JP2010049937A - Backlight device and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a backlight device capable of achieving uniformity of an irradiation light even in case where a gap between a light source and an optical member becomes narrower for the purpose of thinning of the backlight device, and a liquid crystal display using this backlight device. <P>SOLUTION: This backlight device 1 is arranged on the rear face of a display element 2, irradiates irradiation light onto the display element 2, and is equipped with a bottomed frame shape chassis 11 having the bottom face 11a and a sidewall part 11b surrounding the bottom face 11a, a plurality of light sources 12 arranged at the bottom 11a of the chassis 11, and the optical member 10 arranged at the upper end part of the sidewall part 11b of the chassis 11. The optical member 10 has a plurality sheets of transmissivity control sheets in which light diffusion component is contained in a resin film, and the plurality of sheets of the transmissivity control sheets are laminated via a light scattering sheet in which unevenness is formed on a surface of the resin film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a backlight device that irradiates a display element with irradiation light, and a liquid crystal display device that includes the backlight device and includes a liquid crystal panel as a display element, and in particular, uneven luminance of a light source disposed on a bottom surface of a chassis. The present invention relates to a backlight device that can be irradiated with irradiation light with a more uniform brightness and a liquid crystal display device including the backlight device.

  In recent years, liquid crystal display devices having features such as low power consumption, thinness, and light weight have been widely used as display devices such as television receivers. A liquid crystal panel used in a display unit of a liquid crystal display device is a so-called non-light emitting display element that does not emit light. Therefore, in the liquid crystal display device, a backlight device that is a surface-emitting illumination device is provided on the back surface of the liquid crystal panel, and image display is performed using irradiation light emitted from the backlight device.

  Backlight devices are roughly classified into direct type and sidelight (also referred to as edge light) types depending on the arrangement of light sources with respect to the liquid crystal panel. The direct type backlight device has a light source disposed on the back side of the liquid crystal panel, and an optical member such as a diffusion plate or a prism sheet disposed between the light source and the liquid crystal panel, so that the entire back surface of the liquid crystal panel is disposed. For example, it is suitably used in a large-screen liquid crystal display device for a television receiver. In recent years, attention has been paid to the fact that the color light reproducibility is high and the drive circuit can be simplified as a light source of such a direct type backlight device, and a cold cathode fluorescent tube (CCFT: Cold) which has been conventionally used. Instead of Cathode Fluorescent Tubes (LEDs), light emitting diodes (LEDs) are increasingly used.

In the direct type backlight device, since the light source is arranged at a predetermined interval on the bottom surface of the chassis, the brightness of the irradiated light differs between the portion directly above the light source and the portion between the plurality of light sources. It is important how to reduce the uneven brightness. As an optical member used in such a direct type backlight device, a transmittance control sheet in which small bubbles as light diffusing components are generated in a resin film is used. There has been proposed a technique for eliminating luminance unevenness between a portion directly above the light source and a portion other than the portion directly above the light source disposed on the bottom surface of the chassis by the scattering effect (see Patent Document 1 and Patent Document 2).
JP-A-5-477 JP 2004-271567 A

  On the other hand, in order to meet the demand for further thinning of the liquid crystal display device, it is necessary to reduce the thickness of the backlight device that occupies most of the thickness of the liquid crystal display device. Designs have been made to keep this lower.

  However, the reduction in the height of the chassis side wall means that the distance between the light source disposed on the bottom surface of the chassis and the optical member disposed on the upper end of the chassis side wall is reduced. The luminance difference between the portion directly above the light source disposed on the bottom surface of the chassis and the portion other than the portion directly above at the position where the member is disposed becomes larger. Thus, when the luminance difference of the irradiation light from the light source at the arrangement position of the optical member becomes large, the conventional transmittance control sheet cannot exhibit a sufficient luminance uniforming effect. Further, for example, in the method of using two or more transmittance control sheets in a stacked manner, interference unevenness occurs in the stacked transmittance control sheets, and the uniformity of the irradiation light from the backlight device and the irradiation light irradiation luminance are further improved. The problem of being lost arises.

  In view of the above-described problems, the present invention provides a backlight device that can achieve uniform irradiation light even when the distance between the light source and the optical member is narrowed in order to reduce the thickness of the backlight device. An object is to obtain a liquid crystal display device using a backlight device.

  In order to solve the above-described problems, a backlight device of the present invention is a backlight device that is disposed on the back surface of a display element and irradiates the display element with irradiation light, and includes a bottom surface and a side wall that surrounds the bottom surface. A chassis having a bottomed frame shape, a plurality of light sources disposed on the bottom surface of the chassis, and an optical member disposed on an upper end portion of the side wall portion of the chassis, the optical member comprising a resin The film has a plurality of transmittance control sheets containing light diffusing components, and the plurality of transmittance control sheets are laminated via a light scattering sheet in which irregularities are formed on the surface of the resin film. It is characterized by.

  The liquid crystal display device of the present invention includes a liquid crystal panel as a display element, and the liquid crystal panel is irradiated with irradiation light from the backlight device according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, even when the backlight apparatus is thinned and the space | interval of a light source and an optical member becomes narrow, the backlight apparatus which can aim at equalization of irradiated light can be obtained. In addition, by using this backlight device, a liquid crystal display device capable of displaying a display image with less luminance unevenness can be obtained.

  A backlight device according to the present invention is a backlight device that is disposed on the back surface of a display element and irradiates the display element with irradiation light, and has a bottomed frame shape having a bottom surface and a side wall that surrounds the bottom surface. A chassis, a plurality of light sources disposed on the bottom surface of the chassis, and an optical member disposed on an upper end of the side wall of the chassis, the optical member including a light diffusion component in a resin film A plurality of the transmittance control sheets are provided, and the plurality of the transmittance control sheets are laminated via a light scattering sheet in which irregularities are formed on the surface of the resin film.

  With this configuration, since the transmittance control sheet using a plurality of sheets is laminated via the light scattering sheet between them, the occurrence of uneven interference that occurs when the transmittance control sheets are continuously laminated is prevented. be able to. For this reason, even when the backlight device is thinned and the distance between the light source and the optical member becomes narrow, the scattering effect of the irradiation light from the light source by the plurality of transmittance control sheets is achieved without causing uneven interference. It is possible to effectively reduce the uneven brightness of the backlight irradiation light that occurs in the portion directly above the light source and the portion other than the portion directly above the light source.

  In the backlight device having the above-described configuration, it is preferable that the light scattering sheet is a diffusion sheet in which a light scattering substance is fixed to the surface of the resin film. By doing in this way, interference between a plurality of transmissivity control sheets can be reduced effectively.

  In addition, the optical member includes a diffusion plate in which scattering fine particles are dispersed in a resin substrate from the light source side toward the display element, the first transmittance control sheet, and the first diffusion sheet. It is preferable that the second transmittance control sheet and the second diffusion sheet are sequentially laminated. By doing so, it is possible to realize an optical member that achieves both a diffusion effect by the diffusion plate and the diffusion sheet and a luminance uniforming effect by the transmittance control sheet. Even when the optical member is thinned, the irradiation light from the backlight device is realized. Can be made more uniform.

  Moreover, it is preferable that a prism sheet and a polarizing reflection sheet are sequentially laminated on the display element side of the second diffusion sheet of the optical member. By doing so, in addition to the effect of uniforming the brightness by the diffusion plate, the diffusion sheet, and the transmittance control sheet, a backlight device capable of irradiating the display element with irradiation light in a state in which directivity is enhanced is provided. Obtainable.

  The liquid crystal display device according to the present invention includes a liquid crystal panel as a display element, and the liquid crystal panel is irradiated with irradiation light from the backlight device according to the present invention.

  In this way, a thin liquid crystal display device with reduced luminance unevenness of a display image can be obtained by using the backlight device of the present invention in which irradiation light can be made uniform even when the display device is thinned. be able to.

  Hereinafter, a backlight device according to an embodiment of the present invention and a liquid crystal display device including the backlight device will be described with reference to the drawings.

  In the following description of embodiments of the present invention, a configuration example in which a transmissive liquid crystal panel is used as a display element and the present invention is implemented as a liquid crystal television set is shown. However, the following description does not limit the use of the backlight device and the liquid crystal display device according to the present invention. The backlight device of the present invention can be used as a device for irradiating light to, for example, a transflective liquid crystal panel other than a transmissive liquid crystal panel, and other non-light emitting display elements. The application of the liquid crystal display device of the present invention is not limited to a stationary television set, and can be used as a mobile device such as a notebook personal computer, a portable DVD player, or a navigation device. The size of the applied liquid crystal panel can be widely used from a small size of about 10 inches to a super large size exceeding 100 inches.

  For convenience of explanation, the drawings referred to below show only the main members necessary for explaining the present invention in a simplified manner among the constituent members of the embodiment of the present invention. Therefore, the backlight device and the liquid crystal display device according to the present invention can include arbitrary constituent members that are not shown in each of the referenced drawings. Moreover, the dimension of the member in each figure does not necessarily faithfully represent the dimension of the actual component member, the dimension ratio of each member, and the like.

  FIG. 1 is an exploded perspective view showing an overall configuration of a liquid crystal display device using a backlight device according to an embodiment of the present invention.

  As shown in FIG. 1, a liquid crystal display device 100 according to the present embodiment is provided on a transmissive liquid crystal panel 2 that is a display element and on the back side of the liquid crystal panel 2, and irradiates the liquid crystal panel 2 with light. And a backlight device 1 for displaying an image. In general, a front panel made of resin or the like constituting the outer shape of the liquid crystal display device 100 is provided in combination with the backlight device 1 constituting the back surface of the liquid crystal display device 100 as it is. Although it arrange | positions so that it may cover, illustration in FIG. 1 is abbreviate | omitted.

  Since the liquid crystal panel 2 can be a conventional one as it is, a detailed description using the drawings is omitted, but a liquid crystal layer (not shown), a front substrate 21 and a rear substrate 22 sandwiching the liquid crystal layer, A pair of polarizing plates 23 provided on the outer surface of the front substrate 21 and the rear substrate 22 are provided. The liquid crystal panel 2 is provided with a driver circuit for driving the liquid crystal panel 2, and is connected to a drive circuit as a display device via a flexible printed board or the like.

  For example, the liquid crystal panel 2 in the present embodiment is an active matrix type liquid crystal panel 2 and drives the liquid crystal layer in units of pixels by supplying scanning signals and data signals to scanning lines and data lines arranged in a matrix. It is configured to be possible. Each pixel has a potential level of a data signal written from the data line to the pixel electrode when a switching element (TFT) provided in the vicinity of each intersection of the scanning line and the data line is turned on by a scanning line signal. As the alignment state of the liquid crystal molecules changes according to the above, gradation display according to the data signal is performed. That is, the polarization state of the irradiation light emitted from the backlight device 1 is modulated by the liquid crystal layer, and the amount of light transmitted through the pair of polarizing plates 23 is controlled for each pixel, whereby a desired image is displayed.

  The backlight device 1 includes a bottomed frame-shaped chassis 11, a plurality of LEDs 12 that are light sources arranged on the bottom surface 11 a of the chassis 11, and an optical member 10 provided at the upper end of the side wall 11 b of the chassis 11. ing.

  The optical member 10 reduces the luminance unevenness caused by the LEDs 12 being arranged at a predetermined interval, and uniformly radiates light from the LEDs 12 that are light sources arranged on the bottom surface 11a of the chassis 11. A plurality of optical sheets based on a resin plate-like diffusion plate or a resin film are laminated and formed so that the liquid crystal panel 2 can be irradiated as flat surface light. The detailed configuration of the optical member 10 will be described later with reference to FIGS.

  The chassis 11 is made of an aluminum or iron metal having a thickness of about several millimeters, or a resin. As shown in FIG. 1, the chassis 11 has a substantially rectangular bottom surface 11a and four sides that surround the bottom surface 11a. The side wall portion 11b extends in a direction substantially perpendicular to the bottom surface 11a. Thus, the chassis 11 has a bottomed frame shape in which the side wall portion 11b surrounds the bottom surface 11a.

  Since the light irradiated from the backlight device 1 needs to be irradiated to the entire image display area of the liquid crystal panel 2, the shape of the entire backlight device 1 including the chassis 11 is also the image display area of the liquid crystal panel 2. It becomes a rectangular shape corresponding to the shape. Accordingly, the fact that the bottom surface 11a is substantially rectangular means that the overall shape of the bottom surface 11a of the chassis 11 is rectangular, and a protrusion used for fixing the backlight device 1 and the appearance of the liquid crystal display device 100. It is not intended to exclude having fine irregularities and notches as given from the viewpoint of design. Further, the fact that the side wall portion 11b extends in a direction substantially perpendicular to the bottom surface 11a means that the bottom surface 11a and the side wall portion 11b form a bottomed box as a whole. The appearance design of the device 100 does not exclude that a part or all of the side wall portion 11b is inclined obliquely.

  A reflection sheet (not shown) is disposed on the bottom surface 11a of the chassis 11 and the inner surfaces of the side wall portions 11b. This reflection sheet is made of a metal thin film having a high light reflectance such as aluminum or silver, for example, and reflects the light of the LED 12 that is a light source toward the optical member 10, thereby improving the utilization efficiency of the light emitted from the LED 12. Can be increased. In addition to the metal thin film, a synthetic resin sheet material can be used as the reflection sheet. In addition to disposing a sheet as a separate member inside the chassis 11, the reflection sheet reflects light on the inner surface of the chassis 11. By applying a white paint having a high rate, for example, the inner surface of the chassis 11 can function as a reflector.

  The LED 12 as the light source is, for example, a white LED whose upper surface is a 3 mm square and has a thickness of about 0.5 to 2 mm. The power consumption per one is, for example, 0.03 W (3 V, 10 mA). In addition, as a method of obtaining a white light source using the LED 12, in addition to the case where the light emission color of the LED 12 is white, three LEDs 12 of RGB three primary colors are arranged close to each other, and the irradiation light from the three LEDs 12 is used. As a synthesized light, white light can be obtained. Moreover, as a case where white light is obtained using two LEDs 12, it is also conceivable that two LEDs 12 of, for example, green and magenta which is a complementary color thereof are arranged close to each other. Further, there is a field sequential technique in which three RGB LEDs 12 are arranged in a line for each color, and the corresponding color images are displayed while being sequentially switched and lighted, and the three primary colors are superimposed over time. It may be adopted.

  A large number of the LEDs 12 are arranged on the bottom surface 11a of the chassis 11, and the number of the LEDs 12 is, for example, 1000 to 10,000 in the case of a liquid crystal television having a display image size (diagonal) of 42 inches. The arrangement pitch of the LEDs 12 is, for example, about 3 mm to 100 mm, and is optimal from the viewpoints of brightness required for image display on the liquid crystal panel 2, power consumption of the entire liquid crystal display device, and the amount of heat generated by the LEDs 12. A number is selected.

  In addition, in FIG. 1, although the arrangement | sequence of 10 LED12 is shown as 6 rows per row | line | row, of course, this is only schematic and the arrangement | positioning shape is also the vertical direction horizontal direction as shown in FIG. The arrangement is not limited to an aligned matrix arrangement, and a so-called staggered arrangement in which the arrangement positions of the LEDs 12 are shifted for each row or column may be employed.

  The LEDs 12 are arranged on the drive circuit board together with the drive circuit elements and are arranged on the bottom surface 11a of the chassis 11, but the drive circuit board of the LEDs 12 is not shown in FIG. Further, in addition to the drive circuit board for the LED 12, a drive circuit board for the liquid crystal panel 2 (not shown) may be disposed on the back side of the drive circuit board for the LED 12 inside the chassis 11. For this reason, although the space | interval of the upper surface which is the light irradiation surface of LED12, and the optical member 10 is influenced by the display image size which is the magnitude | size of the liquid crystal panel 2, it is about 5 mm-about 50 mm.

  Next, a specific configuration of the optical member 10 will be described with reference to FIG.

  FIG. 2 is a cross-sectional configuration diagram showing the configuration of the backlight device 1 according to the present embodiment. As shown also in FIG. 1, in the backlight device 1 of the present embodiment, the optical member 10 is disposed at the upper end portion of the chassis 11 in which the LED 12 as the light source is disposed on the bottom surface.

  The optical member 10 includes, in order from the LED 12 side, a diffusion plate 13, a transmittance control sheet 14 (first transmittance control sheet), a diffusion sheet 15 (first diffusion sheet), and a transmittance control sheet 16 (second Transmittance control sheet) and diffusion sheet 17 (second diffusion sheet) are sequentially laminated, and two transmittance control sheets 14 and 16 are laminated via a diffusion sheet 15 which is a light scattering sheet. It has a configuration.

  The diffusing plate 13 is formed by dispersing scattering fine particles in a resin substrate. For example, a transparent acrylic plate having a thickness of 2 mm to 3 mm is mixed with resin-made scattering fine particles, and the diffusion plate 13 is formed by using refraction and reflection at the interface between acrylic and scattering fine particles as a base material. The light that passes through is scattered. For this reason, the irradiation light from LED12 which permeate | transmits the diffuser plate 13 is radiated | emitted from the diffuser plate 13 as scattered light. Note that the thickness, material, and the like of the diffusion plate 13 are not limited to the above examples, and various diffusion plates that are generally used in backlight devices of liquid crystal display devices can be used.

  A transmittance control sheet 14 is laminated on the diffusion plate 13. In the present embodiment, the transmittance control sheet 14 stacked on the diffusion plate 13 and the transmittance control sheet 16 stacked on the transmittance control sheet 14 via the diffusion sheet 15 are optical sheets. The same transmittance control sheet is used.

  The transmittance control sheets 14 and 16 are, for example, those in which a light diffusing component such as air bubbles is contained in a film made of a polyester resin, a polyolefin resin, or an acrylic resin as a base material. The total thickness of the transmittance diffusing sheets 14 and 16 is, for example, 30 μm to 200 μm, the volume fraction of the light diffusing component in the resin film as the base material is 0.05% to 30%, and the light diffusing component The particle diameter of is 0.3 μm to 5 μm. In addition, as a light-diffusion component of the transmittance control sheets 14 and 16, fine particles made of a transparent resin can be used in addition to the above-described bubbles.

  A diffusion sheet 15 is laminated on the transmittance control sheet 14. In this embodiment, a diffusion sheet having the same configuration as the optical sheet is used for the diffusion sheet 15 laminated on the transmittance control sheet 14 and the diffusion sheet 17 laminated on the transmittance control sheet 16. Yes.

  The diffusion sheets 15 and 17 are light scattering sheets in which irregularities are formed on the surface of the resin film. As an example of the diffusion sheets 15 and 17, for example, fine acrylic beads as a light-scattering substance are bonded to the surface of a transparent resin film such as polyethylene terephthalate (PET) using a binder resin as an adhesive Can be used. The film thickness of the entire diffusion sheets 15 and 17 is 0.2 mm to 0.3 mm. Further, in the present embodiment, the surfaces on which the acrylic beads are formed are positioned on the light emitting direction side of the backlight device 1, that is, on the side where the liquid crystal panel 2 that is a display element is disposed in both of the diffusion sheets 15 and 17. ing.

  The light scattering sheet interposed between the plurality of transmittance control sheets 14 and 16 is limited to the diffusion sheets 15 and 17 formed by fixing the unevenness on the surface of the resin film described above by adhering a light scattering substance. For example, the surface of the resin film itself may be roughened by physical, chemical or other methods. Moreover, unlike the case of this embodiment, it is also possible to arrange | position the unevenness | corrugation formed in the light-scattering sheet surface toward the light source side. Furthermore, as a light-scattering sheet, a sheet on which both surfaces are roughened to form irregularities can be used.

  Note that the optical properties of the diffusion sheets 15 and 17 change depending on the size of the acrylic bead particles fixed to the film surface. Specifically, when the particle diameter of the acrylic beads to be fixed is large, the action of condensing the transmitted light transmitted through the diffusion sheets 15 and 17 is increased. Conversely, when the particle diameter is small, the transmitted light is transmitted. The spreading effect is increased. The diffusion sheets 15 and 17 used in the present embodiment have relatively high light collecting properties, and the luminance of the emitted light from the diffusion sheets 15 and 17 up to about 30 ° is the luminance of the incident light. It is raised to about 1.3 times. In comparison with this, for example, the diffusion plate 13 described above has only a diffusing function without having a condensing function, and the luminance of the emitted light with an emission angle of 0 ° to 30 ° is the luminance of the incident light. It is about 1.0 times the same.

  A transmittance control sheet 16 is laminated on the diffusion sheet 15. Further, a diffusion sheet 17 is laminated on the transmittance control sheet 16 to constitute the optical member 10 of the backlight device 1 of the present embodiment. As described above, the specific configurations of the transmittance control sheet 16 and the diffusion sheet 17 are the same as those of the transmittance control sheet 14 and the diffusion sheet 15.

  In the backlight device 1 of the present embodiment, as described above, the two transmittance control sheets 14 and 16 of the transmittance control sheet 14 and the transmittance control sheet 16 are used as the optical member 10 and two pieces of transmission are used. The rate control sheets 14 and 16 are not directly laminated, but a diffusion sheet 15 which is a light scattering sheet is interposed therebetween. By doing so, luminance unevenness caused by internal interference between the transmittance control sheets 14 and 16, which is generated when two or more transmittance control sheets 14 and 16 are directly laminated, and luminance reduction of transmitted light. It is possible to exhibit a high brightness uniformizing function without causing the above.

  In particular, as in the present embodiment, the transmittance control sheets 14 and 16 and the diffusion sheets 15 and 17 are alternately combined and laminated, whereby the transmittance control sheet 14 and the LED 12 that could not be eliminated by the diffusion plate 13. The luminance unevenness due to the array distribution can be largely eliminated. Further, the diffusion sheet 15 laminated on the transmittance control sheet can further uniformize the luminance distribution in the region where the luminance unevenness remains. Further, with respect to the transmitted light that has passed through the diffusion sheet 15, the luminance unevenness can be reduced again by the transmittance control sheet 16, and the brightness can be uniformed again by the diffusion sheet 17. For this reason, it is possible to obtain the backlight device 1 having a more uniform luminance distribution of irradiated light, in which the luminance unevenness caused by the arrangement pattern of the LEDs 12 is eliminated.

  In the above embodiment, the diffusion plate 13 is disposed on the side of the optical sheet 10 closest to the LED 12. The reason is that the diffusion plate 13 is a resin plate, so that the strength is higher than that of the optical sheet based on the resin film, and the entire optical member 10 is ensured by being arranged in the lowest layer. The factor that can be done is also taken into consideration.

  Furthermore, in the said embodiment, the example using the optical sheet of a total of 4 layers which laminated | stacked 2 sets of the combination of the transmittance | permeability control sheet | seat and the diffusion sheet was shown. However, when the arrangement pattern of the LEDs 12, particularly when the pitch between the adjacent LEDs 12 is large or when the distance between the LEDs 12 and the optical sheet 10 is particularly narrow, two or more sets of laminates of the transmittance control sheet and the diffusion sheet are combined. It doesn't matter. For example, in the maximum case, it is possible to use a total of 10 optical sheet laminates in which 5 sets of laminates of transmittance control sheets and diffusion sheets are laminated. However, in any case, the transmittance control sheets are not directly laminated, but the transmittance control sheets need to be laminated via a light scattering sheet such as a diffusion sheet.

  Next, another example of the configuration of the backlight device 1 of the present embodiment, particularly the optical member 10, will be described with reference to FIG.

  FIG. 3 is a partial cross-sectional configuration diagram showing a cross-sectional configuration of another configuration of the optical member 10 of the backlight device 1 of the present embodiment. In the optical member 10 having another configuration, a prism sheet 18 and a polarization reflection sheet 19 are further laminated on the second diffusion sheet 17. In the backlight device 1 having another configuration shown in FIG. 3, the configuration of the chassis 11 and the LED 12 that emits the light 20 from the light source incident on the optical member 10 is the configuration described in FIG. Therefore, the illustration and detailed description are omitted.

  As shown in FIG. 3, a prism sheet 18 is laminated on the diffusion sheet 17. The prism sheet 18 is obtained by, for example, laminating a prism array having an apex angle of 90 ° with an acrylic resin or the like on a polyester film layer. The prism sheet 18 is also referred to as a BEF sheet or the like, and improves the brightness in the front direction to, for example, 1.6 times or more of incident light by using refraction and reflection at the prism array interface. The thickness of the prism sheet 18 is about 0.2 mm to 0.3 mm.

  On the prism sheet 18, a polarization reflection sheet 19 is laminated. This polarizing reflection sheet 19 transmits only light transmitted through the polarizing plate 23 on the backlight side, for example, only P-polarized light, in combination with the polarizing plate 23 attached to the backlight device 1 side of the liquid crystal panel 2. For example, it is a sheet that reflects S-polarized light that is not transmitted through the polarizing plate 23 on the backlight device side. By disposing the polarizing reflection sheet 19, also referred to as DBEF, light that does not contribute to image display on the liquid crystal panel 2 because it does not pass through the polarizing plate 23 out of the light emitted from the backlight device 1. It can be reflected and reused on the device 1 side.

  As described above, in another configuration example of the optical member 10 illustrated in FIG. 3, the polarizing plate 13, the transmittance control sheet 14, the diffusion sheet 15, the transmittance control sheet 15, and the diffusion sheet 17 are caused by the arrangement pattern of the light sources. After eliminating the uneven brightness of the light 20 from the light source, the directivity of the irradiation light incident on the liquid crystal panel 2 can be improved, and the light lost at the polarizing plate 23 can be reused. Thereby, the brightness | luminance of the irradiated light from the backlight apparatus 1 which permeate | transmits the liquid crystal panel 2 and contributes to an image display can be improved. For this reason, a liquid crystal display device capable of realizing a brighter display image can be obtained.

  Note that the prism sheet 18 and the polarization reflection sheet 19 in the configuration example of the optical member 10 shown in FIG. 3 are not limited to those disclosed in the above specific examples, and are not limited to the backlight device 1 of the liquid crystal panel 2. The well-known prism sheet and polarization reflection sheet used can be used. In the above description, the optical element formed on the sheet base material has been described as using the prism sheet 18 in which a prismatic prism having an apex angle of 90 ° is used. It is also possible to use a so-called lenticular sheet having a light condensing function and having a semicircular cross section of the optical element formed on the sheet base material.

  As mentioned above, what used LED as the light source of a backlight apparatus has been demonstrated as embodiment of the backlight apparatus concerning this invention and a liquid crystal display device provided with the same. However, the present invention is not limited to this, and as a light source of the backlight device, a fluorescent tube such as a cold cathode fluorescent tube or a hot cathode fluorescent tube, or a light emitting element other than an LED such as an EL element can be used. And, regardless of the type of light source, it is possible to obtain a backlight device in which the brightness of the irradiated light is made more uniform even when the backlight device is thinned and the distance between the light source and the optical member is narrow. it can.

  INDUSTRIAL APPLICABILITY The present invention is industrially applicable as a backlight device for a display element that uses irradiation light for image display, and as a liquid crystal display device in which the display element is a liquid crystal panel.

It is a disassembled perspective view which shows schematic structure of the liquid crystal display device concerning embodiment of this invention. It is a section lineblock diagram showing the composition of the backlight device concerning the embodiment of the present invention. It is a fragmentary sectional block diagram which shows another structural example of the optical member in the backlight apparatus concerning embodiment of this invention.

Explanation of symbols

1 Backlight device 2 Liquid crystal panel (display element)
DESCRIPTION OF SYMBOLS 10 Optical member 11 Chassis 11a Bottom face 11b Side wall part 12 LED (light source)
13 Diffusion plate 14, 16 Transmittance control sheet 15, 17 Diffusion sheet (light scattering sheet)
18 Prism sheet 19 Polarized reflection sheet 100 Liquid crystal display device

Claims (5)

A backlight device disposed on the back surface of the display element to irradiate the display element with irradiation light,
A bottomed frame-shaped chassis having a bottom surface and a side wall surrounding the bottom surface;
A plurality of light sources disposed on the bottom surface of the chassis;
An optical member disposed at the upper end of the side wall of the chassis,
The optical member has a plurality of transmittance control sheets in which a light diffusion component is contained in a resin film, and the plurality of transmittance control sheets have light scattering properties in which irregularities are formed on the surface of the resin film. A backlight device, wherein the backlight device is laminated through sheets.   The backlight device according to claim 1, wherein the light scattering sheet is a diffusion sheet in which a light scattering substance is fixed to the surface of the resin film.   The optical member, from the light source side toward the display element, a diffusion plate in which scattering fine particles are dispersedly arranged in a resin substrate, the first transmittance control sheet, the first diffusion sheet, The backlight device according to claim 2, wherein the second transmittance control sheet and the second diffusion sheet are sequentially laminated.   The backlight device according to claim 3, wherein a prism sheet and a polarizing reflection sheet are sequentially laminated on the display element side of the second diffusion sheet of the optical member. A liquid crystal panel is provided as a display element.
5. A liquid crystal display device, wherein the liquid crystal panel is irradiated with irradiation light from the backlight device according to claim 1.

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