JP4712252B2 - Reflective sheet and backlight unit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection sheet enabling to prevent the damage on a back surface of a light guide plate, and to provide a backlight unit using those reflection sheet, enabling to realize the improvement and uniformity of brightness. SOLUTION: A reflection sheet 1 for the back light unit reducing the scatter of light comprises a base material sheet layer 2 made of white synthetic resin, and a damage prevention layer 3 laminated on the front surface side of the base material sheet layer 2. The damage prevention layer 3 is composed of a binder 4 and beads 5 dispersed in the binder 4, and characterized by soft convex parts almost uniformly formed on the surface.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reflection sheet for a backlight unit that reduces radiation of light rays, and a backlight unit using the reflection sheet.
[0002]
[Prior art]
In the liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back side is widely used, and a backlight unit such as an edge light type or a direct type is provided on the lower surface side of the liquid crystal layer. As shown in FIG. 4, the edge light type backlight unit 30 generally includes a rod-shaped lamp 31 as a light source, and a rectangular plate-shaped light guide plate that is disposed so that the end portion is along the lamp 31. 33, a plurality of optical sheets 32 stacked on the front surface side of the light guide plate 33, and a reflection sheet 36 stacked on the back surface side of the light guide plate 33. Each of the optical sheets 32 has specific optical properties such as refraction and diffusion. Specifically, the light diffusion sheet 34 and the light diffusion sheet 34 disposed on the surface side of the light guide plate 33 are provided. The prism sheet 35 etc. arrange | positioned by the surface side correspond.
[0003]
The function of the backlight unit 30 will be described. First, a light beam incident on the light guide plate 33 from the lamp 31 is reflected by reflection dots (not shown) on the back surface of the light guide plate 33 and each side surface. Emitted. The light beam emitted from the light guide plate 33 enters the light diffusion sheet 34, is diffused, and is emitted from the surface of the light diffusion sheet 34. Thereafter, the light beam emitted from the light diffusion sheet 34 enters the prism sheet 35, and is emitted as a light beam having a distribution having a peak in a substantially normal direction by the prism portion 35 a formed on the surface of the prism sheet 35. In this way, the light beam emitted from the lamp 31 is diffused by the light diffusion sheet 34 and refracted by the prism sheet 35 so as to show a peak in a substantially normal direction, and further the entire liquid crystal layer (not shown) above Illuminate.
[0004]
On the other hand, the light beam diffused from the back surface of the light guide plate 33 is reflected to the front surface side to such an extent that the liquid crystal screen is not glazed (reflectance), and the device disposed on the back surface side of the backlight unit 30; A reflective sheet 36 is disposed on the back side of the light guide plate 33 for the purpose of preventing the frame or the like from being visually recognized (concealment).
[0005]
Conventionally, as the reflection sheet 36, (a) a white pigment such as titanium oxide is dispersed in a synthetic resin sheet, and (b) a void (bubble) for scattering light in the synthetic resin sheet. And (c) a sheet whose surface is formed in a mat shape or the like is used.
[0006]
[Problems to be solved by the invention]
Since the conventional reflection sheet 36 is relatively hard, the back surface of the light guide plate 33 laminated on the front surface side in the backlight unit 30 may be damaged. In particular, a light guide plate 33 having a shallow inclined prism portion on the back surface and imparting directivity in the normal direction to the outgoing light beam, or a relatively soft light guide plate 33 made of an amorphous olefin resin (for example, ZEON Corporation) In the case of “ZEONOR light guide plate” (manufactured by Co., Ltd.), there is a relatively high risk of the back sheet being damaged by the reflective sheet 36. Thus, if the back surface of the light guide plate 33 is scratched, the amount of light emitted to the front surface side is reduced and luminance unevenness is caused.
[0007]
The present invention has been made in view of these disadvantages, and a reflection sheet that can prevent the back surface of the light guide plate from being scratched, and a back that can improve luminance and make luminance uniform using the reflection sheet. The purpose is to provide a light unit.
[0008]
[Means for Solving the Problems]
The invention made to solve the above problems is a reflective sheet for a backlight unit that is disposed on the back side of the light guide plate and reduces the diffusion of light rays, a base sheet layer made of white synthetic resin, and An anti-scratch layer laminated on the surface side of the base sheet layer, and the anti-scratch layer has a binder and beads made of a soft elastomer material dispersed in the binder. The surface of the anti-scratch layer has a surface roughness (Ra) of 5 μm or more and 20 μm or less, and the particle diameter of the beads is 3 μm or more and 40 μm or less. It is a reflection sheet. Here, the “white synthetic resin” means a synthetic resin that exhibits a white color by mixing white pigments or dispersing fine bubbles.
[0009]
According to the said reflective sheet, the reflection property and concealment similar to the conventional reflective sheet can be show | played by the base material sheet layer made from a white synthetic resin. In addition, since the reflection sheet includes a scratch-proof layer having a soft convex portion on the surface, the soft convex portion comes into contact with the back surface of the light guide plate disposed on the front surface side in the backlight unit. It is possible to prevent the back surface of the light guide plate from being damaged.
[0010]
The surface roughness (Ra) of the scratch-preventing layer is 5 μm or more and 20 μm or less. Here, “surface roughness (Ra)” is a value with a cutoff value of 8 mm and an evaluation length of 40 mm. By setting the surface roughness (Ra) of the scratch-preventing layer having a soft convex portion on the surface within the above range, the contact form with the back surface of the light guide plate can be obtained at a number of points due to the soft convex portions distributed substantially uniformly. It can be set as a contact, and the damage prevention property to the back surface of the light guide plate can be promoted.
[0011]
The scratch prevention layer has a structure having a binder and beads made of a soft elastomer material dispersed in the binder, and the soft convex portions are formed by the beads. According to the scratch-preventing layer having such a structure, the soft convex portion can be easily and reliably formed by the beads made of the soft elastomer material dispersed in the binder.
[0012]
As a glass transition temperature of the soft elastomer material which comprises the said bead, -100 degreeC or more and 30 degrees C or less are preferable. Thus, by setting the glass transition temperature of the soft elastomer material constituting the beads in the above range, the hardness of the soft convex portion can be reduced within a range in which the scattered contact with the light guide plate can be maintained. The damage prevention property to the back surface can be promoted.
[0013]
As the beads, soft urethane beads having a relatively low glass transition temperature and excellent solvent resistance, heat resistance and the like are preferable.
[0014]
The beads have a particle size (average primary particle diameter) of 3 μm or more and 40 μm or less. By using beads having a particle diameter in such a range, the surface roughness (Ra) of the scratch-preventing layer can be controlled within the above range, and the scratch-preventing property can be effectively achieved.
[0015]
The scratch-preventing layer may have a structure having a base polymer and bubbles dispersed in the base polymer, and a soft convex portion can be formed by the bubbles. By using an anti-scratch layer with a structure in which bubbles are dispersed in the base polymer as in this means, fine convex portions are formed on the surface, and gas is present in the convex portions, thus preventing scratches. A soft convex part can be easily and reliably formed on the surface of the layer, and the damage preventing property to the back surface of the light guide plate can be exhibited.
[0016]
The average diameter (diameter) of the bubbles is preferably 0.5 μm or more and 50 μm or less. By making the average diameter of the bubbles dispersed in the scratch-preventing layer in the above range, the surface roughness (Ra) of the scratch-preventing layer can be controlled in the above range, and the scratch preventing property can be effectively exhibited. it can.
[0017]
The volume ratio of the bubbles to the base polymer is preferably 1 vol% or more and 80 vol% or less. By setting the volume ratio of the bubbles within the above range, the hardness of the soft convex portion contacting the back surface of the light guide plate can be reduced within the range where the point contact is possible, and the scratch resistance to the back surface of the light guide plate is promoted. Can do.
[0018]
The reflection sheet may further include a high hiding layer laminated on the back side of the base sheet layer, and the high hiding layer may be formed by applying a paint containing a white pigment. According to this means, the high concealment layer laminated on the back surface side of the base sheet layer can significantly improve the reflectivity and concealment of the reflective sheet.
[0019]
Accordingly, (a) a linear lamp, (b) a light guide plate disposed along the lamp and guiding light emitted from the lamp to the surface side, and (c) disposed on the surface side of the light guide plate. And an optical sheet that diffuses light emitted from the light guide plate substantially uniformly and refracts it toward the normal direction side, and (d) the reflection sheet of the present invention disposed on the back side of the light guide plate. As described above, the backlight unit for the liquid crystal display device can prevent the back surface of the light guide plate from being scratched because the reflective sheet exhibits high scratch resistance, and the brightness is reduced due to the scratch on the back surface of the light guide plate. Further, the occurrence of uneven brightness can be prevented. Also, workability such as assembly is good.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. 1 is a schematic cross-sectional view showing a reflective sheet according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing a reflective sheet in a form different from the reflective sheet of FIG. 1, and FIG. It is typical sectional drawing which shows the reflective sheet of a form different from the reflective sheet of FIG.
[0021]
The reflection sheet 1 in FIG. 1 includes a base sheet layer 2 and a scratch preventing layer 3 laminated on the surface of the base sheet layer 2.
[0022]
The base sheet layer 2 is made of a white synthetic resin. This white synthetic resin is a synthetic resin containing dispersed white pigments and microbubbles as described above. The synthetic resin that can be used for the base sheet layer 2 is not particularly limited, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather resistant vinyl chloride. It is done. Among these, polyethylene terephthalate having excellent heat resistance is preferable.
[0023]
Although the thickness of this base material sheet layer 2 is not specifically limited, For example, you may be 50 micrometers or more and 250 micrometers or less. When the thickness of the base material sheet layer 2 is less than the above range, curling may easily occur when the resin composition for forming the scratch-preventing layer 3 is applied. On the other hand, if the thickness of the base sheet layer 2 exceeds the above range, the brightness of the liquid crystal display device may decrease, and the thickness of the backlight unit increases to meet the demand for thinning the liquid crystal display device. It will be contrary.
[0024]
In addition, as a white pigment to contain, it is the same as that of the conventional reflective sheet, and the thing similar to the white pigment 23 of the high concealment layer 22 mentioned later is used specifically. Further, the dispersed bubbles are the same as those of the conventional reflection sheet.
[0025]
The scratch prevention layer 3 has a binder 4 and beads 5 dispersed in the binder 4. By projecting the upper end portion of the bead 5 from the outer surface of the binder 4, a soft convex portion 6 that is smoothly curved is formed on the surface of the reflection sheet 1. Therefore, in the backlight unit, the reflection sheet 1 abuts the light guide plate disposed on the front surface side of the reflection sheet 1 at the soft convex portions 6 to cause scratches on the back surface of the light guide plate. Is reduced. The thickness of the scratch-preventing layer 3 (thickness of the binder 4 portion excluding the beads 5) is not particularly limited, but is, for example, about 3 μm to 30 μm.
[0026]
The lower limit of the surface roughness (Ra) of the scratch-preventing layer 3 is preferably 5 μm, particularly 7 μm, and more preferably 9 μm, and the upper limit thereof is preferably 20 μm, particularly 17 μm, and further 14 μm. This is because when the surface roughness (Ra) of the scratch-preventing layer 3 is smaller than the lower limit, it is difficult to effectively exhibit the scratch-preventing property due to the scattered contact with the back surface of the light guide plate as described above. On the contrary, if the surface roughness (Ra) exceeds the above upper limit, the soft back surface of the light guide plate may be damaged by the rough soft convex portion 6.
[0027]
Examples of the polymer used for the binder 4 include acrylic resins, polyurethanes, polyesters, fluorine resins, silicone resins, polyamideimides, and epoxy resins. In addition to the above-mentioned polymer, for example, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersant, an antistatic agent, and the like may be blended in the binder 4. The binder 4 is generally transparent, but white pigments and bubbles may be dispersed in order to provide reflectivity and concealment like the base sheet layer 2.
[0028]
The beads 5 are made of a soft elastomer material having a low glass transition temperature. Due to the beads 5 made of the soft elastomer material, the hardness of the soft convex portion 6 formed on the surface of the scratch-preventing layer 3 becomes relatively small, and the scratch-preventing property against the back surface of the light guide plate is exhibited.
[0029]
The lower limit of the specific glass transition temperature of the soft elastomer material is preferably −100 ° C., particularly −80 ° C., more preferably −60 ° C., and the upper limit is preferably 30 ° C., particularly 25 ° C., further 20 ° C. This is because when the glass transition temperature of the soft elastomer material constituting the beads 5 exceeds the above upper limit, the hardness of the soft convex portion 6 on the surface of the reflective sheet 1 increases, and the effect of preventing scratches on the back surface of the light guide plate is effective. If the glass transition temperature of the soft elastomer material is lower than the lower limit, the soft convex portion 6 on the surface of the reflective sheet 1 is crushed and the surface of the binder 4 is guided. This is because it will be in contact with the rear surface of the optical plate, and it will not be possible to effectively exhibit the above-described scratch resistance.
[0030]
Specific examples of the soft elastomer material that can be used for the beads 5 include polyurethane, silicone rubber, polystyrene, thermoplastic polyester, and the like. Among them, soft urethane beads are preferable in view of solvent resistance, heat resistance, and the like.
[0031]
The lower limit of the particle diameter of the beads 5 is preferably 3 μm, particularly 5 μm, and more preferably 7 μm, and the upper limit thereof is preferably 40 μm, particularly 30 μm, and more preferably 20 μm. This is because when the particle diameter of the beads 5 is less than the above lower limit, it becomes difficult to protrude the beads 5 from the binder 4 to form the soft convex portion 6, and the surface roughness of the scratch-preventing layer 3. This is because (Ra) cannot be within the above range. Conversely, when the particle diameter of the beads 5 exceeds the above upper limit, the surface roughness (Ra) of the scratch preventing layer 3 exceeds the above range and is scratched. This is because the prevention property is reduced and the formation of the scratch-preventing layer 3 by coating the resin composition or the like becomes difficult.
[0032]
The lower limit of the blending amount of the beads 5 with respect to 100 parts of the polymer content of the binder 4 is preferably 0.1 part, particularly 5 parts, and further 10 parts, and the upper limit thereof is preferably 500 parts, particularly 300 parts, and further 100 parts. Here, the numerical value indicated by “part” means a ratio based on mass. This is because if the blending amount of the beads 5 is less than the lower limit, the surface roughness (Ra) of the scratch-preventing layer 3 cannot be in the above range. This is because it becomes difficult to form the scratch-preventing layer 3 by coating the composition.
[0033]
The beads 5 are preferably transparent, particularly colorless and transparent. By using transparent beads 5 in this way, light diffusibility can be imparted to the scratch-preventing layer 3, and as a result, the light emitted to the surface side is diffused by reflection on the base sheet layer 2 or the like, Concealment can be promoted.
[0034]
As a manufacturing method of the reflection sheet 1, basically, a step of adjusting the coating solution for the scratch-preventing layer 3 by mixing the beads 5 with the resin composition constituting the binder 4, and this coating It comprises a step of laminating the scratch-preventing layer 3 by applying the liquid onto the surface of the base sheet layer 2 and drying it.
[0035]
According to the reflection sheet 1, the white synthetic resin base material sheet layer 2 provides the same reflectivity and concealment as the conventional reflection sheet, and is further provided on the surface side by the scratch prevention layer 3. It is possible to prevent the back surface of the optical plate from being damaged. In addition, since the reflection sheet 1 has irregularities formed on the surface by the beads 5 dispersed in the scratch-preventing layer 3, it is possible to improve the reflectivity toward the surface side and thus the concealment property. Further, the reflection sheet 1 has enhanced light diffusibility due to refraction and reflection of light by the beads 5 dispersed in the scratch-preventing layer 2, and can promote concealment.
[0036]
The reflection sheet 11 in FIG. 2 includes a base sheet layer 2 and a scratch-preventing layer 12 laminated on the surface of the base sheet layer 2 in the same manner as the reflection sheet 1 in FIG. The base sheet layer 2 is the same as the reflection sheet 1 in FIG. 1 except for the structure of the scratch preventing layer 12.
[0037]
The scratch-preventing layer 12 has a base polymer 13 and bubbles 14 dispersed in the base polymer 13, and a large number of soft convex portions 15 are substantially uniformly formed on the surface by the dispersion of the bubbles 14. Is formed. As described above, the soft convex portion 15 on the surface of the reflection sheet 11 is elastic and soft and smoothly curved because the bubbles 14 are contained therein. Therefore, in the backlight unit, the reflective sheet 11 is in contact with the light guide plate disposed on the surface side of the reflective sheet 11 at the soft convex portions 15 to reduce the damage to the back surface of the light guide plate. Is done.
[0038]
In addition, the thickness of this damage prevention layer 3 and the surface roughness (Ra) of the damage prevention layer 3 are the same as those of the reflection sheet 1 in FIG. Further, as the material constituting the base polymer 13, the same material as the binder 4 of the scratch preventing layer 3 of the reflective sheet 1 is used, but it is cured simultaneously with the foaming process of the foaming agent for forming the bubbles 14. A thermosetting resin such as a urea resin, a melamine resin, a phenol resin, an epoxy resin, an unsaturated polyester resin, an alkyd resin, or a urethane resin that can be used is preferably used.
[0039]
The bubble 14 is a minute part containing some gas present in the base polymer 13, and its shape is not particularly limited, and various shapes such as a spherical shape, a granular shape, a polyhedral shape, a confetti shape, a random shape, and a spindle shape are available. Is possible. However, spherical closed cells are preferable as the shape of the bubbles 14 in terms of easy formation of the soft convex portion 15 and promotion of concealability due to high light diffusibility. In addition, the bubbles 14 exist in the base polymer 13 in principle, but there may exist open bubbles on the surface of the base polymer 13, and the formation of the soft convex portion 15 and light may be caused by the open bubbles. Diffusivity is promoted.
[0040]
The gas contained in the bubbles 14 is determined by the method of forming the bubbles 14 and is not particularly limited. For example, when a foaming agent is used as will be described later, air, nitrogen gas, carbon dioxide, ammonia gas or the like is filled depending on the type of foaming agent.
[0041]
The lower limit of the average diameter of the bubbles 14 is preferably 0.5 μm, particularly 1 μm, and more preferably 5 μm, and the upper limit of the average diameter is preferably 50 μm, particularly 40 μm, and more preferably 30 μm. If the average diameter of the bubbles 14 is smaller than the lower limit, it becomes difficult to form the soft convex portion 15, and the surface roughness (Ra) of the scratch-preventing layer 12 can be within the above range. This is because the strength of the scratch-preventing layer 12 decreases when the average diameter exceeds the upper limit.
[0042]
The lower limit of the volume ratio of the bubbles 14 to the base polymer 13 is preferably 1 vol%, particularly 10 vol%, and more preferably 20 vol%, and the upper limit of the volume ratio is preferably 80 vol%, particularly 70 vol%, and more preferably 60 vol%. This is because if the volume ratio of the bubbles 14 is smaller than the lower limit, it is difficult to make the surface roughness (Ra) of the scratch-preventing layer 12 by the soft convex portion 15 within the preferable range, and also due to light diffusibility. This is because the effect of promoting concealment is also reduced, and conversely, if the volume ratio of the bubbles 14 exceeds the above upper limit, the strength and durability of the scratch-preventing layer 12 are reduced.
[0043]
As a method for producing the reflection sheet 11, basically, a foaming agent is added and kneaded into a resin composition (a thermosetting resin is a main polymer) constituting the base polymer 13, and an anti-scratch layer is formed. The step of adjusting the coating solution for No. 12, the step of coating this coating solution on the surface of the base sheet layer 2, and the base polymer 13 is thermally cured by heating and the foaming agent is foamed. And a step of laminating the scratch-preventing layer 12 in which the bubbles 14 are dispersed in the base polymer 13.
[0044]
According to the reflection sheet 11, similarly to the reflection sheet 1, it is possible to prevent damage to the rear surface of the light guide plate disposed on the front surface side by the damage prevention layer 12 on the surface of the base material sheet layer 2. In addition, the reflective sheet 11 can enhance the reflectivity toward the surface side, and consequently the concealability, by the soft convex portion 15 formed on the surface of the scratch preventing layer 12. Furthermore, since the light diffusibility of the reflection sheet 11 is enhanced by refraction and irregular reflection at the interface of the dispersed bubbles 14, the concealability is also enhanced from this point.
[0045]
The reflective sheet 21 in FIG. 3 includes the base sheet layer 2 and the scratch-preventing layer 3 in which the beads 5 are dispersed, like the reflective sheet 1. For this reason, the same parts are denoted by the same reference numerals and description thereof is omitted. The reflection sheet 21 further includes a high hiding layer 22 laminated on the back surface of the base sheet layer 2.
[0046]
The high hiding layer 22 exhibits hiding properties and reflectivity, and is specifically formed by applying a paint 24 containing a white pigment 23 on the back surface of the base sheet layer 2. In addition, as the coating material 24 used for this highly concealing layer 22, it is not specifically limited, A general thing is used.
[0047]
The white pigment 23 is not particularly limited, and examples thereof include titanium oxide (titanium white), zinc oxide (zinc white), lead carbonate (lead white), barium sulfate, calcium carbonate (white chalk), and the like. . Among these, titanium oxide is preferable because it has a large concealing effect.
[0048]
As a minimum of the compounding quantity of white pigment 23 to solid content of paint 24, 70 mass% is preferred and 80 mass% is especially preferred. On the other hand, the upper limit of the amount is preferably 95% by mass, and particularly preferably 90% by mass. This is because if the blending amount of the white pigment 23 is smaller than the lower limit, the effect of improving the reflectivity and concealment by the high hiding layer 22 is reduced. Conversely, if the blending amount of the white pigment 23 exceeds the upper limit, This is because the coating of the paint 24 becomes difficult.
[0049]
The lower limit of the coating amount (in terms of solid content) of the paint 24 is 1 g / m. ² , Especially 5g / m ² 10g / m ² Is preferred. On the other hand, the upper limit of the coating amount (solid content conversion) is 50 g / m. ² , Especially 45g / m ² 40g / m ² Is preferred. This is because if the coating amount of the paint 24 is smaller than the lower limit, the effect of improving the reflectivity and concealment by the high hiding layer 22 is reduced, and conversely, if the coating amount of the paint 24 exceeds the upper limit, This is because the thickness of the high hiding layer 22 is increased, which is contrary to the demand for thinning the backlight unit, and the strength of the high hiding layer 22 is reduced.
[0050]
The particle diameter (average particle diameter) of the white pigment 23 is preferably from 100 nm to 30 μm, particularly preferably from 200 nm to 20 μm. This is because if the particle diameter of the white pigment 23 is smaller than the above range, it becomes difficult to effectively achieve the concealing property. Conversely, if the particle diameter of the white pigment 23 exceeds the above range, This is because it becomes difficult to uniformly disperse and the back surface of the reflection sheet 21 becomes rough.
[0051]
As a manufacturing method of the reflection sheet 21, basically, a step of adjusting the coating liquid for the scratch-preventing layer 3 by mixing the beads 5 with the resin composition constituting the binder 4, and this coating The liquid is applied to the surface of the base sheet layer 2 and dried, the step of laminating the scratch-preventing layer 3, the step of adjusting the paint 24 by blending the white pigment 23, and the paint 24 It consists of the process of laminating the high concealment layer 22 by coating on the back surface of the material sheet layer 2.
[0052]
According to the reflection sheet 21, similarly to the reflection sheet 1, it is possible to prevent damage to the back surface of the light guide plate disposed on the front surface side by the scratch prevention layer 12 on the surface of the base sheet layer 2, Due to the unevenness on the surface of the scratch-preventing layer 12 and the light diffusibility of the beads 5 of the scratch-preventing layer 3, the reflectivity and concealment to the surface can be enhanced. Further, the high concealment layer 22 on the back surface of the base sheet layer 2 can remarkably improve the reflectivity and concealability.
[0053]
Therefore, in the edge light type backlight unit 30 as shown in FIG. 4, when the reflection sheets 1, 11, 21 are used as the reflection sheet 26, the reflection sheets 1, 11, 21 are prevented from being damaged as described above. Therefore, it is possible to prevent the occurrence of luminance unevenness due to scratches on the back surface of the light guide plate 33, and the assembly operation of the backlight unit 30 is facilitated. In particular, when the reflective sheet 21 having the high hiding layer 22 on the back side is used, the loss of light radiated from the back side can be reduced due to the high hiding property and reflectivity of the high hiding layer 22, and the luminance can be improved. Further, it is possible to prevent a frame or the like disposed on the back side from being visually recognized from the screen, and to prevent occurrence of luminance unevenness.
[0054]
The reflective sheet of the present invention is not limited to the above embodiment. For example, the scratch-preventing layer can be formed by any means as long as the soft convex portion can be formed substantially uniformly on the surface. The structure in which 14 is dispersed is not limited. Moreover, as a damage prevention layer, the structure where both the bead 5 and the bubble 14 disperse | distribute in a base polymer is also possible, and, thereby, the said damage prevention property and light diffusibility are accelerated | stimulated.
[0055]
【The invention's effect】
As described above, according to the reflective sheet of the present invention, it is possible to prevent the back surface of the light guide plate from being damaged. Moreover, according to the backlight unit using the reflective sheet of the present invention, it is possible to prevent the occurrence of uneven brightness due to scratches on the back surface of the light guide plate, and to improve the brightness.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a reflective sheet according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing a reflection sheet having a form different from that of FIG.
FIG. 3 is a schematic cross-sectional view showing a reflection sheet having a form different from that of FIGS. 1 and 2;
FIG. 4 is a schematic perspective view showing a general edge light type backlight unit.
[Explanation of symbols]
1 ... Reflective sheet
2 ... Base sheet layer
3 ... Damage prevention layer
4 ... Binder
5 ... Bead
6 ... Soft convex part
11 ... Reflective sheet
12 ... Damage prevention layer
13 ... Base polymer
14 ... Bubble
15 ... Soft convex part
21 ... Reflection sheet
22 ... High hiding layer
23 ... White pigment
24 ... Paint

Claims (5)

A reflective sheet for a backlight unit that is disposed on the back side of the light guide plate and reduces the diffusion of light rays,
It comprises a base sheet layer made of white synthetic resin and a scratch prevention layer laminated on the surface side of the base sheet layer,
This scratch-preventing layer has a binder and beads made of a soft elastomer material dispersed in the binder, and the soft convex portions are substantially uniformly formed on the surface by the beads,
The surface roughness (Ra) of the scratch-preventing layer is 5 μm or more and 20 μm or less,
Reflective sheet particle diameter of the beads, characterized in der Rukoto than 40μm below 3 [mu] m. The reflection sheet according to claim 1 , wherein the soft elastomer material constituting the beads has a glass transition temperature of −100 ° C. or higher and 30 ° C. or lower. The reflective sheet according to claim 1 or 2 , wherein the beads are soft urethane beads. It further comprises a high hiding layer laminated on the back side of the base sheet layer,
The reflective sheet according to claim 1 , wherein the highly concealing layer is formed by applying a paint containing a white pigment. A linear lamp,
A light guide plate disposed along the lamp and guiding the light emitted from the lamp to the surface side;
An optical sheet that is disposed on the surface side of the light guide plate, diffuses light rays emitted from the light guide plate substantially uniformly, and refracts the normal direction side;
The backlight unit for liquid crystal display devices equipped with the reflective sheet of any one of Claims 1-4 arrange | positioned in the back surface side of the said light-guide plate.

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