JP2008140653A - Surface light source device and liquid crystal display device assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device having a structure in which a difference between luminance in a space located in the upper part of a light source and luminance in a space other than that is hardly generated. <P>SOLUTION: This surface light emitting device is equipped with a light guide block 100 and the light source and disposed in the lower part of a liquid crystal display device to illuminate the liquid crystal display device. The light guide block 100 has a light emitting surface 110 facing the liquid crystal display device, a projecting part 111, a recessed part 112, and a side 113 to connect the projecting part with the recessed part are formed on the light emitting surface 110 of the light guide block, a light reflecting layer 120 is formed on the projecting part 111 and the recessed part 112, and light from the light source is emitted to the outside from the side 113 formed on the light emitting surface of the light guide block. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a planar light source device and a liquid crystal display device assembly.

  In the liquid crystal display device, the liquid crystal material itself does not emit light. Therefore, for example, a direct-type planar light source device (backlight) that irradiates the display area of the liquid crystal display device is disposed on the back surface of the display area composed of a plurality of pixels (for example, Document 1: Nikkei Electronics 2004). December 20th 889, pages 123-130). In the color liquid crystal display device, one pixel is composed of, for example, three types of subpixels: a red light emitting subpixel, a green light emitting subpixel, and a blue light emitting subpixel. Then, by operating the liquid crystal cell constituting each pixel or each sub-pixel as a kind of light shutter (light valve), that is, controlling the light transmittance (aperture ratio) of each pixel or each sub-pixel, An image is displayed by controlling the light transmittance of illumination light (for example, white light) emitted from the planar light source device.

  A planar light source device (backlight) usually includes a housing, and includes a plurality of light sources arranged in the housing and a light diffusing plate attached to an upper portion of the housing. For example, a light emitting diode (LED) is used as the light source. The light diffusing plate is usually made of plastic and varies depending on the size of the liquid crystal display device, but the plate thickness is about 2 mm. When the light source in the planar light source device is composed of a red light emitting diode, a green light emitting diode, and a blue light emitting diode, the red light, green light, and blue light emitted from these light emitting diodes are sufficiently mixed. However, it is necessary to use white light.

  Conventionally, a planar light source device in a liquid crystal display device assembly illuminates the entire display area with uniform and constant brightness. However, the planar light source device has a configuration different from such a planar light source device, that is, a plurality of planar light source devices. A planar light source device (partial drive type or split drive type planar light source device) having a configuration that changes the distribution of illuminance in a plurality of display area units is disclosed in, for example, 258403 is known. By controlling the surface light source device, the white level in the liquid crystal display device can be increased and the contrast ratio can be increased due to the decrease in the black level. As a result, the image display quality can be improved. The power consumption of the planar light source device can be reduced.

  A part of the light emitted from the light source of a certain planar light source unit enters another planar light source unit. Therefore, as described above, when the light source luminance of each planar light source unit constituting the planar light source device is controlled, the light source luminance of one planar light source unit is larger than the light source luminance of the other planar light source units. Influence. Therefore, in order to minimize the influence of each planar light source unit on other planar light source units, a partition may be provided between the planar light source unit and the planar light source unit.

JP-A-2005-258403 JP 2001-6416 JP 2001-36151 A Nikkei Electronics December 20th, 2004 No. 889, pages 123-130

  By the way, when a partition is provided between the planar light source unit and the planar light source unit, a luminance difference is generated between the light diffusion plate located above the light source and the light diffusion plate located above the partition. easy. When such a phenomenon occurs, the uniformity of luminance also decreases in the display image of the liquid crystal display device assembly, and the quality of the display image is impaired. Further, when the light source in the planar light source device is composed of three types of light emitting diodes as described above, in order to obtain white light from the red light, green light, and blue light emitted from these light emitting diodes, A space for color mixing having a certain volume is required, and it may be difficult to achieve a reduction in size and thickness of the planar light source device, and luminance loss in the space for color mixing also becomes a problem. .

  For example, Japanese Patent Application Laid-Open Nos. 2001-6416 and 2001-36151 are well-known technologies for forming uneven portions on a light guide plate in order to reduce luminance unevenness in a backlight structure having a light guide plate and a surface light emitting device. . However, even if the concavo-convex portion is simply formed on the surface of the light guide plate, a luminance difference is generated between the space located above the light source and the space located around the space. However, the technology for reducing the luminance difference is not mentioned in these patent publications.

  Accordingly, an object of the present invention is to incorporate a planar light source device having a structure in which a difference between the luminance in the space above the light source and the luminance in other spaces is unlikely to occur, and such a planar light source device. Another object is to provide a liquid crystal display device assembly.

A planar light source device of the present invention for achieving the above object is a planar light source device that includes a light guide block and a light source, is disposed below the liquid crystal display device, and illuminates the liquid crystal display device.
The light guide block has a light emitting surface facing the liquid crystal display device,
The light exit surface of the light guide block is formed with a convex portion, a concave portion, and a side surface connecting the convex portion and the concave portion,
A light reflecting layer is formed on the convex and concave portions,
The light from the light source is emitted to the outside from the side surface formed on the light emission surface of the light guide block.

In order to achieve the above object, the liquid crystal display device assembly of the present invention comprises:
(A) a liquid crystal display device, and
(B) a planar light source device that includes a light guide block and a light source, is disposed below the liquid crystal display device, and illuminates the liquid crystal display device;
A liquid crystal display assembly comprising:
The light guide block has a light emitting surface facing the liquid crystal display device,
The light exit surface of the light guide block is formed with a convex portion, a concave portion, and a side surface connecting the convex portion and the concave portion,
A light reflecting layer is formed on the convex and concave portions,
The light from the light source is emitted to the outside from the side surface formed on the light emission surface of the light guide block.

  In the planar light source device or liquid crystal display device assembly of the present invention (hereinafter, these may be collectively referred to simply as the present invention), the convex portion and the concave portion are formed in a straight line, that is, It can be configured to be formed in a stripe shape. Alternatively, in the present invention, the convex part and the concave part may be arranged concentrically around the normal passing through the central part of the light source. Or in this invention, it can be set as the structure by which the column shape is formed by the convex part and the side surface. Furthermore, the column shape can be a columnar shape or can be a prismatic shape. Note that the cross-sectional shape when the cylindrical shape is cut on a virtual plane perpendicular to the axis includes not only a circular shape but also a shape constituted by an arbitrary smooth closed curve including an oval shape, an elliptical shape, and the like. In addition, the cross-sectional shape when the prismatic shape is cut on a virtual plane perpendicular to the axis is not only an arbitrary quadrilateral including a square, a rectangle, a trapezoid, and a parallelogram, but also a shape composed of a triangle and an arbitrary polygon. Include. For example, the convex portions may be arranged on a straight line, may be arranged on concentric circles, may be arranged on lattice points, or may be arranged on the vertices of a regular triangle or a regular hexagon. May be. The columnar axis may be parallel to the normal passing through the center of the light source, may be tilted, or may be tilted according to the positional relationship with the light source, for example.

  The convex portion and the concave portion on the light emitting surface of the light guide block are configured by “surfaces”, and may be flat or not flat. That is, in the latter case, it may be curved, may be composed of a part of a smooth curved surface, or may be composed of a combination of planes. The side surface of the light exit surface of the light guide block may also be flat or not flat. That is, in the latter case, it may be curved, may be composed of a part of a smooth curved surface, or may be composed of a combination of planes. The side surface may be perpendicular to the convex portion or the concave portion, may be inclined, or may be inclined according to the positional relationship with the light source, for example. It is preferable that the convex portion, the concave portion, and the side surface connecting the convex portion and the concave portion are formed continuously.

  In the present invention, a light reflecting layer is formed on the convex and concave portions on the light exit surface of the light guide block. The light reflecting layer is not only a layer that completely reflects light, but also to some extent. A layer that transmits light (for example, a layer having a light transmittance of 15% or less) is included. That is, the light reflection layer may be provided with a specular reflection function or a light diffuse reflection function. In order to give a specular reflection function to the light reflection layer, a light reflection film or a silver-enhanced reflection sheet is attached to the convex part and the concave part, for example, physical vapor deposition such as plating, vacuum deposition or sputtering. A thin film made of a metal or alloy that reflects light may be formed based on a method (PVD method), a chemical vapor deposition method (CVD method), or the like. On the other hand, in order to give the light reflecting layer a light diffusing reflection function, a film having unevenness (light diffusing reflection film) is applied to the convex part and the concave part, or a white paint in which a light diffusing agent is dispersed is applied. do it. Furthermore, the light reflecting layer can be composed of a combination thereof.

  On the other hand, the material constituting the light guide block may be exposed without forming anything on the side surface of the light exit surface of the light guide block, or a light diffusing and transmitting function may be imparted to the side surface. In order to impart a light diffusing and transmitting function to the side surface, it is possible to form irregularities on the convex and concave portions based on the sandblasting method, to attach a film having irregularities (light diffusing and transmitting film), or from fine particles in the transparent binder resin. A light diffusion / transmission layer in which the light diffusing agent is dispersed may be formed by a coating method.

  The light diffusing agent is a particle having a property of diffusing light from a light source, and is composed of inorganic material particles or organic material particles. Specific examples of the inorganic material constituting the inorganic material particles include silica, aluminum hydroxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, magnesium silicate, and a mixture thereof. On the other hand, as resins constituting organic material particles, acrylic resins, acrylonitrile resins, polyurethane resins, polyvinyl chloride resins, polystyrene resins, polyacrylonitrile resins, polyamide resins, polysiloxane resins, melamine resins Can be illustrated. Examples of the shape of the light diffusing agent include a spherical shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a plate shape, a scale shape, and a fiber shape.

  In the present invention, the light guide block is preferably made of a material that is transparent to light from the light source, that is, a material that does not absorb much light emitted from the light source. Specifically, polymethyl methacrylate resin (PMMA), polycarbonate resin (PC), polyarylate resin (PAR), polyethylene terephthalate resin (PET), acrylic resin, AS resin are used as materials constituting the light guide block. Examples thereof include styrene-based resins, amorphous polypropylene-based resins, and glass. Depending on the material to be constructed, the light guide block is an appropriate molding method (for example, various molding methods based on plastic materials, plate-shaped or sheet-shaped, film-shaped materials such as dicing method or laser). A method of forming a convex part, a concave part, and a side surface by making a cut may be used.

  The light guide block may be composed of a single material, but it is preferable to divide the light guide block to be composed of a plurality of light guide block units and to arrange the light guide block units. In the latter case, a partition wall described later can be provided between the light guide block unit and the light guide block unit, and / or the light guide block units are arranged without gaps, or The light reflection film may be formed on the side wall of the light guide block unit. For example, the light reflecting film can have the same configuration as the light reflecting layer described above. As a result, as described below, when the light source luminance of each planar light source unit constituting the planar light source device is controlled, for example, light emitted from the light source enters (invades) the adjacent light guide block unit. Therefore, the influence of the light source luminance of a certain planar light source unit on the light source luminance of other planar light source units can be eliminated, and the use efficiency of light emitted from the light source can be prevented from being lowered. A light reflecting film may be provided on the bottom surface of the light guide block or the light guide block unit.

  In the present invention including the preferred configurations and forms described above, a plurality of light sources may be driven simultaneously under the same driving conditions. Alternatively, a plurality of light sources may be partially driven. That is, when the planar light source device is assumed to divide the display area of the liquid crystal display device into P × Q virtual display area units, P × Q pieces corresponding to these P × Q display area units are used. The light emission states of the P × Q planar light source units may be a partial drive method or a divided drive method in which the light emission states are individually controlled. In this case, each planar light source unit is provided with a light guide block unit.

  The light source may be disposed in a space formed on the bottom surface of the light guide block. Various shapes such as a pyramid, a cone, a cylinder, a polygonal column including a triangular column and a quadrangular column, a part of a sphere, a part of a spheroid, a part of a rotating parabola, a part of a rotating hyperbola, etc. Can be illustrated. Alternatively, a space (gap) may exist between the light source and the light guide block. That is, the light guide block may be disposed above the light source.

  The light source can be composed of, for example, a light emitting diode (LED), but is not limited to this, and is not limited to this. A cold cathode fluorescent lamp, an electroluminescence (EL) device, a cold cathode field emission device (FED) A plasma display device can also be mentioned. When the light source is composed of a light emitting diode, for example, a red light emitting diode that emits red with a wavelength of 640 nm, for example, a green light emitting diode that emits green with a wavelength of 530 nm, and a blue light emitting diode that emits blue with a wavelength of 450 nm, for example, Thus, white light can be obtained, and white light can also be obtained by light emission of a white light-emitting diode (for example, a light-emitting diode that emits white light by combining ultraviolet or blue light-emitting diodes and phosphor particles). Depending on the case, a light emitting diode that emits a fourth color other than red, green, blue, fifth color,... May be further provided.

  When the light source is composed of a light emitting diode, for example, as a combination of a red light emitting diode that emits red, a green light emitting diode that emits green, and a blue light emitting diode that emits blue, specifically, (one red light emitting diode) Diode, one green light emitting diode, one blue light emitting diode), (one red light emitting diode, two green light emitting diodes, one blue light emitting diode), (two red light emitting diodes, two green light emitting diodes, one Blue light-emitting diodes) and the like, but are not limited thereto.

  When the light source is formed of a light emitting diode, the light emitting diode may have a so-called face-up structure or a flip chip structure. That is, the light-emitting diode includes a substrate and a light-emitting layer formed on the substrate, and may have a structure in which light is emitted from the light-emitting layer to the outside, or light from the light-emitting layer passes through the substrate. It is good also as a structure radiate | emitted outside. More specifically, the light emitting diode (LED) includes, for example, a first compound semiconductor layer having a first conductivity type (for example, n-type) formed on a substrate, and an active layer formed on the first compound semiconductor layer. A first electrode having a stacked structure of a second compound semiconductor layer having a second conductivity type (for example, p-type) formed on the active layer and electrically connected to the first compound semiconductor layer; A second electrode electrically connected to the two-compound semiconductor layer is provided. The layer constituting the light emitting diode may be made of a known compound semiconductor material depending on the emission wavelength. In order to increase the light extraction efficiency from the light emitting diode, it is desirable to attach a hemispherical resin material having a certain size to the light emitting portion of the light emitting diode. If there is an intention to emit light in a specific direction, for example, a two-dimensional direction emission configuration in which light is mainly emitted in the horizontal direction may be provided.

  The planar light source device may include a light diffusing plate, and may further include an optical function sheet group such as a diffusing sheet, a prism sheet, and a polarization conversion sheet, and a reflecting sheet. The optical function sheet group may be configured from various sheets that are spaced apart from each other, or may be stacked and integrated. The light diffusing plate and the optical function sheet group are disposed between the planar light source device and the liquid crystal display device. Examples of the material constituting the light diffusion plate include polycarbonate resin (PC), polystyrene resin (PS), and methacrylic resin. There may be a gap between the light diffusion plate and the light guide block, or the light diffusion plate and the light guide block may be in close contact with each other.

  A partition may be provided between the light guide block unit and the light guide block unit (that is, between the planar light source unit and the planar light source unit). Specific examples of the material constituting the partition include polymethyl methacrylate resin (PMMA), polycarbonate resin (PC), polyarylate resin (PAR), polyethylene terephthalate resin (PET), acrylic resin, ABS resin, and glass. It can be mentioned, It can be set as a transparent structure or an opaque structure with respect to the light radiate | emitted from the light source with which the planar light source unit was equipped. A light diffusion reflection function may be imparted to the partition wall surface, or a specular reflection function may be imparted. In order to impart a light diffusing and reflecting function to the partition wall surface, irregularities may be formed on the partition wall surface based on a sandblasting method, or a film (light diffusion film) having irregularities may be attached to the partition wall surface. In addition, in order to give a specular reflection function to the partition wall surface, a light reflection film may be attached to the partition wall surface, or a light reflection film may be formed on the partition wall surface by, for example, plating.

  The transmissive liquid crystal display device includes, for example, a front panel having a transparent first electrode, a rear panel having a transparent second electrode, and a liquid crystal material disposed between the front panel and the rear panel. Consists of. The liquid crystal display device may be a monochrome liquid crystal display device or a color liquid crystal display device.

  More specifically, the front panel includes, for example, a first substrate made of, for example, a glass substrate or a silicon substrate, and a transparent first electrode (also called a common electrode, for example, ITO provided on the inner surface of the first substrate. And a polarizing film provided on the outer surface of the first substrate. Further, in the transmissive color liquid crystal display device, a color filter covered with an overcoat layer made of acrylic resin or epoxy resin is provided on the inner surface of the first substrate. Examples of the color filter arrangement pattern include a delta arrangement, a stripe arrangement, a diagonal arrangement, and a rectangle arrangement. The front panel further has a configuration in which a transparent first electrode is formed on the overcoat layer. An alignment film is formed on the transparent first electrode. On the other hand, the rear panel more specifically includes, for example, a second substrate made of a glass substrate or a silicon substrate, a switching element formed on the inner surface of the second substrate, and conduction / non-conduction by the switching element. A transparent second electrode to be controlled (also called a pixel electrode, which is made of, for example, ITO) and a polarizing film provided on the outer surface of the second substrate. An alignment film is formed on the entire surface including the transparent second electrode. Various members and liquid crystal materials constituting the liquid crystal display device including these transmissive color liquid crystal display devices can be formed of known members and materials. Examples of the switching element include a three-terminal element such as a MOS type FET and a thin film transistor (TFT) formed on a single crystal silicon semiconductor substrate, and a two-terminal element such as an MIM element, a varistor element, and a diode.

  An area where the transparent first electrode and the transparent second electrode overlap and includes a liquid crystal cell corresponds to one pixel (pixel) or one sub-pixel (sub-pixel). In the transmissive color liquid crystal display device, the red light emitting sub-pixel (which may be referred to as sub-pixel [R]) constituting each pixel (pixel) transmits red light with the liquid crystal cell constituting the region. The green light emitting subpixel (sometimes referred to as subpixel [G]) is composed of a combination of a liquid crystal cell constituting the region and a color filter that transmits green light. The blue light-emitting subpixel (sometimes referred to as subpixel [B]) is composed of a combination of a liquid crystal cell that forms the region and a color filter that transmits blue light. The arrangement pattern of the sub-pixel [R], sub-pixel [G], and sub-pixel [B] matches the arrangement pattern of the color filter described above. The pixel is not limited to a configuration in which three types of sub-pixels [R, G, B], which are a sub-pixel [R], a sub-pixel [G], and a sub-pixel [B], are configured as one set. For example, a set of these three types of sub-pixels [R, G, B] plus one or more types of sub-pixels (for example, one sub-pixel that emits white light to improve brightness) To expand the color reproduction range, one set including sub-pixels that emit complementary colors to expand the color reproduction range, one set including sub-pixels that emit yellow to expand the color reproduction range It can also be composed of a set of subpixels that emit yellow and cyan.

  Here, when the partial drive method or the divided drive method is adopted, the light transmittance (also referred to as aperture ratio) Lt of the pixel or subpixel, the luminance (display luminance) y of the portion of the display area corresponding to the pixel or subpixel, And the brightness | luminance (light source luminance) Y of a planar light source unit is defined as follows.

Y ₁ ... Is the maximum luminance of the light source luminance, for example, and may be hereinafter referred to as the light source luminance and the first specified value.
Lt ₁ ... Is the maximum value of the light transmittance (aperture ratio) of the pixels or sub-pixels in the display area unit, for example, and may be hereinafter referred to as light transmittance / first specified value.
Lt ₂ ... In the display area unit / input signal maximum value x _U-max that is the maximum value of the values of the input signals input to the drive circuit for driving all the pixels constituting the display area unit. This is the light transmittance (aperture ratio) of the pixel or sub-pixel when it is assumed that a control signal corresponding to an input signal having the same value is supplied to the pixel or sub-pixel. Sometimes called. In addition, 0 ≦ Lt ₂ ≦ Lt ₁
y ₂ ... When the light source luminance is the light source luminance and the first specified value Y ₁ and the light transmittance (aperture ratio) of the pixel or sub-pixel is assumed to be the light transmittance and the second specified value Lt ₂ The display brightness obtained in the following is sometimes referred to as “display brightness / second prescribed value”.
Y ₂ ... ・ In the display area unit ・ Assuming that a control signal corresponding to an input signal having a value equal to the input signal maximum value x _U-max is supplied to the pixel or sub-pixel, Assuming that the light transmittance (aperture ratio) of the sub-pixel is corrected to the light transmittance / first prescribed value Lt ₁ , the luminance of the pixel or the sub-pixel is set to the display luminance / second prescribed value (y ₂ ). The light source brightness of the planar light source unit. However, the light source luminance Y ₂ may be corrected in consideration of the influence of the light source luminance of each planar light source unit on the light source luminance of other planar light source units.

When the planar light source device is partially driven, it is assumed that a control signal corresponding to an input signal having a value equal to the input signal maximum value x _U-max in the display area unit is supplied to the pixel. The luminance of the light source constituting the planar light source unit corresponding to the display area unit is controlled by the drive circuit so that the ratio, the display luminance at the first specified value Lt _1, and the second specified value y ₂ ) are obtained. Specifically, for example, the light source luminance Y ₂ is set so that the display luminance y ₂ can be obtained when the light transmittance (aperture ratio) of the pixel or sub-pixel is, for example, the light transmittance · the first specified value Lt _1. What is necessary is just to control (for example, to reduce). That is, for example, the light source luminance Y ₂ of the planar light source unit may be controlled for each image display frame so as to satisfy the following expression (1). Note that Y ₂ ≦ Y ₁ .

Y ₂ · Lt ₁ = Y ₁ · Lt ₂ (1)

When expressed in pixels arranged in a two-dimensional matrix the number M ₀ × N ₀ of _{(pixels) (M 0, N 0)} , the value of (M _0, N _0), specifically, VGA ( 640,480), S-VGA (800,600), XGA (1024,768), APRC (1152,900), S-XGA (1280,1024), U-XGA (1600,1200), HD-TV ( 1920, 1080), Q-XGA (2048, 1536), (1920, 1035), (720, 480), (1280, 960), etc. It is not limited to these values. Further, the relationship between the value of (M ₀ , N ₀ ) and the value of (P, Q) is not limited, but can be exemplified in Table 1 below. Examples of the number of pixels constituting one display area unit include 20 × 20 to 320 × 240, preferably 50 × 50 to 200 × 200. The number of pixels in the display area unit may be constant or different.

  When the partial drive method or the divided drive method is adopted, the drive circuit for driving the liquid crystal display device and the planar light source device includes, for example, a light emitting diode (LED) drive circuit, an arithmetic circuit, a storage device (memory), and the like. The planar light source device control circuit, the planar light source unit drive circuit, and a liquid crystal display device drive circuit including a known circuit such as a timing controller are provided. The luminance of the display area (display luminance) and the luminance of the planar light source unit (light source luminance) are controlled for each image display frame. Note that the number of image information (images per second) sent to the drive circuit as electrical signals per second is the frame frequency (frame rate), and the inverse of the frame frequency is the frame time (unit: seconds).

  In the present invention, the light reflecting layer is formed on the convex portion and the concave portion on the light exit surface of the light guide block, and the light from the light source is externally transmitted from the side surface formed on the light exit surface of the light guide block. Is emitted. Therefore, the light emitted from the light source and directly colliding with the convex portion or concave portion of the light emitting surface of the light guide block is reflected by the convex portion or concave portion of the light emitting surface, so that this light is directly guided. It is not emitted from the light exit surface of the block. On the other hand, the light emitted to the outside from the side surface formed on the light output surface of the light guide block corresponds to a large incident angle with respect to the convex portion or the concave portion of the light output surface of the light guide block, and Since the incident angle is small with respect to the side surface of the light exit surface, the light exits from the side surface of the light exit surface of the light guide block without being totally reflected at the side surface of the light exit surface of the light guide block. Therefore, the difference in luminance between the space located above the light source and the space located around the space is reduced. That is, luminance unevenness can be reduced. As a result, it is possible to reliably prevent the occurrence of a problem that the uniformity of luminance is improved in the display image of the liquid crystal display device assembly and the quality of the display image is impaired.

  In addition, the light emitted from the light source is emitted from the side surface of the light exit surface of the light guide block, but is reflected by, for example, the light reflection layer provided on the convex portion and the concave portion on the light exit surface of the light guide block. In addition to propagating through the light guide block, the light is not only emitted from the side surface of the light output surface of the light guide block, but also reflected by the light reflecting film provided on the side surface of the light guide block. It can propagate and be emitted from the side surface of the light exit surface of the light guide block. Therefore, luminance loss in the space for color mixing can be reduced as much as possible, and miniaturization and thinning can be achieved.

Furthermore, if a partial drive method (divided drive method) is adopted for the planar light source device, a control signal corresponding to an input signal having a value equal to the input signal maximum value x _U-max in the display area unit is supplied to the pixels. The planar light source unit corresponding to the display area unit is configured so that the pixel brightness (light transmittance, display brightness at the first specified value Lt ₁ , second specified value y ₂ ) when it is assumed Since the brightness of the light source is controlled by the drive circuit, not only can the power consumption of the planar light source device be reduced, but also the white level can be increased or the black level can be decreased, and a high contrast ratio (the screen surface of the liquid crystal display device) The luminance ratio of the all-black display portion and the all-white display portion without external light reflection, etc., and the brightness of the desired display area can be emphasized. To improve Can.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings. Prior to this, a transmissive liquid crystal display device suitable for use in the embodiments (specifically, a transmissive color liquid crystal display device) will be described. An outline of the planar light source device will be described with reference to FIGS. 9, 10, 11 (A) and 11 (B), and FIG. 12.

The liquid crystal display device assembly of the example is
(A) a liquid crystal display device, and
(B) a planar light source device that includes a light guide block and a light source, is disposed below the liquid crystal display device, and illuminates the liquid crystal display device;
It has.

More specifically, the liquid crystal display device assembly of the embodiment is:
(A) a transmissive color liquid crystal display device 10 having a display area 11 composed of pixels arranged in a two-dimensional matrix, and
(B) The number of display areas 11 of the color liquid crystal display device 10 is P in the first direction and Q in the second direction extending at right angles to the first direction, for a total of P × Q virtual display areas. The color liquid crystal display device 10 corresponds to the P × Q display area units 12 when assumed to be divided into units 12, each of which includes P × Q planar light source units 42 each having a light source 44. A planar light source device 40 for illuminating the light source from the back side,
It has.

  The planar light source device of the embodiment is a planar light source device that includes a light guide block and a light source, is disposed below the liquid crystal display device, and illuminates the liquid crystal display device. More specifically, the planar light source device 40 of the embodiment illuminates a transmissive color liquid crystal display device 10 having a display area 11 composed of pixels arranged in a two-dimensional matrix from the back side. Corresponding to these P × Q display area units 12 when assuming that the display area 11 of the color liquid crystal display device 10 is divided into P × Q virtual display area units 12, respectively. Comprises P × Q planar light source units 42 having light sources 44.

  In the planar light source device 40 or the liquid crystal display device assembly of the embodiment, the light emission state of the light source provided in the planar light source unit 42 is individually controlled. That is, a partial drive method or a split drive method is adopted.

Specifically, as shown in a conceptual diagram in FIG. 9, the transmissive color liquid crystal display device 10 in the embodiment has M ₀ pieces along the first direction and N ₀ pieces along the second direction. The display area 11 includes a total of M ₀ × N ₀ pixels arranged in a two-dimensional matrix. Here, it is assumed that the display area 11 is divided into P × Q virtual display area units 12. Each display area unit 12 is composed of a plurality of pixels. Specifically, for example, the image display resolution satisfies the HD-TV standard, and the number M ₀ × N ₀ of pixels (pixels) arranged in a two-dimensional matrix is expressed as (M ₀ , N ₀ ). For example, (1920, 1080). Further, a display area 11 (indicated by a one-dot chain line in FIG. 9) composed of pixels arranged in a two-dimensional matrix is divided into P × Q virtual display area units 12 (indicated by a dotted line). ing. The value of (P, Q) is (19, 12), for example. However, in order to simplify the drawing, the number of the display area units 12 (and the planar light source units 42) in FIG. 9 is different from this value. Each display area unit 12 is composed of a plurality of (M × N) pixels, and the number of pixels constituting one display area unit 12 is, for example, about 10,000. Each pixel is configured as a set of a plurality of sub-pixels that emit different colors. More specifically, each pixel has three types of red light emitting subpixel (subpixel [R]), green light emitting subpixel (subpixel [G]), and blue light emitting subpixel (subpixel [B]). Of sub-pixels (sub-pixels). The transmissive color liquid crystal display device 10 is line-sequentially driven. More specifically, the color liquid crystal display device 10 includes scan electrodes (extending along the first direction) and data electrodes (extending along the second direction) that intersect in a matrix. Then, a scanning signal is input to the scanning electrode to select and scan the scanning electrode, and an image is displayed based on the data signal (a signal based on the control signal) input to the data electrode to constitute one screen.

  The color liquid crystal display device 10 includes a front panel 20 provided with a transparent first electrode 24, a rear panel 30 provided with a transparent second electrode 34, and a schematic partial sectional view shown in FIG. The liquid crystal material 13 is disposed between the front panel 20 and the rear panel 30.

  The front panel 20 includes, for example, a first substrate 21 made of a glass substrate and a polarizing film 26 provided on the outer surface of the first substrate 21. A color filter 22 covered with an overcoat layer 23 made of acrylic resin or epoxy resin is provided on the inner surface of the first substrate 21, and a transparent first electrode (also called a common electrode) is provided on the overcoat layer 23. (For example, made of ITO) 24 is formed, and an alignment film 25 is formed on the transparent first electrode 24. On the other hand, the rear panel 30 more specifically includes, for example, a second substrate 31 made of a glass substrate, and switching elements (specifically, thin film transistors and TFTs) formed on the inner surface of the second substrate 31. 32, a transparent second electrode (also referred to as a pixel electrode, made of, for example, ITO) 34 whose conduction / non-conduction is controlled by the switching element 32, and a polarizing film 36 provided on the outer surface of the second substrate 31, It is composed of An alignment film 35 is formed on the entire surface including the transparent second electrode 34. The front panel 20 and the rear panel 30 are joined via a sealing material (not shown) at their outer peripheral portions. Note that the switching element 32 is not limited to a TFT, and may be composed of, for example, an MIM element. Reference numeral 37 in the drawing is an insulating layer provided between the switching element 32 and the switching element 32.

  Since various members and liquid crystal materials constituting these transmissive color liquid crystal display devices can be composed of well-known members and materials, detailed description thereof is omitted.

  The direct-type planar light source device (backlight) 40 includes P × Q planar light source units 42 corresponding to the P × Q virtual display area units 12. The display area unit 12 corresponding to the light source unit 42 is illuminated with white light from the back. The light sources 44 provided in the planar light source unit 42 are individually controlled. The light source 44 has a dot shape when viewed as a whole. The light source luminance of the planar light source unit 42 is not affected by the light emission state of the light sources 44 provided in the other planar light source units 42. Although the planar light source device 40 is positioned below the color liquid crystal display device 10, the color liquid crystal display device 10 and the planar light source device 40 are separately displayed in FIG. The arrangement and arrangement of light emitting diodes and the like in the planar light source device 40 are schematically shown in FIG. 11A, and a schematic liquid crystal display device assembly including the color liquid crystal display device 10 and the planar light source device 40 is shown. A partial cross-sectional view is shown in FIG. The light source 44 includes a light emitting diode 43 that is driven based on a pulse width modulation (PWM) control method. The luminance of the planar light source unit 42 is increased / decreased by duty ratio increasing / decreasing control in the pulse width modulation control of the light emitting diodes 43 constituting the planar light source unit 42.

  As shown in a schematic partial sectional view of the liquid crystal display device assembly in FIG. 11B, the planar light source device 40 includes a casing 51 having an outer frame 53 and an inner frame 54. Yes. The end of the transmissive color liquid crystal display device 10 is held by the outer frame 53 and the inner frame 54 so as to be sandwiched between the spacers 55A and 55B. A guide member 56 is disposed between the outer frame 53 and the inner frame 54 so that the color liquid crystal display device 10 sandwiched between the outer frame 53 and the inner frame 54 does not shift. A light diffusion plate 61 is attached to the inner frame 54 via a spacer 55 </ b> C and a bracket member 57 in the upper portion of the housing 51. On the light diffusion plate 61, an optical function sheet group such as a diffusion sheet 62, a prism sheet 63, and a polarization conversion sheet 64 is laminated. A reflection sheet 65 is provided inside and below the housing 51. Here, the reflection sheet 65 is disposed so that the reflection surface thereof faces the light diffusion plate 61, and is attached to the bottom surface 52 </ b> A of the housing 51 via an attachment member (not shown). The reflection sheet 65 can be composed of, for example, a silver-enhanced reflection film having a structure in which a silver reflection film, a low refractive index film, and a high refractive index film are sequentially laminated on a sheet base material. The reflection sheet 65 reflects light emitted from the plurality of light emitting diodes 43 and light reflected by the side surface 52 </ b> B of the housing 51. Thus, for example, a red light emitting diode 43R that emits red with a wavelength of 640 nm, a green light emitting diode 43G that emits green with a wavelength of 530 nm, for example, and a blue light emitting diode 43B that emits blue with a wavelength of 450 nm, for example. Red light, green light, and blue light emitted from the light are mixed, and white light with high color purity can be obtained as illumination light. The white illumination light is emitted from the planar light source unit 42 through the light diffusing plate 61, passes through the optical function sheet group such as the diffusing sheet 62, the prism sheet 63, and the polarization conversion sheet 64, and the color liquid crystal display device 10. Illuminate from the back. In FIG. 11A, the light emitting diodes 43R, 43G, and 43B are collectively shown as a light source 44.

  In the vicinity of the bottom surface 52A of the casing 51, photodiodes 45R, 45G, and 45B, which are optical sensors, are arranged. The photodiode 45R is a photodiode to which a red filter is attached to measure the light intensity of red light, and the photodiode 45G is a photo to which a green filter is attached to measure the light intensity of green light. The photodiode 45B is a photodiode to which a blue filter is attached in order to measure the light intensity of blue light. Here, one set of photosensors (photodiodes 45R, 45G, and 45B) is arranged in one planar light source unit. The luminance and chromaticity of the light emitting diodes 43R, 43G, and 43B are measured by the photodiodes 45R, 45G, and 45B that are optical sensors.

  As shown in FIGS. 9 and 10, the driving circuit for driving the planar light source device 40 and the color liquid crystal display device 10 based on the input signal from the outside (display circuit) is based on the pulse width modulation control method. Planar light source device control circuit 70 and planar light source unit driving circuit 80 for performing on / off control of the red light emitting diode 43R, the green light emitting diode 43G, and the blue light emitting diode 43B constituting the planar light source device 40, and a liquid crystal display The apparatus driving circuit 90 is configured.

  The planar light source device control circuit 70 includes an arithmetic circuit 71 and a storage device (memory) 72. On the other hand, the planar light source unit driving circuit 80 includes an arithmetic circuit 81, a storage device (memory) 82, an LED driving circuit 83, a photodiode control circuit 84, switching elements 85R, 85G, and 85B composed of FETs, and a light emitting diode driving power source (constant). Current source) 86. These circuits constituting the planar light source device control circuit 70 and the planar light source unit drive circuit 80 can be known circuits. On the other hand, a liquid crystal display device driving circuit 90 for driving the color liquid crystal display device 10 includes a known circuit such as a timing controller 91. The color liquid crystal display device 10 is provided with a gate driver, a source driver, and the like (not shown) for driving the switching element 32 formed of a TFT constituting the liquid crystal cell.

Further, resistors r _R , r _G , r _B for current detection are inserted in series with the light emitting diodes 43R, 43G, 43B downstream of the light emitting diodes 43R, 43G, 43B, and the resistors r _R , r The operation of the light-emitting diode drive power supply 86 is controlled under the control of the LED drive circuit 83 so that the currents flowing through _{G 1} and r _B are converted into voltages, and the voltage drops in the resistors r _R , r _G and r _B have predetermined values. Is controlled. Here, in FIG. 10, a single light emitting diode driving power source (constant current source) 86 is depicted, but actually, the light emitting diode driving power source for driving each of the light emitting diodes 43R, 43G, and 43B. 86 is arranged.

  The light emitting states of the light emitting diodes 43R, 43G, and 43B are measured by the photodiodes 45R, 45G, and 45B, and outputs from the photodiodes 45R, 45G, and 45B are input to the photodiode control circuit 84, and the photodiode control circuit 84 In the arithmetic circuit 81, for example, data (signals) as the luminance and chromaticity of the light emitting diodes 43R, 43G, and 43B are sent to the LED driving circuit 83, and the light emitting diodes 43R, 43G in the next image display frame are sent. , 43B is controlled so that the light emission state is controlled.

  A display area 11 composed of pixels arranged in a two-dimensional matrix is divided into P × Q display area units. When this state is expressed by “row” and “column”, Q rows × It can be said that the display area unit is divided into P columns. The display area unit 12 is composed of a plurality of (M × N) pixels. When this state is expressed by “row” and “column”, it is composed of pixels of N rows × M columns. I can say. Further, the red light emitting subpixel (subpixel [R]), the green light emitting subpixel (subpixel [G]), and the blue light emitting subpixel (subpixel [B]) are collectively collected as “subpixel [ R, G, B] ”and may be referred to as“ sub-pixel ”for controlling the operation of the sub-pixel [R, G, B] (specifically, for example, controlling the light transmittance (aperture ratio)). The red light emitting subpixel / control signal, the green light emitting subpixel / control signal, and the blue light emitting subpixel / control signal input to [R, G, B] are collectively referred to as “control signal [R, G, B] ”and may be referred to as a red light-emitting subpixel / input signal or a green light-emitting subpixel that is input to the drive circuit from the outside in order to drive the subpixels [R, G, B] constituting the display area unit. The input signal and the blue light emitting subpixel / input signal may be collectively referred to as “input signal [R, G, B]”.

As described above, each pixel includes a red light emitting subpixel (red light emitting subpixel, subpixel [R]), a green light emitting subpixel (green light emitting subpixel, subpixel [G]), and a blue light emitting subpixel ( The blue light emitting subpixel and the subpixel [B]) are configured as a set of three subpixels (subpixels). In the following description of the embodiments, it is assumed that the luminance control (gradation control) of each of the sub-pixels [R, G, B] is 8-bit control and is performed in 2 ⁸ steps from 0 to 255. Therefore, the value of the input signal [R, G, B] input to the liquid crystal display device driving circuit 90 to drive each of the sub-pixels [R, G, B] in each pixel constituting each display area unit 12. x _R, x _G, each x _B, takes a value of 2 ⁸ steps. Further, the pulse width modulation output signal values S _R , S _G , S for controlling the respective light emission times of the red light emitting diode 43R, the green light emitting diode 43G, and the blue light emitting diode 43B constituting each planar light source unit. _B also takes a value of 2 ⁸ steps of 0 to 255. However, the present invention is not limited to this. For example, 10-bit control can be performed in 2 ¹⁰ stages from 0 to 1023. In this case, if an 8-bit numerical expression is multiplied by, for example, 4 times Good.

A control signal for controlling the light transmittance Lt of each sub-pixel is supplied from the drive circuit to each sub-pixel. Specifically, a control signal [R, G, B] for controlling the light transmittance Lt of each of the sub-pixels [R, G, B] is transmitted to each of the sub-pixels [R, G, B]. Supplied from the drive circuit 90. That is, in the liquid crystal display device driving circuit 90, a control signal [R, G, B] is generated from the input signal [R, G, B] that is input, and the control signal [R, G, B] is subpixel. [R, G, B] are supplied (output). Since the light source luminance Y ₂ that is the luminance of the planar light source unit 42 is changed for each image display frame, the control signal [R, G, B] is, for example, the value of the input signal [R, G, B]. Values X _R-corr , X _G-corr , and X _B-corr obtained by performing correction (compensation) based on the change in the light source luminance Y _{2 with} respect to the values obtained by raising x _R , x _G , and x _B to the power of 2.2. Have. Then, the control signal [R, G, B] is sent from the timing controller 91 constituting the liquid crystal display device driving circuit 90 to the gate driver and the source driver of the color liquid crystal display device 10 by a known method. Based on [R, G, B], the switching element 32 constituting each subpixel is driven, and a desired voltage is applied to the transparent first electrode 24 and the transparent second electrode 34 constituting the liquid crystal cell. The light transmittance (aperture ratio) Lt of the sub-pixel is controlled. Here, the larger the values X _R-corr , X _G-corr , and X _B-corr of the control signal [R, G, B], the light transmittance (aperture ratio) Lt of the sub-pixel [R, G, B]. And the value of the luminance (display luminance y) of the display area corresponding to the sub-pixel [R, G, B] increases. That is, an image composed of light passing through the sub-pixels [R, G, B] (usually a kind of dot) is bright.

The display brightness y and the light source brightness Y ₂ are controlled for each image display frame, each display area unit, and each planar light source unit in the image display of the color liquid crystal display device 10. Further, the operation of the color liquid crystal display device 10 and the operation of the planar light source device 40 within one image display frame are synchronized. Note that the number of image information (images per second) sent to the drive circuit as electrical signals per second is the frame frequency (frame rate), and the inverse of the frame frequency is the frame time (unit: seconds).

  Example 1 relates to a planar light source device and a liquid crystal display device assembly. As shown in FIGS. 1A and 1B and FIG. 11B, in the planar light source device 40 or the liquid crystal display device assembly of the first embodiment, the light guide block 100 is a transmissive color liquid crystal. A light emitting surface 110 facing the display device 10 is provided. Here, the light emitting surface 110 of the light guide block 100 is formed with a convex portion 111, a concave portion 112, and a side surface 113 connecting the convex portion 111 and the concave portion 112, and on the convex portion 111 and the concave portion 112. A light reflection layer 120 is formed. The light from the light source 44 is emitted to the outside from the side surface 113 formed on the light emitting surface 110 of the light guide block 100. 1A is a schematic partial cross-sectional view of the light guide block 100, and FIG. 1B is a schematic partial plan view of the light guide block 100. 2 is a schematic plan view of an optical block unit 101. FIG. In addition, in FIG. 11B, although the detailed illustration of the light guide block 100 is omitted, the light guide block 100 is disposed in the space 100A.

  Here, in the first embodiment, the light guide block 100 includes a plurality of light guide block units 101, and the light guide block 100 is configured by arranging the light guide block units 101. The light guide block units 101 are arranged without gaps, and a light reflecting film 103 is formed on the side wall 102 of the light guide block unit 101. In FIG. 11B, a light gap block unit 101 is shown with a gap in order to clearly show it. The planar light source unit 42 is provided with one light guide block unit 101. Thereby, when the light source luminance of each planar light source unit 42 constituting the planar light source device 40 is controlled, for example, light emitted from the light source 44 does not enter (enter) the adjacent light guide block unit 101. The influence of the light source luminance of a certain planar light source unit 42 on the light source luminance of another planar light source unit 42 can be eliminated, and a decrease in the utilization efficiency of light emitted from the light source 44 can be prevented. A light reflecting film may be provided on the bottom surface of the light guide block unit 101. In the following description, the light guide block unit 101 may be used instead of the light guide block 100.

  In the first embodiment, the light guide block unit 101 is formed from, for example, an acrylic resin. In addition, a light reflecting layer 120 and a light reflecting film 103 made of a white paint layer in which a light diffusing agent is dispersed are formed on the convex portion 111 and the concave portion 112 and on the side wall 102 of the light guide block unit 101, for example. Yes. On the other hand, nothing is formed on the side surface 113 of the light exit surface 110 of the light guide block unit 101, and the material constituting the light guide block unit 101 is exposed. The plate-shaped light guide block unit 101 molded based on an appropriate molding method is notched based on the dicing method to form the convex portion 111, the concave portion 112, and the side surface 113, and then the entire surface (the convex portion 111, the concave portion). 112 and the side surface 113), the light guide block unit 101 was manufactured by forming a white paint layer based on the coating method and then scraping off the white paint layer formed on the side surface 113. Note that a cylindrical space 104 is provided at one location on the bottom surface of the light guide block unit 101. The light emitting diodes 43 </ b> R, 43 </ b> G, and 43 </ b> B constituting the light source 44 are disposed in a space 104 formed on the bottom surface of the light guide block unit 101. Three spaces may be formed on the bottom surface of the light guide block unit 101, and one light emitting diode may be stored in each space. Further, a plurality of spaces (for example, two places, four places, etc.) may be provided in the light guide block unit 101, and a plurality of light emitting diodes may be stored in each space. The light guide block unit 101 is fixed to the reflection sheet 65 by an appropriate method.

In Example 1, the convex part 111 and the recessed part 112 are formed in linear form. That is, the convex portion 111 and the concave portion 112 are formed in a stripe shape. When the height of the side surface 113 is H, the width of the convex portion 111 is L _H , and the width of the concave portion 112 is L _L ,
H / L _H = H / L _L = L _H / L _L = 1
It is. Specifically, the value of H, the value of L _H , and the value of L _L are all 1.0 mm.

  The convex portion 111 and the concave portion 112 on the light emitting surface 110 of the light guide block unit 101 are constituted by “surfaces”, and are flat in the first embodiment. Further, the side surface 113 of the light exit surface 110 of the light guide block unit 101 is also flat. Further, the side surface 113 is perpendicular to the convex portion 111 and the concave portion 112. The convex portion 111, the concave portion 112, and the side surface 113 connecting the convex portion 111 and the concave portion 112 are formed continuously.

  When the light guide block unit 101 is molded from acrylic resin, the critical angle of total reflection is about 42 degrees. Therefore, as shown in the schematic partial cross-sectional view of FIG. 2C, when the light exit surface 210 of the light guide block unit 201 is flat (the light guide block unit 201 is The light emitted from the light source 44 is emitted from the light emitting surface portion 210A above the light source 44 (indicated by a solid line in FIG. 2C). It is totally reflected at the light emitting surface portion 210B away from above the light source 44 and is not emitted from the light guide block unit 201 (indicated by a dotted line in FIG. 2C). Note that light indicated by solid lines and dotted lines in FIG. 2C is light directly emitted from the light source 44.

  On the other hand, in the light emitted from the light source 44 and colliding with the side surface 113, the light whose incident angle to the side surface 113 is not less than the critical angle is totally reflected on the side surface 113 as shown in FIG. 2 (shown by a dotted line in FIG. 2A), light whose incident angle to the side surface 113 is less than the critical angle is emitted to the outside from the side surface 113 (shown by a solid line in FIG. 2A). This state is schematically shown in FIG. Note that light indicated by solid lines and dotted lines in FIG. 2A is light directly emitted from the light source 44.

  As described above, the light reflection layer 120 is formed on the convex portions 111 and the concave portions 112 of the light exit surface 110 of the light guide block unit 101, and the light from the light source 44 is emitted from the light exit surface of the light guide block unit 101. The light is emitted to the outside from the side surface 113 formed at 110. Accordingly, light emitted from the light source 44 and directly colliding with the convex portion 111 or the concave portion 112 of the light emitting surface 110 of the light guide block unit 101 (indicated by a dotted line in FIG. 2A) is the light emitting surface 110. As a result of reflection at the convex portion 111 or the concave portion 112, this light is not directly emitted from the light emitting surface 110 of the light guide block unit 101. Further, the light whose incident angle to the side surface 113 of the light emitting surface 110 is not less than the critical angle is totally reflected at the side surface 113 and is not emitted from the light emitting surface 110. On the other hand, the light emitted to the outside from the side surface 113 formed on the light exit surface 110 of the light guide block unit 101 is greatly incident on the convex portion 111 or the concave portion 112 of the light exit surface 110 of the light guide block unit 101. It corresponds to a corner and has a small incident angle (incidence angle less than the critical angle) with respect to the side surface 113 of the light emitting surface 110 of the light guide block unit 101, and therefore the side surface of the light emitting surface 110 of the light guide block unit 101. The light is output from the side surface 113 of the light output surface 110 of the light guide block unit 101 without being totally reflected at 113. Therefore, the difference in luminance between the space positioned above the light source 44 and the space positioned around the space is reduced. As a result, it is possible to reliably prevent the occurrence of a problem that the uniformity of luminance is improved in the display image of the liquid crystal display device assembly and the quality of the display image is impaired.

  Further, the light emitted from the light source and emitted from the side surface of the light exit surface of the light guide block is reflected by the light reflecting layer 120 provided on the convex portion 111 and the concave portion 112 on the light exit surface 110 of the light guide block unit 101. The reflected light propagates through the light guide block unit 101 and is emitted from the side surface 113 of the light exit surface 110 of the light guide block unit 101, as well as the light reflection provided on the side wall 102 of the light guide block unit 101. The light is reflected by the film 103, propagates through the light guide block unit 101, and is emitted from the side surface 113 of the light exit surface 110 of the light guide block unit 101. Therefore, the luminance loss in the space for color mixing can be reduced as much as possible, high luminance can be achieved, and, for example, above the boundary region between the planar light source unit 42 and the planar light source unit 42. Luminance unevenness due to the presence of the boundary region relating to the portion of the space that is located is less likely to occur, and miniaturization and thinning can be achieved.

  The result of having simulated the luminance distribution in the light guide block unit 101 of Example 1 and the light guide block unit 201 of Comparative Example 1 is shown in FIG. As is clear from FIG. 3, the light guide block unit 101 of the first embodiment (indicated by “x” in FIG. 3) is lighter than the light guide block unit 201 of the first comparative example (shown as white in FIG. 3). The luminance is uniform over a wider area than that indicated by a square mark.

  Furthermore, the illumination state on the light diffusing plate 61 when using the light guide block unit 101 of Example 1 and the light guide block unit 201 of Comparative Example 1 was photographed. Substitute drawings for this photograph are shown in FIGS. 4A and 4B. As is clear from FIGS. 4A and 4B, the light guide block unit 101 of the first embodiment (see FIG. 4A) is more light guide block unit 201 of the first comparative example (see FIG. 4A). The luminance is uniform in a wider area than in FIG. The state shown in FIG. 4B is schematically shown in FIG. 5, but the area showing red (indicated by a solid line), the area showing green (indicated by a dotted line), and the area showing blue (dashed line) Is present around the white light region, and a state where white light is separated was observed. On the other hand, in the light guide block unit 101 of Example 1, such a state where white light was separated was not observed.

  When the thickness of the light guide block is 5 mm, in Comparative Example 1, the optical path length in the light guide block unit 201 of the light emitted from the light guide block unit 201 in the shortest time from the light source 44 is 5 mm. In the light guide block unit 101 of the first embodiment, the length is about 14 mm. Since the area of the region where the light reaches is proportional to the square of the distance from the light source to the region, the increase in the optical path length means that the light is guided while the influence of the luminance distribution of the light emitting diode is reduced. It can be said that it can be taken out from the light block.

Two types of light guide block units were prepared in which the values of _H , L _H and L _L were all 0.3 mm and 0.5 mm, and the light guide block unit of Example 1 (value of L _H , L _L values were all set to 1.0 mm), and the same results as in Example 1 were obtained.

The second embodiment is a modification of the first embodiment. In the second embodiment, a schematic partial plan view of the light guide block 100 is shown in FIG. 6, or as shown in a schematic plan view of the light guide block unit 101, the convex portion 111 and the concave portion 112 are They are arranged on a concentric circle with the normal passing through the center of the light source 44 as the center. Also in this case, when the height of the side surface 113 is H, the width of the convex portion 111 is L _H , and the width of the concave portion 112 is L _L ,
H / L _H = H / L _L = L _H / L _L = 1
It is. Specifically, the value of H, the value of L _H , and the value of L _L are all 1.0 mm.

  Except for the above points, the surface light source device or liquid crystal display device assembly of the second embodiment can be the same as the surface light source device or liquid crystal display device assembly described in the first embodiment. Is omitted.

  The third embodiment is also a modification of the first embodiment. In the third embodiment, a schematic partial plan view of the light guide block 100 is shown in FIG. 7 or FIG. 8, or, as shown in FIG. The side surface 113 forms a columnar shape, specifically a cylindrical shape. Note that the cross-sectional shape when the cylindrical shape is cut on a virtual plane perpendicular to the axis is not limited to a circle, but can be a shape composed of any smooth closed curve including an oval, an ellipse, etc. . In the example shown in FIG. 7, the convex portions 111 are arranged on the vertices of an equilateral triangle, and in the example shown in FIG. 8, the convex portions 111 are arranged on square lattice points.

  Alternatively, instead of forming a cylindrical shape by the convex portion 111 and the side surface 113, a prismatic shape may be formed although not shown. The cross-sectional shape when the prismatic shape is cut in a virtual plane perpendicular to the axis is not only an arbitrary quadrilateral including a square, a rectangle, a trapezoid, and a parallelogram, but a shape composed of a triangle and an arbitrary polygon. Include.

  Except for the above points, the surface light source device or liquid crystal display device assembly of the third embodiment can be the same as the surface light source device or liquid crystal display device assembly described in the first embodiment. Is omitted.

  Hereinafter, a driving method of the liquid crystal display device assembly in the embodiment will be described with reference to FIGS. 9, 10, and 13. FIG. 13 is a flowchart for explaining a driving method of the liquid crystal display device assembly in the embodiment.

In the embodiment, a control signal for controlling the light transmittance Lt of each sub-pixel is supplied from the drive circuit to each sub-pixel. More specifically, a control signal [R, G, B] that controls the light transmittance Lt of each of the sub-pixels [R, G, B] is supplied to each of the sub-pixels [R, G, B] constituting each pixel. B] is supplied from the drive circuit 90. Then, in each of the planar light source units 42, inputs input to the drive circuits 70, 80, 90 to drive all the pixels (subpixels [R, G, B]) constituting each display area unit 12. A control signal corresponding to an input signal having a value equal to the maximum value x _U-max in the display area unit that is the maximum value x _R , x _G , x _B of the signals [R, G, B]. Of the pixel (sub-pixel [R, G, B]) (light transmittance, display luminance at the first specified value Lt ₁ , second specified value y ₂ ) is obtained. As described above, the luminance of the light source constituting the planar light source unit 42 corresponding to the display area unit 12 is controlled by the planar light source device control circuit 70 and the planar light source unit drive circuit 80. Specifically, for example, the light source luminance Y ₂ is obtained so that the display luminance y ₂ can be obtained when the light transmittance (aperture ratio) of the pixel or the sub-pixel is, for example, the light transmittance · the first specified value Lt _1. May be controlled (for example, decreased). That is, for example, the light source luminance Y ₂ of the planar light source unit 42 may be controlled for each image display frame so as to satisfy the following expression (1). Note that Y ₂ ≦ Y ₁ .

Y ₂ · Lt ₁ = Y ₁ · Lt ₂ (1)

[Step-100]
An input signal [R, G, B] and a clock signal CLK for one image display frame sent from a known display circuit such as a scan converter are input to the planar light source device control circuit 70 and the liquid crystal display device driving circuit 90. (See FIG. 9). Note that the input signals [R, G, B] are output signals from the image pickup tube, for example, when the input light quantity to the image pickup tube is y ′, and are output from, for example, a broadcasting station and the light transmittance of the sub-pixels. This is an input signal that is also input to the liquid crystal display driving circuit 90 to control Lt, and can be expressed as a function of the input light amount y ′ to the power of 0.45. The values x _R , x _G , x _B of the input signals [R, G, B] for one image display frame input to the planar light source device control circuit 70 constitute the planar light source device control circuit 70. The data is temporarily stored in the storage device (memory) 72. Further, the values x _R , x _G , x _B of the input signals [R, G, B] for one image display frame inputted to the liquid crystal display device driving circuit 90 are also stored in the liquid crystal display device driving circuit 90. (Not shown) once stored.

[Step-110]
Next, in the arithmetic circuit 71 constituting the surface light source device control circuit 70, the value of the input signal [R, G, B] stored in the storage device 72 is read, and the (p, q) th [however, first , P = 1, q = 1] for driving the sub-pixels [R, G, B] in all the pixels constituting the (p, q) -th display region unit 12 The arithmetic circuit 71 obtains the display area unit input signal maximum value x _U-max that is the maximum value of the values x _R , x _G , x _B of the input signals [R, G, B]. Then, the in-display area unit / input signal maximum value x _U-max is stored in the storage device 72. This step is executed for all of m = 1, 2,..., M, n = 1, 2,..., N, that is, for M × N pixels.

For example, when x _R is a value corresponding to “110”, x _G is a value corresponding to “150”, and x _B is a value corresponding to “50”, x _U-max is “150”. Is a value corresponding to.

This operation is repeated from (p, q) = (1, 1) to (P, Q), and the display area unit internal input signal maximum value x _U-max in all the display area units 12 is stored in the storage device 72. Remember.

[Step-120]
Then, the control signal [R, G, B] corresponding to the input signal [R, G, B] having a value equal to the maximum value x _U-max in the display area unit is sub-pixel [R, G, B]. ] Corresponding to the display area unit 12 so that the brightness (light transmittance, display brightness at the first specified value Lt ₁ , second specified value y ₂ ) is obtained by the planar light source unit 42. The luminance (light source luminance Y ₂ ) of the light source 44 constituting the planar light source unit 42 to be controlled is increased or decreased under the control of the planar light source unit drive circuit 80. Specifically, the light source luminance Y ₂ may be controlled for each image display frame and for each planar light source unit so as to satisfy the following expression (1). More specifically, the luminance of the light source 44 (light emitting diode 43) is controlled based on the equation (2) which is the light source luminance control function g (x _nol-max ), and the light source is set so as to satisfy the equation (1). The luminance Y ₂ may be controlled. A conceptual diagram of such control is shown in FIGS. 15 (A) and 15 (B). However, as will be described later, correction based on the influence of the other planar light source unit 42 is performed on the light source luminance Y ₂ as necessary. It should be noted that these relations regarding the control of the light source luminance Y ₂ , that is, the value of the control signal corresponding to the input signal having a value equal to the maximum value x _U-max in the display area unit and the input signal maximum value x _U-max . , The display luminance when assuming that such a control signal is supplied to the pixel (sub-pixel), the second specified value y ₂ , the light transmittance (aperture ratio) of each sub-pixel at this time [light transmittance / first 2 specified value Lt ₂ ], and a planar light source that provides display luminance and second specified value y ₂ when the light transmittance (aperture ratio) of each sub-pixel is set to light transmittance and first specified value Lt _1. The relationship of the brightness control parameters in the unit 42 may be obtained in advance and stored in the storage device 72 or the like.

Y ₂ · Lt ₁ = Y ₁ · Lt ₂ (1)
g (x _nol-max ) = a ₁ · (x _nol-max ) ^2.2 + a ₀ (2)

Here, input signals (input signals [R, G, B]) that are input to the liquid crystal display driving circuit 90 to drive the pixels (or the sub-pixels [R, G, B] constituting the pixels). ) _Is the maximum value x _max
x _nol-max ≡ x _U-max / x _max
And a ₁ and a ₀ are constants,
a ₁ + a ₀ = 1
0 <a ₀ <1, 0 <a ₁ <1
Can be expressed as For example,
a ₁ = 0.99
a ₀ = 0.01
And it is sufficient. The value x _R, x _G of the input signal [R, G, B], each x _B, and takes a value of 2 ⁸ steps, the value of x _max is a value corresponding to "255".

  By the way, in the planar light source device 40, for example, assuming brightness control of the planar light source unit 42 of (p, q) = (1, 1), other P × Q planar light source units. 42 may need to be taken into account. Since the influence of such a planar light source unit 42 from other planar light source units 42 is known in advance by the light emission profile of each planar light source unit 42, the difference can be calculated by back calculation, and as a result, the correction is Is possible. The basic form of calculation will be described below.

The luminance (light source luminance Y ₂ ) required for the P × Q planar light source units 42 based on the requirements of the equations (1) and (2) is represented by a matrix [L _PxQ ]. In addition, the luminance of a certain planar light source unit obtained when only a certain planar light source unit is driven and the other planar light source units are not driven is compared with P × Q planar light source units 42. Obtain in advance. Such luminance is represented by a matrix [L ′ _PxQ ]. Further, the correction coefficient is represented by a matrix [α _PxQ ]. Then, the relationship between these matrices can be expressed by the following equation (3-1). The correction coefficient matrix [α _PxQ ] can be obtained in advance.
[L _PxQ ] = [L ′ _PxQ ] · [α _PxQ ] (3-1)
Therefore, the matrix [L ′ _PxQ ] may be obtained from Expression (3-1). The matrix [L ′ _PxQ ] can be obtained from the inverse matrix operation. That is,
[L ′ _PxQ ] = [L _PxQ ] · [α _PxQ ] ⁻¹ (3-2)
Should be calculated. Then, the light source 44 provided in each planar light source unit 42 may be controlled so that the luminance represented by the matrix [L ′ _PxQ ] is obtained. Specifically, the operation and processing are performed by the storage device. The information (data table) stored in the (memory) 72 may be used. In the control of the light emitting diode 43, the value of the matrix [L ′ _PxQ ] cannot take a negative value, and needless to say, the calculation result needs to be kept in a positive region. Therefore, the solution of equation (3-2) may not be an exact solution but an approximate solution.

As described above, the matrix [L _PxQ ] obtained based on the values of the equations (1) and (2) obtained in the arithmetic circuit 71 constituting the surface light source device control circuit 70, and the correction coefficient matrix [α _PxQ ], As described above, a luminance matrix [L ′ _PxQ ] when it is assumed that the planar light source unit is driven alone is obtained. Further, based on the conversion table stored in the storage device 72, 0 to 0 is obtained. Convert to a corresponding integer (value of the pulse width modulation output signal) in the range of 255. In this way, in the arithmetic circuit 71 constituting the planar light source device control circuit 70, the value S _R of the pulse width modulation output signal for controlling the light emission time of the red light emitting diode 43R in the planar light source unit 42, the green light emitting diode 43G The value S _G of the pulse width modulation output signal for controlling the light emission time and the value S _B of the pulse width modulation output signal for controlling the light emission time of the blue light emitting diode 43B can be obtained.

[Step-130]
Next, the values S _R , S _G , and S _B of the pulse width modulation output signal obtained in the arithmetic circuit 71 constituting the surface light source device control circuit 70 are the surfaces provided corresponding to the surface light source unit 42. Is sent to the storage device 82 of the light source unit driving circuit 80 and stored in the storage device 82. The clock signal CLK is also sent to the planar light source unit drive circuit 80 (see FIG. 10).

[Step-140]
Based on the values S _R , S _G , and S _B of the pulse width modulation output signal, the on time t _R-ON and the off time t _{R-OFF of} the red light emitting diode 43R constituting the planar light source unit 42, the green light emitting diode The arithmetic circuit 81 determines the ON time t _G-ON and OFF time t _{G-OFF of} 43G and the ON time t _B-ON and OFF time t _B-OFF of the blue light emitting diode 43B. still,
t _R-ON + t _R-OFF = t _G-ON + t _G-OFF = t _B-ON + t _B-OFF = constant value t _Const
It is. The duty ratio in driving based on pulse width modulation of the light emitting diode is
t _ON / (t _ON + t _OFF ) = t _ON / t _Const
Can be expressed as

The signals corresponding to the _ON times t _R-ON , t _G-ON , t _B-ON of the red light emitting diode 43R, the green light emitting diode 43G, and the blue light emitting diode 43B constituting the planar light source unit 42 are the LED drive circuits. 83, and from the LED drive circuit 83, the switching elements 85R, 85G, 85B turn on the time t _R based on the signal values corresponding to the on times t _R-ON , t _G-ON , t _B-ON. Only _-ON , _{tG -ON} , and _{tB -ON} are turned on, and the LED driving current from the light emitting diode driving power supply 86 is caused to flow to the respective light emitting diodes 43R, 43G, and 43B. As a result, each of the light emitting diodes 43R, 43G, and 43B emits light for the on times t _R-ON , t _G-ON , and t _B-ON in one image display frame. Thus, each display area unit 12 is illuminated at a predetermined illuminance.

The states thus obtained are indicated by solid lines in FIGS. 14A and 14B, and FIG. 14A shows an input signal input to the liquid crystal display device driving circuit 90 for driving the sub-pixels. 15 is a diagram schematically showing the relationship between a value obtained by raising the value of x to the power of 2 (x′≡x ^2.2 ) and the duty ratio (= t _ON / t _Const ). FIG. It is a figure which shows typically the relationship between the value X of the control signal for controlling the light transmittance Lt, and the display brightness | luminance y.

[Step-150]
On the other hand, the values x _R , x _G , x _B of the input signals [R, G, B] input to the liquid crystal display device driving circuit 90 are sent to the timing controller 91, and the timing controller 91 receives the input signals A control signal [R, G, B] corresponding to the input signal [R, G, B] is supplied (output) to the sub-pixel [R, G, B]. The values X _R and X _{G of the} control signal [R, G, B] generated by the timing controller 91 of the liquid crystal display device driving circuit 90 and supplied from the liquid crystal display device driving circuit 90 to the sub-pixels [R, G, B]. , X _B and the values x _R , x _G , x _{B of} the input signals [R, G, B] are expressed by the following equations (4-1), (4-2), and (4-3): There is a relationship. However, _{b1_R} , _{b0_R} , _{b1_G} , _{b0_G} , _{b1_B} , _{b0_B} are constants. Further, since the light source luminance Y ₂ of the planar light source unit 42 is changed for each image display frame, the control signal [R, G, B] basically sets the value of the input signal [R, G, B] to 2. A value obtained by performing correction (compensation) based on a change in the light source luminance Y _{2 with} respect to the squared value. That is, in the embodiment, since the light source luminance Y ₂ changes for each image display frame, the control signal is obtained so that the display luminance and the second specified value y ₂ can be obtained at the light source luminance Y ₂ (≦ Y ₁ ). The values X _R , X _G , and X _B of [R, G, B] are determined and corrected (compensated) to control the light transmittance (aperture ratio) Lt of the pixel or sub-pixel. Here, the functions f _R , f _G , and f _B in the equations (4-1), (4-2), and (4-3) are functions obtained in advance for performing such correction (compensation). is there.

X _R = f _R (b 1 _—R · x _R ^2.2 + b 0 _—R ) (4-1)
X _G = f _G (b 1 _—G · x _G ^2.2 + b 0 _—G ) (4-2)
X _B = f _B (b 1 _—B · x _B ^2.2 + b 0 _—B ) (4-3)

  Thus, the image display operation in one image display frame is completed.

  As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these Examples. The configuration and structure of the light guide block, the light guide block unit, the transmissive color liquid crystal display device and the planar light source device, the planar light source unit, the liquid crystal display assembly, and the drive circuit described in the embodiments are examples. Members, materials, etc. constituting these are also examples, and can be changed as appropriate. Luminance compensation (correction) and temperature control of the planar light source unit may be performed by monitoring the temperature of the light emitting diode with a temperature sensor and feeding back the result to the planar light source unit drive circuit. In the embodiments, the description has been made on the assumption that the display area of the liquid crystal display device is divided into P × Q virtual display area units. However, in some cases, the transmissive liquid crystal display device has P × Q. You may have the structure divided | segmented into the actual display area unit.

  In the embodiment, the light reflection film is provided on the entire side wall of the light guide block unit. However, in some cases, the light reflection is performed only on the lower portion (for example, the lower 2/3 region) of the side wall of the light guide block unit. It is good also as a structure which provides a film | membrane. Moreover, depending on the case, you may change the characteristic of a light reflection layer for every part of the top surface of a light guide block. Specifically, for example, the characteristics of the light reflection layer in the outer peripheral portion of the top surface of the light guide block unit may be different from the properties of the light reflection layer in the center portion of the top surface of the light guide block unit.

1A and 1B are a schematic partial cross-sectional view of a light guide block or a light guide block unit in the planar light source device of Example 1, and a schematic part of the light guide block, respectively. It is a typical top view or a typical top view of a light guide block unit. 2A is a diagram schematically illustrating a state in which light is emitted from the light guide block unit according to the first embodiment. FIG. 2B is a diagram illustrating light of the light guide block unit according to the first embodiment. It is a figure which shows typically the state in which light is totally reflected in the side surface formed in the output surface, (C) of FIG. 2 typically shows the state in which light is radiate | emitted from the light guide block unit in the comparative example 1. FIG. FIG. 3 is a graph showing the result of simulating the luminance distribution in the light guide block unit of Example 1 and Comparative Example 1. 4A and 4B are substitute drawings of photographs taken of the illumination state on the light diffusion plate when the light guide block unit of Example 1 and the light guide block unit of Comparative Example 1 are used, respectively. It is. FIG. 5 is a diagram schematically showing a light state in the comparative example 1 shown in FIG. FIG. 6 is a schematic partial plan view of the light guide block of the second embodiment or a schematic plan view of the light guide block unit. FIG. 7 is a schematic partial plan view of the light guide block of the third embodiment or a schematic plan view of the light guide block unit. FIG. 8 is a schematic partial plan view of another light guide block of the third embodiment or a schematic plan view of a light guide block unit. FIG. 9 is a conceptual diagram of a liquid crystal display device assembly including a color liquid crystal display device and a planar light source device suitable for use in the embodiment. FIG. 10 is a conceptual diagram of a portion of a drive circuit suitable for use in the embodiment. FIG. 11A is a diagram schematically illustrating the arrangement and arrangement of the planar light source units, the light guide block units, and the like in the planar light source device of the example. FIG. 11B is a diagram illustrating the example. It is a typical partial cross section figure of the liquid crystal display device assembly which consists of a color liquid crystal display device and a planar light source device. FIG. 12 is a schematic partial sectional view of a color liquid crystal display device. FIG. 13 is a flowchart for explaining a driving method of the liquid crystal display device assembly in the embodiment. 14A shows a value (x′≡x ^2.2 ) obtained by multiplying the value of an input signal inputted to the liquid crystal display device driving circuit to drive the subpixel by the power of 2.2 (x′≡x ^2.2 ) and the duty ratio (= t _ON / t _Const ) schematically shows the relationship between the control signal value X and the display luminance y for controlling the light transmittance of the sub-pixel. FIG. (A) and (B) in FIG. 15 show the display luminance when assuming that a control signal corresponding to an input signal having a value equal to the input signal maximum value x _U-max is supplied to the pixel. as second predetermined value y ₂ is obtained by the planar light source unit, the light source luminance Y ₂ of the planar light source unit is the conceptual view for describing under the control of the planar light source unit drive circuit, a state of increasing or decreasing .

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Color liquid crystal display device, 11 ... Display area, 12 ... Display area unit, 13 ... Liquid crystal material, 20 ... Front panel, 21 ... 1st board | substrate, 22. ··· Color filter, 23 ... Overcoat layer, 24 ... Transparent first electrode (common electrode), 25 ... Alignment film, 26 ... Polarizing film, 30 ... Rear panel, 31 ..Second substrate 32 ... Switching element 34 ... Transparent second electrode 35 ... Alignment film 36 ... Polarization film 37 ... Insulating layer 40 ... Surface shape Light source device (backlight), 42 ... planar light source unit, 43, 43R, 43G, 43B ... light emitting diode, 44 ... light source, 45, 45R, 45G, 45B ... photodiode (light sensor) ), 51... Housing, 52A Bottom surface of housing, 52B: Side surface of housing, 53 ... Outer frame, 54 ... Inner frame, 55A, 55B, 55C ... Spacer, 56 ... Guide member, 57 ... Bracket Members 61... Light diffusion plate 62 62 diffusion sheet 63 prism sheet 64 polarization conversion sheet 65 reflection sheet 70 planar light source device control circuit 71 ... arithmetic circuit, 72 ... storage device (memory), 80 ... planar light source unit drive circuit, 81 ... arithmetic circuit, 82 ... storage device (memory), 83 ... LED Drive circuit, 84... Photodiode control circuit, 85R, 85G, 85B... Switching element, 86... Light emitting diode drive power source (constant current source), 90.・ Timing control Roller, 100: Light guide block, 101: Light guide block unit, 102: Side wall of light guide block unit, 103: Light reflection film, 104: Space, 110: Light emission Surface, 111 ... convex part, 112 ... concave part, 113 ... side surface, 120 ... light reflecting layer

Claims (7)

A planar light source device that includes a light guide block and a light source, is disposed below the liquid crystal display device, and illuminates the liquid crystal display device,
The light guide block has a light emitting surface facing the liquid crystal display device,
The light exit surface of the light guide block is formed with a convex portion, a concave portion, and a side surface connecting the convex portion and the concave portion,
A light reflecting layer is formed on the convex and concave portions,
A planar light source device, wherein light from a light source is emitted to the outside from a side surface formed on a light emission surface of a light guide block.   The planar light source device according to claim 1, wherein the convex portion and the concave portion are formed in a straight line.   The planar light source device according to claim 1, wherein the convex part and the concave part are arranged concentrically around a normal line passing through a central part of the light source.   The planar light source device according to claim 1, wherein a columnar shape is formed by the convex portion and the side surface.   The planar light source device according to claim 4, wherein the column shape is a cylindrical shape.   The planar light source device according to claim 4, wherein the column shape is a prism shape. (A) a liquid crystal display device, and
(B) a planar light source device that includes a light guide block and a light source, is disposed below the liquid crystal display device, and illuminates the liquid crystal display device;
A liquid crystal display assembly comprising:
The light guide block has a light emitting surface facing the liquid crystal display device,
The light exit surface of the light guide block is formed with a convex portion, a concave portion, and a side surface connecting the convex portion and the concave portion,
A light reflecting layer is formed on the convex and concave portions,
A liquid crystal display device assembly, wherein light from a light source is emitted to the outside from a side surface formed on a light emission surface of a light guide block.