JP2010225314A - Surface light source device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device capable of reducing an unpleasant noise between a light diffusion plate and spacer pins and capable of being manufactured easily, and to provide a liquid crystal display device. <P>SOLUTION: The surface light source device 20 includes a plurality of light sources 21 arranged in parallel each in separation, a lamp box 22 housing the light sources, a light diffusion plate 23 arranged on the lamp box, and a plurality of spacer pins 25 which are arranged in the lamp box 22 and support the light diffusion plate 23. In the surface light source 20, the surface 23a of the light diffusion plate 23 on the lamp box 22 side has an arithmetic average roughness RA of ≤1.0 μm and an irregular average interval RSm of ≤200 μm in a contact region with at least each of the spacer pins 25. In this case, a catching or the like between the light diffusion plate 23 and the spacer pins 25 is reduced, an unpleasant noise between the spacer pins 25 and the light diffusion plate 23 is hardly generated, and thereby the unpleasant noise is reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface light source device and a liquid crystal display device.

  As a liquid crystal display device, for example, a liquid crystal display device in which a surface light source device is disposed as a backlight on the lower surface (back side) of an image display unit in which a pair of polarizing plates are disposed on both upper and lower surfaces of a liquid crystal cell is known. The surface light source device for backlight has a plurality of light sources arranged in a lamp box, and a light diffusion plate that diffuses and emits light output from the light sources so that an image of the light source is not displayed on the image display unit. ing.

  The light diffusing plate is arranged in contact with and fixed to the front surface of the edge frame portion of the lamp box. For example, in a large liquid crystal display device of 32 inches or more, the light diffusing plate is likely to be bent. For this reason, usually, a spacer pin is provided at a predetermined position in the lamp box so as to support the light diffusion plate from the inside of the lamp box.

  By the way, in a liquid crystal display device equipped with a backlight, unnecessary sound (hereinafter referred to as unpleasant sound) is generated in terms of design due to mutual friction caused by thermal expansion of each member constituting the liquid crystal display device. There was a case.

  In order to prevent such an unpleasant noise, for example, in Patent Document 1, friction reducing means such as a low friction sheet is provided at a contact portion between each member of the light diffusing plate and the surface light source device.

JP 2008-209943 A

  However, in Patent Document 1, in order to reduce friction, a process for reducing unpleasant noise must be performed afterwards in addition to main components such as a lamp unit and a light diffusion plate of the surface light source device. It may also occur that the manufacture of is not easy.

  Therefore, the present invention has been made in view of the above circumstances, a surface light source device that can reduce unpleasant noise between the light diffusion plate and the spacer pin and can be manufactured more easily, and a liquid crystal using the same. An object is to provide a display device.

  As a result of intensive studies to achieve the above object, the present inventors have found that the main causes of unpleasant noise are the thermal expansion of the light diffusion plate due to the heat of the light source arranged in the lamp box and the surface roughness of the light diffusion plate. Focused on the relationship. That is, when the liquid crystal display device is activated, a temperature difference is generated between the inside and outside of the lamp box due to the heat of the light source. This difference in temperature causes a difference in thermal expansion in the light diffusing plate, which is considered to cause a slight movement of the light diffusing plate relative to the spacer pins. On the other hand, it is generally known that the light diffusing plate is exposed to the surface of the light diffusing plate, and the surface is roughened. Therefore, when the light diffusing plate is finely moved with respect to the spacer pin due to the thermal expansion of the light diffusing plate, the spacer pin is caught on the surface unevenness, and the spacer pin is released from the catch. As a result, it is assumed that a sound (unpleasant sound) is generated between the spacer pin and the light diffusion plate. Therefore, the present inventors have focused on the fact that the unpleasant noise between the spacer pins and the light diffusing plate can be reduced by adjusting the surface roughness of the light diffusing plate, and have reached the present invention.

That is, the surface light source device according to the present invention includes a plurality of light sources arranged in parallel and spaced apart from each other, a lamp box that houses the plurality of light sources, a light diffusing plate provided on the lamp box, and a lamp box. A plurality of spacer pins for supporting the light diffusing plate, and on the surface of the light diffusing plate on the lamp box side, at least the arithmetic average roughness of the contact area with each spacer pin is 1.0 μm or less and the surface is uneven. The average interval is 200 μm or less,
It is characterized by that.

  In the said structure, when the surface roughness of the surface at the side of the spacer pin of a light diffusing plate is evaluated by the said arithmetic mean roughness (Ra) and the average space | interval (RSm) of an unevenness | corrugation based on JISB0601-1994, the said range By doing so, it is possible to prevent the spacer pin from being caught on the light diffusion plate. As a result, even when the surface light source device is driven, even if thermal expansion occurs in the light diffusing plate due to the heat of the light source, it is possible to reduce unpleasant noise caused by the contact between the spacer pin and the light diffusing plate. Moreover, since the unpleasant noise is reduced by adjusting the surface roughness of the light diffusing plate, for example, in the manufacture of the surface light source device, it occurs between the light diffusing plate and the spacer pin. The process of performing the process for reducing unpleasant noise is unnecessary. Therefore, it is easier to manufacture the surface light source device.

  In the surface light source device according to the present invention, it is preferable that the radius of the tip of the spacer pin is 0.5 mm or more and 1.0 mm or less.

  By using such a radius of the tip, it is possible to further reduce the pinching of the spacer pin to the in-plane unevenness of the light diffusing plate, resulting in contact between the spacer pin and the light diffusing plate. Unpleasant noise can be further reduced.

  The liquid crystal display device according to the present invention includes the above-described surface light source device according to the present invention, and a liquid crystal display unit that is provided on the surface light source device and receives light output from the surface light source device. It is characterized by.

  Since the liquid crystal display device includes the surface light source device according to the present invention described above, the spacer pin, the light diffusion plate, and the light diffusion plate can be used even when the light diffusion plate is thermally expanded by the heat of the light source when the liquid crystal display device is driven. It is possible to reduce unpleasant noise caused by the contact. Moreover, since the unpleasant noise is reduced by adjusting the surface roughness of the light diffusing plate, for example, in the manufacture of the surface light source device, the discomfort that occurs between the light diffusing plate and the spacer pin between them. There is no need to perform a process for reducing the sound. Therefore, it is easier to manufacture the surface light source device. As a result, the liquid crystal display device can be manufactured more easily.

  ADVANTAGE OF THE INVENTION According to this invention, the unpleasant noise between a light diffusing plate and a spacer pin can be reduced, and the surface light source device which can be manufactured more easily, and a liquid crystal display device using the same can be provided.

It is sectional drawing which shows typically the structure of one Embodiment of the liquid crystal display device which concerns on this invention. FIG. 2 is a schematic plan view of a surface light source device included in the liquid crystal display device shown in FIG. 1. It is an enlarged view of the front-end | tip part of the spacer pin contained in a surface light source device. It is sectional drawing of an example of the light diffusing plate which a surface light source device has. It is a schematic diagram which shows coextrusion molding by a multi-hold die | dye, and its post process.

  Hereinafter, embodiments of a surface light source device and a liquid crystal display device according to the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.

  FIG. 1 is a cross-sectional view schematically showing a configuration of an embodiment of a liquid crystal display device according to the present invention. In FIG. 1, the main components of the liquid crystal display device are shown as an exploded view of the liquid crystal display device. FIG. 2 is a schematic plan view of a surface light source device included in the liquid crystal display device shown in FIG. For convenience of explanation, FIG. 2 shows a state in which the light diffusing plate included in the surface light source device is not provided. FIG. 3 is an enlarged view of the tip of the spacer pin included in the surface light source device. FIG. 4 is a cross-sectional view of an example of a light diffusing plate included in the surface light source device.

  The liquid crystal display device 1 shown in FIG. 1 is a so-called liquid crystal television. The liquid crystal display device 1 is configured by providing a surface light source device 20 that is a direct lamp unit on the back side (lower side) of a liquid crystal panel 10 in which polarizing plates 12 and 13 are laminated on upper and lower surfaces of a liquid crystal cell 11. Has been. As the liquid crystal cell 11 and the polarizing plates 12 and 13, those used in a conventional liquid crystal display device can be used. Examples of the liquid crystal cell 11 include known liquid crystal cells such as TFT type and STN type.

  As shown in FIGS. 1 and 2, the surface light source device 20 includes a plurality of linear light sources 21 accommodated in a lamp box 22, and a light diffusion plate 23 provided on the open surface side of the lamp box 22. Yes.

  The plurality of linear light sources 21 are accommodated in the lamp box 22 in a state of being spaced apart and arranged in parallel and held by a holder 24. Examples of the linear light source 21 include a fluorescent lamp (cold cathode ray lamp) extending in one direction. What is necessary is just to determine the number of the linear light sources 21 according to the magnitude | size etc. of the liquid crystal display device 1. FIG.

  The lamp box 22 has a box shape with the side facing the bottom wall surface 22a opened. The inner surface of the lamp box 22 is preferably a light reflecting surface. This is because the light output from the linear light source 21 can be used effectively. In the following description, it is assumed that the inner surface of the lamp box 22 is a light reflecting surface unless otherwise specified.

  In the lamp box 22, resin spacer pins 25 are provided on the bottom wall surface 22 a between the plurality of linear light sources 21 in order to support the light diffusion plate 23. The number and arrangement position of the spacer pins 25 can be determined depending on the size of the liquid crystal display device 1. The spacer pin 25 can be substantially conical. As shown in FIG. 3, the distal end portion of the spacer pin 25 is curved, and the radius (hereinafter referred to as the distal end radius) r of the distal end portion is 0.5 mm to 1.0 mm. As shown in FIG. 2, the radius r can be a radius of an annulus that is visible on the inner side when the spacer pin is viewed from the liquid crystal panel 10 side. The shape of the spacer pin 25 is not limited to a substantially conical shape, and may be a cylindrical shape, for example. Moreover, it is also possible to make the front-end | tip part of the spacer pin 25 flat, and it can be considered that the radius of a flat part is the range mentioned above in that case.

  The light diffusion plate 23 diffuses and irradiates the direct light from the linear light source 21 and the reflected light reflected by the inner surface of the lamp box 22 toward the liquid crystal panel 10 so that the image of each linear light source 21 is not displayed on the liquid crystal panel 10. Is to do. The light diffusing plate 23 is provided in contact with the edge frame portion 22 b of the lamp box 22 and closes the open surface of the lamp box 22.

  The light diffusing plate 23 is configured by adding a diffusing agent for diffusing light to a translucent resin. As the translucent resin, polycarbonate resin, ABS resin (acrylonitrile-styrene-butadiene copolymer resin), methacryl resin, MS resin (methyl methacrylate-styrene copolymer resin), polystyrene resin, AS resin (acrylonitrile-styrene) Copolymer resins), polyolefin resins such as polyethylene and polypropylene, and the like.

Light diffusing plate 23, as shown in FIG. 4, may be an intermediate layer 23 ₁ is a three-layer structure sandwiched formed by two surface layers ₂₃ 2, 23 _3. However, the configuration of the light diffusing plate 23 is not limited to this, and may be, for example, a one-layer or two-layer structure or a four-layer or more layer structure. Although the size of the light diffusing plate 23 depends on the size of the liquid crystal display device 1, a size of about 750 × 450 mm or more is exemplified.

  On the surface (the lower surface in FIG. 1) 23a of the light diffusing plate 23 on the spacer pin 25 side, the arithmetic average roughness Ra based on JISB0601-1994 is 1.0 μm or less, and the average interval RSm of the unevenness is 200 μm or less. is there.

  Here, an example of a method for manufacturing the light diffusing plate 23 will be described by specifically illustrating constituent materials of the light diffusing plate 23 and the like.

  First, styrene resin (Toyo styrene “HRM40”, refractive index 1.59) and MS resin (“MS200NT” manufactured by Nippon Steel Chemical Co., Ltd., refractive index 1.57. Styrene / methyl methacrylate = 80 parts by mass / 20 parts by mass) Prepare). Hereinafter, this styrene resin is referred to as translucent resin A, and MS resin is referred to as translucent resin B.

  Next, based on the translucent resin A and the translucent resin B, a pellet-shaped light diffusing agent master batch A and a pellet-shaped light diffusing agent master batch B are prepared as follows.

  Light diffusing agent master batch A: A light diffusing agent and an ultraviolet absorber are dry-blended with the translucent resin A. Then, the blended product is put into a hopper of a 65 mm twin screw extruder and melt-mixed in a cylinder, and then extruded into a strand shape to be pelletized to obtain a pellet-shaped light diffusing agent master batch A. The temperature in the cylinder is set so that the temperature gradually decreases from the bottom of the hopper: 200 ° C. to the vicinity of the extrusion die: 250 ° C. toward the downstream.

  Light diffusing agent master batch B: The light transmissive resin B is dry blended with a diffusing agent and an ultraviolet absorber. Then, the blended product is put into a hopper of a 65 mm twin screw extruder and melt-mixed in a cylinder, and then extruded into a strand shape to be pelletized to obtain a pellet-shaped light diffusing agent master batch B. The temperature in the cylinder is set so that the temperature gradually decreases from the bottom of the hopper: 200 ° C. to the vicinity of the extrusion die: 250 ° C. toward the downstream.

  The light diffusing plate 23 is produced using the light transmissive resin A, the light transmissive resin B, the light diffusing agent master batch A, and the light diffusing agent master batch B described above as raw materials.

  After the light diffusing agent master batch A is dry blended with the translucent resin A, the temperature in the cylinder is melt-kneaded by a first extruder having a temperature of 190 ° C. to 250 ° C. and supplied to the feed block. Similarly, the light diffusing agent master batch B is melt-kneaded by a second extruder having a temperature in the cylinder of 190 ° C. to 250 ° C. and supplied to the feed block.

The resin resin supplied to the feed block from the first extruder is supplied the intermediate layer (base layer) 23 _1, and from said second extruder to the feed block is a surface layer (both sides) 23 _2, 23 ₃ an extrusion resin temperature 250 ° C. as, as shown in FIG. 5 performs coextrusion multi hold the die 30, by performing the cooling and nipping the three polishing rolls 41, 42, 43, the intermediate layer 23 ₁ on either side surface 23 _2, 23 ₃ to obtain a light diffusion plate 23 is a laminate of three-layer structure provided for. FIG. 5 is a schematic diagram showing coextrusion molding and a subsequent process using a multi-hold die. In this manufacturing method, the thickness between the polishing roll 42 and the polishing roll 43 is adjusted by adjusting the distance 11 between the polishing roll 41 and the polishing roll 42 shown in FIG. By adjusting l2, the surface roughness of the surface 23a of the light diffusion plate 23 can be adjusted.

  In the surface light source device 20 and the liquid crystal display device 1 according to the present embodiment, the surface light source device is obtained by setting the arithmetic average roughness Ra and the average interval RSm of the unevenness of the surface 23a (see FIG. 1) of the light diffusion plate 23 to the above ranges. An unpleasant sound caused by driving 20 (or the liquid crystal display device 1) can be suppressed. Furthermore, the unpleasant noise can be further reduced by setting the tip end radius r of the spacer pin 25 to 0.5 to 1.0 mm, more preferably 0.5 to 0.8 mm. In this specification, the unpleasant sound is a sound that is not assumed in design when a liquid crystal display device using a surface light source device is started, that is, that is unnecessary in design.

  Although the generation mechanism of this unpleasant sound has not been elucidated in detail, the present inventors have made extensive studies and found that the main cause of the unpleasant sound is the light diffusion due to the heat of the linear light source arranged in the lamp box. We focused on the thermal expansion of the plate and the surface roughness of the light diffusion plate.

  That is, when the liquid crystal display device is activated, a temperature difference of about 10 ° C. occurs between the inside and outside of the lamp box due to the heat of the linear light source. Since the light diffusing plate is made of resin, the light diffusing plate is finely moved with respect to the spacer pins, such as a difference in thermal expansion between the two surfaces of the light diffusing plate due to the above temperature difference, causing the light diffusing plate to be warped or bent. May occur. On the other hand, the light diffusing plate is produced by mixing a light diffusing agent in a translucent resin, so that the surface of the light diffusing agent is exposed and roughened. It is also known to roughen the surface in order to reduce the effect of scratches on the surface on the spacer pin side. Therefore, if the light diffusing plate moves slightly with respect to the spacer pin due to the thermal expansion of the light diffusing plate, the spacer pin is caught on the unevenness of the surface of the light diffusing plate, and the spacer pin is released from the catch. As a result, it is considered that sound is generated between the spacer pin and the light diffusion plate.

  Therefore, as shown in the present embodiment, the surface 23a of the light diffusing plate 23 is made smoother, so that the above-described catch and the like are suppressed. As a result, as shown in the examples described later, the light diffusing plate The unpleasant noise between 23 and the spacer pin 25 can be reduced.

  Further, by increasing the tip end radius r of the spacer pin 25 to 0.5 mm or more, it is possible to reduce the catch of the spacer pin 25 on the unevenness generated on the surface 23a. As a result, unpleasant noise can be further effectively reduced. However, if the distal end radius r of the spacer pin 25 is larger than 1.0 mm, the light output from the linear light source 21 may be blocked from entering the light diffusion plate 23. Therefore, the distal end radius r of the spacer pin 25 is 1.0 mm or less is preferable.

  In the surface light source device 20, the surface roughness of the light diffusing plate 23 is adjusted to reduce unpleasant noise generated between the spacer pins 25 and the light diffusing plate 23. In manufacturing, it is possible to omit steps such as providing another member between the spacer pin 25 and the light diffusing plate 23 in order to reduce unpleasant noise generated between them. Further, the surface roughness of the light diffusing plate 23 can be adjusted by adjusting the distance l2 between the polishing rolls 42 and 43 (see FIG. 5). As a result, the surface light source device 20 capable of reducing unpleasant noise generated between the light diffusion plate 23 and the spacer pin 25 can be more easily manufactured.

  Furthermore, since it is not necessary to attach another member between the light diffusion plate 23 and the spacer pin 25, the optical influence of the other member is considered in the surface light source device 20 and the liquid crystal display device 1 using the same. There is no need. Since no other members are required to reduce unpleasant noise generated between the light diffusion plate 23 and the spacer pins 25, the surface light source device 20 having excellent versatility can be obtained.

  As described above, suppression of unpleasant sound by making the surface 23a of the light diffusing plate 23 smoother is the liquid crystal display device 1 having a large screen of 32 inches or more, and the size of the light diffusing plate 23 is about 750. This is particularly effective when it is × 450 mm or more. This is due to the following reason.

  That is, if the screen has a large screen that requires a light diffusion plate of about 750 × 450 mm or more, the number of spacer pins also increases, so the probability that sound will be generated between the spacer pins and the light diffusion plate increases and the inside of the lamp box increases. Due to reverberation in the sound, the influence of unpleasant noise between the spacer pin and the light diffusing plate tends to increase. On the other hand, in this embodiment, since the surface 23a of the light diffusing plate 23 is made smoother, it is possible to prevent the generation of unpleasant noise between the spacer pins 25 and the light diffusing plate 23. As a result, unpleasant noise can be reduced even in the large-screen liquid crystal display device 1 including the light diffusion plate 23 having a size of about 750 × 450 mm or more.

  As mentioned above, although embodiment which concerns on this invention was described, this invention is not limited to the said embodiment. For example, in the above embodiment, in the light diffusing plate 23 of the surface light source device 20, the Ra of the almost entire surface 23 a on the spacer pin 25 side is 1.0 μm or less and the RSm is 200 μm or less. It is only necessary that the arithmetic average roughness Ra and the average interval RSm of the unevenness of at least a portion in contact with the spacer pin 25 in the range are within the above ranges. In the present embodiment, the constituent material of the light diffusing plate 23, the temperature during the manufacturing process, and the like are exemplified, and the manufacturing method thereof has been specifically described. What is necessary is just to change suitably according to the material to do. Moreover, although the linear light source was illustrated as a light source which the surface light source device 20 has, it is not limited to this, The light source used with the surface light source device (backlight apparatus) of a liquid crystal display device can be used.

  Next, by setting the arithmetic average roughness Ra of the surface on the spacer pin side of the light diffusing plate and the average interval RSm of the projections and depressions to the ranges described in the above embodiment, the unpleasant noise is reduced. It demonstrates concretely with reference to. The present invention is not limited to the following examples.

Example 1
In Example 1, with the manufacturing method described by exemplifying the constituent materials in the embodiment, the total light beam has a three-layer structure with a thickness of 1.5 mm (an intermediate layer thickness of 1.4 mm and a surface layer thickness of 0.05 mm). A light diffusion plate 23 having a transmittance of 55% was manufactured. In the manufacture of the light diffusing plate 23, the distance l2 between the polishing rolls 42 and 43 is adjusted to make the surface 23a of the light diffusing plate 23 smoother. The surface roughness of the surface 23a was evaluated based on JISB0601-1994. Specifically, the arithmetic average roughness Ra and the average interval RSm of the unevenness were measured with a surface roughness meter (SJ-201P, manufactured by Mitutoyo). Ra of the light diffusing plate 23 used in Example 1 was 0.62 μm, and RSm was 160 μm.

  Then, a sound noise test was performed using the manufactured light diffusion plate 23 for the surface light source device 20 of the liquid crystal display device 1. In Example 1, a commercially available 32-inch size liquid crystal television is used as the liquid crystal display device 1, and the light manufactured in this example is used in place of the light diffusion plate in the backlight unit (surface light source device) of the liquid crystal television. A diffusion plate 23 was used. The tip end radius r of the spacer pin 25 in Example 1 was 0.4 mm.

  The sounding test was conducted as follows. That is, the light diffusion plate 23 was set as described above with respect to the backlight unit of the liquid crystal television. After turning on the liquid crystal television, the magnitude of unpleasant noise and the number of sounds that were considered to be caused by the contact between the light diffusion plate 23 and the spacer pin 25 were evaluated for 30 minutes. The volume of sound was measured using a sound level meter (manufactured by Yokogawa M & C Co., Ltd., LY10 normal sound level meter). Then, in a 23 dB environment, a sound smaller than 30 dB is added to 1 point, a sound of 30 dB or more is added to 2 points, and a total point of 0 to 4 is “◎”, 5-9 is “◯”, About 10 or more, it was set as "x". The results of the sounding test are shown in Table 1.

(Example 2)
A light diffusing plate 23 was manufactured in the same manner as in Example 1 except that the interval l2 between the polishing rolls 42 and 43 was changed. The light diffusion plate 23 manufactured in Example 2 has the surface roughness shown in Table 1. A sounding test was performed on the light diffusing plate 23 of Example 2 in the same manner as in Example 1. The method for measuring the surface roughness and the method for the sounding test are the same as in Example 1. The tip radius r of the spacer pin 25 of the liquid crystal television used was 0.8 mm. The configuration of the liquid crystal television other than the radius r of the tip of the spacer pin 25 and the roughness of the surface 23a of the light diffusing plate 23 is the same as that of the first embodiment. The test results of the sounding test are shown in Table 1.

(Examples 3 and 4)
In Examples 3 and 4, light diffusing plates 23 and 23 were manufactured in the same manner as in Example 1 except that the interval l2 between the polishing rolls 42 and 43 was changed. The light diffusion plates 23 and 23 manufactured in Examples 3 and 4 have the surface roughness shown in Table 1. Then, a sound generation test was performed in the same manner as in Example 1. The method for measuring the surface roughness and the method for the sounding test are the same as in Example 1. The liquid crystal television used is the same as that in the second embodiment. The test results of the sounding test are shown in Table 1.

(Comparative Example 1)
Comparative Example 1 is the same as in Example 1 except that the interval l2 between the polishing rolls 42 and 43 is not adjusted, that is, the interval l2 is the same as the interval l1 between the polishing rolls 41 and 42. The light diffusing plate was manufactured by the manufacturing method. The surface roughness of the light diffusing plate produced in this comparative example is as shown in Table 1. Then, a sound generation test was performed in the same manner as in Example 1. The method for measuring the surface roughness and the method for the sounding test are the same as in Example 1. The liquid crystal television used was the same as in Example 1, and the test results of the sound generation test are shown in Table 1.

(Comparative Example 2)
In Comparative Example 2, the light diffusing plate manufactured in Comparative Example 1 was applied to the liquid crystal television used in Example 2, and a sounding test was performed. The method for measuring the surface roughness and the method for the sounding test are the same as in Example 1. Table 1 shows the test results of the sound generation test.

  From comparison between Examples 1 to 4 and Comparative Examples 1 and 2 shown in Table 1, in Ra and RSm based on JISB0601-1994, when Ra is 1.0 μm or less and RSm is 200 μm or less, it is more effectively unpleasant. It can be seen that generation of sound can be prevented and unpleasant noise is reduced. Moreover, it can be understood from the comparison between Example 1 and Examples 2 to 4 that the generation of unpleasant noise can be more effectively prevented when the tip radius r of the spacer pin 25 is larger than 0.4 mm. When the tip radius r of the spacer pin 25 is larger than 1.0 mm, the spacer pin 25 tends to block light that should be incident on the light diffusion plate 23 output from the linear light source 21. Therefore, the tip end radius r of the spacer pin 25 is preferably 1.0 μm or less.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 10 ... Liquid crystal panel (liquid crystal display part), 11 ... Liquid crystal cell, 12, 13 ... Polarizing plate, 20 ... Surface light source device, 21 ... Linear light source (light source), 22 ... Lamp box, 22a ... Bottom wall surface, 22b ... edge frame, 23 ... light diffusion plate, 23a ... surface, 23 ₁ ... intermediate layer, 23 ₂ , 23 ₃ ... surface layer, 24 ... holder, 25 ... spacer pin, 30 ... multi-hold die, 41, 42, 43 ... Polishing roll.

Claims (3)

A plurality of light sources arranged in parallel spaced apart from each other;
A lamp box containing the plurality of light sources;
A light diffusing plate provided on the lamp box;
A plurality of spacer pins provided in the lamp box for supporting the light diffusion plate;
With
On the surface of the light diffusing plate on the lamp box side, at least the arithmetic average roughness of the contact area with each of the spacer pins is 1.0 μm or less and the average interval of unevenness is 200 μm or less.
A surface light source device.   The surface light source device according to claim 1, wherein a radius of a tip portion of each spacer pin is 0.5 mm or greater and 1.0 mm or less. The surface light source device according to claim 1 or 2,
A liquid crystal display unit that is provided on the surface light source device and into which light output from the surface light source device is incident;
A liquid crystal display device comprising:

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