KR20200021020A - Backlight unit to be able control viewing angle and block-dimming - Google Patents

Abstract

Disclosed is a backlight unit capable of controlling block-dimming and a viewing angle. The backlight unit comprises: a light guide plate including a lenticular pattern arranged on a first surface and a symmetrical first prism pattern arranged on a second surface opposite to the first surface; first and second light sources individually disposed on first and second sides of the light guide plate to oppose each other; a reflective sheet disposed opposite to the second surface of the light guide plate; an inverted prism sheet disposed opposite to the first surface of the light guide plate and including an asymmetrical second prism pattern arranged on a surface opposite to the first surface; and a buffer sheet disposed between the first surface and the second prism pattern.

Description

BACKLIGHT UNIT TO BE ABLE CONTROL VIEWING ANGLE AND BLOCK-DIMMING}

The present invention relates to a backlight device, and more particularly, to a backlight device capable of block dimming control and a viewing angle control for providing a viewing angle in which the angle of emitted light is shifted upward.

Display devices are widely used in devices such as TVs, smartphones, laptops, and tablets, and include liquid crystal displays (LCDs), organic light-emitting displays (OLEDs), and plasma displays (PDPs); Various kinds such as Plasma Display Panel) are used.

Here, the liquid crystal display (hereinafter, referred to as 'LCD') does not emit light in itself, unlike other display devices, and requires an external light source to realize an image. Therefore, the LCD further includes a surface light source device as a light source in addition to the liquid crystal panel, and the surface light source device uniformly supplies a high brightness light source to the liquid crystal panel, thereby realizing high quality images.

As described above, the surface light source device refers to a backlight unit provided on the rear surface of the liquid crystal panel in order to realize an image of a display device such as an LCD. As a light source of the surface light source device, a light emitting diode (LED) is mainly used. The LED may be a direct lighting type or a side lighting type depending on the position of the LED light source. It is divided into surface light source device.

The direct method is an LED light source disposed below the diffuser plate to illuminate the liquid crystal panel directly through the diffuser plate. The side method is an LED light source disposed at the light guide plate side to indirectly shine through the light guide plate and the optical sheet. It's a way of lighting.

In the side surface type light source device, a plurality of LED light sources are disposed on the side of the light guide plate, and the light emitted from the LED light source is converted into a surface light source in the process of repeating total reflection inside the light guide plate and is emitted to the upper light emitting surface. At this time, the light emitted to the light emitting surface is evenly distributed on the entire surface of the effective light emitting area of the light guide plate. This side surface type light source device is advantageous in thinning because the LED light source is disposed on the light guide plate side, and has the advantage that the light to be uniformly emitted to the light emitting surface.

As described above, the side surface type light source device exhibits excellent light uniformity due to scattering and total reflection of light from an LED light source, but has a low contrast ratio (CR) with a relatively adjacent region. .

In particular, recently, display devices are applied to various kinds of display devices in addition to TVs or smartphones. For example, LCDs are also applied to instrument panels or car navigation systems to provide high quality images. Such a display device controls brightness by local dimming to display information such as fuel information, speed information, and driving information in a specific area. At this time, the image or luminance control for a specific region is generally made by local dimming through the liquid crystal cell array of the liquid crystal panel, but the implementation of local dimming through the liquid crystal cell array has a limitation in contrast ratio. Therefore, in recent years, local dimming of a specific position is performed by using individual on / off control of the LED light source for the corresponding region along with the liquid crystal cell arrangement.

However, the surface light source device of the side-type according to the prior art is focused on the performance of the light guide plate for controlling the light characteristics mainly on the performance of light uniformity, so that when the LED light source is individually emitted, As the light proceeds to show a very low contrast ratio, it is hardly applied to a display device for local dimming.

Korean Patent Application No. 10-2013-0160597

Accordingly, an object of the present invention is to provide a clear block dimming and to provide a viewing angle in which the angle of emitted light is shifted upward, thereby preventing diffuse reflection on the windshield of the vehicle to prevent the driver from driving the vehicle. The present invention provides a backlight device capable of providing block dimming and viewing angle control to provide a viewing angle for safe vehicle operation.

According to an embodiment of the present invention, a backlight device capable of controlling block dimming and viewing angle may include a lenticular pattern arranged on a first surface, and a symmetric first prism pattern arranged on a second surface opposite to the first surface. Light guide plate comprising a; First and second light sources disposed to face the first and second side surfaces of the light guide plate, respectively; A reflection sheet disposed to face the second surface of the light guide plate; An inverse prism sheet disposed opposite the first surface of the light guide plate and including an asymmetric second prism pattern arranged on the surface opposite to the first surface; And a buffer sheet disposed between the first surface and the second prism pattern.

In one embodiment, the light guide plate may have a wedge shape in which the second surface is concave inward from the edge of the second surface toward the center portion.

In one embodiment, the thinnest part of the light guide plate may have a thickness of 25% to 50% of a thickness of a light incident surface on which light is incident from the light source.

In one embodiment, the second prism pattern is a triangular-prism pattern having a triangular cross-sectional shape,

In one embodiment, the vertex angle of the triangular-shaped prism pattern of the triangular prism is 58 ° ± 4 °, the angle of any one of the remaining two interior angle is 59 ° ± 4 °, the other angle is 63 ° ± 4 ° Can be.

In one embodiment, the reflective sheet may have a specular reflectance of 98% or more.

In an exemplary embodiment, the reverse prism sheet may have a peak angle of 6 ° ± 4 ° and a half angle of −10 ° ± 4 °, 20 ° ± of a vertical viewing angle of light emitted from the reverse prism sheet. It may have an optical characteristic of 4 °.

According to the backlight device capable of controlling the block dimming and viewing angle according to the present invention, the driving angle of the vehicle is prevented from being diffusely reflected on the windshield of the vehicle by providing a viewing angle in which the angle of emitted light is shifted upward. There is an advantage that can provide a viewing angle that allows safe vehicle operation.

1 is a cross-sectional view illustrating a backlight device capable of controlling block dimming and viewing angle according to an embodiment of the present invention.
2 is a cross-sectional view showing a state of a backlight device of a comparative example compared to an experimental example of a backlight device capable of block dimming and viewing angle control according to an embodiment of the present invention.
3 shows the results of an experiment for confirming luminance distribution characteristics in the up and down direction and the left and right directions by setting the angle of the second prism pattern of the inverse prism sheet.

Hereinafter, a backlight device capable of controlling block dimming and viewing angle according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific form disclosed, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements. In the accompanying drawings, the dimensions of the structures are shown in an enlarged scale than actual for clarity of the invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described on the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

1 is a cross-sectional view illustrating a backlight device capable of controlling block dimming and viewing angle according to an embodiment of the present invention.

Referring to FIG. 1, a backlight device capable of controlling block dimming and viewing angle according to an embodiment of the present invention includes a light guide plate 110, a first light source 121 and a second light source 122, a reflective sheet 130, and an inverse The prism sheet 140 and the buffer sheet 150 are included.

The light guide plate 110 emits light emitted from the first light source 121 and the second light source 122 toward the reverse prism sheet 140. The light guide plate 110 includes light incident surfaces 110a and 110b facing the first light source 121 and the second light source 122 to receive light, and include a lenticular pattern 111 and a first prism pattern ( 112). The lenticular pattern 111 may be arranged on the first surface of the light guide plate 110. For example, the lenticular pattern 111 may have a semi-circular cross-sectional shape. The first prism pattern 112 may be arranged on the second surface of the light guide plate 110. For example, the first prism pattern 112 may be a triangular-prism pattern having a triangular cross-sectional shape. The first surface may be a light emitting surface, and the second surface may be a reflective surface, and the first surface of the light guide plate 110 may form a plurality of virtual blocks in a vertical direction and a left and right direction.

In addition, the light guide plate 110 has a lenticular pattern arranged on the first surface for block dimming, and a wedge in which the second surface is concave inward from the edge of the second surface toward the center thereof. It may be provided in a shape. The thinnest portion of the light guide plate 110, that is, the central portion having the minimum thickness, has a thickness of 25% to 50% of the thickness of the light incident surface of the light guide plate 110. The thickness of the thinnest part prevents light from propagating to the neighboring upper or lower blocks with respect to the light incident from the light incident surface and traveling in the vertical direction.

The first light source 121 and the second light source 122 are disposed to face the first side and the second side of the light guide plate 110, respectively. In this case, two side surfaces facing the first light source 121 and the second light source 122 become the light guide plate 110. Although not shown, the first light source 121 and the second light source 122 are in the form of an array in which a plurality of LEDs (LEDs) are arranged. As illustrated in the drawing, the first light source 121 is a light source facing the light incident surface 110a below the light guide plate 110, and the second light source 122 is opposed to the light incident surface 110b above the light guide plate 110. It may be a light source.

The reflective sheet 130 is disposed to face the second surface of the light guide plate 110 to reflect light leaking to the second surface of the light guide plate 110 to the first surface to enhance the light efficiency.

The reverse prism sheet 140 includes an asymmetric second prism pattern 141 disposed to face the first surface of the light guide plate 110 and arranged on the surface opposite to the first surface.

The second prism pattern 141 is a triangular-prism pattern having a triangular cross-sectional shape. Here, the vertex angle of the triangular shape of the second prism pattern 141 is 58 ° ± 4 °, one of the remaining two inner angle is 59 ° ± 4 °, the other angle is 63 ° ± 4 ± . Preferably, the triangular vertex a of the second prism pattern 141 is 58 ° ± 4 °, and is in the direction of the first light source 121 facing the light incident surface 110a on the lower side of the light guide plate 110. The angle b of the surface is 63 ° ± 4 °, and the angle c of the surface in the direction of the second light source 122 facing the light incident surface 110b on the upper side of the light guide plate 110 is 59 ° ± 4 °. .

In addition, the reverse prism sheet 140 has a peak angle of 6 ° ± 4 °, and a half angle of −10 ° ± 4 °, and 20 ° of the vertical viewing angle of the light emitted from the reverse prism sheet 140. Has optical properties of ± 4 ±. This may be achieved by setting the vertex angle of the triangular shape of the second prism pattern 141 and the angle of each inner angle.

The buffer sheet 150 is disposed between the first surface of the light guide plate 110 and the second prism pattern 141 of the inverse prism sheet 140, and scratches of the lenticular pattern 111 and the second prism pattern 141 are provided. To prevent.

Hereinafter, up and down direction and left and right direction by the vertical direction luminance distribution characteristic by the wedge structure of the light guide plate of the backlight device capable of block dimming and viewing angle control and the angle setting of the second prism pattern of the inverse prism sheet The luminance distribution characteristic of the will be described.

Vertical luminance distribution characteristics according to wedge shape of light guide plate

2 is a cross-sectional view showing a state of a backlight device of a comparative example compared to an experimental example of a backlight device capable of block dimming and viewing angle control according to an embodiment of the present invention.

As shown in FIG. 2, the backlight device of Comparative Example is provided with a flat light guide plate 10, and the backlight device of Experimental Example 1 has a thickness of the thinnest portion of the wedge-shaped light guide plate 110. It is assumed that the thickness of 110b) is 50%, and in the backlight device of Experimental Example 2, the thickness of the thinnest part of the wedge-shaped light guide plate 110 is set to 25% of the thickness of the light receiving surfaces 110a and 110b, respectively. The LEDs were turned on toward the control target block located at the center of the light guide plate of to measure the luminance distribution of each of Comparative Example, Experimental Example 1 and Experimental Example 2.

division Comparative example (LGP thickness ㅧ 100%) Experimental Example 1 (LGP thickness ㅧ 50%) Experimental Example 2 (LGP thickness: 25%) Luminance Distribution Data

Luminance 3180 nit 3298 nit (3.7% increase) 3420 nit (7.5% increase)

As shown in Table 1, in the comparative example, the luminance of the control target block was 3180 nit, and in Experimental Example 1, the luminance of the control target block was 3298 nit, which was increased by 3.7% compared to the comparative example. In this case, the luminance of the control block represents 3420 nit, indicating that the luminance increased by 7.5% compared to the comparative example.

Therefore, the thinner the thickness of the thinnest portion in the wedge shape of the light guide plate 110 of the backlight device capable of block dimming and viewing angle control according to an embodiment of the present invention increases the brightness of the control target block, the block around the control target That is, the light is blocked toward the peripheral blocks in the up and down direction and the left and right direction, so that a clear block dimming can be achieved.

Luminance distribution characteristics in the vertical direction and the left and right directions by setting the angle of the second prism pattern of the inverse prism sheet

The intensity map of the up-down direction and the left-right direction by setting the angle of the second prism pattern of the inverted prism sheet was used as an intensity map. For example, the A + area (Fig. Minimum sized rectangular area in Zone luminance distribution data of 3), area A (medium sized rectangular area in Zone luminance distribution data of FIG. 3), area B (maximum sized rectangle in Zone luminance distribution data of FIG. Area), and the luminance distribution in the vertical and horizontal directions in each region was measured.

In the present experiment, the comparative example was equipped with a flat light guide plate of the backlight device shown in Figure 2 and measured the luminance distribution in the A + area, A area, B area, Experimental Example 1 to Experimental Example 3 is FIG. The luminance distributions of the A + region, the A region, and the B region according to each angle setting were measured while varying the angles of the two inner angles except for the vertex angle of the second prism pattern 141 of the inverse prism sheet 140 shown in FIG.

Specifically, the left angle of the second prism pattern of Experimental Example 1 was set to 63 ° and the right angle of the second prism pattern was set to 58 °, and the left angle of the second prism pattern of Experimental Example 2 was 63 °. The angle of light was set to be 59 °, and the angle of light was set to 59 °, the left angle of the second prism pattern of Experimental Example 3 was set to 64 °, and the angle of light was set to 59 °. Here, the left angle means an angle b opposite to the light incident surface 110a on the lower side of the light guide plate 110 shown in FIG. 2, and the light angle is a light incident surface on the upper side of the light guide plate 110 shown in FIG. 2. An angle c opposite to 110 b is meant.

The results of the experiment for confirming the luminance distribution characteristic in the up-down direction and the left-right direction by setting the angle of the second prism pattern of the inverted prism sheet are shown in FIG. 3.

Referring to FIG. 3, in the case of A + region, Experimental Example 2 showed the highest value, and in case of A region and B region, Experimental Example 2 also showed the most stable value without diffuse reflection in the left and right directions. . In addition, in Experimental Example 2, the viewing angle in the vertical direction was controlled to be in the range of 10% of the luminance standard of the A + region.

According to the experimental results, in the backlight device capable of controlling block dimming and viewing angle according to an embodiment of the present invention, the vertex angle a of the triangular shape of the second prism pattern 141 is 58 ° ± 4 °, and the light guide plate 110 is used. The angle b of the surface in the direction of the first light source 121 opposite to the light incident surface 110a below the () is 63 ° ± 4 °, and is the agent facing the light incident surface 110b above the light guide plate 110. 2 The angle c of the surface in the direction of the light source 122 is an optical characteristic in which the viewing angle of the light finally emitted from the inverse prism sheet 140 is emitted at 6 ° ± 4 ° according to a setting range of 59 ° ± 4 °. As a result, the angle of emitted light can be shifted upward to provide a viewing angle, thereby preventing diffuse reflection on the windshield of the vehicle on the vehicle display, thereby providing a viewing angle that enables the vehicle to be safely driven when the vehicle is driven. can do.

The description of the presented embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention should not be limited to the embodiments set forth herein but should be construed in the broadest scope consistent with the principles and novel features set forth herein.

Claims (6)

A light guide plate including a lenticular pattern arranged on a first surface, and a symmetric first prism pattern arranged on a second surface opposite to the first surface;
First and second light sources disposed to face the first and second side surfaces of the light guide plate, respectively;
A reflection sheet disposed to face the second surface of the light guide plate;
An inverse prism sheet disposed opposite the first surface of the light guide plate and including an asymmetric second prism pattern arranged on the surface opposite the first surface; And
And a buffer sheet disposed between the first surface and the second prism pattern.
Backlight device with block dimming and viewing angle control. The method of claim 1,
The light guide plate is characterized in that the second surface is provided in a wedge (Wedge) shape concave inwards toward the center from the edge of the second surface,
Backlight device with block dimming and viewing angle control. The method of claim 2,
The thinnest part of the light guide plate is characterized in that the thickness of 25% to 50% of the thickness of the light incident surface incident light from the light source,
Backlight device with block dimming and viewing angle control. The method of claim 2,
The second prism pattern is a triangular-prism pattern having a triangular cross-sectional shape,
The vertex angle of the triangular-prism pattern of the triangular shape is 58 ° ± 4 °, one of the remaining two inner angle is 59 ° ± 4 °, the other one is characterized in that 63 ° ± 4 ° ,
Backlight device with block dimming and viewing angle control. The method of claim 2,
The reflective sheet is characterized in that the specular reflectance of 98% or more,
Backlight device with block dimming and viewing angle control. The method of claim 4, wherein
The inverted prism sheet has a peak angle of 6 ° ± 4 °, a half angle of -10 ° ± 4 °, and a 20 ° ± 4 ° optical angle at a vertical viewing angle of light emitted from the inverse prism sheet. Characterized in that having,
Backlight device with block dimming and viewing angle control.

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