KR20120057807A - Light Guiding Plate for Surface Light Source Device and Back Light Unit using the Same - Google Patents

Abstract

PURPOSE: A light guiding plate for a surface light source device and a backlight unit using the same are provided to simplify manufacturing process and to make a slim module of a liquid crystal display device by reducing the use of optical sheets laminated on the light guiding plate. CONSTITUTION: A light guiding plate for a surface light source device(100) comprises an incidence surface(120), an emitting surface(130), and a rear surface(140). The incidence surface gets light from lamps(110) along a constant axis. The emitting surface emits the incident light. The rear surface faces the emitting surface. Multiple unit cells(160) printed micro prism patterns are dispersedly arranged in the rear surface. In one or more unit prisms among the micro prism patterns, the cross section vertical to a ridge direction is asymmetry triangle.

Description

  Light Guiding Plate for Surface Light Source Device and Back Light Unit using the Same}

  The present invention relates to a light guide plate for a surface light source device and a backlight unit using the same, and more particularly, a plurality of unit cells engraved with a micro prism pattern are disposed on a rear surface of an emission surface, and at least one of the unit prisms of the micro prism pattern is disposed. A light guide plate for a surface light source device and a backlight unit using the same, characterized in that the cross section perpendicular to the ridge direction is an asymmetric triangle.

  A light guide plate is generally applied to a liquid crystal display and used as a means for applying light to an LCD module which is a passive element. That is, light is guided and diffused from the light source disposed at the side or the bottom of the light guide plate, for example, the LED lamp, and applied to the LCD module stacked on the surface side.

  In addition, by forming a backlight by stacking a diffusion sheet, a prism sheet, or the like on the surface side of the light guide plate from which the light is emitted, the luminance amount and the viewing angle of the light are controlled.

  However, in recent years, efforts have been made to reduce the number of components and thus simplify the structure or reduce the cost by implementing various components added to the light guide plate in the light guide plate itself.

  For example, Patent Literature 1 discloses a light guide plate having a diffuse reflection portion composed of fine unevenness on either the lower surface or the surface of the light guide plate, and having a reflecting plate for controlling the amount of diffuse reflection such as a transparent ink. According to such a configuration, a light guide plate having good diffuse reflection efficiency and brightness can be manufactured simply and quickly. However, the proposal only mentions controlling the amount of light through diffuse reflection and attachments. In addition, a manufacturing method using a pattern of intaglio engraving on the back of the light guide plate is generally utilized, which has a small increase in brightness compared to a light guide plate of a printing method, but still requires a large amount of optical sheets. There is a problem of cost increase.

  In order to solve such a problem, there has been an attempt to develop a technology for dramatically increasing luminance by controlling an optical path through pattern molding of a prism structure or the like on the light guide plate. For example, Patent Literature 2 discloses a light guide plate provided with a triangular prism-shaped reflecting portion on the rear surface of a rear light emitting surface. However, in this technique, the triangular prism-shaped back reflecting surface has a characteristic of exhibiting non-uniform optical distribution with excellent luminance but insufficient luminance uniformity because it reflects in a specific direction with a limited amount. There is a problem that moiré phenomenon caused by the combination of prism shapes occurs when using a citro prism.

  In addition, while using the LED lamp as a light source, the problem of brightness uniformity due to the formation of the dark portion between the LED lamp and the lamp, and the problem of moiré generation by the combination of the prism structure on the back of the light guide plate and the prism sheet used as the optical sheet continues. have.

  Accordingly, the present inventors have confirmed that when the prism pattern formed on the rear surface of the light emitting plate or the micro prism pattern formed on the unit cell on the rear surface is formed as an asymmetrical triangle, the moire phenomenon can be suppressed by improving the front luminance distribution. The invention has been completed.

Japanese Patent Laid-Open No. Hei 6-118247 Republic of Korea Patent No. 692203

  An object of the present invention is to provide a light guide plate for a surface light source device that not only has high front luminance but also excellent uniformity of luminance.

  Another object of the present invention is to provide a backlight unit using the light guide plate for the surface light source device.

  A light guide plate for a surface light source device according to an embodiment of the present invention for achieving the above object is an incident surface to which light is incident from a lamp disposed along a predetermined axis, an emitting surface to which the incident light is emitted, and facing the emitting surface. A light guide plate including a rear surface, wherein a plurality of unit cells in which a micro prism pattern is engraved is disposed on the rear surface, and a cross section in which at least one of the unit prisms of the micro prism pattern is perpendicular to the ridge direction is an asymmetric triangle. .

  Preferably, the first angle θ1 formed by the vertical line passing through the vertex of the asymmetric triangle and the light reflection surface is larger than the second angle θ2 formed by the opposite surface of the vertical line and the light reflection surface.

  The first angle θ1 is 35 to 50 °; It is preferable that 2nd angle (theta) 2 is 0-40 degrees.

  The sum of the first angle and the second angle is preferably 38 to 90 degrees.

  The longest diameter of the unit cell is preferably 50 ~ 1000um.

  It is preferable that the pitch of the said micro prism is 5-100um.

  According to another aspect of the present invention, a light guide plate for a surface light source device includes a light incident plate on which a light is incident from a lamp disposed along a predetermined axis, an emission surface on which the incident light is emitted, and a back surface facing the emission surface. A plurality of unit cells engraved with a micro-prism pattern are disposed on the rear surface; At least one of the unit prisms of the micro-prism pattern is asymmetrical in cross section perpendicular to the ridge direction; A lenticular pattern is formed on the exit surface.

  The ridgeline direction of the lenticular pattern is preferably parallel to the incident direction of light.

  The pitch of the lenticular pattern is preferably 50 ~ 300um.

  The backlight unit of the present invention includes the light guide plate; A lamp provided on one side of an incident surface of the light guide plate; And a protective film having a diffusion function stacked on an exit surface of the light guide plate.

  The light guide plate for the surface light source device of the present invention not only has high front luminance in the backlight of the uniaxial LED light source but also has excellent uniformity of luminance. Therefore, when it is used in the backlight unit, it is possible to reduce the use of the optical sheet laminated on the light guide plate, thereby making it possible to slim down the liquid crystal display module and simplify the manufacturing process and lower the manufacturing cost.

1 is a perspective view of a light guide plate 100 for a surface light source device according to an embodiment of the present invention.
Figure 2 is a partially enlarged view of the rear surface 140 of the light guide plate for the surface light source device according to an embodiment of the present invention.
3 is a schematic diagram of a unit prism of a micro prism pattern formed on the unit cell 160 of the light guide plate 100.
4A to 4D are schematic views showing the shape of the unit cell 160 formed on the rear surface 140 of the light guide plate for the surface light source device according to the embodiment of the present invention.
5 is a perspective view of a light guide plate 200 for a surface light source device according to a second embodiment of the present invention.
6A-6D illustrate a pattern that may be formed on an exit surface in another embodiment of the present invention.

  Hereinafter, a light guide plate for a surface light source device according to an embodiment of the present invention will be described with reference to the drawings. 1 is a perspective view of a light guide plate 100 for a surface light source device according to an embodiment of the present invention. In FIG. 1, the light guide plate 100 for a surface light source device of the present invention includes an incident surface 120 through which light is incident from a lamp 110 disposed along a predetermined axis, an exit surface 130 through which the incident light is emitted, and the In the light guide plate including a rear surface 140 facing the exit surface, the plurality of unit cells 160 in which the micro-prism pattern 150 is engraved is disposed on the rear surface 140.

  The light guide plate 100 starts the path of the light toward the exit surface 130 through the action of reflection, refraction, diffraction, etc., starting from the lamp 110 and entering the light guide plate 100 through the entrance surface 120. As a function of changing the material, a polymer material having a high visible light transmittance, high strength, and low deformation and breakage is used. Examples of the polymer used for this purpose include acrylic resins, polycarbonates, and cyclic olefin copolymers, among which acrylic resins are preferred, and polymethyl methacrylate is particularly preferred.

  The lamp 110 functions as a light source. Not only a linear light source but also a lamp in which point light sources are linearly arranged may be used.

  The plurality of unit cells 160 having the micro prism pattern 150 engraved therein are disposed on the rear surface 140 of the light guide plate 100. FIG. 2 is a partially enlarged view showing only a few unit cells 160 engraved with the prism pattern 150 formed on the rear surface 140. In the unit cell 160 illustrated in FIG. 2, the unit cell 160 is engraved on the rear surface 140 in an engraved manner, but the unit cell 160 is not necessarily limited thereto and may be engraved on the back surface 140. In addition, the bottom surface of the micro prism pattern 150 on the unit cell 160 may be the same surface as the rear surface 140. In this case, the shape of the unit cell 160 is provided only by the shape of the micro-prism pattern 150.

  3 is a schematic diagram of a unit prism of a micro prism pattern formed on the unit cell 160 of the light guide plate 100. In FIG. 3, at least one of the unit prisms of the micro-prism pattern 150 is asymmetrical in cross section perpendicular to the ridge direction. In this case, the second angle formed by the opposite surface 152 of the vertical line aa` and the first angle θ1 formed by the vertical line aa` passing through the asymmetric triangle and the light reflection surface 151 is formed. It is preferable that it is larger than (θ2). Here, the light reflection surface refers to a surface close to the light source provided on the side surface of the light guide plate of both surfaces of the triangular prism.

  Specifically, the first angle θ1 is 35 to 50 °; It is preferable that 2nd angle (theta) 2 is 0-40 degrees. If the first angle is out of the range, the output angle is emitted in a direction other than the front, thereby reducing the brightness enhancement effect. If the second angle is out of the range, the light utilization efficiency of the one-side LED lamp applied backlight is reduced.

  On the other hand, the sum of the first angle and the second angle, that is, the vertex angle of the triangular prism is preferably 38 to 90 degrees, more preferably 40 to 50 degrees. When the vertex angle is less than 38 ° or more than 90 °, the emission angle control effect is lost, and light loss occurs due to side lobe phenomenon, thereby eliminating the luminance increase effect.

  It is preferable that the unit prism pitch of the said micro prism is 5-100um. If the pitch is less than 5um, the brightness increase effect by the prism is sharply lowered, and if the pitch is more than 100um, the size of the unit cell including the prism pattern is significantly increased, thereby significantly limiting the luminance uniformity control.

4 is a schematic diagram showing the shape of the unit cell 160 in which the micro-prism pattern 150 is formed. That is, the unit cell 160 may be circular (Fig. 4a), elliptical (4b), square (4c) or hexagonal (4d), and is not necessarily limited to the illustrated form, for example, Of course, it is possible to modify any number of rectangles, diamonds, or a combination thereof. In the case where the shape of the unit cell 160 is circular, the diameter of the unit cell 160 is preferably 50 μm to 1000 μm. If the longest diameter of the unit cell does not reach 50um, the prism length is too short to make the prism itself , and if it exceeds 1000um, it is impossible to uniformly control the brightness between the LED lamp and the LED lamp. In other words, the uniformity control of the luminance between the lamp and the lamp is also achieved through the adjustment of the distribution of the unit cell, because the unit cell exceeding 1000um is limited to the distribution adjustment. On the other hand, when the shape of the unit cell is elliptical, the long axis and / or short axis thereof are polygonal, and the length of one side may be within the above range.

The distribution of the unit cells formed on the rear surface 140 may be adjusted by adjusting the density of the unit cells 160 having the same diameter. That is, the density of the unit cell 160 decreases closer to the side on which light is incident, and may be configured to have a distribution having a gradient that increases as far away. In addition, the distribution of the unit cells may be adjusted by changing the size of the unit cell 160. That is, the unit cell 160 may be configured to have a distribution having a gradient that is smaller as the size of the unit cell 160 is closer to the side on which light is incident, and becomes larger as it is farther.

  5 is a perspective view of a light guide plate 200 for a surface light source device according to another embodiment of the present invention. The light guide plate 200 for a surface light source device according to the second embodiment of the present invention includes an incident surface 220 through which light is incident from a lamp 210 disposed along a predetermined axis, and an exit surface 230 through which the incident light is emitted. And a rear surface 240 facing the exit surface 230, wherein a plurality of unit cells 260 having a micro prism pattern 250 engraved therein are distributedly disposed on the rear surface; At least one of the unit prisms of the micro-prism pattern is asymmetrical in cross section perpendicular to the ridge direction; A lenticular pattern is formed on the exit surface.

  The pattern 270 disposed on the exit surface is a structure that controls the path of the light emitted from the inside of the light guide plate at the outermost angle and condenses by the lens shape of the surface layer. The emission angle of the light reflected from the rear surface 240 is controlled by the pattern 270 to adjust the light distribution having excellent visibility and vertical luminance.

  Figure 6 illustrates a pattern that may be formed on the exit surface in the second embodiment of the present invention. In FIG. 5, the pattern formed on the exit surface is a lenticular pattern of a semi-circular cross section as shown in FIG. 6A. In addition, the exit surface of the light guide plate 200 according to the third embodiment of the present invention has a hypotenuse and a vertical line passing through a vertex. The hypotenuses may be parabolic lenses (Fig. 6b) each having a curvature, a round prism lens pattern (Fig. 6c) having a vertex angle of the prism, and an independent hemispherical lens array (Fig. 6d).

  In the second embodiment of the present invention, when the pattern 270 formed on the exit surface is a lenticular pattern, a parabolic lens pattern or a round prism lens pattern, the direction formed by the ridge line of the pattern is parallel to the light incident from the lamp 210. (Or perpendicular to the arrangement of the lamps).

  When the pattern 270 is a lenticular pattern, a parabolic lens pattern, and a round prism lens pattern, the pitch of the pattern is preferably 50 to 300 um. If the pitch is less than 50 um, the outermost specific surface area for producing the lens function is reduced, and the brightness enhancement function is reduced. If the pitch is more than 300 um, the image quality is deteriorated due to moiré generation with the liquid crystal device.

On the other hand, in the second embodiment of the present invention, the configuration other than the pattern of the exit surface described above, for example, the back unit cell, the prism pattern formed in the unit cell, and the like are the same as described in the first embodiment.

The light guide plate for a surface light source device according to the present invention is used as a backlight unit including a protective film having a light source installed on one side of an incident surface of the light guide plate and having a diffusion function stacked on an exit surface of the light guide plate.

The light guide plate according to each embodiment of the present invention can be produced using an injection method. In this case, a light guide plate is produced by processing each pattern of the back surface and the exit surface in the injection mold, and injecting the polymer material into the mold. In another manufacturing method, a plate serving as a base material of the light guide plate may be prepared, and the plate may be manufactured through pattern processing on the plate. The method of processing the pattern on the plate may be a stamping method by pressing, heating, an imprint method using a UV resin and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples. This is for explaining the present invention more specifically, but the scope of the present invention is not limited to these Examples.

Example 1

1. Manufacturing of light guide plate

  PMMA was used as a raw material to produce a PMMA plate of 3.5mm thickness, 20cm in width, 10cm in length. The PMMA plate utilized an extrusion method, and the extruder used a conventional single screw extruder.

The upper surface of the plate is formed with a lenticular pattern, the lenticular pattern 11 was produced in the shape of pitch 200um, height 40um.

2. Mold manufacturing for pattern processing

A mold disc of copper thickness 30um was produced by copper plating coating on cold alloy steel ball (SKD-11) core mold. The die disk is machined with a diamond bite and the circular unit cell diameter is 100um, the second angle of the unit prism of the micro prism pattern is 40 °, the second angle is 0 °, the sum of the first angle and the second angle (vertical angle) It was set to 40 degrees, and the pattern which consists of unit cells of unit prism pitch 30um was processed. The distribution of unit cells was arranged by adjusting the density at the same diameter. That is, the density of the unit cell decreases as the light source is incident to the light source, and is composed of a distribution having a gradient increasing as far as possible. The unit cell density on the light source side unit area was 10%, the unit cell density per unit area at the center was 70%, and a gradient was given every 0.2 cm distance from the light source side to the center.

3. Cell molding and light guide plate production

In order to form a cell pattern on the lower surface side of the prepared plate, a pre-prepared pattern mold was mounted on a press molding equipment, and press molded at a molding temperature of 200 ° C., a press time of 1 minute, and a press pressure of 10 kg / m ² to prepare a light guide plate.

<Example 2>

A light guide plate was manufactured in the same manner as in Example 1 except that there was no lenticular pattern on the exit surface.

Comparative Example 1

A light guide plate was manufactured in the same manner as in Example 1, except that a unit cell was formed with a triangular prism pitch of 150 μm.

Comparative Example 2

As a light guide plate for LED backlight units, a commercial light guide plate produced by laser processing is formed with a negative circular dome-shaped dot pattern on the bottom surface, and no additional pattern is formed inside the dot pattern, and no pattern is formed on the exit surface. Light guide plate was compared

&Lt; Comparative Example 3 &

In fabricating the micro-prism pattern during fabrication of the die for pattern processing, the light guide plate was manufactured in the same manner as in Example 1 except that the first angle was 47.5 °, the second angle was 47.5 °, and the vertex angle was 95 °.

<Evaluation>

1. Front luminance measurement

  Measuring equipment: Topcon BM-7

  Measuring method: The light guide plate was mounted on a backlight equipped with a 32-inch LED lamp, and the 32-inch area was divided into nine equal parts, and the luminance of each center portion was measured. The luminance was measured by arithmetic average of nine points.

2. Uniformity Measurement

  Measuring equipment: Topcon BM-7

Measuring method: The 32-inch LED lamp was mounted on the backlight, and the 32-inch area was divided into 30 pieces. The luminance of each center part was measured, and the uniformity was calculated by calculating the ratio of the minimum value to the maximum value.

  The evaluation results for the above Examples and Comparative Examples are summarized in Table 1 below.

division Prism angle
(°) Exit surface
Lenticular Prism pitch
(um) Luminance
(cd / cm ² ) Uniformity
(%) Example 1 40 U 30 3250 83 Example 2 40 radish 30 3000 67 Comparative Example 1 40 U 150 2700 80 Comparative Example 2 - radish - 2120 73 Comparative Example 3 95 U 30 2730 79

  As a result of Example 1 and Comparative Example 2 in Table 1, when the dot prism is formed on the lower surface, it is confirmed that the synergistic effect of the remarkable luminance increase effect and the uniformity of the luminance is compared with the case of general laser etching. Can be.

  In addition, when Example 1 and Example 2 were compared, it was confirmed that by forming the upper surface lenticular pattern, the effect of increasing the luminance and the effect of increasing the luminance uniformity could be obtained simultaneously.

  In addition, when comparing Example 1 and Comparative Example 1, it was confirmed that the luminance is reduced when the prism pitch is outside the range (5 ~ 100um) specified above, and the luminance uniformity is also reduced by the side lobe phenomenon.

  On the other hand, when comparing Example 1 and Comparative Example 3, it was confirmed that a significant decrease in luminance occurs when the angle between the prism is out of the range (40 ~ 90 °) specified above.

  In conclusion, a plurality of unit cells are formed on the bottom surface of the light guide plate, and the unit cells have a pattern formed with an engraved pattern therein, and the pattern forms a prism having a triangular cross section in which opposite sides are not symmetrical. It is confirmed that the luminance is improved by effectively controlling the light generated in the light emitting diode, and the lenticular pattern is formed on the upper surface of the light guide plate to effectively control the bright lines generated inside the light guide plate to improve the uniformity of luminance and to obtain additional luminance enhancement effects.

The light guide plate for the surface light source device and the backlight unit including the same of the present invention can be used in LCD, and can be variously used for the purpose of light emission control in a device using an LED lamp.

100, 200 ... Light guide plate 110 ... Lamp
111 ... Lamp array axis 120 ... Incident plane
130 ... exit 140 ... rear
150 ... micro-prism pattern 151 ... first angle
152 ... second angle
160 ... unit cell 270 ... exit surface pattern

Claims (15)

In the light guide plate including an incident surface to which light is incident from a lamp disposed along a predetermined axis, an emitting surface to which the incident light is emitted, and a rear surface facing the emitting surface,
The back of the plurality of unit cells inscribed with a micro-prism pattern is arranged distributed,
A light guide plate for a surface light source device, characterized in that at least one of the unit prisms of the micro-prism pattern is an asymmetrical triangle in a cross section perpendicular to the ridge direction.   The method of claim 1, wherein the first angle θ1 formed by the vertical line passing through the vertex of the asymmetric triangle and the light reflection surface is larger than the second angle θ2 formed by the opposite surface of the vertical line and the light reflection surface. Light guide plate for surface light source device.   The method of claim 2, wherein the first angle θ1 is 35 to 50 °; The second angle θ2 is 0 to 40 °, the light guide plate for the surface light source device.   The light guide plate of claim 2, wherein the sum of the first angle and the second angle is 38 to 90 degrees.   The light guide plate of claim 1, wherein the longest diameter of the unit cell is 50 μm to 1000 μm.   The light guide plate of claim 1, wherein the microprism has a pitch of 5 to 100 um. In the light guide plate including an incident surface to which light is incident from a lamp disposed along a predetermined axis, an emitting surface to which the incident light is emitted, and a rear surface facing the emitting surface,
A plurality of unit cells in which a micro prism pattern is engraved is distributedly disposed on the rear surface;
At least one of the unit prisms of the micro-prism pattern is asymmetrical in cross section perpendicular to the ridge direction;
The lenticular pattern is formed on the exit surface; the light guide plate for a surface light source device.   The method of claim 7, wherein the first angle θ1 formed by the vertical line passing through the vertex of the asymmetric triangle and the light reflection surface is larger than the second angle θ2 formed by the opposite surface of the vertical line and the light reflection surface. Light guide plate for surface light source device.   The method of claim 8, wherein the first angle θ1 is 35 to 50 °; The second angle θ2 is 0 to 40 °, the light guide plate for the surface light source device.   9. The light guide plate according to claim 8, wherein the sum of the first angle and the second angle is 38 to 90 degrees.   The light guide plate of claim 7, wherein the longest diameter of the unit cell is 50 μm to 1000 μm.   The light guide plate of claim 7, wherein the microprism has a pitch of about 5 μm to about 100 μm.   The light guide plate of claim 7, wherein a ridge direction of the lenticular pattern is parallel to an incident direction of light.   The light guide plate according to claim 7, wherein the pitch of the lenticular pattern is 50 to 300 um.   The light guide plate according to any one of claims 1 to 14; A lamp provided on one side of an incident surface of the light guide plate; And a protective film having a diffusion function stacked on an exit surface of the light guide plate.

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