JP4356095B1 - Liquid crystal display device and lighting device - Google Patents

Abstract

【Task】
A reduction in light transmittance due to a color filter in a liquid crystal display device is avoided to reduce power consumption, thereby realizing a reduction in price of the liquid crystal display device.
[Solution]
A convex reflection surface having a curvature set according to the irradiation size, the distance to the irradiation surface, and the inclination width of the convex reflection surface 5 is provided on the bottom surface of the light guide plate 1 in a terraced manner, and the convex reflection surface has a critical angle. Based on the total reflection surface or convex mirror surface based on
The light from the light source is converted into parallel light by the parallel light conversion means, and the parallel light propagating through the light guide plate is incident on the convex reflection surface, and the light beam is expanded and reflected on the irradiated surface .
3 and color light sources, the reference light guide plate three layers, a step portion by the convex reflecting surface distributed in the light guide plate by shifting in the sub-pixel width increments three layers arranged, convex upper side arranged the light guide plate Provide a color filter on the liquid crystal panel by transmitting the reflected light from the convex reflection surface of the light guide plate arranged on the lower layer side between the pitches of the reflection surfaces and irradiating the same pixels on the display surface with the light from the three color light sources Display in color.
[Selection] Figure 4

Description

  The present invention relates to a liquid crystal display device and a lighting device.

A side-light type backlight of a liquid crystal display device is a system in which a light source is installed on the side surface of a light guide plate and is reflected on the liquid crystal side by a number of minute reflectors arranged on the reflective surface side of the light guide plate. Since the light source is diffused light, it is necessary to reduce the probability of radiating to the liquid crystal side as it is closer to the light source. As shown in FIG. 39, the diameter and density of the white paint dots are smaller near the light source and larger as it is farther from the light source. (Patent Document 1). However, the light reflected by the small dots near the light source tends to be a bright spot due to the high luminous flux density, and it is necessary to use a diffusion sheet in combination.
The light that passes through the back of the light guide plate without being reflected by the irregular reflection dots increases as it gets closer to the light source, and the efficiency is significantly reduced. Therefore, a reflective sheet for reuse is required.
The light reflected by the irregular reflection dots radiates light within the critical angle to the liquid crystal side at the light guide plate emission surface, and multiple reflections are reflected to the reflection surface side beyond the critical angle. The light within the critical angle irradiated to the liquid crystal becomes oblique light from the light source side, not in the vertical direction. Since oblique light lowers the luminance, a method in which a prism sheet is provided between the light guide plate and the liquid crystal plate to bring it closer to the vertical direction is often used. (Patent Document 2).
Since the diffuse reflection method involves multiple reflections, the trial evaluation is repeated to make the luminance uniform, and there is a problem that development is inefficient. In order to avoid this, many proposals have been made to approach parallel rays.

There has been proposed a light guide plate in which a reflective plate is provided behind a light guide plate in which metal deposition reflective surfaces and horizontal surfaces of about 45 ° with respect to incident parallel light are alternately arranged. (FIG. 40, patent document 3). Since the light source is diffuse light, the luminous flux density decreases in inverse proportion to the square of the distance from the light source, resulting in large luminance unevenness, and since there are many elevation angle components near the light source, a reflector that reuses the light transmitted through the horizontal plane is required. It has become.
In the above proposal, since there are many elevation rays near the light source, the long side surface is inclined in the range of 1 to 10 degrees according to the distance from the light source, and the short side surface is in the range of 30 to 50 ° with respect to the incident surface. Although a light guide plate that has improved brightness unevenness by gradually increasing is proposed (FIG. 41, Patent Document 4), the function of the distance from the light source and the tilt is not shown.
A method has been proposed in which a quadrangular pyramid with a large reflective area is formed on the bottom surface as the distance from the light source increases, and a lens that focuses on the reflecting surface of the quadrangular pyramid is provided on the light guide plate emission surface to emit parallel rays to the liquid crystal side (patent) Reference 5). Since the quadrangular pyramid is recessed, parallel light cannot enter, and the reflecting surface on the bottom surface is much larger than the quadrangular pyramid, so the reflected light on the bottom surface hits the far lens surface and is reflected multiple times, reducing efficiency. Ray tracing is difficult due to reflection.
A parabolic Fresnel reflector in which a large number of ring-shaped minute paraboloid reflectors are provided on the light guide plate and combined so that the cross section is sawtooth-shaped has been proposed (Patent Document 6). Of the radiation angle from the point light source, the rays that can be collimated are limited to the direction of the parabolic mirror, so a reflector is also used. There is a problem that when the light beam from the reflecting mirror used in combination is reflected by the parabolic mirror, it is reflected in a direction shifted from the parallel light. Patent Document 6 proposes a method in which light from a linear light source installed at the focal line of a parabolic mirror is reflected by a sawtooth Fresnel surface, but parallel light by the parabolic mirror and direct light from the light source are proposed. Since the dependence of the parabolic mirror on the light beam density is very large, it is difficult to make the brightness uniform.

There has been proposed a multiple beam splitter system provided with a reflective surface inclined at 45 ° that linearly decreases the transmittance according to the distance from the light source (Patent Document 7). Since the light source is diffused light, the diffused light is transmitted through the beam splitter near the light source, and only the parallel light component reaches the far beam splitter, so even if the beam splitter transmittance setting is linear, it is non-uniform Become. An example of 10 equal parts is shown, but with a screen size of 300 mm wide, the thickness is 30 mm, which affects the weight and material costs. If the number of divisions is further increased in order to reduce the thickness, it is difficult to control the film thickness, and sputtering is a multi-step process, resulting in an increased manufacturing cost.
In portable devices, a point light source using a white light emitting diode is used for a light guide plate on which concentric minute reflectors are arranged. However, since a bright spot becomes more prominent than in the case of a line light source, a diffusion sheet is used in combination. Since the outside of the directivity range of the light source becomes dark as shown in FIG. 43, the number of light sources is increased to ease the light source (Patent Document 8).
The most orthodox shape of the direct illumination type is a cold cathode tube arranged in a box-shaped flat reflector. When the thickness is reduced, tube reflection is likely to occur. Therefore, the light source is separated, and a uniform shape is achieved by using a corrugated reflector shape (FIG. 42) and a diffusion sheet (Patent Document 9). A method using a cosine function reflector shows a uniform light flux density (Patent Document 10). Because of the function of the distance from the light source and the cold cathode tube pitch, it is difficult to satisfy both the reduction in thickness and the reduction in the number of light sources.
Many methods have been proposed for the shape of the reflector and the ray trajectory is shown, but the uniformity is unclear because many are not treated quantitatively. The thicker the diffusion sheet, the more uniform the brightness, but the efficiency decreases due to absorption.

Many liquid crystal color displays are displayed by an additive color mixing method using a color filter in which pixels are divided into three and red, green, and blue pigments are dispersed. Color filters that absorb unnecessary wavelength components by coloring materials have the advantages of good dispersion and high transmittance in the transmission region due to their solubility when dyes are used. However, transparent electrodes and alignment films are manufactured in the manufacturing process of color filter substrates. Since the process becomes high temperature and the dye is inferior in heat resistance and light resistance, the pigment method is mainly used.
The coloring by the pigment is due to the spectral characteristics of the reflected light when white light hits the pigment particles. If white light penetrates without hitting the particles, the color is lightened. If the pigment content is too high, the transmittance in the transmission region is lowered and darkened. Atomization, pigment dispersion ratio and film thickness control are required to increase the transmittance and sharpen the blocking characteristics.
2/3 which is an unnecessary band is absorbed by the color filter and is absorbed even in the transmission region, so that the light transmittance is 30% or less. The emission spectrum of the three-wavelength cold-cathode tube includes a lot of spectra other than the three wavelengths, and when trying to sufficiently block these, the transmittance in the transmission region is lowered and the light transmittance is further lowered. The transmittance of the color filter is the lowest among the liquid crystal devices, and the transmittance of the entire liquid crystal display device is 8% or less due to about 45% of the polarizing plate.
As a color filter manufacturing method for a liquid crystal substrate, a printing method can be manufactured with a small number of steps, but it is difficult to achieve high resolution, and a photolithography method is often used. However, the photolithography method requires a long process because the cleaning, resist coating, exposure, development, and curing processes are performed for four layers of black matrix, red, green, and blue, and the cost of the liquid crystal panel occupies an expensive device. The proportion is the most expensive.

Cold cathode discharge tubes are widely used in backlights due to their advantages such as high luminous efficiency, but the emission spectrum includes many spectra other than the three primary colors due to the wavelength conversion characteristics of fluorescent materials, and the transmittance is standard. In a color filter, the NTSC ratio is about 70%. Since television has a strong demand for color reproducibility, the NTSC ratio is increased by increasing the density of the color filter, but the transmittance is reduced and the power consumption is increased.
A cold cathode tube requires an inverter, and a white light emitting diode is used in portable applications because of problems such as miniaturization.
White light-emitting diodes are often used for white illumination and the like, in which blue light from blue light-emitting diodes is applied to a yellow phosphor that is a complementary color and converted into white light by additive color mixture of blue and yellow. In the case of a liquid crystal display, since the reproducibility of red or the like is poor in the two-color mixing method, an additive color mixing method in which blue light is applied to yellow, red, green, or red fluorescent materials is employed. However, in order to convert the wavelength of blue light by the ratio of fluorescent material, the variation in the mixing ratio doubles the imbalance, and the imbalance is caused by the change over time. Therefore, it is necessary to make the change over time of the light emitting element and the fluorescent material equal. is there.
There is also an additive color mixing method in which chips of three colors are put in the same package, but there is a large deviation from the focus of a small package, and imbalance occurs due to the directivity of the three chips.

In applications that emphasize color reproducibility, a method of mixing light of red, green, and blue light-emitting diodes with a dichroic prism has been adopted (Patent Document 11), which is large and expensive due to three independent optical systems. is there.
Liquid crystal projectors are also mixed with dichroic prisms, but due to the large irradiation area, a high-luminance white light source such as a metal halide lamp is used and color separation using a dichroic mirror is often employed.

Color filters have a high percentage of the price, and there is a problem that the light utilization efficiency is reduced to 30% or less. A time-sharing method is proposed to make the TFT substrate easier by reducing the number of segment electrodes to 1/3. Has been.
The time division method is a method in which the display period of 16.6 mS is divided into red, green, and blue, and is switched every 5.6 mS to visually mix afterimages. The liquid crystal correctly expresses the gradation and the color during the flat period obtained by subtracting the rising period and the falling period of the liquid crystal response. When the proportion of the flat period decreases, the luminance and contrast decrease.
When a moving image is reproduced in a time-sharing manner, color breakage interference occurs in which three images of red, green, and blue are shifted and synthesized on the viewer's retina. As a method for preventing this, a method of inserting white, black, or an intermediate color in the fourth period has been proposed (Patent Documents 12 and 13), and the response speed needs to be 2 mS or less in the 4-division method. Since the response speed of nematic liquid crystal is 50 to 100 mS, it is limited to a high-speed liquid crystal material. However, a ferroelectric liquid crystal is susceptible to light leakage due to a zigzag defect due to a chevron structure on the other hand, and alignment control becomes difficult. The layer structure is easily destroyed by impact, and there are difficulties such as not self-healing.

  A light-shielding layer is provided at the interface of a plurality of rod-shaped light guides, and a color filter is provided on the end face of each light-guide rod so that a white light source is disposed oppositely, or a plurality of color light-emitting diodes are disposed oppositely to block light of different colors. Thus, a method has been proposed in which a color filter is not used in the liquid crystal panel itself by propagating through the rod-shaped light guide and supplying the liquid crystal stripe (FIG. 45, Patent Document 15). Since the display screen needs to have dimensions that the sub-pixels cannot be clearly seen, most of the stripe width is on the order of 100 μm, and it is a rod-like light guide that is covered with a light-shielding body and then laminated with a filament. is there. Since diffused light propagates through the light-transmitting material partitioned by the respective light shielding layers, in the case of a metal light shielding film, it is absorbed every time it is reflected and becomes darker in the distance. When coating with a material having a refractive index lower than that of the light-transmitting material, diffused light within the critical angle is transmitted and thus mixed. In the manufacturing method of laminating translucent sheets, when the sheet thickness tolerance is integrated, the pixel dimensions of the liquid crystal are not matched.

  When the rear projector projects directly onto the screen from the rear, the rear dimension becomes long, so the depth is shortened by folding back through the reflecting mirror and widening the projection lens (FIG. 44, Patent Document 14). A screen having a width of 1000 mm and a length of 560 mm requires one reflector and a wide-angle lens having a field angle of 60 ° and a depth of about 500 mm. Low-aberration wide-angle lenses are expensive because the number of lenses increases, and there is a proposal that shortens the depth by making the reflecting mirror a convex mirror. Even if such measures are taken, the depth is about 400 mm, and the depth is a restriction in use.

JP-A-6-313883 JP-A-5-127159 Japanese Patent Laid-Open No. 7-20462 JP-A-10-104621 Japanese Patent Laying-Open No. 2005-71928 JP 2004-185020 A JP 2006-11445 A JP 2005-353506 A Japanese Patent Laid-Open No. 2001-13880 JP 2001-17412 A JP 2005-183005 A JP 2002-191055 A JP 2001-281623 A JP-A-6-11767 Japanese Patent Laid-Open No. 2-111922

The diffuse reflection method that changes the density of white paint dots according to the distance from the light source is likely to become a bright spot because the white paint density is low in the part close to the light source, and it is necessary to use a diffusion sheet together, light efficiency, price, thickness Has an effect.
Since the white paint density is low in the portion close to the light source, a reflection sheet for preventing loss of light transmitted behind the light guide plate is required.
Since the irregular reflection in the light guide plate is oblique light, the contrast is lowered, so that the probability center needs to be converted to the vertical direction by the prism sheet.
In order to make multiple reflections, the prototype evaluation is repeated to make the brightness uniform, and development is inefficient.

Since the color filter absorbs unnecessary wavelengths and obtains three primary colors, the light transmittance is about 30% or less, which is the lowest among the liquid crystal devices, and the transmittance of the entire liquid crystal device is 8% or less. Yes.
Coloring in the color filter is due to reflection by the pigment particles. In the vertical alignment and bend alignment due to the scattered light, light leakage occurs due to oblique light hitting the liquid crystal molecules in the black display mode, and contrast is increased. Reduce.
The color filter has many manufacturing processes because black matrix, red, green, and blue are sequentially printed by photolithography, and the ratio of the color filter to the manufacturing cost of the liquid crystal display device is the most expensive.

The emission spectrum of the three-wavelength white light cold cathode tube does not match the three primary colors, and includes many spectra other than the three wavelengths. Cold cathode tubes require an inverter, affecting the size, price and efficiency.
The color balance of the white light emitting diode, which is a mixed color method in which the light of the blue light emitting diode is applied to the red and green phosphors, is significantly affected by the blending ratio of the fluorescent material. A simple color mixing method in which red, green, and blue light emitting diodes are mixed in the same package and the three color lights are mixed causes the color balance to be lost depending on the viewing direction.
The method of balancing each element using a dichroic prism is complicated and expensive.

The time-division method in which red, green, and blue light-emitting diodes are alternately turned on is about 2.6 mS or less by subtracting the display time of about 3 mS from 5.6 mS obtained by dividing the field period of 16.6 mS into three.
The three-division method has the problem of causing color breakup in which high-speed moving images are displayed shifted to red, green, and blue. The four-division method has been proposed, but the four-division method has a high-speed response liquid crystal of about 2 mS or less. Is required.

  A method that does not use a color filter in the liquid crystal panel itself by providing a light-shielding layer at the interface of a plurality of rod-shaped light guides, propagating light by color, propagating through the rod-shaped light guide, and supplying it to the liquid crystal stripe Since diffused light propagates through the light-transmitting material partitioned by the layers, the metal light-shielding film is absorbed every time it is reflected and becomes darker as it goes farther. When coating with a material having a refractive index lower than that of the light-transmitting material, diffused light within the critical angle is transmitted and thus mixed. In the manufacturing method of laminating translucent sheets, when the sheet thickness tolerance is integrated, the pixel dimensions of the liquid crystal are not matched.

  When the rear projector projects directly onto the screen from the rear, the rear dimension becomes longer, and therefore the depth is shortened using a wide-angle lens via a reflecting mirror. A screen with a width of 1000 mm and a length of 560 mm has a depth of about 500 mm with a wide-angle lens having a field angle of 60 degrees. Depth is a usage constraint.

In order to prevent color mixing with light sources of different colors, the light from the light source is formed into parallel light by the parallel light conversion means, and is incident on the light guide plate in which the convex reflection surfaces 5 are distributed and arranged in a terraced manner at a pixel pitch. .
The terraced light guide plate 1 viewed from the side has a terraced structure in which the convex reflection surface 5 is arranged on the reflection surface side facing the liquid crystal side as shown in FIG. The convex reflecting surface 5 reflects a parallel light beam from a light source toward a liquid crystal pixel in a substantially vertical direction, and is a reflecting surface having a negative focal length for enlarging the pixel size because the convex reflecting surface is smaller than the pixel size. is there. Although it is convex in the light guide plate that propagates light, it is concave when viewed from the outer surface of the light guide plate. The convex reflecting surface 5 can be totally reflected when tilted to a critical angle or more as shown in FIG. Reflection may be performed by using a mirror reflection layer such as a vapor deposition film. The critical angle is not limited, but a vapor deposition process is required, resulting in an increase in price.
Between the inclined angle θ _d and the incident angle θ ₁ formed with the horizontal plane on the light source side of the convex reflecting surface 5

From the total reflection condition θ ₁ > θ _c

Need of. Since the light source is not a perfect point light source, there is a parallelism tolerance, so θ _d needs to have a tolerance margin.
FIG. 3 shows a state in which the parallel light expands the light flux on the convex reflection surface and expands to the width W of the transmission portion of the sub-pixel on the irradiated surface. The distance t to the irradiated surface is the sum of the thickness of the light guide plate and the liquid crystal transparent substrate, where W is the width of the transmissive portion of the subpixel and d is the width along the circumference of the convex inclined portion of the light guide plate. The radius of curvature r of the surface is

It is represented by By changing the radius of curvature r in accordance with the change in the thickness t depending on the position of the light guide plate having a terraced structure, it is possible to uniformly irradiate the pixel transmission portion width.

The light from the light source is formed into parallel light by the parallel light conversion means and enters the light guide element, and the parallel light propagating through the light guide plate is incident on the reflection surface provided on the bottom surface of the light guide plate at an incident angle greater than the critical angle. Incident light is totally reflected, or the reflection surface is reflected as a mirror surface, and the light flux is expanded and reflected in a target direction by setting the curvature of the reflection surface according to the irradiated dimension and the distance to the irradiated object. As shown in FIG. 4, three layers of light sources and three layers of terraced light guide plates are used, and the three layers of terraced stepped portions that irradiate the same pixel are shifted by the stripe pitch of the subpixel width. Color display can be performed without providing a color filter on the liquid crystal panel without being obstructed by the inclined reflecting surface. Although a three-layer structure is used to form a convex reflection surface inside the light guide plate, the same function can be realized even with a single light guide plate if the convex reflection surface can be formed inside by extrusion molding or the like.
The convex reflection surface can be displayed as a linear stripe on the liquid crystal surface when the cylindrical surfaces are arranged in a straight line, but a zigzag stripe can also be realized by arranging the convex reflection surface in a zigzag manner.

The radius of curvature of each convex reflecting surface of the light guide plate is set according to Equation 3 in three layers according to the sub-pixel stripe width and the distance to the liquid crystal surface, but since the distance to the liquid crystal surface is different in three layers, the curvature is different for each layer. The radii are different.
FIG. 5 is a perspective view showing a state in which three layers of point light sources and three layers of terraced light guide plates are used and the terraced stepped portion is shifted by the stripe pitch of the sub-pixel width. The curvature radius of the convex reflection surface irradiated to the same pixel is different in the three-layer light guide plate, and the curvature radius on the liquid crystal surface side is set short. The light source uses light emitting diodes of three colors and is provided at the focal point of an off-axis parabolic mirror. The off-axis parabolic mirror can be converted into parallel light by making the thickness direction and width direction of the light guide plate parabolic. Since the dimension in the width direction is set by the focal length, the light flux density distribution, the luminous intensity of the light source, the directivity, etc., it is necessary to lengthen the depth of the paraboloid in order to increase the width.

The curvature of the convex reflecting surface is obtained by shifting the three-layer terraced stepped portion that irradiates the same pixel with the stripe pitch of the sub-pixel width, and converting the light into the parallel light by providing a regular focal length refracting surface on the exit surface of each light guide plate. Color display can be performed by stacking three layers of light guide plates having the same radius in each layer and entering parallel light into sub-pixels of each color. When a regular focal length refracting surface is provided on the exit surface of each light guide plate and converted into parallel light, parallel light can be incident on the sub-pixels of each color, and the curvature radius of the convex reflection surface is the same for each layer. For this reason, three layers of light guide plates of one type are stacked, so that the mold manufacturing cost is low, and since there is only one type, manufacturability is also improved.
Although the three-color light source, the terraced stepped portion are shifted by the stripe pitch of the sub-pixel width, and the light source uses a light-emitting diode of three colors and is provided at the focal point of the off-axis parabolic mirror, the same as described above. Since the distance to the liquid crystal surface is different for each layer, FIG. 6 shows a perspective view when a refracting surface with a normal focal length is provided on the light exit surface side of the light guide plate, and three layers of the terraced light guide plate having the same structure are used.

Parabolic mirrors can generate collimated light and are used with a point light source at the focal point, but if the light source is in the parallel light emission path, the light source not only blocks the collimated light but also directly reflects the reflected parallel light. Adds light and makes it non-uniform. By providing a light source at the focal point of an off-axis parabolic concave mirror or an off-axis parabolic approximate concave spherical mirror having a focal point at a position offset from the path of parallel light as shown in FIGS. The light guide plate can be propagated without being transmitted.
By providing a light emitting diode at the focal point of the paraboloid in both the thickness direction and the width direction of the light guide plate and alternately arranging the light emitting diodes of a plurality of colors in the arrangement order of the liquid crystal stripes, parallel light of a plurality of colors can be supplied.

In the parabolic mirror, the luminous flux density is inversely proportional to the square of the distance between the light source and the point on the reflecting surface, so that the luminous flux distribution of the reflected light decreases as the distance from the optical axis increases.

When the distance between the point (x, y) and the focal point (p, 0) on the parabola shown in Equation 4 is h,

Since the luminous flux density is inversely proportional to the square of the distance between the light source and the point on the reflecting surface, the luminous flux density I is expressed as a function of y.

If p is 1 and y is illustrated in the range of 0 to 4, the light flux density decreases as the distance from the optical axis increases as shown in FIG.
The total luminous flux is obtained by integrating y in the range from 0 to 4.

The integration curve is shown in FIG.
If the light guide plate uses a range close to the optical axis of the parabolic mirror and corrects the reflection area of the light guide plate as an inverse function, the increase in thickness can be suppressed and the light flux density can be made uniform. FIG. 9 shows the position function curve of the step in the parabolic mirror up to the focal point p of the x coordinate and 1.41 p of the y coordinate, and FIG. 10 shows the envelope of the cross section of the light guide plate.

Although the parabolic mirror can generate parallel light, the light flux density characteristic decreases as the distance from the optical axis increases. In order to make the light beam density uniform at the opening end of the parabolic mirror, it is necessary to diffuse the light beam concentrated near the optical axis to the peripheral side and return it to parallel light at the opening end. FIG. 11 is a diagram showing the principle, wherein θ ₁ is an angle at which the light beam is expanded from parallel light, and θ _m is an inclination angle of the reflecting mirror. A state where the light flux density is uniform is shown in FIGS.
This is a diffused ray trajectory for integrating the light flux at the opening end of the parabolic mirror to obtain the total light flux, obtaining a value that is uniform at the opening end on the reflecting mirror, and making the line connected to the coordinates uniform.
The total luminous flux is equally divided at the opening end so as to be uniform in the direction perpendicular to the optical axis. The y coordinate on the reflecting mirror of the light beam obtained by equally dividing the total light beam is obtained from the light beam density distribution, and the x coordinate is also obtained. The diffusion angle can be obtained by connecting this point and the point of the opening end.
FIG. 11 shows the parallel light emission of the parabolic mirror 9. Similarly, the angle at which the tilt of the reflecting mirror is incremented is half of the incremental diffusion angle from the parallel light. In order to obtain the inclination of the reflecting mirror, it is necessary to obtain the tangential inclination m and the normal inclination-1 / m of the parabolic mirror 9.
The slope of the parabola point (x ₀ , y ₀ ) is differentiated by x,

From the tangent equation, m is

It is. Because the normal is perpendicular to the tangent

It is.
Increasing the tilt of the reflecting mirror while maintaining the parabolic envelope is achieved by connecting the fine steep mirror surface and the gentle tilt surface. By dividing the mirror surface of the parabolic mirror and making the half of the diffusion angle from the parallel light to be uniform more than the tangential slope of the parabola, it is possible to diffuse with a uniform light flux density at the opening end of the reflecting mirror.
The mirror surface of the concave mirror is divided to form a steeply inclined mirror surface that is larger than the tangential slope of the parabola, and a gently inclined surface that is a surface facing the focal direction. The reflected light from the surface that increases from the tangential slope of the parabola has a uniform light flux density at the opening end of the concave mirror, and the light from the light source provided at the focal point of the concave mirror is expanded from the parallel light. By providing the distance refracting surface, it can be converted into parallel light having a uniform light flux density. The reflected light of the mirror surface facing the focal direction is emitted as reflected light of a steeply inclined surface that increases more than the tangential inclination of the parabola by irradiating the concave mirror with the light returning to the focal point again.

It is possible to manufacture by mold / vapor deposition, but it is difficult to polish it. For this reason, a method for increasing the slope to form a continuous curve is shown below. If it is continuous, the coordinates move backward, so the light flux density distribution and integral curve must be calculated again. By repeating this calculation, the error can be kept extremely small.
FIG. 13 shows a distribution state in which a light beam expands at a point of y-coordinate on the reflecting mirror, FIG. 14 shows a light beam density distribution by a broken line, and an integral curve of the light beam density by a solid line.
The curve obtained by the above method is

It is. a has a width due to the influence of the axial length of the reflecting mirror, the inclination of the refracting surface of the normal focal length, and the like. In the case of a shallow reflector of x <2, the contribution of the second term is small and correction by the second term is unnecessary, but uniformity is improved by adjusting b and c as x becomes longer. A reflector having a long x, that is, a large aperture y is not as noticeable as a because the light flux density decreases with increasing distance from the optical axis as shown in FIG.
FIG. 15 shows a comparison of the curve at a = 5.8, b = 2.5, c = 2, and p = 1 with the parabola of the light flux density uniformizing mirror.
When this diffused light is incident on the positive focal length refracting surface, it can be returned to parallel light, thereby obtaining parallel light with uniform light flux density. The angle of the refracting surface for returning to parallel light is shown in FIG.
The inclination θ ₃ of the interface to be parallel to the optical axis at the positive focal length refractive surface is

It is. If θ ₃ is obtained for each diffusion angle and a continuous curve is obtained, a refractive surface curve and a lens curve can be obtained. FIG. 16 shows a curve of an analysis result obtained by converting one regular focal length refracting surface into parallel light when entering a translucent material such as a light guide plate. Not only parallel light but also a refracting surface curve can be converted into diffused light having a uniform light flux density and convergent light.
FIG. 17 shows an example of a plano-convex lens having a plurality of refracting surfaces in the case of irradiating diffused light from the light beam density uniformizing mirror into the air.
Refracted light exit angle θ2 converted at the plane of the plano-convex lens

The inclination θ ₃ of the interface for making the refractive surface parallel to the optical axis is

An example of a Fresnel lens in which the lens thickness is made thinner than that of a plano-convex lens having a refractive index of 1.55 is shown in FIG.
When incident on a light guide plate having a regular focal length refracting surface, the steps of the terraced light guide plate become constant and the envelope becomes a straight line, so that the thickness can be made thinner than the compensation methods of FIGS.

  Even with a mirror that equalizes the light flux density, direct light is superimposed, and the direct light is inversely proportional to the square of the distance, so the closer the distance to the irradiation surface, the more uneven the light becomes, and the light flux concentrates near the optical axis. Cheap. For this reason, as shown in FIG. 19, by providing a light shield with an opening in front of the light source to limit the direct light, it is possible to alleviate the light flux concentration caused by superimposing the concave mirror reflected light and the direct light from the light source in front of the light source. I can do it. By setting the size and density of the aperture hole provided in the light shielding body in accordance with the light flux density of the concave mirror reflected light, the light flux can be made uniform. The light shielding body with an opening in front of the light source can be replaced with a convex mirror and reflected by the convex mirror to the concave mirror to increase efficiency. Furthermore, the diffusion state can be controlled by using a concave lens as shown in FIG. 20 for the aperture when the amount of transmitted light is set with the aperture area provided in the convex mirror.

  21 to 23 have a structure having a terraced convex reflection surface in two directions and supply each color with a single light source. When the display surface of the liquid crystal display device is the xy plane and the horizontal direction of the paper is the x axis, the parallel light incident in the y axis direction from the side surface of the light guide plate is inclined in a terrace shape with respect to the yz plane. Conversion is made in the x-axis direction with a minute inclined reflecting surface. The slant reflection surface with minute steps distributed in a terraced shape has a long radius of curvature on the liquid crystal panel side, and if it is a short convex reflection surface on the opposite side, it has a constant y-direction length regardless of the position of the second minute slant reflection surface. In addition, the luminous flux can be enlarged. When the light beam converted in the x direction in the light guide plate is irradiated onto the second minute inclined reflective surface dispersed and arranged in a terraced shape, the light beam is magnified and reflected by the convex cylindrical total reflection surface to the liquid crystal panel in the substantially vertical direction. . Color display can be performed by using three layers of light guide plates, shifting the second terraced stepped portion by the stripe pitch of the sub-pixel width, and irradiating three colors from three light sources. This convex cylindrical reflecting surface can make the light flux incident on the liquid crystal panel uniform by increasing the radius of curvature on the incident side and shortening the far side. The structure of one light guide plate and one light emitting element requires a color filter on the liquid crystal panel, but in the case of light emitting elements with three layers of light guide plates and three colors, color display is possible without using a color filter on the liquid crystal panel. It is. Since the luminous flux is expanded by the convex mirror, a diffusion sheet is unnecessary, and the front luminance can be increased efficiently.

It can be realized with three light sources by using three layers of light guide plates having first and second terraced reflection surfaces and shifting the second terraced stepped portion with a stripe pitch of the sub-pixel width. The three-layer light guide plate has light sources of different colors, and supplies parallel light by parallel light conversion means. FIG. 21 shows a state where three layers are made the same light guide plate. A positive focal length refracting surface is provided on the exit surface side so that the distance dependency to the liquid crystal surface does not occur.
As in the previous section, the first convex reflection surface has a long radius of curvature on the liquid crystal surface side and a short bottom surface side to alleviate the difference between the upper and lower stages of the second terraced light guide plate. When the display surface of the liquid crystal display device is the xy plane, the first terraced convex reflection surface in which parallel light incident in the y-axis direction from the side surface of the backlight light guide element is provided with a stepped shape on the yz plane. In the second terraced light guide plate, the light beam that expands the light beam in the x-axis direction and changes its direction is incident light having a higher light beam expansion rate toward the lower side in the second terraced light guide plate, and the convex reflection surface is cylindrical. In this case, the lower part of the liquid crystal surface is enlarged. By correcting the negative focal length reflecting surface in the axial direction instead of the cylinder, the light can enter the liquid crystal pixel without depending on the position.

  The parallel light propagating in the long axis direction inside the rod-shaped light guide is reflected so that the luminous flux is enlarged by a cylindrical convex reflecting surface arranged in a terraced shape so as to have a constant pitch on the exit surface side, and the convex reflection is further performed. By using a rod-like structure in which elements that convert to parallel light on a positive focal length refracting surface having the same focal point and focal position are arranged along the exit surface, the light is emitted as a line light source and incident on the light guide plate. Parallel light can propagate through the cylindrical regular focal length refracting surface to irradiate the cylindrical convex reflecting surface. For this reason, it is not a structure having the first and second terraced reflection surfaces on one light guide plate, but a structure in which two types are combined as shown in FIG. Since both the convex reflection surface of the rod-shaped light guide and the convex reflection surface of the light guide plate are cylindrical, it is easier to manufacture a mold than the previous item.

  The three liquid crystal display original elements are irradiated with three colors of light according to colors, the reflecting surfaces dispersedly arranged in the three-layer light guide plate are shifted in three colors, and the luminous flux is expanded to the pixel width on the reflecting surface. Color display is possible by mixing three colors on a transmissive screen and combining them on the display surface. The liquid crystal projector combines the three colors and then enters the projection lens. However, since the liquid crystal projector magnifies and projects the light on the three-layer reflecting surface, the three-color light can be mixed and synthesized on the screen without using a cross dichroic prism. Made, simple structure and low price.

When a display original document element is provided on the entrance surface of a substantially wedge-shaped light guide plate having a terrace-like step on the xy plane, and the terraced reflection surface is irradiated, the reflected light is in the xy plane by the light beam expanding function on the convex reflection surface. The image is magnified and reflected on the display surface, and the image of the small liquid crystal display original element can be magnified and displayed on the screen.
Since the image is magnified on the reflecting surface of the terraced light guide plate, the liquid crystal display element on the incident surface has an elongated shape. In the case of enlarging the image only in the terrace inclination direction, the image needs to be flattened by compressing the thickness direction.

The pitch of the steps in the terrace direction is not limited to the pixel width, and color display is possible by projecting a plurality of pixels on one reflecting surface and synthesizing three color lights on the screen. Thereby, it becomes possible to enlarge the pitch of a level | step difference and the reflective surface dimension, and to reduce the number of steps.
The schematic diagram shows a state in which the first layer is red R, the second layer is green G, the third layer is blue B, and 12 pixels are reflected by the first-stage convex reflection surface. The 12 pixels in the terraced terrace direction are A, B, C. . . Let L be. The second and subsequent steps are omitted.
A, B, C.I. . . When a red pixel of L is irradiated on the screen at a constant pitch, a green pixel is irradiated at the same position in the second layer, and a blue pixel is irradiated at the same position in the third layer, Ar and Ag are positioned at position A on the screen. , Ab is irradiated and mixed on the screen. Similarly, Br, Bg, and Bb are irradiated to the B position on the screen, and the colors are mixed on the screen. The following is all the same. It is not possible to distribute to a large number of pixels without limitation in one stage. As shown in FIG. 2, the rear surface side irradiates a larger area than the convex front surface side, and the rear surface side has a light quantity per unit area on the screen. descend. It is necessary to determine the number of distributions to a large number of pixels per stage within a range where luminance nonlinearity is not noticeable.

  Reflection of light transmitted through in the y-axis direction with respect to the display original element provided on the xz plane, reflected by the first terraced structure in which the planes parallel to the projection light are alternately laminated on the z-axis convex reflection surface The surface is inclined with respect to the yz plane in the x direction. As a result, the center of the reflection direction is converted into the x-axis direction, and the light flux is enlarged and reflected. The projection is projected onto a screen in the vertical direction of the xy plane by the cylindrical convex surface of the second terraced reflector having an inclination in the z direction with respect to the xy plane. Three layers of light guide plates that reflect the reflected light on the display surface in the xy plane by enlarging the image are used, and the second terraced stepped portion is shifted by the stripe pitch of the sub-pixel width to display the display element image with three light sources. Can be displayed on the screen in an enlarged manner as compared with the projection display element provided on the xz plane.

As the transparent material for the light guide plate, polymethyl methacrylate resin, alicyclic acrylic resin, cyclic olefin resin, polycarbonate, air, and the like are suitable. In the case of a large screen display using a screen, if the translucent material is a polymer material, the weight, price, molding distortion, etc. are affected. The formation of a mirror surface such as a vapor deposition film on the reflection surface is required to be limited to the convex reflection surface in order to transmit the three-layer light guide plate, and masking and etching processes are required.
Air is used as a transparent material, and a parallel light is incident on the total reflection convex reflection surface by using a translucent material with the incident side of the convex reflection surface perpendicular to the parallel light to form a convex reflection surface. If it is made of a translucent material as a surface substantially perpendicular to the light beam that expands the light beam on the exit side, total reflection can be used instead of the mirror surface. On the exit side, the luminous flux is enlarged, so in the case of a flat surface, it is a substantially vertical exit surface, which is referred to as a terraced total reflection surface plate. With this configuration, most of the light-transmitting layer is air, and since it is a transparent polymer layer for forming a total reflection surface, weight reduction and cost reduction can be realized. When the terraced total reflection face plate is made very thin, it is necessary to support it so that the rigidity is not lowered and the optical characteristics are not impaired. 27 and 28 show an example in which the support substrate 21 that also serves as a frame is provided on the back surface, but the thickness of the terraced total reflection surface plate 39 itself may be increased to increase the rigidity.

Since the terraced light guide plate is generally wedge-shaped, when the arrangement direction of the three layers of light guide plates is aligned, a thick portion is stacked as shown in FIG. When the thick portions of the substantially wedge-shaped light guide plate are alternately arranged, the result is as shown in FIG. 29, and the overall light guide plate thickness can be reduced to about 2/3. Since the rigidity of the light guide plate is increased by the alternate arrangement, it is possible to reduce the single-layer thickness and suppress the increase in thickness due to the three-layer structure.
FIG. 30 shows an example of a rear projector using an air layer and a terraced total reflection face plate as a transparent material. The mechanism for supporting the terraced total reflection face plate in a wedge shape is omitted in the figure.
The screen dimensions are 1000 mm in width and 560 mm in length, the depth is 50 times the magnification, and the short side dimension of the display device is 11.2 mm. The rear projector can be configured with a depth of about 80 mm by using three layers and adding a space of about 30 mm to the screen and the thickness of the casing.

When the direct-lighting type liquid crystal display device is thinned, the light flux is inversely proportional to the square of the distance from the light source, so that tube reflection is likely to occur. Uniform illumination can be obtained by changing the direction of light incident from directly below in the plane direction by the inclined reflecting surface and reflecting light propagating in the plane direction to the liquid crystal panel by the inclined reflecting surface. In order to convert the traveling direction to a right angle, the inclination of the reflection surface is 45 °, so the thickness of the light guide plate needs to be the width of the concave mirror 22. However, as shown in FIG. By doing so, it can be applied to a light guide plate thinner than the concave mirror width. If the horizontal plane is transparent, transmission loss occurs to the upper part. Therefore, as shown in FIG. 33, the horizontal plane is reflected to the light source, and the reflected light from the concave mirror 28 in front of the light source is reused. Loss can be prevented.
Since the reflecting mirror to be returned to the light source is formed by vapor deposition or the like, an additional process is required. However, if a retroreflective element is formed as shown in FIG. 34, it can be formed at the time of resin molding, so that the cost can be reduced. The retroreflective element includes a corner cube or a right-angle prism, but a right-angle prism is easy because it is an extension of the inclined reflection surface.

  In the direct illumination type liquid crystal display device, when the light incident on the light guide plate from directly below is redirected and reflected in the plane direction by the inclined reflective surface, the upper portion of the reflective surface is not illuminated, so the light source is provided in one direction at the end. Propagation. In order to provide a light source other than the end and reflect the light in two opposing directions, it is necessary to illuminate the liquid crystal pixels in the triangular prism portion surrounded by the reflecting surface. When the horizontal reflecting surfaces 29 are dispersed in a terraced shape as shown in FIGS. 33 and 34, the luminance of the triangular prism portion and the other light guide plate surfaces can be matched by setting the aperture ratio to the upper part. When the aperture ratio is small, the light flux can be expanded to the liquid crystal above the triangular prism by making the aperture a negative focal length refracting surface. It consists of a 45 ° inclined reflecting surface that converts in the horizontal direction, a concave surface that expands the luminous flux, and a reflecting mirror that reflects in the light source direction.

In order to provide a light source other than the end and reflect the light in two opposing directions, it is necessary to illuminate the liquid crystal pixels in the triangular prism portion surrounded by the reflecting surface as shown in FIG. In the three-layer light guide plate, since the light source unit becomes an obstacle, it is necessary to exchange different color light between the triangular prisms. FIG. 38 shows a triangular prism in the blue light guide plate 1B, which is divided into three directions, that is, a light guide plate plane direction, a direct upward direction, and an adjacent triangular prism direction. These are shown in FIG.
The triangular prism in the green light guide plate 1G is also divided into three directions of the light guide plate plane direction, the direct upper direction, and the adjacent triangular prism direction, and blue light from the blue triangular prism is incident within the critical angle of the inclined reflecting surface 30. The blue light not only irradiates the upper part of the green light triangular prism but also needs to propagate to the adjacent red light triangular prism. The state of the interface between the green triangular prism and the light guide plate 1R is shown in B1 of FIG. B2 shows a state in which the inclined reflecting surface is transmitted with light within a critical angle.
The red light triangular prism has two layers to form a total reflection surface, and is shown in FIG.

In the present invention, a configuration in which parallel light is redirected by a terraced light guide plate is used to irradiate the liquid crystal layer by shifting the sub-pixel width, so there is no loss due to the color filter, and the transmission efficiency as the liquid crystal device is tripled. I can do it. Illumination with uniform brightness is possible in order to compensate the light flux density distribution by the parallel light conversion element by setting the steps of the terraced light guide plate.
The terraced light guide plate expands the luminous flux in the target direction and totally reflects the parallel light. Therefore, the terraced light guide plate has less loss than the scattering method, and can improve the design efficiency and reduce the member cost.
When color display is performed with a liquid crystal projector, the structure is complicated and expensive because it is mixed with a cross dichroic prism, but the structure is simple and inexpensive because it is mixed on the screen.

FIG. 5 or FIG. 6 shows an example of the embodiment of the present invention as a diagonal 510 mm (20.1 type), XGA (1024 × 768), and sidelight.
The screen dimensions are 408 mm wide, 306 mm long, pixel pitch 399 μm, and sub-pixel pitch 133 μm.
Light from a light source is converted into parallel light and supplied, and an inclined convex reflection surface is provided on a light guide plate having a terraced cross section.
The reflective surface side facing the liquid crystal side has a terraced structure in which 384 cylindrical convex reflective surfaces are arranged at an equal pitch. Since the terraced step of the light guide plate is smaller than the pixel size, the convex reflection surface for enlarging the pixel size reflects parallel light rays from the light source toward the liquid crystal pixels in the vertical direction. By inclining the surface beyond the total reflection critical angle, it is not necessary to form a reflective layer, and manufacturing costs can be reduced. Since the light beam density of the parabolic mirror has a distance dependency from the optical axis, the step on the bottom surface side of the light guide plate far from the optical axis is increased to make the luminance uniform.
As the light source, 64 light emitting diodes for each color are arranged at the off-axis focal point of the terraced light guide plate light source section. The light emitting diode is offset to a position where the reflected light of the parabolic mirror 9 is not blocked as shown in FIG. In this embodiment, by arranging 64 light emitting diodes each having a luminous intensity of 250 mcd on both sides, a luminance of 307 cd / m ² can be obtained at a light transmittance of 40%.

As shown in FIG. 21, the light source is integrally formed with the light guide plate, a white light emitting diode is provided at the off-axis focal point of the parabolic mirror, and parallel light is supplied. The parallel light propagates from the side surface of the light guide plate in the depth direction of the paper, and is reflected in the direction of the second terraced reflection surface by spreading the light flux by the first terraced convex reflection surface. Since the distance to the second terraced reflecting surface is different between the upper and lower stages, the first convex reflecting surface has a smaller radius of curvature toward the lower stage and an enlarged angle. The convex reflection surface is set to a critical angle or more with respect to incident light and uses total reflection.
The second convex reflecting surface is a cylindrical reflecting surface, and the distance to the liquid crystal panel is different between the lower stage and the upper stage, so that the curvature radius is made smaller toward the upper stage. Since this method expands the light flux on the convex reflecting surface, a diffusion sheet is unnecessary. A prism sheet is unnecessary because the emitted light has a narrow beam directivity. Since total reflection is used, a reflection sheet is also unnecessary.

  FIG. 30 shows an example in which the thick light guide plate thickness is reduced to about 2/3 when the thick portions of the substantially wedge-shaped light guide plate are alternately arranged to align the arrangement direction of the three layers of the light guide plate. Since the terraced light guide plate is generally wedge-shaped, when the arrangement directions of the three layers of light guide plates are aligned, the thick portions are stacked as shown in FIG. 5, but the thick portions of the wedge-shaped light guide plates are alternately arranged as shown in FIG. When arranged, the overall light guide plate thickness can be reduced to about 2/3 as compared with FIG. As shown in FIG. 10, the thickness of the single layer of the light guide plate is 4.2 mm and thus becomes 8.4 mm. The optical characteristics are the same as in Example 1.

  An elongated liquid crystal display element having a flattened image whose thickness direction is compressed is arranged on the light guide plate entrance surface, and is enlarged from the elongated liquid crystal display element by the light beam expansion function on the reflection surface dispersedly arranged in the light guide plate. An example of a liquid crystal display device that is enlarged on the screen is shown below. With a diagonal size of 510 mm (20.1 type) and XGA (1024 × 768), the screen dimensions are 408 mm wide, 306 mm long, and a pixel pitch of 399 μm. When the enlargement factor is 50 times in the vertical direction, the pixel size of the liquid crystal display element is 8 μm in length, and the width is 399 μm, which is the same as the display size. Since the liquid crystal display element on the incident surface has an elongated shape and the light guide plate thickness is a single layer of 6 mm, the thickness of the light guide plate becomes 12 mm when three layers are laminated in the alternately arranged direction.

FIG. 30 shows an example of a rear projector using an air layer and a terraced total reflection face plate as a transparent material. The mechanism for supporting the terraced total reflection face plate in a wedge shape is omitted in the figure.
The screen dimensions are 1000 mm in width and 560 mm in length, the depth is 50 times the magnification, and the short side dimension of the display device is 11.2 mm. The rear projector can be configured with a depth of about 80 mm by using three layers and adding a space of about 30 mm to the screen and the thickness of the casing.
Air is used as a transparent material, and a parallel light is incident on the total reflection convex reflection surface by using a translucent material with the incident side of the convex reflection surface perpendicular to the parallel light to form a convex reflection surface. Is made of a translucent material as a surface substantially perpendicular to the light beam that expands the light flux on the emission side. With this configuration, most of the light-transmitting layer is air, and since it is a transparent polymer layer for forming a total reflection surface, weight reduction and cost reduction can be realized. In this example, the plate-like total reflection face plate is required to be supported so as not to deteriorate the rigidity and impair the optical characteristics when it is made very thin.

  FIG. 35 shows an example in which three-color cold-cathode tubes are used to change the direction of light incident from directly below in the plane direction by an inclined reflecting surface and reflect the light propagating in the plane direction to the liquid crystal panel by the inclined reflecting surface. Is shown below. The light source unit uses a concave mirror that converts the light flux density into uniform parallel light, and the inclined surface that converts from the direct downward direction to the light guide plate plane direction is distributed in a terraced manner, and the horizontal plane part is retroreflected from the opening width of the concave mirror. Can be thinned. The light irradiated to other than the inclined reflecting surface is returned to the light source by the retroreflective element, and is finally emitted in the plane direction of the light guide plate by reusing the reflected light of the concave mirror 28 in front of the light source in the light flux density uniform reflecting mirror. I can do it. Since the horizontal plane portions dispersedly arranged on the inclined reflecting surface can be formed at the time of resin molding when a retroreflective element is formed as shown in FIG. 34, the cost can be reduced. Since the retroreflective element is an extension of the inclined reflective surface, it is converted into a right-angle prism, returned to the light source, re-reflected and emitted in the plane direction of the light guide plate.

For convenience of explanation, details are displayed in an enlarged manner, so that they are not necessarily similar.
The axisymmetric characteristic diagram is shown only in the positive range.
The figure shows a state in which the parallel light is converted into parallel light by an off-axis parabolic mirror, the light beam is magnified and totally reflected by the inclined convex reflection surface of the terraced light guide plate, and irradiated to the sub-pixel width. A state in which parallel light is totally reflected by enlarging a light beam by an inclined convex reflection surface of a terraced light guide plate is shown. The relationship between the angle and dimension at which the luminous flux is enlarged by the convex reflecting surface and irradiated to the sub-pixel width is shown. 3 shows a state in which three layers of terraced light guide plates are used to irradiate the liquid crystal layer with three colors of parallel light shifted by sub-pixel widths. The perspective view of the state which has arrange | positioned the parabolic mirror to a three-layer light-guide plate in the width direction and the depth direction is shown. A state in which a regular focal length refracting surface is arranged at the emission part of each layer of the light guide plate to irradiate the sub-pixels with parallel light is shown. The luminous flux density distribution of the parabolic mirror is shown in a range where y is positive. A distribution obtained by integrating the beam density of the parabolic mirror is shown in a range where y is positive. The step distribution of the light-guide plate for equalizing the light flux density of the parallel light by a parabolic mirror is shown. The thickness distribution of the light-guide plate for equalizing a light beam density is shown. The tilted reflected light and the tilt of the reflecting surface for making the light beam density of the parabolic mirror uniform are shown. An angle state in which inclined reflected light for making the light beam density of the parabolic mirror uniform is converted into parallel light on the refracting surface is shown. The inclination distribution of the inclined reflected light for making the light beam density uniform is shown. The light beam density distribution by the light beam density uniformizing mirror and the integration of the light beam density are shown. The curves of the beam density uniformizing mirror and the parabolic mirror are shown in a range where y is positive. FIG. 5 shows parallel light having a uniform light flux density by a reflecting mirror and a positive refractive index surface. FIG. This shows parallel light having a uniform light flux density by a reflecting mirror and a plano-convex lens. Illustrated is a parallel light having a uniform light beam density by a reflector and a Fresnel lens. The direct light in front of the light source is reflected by a concave mirror and reflected as a light beam density uniform concave mirror, and the transmitted light from the front concave mirror opening is irradiated. The state which diffuses and irradiates the transmitted light by a front concave mirror opening part with a lens is shown. Each layer is illuminated with one light source, a light beam in the depth direction is converted to the second terraced reflection surface direction by the first terraced reflection surface, and the liquid crystal panel is irradiated by the second terraced reflection surface. Show. A configuration in which a light beam expanding light obtained by converting a light beam in the depth direction on a first terraced reflection surface is converted into parallel light on a regular focal length refracting surface and propagated in a second terraced reflection surface direction is shown. Each layer is illuminated with one light source, and the light guide plate shape of each layer is a substantially wedge-shaped configuration. A state in which an elongated liquid crystal display element is provided at an incident portion of a light guide plate, and parallel light is irradiated to perform enlarged display on the light guide plate is shown. The projection original element is irradiated with parallel light, the light beam in the depth direction is converted into the second terraced reflection surface direction by the first terraced reflection surface, and the screen is irradiated with a plurality of pixels by the second terraced reflection surface. 1 shows a liquid crystal display device that mixes colors. The state where the light beam expansion light obtained by converting the light beam in the depth direction on the first terraced reflection surface is set to the concave surface on the depth direction of the second rice terrace reflection surface to suppress the light beam expansion of the reflected light. The top view which shows the state which comprised the rear projector by making a translucent layer into air, and formed the 1st terraced-like reflective surface which converts a depth direction light ray with a plate-shaped object. The side view which shows the rear projector by the three-layered terraced-like reflective surface which formed the 2nd terraced-like reflective surface with the plate-shaped body by making most of a translucent layer into air. Each layer is configured to be thinned by alternately arranging substantially wedge-shaped light guide plate shapes. The side view which shows the rear projector which has arrange | positioned so that a thick part may cross | intersect the 3rd terraced-like reflective surface which forms the 2nd terraced-like reflective surface with a plate-shaped body by making most of a translucent layer into air. A side light configuration using three layers of terraced light guide plates and three-color cold cathode tubes is shown. A state in which parallel light having a uniform light beam density by a direct type backlight is converted into a light guide plate in a parallel direction by an inclined reflecting surface is shown. A state in which inclined surfaces are distributed in a terraced shape, the horizontal surface is made a reflecting mirror, returned to the light source, and re-reflected to prevent loss to the top of the horizontal surface is shown. The state which returns the part returned to a light source to a light source by retroreflective element is shown. The structure of a direct type backlight in which three layers of terraced light guide plates are used and three color cold-cathode tubes are arranged at the ends is shown. The principle that the reflective surfaces in the horizontal direction are dispersed in a terraced shape and the luminance of the triangular prism portion and the other light guide plate surfaces are matched by setting the aperture ratio to the top is shown by a single light guide plate. The principle of propagation from the lowermost triangular prism to the upper triangular prism for distributing light to the triangular prism portion of the direct type backlight using three-color cold cathode tubes using three layers of terraced light guide plates is shown. A configuration for distributing light to a triangular prism portion of a direct type backlight using three-color cold-cathode tubes using a terraced light guide plate is shown. The structure of the conventional light-guide plate by an irregular reflection dot is shown. The structure of the conventional light-guide plate which reflects the diffused light from a cold cathode tube with the inclined reflective surface is shown. The structure of the conventional light-guide plate which made the inclination of the vicinity of a light source negative and expanded the far level | step difference is shown. A structure of a conventional reflecting mirror using a wave type reflecting mirror of a direct type backlight is shown. The structure and light beam unevenness of a conventional side light for portable devices are shown. The structure of the conventional rear projector is shown. A structure of a conventional light guide plate in which light guides having a light shielding layer with a stripe width are stacked and a color filter is not used is shown.

Explanation of symbols

Even if the shapes are different, the same function is given the same number.
1: terraced light guide plate 2: sub-pixel 3: gap 5: convex reflecting surface 7: point light source 8: linear light source 9: parabolic mirror 11: concave lens 12: polarizing plate 13: transparent substrate 14: liquid crystal layer 15: parallel Light 20: Wiring board 22: Light flux uniforming concave mirror 23: Regular focal length refracting surface 24: Convex mirror 25: Slit 27: Rod-shaped light guide 28: Concave mirror 29: Reflecting surface 30: Triangular prism 31: Reflecting mirror 33: Total reflection light 34 : Retroreflective element 36: Negative focal length refracting surface 37: Low refractive index layer 39: Translucent material 40: Focus 43: Liquid crystal panel 51: Screen 52: Projection original 56: Projection device 58: Diffusing material layer 60: Diffusing material 61 : Prism 62: Diffuse reflection dot layer 66: Shading body

Claims (17)

The radius of curvature r depends on the irradiated dimension W, the distance t to the irradiated surface, and the inclination width d of the convex reflecting surface.
r = 2 · t · d / (W−d / √2)
The convex reflection surface set in is distributed in a terraced pattern at the pixel pitch on the bottom surface of the light guide plate,
Incident at the critical angle or more parallel light which light from the light source propagates by Ri are converted light guide plate to the parallel light into a parallel light conversion means to the convex reflective surface,
A light guide plate that expands the light flux by total reflection or specular reflection and reflects it to the irradiated surface is a component,
By using three layers of light sources and three layers of light guide plates, color-specific light is incident on each light guide plate, and the stepped portion of the inclined convex reflection surface of the light guide plate is shifted by three layers for each sub-pixel width , The reflected light from the convex reflection surface of the light guide plate arranged on the lower layer side is transmitted between the pitches of the convex reflection surfaces of the light guide plate arranged on the upper layer side,
A liquid crystal display device that performs color display by irradiating light from three color light sources to the same pixel composed of three sub-pixels on a display surface. A regular focal length refracting surface is provided dispersed at a pixel pitch on the exit surface of the light guide plate ,
The convex reflection surface is distributed and arranged in a terraced pattern at the pixel pitch on the bottom surface of the light guide plate ,
The radius of curvature r of the convex reflecting surface depends on the sub-pixel width W, the thickness t from the convex reflecting surface to the light guide plate exit surface, and the convex reflecting surface width d.
r = 2 · t · d / (W−d / √2)
Set with
3-layer stacked light guide plate having the same shape the distribution of curvature radius set to the same each layer,
The light that is incident on the convex reflection surface at a critical angle or more and spreads and reflects the light is converted into parallel light by a regular focal length refracting surface provided on the output surface,
The reflected light from the convex reflection surface of the light guide plate arranged on the lower layer side is transmitted between the pitches of the convex reflection surfaces of the light guide plate arranged on the upper layer side,
The same pixel of three sub-pixels by the incident parallel light of each color liquid crystal display device according to claim 1, characterized in that the color display. When the display surface of the liquid crystal display device is the xy plane,
The first terraced convex reflection surface is the thickest of the substantially wedge-shaped terraced light guide plates, and is provided on the yz plane orthogonal to the display surface.
Convex reflecting surface distributed in a terraced shape with a step is configured with a long curvature radius on the liquid crystal panel side and a short side on the opposite side,
The second terraced convex reflection surface is provided on the basis of the thickest xy plane of the terraced light guide plate below the liquid crystal display surface,
Construct a convex reflection surface distributed in a terraced shape with steps and a curvature according to the irradiated dimension and the distance to the irradiated surface,
The parallel light incident from the side surface parallel to the y-axis direction of the thickest yz plane of the terraced light guide plate is redirected by expanding the light beam in the x-axis direction on the first terraced convex reflection surface,
The second convex reflecting surface is irradiated with a light beam that is converted into the x direction and expands the light beam, and the light beam is expanded and reflected on a liquid crystal panel in a substantially vertical direction, and each light guide plate is colored using three layers of the light guide plate. enters another light, by the stepped portion of the second terraced fields convex reflecting surface is arranged shifted in the stripe pitch of the sub-pixel width, the convex reflecting surface of the light guide plate on the upper side of the light guide plate 3 layers Light reflected by the convex reflection surface of the light guide plate arranged on the lower layer side is transmitted between the pitches, and the color display is performed by irradiating light from three light sources to the same pixel on the display surface in three colors. The liquid crystal display device according to claim 1. When the display surface of the liquid crystal display device is the xy plane,
The first terraced convex reflection surface is the thickest of the terraced light guide plates, and is provided on the yz plane orthogonal to the display surface.
Convex reflecting surface distributed in a terraced shape with a step is configured with a long curvature radius on the liquid crystal panel side and a short side on the opposite side,
The second terraced convex reflection surface is provided on the basis of the thickest xy plane of the terraced light guide plate below the liquid crystal display surface,
The convex reflection surface distributed in a terraced shape with steps is distributed according to the irradiated dimension and the distance to the irradiated surface,
Construct the convex reflective surface as a negative focal length reflective surface in the axial direction,
The light beam that changes the direction of the parallel light beam incident from the side surface parallel to the y-axis direction of the thickest yz plane of the terraced light guide plate in the x-axis direction on the first terraced convex reflection surface is farther from the liquid crystal panel. As the luminous flux expansion rate is higher,
By forming a negative focal length reflecting surface in the axial direction on the second terraced convex reflecting surface, the light beam expansion rate is controlled to the liquid crystal pixel width regardless of the x coordinate of the second terraced convex reflecting surface. The liquid crystal display device according to claim 1.   The parallel light propagating in the long axis direction inside the rod-shaped light guide is expanded by a convex reflecting surface in which the parallel light is distributed in a terraced shape, and reflected to the side surface of the light guiding rod so as to have a constant pitch on the exit surface side. Furthermore, an element for converting into parallel light at the positive focal length refracting surface having the same focal position as that of the convex reflecting surface is arranged along the emitting surface, and the parallel light is emitted from the side surface of the rod-shaped body and incident on the light guide plate. The liquid crystal display device according to claim 1.   By illuminating the three liquid crystal display original elements with three colors of light for each color and disposing the reflecting surfaces dispersedly arranged in the three-layer light guide plate in three colors, the traveling direction is changed by the inclined reflecting surfaces. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device performs color display by expanding the luminous flux to the pixel width without being obstructed and combining the three colors on the screen.   A display document element is provided on the entrance surface of a substantially wedge-shaped light guide plate in which reflection surfaces are distributed in a terraced manner on the xy plane, and the display document element projection light is applied to the terraced reflection surface, and this reflected light is on the xy plane. The liquid crystal display device according to claim 1, wherein the display element image is enlarged and displayed on the screen by enlarging and reflecting the image on the display surface.   An elongated liquid crystal display element with a flattened image compressed in the vertical direction on the light guide plate entrance surface is placed, and the screen dimensions from the elongated liquid crystal display element by the light beam expansion function on the reflective surface distributed in the light guide plate The liquid crystal display device according to claim 1, wherein the liquid crystal display device is enlarged.   A plurality of pixels are projected per one reflecting surface of the terraced reflecting surface to reduce the number of steps distributed and arranged in a terraced shape, thereby facilitating mold manufacture by enlarging the reflecting surface dimension. Item 2. A liquid crystal display device according to item 1.   In the arrangement in which the display surface is the xy plane, the display transmitted light direction is the z axis, the projection display element is provided on the xz plane and the parallel light is irradiated in the y axis direction, a first step having a terraced shape on the yz plane is provided. The terraced convex reflector mirrors the image in the x-axis direction while changing the direction, and irradiates the second terraced convex reflecting surface having a terraced step on the xy plane. The display element image is enlarged on the screen with three light sources by using three layers of light guide plates for reflecting and enlarging the image on the display surface, and shifting the second terraced stepped portion with a stripe pitch of the sub-pixel width. The liquid crystal display device according to claim 1, wherein color display is performed.   Air is used as the transparent material, and the incident side of the terraced reflection surface in the transparent polymer material used to form the total reflection surface is a plane perpendicular to the parallel light, and the parallel light is incident on the total reflection surface, and the emission side. The liquid crystal display device according to claim 1, wherein the surface is made of a translucent material as a surface substantially perpendicular to a reflected light beam for expanding a light beam.   2. The liquid crystal display device according to claim 1, wherein the thickness of the entire light guide plate is reduced by alternately stacking thick portions of the substantially wedge-shaped light guide plate.   In a direct-illumination type liquid crystal display device that converts linear light source light into parallel light and converts parallel light incident from directly under the light guide plate into a plane direction by an inclined reflective surface and reflects it, the 45 ° inclined reflective surface is divided into a terraced shape. The liquid crystal display device according to claim 1, wherein the light guide plate thickness is made thinner than the emission width of the light source by inserting the horizontal portion. In the light guide plate in which the opening width of the light source provided directly below the light guide plate is wider than the thickness of the light guide plate and the light from the light source is reflected in the plane direction of the light guide plate by the 45 ° inclined reflection surface, 2. A flat portion dispersed and inserted in order to make the width wider than the thickness of the light guide plate is formed by a reflecting mirror or a retroreflective element , returned to the light source, and again irradiated to the inclined reflecting surface as parallel light. A liquid crystal display device according to 1. The light guide plate of the direct illumination type liquid crystal display device is provided with a triangular prism-shaped inclined reflecting surface, and the area ratio of the inclined reflecting surface to the transmission opening in the horizontal plane is determined by comparing the area above the triangular prism-shaped inclined reflecting surface and the triangular prism-shaped inclined reflecting surface. It is set by the ratio of the light guide plate area of the part where there is no light, and by controlling the component reflected in the plane direction of the light guide plate and the component transmitted directly above the inclined surface, it is formed into a triangular prism shape of the direct illumination type liquid crystal display device The liquid crystal display device according to claim 1, wherein the brightness of the upper portion of the inclined reflection surface is matched with that of the other light guide plate surface . Parallel light from the three-color light sources of direct illumination is reflected in the plane direction by the triangular prismatic inclined reflecting surface, and the incident on the upper part of the triangular prism and the adjacent triangular prism is within the critical angle by the transmission part provided on the inclined reflecting surface. The liquid crystal display device according to claim 1, wherein the upper part of the adjacent triangular prism is also illuminated by. In a concave mirror that expands the light from the light source from the parallel beam by collimating the parabolic surface so that the light flux density is uniform at the opening of the concave mirror, the mirror surface is divided and increased from the parabolic tangential gradient. It consists of a steeply inclined mirror surface and a gently inclined surface facing the focal direction. The liquid crystal display device according to claim 1, wherein the liquid crystal display device emits the light as reflected light.