JP2008059864A - Planar light source device and liquid crystal display device assembly - Google Patents

Abstract

A structure that eliminates the need for an independent light diffusing plate above a light source and that does not easily cause luminance unevenness in a space portion located above a boundary region between the planar light source unit and the planar light source unit. Provided is a planar light source device.
In a planar light source device configured to illuminate a transmissive liquid crystal display device from the back, which is composed of a plurality of planar light source units, each planar light source unit includes: (A) a top surface, a bottom surface, A light guide block 42 having a side surface 42C and an inner surface 42D; and (B) a light source including a light emitting element 43 disposed inside the light guide block 42 and spaced from the inner surface 422D of the light guide block 42. The light reflection layer 44 is provided on the side surface 42C of the light guide block 42, and the light diffusion / transmission layer 45 is provided on the top surface 42A of the light guide block 42 corresponding to the light emission surface.
[Selection] Figure 1

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 includes, for example, three types of sub-pixels: 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. As the liquid crystal display device becomes larger, the planar light source device is also getting larger.

  Conventionally, a planar light source device in a liquid crystal display device assembly illuminates the entire display region with uniform and constant brightness. For example, Japanese Unexamined Patent Application Publication No. 2005-258403 discloses a planar light source device having a configuration in which the distribution of illuminance in a plurality of display area units is changed.

  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.

Such a planar light source device is controlled based on the method described below. In other words, the maximum luminance of each planar light source unit constituting the planar light source device is Y _1, and the maximum value (specifically, for example, 100%) of the light transmittance (aperture ratio) of the pixel in the display area unit is set. Let Lt ₁ . Further, when each planar light source unit constituting the planar light source device has the maximum luminance Y ₁ , the light transmittance (aperture ratio) of each pixel for obtaining the display luminance y ₂ of each pixel in the display area unit. Is Lt ₂ . Then, in this case, the light source luminance Y ₂ of each planar light source unit constituting the planar light source device is
Y ₂ · Lt ₁ = Y ₁ · Lt ₂
It may be controlled so as to satisfy In addition, the conceptual diagram of such control is shown to (A) and (B) of FIG. Here, the light source luminance Y ₂ of the planar light source unit is changed for each frame (referred to as an image display frame for convenience) in the image display of the liquid crystal display device.

  As a result of such control of the planar light source device (also referred to as split driving of the planar light source device), it is possible to increase the white level in the liquid crystal display device and increase the contrast ratio due to the decrease in the black level. The display quality can be improved, and 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 controlling the light source luminance Y ₂ of the respective surface light source units constituting the surface light source device, the light source luminance of the light source luminance of one planar light source unit is another planar light source unit To affect. Accordingly, in order to minimize the influence of each planar light source unit on the other planar light source units, a partition is provided between the planar light source unit and the planar light source unit.

  Further, when the light source in the planar light source device is composed of a red light emitting element, a green light emitting element, and a blue light emitting element, the red light, green light, and blue light emitted from these light emitting elements are sufficiently mixed, It needs to be white light.

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

  By the way, as described above, as the liquid crystal display device is increased in size, the planar light source device is also increased in size. As a result, the light diffusing plate made of plastic is inevitable to increase in area. However, it is difficult to manufacture a light diffusion plate that is thin and wide in area and transmits and diffuses light uniformly. Further, when a partition wall is provided between the planar light source unit and the planar light source unit, there is a problem that luminance unevenness (a kind of partition wall shadow) is likely to occur in the portion of the light diffusion plate corresponding to the upper portion of the partition wall.

  Further, when the light source in the planar light source device is composed of three types of light emitting elements as described above, in order to obtain white light from red light, green light, and blue light emitted from these light emitting elements, there is a certain 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.

  Therefore, the first object of the present invention is that it is not necessary to provide an independent light diffusion plate above the light source as in the conventional planar light source device, and the planar light source unit and the planar light source unit Provided are a planar light source device having a structure in which luminance unevenness due to the presence of a boundary region relating to a portion of a space located above the boundary region is unlikely to occur, and a liquid crystal display device assembly incorporating such a planar light source device There is to do. In addition, the second object of the present invention is to achieve high brightness, and to the presence of a boundary region related to a space portion located above the boundary region between the planar light source unit and the planar light source unit. It is an object of the present invention to provide a planar light source device having a structure that is less likely to cause uneven luminance and can be reduced in size and thickness, and a liquid crystal display device assembly incorporating such a planar light source device.

  In order to achieve the first and second objects described above, the planar light source device of the present invention has a back surface of a transmissive liquid crystal display device having a display area composed of pixels arranged in a two-dimensional matrix. P × Q corresponding to the P × Q display area units when it is assumed that the display area of the liquid crystal display device is divided into P × Q virtual display area units. It consists of a planar light source unit.

In addition, the liquid crystal display device assembly of the present invention for achieving the first and second objects is as follows.
(A) a transmissive liquid crystal display device having a display area composed of pixels arranged in a two-dimensional matrix, and
(B) From the P × Q planar light source units corresponding to the P × Q display area units when it is assumed that the display area of the liquid crystal display device is divided into P × Q virtual display area units. A planar light source device for illuminating a liquid crystal display device from the back,
A liquid crystal display device assembly.

And the planar light source device which concerns on the 1st aspect of this invention for achieving said 1st objective, or the planar light source in the liquid crystal display device assembly of this invention which concerns on the 1st aspect of this invention In the device
Each planar light source unit
(A) a light guide block having a top surface, a bottom surface, a side surface, and an inner surface extending from the bottom surface to the inside; and
(B) a light source comprising a light emitting element disposed inside the light guide block, spaced from the inner surface of the light guide block;
With
The light emitted from the light emitting element enters the inside from the inner surface of the light guide block,
A light reflection layer is provided on the side of the light guide block,
A light diffusion / transmission layer is provided on the top surface of the light guide block corresponding to the light exit surface.

In addition, the planar light source device according to the second aspect of the present invention for achieving the second object described above, or the planar light source in the liquid crystal display device assembly of the present invention according to the second aspect of the present invention. In the device
Each planar light source unit
(A) a light guide block having a top surface, a bottom surface, a side surface, and an inner surface extending from the bottom surface to the inside; and
(B) a light source comprising a light emitting element disposed inside the light guide block, spaced from the inner surface of the light guide block;
With
The light emitted from the light emitting element enters the inside from the inner surface of the light guide block,
A light reflection layer is provided on the side of the light guide block,
A light diffusion / reflection layer is provided on a part of the top surface of the light guide block.
In the remaining part of the top surface of the light guide block, the top surface of the light guide block is exposed.

  In the planar light source device or the liquid crystal display assembly according to the first aspect or the second aspect of the present invention (hereinafter, these may be collectively referred to simply as the present invention), each planar light source unit The light sources provided in can be individually controlled.

In the present invention, the top surface of the light guide block is composed of any one of a flat surface, a curved surface convex upward, a curved surface convex downward, or a combination thereof. More specifically, as the shape of the top surface of the light guide block,
(1) Plane (2) Convex curved surface (3) Convex curved surface (4) Combination of plane and convex convex surface (5) Combination of plane and convex convex surface (6) Top (7) Combinations of a plane, an upwardly convex curved surface, and a downwardly convex curved surface can be mentioned. In addition, the inner surface of the light guide block is also composed of a curved surface, or a polygonal prism whose top surface is not flat, including a pyramid, a cone, a cylinder whose top surface is not flat, a triangular prism whose top surface is not flat, and a square column whose top surface is not flat. It is composed of Here, specific examples of these curved surfaces include aspherical functions, spherical surfaces, spheroids, paraboloids, and hyperboloids, and when the light guide block is cut along a virtual vertical plane. As a curve constituting the cut portion of the top surface or the cut portion of the inner surface, part of a circle, part of an ellipse, part of a parabola, part of a hyperbola, part of a curve represented by a sine or cosine, 2 A part of a curve represented by a polynomial of the order or higher can be exemplified. Alternatively, as a curve constituting the cut portion of the top surface or the inner surface when the light guide block is cut along a virtual vertical plane, a two-leaf line, a three-leaf line, a four-leaf line, a continuous bead, a cochlear line, a regular leaf line , Spear line, sprint line, likelihood curve, arc line, catenary line, shore line, shore line, star shape, semi-cubic parabola, Lissajous curve, Arnessy curve, outer cycloid, heart shape, inner cycloid, clothoid curve , And the like. Further, examples thereof include a combination of these curved surfaces and curves, a combination of these curved surfaces and planes, and a combination of these curves and line segments, but are not limited thereto.

  Whether the shape of the top surface of the light guide block is a flat surface, an upwardly convex curved surface, a downwardly convex curved surface, or a combination thereof is also determined. The shape of the inner surface of the light guide is determined by the size of the light guide block, the size of the space formed by the inner surface, the shape and arrangement of the light source, the light emission state from the light source, the top surface of the light guide block In addition, it is difficult to uniquely determine depending on the relationship between the shapes of the inner surfaces and the luminance, luminance distribution, and the like required for the planar light source unit. Therefore, for example, simulation and the like may be performed to determine the optimal shape of the top surface and the inner surface of the light guide block. The number of inner surfaces provided in the light guide block may be one or may be two or more.

  In the planar light source device or the liquid crystal display assembly according to the first aspect of the present invention (hereinafter, these may be collectively referred to simply as the first aspect of the present invention), The light diffusing / transmitting layer provided on the surface is composed of, for example, a light diffusing / transmitting layer in which a light diffusing agent composed of fine particles is dispersed in a transparent binder resin. For example, the top surface of the light guide block is formed by various coating methods. It can be formed by various molding methods using resin as a raw material. In the latter case, the light diffusion / transmission layer can be formed integrally with the light guide block, or formed separately from the light guide block, and the light diffusion / transmission layer and the light guide block are assembled in a later process. May be. Alternatively, a light diffusion / transmission layer can be provided on the top surface of the light guide block by attaching the diffusion sheet to the top surface of the light guide block.

  Top surface of light guide block in planar light source device or liquid crystal display assembly according to second aspect of the present invention (hereinafter, these may be collectively referred to simply as the second aspect of the present invention) The light diffusing / reflecting layer provided on the light guide layer, or the light reflecting layer provided on the side surface of the light guide block in the present invention, may be, for example, a physical vapor deposition method (PVD method) such as vacuum deposition or sputtering, It can also be a light diffusion / reflection layer or light reflection layer made of a metal layer or alloy layer formed based on a plating method, etc., or a light diffusion / reflection layer or light reflection layer composed of a light diffusing agent A combination of these (a light diffusing / reflecting layer or light reflecting layer made of a metal layer or an alloy layer is used as an outer layer, and a light diffusing / reflecting layer or light reflecting layer composed of a light diffusing agent is used as an inner layer. Can also be used as an adhesive or adhesive seal It can be a film (light diffusion and reflection film) and bonding the silver increase reflecting sheet with a structure having an uneven top surface or the side surface of the light guide blocks used. However, the light emitted from the light source does not pass through the light diffusing / reflecting layer and is not emitted to the outside, or the light emitted from the light source is incident on the adjacent light guide block ( It is necessary to provide a light reflecting layer that does not penetrate. Thus, when the light source luminance of each planar light source unit constituting the planar light source device is controlled, for example, the influence of the light source luminance of a certain planar light source unit on the light source luminance of another planar light source unit is eliminated. It is possible to prevent a decrease in the utilization efficiency of the light emitted from the light source. In the present invention, a light reflecting layer may also be provided on the bottom surface of the light guide block.

  The light diffusing / reflecting layer composed of a light diffusing agent is composed of, for example, a light diffusing / reflecting layer in which a light diffusing agent composed of fine particles is dispersed in a transparent binder resin. It can be formed on the inner surface of the member, and can be obtained by various molding methods using resin as a raw material. In the latter case, the light diffusing / reflecting layer can be formed integrally with the light guide block, or formed separately from the light guide block, and the light diffusing / reflecting layer and the light guide block are assembled in a later process. May be.

  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, it is preferable that the planar light source device is configured in such a manner that the light guide blocks are spread as much as possible, but in consideration of deformation due to thermal expansion of the light guide blocks, a predetermined amount is provided between the light guide blocks. You may leave a gap. Here, the width of the gap may be appropriately determined in consideration of the size of the light guide block and the degree of thermal expansion. In addition, examples of the planar shape of the top surface of the light guide block include a rectangle, and examples of the outer shape of the light guide block include a rectangular parallelepiped. Alternatively, for example, it can be shaped like a family crest “middle shade weight”. In addition, a light guide block unit is manufactured, and a groove (slit) is formed in an appropriate method (for example, a dicing method or a method using a laser) at a boundary portion between the light guide block and the light guide block in the light guide block unit. A light guide block unit including a plurality of light guide blocks may be produced by forming and embedding a light diffusing / reflecting material in the groove (slit).

  In the present invention, the solid 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, as a material constituting the light guide block, for example, glass or plastic material [for example, PMMA, polycarbonate resin, acrylic resin, amorphous polypropylene resin, styrene resin including AS resin, polyethylene Terephthalate (PET) resin]. What is necessary is just to produce a light guide block based on the suitable shaping | molding method depending on the material to comprise.

  Further, in the second aspect of the present invention including the above preferred embodiment, a lens is disposed on or above a portion where the top surface of the light guide block is exposed (hereinafter sometimes referred to as an opening). It can be set as the structure currently made. Here, the lens as a whole may have a convex lens effect or a concave lens effect. That is, inside the light guide block, the solid angle and luminance profile of the light that is diffused and reflected and finally emitted from the opening, the size of the display area unit to be irradiated by the light emitted from the opening, and the required size are required. The lens may be designed based on the luminance profile on the display area unit. Specifically, it is preferably composed of any one of a biconvex lens, a planoconvex lens, a meniscus convex lens, a biconcave lens, a planoconcave lens, and a meniscus concave lens. Alternatively, it can be composed of a Fresnel lens. The lens may be made from optical glass or plastic. Here, as plastics constituting the plastic lens, thermoplastic resins such as acrylic resins, polycarbonate resins, polyolefin resins, polyester resins, polyurethane resins, polysulfone resins, polystyrene resins, vinyl resins, and halogen resins are used. And thermosetting resins such as epoxy resins, polyimide resins, urea resins, phenol resins, and silicone resins. Although the plastic lens depends on the material, it can be molded by, for example, an injection molding method. One lens may be arranged in one planar light source unit, or one lens unit in which a plurality of lenses are formed is arranged in common (shared) with a plurality of planar light source units. Alternatively, a single lens unit in which a plurality of lenses are formed may be arranged in common (shared) with all the planar light source units. The outer shape of the lens is preferably circular or similar to the opening. In some cases, the lens and the top surface member can be fabricated integrally. Further, the light diffusion / transmission layer in the first aspect of the present invention may be formed on the portion where the top surface of the light guide block is exposed.

  In the present invention, a light emitting diode (LED) can be exemplified as a light source constituting the planar light source unit. The emission color of the light source may be determined based on specifications required for the planar light source device. 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, By doing so, white light can be obtained. In the first aspect of the present invention, 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). In the present invention, a light emitting diode that emits a fourth color other than red, green, blue, fifth color,... May be further provided. A light source composed of a light emitting diode has a small occupied volume and is suitable for a configuration in which a light source is provided independently for each planar light source unit.

  Further, when the light source is composed of light emitting diodes, for example, a plurality of red light emitting diodes emitting red light, a plurality of green light emitting diodes emitting green light, and a plurality of blue light emitting diodes emitting blue light are included in the light guide block. Are arranged and arranged. More specifically, (one red light emitting 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) When it is assumed that the planar light source unit is composed of a light emitting diode unit which is composed of a combination of a light emitting diode, two green light emitting diodes, one blue light emitting diode), etc. and emits white light as a whole, One planar light source unit is provided with at least one light emitting diode unit. Each light emitting diode unit is disposed in a space formed by the inner surface of the light guide block. Alternatively, one planar light source unit is provided with at least one white light emitting diode. As a light emitting element disposed inside the light guide block so as to be separated from the inner surface of the light guide block, one red light emitting diode, one green light emitting diode, and one blue light emitting diode can be used. Red light emitting diode, one green light emitting diode), (one red light emitting diode, one blue light emitting diode), (one green light emitting diode, one blue light emitting diode) may be combined, or the light emission described above It can also be a diode unit.

  The light-emitting diode that constitutes the light source 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) is formed on, for example, a first cladding layer and a first cladding layer made of a compound semiconductor layer having a first conductivity type (for example, n-type) formed on a substrate. The active layer, and a second clad layer stack structure comprising a compound semiconductor layer having a second conductivity type (for example, p-type) formed on the active layer, and electrically connected to the first clad layer. One electrode and a second electrode electrically connected to the second cladding layer are 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.

  In the present invention, the planar light source device may be configured to further include an optical function sheet group such as a diffusion sheet, a prism sheet, and a polarization conversion sheet, and a reflection 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. In the second aspect of the present invention, a light diffusing plate may be arranged as necessary. The light diffusing plate and the optical function sheet group are disposed between the planar light source device and the liquid crystal display device.

  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 a transmissive color liquid crystal display device, a red light emitting sub-pixel (which may be referred to as sub-pixel [R]) constituting each pixel (pixel) is a combination of the region and a color filter that transmits red. The green light emitting subpixel (sometimes referred to as subpixel [G]) is composed of a combination of the region and a color filter that transmits green, and is a blue light emitting subpixel (referred to as subpixel [B]). (In some cases) is composed of a combination of such a region and a color filter that transmits blue. 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.

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.

  The driving circuit for driving the liquid crystal display device and the planar light source device includes, for example, a planar light source device control circuit and a planar light source configured from a light emitting diode (LED) driving circuit, an arithmetic circuit, a storage device (memory), and the like. A 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 first aspect and the second aspect of the present invention, since the light reflecting layer is provided on the side surface of the light guide block, the light emitted from the light source enters (enters) the adjacent light guide block. When the light source luminance of each planar light source unit constituting the planar light source device is controlled, 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 may be eliminated. it can. In addition, since a thin light reflection layer may be provided, the light source block is not provided, and the light source block is guided as compared with a conventional surface light source device in which the surface light source unit is surrounded by a light reflective partition. It is possible to reduce luminance unevenness due to the presence of the boundary region in the space located above the boundary region between the light block and the light guide block.

Furthermore, in the first aspect of the present invention, since the light diffusion / transmission layer is provided on the top surface of the light guide block corresponding to the light output surface, a slight amount is formed in the boundary region between the light guide block and the light guide block. It is possible to eliminate luminance unevenness that may occur in a large amount by the light diffusion effect. Further, as a form in which the light emitted from the light source and passed through the space surrounded by the inner surface of the light guide block is emitted from the top surface of the light guide block through the light diffusion / transmission layer, for example,
(1) A mode in which the light propagates through the light guide block and is immediately emitted from the top surface of the light guide block. (2) Reflected by the light reflecting layer provided on the side surface of the light guide block, passes through the light guide block. Propagating again, not only the form emitted from the top surface of the light guide block,
(3) Reflected by the light reflecting layer provided on the side surface of the light guide block, propagates again in the light guide block, and is partially reflected by the inner surface of the light guide block, from the top surface of the light guide block There is a form to be emitted. Therefore, compared with a conventional planar light source device in which a planar light source unit is surrounded by a light-reflective partition without a light guide block, and a light diffusing plate is disposed above the planar light source unit. The ratio of light emitted to the space located above each planar light source unit can be increased, and by optimizing the shape of the outer peripheral portion of the top surface of the light guide block, the light guide block and the light guide It is possible to reduce luminance unevenness due to the presence of the boundary region in the space above the block boundary region.

  In the second aspect of the present invention, a light reflection layer is provided on the side surface of the light guide block, a light diffusion / reflection layer is provided on the top surface of the light guide block, and an opening is provided. Has been placed. Therefore, the light guide block has a function similar to an integrating sphere, and the light emitted from the light source arranged inside the light guide block is repeatedly reflected and diffused in the light guide block, and finally the top surface. The liquid crystal display device is finally illuminated from the back side. Therefore, the planar light source unit functions as a kind of point light source (or a light source having a small light emitting area), and the light emitted from the planar light source unit is used by an appropriate method (for example, a lens or a light diffusion). By using a plate) and widening the optical path, it can be used as a planar light source having a sufficiently wide light emitting area. Therefore, the luminance loss in the space for color mixing can be reduced as much as possible, high luminance can be achieved, and the space is located above the boundary region between the planar light source unit and the planar light source unit. Luminance unevenness due to the presence of the boundary region relating to the portion is hardly generated, and miniaturization and thinning can be achieved.

  Furthermore, in the present invention, the top surface of the light guide block is composed of an upwardly convex curved surface, a downwardly convex curved surface, or a combination thereof. As a result, the ratio of the light emitted to the space located above each planar light source unit can be increased, and high luminance in the planar light source device can be achieved.

  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. 3, 4, 5 (A) and (B), and FIG. 6.

As shown in the conceptual diagram of FIG. 3, the transmissive color liquid crystal display device 10 in the embodiment has a total of M ₀ ×, which is M ₀ along the first direction and N ₀ along the second direction. A display area 11 in which N ₀ pixels are arranged in a two-dimensional matrix is provided. 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). In addition, a display area 11 (indicated by a one-dot chain line in FIG. 3) composed of pixels arranged in a two-dimensional matrix is divided into P × Q virtual display area units 12 (the boundary is 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 display area units 12 (and a planar light source unit 41 described later) in FIG. 3 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 having a transparent first electrode 24, a rear panel 30 having a transparent second electrode 34, and a schematic partial cross-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 41 corresponding to the P × Q virtual display area units 12. The display area unit 12 corresponding to the light source unit 41 is illuminated from the back. The light sources provided in the planar light source unit 41 are individually controlled. However, the light source luminance of the planar light source unit 41 is not affected by the light emission state of the light sources provided in the other planar light source units 41. 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. 5A, and a schematic partial sectional view of the planar light source device and the liquid crystal display device assembly is shown in FIG. Shown in B). The light source comprises 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 41 is increased / decreased by increasing / decreasing the duty ratio in the pulse width modulation control of the light emitting diodes 43 constituting the planar light source unit 41.

  As shown in a schematic partial cross-sectional view of the liquid crystal display device assembly in FIG. 5B, 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. Details of the planar light source unit 41 will be described later. An optical function sheet group such as a diffusion sheet 61, a prism sheet 62, and a polarization conversion sheet 63 is laminated above the light guide block 42 constituting the planar light source unit 41, and is attached to the casing 51 via a bracket member 57. It is attached. Then, the red light emitted from the red light emitting diode 43R that emits red, the green light emitting diode 43G that emits green, and the blue light emitting diode 43B that emits blue light are mixed, and the color purity is high. White light can be obtained as illumination light. The illumination light is emitted from the planar light source unit 41, passes through an optical function sheet group such as a diffusion sheet 61, a prism sheet 62, and a polarization conversion sheet 63, and irradiates the color liquid crystal display device 10 from the back.

  As shown in FIGS. 3 and 4, the driving circuit for driving the planar light source device 40 and the color liquid crystal display device 10 based on an 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 drive circuit 80 for controlling on / off 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 the liquid crystal display device driving The 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, switching elements 84R, 84G, and 84B composed of FETs, and a light emitting diode driving power source (constant current source) 85. Has been. 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. Here, in FIG. 4, a single light emitting diode driving power source (constant current source) 85 is depicted, but actually, the light emitting diode driving power source for driving each of the light emitting diodes 43R, 43G, and 43B. 85 is arranged.

  A display area 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 × P It can be said that the display area unit is divided into 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. Also, pulse width modulation output signal values S _R , S _G , and S _B 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 are also provided. , Takes a value of 2 ⁸ steps from 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 pixel is supplied from the drive circuit to each 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 which is the luminance of the planar light source unit 41 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 according to a first aspect of the present invention. A schematic end view of the planar light source unit 41 constituting the planar light source device 40 of Example 1 is shown in FIG.

  The planar light source unit 41 has a top surface 42A, a bottom surface 42B, a side surface 42C, and an inner surface 42D extending from the bottom surface 42B to the inside, and is separated from the light guide block 42 and the inner surface 42D of the light guide block 42. The light source includes a light emitting element 43 disposed inside the light guide block 42. Then, the light emitted from the light emitting element 43 enters the inside from the inner surface 42 </ b> D of the light guide block 42. A light reflection layer 44 is provided on the side surface 42C of the light guide block 42, and a light diffusion / transmission layer 45 is provided on the top surface 42A of the light guide block 42 corresponding to the light emission surface. A light emitting diode unit composed of light emitting diodes 43R, 43G, and 43B corresponding to the light source 43 is disposed in a space surrounded by one inner surface 42D, and these light emitting diodes 43R, 43G, and 43B are supporting members. 46 is mounted on. The light guide block 42 (more specifically, the support member 46) is fixed to the bottom surface 52A of the housing by an appropriate method. The light emitting diodes 43R, 43G, and 43B may be directly fixed to the bottom surface 52A of the casing by an appropriate method. Further, a light reflection layer may be further provided on the bottom surface 42B of the light guide block 42.

  Here, the solid light guide block 42 is made of, for example, an acrylic resin, and the light reflecting layer 44 is formed of an aluminum layer formed on the side surface 42C of the light guide block 42 by a vacuum evaporation method. The light diffusion / transmission layer 45 is formed, for example, by dispersing a light diffusion agent composed of fine particles such as titanium oxide in a transparent binder resin, and is formed on the top surface 42A of the light guide block 42 by a coating method. Specifically, the light emitting element 43 includes, for example, a red light emitting diode 43R that emits red light having a wavelength of 640 nm, a green light emitting diode 43G that emits green light having a wavelength of 530 nm, and a blue light emitting light emitting blue light having a wavelength of 450 nm, for example. The diode 43B is configured as a set.

  The top surface 42A of the light guide block 42 is composed of a downwardly convex curved surface, and the inner surface 42D of the light guide block 42 is composed of an upwardly convex curved surface. Specifically, when the light guide block 42 is cut along a virtual vertical plane, the curves constituting the cut portion of the top surface 42A and the cut portion of the inner surface 42D are a part of a circle and a part of an ellipse. is there. The shape of the top surface 42A and the shape of the inner surface 42D of the light guide block 42 are the size of the light guide block 42, the size of the space formed by the inner surface 42D, the shape and arrangement of the light source 43, and the shape from the light source 43. It depends on the light emission state, the relationship between the shape of the top surface 42A and the inner surface 42D of the light guide block 42, the luminance and luminance distribution required for the planar light source unit 41, and it is difficult to determine uniquely. is there. Therefore, for example, simulation and the like may be performed to determine the optimal shape of the top surface 42A and the inner surface 42D of the light guide block 42. In the example shown in FIG. 1A, the light guide block 42 is provided with one inner surface 42D, but the number of inner surfaces 42D to be provided in the light guide block 42 is limited to one. Instead, it can be two places, four places, and the like.

  Example 2 relates to a planar light source device and a liquid crystal display device assembly according to a second aspect of the present invention. A schematic end view of the planar light source unit 141 constituting the planar light source device 140 of Example 2 is shown in FIG. 2A, and the schematic planar shape of the planar light source unit 141 is shown in FIG. ).

  In the second embodiment, the planar light source unit 141 includes a top surface 142A, a bottom surface 142B, a side surface 142C, a light guide block 142 having an inner surface 142D extending from the bottom surface 142B to the inside, and an inner surface 142D of the light guide block 142. A light source 43 composed of a light emitting element disposed inside the light guide block 142 is provided apart from the light source 43. Then, the light emitted from the light emitting element 43 enters the inside from the inner surface 142D of the light guide block 142. The light reflection layer 144 is provided on the side surface 142C of the light guide block 142, and the light reflection layer 144B is provided on the bottom surface 142B of the light guide block 142. Further, a light diffusing / reflecting layer 146 is provided on a part of the top surface 142A of the light guide block 142, and the top surface 142A of the light guide block 142 is formed on the remaining portion of the top surface 142A of the light guide block 142. It is exposed (that is, an opening 147 is provided). The light emitting diode unit composed of the light emitting diodes 43R, 43G, and 43B corresponding to the light source 43 is disposed in a space surrounded by one inner surface 142D, and these light emitting diodes 43R, 43G, and 43B are arranged in a housing. It is fixed to the bottom surface 52A of the body by an appropriate method. The light emitting diodes 43R, 43G, and 43B may be attached to a support member, and the support member may be fixed to the bottom surface 52A of the housing by an appropriate method.

  Here, the solid light guide block 142 and the light reflection layers 144 and 144B have the same configuration as the light guide block 42 and the light reflection layer 44 of the first embodiment. The light emitting element 43 has the same configuration as the light emitting element 43 of the first embodiment. The light diffusing / reflecting layer 146 is formed by dispersing a light diffusing agent made of fine particles such as barium sulfate in a transparent binder resin, and is formed on a part of the top surface 142A by a coating method.

  Furthermore, the top surface 142A of the light guide block 142 is composed of a downwardly convex curved surface, and the inner surface 142D of the light guide block 142 is composed of an upwardly convex curved surface. Specifically, when the light guide block 142 is cut along a virtual vertical plane, the curves constituting the cut portion of the top surface 142A and the cut portion of the inner surface 142D are a part of a circle and a part of an ellipse. is there. Note that the shape of the top surface 142A and the shape of the inner surface 142D of the light guide block 142 are the size of the light guide block 142, the size of the space formed by the inner surface 142D, the shape and arrangement of the light source 43, and the shape from the light source 43. It depends on the light emission state, the relationship between the shape of the top surface 142A and the inner surface 142D of the light guide block 142, the luminance and the luminance distribution required for the planar light source unit 141, and it is difficult to determine uniquely. is there. Therefore, for example, simulation and the like may be performed to determine the optimal shape of the top surface 142A and the inner surface 142D of the light guide block 142. In addition, the planar shape of the light guide block 142 is a shape like a family crest “middle shade weight”. That is, it is composed of two opposing arcs that are convex outward and two opposing arcs that are inward connecting these arcs. However, the planar shape of the light guide block 142 is not limited to such a shape. In the example shown in FIG. 2A, the light guide block 142 is provided with one inner surface 142D, but the number of inner surfaces 142D to be provided in the light guide block 142 is limited to one. Instead, it can be two places, four places, and the like.

  A lens 148 (specifically, a plano-convex lens having a plastic convex lens effect) is disposed on the opening 147 provided on the top surface 142A. The outer shape of the lens 148 is a circle. In the illustrated example, one lens 148 is arranged in one planar light source unit 141, but one lens unit in which a plurality of lenses are formed is shared by a plurality of planar light source units ( It may be arranged (shared), or one lens unit in which a plurality of lenses are formed may be arranged in common (shared) for all the planar light source units.

  The light emitting diodes 43R, 43G, and 43B are not located directly below the opening 147 provided at the center of the top surface 142A, but are located near the side surface 142C. That is, the positional relationship between the opening 147 provided in the top surface member 142 and the light emitting diodes 43R, 43G, and 43B is such that the light emitted from the light emitting diodes 43R, 43G, and 43B is reflected once inside the light guide block 142. It is in the positional relationship which can avoid the state which radiate | emits from the opening part 147, without being carried out. Alternatively, if the light emitting diodes 43R, 43G, and 43B have a function of controlling the radiation angle by, for example, arranging an appropriate lens or the like in the light emitting portion, the light emitting diodes 43R, 43G, and The light emitted from 43B is diffused and reflected at least once inside the light guide block 142 and then emitted from the opening 147.

  Hereinafter, a driving method of the liquid crystal display device assembly according to the first and second embodiments will be described with reference to FIGS. 3, 4, and 7. FIG. 7 is a flowchart for explaining a method of driving the liquid crystal display device assembly according to the first and second embodiments. Here, the light transmittance (also referred to as aperture ratio) Lt of the pixel or sub-pixel, the luminance (display luminance) y of the display area corresponding to the pixel or sub-pixel, and the luminance (light source luminance) of the planar light source unit Y 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.

In the first to second embodiments, a control signal for controlling the light transmittance Lt of each pixel is supplied from the drive circuit to each 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 41, inputs inputted to the drive circuits 70, 80, 90 for driving all the pixels (sub-pixels [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. Further, the luminance of the light source 43 constituting the planar light source unit 41 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 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. 3). 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 Lt of the pixel. Is an input signal that is also input to the liquid crystal display device driving circuit 90 to control the above, and can be expressed by a function of the input light quantity y ′ to the 0.45th power. 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.

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 surface light source unit 41 can obtain the brightness (light transmittance, display brightness at the first specified value Lt ₁ , second specified value y ₂ ). The light source luminance Y ₂ of the planar light source unit 41 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 brightness of the light source 43 is controlled based on the formula (2) which is the light source brightness control function g (x _nol-max ), and the light source brightness Y ₂ is controlled so as to satisfy the formula (1). do it. A conceptual diagram of such control is shown in FIGS. 8A and 8B. 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 brightness control parameters in the unit 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".

Then, based on the conversion table stored in the storage device 72, each of the values x _R , x _G , x _B of the input signal [R, G, B] is converted into a corresponding integer (pulse width) in the range of 0-255. Value of the modulated output signal). Thus, 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 41, 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-120]
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 surfaces provided corresponding to the surface light source unit 41. 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. 4).

[Step-130]
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 41, 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

Then, 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 41 are LED driving circuits. 83, and from the LED drive circuit 83, the switching elements 84R, 84G, and 84B turn on time t _R based on the signal values corresponding to the on times t _R-ON , t _G-ON , and 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 85 is caused to flow to each of the light emitting diodes 43R, 43G, 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. 9A and 9B. FIG. 9A shows an input signal input to the liquid crystal display device driving circuit 90 to drive the sub-pixels. 9 is a diagram schematically showing a relationship between a value obtained by raising the value of x to the power of 2 (x′≡x ^2.2 ) and a 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-140]
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 (3-1), (3-2), and (3-3): 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 41 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 first to second embodiments, the light source luminance Y ₂ changes for each image display frame, and therefore the display luminance / second specified value y ₂ is obtained at the light source luminance Y ₂ (≦ Y ₁ ). As described above, the values X _R , X _G , and X _B of the control signal [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 expressions (3-1), (3-2), and (3-3) 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 ) (3-1)
X _G = f _G (b 1 _—G · x _G ^2.2 + b 0 _—G ) (3-2)
X _B = f _B (b 1 _—B · x _B ^2.2 + b 0 _—B ) (3-3)

  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 configurations and structures of the transmissive color liquid crystal display device, the planar light source device, the light guide block, the planar light source unit, the liquid crystal display assembly, and the drive circuit described in the embodiments are examples, and members constituting these The materials and the like are also examples and can be appropriately changed.

  In the first embodiment, the light reflection layer is provided on the entire side surface of the light guide block. However, in some cases, the light reflection layer is provided only at the lower portion (for example, the lower 2/3 region) of the side surface of the light guide block. It is good also as a structure which provides. In addition, although the light diffusion / transmission layer is provided on the top surface of the light guide block corresponding to the light output surface, the light diffusion / transmission layer may be provided uniformly on the top surface of the light guide block. Depending on the case, the characteristics of the light diffusion / transmission layer may be changed for each portion of the top surface of the light guide block. Specifically, for example, the characteristics of the light diffusion / transmission layer in the outer peripheral portion of the top surface of the light guide block may be different from the characteristics of the light diffusion / transmission layer in the center portion of the top surface of the light guide block. Good.

  FIG. 1B shows a modification of the light guide block in the first embodiment. In this modification, the entire top surface 42A of the light guide block 42 is a curved surface that protrudes downward. The outer peripheral portion of the top surface 42A of the light guide block 42 is composed of an upwardly convex curved surface. Further, the inner surface 42D of the light guide block 42 is composed of a combination of an upward convex curved surface and a downward convex curved surface.

  FIG. 1C shows another modification of the light guide block in the first embodiment. In this modification, the inner surface 42D of the light guide block 42 has a plurality of locations (for example, two locations, 4 locations, and the like). The light emitting element disposed in the light guide block 42 and spaced from the inner surface 42D of the light guide block 42, that is, the light emitting element disposed in the space surrounded by the inner surface 42D. Is a set of (one red light-emitting diode, one green light-emitting diode) and is a light-emitting element disposed inside the light guide block 42 apart from the other inner surface 42D of the light guide block 42, ie, the other The light emitting elements arranged in the space surrounded by the inner surface 42D are a set of (one blue light emitting diode, one green light emitting diode).

  Luminance compensation (correction) and temperature control of the planar light source unit 41 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 80. 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.

FIGS. 1A, 1B, and 1C are schematic end views of the planar light source unit in Example 1 and its modifications, respectively. 2A and 2B are schematic end views of a planar light source unit constituting the planar light source device of Example 2, and diagrams showing a schematic planar shape of the planar light source unit. is there. FIG. 3 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. 4 is a conceptual diagram of a portion of a drive circuit suitable for use in the embodiment. FIG. 5A is a diagram schematically showing the arrangement and arrangement of light emitting diodes and the like in the surface light source device of the example, and FIG. 5B is a color liquid crystal display device and surface of the example. It is a typical partial cross section figure of the liquid crystal display device assembly which consists of a planar light source device. FIG. 6 is a schematic partial cross-sectional view of a color liquid crystal display device. FIG. 7 is a flowchart for explaining a driving method of the liquid crystal display device assembly according to the first embodiment. (A) and (B) of FIG. 8 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 . FIG. 9A shows a value (x′≡x ^2.2 ) obtained by multiplying the value of the input signal input to the liquid crystal display device driving circuit to drive the sub-pixel by the power of ^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.

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, 25 ... Alignment film, 26 ... Polarizing film, 30 ... Rear panel, 31 ... Second 32 ... switching element, 34 ... transparent second electrode, 35 ... alignment film, 36 ... polarizing film, 37 ... insulating layer, 40, 140 ... planar light source device , 41, 141 ... planar light source unit, 42, 142 ... light guide block, 42A, 142A ... top surface of light guide block, 42B, 142B ... bottom surface of light guide block, 42C, 142C ... Side surfaces of light guide blocks, 42D, 14 D: inner surface of light guide block, 43, 43R, 43G, 43B ... light emitting diode (light source), 44, 144, 144B ... light reflection layer, 45 ... light diffusion / transmission layer, 46 ..Support member, 146... Light diffusion / reflection layer, 147... Opening, 148... Lens, 51. , 53 .. Outer frame, 54... Inner frame, 55 A, 55 B... Spacer, 56... Guide member, 57... Bracket member, 61. Prism sheet, 63 ... polarization conversion 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 (memo ), 83 ... LED driving circuit, 84R, 84G, 84B ... switching device, 85 ... light-emitting diode driving power supply, 90 ... liquid crystal display device drive circuit, 91 ... timing controller

Claims (6)

A planar light source device for illuminating a transmissive liquid crystal display device having a display area composed of pixels arranged in a two-dimensional matrix from the back,
It is composed of P × Q planar light source units corresponding to the P × Q display area units when assuming that the display area of the liquid crystal display device is divided into P × Q virtual display area units,
Each planar light source unit
(A) a light guide block having a top surface, a bottom surface, a side surface, and an inner surface extending from the bottom surface to the inside; and
(B) a light source comprising a light emitting element disposed inside the light guide block, spaced from the inner surface of the light guide block;
With
The light emitted from the light emitting element enters the inside from the inner surface of the light guide block,
A light reflection layer is provided on the side of the light guide block,
A planar light source device, wherein a light diffusion / transmission layer is provided on a top surface of a light guide block corresponding to a light emitting surface. A planar light source device for illuminating a transmissive liquid crystal display device having a display area composed of pixels arranged in a two-dimensional matrix from the back,
It is composed of P × Q planar light source units corresponding to the P × Q display area units when assuming that the display area of the liquid crystal display device is divided into P × Q virtual display area units,
Each planar light source unit
(A) a light guide block having a top surface, a bottom surface, a side surface, and an inner surface extending from the bottom surface to the inside; and
(B) a light source comprising a light emitting element disposed inside the light guide block, spaced from the inner surface of the light guide block;
With
The light emitted from the light emitting element enters the inside from the inner surface of the light guide block,
A light reflection layer is provided on the side of the light guide block,
A light diffusion / reflection layer is provided on a part of the top surface of the light guide block.
A planar light source device, wherein the top surface of the light guide block is exposed in the remaining portion of the top surface of the light guide block.   The top surface of the light guide block is configured by any one of a flat surface, a curved surface convex upward, a curved surface convex downward, or a combination thereof. A planar light source device. (A) a transmissive liquid crystal display device having a display area composed of pixels arranged in a two-dimensional matrix, and
(B) From the P × Q planar light source units corresponding to the P × Q display area units when it is assumed that the display area of the liquid crystal display device is divided into P × Q virtual display area units. A planar light source device for illuminating a liquid crystal display device from the back,
A liquid crystal display device assembly comprising:
Each planar light source unit
(A) a light guide block having a top surface, a bottom surface, a side surface, and an inner surface extending from the bottom surface to the inside; and
(B) a light source comprising a light emitting element disposed inside the light guide block, spaced from the inner surface of the light guide block;
With
The light emitted from the light emitting element enters the inside from the inner surface of the light guide block,
A light reflection layer is provided on the side of the light guide block,
A liquid crystal display device assembly, wherein a light diffusion / transmission layer is provided on a top surface of a light guide block corresponding to a light emitting surface. (A) a transmissive liquid crystal display device having a display area composed of pixels arranged in a two-dimensional matrix, and
(B) From the P × Q planar light source units corresponding to the P × Q display area units when it is assumed that the display area of the liquid crystal display device is divided into P × Q virtual display area units. A planar light source device for illuminating a liquid crystal display device from the back,
A liquid crystal display device assembly comprising:
Each planar light source unit
(A) a light guide block having a top surface, a bottom surface, a side surface, and an inner surface extending from the bottom surface to the inside; and
(B) a light source comprising a light emitting element disposed inside the light guide block, spaced from the inner surface of the light guide block;
With
The light emitted from the light emitting element enters the inside from the inner surface of the light guide block,
A light reflection layer is provided on the side of the light guide block,
A light diffusion / reflection layer is provided on a part of the top surface of the light guide block.
A liquid crystal display device assembly, wherein the top surface of the light guide block is exposed in the remaining portion of the top surface of the light guide block. The top surface of the light guide block is configured by any one of a flat surface, a curved surface convex upward, a curved surface convex downward, or a combination thereof. Liquid crystal display assembly.

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