WO2014084525A1

WO2014084525A1 - Light diffusion plate, and backlight unit comprising same

Info

Publication number: WO2014084525A1
Application number: PCT/KR2013/010232
Authority: WO
Inventors: 이명원; 최정민; 금중한; 심재호
Original assignee: 동우화인켐 주식회사
Priority date: 2012-11-29
Filing date: 2013-11-12
Publication date: 2014-06-05
Also published as: TW201421078A; TWI626476B; KR20140072255A

Abstract

The present invention relates to a light diffusion plate and to a backlight unit comprising same, and more particularly, to a light diffusion plate and to a backlight unit comprising same, which are capable of enhancing the brightness and uniformity of the emitted light, wherein the light diffusion plate comprises: a diffusion matrix layer which is interposed between the lower diffusion layer on the light incident surface side and the upper diffusion layer on the light emission surface side, with light diffusing particles dispersed therein, and formed with a liner first pattern having a curved upper surface on the light emission surface side; and the upper diffusion layer is formed with a liner second pattern having a curved surface top on the light emission surface side.

Description

Light diffusion plate and backlight unit including the same

The present invention relates to a light diffusion plate having improved brightness and uniformity of emitted light and a backlight unit including the same.

BACKGROUND ART Image display apparatuses, which are mainly dominated by conventional CRT monitors, have recently been rapidly developed, and wider, lighter and even bent image display apparatuses such as LCDs, OLEDs, and electronic papers have been introduced one after another.

In the case of a non-light emitting device such as a liquid crystal display (LCD), a backlight unit may be provided on a rear surface thereof. The backlight unit can be largely divided into a direct type mainly used for a large display device such as a television, and an edge type type mainly used in a small display device such as a computer monitor and a notebook computer. In particular, in the case of the direct type, a plurality of light sources are arranged in a bar shape (CCFL: Cold Cathode Fluorescent Lamp) or a dot (LED: Light Emitting Diode), so that some areas have high brightness and some areas have low brightness. There is a problem that the front uniformity is lowered. Accordingly, the backlight unit is provided with a light diffusion plate for uniformly distributing the light over the entire liquid crystal display panel, and at least one diffusion film, a prism sheet, and the like are provided on the upper side of the diffusion plate, if necessary, so that the light propagation path is vertical. It is changed in the direction so that it is focused on the front of the display surface.

As described above, in the configuration of the backlight unit for improving the uniformity and brightness of the front surface, at least one diffusion film, a prism sheet, or the like is used in addition to the diffusion plate. However, such a method not only has a problem that it is difficult to achieve low cost and high thickness of the backlight unit, but also shows a limitation when a high brightness of a 32-inch or larger liquid crystal display is required, in which the number of lamps is reduced and the demand is increasing. .

In order to solve this problem, conventionally, a method of manufacturing air containing voids between the light diffusion plate and the prism pattern and a method of embedding air in the light diffusion plate through a foaming method have been attempted, but the process is very difficult. There is a problem that the manufacturing cost is high.

In addition, the method of forming the prism pattern directly on the upper side of the light diffusion plate to increase the light diffusion and condensing efficiency to improve the uniformity and brightness of the front surface, but the uniformity and brightness of the front surface in the state that does not include the air void or air layer There is a limit to improving.

An object of the present invention is to provide a light diffusion plate having high luminance and uniformity of emitted light.

Moreover, an object of this invention is to provide the backlight unit and image display apparatus provided with the said light-diffusion plate.

1. A diffusion base layer interposed between the lower diffusion layer on the light incidence side and the upper diffusion layer on the light exit side and having light diffusing particles dispersed therein and having a linear first pattern on the light emission surface side with a curved upper portion. And the upper diffusion layer having a line-shaped second pattern having an upper surface at a light exit surface side.

2. The light diffusion plate of 1 above, wherein the first pattern and the second pattern are independently a lenticular pattern or a round prism pattern.

3. The light diffusion plate of 1 above, wherein the ratio of the height of the first pattern of the diffusion base layer and the height of the second pattern of the upper layer is 1: 0.5-10.0.

4. In the above 1, wherein the thickness of the diffusion substrate layer is 50 to 90% of the total thickness of the light diffusion plate.

5. In the above 1, wherein the lower diffusion layer is a light diffusion plate formed with irregularities on the light incident surface side surface.

6. In the above 5, wherein the concave-convex light diffusion plate is formed so that the surface roughness (Ra) of the light incident surface side surface of the lower diffusion layer is 0.1 ~ 10.0㎛.

7. The light diffusion plate of 1 above, wherein the lower diffusion layer further includes an intaglio pattern or an embossed pattern on the light incident surface side surface.

8. Backlight unit having a light diffusion plate of any one of the above 1 to 7.

9. The backlight unit of claim 8, further comprising a light source on the lower side of the lower diffusion layer of the light diffusion plate.

10. An image display device having the backlight unit of 9 above.

The light diffusion plate of the present invention can maintain the brightness of the light emitted excellently.

In addition, the light diffusion plate of the present invention is excellent in concealing performance and uniformity to uniformly emit the light of the backlight light source when applied to the direct type backlight unit to prevent the difference in contrast due to the position of the light source on the entire display screen.

In addition, the light diffusing plate of the present invention can be improved in scratch resistance when provided with irregularities in the lower layer.

1 is a perspective view schematically showing an embodiment of the light diffusion plate of the present invention.

2 is a schematic longitudinal cross-sectional view of the lenticular pattern (a) and the round prism pattern (b) as an example according to the present invention.

3 is a vertical longitudinal cross-sectional view schematically showing an embodiment of the light diffusion plate of the present invention.

4 is an enlarged longitudinal cross-sectional view of a portion of the diffusion base layer 100 and the upper diffusion layer 200 of the light diffusion plate of the present invention.

5 is a vertical longitudinal sectional view schematically showing another embodiment of the light diffusion plate of the present invention.

6 is an enlarged photograph of a portion of the diffusion base layer and the upper diffusion layer of Example 1 (a) and Example 2 (b).

7 is a photograph of the light diffusion plates of the embodiments in the test example according to the present invention.

8 is a photograph of the light diffusion plates of the comparative examples in a test example according to the present invention.

The present invention includes a diffusion substrate layer interposed between the lower diffusion layer on the light incident surface side and the upper diffusion layer on the light exit surface side and having light diffusing particles dispersed therein and having a linear first pattern on the light exit surface side. In addition, the upper diffusion layer relates to a light diffusion plate having a brightness and uniformity of the emitted light by providing a line-shaped second pattern having a curved upper surface on the light exit surface side, and a backlight unit having the same.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 schematically shows an embodiment of a light diffusing plate 10 according to the present invention. However, the configuration described in the embodiments and drawings described below are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, which can be replaced at the time of the present application It should be understood that there may be various equivalents and variations.

The light diffusion plate 10 of the present invention includes a diffusion base layer 100, an upper diffusion layer 200, and a lower diffusion layer 300.

The diffusion base layer 100 is a layer interposed between the upper diffusion layer 200 on the light exit surface side and the lower diffusion layer 300 on the light exit surface side. The diffusion base layer 100 includes a first line-shaped pattern having a curved upper surface on the light exit surface side in contact with the upper diffusion layer 200.

The line-shaped pattern whose upper surface is curved has a cross-sectional shape (cross section viewed in the x direction in FIG. 1, hereinafter same) in the form of a rectangular shape having the same height from one end to the opposite end of the light diffusion plate, and the longitudinal cross section (Fig. 1). The upper part of the cross section viewed from 1 in the y direction, hereinafter identical) is a pattern forming a curve. Examples of such a pattern include a lenticular pattern or a round prism pattern. FIG. 2 is a schematic cross-sectional view of the lenticular pattern (a) and the round prism pattern (b).

The lenticular pattern has a cross-sectional shape in the form of a rectangle having the same height from one end to the other end of the light diffusing plate, the longitudinal section is a curved top, preferably a semi-circle or semi-ellipse. The pattern of the diffusion base layer 100 and the upper diffusion layer 200 shown in FIG. 1 is an example of a lenticular pattern.

The round prism pattern is in the form of a rectangle whose cross section has the same height from one end to the other end of the light diffuser plate, and the longitudinal section is a pattern in which the upper vertex portion is arc shaped in a triangular structure. In other words, the line connecting the two end points of the bottom edge of the longitudinal section to the end points of the upper arc of the longitudinal section is a straight line pattern.

Since the first pattern of the diffusion base layer 100 according to the present invention functions to diffuse light transmitted from the inside to the outside at the upper curved interface, the light diffusion plate 10 of the present invention exhibits high luminance and uniformity. Contributes to

The diffusion base layer 100 includes all resins that can be used in the light diffusion plate, but is not limited thereto. Transparent, translucent, white or colored resins and the like can be used, and preferably acrylic resins, styrene-acrylic copolymer resins, styrene resins, styrene-acrylonitrile resins, polys having excellent properties in light transmittance, light resistance, and the like. Carbonate resin and the like may be used alone or in combination of two or more, but is not limited thereto.

The acrylic resin may be a methacrylic acid alkyl ester such as methyl methacrylate, ethyl methacrylate, butyl methacrylate or 2-ethylhexyl methacrylate; Alkyl acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate; Methacrylic acid cycloalkyl esters such as cyclohexyl methacrylate, 2-methylcyclohexyl methacrylate and dicyclopentanyl methacrylate; Acrylic acid cycloalkyl esters such as cyclohexyl acrylate and 2-methylcyclohexyl acrylate; Methacrylic acid aryl esters such as phenyl methacrylate and benzyl methacrylate; It is preferable that it is any one homopolymer or their copolymers chosen from acrylic acid aryl esters, such as phenyl acrylate and benzyl acrylate.

The styrene-acrylic copolymer resin includes at least one selected from alkyl methacrylate, alkyl acrylate, cycloalkyl methacrylate, cycloalkyl ester of acrylic acid, aryl methacrylate and aryl acrylate, and styrene and α-methyl styrene. and at least one copolymer selected from m-methylstyrene, p-methylstyrene and p-methoxystyrene.

The styrene resin is preferably any one homopolymer or copolymer thereof selected from styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxystyrene.

The styrene-acrylonitrile copolymer resin is preferably a copolymer of an acrylonitrile monomer with at least one selected from styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene and p-methoxystyrene.

Polycarbonate resins are groups of linear and branched aromatic polycarbonate homopolymers, polyester copolymers or mixtures of one or more thereof prepared by reacting dihydroxy phenol with phosgene or by reaction of dihydroxy phenol with a carbonate precursor. This is preferred.

In addition, the resin may further include one or more various additives such as ultraviolet absorbers, bluing agents, antioxidants, mold release agents, antistatic agents and the like.

In addition, the light diffusion particles 110 are dispersed in the diffusion base layer 100. 3 schematically shows a vertical longitudinal cross-sectional view of the light diffusing plate 10 of the present invention. The light diffusing particles 110 are means for further enhancing the diffusion of light passing through the diffusion base layer 100 through reflection, refraction, and scattering of light on the surface and the inside thereof.

In the present invention, the light diffusing particles 110 are present in the diffusion base layer 100 and are not present in the upper diffusion layer 200 and the lower diffusion layer 300. The light diffusing plate 10 of the present invention includes the light diffusing particles 110 only in the diffusion base layer 100, thereby obtaining the effect of disposing the light diffusing particles 110 only in the vicinity of the center portion in the thickness direction of the light diffusing plate. This exerts an excellent effect on improving the brightness of the light diffusion plate.

The light diffusing particles 110 may be used as long as the material is used in the art, and organic or inorganic light diffusing particles may be used alone or in combination. For example, crosslinked or uncrosslinked fine particles of polycarbonate-based, olefin-based, silicone-based, acryl-based, styrene-based, methyl-styrene copolymers (MS-based), silica, talc, calcium carbonate, barium sulfate, titanium dioxide ( TiO ₂ ) and the like can be used. Although not limited, the particle size may range from 0.2 to 50 μm, and the amount of the particles may be used in an amount of 0.001 to 40 parts by weight based on 100 parts by weight of the base resin of the diffusion base layer 100, and more preferably 0.005 to 10 parts by weight. Wealth is good. It is possible to achieve the desired total light transmittance and haze in the content in the above range.

The thickness of the diffusion base layer 100 is not particularly limited, but may be, for example, thicker than that of the upper diffusion layer 200 and the lower diffusion layer 300, and preferably, the sum of the upper diffusion layer 200 and the lower diffusion layer 300. It can be thick. For example, it may have a thickness of 50 to 90% of the total thickness of the light diffusion plate. It is preferable to have the thickness range in view of high luminance and uniformity.

The upper diffusion layer 200 is disposed on the light exit surface side of the diffusion base layer 100. As shown in FIG. 1, the upper diffusion layer 200 includes a second line-shaped pattern having a curved upper surface on a surface from which light is emitted. As described above, the line-shaped pattern having an upper curved surface functions to diffuse light transmitted from the inside to the outside. Therefore, by further scattering the light passing through the diffusion base layer 100 according to the present invention, it contributes to further improve the uniformity of the light diffusion plate 10 of the present invention. Like the first pattern described above, the second pattern of the upper diffusion layer 200 may include a lenticular pattern or a round prism pattern.

Since the light diffusing plate 10 of the present invention has both the diffusion base layer 100 and the upper diffusion layer 200 each having a line-shaped pattern having a curved upper surface, the light diffusion plate 10 maximizes the light diffusion characteristics to increase the uniformity and brightness of the light. Can be. Periods of the line-shaped pattern of which the upper surface of each of the diffusion base layer 100 and the upper diffusion layer 200 are curved are independent of each other, and the pattern period of each layer can be appropriately selected. For example, as illustrated in FIGS. 1 and 3, the periods may be the same so that the unit patterns of the line pattern having the curved upper surface of the diffusion base layer 100 and the upper diffusion layer 200 correspond one-to-one.

In another embodiment of the present invention, the height of the first pattern of the diffusion base layer 100 and the height of the second pattern of the upper diffusion layer 200 may be formed at a predetermined ratio. Referring to FIG. 4, in the present invention, the height of a line-shaped pattern having a curved upper surface means a vertical straight distance from a straight line connecting a portion where the pattern starts at the longitudinal end surface of the pattern to the highest point of the pattern. In the present invention, the ratio of the height h1 of the first pattern of the diffusion base layer 100 and the height h2 of the second pattern of the upper diffusion layer 200 is h1: h2 = 1: 0.5-10.0, preferably The ratio of 1: 1.0-8.0 can be maximized to maximize the effect of improving luminance and uniformity. In this case, the height h1 of the first pattern may be 10 to 200 μm.

The material forming the upper diffusion layer 200 may be appropriately selected and used in the same range as the materials forming the diffusion base layer 100 described above.

The lower diffusion layer 300 functions to guide light incident on the light diffusion plate 10 to the diffusion base layer 100.

In another aspect of the present invention, as shown in FIG. 5, the lower diffusion layer 300 may further include irregularities on the surface of the light incident side. The light diffusion plate 10 may be scratched on the bottom surface of the light diffusion plate 300, that is, during the manufacturing process or during use. Such scratches cause a decrease in the uniformity of light. However, the present invention may not only solve such a problem by further providing irregularities on the surface of the light incidence surface side of the lower diffusion layer 300, but also may further improve the light uniformity of the light diffusion plate. Such irregularities may be formed by methods known in the art such as sand blast.

In this aspect, the unevenness of the lower diffusion layer 300 is preferably fine irregularities, for example, unevenness may be generated so that the surface roughness (Ra) is 0.1 ~ 10.0㎛. Within this range, scratch resistance and uniformity improving characteristics may be most effectively exhibited.

In another aspect of the present invention, the lower diffusion layer 300 may further include a pattern on the surface of the light incident side in order to ensure uniformity of the light. The pattern may be an engraved pattern or an embossed pattern. For example, the intaglio pattern may be formed by irradiating a laser onto the light incident surface side of the lower diffusion layer 300, and the embossed pattern may be formed by spraying and curing ink droplets on the light incident surface side of the lower diffusion layer 300. have. The unevenness of the lower diffusion layer 300 described above may be formed after the pattern is formed.

The light diffusing plate 10 of the present invention, like a conventional light diffusing plate, may further include a functional layer in any one of the lower and upper diffusion layers 300 and 200, or impart functionality to the light diffusing plate. have. The base resin of the functional layer may be a resin exemplified as the base resin of the light diffusion plate, which is the diffusion base layer 100, and may be the same as the base resin of the light diffusion plate, but other materials may be used. Such functional layers may further include one or more of ultraviolet absorbers, heat stabilizers, antioxidants, antistatic agents, fluorescent brighteners, mold release agents, and diffusing agents, and include these functional materials in the base resin or to be coated on the surface. It may be.

The manufacturing method of the light diffusion plate 10 is not particularly limited, and various methods such as extrusion molding, vacuum molding, hot press molding, film lamination, solvent bonding, surface coating, ultraviolet curing, and thermal curing can be used. have. However, in view of ease of manufacturing, extrusion molding to ultraviolet curing method is preferable, and extrusion molding is preferable in consideration of manufacturing cost and productivity. The light diffusing plate 10 of the present invention having a three-layer structure can be easily manufactured by a coextrusion method.

The light diffusion plate 10 of the present invention may configure a backlight unit together with a light source. The light emitted from the light source is incident on the lower diffusion layer 300 of the light diffusion plate 10. The light source may be located at the lower side of the lower diffusion layer surface of the light diffusion plate 10. The direct type backlight unit in which the light source is located opposite the lower diffusion layer 300 of the light diffusion plate 10 is preferable, but if a separate reflecting means can properly inject light into the lower diffusion layer surface of the light diffusion plate 10. The light source may be located elsewhere. The light source can be used without limitation, for example, a light emitting diode (LED), an organic light emitting diode (OLED), a hot cathode tube, a cold cathode tube, and the like.

Meanwhile, a diffusion sheet, a micro lens sheet, a prism sheet, a brightness enhancement (DBEF) sheet, a protective sheet, and the like may be further included on the upper side of the upper diffusion layer 200 of the light diffusion plate 10 as necessary.

The light diffusion plate 10 of the present invention may be included as one component of the image display device. The image display device is not particularly limited as long as a separate surface light source is required to display an image, and may be, for example, a liquid crystal display. In addition, the light diffusing plate 100 as described above may also be used as one component for supplying a surface light source to a general lighting device.

Hereinafter, examples of the present invention will be described, but the scope of the present invention is not limited to the following examples.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but these examples are merely illustrative of the present invention and are not intended to limit the scope of the appended claims, which are within the scope and spirit of the present invention. It is apparent to those skilled in the art that various changes and modifications can be made to the present invention, and such modifications and changes belong to the appended claims.

실시예 1-4 및 비교예 1-4Example 1-4 and Comparative Example 1-4

The light diffusion plate was manufactured by coextrusion with the upper diffusion layer, the diffusion base layer, and the lower diffusion layer using polystyrene (refractive index: 1.59) as the base resin. In the diffusion base layer, silicon-based particles were dispersed with light diffusing particles, and the amount of light diffusing particles was all the same.

On the light exit surface side of the diffusion base layer and the upper diffusion layer, the patterns shown in Table 1 were each formed with a pattern period of 300 μm, and the height of the pattern was 100 μm in height h1 of the first pattern, and the height of h2 was determined according to Table 1. Formed while changing.

On the lower surface of the light diffusion plate, as shown in Table 1, a line pattern was formed, and an ink print pattern was formed by screen printing.

For reference, FIGS. 6A and 6B show optical micrographs of the upper and upper diffusion layers of the diffusion base layer among the light diffusing plate longitudinal cross sections of Examples 1 (a) and 2 (b).

Table 1

시험예 Test Example

1. 평균 휘도1. Average luminance

The light diffusing plate manufactured above is positioned above the direct type LED, so that the total light emitted from 9 points (3X3) becomes 1/6, 1/2, and 5/6 horizontally and vertically in the light diffusing plate plane. Average luminance was measured.)

2. 균일도2. Uniformity

The light diffusing plate manufactured above is positioned above the direct type LED, and among light emitted from a total of 9 points (3X3) which becomes 1/6, 1/2, and 5/6 horizontally and vertically in the light diffusing plate plane, respectively. The uniformity of the minimum and maximum luminance was measured.

The measured average brightness and uniformity are shown in Table 2 below. For reference, photographs of light diffusing plates of Examples and Comparative Examples for emitting light in this Test Example are shown in FIGS. 7 (Example) and 8 (Comparative Example).

TABLE 2

Referring to Table 2 and FIGS. 7 and 8, it can be seen that the light diffusing plates of the embodiments are superior in terms of average luminance and uniformity than the comparative example.

Specifically, Comparative Example 3, which does not have a lenticular pattern in the diffusion base layer, can be confirmed that the luminance is almost similar to that of Example 1, but the uniformity is low. In addition, in the case of Comparative Example 1 having no lenticular pattern in both the diffusion base layer and the upper diffusion layer, the average luminance and uniformity were remarkably low even when the light diffusion particles were distributed throughout the light diffusion plate. .

In addition, in the case of Comparative Example 2 in which the light diffusing particles are present in the upper diffusion layer and the lower diffusion layer, compared with Example 1, both the average brightness and the uniformity are lowered, and in particular, the average brightness is much lowered. In the case of Comparative Example 4 in which the light-diffusing particles were distributed in all the layers, it was confirmed that the luminance was particularly remarkably reduced in comparison with Example 1.

On the other hand, it can be seen that in Example 1 and Example 2, Example 1, which has a smaller thickness of the diffusion base layer, is excellent in average brightness but excellent in Example 2 in uniformity. In addition, when comparing Example 2 and Example 3 it can be seen that if the irregularities are formed on the light incident surface side of the lower diffusion layer, not only the scratch resistance mentioned above is improved but also the uniformity is further improved.

10: light diffusion plate

100: diffusion base layer 110: light diffusing particles

200: upper diffusion layer 300: lower diffusion layer

Claims

A diffusion base layer interposed between the lower diffusion layer on the light incident surface side and the upper diffusion layer on the light emission surface side and having light diffusing particles dispersed therein and having a linear first pattern on the light emission surface side with a curved upper surface; The upper diffusion layer is a light diffusion plate having a line-shaped second pattern on the light exit surface side of the upper surface is curved.
The light diffusing plate of claim 1, wherein the first pattern and the second pattern are independently a lenticular pattern or a round prism pattern.
The light diffusion plate of claim 1, wherein a ratio of a height of the first pattern of the diffusion base layer and a height of the second pattern of the upper layer is 1: 0.5-10.0.
The light diffusing plate of claim 1, wherein the diffusion substrate layer has a thickness of 50 to 90% of the total thickness of the light diffusing plate.
The light diffusion plate of claim 1, wherein the lower diffusion layer has irregularities formed on a light incident surface side surface.
The light diffusion plate according to claim 5, wherein the unevenness is formed so that the surface roughness Ra of the light incidence side surface of the lower diffusion layer is 0.1 to 10.0 µm.
The light diffusion plate of claim 1, wherein the lower diffusion layer further includes an intaglio pattern or an embossed pattern on a light incident surface side surface.
The backlight unit provided with the light-diffusion plate of any one of Claims 1-7.
The backlight unit of claim 8, further comprising a light source at a lower side of the lower diffusion layer of the light diffusion plate.
An image display device comprising the backlight unit of claim 9.