JP2006106774A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain image display with high brightness and high quality suppresses by suppressing lowering of light emitting efficiency of a linear light source to prevent deterioration in display quality and by solving the problem of insufficient brightness of a backlight comprising a plurality of arrayed linear light sources in the periphery of a liquid crystal panel. <P>SOLUTION: A liquid crystal display device is provided with a backlight comprising the plurality of arrayed linear light sources CFL each having an electrode part ELD at the end and disposed on the back face of a liquid crystal panel via an optical compensation sheet. The backlight has a lower frame FLM-D formed of a metallic sheet and is provided with a heat radiation member MP surrounding the electrode part ELD of the linear light source CFL making intervene an insulating cushion material GB and thermally connected to the lower frame FLM-D composed of a metal material. A linear light source on the edge of the plurality of arrayed linear light sources CFL is disposed so as to come closer to the liquid crystal panel side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and in particular, suppresses a decrease in luminance due to heat generation of a light source that illuminates the liquid crystal panel, and solves a lack of luminance at an end portion of the liquid crystal panel when a plurality of the light sources are arranged. The present invention relates to a liquid crystal display device having uniform brightness over the entire area of the liquid crystal panel.

  2. Description of the Related Art Liquid crystal display devices are widely used as display devices for notebook computers, display monitors, or television receivers that are capable of high definition, thinness, light weight, and color display.

  This type of liquid crystal display device includes a simple matrix type liquid crystal panel using a liquid crystal panel in which a liquid crystal layer is sandwiched between a pair of substrates on which parallel electrodes formed so as to cross each other are formed on each inner surface, and a pair of liquid crystal display devices There is known an active matrix liquid crystal display device using a liquid crystal panel having a switching element for selecting on a pixel basis on one of the substrates.

  As represented by the twisted nematic (TN) method, the active matrix type liquid crystal panel is a so-called vertical electric field method (generally, a TN type) using a liquid crystal panel in which electrode groups for pixel selection are respectively formed on a pair of upper and lower substrates. And a so-called lateral electric field method (generally referred to as an IPS method) using a liquid crystal panel in which an electrode group for pixel selection is formed on only one of a pair of upper and lower substrates.

  In the former TN liquid crystal panel, the liquid crystal is twisted and aligned, for example, by 90 ° in a pair of substrates (two sheets including a first substrate (lower substrate) and a second substrate (upper substrate)). Two polarizing plates are stacked on the outer surface of the upper and lower substrates of the liquid crystal panel, with the absorption axis direction arranged in a crossed Nicols manner and the absorption axis on the incident side parallel or intersecting the rubbing direction.

  In such a TN type active matrix liquid crystal panel, when no voltage is applied, incident light becomes linearly polarized light by the incident side polarizing plate, and this linearly polarized light propagates along the twist of the liquid crystal layer, and the transmission axis of the outgoing side polarizing plate. Is coincident with the azimuth angle of the linearly polarized light, all the linearly polarized light is emitted to display white (so-called normally open mode).

  When a voltage is applied, the direction of the unit vector (director) indicating the average orientation direction of the liquid crystal molecular axes constituting the liquid crystal layer is directed to the direction perpendicular to the substrate surface, and the azimuth angle of the incident side linearly polarized light is changed. Since it coincides with the absorption axis of the exit-side polarizing plate, black is displayed. (Refer nonpatent literature 1).

  On the other hand, a pixel selection electrode group or an electrode wiring group is formed only on one of a pair of substrates, and a liquid crystal layer is formed by applying a voltage between adjacent electrodes (between the pixel electrode and the counter electrode) on the substrate. In an IPS liquid crystal panel that switches in a direction parallel to the surface, a polarizing plate is arranged so as to display black when no voltage is applied (so-called normally closed mode).

  The liquid crystal layer of the IPS mode liquid crystal panel is homogeneously aligned in parallel with the substrate surface in the initial state, and the director of the liquid crystal layer in a plane parallel to the substrate has a parallel or somewhat angle with the electrode wiring direction when no voltage is applied. When the voltage is applied, the direction of the director of the liquid crystal layer shifts to the direction perpendicular to the electrode wiring direction as the voltage is applied, and the director direction of the liquid crystal layer is 45 ° compared to the direction of the director when no voltage is applied. When tilted in the direction of the electrode wiring, the liquid crystal layer when the voltage is applied rotates the polarization azimuth by 90 ° like a half-wave plate, and the transmission axis of the exit side deflection plate and the azimuth angle of the polarization are the same. Then, it becomes white display.

  This IPS liquid crystal panel has a feature that a change in hue and contrast is small even at a viewing angle, and a wide viewing angle can be achieved (see Patent Document 1).

  The color filter method is the mainstream for full colorization of liquid crystal display devices using the various liquid crystal panels described above. In this case, a pixel corresponding to one dot of color display is divided into three, and color filters corresponding to three primary colors, for example, red (R), green (G), and blue (B) are arranged in each unit pixel. It is realized by doing.

  In such a liquid crystal display device, it is necessary to provide illumination from the outside in order to visualize an electronic image formed on the liquid crystal panel.

  As this illumination means, there are a passive illumination system using ambient light and an active illumination system in which a light source such as a cold cathode fluorescent lamp is installed on the back side or the front side of the liquid crystal panel.

  Of the active illumination methods, a method (generally referred to as a front light method) in which a light source is arranged on the surface side of a liquid crystal panel is often employed in portable information devices. On the other hand, in a liquid crystal display device having a relatively large size such as a personal computer or a display monitor, a light source is generally disposed on the back surface of the liquid crystal panel (this is generally referred to as a backlight).

  In information devices such as notebook computers that require thinning, a backlight is constructed by arranging a linear light source such as a cold cathode fluorescent lamp (hereinafter also referred to as CFL) on the edge of a transparent plate (referred to as a light guide plate). is doing.

  However, in order to obtain sufficient screen brightness (brightness) and to make screen brightness uniform with the increase in the size of liquid crystal panels of liquid crystal display devices used in display monitors and television receivers that support moving images in recent years. In addition, a high-brightness backlight in which a plurality of CFLs are arranged on the back surface of the liquid crystal panel is adopted. This is generally called a direct backlight.

  FIG. 22 is an exploded perspective view for explaining an example of a conventional direct type backlight. In this backlight, a plurality of CFLs are arranged on the upper surface of a lower frame FLM-D, which is generally made of a metal material, so that the longitudinal directions thereof are parallel to each other. The upper frame FLM-U and the lower frame FLM-D are sandwiched and integrated with resin molds MLD-L (left mold) and MLD-R (right mold) on both sides (left and right). In this case, the CFL side surface of the lower frame FLM-D has a function of a reflector. However, although not shown, another member such as a sheet having a light reflecting function is interposed between the lower frames FLM-D and CFL, or a chevron on the entire surface of the lower frame FLM-D along the longitudinal direction of the CFL. In some cases, a reflective plate or a reflective plate or a lower frame FLM-D having a reflective function is provided with a chevron-shaped reflective plate in a portion other than the lower portion of the CFL.

  Then, an optical compensation sheet OPS composed of a light diffusing plate SCT (hereinafter simply referred to as a diffusing plate), a diffusing sheet SCTS, a prism sheet or the like is laminated on the upper frame FLM-U to constitute a direct type backlight. Yes. Some do not have the diffusion sheet SCTS. A liquid crystal panel (not shown, which will be described later) is placed above the backlight, and a power source for driving the CFL, other necessary circuits, and structural members are mounted.

The direct type backlight is not limited to the above-described configuration, and various assembled shapes are known. However, the lower frame FLM-D having a function as a CFL fixing member is essential.
1991, published by the Industrial Research Council, “Basics and Applications of Liquid Crystals” JP-A-5-505247

  FIG. 23 is a schematic cross-sectional view for explaining an arrangement example of linear light sources in a direct type backlight using a plurality of linear light sources. In the conventional backlight described in FIG. 22, as shown in FIG. 23, the plurality of linear light sources CFL are arranged on the inner surface of the lower frame FLM-D on the line LL that is equidistant from the inner surface. Yes. Therefore, as illustrated, in the end region of the diffusion plate SCT, the distance d from the linear light source CFL-E at the end is larger than the distance from the linear light source CFL in the central region. As a result, there is a problem that the amount of illumination light is insufficient in the vicinity of the liquid crystal panel PNL than in the central region, the luminance around the screen is lowered, and the display quality is deteriorated.

  In this type of backlight, the CFL is generally held in the lower frame FLM-D as follows. That is, FIG. 24 is a schematic diagram of a main part showing an example of the CFL support structure of the backlight shown in FIG. In the figure, PBR is a frame member for fixing the CFL, PXH is a CFL fixing recess, and GB is an insulating cushion material such as a rubber material or a urethane foam material.

  The CFL covers the electrode portions at both ends thereof with the insulating cushion material GB, and pushes and holds the insulating cushion material GB into the CFL fixing recess PXH of the frame member PBR. The frame member PBR is fixed to the lower frame FLM-D by appropriate means.

  However, as the applied current value or the number of CFLs increases in order to increase the brightness of the screen of the liquid crystal panel, the amount of heat generated in the electrode part increases and the efficiency of the CFL decreases. In addition, in the CFL fixing structure as shown in the figure, the heat generation of the electrode part is difficult to dissipate, and heat is trapped in the backlight, which affects the liquid crystal layer of the liquid crystal panel, changes its characteristics, and degrades the display quality. There's a problem.

  Furthermore, the diffuser plate used for the conventional direct type backlight has irregularities for diffusing light on both surfaces (a surface facing the linear light source and a surface opposite to the linear light source).

  FIG. 25 is a schematic cross-sectional view of a diffuser plate used in a conventional direct type backlight. The light incident surface (surface facing the linear light source) SF-1 and the light exit surface (linear light source and light source) of the diffuser plate SCT are shown. Are opposite surfaces) SF-E is formed with unevenness DB. The unevenness DB is formed by foaming (surface foaming) the surface of a transparent plate such as an acrylic resin plate.

  The emitted light LE emitted from the light exit surface SF-E and the scattered light LS scattered by the unevenness DB of the light exit surface SF-E become illumination light for illuminating the liquid crystal panel. However, in such a diffuser plate having irregularities formed on both surfaces, a part of incident light L incident from the linear light source indicated by L in the figure, or reflected from the reflecting plate or reflecting sheet is incident on the light incident surface SF. −1 becomes reflected light LR and scattered light LS, and the reflected light LR that is re-reflected by the reflector and reused decreases.

  FIG. 26 is a schematic illustration of a light utilization mode when the lower frame FLM-D having a reflection function is combined with the direct-type backlight having the mountain-shaped reflection plate REF and the diffusion plate having the double-sided unevenness shown in FIG. FIG.

  The light incident surface SF-1 of the diffusion plate SCT becomes reflected light LR and scattered light LS. The reflected light LR is mainly reflected again in the direction of the diffusion plate SCT by the reflection plate REF and reused as illumination light for the liquid crystal panel. A part of the incident light L becomes scattered light LS on the light incident surface SF-1, and the reflected light LR re-reflected by the reflecting plate REF decreases accordingly. For this reason, it is difficult to obtain luminance uniformity on the screen of the liquid crystal panel by controlling the luminance distribution of the illumination light with the reflector.

  This has been an obstacle to improving the light use efficiency in a direct type backlight using a linear light source.

  An object of the present invention is to solve the above-mentioned problems of the prior art, suppress deterioration of CFL luminous efficiency to prevent display quality deterioration, and insufficient luminance around a liquid crystal panel in a backlight in which a plurality of CFLs are arranged. To control the light from the linear light source and the reflected light from the diffuser to improve the light utilization factor and uniformity of the luminance distribution of the linear light source, and to display images with high brightness and high quality. An object of the present invention is to provide a liquid crystal display device obtained.

In order to achieve the above object, in the present invention, an insulating cushion material coated on an electrode portion of a linear light source is surrounded by a heat radiating member such as a metal plate and thermally coupled to the lower frame made of a metal material. Moreover, the linear light source located in the edge part of a lower frame among several linear light sources was arrange | positioned adjacent to the liquid crystal panel side. Furthermore, the luminance distribution of the illumination light of the liquid crystal panel is controlled by making the surface of the diffuser plate facing the linear light source a reflective surface. Hereinafter, representative configurations of the present invention will be described.
(1): a liquid crystal display device having a backlight in which a plurality of linear light sources having electrode portions at an end thereof are arranged and installed on the back surface of the liquid crystal panel via an optical compensation sheet,
The backlight has a lower frame formed of a metal plate, and includes a heat dissipating member thermally coupled to the lower frame made of a metal material surrounding an electrode portion of a linear light source with an insulating cushion material interposed therebetween.

Thereby, the heat of the electrode portion of the linear light source is dissipated from the heat radiating member, and is conducted to the lower frame to efficiently achieve heat dissipation.
(2): The heat dissipation member in (1) is formed by cutting and raising a part of the lower frame.

The heat dissipating member is preferably a metal plate having a high degree of heat transfer, and may be a member separate from the lower frame or a part of the lower frame cut, but it is formed by cutting a part of the lower frame. It is suitable in terms of cost.
(3): a liquid crystal display device having a backlight in which a plurality of linear light sources having electrode portions at an end thereof are arranged and installed on the back surface of the liquid crystal panel via an optical compensation sheet,
The longitudinal direction of the plurality of linear light sources constituting the backlight is arranged in parallel to the back surface of the liquid crystal panel, and the linear light sources located at both ends of the plurality of linear light sources are close to the liquid crystal panel side. Arranged.

With this configuration, the density of illumination light to the edge of the liquid crystal panel is increased, and uniform brightness can be obtained over the entire screen.
(4): The backlight in (3) includes a lower frame made of a metal material, a plurality of linear light sources arranged in parallel to the lower frame, and an upper frame sandwiching the plurality of linear light sources together with the lower frame. And an optical compensation sheet laminated on the upper frame.
(5): The electrode portion of the linear light source in (3) or (4) includes a heat dissipating member thermally coupled to the lower frame made of a metal material surrounded by an insulating cushion material. did.

Thereby, like (1), while the heat_generation | fever of the electrode part of a linear light source is dissipated from a heat radiating member, it can conduct to a lower frame and heat dissipation can be achieved efficiently.
(6): The heat radiating member in (5) was formed by cutting and raising a part of the lower frame.

Similarly to (2), the heat dissipating member is preferably a metal plate having a high thermal conductivity, and may be a member separate from the lower frame, or a part of the lower frame cut out, It is preferable in terms of cost to cut and form.
(7): The optical compensation sheet in (4), (5), and (6) is provided with a diffusion plate positioned immediately above the plurality of linear light sources, and the diffusion plate is used for diffusion on the back surface with respect to the plurality of linear light sources. A surface having irregularities and facing the plurality of linear light sources was a flat surface.

With this configuration, it is possible to obtain a uniform and high-intensity illumination height distribution in which reflected light control by adjusting the reflection characteristics of the reflecting plate for reusing the reflected light from the diffuser plate is not easy.
(8): With respect to the plurality of linear light sources in (7), on the side opposite to the diffusion plate, there is a top along the plurality of linear light sources, and the distance from the top to the diffusion plate increases. A mountain-shaped reflector having a curved surface gradually approaching the linear light source was provided.

  In addition to the effect of the above configuration (7), the reflected light of the diffuser can be used efficiently together with the light of the linear light source, and the liquid crystal panel screen is made uniform by directing in the direction of the diffuser by controlling the luminance distribution. It can be illuminated.

  According to the present invention, in order to increase the brightness of the screen of the liquid crystal panel, the luminous efficiency due to the increase in the amount of heat generated in the electrode portion accompanying the increase in the applied current value of the linear light source constituting the backlight or the increase in the number of the line light source. Deterioration of the display quality of the liquid crystal panel can be avoided by suppressing the decrease.

  In addition, it is possible to provide a liquid crystal display device in which a shortage of luminance around the liquid crystal panel in a backlight in which a plurality of linear light sources are arranged is resolved to obtain a high luminance and high quality image display.

  Furthermore, it is possible to obtain a liquid crystal display device capable of displaying a high-luminance and high-quality image with improved light utilization and uniformity of luminance distribution.

  The present invention is not limited to the above-described configuration, and various modifications can be made without departing from the technical idea of the present invention. Other objects and configurations of the present invention will become apparent from the following description of the embodiments.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings of the examples.

  FIG. 1 is a side view of a main part showing a holding structure of a linear light source constituting a backlight for explaining a first embodiment of a liquid crystal display device according to the present invention, and FIG. 2 is a main view of FIG. FIG. 3 is a front view of FIG. 2 viewed from the direction of arrow B. FIG. In each figure, FLM-D is a lower frame, CFL is a cold cathode fluorescent lamp as a linear light source, ELD is an electrode portion thereof, ESP is a power supply line, GB is a rubber cushion as an insulating cushion material, and MP is a heat sink. .

  In this embodiment, a part of the lower frame FLM-D is cut and raised as shown by an arrow C in FIG. 3 to form a heat radiating plate MP, which is covered around the electrode portion ELD of the cold cathode fluorescent lamp CFL. The cold cathode fluorescent lamp CFL was held and fixed around the rubber cushion GB.

  According to this embodiment, heat generated near the electrode portion of the cold cathode fluorescent lamp CFL is dissipated from the heat radiating plate MP and is also conducted and dissipated to the lower frame FLM-D, thereby preventing a decrease in luminous efficiency of the cold cathode fluorescent lamp CFL. Is done. Therefore, a decrease in luminance is suppressed and a bright image is formed on the screen of the liquid crystal panel.

  FIG. 4 is a side view of a main part showing a holding structure of a linear light source constituting a backlight for explaining a second embodiment of the liquid crystal display device according to the present invention, and FIG. 5 is a view of FIG. 4 viewed from the direction of arrow A. FIG. 6 is a front view of FIG. 5 viewed from the direction of arrow B. In each figure, it corresponds to the same functional part indicated by the same reference numeral in FIGS.

  In this embodiment, a part of the lower frame FLM-D is cut and raised as shown by an arrow C in FIG. 6, and this is bent so as to be concave toward the cold cathode fluorescent lamp CFL, thereby forming the heat radiating plate MP. .

  Also in this embodiment, the heat generated in the vicinity of the electrode portion of the cold cathode fluorescent lamp CFL is dissipated from the heat radiating plate MP and is also conducted and dissipated to the lower frame FLM-D, resulting in a decrease in the luminous efficiency of the cold cathode fluorescent lamp CFL. Is prevented. Therefore, a decrease in luminance is suppressed and a bright image is formed on the screen of the liquid crystal panel.

  FIG. 7 is a side view of a main part showing a holding structure of a linear light source constituting a backlight for explaining a third embodiment of the liquid crystal display device according to the present invention, and FIG. 8 is a main view of FIG. FIG. 9 is a front view of FIG. 8 viewed from the direction of arrow B. FIG. In each figure, PRJ is a bent portion, and the same reference numerals as those in FIGS. 4 to 6 and FIGS. 1 to 3 correspond to the same functional parts.

  In the present embodiment, a part of the lower frame FLM-D is cut and raised as shown by an arrow C in FIG. 9 and is bent so as to be concave toward the cold cathode fluorescent lamp CFL to form the heat radiating plate MP. In addition, the bent portion PRJ is formed by inverting the tip portion.

  Also in this embodiment, the heat generated in the vicinity of the electrode portion of the cold cathode fluorescent lamp CFL is dissipated from the heat radiating plate MP and is also conducted and dissipated to the lower frame FLM-D, resulting in a decrease in the luminous efficiency of the cold cathode fluorescent lamp CFL. Is prevented. Further, the rubber cushion GB covered on the electrode portion of the cold cathode fluorescent lamp CFL is easily inserted by the bent portion PRJ in which the tip portion of the curved heat sink MP is inverted. As a result, as in the above embodiments, a decrease in luminance is suppressed and a bright image is formed on the screen of the liquid crystal panel.

  FIG. 10 is a side view showing a main part of a holding structure for a linear light source constituting a backlight for explaining a fourth embodiment of the liquid crystal display device according to the present invention. In this embodiment, the heat radiating plate MP is formed of a metal plate separate from the lower frame FLM-D, and is fixed to the lower frame FLM-D by welding, screwing or fitting.

  In addition, the shape of the heat sink MP may adopt any of the same examples as those described in FIGS. 1 to 9, and the effect is the same as the effects of the corresponding examples.

  Also in this embodiment, the heat generated in the vicinity of the electrode portion of the cold cathode fluorescent lamp CFL is dissipated from the heat radiating plate MP and is also conducted and dissipated to the lower frame FLM-D, resulting in a decrease in the luminous efficiency of the cold cathode fluorescent lamp CFL. Is prevented. As a result, as in the above embodiments, a decrease in luminance is suppressed and a bright image is formed on the screen of the liquid crystal panel.

  FIG. 11 is an exploded perspective view for explaining the overall structure of a backlight for explaining a fifth embodiment of the liquid crystal display device according to the present invention. In the figure, the same reference numerals as those in FIG. 22 correspond to the same functional parts. Since the schematic structure of the backlight is the same as that shown in FIG. 22, repeated description is minimized.

  In general, a plurality of CFLs are arranged on the upper surface of the lower frame FLM-D made of a metal material so that the longitudinal directions thereof are parallel to each other. The surface on the CFL side of the lower frame FLM-D has a function of a reflector. Another member such as a sheet having a reflection function or a mountain-shaped reflector may be inserted or installed between the lower frames FLM-D and CFL.

  In the present embodiment, among the plurality of linear light sources CFL arranged on the upper surface of the lower frame FLM-D, the attachment positions of the linear light sources CFL-E located at both ends are set higher than the arrangement surface level of the other linear light sources CFL. The distance H is shifted to the diffusion plate SCT side, that is, the liquid crystal panel side.

  FIG. 12 is a schematic cross-sectional view similar to FIG. 23 for explaining an arrangement example of linear light sources in a direct type backlight using a plurality of linear light sources. In the figure, L-L is the arrangement surface level of the linear light sources CFL other than the linear light sources CFL-E located at both ends. The linear light sources CFL-E located at both ends are brought closer to the diffusion plate SCT side by the dimension H with respect to the arrangement surface level LL. The dimension H is determined at the design stage in consideration of the size of the backlight, the number of linear light sources and the light emission amount thereof, the distance D to the periphery of the diffusion plate SCT, and the like.

  Further, as shown in FIG. 11, the upper surface of the lower frame FLM-D corresponding to the linear light source CFL-E located at both ends may be inclined in the liquid crystal panel direction, thereby the linear light source CFL. The utilization efficiency of the light emission of -E can be improved.

  According to the present embodiment, the light emission of the linear light source that irradiates the back surface of the diffusion plate SCT becomes substantially uniform on the front surface, and the liquid crystal panel installed above the diffusion plate can display an image with uniform brightness on the entire surface.

  13 is a cross-sectional view of an essential part taken along line DD in FIG. 11 for explaining an example of the specific structure of the backlight of the liquid crystal display device according to the present invention. FIG. 14 is a specific example of the backlight of the liquid crystal display device according to the present invention. It is principal part sectional drawing along line EE of FIG. 11 explaining an example of a general structure. In this backlight, a plurality of linear light sources CFL are fixed to the inner surface of the lower frame FLM with the structure of any one of the above embodiments, and then the lower frame FLM-D and the upper frame FLM-U are bonded to each other with the claws NL. While fixing to a predetermined position, it is integrally fixed with the left and right molds MLD-L and MLD-R.

  Then, an optical compensation sheet OPS composed of a diffusion plate SCT, a diffusion sheet SCTS, and a prism sheet PRS is placed on the upper surface of the upper frame FLM-U and fixed with screws BT.

  As described above, among the linear light sources CFL installed on the inner surface of the lower frame FLM, the linear light sources CFL-E located at both ends are closer to the diffusion plate SCT side by the distance H than the arrangement level of the other linear light sources CFL. There is.

  In FIG. 14, a reflection plate REF formed in a waveform is installed on the inner surface of the lower frame FLM, and the use efficiency of each light emission of the linear light source is improved by this reflection plate REF.

  FIG. 15 is a developed perspective view showing a more specific configuration example of the direct type backlight according to the present invention. FIG. 15 shows components that are also mounted on the direct type backlight structure shown in FIGS. 11 and 22. One end of a power supply line (cable) ESP is attached to each end of the linear light source CFL, and is covered with a rubber cushion (rubber bush) GB fitted to each power supply line.

  A connector CON is attached to the other end of the power supply line ESP. The connector CON has a structure for receiving a pair of power supply lines ESP adjacent to each other, but the power supply lines are separated from each other inside the connector.

  The connectors CON arranged on the right side of FIG. 15 are connected to the inverter circuit INV mounted on the circuit board attached to the lower surface of the lower frame FLM-D made of a metal material such as aluminum. In FIG. 15, the circuit board on which the inverter circuit is mounted is indicated by INV. In the following, the inverter circuit itself will be described as INV.

  An inverter circuit INV is individually provided for each of the linear light sources CFL, and an end (electrode) of this circuit and the linear light source CFL on the high voltage application side (also called the Hot side, located on the right side in FIG. 2) ) Is wired so that the wiring length between these lines does not vary for each linear light source.

  The voltage supplied from the inverter circuit INV to the linear light source CFL (cold cathode tube) receives a loss corresponding to the length of the power supply line ESP, and the luminance varies among the plurality of linear light sources CFL. Making the wiring length of each power supply line ESP uniform is effective in preventing image degradation of the liquid crystal panel due to this luminance variation, and a plurality of inverter circuits INV are arranged in parallel on the right side of the lower frame FLM-D. The layout to be arranged is one means.

  An insulating sheet INS is disposed between the lower surface of the lower frame FLM-D and the circuit board on which the inverter circuit INV is mounted. The inverter circuit INV (circuit board) is attached to the cover ICOV and passes through the insulating sheet INS. Attached to FLM-D.

  A connector substrate CSUB that extends along the left side of the lower frame FLM-D is provided on the lower surface of the insulating sheet INS. In FIG. 15, the connector CON that receives the power supply line ESP connected to the left side of each linear light source CFL is connected to a terminal of the connector substrate CSUB. One of the connectors CON formed at both ends of the power supply line ESP is connected to another terminal of the connector substrate CSUB, and the other is connected to a low voltage side (reference potential side) terminal of the inverter circuit INV. In such connection, a reference potential is applied to the left electrode (also referred to as the low voltage side or the Cold side) of each linear light source CFL in FIG.

  The above configuration is common to the direct type backlight shown in FIGS. 11 and 22, but the backlight shown in FIG. 15 has the following structural features. The main features are as follows.

  That is, an optical sheet composed of a laminate of a diffusion plate SCT, a diffusion sheet SCTS, and a prism sheet PRS is used for a right mold MLD-R and a left mold MLD-L made of a metal upper frame FLM-U that is preferably made of aluminum and a synthetic resin. It is the point made into the structure fixed on both sides.

  In such a structure, unexpected mechanical shock or thermal shock due to the upper surface of the metal upper frame FLM-U coming into contact with the lower surface of the liquid crystal panel, that is, the main surface of the substrate made of glass or the like, In addition to the bottom surface, the substrate may be damaged. In order to prevent this, a rubber spacer GS is provided on the upper surface of the upper frame FLM-U along the opening of the upper frame FLM-U.

  Each of the diffusing plate SCT, diffusing sheet SCTS and prism sheet PRS constituting the optical sheet is assembled with the direct type backlight shown in FIG. 15, and its end is the lower surface of the upper frame FLM-U, the right mold MLD. -R and the size of the left mold MLD-L so as to overlap each other.

  On the other hand, since the upper frame FLM-U, the right mold MLD-R, and the left mold MLD-L are combined with the screw VLT, a concave HOL for avoiding the screw is formed at each end of these optical sheets. Is formed. By providing the dent HOL not at the corner of each optical sheet, but away from the corner, the optical sheet laminate is gripped by the upper frame FLM-U, the right mold MLD-R, and the left mold MLD-L, and mechanically It will be difficult to shift against a strong vibration. In addition, since the end of the optical sheet is held, problems such as scattering of transmitted light around the optical sheet are solved.

  The direct type backlight shown in FIG. 15 has an upper mold MLD-U and a lower mold MLD-D. Each of the upper mold MLD-U and the lower mold MLD-D has upper surfaces extending in a direction intersecting with the extending direction of the right mold MLD-R and the left mold MLD-L on the lower surface of the diffusion plate SCT and facing each other ( In FIG. 22, they are arranged so as to be in contact with the upper side and the lower side, respectively. Therefore, both of the upper mold MLD-U and the lower mold MLD-D are disposed apart from each other in a region sandwiched between the right mold MLD-R and the left mold MLD-L on the lower surface of the diffusion plate SCT.

  Both the right mold MLD-R and the left mold MLD-L have shapes facing the lower and side surfaces of the peripheral edge of the optical sheet, whereas the upper mold MLD-U and the lower mold MLD-D are the optical sheet. It faces only the lower surface of the peripheral edge. In other words, the upper mold MLD-U and the lower mold MLD-D can reduce the area in the main surface of the substrate of the liquid crystal panel because there is no portion facing the side surface of the optical sheet. It is suitable for so-called narrow frame of the device.

  Further, since the lower portions (lower surfaces) of the upper mold MLD-U and the lower mold MLD-D are supported by the upper surface of the lower frame FLM-D, the stability of the entire direct type backlight is also increased. Thus, the direct type backlight structure shown in FIG. 22 is suitable for thinning the liquid crystal display device.

  As the diffusion plate SCT in the direct type backlight described above, the conventional diffusion plate described in FIGS. 25 and 26 can be used. However, by using the diffusion plate of the embodiment described below, The light utilization rate is improved, and the screen brightness of the liquid crystal panel can be made uniform and high.

  FIG. 16 is a schematic cross-sectional view of a diffusion plate for explaining a sixth embodiment of the liquid crystal display device according to the present invention. The diffusing plate SCT of this embodiment forms a concavo-convex DB only on one surface of a transparent plate which is preferably an acrylic resin plate, that is, a light exit surface (surface opposite to the linear light source) SF-E, and the linear light source CFL. The light incident surface SF-I facing the surface is a flat surface.

  With this configuration, a part of the incident light L becomes the reflected light LR and is directed toward the reflector. Since almost no scattered light LS is generated on the light incident surface SF-I as shown in FIG. 25, the reflected light LR can be directed again by being controlled in the direction of the diffusing plate by the reflecting plate or the reflecting sheet.

  FIG. 17 shows a light utilization form when a lower plate FLM-D having a reflection function is combined with a direct type backlight having a mountain-shaped reflection plate REF and a diffusion plate having irregularities formed only on the exit surface shown in FIG. It is typical explanatory drawing of.

  Most of the light L incident on the incident surface SF-1 from the linear light source is transmitted to the output surface SF-E and becomes illumination light of the liquid crystal panel. The reflected light LR reflected by the light incident surface SF-1 of the diffusion plate SCT is reflected again in the direction of the diffusion plate SCT by the mountain-shaped reflection plate REF and reused as illumination light for the liquid crystal panel. Needless to say, if the lower frame FLM-D has a reflective function or is provided with a reflective sheet, these reflected lights are also reused.

  The amount of the reflected light LR is larger than that of the conventional diffuser, and the brightness distribution on the screen of the liquid crystal panel is controlled to be uniform by adjusting the curved surface shape, height, position, etc. of the mountain-shaped reflector REF. it can. Similarly, the reflected light reflected again by the incident surface SF-I of the diffuser plate SCT is reused.

  Therefore, it becomes easy to obtain the luminance uniformity on the screen of the liquid crystal panel by controlling the luminance distribution of the illumination light with the reflector.

  By using the diffusion plate SCT of the above-described embodiment as the diffusion plate shown in FIGS. 11 to 15, the high quality having the effect in addition to the effects of the configurations of the first to fifth embodiments of the present invention. The liquid crystal display device can be obtained.

  FIG. 18 is an external view showing an example of a display monitor in which the liquid crystal display device according to the present invention is mounted. The backlight constituting the liquid crystal display device mounted on the screen of the monitor, that is, the display unit has the configuration of the embodiment of the present invention described above.

  The liquid crystal display device according to the present invention is not limited to the display monitor as described above, but can be used for a monitor of a desktop personal computer, a notebook personal computer, a television receiver, and other devices.

  FIG. 19 is an explanatory diagram of a configuration and driving system of a general active matrix liquid crystal display device to which the present invention is applied. This type of liquid crystal display device includes a liquid crystal panel PNL and a data line (also referred to as drain signal line or drain line) drive circuit (IC chip), that is, a drain driver DDR, a scanning line (gate signal line or gate line) around the liquid crystal panel PNL. Display control means that has a drive circuit (IC chip), that is, a gate driver GDR, and supplies display data, a clock signal, a gradation voltage, and the like for image display to these drain driver DDR and gate driver GDR. A display control device CRL and a power supply circuit PWU are provided.

  Display data, a control signal clock, a display timing signal, and a synchronization signal from an external signal source such as a computer, a personal computer, or a television receiver circuit are input to the display control device CRL. The display control device CRL includes a gradation reference voltage generation unit, a timing controller TCON, and the like, and converts external display data into data in a format suitable for display on the liquid crystal panel PNL.

  Display data and clock signals for the gate driver GDR and the drain driver DDR are supplied as shown. The carry output of the previous stage of the drain driver DDR is directly supplied to the carry input of the drain driver of the next stage.

  FIG. 20 is a block diagram showing a schematic configuration of each driver of the liquid crystal panel and a signal flow. The drain driver DDR includes a data latch unit for display data such as a video (image) signal and an output voltage generation circuit. The gradation reference voltage generation unit HTV, multiplexer MPX, common voltage generation unit CVD, common driver CDD, level shift circuit LST, gate on voltage generation unit GOV, gate off voltage generation unit GFD, and DC-DC converter D / D are illustrated. 17 power supply circuits PWU are provided.

  FIG. 21 is a timing chart showing display data input from the signal source (main body) to the display control device and signals output from the display control device to the drain driver and the gate driver. The display control device CRL receives a control signal (clock signal, display timing signal, synchronization signal) from a signal source, and supplies a clock D1 (CL1), a shift clock D2 (CL2), and display data as control signals to the drain driver DDR. At the same time, a frame start instruction signal FLM, a clock G (CL3), and display data are generated as control signals to the gate driver GDR.

  In the method using a low-voltage differential signal (LVDS signal) for transmission of display data from a signal source, LVDS reception in which the LVDS signal from the signal source is mounted on a substrate (interface substrate) on which the display control device is mounted. After being converted into the original signal by the circuit, it is supplied to the gate driver GDR and the drain driver DDR.

  As is apparent from FIG. 21, the clock signal D2 (CL2) for shifting the drain driver is the same as the frequency of the clock signal (DCLK) and display data inputted from the main body computer or the like, and about 40 MHz (megahertz) in the XGA display element. ). The liquid crystal display device having such a configuration has features such as a thin shape and low power consumption, and will be widely adopted as a display device in each field in the future.

  Each embodiment of the present invention described above prevents deterioration of display quality by suppressing a decrease in luminous efficiency of the linear light source, and the periphery of the liquid crystal panel in the direct type backlight in which a plurality of the linear light sources are arranged. The brightness deficiency in the light source has been resolved and the light from the linear light source, the light from the linear light source by the reflector and the reflected light from the diffuser are controlled to improve the light utilization rate and the uniformity of the luminance distribution of the linear light source. A liquid crystal display device capable of displaying an image with high brightness and high quality can be obtained.

It is a principal part side view which shows the holding structure of the linear light source which comprises the backlight for describing 1st Example of the liquid crystal display device by this invention. It is the principal part top view which looked at FIG. 1 from the arrow A direction. It is the front view which looked at FIG. 2 from the arrow B direction. It is a principal part side view which shows the holding structure of the linear light source which comprises the backlight for describing 2nd Example of the liquid crystal display device by this invention. It is the principal part top view which looked at FIG. 4 from the arrow A direction. It is the front view which looked at FIG. 5 from the arrow B direction. It is a principal part side view which shows the holding structure of the linear light source which comprises the backlight for describing 3rd Example of the liquid crystal display device by this invention. It is the principal part top view which looked at FIG. 7 from the arrow A direction. It is the front view which looked at FIG. 8 from the arrow B direction. It is a principal part side view which shows the holding structure of the linear light source which comprises the backlight for demonstrating 4th Example of the liquid crystal display device by this invention. It is a development perspective view explaining the composition of the whole backlight for explaining the 5th example of the liquid crystal display by the present invention. FIG. 25 is a schematic cross-sectional view similar to FIG. 23 for explaining an arrangement example of linear light sources in a direct backlight using a plurality of linear light sources. FIG. 12 is a cross-sectional view of a principal part taken along line DD of FIG. 11 for explaining an example of a specific structure of a backlight of the liquid crystal display device according to the present invention. FIG. 12 is a cross-sectional view of a principal part taken along line EE of FIG. 11 for explaining an example of a specific structure of a backlight of the liquid crystal display device according to the present invention. It is an expansion | deployment perspective view which shows the more concrete structural example of the direct type | mold backlight by this invention. It is a schematic cross section of the diffusion plate for explaining the sixth embodiment of the liquid crystal display device according to the present invention. Schematic of the light utilization form when combining a direct-type backlight having a mountain-shaped reflector REF on a lower frame FLM-D having a reflection function with a diffuser plate having irregularities formed only on the exit surface shown in FIG. It is explanatory drawing. It is an external view which shows an example of the display monitor which mounted the liquid crystal display device by this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the structure and drive system of a general active matrix type liquid crystal display device to which this invention is applied. It is a block diagram which shows schematic structure of each driver of a liquid crystal panel, and the flow of a signal. FIG. 4 is a timing chart showing display data input from a signal source (main body) to a display control device and signals output from the display control device to a drain driver and a gate driver. It is an expansion | deployment perspective view explaining an example of the conventional direct type | mold backlight. It is a schematic cross section explaining an arrangement example of linear light sources in a direct type backlight using a plurality of linear light sources. It is a principal part schematic diagram which shows an example of the CFL support structure of the backlight shown in FIG. It is a schematic cross section of the diffuser plate used in a conventional direct type backlight. FIG. 26 is a schematic explanatory view of a light utilization mode when a diffusion plate having double-sided irregularities shown in FIG. 25 is combined with a direct type backlight having a mountain-shaped reflector REF on a lower frame FLM-D having a reflection function. .

Explanation of symbols

FLM-U Upper frame FLM-D Lower frame MLD-L Left mold MLD-R Right mold SCT Diffusion plate SF-I Light incident surface SF-E Light emission surface DB Unevenness SCTS diffusion sheet PRS Prism sheet CFL Linear light source (cold cathode fluorescence) light)
CFL-E Linear light source at the end ELD Electrode part ESP Feed line GB Insulation cushion material (rubber cushion)
MP heat sink.

Claims (6)

A liquid crystal display device comprising a liquid crystal panel and a direct type backlight disposed on the back side of the liquid crystal panel,
The backlight includes a lower frame having a reflection plate and a plurality of linear light sources therein, a diffusion plate that controls the distribution of light emitted from the linear light source, and a right that covers the right end of the linear light source. A mold, and a left mold covering the left end of the cold cathode fluorescent lamp,
The right mold and the left mold have an inclined portion that is inclined with respect to the diffusion plate above the cold cathode fluorescent lamp, and a flat portion that is parallel to the diffusion plate above the inclined portion,
The diffusion plate is supported by the right mold and the left mold plane part,
The electrode part provided at one end of the linear light source is connected to the inverter circuit board,
The electrode part provided at the other end of the linear light source is connected to a connector board,
The liquid crystal display device, wherein the inverter circuit board and the connector board are disposed on a back surface of the lower frame, and the inverter circuit board and the connector board are connected to each other by a power supply line. A plurality of linear light sources having an electrode part at an end, a liquid crystal display device including a backlight installed on the back of a liquid crystal panel via an optical compensation sheet,
The longitudinal direction of the plurality of linear light sources constituting the backlight is arranged in parallel to the back surface of the liquid crystal panel, and the linear light sources positioned at both ends of the plurality of linear light sources are more than the other linear light sources. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is disposed close to the liquid crystal panel side.   2. The liquid crystal display device according to claim 1, wherein an electrode portion of the linear light source is covered with an insulating cushion material, and the insulating cushion is surrounded by a heat radiating member made of a metal material.   4. The liquid crystal display device according to claim 3, wherein the lower frame is made of metal, and the heat radiating member is formed by cutting and raising a part of the lower frame.   The liquid crystal display device according to claim 1, wherein the diffusion plate has a recessed portion on a side. 2. The liquid crystal display device according to claim 1, wherein flat portions of the right mold and the left mold have screw holes, and the right mold and the left mold are fixed to a lower frame by screws.

Images