JP2012242755A - Reflection sheet and backlight unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection sheet capable of preventing an occurrence of damaging on and sticking of superposed surfaces such as a backside of a light guide plate and unlikely to cause bending due to heat or the like from a light source, and to provide a backlight unit capable of improving a luminance and uniformizing the luminance using such reflection sheet.SOLUTION: A reflection sheet 1 for backlight units for reducing diffusion of light includes: a sheet body 2 formed into a sheet shape; and a fiber assembly layer 4 disposed on the surface side of the sheet body. The fiber assembly layer includes multiple fibers, and voids among the multiple fibers.

Description

  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.

  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. 2, the edge-light type backlight unit 30 generally includes a light source 31 composed of LEDs arranged in a bar shape, and a rectangular plate disposed so that an end thereof is along the light source 31. A light guide plate 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 are provided. 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.

  The function of the backlight unit 30 will be described. First, a light beam incident on the light guide plate 33 from the light source 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. As described above, the light emitted from the light source 31 is diffused by the light diffusion sheet 34 and refracted by the prism sheet 35 so as to have a peak in a substantially normal direction. Illuminate.

  On the other hand, light emitted 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 a device (on the back surface side of the backlight unit 30) ( A reflection sheet 36 is disposed on the back surface side of the light guide plate 33 for the purpose of preventing (frame concealment) from being visually recognized.

  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.

  However, since the conventional reflective 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.

  In view of the problem of the occurrence of scratches, there has been proposed one in which a scratch-preventing layer in which beads are dispersed in a binder is provided on the surface side of a reflection sheet (see JP-A-2004-85633).

  However, even the reflective sheet having the scratch-preventing layer may cause scratches on the light guide plate due to the beads depending on the type and shape of the beads.

  In addition, since the temperature of the reflective sheet is higher at a portion closer to the light source of the backlight unit, the conventional reflective sheet described above is bent due to this temperature, and there is a problem that luminance unevenness is generated based on this bending. doing.

JP 2004-85633 A

  The present invention has been made in view of these inconveniences, a reflection sheet that can prevent the occurrence of scratches and sticking on the overlapped surface such as the back surface of the light guide plate, and is less likely to be bent by heat from the light source, and the like. An object of the present invention is to provide a backlight unit that can improve luminance and make luminance uniform by using such a reflection sheet.

The invention made to solve the above problems is
A reflection sheet for a backlight unit that reduces the radiation of light,
A sheet main body formed in a sheet shape, and a fiber assembly layer disposed on the surface side of the sheet main body,
The fiber assembly layer is characterized by having a large number of fibers and a large number of voids between the fibers.

  Since the fiber aggregate layer is disposed on the surface of the reflection sheet, in the backlight unit, the fiber aggregate layer abuts against the light guide plate that is disposed on the surface side of the reflection sheet. Damage to the back surface of the light guide plate can be significantly reduced. Further, even when the reflecting sheets are rubbed with each other when the reflecting sheets are stored or transported, they are prevented from being damaged.

  Further, in the backlight unit, the reflection sheet is in contact with the light guide plate on the surface side by the fibers of the fiber assembly layer, and since this fiber assembly layer has a gap, sticking between the reflection sheet and the light guide plate is prevented. .

  Moreover, since the said reflection sheet is arrange | positioned so that many fibers may have a space | gap, a light ray can be refracted by presence of this space | gap, and, thereby, a high reflectance can be obtained. In particular, since the refractive index of the air in the gap is extremely low, it is possible to obtain a high refractive index difference with other constituent members, thereby making it possible to refract the light greatly and improve the reflectivity. it can.

  Moreover, in the backlight, since the fiber assembly layer of the reflection sheet is located between the light source disposed on the side surface of the light guide plate and the sheet main body of the reflection sheet, the heat from the light source is Since it is relaxed by the fiber assembly layer and transmitted to the sheet main body without being directly transmitted to the sheet main body, it is difficult for the sheet main body to bend due to heat, thereby preventing luminance unevenness due to the bending.

  In the reflection sheet, the fiber assembly layer can be composed of a woven fabric or a knitted fabric, but is preferably composed of a nonwoven fabric. By constituting the fiber assembly layer from a nonwoven fabric, it is excellent in scratch resistance, anti-sticking property, and heat resistance, and can be easily and reliably joined to the lower layer (back side layer) of this fiber assembly layer.

  Moreover, in the said reflection sheet, it is preferable that the fiber of a fiber assembly layer is mainly a white fiber. Thereby, reflectivity and concealment can be obtained by the fiber assembly layer.

  Furthermore, in the said reflection sheet, it is preferable to further provide the adhesive bond layer which adhere | attaches the said fiber assembly layer on the surface of a sheet | seat main body. As a result, the fiber assembly layer is securely and stably adhered by the adhesive layer, and the fiber assembly layer can be prevented from being peeled off.

  It is preferable to employ a configuration in which a part on the front surface side of the adhesive layer is impregnated on a part on the back surface side of the fiber assembly layer. Thereby, the adhesion of the fiber assembly layer can be made stronger and more stable.

  As the adhesive layer, a resin layer containing a white pigment is preferably employed. Thereby, reflectivity and concealment can be obtained by the adhesive layer.

  Moreover, in the said reflection sheet, it is preferable that a sheet | seat main body has a base material sheet layer made from a white synthetic resin. Thereby, reflectivity and concealment can be obtained by the base sheet layer.

  Accordingly, the liquid crystal includes a light source, a light guide plate disposed on the side of the light source, and an optical sheet disposed on the surface side of the light guide plate, and disperses light emitted from the light source and guides the light to the surface side. In a backlight unit for a display device, when the reflection sheet is provided on the back side of the light guide plate, the reflection sheet exhibits high scratch resistance as described above, and thus damage on the back surface of the light guide plate can be prevented. In addition, the anti-sticking property of the reflection sheet can prevent sticking between the reflection sheet and the back surface of the light guide plate, and also can prevent the reflection sheet from being bent due to heat from the light source. Further, the occurrence of uneven brightness can be prevented. Also, workability such as assembly is good.

  As described above, according to the reflective sheet of the present invention and the backlight unit using the same, the fiber aggregate layer can prevent the occurrence of scratches and sticking on the overlapped surface such as the back surface of the light guide plate and can prevent the light from the light source. Deflection due to heat or the like is unlikely to occur, and this can improve luminance and make luminance uniform.

Typical sectional drawing which shows the reflective sheet which concerns on one Embodiment of this invention. Schematic perspective view showing a general edge light type backlight unit

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  A reflection sheet 1 in FIG. 1 includes a sheet body 2, a fiber assembly layer 4 laminated on the surface side of the sheet body 2, and an adhesive layer 5 that bonds the sheet body 2 and the fiber assembly layer 4. .

<Sheet body 2>
Although the said sheet | seat main body 2 can also employ | adopt the thing of a multilayer structure, the sheet | seat main body 2 of this embodiment is comprised from the base material sheet layer 3 made from a white synthetic resin. This white synthetic resin is a synthetic resin containing a white pigment and fine bubbles dispersed therein. The synthetic resin that can be used for the base sheet layer 3 is not particularly limited. For example, polyester resin such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polycarbonate, polystyrene, epoxy resin, phenol resin, acrylic resin. Resins, polyolefins, cellulose acetates, weather resistant vinyl chloride resins and the like can be mentioned. Among these, polyethylene terephthalate having excellent heat resistance is preferable.

  Although the thickness of this base material sheet layer 3 (sheet main body 2) is not specifically limited, For example, it is 50 micrometers or more and 400 micrometers or less. When the thickness of the base sheet layer 3 is less than the above range, curling may easily occur when the resin composition forming the adhesive layer 5 is applied. On the other hand, if the thickness of the base sheet layer 3 exceeds the above range, the thickness of the backlight unit is increased, which is against the demand for thinning of the liquid crystal display device.

<Fiber assembly layer 4>
The fiber assembly layer 4 is a layer having a large number of fibers. Here, the fibers are arranged so that at least a part of the fibers are separated from other fibers, and a gap is formed in the fiber assembly layer 4. That is, the fiber assembly layer 4 has a large number of fibers and voids between the large number of fibers, and has cushioning properties (buffer properties). The fiber assembly layer 4 of this embodiment is composed of a nonwoven fabric in which a large number of fibers are irregularly entangled.

  As this non-woven fabric, it is possible to use one in which a fleece is formed by a dry method, a wet method, or a melt blow method, but a spun pond non-woven fabric in which a fleece is formed by a spunbond method can be suitably used. By employing a spunbonded nonwoven fabric, it is possible to easily and reliably produce a nonwoven fabric having suitable thickness and density and excellent wear resistance.

  Moreover, although a short fiber nonwoven fabric can also be used for a nonwoven fabric, it is preferable to employ a long fiber nonwoven fabric from the viewpoint of strength and flexibility. In addition, it is also possible to use the nonwoven fabric which made the long fiber nonwoven fabric contain the short fiber.

  Furthermore, the fiber which comprises the fiber assembly layer 4 is not specifically limited, A natural fiber and a chemical fiber can be used. Examples of natural fibers include cotton fibers and hemp fibers. Examples of the chemical fiber include aramid fiber, rayon fiber, polyester fiber, polyolefin fiber (polyethylene fiber, polypropylene fiber, etc.), nylon fiber, vinylon fiber, cellulose fiber, and glass fiber. These fibers can be used alone or in combination.

  In the present embodiment, as the fibers constituting the nonwoven fabric, chemical fibers are preferably used from the viewpoint of durability and the like, and among them, a polyolefin resin that can be easily and reliably formed by the spunbond method and has high production efficiency is preferably used. . In particular, among the polyolefin resins, polyethylene fibers having high versatility are preferably used, and among them, it is preferable to use high density polyethylene fibers because of their high heat resistance.

  Moreover, although the fiber which comprises a nonwoven fabric can also be comprised from a transparent fiber, it is preferable to mainly comprise a white fiber. Thereby, the whiteness of the fiber assembly layer 4 becomes high, and reflectivity is obtained in the fiber assembly layer 4.

  The thickness of the fiber is not particularly limited, but the lower limit of the fiber thickness (and linear density) is preferably 0.01 denier, more preferably 0.05 denier, and 0.1 denier. Particularly preferred. On the other hand, the upper limit of the fiber thickness (and linear density) is preferably 30 denier, more preferably 20 denier, and particularly preferably 10 denier. If the fiber thickness (and linear density) is thinner than the above lower limit, the fiber itself may not be elastic and sufficient flexibility may not be obtained in the fiber assembly layer 4, while if the upper limit is exceeded. This is because the rigidity of the fiber itself may become too strong, and the fiber may cause scratches. “Denier” is a unit that represents the thickness and linear density of the fiber, and is a numerical value that represents the mass of a fiber of 9000 m in grams.

  Moreover, although the thickness of a nonwoven fabric is not specifically limited, As a minimum of the average thickness of a nonwoven fabric (fiber assembly layer 4), 50 micrometers is preferable, 100 micrometers is more preferable, and 200 micrometers is more preferable. On the other hand, the upper limit of the average thickness of the nonwoven fabric is preferably 3 mm, more preferably 2 mm, and even more preferably 1 mm. This is because if the average thickness of the nonwoven fabric is smaller than the above lower limit, the effects (heat resistance, etc.) of the fiber assembly layer 4 may not be sufficiently exhibited. On the other hand, if the upper limit is exceeded, the reflective sheet 1 is thick. This is because the thickness of the backlight unit is increased, which may violate the demand for thinner liquid crystal display devices. In addition, the thickness of a nonwoven fabric is the numerical value which measured according to JIS-L-1906, measured thickness at several points (three places) under the pressure of 10 kPa, and calculated | required the average.

Moreover, although the fabric weight of the said nonwoven fabric is not specifically limited, As a minimum of the fabric weight of a nonwoven fabric, 10 g / m < ² > is preferable, 20 g / m < ² > is more preferable, 30 g / m < ² > is further more preferable. On the other hand, as an upper limit of the fabric weight of a nonwoven fabric, 200 g / m < ² > is preferable, 150 g / m < ² > is more preferable, 100 g / m < ² > is further more preferable. If the basis weight of the nonwoven fabric is smaller than the above lower limit, the effect (heat resistance, etc.) by the fiber assembly layer 4 may not be sufficiently exhibited. On the other hand, if the upper limit is exceeded, the nonwoven fabric becomes too thick or This is because the nonwoven fabric may become too hard. In addition, this basis weight (g / m < ² >) is a numerical value measured according to JIS-L-1906.

Furthermore, the average apparent density of the nonwoven fabric is not particularly limited, the lower limit of the average apparent density of the nonwoven fabric is preferably 0.03 g / cm ^3, more preferably 0.05 g / cm ^3, is 0.07 g / cm ³ Further preferred. In contrast, the upper limit of the average apparent density of the nonwoven fabric is preferably 0.6 g / cm ^3, more preferably ^{0.4g / cm 3, 0.2g / cm} 3 is more preferred. This is because if the average apparent density of the nonwoven fabric is smaller than the lower limit, the effects (heat resistance, etc.) of the fiber assembly layer 4 may not be sufficiently exhibited, while if the upper limit is exceeded, the nonwoven fabric becomes hard. This is because there is a risk of passing. In addition, this average apparent density can be calculated based on the numerical values of the basis weight and average thickness measured as described above, and specifically, is a numerical value obtained by dividing the basis weight by the average thickness.

<Adhesive layer 5>
The adhesive layer 5 is a layer composed of an adhesive for adhering the fiber assembly layer 4 to the base sheet layer 3, and is arranged over the entire surface in the plane direction of the base sheet layer 3 and / or the fiber assembly layer 4. It is installed. Part of the surface side of the adhesive layer 5 is impregnated into part of the back side of the fiber assembly layer 4. Specifically, the adhesive layer 5 is not impregnated up to the surface of the fiber assembly layer 4. Are provided so as to impregnate only a part of the fiber assembly layer 4. Here, the thickness of the portion of the adhesive layer 5 impregnated in the fiber assembly layer 4 is preferably 3% or more and 70% or less, more preferably 7% or more and 50% of the average thickness of the fiber assembly layer 4. Or less, particularly preferably 10% or more and 30% or less. If the thickness impregnated with the adhesive layer 5 is less than the above lower limit, the adhesive force of the fiber assembly layer 4 may be weakened. On the other hand, if the upper limit is exceeded, the fiber assembly layer 4 lacks flexibility or the like. This is because the desired function of the layer 4 may not be fully exhibited.

  Although it does not specifically limit as an adhesive agent which comprises the said adhesive bond layer 5, The adhesive agent for lamination or melt extrusion resin is used suitably. Examples of the laminating adhesive include dry laminating adhesive, wet laminating adhesive, hot melt laminating adhesive, non-solvent laminating adhesive, and the like. Among these laminating adhesives, it is excellent in adhesive strength, durability, weather resistance, etc., and has a function of sealing and protecting defects (for example, scratches, pinholes, recesses, etc.) on the surface of the base sheet layer 3. An adhesive is particularly preferred.

  Examples of the dry laminate adhesive include polyvinyl acetate adhesive, homopolymers such as ethyl acrylate, butyl, 2-ethylhexyl ester, and copolymers thereof with methyl methacrylate, acrylonitrile, styrene, and the like. Polyacrylic acid ester adhesive, cyanoacrylate adhesive, ethylene copolymer adhesive consisting of a copolymer of ethylene and monomers such as vinyl acetate, ethyl acrylate, acrylic acid, methacrylic acid, etc., cellulose adhesive Agent, polyester adhesive, polyamide adhesive, polyimide adhesive, urea resin, melamine resin amino resin adhesive, phenol resin adhesive, epoxy adhesive, polyurethane adhesive, reactive type ( (Meth) acrylic adhesive, chloroprene rubber, nitrile rubber Styrene - butadiene made of rubber or the like rubber adhesive, a silicone-based adhesive, an alkali metal silicate, and the like inorganic adhesive made of a low-melting-point glass or the like. Among these adhesives for dry laminating, polyurethane adhesives that prevent deterioration of adhesive strength and delamination caused by long-term use as a backlight, and further reduce deterioration such as yellowing of the adhesive layer 5, particularly Polyester urethane adhesives are preferred. The curing agent is preferably an aliphatic polyisocyanate with little thermal yellowing.

  Examples of the melt-extruded resin include polyethylene resins, polypropylene resins, acid-modified polyethylene resins, acid-modified polypropylene resins, ethylene-acrylic acid or methacrylic acid copolymers, Surlyn resins, and ethylene-vinyl acetate copolymers. One or more thermoplastic resins such as polyvinyl acetate resin, ethylene-acrylic acid ester or methacrylic acid ester copolymer, polystyrene resin, and polyvinyl chloride resin can be used. In addition, when employ | adopting the extrusion lamination method using the said melt extrusion resin, in order to obtain stronger adhesive strength, it is good to give surface treatments, such as the above-mentioned anchor coat process, to the lamination | stacking opposing surface of each said film.

Preferably 1 g / ^{m 2} as the lower limit of the amount of lamination of the adhesive layer 5 (in terms of solid content), more preferably ^{3g / m 2, 5g / m} 2 is particularly preferred. In contrast, the upper limit of the amount of lamination of the binding agent layer 5 is preferably 25 g / ^{m 2,} more preferably 20 g / ^{m 2,} particularly preferably 15 g / ^{m 2.} If the lamination amount of the adhesive layer 5 is smaller than the above lower limit, the adhesive strength may not be obtained. On the other hand, if the lamination amount of the adhesive layer 5 exceeds the above upper limit, the fiber assembly layer 4 is excessively impregnated with the adhesive layer 5 and the flexibility of the fiber assembly layer 4 may be impaired.

  The adhesive layer 5 contains a pigment in a dispersed manner. Specifically, the pigment is dispersed and contained in the adhesive layer 5 by mixing the pigment with the adhesive constituting the adhesive layer 5 (in a laminating adhesive or a melt-extruded resin).

  A white pigment is preferably used as this pigment. The type of the white pigment is not particularly limited, and examples thereof include titanium oxide (titanium white), silica, calcium carbonate (chalk), zinc oxide (zinc white), lead carbonate (lead white), and barium sulfate. Can be mentioned. Among these, titanium oxide is preferable because it has a large concealing effect. The average particle size of the white pigment is preferably 100 nm or more and 30 μm or less, and particularly preferably 200 nm or more and 20 μm or less. This is because if the average particle diameter of the white pigment is smaller than the above range, the reflective sheet 1 may not be provided with sufficient reflectivity and concealing property. Conversely, the average particle diameter of the white pigment exceeds the above range. This is because the reflection property and concealment property of the reflection sheet 1 may be uneven. The configuration of the white pigment of the adhesive layer 5 can also be suitably used for the white pigment of the base sheet layer 3.

  The lower limit of the white pigment content (in terms of solid content) in the adhesive is preferably 70% by mass, particularly preferably 80% by mass. On the other hand, the upper limit of the content is preferably 100% by mass, particularly preferably 90% by mass. This is because if the content of the white pigment is smaller than the lower limit, the effect of improving the reflectivity and concealment by the adhesive layer 5 is reduced, and conversely, if the content of the white pigment exceeds the upper limit, This is because coating becomes difficult.

  In addition, the adhesive constituting the adhesive layer 5 includes, for example, a solvent, a lubricant, a cross-linking agent, an antioxidant, an ultraviolet ray for the purpose of improving and modifying handling properties, heat resistance, weather resistance, mechanical properties, and the like. Various additives such as an absorbent, a light stabilizer, a filler, a reinforcing fiber, a reinforcing agent, an antistatic agent, a flame retardant, a flame retardant, a foaming agent, and an antifungal agent can be appropriately mixed.

<Manufacturing method>
Next, a method for manufacturing the reflection sheet 1 will be described. The reflection sheet 1 was formed by (a) a nonwoven fabric forming step for forming a nonwoven fabric, (b) a sheet body forming step for forming the sheet body 2 (base sheet layer 3), and (c) a nonwoven fabric forming step. A lamination adhesion step of laminating and bonding the nonwoven fabric and the sheet body 2 formed by the sheet body formation step.

  In the said nonwoven fabric formation process, a sheet-like nonwoven fabric is formed by the spunbond method, for example. Moreover, in the said sheet | seat main body 2 formation process, the sheet | seat main body 2 is shape | molded by the extrusion method, for example. Furthermore, in the above laminating and bonding step, the nonwoven fabric and the sheet body 2 are overlapped with an adhesive interposed therebetween, and both are laminated and bonded by, for example, a dry laminating method.

<Backlight unit 30>
The reflection sheet 1 is used as the reflection sheet 36 in the edge light type backlight unit 30 as shown in FIG. That is, in the backlight unit 30 for a liquid crystal display device including the light source 31, the light guide plate 33 disposed on the side of the light source 31, and the optical sheet 32 disposed on the surface side of the light guide plate 33. The reflective sheet 1 is disposed on the back side of the light guide plate 33.

  Since the reflection sheet 1 has the fiber assembly layer 4 disposed on the surface thereof, the reflection sheet 1 comes into contact with the light guide plate 33 disposed on the surface side of the reflection sheet 1 by the fibers of the fiber assembly layer 4, Thereby, the damage to the back surface of the light-guide plate 33 can be reduced significantly. In addition, even when the reflection sheets 1 are rubbed against each other when the reflection sheets 1 are wound or stacked for storage, transportation, etc. of the reflection sheet 1 before being incorporated in the backlight unit 30, they are prevented from being damaged. Is done.

  Furthermore, the reflection sheet 1 is in contact with the light guide plate 33 on the front surface and the fibers of the fiber assembly layer 4, and since the fiber assembly layer 4 has a gap, sticking between the reflection sheet 1 and the light guide plate 33 is prevented. The

  Moreover, since the said reflection sheet 1 is arrange | positioned so that many fibers may have a space | gap, it can refract a light beam by presence of this space | gap, and can thereby obtain a high reflectance. In particular, since the refractive index of the air in the gap is extremely low, a high refractive index difference occurs between the fibers of the fiber assembly layer 4 and the adhesive layer 5, and the light beam is refracted greatly based on this high refractive index difference. And high reflectivity can be achieved.

  In addition, since the fiber assembly layer 4 of the reflection sheet 1 is located between the light source 31 and the sheet body 2 of the reflection sheet 1, heat from the light source 31 is directly transmitted to the sheet body 2. Instead, it is relaxed by the fiber assembly layer 4 and transmitted to the sheet main body 2, so that the sheet main body 2 is unlikely to be bent due to heat, thereby preventing the occurrence of luminance unevenness due to the bending.

  Furthermore, since the reflection sheet 1 includes the adhesive layer 5 that adheres the fiber assembly layer 4 to the surface of the sheet body 2, the fiber assembly layer 4 is securely and stably adhered by the adhesive layer 5. Further, peeling of the fiber assembly layer 4 can be prevented.

  In particular, since the fiber assembly layer 4 is made of a nonwoven fabric, the fiber assembly layer 4 is excellent in the above-described scratch resistance, anti-sticking property, and heat resistance, and can reduce the manufacturing cost. As a result, the bonding between the fiber assembly layer 4 and the adhesive layer 5 becomes more reliable by the penetration of the adhesive.

  Further, in the reflection sheet 1, since the fibers of the fiber assembly layer 4 are mainly white fibers, the adhesive layer 5 contains a white pigment in a dispersed manner, and the base sheet layer 3 is made of a white synthetic resin. High reflectivity and concealment can be obtained by this layer.

<Other embodiments>
In addition, although the said embodiment had the said advantage from the said structure, this invention is not limited to the structure of the said embodiment, A design change is possible suitably within the range which this invention intends.

  That is, in the said embodiment, although the fiber assembly layer 4, the adhesive bond layer 5, and the sheet | seat main body 2 were all demonstrated white, this invention is not limited to this, Desirable reflectivity As long as the above can be obtained, the design can be changed as appropriate. Specifically, even the reflective sheet 1 in which the fibers of the fiber assembly layer 4 are colorless and transparent and the white pigment is dispersed and contained in the adhesive layer 5 is within the range intended by the present invention. Thus, by including a white pigment in the adhesive layer 5 in a dispersed manner, it becomes possible to obtain sufficient reflectivity without reducing the strength of the fiber. That is, if a large amount of white pigment is added to the fiber-forming material resin to give the fiber high reflectivity, the fiber becomes brittle and the strength of the fiber assembly layer 4 may be reduced. Even if a large amount of white pigment is added, the strength of the adhesive layer 5 is relatively easily maintained, so that sufficient reflectivity can be obtained with sufficient strength.

  Moreover, in the said embodiment, although what comprised the fiber assembly layer 4 from a nonwoven fabric was demonstrated, this invention is not limited to this. That is, as the fiber assembly layer 4, in addition to the nonwoven fabric, the warp yarns aligned in one direction (for example, parallel to one side direction of the sheet body) and the warp yarns aligned in the direction intersecting (perpendicular to) this one direction It can comprise from fabrics, such as a textile fabric which consists of the arranged weft. In addition, as the fabric constituting the fiber assembly layer, it is also possible to employ a knitted fabric or the like in which a large number of loops are formed by one (or several) yarns and knitted so that a large number of loops are intertwined. . Furthermore, the fiber assembly layer can be constituted by a flocking layer in which a large number of fibers are flocked to the sheet body. In addition, when employ | adopting fabrics, such as a woven fabric and a knitted fabric, a cotton thread can be used suitably as a fiber which comprises this fabric. Moreover, when it comprises from a knitted fabric, what has the pile which rose from the fabric main body can also be used.

  Further, in the above embodiment, since the adhesive layer 5 is provided, the fiber assembly layer 4 is easily and reliably laminated and bonded to the sheet body 2 through the adhesive layer 5. Is not an essential component in the present invention. In other words, for example, the case where the fiber assembly layer 4 is directly laminated on the sheet body 2 is also within the range intended by the present invention. By doing so, it is also possible to laminate a fiber assembly layer on the sheet body.

  Moreover, in the said embodiment, although the sheet | seat main body 2 demonstrated what consists of the single layer structure of the base material sheet layer 3, this invention is not limited to this. Specifically, for example, a sheet body in which a highly concealing layer is laminated on the back surface of the base sheet layer (the surface on which the fiber assembly layer is not formed) can be employed. This high hiding layer is a layer having high hiding properties and reflectivity. Specifically, it can be formed by applying a paint containing a white pigment on the back surface of the base sheet layer. The coating film forming main element, sub-element and auxiliary element (portion excluding pigment) of the paint used for the high hiding layer are not particularly limited, and general ones are used. In addition, as this white pigment, the thing similar to the white pigment demonstrated in the said embodiment can be used.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Example 1]
A sheet made of white PET (polyethylene terephthalate) (“Lumilla-E60L” manufactured by Toray Industries, Inc.) was used as the sheet body (base sheet layer). A non-woven fabric (“Tyvek” manufactured by DuPont) was laminated and adhered to the surface of the sheet body by dry lamination to produce a reflective sheet of Example 1. Here, as an adhesive for bonding the nonwoven fabric, a dry laminate adhesive (“E263” manufactured by Dainichi Seika Co., Ltd.) mixed with 90% by mass of titanium oxide is used. The minute conversion was 10 g / m ² .

[Example 2]
A reflective sheet of Example 2 was obtained by the same method as in Example 1 except that titanium oxide was not mixed in the adhesive for dry lamination.

[Comparative example]
The white PET sheet of Example 1 was used as a comparative example.

[Characteristic Evaluation 1]
A light guide plate (“ZEONOR light guide plate” manufactured by Nippon Zeon Co., Ltd.) is placed on the surface of the reflection sheet of Example 1, Example 2 and Comparative Example, and the light guide plate is damaged. The occurrence of sticking was examined. The results are shown in Table 1.

  As a result, the reflective sheets of Example 1 and Example 2 had higher resistance to scratching the light guide plate and prevention of sticking than those of the comparative example.

[Characteristic evaluation 2]
The reflection sheets of Examples 1, 2 and Comparative Example were incorporated into a backlight unit, and luminance and spectral reflectance were measured. As the backlight of the liquid crystal display device incorporating the reflection sheet, the backlight of a 42-inch liquid crystal display device of “42LE8500” manufactured by LG Electronics was used. Specifically, the reflective sheet of this backlight is replaced with the reflective sheet of Example 1, Example 2 and Comparative Example (the structure other than the reflective sheet (light guide plate, light source, etc.) is 42 inches made by LG Electronics. Using the backlight as it was, the luminance was measured and the spectral reflectance was measured. The measurement of luminance and chromaticity is an average value of 10 points measured using a “multi-light source spectrocolorimeter (MSC-IS-2DH)” manufactured by Suga Test Instruments Co., Ltd. The measurement results are shown in Table 2 below. Moreover, the measurement of a spectral reflectance is a 10-point average value of the numerical value measured using "UV-visible spectrophotometer V670" manufactured by JASCO Corporation, and the measurement result is shown in Table 3 below.

  As a result, it was found that the reflective sheet of Example 1 had higher brightness than that of the comparative example. Moreover, it turned out that the reflectance of the reflective sheet of Example 1 is constant between wavelengths compared with the thing of a comparative example. Moreover, although the brightness | luminance of the reflective sheet of Example 2 fell a little compared with the thing of a comparative example, it turned out that the difference in reflectance between wavelengths is small compared with the thing of a comparative example.

  As described above, since the present invention is a reflective sheet that exhibits high scratch resistance, anti-sticking properties, and heat resistance, it can be used for a backlight unit to improve luminance, and thus a liquid crystal display. It can be suitably used in an apparatus.

DESCRIPTION OF SYMBOLS 1 Reflective sheet 2 Sheet | seat main body 3 Base material sheet layer 4 Fiber assembly layer 5 Adhesive layer

Claims (8)

A reflection sheet for a backlight unit that reduces the radiation of light,
A sheet body formed in a sheet shape, and a fiber assembly layer laminated on the surface side of the sheet body,
The said fiber aggregate layer has many fibers and the space | gap between many fibers, The reflective sheet characterized by the above-mentioned.   The reflective sheet according to claim 1, wherein the fiber assembly layer is a nonwoven fabric.   The reflective sheet according to claim 1 or 2, wherein the fibers of the fiber assembly layer are mainly white fibers.   The reflective sheet according to claim 1, 2, or 3, further comprising an adhesive layer that adheres the fiber assembly layer to a surface of the sheet body.   The reflection sheet according to claim 4, wherein a part of the surface side of the adhesive layer is impregnated in a part of the back side of the fiber assembly layer.   The reflective sheet according to claim 4 or 5, wherein a white pigment is dispersedly contained in the adhesive layer.   The said sheet | seat main body has a base material sheet layer made from a white synthetic resin, The reflection sheet of any one of Claims 1-6.   A liquid crystal display device comprising a light source, a light guide plate disposed on a side of the light source, and an optical sheet disposed on a surface side of the light guide plate, and dispersing light beams emitted from the light source to guide the surface side A backlight unit for a liquid crystal display device, comprising the reflective sheet according to claim 1 on the back side of the light guide plate.

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