KR20150108211A - Light guiding plate and backlight unit comprising the same - Google Patents

Abstract

The present invention relates to a light guiding plate and a backlight unit comprising the same. More particularly, the present invention relates to a light guiding plate which has high brightness and the straight propagation of light emitted, and a backlight unit comprising the same. An upper surface includes a prism pattern which has an upper apex in an arc type. The prism pattern satisfies a formula 1: 0.350(μm/Radian^2) < {H/ (Radian(A))*(Radian(B))}/(n*100) < 1.400(μm/Radian^2).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light guide plate and a backlight unit including the light guide plate.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light guide plate and a backlight unit including the same.

2. Description of the Related Art [0002] In recent years, an image display device in which a conventional CRT monitor is dominant has been rapidly developed, and a wider, lighter, and even bendable image display device such as an LCD, an OLED, Furthermore, as image display apparatuses are actively researched, large-sized image display apparatuses are being developed in a competitive manner.

However, in recent years, the expansion of the screen has become possible to an extent that exceeds the human vision, reaching its limit, and accordingly, the resolution, the contrast ratio, the color reproducibility, and the like Research focuses on image quality improvement.

Among the recently introduced techniques for improving picture quality, the screen division driving (local dimming, local dimming) divides the backlight unit into a plurality of areas, and associates the brightness (brightness) with the video signal to generate a light source The luminance of the bright portion is increased, the contrast ratio is greatly improved, and the sharpness is improved.

In order to effectively realize such screen division driving, a light guide plate is required which emits the light emitted from the light source uniformly and with high linearity at a high luminance.

In this regard, Korean Patent Laid-Open Publication No. 2011-50270 proposes a light guide plate having a laser engraved pattern and a prism pattern on the lower part, but there is still a problem in improving the straightness of the surface light source.

Korean Patent Publication No. 2011-0050270

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

It is another object of the present invention to provide a backlight unit including the light guide plate.

1. A prism pattern having a top vertex portion in the form of a arc,

Wherein the prism pattern satisfies the following formula (1): &lt; EMI ID = 1.0 &gt;

[Equation 1]

^{0.350 (㎛ / Radian 2) <} {H / Radian (A)) * (Radian (B))} / (n * 100) <1.400 (㎛ / Radian 2)

(Where H (占 퐉) is the height of the vertical section of the prism,

A (°) is the angle between the base of the vertical section of the prism and the hypotenuse,

B (?) Is an angle formed by the connecting line connecting the center of the base at the point where the upper arc of the vertical section of the prism starts,

and n is the refractive index of the material forming the prism pattern).

2. The light guide plate according to item 1 above, wherein the H is 20 to 50 占 퐉.

3. The light guide plate according to item 1 above, wherein A is 25 DEG to 50 DEG.

4. The light guide plate according to item 1 above, wherein B is 10 DEG to 75 DEG.

5. The light guide plate according to item 1, wherein the prism pattern is formed by including at least one selected from the group consisting of a (meth) acrylic resin, a carbonate resin, a styrene resin, an olefin resin, .

6. The light guide plate according to item 1 above, wherein the light guide plate includes a light scattering pattern.

7. The light guide plate according to claim 6, wherein the light scattering pattern is an engraved or embossed pattern.

8. A backlight unit comprising a light guide plate according to any one of claims 1 to 7.

9. An image display apparatus comprising the backlight unit of the above 8.

The light guide plate of the present invention can be usefully used for screen division driving by improving the straightness of emitted light.

Further, in the image display apparatus provided with the light guide plate of the present invention, it is possible to uniformly emit light in the absence of a hot spot.

Further, the image display apparatus provided with the light guide plate of the present invention is capable of displaying a screen having excellent contrast ratio and sharpness because the effect of realizing the divided screen driving is excellent.

1 is a schematic vertical cross-sectional view of one embodiment of a round prism of a light guide plate of the present invention.
2 is a schematic perspective view of the backlight unit of the present invention.
3 is a schematic vertical cross-sectional view of one embodiment of the backlight unit of the present invention.

The present invention relates to a light guide plate having high linearity and brightness of emitted light and a backlight unit having the prism pattern, wherein the upper apex portion includes a prism pattern having a shape of arc on an upper surface thereof and the prism pattern satisfies Equation .

Hereinafter, the present invention will be described in detail.

The light guide plate of the present invention includes a prism (hereinafter referred to as &quot; round prism &quot;) pattern having a top vertex portion in the shape of a arc on its upper surface.

The round prism satisfies the following expression (1), thereby significantly improving the straightness and brightness of the emitted light, thereby realizing effective screen division driving (local dimming).

[Equation 1]

^{0.350 (㎛ / Radian 2) <} {H / Radian (A)) * (Radian (B))} / (n * 100) <1.400 (㎛ / Radian 2)

(Where H (占 퐉) is the height of the vertical section of the prism,

A (°) is the angle between the base of the vertical section of the prism and the hypotenuse,

B (?) Is an angle formed by the connecting line connecting the center of the base at the point where the upper arc of the vertical section of the prism starts,

and n is the refractive index of the material forming the prism pattern).

A schematic view of a vertical section of an embodiment of a round prism pattern according to the present invention is shown in Fig. The vertical cross section of the round prism pattern shown in Fig. 1 is a symmetrical shape in which the upper apex portion of the prism has a shape of arc.

The height H of the vertical section of the round prism of the present invention may be 20 to 50 mu m, preferably 25 to 50 mu m. When H satisfies the above range, the straightness and luminance of light emitted from the light guide plate can be further improved.

The angle (A) between the base of the vertical prism and the hypotenuse of the round prism of the present invention may be 25 to 50, preferably 30 to 50. When A satisfies the above range, the straightness and brightness of light emitted from the light guide plate can be further improved.

The angle B formed by the base line of the vertical section of the round prism of the present invention and the connecting line connecting the centers of the base lines at the point where the upper arc starts may be 10 ° to 75.0 ° and preferably 10 ° to 70 ° good. When B satisfies the above range, the straightness and brightness of light emitted from the light guide plate can be further improved.

The refractive index (n) of the round prism of the present invention may be 1.41 to 1.61, preferably 1.45 to 1.59. When the refractive index (n) satisfies the above range, the straightness and brightness of light emitted from the light guide plate can be further improved.

The bottom end length P of the vertical section of the round prism of the present invention may be 100 to 250 탆, preferably 130 to 210 탆. When P satisfies the above range, the straightness and luminance of the light emitted from the light guide plate can be further improved.

In the present invention, the height (H) of the vertical section of the round prism, the angle (A) between the base and the hypotenuse, the angle (B) between the base and the connecting line connecting the centers of the base at the point where the top arc starts, When both the lengths P satisfy the above-mentioned range, the straightness and brightness of the light emitted from the light guide plate are improved at the same time, so that it is judged that the screen division drive (local dimming) can be realized more effectively.

1 showing an embodiment of the present invention, in the present invention, the center (origin O) of the circle including the upper arc of the round prism corresponds to the above-mentioned four parameters in the above-mentioned specific range , It can be positioned on the lower base or outside of the round prism. Accordingly, the radius R of the sector including the upper arc of the round prism may have various values.

In the present invention, the round prism pattern may be formed by including an optically transparent resin.

The optically transparent resin is not particularly limited as long as it is used in the art, and examples thereof include (meth) acrylic resins, carbonate resins, styrene resins, olefin resins, ester resins and copolymer resins thereof And preferably a methacrylic resin or a (meth) acryl-styrene copolymer resin.

The olefin-based resin is more preferably a cyclic olefin-based resin, and the ester-based resin is more preferably an amorphous ester-based resin.

Examples of the methacrylic resin include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, Phenyl acrylate, and chlorophenyl methacrylate. Of these, methyl methacrylate resins having a high transmittance are more preferable.

The methacrylic resin is preferably copolymerized with the monofunctional unsaturated monomer. When copolymerized, the methacrylic resin is preferably copolymerized in an amount of less than 60% by weight based on the total weight of the copolymer resin, More preferable.

Examples of the monofunctional unsaturated monomer copolymerized with the methacrylic resin include unsaturated acid compounds including methacrylic acid and acrylic acid, styrene, acrylonitrile, maleic anhydride, phenylimide, and cyclohexylmaleimide. It is good to be styrene. These may be used alone or in combination of two or more.

The copolymerization of the methacrylic resin with the monofunctional unsaturated monomer can be easily carried out by those skilled in the art.

The light guide plate of the present invention may further include a light scattering pattern on the bottom surface. The light scattering pattern can further improve the uniformity of light emitted through the upper surface of the light guide plate.

The shape of the light scattering pattern can be applied without any particular limitation as long as it is used in a light scattering pattern in the art. For example, a recessed or embossed pattern may be applied to the light guide plate. Specific examples of the pattern include a lens shape, A prism shape, a polygonal shape, and the lenticular shape may have a semicircular shape, a semi-elliptic shape, or the like in its cross-sectional shape. In addition, these light scattering patterns may be arranged continuously or at predetermined intervals, and the scattering pattern density may be increased or remained constant as the distance from the light source is increased.

The substrate of the light guide plate of the present invention may be made of an optically transparent resin, and the kind thereof is not particularly limited, and an optically transparent resin of the above-mentioned round pattern can be used. Further, the substrate may further include at least one of an ultraviolet absorber, a bluing agent, an antioxidant, and a release agent.

The light guide plate of the present invention may further include a functional layer on either the lower surface or the upper surface, as in a general light guide plate, or may impart functionality to the light guide plate. As the substrate of the functional layer, the resin exemplified as the substrate of the light guide plate as the substrate layer can be used, and the same material as the substrate of the light guide plate may be used, but other materials may be used. The functional layer may further contain at least one of an ultraviolet absorber, a heat stabilizer, an antioxidant, an antistatic agent, a fluorescent whitening agent, and a release agent, and these functional materials may be contained in the substrate.

There is no particular limitation on the method of producing the light guide plate, and various methods such as extrusion molding, vacuum molding, hot press molding, extrusion molding, film lamination, solvent adhesion, surface coating, ultraviolet curing, and thermosetting can be used. However, extrusion molding or ultraviolet curing is preferable from the standpoint of manufacturing easiness, and extrusion molding is preferable considering production cost and productivity.

2, in the case where the light source 200 is positioned on the side surface of the light guide plate 100, the direction of the round prism pattern 130 on the light guide plate 100 is the same as that of the light guide plate 100, The light sources 200 may be disposed at both ends in the longitudinal direction or the light sources 200 may be disposed at positions perpendicular to the direction. Preferably, as shown schematically in FIG. 3, the orientation of the round prism patterns 130 is such that the light sources 200 are positioned at both ends in the longitudinal direction thereof, which reduces hot spots and improves the uniformity of the emitted light It is advantageous. In addition, a reflective sheet 300 may be additionally provided on the lower surface of the light guide plate 100. The reflective sheet 300 reflects the light emitted to the lower portion of the light guide plate 100 and re-enters the light guide plate 100. A typical reflective sheet 300 used in the art can be used without limitation.

On the other hand, a diffusion sheet, a microlens sheet, a prism sheet, a brightness enhancement (DBEF) sheet, a protective sheet, and the like may be further included on the upper surface of the light guide plate 100, if necessary.

The light guide plate 100 of the present invention can be included as one component of an image display apparatus. The image display device is not particularly limited as long as it is an apparatus requiring a separate surface light source for displaying an image, and may be, for example, a liquid crystal display. Further, the light guide plate 100 as described above may also be used as a component for supplying a surface light source to a general illumination device.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Example  And Comparative Example

MMA-styrene (refractive index: 1.55) was used to form a round prism pattern having the components and shape shown in the following Table 1 on the upper surface of the light guide plate (the base length of the vertical section of the pattern is 150 μm). The lower light scattering pattern is a negative ellipsoid and has a depth of 70 占 퐉, the long side is 250 占 퐉, and the short side is 20 占 퐉. In order to maintain the uniformity of the light, the distribution density of the pattern is denser as the distance from the light source is increased.

Example  1-8 and Comparative Example  1-4: Height (H) change

division Pattern component
(Refractive index) Height
(H, 占 퐉) Angle of base and hypotenuse
(A, °) Base and
Angle of connector
(B, °) The value of Equation 1
(unit) Example 1 MS (1.55) 27.0 42.0 10.67 1.276 Example 2 MS (1.55) 31.6 30 51.05 0.437 Example 3 MS (1.55) 40.0 48.0 33.07 0.534 Example 4 MS (1.55) 42.1 48.0 23.83 0.780 Example 5 MS (1.55) 31.6 48.0 14.00 0.996 Example 6 MS (1.55) 35.0 48.0 14.00 1.103 Example 7 MS (1.55) 40.0 48.0 14.00 1.261 Example 8 MS (1.55) 31.6 50.0 12.60 1.060 Comparative Example 1 MS (1.55) 31.6 24.0 83.79 0.333 Comparative Example 2 MS (1.55) 21.0 46.0 3.37 2.869 Comparative Example 3 MS (1.55) 10.0 50.0 12.60 0.336 Comparative Example 4 MS (1.55) 55.0 50.0 12.60 1.848

Test Example  One

On the side of the light guide plate, The light source was arranged and the straightness and the relative luminance of the light emitted from the light guide plate were measured under the conditions of LED light output angle of 120 ° and LED light intensity of 35 lumen.

The straight-line is turned on when the LED light sources of the Nth block (each block includes 8-12 LED light sources) are turned on, and the light sources of the other blocks are turned off. The luminance of the light emitted from the straight line portion was evaluated by the ratio of the luminance of light emitted from the straight line portion connecting the light source of the (N + 3) -th block. The smaller the ratio is, the better the linearity of light is. The luminance was measured using a luminance meter (Model: BM-7, TOPCON, Japan).

The measurement results are shown in Table 2 below.

division Straightness (%) Average brightness (nit) Example 1 2.83 1490.7 Example 2 2.37 1569.7 Example 3 2.24 1689.8 Example 4 1.88 1736.3 Example 5 2.37 1567.7 Example 6 2.31 1637.3 Example 7 2.24 1733.2 Example 8 2.12 1588.7 Comparative Example 1 11.27 1200.4 Comparative Example 2 8.21 1194.5 Comparative Example 3 14.81 1172.2 Comparative Example 4 3.89 1483.4

Example  9-10 and Comparative Example  5-6: Change in the angle of the base and hypotenuse (A)

division Pattern component
(Refractive index) Height
(H, 占 퐉) Angle of base and hypotenuse
(A, °) Base and
Angle of connector
(B, °) The value of Equation 1
(unit) Example 9 MS (1.55) 31.6 36.0 31.24 0.595 Example 10 MS (1.55) 31.6 42.0 20.10 0.793 Example 5 MS (1.55) 31.6 48.0 14.00 0.996 Comparative Example 5 MS (1.55) 31.6 65 31.24 0.330 Comparative Example 6 MS (1.55) 31.6 15 31.24 1.428

Test Example  2

On the side of the light guide plate, The light source was arranged and the straightness and the relative luminance of the light emitted from the light guide plate were measured under the conditions of LED light output angle of 120 ° and LED light intensity of 35 lumen.

The measurement results are shown in Table 4 below.

division Straightness (%) Average brightness (nit) Example 9 2.73 1464.7 Example 10 2.61 1538.4 Example 5 2.37 1567.7 Comparative Example 5 8.74 1127.2 Comparative Example 6 13.42 1012.1

Example  11-13 and Comparative Example  7-8: Change in angle (B) between base and connecting line

division Pattern component
(Refractive index) Height
(H, 占 퐉) Angle of base and hypotenuse
(A, °) Base and
Angle of connector
(B, °) The value of Equation 1
(unit) Example 11 MS (1.55) 40.0 48.0 14.0 1.261 Example 12 MS (1.55) 40.0 48.0 33.10 0.533 Example 13 MS (1.55) 50.0 42.0 69.80 0.361 Comparative Example 7 MS (1.55) 50.0 42.0 80.00 0.315 Comparative Example 8 MS (1.55) 50.0 42.0 9.80 2.573

Test Example  3

On the side of the light guide plate, The light source was arranged and the straightness and the relative luminance of the light emitted from the light guide plate were measured under the conditions of LED light output angle of 120 ° and LED light intensity of 35 lumen.

The measurement results are shown in Table 6 below.

division Straightness (%) Average brightness (nit) Example 11 2.24 1733.2 Example 12 2.18 1689.8 Example 13 2.45 1740.5 Comparative Example 7 6.24 1596.4 Comparative Example 8 11.25 1422.8

Example  14-16 and Comparative Example  9-10: Change of pattern component (refractive index (n))

division Pattern component
(Refractive index) Height
(H, 占 퐉) Angle of base and hypotenuse
(A, °) Base and
Angle of connector
(B, °) The value of Equation 1
(unit) Example 14 MS (1.55) 50 48 53.37 0.413 Example 15 PS (1.59) 50 48 53.37 0.403 Example 16 PMMA (1.49) 50 48 53.37 0.430 Comparative Example 2 MS (1.55) 21 46 3.37 2.869 Comparative Example 9 PS (1.59) 21 46 3.37 2.797 Comparative Example 10 PMMA (1.49) 21 46 3.37 2.984

Test Example  4

The LED light source was disposed on the side of the light guide plate and the linearity and the relative brightness of the light emitted from the light guide plate were measured under the conditions of LED light output angle of 120 ° and LED light intensity of 35 lumen.

The measurement results are shown in Table 8 below.

division Straightness (%) Average brightness (nit) Example 14 2.45 1740.5 Example 15 2.64 1722.2 Example 16 2.91 1728.7 Comparative Example 2 8.21 1194.5 Comparative Example 9 8.49 1216.1 Comparative Example 10 9.20 1214.9

Referring to Tables 2, 4, 6 and 8, it was confirmed that the light guide plate of the present invention improves luminance and straightness of emitted light and is suitable for realizing screen division driving.

However, in the comparative examples deviating from the parameters of the present invention, it was confirmed that the linearity and the average luminance characteristic were remarkably lowered compared with the embodiments.

100: light guide plate
130: upper round prism pattern
200: Light source
300: reflective sheet

Claims (9)

A prism pattern having a top end vertex portion in the form of a arc is included on the upper surface,
Wherein the prism pattern satisfies the following formula (1): < EMI ID = 1.0 &gt;
[Equation 1]
^{0.350 (㎛ / Radian 2) <} {H / Radian (A)) * (Radian (B))} / (n * 100) <1.400 (㎛ / Radian 2)
(Where H (占 퐉) is the height of the vertical section of the prism,
A (°) is the angle between the base of the vertical section of the prism and the hypotenuse,
B (?) Is an angle formed by the connecting line connecting the center of the base at the point where the upper arc of the vertical section of the prism starts,
and n is the refractive index of the material forming the prism pattern).
The light guide plate according to claim 1, wherein the H is 20 to 50 탆.
The light guide plate according to claim 1, wherein the angle A is 25 DEG to 50 DEG.
2. The light guide plate according to claim 1, wherein B is 10 DEG to 75 DEG.
The light guide plate according to claim 1, wherein the prism pattern comprises at least one selected from the group consisting of a (meth) acrylic resin, a carbonate resin, a styrene resin, an olefin resin, an ester resin and a copolymer thereof.
The light guide plate according to claim 1, comprising a light scattering pattern on the bottom surface.
The light guide plate according to claim 6, wherein the light scattering pattern is an engraved or embossed pattern.
A backlight unit comprising a light guide plate according to any one of claims 1 to 7.
An image display apparatus comprising a backlight unit according to claim 8.

Images