KR20090125753A - Direct-lighting backlight apparatus - Google Patents

Abstract

Provided is a direct-lighting backlight apparatus which has high energy efficiency with less periodic illuminance nonuniformity.The direct-lighting backlight apparatus is provided with a plurality of linear light sources, light diffuser plate, and the like. The linear light source has an outer diameter of 5mm-30mm. At least a light outgoing surface or a light incoming surface has an uneven structure at least at one part. The uneven structure, which is in an area where the outer diameter of the linear light source is vertically projected on the light diffuser plate, and the uneven structure, which is in an area having the intermediate position of the adjacent linear light sources at the center and a width the same as the outer diameter of the linear light source, have different shapes.

Description

Direct Backlight Device {DIRECT-LIGHTING BACKLIGHT APPARATUS}

The present invention relates to a direct type backlight device.

Background Art Conventionally, as a backlight device for a liquid crystal display device, for example, a reflecting plate, a plurality of linear light sources arranged in substantially parallel, direct light from these linear light sources, and reflected light from a reflecting plate are incident from a light incidence plane, BACKGROUND ART A direct type backlight device having a light diffusing plate which is emitted from a light emitting surface and becomes a light emitting surface in this order is widely used. On the light emitting surface of such a direct type backlight device, high brightness can be easily obtained, while the brightness of the upper portion of the linear light source on the light emitting surface is high, and the brightness tends to decrease as it moves away from the upper portion. Periodic luminance unevenness may occur.

Therefore, in the direct type backlight device, as a linear light source, it is preferable to arrange the cold cathode tube having a diameter of 4 mm or less as closely as possible, so as to lower the degree of periodic luminance unevenness. However, since the energy efficiency of the cold cathode tube itself is low, the energy efficiency of a backlight device will become remarkably low when there are many cold cathode tubes arrange | positioned in this way.

 As a measure for improving energy efficiency, it is considered to use a hot cathode tube that is thicker than the cold cathode tube and has higher energy efficiency. However, in that case, it is necessary to use a hot cathode tube thicker than the cold cathode tube at intervals than the cold cathode tube, and as a result, periodic luminance unevenness becomes larger than when using the cold cathode tube.

As a method of reducing the luminance unevenness of a backlight device using a cold cathode tube, a light quantity correction pattern having a stripe shape or a dot shape is printed on a light diffusion plate, the amount of light irradiated immediately above the linear light source is reduced, and between the linear light sources. The technique of relatively increasing the quantity of light irradiated is disclosed (patent document 1: Unexamined-Japanese-Patent No. 1994-273760). However, this method did not reach even enough improvement in the period staining when the hot cathode tube was used instead of the cold cathode tube.

Problems to be Solved by the Invention

Accordingly, it is an object of the present invention to provide a direct backlight device having high energy efficiency and low periodical luminance unevenness.

Means to solve the problem

MEANS TO SOLVE THE PROBLEM The present inventors earnestly researched in order to solve the said subject, and discovered that even if a linear light source, such as a hot cathode tube with a large diameter, was used, the luminance unevenness can be reduced by making the shape of a light-diffusion plate into a specific shape. Based on this knowledge, the present invention was completed.

That is, according to this invention, the following is provided.

[1] a plurality of linear light sources arranged substantially parallel to each other, a reflecting plate for reflecting light from the linear light sources, direct light from the linear light source and reflected light from the reflecting plate are incident from the light incidence plane; In the direct type backlight device having a light diffusion plate for diffusing irradiation from the light exit surface, the linear light source has an outer diameter of 5mm to 30mm, at least part of at least one of the light exit surface and the light incident surface. The uneven structure is formed at the position of, and in the light diffusing plate, when the outer diameter of the linear light source is projected perpendicular to the light diffusing plate, the uneven structure of the projected portion and the light diffusing plate And the concave-convex structure of the portion centered on the intermediate position of the linear light sources adjacent to each other and having the same width as the outer diameter of the linear light source is different. Direct backlight apparatus, characterized in that merchant.

[2] The direct type backlight device according to claim 2, wherein the linear light source is a hot cathode tube.

[3] The uneven structure is a prism array in which a plurality of linear prisms extending along a long direction of the linear light source are substantially parallel to each other, and a cross section perpendicular to the long direction of the linear light source of the linear prism is And a curved or polygonal convex portion, a substantially flat portion or a combination thereof.

[4] A cross section perpendicular to the longitudinal direction of the linear light source of the linear prism includes two or more types of convex portions having different shapes, and is continuously or as the abundance ratio of the two or more types of convex portions moves away from the linear light source. The direct type backlight device, characterized in that the step changes.

[5] A cross section perpendicular to the longitudinal direction of the linear light source of the linear prism includes both the convex portion and the substantially flat portion, and their abundance is continuous or stepwise as the distance from the linear light source increases. The direct type backlight device, characterized in that to change.

[6] An optical sheet provided on the light exit surface side of the light diffusing plate is further provided, and in the cross section perpendicular to the longitudinal direction of the linear light source, an arbitrary linear light source is called A, and the linear light source ( A linear light source adjacent to A) is referred to as B, and an intermediate position where the intermediate position of the linear light source A and the linear light source B is projected onto the light incident surface is referred to as X, and the linear light source is Any point on the light incidence plane located between (A) and the linear light source B and closer to the linear light source A than the intermediate position X is called P, and the linear light source The center of (A) is C, and the total light transmittance Tp at the point P of the light incident from the center C in the direction of the point P is the center C. Total light transmittance Tx at the point X of the light incident in the direction of the intermediate position X Also the direct backlight apparatus is smaller.

[7] The length of the line connecting the center C and the point P is LCP, the point at which the center C is projected perpendicular to the light incident surface is Q, and the center C is The length of the line connecting the point Q and the point Q is called LCQ, and the total light transmittance at the point Q of the light incident from the center C in the direction of the point Q is Tq. The direct type backlight device as described above, wherein the relationship of (Tq.LCP / LCQ) ≤ Tp ≤ 5.0 x (Tq.LCP / LCQ) is satisfied.

[8] The direct type backlight device according to claim 8, wherein the uneven structure is formed on both at least a part of the light exit surface and at least a part of the light entrance surface of the light diffusion plate.

[9] The concave-convex structure is a prism array in which a plurality of linear prisms extending along the longitudinal direction of the linear light source are substantially parallel to each other, and a cross section perpendicular to the longitudinal direction of at least part of the linear light source is The polygonal shape, wherein the polygonal shape is symmetrical about an axis parallel to the thickness direction of the light diffusion plate in the cross section, wherein the direct type backlight device.

[10] A slope of at least one of the light emitting surface and the light incidence surface and at least one of the linear prism and the light emitting surface or the light incidence surface are directed away from the linear light source and toward an intermediate position of the adjacent linear light sources. And the angle formed by a plane perpendicular to the thickness direction of the light diffusion plate is increased continuously or stepwise.

[11] Two or more kinds of the linear prism of at least one of the light exit surface and the light incident surface as it faces away from the linear light source and faces an intermediate position of the linear light sources adjacent to each other. The direct backlight is characterized in that the mixing ratio of the linear prism is changed continuously or stepwise, and the ratio of the linear prism having a large inclination angle increases continuously or stepwise as it is directed toward an intermediate position of the linear light sources adjacent to each other. Device.

[12] A liquid crystal display device comprising the direct type backlight device. Since such a liquid crystal display device includes the direct type backlight device of the present invention, there is an effect that the energy consumption is lower and the luminance unevenness is smaller than the height of the luminance.

Effects of the Invention

Since the direct backlight device of the present invention has a linear light source having a diameter equal to or more than a specific diameter such as a hot cathode tube and has a shape of a specific light diffusion plate, it is possible to increase energy efficiency and to reduce periodic luminance unevenness. There is.

1 is a perspective view showing an outline of a direct type backlight device of the present invention;

2 is a partial cross-sectional view that specifically illustrates an example of a surface shape of a light diffusion plate of the direct type backlight device of the present invention;

3 is a partial cross-sectional view showing an example of the uneven structure of the light diffusion plate;

4 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

5 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

6 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

7 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

8 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

9 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

10 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

11 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

12 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

13 is a partial cross-sectional view showing another example of the uneven structure of the light diffusion plate;

14 is a sectional view showing an outline of a direct type backlight device according to Embodiment 1 of the present application;

FIG. 15 is a partial sectional view showing an outline of a light diffusion plate of the direct type backlight device according to Example 1 of the present application; FIG.

16 is a partial cross-sectional view showing the concave-convex structure of the light diffusion plate of the direct type backlight device according to the first embodiment of the present application;

17 is a partial cross-sectional view showing an outline of a light diffusion plate of the direct type backlight device according to Example 2 of the present application;

18 is a partial cross-sectional view showing the concave-convex structure of the light diffusion plate of the direct type backlight device according to the third embodiment of the present application;

19 is a partial cross-sectional view that specifically illustrates an example of optical properties of the light diffusion plate of the direct type backlight device of the present invention;

20 is a partial cross-sectional view showing the outline of a light diffusion plate of the direct type backlight device according to Example 3 of the present application;

21 is a sectional view showing the outline of a direct type backlight device according to Embodiment 6 of the present application;

FIG. 22 is a partial sectional view showing an outline of a light diffusion plate of the direct type backlight device according to Example 6 of the present application; FIG.

Fig. 23 is a partial sectional view showing the concave-convex structure of the light diffusion plate of the direct type backlight device according to the sixth embodiment of the present application.

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described with reference to drawings.

1 is a perspective view illustrating an outline of a direct type apparatus according to an embodiment of the present invention. The direct type backlight device of the present embodiment includes a plurality of linear light sources 102 disposed substantially parallel to each other, a reflector plate 103 reflecting light from these linear light sources 102, and a linear light source 102. A light diffusing plate 101 for diffusing and irradiating the direct light from the light and the reflected light from the reflecting plate 103 is provided. Since the embodiment shown in FIG. 1 is a schematic diagram for showing these positional relationships, in FIG. 1, the light diffusing plate has a sawtooth-shaped prism shape only in the main surface of the upper side, that is, the exit surface. Although shown to have an uneven structure, the direct type backlight device of this invention has the specific structure mentioned later in both the emission surface and the incident surface of the light-diffusion plate 101. As shown in FIG.

In addition, in this specification, "upper" and "lower" direction means "upper" and "lower" in a state where the direct type backlight device is mounted so that its light exit plane is horizontally upward unless otherwise indicated. Direction, and coincide with the upward direction and the downward direction in the drawings of FIGS. 1 to 19.

In the direct type backlight device of this embodiment, the linear light source 102 has an outer diameter of 5 mm to 30 mm, and preferably a hot cathode tube. By employing the above configuration, a backlight device having high energy efficiency can be obtained. In addition, the linear light source 102 preferably has a light emission efficiency of 60 (Lm / W) or more, preferably a length of 700 mm or more and no bending of 2 mm or more even when both ends thereof are supported.

As the shape of the linear light source 102, in addition to the linear shape, two parallel tubes are connected in one semi-circle to form a "Ｕ" shape, and three parallel tubes are connected to two approximately semi-circles to become one. "N" shape, and "W" shape in which four parallel tubes are connected to three substantially semi-circles to become one.

The distance between the centers of the adjacent linear light sources 102 is preferably 35 mm to 200 mm, more preferably 40 mm to 150 mm. By setting the distance in the above range, the power consumption of the direct type backlight device can be reduced, the assembly of the device can be facilitated, and the luminance unevenness of the light emitting surface can be suppressed.

The number of linear light sources 102 is not particularly limited. For example, when the direct type backlight device of the present invention is used for a 32-inch liquid crystal display device, the number of linear light sources may be, for example, even, odd, or odd number of 12, 8, 4, 2, etc. You can do it as a dog.

As a material of the reflecting plate 103, resin, metal, etc. colored by white or silver can be used, and resin is preferable from a viewpoint of weight reduction. In addition, although the color of the reflecting plate 103 is preferably white from the viewpoint of improving the brightness uniformity, white and silver may be mixed in order to highly balance the brightness and brightness uniformity.

The light diffusion plate 101 is a plate that diffuses and irradiates incident light.

As a material which comprises a light-diffusion plate, glass, the mixture of 2 or more types of resins which are difficult to mix, the thing which disperse | distributed the light-diffusion agent to transparent resin, and one type of transparent resin can be used. Among them, resins are preferable in terms of being lightweight and easy to mold, and one type of transparent resin is preferable in terms of easy brightness enhancement, and transparent in terms of easy adjustment of total light transmittance and haze. It is preferable to disperse the light diffusing agent in the resin.

The transparent resin is a resin having a total light transmittance of 70% or more based on JIS K7361-1 based on JIS K7361-1, a 2 mm-thick plate, for example, polyethylene, propylene-ethylene copolymer, polypropylene, polystyrene, aromatic The copolymer of a vinyl monomer and the (meth) acrylic-acid alkylester which has a lower alkyl group, a polyethylene terephthalate, a terephthalic acid- ethylene glycol cyclohexane ethanol copolymer, a polycarbonate, an acrylic resin, resin with an alicyclic structure, etc. are mentioned. In addition, (meth) acrylic acid is acrylic acid and methacrylic acid.

Among these, as transparent resin, water absorption of a polycarbonate, polystyrene, a copolymer of an aromatic vinyl monomer containing 10% or more of an aromatic vinyl monomer and a (meth) acrylic acid alkyl ester having a lower alkyl group, and a resin having an alicyclic structure Since this resin of 0.25% or less has little deformation due to moisture absorption, it is preferable in that a large light diffusing plate with less warpage can be obtained.

Resin which has an alicyclic structure is more preferable at the point that fluidity | liquidity is favorable and a large light-diffusion plate can be manufactured efficiently. The mixture of the resin having an alicyclic structure and the light diffusing agent combines the high transparency and high diffusivity required for the light diffusing plate, and the chromaticity is good.

Resin which has alicyclic structure is resin which has alicyclic structure in main chain and / or side chain. From the viewpoint of mechanical strength, heat resistance and the like, a resin containing an alicyclic structure in the main chain is particularly preferable. Examples of the alicyclic structure include a saturated cyclic hydrocarbon (cycloalkane) structure and an unsaturated cyclic hydrocarbon (cycloalkene, cycloalkyne) structure. From a viewpoint of mechanical strength, heat resistance, etc., a cycloalkane structure and a cycloalkene structure are preferable, and the cycloalkane structure is the most preferable especially. When the number of carbon atoms constituting the alicyclic structure is usually in the range of 4 to 30, preferably 5 to 20, more preferably 5 to 15, the mechanical strength, heat resistance and formability of the light diffuser plate are highly It is balanced and is suitable.

The ratio of the repeating unit having an alicyclic structure in the resin having an alicyclic structure may be appropriately selected depending on the purpose of use, but is usually 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more. . When the ratio of the repeating unit which has alicyclic structure is too small, heat resistance falls and it is unpreferable. In addition, repeating units other than the repeating unit which has an alicyclic structure in resin which has an alicyclic structure are suitably selected according to a use purpose.

Specific examples of the resin having an alicyclic structure include (1) a ring-opening polymer of a norbornene monomer and a ring-opening copolymer of a norbornene monomer with another monomer which can be ring-opened copolymerized with these, and a hydrogenated product thereof and an addition polymer of a norbornene monomer. Norbornene polymers such as addition copolymers of norbornene-based monomers with other monomers copolymerizable therewith; (2) monocyclic cyclic olefin polymer and its hydrogenated substance; (3) a cyclic conjugated diene polymer and its hydrogenated substance; (4) Polymers of vinyl alicyclic hydrocarbon monomers and copolymers of vinyl alicyclic hydrocarbon monomers with other monomers copolymerizable with these, hydrogenated substances thereof, hydrogenated compounds of aromatic rings of polymers of vinyl aromatic monomers and vinyl aromatics Vinyl alicyclic hydrocarbon polymers, such as the hydrogenated material of the aromatic ring of the copolymer of a monomer and the other monomer copolymerizable with this, etc. are mentioned.

Among them, from the viewpoints of heat resistance, mechanical strength and the like, norbornene polymers and vinyl alicyclic hydrocarbon polymers are preferable, and ring-opening polymer hydrogenated compounds of norbornene monomers, ring-opening air of norbornene monomers and other monomers which can be ring-opened copolymerized with these The hydrogenated substance of the aromatic ring of the copolymer of the aromatic hydrogenated substance, the aromatic ring of the polymer of a vinyl aromatic monomer, and the copolymer of the vinyl aromatic monomer and another monomer copolymerizable with this is more preferable.

The light diffusing agent is a particle having a property of diffusing light, and can be broadly classified into an inorganic filler and an organic filler. Examples of the inorganic fillers include silica, aluminum hydroxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, magnesium silicide, and mixtures thereof. Examples of the organic filler include acrylic resins, polyurethanes, polyvinyl chlorides, polystyrene resins, polyacrylonitriles, polyamides, polysiloxane resins, melamine resins, and benzoguanamine resins. Among these, as an organic filler, the fine particle which consists of a polystyrene resin, a polysiloxane resin, and these crosslinked material is preferable at the point which does not have high dispersibility, high heat resistance, and coloring (yellowing) at the time of shaping | molding, Among these, it is excellent in heat resistance More preferable are fine particles made of a crosslinked product of polysiloxane resin.

As the shape of the light diffusing agent, for example, a spherical shape, a cubic shape, a needle shape, a rod shape, a fusiform shape, a plate shape, a scale shape, a fiber shape, and the like can be cited. Among them, the light diffusion direction is isotropic. A spherical shape is preferable at the point which can be made into. The light diffusing agent is used in the state of being uniformly dispersed in the transparent resin.

The ratio of the light diffusing agent to be dispersed in the transparent resin can be appropriately selected depending on the thickness of the light diffusing plate, the spacing of the linear light sources, or the like. However, the content of the light diffusing agent is usually such that the total light transmittance of the dispersion is 60% to 98%. It is preferable to adjust the content, and it is more preferable to adjust the content of the light diffusing agent so as to be 65% to 95% or the like. By making total light transmittance into the said suitable range, a brightness | luminance and a brightness | luminance uniformity can be improved more.

In addition, total light transmittance is the numerical value measured on the board of 2 mm thickness which is smooth on both sides based on JIS K7361-1, and haze is the numerical value measured on the board of 2 mm thickness which is smooth on both sides by JIS K7136.

It is preferable that it is 0.4 mm-5 mm, and, as for the thickness of the light-diffusion plate 101, it is more preferable that it is 0.8 mm-4 mm. By setting the thickness of the light diffusion plate to the appropriate range, warpage due to its own weight can be suppressed and the shaping can be facilitated.

Next, the outline of the light diffusion plate 101 will be described.

FIG. 2 is a front partial cross-sectional view illustrating the surface shape of the light diffusion plate 101 of the direct type backlight device according to the embodiment of FIG. 1 in more detail. For convenience of description, in FIG. 2, only two adjacent linear light sources 102a and 102b are partially shown among the plurality of linear light sources 102.

The light diffusion plate 101 includes a light incident surface S260 to which light from the linear light source 102 is incident, and a light exit surface S250 to diffusely irradiate light incident from the light incident surface, The uneven structure is formed in a part of at least one of the light exit surface and the light incident surface.

In the light diffusing plate, when the outer diameter of the linear light source is projected perpendicular to the light diffusing plate, the uneven structure of the projected portion and the intermediate positions of the linear light sources adjacent to each other in the light diffusing plate are determined. The uneven structure of the part which is centered and has the same width as the outer diameter of the said linear light source is a shape different from each other. Here, "it has a different shape" includes the case where the shape of the uneven structure is different in at least one of the light incident surface and the light exit surface of the light diffusion plate. In addition, the "different shape" is, for example, where the concave-convex structure is constituted by a plurality of convex portions (prism portions), and each convex portion is polygonal, the vertex angle (right angle) of the convex portion is ± 1 degree. Speaks the same shape as above. In this case, the case where the shape of the concave-convex structure is different also includes a case in which at least one convex portion among the plurality of convex portions has a different shape.

In the example shown in FIG. 2, the uneven structure in the regions R271, R281, R273, and R283 projecting the outer diameters of the linear light sources 102a and 102b perpendicular to the light diffusion plate 101 and the linear light sources ( The concave-convex structures in the regions R272 and R282 on the light diffusion plate having the same width as the linear light source 102 and centered on the intermediate position 241 of the 102a and 102b are different shapes. That is, the following conditions (i) and (ii):

(i) R272 has a different uneven structure than R271 and R273,

(Ii) R282 has a different uneven structure than R281 and R283

At least any one of these conditions is satisfied, so that "the uneven structure in the area | region which projected the outer diameter of the said linear light source perpendicular to a light-diffusion plate, and the intermediate position of the said linear light source are centered, The uneven structure in the area | region on the light-diffusion plate of the same width as the outer diameter of a linear light source differs. "

Although it does not specifically limit about the structure of the light-incidence surface S260 of the light-diffusion plate 101, and the other area | region (namely, the area which is not contained in area | region R271-R273 and R281-R283) of the light emission surface S250. For example, an uneven structure in an area group including an area in which the outer diameter of the linear light source is projected perpendicular to the light diffusing plate, and a width equal to the outer diameter of the linear light source centered on an intermediate position of the linear light source. The uneven structure in the region group including the region on the light diffusion plate can be different.

More specifically, for example, as shown in FIG. 2, a region group including a region where the light incident surface S260 and the light emitting surface S250 respectively project the linear light source outer diameter perpendicular to the light diffusion plate ( R251, R261, R253, and R263) and the area groups R252 and R262 including the regions on the light diffusion plate having the same width as the linear light source with respect to the intermediate position of the linear light source. The concave-convex structure may be different among the region groups.

Among the region groups R251, R261, R253, and R263 and the region groups R252 and R262, the "uneven structure" is specifically, the following aspect is mentioned, for example.

(1) R251-R252-R253: uneven structure (A)-flat surface-uneven structure (A)

    R261-R262-R263: Flat Surface-Flat Surface-Flat Surface

(2) R251-R252-R253: flat surface-uneven structure (B)-flat surface

    R261-R262-R263: Flat Surface-Flat Surface-Flat Surface

(3) R251-R252-R253: uneven structure (A)-uneven structure (B)-uneven structure (A)

    R261-R262-R263: Flat Surface-Flat Surface-Flat Surface

(4) R251-R252-R253: flat surface-uneven structure (B)-flat surface

    R261-R262-R263: Uneven structure (A)-Flat surface-Uneven structure (A)

(5) R251-R252-R253: uneven structure (A)-uneven structure (A)-uneven structure (A)

    R261-R262-R263: Flat surface-Uneven structure (B)-Flat surface

(6) R251-R252-R253: uneven structure (A)-uneven structure (A)-uneven structure (A)

    R261-R262-R263: uneven structure (B)-flat surface-uneven structure (B)

(7) R251-R252-R253: flat surface-uneven structure (B)-flat surface

    R261-R262-R263: uneven structure (A)-uneven structure (A)-uneven structure (A)

(8) R251-R252-R253: uneven structure (B)-flat surface-uneven structure (B)

    R261-R262-R263: uneven structure (A)-uneven structure (A)-uneven structure (A)

(9) R251-R252-R253: uneven structure (B)-uneven structure (C)-uneven structure (B)

    R261-R262-R263: uneven structure (A)-uneven structure (A)-uneven structure (A)

(10) R251-R252-R253: uneven structure (A)-uneven structure (A)-uneven structure (A)

     R261-R262-R263: uneven structure (B)-uneven structure (C)-uneven structure (B)

(11) R251-R252-R253: uneven structure (A)-flat surface-uneven structure (A)

     R261-R262-R263: uneven structure (B)-uneven structure (C)-uneven structure (B)

(12) R251-R252-R253: Uneven structure (A)-Uneven structure (D)-Uneven structure (A)

     R261-R262-R263: uneven structure (B)-uneven structure (C)-uneven structure (B)

(13) The structure of R251-R252-R253 which replaced the structure of R261-R262-R263 in each of said (1)-(12).

In the above, the uneven structure (A) to the uneven structure (D) refers to a shape different from each other.

The light diffusing plate may have an uneven structure on only one surface thereof, as in the above aspects (1) to (3), but preferably the uneven structure is at least a part of the light exit surface and at least a part of the light incident surface of the light diffusion plate. It can be formed on both sides of. Particularly, in the light incidence surface, an uneven structure is provided in a region (region R282 in FIG. 2) on the light diffusion plate incidence surface having the same width as that of the linear light source, centered at least on the intermediate position of the linear light source. It is desirable to have.

By providing the concave-convex structure on the light incident surface side, the Fresnel reflection when the light from the linear light source enters into such an area as the region R282, and when the light from the linear light source enters into such an area. It is possible to prevent the increase in the projection area of the linear light source. Thereby, the light incident amount per unit area of the light incident surface between the linear light sources can be improved, and the dark part between the linear light sources can be brightened.

On the other hand, by providing a concave-convex structure on at least a part of the light exit surface, the light incident from the light exit surface can be refracted in the desired direction and exited. The light can be reversed, darkening the light just above the linear light source. From the above, luminance unevenness can be reduced more.

In the present invention, the concave-convex structure on the light diffusing plate is, for example, substantially parallel to the longitudinal direction of the linear light source 102 (in the range of parallel ± 5 °), for example, as shown in FIG. 1. Examples of the prism alignment are formed in which the linear prisms extending substantially parallel are arranged, and the cross section perpendicular to the longitudinal direction of the linear light source 102 has various cross-sectional shapes. In addition, the angle formed by the linear light source 102 and the linear prism may be in the range of the parallel ± 60 degrees.

As said cross-sectional structure, the convex part of the shape containing a curve, the convex part of a polygonal shape, a substantially flat part, and a combination shape thereof are mentioned, for example. As convex part of the shape containing the said curve, the convex part included in the part which protrudes curves, such as a circular arc, an ellipse arc, a parabolic arc, and the curve which these are distorted, is mentioned. Examples of the convex portions of the polygonal shape include various convex portions such as triangles, trapezoids, and the like, pentagons, hexagons, and heptagons. Particularly, the left and right bottom angles are approximately equal (within a range of ± 10 °). In particular, the cross-sectional structure is preferably symmetric about an axis parallel to the thickness direction of the light diffusion plate in the cross section. By adopting such a cross-sectional structure, advantages such as easy design and unevenness in luminance can be obtained even if observed from either of the left and right sides. In addition, when the emitting surface of the backlight device is made upright in the direction in which prism alignment is horizontal, the light is emitted from the upper and lower direction (that is, when the light emitting surface is observed from the upper right direction in the drawing in FIG. The luminance distribution in the case where the exit surface is observed can be symmetrical.

The following are mentioned as an example of a more specific cross-sectional structure.

As shown in Fig. 3, the first example of the cross-sectional structure is a triangle 321 in which the convex portions of the polygonal shapes are substantially equal to the left and right bottom angles 322 and 323, and the bottom angle portions of the adjacent triangles 321 are mutually equal. It is a structure arranged to contact.

As shown in Fig. 4, the second example of the cross-sectional structure is a trapezoid 421 having a flat portion (normal flat portion) 422 at which the polygonal convex portions are substantially flat on the top, and the bottom of the adjacent trapezoid 421 is located. Each part is arranged to be in contact with each other.

As shown in FIG. 5, the third example of the cross-sectional structure is a triangle 521 having a polygonal convex portion having substantially equal left and right bottom angles, and having a substantially flat portion 522 provided between adjacent triangles 521. , A combination of triangles 521 and approximately flat portions 522.

As shown in FIG. 6, the fourth example of the cross-sectional structure is a pentagon with a triangle 621 having a bottom angle smaller than the bottom angle of the trapezoid 622 is added to the top flat portion of the trapezoid 622 of the polygonal shape. The bottom angle portions of adjacent trapezoids 622 are arranged to be in contact with each other.

As shown in FIG. 7, the fifth example of the cross-sectional structure is a pentagon with a triangle 721 having a bottom angle wider than the bottom angle of the trapezoid 722 at the top flat portion of the trapezoid 722 of the polygonal shape. The bottom angle portions of the adjacent trapezoids 722 are arranged to be in contact with each other.

As shown in FIG. 8, in the 6th example of sectional structure, the convex part of the shape containing a curve is a semicircle 821, and is arrange | positioned so that adjacent semicircle 821 may contact each other.

As shown in FIG. 9, the 7th example of sectional structure is a structure in which the convex part of the shape containing a curve is a semi-ellipse 921, and is arrange | positioned so that adjacent semi-elliptic 921 may contact each other.

As shown in FIG. 10, the 8th example of a cross-sectional structure is a structure where the convex part of the shape containing a curve is a parabolic arc 1021, and arrange | positioned so that adjacent parabolic arcs 1021 may mutually contact.

As shown in FIG. 11, the 9th example of sectional structure is a structure which the convex part of the shape containing a curve alternately combined the semicircle 1121 and the semiellipse 1112. As shown in FIG.

As shown in FIG. 12, in the tenth example of the cross-sectional structure, a convex portion of a shape including a curve includes a semicircle 1221 and a semi-elliptic 1222, and a plurality of semicircular 1221 and the semi-elliptic 1222 are spaced apart. It is a structure combined.

As shown in FIG. 13, the 11th example of sectional structure is a structure which the convex part of the shape containing a curve alternately combined the semicircle 1321 and the triangle 1322. As shown in FIG.

In the present invention, the preferred height of the concave-convex structure is Ra (max), the maximum value of the centerline average roughness Ra measured along various directions on the light incidence plane or the light exit surface of the light diffusion plate, (max) is 1 micrometer-1,000 micrometers.

In addition, in this specification, a "roughly flat part" may have fine unevenness | corrugation on the surface. For example, in the shape shown in FIG. 5, although no unevenness | corrugation is shown on the substantially flat part 522, you may provide relatively fine unevenness | corrugation in this part compared with the triangle 521. FIG. The preferred height of the fine unevenness is 0.0001 mu m to 3 mu m as Ra (max). In addition, the height of the minute unevenness may be in the range of 0.0001% to 5% with respect to Ra of the uneven structure.

In the above embodiment, the region group includes a region in which the linear light source outer diameter is projected perpendicular to the light diffusing plate, and an area on the light diffusing plate having the same width as the outer diameter of the linear light source centering on the intermediate position of the linear light source. Although the different uneven structure was provided in the 2 area | region group of the area | region group containing these, as another embodiment of this invention, you may arrange | position an uneven structure different from this. For example, the aspect which the cross section perpendicular | vertical to the longitudinal direction of the linear light source of the said uneven structure contains two or more types of convex parts of different shape, and changes as the abundance ratio of the two or more types of convex parts moves away from the said linear light source. You can do More preferably, in the linear prism of at least one of the light exit surface and the light incident surface as it faces away from the linear light source and faces an intermediate position of the linear light sources adjacent to each other, The mixing ratio of two or more types of linear prisms may be changed continuously or stepwise, and the ratio of linear prisms having a large inclination angle may increase continuously or stepwise as they are directed toward the intermediate position of the linear light sources adjacent to each other. By arranging such a linear prism, the change in the shape of the uneven structure gradually changes as the distance from the linear light source increases, and as a result, the luminance unevenness can be reduced as compared with the case where the uneven shape changes abruptly.

Specifically, for example, as shown in FIG. 16, as the uneven structure, the convex portions 1621a and 1621b having different shapes are arranged in units at a predetermined ratio (1: 4 in FIG. 16) as a unit. This unit may be repeated and the abundance ratio of the convex parts 1621a and 1621b may be changed as it moves away from the linear light source.

The change in abundance may be continuous or stepwise. For example, as shown in FIG. 15, the distance corresponding to the center of the linear light source from the intermediate position 1441 of the distance between the centers of adjacent linear light sources 1402a and 1402b is divided into several zones (FIG. 15, A, B, C, and D), and the abundance ratio of the two or more convex portions in each region corresponding to the light incidence plane and / or the light exit plane of the light diffusion plate 1401. Can be set to a predetermined value. The number of these zones is not particularly limited, but may be increased to 15 to 20 steps and the like without being limited to the above.

Also, as the arrangement of the separate uneven structure, for example, a cross section perpendicular to the longitudinal direction of the linear light source of the uneven structure includes both the convex portion and the substantially flat portion, and their abundance ratio is from the linear light source. The sun can be changed continuously or stepwise as it moves away.

Specifically, for example, as shown in Fig. 18, the convex-concave structure is a unit of a state in which convex portions 1821a and flat portions 1821b which are substantially flat portions are alternately arranged, and the unit is repeated. In addition, it is possible to have a structure in which the width 1822b of the flat portion 1821b is continuously or stepwise changed as it moves away from the linear light source.

Here, the width 1822b of the flat portion 1821b is set to a predetermined value for each of a plurality of zones on the light incident surface and / or the light exit surface of the light diffusion plate, as described above with reference to FIG. It is also possible to achieve intermittent changes. In addition, the number of these zones is not particularly limited, but is not limited to four zones, and may be increased in 15 to 20 steps and the like. For example, as shown in FIG. 19, according to the distance Ln from the linear light source on the light diffusion plate, or at an angle θs with respect to the linear light source closest to the surface of the light diffusion plate. Accordingly, it is also possible to continuously change the width 1822b of the flat portion 1821b to achieve a continuous change.

Another arrangement of the uneven structure, the slope of the linear prism of at least one of the light exit surface or the light incidence plane as it moves away from the linear light source and faces an intermediate position of the linear light sources adjacent to each other The angle formed by the plane perpendicular to the thickness direction of the light diffusion plate may be increased continuously or stepwise.

Specifically, for example, similarly to the other examples described above, the light incidence plane and / or light exit plane of the light diffusion plate is divided into a plurality of zones, and linear prisms having the same structure are disposed in each zone, The farther the area is from the linear light source, the larger the angle between the slope of the linear prism and the plane perpendicular to the thickness direction of the light diffusion plate is, so that the angle can be increased in steps. In such a configuration, the change in the shape of the uneven structure gradually changes as the shape of the uneven structure moves away from the linear light source. As a result, the luminance unevenness can be reduced as compared with the case where the uneven shape changes abruptly.

As a more preferable aspect of the direct type backlight device of the present invention, there is further provided an optical sheet provided on the light exit surface side of the light diffusing plate, and the concave-convex structure is configured to show the distribution of the predetermined preferred total light transmittance described in detail below. have. That is, in the direct type backlight device, in the cross section perpendicular to the longitudinal direction of the linear light source, any linear light source is called A, and the linear light source adjacent to the linear light source A is called B. And an intermediate position at which the intermediate position of the linear light source A and the linear light source B is projected on the light incidence plane is X, and between the linear light source A and the linear light source B. Any point on the light incidence plane located at and closer to the linear light source A than the intermediate position X is P, and the center of the linear light source A is C, and the center The total light transmittance Tp at the point P of the light incident from (C) in the direction of the point P is from the point C of the light incident in the direction of the intermediate position X from the center C. It is preferable to become smaller than the total light transmittance Tx in X). At this time, it is more preferable that the concave-convex structure is provided on the surface of the light diffusing plate so that the point P approaches the point X and increases substantially. In addition, the "approximately high" includes the case of mainly increasing continuously or stepwise, but also includes the case of partially lowering. It is preferable to satisfy such an "approximately high" aspect in 50% of the range of the total area of light incidence surface at least.

The said preferable aspect is demonstrated with reference to FIG. In FIG. 19, the relationship of the said angle in the cross section perpendicular | vertical to the longitudinal direction of a linear light source is shown. In the example of FIG. 19, the linear light source 102a and the linear light source 102b are shown as the linear light source A and the linear light source B mentioned above. A line perpendicular to the light diffusing plate 101 at the bisector of the distance L between the center 1973a (= the point C) of the linear light source 102a and the center 1973b of the linear light source 102b. The intersection 1974 of 1942 and the light incident surface S1960 corresponds to the point X. The total light transmittance at said point X of the light which entered the point X from the center 1973a (point C) of the linear light source 102a (linear light source A) is Tx. On the other hand, at the point P of light incident from the center 1973a (point C) to the point P on the light incident surface on the side closer to the linear light source 1973a (A) than the point X, The total light transmittance of Tp is Tp. It becomes a said preferable aspect by Tp becoming smaller than Tx here. Moreover, Tp becomes substantially high as point P approaches X, and it becomes a more preferable aspect than the above. By such an aspect, a high brightness uniformity can be achieved.

The optical sheet may be one sheet or a plurality of sheets. As said optical sheet, it is preferable to contain one or more sheets which have a function as a light-ray direction conversion element. The sheet having a function as a light beam direction conversion element is a sheet in which the incident angle of the incident light and the exit light of the exiting light are different, and the directions in which the peaks of the incident light and the exiting light peak are different may be different. You may have it.

In addition, it is preferable that the optical sheet contains at least one reflective polarizer. It is preferable to provide a reflective polarizer on the light exit surface side. As a reflective polarizer, a reflective polarizer (for example, described in Japanese Patent Publication No. 1994-508449) using a difference in reflectance of a polarization component by a Brewster angle; Reflective polarizer using selective reflection characteristics by cholesteric liquid crystal; Specifically, the laminating agent (for example, the thing of Unexamined-Japanese-Patent No. 1991-45906) of the film which consists of a cholesteric liquid crystal, and a quarter wave plate; Reflective polarizers having a fine metal linear pattern (for example, those described in Japanese Patent Laid-Open No. 1990-308106); A reflective polarizer (for example, described in JP-A-1997-506837) which laminates at least two polymer films and uses anisotropy of reflectance due to refractive anisotropy; A reflective polarizer having a sea island structure formed of at least two kinds of polymers in the polymer film and using the anisotropy of reflectance due to refractive anisotropy (for example, described in the specification of US Patent No. 5,825,543); Reflective polarizer which disperse | distributes a particle | grain in a polymer film, and uses the anisotropy of the reflectance by refractive index anisotropy (for example, the thing of Unexamined-Japanese-Patent No. 1999-509014); A reflective polarizer (for example, described in JP-A-1997-297204) and the like may be used in which the inorganic particles are dispersed in the polymer film and use the anisotropy of reflectance based on the scattering ability difference by size.

In the direct type backlight device of the present invention, as a more preferable aspect, the length of the line connecting the center C and the point P is referred to as LCP, and the center C is projected perpendicular to the light incident surface. One point is called Q, and the length of the line connecting the center C and the point Q is called LCQ, and the point Q of the light incident from the center C in the direction of the point Q is The total light transmittance in is referred to as Tq, and it is preferable to satisfy the relationship of 0.2 × (Tq · LCP / LCQ) ≦ Tp ≦ 5.0 × (Tq · LCP / LCQ).

The more preferable aspect is demonstrated again with reference to FIG. In the example of FIG. 19, the length of the line segment 1943 connecting the point P and the point 1973a (point C) corresponds to the length LCP mentioned above. On the other hand, the intersection of the straight line 1945 perpendicular to the light diffusion plate 101 and the light incident surface S1960 passing through the point 1973a (point C) becomes the point Q, and the point C The total light transmittance at the point Q of light incident in the direction of (Q) is Tq, and the distance between CQs is LCQ. By satisfying the above relationship, Tp, Tq, LCP, and LCQ can be used as the above-mentioned preferred embodiments, and higher luminance uniformity can be achieved. Although the above relationship is preferably established on the entire surface of the light diffusion plate, a favorable effect can be obtained when this relationship is established in an area of 50% of the entire surface of the light diffusion plate.

The direct type backlight device of the present invention is not limited to the above embodiment, and can be changed within an equivalent range. In addition, other optional components may 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. As such an optical member, a diffusion sheet and a prism sheet are mentioned, for example. These optical members can be provided in the light-diffusing plate on the light emission surface side, for example. Moreover, the housing, the electricity supply device, etc. for configuring a backlight device can be provided suitably. In addition, the direct type backlight device of the present invention can be suitably used for a method of controlling the lighting and turning off of the light source in accordance with the brightness in the screen of the liquid crystal display device.

The liquid crystal display of the present invention includes the direct type backlight device of the present invention. The liquid crystal display of the present invention is, for example, twisted nematic (TN) mode, super twisted nematic (STN) mode, hybrid alignment nematic (HAN) mode, vertical alignment (VA) mode, multi-domain vertical alignment (MVA). ) Mode, in-plane switching (IPS) mode, optically compensated birefringence (OCB) mode, and the like.

Example

Although an Example is given to the following and this invention is demonstrated in more detail, this invention is not limited at all by these Examples. In addition, a part and% are a basis of weight unless there is particular restriction.

Production Example 1 [Pallet (A) for Light Diffusion Plate]

As a transparent resin, a resin having an alicyclic structure (manufactured by Nippon Xeon, Zeonoa 1060R, water absorption rate 0.01%) was kneaded with a twin screw extruder, extruded into a strand shape, cut with a fertilizer, and the pallet for light diffusion plate (A) Manufactured. Using this light-diffusion plate pallet (A) as a raw material, the test board of thickness 100mm x 50mm was formed by using both injection molding machines (mold clamping force 1000kN) and thickness 2mm smooth. The total light transmittance and the haze of this test plate were measured based on JIS K7361-1 and JIS K7136 using an integrating sphere system color shade turbidimeter. The test plate had a total light transmittance of 92% and a haze of 0.3%.

Production Example 2 [Pallet for Light Diffusion Plate (B)]

Instead of the resin, 99.9 parts of the resin and 0.1 part of fine particles made of a crosslinked product of a polysiloxane polymer having an average particle diameter of 2 μm as a light diffusing agent were mixed, and a light diffusion plate pallet (B) was produced in the same manner as in Production Example 1. did. Using the light-diffusion plate pallet (B) as a raw material, the test plate similar to the said manufacture example 1 was created, and the total light transmittance and haze were measured by the same method. The test plate had a total light transmittance of 94% and a haze of 89%.

<Example 1>

A backlight device schematically shown in FIG. 14 was created. A reflector sheet (RF188, manufactured by Tsujiden Co., Ltd.) was affixed to an inner surface of an aluminum case (not shown) having a width of 730 mm, a depth of 405 mm, and a depth of 32.5 mm to form a reflector plate 1403, and a diameter of 15.5 mm and a length of 800 mm were obtained. Hot cathode tubes (Erebam Co., Ltd.) 1402 were installed in parallel in four internal dimension width directions. The distance 1413 between centers of a hot cathode tube was 100 mm, and the distance 1411 from the reflecting plate to the center of a hot cathode tube was 8.75 mm. The vicinity of the electrode portion was fixed with a silicone sealant to install an inverter.

Next, using a mold part having a predetermined shape in an injection molding machine (mold clamping force 4,410 kN), using the light diffusion plate pallet A obtained in Production Example 1 as a raw material, the light was subjected to a cylinder temperature of 280 degrees and a mold temperature of 85 degrees. The diffuser plate was molded. The obtained light-diffusion plate was 2 mm thick and 750 mm x 430 mm rectangular flat plate shape, The predetermined | prescribed pattern of the uneven | corrugated structure in which the triangular prism was lined substantially parallel was formed in one surface. The said predetermined pattern is explained in full detail below.

Next, the obtained light diffusing plate was placed on an aluminum case provided with the hot cathode tube with the other side (the surface without the uneven structure: the light incident surface) being the hot cathode tube side. At this time, the distance between the center of the hot cathode tube and the light incidence plane of the light diffusion plate was 25 mm.

The uneven structure on the light diffusing plate used in the present embodiment will be described with reference to FIGS. 15 and 16. In the state where the light diffusion plate 1401 is provided, the distance corresponding to the center of the hot cathode tube from the middle 1441 of the distance between the centers of the adjacent hot cathode tubes (1402a and 1402b in FIG. 15) is A (4 mm), It was divided into four sections: B (30 mm), C (10 mm) and D (6 mm). In each zone of the light exit surface of the light diffusion plate 1401, a prism-shaped convex portion 1621a having a triangular cross section with a vertex angle of 60 ° as shown in FIG. 16, and a triangular cross section with a vertex angle of 95 ° The prism-shaped convex part 1621b which has the structure was provided in the aspect shown below.

A: 1616a / 1621b = 1/4

B: 1616a / 1621b = 1/3

C: 1616a / 1621b = 1/4

D: 1616a / 1621b = 1/5

The above notation indicates the arrangement of the convex portions 1621a and 1621b in the repeating unit of the uneven structure pattern. For example, in the case of "1621a / 1621b = 1/4", as shown in FIG. 16, one triangular convex part 1621a of 60 degrees of vertices, and the triangular convex part 1621b of 95 degrees of vertices is shown. Four uneven structures lined up are one unit, and the unit repeats this structure.

The bottom sides 1622a and 1622b of the convex portions 1621a and the convex portions 1621b were 70 µm. In addition, the light incidence surface was made into the flat surface.

Moreover, on the upper surface (light emission surface) of this light-diffusion plate, a diffusion sheet ("188GM3", the product made by Kimoto), a prism sheet ("BEFIII-10T", the Sumitomo rims company make), and a reflective polarizer ("DBEF") -D ", manufactured by Sumitomo Industries, Inc., and a polarizing plate (" HCL2-2518 ", manufactured by Sanrittsu Co., Ltd.) were disposed in this order.

Subsequently, the obtained direct type backlight device was energized with a tube current of 175 mA, the hot cathode tube was turned on, and the front of the 100 points at equal intervals on the center line in the shorter direction (inner direction of the case) using a two-dimensional color distribution measuring device. The luminance in the direction was measured. The measurement value of the center luminance was 8462 cd / m ² . In addition, according to the following formulas 1 and 2, the luminance average value (front luminance) La and the luminance unevenness Lu in the front direction were obtained. The luminance unevenness was 1.4%. The results are shown in Table 1.

Luminance average value La = (L1 + L2) / 2 (Equation 1)

Luminance Stain Lu = ((L1-L2) / La) × 100 (Equation 2)

L1: Average of the luminance maximum value just above the plurality of hot cathode tubes installed

L2: Average of local minima interspersed with local maxima

In addition, the luminance unevenness is an index indicating the uniformity of the luminance, and the numerical value increases when the luminance unevenness is bad.

<Example 2>

The direct type backlight device was produced similarly to Example 1 except having made the uneven structure pattern of the light-diffusion plate as mentioned above.

The uneven structure on the light diffusion plate used in the present embodiment will be described with reference to FIGS. 17 and 18. In the state where the light diffusion plate 1701 is provided, the distance corresponding to the center of the hot cathode tube from the middle 1441 of the distance between the centers of adjacent hot cathode tubes (1402d and 1402e in FIG. 17) is A (5 mm), It was divided into five sections: B (5 mm), C (5 mm), D (20 mm), and E (15 mm). In each zone of the light exit surface of the light diffusion plate 1701, a prism-shaped convex portion 1821a having a triangular cross section with a vertex angle of 90 degrees as shown in Fig. 18, and a flat portion 1821b are alternately arranged. Prepared. The bottom side 1822a of the convex part 1821a was 70 micrometers in the whole area, while the width 1822b of the flat part 1821b was as follows for each area.

A: 46.67 mu m

B: 35㎛

C: 17.5㎛

D: 7㎛

E: 0 μm

In addition, the light incidence surface was made into the flat surface. The obtained direct type backlight device was evaluated similarly to Example 1. The results are shown in Table 1.

<Example 3>

The direct type backlight device was produced similarly to Example 1 except having made the uneven structure pattern of the light-diffusion plate as mentioned above.

The uneven structure on the light diffusion plate used in the present embodiment will be described with reference to FIG. 20 and the like. In the state where the light diffusion plate 2001 is provided, the distance corresponding to the center of the hot cathode tube from the middle 1441 of the distance between the centers of the adjacent hot cathode tubes (1402f and 1402g in FIG. 20) is A (15 mm), It was divided into three sections: B (10 mm) and C (25 mm).

On the light exit surface S2050 of the light diffusion plate 2001, a prism-shaped convex portion having a triangular cross section having a vertex angle of 100 ° and a bottom side of 70 μm on the front surface thereof is provided without a gap of a flat portion (a flat portion does not exist). In other words, the bottom triangular portions adjacent to each other are in contact with each other.

In addition, in each area | region of the light-incidence surface S2060 of the light-diffusion plate 2001, area | region A was made into the flat surface. In the zone B, prismatic protrusions and flat portions having a triangular cross section as shown in Fig. 18 were alternately provided. However, the angle of vertex of a triangular shape was 130 degrees, the bottom side was 70 micrometers, and the width | variety of the flat part was 70 micrometers. In the region C, prismatic protrusions having a triangular cross section having a vertex angle of 130 ° and a bottom side of 70 μm were provided without a gap of a flat portion.

The obtained direct type backlight device was evaluated similarly to Example 1. The results are shown in Table 1.

<Example 4>

The linear light source was 8.0 mm in diameter and 800 mm in length of a hot cathode tube (manufactured by Erebam Co., Ltd.), and the distance 1411 from the reflecting plate to the center of the hot cathode tube was 8.75 mm. A backlight device was created. The obtained direct type backlight device was evaluated similarly to Example 1. The results are shown in Table 1.

<Example 5>

The linear light source was 8.0 mm in diameter and 800 mm in length of a hot cathode tube (manufactured by Erebam Co., Ltd.), and the distance 1411 from the reflecting plate to the center of the hot cathode tube was 5.0 mm. A backlight device was created. The obtained direct type backlight device was evaluated similarly to Example 1. The results are shown in Table 1.

Comparative Example 1

The direct type backlight device was created and evaluated similarly to Example 1 except having printed the uneven structure pattern of the light-diffusion plate as follows. The results are shown in Table 1.

A prism shape having a prism shape having a triangular cross section of a vertex angle of 130 ° and a bottom side of 70 μm on the incidence side is provided without a gap of a flat portion, and a prism shape having a triangular cross section of a vertex angle of 100 ° and a bottom side of 70 μm on an exit side The convex part of was provided without the gap of a flat part.

Comparative Example 2

The direct type backlight device was created and evaluated similarly to Example 1 except having made the uneven structure pattern of the light-diffusion plate as follows. The results are shown in Table 1.

The prism-shaped convex part which has a triangular cross section of a vertex angle of 90 degrees and a bottom side of 70 micrometers was provided only on the exit side, without the gap of a flat part.

Comparative Example 3

Except having made the linear light source the same as Example 4, the direct type backlight device was created and evaluated similarly to the comparative example 1. The results are shown in Table 1.

<Comparative Example 4>

Except having made the linear light source the same as Example 4, the direct type backlight device was created and evaluated similarly to the comparative example 2. The results are shown in Table 1.

TABLE 1

TABLE 2

<Example 6>

A backlight device schematically shown in FIG. 21 was created. The inner surface of an aluminum case (not shown) with a width of 730 mm, a depth of 405 mm, and a depth of 25 mm was attached to a reflector sheet (1032 manufactured by Tsujiden Co., Ltd., RF188) to form a reflector plate 2103. Four cathode tubes (Erebam Co., Ltd.) 1402 were installed in parallel with the inner dimension width direction. The distance 2113 between the centers of the hot cathode tubes was 90 mm, and the distance 2111 to the center of the hot cathode tubes was 9.75 mm using a reflecting plate. The vicinity of the electrode portion was fixed with a silicone sealant to install an inverter.

Next, using a mold part of a predetermined shape in an injection molding machine (mold clamping force 4,410 kN), using the light diffusion plate pallet A obtained in Production Example 1 as a raw material, under the conditions of a cylinder temperature of 280 degrees and a mold temperature of 85 degrees The diffuser plate was molded. The light diffusing plate thus obtained is a rectangular plate having a thickness of 2 mm and a size of 750 mm x 430 mm. On one surface thereof, a predetermined pattern of a concave-convex structure in which a plurality of triangular prisms are arranged substantially in parallel is formed. Predetermined patterns were formed in which the prisms were mixed in a predetermined gradation. The said predetermined pattern is explained in full detail below.

Next, the obtained light diffusing plate was placed on an aluminum case provided with the hot cathode tube, with the other side being the hot cathode tube side. At this time, the distance between the center of the hot cathode tube and the light incidence plane of the light diffusion plate was 15.25 mm. In addition, the distance (2111 + 2112) between the light incident surface of the reflecting plate 2003 and the diffusion plate 2001 was 25 mm.

The uneven structure on the light diffusing plate used in the present embodiment will be described with reference to FIGS. 22 and 23. In the state where the light diffusion plate 2101 is provided, the distance corresponding to the center of the hot cathode tube from the middle 2141 of the distance between the centers of adjacent hot cathode tubes (2102a and 2102b in FIG. 22) is A (20 mm), It was divided into nine sections: B (1.5 mm), C (1 mm), D (1.5 mm), E (6 mm), F (1.5 mm), G (1 mm), H (1.5 mm) and I (11 mm). Each region of the light incidence plane of the light diffusion plate 2101 has a prism-shaped convex portion 2321a having a triangular cross section with a vertex angle of 170 ° as shown in FIG. 23, and a triangular cross section with a vertex angle of 160 °. The prism shape convex part 2321b which has a prism shape, and the prism shape convex part 2321c which has a triangular cross section with a vertex angle of 150 degrees were provided in the aspect shown below.

A: 2321a / 2321b / 2321c = 1/0/0

B: 2321a / 2321b / 2321c = 3/1/0

C: 2321a / 2321b / 2321c = 1/1/0

D: 2321a / 2321b / 2321c = 1/3/0

E: 2321a / 2321b / 2321c = 0/1/0

F: 2321a / 2321b / 2321c = 0/3/1

G: 2321a / 2321b / 2321c = 0/1/1

H: 2321a / 2321b / 2321c = 0/1/3

I: 2321a / 2321b / 2321c = 0/0/1

The above notation indicates the arrangement of the convex portions 2321a, 2321b, and 2321c in the repeating unit of the uneven structure pattern. For example, in the case of "2321a / 2321b / 2321c = 1/0/0", only the triangular convex part 2321a of the vertex angle 170 degree | times shows the structure which is repeated. In the case of `` 2321a / 2321b / 2321c = 3/1/0 '', the concave-convex structure in which three triangular convex portions 2321a with a vertex angle of 170 degrees and one triangular convex portion 2321b with a vertex angle of 160 degrees line up is 1 Let it be a unit and the structure which this unit is repeating is shown. In the case of `` 2321a / 2321b / 2321c = 0/3/1 '', the concave-convex structure in which three triangular convex portions 2321b with a vertex angle of 160 degrees and one triangular convex portion 2321c with a vertex angle of 150 degrees line up is 1 Let it be a unit and the structure which this unit is repeating is shown.

The bottom edges 2322a, 2322b, and 2322c of the convex portions 2321a, the convex portions 2321b, and the convex portions 2321c were 70 mu m.

On the other hand, in the light exit surface, as shown in FIG. 3, the prism shape of the prism shape of a vertex angle of 100 degrees and a bottom side of 70 micrometers was provided in the front surface.

Moreover, on the upper surface (light emission surface) of this light-diffusion plate, the diffusion sheet ("188GM3", the product made by Kimoto), the prism sheet ("BEFIII-10T", the Sumitomo rims company make), and the reflective polarizer ("DBEF") as an optical sheet -D ", manufactured by Sumitomo Co., Ltd., and a polarizing plate (" HCL2-2518 ", manufactured by Sanrittsu Co., Ltd.) were installed in this order.

Subsequently, the obtained direct type backlight device was energized at a tube current of 175 mA, the hot cathode tube was turned on, and a two-dimensional color distribution measuring device was used to equip 100 points at equal intervals on the center line in the shorter direction (inner direction of the case). The luminance in the front direction was measured. The measured value of the brightness | luminance of the center was 8261cd / m <^2> . Moreover, according to said Formula (1) and Formula (2), the brightness average value (front luminance) La and the brightness unevenness Lu in the front direction were obtained. The luminance unevenness was 1.5%.

<Example 7>

Except having changed the pattern of the light-diffusion plate into what is described below, it carried out similarly to Example 6, and created the backlight device shown schematically in FIG.

The uneven structure on the light diffusing plate used in the present embodiment will be described with reference to FIG. 20. With the light diffusion plate (2001 in FIG. 20) provided, a distance corresponding to the center of the hot cathode tube from the middle (1441 in FIG. 20) of the distance between the centers of adjacent hot cathode tubes (1402f and 1402g in FIG. 20) It was divided into three sections: A (5 mm), B (5 mm) and C (80 mm). In each region of the light exit surface of the light diffusion plate (2001 in Fig. 20), a prism-shaped convex portion having a triangular cross section with a vertex angle of 105 ° and a prism-shaped convex portion having a triangular cross section with a vertex angle of 160 ° are provided in each region. It prepared with the sun shown below.

In the zone A, the concavo-convex structure in which one triangular convex part having a vertex angle of 105 ° and one triangular convex part having a vertex angle of 160 ° was lined as one unit, and the unit was repeated.

In the zone B, the uneven structure in which two triangular convex portions having a vertex angle of 105 ° and one triangular convex portion having a vertex angle of 160 ° was lined as one unit, and the unit was repeated.

In zone (C), the uneven structure in which three triangular convex portions having a vertex angle of 105 ° and one triangular convex portion having a vertex angle of 160 ° was lined as one unit, was used as a structure in which this unit was repeated.

The bottom side of the triangular shape of the corner angle 105 degrees, and the triangle shape of the corner angle 160 degrees was 70 micrometers in all.

On the other hand, in the light incident surface, with the aspect shown in FIG. 3, the prism shape of the prism shape of a vertex angle of 130 degrees and a bottom side of 70 micrometers was provided in the whole surface.

Subsequently, the obtained direct type backlight device was energized at a tube current of 175 mA, the hot cathode tube was turned on, and a two-dimensional color distribution measuring device was used to equip 100 points at equal intervals on the center line in the shorter direction (inner direction of the case). The luminance in the front direction was measured. Moreover, according to said Formula (1) and Formula (2), the brightness average value (front luminance) La and the brightness unevenness Lu in the front direction were obtained. The measured value of the brightness | luminance of the center was 8344 cd / m <^2> . The luminance unevenness was 1.9%.

Comparative Example 5

A direct type backlight device was prepared in the same manner as in Example 6 except that the linear light source was a cold cathode tube (manufactured by Harison Toshiba Lighting Co., Ltd.) having a diameter of 3.0 mm and a length of 800 mm, and the tube was energized with a tube current of 4 mA to turn on the cold cathode tube. , Evaluated. The measured value of the brightness | luminance of the center was 2615 cd / m <^2> . Luminance unevenness was 5.2%.

TABLE 3

Claims (11)

A plurality of linear light sources arranged substantially parallel to each other, a reflecting plate for reflecting light from the linear light sources, direct light from the linear light source, and reflected light from the reflecting plate, incident from the light incidence plane, In the direct type backlight device provided with the light-diffusion plate irradiated from the light, The linear light source has an outer diameter of 5 mm to 30 mm, In at least one of the light exit surface and the light entrance surface, an uneven structure is formed at at least a portion of the light exit surface, In the light diffusing plate, when the outer diameter of the linear light source is projected perpendicular to the light diffusing plate, the uneven structure of the projected portion and the intermediate position of the linear light sources adjacent to each other in the light diffusing plate And the uneven structure of the portion having the same width as the outer diameter of the linear light source is a different shape. Direct type backlight device. The method of claim 1, The linear light source is characterized in that the hot cathode tube Direct type backlight unit. The method of claim 1, The concave-convex structure is a prism array in which a plurality of linear prisms extending along a long direction of the linear light source are arranged substantially in parallel. A cross section perpendicular to the longitudinal direction of the linear light source of the linear prism is a curved or polygonal convex portion, a substantially flat portion, or a combination thereof. Direct type backlight unit. The method of claim 3, wherein A cross section perpendicular to the longitudinal direction of the linear light source of the linear prism includes two or more kinds of convex portions of different shapes, and changes continuously or stepwise as the abundance ratio of the two or more kinds of convex portions moves away from the linear light source. Characterized by Direct type backlight unit. The method of claim 3, wherein The cross section perpendicular to the longitudinal direction of the linear light source of the linear prism includes both the convex portion and the substantially flat portion, and changes their abundance continuously or stepwise as they move away from the linear light source. Characterized Direct type backlight unit. The method of claim 1, Further provided with an optical sheet provided on the light exit surface side of the light diffusion plate, In the cross section perpendicular to the longitudinal direction of the linear light source, An arbitrary linear light source is called A, and the linear light source adjacent to this linear light source A is called B, The intermediate position which projected the intermediate position of the said linear light source A and the said linear light source B to the said light incident surface is called X, Any point on the light incidence plane located between the linear light source A and the linear light source B and closer to the linear light source A than the intermediate position X is called P. , The center of the linear light source A is called C, The total light transmittance Tp at the point P of the light incident from the center C in the direction of the point P is in the direction of the intermediate position X from the center C. Smaller than the total light transmittance Tx at the point X of the incident light. Direct type backlight unit. The method of claim 6, The length of the line connecting the center (C) and the point (P) is called LCP, A point at which the center C is projected perpendicular to the light incident plane is Q, The length of the line connecting the center (C) and the point (Q) is called LCQ, The total light transmittance at the said point Q of the light incident in the direction of the said point Q from the said center C is called Tq, Characterized by satisfying the relationship of 0.2 × (Tq · LCP / LCQ) ≦ Tp ≦ 5.0 × (Tq · LCP / LCQ) Direct type backlight device. The method of claim 1, The uneven structure is formed on both at least a part of the light exit surface and at least a part of the light incident surface of the light diffusion plate. Direct type backlight device. The method of claim 8, The uneven structure is a prism array in which a plurality of linear prisms extending along a longitudinal direction of the linear light source are arranged in substantially parallel, and a cross section perpendicular to the longitudinal direction of at least part of the linear light sources is polygonal, The polygonal shape is symmetrical about an axis parallel to the thickness direction of the light diffusion plate in the cross section. Direct type backlight device. The method of claim 8, A slope of at least one of the light emitting surface or the light incidence surface and the light as the light source or the light incident surface face toward an intermediate position away from the linear light source and adjacent to each other. The angle formed by the plane perpendicular to the thickness direction of the diffusion plate is characterized in that it is increased continuously or stepwise Direct type backlight device. The method of claim 8, Two or more types of linear prisms in the linear prism of at least one of the light exit surface and the light incident surface as they face an intermediate position of the linear light sources far from the linear light sources and adjacent to each other. The proportion of linear prisms with a large inclination angle increases continuously or stepwise as the mixing ratio of is changed continuously or stepwise and toward the intermediate position of the linear light sources adjacent to each other. Direct type backlight device.

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