JP4724690B2 - Light guide plate and flat illumination device - Google Patents

Description

  The present invention relates to a light guide plate and a flat illumination device used for a liquid crystal display device or the like. For any light source, the light source is continuously or continuously located at a position corresponding to the luminance distribution or light energy distribution of the light source. An optical element having an inclined surface corresponding to the light bundle has a density distribution that increases functionally in proportion to the distance from the light source, so that even a small light source such as a directional point light source is bright, linear, etc. The present invention relates to a light guide plate and a flat illumination device that can obtain bright emitted light even with a light source having a directivity distribution and having a shape of.

Conventional light guide plates and flat illumination devices use a method that uses scattering on the back surface of the light guide plate. In this method, a dot or a rectangular shape is printed with an ink mixed with a white material such as titanium oxide as the distance from the light source increases, and scattered light is obtained as the distance from the light source increases. We are trying to obtain the uniformity of the emitted light.
Further, an injection molding method is used, in which scattering is used for the front surface portion and the back surface portion of the light guide plate, and a minute uneven shape is randomly formed.

  Similarly, as a light guide plate and a flat illumination device using an injection molding method, one using a method utilizing refraction or reflection on the front surface portion or the back surface portion of the light guide plate is known. In this method, the convex shape and the concave shape are simply formed so as to be distributed (gradation) more away from the light source, and the probability of refraction and reflection increases as the distance from the light source increases, and the light emitted from the light guide plate is made uniform. Yes.

Further, as a light guide plate and a flat illumination device using an injection molding method, one using a method using refraction or reflection on the front surface portion or the back surface portion of the light guide plate is also known. In this method, a prism shape is formed in parallel with the light source, and light rays from the light source are refracted or reflected by the sides of the prism to be deflected to the emission surface or emitted from the emission surface.
Similarly, a method is known in which a prism shape is provided in parallel with the light source on the front surface portion and the back surface portion of the light guide plate. In this method, the height or depth of the prism is set higher or deeper as the distance from the light source increases, the more light rays from the light source are received as the distance from the light source increases, and the reflected light or refractive light is used more. The emitted light is made uniform.

  Conventional light guide plates and flat illumination devices use a method of utilizing scattering on the back surface of the light guide plate, and the more the circular or rectangular shape is separated from the light source by using ink mixed with a white material such as titanium oxide. Many dots were printed, and scattered light was obtained as the distance from the light source was increased to obtain uniformity of light emitted from the light guide plate. However, the light was absorbed by the white material or ink, and the light was scattered. As a result, the light beam does not reach only the exit surface, and there is a problem in luminance because the absolute amount of emitted light is low.

  In addition, there is no loss due to light absorption in the method in which fine irregularities are randomly formed on the front and back surfaces of the light guide plate by injection molding, and the light from the light source is scattered. Are scattered, the light beam does not reach only the exit surface, the brightness of the exit light is low, and the uneven distribution is random, causing problems with brightness spots and the like.

  Similarly, when the distribution of the convex shape or concave shape increases as the distance from the light source is increased (gradation), it is improved compared to printing of ink or the like, or random shaping of fine uneven shapes, but it is merely away from the light source. The probability of refraction and reflection is only increased, and it does not correspond to the directivity (luminance distribution) of the light beam or the shape of the light source. There are no challenges.

  Furthermore, a method of forming a prism shape in parallel with the light source on the front surface portion and the back surface portion of the light guide plate, refracting or reflecting light rays from the light source on the sides of the prism and deflecting to the output surface, or emitting from the output surface, This is true if all of the prism ridge lengths have the same condition (in the case of a simple ideal state), but in reality, the light source directivity (luminance distribution) and the shape of the light source are not supported. There is a problem that the amount of light, directivity, and energy are not fully utilized.

  Similarly, a prism shape is provided on the front and back surfaces of the light guide plate in parallel with the light source, and the height and depth of the prism are set higher or deeper as the distance from the light source increases, and more light from the light source is received as the distance from the light source increases. Thus, a method that uses a lot of reflected light and refracted light to make the emitted light uniform regardless of the distance from the light source is good as a method away from the light source, but the prism itself is actually pointing the light source. However, there is a problem that the light amount, directivity, and energy of the light source are not sufficiently used because they are not compatible with the characteristics (luminance distribution) and the shape of the light source.

  In any case, these conventional methods do not correspond to the directivity of the light amount of the light source, the energy distribution, the shape of the light source, and the like, and these conventional methods are limited.

  The present invention has been made in order to solve the above-described problems. Compared to the conventional technique, the present invention always continuously corresponds to the light flux from the light source at a position corresponding to the directivity and energy distribution of the light amount from the light source. By providing an optical element having an inclined surface, the same luminance and energy are always emitted from the light source to the output surface side by performing total reflection and refraction by the inclined surface of the equivalent optical element continuously at the position where the luminance and energy from the light source are equal. The optical element density distribution is increased in proportion to the distance from the light source as the luminance and energy from the light source are attenuated, so that the product of the emitted light amount and the outgoing angle is equal at any position of the light guide plate. An object of the present invention is to provide a light guide plate and a flat illumination device that can emit light.

  In addition, by continuously providing an optical element having an inclined surface corresponding to the light flux from the light source at a position corresponding to the directivity of the light amount from the light source and the energy distribution, the directivity and energy of the light amount from the light source are always provided. It is possible to emit the same brightness and energy to the exit surface side by performing the total reflection and refraction by the inclined surface of the equivalent optical element continuously at the same position, and the optical with the attenuation of the brightness and energy from the light source Provided is a light guide plate and a flat illumination device capable of increasing the element density distribution in proportion to the distance from the light source so that the product of the amount of light emitted at any position of the light guide plate and the solid angle can be emitted equally. There is.

The light guide plate according to claim 1 of the present invention includes an incident portion that guides light from a plurality of light sources having directivity, a surface portion that emits the light, and a back surface portion that is located on the opposite side of the surface portion. In the light guide plate having the side part connecting the surface part and the back part and provided inside the side part surrounded by the side part, the incident part is curved, and the front part or the back part has an optical element having an inclined surface corresponding to the light beam from the continuous or continuous light source at a position corresponding to the luminance distribution or light energy distribution of the light source, the curve to set away from the incident portion as opposed to the light source further optical element with respect to a distance direction from the light source is characterized by having a density distribution in proportion to the distance from the light source increases functionally.

The light guide plate according to claim 1 includes an incident portion that guides light from a plurality of light sources having directivity, a surface portion that emits the light, a back surface portion that is located on the opposite side of the surface portion, and these surfaces. In the light guide plate provided in the inside having the incident part surrounded by the side part, the incident part is curved, and the luminance of the light source is on the front part or the rear part. distribution or an optical element having an inclined surface corresponding to the light beam from the continuous or continuous light source at a position corresponding to the optical energy distribution, only curvedly set away from the incident portion as opposed to the light source, further light source The optical element has a density distribution that increases functionally in proportion to the distance from the light source with respect to the distance direction from the light source. Reflected and refracted continuously on the exit surface side It can emit the same brightness and energy. Moreover, the product of the amount of light emitted at every position of the light guide plate and the solid angle is equally emitted so that the optical element density distribution increases in proportion to the distance from the light source as the luminance and energy from the light source decrease. can do. In addition, by controlling the length of the optical element and the interval between adjacent optical elements, the product of the amount of light emitted from the optical element and the solid angle is equal, but the optical element is lost. It is possible to obtain light energy lower than that of the optical element.

  Furthermore, the light guide plate according to claim 2 is characterized in that the cross section of the optical element is triangular, trapezoidal, or arcuate and continuous or continuous.

  In the light guide plate according to claim 3, since the cross section of the optical element is triangular, trapezoidal, arc-shaped and continuous or continuous, the light rays entering the light guide plate from the incident portion of the light guide plate are triangular, The trapezoidal and arcuate inclined surfaces can exist at positions corresponding to the light flux from the light source. If these are continuous, the same luminance and energy can be emitted at any position, and the same luminance and energy can be emitted continuously at any position.

  The light guide plate according to claim 3 is characterized in that the height of the optical element is increased or / and partially raised or lowered as the optical element is moved away from the light source.

  In the light guide plate according to the third aspect, the height of the optical element is increased or / and partially raised / lowered as the optical element is moved away from the light source, so that even the optical element far from the light source receives light rays from the light source and performs total reflection. The amount of light emitted from the light guide plate and the angle of light emission can be changed by partially raising or lowering the height.

  Furthermore, the light guide plate according to claim 4 is characterized in that an angle between the inclined surface and the front surface portion and the back surface portion is in a range from π / 2-2 · critical angle to critical angle.

  In the light guide plate according to claim 4, since the angle between the inclined surface and the front surface portion and the back surface portion is in the range of π / 2-2 · critical angle to critical angle, from the maximum incident angle of the light beam guided into the light guide plate By using the range up to the minimum angle that breaks the critical angle, all the reflected light can break the critical angle.

  Further, the light guide plate according to claim 5 is characterized in that an angle formed between the front surface portion and the back surface portion of the inclined surface in proportion to the distance from the light source approaches a critical angle.

  In the light guide plate according to the fifth aspect, the angle formed between the front surface portion and the back surface portion in proportion to the distance from the light source is close to the critical angle. The reflected light that is totally reflected in proportion to the distance is emitted at a small emission angle. For this reason, the product of the light quantity emitted and the solid angle can be emitted equally at any position on the emission surface of the light guide plate.

  Further, the light guide plate according to claim 6 is configured such that the inclined surface has an arc inside or outside with the central portion of the inclined surface as a center, or a circular arc partially inside and outside the inclined surface. Features.

In the light guide plate according to the sixth aspect of the present invention, the inclined surface has a circular arc inside or outside with respect to the central portion of the inclined surface, or partly inside and outside the inclined surface. In the case where the emission position in the light guide plate is an arc on the inside of the inclined surface, it can be brought closer to the light source side. Further, when the light source is near, the totally reflected light becomes parallel light, and when the light source is far, the totally reflected light can be condensed.
Further, when the emission position in the light guide plate having the same size is formed as an arc on the outer side of the inclined surface, it can be moved away from the light source side. Further, when the light source is near, the totally reflected light becomes parallel light, and when the light source is far, the totally reflected light can be diffused.
Further, different actions such as condensing and diffusing can be obtained on one inclined surface by forming a circular arc partially inside and outside on one inclined surface.

The planar illumination device according to claim 7 is located on the opposite side of the surface portion, a plurality of directional light sources, an incident portion that guides light from the light source, a surface portion that emits the light. It has a back surface part and a side surface part that connects the front surface part and the back surface part, is provided in a curved shape inside the incident part surrounded by the side surface part, and is continuous at a position corresponding to the luminance distribution or light energy distribution of the light source or have a continuously inclined surface corresponding to the light beam from the light source, the light source curvedly disposed away from the incident portion as opposed to the further relative distance direction from the light source, in proportion to the distance from the light source A light guide plate having an optical element that can be applied to a functionally increasing density distribution and can change the inclination of the inclined surface on the front surface portion or the back surface portion, and a correction sheet that corrects fine luminance unevenness of light emitted from the light guide plate, Covers the light guide plate except the entrance and exit surfaces Characterized by comprising a reflector for reflecting the leaked light again light guide plate from the light plate.

The flat illumination device according to claim 7 includes a plurality of light sources having directivity, an incident portion that guides light from the light source, a front surface portion that emits the light, and a back surface portion that is located on the opposite side of the front surface portion. And a side surface portion connecting the front surface portion and the back surface portion, and the incident portion is provided in a curved shape inside the side surface portion, and is continuous or continuous at a position corresponding to the luminance distribution or light energy distribution of the light source. to have a sloped surface corresponding to the light beam from the light source, curvilinearly disposed away from the incident portion as opposed to the light source, further with respect to the distance direction from the light source, in proportion to the distance from the light source A light guide plate having an optical element on the front surface or back surface that can be applied to a functionally increasing density distribution and can change the inclination of the inclined surface; a correction sheet that corrects fine luminance spots of light emitted from the light guide plate; A light guide plate that covers the light plate except the entrance and exit surfaces And a reflector that reflects the leaked light again into the light guide plate, so that total reflection or refraction is always performed by the inclined surface of the optical element continuously or continuously at a position where the luminance and energy from the light source are equal, Equivalent brightness and energy can be emitted continuously or continuously to the emission surface side. In addition, the density distribution of the optical element increases functionally in proportion to the distance from the light source as the brightness and energy from the light source decay, and the amount of light emitted from any position of the light guide plate and its solid angle It is possible to emit the same product or to freely control the exit angle from the exit surface by setting the angle of the inclined surface.

As described above, the light guide plate according to claim 1 includes an incident portion that guides light from a plurality of directional light sources, a front surface portion that emits the light, and a rear surface that is located on the opposite side of the front surface portion. And a light guide plate provided in the interior of the light receiving plate surrounded by the side surface portion, the incident portion is curved, and the surface portion or the back surface portion. The optical element having an inclined surface corresponding to the light flux from the light source continuously or continuously at a position corresponding to the luminance distribution or light energy distribution of the light source is curved so as to be away from the incident portion as it faces the light source. setting only, further since relative distance direction from the light source optical element has a density distribution in proportion to the distance from the light source increases functionally, always luminance and energy are equal position from the light source continuity optics Performs total reflection and refraction by the inclined surface of Can be morphism surface emitting equivalent brightness and energy continuity. Moreover, the product of the amount of light emitted from any position of the light guide plate and its solid angle so that the optical element density distribution increases functionally in proportion to the distance from the light source as the luminance and energy from the light source decay. Can be emitted equally, so that emitted light with uniform brightness and viewing angle can be obtained.
In addition, by controlling the length of the optical element and the interval between adjacent optical elements, the product of the amount of light emitted from the optical element and the solid angle is equal, but the optical element is lost. Thus, it is possible to obtain lower light energy than the place where the optical element is present, and to express a desired luminance distribution on the light guide plate.

  Furthermore, the light guide plate according to claim 2 is such that the cross section of the optical element has a triangular shape, a trapezoidal shape, and an arc shape, and is continuous or continuous. Therefore, light rays that have entered the light guide plate from the incident portion of the light guide plate are triangular. An inclined surface having a shape, a trapezoidal shape, and an arc shape can exist at a position corresponding to the light flux from the light source. And when these are continuous, the same brightness | luminance and energy can be radiate | emitted at any position, and even if it is continuous, the same brightness | luminance and energy can be radiate | emitted continuously at every position.

  Further, the light guide plate according to claim 3 increases the height of the optical element or / and partially raises or lowers the height of the optical element as the optical element is moved away from the light source. Can be reflected. For this reason, it is possible to obtain a large amount of emitted light even at a position far from the light source to obtain a uniform emission brightness from the light guide plate regardless of the distance of the light source, or to set the height of the light guide plate at any position. The amount of light emitted from can be increased or decreased, and the angle of light emitted from an arbitrary position of the light guide plate can be changed. As a result, it is possible to control the luminance and the viewing angle at any desired position of the light guide plate.

  Furthermore, in the light guide plate according to claim 4, since the angle between the inclined surface and the front surface portion and the back surface portion is in the range of π / 2-2 · critical angle to critical angle, the maximum incidence of the light beam guided into the light guide plate Since the range from the angle to the minimum angle that breaks the critical angle is used, all the reflected light can break the critical angle. Thereby, since the emission angle range from the emission surface of the light guide plate can be made large, the required emission angle can be freely selected and can be adapted to the purpose.

  Further, in the light guide plate according to claim 5, since the angle formed between the front surface portion and the back surface portion in proportion to the distance from the light source approaches the critical angle, even with the attenuation of luminance and energy from the light source, The reflected light totally reflected in proportion to the distance from the light source is emitted at a small emission angle. For this reason, the product of the quantity of light emitted and the solid angle thereof can be emitted equally at any position on the emission surface of the light guide plate, and a uniform emission amount and a uniform viewing angle can be obtained.

  Furthermore, since the light guide plate according to claim 6 forms an arc on the inner side or the outer side with the inclined surface as the center of the central portion of the inclined surface, or partially on the inner side and the outer side of the inclined surface, When the emission position in the light guide plate of the same size is formed as an arc inside the inclined surface, it can be brought closer to the light source side. Further, when the light source is near, the totally reflected light becomes parallel light, and when the light source is far, the totally reflected light can be condensed. Furthermore, when the exit position in the light guide plate of the same size is formed as an arc outside the inclined surface, it can be moved away from the light source side. In addition, when the light source is close, the totally reflected light becomes parallel light, and when the light source is far, the totally reflected light can be diffused. By two different arcs, it is possible to obtain actions and effects such as condensing and diffusing on one inclined surface. Thereby, the size of the light guide plate, the necessary amount of emitted light, the viewing angle, and the like can be freely controlled.

The planar illumination device according to claim 7 is located on the opposite side of the surface portion, a plurality of directional light sources, an incident portion that guides light from the light source, a surface portion that emits the light. It has a back surface part and a side surface part that connects the front surface part and the back surface part, is provided in a curved shape inside the incident part surrounded by the side surface part, and is continuous at a position corresponding to the luminance distribution or light energy distribution of the light source or have a continuously inclined surface corresponding to the light beam from the light source, the light source curvedly disposed away from the incident portion as opposed to the further relative distance direction from the light source, in proportion to the distance from the light source A light guide plate having an optical element that can be applied to a functionally increasing density distribution and can change the inclination of the inclined surface on the front surface portion or the back surface portion, and a correction sheet that corrects fine luminance unevenness of light emitted from the light guide plate, Covers the light guide plate except the entrance and exit surfaces Since it has a reflector that reflects the light leaked from the light plate again into the light guide plate, it always performs total reflection and refraction on the inclined surface of the optical element continuously or continuously at the same brightness and energy from the light source. The same brightness and energy can be emitted continuously or continuously to the emission surface side. In addition, the density distribution of the optical element increases functionally in proportion to the distance from the light source as the brightness and energy from the light source decay, and the amount of light emitted from any position of the light guide plate and its solid angle It is possible to emit the same product or to freely control the exit angle from the exit surface by setting the angle of the inclined surface. As a result, according to the required purpose of the flat illumination device, it is possible to realize a design with a high degree of freedom and a flat illumination device such as emphasizing luminance, viewing angle, or uniformity.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In the present invention, an optical element having an inclined surface corresponding to a light flux from a light source is continuously or continuously provided at a position corresponding to the luminance distribution or light energy distribution of the light source at a distance from the light source on the front surface portion or the back surface portion. The present invention provides a flat illumination device including a light guide plate having a density distribution that increases in proportion to a function and a light source having directivity and directivity distribution.

1 and 2 are schematic views of a light guide plate according to the present invention, and FIG. 3 is a schematic locus diagram of light rays of the light guide plate according to the present invention.
The flat illumination device is generally composed of a light guide plate 2, a light source 4, a reflector (not shown), a correction film (not shown), and a reflection case (not shown) shown in FIGS.

  The light guide plate 2 is formed of a transparent acrylic resin (PMMA) or polycarbonate (PC) having a refractive index of about 1.4 to 1.7. The light guide plate 2 includes a side surface portion 11, a front surface portion 8 for light emission, and a back surface portion 9 located on the opposite side and an incident portion 5 that guides light from the light source 4.

As shown in FIGS. 1 and 2, the light guide plate 2 can be configured to continuously apply the optical element 20 to the front surface portion 8 or the back surface portion 9 at a position corresponding to the luminance distribution or light energy distribution of the light source 4. .
Here, in order to make it difficult to illustrate, the illustration in which the optical element 20 is continuously provided is omitted.

Here, the length of the optical element 20 is shortened to reduce the total reflection amount on the inclined surface, or the length is increased to increase the total reflection amount on the inclined surface. Thereby, the total reflection amount from the optical element 20 can be controlled.
Further, the interval between adjacent optical elements 20 is increased or decreased. As a result, the product of the amount of light emitted from the optical element 20 and the solid angle thereof are equal, but light energy lower than that of the optical element 20 is obtained where the optical element 20 is missing (interval). Thereby, a desired luminance distribution can be expressed in the light guide plate 2.

  Furthermore, the brightness and energy from the light source 4 attenuate as the light guide plate 2 moves away from the light source 4. For this reason, the optical element 20 is increased as the distance from the incident portion 5 increases. The optical element 20 applied to the front surface portion 8 or the back surface portion 9 has a density distribution that increases exponentially in proportion to the distance from the light source 4. Thereby, the product of the unit area of the optical element 20 in the vicinity of the incident part 5 and the strong light intensity, and the product of the unit area of the optical element 20 in the vicinity of the end portions 6 and 6b far from the incident part 5 and the weak light intensity. And become equal.

  The light guide plate 2 has a triangular, trapezoidal, and arcuate cross section so that the optical element 20 has an inclined surface corresponding to the light flux from the light source 4, and efficiently inclines the light from the light source 4 without loss. Make a total reflection on the surface.

  Further, although not shown, the light guide plate 2 increases the height of the optical element 20 as the optical element 20 is moved away from the light source 4. Thereby, the height of an inclined surface part can be made high, and the area of an inclined surface part can be enlarged. As a result, the optical element 20 far from the light source 4 can receive a large amount of light from the light source 4. The received light is totally reflected on the inclined surface and deflected in the direction of the exit surface, so that a large amount of the exit light can be emitted even at a position far from the light source 4, and the light can be uniformly guided regardless of the distance of the light source 4. The emission brightness from the optical plate 2 can be obtained.

  Although not shown, the light guide plate 2 can raise or lower the height of the inclined surface portion by partially raising or lowering the optical element 20. Thereby, the area of an inclined surface part can be enlarged or reduced. As a result, the amount of light emitted from an arbitrary position of the light guide plate 2 can be increased or decreased, and the angle of emission from an arbitrary position of the light guide plate can be changed. As a result, it is possible to control the luminance at a desired position of the light guide plate 2 and the viewing angle.

  It should be noted that by partially changing the height of the optical element 20, for example, when the cross-sectional area is a triangular optical element 20, the height of one continuous triangular ridge can be continuously changed. The change of the emitted light can be made continuous.

In addition, the angle between the inclined surface of the optical element 20 and the front surface portion 8 and the back surface portion 9 is in the range of π / 2-2 · critical angle γ to critical angle γ. That is, the angle formed between the front surface portion 8 and the back surface portion 9 is made closer to the critical angle γ as the inclined surface is separated from the light source 4 in proportion to the distance from the light source 4.
Here, when the light from the light source 4 is guided from the incident portion 5 to the inside of the light guide plate 2, for example, when the material of the light guide plate 2 is polycarbonate (PC) resin, the refractive index of the polycarbonate resin is n = 1.59. Therefore, the light ray L0 that enters the light guide plate 2 from the air layer and exists in the light guide plate 2 is expressed by the equation 0 ≦ | α | ≦ sin ⁻¹ (1 / n) (where n is an air layer) And refractive index n = 1) substantially in the range of refraction angle α = ± 38.997 °.

  Further, the light incident on the light guide plate 2 within the range of the refraction angle α = ± 38.997 ° is sin γ = (1 / n at the boundary surface between the light guide plate 2 and the air layer (refractive index n = 1). ) Can be used to express the critical angle. For example, since the refractive index of polycarbonate resin which is a resin material used for the general light guide plate 2 is about n = 1.59, the critical angle γ is about γ = 38.97 °. In the case of a light guide plate using an acrylic resin (PMMA) material, the refractive index n of the acrylic resin is about n = 1.49, and the refraction angle α is about α = ± 42.38 °. The critical angle γ is also about γ = 42.38 °.

  For example, the refractive index n of the light guide plate 2 made of acrylic resin is about n = 1.49, and in the example of FIG. 3, the refraction angle α of the light beam entering the light guide plate 2 is about α = 42.38 °. Accordingly, the optical element 20 provided on the back surface portion 9 of the light guide plate 2 has an angle θ formed with the back surface portion 9 (from π / 2-2 · 42.38 °) in the range of 5.24 ° to 42.38 °. Among them, an inclined surface 21 having an angle θ1 = 5.24 ° which is the minimum value is provided in the vicinity of the incident portion 5, and an inclined surface 22 having an angle θ2 = 42.38 ° which is the maximum value is provided at a position away from the incident portion 5. Is provided.

  Among the light beams guided into the light guide plate 2 having the above-described configuration, the light beam L1 having an incident angle β of approximately 42 ° that is close to the incident portion 5 is the inclined surface 21 of the optical element 20 (the inclination θ1 = 5.24 °). Total reflection. The totally reflected light beam L11 travels in the direction of the surface portion 8 of the light guide plate 2. Here, the light beam L11 breaks the critical angle γ (outgoing angle of about 61 °) and exits from the surface portion 8 (outgoing angle of about 61 °). The light is emitted as L12.

  As described above, the light beam having a small refraction angle among the light beams that have entered the light guide plate 2 is a light beam having a large incident angle other than the light beam that travels in the extending direction of the light guide plate 2 (the direction opposite to the light incident portion 5). There are many in the vicinity of. Therefore, the inclined surface 21 of the optical element 20 provided in the vicinity of the incident portion is inclined even by a light beam having a large incident angle so that the angle formed with the rear surface portion 9 is reduced by 90.degree. The light is totally reflected at the surface 21, proceeds in the direction of the surface portion 8, breaks the critical angle γ of the light guide plate 2, and can be emitted from the surface portion 8.

  Further, among the light beams guided into the light guide plate 2, the light beam L2 having an incident angle β = 2 °, which travels in a direction away from the incident portion 5, is inclined by the inclined surface 22 of the optical element 20 (inclination θ1 = 42.38). Total reflection at °). The totally reflected light beam L21 travels in the direction of the surface portion 8 of the light guide plate 2, where the light beam L21 breaks the critical angle γ (outgoing angle 2.24 °) outside the surface portion 8 (about 1.5 °). About) The light is emitted as outgoing light L22.

  In this way, light rays having a small refraction angle among the light rays that have entered the light guide plate 2 travel in the opposite direction (extension direction) to the incident portion 5 of the light guide plate 2, and enter the optical element 20 provided in the vicinity of the incident portion 5. There is little probability of collision. For this reason, the inclined surface 22 of the optical element 20 provided at a position distant from the incident portion 5 is set so that the angle formed with the rear surface portion 9 is equal to the critical angle γ, and even the light having a small incident angle is totally reflected by the inclined surface 22. Then, it can proceed in the direction of the surface portion 8, break the critical angle γ of the light guide plate 2, and emit from the surface portion 8.

Therefore, as can be understood from the explanation of the two extreme cases as described above, in the light guide plate of this example, the inclination angle of the inclined surface of the optical element 20 increases as the distance from the incident portion 5 increases with respect to the light beam from the incident portion 5. The angle formed with the back surface portion 9 is made closer to the critical angle γ in proportion to the distance from the light source 4 so that the inclined surface 21 gradually becomes the inclined surface 22. As a result, the product of the amount of light emitted from any position on the exit surface of the light guide plate 2 by the optical element 20 corresponding to the distance from the light source 4 and the solid angle is equal even with the luminance and energy attenuation from the light source 4. Can be emitted.
Although the concave optical element 20 has been described here as an example, in the case of a convex shape, the inclined surface 21 located on the opposite side of the inclined surface 21 or the inclined surface 22 faces the light source side. The same operations and effects as described above can be obtained.

  Here, the optical element 20 having the inclined surface provided on the back surface portion 9 has been described. However, as described above, the light incident from the incident portion is, for example, acrylic resin, the refraction angle α is α = ± 42. In the case of polycarbonate resin, the angle of refraction α is α = ± 38.997 °, which proceeds in the direction of the front surface portion 8 and the rear surface portion 9, so that the optical element 20 is provided on the front surface portion 8 and is the same as described above. When configured, the light guide plate 2 used for the front light can be obtained. Further, the emitted light can be freely controlled by selecting the angle of the inclined surface of the optical element 20 so that the light beam once totally reflected by the front surface portion is again totally reflected by the back surface portion 9 again.

  Further, by forming an arc inward or outward with the central portion of the inclined surface 21 or the inclined surface 22 of the optical element 20 as the center, the emission position within the light guide plate 2 of the same size is set to the inclined surface 21 or the inclined surface 22. When the inner side of the surface is an arc, it can be brought closer to the light source side, and when the outer side of the inclined surface 21 or the inclined surface 22 is an arc, it can be moved away from the light source side.

Further, when the outside of the inclined surface 21 or the inclined surface 22 is an arc, the totally reflected light becomes parallel light when the light source 4 is near, and the totally reflected light can be diffused when the light source 4 is far. .
Further, when the inside of the inclined surface 21 or the inclined surface 22 is an arc, the totally reflected light becomes parallel light when the light source 4 is near, and the totally reflected light is condensed when the light source 4 is far. it can.

  Also, two inclined arcs 21 and 22 on the optical element 20 are provided on one inclined surface, for example, close to the surface portion 8 and the back surface portion 9 of the inclined surface 21 or the inclined surface 22. By forming an arc in the inner direction at the location and an arc in the outer direction at a location far from the front surface portion 8 and the back surface portion 9, it is possible to obtain two different light collection and diffusion effects on one inclined surface. it can.

  Here, as shown in FIG. 1, the optical element 20 to be described in detail shows that when the light source 4 is a point light source such as a semiconductor light emitting element (LED), the light source 4 is a semiconductor light emitting element. Since the center has particularly high luminance and the center other than the center is attenuated, the distribution corresponds to these. That is, a circular (or polygonal) incident portion 5 is provided at the center of the light guide plate 2, the direction with a strong luminance distribution is set to the four end portions 6 of the light guide plate 2, and a portion with low luminance approaches the incident portion 5. The optical elements 20 are provided so that the positions where the luminance and the like are equal become a completely continuous circumference, and the pitch and distribution become finer as it approaches the outer circumferential direction of the light guide plate 2.

  Similarly, as shown in FIG. 2, when the light source 4 is a point light source such as a semiconductor light emitting element (LED), the optical element 20 has a center of the semiconductor light emitting element because the light source 4 is a semiconductor light emitting element. Since the brightness is high and the areas other than the center are attenuated, the distribution corresponds to these. That is, a substantially elliptical incident portion 5 is provided in the lower center of the light guide plate 2, the direction with a strong luminance distribution is set to the two upper end portions 6 of the light guide plate 2 and one central lower portion, and a portion with low luminance is incident. The optical element 20 is provided so as to approach the portion 5 and have a position where equal brightness and the like are completely continuous, and the pitch and distribution become finer as it approaches the lower end 6b direction and the outer peripheral direction of the light guide plate 2. .

The optical element 20 has a triangular, trapezoidal, or arcuate cross section, and has a continuous concave shape or convex shape that ends at the end of the light guide plate 2 having a base width of, for example, about 5 μm to 100 μm. Can be configured.
Similarly, the optical element 20 has a triangular shape, a trapezoidal shape, and an arc-shaped cross section, for example, has a concave shape or a convex shape with a base width of about 5 μm to 100 μm, and the surface portion 8 of the light guide plate 2 or the like. On the back surface part 9, it can be set as the structure continuously provided in the position corresponding to the brightness | luminance and light energy distribution of the light source 4. FIG.

In this way, by providing the continuous or continuous optical element 20 on the front surface portion 8 or the back surface portion 9 of the light guide plate 2, the light beam that has entered the light guide plate 2 from the light source 4 by the inclined surface of the optical element 20 is totally reflected. However, directivity and energy with the same amount of light can be emitted continuously or continuously at any position.
Further, the adjacent interval between the continuous optical elements 20 may be controlled according to a target luminance balance or the like.

For example, the light source 4 is a semiconductor light-emitting element, which is composed of an LED, a laser, or the like, and is white light that is converted to white light by using monochromatic light or white (RGB, red, green, blue) or fluorescent material, and converted to white light. Used.
Further, in the case of having a plurality of incident portions 5, white light may be emitted from the entire light guide plate 2 using light sources 4 of different emission colors for each incident portion.

  The reflector (not shown) is made of a sheet or metal on which a white insulating material or a metal such as aluminum is vapor-deposited, surrounds the incident portion 5 of the light guide plate 2 and the light source 4, and reflects light from the light source 4. Then, the reflected light is incident again on the incident portion 5 of the light guide plate 2.

A correction sheet (not shown) is made of a permeable resin or the like, and has an uneven surface for deflecting light on the surface. This correction sheet corrects the emitted light from the light guide plate 2, so that the emitted light with high luminance is diffused, the emitted light with low luminance is condensed, or the whole is diffused or partially diffused. Select the diffusion sheet, condensing sheet, scattering sheet, diffusing condensing sheet, etc. to be condensed or corrected according to the purpose, and use the forward direction or reverse direction with the processed surface facing upward Use in the same way.
Note that this correction sheet may not be used when outgoing light having directivity is required depending on the distribution and shape of the optical element 20.

  The reflector (not shown) is made of a sheet in which a white material such as titanium oxide is mixed in a thermoplastic resin or a metal sheet such as aluminum on a sheet of a thermoplastic resin, a metal foil laminated, or a sheet-like metal. Become. The reflector covers portions other than the incident portion 5 and the surface portion 8, reflects or irregularly reflects light other than light emitted from the light source 4 to the surface portion 8 by the light guide plate 2, and makes it incident on the light guide plate 2 again. All the light from the light source 4 is emitted from the surface portion 8.

Schematic of light guide plate according to the present invention Schematic of light guide plate according to the present invention Schematic locus diagram of light rays of a light guide plate according to the present invention

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Light-guide plate, 4 ... Light source, 5 ... Incident part, 6, 6b ... End part, 8 ... Front surface part, 9 ... Back surface part, 20 ... Optical element, 21, 22 ... Inclined surface, (beta) ... Incident angle, (alpha) ... Refraction angle, γ ... critical angle, n ... refractive index, θ ... angle formed by the front and back surfaces and the inclined surface, L1, L11, L12, L2, L21, L22 ... light rays.

Claims (7)

An incident part that guides light from a plurality of light sources having directivity, a surface part that emits the light, a back part that is located on the opposite side of the surface part, and the surface part and the back part are connected to each other. A light guide plate provided in an interior surrounded by the side surface portion, wherein the incident portion is curved, and the luminance distribution of the light source is provided on the front surface portion or the back surface portion. or an optical element having an inclined surface corresponding to the light beam from the continuous or continuous light source at a position corresponding to the optical energy distribution, curvilinearly set away from the incident portion as opposed to the light source, Furthermore, the optical element has a density distribution that increases functionally in proportion to the distance from the light source in the distance direction from the light source. The light guide plate according to claim 1, wherein the optical element has a triangular shape, a trapezoidal shape, or an arc shape in cross section and is continuous or continuous. 2. The light guide plate according to claim 1, wherein the optical element increases or decreases a height of the optical element as the distance from the light source increases. 3. The light guide plate according to claim 1, wherein an angle formed between the inclined surface and the front surface portion and the back surface portion is in a range of π / 2-2 · critical angle to critical angle. The light guide plate according to claim 1, wherein an angle formed between the inclined surface and the front surface portion and the back surface portion approaches a critical angle in proportion to a distance from the light source. 2. The inclined surface is characterized in that an arc is formed inside or outside with respect to a central portion of the inclined surface, or an arc is partially formed inside and outside the inclined surface. Light guide plate. A plurality of light sources having directivity, an incident portion that guides light from the light source, a surface portion that emits the light, a back surface portion that is located on the opposite side of the surface portion, and the surface portion and the back surface And a light source that is continuously or continuously provided at a position corresponding to the luminance distribution or light energy distribution of the light source. have a sloped surface corresponding to the light beam from the light source curvedly formed so as as to face away from the entrance portion with respect to further distance direction from the light source, in proportion to the distance from the light source A light guide plate having an optical element that can be applied to a density distribution that increases functionally and can change the inclination of the inclined surface on the front surface portion or the back surface portion, and a correction sheet that corrects fine luminance spots of light emitted from the light guide plate And the incidence of the light guide plate And planar illumination device characterized by comprising a reflector for reflecting again the light guide plate leak light from covering the non-emitting surface the light guide plate.

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