has a refractive index of 1.50 to 1.68 after curing.

The light reflecting material is preferably TiO ₂ or ZnO.

It is preferable that the light reflection material has a refractive index difference of 0.8 to 1.3 from the binder resin.

By using the light reflecting composition of the present invention, a plurality of light reflecting dots are formed inside the condensing film so that a portion having a large light output has a large density distribution and a portion having a small light output has a small density distribution. The uniformity of brightness can be obtained by improving the lamp mura with low manufacturing costs while maintaining the thin thickness of the backlight without film and additional light sources.

1 schematically shows a configuration of a general direct type backlight unit.
FIG. 2 represents brightness with respect to the position of a portion of the diffuser plate in a direct backlight with LED as the light source.
3 shows a distribution in which the density of light reflection dots is adjusted according to the luminance.
FIG. 4 shows an exemplary cross section of a lenticular film including a light reflection dot layer serving as a light transmittance adjusting means.
5 is for showing the light source concealment performance by the light collecting film of the present invention, (b), (c) and (d) is a backlight unit using a half of the number of the light source of (a), the present invention It shows the excellent light source hiding performance of (d) using an exemplary light collecting film of.

Hereinafter, the present invention will be described more specifically.

FIG. 2 shows light uniformity of a part of a diffuser plate in a direct backlight having an LED as a light source, and expresses brightness according to a position. Figure 2 (A) is a portion where the light source is located is brighter than the surroundings (B) is a portion corresponding to the light source and the light source is darker than the surroundings. In order to improve the brightness non-uniformity, in the present invention, a means for changing the light transmittance according to the position is given to one surface of the light converging film to improve the light non-uniformity. A reflective dot is formed.

To this end, the present invention provides a light reflection composition used to form the light reflection dot, the light reflection composition of the present invention comprises 100 parts by weight of the binder resin and 5 to 50 parts by weight of the light reflection material.

The light reflecting composition preferably has a reflectance of 10% or more and 50% or less. When the reflectance of the light reflecting composition is less than 10%, there is a limit in expressing a difference in light reflecting dot density, and the reflectance is greater than 50%. In this case, there is a problem that luminance unevenness may occur due to the light reflection dot pattern itself.

The refractive index after curing of the binder resin is preferably less the difference in refractive index with the adjacent portion of the lens portion or the rear portion, and most preferably has the same refractive index. Since the refractive index of the resin currently used in the optical film is about 1.50 to 1.68, the refractive index after curing of the binder resin is preferably about 1.50 to 1.68.

The binder resin may be used alone or in combination of two or more selected from the group consisting of urethane acrylate, epoxy acrylate, polyester acrylate, ether acrylate and radical generating monomer.

On the other hand, the light reflecting material preferably has a refractive index difference of 0.8 to 1.3 from the binder resin, and when the difference in refractive index is less than 0.8, there is a problem in that the transmission property is stronger than the reflection property, and the difference in refractive index If is greater than 1.3, there is a problem of low economic efficiency. As the light reflection material, for example, TiO ₂ or ZnO is preferable.

In order to change the light transmittance according to the position of the light collecting film by using the light reflecting composition of the present invention, a light reflecting dot is formed on one surface of the light collecting film, wherein the number of light reflecting dots per unit area, that is, light The density of the reflective dot is adjusted according to the position of the light collecting film.

According to another aspect of the present invention, a portion having a large light output with respect to the light output amount of the diffusion plate has a large density distribution and a portion having a small light output includes a plurality of light reflection dots formed in a pattern having a small density distribution. There is provided a light collecting film including a light reflection dot layer therein.

That is, the light reflection dot is to improve the phenomenon that the brightness of the light periodically changes according to the lamp position of the backlight unit (lamp mura) and to make the brightness of the light uniform. According to the deviation of the light output according to the distribution density is characterized in that different.

In more detail, the density distribution of the light reflection dot is determined to measure the uniformity of the light emitted from the diffuser plate and to correct it. As shown in FIG. 3, in the light portion corresponding to the portion directly above the light source, the light reflection Increase the density of the dots to reduce the light transmittance (A ') and in the dark areas between the lamps and the lamps, reduce the density of the light reflecting dots (B') to increase the light transmittance so that the light transmittance is uniformly adjusted. . That is, it is possible to improve the lamp mura by equalizing the brightness distribution according to the position by reducing the light transmittance at the position of the bright part and conversely by increasing the light transmittance at the position of the dark part.

The adjustment of the density distribution of the light reflection dot according to the degree of light emission may be different depending on the light distribution of the light source and the distance between the light sources. For example, the density of the dots may be represented by the following equation. In the following formula, a denotes a vertical distance between light sources, b denotes a horizontal distance between light sources, m denotes a vertical number between light sources, and n denotes a horizontal number between light sources.

More specifically, a plane with a light source is called an xy plane and a is an x-axis distance and b is a y-axis distance among the distances between the respective light sources, and the reference for the number of light sources is based on the entire backlight. For example, in an LED TV, if there are 16 horizontal, 9 vertical, and 144 total LEDs in a rectangular array, m is 16, n is 9, and a and b are approximately the length of the LED TV. / 16), and b means (vertical length / 9).

In the LED direct backlight, since the lamp mura often has a rhombic or rectangular pattern, the density distribution of the light reflection dots may have a rhombic or rectangular pattern as a whole, but is not limited thereto. As can be formed according to any shape formed by the deviation of the amount of light emitted.

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. That is, in a dark position between the lamps, the dot density is increased by increasing the distance between the dots or keeping the distance between the dots constant and decreasing the size of the dots as the distance from the lamp becomes darker. Can be adjusted. Similarly, in a bright location directly above the lamp, the dot density can be reduced by reducing the spacing between the dots, or by increasing the size of the dot toward the bright part just above the lamp while keeping the spacing between the dots constant. Can be adjusted.

On the other hand, the diameter of the light reflection dot forming the distribution of the pattern may be made of a fine dot shape of 20 μm to 100 μm, and when the diameter of the light reflection dot is less than 20 μm, fine size dots are attached to each other when the pattern is printed. There is a difficulty in forming a dot such as throwing away, and when it exceeds 100 μm, the visibility of the dot itself increases, so that the dot may be recognized as a foreign material. The diameters of the plurality of light reflection dots forming the pattern may be different, but are preferably formed in the same size, but may have a size randomly formed within the range of 10%. Further, in order to further reduce the visibility of the light reflection dots, the arrangement of the light reflection dots may be randomly formed as shown in the enlarged view of FIG. 3.

On the other hand, the shape of the dot is not particularly limited, may be circular, may be a square or other polygonal shape.

The pattern of the light reflection dots may be formed at the interface between the lens portion and the base portion of the light collecting film, or may be formed at the interface between the base portion and the rear portion of the light collecting film. In the present specification, the layer on which the pattern of dots formed as described above is formed is referred to as a 'light reflection dot layer'.

Figure 4 (a) is an overall view showing an example of a lenticular film including a light reflection dot layer as a light transmittance adjusting means therein, Figure 4 (b) is a lens portion of the light collecting film of the light collecting film is a light reflection dot layer FIG. 4 (c) shows a case where the light reflection dot layer is disposed between the base portion 12 and the rear portion 13 of the light converging film. The case is illustrated by way of example. As described above, since the light reflection dot layer is formed inside the light converging film so as not to be exposed to the outside, mechanical damage such as cracking or detachment of the light reflection dots can be prevented.

If necessary, the light collecting film of the present invention may further include a protective layer for protecting the light reflection dot pattern, and the 'back portion' referred to herein may mean any protective layer as described above. The protective layer may be formed by injecting a curable resin between the film and the flat roll or the intaglio embossing roll. The rear part as described above improves the appearance of the backlight unit, and furthermore, may serve to protect the light reflection dot pattern in the present invention.

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

On the other hand, the light reflection dot layer of the present invention can be implemented by printing a pattern using the light reflection composition on the upper or lower surface of the base portion 12. That is, it is preferable that the light reflection dot pattern is printed on the surface of the substrate in both the case where the light reflection dots are disposed between the lens portion and the substrate portion of the light collecting film or between the substrate portion and the back portion.

In the case where the light reflection dots are located between the lens portion and the substrate portion or between the substrate portion and the back portion, first, the light reflection dot pattern is printed on the substrate, for example, ink may be printed on a silk screen through a roller.

Thereafter, a light collecting film may be prepared by injecting and curing a curable resin into a roll mold in which a lens part having a shape such as lenticular or a roll embossed roll is formed on a substrate on which light reflection dots are printed. However, this is merely illustrative and the present invention is not limited thereto.

The light reflection composition used to form the light reflection dot is as described above, and includes 100 parts by weight of the binder resin and 5 to 50 parts by weight of the light reflection material. The light reflecting composition preferably has a reflectance of 10% or more and 50% or less. When the reflectance of the light reflecting composition is less than 10%, there is a limit in expressing a difference in light reflecting dot density, and the reflectance is greater than 50%. In this case, luminance unevenness may occur due to the light reflection dot pattern itself.

The binder resin preferably has a refractive index of about 1.50 to 1.68 after curing, and as the binder resin, a general binder resin used in the art may be used, but is not limited thereto. For example, urethane acrylate and epoxy acrylate. Selected from the group consisting of polyester acrylate, ether acrylate and radical generating monomer can be used alone or in combination of two or more thereof.

On the other hand, the light reflecting material preferably has a refractive index difference of 0.8 to 1.3 from the binder resin, and the light reflecting material is preferably TiO ₂ having excellent reflectance or ZnO having excellent light resistance.

On the other hand, the light reflection composition used in the present invention may further include an oil, an inorganic additive, a solvent and the like as the 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, and fluorine derivatives, and solvents include methyl acetate, ethyl acetate, and propyl acetate. Ester solvents such as 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 at least one cellosolve solvent such as methyl cellosolve, ethyl cellosolve, or butyl cellosolve.

Hereinafter, the present invention will be described in more detail with reference to specific examples, and the following examples are provided to more specifically describe the present invention, and the present invention is not limited by the following examples.

<Examples>

Example 1 Preparation of Light Reflective Composition According to the Present Invention

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 at 3: 7.

Example 2. Preparation of a light collecting film having a light reflection dot formed using the light reflection composition of the present invention

Using the light reflection composition prepared in Example 1, a circular dot-shaped light reflection pattern having a diameter of 50 μm was formed on one surface of the substrate by an offset printing method. Density is determined by the number of dots contained in an area of about 1 mm in width and width, and the light source (LED) is arranged densely and the light source is arranged sparsely. In more detail, the density distribution of the light reflection pattern follows the following formula.

In this embodiment, the measurement was performed using a 55-inch LED TV of LG Electronics. In the LED TV, there are 16 horizontally, 9 vertically, and 144 total LEDs in a rectangular arrangement, where m is 16 and n is 9. And a and b were approximately (length / 16) of the LED TV, respectively, and b was (length / 9).

A urethane acrylate elastic resin having a refractive index of 1.54 is injected between one surface of the substrate portion on which the light reflection pattern is formed and the mold having the shape of the lenticular lens portion engraved, and then cured to form a lenticular lens portion. The urethane acrylate elastic resin having a refractive index of 1.54 was injected and then cured to form a rear portion.

3. Light source concealment performance by the light collecting film of the present invention

(1) A diffuser plate and two lenticular films (LG Chemistry) were sequentially placed on a backlight used in a 55-inch LED TV of LG Electronics, and a CCD (Konica Minolta, CA-2000) image was confirmed. as shown in a).

(2) In order to confirm the concealment performance, only the diffusion plate was placed on the backlight of which the number of LEDs was cut in half, and the CCD image was confirmed. As a result, as shown in FIG. Can be.

(3) The first lenticular film (LG chemistry) and the second lenticular film (LG chemistry) were further placed on the diffusion plate in sequence on the same backlight as used in the above (2), and the CCD image was confirmed. As shown in (c) of FIG. 5, the light source concealment performance was improved than in the case of (2), but it was confirmed that the light source concealment performance was still insufficient.

(4) The diffusion plate, the light collecting film of the present invention prepared in Example 2, and the lenticular film (LG chemistry) were sequentially placed on the same backlight as used in (2) above, and the CCD image was confirmed. As shown in Figure 5 (d) it was confirmed that the excellent light source concealment performance.

This can be inferred that the light source occlusion function is remarkably improved, considering that only half of the LEDs of the LEDs of the backlight used in (1) is used.

1: reflector 11: lens
2: light source 12: base part
3: diffuser plate 13: rear panel
4: diffusion film
5, 5 ': condensing film

Claims (18)

A light reflection composition comprising 100 parts by weight of the binder resin and 5 to 50 parts by weight of the light reflection material, and having a reflectance of 10% or more and 50% or less.
delete The light reflection composition of claim 1, wherein the binder resin is at least one selected from the group consisting of urethane acrylate, epoxy acrylate, polyester acrylate, ether acrylate, and radical generating monomer.
The light reflecting composition of claim 1, wherein the binder resin has a refractive index of 1.50 to 1.68 after curing.
The light reflecting composition of claim 1, wherein the light reflecting material is TiO ₂ or ZnO.
The light reflection composition of claim 1, wherein the light reflection material has a refractive index difference of 0.8 to 1.3 from that of the binder resin.
A light reflection dot layer including a plurality of light reflection dots therein;
Density distribution of the light reflection dot is a light collecting film formed by the following formula (1).

Equation (1)
In the formula (1), based on the exact center of the arbitrarily selected light source,
x is the distance vertically away from the criterion (in mm),
y is the horizontal distance from the criterion in mm
a is the distance (unit is mm) between light sources arranged vertically from the reference,
b is the distance (unit is mm) between light sources arranged horizontally from the reference,
m is the number of light sources arranged in a line in the vertical direction,
n is the number of light sources arranged in the horizontal direction,
Density (x, y) is the density of light reflection dots at positions apart from the reference by x in the vertical direction and y in the horizontal direction.
The condensing film of claim 7, wherein the dot has a diameter of 20 μm to 100 μm.
The condensing film of claim 7, wherein the plurality of dots have the same diameter.
The light collecting film of claim 7, wherein the light reflection dot layer is formed at an interface between the lens unit and the base unit of the light collecting film.
The light collecting film of claim 7, wherein the light reflection dot layer is formed at an interface between the base portion and the rear portion of the light collecting film.
The light converging film of claim 7, wherein the light reflecting dot is formed using a light reflecting composition comprising 100 parts by weight of the binder resin and 5 to 50 parts by weight of the light reflecting material and having a reflectance of 10% or more and 50% or less.

delete The light condensing film of claim 12, wherein the binder resin is at least one selected from the group consisting of urethane acrylate, epoxy acrylate, polyester acrylate, ether acrylate, and radical generating monomer.
The light collecting film of claim 12, wherein the binder resin has a refractive index of 1.50 to 1.68 after curing.
The light collecting film of claim 12, wherein the light reflecting material is TiO ₂ or ZnO.
The light converging film of claim 12, wherein the light reflecting material has a refractive index difference of 0.8 to 1.3 from that of the binder resin.
delete

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