JPH05158417A - Optical waveguide device for surface illumination - Google Patents

Abstract

PURPOSE:To uniformalize the brightness of the surface of a liquid crystal display device, etc., and to maintain high brightness as well with the optical waveguide device for illuminating this surface. CONSTITUTION:Plural planar optical waveguide layers 5a, 5b, 5c... successively having refractive indices N1>N2>...>NK>>NL, are laminated on a low- refractive index layer (N1) or high-reflectivity layer 4. The light of a light source 2 is made incident on this device from the light incident end face 7a thereof and a light diffusion layer 3 of refractive indices NH>N1 is brightened by the light emitted from the light exit end face 7b of a flat surface. The light propagating in the underlying long planar optical waveguide layer 5a weakens but the light of the adjacent planar optical waveguide layer 5b is propagated by total reflection between the overlying planar optical waveguide layer 5c and the low-refractive index layer or the high-reflectivity layer 4. This light is made incident on the planar optical waveguide layer 5a and makes interference to compensate the deficiency of the light quantity thereof and, therefore, the brightness of the surface is uniformalized. Since the layers are so constituted as not to generate a light loss in the optical path, the high-brightness illumination is assured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various surface illuminating devices such as signboards, display boards, liquid crystal display backlights, etc., in which the brightness within the surface is made uniform and high brightness can be maintained. The present invention relates to an improvement of an optical waveguide device for illumination.

[0002]

2. Description of the Related Art In recent years, with the spread of various displays such as word processors, personal computers, desktop electronic calculators, liquid crystal televisions, liquid crystal watches, etc., it has become possible to provide a surface illuminating device which has a uniform brightness within the surface and high brightness. In order to meet the increasing demand, a surface illumination device as shown in FIG. 8 and a display panel using the same have been already proposed (Japanese Patent Laid-Open No. 64-78283).

This is an optical transmission body A formed of a plurality of transparent plate-like bodies a stacked on each other, a light source c arranged on the light incident side b of the optical transmission body A, and the transparent plate-like body a. On the other hand, a light reflector e having a predetermined inclination angle and provided on the light emitting side d of the light transmission body A is provided. And the light reflector e
The light from the light emitting side d is reflected by the light conversion side d to be converted into diffused light, which is scattered by the plate-shaped light scatterer f that is in surface contact with the light transmission body A to illuminate the surface of the liquid crystal panel g. This is the surface lighting device.

Further, a light diffuser as shown in FIG. 9 has also been proposed (Japanese Patent Laid-Open No. 60-87387), in which a light transmitting end face h and a light emitting end face i are provided on a light transmitting body B. The optical transmission body B is composed of a plurality of stacked plate-like bodies j having a light-transmitting property, and each inclined surface k of the plate-like body j is continuous. Thus, the light emitting end face i is formed in a flat shape, and the light ray 1 of the light source c is incident on the light diffusing plate m from there.

[0005]

However, the above-mentioned conventional optical waveguide device for a surface illumination device has the following problems. That is, in the surface lighting device of FIG. 8 which is the former, in order to avoid crosstalk between the transparent plate-shaped bodies a, an adhesive or an air layer having a small refractive index is interposed to stack the light-transmitting bodies. A is formed so that light is independently propagated in each transparent plate a, and this light is reflected by the light reflector e as described above to obtain diffused light, which is then scattered by light. It is attempted to make the surface of uniform illumination by allowing the body f to enter the liquid crystal panel g.

However, since the lengths of the transparent plate-shaped bodies a are different from each other, their propagation losses are naturally different.
There is also a difference in the amount of light reflected by the light reflector e provided on the light emitting side d of the transparent plate a, and as a result, uneven brightness occurs between the central portion and the peripheral portion of the liquid crystal panel g. Becomes In addition, among the respective lights reflected by the light reflector e, the lights reflected in the direction perpendicular to the liquid crystal panel g surface (that is, when the reflection angle is about 45 degrees) are the respective transparent plate-shaped bodies a and Although it passes through the adhesive or air layer having a small refractive index and reaches the liquid crystal panel g surface, if the reflection angle is much smaller or larger than that, an adhesive or air layer having a small refractive index is used. The light is reflected or refracted and returns to the light incident side b of the transparent plate a as reflected return light, which does not reach the surface of the liquid crystal panel g, resulting in a decrease in its brightness.

Next, in the latter case of the light diffuser shown in FIG. 9 as well, since the lengths of the light transmission bodies B made up of a plurality of laminated plate-like bodies j are different from each other, the light emitting end surface is also different. Since unevenness occurs in each light quantity of i, the reason is that the optical transmitter B
This is because the shorter the length, the brighter it becomes, and the longer the length becomes darker. That is, the transmission loss is different due to the difference in the length of each plate-like body j of the light transmission body B, and it is difficult to make the light from the light source c uniformly incident on each plate-like body j, and In this case also, since light propagates independently in each plate-like body j, it is not possible to keep the amount of light from each inclined end face k uniform, and as described above, Since the light propagating in the plate-like body j is propagated under the confined state, it is seen from the light propagation direction side and the reflection side in the light diffusing plate surface m. Therefore, the difference between the forward scattered light and the back scattered light is large,
Irregularity of illumination depending on this cannot be avoided.

Therefore, in the present application, as a result of studying the defects of the conventional device, in the optical waveguide device for surface certification of claim 1, the transparent plate-shaped body a and the plate-shaped body j are formed as in the prior art. The plate-shaped optical waveguide layers are laminated, but not only the appropriate phase difference is set between the respective refractive indexes of these plate-shaped optical waveguide layers, but also the low-refractive index layer or the high-reflecting layer having an appropriate refractive index with which these are laminated. In addition to the above, a light diffusing layer having an appropriately selected refractive index is also laminated on the light emitting end face formed by the plate-shaped optical waveguide layer, so that light can be transmitted through only one plate-shaped optical waveguide layer. Not only pass through each independently, but also allow light to interfere with other plate-shaped optical waveguide layers, making the in-plane brightness uniform and illuminating with high brightness. The aim is to obtain a device.

According to a second aspect of the present invention, in the surface-illuminating optical waveguide device according to the first aspect, further, by setting the minimum relative refractive index difference between the plate-shaped optical waveguide layers to be 1% or less, low order Most of the mode light is propagated in its own plate-like optical waveguide layer so that the light diffusing layer can be illuminated brightly, and the higher-order mode propagation light interferes with other plate-like optical waveguide layers. Therefore, it is attempted to further improve the uniform brightness and brightness in the plane of the light diffusion layer.

In claim 3, claim 1 and claim 2 above.
The light-incident end surface of the optical transmission body formed by stacking the plate-shaped optical waveguide layers is formed by appropriately inclining the light-incidence end surface so as to make the light incidence from the light source efficient. However, similarly to this, by making the light incident end face a curved surface, the light incident efficiency is further improved.

In the case of claim 5, it is also shown that the low refractive index layer or the high reflectance layer in claims 1 and 2 can exert the same effect even when it is a curved surface instead of a flat surface. According to claim 6, the plate-shaped optical waveguide layer has a tapered shape rather than a uniform thickness to strengthen the interference of the light of the higher-order modes, thereby further homogenizing the amount of light in the light diffusion layer. Trying to promote.

According to a seventh aspect of the present invention, the structure according to the first aspect is provided on both left and right sides so that practically more uniform brightness and high brightness can be obtained in a wider area. According to the eighth aspect, the inclination angle of the low refractive index layer or the high reflectance layer according to the seventh aspect is 45 degrees or less, so that the entire device can be thinned and the screen can be easily enlarged. ..

According to a ninth aspect, not only the light source used in the structure of the seventh aspect but also a third light source irradiates light from the back side to the vicinity of the top of the low refractive index layer, Brightness compensation in the central portion of the surface is attempted more sufficiently, and in the case of claim 10, the plate-shaped optical waveguide layer in the structure of claim 7 is formed in a bent shape by the inclined layer portion and the lateral layer portion. By doing so, the light from the light source can be uniformly and efficiently incident from the light incident end face.

[0014]

The present Means for Solving the Problems] To achieve the above object, the low refractive index layer or the high reflectivity layer of claim 1, the refractive index N _L, both larger than the refractive index N _L ,
Refractive indices N ₁ , N ₂ , ... N _K (N
₁ > N ₂ >...> N _K >> N _L ), a plurality of required plate-shaped optical waveguide layers are stacked to form an optical transmission body, and the plate-shaped optical waveguide is provided in the optical transmission body. One end surface of the layer is formed as a light incident end surface formed by continuing from one end of the low refractive index layer or the high reflectance layer, and a light source is provided on the light incident end surface side and the plate-shaped optical waveguide is formed. The other end face of the layer is continuous from the other end of the low refractive index layer or the high reflectivity layer as above, and is connected to the light incident end face to form a flat light emitting end face, and on this light emitting end face An optical waveguide device for surface illumination is provided in which a light diffusion layer having a refractive index N _H larger than the refractive index N _{1 of the} underlying plate-shaped optical waveguide layer is formed. ..

According to a second aspect of the present invention, in addition to the structure of the first aspect, the plate-like optical waveguide layer is selected for multimode optical transmission, and the minimum relative refractive index in these plate-like optical waveguide layers is selected. The difference Δ ₁ = [(N _K −N _L ) / N _K ] × 100% is
The content is set to be 1% or more. In claim 3, the light incident end surface of the light transmission body is formed by an inclined surface that is inwardly inclined by a desired angle with respect to the normal line of the light emission end surface. In claim 4, same as above, the light incident end face is formed into a curved surface with respect to the light source, and in claim 5, the surface of the low refractive index layer or the high reflectance layer is formed into a flat surface or a curved surface, and According to claim 6, the plate-shaped optical waveguide layer has a uniform thickness or is formed so as to taper in the light propagation direction. ..

According to a seventh aspect of the present invention, the refractive index N is provided on each of the left and right inclined surfaces.
A low-refractive-index layer or a high-reflectivity layer of _L is formed into a roof-like base, and both the above-described low-refractive index layers or high-reflectivity layers,
Both larger than the refractive index N _L, the refractive index N ₁ to be sequentially smaller _{value, N 2, ‥‥‥ N K (} N 1> N 2> ‥‥‥
> N _K >> N _L ), a plurality of required plate-shaped optical waveguide layers are stacked to form an optical transmission body, and the outer end surface of the plate-shaped optical waveguide layer on each of the left and right sides of the optical transmission body is formed. A light source is provided on the light incident end face formed continuously from the outer ends of the left and right inclined surfaces, and the inner end face of the plate-shaped optical waveguide layer is the same as the top of the left and right inclined faces. A light emitting end face which is continuous to form a flat surface and is continuous with the light incident end face is formed, and a refractive index larger than the refractive index N _{1 of the} underlying plate-shaped optical waveguide layer is formed on the light emitting end face. The present invention provides an optical waveguide device for surface illumination, wherein an N _H light diffusion layer is formed.

According to an eighth aspect, in the optical waveguide device for surface illumination according to the seventh aspect, each of the left and right inclined surfaces on which the low refractive index layer or the high reflectance layer is formed is 45 degrees. The content is to be formed at the following inclination angles.

According to a ninth aspect of the present invention, the low refractive index layer having a refractive index N _L is formed on each of the left and right inclined surfaces to form a roof-like base portion, and both of the low refractive index layers have the above refractive index N _L. Refractive index N ₁ , N ₂ , ... N _K
A plurality of required plate-shaped optical waveguide layers having (N ₁ > N ₂ > ... ・ ・ ・ N _K >> N _L ) are stacked to form an optical transmission body. A light source is provided on the light incident end face side formed by continuing the outer end face of the plate-shaped optical waveguide layer on the side from the outer end of the left and right inclined faces,
The inner end surface of the plate-shaped optical waveguide layer is continuous so as to be a flat surface with reference to the apex of the left and right inclined surfaces, and a light emitting end surface is formed continuously with the light incident end surface. A light diffusing layer having a refractive index N _H greater than the refractive index N _{1 of the} underlying plate-shaped optical waveguide layer is formed on the end face, and a cavity is formed near the central axis of the roof-shaped base. An optical waveguide device for surface illumination is provided, in which the cavity is also provided with a light source for irradiating the vicinity of the top of the low refractive index layer from the back surface side.

According to a tenth aspect of the present invention, a roof-shaped base portion is formed by forming a low-refractive index layer or a high-refractive index layer having a refractive index N _{L on} each of the left and right inclined surfaces, and both the low-refractive index layers described above. In the high-reflectance layer, the refractive indices N ₁ , N ₂ , ... N _K (N ₁ > N), which are both higher than the above-mentioned refractive index N _L and successively decrease.
₂ >..................> N _K >> N _L ) and a plurality of required plate-shaped optical waveguide layers are stacked to form an optical transmission body. In the optical transmission body, plate-shaped optical waveguides on the left and right sides of the optical transmission body are formed. The corrugated layer is formed by an inclined layer portion stacked on each of the inclined surfaces and a lateral layer portion horizontally bent from the outer end thereof, and the outer end surface is formed from the outer ends of the left and right lateral layer portions. A light incident end face is continuously formed, and a light source is provided on the light incident end face side, and the inner end face of the plate-shaped optical waveguide layer is continuously formed as a flat surface with reference to the tops of the left and right inclined surfaces. And
A light emitting end face continuous with the light incident end face is formed, and a light diffusing layer having a refractive index N _H larger than the refractive index N _{1 of the} underlying plate-shaped optical waveguide layer is formed on the light emitting end face. It is intended to provide an optical waveguide device for surface illumination, which is characterized in that

[0020]

According to the optical waveguide device for surface illumination of claim 1,
The light from the light source is incident on the first plate-shaped optical waveguide layer having the refractive index N ₁ which is the lowest layer from the end face of the incident layer and is the _second layer having the refractive index N ₂ (N ₂ <N ₁ ) which is the upper layer. A plate-shaped optical waveguide layer,
The light propagates while being totally reflected between the low-refractive index layer or the high-refractive index layer having a refractive index N _L (N _L << N ₁ ) of the underlay, and enters the light diffusion layer from the end face of the emission layer, Although the incident portion is made brighter, this amount of light becomes relatively weak because the length of the second plate-shaped optical waveguide layer is the largest.

However, the light from the light source incident from the end surface of the incident layer of the second plate-shaped optical waveguide layer described above has a third plate-shaped optical waveguide layer having a refractive index N ₃ (N ₃ <N ₂ ) of the upper layer. And the low-refractive index layer described above are propagated while totally reflecting and enter the light diffusing layer, thereby not only brightening the incident portion to the light diffusing layer corresponding to the end face of the emitting layer, but also the second plate. Since the light from the optical waveguide layer also interferes with the first plate-shaped optical waveguide layer, this plays a role of compensating the amount of light in the first plate-shaped optical waveguide layer.

In the same manner as described above, the light incident on the third plate-like optical waveguide layer having a refractive index N ₃ has a refractive index N as an upper layer.
₄ (N ₄ <N ₃ ), which propagates while being totally reflected between the fourth plate-shaped optical waveguide layer and the low refractive index layer, enters the light diffusion layer, and
The light quantity of the second plate-shaped optical waveguide layer is compensated, and the corresponding portion of the light diffusion layer corresponding to the emitting layer end face of the third plate-shaped optical waveguide layer is brightened. The same action as above is performed on the layers. Then, most of the light incident on the uppermost plate-shaped optical waveguide layer having the refractive index N _K laminated on the uppermost layer is incident on the light diffusing layer and brightens the portion on the outermost end side.

In other words, the lights incident on the plate-shaped optical waveguide layers stacked in a plurality of layers interfere with each other and are propagated, whereby the lowermost stacked plate-shaped optical waveguide layers are propagated. The fact that the light quantity is weak is solved, and moreover, the light quantity from each plate-shaped optical waveguide layer is made uniform by the above-mentioned compensation, and the uneven brightness is eliminated. Furthermore, by the time the light reaches the light diffusing layer, there is nothing that prevents this, and there is no occurrence of reflected light toward the light incident side.
Since the refractive index N _H of the light diffusing layer is larger than the refractive index N _{1 of} the first plate-shaped optical waveguide layer, high brightness of the surface is realized.

Next, according to the optical waveguide device for surface illumination of claim 2, light is transmitted through the plate-shaped optical waveguide layer by multimode transmission, and the minimum relative refractive index difference is Δ ₁ = [(N _K − N _L ) / N
_{Since K} ] × 100% ≧ 1% or more, most of the low-order mode light propagating in each plate-like optical waveguide layer propagates independently in its own plate-like optical waveguide layer. , Which contributes to brightly illuminate the light diffusing layer, while the higher-order mode propagating light interferes with other plate-shaped optical waveguide layers having a higher refractive index than its own plate-shaped optical waveguide layer. By propagating, the amount of emitted light due to the difference in the length of each plate-shaped optical waveguide layer can be more sufficiently compensated, and the brightness in the plane of the light diffusion layer can be illuminated uniformly.

In both the third and fourth aspects, the light incident end face is inclined by a desired angle or is formed into a concave curved surface so that the light from the light source is efficiently incident on the light emitting end face. In the fifth aspect, even if the low refractive index layer or the high reflectance layer is a curved surface, the light transmission effect equivalent to that of a flat surface can be obtained. In the sixth aspect, the plate-shaped optical waveguide layer is tapered. As a result, the interference of the light of the higher-order mode can be strengthened, and the uniformity of the amount of light in the light diffusion layer can be further promoted.

According to claim 7, since the structure of claim 1 is symmetrically provided, the first and second etc. lower stacks which are near the tops of the left and right inclined surfaces which are particularly roof-like. Both of the lights emitted from the long plate-shaped optical waveguide layer are superposed around the central part of the light diffusion layer, eliminating the concern that the central part will be dark and ensuring a more uniform brightness on a wide surface. it can. In claim 8, the low refractive index layer or the high reflectance layer and the reflectance layer according to claim 7 are
By using a small inclination angle of 5 degrees or less, it is possible to make the whole thinner and to increase the screen size.

In the case of claim 9, since the third light source is added to the cavity formed in the base according to claim 7, this light is incident from the back surface side of the low refractive index layer. Was
This will be irradiated near the top of the low refractive index layer,
The lack of brightness in that portion can be sufficiently supplemented.

According to a tenth aspect of the present invention, the horizontal layer portion is provided on the incident layer end face side of the low refractive index layer according to the seventh aspect, and the inclined layer portion is connected to this in a bent shape. Light can be efficiently incident on the low refractive index layer, and more satisfactory results can be obtained for the interference of light.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to a so-called edge light type optical waveguide device for surface illumination that allows light to enter from both the left and right sides as shown in FIG. 1. In claim 1, only the left side or the right side of the central axis line XX. Whereas the content of the configuration is
In claim 7, the left side and the right side are the central axis X- as shown in the figure.
The structure is left-right symmetrical with respect to the X axis, and will be described in detail below by taking the left half structure as an example.

That is, the light transmission body 1 and the light source 2 and the light diffusion layer 3 on which various display panels such as liquid crystal are stacked are formed. The light transmission body 1 has a flat surface or a curved surface as shown in the drawing. The formed low refractive index layer or high reflectance layer 4 having a refractive index N _L and a plurality of required plate-like optical waveguide layers 5a, 5b, 5c, 5d, 5e, 5f mounted on the surface thereof. In this case, the low refractive index layer or the high reflectance layer 4 is formed on the surface of the base portion 6.

Examples of the low refractive index layer include plastics such as Teflon and polyvinylidene fluoride, SiO ₂ or SiO _2, and Ti, Ge, P, B, F, Al, Ta and Z.
Materials containing at least one refractive index control additive such as r, Zn, Na, and K, glass such as Pyrex, and compounds such as MgF ₂ and ZnS—MgF ₂ can be used. That is, the refractive index N _L is lower than the respective refractive indices N ₁ , N ₂ , ... N _K of the plate-shaped optical waveguide layers 5a, 5b, 5c, 5d, 5e, 5f.
Desirably low enough, for example 1.42
The thickness is preferably about 1.47, and it is sufficient that the film thickness is 0 comma number μm or more.

Al, Cr, Ag are contained in the above high reflectance layer.
, A metal film such as metal can be used as the base 6, and the plate-shaped optical waveguide layers 5a, 5b ... In order to propagate the light in the above-mentioned manner, it is necessary to select a transparent material having a good light transmittance, and the refractive index N ₁ , N ₂ ,
For N _K, it is necessary to satisfy the following relationship. N ₁ > N ₂ > N ₃ > N ₄ > N ₅ > N _K >> N _L That is, the bottommost first plate-shaped optical waveguide layer 5 a directly mounted on the low refractive index layer or the high reflectance layer 4 Refractive index N
₁ is the largest and the second and third plate-like optical waveguide layers 5b in order,
5c, toward ‥‥‥, a refractive index N _2, N _3, ‥‥‥
Becomes smaller, and these plate-like optical waveguide layers 5a, 5b ...
, But all have a refractive index larger than N _L as described above.

Here, the above-mentioned plate-like optical waveguide layers 5a, 5b ...
For example, polymethyl methacrylate (refractive index 1.49), polymethyl methacrylate to which a refractive index control additive is added (refractive index 1.50 to 1.55), polyurethane (refractive index 1 .555), organic materials such as photoresist (refractive index 1.615), Corning 7059 (refractive index 1.544), slide glass (refractive index 1.512).
Glass materials such as TiO ₂ , Al ₂ O ₃ , SnO ₂ , G
An oxide material such as eO ₂ or Sb ₂ O ₃ can be used. Further, these plate-like optical waveguide layers 5a, 5b ...
Of course, there may be two or more layers, but a multilayer is preferable, and the total thickness of the laminated layers may be in the range of several mm to several tens of mm depending on the application. It is about 1 mm to 10 mm.

As described above, the plate-shaped optical waveguide layers 5a and 5b are provided.
By stacking layers, the light transmission body 1 is provided with an incident layer end face 5a of each of the plate-shaped optical waveguide layers 5a, 5b from the left end of the low refractive index layer or the high reflectance layer 4. ', 5b' ...
The light incident end face 7a is formed continuously, and the light source 2 is provided on the left side of the light incident end face 7a so that the light from this is incident on the incident layer end faces 5a ', 5b'. In the figure, 2a is a reflecting mirror provided behind the light source 2, which allows the light from the light source 2 to pass through the respective plate-shaped optical waveguide layers 5a,
It is designed to be able to efficiently excite within 5b. Further, as the light source 2, for example, a cold cathode tube can be used, and specifically, a commercially available tube having a diameter of 4 mm, a length of about 28 cm, and an input power of 8 W can be used.

Further, from the right end of the low-refractive index layer or high-reflectance layer 4, the exit layer end faces 5a ", 5b" ... Of the respective plate-like optical waveguide layers 5a, 5b ... The light emitting end face 7b is formed as a flat surface, and the light emitting end face 7b and the light incident end face 7a are connected in a bent shape. In the embodiment of FIG. 1, the light incident end face 7a is the light emitting end face. 7b is inclined inward by a desired angle θ so that the light from the light source 2 can be efficiently incident into the plate-shaped optical waveguide layers 5a and 5b. This θ is up to 30 degrees. It is preferable to set the range, and in the embodiment of FIG. 3, the light incident end face 7a is formed to be a curved surface with respect to the light source 2, so that the light from the light source 2 can be more efficiently. The plate-shaped optical waveguide layers 5a, 5b ... The light incident end face 7a is preferably coated with an antireflection film.

Further, in FIG. 2, the width W of the exit layer end faces 5a ", 5b", ... of the plate-like optical waveguide layers 5a, 5b, ... is made uniform, but of course, the width is not uniform. As shown in FIG. 4, the plate-shaped optical waveguide layers 5a and 5b may be
It is also possible to taper in a taper shape along the light propagation direction without making the thickness of the light uniform. By doing so, the light of the higher mode described in detail in claim 2 described later is obtained. It is desirable to be able to strengthen the interference of.

Next, the front light diffusing layer 3 will be explained. This is formed on the light emitting end face 7b of the light transmission body 1 formed as the above flat surface, and at this time, its refractive index N _H.
Is set so that N _H > N ₁ , that is, the refractive index is larger than N ₁ which has the largest refractive index in the plate-shaped optical waveguide layer. 5
The light emitted from b ″ is incident on the light diffusing layer 3 in a staggered manner.

Here, as for the light diffusion layer 3, it is preferable that the upper surface of the light diffusion layer 3 has a periodically or aperiodically deformed structure due to fine unevenness or the like to diffusely reflect the light. The uniformity of brightness in the diffusion layer 3 can be further enhanced. Further, as the material, the same material as the above-mentioned plate-like optical waveguide layer can be used, and it is desirable that the fluorescent material is contained in or on the surface of the light diffusion layer 3 so as to achieve high brightness. At this time, specifically, it is preferable to mix a fluorescent dye (blue dye) having an emission maximum wavelength in a wavelength range of 400 to 700 mm, and a liquid crystal (not shown) to be illuminated on the light diffusion layer 3. A display panel such as a panel will be loaded.

Next, in an optical waveguide device for surface illumination according to a seventh aspect, only one pair of the one shown in the first aspect is provided symmetrically with respect to the illustrated central axis line XX. For this reason, in the illustrated example, the low refractive index layers or the high reflectance layers 4 and 4 are formed in a roof shape on both the left and right inclined surfaces 6a, 6a of the base 6 having a triangular cross section. In each of the pair of optical transmission bodies 1 and 1, the light incident end face 7 is provided.
a, 7a and light emitting end faces 7b, 7b are formed, and the respective light sources 2, 2 are arranged on the left and right, and the light emitting end face 7 is formed.
b and 7b are formed on a straight line as flat surfaces with reference to the apex 6b of both inclined surfaces 6a and 6a.

Here, the left and right inclined surfaces 6 formed above
The inclination angle α of a and 6a is preferably 45 degrees or less. By reducing the inclination angle α in this way, the thickness of the device can be reduced and a large screen can be achieved. ..

According to the first aspect of the invention configured as described above, the light from the light source 2 is incident on the light incident end face 7a, but is incident from the incident layer end face 5a 'of the plate-like optical waveguide layer 5a. Light has a low refractive index layer or high reflectance layer 4 having the lowest refractive index N _L and a plate-shaped optical waveguide layer 5b having a refractive index N ₂ smaller than the refractive index N _{1 of} the plate-shaped optical waveguide layer 5a. Propagates while undergoing total reflection between the output layer end face 5a ″ and N
_It is incident on the light diffusion layer 3 having a refractive index N _H larger than ₁ to make the relevant portion bright. Therefore, if the amount of light is only the above amount, the plate-shaped optical waveguide layer 5a of the bottom stack is the longest, and the brightness of the light diffusion layer 3 corresponding to the above portion is weak.

However, in the present invention, the light incident on the next stacked plate-shaped optical waveguide layer 5b from the incident layer end face 5b 'has a refractive index N ₃ higher than that of the plate-shaped optical waveguide layer 5b. Is propagated by being totally reflected between the small plate-shaped optical waveguide layer 5c and the low refractive index layer or the high-reflectance layer 4, and therefore the light also propagates in the plate-shaped optical waveguide layer 5a. Therefore, the light emitted from the emitting layer end surface 5a ″ of the plate-shaped optical waveguide layer 5a is compensated for by adding the light amount by the total reflection to the above-described light amount. The light from the emitting layer end surface 5b ″ of the plate-shaped optical waveguide layer 5b also brightens the corresponding portion of the light diffusion layer 3.

In this way, the light sequentially incident on the stacked plate-like optical waveguide layers is also totally reflected as described above and propagates also to the stacked plate-like optical waveguide layers below it to perform light quantity compensation. In other words, in other words, the lights propagating in the respective plate-shaped optical waveguide layers can be propagated by interfering with each other. In the uppermost stacked plate-shaped optical waveguide layer 5f, Most of the incident light enters the light diffusion layer and brightly illuminates the corresponding portion. Further, in the case of claim 7, since the light transmitters 1 and 1 are arranged on both the left and right sides, the central portion of the light diffusing layer 3 in this case enters from the plate-like optical waveguides on both the left and right lower stacking sides. The incoming light provides sufficient brightness, and the defects of the conventional example can be further eliminated. Further, in any one of claims 1 and 7, since the light emitted from the optical transmission bodies 1 and 1 is directly incident on the light diffusion layer 3, there is no factor of the brightness reduction in the conventional example, and the incident light is incident. No unintended reflected light is generated to the side.

Next, the case of claim 2 will be explained.
The plate-shaped optical waveguide layers 5a, 5b, ...
The optical transmission mode propagating in 5f is set to multimode transmission. At this time, the minimum relative refractive index difference Δ ₁ is Δ ₁
= [(N _K −N _L ) / N _K ] × 100% ≧ 1% is satisfied. As a result, the light from the light source 2 is efficiently confined and propagates in the plate-shaped optical waveguide layer, and a large amount of high-order mode light is propagated. Light propagates by interfering with the plate-shaped optical waveguide layer having a higher refractive index than that of the plate-shaped optical waveguide layer itself, and this causes a sufficient difference in length between the plate-shaped optical waveguide layers. Based on this, the amount of emitted light is compensated, the more uniform brightness uniformity in the plane of the light diffusion layer 3 is maintained, and high brightness is contributed.

The present invention is not limited to the above-described embodiments, and the base 6 does not need to have a triangular cross section, and the base may be formed as long as the shape of the optical transmission body 1 can be maintained. Alternatively, a low refractive index layer or a high reflectance layer may be simply formed on the lower surface of the plate-shaped optical waveguide layer 5a, and FIG.
As shown in FIG. 6, the top of the base 6 having a roof shape may be bent in an arc shape, and in the embodiment shown in FIG. 6, the inclined surfaces 6a, 6a of the base 6 described above. Is formed in an upward protruding arc shape, and the plate-like optical waveguide layer 5 is formed in accordance with this.
Also, a, 5b, etc. are not curved but curved in a bow shape.

Further, in FIG. 6 of the above, not only a pair of light sources 2 are provided on the left and right, but a third light source 2'according to claim 9 is added. That is, a cavity 6c is formed in the vicinity of the central axis line XX in the roof-shaped base portion 6, and the light emitted from the third light source 2'provided here is formed in the low refractive index layer. Irradiation is performed from the back surface side, which makes it easier to reduce the brightness of the top portion 6b.
The shortage of the amount of light in the vicinity can be further compensated. Therefore, the power consumption of the third light source 2'may be smaller than that of the light source 2.

Next, in the embodiment of FIG. 7 according to claim 10, the plate-like optical waveguide layers 5a, 5b, ... Are formed in a bent flat plate instead of a simple flat plate. This is different from the other embodiments. That is, the plate-shaped optical waveguide layers 5a, 5b, ... Shown here are the inclined layer portions 5S stacked in parallel with the inclined surfaces 6a, 6a of the base portion 6 and the outer ends thereof. It is formed by a horizontally oriented layer portion 5H bent and extended in a horizontal shape, and each outer edge of the horizontally oriented layer portion 5H is continuous to form a light incident end face 7a. By doing so, when the light incident end face 7a is arranged orthogonal to the light emitting end face 7b, the light from the light source 2 is most efficiently incident on each of the plate-shaped optical waveguide layers 5a, 5b. Since the light enters from the lateral layer portion 5H to the bent inclined layer portion 5S, the above-mentioned interference effect due to total reflection can be sufficiently expected.

[0048]

Since the present invention is constituted as described above, according to claim 1, a low refractive index layer or a high reflectance layer, a plurality of plate-like optical waveguide layers, and a light diffusion layer are provided. By properly selecting the refractive index so that not only the light propagates independently through each plate-shaped optical waveguide layer, but also the light interferes with each other, the amount of light from the long plate-shaped optical waveguide layer is By compensating the amount of light by the light from the adjacent plate-shaped optical waveguide layer, the in-plane brightness of the display panel can be kept uniform.

Further, due to the interference of light due to the above-described total reflection, the light emission from each plate-like optical waveguide layer enters the light diffusion layer in a considerably wide angle range, so that the uneven brightness depending on the viewing direction as in the conventional case. Since the problem of angle dependence such as occurrence of is eliminated, the optical transmission body does not include a layer that causes unnecessary optical loss as in the conventional example, and unnecessary reflected light to the incident end side does not occur. Can assure high brightness lighting.

According to the second aspect, by further setting the minimum relative refractive index difference to 1% or more, the mutual interference action of light in the first aspect is promoted, and the light quantity compensation effect can be improved.

According to the seventh aspect, since the pair of the first aspect is symmetrically provided, it is possible to efficiently and uniformly illuminate a wide surface and maintain high brightness. ..

In case of claim 9, in addition to the structure of claim 7, since the light is made to enter from the back surface side of the low refractive index layer by the third light source, the brightness in the light diffusion layer is made uniform. That is, it contributes to the improvement of brightness.

In the tenth aspect, since the plate-shaped optical waveguide layer is formed in a bent shape with the inclined layer portion and the lateral layer portion, the light incidence efficiency of the light source and the light interference effect can be enhanced.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional front view of a main part showing an embodiment showing an optical waveguide device for surface illumination of the present invention.

2 shows only the optical transmission body of FIG. 1, (A) is a schematic vertical sectional front view thereof, and (B) is a partially cutaway plan view.

FIG. 3 is a schematic vertical sectional front view of a main part showing another embodiment of the same device according to the present invention.

FIG. 4 is a schematic vertical sectional front view showing another embodiment of the optical transmission body in the same apparatus.

FIG. 5 is a schematic vertical sectional front view showing a different embodiment of the optical transmission body in the same apparatus.

FIG. 6 is a schematic vertical sectional front view showing a different embodiment of the same apparatus.

FIG. 7 is a schematic vertical sectional front view showing another different embodiment of the same device.

FIG. 8 is a schematic vertical sectional front view showing a conventional surface illumination device and a display panel.

FIG. 9 is a front explanatory view of a main part showing a conventional light diffuser.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical transmission body 2 Light source 3 Light diffusion layer 4 Low refractive index layer or high reflectance layer 5a Plate-shaped optical waveguide layer 5b Plate-shaped optical waveguide layer 5c Plate-shaped optical waveguide layer 5d Plate-shaped optical waveguide layer 5e Plate-shaped optical waveguide layer 5f Plate-shaped optical waveguide layer 5a 'Incident layer end face 5b' Incident layer end face 5a "Emitting layer end face 5b" Emitting layer end face 6 Base 6a Left and right inclined surfaces 6b Top 7a Light incident end face 7b Light emitting end face N _L Low refractive index layer Refractive index N _1, N _{2 to} N _K Refractive index of plate optical waveguide layer N _H Refractive index of light diffusing layer α Inclination angle of inclined surface θ Desired angle of light incident end surface Δ ₁ Minimum relative refractive index difference

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Hashimoto 3-6-20-303 Katahira, Aso-ku, Kawasaki-shi Techno System Co., Ltd. (72) Inventor Hirotake Imoto Makinosato, Meito-ku, Nagoya 3-chome 501 Takagare House 5-402

Claims (10)

[Claims] [Claim 1] A low refractive index layer or the high reflectivity layer of refractive index N _L, both larger than the refractive index N _L, the refractive index N _1, N ₂ to be successively smaller values, ‥‥‥ N _K (N ₁ ＞ N ₂ ＞
.. ..> N _K >> N _L ), a plurality of required plate-shaped optical waveguide layers having the above-mentioned structure are stacked to form an optical transmission body,
One end surface of the plate-shaped optical waveguide layer is a light incident end surface formed by continuing from one end of the low refractive index layer or the high reflectance layer, and a light source is provided on the light incident end surface side. The other end face of the plate-shaped optical waveguide layer is continuous from the other end of the same low-refractive index layer or high-reflectivity layer, and the light exit end face is a flat surface continuous with the light entrance end face, An optical waveguide device for surface illumination, wherein a light diffusing layer having a refractive index N _H larger than the refractive index N _{1 of the} underlying plate-shaped optical waveguide layer is formed on the light emitting end face. Wherein the low refractive index layer or the high reflectivity layer of refractive index N _L, both larger than the refractive index N _L, the refractive index N _1, N ₂ to be successively smaller values, ‥‥‥ N _K (N ₁ ＞ N ₂ ＞
.. ..> N _K >> N _L ), a plurality of required plate-shaped optical waveguide layers having the above-mentioned structure are stacked to form an optical transmission body,
One end surface of the plate-shaped optical waveguide layer is a light incident end surface formed by continuing from one end of the low refractive index layer or the high reflectance layer, and a light source is provided on the light incident end surface side. The other end face of the plate-shaped optical waveguide layer is continuous from the other end of the same low-refractive index layer or high-reflectivity layer, and the light exit end face is a flat surface continuous with the light entrance end face, A light diffusing layer having a refractive index N _H larger than the refractive index N _{1 of the} underlying plate-shaped optical waveguide layer is formed on the light emitting end face so that the plate-shaped optical waveguide layer can perform multimode optical transmission. Have been selected,
Minimum relative refractive index difference in these plate-shaped optical waveguide layers Δ ₁ =
[(N _K −N _L ) / N _K ] × 100% is set to be 1% or more. 3. The optical waveguide for surface illumination according to claim 1, wherein the light incident end surface of the light transmission body is formed by an inclined surface which is inwardly inclined by a desired angle with respect to a vertical line of the light emitting end surface. apparatus. 4. The optical waveguide device for surface illumination according to claim 1, wherein the light incident end face of the light transmission body is formed in a curved shape with respect to the light source. 5. The method according to claim 1, wherein the surface of the low refractive index layer or the high reflectance layer is a flat surface or a curved surface.
An optical waveguide device for surface illumination as described above. 6. The surface illumination according to claim 1, wherein the plate-shaped optical waveguide layer of the optical transmission body has a uniform thickness or is formed so as to taper in a light propagation direction. Optical waveguide device. 7. A roof-shaped base having a low-refractive index layer or a high-refractive index layer having a refractive index N _L formed on the left and right inclined surfaces, respectively, and both the low-refractive index layer and the high-refractive index layer, both larger than the refractive index N _L, the refractive index N _1, N ₂ to be successively smaller _{values, ‥‥‥ N K (N 1>} N 2>‥‥‥> N K »
N _L ), a plurality of required plate-shaped optical waveguide layers are stacked to form an optical transmission body, and the outer end surface of the plate-shaped optical waveguide layer on each of the left and right sides of the optical transmission body is defined by the left and right sides. The light incident end face is continuously formed from the outer end of the inclined surface, and a light source is provided on the light incident end face side, and the inner end face of the plate-shaped optical waveguide layer is the same as the top of the left and right inclined faces. A light emitting end face which is continuous to form a flat surface and is continuous with the light incident end face is formed, and a refractive index larger than the refractive index N _{1 of the} underlying plate-shaped optical waveguide layer is formed on the light emitting end face. An optical waveguide device for surface illumination, wherein an N _H light diffusion layer is formed. 8. The optical waveguide device for surface illumination according to claim 7, wherein the left and right inclined surfaces on which the low refractive index layer and the high reflectance layer are formed are each formed at an inclination angle of 45 degrees or less. .. 9. A roof-shaped base having low-refractive-index layers each having a refractive index N _L formed on each of the left and right inclined surfaces, and both low-refractive-index layers having a refractive index larger than the refractive index N _L. , N ₁ , N ₂ , ... N _K (N ₁ > N ₂₎
> N _K >> N _L ), a plurality of required plate-shaped optical waveguide layers having the above-mentioned structure are stacked to form an optical transmission body, and the plate-shaped optical waveguide on each of the left and right sides of the optical transmission body is formed. The outer edge of the layer,
A light source is provided on the light incident end face side formed continuously from the outer ends of the left and right inclined faces, and the inner end face of the plate-shaped optical waveguide layer is flattened with the tops of the left and right inclined faces as a reference. A light exit end face continuous with the light entrance end face and continuous with the light entrance end face, and a refractive index N larger than the refractive index N _{1 of the} underlying plate-shaped optical waveguide layer is formed on the light exit end face. A light diffusion layer of _H is formed, and further, a cavity is formed in the vicinity of the central axis of the roof-shaped base,
An optical waveguide device for surface illumination, wherein a light source for irradiating the vicinity of the top of the low refractive index layer from the back side is also provided in the cavity. 10. A roof-shaped base having low refractive index layers or high reflectance layers each having a refractive index N _L formed on the left and right inclined surfaces, and the low refractive index layers or high reflectance layers described above, both larger than the refractive index N _L, the refractive index N _1, N ₂ to be successively smaller _{values, ‥‥‥ N K (N 1>} N 2>‥‥‥> N K »
N _L ), a plurality of required plate-shaped optical waveguide layers are stacked to form an optical transmission body, and the plate-shaped optical waveguide layers on the left and right sides of the optical transmission body are provided on the inclined surfaces. It is formed by a stacked inclined layer portion and a horizontal layer portion that is bent horizontally from its outer end, and its outer end surface is made into a light incident end surface by continuing from the outer edge of the left and right horizontal layer portions. A light source is provided on the light incident end surface side, and the inner end surface of the plate-shaped optical waveguide layer is continuous so as to be a flat surface with reference to the apex of the left and right inclined surfaces, and the light incident end surface is formed. A continuous light emitting end face is formed, and a light diffusing layer having a refractive index N _H larger than the refractive index N _{1 of the} underlying plate-shaped optical waveguide layer is formed on the light emitting end face. Optical waveguide device for surface illumination.