JP4436752B2 - Light source device and liquid crystal display device - Google Patents

Description

  The present invention relates to a light source device and a liquid crystal display device using the light source device.

  Liquid crystal display devices are widely used as liquid crystal televisions, monitors, mobile phones and the like as flat panel displays having features such as thinness and light weight. Various display methods for liquid crystal display devices have been proposed, but the most widely used method is a method using two or one polarizing plate. In a liquid crystal display device, a twisted nematic mode (hereinafter referred to as “TN mode”) in which display is performed by controlling the optical rotation of the liquid crystal layer by an electric field, and a birefringence mode in which display is performed by controlling the birefringence of the liquid crystal layer by an electric field. (Hereinafter, referred to as “ECB mode”) or a mixed mode in which the TN mode and the ECB mode are combined is mainly used.

  However, a liquid crystal display device using these modes generally has a very low light use efficiency of 10% or less. The main reason for greatly reducing the utilization efficiency is the use of polarizing plates and absorption type color filters. When a polarizing plate is used, only about 45% of light can be used. In addition, when an absorption color filter is used, only about 30% of light can be used depending on the density of the color filter.

  Therefore, in order to improve the light utilization efficiency, various systems have been proposed as a system that does not use a polarizing plate or a color filter that significantly reduces the light utilization efficiency. Examples of methods that do not use color filters include guest-host methods, methods that use cholesteric liquid crystals, field sequential methods, methods that use phosphors that convert colors, and methods that use spectral elements such as diffraction gratings and holograms. It is done.

  However, the guest host method and the method using cholesteric liquid crystal have problems such as a low contrast ratio and a high drive voltage. The field sequential method and the method using a phosphor that converts color are advantageous in that a conventional liquid crystal layer is used for the driving part. However, the field sequential method is disadvantageous in that a problem of color braking occurs in principle. In addition, a method using a phosphor that converts color has a problem in that a parallax is generated and a display appearance is poor because a polarizing plate needs to be disposed between the phosphor and the liquid crystal layer.

A liquid crystal display device using a spectroscopic element such as a diffraction grating or a hologram is disclosed in Patent Document 1, for example. In the liquid crystal display device of Patent Document 1, a single-layer hologram that diffracts incident light at different diffraction angles depending on the wavelength is disposed on the backlight incident side, and red, green, and blue diffracted and spectrumd by the hologram The wavelength component is made incident on a pixel displaying the corresponding hue.
Japanese Patent No. 3400000

  However, the optical characteristics of spectral elements such as diffraction gratings and holograms vary greatly depending on the incident angle of incident light. Therefore, as in the liquid crystal display device disclosed in Patent Document 1, in order to make red, green, and blue wavelength components efficiently incident on pixels that display the corresponding hue, incident light is substantially parallel light. Need to be. However, a backlight for a liquid crystal display device that is currently generally used has high diffusivity and is far from parallel light. Therefore, in the liquid crystal display device disclosed in Patent Document 1, the characteristics of the spectroscopic element cannot be effectively used, and red, green, and blue wavelength components are efficiently used for pixels that display the corresponding hue. It cannot be made incident.

  One of the objects of the present invention is to collect light dispersed without using a spectroscopic element onto pixels that display hues corresponding to the light. Another object of the present invention is to realize a liquid crystal display device that minimizes light absorption by a color filter and has high light utilization efficiency. Still another object of the present invention is to realize a liquid crystal display device capable of color display without using a color filter.

The light source device of the present invention includes a plurality of light sources and a light guide that emits a plurality of colored lights respectively emitted from the plurality of light sources to an irradiation object. The light guide includes a reflecting portion serving as a paraboloid for reflecting the plurality of color lights as substantially parallel light in a predetermined direction different for each color light. The plurality of light sources include a first light source that emits first color light, a second light source that emits second color light different from the first color light, and a third color light that emits third color light different from the first color light and the second color light. And a light source. The first light source is configured such that the center of the light emitting point coincides with the focal point of the paraboloid. The second light source is provided so that the center of the light emitting point does not coincide with the focal point of the paraboloid and is adjacent to the first light source. The third light source is provided so that the center of the light emitting point does not coincide with the focal point of the paraboloid and adjacent to the first light source on the opposite side to the second light source. In this specification, “substantially parallel light” includes not only parallel light but also light that is inclined by a predetermined angle and is close to parallel light.

  According to the present invention, it is possible to emit a plurality of color lights as substantially parallel light in a predetermined direction different for each color light with respect to an irradiation object such as a liquid crystal display element. Therefore, the color light of a certain hue can be efficiently condensed on the pixel displaying the corresponding hue.

The light source includes a first light source that emits first color light, a second light source that emits second color light different from the first color light, and a third color light that emits third color light different from the first color light and the second color light. In the first to third light sources, the first to third color lights are reflected in different directions by the reflection unit. Therefore, it is possible to obtain the dispersed light without using any spectroscopic element, and it is possible to condense the first to third color lights (for example, RGB light) onto the pixels displaying the corresponding hues. it can.

  The light source device of the present invention includes an embodiment of a direct type backlight. In the light source device of this aspect, each of the plurality of light sources may be a linear light source. Moreover, it is preferable that the said cut part draws a parabola in the cut surface cut | disconnected by the virtual plane which makes a normal line the line parallel to the longitudinal direction of the said line light source.

  The light source device of the present invention also includes a side (edge) type backlight. In the light source device of this aspect, each of the plurality of light sources may be a point light source. The light guide includes a first light guide that emits the plurality of color lights as substantially parallel light, and a second light that emits the substantially parallel light emitted from the first light guide to the object to be irradiated. You may have a light guide. In this case, the first light guide has the reflecting portion, and the second light guide has an angle formed by the substantially parallel light incident from the reflecting portion and the light emitted to the irradiated object. It is preferable to have a control unit that controls the angle at a predetermined angle for each color light.

  The present invention also provides a liquid crystal display device. The liquid crystal display device of the present invention includes the light source device of the present invention, a liquid crystal display element having a plurality of pixels, the light source device and the liquid crystal display element, and the plurality of light beams emitted from the light source device. A condensing element for condensing the colored light on the pixels displaying the corresponding hue. The liquid crystal display element may include a plurality of hue color filters.

  According to the liquid crystal display device of the present invention, the light source device of the present invention can efficiently focus the color light of a certain hue onto the pixel displaying the corresponding hue, so that the liquid crystal with very high light utilization efficiency. A display device can be realized.

  In the liquid crystal display device of the present invention, at least one of the plurality of pixels may have a reflective region that reflects external light and a transmissive region that transmits light from the light source device. In this case, it is preferable that the condensing element condenses the color light on the transmission region. As a result, in addition to the transmissive display using the backlight, which has a very high light utilization efficiency, it is possible to perform a reflective display using external light or the like. Therefore, it is possible to realize a liquid crystal display device capable of good display regardless of whether it is a dark place or a bright place.

  In this specification, the minimum unit of display is referred to as a “pixel”. For example, in a color liquid crystal display device, pixels of different hues constitute one “picture element”. Typically, three pixels of R, G, and B constitute one “picture element”.

  According to the present invention, it is possible to focus light dispersed without using a spectroscopic element onto pixels that display hues corresponding to the light. In another aspect of the present invention, a liquid crystal display device with high light utilization efficiency can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In addition, in order to collectively represent the homologous components, the reference numerals may be omitted, and only the reference numerals may be indicated. For example, the first and second light guides 1a and 1b may be collectively referred to as the light guide 1.

(Embodiment 1)
FIG. 1 is a perspective view schematically showing a liquid crystal display device of the present embodiment. The liquid crystal display device of this embodiment includes a surface light source device BL and a liquid crystal display element 10 having color filters 13, 14, and 15. First, the surface light source device BL will be described.

  FIG. 2 is a perspective view schematically showing the surface light source device BL. The surface light source device BL includes a plurality of point light sources 3 and a light guide that emits a plurality of color lights respectively emitted from the plurality of point light sources 3 to the liquid crystal display element 10 as an irradiated object. More specifically, the surface light source device BL includes two transparent first light guides 1a and 1b each having a curved surface, and three-color LEDs (light emission) provided on the first light guides 1a and 1b. Diode) 3 and a flat plate-like second light guide 4 that emits the light emitted from the first light guides 1a and 1b to the outside (the liquid crystal display element 10 side). The three-color LED 3 includes a red LED 3a that emits red light, a green LED 3b that emits green light, and a blue LED 3c that emits blue light. Light that guides the inside of the second light guide 4 is emitted to the outside of the second light guide 4 on the bottom surface (surface opposite to the liquid crystal display element 10 side) of the second light guide 4. A prism 5 is formed.

  FIG. 3 is a plan view of one of the first light guides 1a. FIG. 3 (a) shows a green light path, FIG. 3 (b) shows a red light path, and FIG. 3 (c) shows a blue light path. Each optical path is shown. The first light guide 1a has four surfaces 2a, 2b, 2c, and 2d. The surface 2d is a light incident part to which the LED 3 is fixed using an adhesive or the like and light emitted from the LED 3 is incident. The surface 2a facing the light incident portion 2d is a light reflecting portion that reflects the light emitted from the LED 3, and is formed by depositing a metal such as silver or aluminum or adhering a metal thin film such as an aluminum foil. Yes. The surface 2 c is a light emitting part from which the light reflected by the light reflecting part 2 a is emitted to the second light guide 4. It is preferable that the three surfaces 2a, 2c, and 2d have high flatness by performing polishing (mirror finishing) or the like. The first light guides 1a and 1b can be manufactured by an injection molding method using a highly transparent acrylic resin.

  When the light reflecting portion 2a is a mirror surface with high flatness, the light reflecting portion 2a becomes a paraboloid with the center of the light emitting point of the green LED 3b as a focal point. As a result, as shown in FIG. 3A, the light emitted from the green LED 3b is reflected by the light reflecting portion 2a and emitted from the light emitting portion 2c as parallel light parallel to the normal direction of the light emitting portion 2c. . On the other hand, the red LED 3a is arranged so that the center of the light emitting point does not coincide with the focal point of the paraboloid of the light reflecting portion 2a, and the light emitted from the red LED 3a is reflected by light as shown in FIG. The light is reflected by the portion 2a and emitted as light close to parallel light that is inclined by a certain angle θa from the normal direction of the light emitting portion 2c. Similarly, the blue LED 3c is also arranged such that the center of the light emitting point does not coincide with the focal point of the paraboloid of the light reflecting portion 2a, and the light emitted from the blue LED 3c is light as shown in FIG. The light is reflected by the reflecting portion 2a and emitted as light close to parallel light that is inclined by a certain angle θc from the normal direction of the light emitting portion 2c.

  Next, the relationship between the center position of the light emitting point of the LED 3 and the angles θa and θc of the light emitted from the light emitting unit 2c will be described with reference to FIG. FIG. 4A is a diagram showing the XY coordinate system of the first light guide 1a, and FIG. 4B is a graph showing the relationship between the arrangement of the LEDs 3 and the emission angle θ of the emitted light in this coordinate system. . The XY coordinate system of the first light guide 1a is light from the origin with the center position of the light emitting point of the green LED 3b as the origin, the direction parallel to the light emitting portion 2c as the X axis, and the direction parallel to the surface 2b as the Y axis. The direction approaching the reflection part 2a was each positive. In one first light guide 1a shown in FIG. 4A, the right direction on the paper surface is the positive direction of the X axis, while in the other first light guide body 1b, the left direction of the paper surface is the positive direction of the X axis. Direction.

  In the first light guide 1a shown in FIG. 4A, when the distance from the center position of the light emitting point of the green LED 3b (that is, the origin of the XY coordinate system) to the intersection of the Y axis and the light reflecting portion 2a is f, An ideal parabola of the light reflecting portion 2a is expressed by the following equation.

Y = f−X ² / 4f
The graph shown in FIG. 4B is an average of the angles of light emitted from the light emitting part 2c (angles formed with respect to the normal line of the light emitting part 2c in plan view) when there is a light emitting point at an arbitrary coordinate. The values are plotted. FIG. 4B shows a case where the distance f is 10 mm.

  By using FIG. 4B, the position where the LED 3 of each color is arranged is determined according to the required light emission angle. In the present embodiment, the red LED 3a is disposed at a position where X = −0.44 mm and Y = 0.44 mm, and the blue LED 3c is disposed at a position where X = 0.44 mm and Y = −0.44 mm, respectively. = Parallel light tilted by 4 ° and θc = -4 ° is emitted.

  As shown in FIGS. 2 and 3, the two first light guides 1 a and 1 b have the light of the second light guide 4 so that the sides where the light reflecting part 2 a and the light emitting part 2 c intersect are common. They are arranged side by side on the incident surface. The other first light guide 1b has the same structure as the first light guide 1a, but in order to make the light of the same hue emitted from the two first light guides 1a and 1b parallel, In the other first light guide 1b, the positions of the red LED 3a and the blue LED 3c are interchanged. That is, the red LED 3a is disposed at a position where X = 0.44 mm and Y = −0.44 mm, and the blue LED 3c is disposed at a position where X = −0.44 mm and Y = 0.44 mm.

  FIG. 5 is a schematic cross-sectional view of the surface light source device BL of the present embodiment cut in the light guide direction. The second light guide 4 includes a light incident portion (side surface) 4a on which light emitted from the first light guide 1 is incident, a light emitting portion 4b (upper surface) that emits light toward the liquid crystal display element 10 side, 2 It has the light reflection part (bottom surface) 4c which reflects the light confine | sealed inside the light guide 4 to the light-projection part 4b. The light reflecting portion 4 c of the second light guide 4 is formed with a prism 5 that emits light that guides the inside of the second light guide 4 to the outside of the second light guide 4. In other words, the prism 5 is a control unit that controls the angle formed by the substantially parallel light incident from the light reflecting portion 2a of the first light guide 1 and the light emitted to the liquid crystal display element 10 to a predetermined angle for each color light. It is.

  The light emitting portion 4b and the light reflecting portion 4c are processed so that light can be guided while being totally reflected without being scattered by performing polishing (mirror finishing) or the like. The second light guide 4 can be manufactured by an injection molding method using a mold in which an acrylic resin having high translucency is used and a protruding portion corresponding to the prism 5 is formed by cutting. Using an adhesive or the like, the light emitting part 2c of the first light guides 1a and 1b and the light incident part 4a of the second light guide 4 are joined, and an air layer is interposed between the members 2c and 4a. The surface light source device BL of this embodiment can be manufactured by closely fixing so as not to occur.

  The light emitted from the light emitting part 2c of the first light guides 1a and 1b enters the light incident part 4a of the second light guide 4 and guides the inside of the second light guide 4 while being totally reflected. The light 6 incident on the prism 5 formed in the light reflecting portion 4c is reflected at an angle that does not totally reflect the inside of the second light guide 4, and is emitted from the light emitting portion 4b to the outside of the second light guide 4.

  The prism 5 extends in a direction (typically a direction substantially orthogonal) intersecting the traveling direction of the light incident on the light incident portion 4a. Therefore, the green color light 6b that is incident in substantially the same direction as the normal direction of the light incident portion 4a is emitted in substantially the same direction as the normal direction of the light emitting portion 4b. On the other hand, the red color light 6a and the blue color light 6c are guided through the second light guide 4 by being inclined by an angle θa and an angle θc, respectively, with respect to the normal direction of the light incident portion 4a, and therefore are shown in FIG. As described above, the light is emitted with an angle θa and an angle θc inclined with respect to the normal direction of the light emitting portion 4b. That is, the color light emitted from the LED 3 is emitted out of the second light guide 4 as the light 6 having very high directivity. This emitted light enters the liquid crystal display element 10 and is used as display light.

  FIG. 6 is a graph showing the spectral characteristics of color light by the surface light source device BL of this embodiment. The horizontal axis of the graph shown in FIG. 6 indicates the polar angle with respect to the direction parallel to the direction in which the prism 5 extends. As shown in FIG. 6, the blue color light 6c has a peak at about -4 °, the green color light 6b has a peak at about 0 °, and the red color light 6a has a peak at about 4 °. It can be seen that the surface light source device BL that spectrally emits as extremely high light can be manufactured.

  Although not shown, the formation density of the prisms 5 may be different within the plane. For example, the formation density of the prisms 5 may be lowered on the light incident part 4a side and gradually increased toward the opposite side. Thereby, the intensity | strength of display light can be equalize | homogenized within a surface. Further, since the emission direction of the emitted light 6 is desirably close to perpendicular to the light emitting portion 4b, a prism sheet or the like may be laminated on the light emitting portion 4b to change the direction of the emitted light 6.

  Next, the liquid crystal display element 10 will be described with reference to FIG. FIG. 7 is a cross-sectional view schematically showing a cross section of the liquid crystal display element 10. The liquid crystal display element 10 of the present embodiment has a plurality of pixels arranged in a matrix with the liquid crystal alignment mode being a TN mode. The liquid crystal display element 10 includes an element substrate, a color filter substrate on which a color filter is formed, and a liquid crystal layer 20 interposed between the two substrates. The element substrate includes a first transparent substrate 12 made of a glass plate or a polymer film, a thin film transistor (not shown) formed on the first transparent substrate 12, and a transparent pixel electrode connected to the thin film transistor and arranged in a matrix. 19a and an alignment film (not shown) covering the transparent pixel electrode 19a. The color filter substrate includes a second transparent substrate 11 made of a glass plate or a polymer film, red, green, and blue color filters 13, 14, and 15 formed on the second transparent substrate 11, and a color filter for each hue. It has a black matrix 16 formed therebetween, a transparent full-surface electrode 19b formed on the color filters 13, 14, 15 and the black matrix 16, and an alignment film (not shown) covering the transparent full-surface electrode 19b.

  A diffusion layer 22 and a first polarizing plate 21b are formed on the outer surface (observer side surface) of the first transparent substrate 12, and the second transparent substrate 11 has a first surface on the outer surface (surface facing the surface light source device). A second polarizing plate 21a having a polarization axis substantially orthogonal to the polarization axis of the first polarizing plate 21b is formed.

  The element substrate and the color filter substrate can be formed by a photolithography method, a printing method, or the like. The element substrate and the color filter substrate are bonded to each other with an interval of several μm so that the surfaces of both electrodes 19a and 19b face each other, and then a liquid crystal material is filled between the substrates to form the liquid crystal layer 20. Furthermore, the liquid crystal display element 10 of this embodiment can be formed by bonding the diffusion layer 22 and the pair of polarizing plates 21a and 21b.

  The red, green, and blue color filters 13, 14, and 15 are arranged in this order in the form of stripes in the direction in which the prism 5 extends. The pixels of each hue are defined by the transparent pixel electrode 19a, the transparent whole surface electrode 19b, and the red, green, and blue (RGB) color filters 13, 14, and 15. Strictly speaking, however, the region of each hue corresponding to the opening of the black matrix 16 among the regions to which the voltage is applied according to the state to be displayed is the pixel region. By changing the applied voltage between the electrodes 19a and 19b, the alignment state of the liquid crystal molecules for each pixel changes. Thereby, since the light transmission state and the non-transmission state can be changed, the intensity of the corresponding hue can be adjusted for each pixel.

  A lens array as a condensing element is formed between the surface light source device BL and the liquid crystal display element 10, specifically, on the outer surface of the second polarizing plate 21 a (the surface facing the surface light source device). As the lens array, a bowl-shaped microlens array having a condensing function in the vertical and horizontal directions, or a bowl-shaped lenticular lens having a condensing function in only one of the vertical and horizontal directions is preferably used. Hereinafter, a case where the lenticular lens 17 is used as the lens array will be described.

  FIG. 8 is a plan view showing the arrangement of the lenticular lens 17. As shown in FIGS. 1 and 8, one lenticular lens 17 is arranged for each of the three color filters 13, 14, 15 of RGB. FIG. 9 is a schematic cross-sectional view for explaining the operation of the lenticular lens 17. As shown in FIG. 9A, the green color light 6b incident from the normal direction of the first transparent substrate 12 enters a pixel in which the green color filter 14 is disposed. On the other hand, as shown in FIG. 9B and FIG. 9C, the red color light 6a and the blue color light 6c incident with inclination from the normal direction of the first transparent substrate 12 are provided with the red color filter 13. And the pixels on which the blue color filter 15 is disposed.

  The RGB color filters 13, 14, and 15 transmit only light corresponding to each color, and absorb other colors. Therefore, the light incident from the normal direction of the first transparent substrate 12 and incident on the G pixel is incident on the green color light 6b with an inclination from the normal direction of the first transparent substrate 12, and is incident on the R pixel. The light is incident on the red color light 6a with an inclination from the normal direction of the first transparent substrate 12, and the light incident on the B pixel is set to the blue color light 6c. The ratio can be kept to a minimum.

  The incident angle of light incident on the R and B pixels is determined by the pixel pitch, the distance from the lenticular lens 17 to the pixel, and the radius of curvature of the lenticular lens 17. In this embodiment, the pixel pitch is 51 μm, the distance from the lenticular lens 17 to the pixel is 1.1 mm, and the radius of curvature of the lenticular lens 17 is 0.38 mm.

  The lenticular lens 17 can be easily manufactured by roll molding using, for example, a roll-shaped mold having a concave surface continuous in the longitudinal direction. After the lenticular lens 17 thus obtained is cut out to the same size as the liquid crystal display element 10, it is precisely aligned so that the vertex of the lenticular lens 17 coincides with the center of the light transmission region of the G pixel, Fix using adhesive or the like.

  When the liquid crystal display element 10 obtained in this way is stacked on the surface light source device BL, RGB light emitted from the surface light source device BL is appropriately incident on the RGB pixels of the liquid crystal display element 10 and is almost absorbed. It is possible to pass through the RGB color filter without being done.

  When the liquid crystal display device is viewed from an oblique direction, the dispersed RGB colors may not be mixed completely, and a specific color may appear strong. However, since the liquid crystal display device of the present embodiment has the diffusion layer 22, the influence can be reduced. In order to prevent blurring of the display image, it is preferable that the distance between the liquid crystal layer 20 and the diffusion layer 22 is short.

(Comparative example)
A liquid crystal display device manufactured in the same manner as in the first embodiment except that the lenticular lens 17 is not disposed, and a side (edge) type backlight (surface light source) that is generally used at present and emits white light A liquid crystal display device was manufactured as a comparative example. When the luminance was measured for the first embodiment and the comparative example, the luminance improvement effect about 2.5 times that of the comparative example was obtained in the first embodiment. The reason is that in the comparative example, the white light emitted from the surface light source device irradiates the color filters of the respective hues of the liquid crystal display element evenly, so that the absorption by the color filters is large, whereas in the first embodiment, This is because light absorbed by the color filter can be minimized.

(Embodiment 2)
In the first embodiment, the case where the lenticular lens 17 is used as the lens array has been described. However, a microlens array may be used instead of the lenticular lens. FIG. 10 is a plan view showing the arrangement of the microlens array 18 of the present embodiment. As shown in FIG. 10, one microlens is arranged for every three pixels of RGB. The microlens array 18 can be manufactured by, for example, manufacturing a mold by cutting and performing injection molding using the mold.

  When the microlens array 18 is used, a high luminance improvement effect can be obtained for a high-resolution liquid crystal display device, a transflective liquid crystal display device capable of display in a transmission mode and a reflection mode, and the like. In particular, a higher luminance improvement effect can be obtained for a liquid crystal display device having a low aperture ratio in the light transmission region. In the transflective liquid crystal display device, at least one pixel has a light reflection region that reflects external light and a light transmission region that transmits light from the surface light source device. The microlens array 18 condenses the color light emitted from the surface light source device BL onto the transmission region of the pixel displaying the corresponding hue.

(Embodiment 3)
FIG. 11 is a cross-sectional view schematically showing a cross section of the liquid crystal display element 10 of the third embodiment. The liquid crystal display element 10 of this embodiment includes a prism sheet 23 instead of the diffusion layer 22. In addition, the description about the component of the same referential mark is abbreviate | omitted by attaching | subjecting the same referential mark to the same component as Embodiment 1. FIG.

  As shown in FIG. 11, the prism sheet 23 is composed of a laminate of a high refractive index resin 23a and a low refractive index resin 23b, and has a function of refracting light at the boundary surface. By appropriately designing the refractive index and the inclination angle of the prism sheet 23 in the pixels of each hue, the light separated into RGB can be refracted in the front direction and mixed effectively.

  For example, in a region corresponding to the R and B pixels, a polythiourethane resin (refractive index 1.6) as a high refractive index resin and a fluorine resin (refractive index 1.34) as a low refractive index resin. By disposing a prism (tilt angle of 16 °) using, RGB light can be refracted in the front direction and mixed effectively. In order to prevent blurring of the display image, the distance between the liquid crystal layer 20 and the prism sheet 23 is preferably short.

(Embodiment 4)
The shape of the first light guide 1 is not limited to that of the first embodiment, and may be any other shape as long as the light emitted from the LED 3 is emitted from the light emitting portion of the first light guide 1 as substantially parallel light. . FIG. 12 is a perspective view schematically showing the surface light source device BL of the fourth embodiment. In the first light guides 1a and 1b shown in FIG. 12, three LEDs 3 are formed in each light emitting portion. As in the first embodiment, the light reflecting portions of the first light guides 1a and 1b are paraboloids, and the center of the light emitting point of the green LED 3b is located at the focal point. According to the present embodiment, since the first light guides 1a and 1b can be made smaller than in the first embodiment, it is possible to cope with the downsizing required for mobile phones and portable information terminals. .

(Embodiment 5)
In Embodiments 1 to 4, the case where the light source device of the present invention is applied to a side (edge) type backlight has been described. However, the light source device of the present invention can also be applied to a direct type backlight. In the present embodiment, a liquid crystal display device having a direct type surface light source device BL will be described. FIG. 13 is a perspective view schematically showing a cross section of the liquid crystal display device of the present embodiment. Since the liquid crystal display element 10 shown in FIG. 13 is the same as that described in the first embodiment, description of the liquid crystal display element 10 is omitted.

  The surface light source device BL includes a plurality of line light sources 24 extending in the longitudinal direction, respectively, and a light guide that emits a plurality of color lights respectively emitted from the plurality of line light sources 24 to the liquid crystal display element 10 as an irradiation object. . More specifically, the surface light source device BL includes a plurality of transparent (three in FIG. 13) light guides 25 each having a curved surface and a surface of the light guide 25 on the side facing the liquid crystal display element 10 (hereinafter referred to as “light source”). , Also referred to as the top surface). The three-color fluorescent tube 24 includes a red fluorescent tube 24a that emits red light, a green fluorescent tube 24b that emits green light, and a blue fluorescent tube 24c that emits blue light.

  The bottom portion 26 of the light guide 25 is a light reflecting portion that reflects the light emitted from the fluorescent tube 24. The light guide 25 can be manufactured by an injection molding method using a highly transparent acrylic resin. The light reflecting portion 26 is formed by depositing a metal such as silver or aluminum on the bottom of the light guide 25 or by adhering a metal thin film such as an aluminum foil. The light guide 25 has a bowl-like shape, and the light reflecting portion 26 has a cut surface cut by a virtual plane having a normal line parallel to the longitudinal direction of the fluorescent tube 24 as a parabola.

  The light reflecting portion 26 is a paraboloid, and draws a parabola with the center of the emission point of the green fluorescent tube 24b as the focal point on the cut surface cut by the virtual plane. In other words, the focal point of the parabolic light reflecting portion 26 coincides with the center of the light emitting point of the green fluorescent tube 24b. As a result, as shown in FIG. 13, the light emitted from the green fluorescent tube 24b is reflected by the light reflecting section 26 and is emitted as parallel light parallel to the normal direction of the upper surface. On the other hand, the red fluorescent lamp 24a is arranged so that the center of the light emitting point does not coincide with the focal point of the paraboloid of the light reflecting portion 26, and as shown in FIG. The light is reflected by the reflecting portion 26 and emitted as light close to parallel light that is inclined by an angle from the normal direction of the upper surface. Similarly, the blue fluorescent lamp 24c is also arranged so that the center of the light emitting point does not coincide with the focal point of the paraboloid of the light reflecting portion 26. As shown in FIG. 13, the light emitted from the blue fluorescent lamp 24c is The light is reflected by the light reflecting portion 26 and emitted as light close to parallel light that is inclined by a certain angle from the normal direction of the upper surface. That is, the RGB light is split by the light reflecting section 26, and the split RGB color light is reflected as substantially parallel light in different predetermined directions for each color light.

  Therefore, as in the first embodiment, the green color light 6b incident from the normal direction of the first transparent substrate 12 to the lenticular lens 17 arranged for each of the three color filters 13, 14, 15 of RGB. Enters the pixel in which the green color filter 14 is arranged. On the other hand, as shown in FIG. 13, the red color light 6 a and the blue color light 6 c that are inclined with respect to the normal line direction of the first transparent substrate 12 include the pixel in which the red color filter 13 is disposed and the blue color filter 15. Is incident on each pixel.

  That is, by stacking the same liquid crystal display element 10 as in the first embodiment on the surface light source device BL of the present embodiment, RGB light emitted from the surface light source device BL is transmitted to the RGB pixels of the liquid crystal display element 10. Each of them is appropriately incident and can pass through the RGB color filter with almost no absorption.

  The number of light guides 25 is independent of the number of lenticular lenses 17, and the number of light guides 25 to be installed can be determined according to the number of fluorescent tubes 24 to be used.

  As mentioned above, although preferable embodiment of this invention was described, the technical scope of this invention is not limited to the range as described in the said embodiment. It is understood by those skilled in the art that the above embodiment is an exemplification, and that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. By the way.

  For example, in Embodiments 1 to 5, the liquid crystal display element 10 includes the color filters 13, 14, and 15 in order to block light that has not been properly dispersed. However, since the surface light source device of the present invention can condense a plurality of color lights emitted from the light source onto the pixels displaying the corresponding hues, the liquid crystal display element does not have a color filter. In addition, a liquid crystal display device capable of color display can be realized.

  In the first to fifth embodiments, the G pixel is arranged at the center of the lens. However, the present invention is not limited to this. If the display color of the pixel corresponds to the hue of the dispersed light from the surface light source device, The order of RGB pixels may be changed. In the first to fifth embodiments, a light source that emits light of three colors of RGB is used, but the type of hue and the number of hues are not limited thereto. For example, other hues such as cyan, magenta, and yellow may be added to RGB, and light of four or more hues may be used. Furthermore, in Embodiments 1 to 5, one of the three RGB light sources is located at the focal point of the paraboloid, but the light source of any hue may be deviated from the focal point of the paraboloid. In the first to fifth embodiments, a lens array is used as a condensing element, but a hologram diffraction grating may be used as a condensing element.

  The surface light source device of the present invention can be used as a backlight of a liquid crystal display device. In addition, the liquid crystal display device of the present invention can be used for various electric devices. For example, it can be used for mobile phones, PDAs (Personal Digital Assistance), personal computers, flat-screen TVs, medical displays, car navigation systems, amusement devices, and the like.

1 is a perspective view schematically showing a liquid crystal display device of Embodiment 1. FIG. It is a perspective view which shows typically the surface light source device BL of Embodiment 1. FIG. It is a top view of one 1st light guide 1a. FIG. 4A is a diagram showing the XY coordinate system of the first light guide 1a, and FIG. 4B is a graph showing the relationship between the arrangement of the LEDs 3 and the emission angle θ of the emitted light in this coordinate system. . It is typical sectional drawing which cut | disconnected the surface light source device BL of Embodiment 1 in the light guide direction. 4 is a graph showing spectral characteristics of colored light by the surface light source device BL of Embodiment 1. 2 is a cross-sectional view schematically showing a cross section of a liquid crystal display element 10. FIG. 4 is a plan view showing the arrangement of lenticular lenses 17. FIG. 5 is a schematic cross-sectional view for explaining the operation of the lenticular lens 17. FIG. 6 is a plan view showing the arrangement of microlenses 18 according to Embodiment 2. FIG. 4 is a cross-sectional view schematically showing a cross section of a liquid crystal display element 10 of Embodiment 3. FIG. It is a perspective view which shows typically the surface light source device BL of Embodiment 4. FIG. FIG. 10 is a perspective view schematically showing a cross section of a liquid crystal display device of Embodiment 5.

1a, 1b 1st light guide 2a Light reflection part 2c Light emission part 2d Light incident part 3a Red LED
3b Green LED
3c Blue LED
4 Second light guide 4a Light incident part 4b Light emitting part 4c Light reflecting part 5 Prism 6a Colored light (red)
6b Color light (green)
6c Color light (blue)
DESCRIPTION OF SYMBOLS 10 Liquid crystal display element 11 2nd transparent substrate 12 1st transparent substrate 13 Color filter (red)
14 Color filter (green)
15 Color filter (blue)
16 Black matrix 17 Lenticular lens 18 Micro lens array 19a Transparent pixel electrode 19b Transparent entire surface electrode 20 Liquid crystal layer 21a Second polarizing plate 21b First polarizing plate 22 Diffusion layer 23 Prism sheet 24a Red fluorescent tube 24b Green fluorescent tube 24c Blue fluorescent tube 25 Light guide 26 Light reflection part (bottom part)
BL surface light source device

Claims (5)

A light source device comprising: a plurality of light sources; and a light guide that emits a plurality of colored lights respectively emitted from the plurality of light sources to an irradiated object,
The light guide body, have a reflective portion serving as the plurality of parabolic reflecting different predetermined direction for each color light as substantially parallel light color light,
The plurality of light sources include a first light source that emits first color light, a second light source that emits second color light different from the first color light, and a third color light that emits third color light different from the first color light and the second color light. Consisting of a light source,
The first light source is configured such that the center of the light emitting point coincides with the focal point of the paraboloid,
The second light source is provided so that the center of the light emitting point does not coincide with the focal point of the paraboloid and adjacent to the first light source,
The third light source is a light source device provided so that the center of the light emitting point does not coincide with the focal point of the paraboloid and adjacent to the first light source on the opposite side to the second light source.   2. The light source according to claim 1, wherein each of the plurality of light sources is a line light source, and the reflecting section has a parabola cut along a virtual plane having a normal line parallel to a longitudinal direction of the line light source. apparatus. Each of the plurality of light sources is a point light source, and the light guide includes a first light guide that emits the plurality of color lights as substantially parallel light, and the substantially parallel light emitted from the first light guide. The light source device according to claim 1, further comprising: a second light guide that emits to the irradiation object.
The first light guide has the reflection portion, and the second light guide has an angle formed by the substantially parallel light incident from the reflection portion and light emitted to the irradiated object for each color light. A light source device having a control unit for controlling the angle to a predetermined angle. The light source device according to any one of claims 1 to 3 , a liquid crystal display element having a plurality of pixels, and the light source device and the liquid crystal display element interposed between the light source device and the light source device. A liquid crystal display device comprising: a condensing element that condenses a plurality of color lights onto the pixels displaying a corresponding hue. At least one of the plurality of pixels has a reflection region that reflects external light and a transmission region that transmits light from the light source device, and the light collecting element collects the color light in the transmission region. The liquid crystal display device according to claim 4 , wherein the liquid crystal device is made to emit light.

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