WO2018008938A1

WO2018008938A1 - Optical sheet, back light unit, and display device including same

Info

Publication number: WO2018008938A1
Application number: PCT/KR2017/007071
Authority: WO
Inventors: 이기욱; 이병훈; 임채리; 이민수
Original assignee: 주식회사 엘엠에스
Priority date: 2016-07-08
Filing date: 2017-07-04
Publication date: 2018-01-11
Also published as: KR20180006121A; KR101933141B1

Abstract

Disclosed are an optical sheet and a display device including the same, the optical sheet comprising a base layer, a first diffusion layer disposed on one side of the base layer, and a second diffusion layer disposed on the other side of the base layer, wherein the first diffusion layer or the second diffusion layer includes a light absorbent that absorbs light of a predetermined wavelength band.

Description

Optical sheet, backlight unit, and display device including the same

The present invention relates to an optical sheet for converting color coordinates of incident light.

Liquid crystal displays are display devices used in notebooks, personal computers, mobile terminals, TVs, and the like, and their characteristics are improved year by year as demand for liquid crystal displays increases.

A liquid crystal display device, which is a non-light emitting element, includes a back light unit as a light source. The backlight includes a light source and a plurality of optical sheets. The optical sheet collects or diffuses incident light to supply uniform light to the liquid crystal panel.

In general, the light provided by the backlight unit provides a relatively yellowish white light. However, since the white light has a low color temperature, the light efficiency is lowered, so there is a problem that an LED having a high color temperature must be used to compensate for the white light.

An object of the present invention is to provide an optical sheet capable of increasing the color temperature by converting the color coordinates of incident light.

The technical problem of the present invention is not limited to the above description, and will be more readily understood in the course of describing specific embodiments of the present invention.

Optical sheet according to an embodiment of the present invention, the base layer; A first diffusion layer disposed on one surface of the base layer; And a second diffusion layer disposed on the other surface of the base layer, wherein the first diffusion layer or the second diffusion layer includes a light absorbing agent that absorbs light of a predetermined wavelength band.

The optical sheet may convert color coordinates of incident light.

The y coordinate change amount Δy of the converted color coordinates may be -0.010 to -0.0030.

Luminance of the light emitted from the optical sheet may satisfy 96% to 100% based on 100% of the luminance of the light incident on the optical sheet.

The light absorbing agent may have an absorption peak in the wavelength range of 580nm to 650nm.

The light absorbing agent may be included in 0.0005wt% to 0.006wt%.

The light absorbing agent may be included in 0.0005wt% to 0.0015wt%.

A display device according to an embodiment of the present invention, the backlight unit having any one of the above-described optical sheet; And a display panel for generating an image using the light whose color coordinate is converted by the optical sheet.

According to the present invention, the color temperature can be increased by converting the color coordinates of the light provided by the backlight unit. Therefore, it is possible to use an LED grade with low brightness, thereby reducing the manufacturing cost.

Various and advantageous advantages and effects of the present invention are not limited to the above description, and will be more readily understood in the course of describing specific embodiments of the present invention.

1 is a conceptual diagram of a diffusion sheet according to an embodiment of the present invention,

2 is a view for explaining a state in which the color coordinates change by the diffusion sheet according to an embodiment of the present invention,

Figure 3 is a graph measuring the change in transmittance according to the content of the light absorber,

Figure 4 is a graph measuring the change in brightness and color coordinates according to the content of the light absorber,

5 is a conceptual diagram of a diffusion sheet according to another embodiment;

6 is a graph measuring luminance by varying the surface roughness of the upper diffusion layer and the lower diffusion layer of the diffusion sheet,

7 is a graph measuring luminance by controlling die concentrations of an upper diffusion layer and a lower diffusion layer of a diffusion sheet differently;

8 is a graph measuring luminance by controlling thicknesses of an upper diffusion layer and a lower diffusion layer of a diffusion sheet differently;

9 is a conceptual diagram of a display apparatus according to an exemplary embodiment.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated and described in the drawings. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers, such as second and first, may be used to describe various components, but the components are not 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 second component may be referred to as the first component, and similarly, the first component may also be referred to as the second component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

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, operation, component, part, or combination thereof described in 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, components, or a combination 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 are not construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted.

1 is a conceptual diagram of a diffusion sheet according to an embodiment of the present invention, Figure 2 is a view for explaining a state in which the color coordinates change by the diffusion sheet according to an embodiment of the present invention.

Referring to FIG. 1, the optical sheet 12 according to an embodiment of the present invention includes a base layer 121, a first diffusion layer 122 disposed on one surface of the base layer 121, and a base layer 121. It includes a second diffusion layer 123 disposed on the other side of the. The optical sheet 12 described in this embodiment may be a diffusion sheet.

The base layer 121 may be various kinds of polymer films. For example, the base layer 121 is a light transmissive polyethylene terephthalate film, a polycarbonate film, a polypropylene film. It may be any one of polyethylene films. The thickness of the base layer 121 may be 10 μm to 100 μm, but is not limited thereto.

The first diffusion layer 122 may be disposed on one surface of the base layer 121. The first diffusion layer 122 includes a first resin layer 122a and a light absorbing agent P dispersed in the first resin layer 122a. If necessary, it may further include particles for inducing diffusion (bead particles, etc.). The thickness of the first diffusion layer 122 may be about 5 μm to 10 μm, but is not limited thereto.

The first resin layer 122a may be prepared by applying a polymer resin to the base layer 121 and then curing it. The polymer resin is any one selected from acrylic resin, urethane resin, polyethylene resin, polypropylene resin, polystyrene resin, polyamide resin, and the like. The above may be, but is not limited thereto.

The first diffusion layer 122 may have a diffusion pattern having a shape for diffusing incident light, such as a lens pattern and a semi-circular pillar pattern. This diffusion pattern may be formed regularly or irregularly. There is no restriction on the shape of the diffusion pattern. Alternatively, the diffusion function may be provided using bead particles or the like without such a diffusion pattern.

The second diffusion layer 123 is disposed on the other surface of the base layer 121. The second diffusion layer 122 may include a second resin layer 123a and a light absorbing agent P. The structure of the second diffusion layer 123 may be the same as that of the first diffusion layer 122.

The first diffusion layer 122 or the second diffusion layer 123 includes a light absorbing agent (P). The light absorbing agent P absorbs light of a predetermined wavelength band. Light absorbing agent (P) may have an absorption peak in the wavelength range of 580nm to 650nm. The light absorbing agent P may be dispersed in any one or more layers of the first diffusion layer 122 or the second diffusion layer 123.

When the light absorbing agent P is dispersed in the first diffusion layer 122 and the second diffusion layer 123, the light absorption rate may be increased as compared with the case where the light absorbing agent P is dispersed in only one layer. The light absorbing agent P may be a die or a particle that absorbs light of a predetermined wavelength band.

Referring to FIG. 2, the color coordinates of light emitted from the optical sheet 12 according to the present invention (hereinafter referred to as light emitted by L2) may be different from the color coordinates of light incident to the optical sheet 12 (hereinafter referred to as light L1). have. By the conversion of the color coordinates, the color temperature of the outgoing light L2 may be higher than the incident light L1.

When the incident light L1 is a yellow light having a relatively yellow color, the color temperature may be relatively low. However, while passing through the optical sheet 12 according to an embodiment of the present invention light is absorbed in the wavelength range of 580nm to 650nm may change the color coordinates and increase the color temperature. That is, the emitted light L2 may be converted into relatively blue white light, thereby increasing the color temperature.

Figure 3 is a graph measuring the change in transmittance according to the content of the light absorber, Figure 4 is a graph measuring the change in luminance and color coordinates according to the content of the light absorber.

Referring to FIG. 3, when the optical sheet does not have a light absorbing agent (Base polymer), it can be seen that the transmittance of the entire visible light wavelength band exceeds 90%. However, the transmittance of the emitted light is relatively yellow because the transmittance of the wavelength range of 580nm to 650nm is relatively high. However, when light is absorbed by the light absorbing agent in the wavelength range of 580 nm to 650 nm and the transmittance decreases, the emitted light becomes blue and the light efficiency may be increased. Therefore, a low rank LED can be used as a light source.

In the case of suppressing light transmittance in the wavelength range of about 580nm to 600nm, it is possible to effectively shift the y-coordinate on the CIE color coordinates can be adjusted to the desired color temperature. The y color coordinate change amount? y is preferably -0.010 to -0.003 based on the y color coordinate of the incident light. In this case, white light having a yellow color may be converted into white light having a blue color.

Referring to FIG. 3, it can be seen that the transmittance of the wavelength band of about 580 nm decreases as the content (wt%) of the light absorber increases. In addition, when the content (wt%) of the light absorbing agent is 0.0007 wt% or less, as shown in FIG. 4, the y-coordinate change amount (Δy) is -0. There is a problem that does not satisfy 003 to -0.010.

The half peak width (FWHM) of the absorption peak is preferably 60 nm or less. If the full width at half maximum exceeds 60 nm, the transmittance of adjacent wavelengths decreases, resulting in a large loss of color coordinates and luminance. That is, in order to effectively remove only the wavelength band corresponding to yellow, the half width of the absorption curve of the light absorbing agent P may be adjusted to 60 nm or less.

Referring to Figure 4, it can be seen that the higher the content of the light absorbing agent is lower the brightness of the emitted light. The luminance of the emitted light is preferably controlled to 95% to 100% based on 100% of the incident light. Therefore, the light absorbing agent (P) is preferably 0.0007 wt% to 0.002 wt%. In consideration of both color coordinate conversion and brightness, the content of the light absorbing agent (P) is preferably 0.0007 wt% to 0.002 wt% with respect to the weight of the polymer resin constituting the absorbing layer.

5 is a conceptual diagram of a diffusion sheet according to another embodiment, and FIG. 6 is a graph of luminance measured by varying the surface roughness of the upper diffusion layer and the lower diffusion layer of the diffusion sheet, and FIG. 7 is an absorbent of the upper diffusion layer and the lower diffusion layer of the diffusion sheet. The luminance is measured by controlling the concentration differently, and FIG. 8 is a graph measuring luminance by controlling the thicknesses of the upper diffusion layer and the lower diffusion layer of the diffusion sheet differently.

Referring to FIG. 5, in the diffusion sheet according to the embodiment, surface roughnesses of the first diffusion layer 122 and the second diffusion layer 123 may be different from each other. In this case, the surface roughness may be defined as an average value of mountains and valleys formed on the surfaces of the first and second diffusion layers 122 and 123.

In addition, the concentrations of the light absorbers dispersed in the first and second diffusion layers 122 and 123 may be different from each other, and the thicknesses of the first and second diffusion layers 122 and 123 may also be different from each other. Can be. Hereinafter, based on the drawings, the second diffusion layer 123 into which the light L1 emitted from the light source is incident is defined as a lower layer and the first diffusion layer 122 is defined as an upper layer.

Referring to FIG. 6, Experimental Example 1 controlled the surface roughness of the diffusion layers on both sides to 1.2 μm and measured luminance. Experimental Example 2 controlled the surface roughness in the same manner as Experimental Example 1 and added a light absorber. Experimental Example 2 can be seen that the luminance is reduced by about 5% compared to Experimental Example 1. That is, it can be seen that the brightness decreases when the light absorber is added under the same conditions.

However, in Experimental Example 3 in which the surface roughness of the upper layer was set to 2.1 µm and the surface roughness of the lower layer was controlled to 0.9 µm, the luminance was measured to be 99.2%. In other words, it can be seen that the brightness is increased compared to Experimental Example 2 even though the light absorbing agent is added.

In contrast, in the case of Experimental Example 4 in which the surface roughness of the lower layer was set to 2.1 µm and the surface roughness of the upper layer was controlled to 0.9 µm, no increase in luminance was observed.

In addition, it can be seen that Experimental Example 5 in which the surface roughness of the upper layer was set to 1.2 µm and the surface roughness of the lower layer was controlled to 0.9 µm increased in brightness than that of Experimental Example 2. On the contrary, in Experimental Example 6 in which the surface roughness of the upper layer was set to 0.9 μm and the surface roughness of the lower layer was controlled to 1.2 μm, it can be seen that the luminance rise is relatively small.

As a result of the synthesis, it can be seen that when the surface roughness of the upper layer is rougher than the lower surface roughness, that is, when the surface of the lower layer is smoother than the surface of the upper layer, the luminance is relatively excellent. As a result of the experiment, when the surface roughness Ra of the first diffusion layer is 2.1 to 2.7 and the surface roughness Ra of the second diffusion layer satisfies 1.8 to 2.3, a brightness increase was observed.

Referring to FIG. 7, based on 100% of the brightness of Experimental Example 7 without adding the light absorbing agent, Experimental Example 8 having 0.002pt of light absorbing agent dispersed in each of the upper and lower layers measured 96.8% of brightness. In addition, Experimental Example 10 in which a light absorber of 0.004 pt was dispersed only in the upper layer had a luminance of 96.6%.

Experimental Example 8 and Experimental Example 10 can be seen that the brightness is similar. On the contrary, in case of Experiment 9 in which the light absorbent was dispersed only in the lower layer, the luminance was measured higher than in Experiment 8 and Example 10.

In addition, it can be seen that the color coordinate change is smaller in Experimental Example 9 than in Experimental Examples 8 and 10. That is, it can be inferred that the color coordinate improvement effect is small when the light absorber is added to the lower layer.

Referring to FIG. 8, in Experimental Example 12 having a thickness of 56 μm, the brightness was decreased by 1.1% compared to Experimental Example 11, and in Experimental Example 13, the brightness was decreased by 1.8% compared to Experimental Example 11, and in Experimental Example 14 When the brightness is reduced by 3.3% compared to Experimental Example 11. Therefore, it can be seen that the luminance gradually decreases as the thickness of the diffusion layer increases.

Referring to FIG. 9, a display apparatus according to an exemplary embodiment of the present invention includes a backlight unit 10 and a display panel 20. The display panel 20 implements an image by adjusting the amount of light transmitted from the backlight unit 10. The display panel 20 may be a liquid crystal panel. Specifically, the display panel 20 includes a TFT substrate 22, a color filter 14, and a liquid crystal 23 filled between the TFT substrate 22 and the color filter 24.

Although not shown, polarizers may be further disposed on the upper and lower surfaces of the display panel 20. Therefore, the amount of light can be adjusted by modifying the arrangement direction of the liquid crystal by adjusting the voltage applied to the liquid crystal 23.

The backlight unit 10 reflects the plurality of light sources 16 and the light guide plate 11 that converts the light emitted from the light source 16 into the surface light source, and the light emitted from the light guide plate 11 toward the display panel 20. Reflective sheet 15 and a plurality of

optical sheets

12, 13, 14. The plurality of optical sheets may be a diffusion sheet 12 and a pair of

prism sheets

13 and 14.

In this case, the above-described configuration of the diffusion sheet 12 and the reflection sheet 15 may be applied as it is. Accordingly, the light emitted from the light source 16 may be converted into color coordinates by the diffusion sheet 12 and the reflection sheet 15 and provided to the liquid crystal panel. Thus, the light source 16 can be replaced with a relatively low LED rating.

Claims

Base layer;

A first diffusion layer disposed on one surface of the base layer; And

A second diffusion layer disposed on the other surface of the base layer,

At least one of the first diffusion layer and the second diffusion layer is an optical sheet including a light absorber for absorbing light of a predetermined wavelength band.
The method of claim 1,

The optical sheet is an optical sheet for converting the color coordinates of the incident light.
The method of claim 2,

The y-coordinate change amount Δy of the converted color coordinates is -0.010 to -0.003.
The method of claim 1,

The brightness of the light emitted from the optical sheet is an optical sheet of 96% to 100% based on 100% of the incident light.
The method of claim 1,

The light absorbing agent has an absorption peak in the wavelength band of 580nm to 650nm.
The method of claim 1,

The light absorbing agent is an optical sheet is 0.0007wt% to 0.002wt%.
The method of claim 1,

The surface roughness Ra of the first diffusion layer is different from the surface roughness Ra of the second diffusion layer.
The method of claim 7, wherein

The surface roughness Ra of the first diffusion layer is 2.1 to 2.7, and the surface roughness Ra of the second diffusion layer is 1.8 to 2.3.
The method of claim 1,

An optical sheet having a content of the light absorbing agent included in the first diffusion layer is higher than that of the light absorbing agent included in the second diffusion layer.
The method of claim 1,

An optical sheet having a thickness of the first diffusion layer and the second diffusion layer is 4 ~ 10㎛.
Light source; And

An optical sheet for diffusing the first light emitted from the light source,

The optical sheet,

Base layer;

A first diffusion layer disposed on one surface of the base layer to receive the first light; And

A second diffusion layer disposed on the other surface of the base layer to emit the first light,

At least one of the first diffusion layer and the second diffusion layer includes a light absorber for absorbing light of a predetermined wavelength band.
The method of claim 11,

The surface roughness Ra of the first diffusion layer is different from the surface roughness Ra of the second diffusion layer.
The method of claim 12,

The surface roughness Ra of the first diffusion layer is 2.1 to 2.7, and the surface roughness Ra of the second diffusion layer is 1.8 to 2.3.
The method of claim 11,

The backlight unit of which the content of the light absorber included in the first diffusion layer is higher than the content of the light absorber included in the second diffusion layer.
The method of claim 11,

And a thickness of the first diffusion layer and the second diffusion layer is 4 to 10 μm.
A backlight unit according to any one of claims 11 to 15; And

And a display panel configured to generate an image using light whose color coordinates are converted by the optical sheet.