JP2007140495A - Optical sheet-supporting body, backlight for liquid crystal display using same, liquid crystal display, and rear projection type display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet-supporting body which is capable of supporting an optical sheet, which is used for displays, without using a resin plate, further which is thin, light-weighted, and excellent in compactness and impact resistance, while being produced at lower cost. <P>SOLUTION: The supporting body comprises a fabric which has a total light transmittance of not less than 25% and not more than 90%, and which supports the optical sheet to be installed on the display. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an optical sheet support used for a display and a backlight for a liquid crystal display using the same, and more particularly, an optical sheet support suitable for a backlight for a direct liquid crystal display and a liquid crystal display using the same. It is related with the backlight etc.

  In recent years, displays using various principles have been used in various applications such as portable devices, televisions, monitors, and notebook computers. Among them, liquid crystal displays (LCDs) are widely used from small screen products for portable devices to large screen products such as monitors and televisions. In the LCD, an image is displayed by providing a backlight, which is a surface light source, on the back side of the screen in order to irradiate the liquid crystal element sandwiched between the polarizing plates uniformly from the back side of the screen.

  Backlights used in LCDs are roughly classified into two types: (1) a direct type in which one or more fluorescent tubes are arranged directly under the screen, and (2) a light guide plate processed with a transparent acrylic plate, etc. Sidelight type that takes out light in the observation direction while light rays are incident on the light guide plate from the fluorescent tube arranged on the side of the light guide plate, and the light rays are spread in a plane using the action of scattering dots engraved on the light guide plate There is. Taking advantage of each feature, the direct type is a type that can easily cope with an increase in size, and the sidelight type is a type that can easily cope with a reduction in size and thickness.

  These backlights are required not only to receive light from the back side of the screen but also to make the entire screen shine uniformly and brightly. In order to satisfy such a requirement, an optical functional sheet (hereinafter referred to as an optical sheet) such as a light diffusion sheet, a prism sheet, or a brightness enhancement sheet (polarization separation sheet) is incorporated in the backlight.

  Among these optical sheets, the light diffusion sheet functions as follows. For example, in the case of a direct type backlight, the fluorescent tube is arranged directly under the screen. Therefore, luminance unevenness corresponding to the shape of the fluorescent tube appears remarkably. Therefore, a light diffusing plate (light diffusing sheet) having a thickness of 2 to 3 mm having light scattering properties is disposed on the upper side of the fluorescent tube to shield the fluorescent tube image and equalize the light emission distribution. The light diffusing plate for this direct type backlight is, for example, a light diffusing plate obtained by kneading and mixing a transparent resin such as methacrylic resin and a silicone resin particle using an injection molding method or an extrusion molding method. (Light diffusion sheet) or the like is used (see Patent Document 1). The light diffusing plate also has a function of supporting an optical sheet such as a prism sheet or a brightness enhancement sheet (polarization separation sheet) laminated thereon.

  However, the use of a light diffusing plate having a thickness of 2 to 3 mm has the following problems. (1) Although it is a big attraction that the liquid crystal display is thin, the thickness becomes thick. (2) When it is used for a large-sized liquid crystal display suitable for a direct type, it becomes very heavy and high in cost. (3) There is a drawback that cracks occur when an impact is applied, such as cracks and cracks.

  Patent Document 2 discloses that a light diffusion sheet made of woven fabric is supported and fixed by a resin plate made of a transparent substrate. However, the technique described in this document does not solve the above-mentioned problems because the resin plate is used, and further, it is necessary to embed, hold and adhere the fabric to the resin plate without wrinkles or sagging. There was a hassle that the relationship between the refractive index and the plate had to be selected optimally. Furthermore, since the optical sheet is supported in a state where it is raised by the thickness of the resin plate, the optical sheet becomes far from the light source by the thickness of the resin plate. When the distance from the light source is increased, the intensity of light is weakened and the light transmitted through the optical sheet is weakened, so that the screen of the liquid crystal display backlight tends to be dark.

Patent Document 3 discloses a light diffusion sheet in which a gap between woven and knitted fabrics is filled with a resin. However, the light diffusion sheet described in this document is also attached to a support such as a film and is used by supporting it with another diffusion plate, and is similar to the technique described in Patent Document 2. There was a problem.
JP-A-6-73296 JP-A-8-160205 JP 2005-188953 A

  In view of the problems of the prior art, the present invention is a support capable of supporting an optical sheet used in a display without using a resin plate, and is thin, light, and excellent in compactness. An object of the present invention is to provide an optical sheet support that is excellent in impact resistance and that can reduce costs.

The present invention for solving this problem is characterized by the following configurations (1) to (11).
(1) An optical sheet support provided on a display, comprising a fabric made of fibers, wherein the total light transmittance of the fabric is 25% or more and 90% or less. body.
(2) The optical sheet support according to (1) above, wherein the fabric has a haze of 20% to 100%.
(3) The optical sheet support according to (1) or (2), wherein 80 to 100% of the fibers constituting the fabric have a substantially circular cross section.
(4) The optical sheet support according to any one of (1) to (3) above, wherein the fibers constituting the fabric contain fibers having a total fineness of 5 dtex or more and 450 dtex or less.
(5) The optical sheet support according to any one of the above (1) to (3), wherein the fibers constituting the fabric include fibers having a total fineness of 15 dtex or more and 150 dtex or less.
(6) The optical sheet support according to any one of (1) to (5) above, wherein an average single yarn fineness of fibers constituting the fabric is 0.001 dtex or more and 30 dtex or less.
(7) The optical sheet support according to any one of (1) to (6), wherein the fabric is a woven fabric.
(8) The optical sheet support according to (7) above, wherein a cover factor of the woven fabric is 1200 or more and 2500 or less.
(9) The optical sheet support according to any one of the above (1) to (8), wherein the fabric is subjected to ultraviolet resistance treatment.
(10) The optical sheet support according to any one of (1) to (9) above, which is mounted on a backlight of a liquid crystal display.
(11) A backlight for a liquid crystal display, comprising the optical sheet support according to any one of (1) to (10) above.
(12) The backlight for a liquid crystal display according to (11), wherein at least one of a prism sheet and a polarization separation sheet is supported by the optical sheet support.
(13) A liquid crystal display comprising the liquid crystal display backlight according to (11) or (12).
(14) A rear projection display comprising the optical sheet support according to any one of (1) to (10).

  According to the optical sheet support of the present invention, the optical sheet mounted on the display can be supported at a position closer to the light source without using a resin plate. In addition, the optical sheet support of the present invention is thin, light, compact and excellent in impact resistance, and it is possible to reduce costs. As a result, it is possible to increase the luminance of a liquid crystal display backlight, a liquid crystal display, a rear projection display, and the like, and to make it light and compact, excellent in impact resistance, and inexpensive.

  Hereinafter, modes for carrying out the present invention will be described.

  The support of the present invention is a support for an optical sheet equipped in a display, and has a fabric composed of fibers. That is, according to the present invention, when assembling a display member such as a backlight, the optical sheet provided in the display is supported by the cloth instead of the resin plate. As a result, in particular, the optical sheet provided in the display can be supported at a position closer to the light source (including the light guide plate and the reflection sheet). And since it is a fabric, it is thin, light and excellent in compactness, and further, since it does not crack during assembly or transportation, it is excellent in impact resistance, and cost can be reduced.

  Such a fabric needs to sufficiently introduce light from the light source into the optical sheet. Therefore, such a fabric has a total light transmittance of 25% or more and 90% or less. If the total light transmittance is less than 25%, the amount of light transmitted through the fabric is small, the amount of light emitted from the backlight is small, and the display screen becomes dark. If the total light transmittance is greater than 90%, the amount of light transmission is sufficient and the display screen becomes bright, but light diffusion within the supporting fabric is insufficient, and uneven brightness tends to occur on the screen. Specifically, for example, in the case of a direct backlight used in a liquid crystal display, one or more fluorescent tubes are set directly below the screen, but bright on the liquid crystal display screen to reflect the position and shape of the fluorescent tube. A portion and a dark portion are formed, and uneven brightness tends to occur. The total light transmittance is preferably 25% to 70%, more preferably 30% to 55%.

  In the present invention, the haze of the fabric is preferably 20% or more and 100% or less. If the haze is less than 20%, the light diffusibility of the support fabric is insufficient, and the light from the light source is transmitted through almost straight light, and as described above, uneven brightness tends to occur on the display screen. 100% is the measurement limit. The haze is more preferably from 50% to 100%, and most preferably from 70% to 100%.

  As described above, the optical sheet support preferably has a total light transmittance of 25% or more and 90% or less and a haze of 20% or more and 100% or less so that luminance is high and luminance unevenness is reduced. .

The total light transmittance and haze are measured in accordance with method A of JIS-K-7105 (1981). The outline is as follows. Note that the measuring device is an integrating sphere type that satisfies the optical conditions described in JIS-K-7105 (1981), paragraph 5.5.2 (1) (light transmittance and total light reflectance measurement method A device). A light transmittance measuring device is used.
(1) Cut a fabric that has been conditioned for 48 hours or more in a dark place at a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5% in advance into 50 × 50 mm test pieces (the number of test pieces is 3). .
(2) A standard white plate is attached, and the amount of incident light is adjusted by adjusting the instruction of the apparatus to 100 (T1).
(3) With the standard white plate attached, the test piece is attached and the total light transmitted light amount (T2) is measured.
(4) Remove the standard white plate and the test piece, attach a light trap, and measure the amount of scattered light (T3) of the device.
(5) With the light and wrap attached, attach the test piece and measure the amount of scattered light (T4) from the device and the test piece.
(6) The total light transmittance (Tt (%)) and haze (H (%)) are calculated using the following equations.

Tt = T2 (1)
H = Td / Tt (2)
here,
Td = T4-T3 (T2 / 100) (3)
(7) The total light transmittance and haze are measured for three test pieces, and the respective average values are obtained (the first decimal place is rounded off). These average values are defined as the total light transmittance and haze of the fabric in the present invention.

  In the present invention, the fabric may be composed of the following fibers. That is, acrylic fibers such as polymethyl methacrylate and polyacrylonitrile, polyester fibers such as polyethylene terephthalate and polytrimethylene terephthalate, polybutylene terephthalate, polyamide fibers such as nylon 6 and nylon 66, polyurethane fibers, polyolefin fibers such as polyethylene and polypropylene, Polyimide fiber, polyacetal fiber, polyether fiber, polystyrene fiber, polycarbonate fiber, polyesteramide fiber, polyphenylene sulfide fiber, polyvinyl chloride fiber, polyether ester fiber, polyvinyl acetate fiber, polyvinyl butyral fiber, polyvinylidene fluoride fiber, ethylene Such as vinyl acetate copolymer fiber, fluororesin fiber, styrene-acrylic copolymer fiber, aramid fiber, etc. May contain synthetic fibers deviation, 1 to type may be made of synthetic fibers, it may be composed of two or more synthetic fibers. However, polyester fibers, polyphenylene sulfide fibers, fluororesin fibers, and the like can be preferably used from the viewpoint of moisture absorption stability, thermal stability, and the like, and polyester fibers can be preferably used from the viewpoint of versatility.

  The fibers constituting the fabric may be spun yarns obtained by spinning staples that have been crimped and cut to a predetermined length, or may be filament yarns made of continuous synthetic fibers. Further, the fiber may be a single monofilament yarn or a multifilament yarn composed of two or more single yarns. However, since the light transmittance is high, a filament yarn can be preferably used.

  The fibers constituting the fabric of the present invention include fibers having a substantially circular cross section, irregular cross sections such as a substantially triangular shape and a substantially cross shape, and fibers having any cross section such as a hollow cross section and a composite cross section, depending on required optical characteristics. Can be used.

  Among these, when a transmitted light amount is required, it is preferable that 80 to 100% of the fibers constituting the fabric are fibers having a substantially circular cross-sectional shape.

  The ratio of fibers having a substantially circular cross-sectional shape is measured as follows. First, when the fabric is a knitted or woven fabric, the fabric is loosened, and a cross section of the fibers constituting the fabric is enlarged and photographed with an optical microscope or a reflection electron microscope so that the fiber diameter is about 1 cm. On the other hand, in the case of non-woven fabric, a sample with a width of 5 mm is cut out from the fabric (the length depends on the measuring device), and the cross section of the sample is enlarged with an optical microscope or a reflection electron microscope so that the fiber diameter can be seen about 1 cm. Take a photo. From these photographs, an inscribed circle and a circumscribed circle of each cross section of the fiber are taken, and if the ratio of the circumscribed circle / inscribed circle is 1.1 or less, it is judged as a substantially circular cross section, and if it exceeds 1.1, it is judged as an irregular cross section. The operation is repeated for all the photographed cross sections, and the ratio is calculated from the substantially circular cross section number / total cross section number × 100.

  The fabric needs to sufficiently introduce light from the light source to the optical sheet. However, when the cross-sectional shape of substantially all (ie, 80 to 100%) fibers constituting the fabric is a substantially circular cross-section, the side surface of the fiber is used. Is formed of a curved surface, so that a gap is easily generated between the single yarns. Therefore, when the fabric is irradiated with light, the light not only transmits through the inside of the single yarn, but also reaches the fabric surface while passing through the gaps between the fibers or being scattered by the curved surface of the fibers. As a result, the amount of light transmitted through the entire fabric is increased. In addition, as for the fiber of a substantially circular cross section, it is more preferable that it is 90 to 100% of the fiber which comprises a fabric.

  The fibers constituting the fabric preferably have a fineness of 5 dtex or more and 450 dtex or less, and further a fineness of 15 dtex or more and 150 dtex or less. The fineness is also called the total fineness, and means a mass (g) of 10000 m of a yarn composed of one or two or more single yarns or staples. Further, the average total fineness may be 5 dtex or more and 450 dtex or less, and the average total fineness is preferably 15 dtex or more and 150 dtex or less. If the fineness (total fineness) of the fibers constituting the fabric is substantially less than 15 dtex, the fabric becomes too thin, the light source is easily visible, and uneven brightness tends to increase. On the other hand, when the fineness is substantially larger than 150 dtex, the fabric becomes too thick, the amount of light transmitted is reduced, and the luminance is likely to be reduced. Therefore, 15 dtex or more and 150 dtex or less are good. Furthermore, 50 dtex or more and 100 dtex or less are preferable.

  Moreover, in this invention, it is preferable that the average single yarn fineness of the fiber which comprises a fabric is 0.001 or more and 30 dtex or less. If the single yarn fineness is less than 0.001 dtex, the single yarn strength is insufficient and the cutting becomes easy and the handleability deteriorates. On the other hand, if it exceeds 30 dtex, there is no problem in terms of single yarn strength, but the single yarn fiber diameter becomes thick. For this reason, fiber gaps are likely to be generated, and light unevenness is likely to occur. Also, when multifilaments are used, the thickness of the fabric tends to increase due to the overlap of the fibers, and the average brightness tends to decrease.

  According to JIS-L1096 (1999), the average total fineness and the average single yarn fineness were obtained by taking three test pieces of 20 cm × 20 cm from the sample, unwinding 25 warp yarns and weft yarns for each one. The mass is weighed, the apparent fineness is obtained by the following formula, and the average value of the warp yarn and the weft yarn is calculated three times to obtain the average total fineness. Further, the value obtained by dividing the length of the warp yarn by the number of one filament is defined as the average single yarn fineness.

T = 0.2 × W × 10
Here, T: Average total fineness (dtex) of yarn
W: Mass of 25 samples (mg)
Furthermore, in the present invention, the fabric may be of any configuration such as a woven fabric, a knitted fabric, a dry nonwoven fabric, and a wet nonwoven fabric, but a woven fabric having good dimensional stability during handling and small thickness unevenness is preferable. In general, the thickness of a fabric-rich portion (dense portion) is thicker, the thickness of a fabric-reduced portion (coarse portion) is thinner, and the portion with more fibers is darker due to less light transmission. Therefore, the portion with less fiber becomes brighter because the amount of transmitted light increases. Therefore, when the thickness unevenness is large, the brightness unevenness is increased. Also, if the dimensional stability is poor, the fabric itself is deformed and stretched (shrinked) when it is fixed by stretching or the like. Therefore, the stretched (shrinked) portion has a smaller amount (more) of the fiber, and the portion has a larger (smaller) amount of light transmission than the non-deformed portion, resulting in uneven brightness. Furthermore, when the optical sheet is laminated on the support, the support itself stretches due to the weight of the optical sheet, and sagging occurs, and the sagging part is closer to the light source, so it becomes brighter than the other parts and becomes brighter on the backlight screen. Unevenness occurs. Therefore, a fabric with small thickness unevenness and good dimensional stability is preferable. The woven structure of the woven fabric is not particularly limited, and may be any structure such as a plain weave, a twill weave, and a satin weave.

  When the support is composed of a woven fabric, the cover factor of the woven fabric is preferably 1200 or more and 2500 or less.

The cover factor is a factor calculated by the following equation.
Cover factor = warp yarn density (main / 2.54 cm) × (warp yarn fineness (dtex)) ^1/2
+ Weft density (main / 2.54 cm) × (Weft fineness (dtex)) ^1/2
When the cover factor is smaller than 1200, the amount of fibers constituting the fabric is too small, so that the diffusion of light in the fabric becomes small and the luminance unevenness becomes too large. On the other hand, if the cover factor is greater than 2500, the amount of fibers constituting the fabric is too large, and light cannot be sufficiently transmitted, sufficient luminance cannot be obtained, and the display screen tends to be dark. The cover factor is more preferably 1300 or more and 2200 or less, and particularly preferably 1500 or more and 2000 or less.

  Moreover, when the fabric of this invention is comprised with a woven fabric, it is preferable that ratio of the weave density of warp yarn and weft yarn is 1: 2 to 2: 1. The light diffusion performance required for the fabric may require not only uniform dispersion but also anisotropic diffusion depending on the performance of the optical sheet placed on the cloth. In order to develop this anisotropy, It is preferable to change the weaving density ratio between the warp yarn and the weft yarn. However, if the weaving density ratio exceeds 2, the joints of the fabric tend to be large, and light traveling straight from there tends to cause unevenness of light.

  The method for measuring the weaving density is in accordance with JIS-L1096 (1999). A test piece of 2.54 cm × 2.54 cm is taken out from the sample at a right angle or parallel to the warp and the weft, and the warp and the weft are taken from the test piece. Loosen the yarn and count the number of each. That value is the folding density.

In order to express the optical anisotropy of the fabric more remarkably, it is preferable that one of the warp yarn and the weft yarn constituting the woven fabric is constituted by a monofilament. By combining multifilaments and monofilaments, it is possible to obtain a fabric having high optical anisotropy that cannot be achieved by the configuration of warp and weft yarns and multifilaments.
In the present invention, the fabric is preferably heat-treated in the state of the fabric in order to reduce dimensional deformation due to tension at the time of stretching and fixing described later. A fabric subjected to heat setting or the like is also preferable.
Specifically, it is preferable to apply a load of 4.9 N / 5 cm and the elongation rate after 24 hours (hereinafter referred to as creep) is 10% or less in both the longitudinal and lateral directions of the fabric. . Since the support is used for a long time in a state where the weight of the fabric and the weight of the optical sheet are added, if the creep is large, the support is gradually extended, resulting in sagging and uneven brightness as described above. Therefore, the creep is preferably 10% or less. More preferably, it is 5% or less, More preferably, it is 3% or less.

  The creep measurement method is as follows.

  Cut the fabric into 30 cm long and 5 cm wide test pieces (n = 3 each in the vertical and horizontal directions), hold the test piece at a grip interval of 20 cm, and apply a tension of 4.9 N / 5 cm almost uniformly in the width direction. The fabric is suspended so that the length direction is vertical and kept at room temperature (about 25 ° C.) for 24 hours. After 24 hours, the grip interval (L (cm)) is measured, the elongation is calculated by the following formula, and the average value of n = 3 for each of the vertical and horizontal is calculated.

Elongation rate (creep) (%) = (L (cm) −20 (cm)) / 20 (cm) × 100
Further, the support is sometimes exposed to ultraviolet rays contained in the light source while the light source of the display is lit, and may turn yellow and deteriorate in strength. When the support turns yellow, the color tone of the light transmitted through the yellowed support changes, and the color tone of the screen displayed on the display also changes. Therefore, it is preferable that the support of the present invention is a fabric that has been subjected to ultraviolet resistance treatment.

Ultraviolet resistant treatment is treatment using a light stabilizer such as an ultraviolet absorber. The light stabilizer is any one of (1) shielding and absorption of ultraviolet rays, (2) non-radical decomposition of hydroperoxide, (3) quenching of excited compounds, (4) trapping of trace heavy metals, and (5) trapping of radicals. It has one or more functions. Specific examples of the light stabilizer mainly include triazine compounds, benzotriazole compounds, benzophenone compounds, dibenzophenone compounds, salicylate compounds, cyanoacrylate compounds, oxanilide compounds, formamidine compounds, and the like. Ultraviolet absorbers that have ultraviolet shielding and absorption effects, as well as phenolic compounds, phosphorus compounds, organocopper complex compounds, hydrazine compounds, and other antioxidants that mainly have radical scavenging effects, radical scavenging ability and hydroper Hindered amine light stabilizers having oxide resolution and metal ion scavenging ability. The light stabilizer is not particularly limited to these, and can be selected according to the type of fiber constituting the fabric and the processing method for performing the light stabilization treatment. Moreover, one type of light stabilizer may be used, or two or more types may be used in combination.
The method for imparting the light stabilizer may be a method for imparting to the surface of the fiber, such as a spray method, a coating method, or a printing method, or a method for diffusing into the interior of the fabric or fiber. As a method of diffusing inside the fabric or fiber, a dyeing method in a bath where the fabric or fiber is immersed in an aqueous solution containing a light stabilizer and heating, or a fabric or fiber immersed in an aqueous solution containing a light stabilizer, mangle, etc. Then, a pad-cure method or the like in which dry heat treatment is performed after the amount of adhesion is reduced to a predetermined amount can be employed. The light stabilizer may be applied to the fibers before forming the fabric or may be applied after forming the fabric. However, the latter has higher processing stability and can reduce the cost. preferable.

  When the light stabilizer is diffused into the fabric or fiber, the amount of the light stabilizer applied is 0.1 to 5.0% by weight, more preferably 0.5 to 3.0% by weight, based on the weight of the fabric. Good. If the amount is less than 0.1% by weight, the intended UV resistance may not be exhibited. If the amount exceeds 5% by weight, the strength of the fiber may decrease or the cost may increase. .

  In the case of a method of applying a light stabilizer to the surface, such as a spray method, a coating method, or a printing method, the adhesion amount of an ultraviolet absorber or the like is 0.1 to 10.0% by weight, more preferably based on the weight of the fabric. It is 0.5 to 8.0 weight%, More preferably, it is 0.5 to 5.0 weight%. If the amount is less than 0.1% by weight, the target UV resistance may not be achieved as in the case of exhaustion. If the amount exceeds 10.0% by weight, the cost increases or the attached light stability is increased. In some cases, light transmission is hindered by the agent, resulting in a decrease in luminance.

  In the present invention, the fabric has a bending resistance measured in accordance with JIS-L1096 (1999) 8.19 bending resistance A method (45 degree cantilever method) of 100 mm or less in both the vertical and horizontal directions. Is preferred. This is because if the bending resistance exceeds 100 mm, an excessive working tension is required to maintain the surface smoothness during fabric stretching described later. The bending resistance is more preferably 70 mm or less, and further preferably 50 mm or less.

  Specifically, the bending resistance is obtained as follows. First, five 2 cm x 15 cm test pieces are sampled from the sample in each of the vertical and horizontal directions, and the short side of the test piece is used as a scale reference on a smooth surface with a 45-degree slope at one end. Put together. Next, the test piece is gently slid in the direction of the slope, and when the center point of one end of the test piece is in contact with the slope, the position of the other end is read with a scale. The bending resistance is indicated by the length (mm) that the specimen has moved. In the present invention, it is obtained by measuring the front and back of each of the five sheets and calculating the average values in the vertical and horizontal directions.

  In the present invention, the fabric preferably has a tensile strength of 100 N / 5 cm or more in order to prevent damage to the fabric itself, such as during stretch fixation. When supporting the optical sheet, it is considered that a tension of, for example, 50 N / 5 cm is sufficient. Therefore, by setting the tensile strength to 100 N / 5 cm or more, problems such as breaking of the fabric during stretching do not occur, leading to process stabilization.

Furthermore, in the present invention, considering that the optical sheet support is used for a direct backlight for a liquid crystal display, it is preferable that the uneven brightness of the fabric is 50 to 350 cd / m ² . When the luminance unevenness exceeds 350 cd / m ² , the difference between light and dark becomes large, and when a display is used, problems such as the screen appearing mottled tend to occur. Further, 50 cd / m ² is the limit in a direct type backlight in which a plurality of fluorescent tubes are arranged.

The method of measuring the brightness unevenness of the fabric is as follows. First, remove the diffusion plate installed on the fluorescent lamp of the direct type backlight, place a transparent plastic plate with the same thickness as the diffusion plate, install a fabric on it, and light the fluorescent tube for 60 minutes And stabilize the light source. After that, using the brightness measurement device EYSCALE-3 (manufactured by Eye System Co., Ltd.) from the measurement sample side, the attached CCD camera is placed at a point 90 cm from the center of the direct backlight light emitting surface. It installs so that it may become a front with respect to a surface, and a brightness | luminance (cd / m < ² >) is measured. The measurement locations are two luminances (L _max ) directly above the two fluorescent tubes near the center point, and three luminances (L _min ) between the two measured fluorescent tubes and the adjacent fluorescent tubes. Measure. The brightness unevenness is calculated from the following formula, and the brightness unevenness is better as the value is smaller.

Brightness unevenness (cd / m ² ) = (average value of L _max ) − (average value of L _min )
In consideration of handling and light transmittance in the working process, the weight of the fabric in the present invention is preferably 10 g / m ² or more and 300 g / m ² or less. At this time, the weight is calculated by cutting three samples into 20 cm square, measuring the weight, and calculating the average value (m (g)) of the three sheets. Using the value, the weight per m ² (M (g / m ² )) is calculated by the following formula.

M (g / m ² ) = m (g) / (0.2 (m) × 0.2 (m))
If the fabric weight is less than 10 g / m ² , the lightness is excellent, but the rigidity of the fabric is easily lost and the handle is too soft, and if it exceeds 300 g / m ² , the light transmittance is deteriorated, which is not preferable.

  The fibers and fabrics constituting the present invention as described above may be manufactured by any method. For example, they can be manufactured as follows. Dimethyl terephthalic acid, ethylene glycol, and tetrabutyl titanate were used as catalysts. After transesterification while distilling methanol at 140 ° C. to 230 ° C., polymerization was performed at a constant temperature of 285 ° C. for 3 hours, and the intrinsic viscosity [ A polyethylene terephthalate polymer having [η] of 0.65 is obtained. This polymer is melted at 290 ° C. using a known spinning machine, and weighed with a lightweight pump, discharged from a die having a circular discharge hole diameter of 0.23 mmφ, a discharge hole length of 0.3 mm, and a discharge hole number of 72 H, and converged while cooling. In order to improve the properties, an oil agent is applied and the undrawn yarn is wound up at 1800 m / min. This undrawn yarn was drawn 3.2 times using a drawing machine having a first hot roll of 90 ° C. and a second hot roll of 130 ° C., and was substantially circular with an average total fineness of 84 dtex and an average single yarn fineness of 1.17 dtex. A drawn yarn having a cross section is obtained. The fabric is obtained by weaving the fibers obtained in this way for warp and weft, scouring, and applying a weathering agent.

  Subsequently, the optical sheet support of the present invention preferably has a member for stretching and fixing the fabric in addition to the fabric as described above. As a result, the fabric is stretched and fixed on the display, and the optical sheet is supported by the tension due to the stretching and fixing.

  The method for stretching and fixing the optical sheet support is not particularly limited, and examples thereof include the following method using a frame.

  (1) The frame includes at least a pair of recesses and projections, one of which is fixed to the fabric, and the fabric is fixed by fitting the recesses and the projections. That is, for example, a fabric fixed to a frame having a convex portion and a housing having a concave portion are prepared, and the concave portion and the convex portion are fitted to fix and stretch the fabric.

  (2) The frame includes at least a pair of concave portions and convex portions, and the fabric is sandwiched and fixed between the concave portions and the convex portions. That is, for example, a method of preparing a frame body having a convex portion and a housing having a concave portion, and holding the fabric between the concave portion and the convex portion to stretch and fix.

  (3) A method in which the fabric is stretched and fixed to the frame with an adhesive and / or an adhesive tape interposed.

  (4) A method in which the fabric is sewn and fixed to the casing.

  (5) A method in which an elastic body portion is provided on the frame and the fabric is stretched and fixed by this elastic force.

  (6) A method in which the fabric is stretched and fixed on the frame by a weight.

  At this time, the frame may be originally provided as a member of the display, or may be handled as a separate member.

  The stretching tension at the time of stretching and fixing is preferably 10 N / 5 cm or more and 100 N / 5 cm or less. That is, it is preferable to stretch and fix while applying a force of 10 N or more and 100 N or less per 5 cm width of the fabric. If it is less than 10 N / 5 cm, sagging tends to occur, and if it exceeds 100 N / 5 cm, the fabric stretches, which is not preferable. The tension at the time of stretching can be applied, for example, by sandwiching the end of the fabric with a flat plate or the like so as to apply a uniform force, and pulling while measuring the tension with a spring gauge.

  As a criterion for determining whether or not the appropriate tension is appropriate, the amount of deflection at the center of the light emitting surface when an optical sheet such as a prism sheet or a polarization separation sheet is placed is raised. The amount of deflection when the optical sheet is placed is preferably 10 mm or less. If the amount of deflection exceeds 10 mm, a difference occurs in the amount of light between the central portion and the end portion of the light emitting surface, and light unevenness tends to occur, which is not preferable.

  According to the support of the present invention as described above, the thickness can be reduced, the optical sheet can be supported at a position closer to the light source, the light emitted from the light source can be transmitted in a stronger state, and the display screen can be brightened. become. In addition, since it is thin, it is excellent in compactness, light and excellent in impact resistance, and it is possible to prevent the occurrence of problems such as cracking and cracking during transportation and display assembly process. As a result, it is possible to significantly reduce costs.

  Next, preferred configurations of a backlight for a liquid crystal display using the support of the present invention are illustrated in FIGS. 1 and 2, but the present invention is not limited to these configurations.

  FIG. 1 is a diagram schematically showing the configuration of a backlight when the support of the present invention is incorporated in a sidelight-type backlight of a liquid crystal display. In FIG. 1, the sidelight-type backlight includes a light guide plate 3 obtained by processing a transparent acrylic plate, one or a plurality of linear fluorescent tubes (light sources) 5 disposed on the side surface, and a bottom surface of the light guide plate 3. A reflection sheet 4 disposed on the side, a support of the present invention disposed on the surface side of the light guide plate 3, and a brightness enhancement sheet such as a prism sheet or a polarization separation sheet disposed further above the support 2 ( Optical sheet) 1 and the like.

  FIG. 2 is a diagram schematically showing a configuration of a backlight when the support of the present invention is incorporated in a direct type backlight of a liquid crystal display. In FIG. 2, the direct type backlight has a plurality of linear fluorescent tubes 5 arranged inside a casing 6 in which a reflection sheet 4 is spread, and the support 2 of the present invention is arranged above the fluorescent tubes 5. Further, a brightness enhancement sheet (optical sheet) 1 such as a prism sheet or a polarization separation sheet is disposed on the support 2. And in this embodiment, in order to prevent the support body 2 from bending greatly, the support pillar 7 is also installed.

  A liquid crystal display is configured by disposing a liquid crystal cell above the optical sheet of the backlight shown in FIGS.

  Moreover, the support body of this invention mentioned above can be used preferably also for a rear projection type display.

  The rear projection display is a display that displays an image by enlarging and projecting an image generated by a CRT, a liquid crystal panel, or the like onto a rear projection screen using a projection lens. The screen used here plays a role of appropriately distributing projection light and enabling good image recognition. As the screen, for example, it is possible to use a diffuser plate with isotropic diffusivity mixed with diffusing particles. However, since the incident light is divergently incident, the periphery of the screen is directed outward. When observed from the front side of the screen, the brightness unevenness on the screen becomes noticeable, such as bright and dark at the center and dark when viewed from an oblique direction and darker near and brighter. In order to eliminate such luminance unevenness, it is common to arrange a Fresnel lens sheet on the projection lens side, but in order to support an optical sheet such as this Fresnel lens sheet, the support of the present invention is used. Can be used.

  The Fresnel lens sheet functions to convert the projection light divergingly incident on the screen from the projection lens into parallel light substantially perpendicular to the screen. Therefore, if the direction of light in each part of the screen is changed to a direction perpendicular to the screen surface and then diffused, almost uniform brightness can be realized over the entire screen regardless of the direction of observation. it can. And if it laminates | stacks on this Fresnel lens sheet with the support body of this invention, it can diffuse not only the Fresnel lens sheet but the light which became parallel light through it.

  Conventionally, the lenticular lens sheet generally plays a role of supporting the Fresnel lens sheet and diffusing light from the sheet. The lenticular lens sheet is a sheet having anisotropic diffusivity that diffuses parallel light incident with image light in the horizontal direction and expands the viewing angle. However, the lenticular lens sheet usually has a thickness of about 2 to 3 mm and has the above-described problems. Therefore, in the rear projection type display, if the support of the present invention is used instead of the lenticular lens sheet, the same effect as the above-described liquid crystal display can be obtained.

Hereinafter, although an example is given and the present invention is explained, the present invention is not necessarily limited to this.
(Characteristic measurement method)
A. Total light transmittance and haze As described above, in accordance with method A of JIS-K-7105 (established 1981), fully automatic direct reading haze computer HGM-2DP (for C light) (manufactured by Suga Test Instruments Co., Ltd.) And measured.

B. Fabric thickness Measured using a thickness gauge (pressing pressure 0.98 N / cm ² ).

C. Weight of Fabric Three samples were cut into 20 cm square, the weight was measured, and the average value (m (g)) of the three sheets was calculated. Using this value, the weight per m ² (M (g / m ² )) was calculated using the following formula.

M (g / m ² ) = m (g) / (0.2 (m) × 0.2 (m))
D. Tensile strength JIS-L1096 (1999)-8.12.1 In accordance with the labeled strip method of the A method (strip method), three specimens were sampled in each of the vertical and horizontal directions, from both sides of the width. Measure the breaking strength when testing with a constant speed tension type tester at a gripping interval of 150 mm and a pulling speed of 200 mm / min with a constant speed tension type tester by removing the yarn and calculating an average value in each of the vertical and horizontal directions. did.

E. Luminance unevenness of optical sheet support Remove the diffusion plate installed on the fluorescent tube of the direct type backlight, and in the case of fabric, place a transparent plastic plate with the same thickness as the diffusion plate, and place the fabric on it In the case of a milky white plate, it was installed without a transparent plastic plate, and the fluorescent tube was turned on for 60 minutes to stabilize the light source. After that, using the luminance measurement device EYSCALE-3 (manufactured by I-System Co., Ltd.) from the measurement sample side, the attached CCD camera is placed at a point 90 cm from the center of the light emitting surface of the direct type backlight, It installed so that it might become the front with respect to a surface, and the brightness | luminance (cd / m < ² >) was measured. The measurement locations were two locations (L _max ) just above the two fluorescent tubes on the left and right of the center point, and three luminance locations (L _min ) between the two measured fluorescent tubes and the adjacent fluorescent tubes. . The brightness unevenness is calculated from the following formula, and the brightness unevenness is better as the value is smaller.

Brightness unevenness (cd / m ² ) = (average value of L _max ) − (average value of L _min )
F. The amount of deflection at the center of the light emitting surface in the backlight The amount of deflection at the center of the light emitting surface was measured by passing a non-deflable metal rod directly above the center and measuring the gap between the bottom surface of the metal rod and the film with a caliper.

G. Visual evaluation of backlight brightness and brightness unevenness Visual evaluation was performed by 10 persons, and brightness and brightness unevenness were observed in four stages of A (excellent), B (good), C (possible), and D (impossible). The most popular evaluation was adopted. In the case of the same number of people, a higher evaluation was adopted.

H. Impact Resistance A 50 cm square sample was placed on a concrete floor, and an iron ball weighing 3 kg was dropped from a height of 2 m at the center.

<Example 1>
The fabric produced as described below was subjected to UV resistance treatment, and various properties of the fabric were evaluated as described above. Then, the backlight was comprised as follows and the supportability of the optical sheet, the brightness | luminance in a backlight, and the brightness nonuniformity were evaluated.

  The evaluation results are shown in Table 1.

  The optical sheet can be satisfactorily supported, sufficient luminance can be obtained as a backlight, and luminance unevenness has no problem.

(Fabric composition)
1. Yarn used: warp, horizontal yarn 84 dtex-72 filament, polyester 100% filament yarn 2. Weaving organization: Plain weave Weaving density: warp weave density 110 / 2.54cm, weft density 90 / 2.54cm
(UV resistant)
An ultraviolet absorption treatment solution containing a triazine-based ultraviolet absorber (trade name: CIBAFAST P, manufactured by Ciba Specialty Chemicals Co., Ltd.) 2% by weight of the fabric and 1.0 g / l of ammonium sulfate, and a fabric having the above-described structure In the bath, the volume ratio was fabric: aqueous solution = 1: 20. The treatment conditions were as follows: dyeing in a bath at 130 ° C. for 60 minutes, followed by washing with hot water at 60 ° C. for 10 minutes and rinsing with running water for 5 minutes. Then, it dried at 120 ° C. for 3 minutes. The adhesion amount of the ultraviolet absorber was 0.8% by weight.

(Optical sheet support, backlight brightness, uneven brightness)
The 32-inch direct type backlight shown in FIG. 2 was constructed. The fabric was stretched without sagging or wrinkles and fixed to the four sides of the housing with double-sided tape. As an optical sheet, a prism sheet and a polarization separation sheet were placed, and the amount of deflection at the center of the light emitting surface was measured.

Furthermore, the fluorescent lamp was turned on, and the luminance and luminance unevenness of the backlight were evaluated.
<Example 2>
The fabric produced as described below was subjected to UV resistance treatment, and various properties of the fabric were evaluated as described above. Then, the backlight was comprised as follows and the supportability of the optical sheet, the brightness | luminance in a backlight, and the brightness nonuniformity were evaluated.

  The evaluation results are shown in Table 1.

The optical sheet can be satisfactorily supported, and sufficient luminance can be obtained as a backlight, and luminance unevenness has no problem.
(Fabric composition)
1. Yarns used: warp, weft 56 dtex-36 filament, 100% polyester filament yarn 2. Weaving organization: Plain weave Weaving density: Vertical weave density 170 / 2.54cm, Horizontal weave density 120 / 2.54cm
(UV resistant)
A benzotriazole ultraviolet absorber (trade name: Antifade 8001, manufactured by Meisei Chemical Industry Co., Ltd.) was adjusted to a concentration of 20 g / l, and the fabric of Example 2 was immersed therein and squeezed once with a mangle. . The amount of wet pickup was 30% by weight relative to the fabric weight. This fabric was pre-dried at 110 ° C. for 1 minute, and then cured at 180 ° C. for 1 minute.

(Optical sheet support, backlight brightness, uneven brightness)
The 32-inch direct type backlight shown in FIG. 2 was constructed. The fabric was stretched without sagging or wrinkles and fixed to the four sides of the housing with double-sided tape. A prism sheet and a polarization separation sheet were placed thereon as an optical sheet, and the amount of deflection at the center of the light emitting surface was measured.

Furthermore, the fluorescent lamp was turned on, and the luminance and luminance unevenness of the backlight were evaluated.
<Example 3>
The fabric produced as described below was subjected to UV resistance treatment, and various properties of the fabric were evaluated as described above. Then, the backlight was comprised as follows and the supportability of the optical sheet, the brightness | luminance in a backlight, and the brightness nonuniformity were evaluated.

  The evaluation results are shown in Table 1.

  The optical sheet can be satisfactorily supported, sufficient luminance can be obtained as a backlight, and luminance unevenness has no problem.

(Fabric composition)
1. Yarn used: warp, weft 22 dtex-15 filament, 100% polyester filament yarn 2. Weaving organization: Plain weave Weaving density: 150 weave / 2.54 cm, Weft density 140 / 2.54 cm
(UV resistant)
Same as Example 1 (supportability of optical sheet, luminance of backlight, luminance unevenness)
The 32-inch backlight shown in FIG. 2 was constructed. The fabric was stretched without sagging or wrinkles and fixed to the four sides of the housing with double-sided tape. A prism sheet and a polarization separation sheet were placed thereon as an optical sheet, and the amount of deflection at the center of the light emitting surface was measured.

Furthermore, the fluorescent lamp was turned on, and the luminance and luminance unevenness of the backlight were evaluated.
<Comparative Example 1>
Add 3 parts by weight of silicone resin particles (Tospearl 120, manufactured by GE Toshiba Silicone Co., Ltd.) with an average particle diameter of 2 μm to 100 parts by weight of methacrylic resin, melt and extrude using an extruder, and a 2 mm thick milk plate The various characteristics of the milky white plate were evaluated as described above. Then, the backlight was comprised as follows and the supportability of the optical sheet, the brightness | luminance in a backlight, and the brightness nonuniformity were evaluated.

  The evaluation results are shown in Table 1.

  Although the optical sheet could be supported, the milky white plate was heavy and the workability was poor. Further, as the backlight, although there was no luminance unevenness, when the backlight and the luminance obtained in Examples 1 to 3 were compared visually, the luminance was clearly low and dark.

(Optical sheet support, backlight brightness, uneven brightness)
In constructing the 32-inch backlight shown in FIG. 2, the evaluation was performed in the same manner as in Example 1 except that a milky white plate was installed instead of the support.

<Examples 4 to 8>
The fabric produced by changing the cross-sectional shape and weaving density of the fibers constituting the fabric as described below was subjected to UV resistance treatment, and the various properties of the fabric were evaluated as described above. Then, the backlight was comprised as follows and the supportability of the optical sheet, the brightness | luminance in a backlight, and the brightness nonuniformity were evaluated.

  The evaluation results are shown in Table 1.

  In either case, the optical sheet could be supported well, and sufficient luminance was obtained as a backlight, and there was no problem with luminance unevenness.

(Fabric composition)
1. Yarn used: Changed as shown in Table 1.
2. 2. Weaving organization: Plain weave Weaving density: changed as shown in Table 1.

(UV resistant)
An ultraviolet absorption treatment solution containing a triazine-based ultraviolet absorber (trade name: CIBAFAST P, manufactured by Ciba Specialty Chemicals Co., Ltd.) with 2% by weight of the fabric and 1.0 g / L of ammonium sulfate, and a fabric having the above-described structure In the bath, the volume ratio was fabric: aqueous solution = 1: 20. The treatment conditions were as follows: dyeing in a bath at 130 ° C. for 60 minutes, followed by washing with hot water at 60 ° C. for 10 minutes and rinsing with running water for 5 minutes. Then, it dried at 120 ° C. for 3 minutes. The adhesion amount of the ultraviolet absorber was 0.8% by weight.

(Optical sheet support, backlight brightness, uneven brightness)
The 32-inch backlight shown in FIG. 2 was constructed. The fabric was stretched without sagging or wrinkles and fixed to the four sides of the housing with double-sided tape. A prism sheet and a polarization separation sheet were placed thereon as an optical sheet, and the amount of deflection at the center of the light emitting surface was measured.

  Furthermore, the fluorescent lamp was turned on, and the luminance and luminance unevenness of the backlight were evaluated.

It is a schematic diagram of the sidelight type backlight used for a liquid crystal display. It is a schematic diagram of the direct type backlight used for a liquid crystal display.

Explanation of symbols

1 Brightness improvement sheet (optical sheet)
2 Support fabric 3 Light guide plate 4 Reflective sheet 5 Fluorescent tube 6 Housing 7 Support column

Claims (14)

  An optical sheet support, which is a support for an optical sheet mounted on a display, comprising a fabric composed of fibers, wherein the total light transmittance of the fabric is 25% or more and 90% or less.   The optical sheet support according to claim 1, wherein the fabric has a haze of 20% to 100%.   The optical sheet support according to claim 1 or 2, wherein 80 to 100% of the fibers constituting the fabric have a substantially circular cross section.   The optical sheet support according to any one of claims 1 to 3, wherein the fibers constituting the fabric include fibers having a total fineness of 5 dtex or more and 450 dtex or less.   The optical sheet support according to any one of claims 1 to 3, wherein the fibers constituting the fabric include fibers having a total fineness of 15 dtex or more and 150 dtex or less. The optical sheet support according to any one of claims 1 to 5, wherein an average single yarn fineness of fibers constituting the fabric is 0.001 dtex or more and 30 dtex or less.   The optical sheet support according to claim 1, wherein the fabric is a woven fabric.   The optical sheet support according to claim 7, wherein a cover factor of the woven fabric is 1200 or more and 2500 or less.   The optical sheet support according to any one of claims 1 to 8, wherein the fabric is subjected to ultraviolet resistance treatment.   The optical sheet support according to claim 1, which is mounted on a backlight of a liquid crystal display.   A backlight for a liquid crystal display, comprising the optical sheet support according to claim 1.   The backlight for a liquid crystal display according to claim 11, wherein at least one of a prism sheet and a polarization separation sheet is supported by the optical sheet support.   A liquid crystal display comprising the liquid crystal display backlight according to claim 11.   A rear projection display comprising the optical sheet support according to claim 1.

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