KR20140055558A - Light guide plate and transparent display device comprising the same - Google Patents

Abstract

The present invention relates to a light guide plate, a method of manufacturing the same, and a transparent display device including the same. More specifically, the present invention relates to: a light guide plate comprising a front surface, a rear surface facing the front surface, and a side surface connecting the front surface and the rear surface, wherein an optical pattern including at least one of a cone and a prism bar is formed on the rear surface, and light diffusers are distributed at the rear surface; a method of manufacturing the same; and a transparent display device including the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a light guide plate and a transparent display device including the light guide plate.

The present invention relates to a light guide plate and a transparent display device including the same. More specifically, the present invention relates to a light guide plate for a transparent display, which can increase the light efficiency and the light uniformity, has no problem that the optical pattern line is apparently visible, can improve the appearance, viewing angle and brightness, and a transparent display device including the same will be.

The transparent display device is a device driven to view all the situations before and after the display while viewing the display information or the screen. The display device may be used in a street or in a showcase of a store, a front door of a home appliance, a window, a desk, or the like.

A transparent display device can display information or a screen even if there is light on the back side or light emission on the display in the daytime. Separately, it is important to display only the display screen or information if there is no light on the back or at night.

In the light guide plate used in the conventional transparent display device, a small amount of silicon spherical beads is contained in the entire light guide plate. These beads can reflect light incident from an LED light source and change the path of light back and forth to the panel. The beads are advantageous in that they are small in size, are not visible to the eye, and have good transparency. However, the bead has a spherical shape and has a limitation in improving the light efficiency by reflecting light at about 1: 1 before and behind the panel, and there is a problem that a small amount of the bead is produced and the price is high.

In this regard, Korean Patent Laid-Open Publication No. 2008-0097880 discloses a light guide plate in which light loss is reduced by combining bead and air bubbles in a light guide plate and combining a vertical or horizontal prism with a light guide plate having light scattering, refraction and diffusion means have.

It is an object of the present invention to provide a light guide plate capable of enhancing light efficiency and light uniformity and solving the problem that an optical pattern line is apparently visible.

Another object of the present invention is to provide a light guide plate having good appearance and viewing angle and capable of increasing brightness.

It is still another object of the present invention to provide a transparent display device including the light guide plate.

An optical waveguide according to an embodiment of the present invention includes a front surface, a rear surface opposite to the front surface, and a side surface connecting the front surface and the rear surface, wherein an optical pattern including at least one of a cone and a prism bar is formed on the rear surface , And a light diffusion agent may be localized on the back side.

The transparent display device according to another aspect of the present invention may include the light guide plate.

The present invention can solve the problem of low optical efficiency in a light guide plate for a transparent display including only a bead, and can solve the problem that the optical pattern line is visually recognized even when the light is on and off while the light efficiency and the light uniformity are increased. And has the effect of providing the light guide plate which can be manufactured by a simple method using the existing bare light guide plate material.

1 is a perspective view showing a combination of a light guide plate and a light source according to an embodiment of the present invention.
2 is a perspective view of an embodiment of a conical optical pattern.
3 is a perspective view of one embodiment of the prism bar optical pattern.
4 is a side view of a light guide plate according to an embodiment of the present invention.
5 is a plan view of a combination of a light guide plate and a light source according to one embodiment of the present invention.
6 is a plan view of a combination of a light guide plate and a light source according to another embodiment of the present invention.
7 is a plan view of a combination of a light guide plate and a light source according to another embodiment of the present invention.
8 is a plan view of a combination of a light guide plate and a light source according to another embodiment of the present invention.
9 is a conceptual diagram of a prism bar optical pattern.

An optical waveguide according to an embodiment of the present invention includes a front surface, a rear surface opposite to the front surface, and a side surface connecting the front surface and the rear surface, wherein an optical pattern including at least one of a cone and a prism bar is formed on the rear surface , And a light diffusion agent may be localized on the back side.

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

1 is a perspective view showing a combination of a light guide plate and a light source of the present invention.

1, the light guide plate 100 includes a front surface 20 for emitting light from a side light source 10 toward a panel (not shown), a rear surface 30 facing the front surface 20, 40b, 40c, and 40d that connect the back surface 20 and the back surface 30 to each other.

The light source 10 is disposed on the side of the light guide plate to emit light.

The light source may include one or more of a linear light source or a point light source.

The source of light can include one or more of a CCFL lamp, a light guide bar, a laser, a combination of an LED and a lens, a combination of an LED and a light guide bar, and an interior lamp. The point light source may include an LED.

FIG. 1 shows a point light source as a light source.

The light source may be disposed on one side surface (40a direction) of the light guide plate as shown in FIG. 1, but may be disposed on both side surfaces (40a, 40b).

The front side 20 may face a panel of a transparent display device (e.g., a transparent LCD panel, not shown in FIG. 1). The front surface 20 may emit light from the side light source 10 to the panel so that the display is displayed.

The back surface 30 faces the front surface 20 and a part of the light from the side light source 10 can be reflected back to the front surface 20 to increase the light efficiency.

And the side surface connects the front surface 20 and the back surface 30. [ The side surface includes a first side surface 40a on which the side light source is located, a second side surface 40b opposed to the first side surface 40a, and a second side surface 40b connecting the first side surface 40a and the second side surface 40b And may include a third side 40c and a fourth side 40d.

An optical pattern 50 may be formed on the back surface 30. The optical pattern 50 can increase the light efficiency of the light guide plate by allowing the light of the light source to be incident on the optical pattern 50 and being totally reflected and emitted to the panel through the front surface 20. [

The optical pattern is not limited to embossed, embossed, or mixed shapes thereof, as long as it can reflect light from the side light source.

The back surface 30 may include a light diffusing agent (not shown).

The optical pattern may include at least one of a cone and a prism bar optical pattern.

Figures 2 and 3 show the cone and prism bar optical patterns, respectively.

In the conical optical pattern of FIG. 2, the height H1 may be 4 占 퐉 - 30 占 퐉, preferably 6 占 퐉 - 30 占 퐉, and the diameter D1 of the conical bottom face 50a may be 10 占 퐉 - 35 占 퐉. In this range, it is possible to reflect the light to increase the light efficiency, prevent the pattern line from being visible, and emit light to the front. The apex angle α of the conical optical pattern can be 45-60 °. Within this range, it may be possible to emit light to the front.

The vertex angle alpha may be an angle that is opposite to the diameter D1 of the conical bottom surface 50a in a triangular section of a cone having a vertical height and a maximum height at the bottom of the cone.

In the prism bar pattern of FIG. 3, the height H2 may be 6 占 퐉 to 30 占 퐉, the length L2 of the bottom face 50b may be 10 占 퐉 to 35 占 퐉, and the width P2 may be 10 占 퐉 to 35 占 퐉 , And the apex angle? Can be 70-90 degrees. In this range, it is possible to reflect the light to increase the light efficiency, prevent the pattern line from being visible, and emit light to the front. In addition, the pattern at the time of lighting can not be visually recognized, the object at the rear face can be seen, and the pattern may not be visually recognized at the time of lighting.

The apex angle? May refer to an angle of the triangular side surface of the prism bar pattern opposite to the width of the prism bar pattern.

The optical pattern may be randomly formed in the back surface.

As the optical pattern moves away from the light source, the number of patterns may increase. This is to increase the total number of patterns by increasing the number of patterns since the light is reduced from the light source.

The distance from the first side of the optical pattern to the optical pattern may decrease. As a result, as the distance from the light source increases, the reflectance of the light increases, thereby ensuring an evenly bright appearance throughout the view area.

The spacing distance between the optical patterns is not limited, but may be 10 탆 to 200 탆.

The number or density of the optical pattern may increase as the optical pattern moves away from the first side. As a result, as the distance from the light source increases, the reflectance of the light increases, thereby ensuring an evenly bright appearance throughout the view area.

The size and height of the optical pattern may be the same or different. Preferably, the size of the optical pattern is made the same so that the pattern line is not visually recognized.

The backside may comprise a light diffusing agent. The light diffusing agent can improve the appearance by diffusing light from the side light source.

As shown in FIG. 4, the light diffusing agent 60 may be localized on the back surface 30 side of the light guide plate. In the conventional light guide plate, only a small amount of light diffusing agent (for example, beads) is contained in the entire light guide plate, and the beads reflect light incident from the light source to change the path of light back and forth. This is because the light is scattered by the bead 1: 1 on the back and front side, respectively, and the light efficiency is low.

On the other hand, in the light guide plate of the present invention, light is reflected by an optical pattern formed on the back surface, and a light diffusion agent is localized on the back side. As a result, the light diffusing agent can further diffuse the light reflected from the optical pattern, thereby further increasing the light efficiency.

The light diffusing agent 60 is localized on the back surface 30 side of the light guide plate.

The front surface 20 of the light guide plate can be opposed to the liquid crystal display panel 90. [

The light diffusing agent 60 may be localized within 0% -3% distance from the back surface of the thickness T of the light guide plate. In this range, the light efficiency of light reflected due to the optical pattern can be increased.

The light guide plate is composed of a first region including a light diffusing agent and a second region containing no light diffusing agent.

The first region may include a back surface, and may mean an area ranging from 0% to 3% from the back side of the thickness of the light guide plate. The second region may include a front surface, and may mean an area ranging from 0% to 97% from the entire thickness of the light guide plate.

The light diffusing agent may be included on the back surface of the light guide plate, but may also be included on the front surface of the light guide plate.

The light-diffusing agent may be coated on the back surface of the light guide plate coated with a UV resin made at a concentration of 1,000-5,000 ppm. In the above range, the appearance may be improved, and the haze of the light guide plate may be 20% or less so as not to deteriorate the turbidity.

The shape of the light diffusing agent is not limited, and may include bead shape considering light efficiency, visibility, appearance, and the like.

The diameter of the light diffusing agent may be 1 탆 to 8 탆. In the above range, when the light guide plate is included in the back surface of the light guide plate, transparency of the light guide plate may be good without being visually recognized.

The light diffusing agent is not limited as long as it is a substance capable of diffusing light, and may include one or more of acrylic, silicone, styrene, methacrylic, polycarbonate, olefin, polyester and aluminum .

5 to 6 are plan views of a combination of a light guide plate and a light source according to an embodiment of the present invention. The light source is the source of light.

5, when the light source 10 is a light source, a prism bar optical pattern 50 is formed on the back surface 30, and the light guide plate may include a light diffusing material 60. The prism bar optical pattern may be formed randomly, and the direction in which light is incident from the light source 10 and the longitudinal direction of the prism bar may be -90 degrees or +90 degrees.

6, when the light source 10 is a source of light, a conical optical pattern 50 is formed on the back surface 30 and a light diffusing agent 60 may be included. The conical optical pattern may be formed at random.

When the light source is a source of light, an optical line is not generated, so that a prism bar or a conical pattern having a good light efficiency can be formed on the back surface.

7 and 8 are plan views of a combination of a light guide plate and a light source according to another embodiment of the present invention. The light source is a point light source.

Referring to FIGS. 7 and 8, when the light source 10 is a point light source, a prism bar optical pattern 50 is formed on the back surface, and the light guide plate may include the light diffusing material 60. The prism bar optical pattern can be arranged at random.

In the case of a point light source, when the longitudinal direction of the prism bar and the direction in which the light is incident from the light source are parallel to each other, the light is totally reflected to the front surface so that the optical line can be viewed. In order to prevent this, when the light source is a point light source, the prism bar optical pattern is rotated and rotated from 0 ° to 180 °. As a result, the optical line can be canceled by rotating the optical line caused by the point light source. The rotation angle can be in units of 1 degree.

7 and 8, a plurality of optical patterns 50 having a shape in which the longitudinal direction of the optical pattern is randomly rotated on the basis of the direction in which light is incident from the light source may be distributed over the back surface 30 as a whole have. Through this, it is possible to improve the appearance of the optical line due to the total reflection of the rotated optical pattern of the prism bar. The light totally reflected on the prism bar rotated arbitrarily can be bent and mixed with each other. At this time, the light diffusing agent may be formed entirely in the back surface.

9 is a conceptual diagram of rotation of a prism bar optical pattern disposed on the back surface when the light source is a point light source.

9, the length L2 direction of the bottom surface 50b of the optical pattern 50 may be in an angle gamma range of 0 DEG to 180 DEG with respect to the direction (arrow direction) in which light is incident from the light source.

In one embodiment, as shown in FIG. 9, when the angle formed by the direction in which light is incident from the light source and the longitudinal direction of the prism bar is?, The following equation 1 can be established:

<Formula 1>

γ ₁ ≠ γ ₂

? ₂ ?? ₃

...

γ _n-1 ≠ γ _n

(Where? ₁ is an angle formed by the longitudinal direction of the first prism bar with respect to the direction in which light is incident,

? ₂ is the angle formed by the longitudinal direction of the second prism bar with respect to the direction in which the light is incident,

₁ is an angle formed by the longitudinal direction of the (n-1) th prism bar with respect to the direction in which light is incident,

_n is an angle formed by the longitudinal direction of the n-th prism bar with respect to the direction in which light is incident,

n is an integer from 2 to 180).

and? ₁ to? _n may be 0 ° to 180 °.

In one embodiment,? ₁ through? _N may all be different.

In another embodiment, at least one or more of gamma ₁ through gamma _n may be the same.

γ _n-1 and γ _n may differ by 1-10 °.

Another method of manufacturing a light guide plate, which is another aspect of the present invention, may include applying a polymer solution including a light diffusing agent to a base layer, and imprinting one or more optical pattern forming portions on the applied polymer solution layer.

The polymer has a refractive index of 1.43 to 1.45 and can be an optically transparent resin used in the production of a light guide plate. For example, the optically transparent resin may include one or more polyester resins including (meth) acrylic, polycarbonate, styrene, olefin, polymethylmethacrylate, and the like.

The light diffusing agent is a material capable of diffusing light using the above-mentioned material, and may be contained in 1,000-5,000 ppm of the final light guide plate.

As the base layer, the same or different resins as the above-mentioned polymers can be used. Preferably, it is made of the same resin as the above-mentioned polymer in order to improve transparency of the light guide plate. Preferably, the substrate layer may be formed of polymethylmethacrylate.

A light guide plate can be manufactured by applying a polymer solution containing the prepared light diffusing agent to a substrate layer and then imprinting a predetermined optical pattern forming portion on the applied layer.

The transparent display device according to another aspect of the present invention may include the light guide plate. The apparatus may further include a panel, a light source, and the like in addition to the light guide plate.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Example  One

The beads made of a silicone resin were mixed with the polymethylmethacrylate resin and applied to the polymethylmethacrylate base layer. Then, the optical pattern forming portion having the cone-shaped optical pattern formed in a convex pattern was imprinted on the application layer, Thereby preparing a light guide plate having a back surface.

Example  2

The polymethylmethacrylate resin and the silicone resin beads were mixed and applied to the polymethylmethacrylate base layer. Then, the optical pattern forming portion in which the prism bar optical pattern was formed in a positive angle was imprinted on the application layer, A light guide plate having a back surface was produced.

Example  3

The polymethylmethacrylate resin is mixed with beads made of a silicone resin and applied to the polymethylmethacrylate base layer. Then, an optical pattern forming portion in which the prism bar optical pattern is formed in a positive angle is imprinted on the application layer, A light guide plate having a back surface was produced.

Comparative Example  One

A light guide plate containing beads made of silicone resin and having no optical pattern was used on the entire light guide plate.

The following properties of the light guide plate were evaluated.

Place the image on the back and use a jig in front of the image to fix the LED light source and LGP together, then place the panel in front of LGP. Evaluate the image and appearance on the panel when the LED light source lights up or flashes.

As a result, there was no difference in the images according to the use of the light guide plate of the embodiment and the comparative example when the LED light source was blinking. However, when the light source is lit, the rear image can be seen when the light guide plate of the comparative example is used. However, when the light guide plate of the embodiment is used, the rear image can not be seen well. .

In the examples and comparative examples, the length of the light guide plate is 480 mm and the thickness of the light guide plate is 300 mm. A light guide plate having a distance from the side LED light source of 90 mm, 240 mm, and 390 mm is defined as any three points. The average luminance is measured at each point by the EZ-Contrast method, and the light efficiency is calculated therefrom. The light efficiency is a ratio value of the luminance measured in the embodiment, assuming that the luminance of Comparative Example 1 is 100. In addition, the uniformity of the three points is the percentage of the minimum / maximum value among the three points of luminance. The pattern visibility was evaluated by visually observing the lines emitted from the light source after arranging the light sources corresponding to Figs. 5-7 for the manufactured light guide plate. In Comparative Example 1, a point light source was used. The results are shown in Table 1 below.

Example 1 Example 2 Example 3 Comparative Example 1 Average luminance (cd / m ² ) 216 176 211 82 Luminous efficiency (%) 263 214 257 100 Uniformity (%) 37 42 47 25 Whether the pattern is visible radish radish radish radish

As shown in Table 1, the light guide plate of the present invention not only improves the light efficiency by more than twice the average brightness by increasing the average brightness, but also increased the uniformity of light. On the other hand, the light guide plate of the comparative example including only the beads on the entire light guide plate without the optical pattern had lower brightness and uniformity than the present invention, and had lower light efficiency.

It is to be understood that the present invention is not limited to the above-described embodiments, but may be formed in various other forms, and that the embodiments described above are illustrative and non-restrictive in all aspects.

Claims (20)

A front surface, a rear surface facing the front surface, and a side surface connecting the front surface and the rear surface,
An optical pattern including at least one of a cone and a prism bar is formed on the back surface,
And a light diffusion agent is distributed on the back side. The light guide plate according to claim 1, wherein the optical pattern is randomly formed. The light guide plate according to claim 1, wherein the side surface includes a first side where a light source is located and a second side opposite to the first side. The light guide plate according to claim 3, wherein the distance between the optical patterns decreases as the distance from the first side increases. The light guide plate according to claim 3, wherein the number of the optical patterns increases as the distance from the first side increases. The light guide plate according to claim 1, wherein the prism bar has an angle of -90 ° or + 90 ° with respect to a direction in which light is incident from a light source and a length direction of the prism bar. The light guide plate according to claim 1, wherein the prism bar has an angle of 0 ° to 180 ° with respect to a direction in which light is incident from a light source and a length direction of the prism bar. 2. The light guide plate according to claim 1, wherein, when an angle formed by a direction in which light is incident from the light source and a longitudinal direction of the prism bar is?
<Formula 1>
γ ₁ ≠ γ ₂
? ₂ ?? ₃
...
γ _n-1 ≠ γ _n
(Where? ₁ is an angle formed by the longitudinal direction of the first prism bar with respect to the direction in which light is incident,
? ₂ is the angle formed by the longitudinal direction of the second prism bar with respect to the direction in which the light is incident,
₁ is an angle formed by the longitudinal direction of the (n-1) th prism bar with respect to the direction in which light is incident,
_n is an angle formed by the longitudinal direction of the n-th prism bar with respect to the direction in which light is incident,
n is an integer of 2-180,
? ₁ to? and? _n is 0 ° to 180 °). 9. The light guide plate according to claim 8, wherein at least one of? ₁ to? _N is the same. The light guide plate according to claim 1, wherein the optical pattern is embossed or embossed. The light guide plate according to claim 1, wherein the vertex angle of the cone is 45 to 60 degrees and the vertex angle of the prism bar is 70 to 90 degrees. The light guide plate according to claim 1, wherein a height of the optical pattern is 6 to 30 占 퐉. The light guide plate according to claim 1, wherein the prism bar has a length of 10 mu m to 35 mu m and the prism bar has a width of 10 mu m to 35 mu m. The light guide plate according to claim 3, wherein the density of the light diffusing agent increases as the distance from the first side increases. The light guide plate according to claim 1, wherein the light diffusing agent is distributed in a range of 0% to 3% from the back surface of the entire thickness of the light guide plate. The light guide plate according to claim 1, wherein the light diffusing agent is contained in the light guide plate at a concentration of 1,000-5,000 ppm. The light guide plate according to claim 1, wherein the light diffusing agent comprises beads. The light guide plate according to claim 17, wherein the diameter of the beads is 1 탆 to 8 탆. The light guide plate according to claim 1, wherein the front surface is further coated with a light diffusion agent. A transparent display device comprising a light guide plate according to any one of claims 1 to 19.

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