JP2009117245A - Direct backlight device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device capable of improving energy efficiency, reducing luminance unevenness, and prolonging a life, and provide a liquid crystal display device using the backlight device. <P>SOLUTION: The direct backlight device includes a plurality of parallel fluorescent lamps, a reflector, and a light diffusion plate. The fluorescent lamp includes a fluorescent tube and a filament part. The fluorescent tube includes a glass tube and a fluorescent layer, and the filament part includes a filament and an emitter. The emitter is preheated to maintain a surface temperature at 700-950°C. An incident side light control part, which has a heat transmission function, and controls incident light quantity, is provided on a light incident surface in an area X in which an outer diameter of the fluorescent tube is vertically projected on the light diffusion plate. As for the light diffusion plate, transmissivity in the area X, and transmissivity in an area Y having a width equal to the outer diameter of the fluorescent tube where a center is an intermediate position of mutually adjacent fluorescent lamps is different by more than 5%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a direct-type backlight device and a liquid crystal display device, and more particularly to a direct-type backlight device and a liquid crystal display device that can increase energy efficiency, reduce luminance unevenness, and extend the life. About.

  Conventionally, as a backlight device for a liquid crystal display device, for example, a plurality of linear light sources arranged substantially parallel to each other, a reflecting plate that reflects light from these linear light sources on its surface, and a linear shape A light source that includes a light diffusing plate in which direct light from a light source and reflected light from the surface of a reflecting plate are incident from a light incident surface and is emitted from a light emitting surface is widely used. As the linear light source, a cold cathode tube (CCFL) having a small outer diameter (outer diameter of less than 4 mm) is usually used from the viewpoint that the backlight itself can be thinned. However, in recent years, since the energy efficiency is higher than that of CCFL, a direct type backlight device using a hot cathode tube (HCFL) having a larger outer diameter than CCFL as a linear light source has been developed.

  However, in the direct type backlight device using the HCFL, the outer diameter of the linear light source is larger than that of the conventional type. Therefore, when the direct type backlight device having the same thickness as the conventional type is created, the distance between the HCFL and the light diffusion plate is reduced. Therefore, the brightness of the light exit surface of the light diffusing plate is higher at the location where the HCFL is projected than at other locations, resulting in uneven brightness on the light emitting surface. Therefore, for example, in Patent Document 1, in a direct type backlight device, a light suppression unit having a thickness larger than that of other portions is provided at a position where a linear light source (for example, HCFL) is projected on a light incident surface to emit light. A technique for reducing the luminance unevenness of the surface is disclosed.

  By the way, in the direct type backlight device, it is also a problem to extend its life. As a technique for extending the life of the HCFL, for example, a technique for preheating an emitter constituting the filament part of the HCFL to a predetermined temperature is known.

  Therefore, the present inventors combine the technique shown in Patent Document 1 with the technique of preheating the filament portion to achieve high energy efficiency, little luminance unevenness on the light emitting surface, and long life. Tried to develop a light device.

Japanese Unexamined Patent Publication No. 2007-95484

However, when the filament portion is always preheated, both end portions of the HCFL are heated to cause the light diffusing plate to be shaped (warp or the like) or colored, and to be deteriorated in the light suppressing portion. For this reason, there has been a problem that luminance unevenness occurs on the light emitting surface in a relatively short period of time, and a direct type backlight device with little luminance unevenness and a long lifetime cannot be provided.
SUMMARY OF THE INVENTION An object of the present invention is to provide a backlight device that can increase energy efficiency, reduce luminance unevenness, and achieve a long life, and a liquid crystal display device using the backlight device. is there.

  The inventors of the present invention have intensively studied in view of the above-described problems. As a result, an incident-side light control unit having a heat transfer function is provided in a region where the outer diameter of the fluorescent tube is vertically projected on the light diffusion plate on the light incident surface. It was found that, by providing the light diffuser plate in a predetermined manner, the temperature in the backlight device can be made uniform, thereby reducing both luminance unevenness and extending the life.

According to the present invention, the following direct backlight device and liquid crystal display device are provided.
(1) A plurality of fluorescent lamps arranged substantially parallel to each other, a reflecting plate that reflects light from these fluorescent lamps on the surface, direct light from the fluorescent lamp and reflection from the surface of the reflecting plate A direct-type backlight device including a light diffusing plate that receives light from a light incident surface and emits light from the light output surface, wherein the fluorescent lamp includes a cylindrical fluorescent tube and both ends of the fluorescent tube. Each of the filament parts includes a glass tube and a fluorescent layer provided on the inner surface of the glass tube. Each filament part includes a filament and an emitter provided on an outer peripheral portion of the filament. The emitter is preheated so that the surface temperature thereof is always maintained at 700 to 950 ° C., and the light incident surface in the region X in which the outer diameter of the fluorescent tube is vertically projected onto the light diffusion plate Is provided with an incident-side light control unit that has a heat transfer function and controls the amount of incident light, and the transmittance of the light diffusing plate in the region X is centered at an intermediate position between adjacent fluorescent lamps. And a direct type backlight device that is 1% or more lower than the transmittance in the region Y having the same width as the outer diameter of the fluorescent tube.

(2) A plurality of fluorescent lamps arranged substantially parallel to each other, a reflecting plate that reflects light from these fluorescent lamps on the surface thereof, direct light from the fluorescent lamp and reflection from the surface of the reflecting plate A direct-type backlight device including a light diffusing plate that receives light from a light incident surface and emits light from the light output surface, wherein the fluorescent lamp includes a cylindrical fluorescent tube and both ends of the fluorescent tube. Each of the filament parts includes a glass tube and a fluorescent layer provided on the inner surface of the glass tube. Each filament part includes a filament and an emitter provided on an outer peripheral portion of the filament. The emitter is preheated so that the surface temperature thereof is always maintained at 700 to 950 ° C., and the light incident surface in the region X in which the outer diameter of the fluorescent tube is vertically projected onto the light diffusion plate Is provided with an incident-side light control unit that controls the amount of incident light, and the transmittance of the light diffusion plate in the region X is centered on an intermediate position between adjacent fluorescent lamps, and of the fluorescent tube. A direct type backlight device in which the light diffusion plate has a residual stress of 10 MPa or less, which is 1% or more lower than the transmittance in the region Y having the same width as the outer diameter.

(3) A plurality of fluorescent lamps arranged substantially parallel to each other, a reflecting plate that reflects light from these fluorescent lamps on the surface thereof, direct light from the fluorescent lamp and reflection from the surface of the reflecting plate A direct-type backlight device including a light diffusing plate that receives light from a light incident surface and emits light from the light output surface, wherein the fluorescent lamp includes a cylindrical fluorescent tube and both ends of the fluorescent tube. Each of the filament parts includes a glass tube and a fluorescent layer provided on the inner surface of the glass tube. Each filament part includes a filament and an emitter provided on an outer peripheral portion of the filament. The emitter is preheated so that the surface temperature thereof is always maintained at 700 to 950 ° C., and the light incident surface in the region X in which the outer diameter of the fluorescent tube is vertically projected onto the light diffusion plate Is provided with an incident-side light control unit that controls the amount of incident light, and the transmittance of the light diffusion plate in the region X is centered on an intermediate position between adjacent fluorescent lamps, and of the fluorescent tube. The light diffusing plate has a difference between the maximum value of the residual stress in the plane and the minimum value of the residual stress in the plane of 10 MPa, which is 1% or more lower than the transmittance in the region Y having the same width as the outer diameter. Direct type backlight device which is the following.

(4) A plurality of fluorescent lamps arranged substantially parallel to each other, a reflecting plate that reflects light from these fluorescent lamps on the surface, direct light from the fluorescent lamp and reflection from the surface of the reflecting plate A direct-type backlight device including a light diffusing plate that receives light from a light incident surface and emits light from the light output surface, wherein the fluorescent lamp includes a cylindrical fluorescent tube and both ends of the fluorescent tube. Each of the filament parts includes a glass tube and a fluorescent layer provided on the inner surface of the glass tube. Each filament part includes a filament and an emitter provided on an outer peripheral portion of the filament. The emitter is preheated so that the surface temperature thereof is always maintained at 700 to 950 ° C., and the light incident surface in the region X in which the outer diameter of the fluorescent tube is vertically projected onto the light diffusion plate Is provided with an incident-side light control unit that controls the amount of incident light, and the transmittance of the light diffusion plate in the region X is centered on an intermediate position between adjacent fluorescent lamps, and of the fluorescent tube. A direct type backlight device that is 1% or more lower than the transmittance in the region Y having the same width as the outer diameter, and the incident side control unit further has a function of reflecting and / or refracting infrared rays.

(5) Between the reflecting plate and the light diffusing plate, one or two or more supporting pins for supporting the light diffusing plate so as not to bend are provided, and the supporting pin is closest to the supporting pin. The direct type backlight device having a distance from the emitter of 250 mm or less.

(6) Two or more support pins are provided, and when any one of the two or more support pins is selected, the support pin is positioned between this support pin and another support pin closest to the support pin. The direct type backlight device having a distance of 200 mm or less.

(7) The direct-type backlight device in which an emission-side light control unit that controls the amount of emitted light is provided on the light emission surface.

(8) The direct-type backlight device further comprising a ballast for passing a current to the filament part, and a current supplied from the ballast to the filament part is 100 to 1000 mA.

(9) The direct type backlight device, wherein the emitter includes an alkaline earth metal oxide.

(10) The direct-type backlight device, wherein the ballast is a ballast choke inverter.

(11) The direct type backlight device in which the light transmittance of the fluorescent tube is 80% or more.

(12) The direct type backlight device, wherein the glass tube has an outer diameter of 4.0 to 25.5 mm.

(13) The direct-type backlight device, wherein the glass tube has a thickness of 0.3 to 1.5 mm.

(14) The direct-type backlight device, wherein the glass tube has a flat circular cross section.

(15) The direct-type backlight device, wherein a distance between the surface of the reflecting plate and the light incident surface is within 100 mm.

(16) The direct-type backlight device in which a protrusion that protrudes toward the light incident surface is provided on a surface of the reflection plate.

(17) The direct-type backlight device, wherein the incident-side light control unit has a concavo-convex structure with an arithmetic average roughness Ra of 3 to 1000 μm formed on a surface of the light incident surface.

(18) The direct-type backlight device, wherein the incident-side light control unit is a printing layer provided on the light incident surface.

(19) The direct type backlight device in which the distance between the centers of adjacent fluorescent lamps is 60 mm or more.

(20) An optical sheet is further provided on the light emitting side of the light emitting surface, and this optical sheet brings the direction of light emitted from the light emitting surface closer to a direction parallel to the normal line of the optical sheet. The direct type backlight device for converting as follows.

(21) The direct type backlight device, wherein the optical sheet is a prism sheet or a diffusion sheet.

(22) The direct type backlight device in which a width dimension of the incident-side light control unit, that is, a dimension in a fluorescent lamp array direction is 10 μm or more.

(23) A liquid crystal display device comprising the direct type backlight device and a liquid crystal cell disposed on a light emitting side of the backlight device, wherein the liquid crystal cell is in a VA mode or an IPS mode.

  According to the direct type backlight device of the present invention, the incident side light control unit has a heat transfer function in a region having an energy efficient fluorescent tube and an outside diameter of the fluorescent tube projected perpendicularly to the light diffusion plate. Since the temperature at both ends of the fluorescent lamp can be efficiently released and the temperature in the direct type backlight device can be made uniform, the energy efficiency can be improved and the luminance unevenness can be reduced and long. There is an effect that the life can be extended.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a direct type backlight device according to the present embodiment.
As shown in FIG. 1, the direct type backlight device 1 of the present embodiment includes a plurality of fluorescent lamps 10 arranged substantially parallel to each other, a reflecting plate 20 that reflects light from the fluorescent lamps 10 on the surface, A light diffusing plate 30 that diffuses and irradiates direct light from the fluorescent lamp 10 and reflected light from the reflecting plate 20, a ballast 40 for causing the fluorescent lamp 10 to emit light, and a support pin 50 that supports the light diffusing plate 30. I have.

  The fluorescent lamp 10 is preferably a hot cathode tube (HCFL). With such a configuration, a direct-type backlight device with high energy efficiency can be obtained. The fluorescent lamp 10 preferably has a luminous efficiency of 60 (lm / W) or higher. By setting the distance between the centers of the adjacent fluorescent lamps 10 to the preferred range, the number of fluorescent lamps 10 used is reduced, so that the power consumption of the direct type backlight device can be reduced and the assembly of the device is easy. Can be.

FIG. 2 is a diagram schematically showing the configuration of the fluorescent lamp and the ballast.
As shown in FIG. 2, the fluorescent lamp 10 includes a cylindrical fluorescent tube 110 and filament portions (electrodes) 120 provided at both ends of the fluorescent tube 110. The fluorescent tube 110 has a light transmittance of the glass tube 112 (in the case where a light transmission suppressing portion such as printing is provided on the light emitting side of the glass tube, a member including both the glass tube and the light transmission suppressing portion). The light transmittance is preferably “80% or more”, and more preferably 85% or more. By setting the light transmittance of the glass tube 112 within the above preferable range, there is an advantage that light from the lamp can be efficiently extracted. The light transmittance of the glass tube 112 can be measured with a turbidimeter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. with the same glass material in a plate shape. Moreover, it is preferable that the length of the fluorescent tube 110 is 700 mm or more, and when a fluorescent tube having a length of 700 mm is used, it is preferable that bending does not occur 2 mm or more when both ends thereof are supported.

  The fluorescent tube 110 includes a glass tube 112 having a circular cross section, for example, and a fluorescent layer 114 provided on the inner surface of the glass tube 112. The fluorescent layer 114 can be formed by coating or the like using a known fluorescent material.

  The glass tube 112 of the present embodiment has a circular cross section. However, as a cross-sectional shape of the glass tube 112, for example, from the viewpoint of reducing luminance unevenness, a flattened circular shape such as a shape obtained by flattening a part of a circle or an elliptical shape may be used. The outer diameter (tube diameter) of the glass tube 112 is preferably 4.0 to 25.5 mm, more preferably 6.0 to 20.0 mm, and further preferably 8 mm to 15.5 mm. By making the outer diameter within the preferred range, the backlight device itself can be thinned, and the light diffusing plate due to the vicinity of the filament portion 120 (tube wall temperature) becoming high (eg, over 150 ° C.). There is an advantage that thermal degradation of 30 can be suppressed and sufficient luminance can be achieved. The tube thickness (thickness) of the glass tube 112 is preferably 0.3 to 1.5 mm, more preferably 0.4 to 1.0 mm, and 0.5 mm to 0.7 mm. Is more preferable. By setting the tube thickness within the above-mentioned preferable range, it is possible to prevent the vicinity of both end portions of the fluorescent tube 10 from becoming dark and to reduce the luminance unevenness of the light emitting surface.

  The filament part 120 is a member that receives an electric current from the ballast 40 and emits electrons from one filament part 120 toward the other filament part 120. The current supplied to the filament part 120 is preferably 100 to 1000 mA. By setting the current within the above preferred range, there is an advantage that consumption of the emitter applied to the filament can be suppressed and the electrode life can be extended.

The filament portion 120 includes a filament 122 made of tungsten or the like, and an emitter 124 provided on the outer peripheral portion of the filament 122 by coating or the like.
The emitter 124 is a member for facilitating electron emission from the filament 122. As a material constituting the emitter 124, for example, an alkaline earth metal oxide can be used. Specifically, calcium oxide (CaO), magnesium oxide (MgO), strontium oxide (SrO), and barium oxide ( BaO) and the like.

  The filament section 120 is preheated at all times, that is, when an image is displayed on the liquid crystal display device. At this time, the surface temperature of the emitter 124 is always maintained at 700 to 950 ° C. The backlight fluorescent lamp responds to high-speed flashing (flashing for 0.1 seconds or less) during dimming or blinking mode, and sometimes turns off, but the filament 120 is preheated even in such a case. Yes. By performing such preheating, the life of the fluorescent lamp 10 can be extended. Here, when the filament portion 120 is always preheated, for example, when the outer diameter of the glass tube is 8.0 mm, the filament portion temperature (here, the filament portion temperature is the surface of the tube wall and The temperature at the nearest location is about 140 ° C., and is about 50 to 55 ° C. at the intermediate position of the glass tube 112. Moreover, when the outer diameter of a glass tube is 15.5 mm, it turns out that a filament part will be about 120 degreeC and it will be about 50-55 degreeC in the intermediate position of the glass tube 112. FIG. For this reason, local heating is applied to the light diffusing plate, but the problem due to this heating can be solved by devising the configuration of the light diffusing plate as described later. In the case where the preheating is not performed, when the tube diameter is 8.0 mm, the filament portion is about 100 to 110 ° C., and the glass tube 112 is about 50 to 55 ° C. in the middle position. When the tube diameter is 15.5 mm, the filament portion is about 80 ° C., and is about 50 to 55 ° C. at the intermediate position of the glass tube 112.

  As a configuration for achieving preheating of the filament part, the backlight device of the present invention can include a circuit for supplying a current for preheating as part of a circuit for causing the fluorescent lamp to emit light.

  The number of fluorescent lamps 10 used is not limited. For example, when the direct type backlight device of the present invention is used in a 32-inch liquid crystal display device, the number of fluorescent lamps is, for example, an even number such as 16, 14, 12, 8, 4, etc. , Can be an odd number.

  In the present embodiment, the plurality of fluorescent lamps 10 are arranged substantially parallel to each other. The average distance between the central axes of arbitrary adjacent fluorescent lamps 10 is substantially constant. Note that “substantially parallel” means within a range of ± 5 degrees from a truly parallel state. However, the plurality of fluorescent lamps may not be arranged in parallel. Further, the average distance between the central axes of the adjacent fluorescent lamps may be random, or may have regularity that increases or decreases continuously or stepwise toward a specific location. Good. Here, the specific location is, for example, a central location including a line connecting one long side of a rectangular light diffusing plate or the central locations of opposing short sides.

  The average distance between the central axes of the adjacent fluorescent lamps 10 can be 60 mm to 300 mm, and preferably 70 mm to 250 mm. By setting the average distance in the above range, it is possible to reduce power consumption in the direct type backlight device, to easily assemble the device, and to suppress luminance unevenness of the light emitting surface.

  The average distance b (mm / FIG. 1) between the central axis of the fluorescent lamp 10 and the light incident surface 30A of the light diffusing plate 30 may be designed in consideration of the thickness and luminance uniformity of the direct type backlight device. It can be 2 mm to 35 mm, and is preferably 3 mm to 30 mm. By setting the average distance b in the above range, luminance unevenness can be reduced, and a reduction in the luminous efficiency of the lamp can be prevented, and the backlight device can be made thinner. In the present embodiment, the plurality of fluorescent lamps 10 are arranged such that the average distance b with respect to the light incident surface 30A is substantially constant for all the fluorescent lamps. Note that “almost constant” means that the maximum value of the average distance b / the minimum value of the average distance b ≦ 1.3. However, a plurality of fluorescent lamps may be arranged so that some of the fluorescent lamps are closer to the light incident surface 30A than the other fluorescent lamps. For example, it may be random or may have regularity that becomes larger or smaller as it goes to a specific location. Here, the specific location is, for example, a central location including a long side of a rectangular light diffusing plate or a line connecting the central locations of opposing short sides.

  The ballast 40 is a member that rectifies an alternating current from a commercial power source and supplies a predetermined current to the filament unit 120 to promote electron emission from the filament unit 120. The ballast 40 of this embodiment is a ballast choke inverter (not shown) that enables instantaneous light emission.

  The support pin 50 is a pin-shaped member that is disposed between the reflection plate 20 and the light diffusion plate 30, that is, on the reflection plate 20, and supports the light diffusion plate 30 so as not to bend. In the present embodiment, two support pins 50 (50A, 50B) are arranged in the vicinity of a certain filament portion 120. In the present embodiment, each of the support pins 50A and 50B has a circular contact surface shape that contacts the light incident surface of the light diffusion plate. However, the shape of the contact surface is not limited to a circle, and may be another shape such as an ellipse or a polygon.

  Here, the distance between each support pin 50A, 50B and the emitter constituting the filament portion 120 is preferably within 250 mm, and more preferably within 200 mm. The reason will be described below. Here, by always preheating the emitter, the surface temperature of the glass tube near the filament portion of the fluorescent tube becomes 100 ° C. or higher. For this reason, the light incident surface of the light diffusing plate in the vicinity of the filament portion is heated, causing deformation such as a convexity toward the fluorescent tube, and uneven brightness may occur. Therefore, by disposing the support pins within the preferable range, local deformation in the vicinity of the filament portion can be suppressed and occurrence of luminance unevenness can be suppressed.

  Furthermore, the distance between the support pins 50A and 50B is preferably within 200 mm, and more preferably within 150 mm. As described above, the light incident surface of the light diffusing plate in the vicinity of the filament portion is heated, causing deformation such as a convexity toward the fluorescent tube, and uneven brightness may occur. For this reason, by making the distance between the support pins in the above-mentioned preferable range in the vicinity of the filament portion, local deformation in the vicinity of the filament portion can be suppressed, and the occurrence of luminance unevenness can be further suppressed.

  Note that the distance between the support pin 50 and the emitter refers to the position of the center of gravity of the contact surface 50X (FIG. 1) at the tip of the support pin that contacts the light incident surface of the light diffusing plate 30 and the emitter perpendicular to the light incident surface. It is the shortest distance from the selected position. The distance between the support pins is the distance between the gravity center positions of the contact surfaces at the tips of the support pins. In the present embodiment, the direct type backlight device is configured by including the two support pins 50, but the number of support pins may be one, or three or more. In addition, the support pin may or may not have the function of a fluorescent tube holder that prevents the fluorescent tube from being bent.

  The shape of the reflecting plate 20 is usually a flat plate, but from the viewpoint of further reducing unevenness in luminance of the light emitting surface, a protruding portion that protrudes toward the light diffusing plate in a region corresponding to between the fluorescent lamps in the reflecting plate 20. May be provided. The protrusions may extend along the longitudinal direction of the plurality of fluorescent lamps. At this time, the protrusion is preferably provided at a substantially intermediate position between the adjacent fluorescent lamps, but may be provided on the back surface of the fluorescent lamp 10. Furthermore, the cross-sectional shape in the short direction of the protrusion is not particularly limited, but isosceles triangle, isosceles trapezoid, circular cut shape, elliptical shape cut by a line segment parallel to the short axis, and elliptical shape is long. Examples include a shape cut along a line segment parallel to the axis, a shape in which convex curves are connected so as to be a line object, and a shape in which convex curves are connected so as to be line symmetric. The apex portions of these shapes may be pointed or rounded. A triangular shape is preferable from the viewpoint of reducing luminance unevenness and the ease of manufacture. Moreover, it is preferable that the cross-sectional shape of the protrusion is line symmetric with respect to a line segment perpendicular to the thickness direction of the light diffusion plate. By setting it as such a structure, the brightness nonuniformity in the light-projection surface of a light diffusing plate can be suppressed. The protrusions may be continuous in a bowl shape or intermittent as a series of pits, but are preferably continuous because the luminance uniformity can be further improved.

  The protrusions may be installed by coating a metal frame with protrusions in white or silver, attaching a white or silver reflective sheet to the metal frame with protrusions, white or silver flat Examples thereof include a method of bending the reflecting sheet and placing it on a flat metal frame, a method of molding a white or silver resin using a mold having a predetermined shape, and the like.

  As a material constituting the reflection plate 20, a resin colored in white or silver, a metal, or the like can be used, and a resin is preferable from the viewpoint of weight reduction. The color of the reflector 20 is preferably white from the viewpoint of improving the luminance uniformity, but may be a mixture of white and silver in order to balance the luminance and the luminance uniformity highly.

  The light diffusion plate 30 is a plate material that diffuses and emits the direct light from the fluorescent lamp 10 and the reflected light from the surface of the reflection plate 20. As a material constituting the light diffusing plate 30, glass, a mixture of two or more kinds of resins that are difficult to mix, a transparent resin in which a light diffusing agent is dispersed, one kind of transparent resin, and the like can be used. Among these, a resin is preferable because it is lightweight and easy to mold, and one kind of transparent resin is preferable from the viewpoint that luminance can be easily improved, and adjustment of total light transmittance and haze is easy. From the viewpoint, a transparent resin in which a light diffusing agent is dispersed is preferable.

  The transparent resin is a resin having a total light transmittance of 70% or more measured with a 2 mm-thick plate smooth on both sides based on JIS K7361-1, for example, polyethylene, propylene-ethylene copolymer, Polypropylene, polystyrene, copolymer of aromatic vinyl monomer and (meth) acrylic acid alkyl ester having a lower alkyl group, polyethylene terephthalate, terephthalic acid-ethylene glycol-cyclohexanedimethanol copolymer, polycarbonate, acrylic resin, And a resin having an alicyclic structure. In addition, (meth) acrylic acid is acrylic acid and methacrylic acid.

  The thickness of the light diffusing plate 30 is preferably 0.4 to 5.0 mm, and more preferably 0.8 to 4.0 mm. By setting the thickness of the light diffusing plate within the above preferable range, it is possible to suppress bending due to its own weight and to facilitate the molding. In addition, the distance between the light incident surface 30A of the light diffusing plate 30 and the surface of the reflecting plate 20 is preferably within 100 mm, more preferably within 40 mm, and within 25 mm from the viewpoint of reducing the thickness of the direct type backlight device. Is more preferable.

  The light diffusing plate 30 has a residual stress of preferably 10 MPa or less, more preferably 5 MPa or less, and even more preferably 3 MPa or less. Here, the residual stress of the light diffusing plate can be obtained as follows. That is, first, a 100 × 10 mm strip sample is cut out from one light diffusion plate. Next, the surface of the sample (for example, the surface on the gate side when the light diffusion plate is formed by an injection molding machine having a gate in the surface) is polished with sandpaper while being cooled with water. After polishing 1 mm, the strain amount ε is obtained using the following formula (1). In calculating the amount of strain, the thickness t (mm) of the sample is measured by three-point measurement using a dial gauge, the deflection amount δ (mm) after polishing is measured, and the length l (mm) in the longitudinal direction of the sample is measured. To do. The residual stress can be obtained by the following formula (2) using the strain amount ε and the elastic modulus E of the sample.

  As described above, by always preheating the emitter, the vicinity of the filament portion of the light incident side surface of the light diffusion plate is exposed to a high temperature. Here, when the residual stress of the light diffusing plate is large, there is a possibility that a difference in shape change occurs between the vicinity of the filament portion and the intermediate position of the fluorescent tube due to heat. The diffuser plate may become a wave shape and uneven brightness may occur. For this reason, generation | occurrence | production of the brightness nonuniformity by a shape change etc. can be suppressed by making the residual stress of a light diffusing plate into the said suitable range.

  The light diffusing plate 30 preferably has a difference (Emax−Emin) between the maximum value Emax of the residual stress in the plane and the minimum value Emin of the residual stress in the plane of 10 MPa or less. Is more preferable, and 3 MPa or less is more preferable. As described above, the surface of the light diffusing plate on the light incident side is exposed to a high temperature by always preheating the emitter. Here, when the difference in residual stress in the plane of the light diffusing plate is large, the light diffusing plate has a wave shape due to different deformation methods depending on the location, and luminance unevenness may occur. For this reason, by making the residual stress difference of the light diffusing plate within the above suitable range, it is possible to suppress the occurrence of luminance unevenness due to a shape change or the like.

  Moreover, it is preferable that the incident side light control part further has the function to reflect and / or refract infrared rays. In the present embodiment, the concavo-convex structure is used as the incident-side light control unit. However, according to the concavo-convex structure, infrared rays can be refracted.

  As described above, the amount of infrared rays emitted from the vicinity of the filament portion is increased by always preheating the emitter. For this reason, by using the incident side light control unit having the above function, the amount of infrared rays is made uniform in the direct type backlight device, thereby making the temperature distribution of the liquid crystal panel uniform and suppressing display unevenness. . In addition, the amount of infrared rays can be measured, for example, by Fastvert S-2400 manufactured by Soma Optics. Specifically, on the light emitting side of the direct type backlight device, the amount of infrared light emitted with a wavelength of 800 to 900 nm in the normal direction of the main surface of the light diffusing plate can be measured and determined at each location.

  Here, the amount of infrared rays is made uniform means that the emission intensity at a wavelength showing a peak among the measured infrared rays of 800 to 900 nm is obtained, and the filament part of the fluorescent lamp is projected perpendicularly to the light incident surface. Is compared with the emission intensity β at the position where the intermediate position of the filament part on the same side of the adjacent fluorescent lamp is projected perpendicularly to the light incident surface, β / α ≧ 0.45, preferably Is β / α ≧ 0.50, more preferably β / α ≧ 0.55.

Next, the outer shape of the light diffusing plate 30 will be described.
FIG. 3 is a cross-sectional view for more specifically explaining the surface shape of the light diffusion plate 30 constituting the direct type backlight device. For convenience of explanation, in FIG. 3, only two adjacent fluorescent tubes 10 </ b> A and 10 </ b> B among the plurality of fluorescent tubes 10 are partially illustrated.

  The light diffusing plate 30 includes a light incident surface 30A on which light from the fluorescent tube 110 is incident and a light emitting surface 30B that diffuses and irradiates light incident from the light incident surface 30A. Here, in the light diffusing plate 30, a region obtained by projecting the outer diameter of the fluorescent tube 110 constituting the fluorescent lamp 10 perpendicularly to the light diffusing plate 30 is defined as a region X, with an intermediate position between the adjacent fluorescent lamps 10 as a center, A region having the same width as the outer diameter of the fluorescent tube 110 is defined as a region Y.

  The light diffusing plate 30 has a light transmittance in the region X that is 1% or more lower than that in the region Y. This light transmittance is a light transmittance when light is incident from the center of the fluorescent lamp toward the center of each region. The light transmittance in the region X is more preferably 5% or more and more preferably 10% or more lower than the light transmittance in the region Y. In order to realize this, in the light diffusing plate 30, the uneven structure in the region X and the uneven structure in the region Y have different shapes.

In the backlight device of the present invention, the transmittance of the light diffusing plate in the region X is more preferably 5% or more lower than the transmittance of the light diffusing plate in the region Y. Here, the reference to the difference in transmittance such as “lower than 5%” indicates the difference between a certain value of transmittance in percentage and another value. For example, if the transmittance at a certain point P _A is 50% and the transmittance at another certain point P _B is 55%, the transmittance at the point P _A is 5% lower than the transmittance at the point P _B.

  Here, “different shape” includes a case where the shape is different on at least one of the light incident surface and the light emitting surface of the light diffusion plate. In addition, the “different shape” means, for example, that when the concavo-convex structure is constituted by a plurality of linear prisms and each linear prism is a polygon, the apex angle of the linear prism exceeds ± 1 degree. Such a shape. In this case, the “different shape” includes a case where at least one linear prism constituting the plurality of linear prisms has a different shape.

“The concavo-convex structure in the region X and the concavo-convex structure in the region Y have different shapes” means that the ranges R271, R281, R273 in the region X in which the outer diameters of the fluorescent lamps 10A and 10B are vertically projected on the light diffusion plate 30. And the concavo-convex structure in R283 and the concavo-convex structure in the ranges R272 and R282 in the region Y on the light diffusion plate having the same width as the fluorescent tube 10 with the intermediate position 241 between the fluorescent lamps 10A and 10B as the center. It is.
That is, the following conditions (I) and (II):
(I) R272 has an uneven structure different from R271 and R273,
(II) R282 has a concavo-convex structure different from R281 and R283, satisfying at least one of the conditions.

  The structure of other regions (that is, regions not included in the regions R271 to R273 and R281 to R283) of the light incident surface 30A and the light emitting surface 30B is not particularly limited. Concavity and convexity structure in the region group including the region projected perpendicularly to the diffusing plate 30 and concavity and convexity in the region group including the region on the light diffusing plate 30 having the same width as the outer diameter of the fluorescent tube 110 around the intermediate position of the fluorescent tube 110. The structure can be different.

  More specifically, for example, as shown in FIG. 3, region groups R251 and R261 each including a region in which the light incident surface 30A and the light emitting surface 30B are each projected from the outer diameter of the fluorescent tube 110 perpendicularly to the light diffusion plate 30. , R253 and R263, and a region group R252 and R262 including the region on the light diffusing plate having the same width as the fluorescent tube 110 with the middle position of the fluorescent tube 110 as the center. The structure can be different.

  Specifically, the “concave and convex structure is different” between the region groups R251, R261, R253, and R263 and the region groups R252 and R262, for example, includes the following aspects:

(1) R251-R252-R253: flat surface-flat surface-flat surface R261-R262-R263: uneven structure A-flat surface-uneven structure A
(2) R251-R252-R253: Uneven structure α-flat surface-uneven structure α
R261-R262-R263: Uneven structure A-flat surface-uneven structure A
(3) R251-R252-R253: Flat surface-Uneven structure α-Flat surface R261-R262-R263: Uneven structure A-Flat surface-Uneven structure A
(4) R251-R252-R253: concavo-convex structure α-concavo-convex structure β-concavo-convex structure α
R261-R262-R263: Uneven structure A-flat surface-uneven structure A
(5) R251-R252-R253: concavo-convex structure α-concavo-convex structure α-concavo-convex structure α
R261-R262-R263: Uneven structure A-flat surface-uneven structure A
(6) R251-R252-R253: Flat surface-Flat surface-Flat surface R261-R262-R263: Uneven structure A- Uneven structure B- Uneven structure A
(7) R251-R252-R253: Uneven structure α-flat surface-uneven structure α
R261-R262-R263: concavo-convex structure A- concavo-convex structure B- concavo-convex structure A
(8) R251-R252-R253: Flat surface-Uneven structure α-Flat surface R261-R262-R263: Uneven structure A-Uneven structure B-Uneven structure A
(9) R251-R252-R253: concavo-convex structure α-concavo-convex structure β-concavo-convex structure α
R261-R262-R263: concavo-convex structure A- concavo-convex structure B- concavo-convex structure A
(10) R251-R252-R253: concavo-convex structure α-concavo-convex structure α-concavo-convex structure α
R261-R262-R263: concavo-convex structure A- concavo-convex structure B- concavo-convex structure A
(11) R251-R252-R253: Uneven structure α-flat surface-uneven structure α
R261-R262-R263: concavo-convex structure A- concavo-convex structure A- concavo-convex structure A
(12) R251-R252-R253: Flat surface-Uneven structure α-Flat surface R261-R262-R263: Uneven structure A-Uneven structure A-Uneven structure A
(13) R251-R252-R253: concavo-convex structure α-concavo-convex structure β-concavo-convex structure α
R261-R262-R263: concavo-convex structure A- concavo-convex structure A- concavo-convex structure A

  The uneven structure A and the uneven structure B have different shapes. The uneven structure α and the uneven structure β are different in shape. The uneven structure α is the uneven structure A or the uneven structure B. The concavo-convex structure β is the concavo-convex structure A, the concavo-convex structure B, or the concavo-convex structure C. The concavo-convex structure C is different in shape from the concavo-convex structure A and the concavo-convex structure B. The flat surface may be a surface having an arithmetic average roughness Ra of 3 μm or less, although there may be fine irregularities on the surface.

  In the present invention, the concavo-convex structure is a prism row in which linear prisms extending substantially in parallel (within a range of ± 5 ° in parallel) in the longitudinal direction of the fluorescent lamp 10 are arranged in parallel. There may be mentioned those whose cross section perpendicular to the direction has various cross sectional shapes. The angle formed between the fluorescent lamp 10 and the linear prism may be within a range of parallel ± 60 °.

  Examples of the concavo-convex structure include a convex portion having a curved shape, a polygonal convex portion, a substantially flat portion, and a combination shape thereof. Examples of the convex portion including the curved line include a convex portion including a curved line such as an arc, an elliptical arc, a parabolic arc, and a curved line in which these are distorted. Examples of the polygonal convex portions include various polygonal convex portions such as triangles, trapezoids and other quadrangular shapes, pentagons, hexagons, heptagons, etc. Particularly, the left and right base angles are substantially equal (± 10 °). The polygonal shape is preferable because it is easy to design and has no uneven brightness even when viewed from the left or right.

  The present embodiment corresponds to the configuration of (10). In the present embodiment, the light incident surface 30A has a concavo-convex structure as an incident side light control unit that controls the amount of light incident on the light diffusion plate 30. Is provided on almost the entire surface. This concavo-convex structure is a prism array in which an arithmetic average roughness Ra is in a range of 3 to 1000 μm and a plurality of linear prisms having an isosceles cross section are arranged substantially in parallel with each other. In this specification, “substantially parallel” means within a range of ± 5 ° from the case of being truly parallel. Moreover, as an apex angle of the said triangle, it can be set as 40-170 degrees, for example. Further, the adjacent linear prisms may be configured such that the vertices of the bottom corners are connected to each other, or may be configured such that the vertices of the bottom corners are separated from each other. In the present embodiment, the configuration (10) is adopted, but the present invention is not limited to this configuration.

  Specifically, the concavo-convex structure of the present embodiment includes two or more types of linear prisms having different cross-sectional shapes, and the abundance ratio of the two or more types of linear prisms changes as the distance from the fluorescent lamp 10 increases. It is an aspect to do. Specifically, as shown in FIG. 4, for example, as the concavo-convex structure, linear prisms 1621a and 1621b having different shapes (the apex angle is different) are set to a predetermined ratio (1: 4 in FIG. 4). As a unit, the unit is repeated, and the abundance ratio of the linear prisms 1621a and 1621b is changed as the unit is further away from the fluorescent lamp 10.

  The change in the abundance ratio can be continuous or stepwise. For example, as shown in FIG. 5, the distance corresponding to the center of the fluorescent lamp from the intermediate position 1441 of the distance between the centers of the adjacent linear light sources 1402a and 1402b is set to a plurality of zones (in FIG. 5, A, B, C And the ratio of the two or more types of convex portions can be set to a predetermined value for each region corresponding to each zone on the light incident surface. In addition, the number of these zones is not specifically limited, It is good not only in the above but 15-20 steps.

  As described above, since the concavo-convex structure is formed on almost the entire surface of the light incident surface 30A, at least the light incident surface 30A in the region X obtained by projecting the outer diameter of the fluorescent tube 110 perpendicularly to the light diffusion plate 30 includes: An incident-side light control unit is provided.

  Here, since the concavo-convex structure is composed of a plurality of linear prisms, the heat transfer function in the longitudinal direction is excellent, so heat generated in the filament portion 120 of the fluorescent lamp 10 is moved to the intermediate position side of the fluorescent lamp 10. Heat can be transferred, and the temperature in the direct type backlight device 1 can be made uniform. Further, in the case of having a concavo-convex structure, since the area of the light receiving portion is increased compared to the case of not having the concavo-convex structure (that is, in the case of a flat surface), deterioration such as discoloration due to light can be suppressed. . For this reason, partial deterioration of the light diffusing plate 30 does not occur, and the direct type backlight device 1 with less luminance unevenness can be used for a long time.

  The heat transfer function means that the difference between the temperature of the light incident surface at the position near the filament portion and the temperature of the light incident surface at the center portion in the longitudinal direction of the fluorescent tube is a light diffusion without an uneven structure. The case where it becomes 0.5 degrees C or more when a 700 mm fluorescent tube is used rather than the value of the said difference in a board (flat plate diffusion plate) is shown. The temperature in the vicinity of the filament part of the fluorescent tube is 120 ° C. to 140 ° C., which is higher than the glass transition temperature (Tg) of the transparent resin constituting the light diffusing plate. Therefore, it is possible to prevent local warpage and yellowing and to suppress increase in luminance unevenness due to them.

The dimension (width dimension) in the short direction of each linear prism can be 10 μm or more, preferably 20 μm or more, and more preferably 30 μm or more. However, from the viewpoint of uneven brightness, the dimension is preferably 1000 μm or less.
By setting it in such a suitable range, the rigidity of the incident side light suppressing portion can be increased, and the change in shape due to the constant preheating of the emitter (especially, the skirt of the top and bottom) can be prevented. No matter what happens, the required optical characteristics can be maintained by reducing the ratio of the lost part.

  The light exit surface 30B is provided with a second concavo-convex structure as an exit-side light control unit that controls the amount of light exiting from the light diffusion plate 30 over substantially the entire surface. The second concavo-convex structure is a prism array in which an arithmetic average roughness Ra is in a range of 3 to 1000 μm, and a plurality of linear prisms having an isosceles cross section having the same shape are arranged substantially parallel to each other. Providing such a second concavo-convex structure has the effect of improving the luminance in the front direction and further reducing the luminance unevenness of the light emitting surface.

  In the present embodiment, the incident-side light control unit is provided on almost the entire surface of the light incident surface 30A. However, the incident-side light control unit may be provided only at a position corresponding to the region X. In short, it corresponds to the region X. What is necessary is just to provide an incident side light control part so that the location to perform may be included. Moreover, as an uneven | corrugated structure which comprises an incident side light control part, various aspects other than this embodiment can be mentioned as shown below. 6 to 16 show the light incident surface and the light emission surface upside down for convenience.

  As shown in FIG. 6, as another first example of the concavo-convex structure, the cross-sectional shape of the linear prism is a triangle 321 in which the left and right base angles 322 and 323 are substantially equal, and the base angle of the adjacent triangle 321 is the same. It is the structure arrange | positioned so that a part may mutually contact.

  As shown in FIG. 7, the second example of the concavo-convex structure is a trapezoid 421 in which the cross-sectional shape of the linear prism has a substantially flat flat part (top carrier part) 422 on the top, This is a structure in which the base corner portions are in contact with each other.

  As shown in FIG. 8, the third example of the concavo-convex structure is a triangle 521 in which the cross-sectional shape of the linear prism is substantially equal on the left and right base angles, and a substantially flat portion 522 is provided between adjacent triangles 521. The combination structure in which the triangle 521 and the substantially flat portion 522 are arranged.

  As shown in FIG. 9, the fourth example of the concavo-convex structure is a pentagon in which the cross-sectional shape of the linear prism is obtained by adding a triangle 621 having a base angle smaller than the base angle of the trapezoid 622 to the top of the trapezoid 622. In this structure, the base corners of adjacent trapezoids 622 are arranged so as to contact each other.

  As shown in FIG. 10, the fifth example of the concavo-convex structure is a pentagon in which the cross-sectional shape of the linear prism is a triangle 721 having a base angle wider than the base angle of the trapezoid 722 added to the top of the trapezoid 722. In this structure, the base corners of adjacent trapezoids 722 are in contact with each other.

  As shown in FIG. 11, the sixth example of the concavo-convex structure is a structure in which the cross-sectional shape of the linear prism is a semicircle 821, and the adjacent semicircles 821 are in contact with each other.

  As shown in FIG. 12, the seventh example of the concavo-convex structure is a structure in which the cross-sectional shape of the linear prism is a semi-elliptical shape 921 and the adjacent semi-elliptical shapes 921 are in contact with each other.

  As shown in FIG. 13, the eighth example of the concavo-convex structure is a structure in which the cross-sectional shape of the linear prism is a parabolic arc 1021 and adjacent parabolic arcs 1021 are in contact with each other.

  As shown in FIG. 14, the ninth example of the concavo-convex structure is a structure in which linear prisms having a semicircular section 1121 and linear prisms having a semielliptical section 1122 are alternately combined.

  As shown in FIG. 15, the tenth example of the concavo-convex structure includes a linear prism having a semicircular cross-section 1221 and a linear prism having a semi-elliptical 1222 cross-sectional shape. And a plurality of semi-elliptical 1222 linear prisms.

  As shown in FIG. 16, the eleventh example of the concavo-convex structure is a structure in which linear prisms having a semicircular cross section 1321 and linear prisms having a triangular cross section 1322 are alternately combined.

  In addition, the concavo-convex structure may be configured by, for example, a linear prism having a triangular cross section, and the apex angle may be continuously or stepwise reduced as the distance from the fluorescent lamp increases.

(Method for forming uneven structure)
The method for forming the concavo-convex structure on the surface of the light diffusing plate is not particularly limited. For example, the method may be a method of forming the concavo-convex structure on the surface of the flat light diffusing plate, or may be a base material for the light diffusing plate. It is good also as a method of forming a concavo-convex structure integrally with formation of a flat part (it may be called a light diffusing plate base in this specification).

  Examples of a method for forming a concavo-convex structure on the surface of the flat light diffusion plate include a method of cutting the surface of the flat light diffusion plate, a prism sheet having a desired shape on the flat light diffusion plate, and the like. A method of laminating or pasting a sheet having a concavo-convex structure, applying a photo-curing resin or a thermosetting resin to the surface of a flat light diffusing plate, transferring a desired shape to the coating film with a roll or a die, and the state And a method of curing the coating film and an embossing method in which the surface of the flat light diffusion plate is pressed with a roll or a stamp having a desired shape.

  In addition, as a method of integrally forming the concavo-convex structure simultaneously with the formation of the light diffusion plate base, a casting method using a casting mold capable of forming a desired concavo-convex structure, and injection using a mold capable of forming a desired concavo-convex structure Examples thereof include a molding method. As described above, the injection molding method and the casting method have a simple process because the concavo-convex structure can be formed simultaneously with the formation of the light diffusion plate base. The casting method can be performed in a mold capable of forming a plate, or can be performed continuously while pouring a raw material between two continuous belts and moving the belt. In the injection molding method, in order to increase the shape transfer rate, it is preferable to raise the mold temperature at the time of injecting the resin and rapidly cool the mold during cooling. Moreover, you may apply the injection compression molding method which expands a type | mold when injecting resin and closes a type | mold after that.

  Moreover, in this embodiment, although the output side light control part which consists of prism rows was formed, it does not need to provide especially. Further, the shape of the prism array can be various aspects as in the case of the incident side light control unit having a concavo-convex structure.

Further, as another arrangement of the concavo-convex structure, for example, a cross section of the concavo-convex structure perpendicular to the longitudinal direction of the fluorescent lamp includes both the convex portion and the substantially flat portion, and the abundance ratio thereof is a linear light source. It can be set as the aspect which changes continuously or in steps as it distances from.
Specifically, for example, as shown in FIG. 17, the concavo-convex structure has a unit in which convex portions 1821A and flat portions 1821B, which are substantially flat portions, are alternately arranged, and this unit is repeated, and further, As the distance from the light source increases, the width 1822B of the flat portion 1821B can be changed continuously or stepwise. Here, the width 1822B of the flat portion 1821B can be set to a predetermined value for each of a plurality of zones on the light incident surface and / or the light emitting surface of the light diffusing plate to achieve intermittent changes. The number of these zones is not particularly limited, but is not limited to four zones, and may be increased to 15 to 20 levels.

  As a further preferred embodiment of the direct type backlight device of the present invention, the optical sheet further provided on the light emitting surface side of the light diffusing plate, and the uneven structure has a predetermined preferable total light transmittance distribution described in detail below. Can be mentioned. That is, in the direct type backlight device, in a cross section perpendicular to the longitudinal direction of the linear light source, an arbitrary fluorescent lamp is A, a fluorescent lamp adjacent to the fluorescent lamp A is B, and the fluorescent lamp A and the fluorescent lamp are combined. An intermediate position obtained by projecting an intermediate position with respect to the lamp B onto the light incident surface is set as X, is positioned between the fluorescent lamp A and the fluorescent lamp B, and is closer to the fluorescent lamp A than the intermediate position X. An arbitrary point on the light incident surface on the side is P, the center of the fluorescent lamp A is C, and the total light transmittance TP at the point P of light incident from the center C toward the point P is It is preferable that the total light transmittance TX at the point X of the light incident from the center C toward the intermediate position X is smaller. At this time, it is more preferable that an uneven structure is provided on the surface of the light diffusing plate so that the point P becomes substantially higher as it approaches the point X. Note that “substantially higher” mainly includes a case where the level increases continuously or stepwise, but also includes a case where the level becomes slightly lower. Such a “substantially higher” aspect is preferably satisfied in a range of at least 50% of the entire area of the light incident surface.

  The preferred embodiment will be described with reference to FIG. FIG. 18 shows the relationship between the angles on a cross section perpendicular to the longitudinal direction of the fluorescent lamp. In the example of FIG. 18, a fluorescent lamp 102A and a fluorescent lamp 102B are illustrated as the fluorescent lamp A and the fluorescent lamp B described above. An intersection 1974 between a line 1941 perpendicular to the light diffusing plate 101 at a bisector of a distance L between the center 1973A of the fluorescent lamp 102A (= the above point C) and the center 1973B of the fluorescent lamp 102B and the light incident surface S1960. , Corresponding to the above point X. The total light transmittance at the point X of light incident on the point X from the center 1973A (point C) of the fluorescent lamp 102A is TX. On the other hand, the total light transmittance at the point P of light incident from the center 1973A (point C) to the point P on the light incident surface closer to the fluorescent lamp 1973A (A) than the point X is TP. Here, when TP becomes smaller than TX, the above-mentioned preferable mode is obtained. Further, as point P approaches X, TP becomes substantially higher, which is a more preferable aspect. By setting it as such an aspect, a high brightness | luminance uniformity can be achieved.

  The optical sheet may be a single sheet or a plurality of sheets. As the optical sheet, a sheet (prism sheet or diffusion sheet) having a function as a light beam direction conversion element that converts the direction of the light emitted from the light emitting surface so as to approach the direction parallel to the normal line of the optical sheet. It is preferable that 1 or more is included. A sheet having a function as a light beam direction conversion element is a sheet having a different incident angle of incident light and an outgoing angle of outgoing light, and it is sufficient that the incident light and the outgoing light have different peak directions. It may diffuse and have a distribution.

  In addition, the optical sheet preferably includes one or more reflective polarizers. The reflective polarizer is preferably provided on the light exit surface side. As the reflective polarizer, a reflective polarizer that utilizes the difference in reflectance of the polarization component depending on the Brewster angle (for example, the one described in JP-T-6-508449); selective reflection characteristics by cholesteric liquid crystal are used. Reflective polarizer; specifically, a laminate of a film made of cholesteric liquid crystal and a quarter-wave plate (for example, one described in JP-A-3-45906); a fine metal linear pattern is applied Reflective polarizers (for example, those described in JP-A-2-308106); at least two kinds of polymer films are laminated, and the reflective polarization using the anisotropy of the reflectance due to the refractive index anisotropy Child (for example, those described in Japanese Patent Publication No. 9-506837); having a sea-island structure formed of at least two kinds of polymers in a polymer film, and anisotropy of reflectance due to refractive index anisotropy Profit Reflective polarizer used (for example, those described in US Pat. No. 5,825,543); particles are dispersed in a polymer film, and anisotropy of reflectance due to refractive index anisotropy is utilized Reflective polarizer (for example, the one described in JP-A-11-509014); reflection utilizing anisotropy of reflectance based on scattering ability difference depending on size, in which inorganic particles are dispersed in a polymer film Type polarizers (for example, those described in JP-A-9-297204) can be used.

  In a more preferred embodiment of the direct type backlight device of the present invention, the length of the line segment connecting the center C and the point P is LCP, and the point obtained by projecting the center C perpendicularly to the light incident surface is Q When the length of the line segment connecting the center C and the point Q is LCQ, and the total light transmittance at the point Q of light incident from the center C in the direction of the point Q is TQ, 0 .2 × (TQ · LCP / LCQ) ≦ TP ≦ 5.0 × (TQ · LCP / LCQ) is preferably satisfied.

  The further preferable aspect will be described with reference to FIG. 18 again. In the example of FIG. 18, the length of the line segment 1943 connecting the point P and the point 1973A (point C) corresponds to the length LCP referred to above. On the other hand, the intersection of the straight line 1945 passing through the point 1973A (point C) and perpendicular to the light diffusing plate 30 and the light incident surface S1960 becomes the point Q, and all the light incident at the point Q from the point C in the direction of the point Q The light transmittance is TQ, and the distance between CQs is LCQ. Here, when TP, TQ, CP, and LCQ satisfy the above relationship, the above-described preferred embodiment can be obtained, and a higher luminance uniformity can be achieved. The relationship is preferably established over the entire surface of the light diffusing plate, but a favorable effect can be obtained when the relationship is established with an area of 50% of the entire surface of the light diffusing plate.

<Second Embodiment>
Next, a direct type backlight device according to a second embodiment of the present invention will be described.
This embodiment is different from the first embodiment in that the incident side light control unit is configured by a printing layer. Referring to FIG. 1, the light diffusing plate 130 constituting the direct type backlight device of the present embodiment has a flat light incident surface, and the light exit surface has the same prism as that of the first embodiment. On the light incident surface, which is a flat surface, a print layer 132 is provided as an incident side light control unit. Note that various structures can be adopted as the structure of the light incident surface and the light emitting surface, as in the first embodiment.

  Here, the printing layer is a layer formed, for example, in a dot shape using a white ink or a transparent pigment in which a filler (inorganic or organic) is added to a polymer, and has a function of suppressing light transmission. It is. As the white ink, for example, a white pigment and a white dye can be used. The filler is preferably an inorganic filler (titanium dioxide or the like) from the viewpoint of enhancing thermal conductivity. In the light diffusing plate of this embodiment, the light transmittance in the region X is different from the light transmittance in the region Y. In order to realize this, in the light diffusing plate 130, the configuration of the printing layer in the region X is different from the configuration of the printing layer in the region Y. The difference in the configuration of the print layer is that the number of dot-shaped portions per unit area and the area of the dot-shaped portions are different from each other.

  In the case of using the dot-shaped print layer described above, the light transmittance may be constant within the print range, or the light transmission is increased as the distance from the nearest fluorescent lamp increases. The rate may be increased. From the viewpoint of reducing luminance unevenness, it is preferable to control so that the light transmittance increases as the distance from the fluorescent lamp at the closest position increases. As the method of increasing the light transmittance as the distance from the fluorescent lamp increases, for example, as the distance from the fluorescent lamp increases, the method of decreasing the formation area of the printed layer, the method of decreasing the thickness of the printed layer, the printed layer And a method using an ink having a low ink density. The reduction in the formation area means that the number and area of dot-like print layers per unit area are reduced. As a method of increasing the light transmittance of the printing layer, it may be continuously increased or gradually increased as the distance from the fluorescent lamp is increased.

As an aspect in which the configuration of the print layer in the region X is different from the configuration of the print layer in the region Y, for example, the following modes can be cited using FIG.
(1) R251-R252-R253: No printing layer-No printing layer-No printing layer R261-R262-R263: Printing layer A-No printing layer-Printing layer A
(2) R251-R252-R253: Print layer α-No print layer-Print layer α
R261-R262-R263: Print layer A-No print layer-Print layer A
(3) R251-R252-R253: No printing layer-Printing layer α-No printing layer R261-R262-R263: Printing layer A-No printing layer-Printing layer A
(4) R251-R252-R253: Print layer α-Print layer β-Print layer α
R261-R262-R263: Print layer A-No print layer-Print layer A
(5) R251-R252-R253: Print layer α-Print layer α-Print layer α
R261-R262-R263: Print layer A-No print layer-Print layer A
(6) R251-R252-R253: No printing layer-No printing layer-No printing layer R261-R262-R263: Printing layer A-Printing layer B-Printing layer A
(7) R251-R252-R253: Print layer α-No print layer-Print layer α
R261-R262-R263: Print layer A-Print layer B-Print layer A
(8) R251-R252-R253: No printing layer-Printing layer α-No printing layer R261-R262-R263: Printing layer A-Printing layer B-Printing layer A
(9) R251-R252-R253: Print layer α-Print layer β-Print layer α
R261-R262-R263: Print layer A-Print layer B-Print layer A
(10) R251-R252-R253: Print layer α-Print layer α-Print layer α
R261-R262-R263: Print layer A-Print layer B-Print layer A
(11) R251-R252-R253: Print layer α-No print layer-Print layer α
R261-R262-R263: Print layer A-Print layer A-Print layer A
(12) R251-R252-R253: No printing layer-Printing layer α-No printing layer R261-R262-R263: Printing layer A-Printing layer A-Printing layer A
(13) R251-R252-R253: Print layer α-Print layer β-Print layer α
R261-R262-R263: Print layer A-Print layer A-Print layer A

  The printed layer A and the printed layer B have different shapes. Further, the shape of the printing layer α and the printing layer β are different. The print layer α is the print layer A or the print layer B. The printing layer β is the printing layer structure A, the printing layer B, or the printing layer C, and the printing layer C is different in shape from the printing layer A and the printing layer B.

  In addition, as an aspect in which the light transmittance in the region X and the light transmittance in the region Y are different, an embodiment using a combination of a concavo-convex structure and a printed layer can also be mentioned.

  As a preferable aspect of the print layer, for example, a configuration in which the formation area of the print layer decreases as the distance from the fluorescent lamp 10 located closest to the print layer is increased. The reduction in the formation area means that the number and area of dot-like print layers per unit area are reduced. As a method of reducing the formation area of the print layer, the print layer may be continuously reduced or gradually decreased as the distance from the linear light source is increased.

  Here, since the printing layer is configured to include a filler having thermal conductivity, heat generated in the filament portion 120 of the fluorescent lamp 10 can be transferred to the intermediate position side of the fluorescent lamp 10, and the direct type backlight device 1 The temperature inside can be made uniform. In addition, in the case of having a printing layer, since reflection at a light receiving portion is larger than in the case of having no printing layer (that is, in the case of a flat surface), deterioration such as discoloration due to light can be suppressed. . For this reason, the direct-type backlight device with little luminance unevenness can be used over a long period of time without causing any partial deterioration of the light diffusion plate.

  Here, the printing layer of the present embodiment has a function of reflecting infrared rays by using a predetermined filler. As described above, since the temperature in the vicinity of the filament portion of the fluorescent tube becomes high, the amount of infrared rays emitted from the fluorescent tube increases at this location. On the other hand, in the present embodiment, the light incident side control unit having the infrared reflection function is configured by the printing layer, so that the infrared light is reflected and the infrared distribution inside the direct type backlight device is made uniform. For this reason, the temperature distribution in the direct type backlight device can be made uniform, local deformation of the light diffusion plate in the vicinity of the filament portion can be prevented, and the occurrence of uneven brightness can be suppressed. Furthermore, the temperature distribution transmitted to the liquid crystal panel disposed on the light emitting side of the direct type backlight device can be made uniform, and display unevenness can be suppressed.

  The direct type backlight device of the present invention is not limited to the above embodiment, and can be changed within an equivalent range. Moreover, other arbitrary components can be further included. For example, in the direct type backlight device according to each of the above embodiments, an optical member for further improving luminance and luminance uniformity may be appropriately disposed. Examples of such an optical member include a diffusion sheet and a prism sheet. These optical members can be provided on the light exit surface side of the light diffusion plate, for example. In addition, a housing for forming the backlight device, a power supply device, and the like can be provided as appropriate. The direct type backlight device of the present invention can also be suitably used for a method of controlling turning on and off of the light source according to the brightness in the screen of the liquid crystal display device.

  The liquid crystal display device of the present invention includes the direct type backlight device of the present invention. The liquid crystal display device of the present invention includes, for example, a twisted nematic (TN) mode, a super twisted nematic (STN) mode, a hybrid alignment nematic (HAN) mode, a vertical alignment (VA) mode, a multi-domain vertical alignment (MVA) mode, an in-plane It can be based on display modes such as switching (IPS) mode, optically compensated birefringence (OCB) mode. The vertical alignment (VA) mode and the in-plane switching (IPS) mode have a wide viewing angle and can be easily obtained. However, since the alignment of liquid crystal molecules is relatively complicated, it is easily affected by the heat from the backlight. The present technology can reduce the influence.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Parts and% are based on weight unless otherwise specified.

  In the following Examples and Comparative Examples, various physical properties were evaluated as follows.

(1) Light transmittance of glass tube The glass of the same material was made into a plate shape and measured with a turbidimeter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. About the light transmittance of the glass tube which printed the surface, the glass plate which gave the same printing was measured as a sample.
(2) Light transmittance of resin constituting light diffusing plate Based on JIS K7361-1, the total light transmittance of a 2 mm thick flat plate made of the same material as the resin constituting the light diffusing plate was measured. .
(3) Light transmittance of region X and region Y of the light diffusion plate
1. Several types of light diffusing plates having different light transmittances are prepared. These diffusing plates were set in Radiant Imaging, Inc. light source light distribution measurement system IS-LI, and light source LS-1 manufactured by OCEAN Optics and optical fiber P400-2-VIS / NIR manufactured by OCEAN Optics were used. Light is incident perpendicularly to the main surface of the diffuser and the light beam emitted from the opposite surface is measured.
2. The light transmittance of the light diffusing plate is plotted against the light flux measured above, and a calibration curve for the light transmittance is created.
3. Using the same measurement system as in 1 above, when the light diffusing plate to be measured is incorporated into the backlight, the surface that becomes the light source side is set as the incident surface, light is incident at the incident angle calculated from the set position of the light source, and from the opposite surface The emitted light beam is measured.
4). The light transmittance is calculated using the calibration curve created in 2 above.

<Example 1>
A reflector, a fluorescent tube, and a light diffusing plate constituting the backlight device were prepared.

(a reflector)
A reflective plate (“E6SV”, manufactured by Toray Industries, Inc.) was attached to the inner surface of an aluminum case having an inner size width of 1017 mm, a depth of 572 mm, and a depth of 25 mm, thereby creating a reflector.

(Hot cathode tube)
A valve made of straight pipe soda lime glass was prepared. This bulb has an outer diameter of about 15.5 mm, a glass thickness of 0.7 mm, a glass transmittance of 90%, and a tube length of 1020 mm. At both ends of the bulb, electrodes having an emitter (electron emitting material) containing BaO, SrO, and CaO in a ratio of 1: 1: 1 on a tungsten coil of a triple coil were installed. Further, a three-wavelength light emitting phosphor is formed on the inner wall surface of the bulb, and mercury and 1 kPa of argon are enclosed in the bulb.

(Light diffusion plate)
Using a mold part of a predetermined shape for an injection molding machine (clamping force 9,810 KN), using an alicyclic olefin polymer (manufactured by Zeon Corporation, “Zeonor 1420R”) as a raw material, cylinder temperature 320 ° C., holding pressure 50 MPa The light diffusion plate was molded under the conditions of a holding time of 3 seconds and a mold temperature of 130 ° C. The obtained light diffusing plate was a rectangular flat plate having a thickness of 2 mm, 1018 mm × 573 mm. On one surface of the light diffusing plate, a predetermined pattern having a concavo-convex structure in which a plurality of triangular linear prisms (triangular prisms) having a vertical angle of 100 degrees are arranged in parallel at a pitch of 70 μm was formed. Further, a predetermined pattern in which a plurality of types of triangular prisms having different apex angles are arranged at a predetermined mixing ratio is formed on the other surface of the light diffusing plate. The predetermined pattern will be described later. When the triangular prism surface having an apex angle of 100 degrees of this light diffusion plate was polished and the residual stress was measured, the maximum was 1 MPa and the minimum was 0.3 MPa. In all of the embodiments and comparative examples of the present application as well as the present embodiment, the linear prisms on the entrance surface and exit surface of the light diffusion plate are substantially parallel to the direction of the long side of the light diffusion plate and the long axis direction of the light source. It was provided.

The pattern of the concavo-convex structure will be described with reference to FIG.
In a state where the light diffusion plate is assembled in the direct type backlight device, a section corresponding to a distance from the center of the hot cathode tube 1402a to the middle 1441 of the distance between the center of the hot cathode tube 1402b and the center of the adjacent hot cathode tube 1402b is obtained. A-Q was divided into 17 zones. The range of each zone (the distance in the horizontal direction in FIG. 19) was as shown in Table 1. In each zone of the light incident surface of the light diffusing plate, prism-shaped convex portions having a triangular cross section with an apex angle of 140 ° to 170 ° were provided at a mixing ratio shown in Table 1. The prism pitch was 70 μm.

The notation in Table 1 indicates the arrangement of the convex portions in the repeating unit of the concave-convex structure pattern. For example, in the case of the D region, a structure in which a concavo-convex structure including one triangular convex portion having an apex angle of 170 ° and three triangular convex portions having an apex angle of 160 ° is taken as one unit, and this unit is repeated. Indicates.
In the direct type backlight device, the transmittances of the portions corresponding to the region X and the region Y were 45% and 84%, respectively.

Six of the hot cathode tubes were attached in parallel to the inner dimension width direction of the reflector. The distance between the centers of the hot cathode tubes was 90 mm, and the distance from the reflector to the center of the hot cathode tube was 9.75 mm. The vicinity of the electrode part was fixed with a silicone sealant, and an operation circuit was attached. This operation circuit (corresponding to a ballast) includes a lighting circuit and a preheating circuit each including a ballast choke type inverter circuit.
Further, the height 2131 is a shape made of a polycarbonate resin (Taflon URZ2502 manufactured by Idemitsu Kosan Co., Ltd.) and shown in FIG. A 25 mm support pin was attached at the position shown in FIG. At this time, all the positions of the pins are the center positions of the hot cathode tube and the adjacent hot cathode tube. The distance 2111 shown in the figure is 100 mm, and the distance 2112 from the intermediate line 2151 in the width direction of the case is also 100 mm. The distance 2121 of the pin closest to the emitter position of the hot cathode tube 1402a is measured to be 103 mm. The distance 2122 between the pin and the nearest pin is 135 mm.
Next, the surface on which the pattern shown in Table 1 was formed was directed to the hot cathode tube side, and the light diffusing plate was placed on a reflecting plate made of an aluminum case with a reflecting sheet attached. At this time, the distance between the center of the hot cathode tube and the light incident surface of the light diffusion plate was 15.25 mm.

  Further, on the light emitting side of the light diffusion plate, a diffusion sheet (manufactured by Kimoto Co., “188GM3”), a prism sheet (manufactured by Sumitomo 3M Co., “BEFIII-10T”), and a diffusion sheet (corresponding to an optical sheet) Kimoto Co., Ltd., “188GM3”) was installed in this order.

Next, with respect to the obtained direct backlight device, the preheating circuit was adjusted, and the filament portion was energized with a current of 400 mA to maintain the emitter surface temperature at 800 ° C. Further, the lighting circuit was adjusted, and a voltage of 400 V was applied between the filaments at both ends to light the hot cathode tube. The current due to the voltage applied to the lighting was 150 mA. Using a two-dimensional color distribution measuring device, the luminance in the front direction of 100 points was measured at equal intervals along the long side direction of the case on the center line in the short side direction of the aluminum case. The central brightness measurement was 10,000 cd / m ² . Further, according to the following formulas 1 and 2, the average luminance value (front luminance) LA and luminance unevenness LU in the front direction were obtained. The luminance unevenness was 0.5%. When the time until the luminance reached 50% of the initial brightness was regarded as the lifetime of the backlight, the lifetime was 60,000 hours. The results are shown in Table 2.
Brightness average value LA = (L1 + L2) / 2 (Formula 1)
Luminance unevenness LU = ((L1-L2) / LA) × 100 (Equation 2)
L1: Average brightness maximum value just above a plurality of installed hot cathode tubes L2: Average minimum value sandwiched between maximum values Note that brightness unevenness is an index indicating brightness uniformity, and brightness unevenness When it is bad, the figure increases.
The surface temperature of the light diffusing plate incident surface was measured. One hour after the surface temperature reached equilibrium, the temperature immediately above the filament was 95 ° C., and it was 50 ° C. directly above the center of the hot cathode tube.
With the diffusion sheet, the prism sheet, and the diffusion sheet placed, the infrared distribution was measured with a Fastvert S-2400 manufactured by Soma Optical Co., Ltd. (wavelength 843 nm, measured value immediately above the lamp 20 mm away from the hot cathode tube electrode) α, and a measured value β at the intermediate position between the lamp moved parallel to the light diffusion plate short side from that position).
α = 0.050 μW / (cm ² · nm), β = 0.035 μW / (cm ² · nm), β / α = 0.70. Even when the VA type liquid crystal panel taken out from the liquid crystal television (Aquos LC-46GX1W manufactured by Sharp Corporation) was mounted on this backlight and turned on for 100 hours, the display was not particularly disturbed. Even in an IPS type liquid crystal panel taken out from a liquid crystal television (HDTV Model: 47LB5D manufactured by LG Electronics), the display was not disturbed in 100 hours.
Further, no warping was observed on the light diffusion plate during the life test, and the luminance unevenness in the vicinity of the electrode was not increased.

<Example 2>
A direct type backlight device was produced in the same manner as in Example 1 except that the filament current for preheating was 500 mA and the emitter surface temperature was maintained at 820 ° C. The obtained direct backlight device was evaluated for luminance and luminance unevenness in the same manner as in Example 1. The results are shown in Table 2.

<Example 3>
A direct type backlight device was produced in the same manner as in Example 1 except that the filament current for preheating was 600 mA and the emitter surface temperature was maintained at 850 ° C. The obtained direct type backlight device was evaluated in the same manner as Example 1 in terms of luminance and luminance unevenness. The results are shown in Table 2.

<Example 4>
The direct-type backlight is the same as in Example 2 except that the uneven structure pattern of the light diffusion plate is as described in detail below, the interval between the hot cathode tubes is 100 mm, and the depth of the reflection plate is 32.5 mm. Created a device.
The uneven structure on the light diffusion plate used in this example will be described with reference to FIG. As shown in FIG. 20, with the light diffusing plate attached, the distance between the center of the hot cathode tube 1402b from the center of the hot cathode tube 1402b is set to an intermediate 1441, and from the intermediate 1441 to the hot cathode tubes 1402a and 1402b. The distance corresponding to the center was divided into three zones: A (9 mm), B (17.5 mm) and C (23.5 mm).

  In FIG. 20, the light exit surface 30B of the light diffusing plate 30 is provided with prism-shaped convex portions having a triangular cross section with an apex angle of 100 ° and a base of 70 μm on the entire surface without a flat portion gap (flat surface). The triangular base corner portions adjacent to each other are provided so as not to exist, that is, adjacent to each other.

  On the other hand, among the zones of the light incident surface 30A of the light diffusion plate 30, the zone A is a flat surface. In the zone B, prism-shaped convex portions 1821a having a triangular cross section as shown in FIG. 17 and flat portions 1821b are alternately provided. However, the apex angle of the triangular shape was 130 °, the base 1822a was 70 μm, and the flat portion width 1822b was 70 μm. In the zone C, prism-shaped convex portions having a triangular cross section having an apex angle of 130 ° and a base of 70 μm were provided without a flat portion gap. In the direct type backlight device, the transmittance corresponding to the region X and the region Y was 55% and 90%, respectively. The obtained direct type backlight device was evaluated in the same manner as Example 2 in terms of luminance and luminance unevenness. The results are shown in Table 2.

<Example 5>
A direct type backlight device was produced in the same manner as in Example 2 except that the light diffusion plate was changed to the following mode. The obtained direct type backlight device was evaluated in the same manner as Example 2 in terms of luminance and luminance unevenness. The results are shown in Table 2.

  The mode on the light diffusing plate used in this example will be described with reference to FIG. As shown in FIG. 20, with the light diffusing plate attached, the distance between the center of the hot cathode tube 1402b from the center of the hot cathode tube 1402b is set to an intermediate 1441, and from the intermediate 1441 to the hot cathode tubes 1402a and 1402b. The distance corresponding to the center was divided into three zones A (10 mm), B (20 mm) and C (15 mm).

  The light emitting surface 30B of the light diffusing plate 30 has prism-shaped convex portions having a triangular cross section with an apex angle of 100 ° and a base of 70 μm on the entire surface, without a flat portion gap (there is no flat portion). In other words, the triangular base corner portions adjacent to each other are in contact with each other).

On the other hand, among each zone of the light incident surface 30A of the light diffusing plate 30, in the zone A, white ink containing 25% by weight of titanium dioxide as a pigment is printed with circular dots having a diameter of 100 μm on 50% of the surface area of the diffusing plate. did. In zone B, the same circular dots were printed on 20% of the diffuser surface area. In zone C, neither printing nor convex portions were provided. In the direct type backlight device, the transmittance corresponding to the region X and the region Y was 60% and 70%, respectively.
With the diffusion sheet, the prism sheet, and the diffusion sheet placed, the infrared distribution was measured with a Fastvert S-2400 manufactured by Soma Optical Co., Ltd. (wavelength 843 nm, measured value immediately above the lamp 20 mm away from the hot cathode tube electrode) α, and a measured value β at the intermediate position between the lamp moved parallel to the light diffusion plate short side from that position).
α = 0.045 μW / (cm ² · nm), β = 0.036 μW / (cm ² · nm), β / α = 0.80. Even when the same VA type liquid crystal panel as in Example 1 was mounted on this backlight and turned on for 100 hours, the display was not particularly disturbed. Even in the same IPS type liquid crystal panel as in Example 1, the display was not disturbed in 100 hours.

<Example 6>
The resin used for the light diffusing plate is a resin composition in which 0.3 part of fine particles made of a cross-linked polysiloxane polymer having an average particle diameter of 2 μm and 99.7 parts of ZEONOR 1420R are mixed. A direct type backlight device was produced in the same manner as in Example 2 except that the plate was changed to the following mode. The obtained direct backlight device was evaluated for luminance and luminance unevenness in the same manner as in Example 2. The results are shown in Table 2.

  On the entire surface of the light emitting surface 30B of the light diffusing plate 30, a part of a circle having a width of 70 μm, a depth of 22.3 μm, a pitch of 70 μm and a radius of 38.6 μm (a part slightly smaller than a semicircle) The convex part of the shape was provided without a gap in the flat part (so that the flat part does not exist, that is, the base corner parts of the saddle shape adjacent to each other are in contact with each other).

  On the other hand, the light incident surface 30 </ b> A of the light diffusing plate 30 was a surface having no unevenness, and printing similar to that in Example 5 was performed. In the direct type backlight device, the transmittance corresponding to the region X and the region Y was 60% and 70%, respectively.

  The light reflecting plate of this example is MCPET (product name of Furukawa Denki Kogyo Co., Ltd.) as the reflecting sheet to be attached, and an aluminum protrusion having a triangular cross section with a vertex angle of 90 ° and a height of 20 mm at the center of the hot cathode tube. It was attached to the tube side so as to be convex, and the surface was formed by attaching MCPET.

<Example 7>
The resin used for the light diffusing plate is a resin composition in which 2.6 parts of fine particles made of a cross-linked polysiloxane polymer having an average particle diameter of 2 μm and 97.4 parts of ZEONOR 1420R are mixed. A direct type backlight device was produced in the same manner as in Example 6 except that the following embodiment was used and the interval between the hot cathode tubes was set to 100 mm.

The mode on the light diffusing plate used in this example will be described with reference to FIG. As shown in FIG. 20, with the light diffusion plate attached, the distance between the center of the hot cathode tube 1402a and the center of the adjacent hot cathode tube 1402b is set to 1441, and from the intermediate 1441 to the center of each hot cathode tube. The corresponding distance was divided into three zones: A (10 mm), B (20 mm) and C (20 mm). Of the zones on the light incident surface 30A of the light diffusion plate 30, the same white ink as in Example 5 was printed in the zone A with circular dots having a diameter of 100 μm on 65% of the surface area of the diffusion plate. In zone B, the same circular dots were printed on 30% of the diffuser surface area. In zone C, neither printing nor convex portions were provided. On the other hand, the light exit surface 30B of the light diffusing plate 30 was not provided with printing or protrusions on the entire surface.
In the direct type backlight device, the transmittance corresponding to the region X and the region Y was 30% and 40%, respectively. The direct type backlight device thus obtained was evaluated in the same manner as Example 6 in terms of luminance and luminance unevenness. The results are shown in Table 2.

<Example 8>
Using a hot cathode tube with an outer diameter of 32.5 mm, changing the pin height 2131 to make the distance between the reflector and the diffuser 42.0 mm, and the distance from the reflector to the center of the hot cathode tube A direct type backlight device was produced in the same manner as in Example 2 except that the thickness was 18.25 mm. The obtained direct type backlight device was evaluated in the same manner as Example 2 in terms of luminance and luminance unevenness. The results are shown in Table 3. The transmittances of the portions corresponding to the regions X and Y were 45% and 90%, respectively.

<Example 9>
A direct type backlight device was prepared in the same manner as in Example 2 except that the glass thickness of the hot cathode tube was 3 mm. The obtained direct type backlight device was evaluated in the same manner as Example 2 in terms of luminance and luminance unevenness. The results are shown in Table 3.

<Example 10>
A direct type backlight device was produced in the same manner as in Example 2 except that the inverter was a transformer type. The obtained direct backlight device was evaluated for luminance and luminance unevenness in the same manner as in Example 2. The results are shown in Table 3.

<Example 11>
A direct type backlight device was produced in the same manner as in Example 2 except that the pin height 2131 was changed so that the distance between the reflector and the diffuser was 200 mm. The obtained direct backlight device was evaluated for luminance and luminance unevenness in the same manner as in Example 2. The results are shown in Table 3. The transmittances of the portions corresponding to the regions X and Y were 45% and 65%, respectively.

<Example 12>
A light diffusing plate and a backlight device were produced in the same manner as in Example 1 except that the prism pitch was 10 μm on both sides. In the direct type backlight device, the transmittances of the portions corresponding to the region X and the region Y were 45% and 84%, respectively. For this apparatus, the luminance and the luminance unevenness were evaluated in the same manner as in Example 1. The results are shown in Table 4. The luminance unevenness at the center was as small as 0.5%, but the prism apex was deviated near the electrode, resulting in a large luminance unevenness of 2.5%.

<Example 13>
Using an injection molding machine (clamping force 9,810 KN), an alicyclic olefin polymer (manufactured by Nippon Zeon Co., Ltd., “ZEONOR 1420R”) as a raw material, cylinder temperature 320 ° C., holding pressure 75 MPa, holding time 6 seconds, A light diffusion plate and a backlight device were produced in the same manner as in Example 1 except that the molding was performed at a mold temperature of 120 ° C. In the direct type backlight device, the transmittances of the portions corresponding to the region X and the region Y were 45% and 84%, respectively. For this apparatus, the luminance and the luminance unevenness were evaluated in the same manner as in Example 1. When the triangular prism surface having an apex angle of 100 degrees of this light diffusion plate was polished and the residual stress was measured, the maximum was 15 MPa and the minimum was 2 MPa. The results are shown in Table 4. The luminance unevenness at the center was as small as 0.5%, but warpage occurred near the electrode, resulting in a large luminance unevenness of 3.2%.

<Example 14>
Evaluation of luminance and luminance unevenness was performed in the same manner as in Example 1 except that the pin arrangement was as shown in FIG. At this time, the distance 2113 is 300 mm, and the distance 2123 of the pin closest to the hot cathode tube 1402a is 302 mm. The results are shown in Table 4.
A convex 2.5 mm warp was generated on the hot cathode tube side in the vicinity of the electrode part, and a 1.5 mm warp in the same direction was also generated in the center part. As a result, the luminance unevenness in the vicinity of the central portion was slightly large at 1.8%, and was further increased to 3.5% in the vicinity of the electrode.

<Comparative Example 1>
The resin used for the light diffusing plate is a resin composition in which 0.8 parts of fine particles made of a cross-linked polysiloxane polymer having an average particle diameter of 2 μm and ZEONOR 1420R99.2 parts are mixed. A flat plate having an uneven structure and no printing, and a glass tube of a hot cathode tube having silicon dioxide particles adhered to the half surface on the light diffusion plate side so that the light transmittance is 70%, and the interval of the hot cathode tube A light diffusing plate and a direct type backlight device were prepared in the same manner as in Example 1 except that the thickness was set to 50 mm. In the direct type backlight device, the transmittances of the portions corresponding to the region X and the region Y were 65% and 59%, respectively. For this apparatus, the luminance and the luminance unevenness were evaluated in the same manner as in Example 1. The results are shown in Table 5.

<Comparative example 2>
The resin used for the light diffusing plate is a resin composition in which 0.8 parts of fine particles made of a cross-linked polysiloxane polymer having an average particle diameter of 2 μm and ZEONOR 1420R99.2 parts are mixed. A light diffusing plate and a direct type backlight device were prepared in the same manner as in Example 1 except that the concavo-convex structure and a flat plate without printing were used. In the direct type backlight device, the transmittances of the portions corresponding to the region X and the region Y were 65% and 49%, respectively. For this apparatus, the luminance and the luminance unevenness were evaluated in the same manner as in Example 1. The results are shown in Table 5.
With the diffusion sheet, the prism sheet, and the diffusion sheet placed, the infrared distribution was measured with a Fastvert S-2400 manufactured by Soma Optical Co., Ltd. (wavelength 843 nm, measured value immediately above the lamp 20 mm away from the hot cathode tube electrode) α, and a measured value β at the intermediate position between the lamp moved parallel to the light diffusion plate short side from that position).
α = 0.056 µW / (cm ² · nm), β = 0.025 µW / (cm ² · nm), β / α = 0.45. When the same VA type liquid crystal panel as in Example 1 was mounted on this backlight and turned on for 100 hours, the display near the electrodes was disturbed. Even in the same IPS type liquid crystal panel as in Example 1, disorder occurred in 100 hours.
The surface temperature of the light diffusing plate incident surface was measured. One hour after the surface temperature reached equilibrium, the temperature immediately above the filament was 100 ° C., and 50 ° C. immediately above the center of the hot cathode tube. The position immediately above the filament after the life test was yellowed.

<Comparative Example 3>
A direct type backlight device was prepared in the same manner as in Example 1 except that the filament current for preheating was 1200 mA and the emitter surface temperature was maintained at 1050 ° C., and the luminance and luminance unevenness were evaluated. The results are shown in Table 5.

<Comparative example 4>
A direct type backlight device was prepared in the same manner as in Example 1 except that the filament current for preheating was set to 0 mA, and the luminance and luminance unevenness were evaluated. The emitter was discharged from one point, and the surface temperature of that portion was about 1050 ° C. The results are shown in Table 5.

<Comparative Example 5>
Light diffusion is performed in the same manner as in Example 1 except that a prism having a cross-sectional triangle with an apex angle of 90 ° and a pitch of 70 μm is formed only in a region where the hot cathode tube is projected perpendicularly to the light diffusion plate on the exit surface of the light diffusion plate. A plate and a direct backlight device were prepared. In the direct type backlight device, the transmittance corresponding to the region X and the region Y was 52% and 60%, respectively. This apparatus was evaluated in the same manner as in Example 1. In this comparative example, the initial luminance unevenness was 4.0%, but at the time when 15000 hours had elapsed, it doubled to 8.0%, so that time was regarded as the lifetime.
The surface temperature of the light diffusing plate incident surface was measured. One hour after the surface temperature reached equilibrium, the temperature immediately above the filament was 100 ° C., and 50 ° C. immediately above the center of the hot cathode tube. The position immediately above the filament after the life test was yellowed.

<Comparative Example 6>
Except that the emitter was not coated on the tungsten filament, a direct type backlight device was prepared in the same manner as in Example 2, and the luminance and luminance unevenness were evaluated. The electrode of the hot cathode tube was cut in 2 minutes, and the numerical value could not be evaluated. In addition, when the same experiment as this comparative example was repeated several times, in all cases, the electrode was cut in several seconds to several minutes.

It is sectional drawing which shows the outline of the direct type | mold backlight apparatus which concerns on one Embodiment of this invention. It is a figure which shows typically the example of a structure of the fluorescent lamp and the ballast in the apparatus of this invention. It is sectional drawing for demonstrating the more specific example of the surface shape of the light diffusing plate in the apparatus of this invention. It is sectional drawing which shows the example of the uneven structure of a light-diffusion plate typically. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically another example of the uneven structure of a light diffusing plate. It is sectional drawing which shows typically the example of another arrangement | positioning of an uneven structure. It is sectional drawing explaining the example of the optical property of a light diffusing plate concretely. It is sectional drawing explaining the zone of the light diffusing plate surface in the Example of this application. It is sectional drawing explaining the zone of the light diffusing plate surface in another Example of this application. It is a top view explaining arrangement | positioning of the fluorescent lamp and support pin in the Example of this application. It is a top view explaining arrangement | positioning of the fluorescent lamp and support pin in another Example of this application. It is a figure explaining the shape of the support pin in the apparatus of this application.

Claims (8)

A plurality of fluorescent lamps arranged substantially parallel to each other, a reflecting plate that reflects light from these fluorescent lamps on its surface, direct light from the fluorescent lamp and reflected light from the surface of the reflecting plate are light A direct-type backlight device comprising a light diffusing plate that is incident from an incident surface and is emitted from a light exit surface,
The fluorescent lamp includes a cylindrical fluorescent tube, and a filament portion provided at at least one end of the fluorescent tube,
The fluorescent tube comprises a glass tube and a fluorescent layer provided on the inner surface of the glass tube,
The filament portion includes a filament and an emitter provided on an outer peripheral portion of the filament,
The emitter is preheated so that its surface temperature is always maintained at 700-950 ° C.,
The light incident surface in the region X obtained by projecting the outer diameter of the fluorescent tube perpendicularly to the light diffusion plate is provided with an incident side light control unit that has a heat transfer function and controls the amount of incident light. ,
A direct type backlight in which the transmittance of the light diffusing plate in the region X is 1% or more lower than the transmittance in a region Y having the same width as the outer diameter of the fluorescent tube centering on an intermediate position between adjacent fluorescent lamps apparatus. In the direct type backlight device according to claim 1,
The light diffusing plate is a direct type backlight device having a residual stress of 10 MPa or less. The direct type backlight device according to claim 1 or 2,
The light diffusing plate is a direct type backlight device in which a difference between a maximum value of the residual stress in the surface and a minimum value of the residual stress in the surface is 10 MPa or less. The direct type backlight device according to any one of claims 1 to 3,
The incident side control unit is a direct type backlight device further having a function of reflecting and / or refracting infrared rays. The direct type backlight device according to any one of claims 1 to 4,
Between the reflecting plate and the light diffusing plate, one or more support pins for supporting the light diffusing plate so as not to bend are provided,
A direct type backlight device in which the distance between each support pin and the emitter closest to the support pin is within 250 mm. In the direct type backlight device according to claim 5,
With two or more support pins,
A direct type backlight device in which, when any one of the two or more support pins is selected, a distance between the support pin and another support pin closest to the support pin is within 200 mm . The direct type backlight device according to any one of claims 1 to 6,
A direct-type backlight device in which an emission-side light control unit that controls the amount of emitted light is provided on the light emission surface. The direct type backlight device according to any one of claims 1 to 7,
A liquid crystal cell disposed on the light emitting side of the backlight device,
A liquid crystal display device in which the liquid crystal cell is in a VA mode or an IPS mode.

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