JP3012462B2 - Light guide plate, surface light source and non-light emitting display device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate suitable for a non-light-emitting display device such as a liquid crystal display device, a surface light source and a non-light-emitting display device using the same.

[0002]

2. Description of the Related Art FIG. 8A shows a conventional edge light type surface light source of this kind. On one end surface of the light guide plate 10, a straight tube-shaped illuminating lamp 12 in a direction perpendicular to the paper surface along this end surface is arranged.
The illuminating light is converted into surface illuminating light for a transmission type liquid crystal display panel (not shown) arranged on the plane 10a side of the light guide plate 10.

[0003] transmission type liquid crystal display panel is, because it has a viewing angle characteristic, by injecting the directivity of light in accordance with the characteristics of the plane 10a of the light guide plate 10, thereby improving the light utilization efficiency, low consumption Electricity can be achieved. For this purpose, a lenticular lens is superimposed on the plane 10a (Japanese Patent Laid-Open No. 6-222207) . However, since the lenticular lenses are superimposed, the surface light source becomes thick and heavy, and is expensive. Further, when a lenticular lens is used for a reflection type liquid crystal display panel, the display of the liquid crystal display panel becomes difficult to see due to the blur of the total reflection layer.

[0004] their in this, for transmissive liquid crystal display panel, is inclined surface 10b to the plane 10a, surfaces 10b
A surface light source that forms a step as shown in FIG. 8 (B), sets the step inclination angle to 45 °, and reflects the light incident from the end face 10c in a direction substantially perpendicular to the plane 10a at the step inclination surface. Has been proposed. In the figure, 14 is a reflector, 16 and 1
8 is a reflection plate, and 20 is a diffusion plate. However, the plane 10a
However, since the surface 10b is inclined, the manufacturing is not easy and the cost is high. In addition, since the surface light source must be mounted so that the plane 10a is parallel to the display panel, the mounting operation is not easy.

[0005]

However, since the surface 10b is inclined with respect to the plane 10a, manufacturing is not easy and the cost is high, and the surface light source is arranged so that the plane 10a is parallel to the display panel. Installation work is not easy because it must be installed. It is an object of the present invention to provide a light guide plate which is easy to manufacture and can be easily attached to a non-light-emitting display device, and a surface light source and a non-light-emitting display device using the same.

Another object of the present invention is to provide a light guide plate capable of improving the visibility of a reflective and non-light-emitting display device, and a surface light source and a non-light-emitting display device using the same. It is in.

[0007]

The invention according to claim 1 is a light guide plate for emitting light incident from an end face from a first plane, wherein the light guide plate is provided on a second face opposed to the first plane. A prism array having a plurality of top lines and valley lines is formed, and an angle α between an imaginary surface contacting the plurality of top lines and one surface of each prism of the prism eye is formed with respect to air.
The angle β substantially equal to the critical angle of the light guide plate and formed by the virtual surface and the other surface of each prism of the prism array is smaller than the angle α.

Is the critical angle of the light guide plate with respect to air.
Since they are substantially equal, light incident from one end surface of the light guide plate
From the first plane with respect to its normal
The light is emitted approximately symmetrically, and the illumination light is
Usage efficiency is improved. Further, since the angle β is smaller than the angle α, the intensity distribution of light emitted from the first plane can be suppressed from becoming particularly large on the one end surface side of the light guide plate, and furthermore, the unevenness of the prism array surface is relatively small. When the light guide plate of the present invention is applied to a reflective and non-light emitting display device, blurring on the display surface of the display device can be reduced as compared with the case where a lenticular lens is used, and visibility can be improved.

Further, the second plane is made substantially parallel to the first plane.
Since Rukoto is possible, allowed to be manufactured easily and less expensive than conventional light guide plate having an inclined surface with respect to the first plane
In addition, it is easy to attach the light guide plate to the non-light emitting display device.

According to a second aspect of the present invention, in the first aspect, the critical angle is 42 ° and the angle α is 43 °.
There, the angle β is less than 10 °, the prism depth in the prism array is 5 to 50 [mu] m. Is too large pli <br/> prism depth, distribution of light intensity emitted from the first plane becomes uneven, too small, the area of the total reflection prism inclined surfaces is too narrow. When this interval is constant, if the angle β is too large, the prism pitch becomes too short, and the amount of light reflected on the prism inclined surface on one end surface side where the illumination lamp is arranged increases, and the other opposing one The amount of light that advances to the end face side decreases, and the area that can be made incident on the prism inclined surface by the front prism decreases. Conversely, if the angle β is too small, the average optical path length of light in the light guide plate becomes too long, and the loss due to attenuation increases. From these, there is a preferable range of the prism depth and the angle β. Claim 2 is an embodiment of this preferred range.

According to the third aspect of the present invention, there is provided the light guide plate according to the first aspect.
The end face has a convex shape. Due to this convex shape, the angle
Since the amount of light transmission to the inclined surface of α is reduced, light loss
Can be reduced.

According to a fourth aspect of the present invention, in the light guide plate according to the first aspect, the angle β increases as the distance from the end surface increases.
Have . According to this light guide plate, it is possible to make the distribution of the intensity of light emitted from the first plane more uniform. Claim 5
The light guide plate according to claim 1, wherein the second surface includes a first region and a second region divided by a division line,
The prism arrays in the first and second regions are substantially symmetric about the parting line. If the illuminating lamp is arranged along the end face on the first area side and the end face on the second area side of the light guide plate, the first
The distribution of the light intensity emitted from the plane can be made more uniform than when illuminating lamps are arranged not symmetrically but along one end face.

[0013] In the surface light source according to claim 6, any one of the above-mentioned ones.
And a light guide disposed along the end surface of the light guide plate.
And a light emitted from the illumination light to the side opposite to the end face.
A reflector for reflecting light toward the end face. Claim 7
In the light source, two surface light sources according to claim 6 are opposite to each other.
Are arranged doubly.

According to this surface light source, the light emitted from the light source surface
The distribution of intensity can be made more uniform. Claim 8
In the surface light source, the light guide plate according to claim 5 and the nuclear light guide plate,
A first illuminating lamp arranged along the first end face on the first area side;
If, emitted from抜第1 lighting to the side opposite to the first end surface
A first reflector for reflecting light toward the first end face, and the light guide plate
Of the second region arranged along the second end face on the second region side
An illuminating lamp and an emission from the second illuminating lamp to a side opposite to the second end surface
And a second reflector for reflecting the reflected light toward the second end face.
I do.

In the surface light source according to the ninth aspect , one of the opposing planes may be used.
A prism array with multiple top and valley lines
A virtual surface in contact with the plurality of top lines and the prism array.
The angle between one side and the other side of each prism of the ray
The light guide plate further includes a prism array plate disposed on the first plane side of the light guide plate so as to face the prism top line in a direction substantially perpendicular to the prism top line of the light guide plate. According to this surface light source, the directivity in a plane perpendicular to the first plane of the light guide plate and passing through the top line is also improved.

According to the tenth aspect of the present invention, in the ninth aspect,
Further, the light guide plate is disposed to face the first plane side.
Diffused plate, and an oppositely disposed diffuser disposed on the second surface side of the surface light source.
And a firing plate. In the non-light emitting display device according to claim 11,
The surface light source according to claim 10 and the first plane of the light guide plate.
A transmissive and non-light emitting display panel
Having. In the non-light emitting display device according to claim 12, claim
6. The surface light source according to 6 , facing the first plane side of the light guide plate
Having a reflective and non-luminous display panel disposed
You.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or similar components are denoted by the same or similar reference numerals. [First Embodiment] FIG. 2 shows a surface light source according to a first embodiment.

On one end face of the light guide plate 10A, a straight tube-type illuminating lamp 12, for example, a cold cathode tube or a hot cathode tube, which is perpendicular to the plane of the drawing and is arranged along this end face, is used to illuminate the plane 10a of the light guide plate 10. Is converted into surface illumination light emitted from the light source. This surface light source is used for a non-light emitting and transmission type display device, for example, a transmission type liquid crystal display panel 50. In order to improve the light use efficiency of the transmissive liquid crystal display panel 50 having the viewing angle characteristic, the light guide plate 10A has a surface 10d opposite to the plane 10a.
Is formed with a prism array. In this prism array, mutually parallel top lines T and valley lines V extending in the direction perpendicular to the paper surface are alternately present, all valley lines V are present in the virtual plane A1, and all top lines T are in the virtual plane A1. The virtual planes A1 and A2 exist in A2 and are parallel to the plane 10a. The inclination angles of the inclined surfaces S1 and S2 on both sides of the valley line V with respect to the virtual surface A2 are defined as angles α and β, respectively.

First, preferred values of the angle α will be described with reference to FIG. From the end face 10c, the angle θ with respect to the normal line
The light that has entered the light guide plate 10A at the point (a) travels as shown by the dashed line, enters the inclined surface S1 at an angle γ, and
And exits from the plane 10a at an angle η. In this case, the following relational expression holds.

Δ = 90 ° − (θ + 2α) (1) γ = 90 ° − (θ + α) (2) sinη = n · sinδ (3) where n is the conductivity of air. This is the refractive index of the light plate 10A. Hereinafter, the light guide plate 10A is made of an acrylic resin and has a refractive index n.
Is 1.492.

The critical angle in this case is 42 ° and the plane 1
The condition under which the light is totally reflected at 0a and light can propagate in the light guide plate 10A is −48 ° ≦ θ ≦ 48 °. The condition that the light incident on the inclined surface S1 is totally reflected by the inclined surface S1 is γ ≧ 42 °. The condition for total reflection on the inclined surface S1 and then transmission on the plane 10a is δ <42. By using these conditions and the equations (1) to (3), the following numerical relationships are obtained.

Angle α [゜] Angle θ [゜] Angle γ [゜] Angle η [゜] 300 to 18 42 to 60 18 to 48 40 to 8 42 to 50 3 to 15 43 0 to 8 42 to 47 −6 to 6450 to 3 42 to 45 −4.5 to 0480 −6-9 From the above numerical relationships, the following conclusions can be obtained for the angle α.

(1) If the angle α exceeds 48 °, light cannot be emitted from the plane 10a. (2) When the angle α is small, the range of the angle θ is widened, but the light emitted from the plane 10a is not preferable because it has directivity in an oblique direction. (3) The positive range and the negative range of the angle η are equal when α = 43 °.

Therefore, when the plane 10a is made of an acrylic resin, α is set to 43 °, and in general, the angle α is set to the critical angle of the light guide plate 10A with respect to the air, so that the normal to the plane 10a is On the other hand, light having a symmetrical intensity distribution is emitted from the plane 10a, which is a preferable condition for the transmission type liquid crystal display panel 50. On the other hand, preferable values of the angle β and the prism depth d (the interval between the virtual planes A1 and A2) are as follows.

If the prism depth d is too large, the plane 10
If the distribution of the light intensity emitted from a becomes non-uniform and is too small, the area of the total reflection prism inclined surface S1 becomes too small. When the prism depth d is constant, if the angle β is too large, the interval between the adjacent top lines T, that is, the prism pitch becomes too short, and the amount of light reflected on the inclined surface S1 on the end face 10c side increases, The amount of light traveling toward the end face 10e side is reduced, and the area that can be incident on the inclined surface S1 by the front prism is reduced. Conversely, if the angle β is too small, the average optical path length of the light in the light guide plate 10A becomes too long, and the loss due to attenuation increases.

Thus, there is a preferable range for the angle β and the prism depth d for a surface light source. It has been found that, in this practical range, the angle β is generally 10 ° or less and the depth d is about 5 μm or more and 50 μm or less. The value of the angle β, which is particularly preferable for a surface light source of a transmissive or reflective liquid crystal display device, is a value obtained by numerical analysis.
Under practical conditions where 0A is an acrylic resin, depth d is within the above range, and the length (width) between the end faces 10c and 10e is within a range of 30 to 200 mm, the angle is a very small angle of about 2 °. The present inventors have found that.

In FIG. 2, the inner shape of the reflector 14 surrounding the illumination lamp 12 and extending in the direction perpendicular to the paper surface is the end face 10.
It is preferable that most of the light incident on c is in the range of -8 ° ≦ θ ≦ 8 °, that is, it is preferable that light does not pass through the inclined surface S1. In addition, in order to reduce the loss of light transmitted through the prism array surface 10d, a reflection plate 16 is disposed to face the prism array surface 10d, and in contact with the end surface 10e in order to reduce the loss of light transmitted through the end surface 10e. A reflection plate 18 is provided. Further, a diffusion plate 20 is arranged in contact with the flat surface 10a in order to make the emission light intensity distribution uniform. As the reflection plates 16 and 18 and the diffusion plate 20, thin sheets or films can be used.

The light guide plate 10A is hot-pressed on one surface of an injection-molded resin-made transparent parallel plate with a template on which a pattern of a prism array is engraved, and then cooled.
It is easily obtained and can be manufactured more easily and at lower cost than the light guide plate 10 of FIG. 8 having an inclined surface. Virtual surface A
2 is parallel to the plane 10a, so that the surface light source can be easily attached to the transmissive liquid crystal display panel 50.

[Second Embodiment] FIG. 3 shows a surface light source according to a second embodiment. In this surface light source, the end face 10f of the plane 10a is made to be a convex surface like a cylindrical lens, and light incident on the end face 10c is -8 ° ≦ θ ≦ 8 as compared with the case of FIG.
° to be within the range.

As a result, the amount of light transmitted through the prism array surface 10d is reduced, and the directivity of light emitted from the plane 10a becomes more symmetric with respect to the normal line. Also, the diffusion plate 2
0 and the plane 10a, for example,
7, a prism array plate 22 as shown in FIG. The prism array plate 22 is for improving the directivity by bending light obliquely incident on the prism array plate 22 toward the normal side. As shown in FIG. 3B, the prism array plate 22 has α = β in the prism array of the light guide plate 10A.
The apex angle is, for example, 94 °.

The prism array plate 22 is arranged with the prism top line perpendicular to the prism top line T on the prism array surface 10d. By arranging in this way,
Directivity in a plane perpendicular to the paper surface is also improved. Third Embodiment FIG. 4 shows a surface light source according to a third embodiment.

In the surface light source shown in FIG. 2, since the angles β are all the same, even if the angle β is reduced, the amount of light incident on the inclined surface S1 on the end face 10e side is reduced. Therefore, the light guide plate 1
With respect to the 0g prism array surface 10g, the prism pitch p is gradually shortened by increasing the angle β from the end surface 10c to the end surface 10e side. Thus, the slope S1 per unit area becomes wider as approaching the end face 10e, so that the distribution of the intensity of light emitted from the plane 10a can be made more uniform than in the case of FIG.

Incidentally, the prism array surface 10g may be divided into a plurality of regions, and the prism pitch p may be changed for each region. When the angle β is increased, the area that can be incident on the inclined surface S1 is reduced by being hindered by the prism on the near side, so that the range of the angle β should preferably be 10 ° or less as described above.

[Fourth Embodiment] FIG. 5 shows a surface light source according to a fourth embodiment. This surface light source uses the two surface light sources of FIG. 1 in opposite directions and is superposed. However, the surface light source on the light emission side omits the reflection plate 16 and the other surface light source omits the diffusion plate 20.

According to the fourth embodiment, the distribution of the light intensity emitted from the light guide plate surface on the side of the diffusion plate 20 can be made more uniform than in the case of FIG. [Fifth Embodiment] The surface light source shown in FIG. Therefore, in the surface light source of the fifth embodiment, as shown in FIG. 6, the prism array surface 10h of the light guide plate 10C is formed into a region R1 and a region R2 by a straight line perpendicular to the middle of the end surfaces 10c and 10e. Divided into prism array surface 10
The shape of h is symmetrical with respect to this division line. And
Symmetrically to the illumination lamp 12 and the reflector 14 on the end face 10c side,
The illumination lamp 32 and the reflector 34 are arranged on the end face 10e side.

According to the fifth embodiment, the distribution of the intensity of light emitted from the plane 10a can be made more uniform than that of the surface light source shown in FIG. 5, and the light guide plate shown in FIG. Sixth Embodiment The above surface light source is for a transmissive and non-luminous display panel, but as shown in FIG. 7, a reflective and non-luminous display panel, for example, a reflective liquid crystal display panel 50A. Can also be used as a surface light source. This surface light source has a configuration in which the diffusion plate 20 and the reflection plate 16 are omitted in FIG. 2, the transmissive liquid crystal display panel 50 is replaced with a reflective liquid crystal display panel 50A, and is inverted in the vertical direction.

Without this surface light source, it is difficult to see the display on the reflective liquid crystal display panel 50A in a dark place. By arranging such a surface light source on the reflective liquid crystal display panel 50A, the display is easy to see even in a dark place. Moreover, the illumination light from the illumination lamp 12 can be efficiently used due to its directivity, and power saving can be achieved. Also, α
= 43 °, β = 2 °, so that most of the prism array surface 10d is almost flat, and blurring on the display surface of the reflective liquid crystal display panel 50A is significantly reduced as compared with the case where a lenticular lens is used. And good visibility.

Since it is sufficient to turn off the illumination lamp 12 in a bright place, power consumption can be reduced as compared with the transmission type liquid crystal display device.
It is suitable for portable OA equipment. The present invention includes various other modifications. For example, it is a matter of course that the configuration shown in FIG. 7 may be obtained by applying the method shown in FIGS.

The light guide plate 10 is not limited to a transparent material such as an acrylic resin. The light guide plate 10 is made of a material having a light scattering property such that blur is inconspicuous in order to make the intensity distribution of light emitted from the plane 10a more uniform. For example, it may be formed of a copolymer of methyl methacrylate and a vinyl-based low molecule such as vinyl benzoate or trifluorinated methyl methacrylate.

[0040]

[0041]

[0042]

[0043]

[Brief description of the drawings]

FIG. 1 is an optical path diagram showing a principle configuration of the present invention.

FIG. 2 is a sectional view showing a surface light source according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a surface light source according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a surface light source according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing a surface light source according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing a surface light source according to a fifth embodiment of the present invention.

FIG. 7 is a sectional view showing a surface light source according to a sixth embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a conventional surface light source.

[Explanation of symbols]

 10, 10A to 10C Light guide plate 10d, 10g, 10h Prism array surface 12, 32 Illumination lamp 14, 34 Reflector 16, 18 Reflector plate 20 Diffuser plate 22 Prism array plate 50 Transmissive liquid crystal display panel 50A Reflective liquid crystal display panel V Valley Line T Top Line

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-294745 (JP, A) JP-A-6-194465 (JP, A) JP-A-6-202107 (JP, A) JP-A-7-294 225320 (JP, A) JP-A-6-160638 (JP, A) JP-A-6-222364 (JP, A) JP-A-3-67381 (JP, U) JP-A 61-36911 (JP, U) Japanese Utility Model Application Hei 3-56974 (JP, U) Japanese Utility Model Application Hei 4-91337 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/00 F21V 8/00 G02F 1/1335 G09F 9/00

Claims (12)

(57) [Claims] 1. A light guide plate for emitting light incident from an end surface from a first plane, wherein a prism array having a plurality of top lines and valley lines is provided on a second surface opposed to the first plane. The angle α formed between the imaginary surface formed in contact with the plurality of top lines and one surface of each prism of the prism array is equal to the conduction angle with respect to air.
A light guide plate substantially equal to a critical angle of the light plate , wherein an angle β between the virtual surface and the other surface of each prism of the prism array is smaller than the angle α. 2. The critical angle is 42 ° and the angle α
2. The light guide plate according to claim 1 , wherein the angle β is equal to or less than 10 °, and the prism depth in the prism array is 5 to 50 μm. 3. The light guide plate according to claim 1, wherein said end face has a convex shape. 4. The angle β increases as the distance from the end surface increases.
The light guide plate according to claim 1, wherein the light guide plate is large . 5. The apparatus according to claim 1, wherein the second surface includes a first area and a second area divided by a dividing line, and the prism arrays in the first and second areas are substantially symmetric with respect to the dividing line. The light guide plate according to claim 1, wherein: 6. The light guide plate according to claim 1, an illuminator disposed along the end surface of the light guide plate, and a light emitted from the illuminator to a side opposite to the end surface. And a reflector for reflecting light toward the end face. 7. A surface light source according to claim 6, wherein two surface light sources according to claim 6 are arranged double in opposite directions. 8. The light guide plate according to claim 5, a first light source disposed along a first end face of the nuclear light guide plate on the first region side, and a first end face from the first light source. A first reflector that reflects light emitted to the side opposite to the first end surface side; a second illumination lamp disposed along the second end surface of the light guide plate on the second region side; A second reflector that reflects light emitted from the second illumination lamp to the side opposite to the second end face toward the second end face. 9. A plurality of top lines and valleys on one of the opposing planes.
And a plurality of top lines are formed.
Of a virtual surface in contact with
A prism array in which the angles formed by the first and second surfaces are equal to each other, and the prism array is disposed on the first plane side of the light guide plate so as to face the prism top line in a direction substantially perpendicular to the prism top line of the light guide plate. The surface light source according to claim 6, further comprising: a plate. 10. The light guide plate according to claim 1, further comprising: a diffusion plate facing the first plane side of the light guide plate; and a reflection plate facing the second surface side of the surface light source. 9. The surface light source according to 9. 11. A non-light-emitting display, comprising: the surface light source according to claim 10; and a transmissive and non-light-emitting display panel opposed to the first plane side of the light guide plate. apparatus. 12. A non-luminous display comprising: the surface light source according to claim 6; and a reflective and non-luminous display panel disposed to face the first plane side of the light guide plate. apparatus.