JP2001357714A - Surface illumination device and a liquid crystal display using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost surface illumination device and a liquid crystal display using it, which have a simple structure and can be easily assembled while having higher illumination efficiency and can be suitably used for a portable liquid crystal display or the like, by utilizing a point light source such as a white LED although it has been difficult to be applied to the surface illumination device because it is a point light source despite its advantage a light source. SOLUTION: In the surface illumination device which is composed of a point light source that is arranged on a side end part of almost a transparent light guide 11 with a light emitting surface on its one face and in which a light drawing out mechanism 14 is installed at the light guide, the point light source 12 is arranged on at least one corner part 13 of the light guide 11, and a corner cut surface 13a is formed on the corner 13 so that a light incident surface is directed almost a central direction of the light emitting surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface illumination device and a liquid crystal display using the same. 1. Field of the Invention The present invention relates to a surface illumination device which is composed of components and has excellent assemblability and a liquid crystal display using the same.

[0002]

2. Description of the Related Art In recent years, a transmissive liquid crystal display device has been frequently used as a display device such as a monitor for a personal computer. In such a liquid crystal display device, a planar illuminating device, ie, A backlight is provided, illuminates the liquid crystal panel from the back, and the amount of light transmitted through the panel is controlled by the shutter mechanism of the liquid crystal element,
It is a mechanism for displaying images.

Here, the transmission type liquid crystal cell has a structure in which emitted light must pass through layers that cause a large number of light losses, such as a polarizing plate, a color filter, and an electrode. Must be extremely large, and it is difficult to increase the brightness of the display screen. For this reason, in a liquid crystal display device that is frequently used outdoors such as a portable personal computer and a portable information terminal, there has been a problem that it is difficult to visually recognize a display image in an environment where the periphery is extremely bright. .

Therefore, as a liquid crystal display device for these applications, a reflection type liquid crystal display in which a reflection plate is provided in a liquid crystal cell and an external light is directly reflected and displayed is being used. It has been confirmed that a transmissive liquid crystal display can clearly capture an image even in an outdoor environment where the contrast is reduced and visibility is difficult.

However, due to the characteristics of the reflection type liquid crystal display which directly uses external light, there is a disadvantage that the external light used for display is limited in an indoor environment where the surroundings are dark or in a vehicle of a transportation facility, so that it is difficult to visually recognize the external light. In order to improve this disadvantage, contrary to the transmissive liquid crystal display, an illumination device that illuminates the liquid crystal panel in front of the liquid crystal panel, that is, a front light is attached, and images can be displayed even in an environment where external light is not sufficient. It is devised so that it can be captured clearly.

[0006]

As described above, it is important that the backlight and front light of a liquid crystal display used in these portable devices have high efficiency, and various proposals have been made so far. I have. But,
The illumination efficiency and the illuminance unevenness in the display surface are not yet satisfactory, and there has been a problem that there is no one having sufficient performance as a front light of a reflection type liquid crystal display.

In particular, a white LED light source that can be easily miniaturized, generates less heat, and consumes less power is extremely suitable as an illumination light source for a liquid crystal display used in these portable devices. However, unlike a discharge tube such as a cold cathode tube which is a linear light source, it is difficult to secure a uniform illumination intensity in a planar shape because it is a point light source.

For this reason, the point light source 3 is temporarily converted to a linear light source by using the optical rod (second light guide having the light emitting function 2) 1 shown in FIG. 10, as shown in FIG. Surface illumination is obtained by using the light incident on the light guide 11 as a linear light source, for example, by arranging the LEDs 4 in an array to form a pseudo linear light source 5. However, in the method using the optical rod 1, there is a problem that the light loss is large and sufficient illumination intensity cannot be obtained. In the method using the LED array 4, the number of components is extremely increased, and the assemblability is deteriorated. Therefore, there has been a problem that the cost increases.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem, and is applied to a surface illuminating device because it is a point light source while having essentially advantageous characteristics as a light source. Utilizing a point light source such as a white LED, which has been difficult to achieve, while providing higher illumination efficiency, a simple structure, excellent assemblability, and a low-cost surface illumination device that can be suitably used for a portable liquid crystal display device and the like. It is to provide a liquid crystal display using the same.

[0010]

SUMMARY OF THE INVENTION The present invention is a surface lighting device, and is configured as follows to solve the above-mentioned technical problem. That is, the present invention provides a point light source at a side end of a substantially transparent light guide having one surface as a light emitting surface,
In a surface illumination device in which a light guide is provided with a light extraction mechanism, a point light source is disposed at at least one corner of the light guide, and light enters the corner substantially in the direction of the center of the light exit surface. A corner cut surface is formed so as to face the surface.

<Specific Configuration in the Present Invention> The surface lighting device of the present invention is composed of the above-mentioned essential components. However, the present invention can be established even when the specific components are as follows. The concrete component is that the corner cut surface is subjected to unevenness processing or rough surface processing, or a light guide is provided on the front surface of the illuminated body to illuminate the illuminated body, and a point light source is formed by nitriding. A gallium-based or selenium-zinc-based white light-emitting diode element is used.

Further, in the surface illumination device of the present invention, as a light extraction mechanism provided on the light guide, a pattern consisting of a rough surface, a projection or a concave portion is formed or patterned on the surface of the light guide, and this pattern is cornered. It is characterized in that the occupied area increases as the distance from the cut surface increases. As a light extraction mechanism provided in the light guide, when the surface on the side on which the illuminated body is provided is a light emitting surface, the surface on the side opposite to this surface has an inclination angle θ of 1 to 20 degrees. An inclined surface array can be provided so that the ridge line of the inclined surface array is substantially parallel to the corner cut surface.

Further, in the surface lighting device of the present invention, a rough surface constituting a pattern formed on the surface on the side on which the illuminated object is provided is provided as a light extraction mechanism provided on the light guide, and the roughness is reduced. The Rz value specified in JIS B0601 is 0.2
It is preferred to be in the range of μm to 15 μm. Further, the pattern formed as the light extraction mechanism provided in the light guide has two directions: a diagonal direction connecting the corner where the point light source is provided and another corner facing the other, and a direction orthogonal to the diagonal. It is preferable to change in the axial direction to make the illumination intensity distribution uniform. Further, it is preferable that at least one of the one surface of the light guide and the surface facing the light guide is subjected to an antireflection treatment.

Further, the present invention relates to a liquid crystal display,
The surface illumination device of the present invention having the above-described features can be configured by being disposed on the back surface of a liquid crystal panel as backlight light source means. Furthermore, the liquid crystal display of the present invention can be configured by disposing the surface illumination device of the present invention having the above-described features as a front light source means on the front surface of a reflective liquid crystal display panel.

Furthermore, in the liquid crystal display of the present invention, when the surface illumination device having the above-mentioned features is used as the front light source means, the light extraction mechanism is constituted by a substantially parallel line pattern. It is preferable that the inclination angle α of the pattern is in the range of 5 ° to 40 °.

Further, it is preferable to provide an air layer having a thickness of 0.1 μm or more and 100 μm or less between the white light emitting diode element and the light guide, which are suitably used in the surface illumination device of the present invention. It is also preferable to attach a regular reflection film having a reflectance of 85% or more to the side end of the light guide.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a surface illumination device according to the present invention and a liquid crystal display using the same. FIG. 1 shows a main part of a surface illumination device 10 according to one embodiment of the present invention. The surface lighting device 10 according to this embodiment includes a substantially transparent light guide 11 having one surface as a light exit surface.

FIG. 1 is a plan view of the light guide 11 viewed from above, and a light source 12 is disposed at a side end of the light guide 11. The side end where the light source 12 is disposed is a corner portion 13 of the light guide 11, and a corner cut surface 13 a facing the center direction of the light guide 11 is formed in this corner portion.

As described above, the corner portion 13 of the light guide 11 is
By arranging the light source 12 on the corner cut surface 13a formed by cutting the light, the light from the light source 12 is incident substantially toward the center of the light guide 11 and propagates. At this time, the light source 12 disposed at the corner 13 which is the side end of the light guide 11 is a point light source. The point light source 12 is not particularly limited as long as it is white and can be miniaturized, but representative examples include a light emitting diode element, a halogen bulb, and an EL element (inorganic, organic).

The illuminating light beam entering the light guide 11 from the side end of the light guide 11 is irradiated by a light extraction mechanism 14 having a rough surface, irregularities, and an inclined surface provided on the light guide 11. Out of one surface to illuminate the illuminated body. For the point light source 12, it is particularly preferable to use a white light emitting diode element in terms of luminous efficiency, low driving voltage, and easy downsizing, and typically, a gallium nitride-based or selenium zinc-based element is used. A white light-emitting diode element is used in which a blue light-emitting diode is used as a light source and a part of the emitted light is converted into a complementary color using a fluorescent substance that performs wavelength conversion to obtain white light.

By the way, in order to reduce the non-uniformity of the illumination intensity in the plane, the light is generally made as uniform as possible over a wide area at the light guide side end as shown in FIG. It is effective to make the light incident, and in a mode in which the linear light source 6 such as a cold cathode tube is used, the entire surface of the side end 11a can be a light incident surface. Therefore, it was possible to reduce illumination unevenness by adjusting the arrangement of the light extraction mechanism.

However, in a mode in which a point light source such as a light-emitting diode element is used as a light source, it is extremely difficult to reduce illumination unevenness as compared with a linear light source. 2 light guides) 1 or
Alternatively, as shown in FIG. 10, light emitting diode elements are arranged in an array to form a pseudo linear light source.
Illumination non-uniformity was reduced by making the light uniformly incident on the side end surface 11a.

On the other hand, in the lighting device 10 according to the embodiment of the present invention, the point light source 12 is
Is provided at a corner portion 13, and a corner cut surface 13 a is provided at the corner portion 13, and a light ray incident on the light guide 11 is incident substantially toward the center of the light guide 11 and propagates. It will be.

By doing so, for example, FIG.
When the point light source 12 is disposed at the center of the side end face as shown in FIG. 1, while the area covering almost 180 degrees has to be uniformly illuminated as shown by reference numeral 15, As shown in FIG. 2 (b), it is only necessary to spread the incident light in a range of only 90 degrees. Since the incident light is easily spread evenly in the light guide 11, the unevenness of the illumination is remarkably reduced. Adjustment is easy.

Further, in the surface lighting device 10 according to the present embodiment, as shown in FIGS. 3A to 3D, the corrugated portion 16 is preferably formed on the corner cut surface 13a. Alternatively, the rough surface 17 is processed. Such uneven portion 1
6 and rough surface 17, the corner cut surface 13
Since the incident light from the point light source 12 is appropriately scattered at a, the light is more evenly distributed in the light guide 11, and illumination unevenness can be reduced.

Here, as the concavo-convex portion 16 formed on the corner cut surface 13a, typically, as shown in FIG. 3A, a triangular prism-shaped portion 16a having a vertex angle of 30 to 150 degrees is processed. 3B, processing of corrugated plate-like portion 16b having a pitch of 3 mm or less, as shown in FIG.
As shown in (1), processing of the comb-tooth-like portion 16c is typically given. In addition, as shown in FIG.
As for the processing of No. 7, the roughness of the rough surface portion is JIS B0601
The Rz value is 0.2, μm or more.

Further, the corner portion 13 where the point light source 12 is provided is not limited to one as shown in FIG. 1, but may be formed as shown in FIG.
As shown in FIG. 4, two lamps are arranged at two places, or FIG.
As shown in (b), it is possible to use a mode such as a four-lamp type by arranging at four places. In the embodiment of the present invention shown in FIGS. 1 and 4, the light guide 11 has a rectangular shape when viewed in a plane, and therefore, there are four corner portions 13.

However, in the surface illumination device of the present invention, the planar shape of the light guide 11 is not limited to a rectangular shape, but a polygon excluding a circle (including an ellipse) having no corner portion. It goes without saying that it can be applied to all things. However, in the case of a polygon having a large number of corner portions, a state similar to that described with reference to FIG. 2A is approached. Therefore, a rectangle including a rectangle or a square is preferably used.

In the surface illumination device of the present invention, the distance between the white light-emitting diode element and the light guide (preferably a short distance when the light guide has irregularities) is 0.1 μm or more.
An air layer having a thickness of 100 μm, preferably 0.1 to 50 μm, and more preferably 0.1 to 30 μm is provided. That is, the light emitted from the white light emitting diode element is easily propagated in the light guide due to the presence of the air layer. Therefore, the light component which is lost near the light source as a bright line is reduced, and the efficiency of the surface illumination device is improved. Can be.

Further, in the surface illumination device 10 according to the embodiment of the present invention, the light extraction mechanism 14 provided on the light guide 11 is not particularly limited, and a commonly used dispersed ink such as titania or silica is used. Patterning,
Patterning with a rough surface, patterning of a concavo-convex shape, and the like are preferably used.

The surface illuminating device of the present invention is also suitably used as a so-called front light, which is used by illuminating the illuminated object in front of the illuminated object.
As a light extraction mechanism 14 suitable for this application, typically, as shown in FIG.
FIG. 5 shows a mode in which a 0-degree inclined surface 18 is provided in the form of an array on the surface 11b of the light guide 11 opposite to the side on which the illuminated body is arranged, FIG.
As shown in FIG. 5B, an embodiment in which a pattern composed of irregularities 19a and 19b is provided on one surface 11c of the light guide 11 (the surface on the side where the illuminated body is provided, that is, the light emission surface), FIG. , One surface 11c on the side on which the illuminated body is disposed
Rz value specified in JIS B0601 0.2 μm to 15
A mode in which the rough surface 20 in the range of μm is provided, and the like.

Here, the inclined surface 18 provided in an array shape
In the case of using a shape in which a large number of substantially parallel linear patterning are viewed from the top, such as a mode using an inclined surface array (hereinafter referred to as an inclined surface array), the parallel linear pattern is formed as shown in FIG. ), It is preferable that the direction is substantially perpendicular to the propagation direction of the light beam from the point light source. In other words, the inclined surface array 18 is formed such that the ridge line 18a is substantially parallel to the corner cut surface 13a.

This not only improves the light emission efficiency, but also prevents the occurrence of moire fringes due to interference with the gate array of the thin film transistor used in the liquid crystal element. is there. That is, such a parallel linear pattern is originally
Because of its periodicity, interference with the liquid crystal panel is inherently liable to occur. Therefore, the inclination of the parallel lines with respect to the display screen is effective in suppressing interference fringes.

More specifically, as shown in FIG. 6B, which is an enlarged view of the portion A in FIG. 6A, the two side end surfaces defining the corner portion 13 are formed with one side end surface 11a. When the angle is the inclination angle α of the parallel linear pattern, the angle α is selected from the range of 5 ° to 45 °, preferably 10 ° to 40 °, and more preferably 15 ° to 40 °. This is because if the inclination angle between the imaginary axis 21 perpendicular to one side end surface 11a and the parallel linear pattern is α1, α ≦ α1
Becomes

Further, as shown in FIG.
9a and the projection 19b and the rough surface 20 shown in FIG.
Is advantageous in that it is generally easy to adjust illumination unevenness. Such a pattern advantageously utilizes these features also in the surface illumination device of the present invention. Representative examples are shown in FIGS. 7A to 7F.

That is, as shown in FIGS. 7A to 7D, the pattern composed of the concave portion 19a, the projecting portion 19b, the rough surface 20, and the like has almost the same shape such as an ellipse, a triangle, and a quadrilateral. For example, a pattern 23 formed by arranging (patterning) the dots 22 in a staggered pattern, or a linear portion (including a curve / straight line) 24 as shown in FIGS. 7 (e) and 7 (f). An example of the mesh pattern 25 formed in combination is given. In FIGS. 5A and 7, P indicates the pitch between the inclined surface arrays 18, the dots 22, or the linear portions 24.

As described above, the irregularities 19a and 19b and the rough surface 20
When patterning the dots 22 and the linear portions 24 formed in the above as a pattern, the scattering intensity is increased by increasing the area of the dot pattern as the distance from the light source 12 or increasing the arrangement density, This makes it possible to minimize illumination unevenness.

In particular, as the area of the light guide 11 becomes larger, it becomes more difficult to make the illumination unevenness uniform. In order to make the illumination unevenness more precise, as shown in FIG.
A diagonal direction (direction of arrow 27a, ie, change direction 1) connecting the corner portion 13 where the point light source 12 is provided and the corner portion 26 facing the same, and a direction orthogonal to this diagonal line (direction of arrow 27b, ie, change direction 2) It is effective to change the area and arrangement density of the pattern in the two axial directions. In FIG. 8, the area of the dot 22 is set in the biaxial directions 27a, 2a.
7B shows an example in which it is changed to 7b.

Further, it is necessary to make the inclined surface array 18 and the patterns 23 and 25 shown in FIG. 7 invisible to the naked eye. Specifically, the pitch P is 500 μm.
The thickness is set to 200 μm or less, more preferably 100 μm or less.

It is preferable that a reflector is provided around the point light source 12 so that the emitted light is incident on the corner cut surface 13a with as little waste as possible. The material used for the reflector is not particularly limited as long as it has high light reflectivity. For example, a white plastic film having a thickness of about 0.1 to 0.25 mm is preferably used.

Further, in order to sufficiently use up the light beam propagating in the light guide, specular reflection having a reflectance of 85% or more is provided at the side end of the light guide other than the corner cut surface where the point light source is disposed. Paste the reflective film of the nature, more specifically,
It is preferable to attach a reflection film having a surface coated with silver or aluminum as a reflection surface.

In a preferred embodiment of the surface lighting device of the present invention, the light guide 11 is formed of a resin material. In particular, an acrylic resin, a polycarbonate resin, a polyester resin, or a cyclic polyolefin resin is preferably used. In addition, since the light guide 11 is disposed on the front surface of the illuminated body, at least one surface of the light guide 11 is subjected to an anti-reflection treatment in order to prevent deterioration of image quality due to reflection of external light. It is preferred that In particular,
Typical examples include an antireflection film treatment by a thin film coating of a low refractive index substance such as magnesium fluoride and a fluorine resin, an antiglare treatment by bead coating on a surface portion, and a mat treatment.

A preferred use of the surface illumination device of the present invention is as a front light device for illuminating a liquid crystal panel by arranging it in front of a reflection type liquid crystal display. Here, the reflection type liquid crystal display is a liquid crystal display in which a reflection plate having a high reflectance is arranged in the liquid crystal cell surface or on the back surface to reflect external light and used for display. Liquid crystal display elements such as a nematic mode, an active matrix driven twisted nematic mode, and a simple matrix driven guest-host mode are listed. By arranging the surface illumination device of the present invention on the front of these liquid crystal displays, visibility is improved even in a dark place. It is possible to provide a good reflective liquid crystal display device.

[0044]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. (Example 1) 42.0 × 32.0 m as the light guide 11
An acrylic resin having a thickness of 1 mm and a thickness of 1 mm was used, and a light source 12 composed of a white LED was provided at one corner 13, and the pitch P was designed to gradually decrease as the distance from the light incident surface, which was the cut surface 13 a, increased. , The mesh-like pattern consisting of the rough surface is SU
The light guide 11 is formed on an S mold material by injection molding using the stamper as a stamper.
The mesh pattern 25 made of 0 was transferred (this embodiment 1 uses a surface illumination device as a backlight as described later). The mesh pattern 25 is shown in FIG.
, The line width is 20 μm, and the pitch is at least 70 μm.
μm, and a maximum of 180 μm.

FIG. 1 shows a corner 13 where a light source is provided.
, A corner cut surface 13a facing the center direction of the light guide 11 is provided, and the upper surface 11b is used as a rough dot pattern transfer side, and the corner cut surface 13a has a size of 2.
A 4 mm GaN-based white LED was provided as the point light source 12. The corner cut surface 13a serving as a light incident surface is subjected to V-groove processing at a pitch of 200 μm and a vertex angle of 90 ° to form a white LE.
The incident light from the D light source 12 is scattered by the V-groove processing portion so that the incident light can be distributed more uniformly in the light guide 11.

The obtained surface illumination device was used as a backlight, and a liquid crystal panel was constructed by arranging an induction type twisted nematic mode liquid crystal cell above the backlight.
The backlight was turned on using a DC power supply with a driving voltage of 4.5 V.

The luminance distribution on the display surface during white display has a very high degree of uniformity, and there is no dark area near the point light source which normally occurs when a point light source is used, and the image quality is very excellent. In addition, since no optical rod is used, the assemblability is good and the yield rate in mass production is improved.

(Embodiment 2) 47.0 × light guide 11
A light source 12 composed of a white LED is used at one corner 13 using an acrylic resin having a thickness of 40.0 mm and a thickness of 1.2 mm.
Is provided, a corner cut surface 13a is provided, and an inclined surface array having an inclination angle θ of 5 ° is provided so that a ridge line of the inclined surface array 18 is formed substantially parallel to the corner cut surface 13a. The take-out mechanism 14 was used. The pitch P of the inclined surface array 18 is set to 120 μm. Further, the surface 1 of the light guide 11 on which the inclined surface array 18 is not provided.
1c was coated with a fluorine-based antireflection coating material (manufactured by Asahi Glass Co., Ltd., Cytop) after being subjected to anchor coating treatment, and subjected to antireflection treatment.

As described above, the corner portion 13 where the point light source 12 is arranged is provided with a corner cut surface 13a facing the center of the light guide 11, and the upper surface 11b is formed as an inclined surface array 18 as shown in FIG.
The point light source 12 of 2.4 mm size GaN-based white LED was disposed on the corner cut surface 13a as the side provided with. The corner cut surface 13a serving as a light incident surface has J
A rough surface having an Rz value of 7.4 μm defined in IS B0601 is provided, and the incident light from the white LED light source 12 is scattered by the rough surface processing portion so that the incident light can be distributed more uniformly in the light guide 11. .

Using the obtained surface illumination device as a front light, a reflection type twisted nematic mode liquid crystal cell was arranged below the front light to form a liquid crystal panel.
The front light is turned on using a DC power supply with a drive voltage of 4.5 V.

The luminance distribution on the display surface during white display was extremely high in uniformity, and the image quality was very excellent. Further, in the present embodiment, the ridge line of the inclined surface array 18 is oblique to the liquid crystal panel, so that the moire pattern does not occur due to interference with the gate array of the liquid crystal panel, so that high image quality is maintained. Was. In addition, since no optical rod or LED array is used, the assemblability is good,
It was low in cost and high in yield during mass production.

(Embodiment 3) In the surface illumination device described in Embodiment 1, a cylindrical projection pattern having a projection amount of 50 μm is used as the light extraction mechanism 14, and the diameter of the cylindrical projection pattern increases as the distance from the light source 12 increases. The surface 11c of the light guide 11 was patterned to adjust the illumination intensity distribution.

More specifically, the diagonal direction 2 connecting the corner portion 13 where the point light source 12 is disposed and the corner portion 26 which faces the corner portion 13 in order to precisely uniform the illumination unevenness.
7a and 2 in a direction 27b orthogonal to the diagonal line 27a.
The illumination intensity distribution is adjusted by changing the pattern diameter in the axial direction.

A reflection type liquid crystal display was constructed by using this surface illumination device as a front light in the same manner as in the second embodiment. As with Example 2, high image quality is maintained, and illumination unevenness is precisely adjusted in the plane by adjusting the patterning two-axis directions 27a and 27b. Therefore, an extremely high quality front light device with no illumination unevenness is provided. A reflective liquid crystal display was obtained.

[0055]

As described above, according to the surface illuminating device of the present invention, it is difficult to apply the surface illuminating device to the surface illuminating device because it is a point light source while having essentially advantageous characteristics as a light source. Utilizing a point light source such as a white LED, which has higher illumination efficiency, has a simple structure and is easy to assemble,
Further, it is possible to provide an illumination optical system having characteristics extremely suitable as a surface illumination device used for a low-cost portable liquid crystal display device or the like.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a main part of a surface illumination device according to an embodiment of the present invention.

FIG. 2 is a plan view schematically showing a light diffusion direction when point light sources are arranged near a center of a side end of a light guide and at a corner.

FIG. 3 is a partial plan view showing, in an enlarged manner, a state in which a corner cut surface formed in a corner portion of the light guide is subjected to unevenness processing and rough surface processing.

FIG. 4 is another embodiment of the present invention, two-light and four-light.
It is a top view which shows the principal part of each surface illumination device of a lamp type | formula roughly.

FIG. 5 is a partially enlarged cross-sectional view showing a light extraction mechanism formed on the surface of the light guide.

FIG. 6A schematically shows a pattern arrangement in a case where a parallel linear pattern such as an inclined array is used as a light extraction mechanism formed on the surface of a light guide; FIG. 6B is a partial configuration explanatory view for explaining the forming conditions of the parallel linear pattern by enlarging the portion A in FIG. 6A.

FIG. 7 is a partial plan view showing various patterns formed by uneven portions and a rough surface as a light extraction mechanism formed on the surface of the light guide.

FIG. 8 is a configuration explanatory view schematically showing a state in which a pattern composed of uneven portions and a rough surface is changed in two axial directions to make illumination unevenness uniform as a light extraction mechanism formed on the surface of the light guide. is there.

FIG. 9 is a schematic plan view of a surface illumination device showing a state in which a conventional linear light source is disposed at a side end of a light guide.

FIG. 10 is a plan view schematically showing a conventional surface illumination device in which an optical rod conventionally used as a mechanism for converting a point light source into a linear light source is disposed at a side end of a light guide. FIG.

FIG. 11 is a plan view schematically showing a conventional surface lighting device in which point light sources such as light-emitting diode elements are arranged in an array and are quasi-linear light sources which are arranged at side ends of a light guide. It is.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Surface illumination device 11 Light guide 12 Point light source 13 Corner part 13a Corner cut surface 14 Light extraction mechanism 15 Light diffusion direction 16 Uneven part 16a Triangular prism part 16b Corrugated part 16c Comb part 17 Rough surface 18 Slope 18a Ridge line of inclined surface 19a Depression 19b Projection 20 Rough surface 21 Virtual axis 22 Dot 23 Dot pattern 24 Linear portion 25 Mesh pattern formed by combining linear portions 26 Corner 27a Diagonal direction of light guide 27b Direction perpendicular to diagonal direction 27a

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // F21Y 101: 02 G02F 1/1335 530 F term (reference) 2H038 AA52 AA55 BA06 2H091 FA14X FA14Z FA21X FA21Z FA23X FA23Z FA31X FA31Z FA45X FA45Z FD06 LA11 LA16 5G435 AA00 AA17 BB12 EE27 GG23 LL07

Claims (14)

[Claims] 1. A surface illumination device comprising: a point light source disposed at a side end of a substantially transparent light guide having one surface as a light exit surface, wherein the light guide is provided with a light extraction mechanism; The point light source is disposed at at least one corner portion of the light guide, and a corner cut surface is formed at the corner portion so that a light incident surface is directed substantially toward the center of the light exit surface. A surface lighting device characterized by the above-mentioned. 2. The surface illuminating device according to claim 1, wherein the corner cut surface is subjected to an uneven processing. 3. The surface lighting device according to claim 1, wherein the corner cut surface is roughened. 4. The light guide is disposed in front of the illuminated body to illuminate the illuminated body, and a gallium nitride based or selenium zinc based white light emitting diode element is used as the point light source. The surface lighting device according to claim 2 or 3, wherein: 5. A light extraction mechanism provided on the light guide, wherein a pattern comprising a rough surface, a protrusion or a concave portion is patterned on a surface of the light guide, and the pattern is separated from the corner cut surface as the distance from the corner cut surface increases. The surface lighting device according to any one of claims 2 to 4, wherein the surface lighting device is formed so as to increase an occupied area. 6. When the surface on the side on which the illuminated body is provided is the light-emitting surface, the surface on the side opposite to the surface has an inclination angle. The surface illumination device according to claim 4, wherein an inclined surface array having θ of 1 to 20 degrees is provided, and a ridge line of the inclined surface array is substantially parallel to the corner cut surface. 7. The rough surface constituting the pattern formed on the surface on the side on which the illuminated body is provided as the light extraction mechanism provided on the light guide has a roughness of JIS.
0.2 μm to 15 μm as the Rz value defined in B0601
The surface lighting device according to claim 4, wherein the range is m. 8. The pattern formed as the light extraction mechanism provided on the light guide includes a diagonal line connecting the corner where the point light source is provided and another corner facing the corner. The surface illumination device according to claim 5, wherein the illumination intensity distribution is changed in two axial directions, that is, a direction orthogonal to a diagonal line, to uniformize the illumination intensity distribution. 9. The light guide according to claim 4, wherein at least one of the one surface and the surface opposite to the one surface of the light guide is subjected to an anti-reflection treatment. Surface lighting device. 10. A liquid crystal display in which the surface illumination device according to claim 1 is disposed as a backlight light source means on a rear surface of a liquid crystal panel. 11. A liquid crystal display in which the surface illumination device according to claim 2 is disposed as a front light source means on a front surface of a reflective liquid crystal display panel. 12. A liquid crystal display using the surface illuminating device according to claim 5 as a front light source means, wherein the light extraction mechanism comprises a substantially parallel pattern, and an inclination angle of the parallel pattern. α is 5
A liquid crystal display characterized in that the angle is in the range of ° to 40 °. 13. An air layer having a thickness of 0.1 μm or more and 100 μm or less is provided between the white light emitting diode element and the light guide. Surface lighting device. 14. A light guide having a reflectance of 85 at a side end thereof.
The surface lighting device according to any one of claims 1 to 9, wherein a reflective film having a regular reflection ratio of at least 10% is attached.