KR100620574B1 - surface light source apparatus with concave pentagonal prism sheet - Google Patents

Abstract

The present invention relates to a surface light source device having a concave pentagonal prism sheet in which the individual prisms constituting the prism array of the prism sheet are arranged conversely on the light guide plate to be inverted on the light guide plate so that the brightness can be increased and the viewing angle can be improved. will be.

The present invention provides a plate-shaped light guide plate having one main surface as a light emission surface and at least one cross section as a light entrance surface, a linear light source arranged to extend along the light entrance surface of the light guide plate, and a light exit surface of the light guide plate. In the surface light source device having a prism sheet for changing the light propagation direction disposed on the prism sheet, the prism sheet is supported in a plate-shaped base portion having a predetermined thickness and having a flat upper surface and one surface thereof inverted under the base portion. And a plurality of concave pentagonal prisms that are symmetrical in left and right directions based on a vertical line passing through the center of the support surface, including a prism array arranged side by side.

In the above-described configuration, the interior angle Θ ₁ = Θ ₂ formed by the support surface and the concave surface is 5 ° ≦ Θ ₁ = Θ ₂ ≤85 °; The inner angle (Θ ₃ = Θ ₄ ) of the bending point of the concave surface is Θ ₃ = Θ ₄ > 180 °; Cabinet (Θ ₅₎ the two to meet the concave surface forming can be a 30 ° ≤Θ ₅ ≤120 °.

Prism, concave, surface light source, pentagon

Description

Surface light source apparatus with concave pentagonal prism sheet

1 is a perspective view schematically showing the structure of a surface light source device according to a conventional embodiment;

2 is a cross-sectional view showing a detailed structure of a prism sheet in the surface light source device of FIG.

3A to 3C are views illustrating an emission path of light incident at various angles in the prism sheet shown in FIG. 2;

4 is a cross-sectional view schematically showing the structure of a surface light source device having a concave pentagonal prism sheet of the present invention;

5 is a cross-sectional view showing a preferred structure of each prism of the prism sheet in FIG.

6a to 6b are views showing the emission path of the light incident at various angles in the prism sheet shown in FIG.

FIG. 7A is a graph showing viewing angles and luminance characteristics when the concave pentagonal prism sheet of the present invention is disposed on a light guide plate having a predetermined diffusion sheet, and FIG. 7B is a surface light source device having the concave pentagonal prism sheet of the present invention. This graph shows the intensity of the emitted light.

*** Explanation of symbols for the main parts of the drawing ***

12, 32: light guide plate, 12-1, 32-1: light incident surface,

12-2, 32-2: cross section, 12-3, 32-3: light exit surface,

12-4, 32-4: lower surface, 14, 34: linear light source,

16, 36: reflector, 18, 38: light reflection member,

20, 40: prism sheet, 20a, 40a: prism array,

20b, 40b: base material portion, 20-1, 40-1: light incident surface,

20-2, 40-2: light exit surface

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device having a concave pentagonal prism sheet. In particular, an individual prism constituting a prism array of a prism sheet has a concave pentagonal structure and is disposed inversely on the light guide plate to increase brightness and improve a viewing angle. A surface light source device having a concave pentagonal prism sheet.

Liquid crystal display (hereinafter, simply referred to as 'LCD') is an image display mechanism, and has the advantage of being thinner, smaller, and lower power consumption than other image display mechanisms, CRT (Cathode Ray Tube). It is rapidly replacing CRT. However, unlike the CRT, since the LCD does not emit light by itself, it requires a surface light source device in addition to the liquid crystal display.

1 is a perspective view schematically showing the structure of a surface light source device according to a conventional embodiment. In FIG. 1, reference numeral 12 denotes a plate-shaped light guide plate having a rectangular cross section, 14 denotes a linear light source extending along one cross section of the light guide plate 12, and 16 is attached to the linear light source 14. The reflector is shown, and 20 is a prism sheet that switches the light traveling direction.

On the other hand, in the light guide plate 12, one end face 12-1 extending in the longitudinal direction is used as the light incident surface, and the upper surface 12-3 is used as the light exit surface. The light reflection member 18 is attached to the lower surface 12-4 of the light guide plate 12. A light reflecting member (not shown) is typically shown in the case of a cross section opposite to the light incident surface 12-1, but additional linear light sources may be provided instead.

In the above-described configuration, the light incident from the linear light source 14 into the light guide plate 12 is totally reflected by the lower surface 12-4 and the light exit surface 12-3 on which the light reflection member 18 is placed. Is repeatedly received and transmitted toward the end face 12-2 opposite the light incident surface 12-1. Some of the light exiting from the lower surface 12-4 during the light transmission is reflected by the light reflecting member 18 and then reincident to the light guide plate 12 from the lower surface 12-4. In addition, a part of light is emitted from the light exit surface 12-3 during this light transmission, and the light exit angle is determined by the light exit surface 12-1 or the light exit surface 12-3 of the light guide plate 12. By changing the structure or adjusting the refractive index of the light guide plate 12, it can be limited to an appropriate range, for example, in the range of 50 ° to 85 ° with respect to the surface normal of the light exit surface 12-3 of the light guide plate 12. have.

FIG. 2 is a cross-sectional view illustrating a detailed structure of a prism sheet in the surface light source device of FIG. 1. As shown in FIG. 2, the prism sheet 20 includes a lower prism array 20a having an upper triangular prismatic surface and an upper sheet-like base portion 20b having an upper surface flat. In this case, the light incidence surface 20-1 is a prism face in which a plurality of longitudinal columnar prisms are arranged in parallel, and the light exit face is a flat face.

3A to 3C are diagrams illustrating an emission path of light incident at various angles in the prism sheet shown in FIG. 2. First, as shown in FIG. 3A, when light is incident from the light exit surface 12-3 of the light guide plate 12 perpendicularly to the left bevel of the light incident surface 20-1 of the prism sheet 20, the light is then right. After the internal reflection from the emitted again to the outside, at this time, as shown in the inclined emission from the plane normal, there was a problem that the brightness is reduced.

On the other hand, as shown in FIG. 3B, even when light is incident perpendicularly to the right oblique surface of the light incident surface 20-1, since the light is refracted and emitted after causing internal reflection, the light is emitted while being inclined to the plane normal so that the luminance is decreased. There was a problem letting. In addition, even when the light is obliquely incident on the left oblique surface of the light incident surface 20-1, as shown in FIG. 3C, the light rays incident into the prism array are deflected again and emitted toward the light guide plate 12 to thereby increase luminance. There was a problem reducing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the concave structure of the prism array of the prism sheet has a concave pentagonal structure in which the concave pentagon has a concave pentagonal structure arranged in the upper part of the light guide plate to increase brightness and improve a viewing angle. It is an object to provide a surface light source device having a pentagonal prism sheet.

The present invention for achieving the above object is a plate-shaped light guide plate having one main surface as a light exit surface and at least one cross-section as a light incident surface, a linear light source arranged to extend along the light incident surface of the light guide plate And a prism sheet for changing the light propagation direction arranged on the light exit surface of the light guide plate, wherein the prism sheet has a predetermined thickness and has a flat upper surface and a lower surface of the base. The inverted shape is supported, and a plurality of concave pentagonal prisms symmetrical from side to side based on a vertical line passing through the center of the supporting surface includes a prism array arranged side by side.

In the above-described configuration, the interior angle Θ ₁ = Θ ₂ formed by the support surface and the concave surface is 5 ° ≦ Θ ₁ = Θ ₂ ≤85 °; The inner angle (Θ ₃ = Θ ₄ ) of the bending point of the concave surface is Θ ₃ = Θ ₄ > 180 °; Cabinet (Θ ₅₎ the two to meet the concave surface forming can be a 30 ° ≤Θ ₅ ≤120 °.

Hereinafter, a preferred embodiment of a surface light source device having a concave pentagonal prism sheet of the present invention will be described in detail with reference to the accompanying drawings. Prior to the description, the principle of light will be briefly described.

Refraction is a phenomenon in which light goes straight through one material and its path is bent at the interface with another material. Such refraction is used as a microscope, a telescope, and a surface light source device. On the other hand, the prism is applied with Snell's law of optical refraction theory, which is the sine of the refractive angle (Θ ₂ ) and the incident angle (Θ ₁ ) when light proceeds from medium 1 with refractive index n ₁ to medium 2 with refractive index n ₂ . The ratio of values refers to the law that is always constant, which is expressed by Equation 1 below.

n ₁ * sin Θ ₁ = n ₂ * sinΘ ₂

On the other hand, when the light proceeds from a medium having a high refractive index (dense medium; n ₂ ) to a medium having a small refractive index (small medium; n ₁ ), total reflection occurs when the incident angle is larger than the critical angle (i _c ). When expressed as shown in Equation 2 below.

sin i _c = 1 / n _1,2 = n ₁ / n ₂

In Equation 2, n _1,2 is the refractive index of the dense medium with respect to the small medium.

4 is a cross-sectional view schematically showing the structure of a surface light source device having a mixed pentagonal prism sheet of the present invention. In FIG. 4, reference numeral 32 denotes a plate-shaped light guide plate which is generally formed in a rectangular shape, 34 denotes a linear light source extended along one end surface of the light guide plate 32, and 36 is a reflector attached to the linear light source 34. 40 denotes a prism sheet that switches the light traveling direction.

On the other hand, in the light guide plate 32, one end face 32-1 extending in the longitudinal direction is used as the light incident surface, and the upper surface 32-3 is used as the light exit surface. The light reflection member 38 is attached to the lower surface 32-4 of the light guide plate 32. A light reflecting member (not shown) is typically shown in the case of a cross section opposite to the light incident surface 32-1, but additional linear light sources may be provided instead.

In the above-described configuration, the light incident from the linear light source 34 into the light guide plate 32 is totally reflected by the lower surface 32-4 and the light exit surface 32-3 on which the light reflection member 38 is placed. Is repeatedly received and transmitted toward the end face 32-2 opposite to the light incident surface 32-1. Some of the light exiting from the lower surface 32-4 during such light transmission is reflected by the light reflecting member 38 and then reincident to the light guide plate 32 from the lower surface 32-4. In addition, some light is emitted from the light exit surface 32-3 during this light transmission, and the light exit angle is changed by changing the structure of the light exit surface or the light exit surface of the light guide plate 32 or by adjusting the refractive index. It may be limited to an appropriate range.

On the other hand, the prism sheet 40 is arranged side by side in a form in which the base portion 40b of a predetermined thickness having a flat light exit surface 40-2 on the top thereof and the bottom surface thereof is inverted in the lower portion of the base portion 40b. It consists of a plurality of pentagonal prism array 40a, whereby the prism array 40a becomes a light incident surface 40-1 and the upper surface of the base portion 40b is a light exit surface 40-2. )

5 is a cross-sectional view showing a preferred structure of each prism in FIG. As shown in FIG. 5, each prism constituting the prism array 40a in the prism sheet 40 of the present invention is deformed so that both oblique sides are bent inwardly by a predetermined angle in the inverted isosceles triangles Concave pentagonal structure, so that the sum of the interior angles is always 540 ° regardless of its shape. The concave pentagonal prism is preferably configured to be symmetrical with respect to the vertical line passing through the center.

In the above configuration, the internal angle Θ ₁ formed by the upper surface and the right concave surface and the internal angle Θ ₂ formed by the upper surface and the left concave surface are respectively 5 ° ≤Θ ₁ = Θ ₂ ≤85 °, preferably 30 ° ≤Θ ₁ = Θ ₂ ≤60 °, the internal angle of the bending point of the right concave surface (Θ ₃ ) and the internal angle of the bending point of the left concave surface (Θ ₄ ) is Θ ₃ = Θ ₄ > 180 °, Preferably, it may be 181 ° ≤Θ ₃ = Θ ₄ ≤200 °, and the internal angle Θ ₅ formed by the two concave surfaces is 30 ° ≤Θ ₅ ≤120 °, preferably 40 ° ≤Θ ₅ ≤100 It can be °. Further, the length w of the upper surface may be 15 μm ≦ w ≦ 100 μm, preferably 40 μm ≦ w ≦ 60 μm. In the embodiment of FIG. 5, Θ ₁ = Θ ₂ = 45 °, Θ ₃ = Θ ₄ = 182 °, Θ ₅ = 86 °, the length of the upper surface w is 50 [μm], and the height h is 26 [. [Mu] m], a concave pentagonal prism is shown.

On the other hand, in the prism sheet 40, the prism array 40a can be comprised using active-energy-ray-curable resin material, such as ultraviolet curing, for example, The base part 40b is polyester resin, acrylic type, for example. It can comprise using materials, such as resin, a polycarbonate resin, a vinyl chloride resin, and a polymethacrylimide resin. As the base material part 40b, you may use a polarizing sheet, a polarization conversion sheet, or a light-diffusion sheet as needed. Of course, it can also be integrally formed using the same material, without distinguishing between the prism array 40a and the base part 40b. At this time, the material of the resin can be appropriately selected to have a refractive index that can match the range of the emission angle of the desired light beam. Furthermore, in manufacturing a prism sheet, the transparent synthetic resin plate may be formed by thermocompression bonding using a mold member having a desired expression structure, and may be simultaneously provided with a shape when manufactured by extrusion molding or injection molding. .

6A and 6B illustrate an emission path of light incident at various angles in the prism sheet shown in FIG. 4. As can be seen in FIGS. 6A and 6B, light is incident from the light exit surface 32-3 of the light guide plate 32 into the concave surface on the left side of the light incident surface 40-1 of the prism sheet 40, or It does not emit downward toward the light guide plate 32 as in the prior art, regardless of whether it is incident on the right side of the concave surface, so that it is always emitted upward through the internal reflection from the direct concave side or the opposite side, thereby increasing the luminance and improving the viewing angle.

FIG. 7A is a graph showing viewing angles and luminance characteristics when the concave pentagonal prism sheet of the present invention is disposed on a light guide plate having a predetermined diffusion sheet, and FIG. 7B is a surface light source device having the concave pentagonal prism sheet of the present invention. This graph shows the intensity of the emitted light. First, as shown in FIG. 7A, it can be seen that the concave pentagonal prism sheet of the present invention has a wide viewing angle and luminance characteristics when disposed on a light guide plate having a predetermined diffusion sheet. Further, as shown in FIG. 7B, the light emitted from the prism sheet having the viewing angle and the luminance has a high intensity characteristic at the center of the surface light source.

The surface light source device having the concave pentagonal prism sheet of the present invention is not limited to the above-described embodiments, and can be modified in various ways within the range permitted by the technical idea of the present invention.

According to the surface light source device having the concave pentagonal prism sheet of the present invention as described above, the remarkable effect of increasing the brightness and improving the viewing angle is exerted.

Claims (2)

delete A plate-shaped light guide plate having one main surface as a light exit surface and at least one cross section as a light entrance surface, a linear light source arranged to extend along the light entrance surface of the light guide plate, and disposed on the light exit surface of the light guide plate In the surface light source device having a prism sheet for switching the light traveling direction, The prism sheet has a predetermined thickness and a flat plate-shaped base portion and a bottom portion of the base portion are supported in the form of inverted, and when the vertical line passing through the center of the support surface is symmetrical concave A plurality of pentagonal prisms are made in a row including a prism array arranged side by side, An inner angle (Θ1 = Θ2) formed by the support surface and the concave surface is 5 ° ≦ Θ1 = Θ2 ≦ 85 °; The inner angle (Θ3 = Θ4) of the bending point of the concave surface is Θ3 = Θ4> 180 °; And an inner angle Θ5 formed by the two concave surfaces is 30 ° ≦ Θ5 ≦ 120 °.

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