JP2006058483A - Backlight device for liquid crystal display and transmissive liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To heighten luminance of a transmissive liquid crystal panel by providing a large number of light emitting diodes and to provide a backlight device for liquid crystal display, suppressing occurrence of color irregularity or a lateral thread and a transmissive liquid crystal display device. <P>SOLUTION: A color liquid crystal display panel 110 of the transmissive liquid crystal display device 100 is illuminated from the rear face side with the backlight device 140 for liquid crystal display, which is constructed by aligning a plurality of side face light emitting diodes 121R, 121G, 121B each equipped with an optical component 150 to make light generated from a light source be emitted from the side face, and which has light shielding parts 151 to cover at least center parts of the front faces of the optical components 150 arranged on the side face light emitting diodes 121R, 121G, 121B formed thereon. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a backlight device for a liquid crystal display that illuminates a transmissive color liquid crystal display panel such as a transmissive color liquid crystal display (LCD) from the back side with display light emitted from a large number of light emitting diodes. The present invention also relates to a transmissive color liquid crystal display device including the backlight device for liquid crystal display.

  The liquid crystal display device has a larger display screen, lighter weight, thinner thickness, lower power consumption, etc., compared with a cathode ray tube (CRT), for example, a self-luminous PDP (Plasma Display). Panel) and the like are used for television receivers and various displays. A liquid crystal display device encapsulates liquid crystal between two transparent substrates of various sizes, and changes the light transmittance by changing the direction of liquid crystal molecules by applying a voltage to optically display a predetermined image or the like. To do.

  Since the liquid crystal display device is not a light emitter, the liquid crystal display device includes a backlight unit that functions as a light source, for example, on the back surface of the liquid crystal panel. The backlight unit includes, for example, a primary light source, a light guide plate, a reflective film, a lens sheet, or a diffusion film, and supplies display light to the entire liquid crystal panel. For the backlight unit, a cold cathode fluorescent lamp (CCLF: Cold Cathode Fluorescent Lamp) in which mercury or xenon is enclosed in a fluorescent tube is used as the primary light source. However, it is necessary to solve problems such as short or low luminance region on the cathode side and poor uniformity.

  In a large-sized liquid crystal display device, an area light type backlight (area light backlight) device is generally provided that places a plurality of long cold-cathode fluorescent lamps on the back of a diffusion plate and supplies display light to the liquid crystal panel. It has been. Even in such an area light type backlight device, it is necessary to solve the problems caused by the cold cathode fluorescent lamp described above. In particular, in a large-sized television receiver exceeding 40 inches, high brightness and high uniformity are obtained. The problem of conversion has become more prominent.

  In the area light type backlight device, instead of the cold cathode fluorescent lamp described above, a large number of light primary diodes of red, green and blue (hereinafter referred to as LEDs) are provided on the back side of the diffusion film. An LED area light type backlight that obtains white light by two-dimensionally arranging a diode) has attracted attention. Such an LED backlight device is designed to reduce the cost as the cost of the LED is reduced and to display a high luminance on a large liquid crystal panel with low power consumption.

  In various backlight devices, an optical function sheet block, a diffusion light guide plate, a light diffusion plate, a reflection, and the like that perform functional conversion of display light emitted from the light source and make it uniform between the light source unit and the transmissive liquid crystal panel. Various optical members such as a sheet are arranged. In the backlight device, the light diffusing plate is generally formed of a transparent acrylic resin or the like, and has a function of transmitting a part of the display light incident on a portion facing the light source and reflecting a part thereof. Is formed. A plurality of strip-shaped dimming patterns formed in a region facing the fluorescent tube each include a light diffusing plate formed of a large number of reflective dots. The light diffusing plate is formed such that the area of the reflection dot decreases as the distance from the axis of the fluorescent tube decreases, so that the light transmittance increases as the distance from the fluorescent tube increases, and uniform light is emitted as a whole. (For example, refer patent document 1).

  Further, as an LED used in a backlight device, a side-emitting LED provided with an optical component that emits light emitted from a light source from the side surface, that is, a main component of emitted light is emitted in the outer peripheral direction of the light emitting bulb. A so-called side emission type LED having directivity is known (see, for example, Patent Document 2 and Patent Document 3).

Japanese Patent Laid-Open No. 6-301034 JP 2003-8068 A JP 2004-133391 A

  Also in the LED backlight device, a light diffusing plate is arranged between a transmissive liquid crystal panel and a light source unit formed by arraying a light source block on which a large number of LEDs are mounted. For example, each LED is placed on the light diffusing plate. The correspondence of forming a large number of dimming patterns so as to face each other is also considered. In each dimming pattern, display light is supplied from the entire surface of the light diffusing plate to the liquid crystal panel with a uniform amount of light by controlling the transmission / reflection operation of the light diffusing plate for the display light emitted from the opposing LEDs. In this way, high brightness and high uniformity can be achieved.

  Here, even if a side-emitting light emitting diode provided with an optical component that radiates light emitted from the light source from the side surface is used, there is light that emerges in front of the LED as leakage light. Although this leaked light is weak in intensity, the distance to the optical sheet facing it is extremely short compared to the light emitted in the lateral direction, so the influence of uneven color is inevitable. In order to avoid this, in the current backlight structure, it is necessary to employ a diffusion light guide plate in which a dot pattern with adjusted transmittance is arranged immediately above the LED.

  However, in an LED backlight device, a large amount of heat generated from a large number of LEDs acts on a light diffusing plate formed of acrylic resin, thereby causing a large dimensional change in the light diffusing plate and opposing LEDs. There may be a positional shift between the light control pattern and the light control pattern. Further, in the LED backlight device, a positional deviation between the opposing LED and the dimming pattern occurs due to variations in the dimensional accuracy and assembly accuracy of the liquid crystal panel, the light source unit, or the light diffusion plate, and the dimming pattern printing accuracy. Sometimes.

  In the LED backlight device, it is extremely difficult to accurately position the LED and the dimming pattern because of the various factors described above. In the LED backlight device, the constituent members must be manufactured with high accuracy and precise assembly must be performed, which makes it difficult to reduce the cost. In the LED backlight device, as the size of the liquid crystal display device increases and the brightness increases, the positional deviation between the LED and the dimming pattern also increases, and problems such as color unevenness and the generation of a lamp image are noticeable on the liquid crystal panel. Become.

  Further, in the LED backlight device, the light source unit is configured as an area light type by arranging a plurality of light source blocks on which a plurality of LEDs are mounted at a predetermined interval from each other. A phenomenon occurs in which the emitted display light is concentrated from both sides between the rows of the respective light source blocks to generate a portion having a high luminance. In the LED backlight device, for this reason, there is a problem that a high luminance region is generated in a horizontal streak state in a region facing each row of each light source block of the light diffusion plate, and color unevenness of the horizontal streak occurs in the liquid crystal panel.

  In the LED backlight device, for example, it is possible to cope with the above-described problem by forming a dimming pattern with a large area on the light diffusion plate or molding it with milky white synthetic resin, but the display light is blocked. Since the light transmittance is greatly reduced, the brightness of the liquid crystal panel is lowered. In an LED backlight device, for example, when trying to cope with higher brightness by using more LEDs, not only the cost and power consumption increase, but also it becomes extremely difficult to cope with larger heat generation. .

  SUMMARY OF THE INVENTION An object of the present invention is to provide a backlight device for liquid crystal display and a transmissive liquid crystal display device that are provided with a large number of light emitting diodes to increase the luminance of the transmissive liquid crystal panel and prevent uneven color and horizontal stripes. It is to provide.

  Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of embodiments described below.

  The present invention is a backlight device for liquid crystal display that illuminates a transmissive color liquid crystal display panel from the back side, and includes a plurality of side-emitting light emitting diodes provided with optical components that radiate light emitted from a light source from the side. A light-shielding portion that is arranged and covers at least the central portion of the front surface of the optical component provided in the side-emitting LED is formed.

  The transmissive liquid crystal display device according to the present invention includes a plurality of side emitting light emitting diodes provided with an optical component that emits light emitted from a light source from the side surface, and is provided in the side emitting light emitting diode. A liquid crystal display backlight device having a light shielding portion covering at least a central portion of the front surface of the optical component, and a transmissive color liquid crystal display panel illuminated from the back side by the liquid crystal display backlight device. It is characterized by that.

  According to the present invention, by arranging a plurality of side-emitting light emitting diodes provided with optical components that emit light emitted from a light source from the side, the luminance of the transmissive liquid crystal panel is increased and the side-emitting light is emitted. By forming a light-shielding portion that covers at least the central portion of the front surface of the optical component provided in the diode, the light leakage in the front direction of the side-emitting LED can be shielded by the light-shielding portion. Generation can be reduced.

  Further, in the present invention, since the light-shielding portion that covers at least the central portion of the front surface of the optical component provided in the side-emitting LED is formed, it is not necessary to provide a light control pattern on the light diffusion plate, and a large number of light emission The manufacturing cost and assembly of each constituent member are not affected by the dimensional change of the constituent members due to the influence of heat generated from the diode, the dimensional accuracy or assembly accuracy of the constituent members, and the variation in the printing accuracy of the dimming pattern. Costs can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Needless to say, the present invention is not limited to the following examples, and can be arbitrarily changed without departing from the gist of the present invention.

  The present invention is applied to, for example, a transmissive color liquid crystal display device 100 configured as shown in FIG.

  The transmissive color liquid crystal display device 100 includes a transmissive color liquid crystal display panel 110 and a liquid crystal display backlight device 140 provided on the back side of the liquid crystal display panel 110. Although not shown, the transmissive color liquid crystal display device 100 includes a receiving unit such as an analog tuner and a digital tuner that receives terrestrial and satellite waves, and a video signal that processes a video signal and an audio signal received by the receiving unit, respectively. An audio signal output unit such as a processing unit, an audio signal processing unit, a speaker that outputs an audio signal processed by the audio signal processing unit, and the like may be provided.

  In the transmissive color liquid crystal display panel 110, two transparent substrates (TFT substrate 111 and counter electrode substrate 112) made of glass or the like are arranged to face each other, and, for example, twisted nematic (TN) liquid crystal is provided in the gap. The liquid crystal layer 113 encapsulating the liquid crystal layer 113 is provided. On the TFT substrate 111, signal lines 114 arranged in a matrix, scanning lines 115, thin film transistors 116 serving as switching elements arranged at intersections of the signal lines 114 and the scanning lines 115, and pixel electrodes 117 are formed. Has been. The thin film transistor 116 is sequentially selected by the scanning line 115 and writes the video signal supplied from the signal line 114 to the corresponding pixel electrode 117. On the other hand, a counter electrode 118 and a color filter 119 are formed on the inner surface of the counter electrode substrate 112.

  In the transmissive color liquid crystal display device 100, the transmissive color liquid crystal display panel 110 having such a configuration is sandwiched between two polarizing plates 131 and 132, and white light is irradiated from the back side by the backlight device 140 for liquid crystal display. In this state, a desired full-color image can be displayed by driving with an active matrix method.

  The liquid crystal display backlight device 140 illuminates the color liquid crystal display panel 110 from the back side. As shown in FIG. 1, the backlight device 140 for liquid crystal display includes a backlight housing unit 120 in which a light source (not shown) and a function of mixing light emitted from the light source into white light are incorporated. It has a configuration including a diffusion plate 141, an optical sheet group 145 such as a diffusion sheet 142, a prism sheet 143, and a polarization conversion sheet 144 arranged on the diffusion plate 141. The diffusing plate 141 makes the luminance emitted from the surface emission uniform by internally diffusing the light emitted from the light source. Further, the optical sheet group 145 functions to increase the luminance in surface emission by raising the white light emitted from the diffusion plate 141 in the normal direction of the diffusion plate 141.

  FIG. 2 shows a schematic configuration diagram in the backlight housing 120. As shown in FIG. 2, the backlight housing 120 includes a red (R) light emitting diode 121R that emits red (R) light, a green (G) light emitting diode 121G that emits green light, and a blue light. A blue (B) light emitting diode 121B is used as a light source. In the following description, when the red light emitting diode 121R, the green light emitting diode 121G, and the blue light emitting diode 121B are collectively referred to, they are simply referred to as the light emitting diode 121.

  As shown in FIG. 2, the light emitting diodes 121 are arranged in a line in a desired order on the substrate 122 to form a light emitting diode unit 121n (n is a natural number). For example, as shown in FIG. 2, four light emitting diodes 121 are arranged in the order of green light emitting diode 121G, red light emitting diode 121R, green light emitting diode 121G, and blue light emitting diode 121B, as shown in FIG. In this arrangement, the light emitting diodes 121 are used as repeating units.

  The light emitting diode units 121n are arranged in a plurality of rows in the backlight housing unit 120 in accordance with the size of the liquid crystal display panel 110 illuminated by the liquid crystal display backlight device 140. As shown in FIG. 2, the arrangement of the light emitting diode unit 121n in the backlight housing 120 may be arranged such that the longitudinal direction of the light emitting diode unit 121n is horizontal, not shown. However, the light emitting diode unit 121n may be arranged so that the longitudinal direction thereof is the vertical direction, or a combination of the two may be used.

  In addition, since the method of arranging the longitudinal direction of the light emitting diode unit 121n to be the horizontal direction or the vertical direction is the same as the way of arranging the fluorescent tube, which is often used as the light source of the backlight device, Accumulated design know-how can be used, cost reduction and time required for manufacturing can be shortened.

  The light emitted from the red (R) light emitting diode 121R, the green (G) light emitting diode 121G, and the blue (B) light emitting diode 121B disposed as the light emitting diode unit 121n in the backlight housing 120 is transmitted to the backlight housing. Color is mixed in the body part 120 to be white light. At this time, each light emitting diode is so arranged that the red (R) light, the green (G) light, and the blue (B) light emitted from each light emitting diode 121 are uniformly mixed in the backlight housing 120. In 121, a lens, a prism, a reflecting mirror, and the like are disposed so that outgoing light with a wide directivity can be obtained.

  Although not described in detail, each light emitting diode 121 has a light emitting bulb held by a resin holder and a pair of terminals protruding from the resin holder. Each light emitting diode 121 is provided with an optical component 150 that emits light emitted from the light source from the side surface, that is, has a directivity for emitting the main component of the emitted light in the outer peripheral direction of the light emitting bulb. So-called side emission type LEDs are used.

  As shown in FIG. 3, the optical component 150 provided in the light emitting diode 121 is formed with a light shielding portion 151 that covers at least the central portion of the front surface. The light-shielding portion 151 is formed by applying a semi-transmissive paint or forming an optical reflective film on a region covering at least the central portion of the conical reflective surface in front of the optical component 150. Light leakage in the front direction of the diode 121 is shielded.

  The light shielding portion 151 is formed so as to cover the entire conical reflection surface in the maximum state, but if it is formed so as to cover at least the central portion, light leakage in the front direction is shielded. Can do.

  As shown in FIG. 4, diffusion for mixing red (R) light, green (G) light, and blue (B) light emitted from the respective light emitting diodes 121 in the backlight housing 120. A light guide plate 125 is provided so as to cover the light emitting diode unit 121n which is a light source.

  The diffusion light guide plate 125 diffuses light emitted from the light emitting diode 121 and light reflected by a reflection sheet 126 described later.

  The diffusion plate 141 shown in FIG. 1 is a plate that diffuses milky white light having a predetermined plate thickness (for example, about 2 mm), diffuses the light mixed by the diffusion light guide plate 125, and emits white light with uniform luminance. To the optical sheet group 145. The optical sheet group 145 raises the brightness by raising the white light in the normal direction of the diffusion plate 141.

  FIG. 4 is a partial cross-sectional view taken along the line XX attached to the liquid crystal display device 100 shown in FIG. 1 when the liquid crystal display device 100 is assembled. As shown in FIG. 4, the liquid crystal display panel 110 that constitutes the liquid crystal display device 100 is sandwiched between the external frame 101 serving as an external housing of the liquid crystal display device 100 and the internal frame 102 via spacers 103 a and 103 b. Retained. Further, a guide member 104 is provided between the outer frame 101 and the inner frame 102, and the liquid crystal display panel 110 sandwiched between the outer frame 101 and the inner frame 102 is displaced in the longitudinal direction. Suppressed.

  On the other hand, the liquid crystal display backlight device 140 constituting the liquid crystal display device 100 includes the light guide plate 141 on which the optical sheet group 145 is laminated and the diffusion light guide plate 125 as described above. Further, a reflection sheet 126 is disposed between the diffusion light guide plate 125 and the backlight housing 120. The reflection sheet 126 is disposed so that the reflection surface thereof faces the light incident surface 125 a of the diffusion light guide plate 125 and is closer to the backlight housing 120 than the light emitting direction of the light emitting diode 121.

  The reflective sheet 126 is, for example, a silver-enhanced reflective film formed by sequentially laminating a silver reflective film, a low refractive index film, and a high refractive index film on a sheet base material. The reflection sheet 126 mainly emits light from the light emitting diode 125 and reflects incident light reflected by the diffusion light guide plate 125.

  As shown in FIG. 4, the diffusing plate 141, the diffusing light guide plate 125, and the reflecting sheet 126 provided in the liquid crystal display backlight device 140 are arranged so as to face each other. The optical stat 105 provided is held in the backlight casing 120 of the liquid crystal display backlight device 140 while maintaining a spacing between the two. At this time, the diffusing plate 141 is also held by the bracket member 108 provided in the backlight housing 120.

  In the backlight device 140 for liquid crystal display in the color liquid crystal display device 100 having such a configuration, as shown in FIG. 3, a side light emitting device provided with an optical component 150 that emits light emitted from the light source, that is, the LED chip 121a, from the side surface is provided. By arranging a plurality of light emitting diodes 121, the transmissive liquid crystal panel 110 is increased in luminance, and a light shielding portion 151 is formed to cover at least the central portion of the front surface of the optical component 150 provided in the side emission light emitting diode 121. Therefore, the leakage light in the front direction of the side-emitting diode 121 can be shielded by the light shielding portion 151, and the occurrence of uneven color and horizontal stripes can be reduced.

  Further, in the backlight device 140 for liquid crystal display, since the light shielding portion 151 that covers at least the central portion of the front surface of the optical component 150 provided in the side emission light emitting diode 121 is formed, the dimming pattern is formed on the diffusion light guide plate 125. The dimensional change of each component due to the influence of heat generated from a large number of light-emitting diodes 121, the dimensional accuracy or assembly accuracy of each component, and the variation of the dimming pattern printing accuracy, etc. Therefore, the manufacturing cost and assembly cost of each constituent member can be reduced.

  Further, in the backlight device 140 for liquid crystal display, since it is not necessary to provide a dimming pattern on the diffusion light guide plate 125 as described above, the diffusion light guide plate 125 may be omitted.

  The color liquid crystal display device 100 is driven by, for example, a drive circuit 200 as shown in FIG. The driving circuit 200 is supplied from the outside, a power supply unit 210 that supplies driving power to the liquid crystal display panel 110 and the backlight device 140 for liquid crystal display, an X driver circuit 220 and a Y driver circuit 230 that drive the liquid crystal display panel 110. An RGB process processing unit 250 that receives a video signal or a video signal received by a receiving unit (not shown) included in the color liquid crystal display device 100 and processed by the video signal processing unit, via the input terminal 240, and this RGB process An image memory 260 and a control unit 270 connected to the processing unit 250, a backlight drive control unit 280 for driving and controlling the backlight device 140 for liquid crystal display, and the like are provided.

  In the driving circuit 200, the video signal input via the input terminal 240 is subjected to signal processing such as chroma processing by the RGB process processing unit 250, and further, RGB signals suitable for driving the liquid crystal display panel 110 from the composite signal. It is converted into a separate signal, supplied to the control unit 270, and supplied to the X driver 220 via the image memory 260.

  Further, the control unit 270 controls the X driver circuit 220 and the Y driver circuit 230 at a predetermined timing according to the RGB separate signal, and the RGB separate supplied to the X driver circuit 220 via the image memory 260. By driving the liquid crystal display panel 110 with a signal, an image corresponding to the RGB separate signal is displayed.

  The backlight drive control unit 280 generates a pulse width modulation (PWM) signal from the voltage supplied from the power supply 210 and drives each light emitting diode 121 that is a light source of the liquid crystal display backlight device 140. In general, the color temperature of a light emitting diode has a characteristic that it depends on an operating current. Therefore, in order to reproduce the color faithfully (with a constant color temperature) while obtaining a desired luminance, it is necessary to drive the light emitting diode 121 using a pulse width modulation signal to suppress a change in color.

  The user interface 300 selects a channel received by the above-described receiving unit (not shown), adjusts an audio output amount output by an audio output unit (not shown), and illuminates the liquid crystal display panel 110. 140 is an interface for executing brightness adjustment of white light from 140, white balance adjustment, and the like.

  For example, when the user adjusts the brightness from the user interface 300, the brightness control signal is transmitted to the backlight drive control unit 280 via the control unit 270 of the drive circuit 200. In response to the luminance control signal, the backlight drive control unit 280 changes the duty ratio of the pulse width modulation signal for each of the red light emitting diode 121R, the green light emitting diode 121G, and the blue light emitting diode 121B, thereby changing the red light emitting diode 121R and the green light emitting diode 121R. The light emitting diode 121G and the blue light emitting diode 121B are driven and controlled.

It is a disassembled perspective view which shows typically the principal part structure of the color liquid crystal display device to which this invention is applied. It is a typical perspective view which shows schematic structure of the backlight apparatus for liquid crystal displays with which the said color liquid crystal display device was equipped. It is typical sectional drawing which shows the principal part structure of the side emission light emitting diode provided with the optical component which radiates | emits the light emitted from the light source used as a light emitting diode which comprises the said backlight apparatus for liquid crystal displays from a side surface. It is sectional drawing of the said color liquid crystal display device cut | disconnected by the XX line | wire shown in FIG. It is a block diagram which shows the structure of the drive circuit which drives the said color liquid crystal display device.

Explanation of symbols

  100 color liquid crystal display device, 110 color liquid crystal display panel, 121, 121R, 121G, 121B side emission light emitting diode, 121a LED chip, 121n (n is a natural number) light emitting diode unit, 125 diffusion light guide plate, 126 reflection sheet, 150 optical components 151 Light-shielding part, 140 Liquid crystal display backlight device

Claims (2)

A backlight device for liquid crystal display that illuminates a transmissive color liquid crystal display panel from the back side,
A plurality of side emitting light emitting diodes provided with optical components that radiate light emitted from the light source from the side surface,
A backlight device for a liquid crystal display, wherein a light-shielding portion is formed to cover at least a central portion of the front surface of the optical component provided in the side-emitting diode. A light-shielding portion that includes a plurality of side emission light emitting diodes provided with an optical component that emits light emitted from a light source from the side surface and covers at least a central portion of the front surface of the optical component provided in the side emission light emitting diode A backlight device for a liquid crystal display,
A transmissive liquid crystal display device comprising: a transmissive color liquid crystal display panel illuminated from the back side by the liquid crystal display backlight device.

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