JP2007324047A - Surface light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device having a structure which hardly generates luminance unevenness between adjacent surface light source units. <P>SOLUTION: The surface light source device for lighting a transmissive liquid crystal display device from a rear surface is provided with a diffusing plate 61, and is formed of P×Q surface light source units 42. Light sources 41 provided in the surface light surface units 42 are respectively controlled. A barrier rib 44 partitions between the surface light source unit 42 and the surface light source unit 42. A clearance exists between a top face 45 of the barrier rib 44 and the diffusing plate 61. The barrier rib 44 is formed of a transparent material. In letting a thickness direction of the barrier rib as an X direction, an extending direction as a Y direction, and a height direction as a Z direction, a length along the X direction of a part 45' corresponding to the top face 45 of the barrier rib 44 in a barrier wall cross sectional shape when the barrier rib 44 is cut in an XZ plane passing a center of the light source 41 is longer than a length along the X direction of other part of the barrier rib 44 in the barrier rib cross sectional shape. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a planar light source device.

  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. In the color liquid crystal display device, one pixel includes, for example, three sub-pixels of a red light-emitting sub pixel, a green light-emitting sub pixel, and a blue light-emitting sub pixel. 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.

  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. 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.

Such a planar light source device is controlled based on the method described below. That is, the maximum luminance of each planar light source unit constituting the planar light source device is set to Y _max, and the maximum value (specifically, for example, 100%) of the light transmittance (aperture ratio) of the pixel in the display area unit. Let Lt _max . Further, when each planar light source unit constituting the planar light source device has the maximum luminance Y _max , the light transmittance (aperture ratio) of each pixel for obtaining the display luminance y ₀ of each pixel in the display area unit. Is Lt ₀ . Then, in this case, the light source luminance Y ₀ of each planar light source unit constituting the planar light source device is
Y ₀ · Lt _max = Y _max · Lt ₀
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 ₀ 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 the light source luminance Y ₀ 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 the light source luminance of 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.

JP-A-2005-258403

  By the way, as schematically shown in FIGS. 10A and 10B, a part of the light emitted from the light source 241 of a certain planar light source unit 242 is the first of the partition walls 244 facing the light source 241. Is incident from the side surface 246A, passes through the partition wall 244, is emitted from the second side surface 246B opposite to the first side surface 246A, and enters the adjacent planar light source unit 242. Note that FIG. 10B is an enlarged view of the vicinity of the top surface 245 of the partition 244 shown in FIG. Further, a light beam (indicated by a dotted line in FIGS. 10A and 10B) that is incident from the first side surface 246A of the partition wall 244, passes through the partition wall 244, and collides with the top surface 245 of the partition wall 244, Usually, the light is totally reflected at the top surface 245 of the partition wall 244 and returns to the inside of the partition wall 244. Here, the light beams emitted from the light source 241 of the planar light source unit 242 collide with the regions indicated by “A” and “B” of the diffuser plate 261, but are indicated by “C” of the diffuser plate 261. The light beam emitted from the light source 241 of the planar light source unit 242 does not collide with the area. Therefore, a kind of shadow of the partition wall 244 is generated, the luminance of the region “C” of the diffusion plate 261 is lowered, and luminance unevenness occurs in the diffusion plate 261. This luminance unevenness occurs even when the partition 244 is made of a transparent material. If luminance unevenness occurs in the diffuser plate 261, that is, if luminance unevenness occurs between adjacent planar light source units, the quality of image display deteriorates. If the height of the partition wall 244 is lowered, luminance unevenness between adjacent planar light source units is reduced, but the influence of the light source luminance of one planar light source unit 242 on the light source luminance of another planar light source unit 242 is affected. growing. In FIG. 10A, reference numeral 252A indicates the bottom surface of the casing constituting the planar light source device.

  Even when the cross-sectional shape of the partition wall 244 is a triangle with the bottom face down, the light transmitted through the partition wall 244 is refracted by the partition wall 244 and irradiates a wider area of the diffusion plate 261, so that the region “C "Is more widened and does not lead to a reduction in luminance unevenness.

  Accordingly, an object of the present invention is to provide a planar light source device having a structure in which luminance unevenness hardly occurs between adjacent planar light source units.

In order to achieve the above object, a planar light source device of the present invention is a planar light source device that illuminates a transmissive liquid crystal display device having a display region composed of pixels arranged in a two-dimensional matrix from the back. There,
It has a diffusion plate that faces the liquid crystal display device,
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,
The light sources provided in the planar light source unit are individually controlled,
The planar light source unit and the planar light source unit are partitioned by a partition wall,
There is a gap between the top surface of the partition and the diffusion plate,
The partition wall is made of a material that is transparent to the light emitted from the light source constituting the planar light source unit,
When the partition wall thickness direction is the X direction, the partition wall extending direction is the Y direction, and the partition wall height direction is the Z direction, the partition wall top shape in the partition wall cross-sectional shape when the partition wall is cut along the XZ plane passing through the center of the light source. The length along the X direction of the portion corresponding to the surface is longer than the length along the X direction of the other portion of the partition wall in the partition wall cross-sectional shape.

  In the planar light source device of the present invention, the upper part of the partition cross-sectional shape is an isosceles trapezoid, the lower part of the partition cross-sectional shape is a rectangle, and the upper side of the isosceles trapezoid corresponds to the top surface of the partition wall in the partition cross-sectional shape. A configuration corresponding to the portion is preferable. In this case, the side surface of the lower part of the partition wall having a rectangular partition wall cross-sectional shape is preferably a surface that reflects the light emitted from the light source provided in the planar light source unit. It is preferable that the side surface of the upper part of the partition wall that is an isosceles trapezoid is a surface that diffuses and transmits light emitted from the light source provided in the planar light source unit.

Moreover, in the planar light source device of the present invention including the preferred configuration described above,
An intersection point between the portion corresponding to the top surface of the partition wall in the partition wall cross-sectional shape and the portion corresponding to the first side surface located on the light source side of the partition wall in the partition wall cross-sectional shape is defined as an intersection point A,
An intersection point between a portion corresponding to the top surface of the partition wall in the partition wall cross-sectional shape and a portion corresponding to the second side surface facing the first side surface of the partition wall in the partition wall cross-sectional shape is defined as an intersection point B,
When the point where the straight line connecting the center D of the light source and the intersection A intersects the diffuser plate is defined as the intersection C,
A light beam emitted from a light source provided in the planar light source unit, incident from the first side surface of the partition wall, and emitted from the second side surface portion of the partition wall corresponding to the intersection point B collides with the intersection point C. It is preferable to do.

  In the planar light source device of the present invention, the partition wall is made of a material transparent to the light emitted from the light source constituting the planar light source unit. Specifically, the partition wall is made of polycarbonate resin, acrylic resin, polyethylene terephthalate (PET). ) Resins and glass can be mentioned. Further, as a method for making the light emitted from the light source provided in the planar light source unit a surface that diffuses and transmits, that is, as a method for imparting a light diffusing and transmitting function to the partition surface, for example, the partition wall surface based on the sandblast method And a method of forming a concavo-convex layer, and a method of attaching a film (light diffusive transmission film) having concavo-convex on the partition wall surface using an adhesive or an adhesive sheet.

  In the planar light source device of the present invention including the preferred embodiments and configurations described above (hereinafter, these may be collectively referred to simply as the planar light source device of the present invention), the top surface of the partition wall and the diffusion plate There is a gap between them. The value of the gap is a value determined by the height from the light source to the diffusion plate, for example, the inclination of the side surface of the isosceles trapezoid, the width of the top surface, and the distance from the light source to the partition wall. Note that when the liquid crystal display device is used, the liquid crystal display device is disposed substantially vertically, so the value of the gap is the value in this state.

  In the planar light source device of the present invention, examples of the material constituting the diffusion plate include polymethyl methacrylate (PMMA) and polycarbonate resin (PC).

  In the planar light source device of the present invention, one planar light source unit is surrounded by four partition walls, or is surrounded by three partition walls and one side surface of a housing (described later), or alternatively, It is surrounded by two sides of the partition and the housing.

  In the planar light source device of the present invention, the light source of the planar light source unit constituting the planar light source device may include a light emitting diode (LED), or a cold cathode ray fluorescent lamp, electroluminescence ( EL) devices, cold cathode field electron emission devices (FED), plasma display devices, and ordinary lamps. When the light source is composed of a light emitting diode, for example, a red light emitting diode that emits red light with a wavelength of 640 nm, for example, a green light emitting diode that emits green light with a wavelength of 530 nm, and a blue light emitting diode that emits blue light with a wavelength of 450 nm, for example. It can be configured to obtain white light, or white light can be obtained by light emission of a white light emitting diode (for example, a light emitting diode that emits white light by combining an ultraviolet or blue light emitting diode and phosphor particles). You may further provide the light emitting diode which light-emits 4th color other than red, green, blue, 5th color ....

  When the light source is composed of light emitting diodes, a plurality of red light emitting diodes that emit red light, a plurality of green light emitting diodes that emit green light, and a plurality of blue light emitting diodes that emit blue light are arranged and arranged in a housing. Has been. 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) A light source can be composed of a light emitting diode unit composed of a combination of a light emitting diode, two green light emitting diodes, and one blue light emitting diode). One planar light source unit is provided with at least one light emitting diode unit.

  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) 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.

  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 ... Maximum value of drive signal values input to the drive circuit to drive all the pixels constituting the display area unit when the light source brightness is the light source brightness / first specified value Y _1. The light transmittance of the pixel or sub-pixel when it is assumed that a control signal corresponding to the drive signal having a value equal to the value within the display area unit x _U-max is supplied to the pixel or sub-pixel. Hereinafter, it may be referred to as light transmittance / second prescribed value. 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 ... It is assumed that a control signal corresponding to a drive signal having a value equal to the drive signal maximum value x _U-max is supplied to the pixel or sub-pixel, and the pixel or sub-pixel at this time 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 of the present invention is driven, the luminance of the pixel when it is assumed that a control signal corresponding to the drive signal having a value equal to the drive area maximum value x _U-max in the display area unit is supplied to the pixel ( The drive circuit controls the brightness of the light source constituting the planar light source unit corresponding to the display area unit so that the light transmittance, the display brightness at the first specified value Lt _1, and the second specified value y ₂ ) can be obtained. Specifically, for example, the light source luminance Y 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. 2} may be controlled (for example, it may be 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)

  The drive circuit is, for example, a planar light source device control circuit (back) composed of a pulse width modulation (PWM) signal generation circuit, a duty ratio control circuit, a light emitting diode (LED) drive circuit, an arithmetic circuit, a storage device (memory), etc. A light control unit and a planar light source unit driving circuit), and a liquid crystal display device driving circuit including a known circuit such as a timing controller.

  When the light emitted from the light emitting diode is directly incident on the liquid crystal display device positioned above, that is, when the light is emitted from the light emitting diode exclusively along the z-axis direction, the surface light source device has uneven luminance. May occur. As a means for avoiding such a phenomenon, a light emitting diode assembly in which a light extraction lens is attached to a light emitting diode is used as a light source, and a part of the light emitted from the light emitting diode is reflected on the top surface of the light extraction lens. And a two-dimensional direction emission configuration in which the light is totally reflected and emitted mainly in the horizontal direction of the light extraction lens.

  The planar light source device may 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 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.

  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 (sub-pixel [R]) that constitutes each pixel (pixel) is composed of a combination of the region and a color filter that transmits red, and green. The light emitting sub-pixel (sub-pixel [G]) is composed of a combination of the region and a color filter that transmits green, and the blue light-emitting sub-pixel (sub-pixel [B]) is a color filter that transmits the region and blue. It is comprised from the combination. 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 sub-pixels of a red light-emitting subpixel, a green light-emitting subpixel, and a blue light-emitting subpixel are configured as one set. Alternatively, one set including a plurality of sub-pixels (for example, one set including a sub-pixel emitting white light for improving luminance, one set adding a sub-pixel emitting sub-color to expand a color reproduction range, In order to expand the color reproduction range, one set including a sub-pixel emitting yellow and one set including a sub-pixel emitting yellow and cyan in order to expand the color reproduction range may be used.

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), and some other image display resolutions. 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.

  In the planar light source device of the present invention, there is a gap between the top surface of the partition wall and the diffusion plate, and the partition wall is made of a material that is transparent to the light emitted from the light source constituting the planar light source unit. The length along the X direction of the part corresponding to the top surface of the partition wall in the partition wall cross-sectional shape is longer than the length along the X direction of the other part. Therefore, the light emitted from the light source provided in the planar light source unit is bent by the refraction, so that the shadow of the partition wall is not easily generated on the diffusion plate, and the uneven luminance between adjacent planar light source units. Therefore, it is possible to improve the quality of image display.

  Moreover, in the planar light source device of the present invention, the light emitted from the light source provided in the planar light source unit is incident from the first side surface of the partition wall and is emitted from the second side surface portion of the partition wall. However, in a planar light source unit adjacent to the conventional planar light source device, it collides with the diffusion plate region on the light source side, so that light from a certain planar light source unit is reflected by another planar light source unit. The influence on the light source luminance can be reduced. Further, if a light reflecting layer is formed on a part of the surface of the partition wall, the influence of light from a certain planar light source unit on the light source luminance of other planar light source units can be reduced.

Further, in the planar light source device of the present invention, the luminance of the pixel when it is assumed that the control signal corresponding to the drive signal having a value equal to the drive area 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 (light transmittance, display brightness at the first specified value Lt ₁ , second specified value y ₂ ) is obtained. For example, not only can the power consumption of the surface 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 (not including external light reflection on the screen surface of the liquid crystal display device) (Brightness ratio between the all-black display portion and the all-white display portion) and the brightness of a desired display area can be emphasized, so that the quality of image display can be improved.

  Hereinafter, the planar light source device of the present invention will be described based on embodiments with reference to the drawings. Prior to that, an outline of a transmissive color liquid crystal display device and a planar light source device suitable for use in each embodiment will be described. 3, FIG. 4, FIG. 5 (A) and (B), and FIG. 6, it demonstrates.

As shown in a conceptual diagram of FIG. 3, the transmissive color liquid crystal display device 10 of the _zero M along a first direction, N ₀ along the second direction, ₀ total M ₀ × N Are provided with a display region 11 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). 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 planar light source units 42 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 light emitting subpixels (subpixel [R]), a green light emitting subpixel (subpixel [G]), and a blue light emitting subpixel (subpixel [B]). It consists 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 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 from the back. The light sources provided in the planar light source unit 42 are individually controlled. 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 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 includes a light emitting diode 41 driven based on a pulse width modulation (PWM) control method.

  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. A 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 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 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 is formed by the light emitted from the plurality of light emitting diodes 41 (light sources 41), the side surface 52B of the housing 51, or in some cases, (A), (B) in FIG. ), (B), or the light reflected by the partition walls 44 and 144 shown in FIG. Thus, the light is emitted from a plurality of red light emitting diodes 41R (light source 41R) that emits red light, a plurality of green light emitting diodes 41G (light source 41G) that emits green light, and a plurality of blue light emitting diodes 41B (light source 41B) that emit blue light. The red light, green light, and blue light thus mixed are mixed, and white light with high color purity can be obtained as illumination light. The illumination light passes through the optical function sheet group such as the diffusion plate 61, the diffusion sheet 62, the prism sheet 63, and the polarization conversion sheet 64, and irradiates the color liquid crystal display device 10 from the back side.

  In the vicinity of the bottom surface 52A of the housing 51, photodiodes 43R, 43G, and 43B, which are optical sensors, are arranged. The photodiode 43R is a photodiode with a red filter attached to measure the light intensity of red light, and the photodiode 43G is a photo diode with a green filter attached to measure the light intensity of green light. The photodiode 43B 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 43R, 43G, 43B) is arranged in one planar light source unit 42. The light emission states of the light sources 41R, 41G, and 41B measured by the photodiodes 43R, 43G, and 43B that are optical sensors are the luminance and chromaticity of the light emitting diodes 41R, 41G, and 41B.

  The arrangement state of the light emitting diodes 41R, 41G, and 41B includes, for example, a red light emitting diode 41R that emits red light (for example, a wavelength of 640 nm), a green light emitting diode 41G that emits green light (for example, a wavelength of 530 nm), and a blue light (for example, A plurality of light emitting diode units each including a blue light emitting diode 41B that emits light having a wavelength of 450 nm may be arranged in a horizontal direction and a vertical direction. In this case, one light emitting diode unit is arranged in one planar light source unit 42, and the center of the light emitting diode unit corresponds to the center of the light source.

  The planar light source unit 42 and the planar light source unit 42 constituting the planar light source device 40 are partitioned by partition walls 44 and 144. One planar light source unit 42 is surrounded by four partition walls 44 and 144, or alternatively, surrounded by three partition walls 44 and 144 and one side surface 52B of the casing 51, or alternatively, two partition walls 44 and 144. And two side surfaces 52B of the casing 51. The partition walls 44 and 144 are attached to the bottom surface 52 </ b> A of the housing 51 via attachment members (not shown).

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 a driving signal from the outside (display circuit) is based on the pulse width modulation control method. Backlight control unit 70 and planar light source unit driving circuit 80 for performing on / off control of the red light emitting diode 41R, green light emitting diode 41G and blue light emitting diode 41B constituting the light source device 40, and a liquid crystal display device driving circuit 90 It is composed of The backlight control unit 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 and the like constituting the backlight control unit 70 and the planar light source unit driving 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. The light emitting states of the light emitting diodes 41R, 41G, and 41B in an image display frame are measured by the photodiodes 43R, 43G, and 43B, and the outputs from the photodiodes 43R, 43G, and 43B are input to the photodiode control circuit 84, and the photo In the diode control circuit 84 and the arithmetic circuit 81, for example, data (signals) as the luminance and chromaticity of the light emitting diodes 41R, 41G, and 41B are transmitted to the LED driving circuit 83, and light emission in the next image display frame is performed. A feedback mechanism is formed in which the light emission states of the diodes 41R, 41G, and 41B are controlled. Further, resistors r _R , r _G , r _B for current detection are inserted in series with the light emitting diodes 41R, 41G, 41B downstream of the light emitting diodes 41R, 41G, 41B, 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, FIG. 4 shows one light emitting diode driving power source (constant current source) 86, but actually, the light emitting diode driving power source for driving each of the light emitting diodes 41R, 41G, and 41B. 86 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. It is arranged in a two-dimensional matrix and is located at the qth row and the pth column [where q = 1, 2,..., Q and p = 1, 2,. The display area unit and the planar light source unit to be displayed are represented as a display area unit 12 _{(q, p)} and a planar light source unit 42 _{(q, p)} , respectively, and the display area unit 12 _{(q, p)} or the planar light source. The subscript “(q, p)” or “-(q, p)” may be added to the elements and items related to the unit 42 _{(q, p)} . Here, 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 emission control signal, the green light emission control signal, and the blue light emission control signal input to [R, G, B] may be collectively referred to as “control signal [R, G, B]”. , A red light emission subpixel drive signal, a green light emission subpixel drive signal, and a blue light emission subpixel drive that are input from the outside to the drive circuit to drive the subpixels [R, G, B] constituting the display area unit. The signals may be collectively referred to as “driving signals [R, G, B]”.

Each pixel has three subpixels (subpixels): a subpixel [R] (red light emitting subpixel), a subpixel [G] (green light emitting subpixel), and a subpixel [B] (blue light emitting subpixel). However, in the description of the following embodiments, the luminance control (gradation control) of each of the sub-pixels [R, G, B] is 8-bit control, and 2 from 0 to 255. ^{This is} done in ⁸ stages. Therefore, the value of the drive signal [R, G, B] input to the liquid crystal display device drive 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 41R, the green light emitting diode 41G, and the blue light emitting diode 41B 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, the control signal [R, G, B] is generated from the input drive signal [R, G, B], and the control signal [R, G, B] is subpixel. [R, G, B] are supplied (output). 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 changes the value of the drive signal [R, G, B]. 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. Then, a 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 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 value of the control signal [R, G, B], the higher the light transmittance (subpixel aperture ratio) Lt of the subpixel [R, G, B], and the subpixel [R, G, B]. B] brightness (display brightness y) increases. That is, an image (usually one kind of dot-like) composed of light passing through the sub-pixels [R, G, B] 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 of the present invention. Partial conceptual diagrams of the planar light source device of Example 1 are shown in FIGS. 1A and 1B. The planar light source device 40 according to the first embodiment is a planar light source device that illuminates a transmissive color liquid crystal display device 10 having a display region 11 composed of pixels arranged in a two-dimensional matrix from the back. The planar light source device 40 according to the first embodiment includes a diffusion plate 61 that faces the color liquid crystal display device 10. The display region 11 of the color liquid crystal display device 10 is converted into P × Q virtual display region units 12. It is composed of P × Q planar light source units 42 corresponding to these P × Q display area units 12 when it is assumed that they are divided. Here, the light sources 41 (41R, 41G, 41B) provided in the planar light source unit 42 are individually controlled. However, the light source luminance of the planar light source unit 42 is affected by the light emission state of the light sources 41 (41R, 41G, 41B) provided in the other planar light source units 42. It is desirable to control the light emission state of the light source 41.

As shown in partial conceptual diagrams in FIGS. 1A and 1B, the planar light source unit 42 and the planar light source unit 42 are partitioned by a partition wall 44, and the top surface of the partition wall 44. There is a gap (value: Gp ₁ ) between 45 and the diffusion plate 61. The partition 44 is made of a material transparent to the light emitted from the light source 41 constituting the planar light source unit 42, specifically, a polycarbonate resin (refractive index n ₀ = 1.59). When the thickness direction of the partition wall 44 is the X direction, the extending direction of the partition wall 44 is the Y direction, and the height direction of the partition wall 44 is the Z direction, as shown in FIG. The length along the X direction of the portion 45 ′ corresponding to the top surface 45 of the partition wall 44 in the partition wall cross-sectional shape when the partition wall 44 is cut along the XZ plane passing through is the X direction of the other part of the partition wall 44 in the partition wall cross-sectional shape. Longer than the length along.

  More specifically, the upper part 47A of the partition wall cross-sectional shape is an isosceles trapezoid, the lower part 47B of the partition wall cross-sectional shape is a rectangle, and the upper side of the isosceles trapezoidal shape corresponds to the top surface 45 of the partition wall 44 in the partition wall cross-sectional shape. Corresponds to portion 45 '. In addition, the height of the lower part 47B is 10 mm, and the thickness of the lower part 47B is 1 mm.

An intersection point of a portion 45 ′ corresponding to the top surface 45 of the partition wall 44 in the partition wall cross-sectional shape and a portion 46A ′ corresponding to the first side surface 46A located on the light source side of the partition wall in the partition wall cross-sectional shape is an intersection point A (−a ₁ , B ₁ ). Further, an intersection of a portion 45 ′ corresponding to the top surface 45 of the partition wall 44 in the partition wall cross-sectional shape and a portion 46B ′ corresponding to the second side surface 46B facing the first side surface 46A of the partition wall in the partition wall cross-section shape is an intersection. Let B (a ₁ , b ₁ ). Furthermore, a point where a straight line LN ₁₁ connecting the center D (−a ₀ , 0) of the light source 41 and the intersection point A intersects with the diffusion plate 61 is defined as an intersection point C (a ₂ , b ₂ ). However, a ₀ > 0, a ₂ > a ₁ > 0, and b ₂ > b ₁ > 0. Here, b ₂ = 30 mm.

At this time, a light beam emitted from the light source 41 provided in the planar light source unit 42, incident from the first side surface 46A of the partition wall 44, and emitted from the second side surface 46B portion of the partition wall 44 corresponding to the intersection B. (Indicated by straight lines LN ₂₁ and LN ₂₂ in FIG. 1B) collides with the intersection C. Therefore, the light that has entered the inside of the partition wall 44 from the first side surface 46A of the partition wall 44 and collided with the top surface 45 of the partition wall 44 is totally reflected at the top surface 45 of the partition wall 44 and returns to the inside of the partition wall 44. Unlike the state shown in FIGS. 10A and 10B, the partition 44 is not shaded. Accordingly, it is possible to reliably avoid the phenomenon that the luminance of the diffusion plate 61 is lowered and the luminance unevenness occurs in the diffusion plate 61. That is, luminance unevenness does not occur between adjacent planar light source units, so that the image display quality does not deteriorate.

  When the height of the partition wall is 2/3 of the distance from the light source to the diffusion plate, the value of the width of the top surface of the partition wall is as follows.

a ₀ = 15 mm
a ₁ = 1.17 mm
b ₁ = 20 mm
a ₂ = 5.67 mm

In Embodiment 1 or Embodiments 2 to 3 to be described later, 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. In each of the planar light source units 42 _{(q, p)} , all the pixels (sub-pixels [R, G, B] _{(q, p)} ) constituting each display area unit 12 _{(q, p} ) are driven. In order to achieve this, the values x _{R- (q, p)} , x _{G- (q,} x _{) of} the drive signals [R, G, B] _{(q, p)} input to the drive circuits 70, 80 _{(q, p)} , 90 _p) , x _{B- (q, p)} is the maximum value within the display area unit / drive signal maximum value x _{U-max (q, p).} Of the pixel (sub-pixel [R, G, B] _{(q, p)} ) (light transmittance, display brightness at the first specified value Lt ₁ , second specified value y _{2− ( q, p)} ) is obtained so that the luminance of the light source 41 _{(q, p)} constituting the planar light source unit 42 _{(q, p)} corresponding to the display area unit 12 _{(q, p)} is the planar light source. Control is performed by the unit drive circuit 80 _{(q, p)} .

  Hereinafter, the driving method of the liquid crystal display device assembly according to the first embodiment or the second to third embodiments described later will be described with reference to FIGS.

[Step-100]
The drive signal [R, G, B] and the clock signal CLK for one image display frame sent from a known display circuit such as a scan converter are input to the backlight control unit 70 and the liquid crystal display device drive circuit 90 ( (See FIG. 3). The drive signals [R, G, B] are output signals from the image pickup tube, for example, when y ′ is the input light quantity to the image pickup tube. Is a drive signal that is also input to the liquid crystal display device drive circuit 90 to control the above, and can be expressed as a function of the input light amount y ′ to the power of 0.45. Then, the values x _R , x _G , x _B of the drive signals [R, G, B] for one image display frame input to the backlight control unit 70 are stored in a storage device (memory) constituting the backlight control unit 70. ) 72 is temporarily stored. Further, the values x _R , x _G , x _B of the drive signals [R, G, B] for one image display frame input 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 backlight control unit 70, the value of the drive signal [R, G, B] stored in the storage device 72 is read and the (p, q) th [however, first, p = 1, q = 1] in the display area unit 12 _{(q, p)} , the sub-pixels [R, G in all the pixels constituting the (p, q) -th display area unit 12 _{(q, p)} , B] _{(q, p)} for driving the signals [R, G, B] _{(q, p)} x _{R- (q, p)} , x _{G- (q, p)} , x _{B- In} the display area unit / drive signal maximum value x _{U-max (q, p)} , which is the maximum value of _{(q, p)} , is obtained by the arithmetic circuit 71. The in-display area unit / drive signal maximum value x _{U-max (q, p)} 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, x _{R- (q, p)} is a value corresponding to “110”, x _{G- (q, p)} is a value corresponding to “150”, and x _{B- (q, p)} is “ In the case of a value corresponding to “50”, x _{U−max (q, p)} is a value corresponding to “150”.

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

Then, the control signal [R, G, B corresponding to the drive signal [R, G, B] _{(q, p)} having a value equal to the in-display area unit / maximum drive signal value x _{U-max (q, p).} ] _{(Q, p)} is assumed to be supplied to the sub-pixel [R, G, B] _{(q, p)} (light transmittance, display brightness at the first specified value Lt ₁ , second specified value y) _{2- (q, p))} as obtained by the surface light source unit 42 _{(q, p),} the light source luminance of the planar light source unit 42 corresponding to the display area unit _{12 (q, p) (q} , p) Y _{2- (q, p)} is increased or decreased under the control of the planar light source unit drive circuit 80 _{(q, p)} . 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 41 _{(q, p)} is controlled based on the formula (2) which is the light source brightness control function g (x _nol-max ), and the light source is set so as to satisfy the formula (1). The luminance Y ₂ may be controlled. A conceptual diagram of such control is shown in FIGS. 7A and 7B. However, as described later, the correction based on the influence of other planar light source units 42, it is necessary to apply to the light source luminance Y _2. 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 drive signal having a value equal to the maximum value x _U-max in the display area unit and the drive 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 between the 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, driving signals (driving signals [R, G, B]) input to the liquid crystal display device 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 of the drive signals [R, G, B], x G, 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, for example, assuming brightness control of the planar light source unit 42 _(1,1) of (p, q) = (1,1), other P × Q pieces It is necessary to consider the influence from the planar light source unit 42. 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, what is necessary is just to obtain | _require matrix [L' _PxQ ] from Formula (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 41 _{(q, p)} may be controlled so that the luminance represented by the matrix [L ′ _PxQ ] is obtained. Specifically, the operation and processing are stored in the storage device (memory) 82. What is necessary is just to perform using the information (data table). In the control of the light source 41 _{(q, p)} , since the value of the matrix [L ′ _PxQ ] cannot take a negative value, it is needless to say that 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 ] and the correction coefficient matrix [α _PxQ ] obtained based on the values of the equations (1) and (2) obtained in the arithmetic circuit 71 constituting the backlight control unit 70 are obtained. As described above, the luminance matrix [L ′ _PxQ ] is _calculated when it is assumed that the planar light source unit is driven alone. Further, based on the conversion table stored in the storage device 72, 0 to 255 is obtained. Convert to a corresponding integer in the range. Thus, the value of the pulse width modulation output signal for controlling the light emission time of the red light emitting diode 41R _{(q, p) in} the planar light source unit 42 _{(q, p)} in the arithmetic circuit 71 constituting the backlight control unit 70. S _{R- (q, p),} a green light emitting diode 41G _{(q, p)} of the pulse width modulation output signal for controlling the light emission time of the value S _{G- (q, p),} the blue light emitting diode 41B _{(q, p )} , The value S _{B− (q, p)} of the pulse width modulation output signal for controlling the light emission time can be obtained.

[Step-120]
Next, the values S _{R- (q, p)} , S _{G- (q, p)} , S _{B- (q, p ) of} the pulse width modulation output signal obtained in the arithmetic circuit 71 constituting the backlight control unit 70. ₎ Is sent to the storage device 82 of the planar light source unit drive circuit 80 _{(q, p)} provided corresponding to the planar light source unit 42 _{(q, p)} and stored in the storage device 82. The clock signal CLK is also sent to the planar light source unit drive circuit 80 _{(q, p)} (see FIG. 4).

[Step-130]
Then, the planar light source unit 42 _{(q, p)} is configured based on the values S _{R- (q, p)} , S _{G- (q, p)} , S _{B- (q, p)} of the pulse width modulation output signal. ON time t _R-ON and OFF time t _{R-OFF of} the red light emitting diode 41R _{(q, p )} , ON time t _G-ON and OFF time t _{G-OFF of} the green light emitting diode 41G _{(q, p)} , blue The arithmetic circuit 81 determines the on time t _B-ON and the off time t _B-OFF of the light emitting diode 41B _{(q, p)} . 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 on-time t _{R− of} the red light emitting diode 41R _{(q, p)} , the green light emitting diode 41G _{(q, p)} , and the blue light emitting diode 41B _{(q, p)} constituting the planar light source unit 42 _{(q, p).} Signals corresponding to _{ON- (q, p)} , t _{G-ON- (q, p)} , t _{B-ON- (q, p)} are sent to the LED drive circuit 83, and from this LED drive circuit 83, Based on the value of the signal corresponding to the on-time tR _{-ON- (q, p)} , _{tG-ON- (q, p)} , _{tB-ON- (q, p)} , the switching element 85R _{(q, p )} , 85G _{(q, p)} , 85B _{(q, p)} are turned on times t _{R-ON- (q, p)} , t _{G-ON- (q, p)} , t _{B-ON- (q, p )} , The LED driving current from the light emitting diode driving power supply 86 is caused to flow to each of the light emitting diodes 41R _{(q, p)} , 41G _{(q, p)} , 41B _{(q, p)} . As a result, each of the light emitting diodes 41R _{(q, p)} , 41G _{(q, p)} , 41B _{(q, p)} has an on time t _{R-ON- (q, p)} , t _{G- in} one image display frame. Only _{ON- (q, p)} and t _{B-ON- (q, p)} emit light. Thus, the (p, q) -th display area unit 12 _{(q, p)} is illuminated at a predetermined illuminance.

The states obtained in this way are indicated by solid lines in FIGS. 8A and 8B. FIG. 8A shows a drive signal input to the liquid crystal display device drive 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.

On the other hand, the values x _{R- (q, p)} , x _{G- (q, p)} , x _{B- ( ) of} the drive signals [R, G, B] _{(q, p)} input to the liquid crystal display device driving circuit 90. _{q, p)} is sent to the timing controller 91. In the timing controller 91, a control signal [R, G, B] _{( q, p)} corresponding to the input drive signal [R, G, B] _{(q, p) ( q (p)} is supplied (output) to the sub-pixel [R, G, B] _{(q, p)} . Control signals [R, G, B] _(q 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] _{(q, p) , p)} values X _{R- (q, p)} , X _{G- (q, p)} , X _{B- (q, p)} and the value x of the drive signal [R, G, B] _{(q, p) R- (q, p)} , _{xG- (q, p)} , _{xB- (q, p)} are the following expressions (4-1), (4-2), and (4-3): Are in 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- (q, p)} of the planar light source unit 42 _{(q, p)} is changed for each image display frame, the control signal [R, G, B] _{(q, p)} In particular, correction (compensation) is performed on the value obtained by multiplying the value of the drive signal [R, G, B] _{(q, p) by} the power of 2.2 based on the change in the light source luminance Y _{2- (q, p).} Have a value. In other words, in the embodiment, since the light source luminance Y _{2− (q, p)} changes for each image display frame, the display luminance / second luminance is changed at the light source luminance Y _{2− (q, p)} (≦ Y ₁ ). 2 The values X _{R- (q, p)} , X _{G- (q, p)} , X of the control signal [R, G, B] _{(q, p)} so that the specified value y _{2-(q, p)} is obtained. X _{B- (q, p)} is 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- (q, p) =} f R (b 1_R · x R- (q, p) 2.2 + b 0_R) (4-1)
_{X G- (q, p) =} f G (b 1_G · x G- (q, p) 2.2 + b 0_G) (4-2)
_{X B- (q, p) =} f B (b 1_B · x B- (q, p) 2.2 + b 0_B) (4-3)

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

  The second embodiment is a modification of the first embodiment. FIG. 2 shows a partial conceptual diagram of the planar light source device of the second embodiment. In the second embodiment, the planar light source unit 42 is formed on the side surface of the partition wall lower portion 47B having a rectangular partition wall cross-sectional shape. A light reflection layer 48 that reflects light emitted from the light source 41 provided is provided. The light reflecting layer 48 forms a rough surface by sticking a light diffusing film having a substantially complete diffusive reflecting surface to the partition wall surface using an adhesive sheet, but the present invention is not limited to this. It is also possible to form a metal layer or alloy layer formed on the partition wall surface by a silver-enhanced reflection sheet or a light reflection film attached to the partition wall surface by using a plating method, a vapor deposition method, a sputtering method, or the like.

  The third embodiment is a further modification of the first embodiment. In the third embodiment, a light diffusion surface for transmitting and diffusing light emitted from the light source 41 provided in the planar light source unit 42 is formed on the side surface of the partition upper portion 47A whose partition sectional shape is an isosceles trapezoid. Has been. Specifically, a light transmission diffusion surface is formed by sticking a light transmission diffusion film having a haze of 80% to the surface of the upper partition wall 47A using an adhesive sheet. However, the present invention is not limited to this, and based on the sandblast method. A light diffusion surface can also be obtained by forming an uneven surface on the surface of the partition wall 44.

  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 planar light source unit, the liquid crystal display device assembly, and the drive circuit described in the embodiments are examples, and members, materials, and the like constituting these are also examples. This is an example, and can be changed as appropriate. Luminance compensation (correction) and temperature control of the planar light source unit 42 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.

1A and 1B are partial conceptual diagrams of a planar light source device including a partition wall and the like in the first embodiment. FIG. 2 is a partial conceptual diagram of a planar light source device including partition walls and the like in the second embodiment. 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. (A) and (B) of FIG. 7 show the display luminance when it is assumed that a control signal corresponding to a drive signal having a value equal to the drive region 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. 8A shows a value (x′≡x ^2.2 ) obtained by multiplying the value of the drive signal input to the liquid crystal display device drive 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. 9A and 9B are conceptual diagrams for explaining the relationship among the light source luminance of the planar light source device, the light transmittance (aperture ratio) of the pixel, and the display luminance in the display area. 10A and 10B are diagrams schematically showing a state in which a part of light emitted from a light source of a certain planar light source unit is incident on the partition wall and is emitted from the partition wall.

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 ... planar light source device 41 , 41R, 41G, 41B ... light emitting diode (light source), 42 ... planar light source unit, 43, 43R, 43G, 43B ... photodiode (light sensor), 44, 144 ... partition wall, 45 ... Top surfaces of partition walls, 46A, 46B -Side wall of partition wall, 47A ... Upper part of partition wall cross-sectional shape, 47B ... Lower part of partition wall cross-sectional shape, 48, 148 ... Light reflecting layer, 51 ... Housing, 52A ... Bottom surface of housing , 52B: side surface of casing, 53: outer frame, 54: inner frame, 55A, 55B ... spacer, 56 ... guide member, 57 ... bracket member, 61 ... Diffusion plate, 62 ... diffusion sheet, 63 ... prism sheet, 64 ... polarization conversion sheet, 65 ... reflection sheet, 70 ... backlight control unit, 71 ... arithmetic circuit, 72. ..Storage device (memory), 80... Planar light source unit drive circuit, 81... Arithmetic circuit, 82... Storage device (memory), 83. Control circuit, 85R, 85G, 85 ... switching device, 86 ... light-emitting diode driving power supply, 90 ... liquid crystal display device drive circuit, 91 ... timing controller

Claims (5)

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 has a diffusion plate that faces the liquid crystal display device,
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,
The light sources provided in the planar light source unit are individually controlled,
The planar light source unit and the planar light source unit are partitioned by a partition wall,
There is a gap between the top surface of the partition and the diffusion plate,
The partition wall is made of a material that is transparent to the light emitted from the light source constituting the planar light source unit,
When the partition wall thickness direction is the X direction, the partition wall extending direction is the Y direction, and the partition wall height direction is the Z direction, the partition wall top shape in the partition wall cross-sectional shape when the partition wall is cut along the XZ plane passing through the center of the light source. A planar light source device characterized in that the length along the X direction of the portion corresponding to the surface is longer than the length along the X direction of the other portion of the partition wall in the partition wall cross-sectional shape. The upper part of the bulkhead cross section is an isosceles trapezoid,
The lower part of the partition wall cross-sectional shape is rectangular,
The planar light source device according to claim 1, wherein an upper side of the isosceles trapezoid corresponds to a portion corresponding to a top surface of the partition wall in the partition wall cross-sectional shape.   3. The planar light source device according to claim 2, wherein a side surface of the lower part of the partition wall having a rectangular sectional shape is a surface that reflects light emitted from a light source provided in the planar light source unit. .   3. The surface according to claim 2, wherein a side surface of the upper portion of the partition wall having a trapezoidal cross-sectional shape is a surface that diffuses and transmits light emitted from a light source provided in the planar light source unit. Light source device. An intersection point between the portion corresponding to the top surface of the partition wall in the partition wall cross-sectional shape and the portion corresponding to the first side surface located on the light source side of the partition wall in the partition wall cross-sectional shape is defined as an intersection point A,
An intersection point between a portion corresponding to the top surface of the partition wall in the partition wall cross-sectional shape and a portion corresponding to the second side surface facing the first side surface of the partition wall in the partition wall cross-sectional shape is defined as an intersection point B,
When the point where the straight line connecting the center D of the light source and the intersection A intersects the diffuser plate is defined as the intersection C,
A light beam emitted from the light source provided in the planar light source unit, incident from the first side surface of the partition wall, and emitted from the second side surface portion of the partition wall corresponding to the intersection point B collides with the intersection point C. The planar light source device according to claim 1, wherein:

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