TW201416734A - Light guide plate and transparent display device including the same - Google Patents

Abstract

A light guide plate, a method for manufacturing the same and a transparent display device including the same. The light guide plate includes: a front surface; a rear surface opposite the front surface; and side surfaces connecting the front surface to the rear surface, wherein optical patterns including at least one shape of cones or prism bars are formed on the rear surface, and a light diffusing agent is distributed on the rear surface.

Description

Light guide plate and transparent display device including the same Field of invention

The invention relates to a light guide plate and a transparent display device comprising the light guide plate. More specifically, the present invention relates to a light guide plate for a transparent display device, which can increase light efficiency and light uniformity, avoid the problem of optical pattern lines appearing on an outer surface, and improve viewing angle characteristics, and increase Brightness, and a transparent display device including one of the light guide plates.

Background of the invention

The transparent display device allows a user to see all the conditions on the front side and the back side of the display when viewing the display information or screen. The display device can be applied to a display case on a street or in a store, a front door of a household appliance, a glass window, a table top, or the like.

When illuminated from the rear surface or between white, the transparent display device can display information or pictures even if it is not illuminated to the display, and must be transparent in order to achieve this item. On the other hand, when no light is incident on the rear surface or at night, it is important that the transparent display device only display a picture or information.

A light guide plate used in a conventional transparent display device contains a small amount of spherical polycrystalline oxygen beads dispersed throughout the entire surface. Beads can be reflected from LED light source The light input changes the light path toward the front side and the back side of a panel. Beads have advantages such as small size, invisible to the naked eye, and excellent transparency. However, since the beads only allow one-to-one reflection of light to the front side and the back side of the panel due to the shape of the sphere, the improvement in light efficiency is limited, and the price is high due to the small amount of production.

Korean Patent Publication No. 2008-0097880A discloses a light guide plate containing beads and bubbles to scatter, refract, and disperse light, and includes vertical or horizontal ridges to reduce light loss.

Summary of invention

According to one aspect of the invention, a light guide plate includes: a front surface; a rear surface opposite the front surface; and a side surface connecting the front surface to the rear surface, including at least one of a cone or a prismatic strip A shaped optical pattern is formed on the back surface, and a light diffusing agent is distributed on the back surface.

The optical patterns can be randomly formed.

The side surfaces may include a first side surface on which a light source is disposed and a second side surface opposite the first side surface.

The spacing between the optical patterns may decrease as the distance of the optical patterns from the first side surface increases.

This number of optical patterns may increase as the distance of the optical patterns from the first side surface increases.

The prismatic strips may have an angle defined by one of the prismatic strips longitudinally defining a direction of -90 degrees or +90 degrees between one of the directions of incidence of light from the source.

The prismatic strips have one of the prismatic strips longitudinally associated with One direction of light incident from the source defines an angle of between about 0 and 180 degrees.

13] when one of the prismatic strips is longitudinally defined with an angle defined between a direction in which the light system is incident from the light source When, Equation 1 is satisfied:

(here a corner defined by the longitudinal direction of the first prismatic strip and the incident direction of the light therein, a corner defined by the longitudinal direction of the second prism strip and the incident direction of the light therein, a corner defined between the longitudinal direction of the n-1 prismatic strip and the incident direction of the light therein, It is an angle defined between the longitudinal direction of the n-th prism strip and the incident direction of the light, and n is an integer from 2 to 180).

to At least one of them may be the same.

The optical patterns can be recesses or protrusions.

The cones can have a vertical angle of from about 45 degrees to about 60 degrees, and the prismatic strips can have a vertical angle of from about 70 degrees to about 90 degrees.

The optical patterns can have a height of from about 6 microns to about 30 microns.

The prismatic strips can have a length of from about 10 microns to about 35 microns and a width of from about 10 microns to about 35 microns.

The density of one of the light diffusing agents may increase as the distance of the light diffusing agent from the first side surface increases.

The light diffusing agent may be distributed in a range of from about 0% to about 3% of the thickness of the light guide plate from the rear surface.

In the light guide plate, the light diffusing agent may be present in a concentration of from about 1,000 ppm to about 5,000 ppm.

The light diffusing agent can include beads.

The beads can have a diameter of from about 1 micron to about 8 microns.

The light diffusing agent can be further coated on the front surface.

According to another aspect of the present invention, a transparent display device including one of the light guide plates is proposed.

10‧‧‧Light source

20‧‧‧ front surface

30‧‧‧Back surface

40a-d‧‧‧ side surface

50‧‧‧ optical pattern

50a-b‧‧‧ bottom surface

60‧‧‧Light diffusing agent

90‧‧‧LCD panel

100‧‧‧Light guide plate

D1‧‧‧ diameter

H1-2‧‧‧ Height

L2‧‧‧ portrait

P2‧‧‧Width

、, β, ‧‧‧angle

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; FIG. 2 is a perspective view of a conical optical pattern; and FIG. 3 is a perspective view of an embodiment of a prismatic strip optical pattern. Figure 4 is a schematic view of a light guide plate according to an embodiment of the present invention; Figure 5 is a schematic view showing a combination of a light guide plate and a light source according to an embodiment of the present invention; and Figure 6 is a schematic view showing the light source according to the present invention; One embodiment is a combination of a light guide plate and a light source; FIG. 7 is a schematic view showing a combination of a light guide plate and a light source according to an embodiment of the present invention; and FIG. 8 is a schematic view showing a light guide plate according to an embodiment of the present invention. In combination with a light source; Figure 9 is a conceptual view of a prismatic strip optical pattern.

Detailed description of the preferred embodiment

According to an embodiment of the present invention, a light guide plate includes: a front surface; a rear surface opposite the front surface; and a side surface connecting the front surface to the rear surface, including at least a cone or a prism strip An optical pattern of one shape is formed on the rear surface, and a light diffusing agent is distributed on the rear surface.

Specific embodiments of the present invention will now be described in detail with reference to the drawings.

1 is a perspective view showing a combination of a light guide plate and a light source in accordance with an embodiment of the present invention.

Referring to FIG. 1, a light guide plate 100 includes a front surface 20 that outputs light from a side light source 10 toward a panel (not shown), a rear surface 30 opposite the front surface 20, and a connection thereto. The front surface 20 to the side surfaces 40a, 40b, 40c, 40d of the rear surface 30.

The light source 10 can be disposed on one side surface of the light guide plate to emit light.

The light source can include at least one of a line source and a point source.

The line source can include at least one of a CCFL lamp, a light guide strip, a laser, a combination of an LED and a lens, a combination of an LED and a light guide strip, and an interior light. The point source can include a light emitting diode (LED).

Figure 1 shows that the source is a point source.

The light source may be disposed on one side surface (40a) of the light guide plate. In addition, the light sources may be disposed on opposite side surfaces 40a, 40b of the light guide plate, respectively.

The front surface can face a panel of a transparent display device (e.g., a transparent LCD panel, not shown in Figure 1). The front surface 20 can output light from the side light source 10 toward the panel to display an image.

The rear surface 30 is opposed to the front surface 20, and reflects a portion of the light emitted from the side light source 10 toward the front surface 20, again improving light efficiency.

The side surfaces join the front surface 20 to the back surface 30. The side surface includes a first side surface 40a on which the side light source is disposed, a second side surface 40b opposite to the first side surface 40a, and the first side surface 40a to the second A third side surface 40c and a fourth side surface 40d of the side surface 40b.

The optical patterns 50 can be formed on the rear surface 30. The optical patterns 50 are assembled such that light emitted from the light source collides with the optical patterns 50 to be totally reflected and output through the front surface 20 toward the panel, thereby improving the optical efficiency of the light guide.

The optical patterns 50 are formed into a dot shape. The term "dot shape" herein refers to a shape in which an optical pattern is separated from an adjacent optical pattern. For example, a point may have an island structure surrounded by a non-patterned area. The non-patterned area can be flat.

As long as the optical patterns are capable of reflecting light from the side source, they can have any shape, including recesses, protrusions, or combinations thereof, but are not limiting.

The back surface 30 can contain a light diffusing agent (not shown).

The optical patterns can include at least one of a cone shape and a prism strip shape.

2 and 3 respectively show a cone-shaped optical pattern and a prismatic strip-shaped optical pattern.

In the cone-shaped optical pattern of Figure 2, the cone-shaped optics The pattern can have a height H1 of from about 4 microns to about 30 microns, preferably from about 6 microns to about 30 microns, and a diameter D1 from about 10 microns to about 35 microns of the bottom surface 50a. Within this range, the optical pattern can reflect light to increase light efficiency, the pattern lines are not visible from the outside, and light can be output to the front surface. The cone-shaped optical patterns can have a vertical angle a of from about 45 degrees to about 60 degrees. Within this range, light can be output to the front surface.

Here, the vertical angle α may refer to an angle of the diameter D1 facing the bottom surface 50a in a triangular cross section in which the cone is perpendicular to the bottom surface of the cone and has the largest height.

In FIG. 3, the prismatic strip optical patterns have a height H2 of from about 6 microns to about 30 microns, a length L2 of from about 10 microns to about 35 microns of the bottom surface 50b, a width P2 of from about 10 microns to about 35 microns, And a vertical angle β of about 70 degrees to about 90 degrees. Within this range, the optical pattern can reflect light to increase light efficiency, the pattern lines are not visible from the outside, and light can be output to the front surface. Again, when the light source is turned off, the pattern is not visible, and an object on the back surface is visible; and when the light source is turned on, the pattern is invisible.

Here, the vertical angle β may refer to an angle in the triangular side surface of the prism strip pattern facing a width of one of the prism strip patterns.

The optical patterns can be randomly formed on the rear surface. The term "randomly" as used herein means that the optical patterns are arranged irregularly in terms of direction, spacing, or size.

The number of optical patterns may increase as the distance of the optical patterns from the source increases. As the distance of the optical patterns from the source increases, the intensity of the light emitted by the source decreases. So, the total reflection can be borrowed Increasing the number of optical patterns increases.

The spacing between the optical patterns may decrease as the distance of the optical patterns from the first side surface increases. As a result, as the distance between the optical patterns and the light source increases, the reflectance increases, thereby obtaining an appearance in which the brightness of the total viewing area is uniform.

The spacing between the optical patterns can range from about 10 microns to about 200 microns, but is not limiting.

The number or density of the optical patterns may increase as the distance of the optical patterns from the first side surface increases. As a result, as the distance between the optical patterns and the light source increases, the reflectance increases, thereby obtaining an appearance in which the brightness of the total viewing area is uniform.

The size and height of the optical patterns may be the same or different. Preferably, the optical patterns are of equal size such that the pattern lines are invisible from the outside.

The rear surface can include a light diffusing agent. The light diffusing agent diffuses light from the side source to provide an excellent appearance.

As shown in FIG. 4, the light diffusing agent 60 may be distributed on the rear surface 30 of the light guide plate. In the related art, a light guide plate contains only a small amount of light diffusing agent (for example, beads) such that the beads reflect light input from the light source to change the light path to the front and rear sides of the panel. In this case, the light system is dispersed from the beads to the rear surface and the front surface at a ratio of 1:1, thereby providing low light efficiency.

In another aspect, in the light guide plate according to the present invention, the light system is reflected by the optical patterns formed on the rear surface, and the light diffusing agent is distributed on the rear surface. As a result, the light diffusing agent can disperse light reflected from the optical patterns, thereby further improving light efficiency.

The light diffusing agent 60 is dispersed on the rear surface 30 of the light guide plate.

The front surface of the light guide plate may face a liquid crystal display panel 90.

The light diffusing agent 60 may be distributed over a range of from about 0% to about 3% of the thickness of the light guide plate from the rear surface. Within this range, the light efficiency of the light reflected by the optical patterns can be improved.

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

The first region includes the back surface and may refer to a region within the range of from about 0% to about 3% of the thickness of the light guide plate from the back surface. The second region includes a front surface and can refer to a region within the range of from about 0% to about 97% of the thickness of the front surface of the light guide.

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

The light diffusing agent may be formed on the rear surface of the light guide plate by coating a UV resin having a concentration of about 1,000 ppm to about 5,000 ppm onto the rear surface of the light guide plate. Within this range, the light diffusing agent provides an improved appearance, and by maintaining the turbidity of the light guide plate within about 20%, the turbidity of the light guide plate is not too poor.

The light diffusing agent can be prepared in any form that can include beads in view of light efficiency, visibility, and appearance.

The light diffusing agent can have a diameter ranging from about 1 micron to about 8 microns. Within this range, the light diffusing agent contained on the rear surface is invisible, thereby ensuring excellent transparency of the light guide plate.

Any material capable of diffusing light can be used for the light diffusing agent No special restrictions. For example, the light diffusing agent may include the one selected from the group consisting of an acrylic resin, a polyoxynoxy resin, a styrene resin, a methacrylic resin, a polycarbonate, an olefin resin, a polyester, and aluminum. At least one material in the group.

5 and FIG. 6 are schematic diagrams showing a combination of a light guide plate and a light source according to an embodiment of the invention. The light source is a line source.

Referring to FIG. 5, when a light source 10 is a line source, the light guide plate may include a prism strip optical pattern 50 and a light diffusing agent 60 on the rear surface 30. The prismatic strip optical patterns may be randomly formed and may have an angle of -90 degrees or +90 degrees between the longitudinal direction of the prismatic strips and the direction of incidence of light from the source 10.

Referring to FIG. 6, when the light source 10 is a line source, the light guide plate may include a cone-shaped optical pattern 50 and a light diffusing agent 60 on the rear surface 30. The cone-shaped optical patterns can be formed randomly.

When the light source is a line source, since no light is generated, a prismatic strip or a cone-shaped pattern that provides excellent light efficiency can be formed on the rear surface.

7 and FIG. 8 are schematic diagrams showing a combination of a light guide plate and a light source according to an embodiment of the invention. The light source is a point source.

Referring to FIGS. 7 and 8, when a light source 10 is a point source, the light guide plate may include a prism strip optical pattern 50 and a light diffusing agent 60 on the rear surface. The prismatic strip optical patterns can be randomly arranged.

Taking the point source as an example, when the longitudinal direction of the prism strip is parallel to the incident direction of light from the light source, the light can be totally reflected to the front surface, and the light is visible visually. In order to prevent this phenomenon, when the light source is a point light source, the prismatic strip optical patterns can be arranged in a random rotation state of about 0 degrees to about 180 degrees. Set. Thus the light generated by the point source can be offset by the rotating light. The rotation can be performed in units of 1 degree.

As shown in FIGS. 7 and 8, a plurality of optical patterns whose longitudinal direction is rotated with respect to the incident direction of light from the light source can be dispersed on the rear surface 30. With this configuration, the outer contour of the light can be improved by the total reflection of light caused by the randomly rotating prismatic strip optical pattern. Light totally reflected by the randomly rotating prismatic strip optical pattern can be deflected and mixed. Here, the light diffusing agent may be distributed on the rear surface.

Figure 9 is a conceptual view showing the rotation of a prismatic strip optical pattern disposed on the back surface when the light source is a point source.

Referring to FIG. 9, a longitudinal direction L2 of the bottom surface 50b of the optical pattern 50 and an angle defined between an incident direction (arrow direction) of light from the light source ( It can range from about 0 degrees to about 180 degrees.

In one embodiment, the angle defined between the direction of incidence of light from the source and the longitudinal direction of the prismatic strips is Equation 1 can be satisfied.

(here a corner defined by the longitudinal direction of the first prismatic strip and the incident direction of the light therein, a corner defined by the longitudinal direction of the second prism strip and the incident direction of the light therein, a corner defined between the longitudinal direction of the n-1 prismatic strip and the incident direction of the light therein, An angle defined between the longitudinal direction of the n-th prism strip and the incident direction of the light, and n is an integer from 2 to 180)

to It can be from 0 to 180 degrees.

In one embodiment, to Can be different.

In another embodiment, to At least one of them may be the same.

versus The difference between the two may be from about 1 degree to about 10 degrees.

In another aspect of the invention, a method of fabricating a light guide plate can include applying a polymer solution containing a light diffusing agent to a substrate layer, and imprinting at least one optical pattern to an polymerization formed on the substrate layer. On the solution layer.

The polymer may have a refractive index of from about 1.43 to about 1.45 and may be an optically clear resin used to make a light guide. For example, the optically transparent resin may include at least one polyester resin selected from the group consisting of (meth)acrylic, polycarbonate, styrene, olefinic, and polymethyl methacrylate resins.

The light diffusing agent is a material capable of diffusing light and may be present at a concentration of from about 1,000 ppm to about 5,000 ppm.

The base layer may be made of the same polymer as described above or may be made of a different polymer. Preferably, the base layer is made of the same resin as described above to improve the transparency of the light guide plate. For example, the base layer can be made of polymethyl methacrylate.

In one embodiment, the light guide plate may apply a polymer solution containing the prepared light diffusing agent to the substrate layer, and imprint the optical pattern forming section onto the polymer solution layer.

In still another aspect of the present invention, a transparent display device can include The light guide plate. The transparent display device can further include a panel and a light source.

Next, the present invention will be described in further detail with reference to the embodiments. However, it is to be understood that the examples are for illustrative purposes only and should not be construed as limiting the invention. A detailed description that is apparent to those skilled in the art will be deleted.

Example 1

A light guide plate including a rear surface as shown in FIG. 6 is prepared by mixing polyoxyxylene resin beads and polymethyl methacrylate resin, applying the mixture to a polymethyl methacrylate base layer, and pressing An optical pattern forming section having an embossed cone-shaped optical pattern is printed to the applied mixture layer.

Example 2

A light guide plate comprising a rear surface as shown in FIG. 5 is prepared by mixing polyoxyxylene resin beads and polymethyl methacrylate resin, applying the mixture to a polymethyl methacrylate base layer, and pressing An optical pattern forming section having an embossed prismatic strip optical pattern is printed to the applied mixture layer.

Example 3

A light guide plate comprising a rear surface as shown in FIG. 7 is prepared by mixing polyoxyxylene resin beads and polymethyl methacrylate resin, applying the mixture to a polymethyl methacrylate base layer, and pressing An optical pattern forming section having an embossed prismatic strip optical pattern is printed to the applied mixture layer.

Comparative example 1

Manufacture of beads containing polyoxyl resin over the entire portion without Optical pattern of light guide plate.

The light guide plate manufactured was evaluated for the following properties.

An image is disposed on a rear surface of the light guide plate, the light guide plate is coupled to an LED light source by a clamp in front of the image, and a panel is disposed in front of the light guide plate. The image and its appearance on the panel are evaluated when the LED light source is turned on or off.

When the light source was turned off, there was no difference between the images of the examples and the comparative examples. However, when the light source was turned on, the back surface image was visible using the light guide plate of the comparative example; however, the back surface image was not easily seen when the light guide plates of the respective embodiments were used. This is an excellent reason for not having to consider the back surface of the display at night or when the backlight is not present.

In the examples and comparative examples, the light guide plates each have a length of 480 mm and a thickness of 300 mm. On the light guide plate, three arbitrary points are determined at a separation point of a distance of 90 mm, 240 mm, and 390 mm from one side of the LED light source. The average brightness of these points is measured by the EZ contrast method, and the light efficiency is calculated from the average brightness. The light guide plate prepared in Comparative Example 1 was set to have a luminance of 100, and the light efficiency was the percentage of luminance measured in the examples. The degree of consistency of each of the three points is a percentage of the minimum/maximum of the brightness at each of the three points. For the light guide plates, after the light guide plates are disposed using the light sources as shown in FIGS. 5 to 7, the visibility of the patterns is evaluated based on the visibility of the light output from the light sources. Comparative Example 1 used a point. The results are shown in Table 1.

As shown in Table 1, the light guide plate of the embodiment improved the light efficiency by two times or more by increasing the average brightness while improving the uniformity of light. In contrast, a comparative light guide plate containing only beads without any optical pattern has lower brightness, lower light uniformity, and lower light efficiency than the light guide of the comparative embodiment.

Although a few embodiments have been disclosed herein, it is to be understood by those skilled in the art that these embodiments are intended to be illustrative, and modifications, variations and changes may be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be limited only by the scope of the appended claims and their equivalents.

10‧‧‧Light source

20‧‧‧ front surface

30‧‧‧Back surface

40a-d‧‧‧ side surface

50‧‧‧ optical pattern

100‧‧‧Light guide plate

Claims (20)

A light guide plate comprising: a front surface; a rear surface opposite to the front surface; and a side surface connecting the front surface to the rear surface, wherein the optical pattern includes at least one of a shape of a cone or a prism strip It is formed on the rear surface, and a light diffusing agent is distributed on the rear surface. The light guide of claim 1, wherein the optical patterns are randomly formed. The light guide plate of claim 1, wherein the side surfaces comprise a first side surface on which a light source is disposed and a second side surface opposite to the first side surface. The light guide of claim 3, wherein the spacing between the optical patterns decreases as the distance of the optical patterns from the first side surface increases. The light guide plate of claim 3, wherein the number of optical patterns increases as the distance of the optical patterns from the first side surface increases. A light guide plate according to claim 1, wherein the prismatic strips have an angle defined by one of the prismatic strips longitudinally defining a direction of -90 degrees or +90 degrees between one of the incident directions of light from the light source. A light guide plate according to claim 1, wherein the prismatic strips have an angle defined by one of the longitudinal prism strips and a direction in which light from the light source is incident from about 0 degrees to about 180 degrees. The light guide plate of claim 1, wherein a corner defined by one of the prismatic strips and a direction in which the light system is incident from the light source is When, Equation 1 is satisfied: (here a corner defined by one of the longitudinal edges of a first prismatic strip and the direction of incidence of light therein, a corner defined by one of the longitudinal edges of a second prismatic strip and the direction of incidence of light therein, a corner defined by one of the longitudinal edges of an n-1 prismatic strip and the incident direction of the light therein, It is an angle defined by one of the n-th prism strips and the direction in which the light is incident, and n is an integer from 2 to 180). The light guide plate of claim 8, wherein to At least one of them is the same. The light guide plate of claim 1, wherein the optical patterns are recesses or protrusions. The light guide of claim 1, wherein the conical systems have a vertical angle of from about 45 degrees to about 60 degrees, and the prismatic strips have a vertical angle of from about 70 degrees to about 90 degrees. The light guide of claim 1, wherein the optical patterns have a height of from about 6 microns to about 30 microns. The light guide of claim 1, wherein the prismatic strips have a length of from about 10 microns to about 35 microns and a width of from about 10 microns to about 35 microns. The light guide plate of claim 3, wherein the density of one of the light diffusing agents increases as the distance of the light diffusing agent from the first side surface increases. The light guide plate of claim 1, wherein the light diffusing agent is distributed in a range of about 0% to about 3% of the thickness of the light guide plate from the rear surface. The light guide of claim 1, wherein the light diffusing agent is present in a concentration of from about 1,000 ppm to about 5,000 ppm. The light guide of claim 1, wherein the light diffusing agent comprises beads. The light guide of claim 17, wherein the beads have a diameter of from about 1 micron to about 8 microns. The light guide plate of claim 1, wherein the light diffusing agent is further coated on the front surface. A transparent display device comprising the light guide plate according to any one of claims 1 to 19.