JP4622935B2 - Surface light source device - Google Patents

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. The planar light source device includes a housing, and includes a plurality of light sources disposed in the housing and a diffusion plate attached to the top of the housing. As the light source, a light emitting diode (LED) or a cold cathode fluorescent lamp is used.

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.

JP-A-2005-258403 JP-A-2005-352426

By the way, 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, the light source luminance of each planar light source unit must be corrected in consideration of such influences. However, when the light source luminance of a certain planar light source unit affects the light source luminance of many other planar light source units (for example, all other planar light source units), such correction is performed. For this reason, there is a problem in that the amount of computation for increasing dramatically.

  On the other hand, if a partition is arranged between the planar light source unit and the planar light source unit, it is possible to reduce the influence of the light source luminance of one planar light source unit on the light source luminance of another planar light source unit. is there. However, in such a solution, there is a possibility that the light emitted from the light source causes a shadow of the partition wall, and the shadow causes uneven brightness on the diffusion plate. If luminance unevenness occurs in the diffusion plate, that is, if luminance unevenness occurs between adjacent planar light source units, the quality of image display is degraded.

  In addition, when the light source luminance of a certain planar light source unit has a large influence on the light source luminance of another planar light source unit, it is difficult to increase the white level or decrease the black level, resulting in a high contrast ratio (liquid crystal display). The luminance ratio of the all-black display portion to the all-white display portion that does not include external light reflection or the like on the screen surface of the apparatus cannot be obtained, and it is difficult to emphasize the brightness of a desired display area. .

  Dielectric multilayer in which at least one high refractive index film and low refractive index film are laminated between the diffuser plate and the light source so that the transmitted light and reflected light of the incident light have a predetermined ratio A backlight device having a structure in which transmission / reflection means made of a film is disposed is known from, for example, Japanese Patent Application Laid-Open No. 2005-352426. By the way, the transmission / reflection means disclosed in this patent publication is planar, and the light emitted from the light source and reflected by the transmission / reflection means is not directly returned toward the light source. Therefore, when the transmission and reflection means disclosed in this patent publication is applied to a planar light source device that is driven separately, the influence of the light source luminance of one planar light source unit on the light source luminance of another planar light source unit is affected. It is difficult to make it smaller. Moreover, the light use efficiency of the light source when viewed from one planar light source unit is low.

  Therefore, an object of the present invention is to reduce 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 as much as possible, and between adjacent planar light source units. An object of the present invention is to provide a planar light source device having a structure in which luminance unevenness is unlikely to occur.

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 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,
(A) a diffusion plate whose upper surface faces the liquid crystal display device; and
(B) a light transmission control member disposed between the light source and the diffusion plate or on the lower surface of the diffusion plate;
With
The light transmission control member is composed of P × Q light transmission control member units corresponding to P × Q planar light source units,
Each light transmission control member unit
(A) a plurality of first inclined surfaces arranged concentrically about a vertical axis passing through the central portion of the light source constituting the planar light source unit corresponding to the light transmission control member unit;
(B) a second inclined surface connecting the first inclined surface and the first inclined surface, and
(C) an optical thin film formed on the surfaces of the first inclined surface and the second inclined surface, the light transmittance of which varies depending on the incident angle of light,
With
In each light transmission control member unit, the light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit and directed toward the first inclined surface constituting the light transmission control member unit Passes through the optical thin film formed on the first inclined surface and enters the diffusion plate,
In each light transmission control member unit, the light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit, and adjacent to the light transmission control member unit adjacent to the light transmission control member unit At least a part of the light traveling is reflected by the optical thin film formed on the first inclined surface or the second inclined surface constituting the adjacent light transmission control member unit, and the planar light source unit corresponding to the light transmission control member unit It is returned to the inside.

In the planar light source device of the present invention, at least a part (or all in some cases) of the light traveling toward the adjacent light transmission control member unit is the first inclined surface or the second inclined surface constituting the adjacent light transmission control member unit. The light is reflected by the optical thin film formed thereon and returned to the planar light source unit corresponding to the light transmission control member unit. The specific light behavior is as follows.
(1) A mode in which all light is reflected by the optical thin film formed on the second inclined surface constituting the adjacent light transmission control member unit and returned into the planar light source unit corresponding to the light transmission control member unit (2 ) A part of the light is reflected by the optical thin film formed on the second inclined surface constituting the adjacent light transmission control member unit, returned to the planar light source unit corresponding to the light transmission control member unit, and the other light Is transmitted through the optical thin film on the second inclined surface and incident on the diffusion plate, and / or reflected by the optical thin film on the second inclined surface, to the adjacent planar light source unit corresponding to the adjacent light transmission control member unit. Form that enters and / or is reflected by the optical thin film on the second inclined surface and enters the adjacent planar light source unit corresponding to another light transmission control member unit (3) Adjacent light transmission control Form in which all light is reflected by the optical thin film formed on the first inclined surface constituting the material unit and returned into the planar light source unit corresponding to the light transmission control member unit (4) Adjacent light transmission control member unit A part of the light is reflected by the optical thin film formed on the first inclined surface constituting the light and returned to the planar light source unit corresponding to the light transmission control member unit, and the other light is reflected on the first inclined surface. Transmitted through the optical thin film and incident on the diffusing plate and / or reflected by the optical thin film at the first inclined surface to enter the adjacent planar light source unit corresponding to the adjacent light transmission control member unit, and / or A mode of being reflected by the optical thin film on the first inclined surface and entering an adjacent planar light source unit corresponding to another light transmission control member unit

  In the planar light source device of the present invention, in each light transmission control member unit, the light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit, the light transmission control It is preferable that the light traveling toward the second inclined surface constituting the member unit is reflected by the optical thin film formed on the second inclined surface. The reflected light returns to the planar light source unit corresponding to the light transmission control member unit. However, in some cases, the reflected light may enter the adjacent planar light source unit corresponding to the adjacent light transmission control member unit.

Further, in the surface light source device of the present invention including the above-optical thin film has a maximum light transmittance TR _MAX next when the incident angle of the light incident angle theta _MAX, the light transmission control member unit The incident angle θ is within the angle range of the incident angle of the light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit with respect to the first inclined surface constituting the light transmission control member unit. It is desirable that the _MAX be included. Here, the inclination of the first inclined surface when the light transmission control member unit is cut in a virtual vertical plane including a vertical axis passing through the central portion of the light source constituting the planar light source unit is, for example, the extension of the first inclined surface. It becomes the largest when the angle between the direction and the virtual vertical plane is a right angle. That is, the incident angle of light on the optical thin film becomes the largest. Since the inclination of the first inclined surface may change depending on the positional relationship between a certain point on the first inclined surface and the light source as described above, “the planar light source unit corresponding to the light transmission control member unit is configured. “An incident angle θ _MAX is included in the angle range of the incident angle of the light emitted from the light source to the first inclined surface constituting the light transmission control member unit” means that the plurality of first inclined surfaces are When any one first inclined surface is taken up, it means that the incident angle at any point of the one first inclined surface becomes equal to the incident angle θ _MAX .

Furthermore, in the planar light source device of the present invention including the various preferred configurations described above, the optical thin film includes a low refractive index layer and a high refractive index layer having a higher refractive index than the low refractive index layer. It is preferably made of a multilayer film laminated (for example, a plurality of layers laminated alternately). Here, SiO _x can be cited as a material constituting the low refractive index layer, and niobium pentoxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ), zirconium oxide ( ZrO ₂ ). In addition, the light transmittance depending on the incident angle of light can be changed to a desired value by appropriately selecting a material to be used, a laminated structure, a thickness of each layer, and the like.

  Furthermore, in the planar light source device of the present invention including the various preferred configurations described above, the normal line of the first inclined surface extending toward the light source side extends in the direction approaching the light source, and toward the light source side. The normal line of the second inclined surface extending in a direction extending away from the light source can be used. In this case, the first inclined surface generally faces the light source constituting the planar light source unit corresponding to the light transmission control member unit including the first inclined surface, and the second inclined surface is It can be said that it generally faces the light source constituting the planar light source unit corresponding to the adjacent light transmission control member unit. Alternatively, the normal line of the first inclined surface extending toward the light source side extends in a direction away from the light source, and the normal line of the second inclined surface extending toward the light source side extends in a direction approaching the light source. You can also. In this case, the second inclined surface generally faces the light source constituting the planar light source unit corresponding to the light transmission control member unit including the second inclined surface, and the first inclined surface is It can be said that it generally faces the light source constituting the planar light source unit corresponding to the adjacent light transmission control member unit.

  In the planar light source device of the present invention, the first inclined surface and the first inclined surface are connected by the second inclined surface. More specifically, the top of the first inclined surface and the first inclined surface The bottom of the first inclined surface adjacent to the first inclined surface is connected by the second inclined surface. As a shape formed by the first inclined surface and the second inclined surface when the light transmission control member unit is cut in a virtual vertical plane including a vertical axis passing through the center of the light source constituting the planar light source unit, specifically, Can be illustrated as a sawtooth, a sawtooth with rounded top and bottom, and a curve including a waveform or a sine wave.

  A certain light transmission control member unit and an adjacent light transmission control member unit adjacent to this light transmission control member unit constitute a first inclined surface and an adjacent light transmission control member unit constituting a certain light transmission control member unit. A first inclined surface that is connected to the second inclined surface that constitutes a certain light transmission control member unit and a second inclined surface that constitutes an adjacent light transmission control member unit. May be connected, or a first inclined surface constituting a certain light transmission control member unit and a second inclined surface constituting an adjacent light transmission control member unit may be connected. The second inclined surface constituting a certain light transmission control member unit may be connected to the first inclined surface constituting the adjacent light transmission control member unit. Good and with diffuser It may be connected by parallel planes.

  The plurality of first inclined surfaces are arranged concentrically around a vertical axis passing through the central portion of the light source constituting the planar light source unit. However, when P ≧ 2 and Q ≧ 2, the first inclined surface is The planar shape when viewed from the light source side is preferably substantially similar to the outer shape of the light transmission control member unit, but may be a concentric annular shape (donut shape). Specifically, when the outer shape of the light transmission control member unit is, for example, a rectangle, the planar shape when the first inclined surface is viewed from the light source side is a concentric rectangular “B” shape, and the corner is rounded. And a concentric rectangular “B” shape and a concentric ring shape (doughnut shape). Further, the value of P, which is a value along the column direction (first direction described later), is 1 (P = 1), and the value of Q, which is a value along the row direction (second direction described later). Is 2 or more (Q ≧ 2), the first inclined surface and the second inclined surface extend only in the column direction (first direction). In this case, “the plurality of first inclined surfaces are concentrically arranged” means that the plurality of first inclined surfaces pass through the light source and are symmetrical with respect to a virtual vertical plane parallel to the column direction (first direction). It means that 1 inclined surface (and 2nd inclined surface) is arrange | positioned. On the other hand, the value of P that is a value along the column direction (first direction) is 2 or more (P ≧ 2), and the value of Q that is a value along the row direction (second direction) is 1 ( In the case of Q = 1), the first inclined surface and the second inclined surface extend only in the row direction (second direction). In this case, “the plurality of first inclined surfaces are concentrically arranged” means that the plurality of first inclined surfaces pass through the light source and are symmetrical with respect to a virtual vertical plane parallel to the row direction (second direction). It means that 1 inclined surface (and 2nd inclined surface) is arrange | positioned.

In each light transmission control member unit, the light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit, and traveling toward the first inclined surface constituting the light transmission control member unit Passes through the optical thin film formed on the first inclined surface and enters the diffusion plate. At this time, the light transmittance TR ₁₁ in the optical thin film formed on the first inclined surface is 0. It is desirable that 7 × TR _MAX ≦ TR ₁₁ ≦ TR _MAX . Further, in each light transmission control member unit, the light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit, the adjacent light transmission control member adjacent to the light transmission control member unit At least a part of the light traveling toward the unit is reflected by the optical thin film formed on the first inclined surface or the second inclined surface constituting the adjacent light transmission control member unit, and the light transmittance in the optical thin film at this time TR ₂ is preferably TR ₂ ≦ 0.3 × TR _MAX . Further, in each light transmission control member unit, light emitted from a light source constituting a planar light source unit corresponding to the light transmission control member unit, and a second inclined surface constituting the light transmission control member unit In this case, the light transmittance in the optical thin film formed on the second inclined surface is essentially arbitrary. Value.

  In the planar light source device of the present invention, the light transmission control member is disposed between the light source and the diffusion plate, or is disposed on the lower surface of the diffusion plate. In the former configuration, there is a gap between the light transmission control member and the light source, and there is also a gap between the light transmission control member and the diffusion plate. On the other hand, in the latter configuration, the light transmission control member can be configured to be fixed to the lower surface of the diffusion plate, or the light transmission control member and the diffusion plate can be integrally formed. You can also.

  In the structure in which the light transmission control member is manufactured separately from the diffusion plate, a polyethylene terephthalate (PET) resin is used as the base material on which the light transmission control member is formed and the first inclined surface and the second inclined surface are formed. And materials such as polyester resins such as polybutylene terephthalate (PBT) resin; polycarbonate resins (PC); acrylic resins; methacrylic resins, and the like. In this case, examples of the material constituting the diffusion plate include polycarbonate resin (PC); polystyrene resin (PS); methacrylic resin. The surface of the light transmission control member that faces the diffusion plate may be substantially parallel to the first inclined surface and the second inclined surface (that is, may be an uneven surface), or substantially parallel to the diffusion plate. It may be a flat surface. On the other hand, in the structure in which the light transmission control member and the diffusion plate are integrally manufactured, as a material constituting the diffusion plate that also serves as the light transmission control member, polycarbonate resin (PC); polystyrene resin (PS); A methacrylic resin can be mentioned. In this case, the light diffusion efficiency of the diffusion plate may change along the thickness direction of the diffusion plate. Specifically, the light transmittance of the diffusion plate may gradually increase toward the lower surface of the diffusion plate.

  In the optical thin film, not only the light transmittance changes depending on the incident angle of light, but also the light transmittance may change depending on the wavelength of light. For example, as will be described later, when the light source is configured as a set of a red light emitting diode, a green light emitting diode, and a blue light emitting diode, an optical thin film for red that controls exclusively transmission / reflection of red light, green light An optical thin film having a structure in which a green optical thin film that exclusively controls transmission / reflection of light and a blue optical thin film that exclusively controls transmission / reflection of blue light may be laminated.

  As a method for forming an optical thin film on a substrate or the lower surface of a diffusion plate, various chemical vapor deposition methods (CVD methods), various physical vapor deposition methods (PVD methods), and nano-imprint are representative. A printing method can be exemplified. Moreover, although it depends on the material to be used as a method for forming the base material, a molding method using a plastic material, a combination of the molding method and a shaping method by heating / pressurization can be exemplified.

  In the surface light source device of the present invention, one surface light source unit is surrounded by four surface light source units, or is also surrounded by three surface light source units and one side surface of a housing (described later). Alternatively, it is surrounded by two planar light source units and two sides of 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. When the light source is composed of a light emitting diode unit, the center of the light emitting diode unit corresponds to the center of the light source.

  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.

  In the planar light source device of the present invention, light for measuring the light emission state of the light source (specifically, for example, the luminance of the light source, or the chromaticity of the light source, or the luminance and chromaticity of the light source). It is desirable that a sensor is provided. The number of photosensors may be at least one, but a configuration in which one set of photosensors is arranged in one planar light source unit ensures the light emission state of each planar light source unit. It is desirable from the viewpoint of measurement. As the optical sensor, a known photodiode or CCD device can be cited. When the light source is configured, for example, as a set of a red light emitting diode, a green light emitting diode, and a blue light emitting diode, the light emission state of the light source measured by the optical sensor is the luminance and chromaticity of the light source. Also, in this case, a pair of photosensors is connected to a photodiode with a red filter attached to measure the light intensity of red light, a photodiode attached with a green filter to measure the light intensity of green light, And, it can be composed of a photodiode with a blue filter attached to measure the light intensity of blue light.

  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.

  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), 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.

  In the planar light source device of the present invention, in each light transmission control member unit, the light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit, the light transmission control The light traveling toward the first inclined surface constituting the member unit is transmitted through the optical thin film formed on the first inclined surface, is incident on the diffusion plate, is diffused by the diffusion plate and is emitted, and the liquid crystal display device Is irradiated from the back. On the other hand, in each light transmission control member unit, the light emitted from the light source constituting the planar light source unit corresponding to this light transmission control member unit, and adjacent light transmission control member adjacent to this light transmission control member unit At least a part of the light traveling toward the unit is reflected by the optical thin film formed on the first inclined surface or the second inclined surface constituting the adjacent light transmission control member unit, and the surface shape corresponding to the light transmission control member unit Returned to the light source unit. Therefore, the influence of the light source luminance of a certain planar light source unit on the light source luminance of other planar light source units can be reduced as much as possible, and luminance unevenness hardly occurs between adjacent planar light source units. In addition, since the optical path length of the light emitted from the planar light source device is extended and light can be sufficiently mixed in the planar light source unit or the planar light source device, the planar light source device can be made thinner. Can be achieved. Furthermore, it is possible to increase the white level and decrease the black level in the liquid crystal display device, to achieve a high contrast ratio, to enhance the brightness of a desired display area, and to The display quality can be improved. Further, it is possible to reduce the amount of calculation for correcting the light source luminance when the light source luminance of a certain planar light source unit affects the light source luminance of many other planar light source units. Furthermore, it is possible to improve the light use efficiency of the light source when viewed from one planar light source unit, and ultimately it is possible to reduce power consumption in the planar light source device.

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 planar light source device be further reduced, but also the white level can be increased and the black level can be further reduced to obtain a higher contrast ratio.

  Hereinafter, the planar light source device of the present invention will be described based on examples with reference to the drawings, but prior to that, an outline of a transmissive color liquid crystal display device and a planar light source device suitable for use in the examples, This will be described with reference to FIGS. 5, 6, 7 (A) and (B), and FIG. 8.

As shown in the conceptual diagram of FIG. 5, the transmissive color liquid crystal display device 10 has a total of M ₀ × N ₀ , M ₀ pieces along the first direction and N ₀ pieces along the second direction. 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. 5) 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 42 described later) in FIG. 5 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.

  As shown in the schematic partial cross-sectional view of FIG. 8, 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 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. In addition, although the planar light source device 40 is located 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. 7A, 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. In FIG. 7A, the boundary of the planar light source unit 42 is indicated by a dotted line. 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. 7B, 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 reflects light emitted from the plurality of light emitting diodes 41 (light sources 41) and light reflected by the side surface 52B of the housing 51. 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 a light transmission control member 100 described later, and further passes through an optical function sheet group such as a diffusion plate 61, a diffusion sheet 62, a prism sheet 63, and a polarization conversion sheet 64, and passes through the color liquid crystal display device 10. Irradiate from the back.

  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.

As shown in FIGS. 5 and 6, the driving circuit for driving the planar light source device 40 and the color liquid crystal display device 10 based on the 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. 6 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 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 of the present invention. A schematic partial cross-sectional view of the surface light source device of Example 1 is shown in FIG. FIG. 1 or FIGS. 2 to 4 described later are virtual vertical planes including a vertical axis passing through the central portion of the light source constituting the planar light source unit, and the directions in which the first inclined surface and the second inclined surface extend. FIG. 6 is a schematic partial cross-sectional view of a planar light source device when a light transmission control member unit or the like is cut on a virtual vertical plane located in a direction perpendicular to the vertical direction.

  As described above, the planar light source device 40 according to the first embodiment illuminates the transmissive color liquid crystal display device 10 having the display area 11 composed of pixels arranged in a two-dimensional matrix from the back side. It is. The planar light source device 40 assumes that the display region 11 of the color liquid crystal display device 10 is divided into P × Q virtual display region units 12, and these P × Q display region units 12. And the light source 41 provided in the planar light source unit 42 is individually controlled. However, since the light source luminance of the planar light source unit is influenced by the light emission state of the light source provided in the other planar light source unit, it is desirable to control the light emission state of the light source in consideration of this influence.

The planar light source device 40 further includes:
(A) a diffusion plate 61 made of an acrylic resin sheet and having an upper surface facing the liquid crystal display device; and
(B) a light transmission control member 100 disposed between the light source 41 and the diffusion plate 61;
It has. The light transmission control member 100 is attached to the inner frame 54 via an attachment member (not shown).

Here, the light transmission control member 100 includes P × Q light transmission control member units 110 corresponding to the P × Q planar light source units 42. And each light transmission control member unit 110 is
(A) A plurality of first inclined surfaces arranged concentrically around a vertical axis NL ₀ passing through the center of the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110 (in FIG. 1) Are indicated by the first inclined surfaces A ₁ , A ₂ , A ₃ , and may be collectively referred to as the first inclined surface 111 in the following description)
(B) A second inclined surface connecting the first inclined surface 111 and the first inclined surface 111 (shown as second inclined surfaces B ₁ , B ₂ , and B ₃ in FIG. 1; And may be collectively referred to as the inclined surface 112), and
(C) An optical thin film 113 formed on the surfaces of the first inclined surface 111 and the second inclined surface 112 and whose light transmittance changes depending on the incident angle of light (in FIG. 1, the first inclined surface 111 and the first inclined surface 111 2 is not particularly distinguished from the inclined surface 112),
It has. In addition, the number of the 1st inclined surface and the 2nd inclined surface shown in FIG. 1 or FIGS. 2-4 mentioned later is an illustration, and is not limited to the number which concerns. The adjacent light transmission control member unit adjacent to the light transmission control member unit 110 is referred to as an adjacent light transmission control member unit 110 ′, and the first inclined surface constituting the adjacent light transmission control member unit 110 ′ is the first inclined surface. 111 ′, the second inclined surface is called the second inclined surface 112 ′, the optical thin film is called the optical thin film 113 ′, and the surface light source unit corresponding to the adjacent light transmission control member unit 110 ′ and the surface light source unit are configured The light sources to be called may be referred to as a planar light source unit 42 ′ and a light source 41 ′, respectively.

In each light transmission control member unit 110, light emitted from the light source 41 constituting the planar light source unit 42 corresponding to this light transmission control member unit 110, which constitutes this light transmission control member unit 110. The light traveling toward the first inclined surface 111 passes through the optical thin film 113 formed on the first inclined surface 111 and enters the diffusion plate 61. This light beam is indicated by a one-dot chain line in FIG. 1 or FIGS. Further, in each light transmission control member unit 110, the light emitted from the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110 and adjacent to the light transmission control member unit 110. At least a part of the light traveling toward the adjacent light transmission control member unit 110 ′ (all in the first embodiment, these light rays are indicated by dotted lines in FIG. 1 or FIGS. 3 to 4 described later) is adjacent. An optical thin film formed on the first inclined surface or the second inclined surface constituting the light transmission control member unit 110 ′ (in the first embodiment, more specifically, formed on the second inclined surface 112 ′. In FIG. 1, the second inclined surface 112 ′ is reflected by the second inclined surfaces b ₁ , b ₂ , and b ₃ ), and corresponds to the light transmission control member unit 110. Planar Returned to the light source unit 42.

  Further, in each light transmission control member unit 110, the light emitted from the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110, which constitutes this light transmission control member unit 110. The light traveling toward the second inclined surface 112 is reflected by the optical thin film 113 formed on the second inclined surface 112 and is mainly returned to the planar light source unit 42 in the first embodiment.

The optical thin film 113 is formed by alternately laminating a plurality of low refractive index layers made of SiO _x and high refractive index layers made of niobium pentoxide (Nb ₂ O ₅ ) having a higher refractive index than the low refractive index layer. It consists of a multilayer film. The structure of the multilayer film is shown in Table 2 below. The base material on which the first inclined surface 111 and the second inclined surface 112 are formed is a sheet made of polyethylene terephthalate (PET) resin. Graphs obtained by measuring the relationship between the incident angle on the optical thin film 113 and the light transmittance are shown in FIGS. 11, 12, and 13, and FIG. 11 is data when light having a peak wavelength of 640 nm is incident thereon. FIG. 12 shows data when light having a peak wavelength of 530 nm is incident, and FIG. 13 shows data when light having a peak wavelength of 450 nm is incident. The light transmittance of the optical thin film 113 starts to increase rapidly from the vicinity of an incident angle of 25 degrees for any light, reaches a maximum at an incident angle of 50 to 60 degrees, and gradually decreases.

The optical thin film 113 has the maximum light transmittance TR _MAX when the incident angle of light is the incident angle θ _MAX , and each light transmission control member unit 110 has the planar light source unit 42 corresponding to the light transmission control member unit 110. The incident angle θ _MAX is included in the angle range of the incident angle of the light emitted from the constituting light source 41 with respect to the first inclined surface 111 constituting the light transmission control member unit 110. The inclination of the first inclined surface 111 when the light transmission control member unit 110 is cut in a virtual vertical plane including the vertical axis NL ₀ passing through the center of the light source 41 constituting the planar light source unit 42 is the first inclined surface 111. Is the largest when the angle formed between the extending direction and the virtual vertical plane is a right angle. That is, the incident angle of light to the optical thin film 113 is the largest. When any one first inclined surface 111 of the plurality of first inclined surfaces 111 is taken up, the incident angle at any point of the one first inclined surface 111 becomes equal to the incident angle θ _MAX .

A normal line NL ₁ of the first inclined surface 111 extending toward the light source side (the direction in which the normal line NL ₁ extends is indicated by an arrow in FIG. 1) extends in a direction approaching the light source 41, and is a second inclination extending toward the light source side. A normal line NL ₂ (the direction in which the normal line NL ₂ extends is indicated by an arrow in FIG. 1) of the surface 112 extends in a direction away from the light source 41. More specifically, the first inclined surface 111 generally faces the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110 including the first inclined surface 111, and the second inclined surface 111 The inclined surface 112 generally faces the light source 41 ′ constituting the planar light source unit 42 ′ corresponding to the adjacent light transmission control member unit 110 ′.

In addition, the first inclined surface 111 and the first inclined surface 111 are connected by the second inclined surface 112. More specifically, the top of the first inclined surface 111 and the first inclined surface 111 are adjacent to each other. The bottom portion of the first inclined surface 111 is connected by the second inclined surface 112. It is formed by the first inclined surface 111 and the second inclined surface 112 when the light transmission control member unit 110 is cut along a virtual vertical plane including the vertical axis NL ₀ that passes through the center of the light source 41 constituting the planar light source unit 42. The shape is a saw shape. The second inclined surface 112 (second inclined surface B ₃ ) constituting the light transmission control member unit 110 and the second inclined surface 112 ′ (second inclined surface b ₃ ) constituting the adjacent light transmission control member unit 110 ′. Are connected to each other, and the light transmission control member unit 110 and the adjacent light transmission control member unit 110 ′ adjacent to the light transmission control member unit 110 are connected.

Further, the plurality of first inclined surfaces 111 are arranged concentrically around a vertical axis NL ₀ that passes through the central portion of the light source 41 that constitutes the planar light source unit 42. The planar shape when the surface 111 is viewed from the light source side is substantially similar to the outer shape of the light transmission control member unit 110. More specifically, the outer shape of the light transmission control member unit 110 is a rectangle, and the planar shape when the first inclined surface 111 is viewed from the light source side is a concentric rectangle “round” with rounded corners. "".

In each light transmission control member unit 110, the light emitted from the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110, and the first light constituting the light transmission control member unit 110. The light traveling toward the inclined surface 111 passes through the optical thin film 113 formed on the first inclined surface 111 and enters the diffusion plate 61. The optical thin film formed on the first inclined surface 111 at this time The light transmittance TR _{11 at} is 0.7 × TR _MAX ≦ TR ₁₁ ≦ TR _MAX . Specifically, the inclination angle of the first inclined surface 111 is determined so that the incident angle is 45 degrees to 65 degrees. Further, in each light transmission control member unit 110, the light emitted from the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110 and adjacent to the light transmission control member unit 110. The light traveling toward the second inclined surface 112 ′ constituting the adjacent light transmission control member unit 110 ′ is reflected by the optical thin film 113 ′ formed on the second inclined surface 112 ′, and the second inclined surface at this time The light transmittance TR ₂ in the optical thin film 113 ′ formed on the surface 112 ′ is TR ₂ ≦ 0.3 × TR _MAX . Further, in each light transmission control member unit 110, light emitted from the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110, which constitutes the light transmission control member unit 110. The light traveling toward the second inclined surface 112 is reflected by the optical thin film 113 formed on the second inclined surface 112.

In the first embodiment, 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, a driving method of the liquid crystal display device assembly according to the first embodiment 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. 5). 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. 9A and 9B. 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. 6).

[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 thus obtained are indicated by solid lines in FIGS. 10A and 10B. FIG. 10A shows a drive signal input to the liquid crystal display device drive circuit 90 to drive the sub-pixels. 10 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. That is, in the first embodiment, since the light source luminance Y _{2− (q, p)} changes for each image display frame, the display luminance / light source luminance Y _{2− (q, p)} (≦ Y ₁ ) The values X _{R- (q, p)} and X _{G- (q, p)} of the control signal [R, G, B] _{(q, p)} so that the second 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.

  As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to this Example. 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, the light transmission control member, and the drive circuit described in the embodiments are examples, and constitute these. Members, materials, etc. are also examples, 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.

As shown in a schematic partial cross-sectional view in FIG. 2, the normal line of the first inclined surface 111 extending from the first inclined surface 111 and the second inclined surface 112 to the light source side extends in a direction away from the light source 41. The normal line of the second inclined surface 112 extending to the light source side may be configured to extend in a direction approaching the light source 41. Specifically, the second inclined surface 112 substantially faces the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110 including the second inclined surface 112, and the first inclined surface 112 The surface 111 can be configured to generally face the light source 41 ′ constituting the planar light source unit 42 ′ corresponding to the adjacent light transmission control member unit 110 ′. Even in this case, a certain light transmission control member unit 110 and an adjacent light transmission control member unit 110 ′ adjacent to this light transmission control member unit 110 constitute a certain light transmission control member unit 110. The second inclined surface 112 (second inclined surface B ₂ ) and the second inclined surface 112 ′ (second inclined surface b ₂ ) constituting the adjacent light transmission control member unit 110 ′ are connected. ing. In the example shown in FIG. 2, in each light transmission control member unit 110, the light emitted from the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110, The light traveling toward the first inclined surface 111 constituting the light transmission control member unit 110 passes through the optical thin film 113 formed on the first inclined surface 111 and enters the diffusion plate 61. On the other hand, in each light transmission control member unit 110, the light emitted from the light source 41 constituting the planar light source unit 42 corresponding to the light transmission control member unit 110, adjacent to the light transmission control member unit 110. At least a part of the light traveling toward the adjacent light transmission control member unit 110 ′ is reflected by the optical thin film 113 ′ formed on the second inclined surface 112 ′ constituting the adjacent light transmission control member unit 110 ′. It is returned to the planar light source unit 42 corresponding to the control member unit 110.

  In the first embodiment, a gap is formed between the light transmission control member 100 and the diffusion plate 61, but the light transmission control member may be disposed on the lower surface of the diffusion plate 61. In this case, the light transmission control member can be fixed to the lower surface of the diffusion plate as shown in FIG. 3, and the light transmission control member and the diffusion plate are integrally manufactured as shown in FIG. It can also be set as the structure made. Note that the modification shown in FIG. 3 or 4 can also be applied to the modification shown in FIG.

  As the light source, a cold cathode ray type fluorescent lamp can be used instead of the LED. When the fluorescent lamps are arranged so as to extend along the column direction (first direction) and a plurality of fluorescent lamps are arranged along the row direction (second direction), the row direction (second direction) Partial cross-sectional views when the planar light source device is cut along a parallel virtual vertical plane are the same as those shown in FIGS. In this case, the plurality of first inclined surfaces are arranged symmetrically with respect to a virtual vertical plane that passes through the light source and is parallel to the column direction (first direction). On the other hand, when the fluorescent lamps are arranged so as to extend along the row direction (second direction) and a plurality of fluorescent lamps are arranged along the column direction (first direction), the column direction (first direction) A partial cross-sectional view when the planar light source device is cut along a virtual vertical plane parallel to) is the same as that shown in FIGS. In this case, the plurality of first inclined surfaces are arranged symmetrically with respect to a virtual vertical plane passing through the light source and parallel to the row direction (second direction).

  In some cases, the planar light source unit 42 and the planar light source unit 42 constituting the planar light source device 40 may be partitioned by a partition wall. However, it is necessary to make the partition walls low enough not to cause shadows on the partition walls by the light emitted from the light source.

FIG. 1 is a schematic partial cross-sectional view of a planar light source device including a light transmission control member and the like in the first embodiment. FIG. 2 is a schematic partial cross-sectional view of a modification of the light transmission control member and the diffusion plate in the first embodiment. FIG. 3 is a schematic partial cross-sectional view of another modification of the light transmission control member and the diffusion plate in the first embodiment. FIG. 4 is a schematic partial cross-sectional view of still another modified example of the light transmission control member and the diffusion plate in the first embodiment. FIG. 5 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. 6 is a conceptual diagram of a portion of a drive circuit suitable for use in the embodiment. FIG. 7A 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. 7B 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. 8 is a schematic partial cross-sectional view of a color liquid crystal display device. (A) and (B) of FIG. 9 show the display luminance when assuming that a control signal corresponding to the drive signal having a value equal to the drive 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. 10A shows a value (x′≡x ^2.2 ) obtained by multiplying the value of the drive signal input to the liquid crystal display device driving circuit to drive the subpixel by the power of 2.2 (x′≡x ^2.2 ) and the duty ratio (= t _ON / t _Const ) is a diagram schematically showing the relationship between the control signal value X for controlling the light transmittance of the sub-pixel and the display luminance y. FIG. FIG. FIG. 11 is a graph showing the results of measuring the relationship between the incident angle to the optical thin film and the light transmittance when light having a peak wavelength of 640 nm is incident on the optical thin film of Example 1. FIG. 12 is a graph showing the results of measuring the relationship between the angle of incidence on the optical thin film and the light transmittance when light having a peak wavelength of 530 nm is incident on the optical thin film of Example 1. FIG. 13 is a graph showing the results of measuring the relationship between the angle of incidence on the optical thin film and the light transmittance when light having a peak wavelength of 450 nm is incident on the optical thin film of Example 1. 14A and 14B 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 region.

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 , 41 ', 41R, 41G, 41B ... Light emitting diode (light source), 42, 42' ... Planar light source unit, 43, 43R, 43G, 43B ... Photodiode (light sensor), 51 ... -Housing, 52A ... Bottom 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 ... Calculation circuit, 72 ... Storage device (Memory), 80 ... planar light source unit drive circuit, 81 ... arithmetic circuit, 82 ... storage device (memory), 83 ... LED drive circuit, 84 ... photodiode control circuit, 85R , 85G, 85B... Switching element, 86... Light emitting diode drive power supply, 90... Liquid crystal display drive circuit, 91. 0, 110 '... light transmission control member unit, 111, 111' ... first inclined surface, 112, 112 '... second inclined surface, 113, 113' ... optical thin film

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,
The light sources provided in the planar light source unit are individually controlled,
(A) a diffusion plate whose upper surface faces the liquid crystal display device; and
(B) a light transmission control member disposed between the light source and the diffusion plate or on the lower surface of the diffusion plate;
With
The light transmission control member is composed of P × Q light transmission control member units corresponding to P × Q planar light source units,
Each light transmission control member unit
(A) a plurality of first inclined surfaces arranged concentrically about a vertical axis passing through the central portion of the light source constituting the planar light source unit corresponding to the light transmission control member unit;
(B) a second inclined surface connecting the first inclined surface and the first inclined surface, and
(C) an optical thin film formed on the surfaces of the first inclined surface and the second inclined surface, the light transmittance of which varies depending on the incident angle of light,
With
In each light transmission control member unit, the light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit and directed toward the first inclined surface constituting the light transmission control member unit Passes through the optical thin film formed on the first inclined surface and enters the diffusion plate,
In each light transmission control member unit, the light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit, and adjacent to the light transmission control member unit adjacent to the light transmission control member unit At least a part of the light traveling is reflected by the optical thin film formed on the first inclined surface or the second inclined surface constituting the adjacent light transmission control member unit, and the planar light source unit corresponding to the light transmission control member unit A planar light source device which is returned to the inside.   In each light transmission control member unit, the light emitted from the light source that constitutes the planar light source unit corresponding to the light transmission control member unit and directed toward the second inclined surface that constitutes the light transmission control member unit The surface light source device according to claim 1, wherein the surface light source device is reflected by an optical thin film formed on the second inclined surface. The optical thin film has a maximum light transmittance TR _MAX when the incident angle of light is the incident angle θ _MAX .
In each light transmission control member unit, the angle of incidence of light emitted from the light source constituting the planar light source unit corresponding to the light transmission control member unit with respect to the first inclined surface constituting the light transmission control member unit The planar light source device according to claim 1, wherein the range includes an incident angle θ _MAX .   2. The planar light source device according to claim 1, wherein the optical thin film comprises a multilayer film in which a low refractive index layer and a high refractive index layer having a higher refractive index than the low refractive index layer are laminated. The normal line of the first inclined surface extending to the light source side extends in a direction approaching the light source,
The planar light source device according to claim 1, wherein the normal line of the second inclined surface extending toward the light source side extends in a direction away from the light source. The normal line of the first inclined surface extending to the light source side extends in a direction away from the light source,
The planar light source device according to claim 1, wherein the normal line of the second inclined surface extending toward the light source side extends in a direction approaching the light source.

Images