JPH07230004A - Light reflector for back light unit of liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a light reflector for a back light unit which is a light reflector for the back light unit of an liquid crystal display device having an excellent electric insulating characteristic and light reflection efficiency in combination and having moderate rigidity and flexibility and is integrally formed with a lamp holder and a light reflection sheet. CONSTITUTION:This light reflector for the back light unit of the liquid crystal display device consisting of a porous resin sheet is integrally formed with the lamp holder part 2 and the light reflection sheet part 4 and contains 100 to 300 pts.wt. inorg. filler in 100 pts.wt. thermoplastic resin. In addition, the ray reflectivity of a wavelength 550nm is >=95%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light reflector for a backlight unit of a liquid crystal display device made of a porous resin sheet. More specifically, the present invention relates to a light reflector for a backlight unit of a liquid crystal display device, which is made of a porous resin sheet having excellent electrical insulation properties, high light reflection efficiency, and appropriate flexibility and rigidity. A light reflector for a backlight unit of a liquid crystal display device according to the present invention is mainly used for a word processor, a personal computer, a television, etc., and a light reflector for a lamp holder of a light source unit in a backlight unit of the liquid crystal display device and The present invention relates to a light reflection sheet arranged below a light guide plate, in which both are integrally formed.

[0002]

2. Description of the Related Art In recent years, light reflectors have been used in various fields, and in particular, many are used as main parts of liquid crystal display devices such as word processors, personal computers, and televisions. It is important that the liquid crystal display device is thin and can save power. Also,
It is desired to increase the area of the liquid crystal display device and improve the display quality, and for this purpose, it is necessary to supply a large amount of light to the liquid crystal portion. Enables power saving of liquid crystal display devices,
In order to reduce the size and thickness and increase the amount of light supplied from the backlight unit, the reflection efficiency of the light reflector must be high.

In the backlight unit of the liquid crystal display device, there are a method in which the light source is directly placed under the liquid crystal portion and a method in which the light source is placed next to the transparent light guide plate. The latter method is suitable for thinning the liquid crystal display device. In the latter method, the light reflectors are used in two places, the lamp holder part and the lower part of the light guide plate. When light is absorbed and a leak current is generated in the lamp holder part, the amount of light supplied to the liquid crystal display part is reduced. Therefore, the material of the lamp holder placed beside the light guide plate is required to have high light reflection efficiency and high electric insulation.

Conventionally, as a material for a lamp holder, a light reflector in which a light reflection sheet (silver reflection sheet) having a metal thin film layer containing silver as a main component is attached to the surface of a metal plate such as aluminum, or a light reflector is disclosed. A metal plate such as aluminum coated with a white pigment as described in JP-A-2-13925 has been used. However, since these light reflectors have low electric resistance, a leak current due to an induced current from the light source is generated, so that the current actually used for light emission is reduced and the light emission efficiency is deteriorated.

Recently, a polyethylene terephthalate sheet (hereinafter abbreviated as a white PET sheet) containing a white inorganic filler or the like has been used as a light reflector in order to suppress a leak current. However, since the white PET sheet has high rigidity in itself, when used in a form of enclosing the light source, a gap is created between the light source and the white PET sheet, and light leaks and the amount of light transmitted to the liquid crystal display unit decreases. There was a flaw. In order to solve this drawback, attempts have been made to reduce the thickness of the white PET sheet, but the amount of light transmitted through the sheet increases, and as a result, a new problem occurs that the light reflection efficiency decreases. There is.

Further, as a light reflecting sheet disposed below the light guide plate, a sheet described in JP-A-63-161029, that is, polyethylene terephthalate containing 5 to 30% by weight of particulate calcium carbonate is conventionally used. A polymer chip obtained by melt-extruding the contained polymer chips and biaxially stretched, wherein a ≧ 4 when the whiteness of the polymer chips is a% and the void ratio of the film after the biaxial stretching is b%
A white PET sheet satisfying 5, 7 ≦ b ≦ 30 and a × logb ≧ 65 is used. Also, Japanese Patent Laid-Open No. 4-2
No. 39540 discloses a liquid crystal display in which the surface has an average reflectance of 90% or more in a wavelength range of light of 400 to 700 nm and a reflectance (maximum value-minimum value) of 10% or less in the wavelength range. A white PET sheet for a reflector is disclosed. Then, in the embodiment, white P having a thickness of 188 μm is used.
ET sheet is described.

However, the thick white PET sheet having a thickness of about 188 μm as described above is not suitable for forming a lamp holder portion of a backlight unit of a liquid crystal display device because of its high rigidity. Further, when the thickness is made thin, the lamp holder part can be easily formed, but the light reflection sheet arranged below the light guide plate is too thin and the light transmittance becomes large, resulting in a high reflection efficiency. descend. In order to eliminate these drawbacks, there is a method of using sheets with different thickness for the lamp holder and the light reflection plate, but it requires a step of slitting the lamp holder and a step of applying adhesive on two ends of the lamp holder. Therefore, there is a problem that the number of steps and the cost increase. Further, since the lamp holder has a narrow width, it is difficult to mount the lamp holder on the backlight unit. Therefore, there is a demand for a reflector in which a lamp holder and a light reflecting sheet arranged below the light guide plate are integrally formed. However, there is no conventional light reflector having both rigidity and light ray reflectance suitable for integrally forming the both, and it is difficult to integrally form the both.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a backlight unit for a liquid crystal display device which has excellent electrical insulation and light reflection efficiency, and which has appropriate rigidity and flexibility. A light reflector for a lamp holder of a light source forming a backlight unit of the liquid crystal display device, and a light reflecting sheet disposed below the light guide plate are integrally formed. It is to provide a light reflector for a backlight unit.

[0009]

Means for Solving the Problems As a result of intensive investigations by the present inventors, a porous sheet having a specific light reflectance obtained by blending a specific amount of an inorganic filler with a thermoplastic resin has the above problems. The inventors have found that the light reflector for a backlight unit of a liquid crystal display device can solve the above problems, and have reached the present invention.

That is, the present invention is a light reflector for a backlight unit of a liquid crystal display device comprising a porous resin sheet, wherein the light reflector (1) is integrally formed with a lamp holder portion and a light reflection sheet portion. , (2) Thermoplastic resin 100
100 to 300 parts by weight of an inorganic filler is included with respect to parts by weight, and (3) the light reflectance at a wavelength of 550 nm is 95%.
The above is a light reflector for a backlight unit of a liquid crystal display device characterized by the above.

The feature of the light reflector for the backlight unit of the liquid crystal display device of the present invention is that it is a porous sheet containing a specific amount of a thermoplastic resin and an inorganic filler and has a specific light reflectance. is there. The light reflector for a backlight unit of the liquid crystal display device of the present invention is a porous sheet containing a specific amount of a thermoplastic resin and an inorganic filler, and thus has excellent electrical insulation. Further, since it is a porous sheet having a specific composition, a large number of reflective layers are contained on the surface of the sheet and inside thereof, so that it has an excellent light reflectance. Moreover, since it is highly flexible and has low rigidity, no gap is formed between it and the light source even if the thickness of the sheet is increased. Therefore, since it is not necessary to reduce the thickness of the sheet, light transmission can be suppressed.

The light reflector for the backlight unit of the liquid crystal display device of the present invention will be described in detail below. The light reflector for the backlight unit of the liquid crystal display device of the present invention,
A specific amount of an inorganic filler is added to a thermoplastic resin and mixed to form a resin composition, and an unstretched sheet is molded from the obtained resin composition by, for example, melt extrusion molding, and then the unstretched sheet obtained. Is uniaxially or biaxially stretched.

The thermoplastic resin used in the present invention includes high density polyethylene, low density polyethylene, linear low density polyethylene which is a copolymer of ethylene and α-olefin,
Polypropylene, ethylene-propylene copolymer, polyolefin resin represented by poly-4-methylpentene resin, polyester resin represented by polyethylene terephthalate, polybutylene terephthalate, polystyrene resin, poly-p-xylylene resin Resin, polyvinyl acetate-based resin, polyacrylic acid ester-based resin typified by polymethyl acrylate, polyethyl acrylate, etc., polymethacrylic acid ester-based resin typified by polymethyl methacrylate, polyvinyl chloride-based resin , Polyvinylidene chloride-based resin, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, a fluorine-based resin represented by a copolymer of tetrafluoroethylene and hexafluoropropylene, and the like, Polyac Polyvinyl ether resin represented by ronitrile resin, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl-n-butyl ether, polyvinyl isopropyl ether, polyvinyl isobutyl ether, polymethyl vinyl ketone, polymethyl isobropenyl ketone, polyethyl vinyl Polyvinyl ketone resin represented by ketone, polyphenyl vinyl ketone, polynaphthyl vinyl ketone, poly-p-chlorophenyl ketone, polyoxyalkyl vinyl ketone, etc., polyether represented by polyacetaldehyde, polyethylene oxide, polypropylene oxide, etc. Resin, Nylon 6, Nylon 6-6, Nylon 6
Polyamide resin represented by -10, nylon 11, nylon 12, etc., diene resin represented by polyisoprene, polybutadiene etc., polyurethane resin, polyacetal, aromatic polyamide, polyphenylene, polyarylate, polyphenylene oxide, polyphenylene sulu Fide, polyetheretherketone, polysulfone, polyethersulfone, polyimide, polyamideimide, polyesterimide, polyetherimide, polybenzimidazole, polyquinazolinedione, polybenzoxazinone, polyacene, polyimidazopyrrolone, polyquinoline, polynaphthyridine, polyimide Heat resistant resins represented by quinoxaline and the like can be mentioned.

Of these thermoplastic resins, taking into consideration the moldability into a sheet, the heat resistance and the stretchability of the obtained sheet, etc., preferably a polyolefin resin or a polyester resin, more preferably ethylene. And α-
Linear low density polyethylene resin, polypropylene resin, ethylene-propylene copolymer and polyethylene terephthalate resin which are copolymers with olefins (hereinafter referred to as P
Abbreviated as ET resin), more preferably linear low density polyethylene resin which is a copolymer of ethylene and α-olefin, polypropylene resin, ethylene-propylene copolymer.

The molecular weight of the thermoplastic resin affects the formability into a sheet, and if the molecular weight is too high or too low, the film-forming property deteriorates. Considering this point, in the case of a polyolefin resin, the melt index (hereinafter referred to as MI) which is a parameter of the molecular weight is about 0.5 to 7 g / 10 min in the case of a polyethylene resin (190 ° C., load 2.16 kg). ), 1-1 for polypropylene resin
About 0g / 10min (230 ℃, load 2.16k
g), 10 in the case of poly-4-methylpentene resin
About 70g / 10min (260 ℃, load 5.0kg)
Is preferred. In the case of PET resin, the intrinsic viscosity (IV) which is a parameter of molecular weight is 0.6 to
About 1.1 dl / g is preferable. In addition, MI of the polyolefin resin in the present invention is ASTM D-1238.
It is the value measured under the above conditions by the method specified in 1. The intrinsic viscosity, which is a parameter of the molecular weight of PET resin, is a solution viscosity measured at 25 ° C. using tetrahydrofuran as a solvent and an Ubbelohde viscometer.

As the inorganic filler used in the present invention, metal salts, metal hydroxides, metal oxides and the like are preferably used. Examples of these include barium sulfate, calcium sulfate, magnesium sulfate, aluminum sulfate, barium carbonate, calcium carbonate, magnesium chloride, metal salts such as basic magnesium carbonate, magnesium hydroxide, aluminum hydroxide, calcium hydroxide and the like. Examples thereof include metal hydroxides, calcium oxide, zinc oxide, magnesium oxide, titanium oxide, alumina, silica, and other metal oxides. Furthermore, clays such as calcium silicates, cements, zeolites and talc can also be used.

Of these, considering comprehensively the mixing or dispersibility with the thermoplastic resin, the stretchability of the sheet and the porosity and porosity of the resulting porous sheet, barium sulfate, calcium carbonate, Titanium oxide, alumina and magnesium hydroxide are preferred. More preferred are barium sulfate and calcium carbonate, and particularly preferred is barium sulfate. When barium sulfate is used, precipitated barium sulfate, which has good dispersibility and mixability with the thermoplastic resin, is preferable. Further, since the particle size of the inorganic filler affects the surface state of the obtained porous sheet, the inorganic filler having an average particle diameter of about 0.1 to 7 μm is preferable. More preferably, it is 0.2 to 5 μm.

The amount of the inorganic filler added affects the light reflectance of the resulting porous sheet. If the amount of the inorganic filler added is small, the porosity of the resulting porous sheet will be low, and conversely, if it is large, the porosity will be high. A porous sheet having a low porosity reduces the amount of light reflected at the interface between the resin layer and the air layer, and a porous sheet having a high light reflectance cannot be obtained. Therefore, a porous sheet suitable for a light reflector has an appropriate aperture ratio and a high light reflectance. Also,
When the amount of the inorganic filler added is large, the porosity of the porous sheet increases and the light reflectance increases, but the productivity of the sheet and the strength of the porous sheet decrease. Taking these points into consideration, the addition amount of the inorganic filler is 100 to 300 parts by weight with respect to 100 parts by weight of the thermoplastic resin. When the inorganic filler is barium sulfate, the preferable addition amount range is 180 to 300 parts by weight with respect to 100 parts by weight of the thermoplastic resin. More preferably, it is 180 to 250 parts by weight. In the case of other inorganic fillers, the preferable addition amount range is 120 to 2 with respect to 100 parts by weight of the thermoplastic resin.
It is 00 parts by weight.

For the light reflector of the present invention, a resin composition obtained by adding and mixing a specific amount of the above-mentioned inorganic filler to the above-mentioned thermoplastic resin is used, but within the range that does not impair the object of the present invention, a stabilizer is used. Other additives such as a lubricant, a dispersant, an ultraviolet absorber, a white pigment and a fluorescent whitening agent may be added.

Among these other additives, it is preferable to add one having an ultraviolet absorbing ability. 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, as an additive having an ultraviolet absorbing ability,
2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-2'-
Carboxybenzophenone, 2-hydroxy-4-n-
Octoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-
Hydroxybenzophenone, bis (5-benzoyl-4)
Benzophenone compounds such as -hydroxy-2-methoxyphenyl) methane, 2- (2'-hydroxy-5'-
Methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-
3'-tert-butyl-5'-methylphenyl) -5
-Chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-
Chlorobenzotriazole, 2- (2'-hydroxy-
5'-tert-octylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-ter
t-amylphenyl) benzotriazole, 2- [2 ′
-Hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl] benzotriazole, 2,2'-methylenebis [4
-(1,1,3,3-tetramethylbutyl) -6- (2
[H-benzotriazol-2-yl) phenol] and other ultraviolet absorbers represented by benzotriazole compounds. Also, titanium oxide or the like can be used.

For example, in the case of an ultraviolet absorber, the addition amount thereof is preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin. More preferably 0.05
~ 2 parts by weight. In the case of titanium oxide, the amount is preferably 1 to 30 parts by weight with respect to 100 parts by weight of the thermoplastic resin.

Thermoplastic resin and inorganic filler, and if necessary, ultraviolet absorber, stabilizer, lubricant, dispersant, white pigment,
There is no particular limitation on the method for producing the resin composition by mixing with other additives such as an optical brightener. For example, a method of mixing at room temperature or a temperature in the vicinity thereof using a ribbon blender, a Henschel mixer, a super mixer, a tumbler mixer and the like can be mentioned. Further, after mixing, using a single-screw or twin-screw type extruder equipped with a strand die, a temperature above the melting point or softening point of the thermoplastic resin used, preferably above the melting point or softening point + 20 ° C., thermoplastic resin Kneading in the temperature range below the decomposition temperature of, melt-extruded to form a molten strand, after cooling,
A method of cutting and forming into pellets is also included. In order to uniformly disperse and mix the inorganic filler in the thermoplastic resin, a method of molding into pellets is preferable.

There is no particular limitation on the method of molding a sheet from the thermoplastic resin composition obtained as described above. For example, known methods such as an extrusion molding method using a single-screw or twin-screw extruder equipped with a T die, an inflation molding method using an extruder equipped with a circular die, and a calender molding method can be mentioned. Although the molding temperature of the sheet varies depending on the thermoplastic resin used, it is usually a temperature equal to or higher than the melting point or softening point of the resin used, preferably a melting point or softening point + 20 ° C. or higher and lower than the decomposition temperature.

The unstretched resin sheet thus obtained is subjected to a roll method,
It is stretched in at least a uniaxial direction by a known method such as a tenter method. The stretching may be carried out in one stage or may be carried out in multiple stages. Further, it may be biaxially stretched. Further, after stretching, if necessary, a heat-setting treatment may be performed in order to stabilize the shape of the obtained pores.

In order to prevent the sheet from being cut during stretching and to perform uniform stretching to obtain a porous sheet having a preferable porosity, the stretching temperature is a Vicat softening point (JIS).
It is preferably less than the value measured by the method defined in K-6760). In addition, the draw ratio affects the porosity of the obtained stretched sheet, similarly to the amount of the inorganic filler added. When the stretching ratio is low, the porosity of the obtained stretched sheet is low, and when it is high, the porosity is high. However, if the stretching ratio is too high, the sheet may be cut during stretching, which is not preferable. From this viewpoint, it is 5 to 8 times in the case of uniaxial stretching, and 4 to 7 in the uniaxial direction in the case of biaxial stretching.
It is preferable that the length is about twice and about 1.1 to 3 times in the direction perpendicular to the direction. More preferable stretching ratio is 5.5 to 7.5 times in the case of uniaxial stretching, 4.5 to 6.5 times in the uniaxial direction in the case of biaxial stretching, and 1.1 to in the direction perpendicular to that direction.
It is about 2.5 times.

When the thickness of the porous resin sheet is thin, the light transmittance tends to increase and the light ray reflectance tends to decrease. Also,
If it is thick, the productivity of the sheet will decrease. Therefore, the thickness of the porous resin sheet of the present invention used as a light reflector for a liquid crystal display backlight unit is usually 50 to 300 μm. The thickness is preferably 70 to 300 μm, more preferably 100 to 300 μm.

The porous resin sheet obtained with the above composition and production conditions is a porous resin sheet having a porosity of 40% or more. In order to use the porous resin sheet as a light reflector for a backlight unit of a liquid crystal display device, it is desired to have a high light ray reflectance. If the porosity of the porous resin sheet is less than 40%, the interface between the resin layer and the air layer is reduced, so that the light reflectance is reduced. The porous resin sheet used as the light reflector for the backlight unit of the liquid crystal display device of the present invention has a porosity of at least 40% or more and a light ray reflectance of light having a wavelength of 550 nm is 95% or more. Is preferred. The higher the porosity of the porous resin sheet used as the light reflector for the backlight unit of the liquid crystal display device, the more preferable. However, the upper limit thereof is about 70% in consideration of the formability and stretchability of the stretched sheet. Therefore,
A preferred porous resin sheet has a porosity of 40 to 70% among the porous resin sheets obtained by the above method.

The porous resin sheet obtained by the present invention is used as a light reflector for a lamp holder of a light source forming a backlight unit of a liquid crystal display device and a light reflection sheet arranged below a light guide plate. Moreover, both are integrally formed.

The light reflector for the backlight unit of the liquid crystal display device of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a backlight unit of a typical liquid crystal display device in which a lamp holder of a light source unit and a light reflection sheet arranged below a light guide plate are integrally formed.
In the figure, a porous resin sheet is used as a lamp holder 2 (reflector) and a light reflection sheet 4 disposed below the light guide plate 3, both are integrally formed, and an adhesive 5 is formed on the light guide plate 3. Fixed by. The integral formation means that the lamp holder 2 and the light reflection sheet 4 arranged below the light guide plate 3 are formed of the same porous resin sheet. The light beam generated from the light source 1 is applied to the integrally formed lamp holder 2, the light reflection sheet 4, the light guide plate 3, and the light diffusion sheet 6 disposed above the light guide plate 3. Lamp holder 2 and light reflection sheet 4 formed integrally
The light rays radiated on the light are reflected by these, and the light guide plate 3
Through the light diffusing sheet 6 to be used for liquid crystal display.

Since the porous resin sheet used in the present invention has an excellent light reflectance, it can be produced from a light source by using this as a material for the light reflecting sheet disposed below the lamp holder and the light guide plate. The reflected light can be reflected efficiently. Further, since the porous resin sheet used in the present invention is also excellent in heat resistance, it can sufficiently withstand the irradiation heat of the light source.

The porous resin sheet obtained by the present invention may be used as a single sheet as a light reflector, or may be used by laminating a plurality of sheets. Further, for reasons such as supplementing strength, another sheet or the like may be appropriately laminated on the non-reflective side of the porous resin sheet obtained by the present invention. Further, the porous resin sheet obtained by the present invention may be used as the inner and outer layers and another sheet may be used as the intermediate layer to form a three-layer structure. Further, when laminating, it is not always necessary to laminate on the entire surface of the porous sheet, and it may be laminated only on a part. For example, it may be laminated only on the portion corresponding to the lower part of the light guide plate. The reinforcing sheet preferably has electrical insulation. For example, thermoplastic resin sheets, non-woven fabrics, papers and the like can be mentioned. When stacking the reinforcing sheets, it is important to stack the porous resin sheets so as to be arranged on the light source side such as a fluorescent tube. Examples of the method for laminating the porous resin sheet and another sheet include a method of bonding using various adhesives, a method of thermal bonding, and the like.

[0032]

EXAMPLES The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples. The porosity, brightness, light reflectance and rigidity are values measured by the following methods.

(1) Method of measuring porosity (%) From the true specific gravity (A) of the resin composition used and the bulk specific gravity (B) of the obtained porous resin sheet, the numerical formula (1) [Equation 1]

[0034]

[Equation 1] The open area ratio (C) is calculated by.

(2) Luminance measuring method (relative value) A back of a liquid crystal display device of the type shown in FIG. 1 and formed from a light source, a lamp holder, a light reflection sheet, a light guide plate and a light diffusion sheet. As a lamp holder and a light reflection sheet of a light unit (manufactured by Fujitsu Kasei Co., Ltd.), the porous resin sheets obtained in the examples or comparative examples of the present invention were mounted, and the luminance on the light guide plate was measured by a luminance meter (Minolta camera). (Manufactured by KK, type: LS-110 type). The brightness is a white PET sheet with a thickness of 113 μm (manufactured by Kimoto Co., Ltd., product name: Ref White RW75C).
The brightness is shown as a relative value when the brightness is set to 100.

(3) Method for measuring light reflectance (%) In accordance with JIS K-7105 measuring method B, a spectrophotometer (manufactured by Hitachi, Ltd., model: U-3400) having a wavelength of 550 nm was used. Measure the light reflectance. The reflectance when using an aluminum oxide plate as the standard reflector is 1
It is shown as a relative value when 00 is set.

(4) Rigidity measuring method (mm) The rigidity is measured according to the method (cantilever method) specified in JIS L-1096.

Examples 1 to 3 Density 0.920 g / cm ³ , melt index (M
I) Precipitable sulfuric acid having an average particle diameter of 0.94 μm with respect to 100 parts by weight of 2.0 g / 10 min linear low density polyethylene (manufactured by Mitsui Petrochemical Co., Ltd., trade name: ULTOZEX 2021L: hereinafter referred to as LLDPE) Barium (manufactured by Barite Industry Co., Ltd., trade name: HD) 230 parts by weight, ultraviolet absorber (manufactured by ADEKA ARGUS CORPORATION, trade name:
0.5 parts by weight of MARK LA-36) and 3 parts by weight of calcium stearate were mixed using a tumbler mixer to obtain a resin composition. The obtained resin composition was processed into pellets using a vent type twin-screw extruder. These pellets were melt-extruded at 230 ° C. using an extruder equipped with a T-die to obtain an unstretched sheet. The obtained unstretched sheet was uniaxially stretched between a preheating roll heated to 85 ° C. and a stretching roll at a stretching ratio of 6.5 times to obtain a porous resin sheet having a thickness shown in [Table 1]. . The porosity, brightness, light reflectance and rigidity of the obtained porous resin sheet were evaluated by the methods described above. The composition of the sheet (parts by weight) and the evaluation results are shown in [Table 1].

Example 4 A porous resin sheet was obtained in the same manner as in Example 2 except that the blending ratios of linear low density polyethylene (LLDPE) and barium sulfate were changed to the weight ratios shown in [Table 1].
The evaluation results of the obtained sheet are shown in [Table 1].

Example 5 Density 0.900 g / cm ³ , MI 1.5 g / 10 min
A porous resin sheet having a thickness of 125 μm was obtained in the same manner as in Example 1 except that the propylene homopolymer (trade name: FO-50F: hereinafter referred to as PP) manufactured by Mitsui Toatsu Chemicals, Inc. was used. . The evaluation results of the obtained sheet are shown in [Table 1].
Shown in.

Example 6 Density 0.900 g / cm ³ , MI 1.5 g / 10 min
A porous resin sheet having a thickness of 125 μm was obtained in the same manner as in Example 1 except that the ethylene-propylene copolymer (manufactured by Mitsui Toatsu Chemicals, Inc., trade name: MJS-G: hereinafter referred to as EP) was used. It was The evaluation results of the obtained sheet are shown in [Table 1].

[0042]

[Table 1]

Example 7 Instead of the ultraviolet absorbent used in Example 2, titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., trade name: TYPEK R-670) was used.
A porous resin sheet was obtained in the same manner as in Example 2 except that 16 parts by weight was added to 100 parts by weight of linear low density polyethylene. The evaluation results of the obtained sheet are shown in [Table 2].

Example 8 The ultraviolet absorber used in Example 2 and the titanium oxide used in Example 7 were used in amounts of 0.5 parts by weight and 16 parts by weight, respectively, per 100 parts by weight of linear low-density polyethylene. A porous resin sheet was obtained in the same manner as in Example 2.
The evaluation results of the obtained sheet are shown in [Table 2].

Example 9 A white PET sheet having a thickness of 38 μm (Toray Industries, Inc.) was formed on the entire one surface of a porous resin sheet obtained by the same method as in Example 2.
Made by trade name: E-20) with adhesive (Dainichi Seika Kogyo Co., Ltd.)
Manufactured by Seiko Bond E-295 / C-75N) under the trade name to obtain a porous resin sheet laminate. The evaluation results of the obtained laminate are shown in [Table 2]. In addition, the sheet thickness, light reflectance and rigidity in [Table 2] are values for the laminate, and the porosity is a value only for the porous resin sheet portion.

Example 10 A white PET sheet having a thickness of 38 μm (manufactured by Toray Industries, Inc., trade name: E) was formed only on the portion corresponding to the bottom of the light guide plate on one side of the porous resin sheet obtained by the same method as in Example 2. -20) is an adhesive (manufactured by Dainichiseika Kogyo Co., Ltd., trade name: Seika Bond E)
-295 / C-75N) to obtain a porous resin sheet laminate. The evaluation results of the obtained laminate are shown in [Table 2]. In addition, the sheet thickness and light reflectance in Table 2 are values for the laminate, and the porosity and rigidity are values only for the porous resin sheet portion.

Example 11 Calcium carbonate having an average particle diameter of 1.1 μm as an inorganic filler (manufactured by Dowa Calfine Co., Ltd., trade name: SST-4)
0) in the weight ratio shown in [Table 2], and instead of calcium stearate, castor oil (made by Ito Oil Co., Ltd., trade name: rhombus special A) is used for 7.5 parts by weight with respect to 100 parts by weight of the resin. A porous resin sheet was obtained in the same manner as in Example 2 except for the above. The evaluation results of the obtained sheet are shown in [Table 2].

Example 12 Density 1.34 g / cm ³ , intrinsic viscosity (IV) 0.76 d
1 / g of polyethylene terephthalate (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Dyanite PA-500, hereinafter,
PET) was used and the extrusion molding temperature was 280 ° C., and the stretching preheating roll temperature was 100 ° C., to obtain a porous resin sheet in the same manner as in Example 2. The evaluation results of the obtained sheet are shown in [Table 2].

[0049]

[Table 2]

Comparative Example 1 A white PET sheet having a thickness of 113 μm as a light reflector (manufactured by Kimoto Co., Ltd., trade name: Ref White RW75C)
Was evaluated by the above method, and the results are shown in [Table 3]. Since this sheet has a low light reflectance, the brightness was low.

Comparative Example 2 A white PET sheet (manufactured by Toray Industries, Inc., trade name: E-60) having a thickness of 188 μm as a light reflector was evaluated by the above method, and the results are shown in [Table 3]. Since this sheet has a high rigidity, a gap was created between the light source and the sheet when the light source was wrapped.

Comparative Example 3 A polyolefin sheet was obtained in the same manner as in Example 2 except that an unstretched sheet having a thickness of 125 μm was produced and was not stretched. The evaluation results of the obtained sheet are shown in [Table 3]. This sheet had low porosity and low light reflectance, and thus had low brightness.

Comparative Example 4 A porous resin sheet was obtained in the same manner as in Example 2 except that the mixing ratio of linear low density polyethylene (LLDPE) and barium sulfate was changed to the weight ratio shown in [Table 3]. The evaluation results of the obtained sheet are shown in [Table 3]. This sheet had low porosity and low light reflectance, and thus had low brightness.

[0054]

[Table 3]

[0055]

The light reflector comprising the porous resin sheet of the present invention has excellent electrical insulation and light reflectance because it is a porous sheet containing a specific amount of thermoplastic resin and an inorganic filler. . Moreover, it is highly flexible and has low rigidity. By integrally forming and using this as a lamp holder light reflector forming a backlight unit of a liquid crystal display device and a light reflection sheet disposed below the light guide plate, a light source such as a fluorescent tube and a lamp holder It is possible to prevent the occurrence of leakage current between the two, and because it has appropriate rigidity and flexibility, it is easy to seal the light source such as a fluorescent tube, and it is possible to prevent light leakage from the lamp holder. Is. Further, since the light ray reflectance is high, it is possible to improve the brightness as compared with the conventional backlight unit.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a backlight unit of a typical liquid crystal display device in which a lamp holder of a light source unit and a light reflection sheet arranged below a light guide plate are integrally formed.

[Explanation of symbols] 1. Light source 2. Lamp holder 3. Light guide plate 4. Light reflection sheet 5. Adhesive 6. Light diffusion sheet

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 21, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction content]

[0042]

[Table 1]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction content]

[0049]

[Table 2]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0054

[Correction method] Change

[Correction content]

[0054]

[Table 3]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display location // C08L 23:02 67:00 (72) Inventor Tsutomu Izeki 2 Tango Dori, Minami-ku, Aichi Prefecture 1-chome Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Naoko Sawada 2-1-1 Tango Dori, Minami-ku, Aichi Prefecture Nagoya Mitsui Toatsu Chemical Co., Ltd.

Claims (7)

[Claims] 1. A light reflector for a backlight unit of a liquid crystal display device comprising a porous resin sheet, wherein the light reflector comprises (1) a lamp holder portion and a light reflection sheet portion, which are integrally formed (2). A backlight unit for a liquid crystal display device, comprising 100 to 300 parts by weight of an inorganic filler with respect to 100 parts by weight of a thermoplastic resin, and (3) having a light reflectance of 95% or more at a wavelength of 550 nm. For light reflector. 2. The light reflector for a backlight unit of a liquid crystal display device according to claim 1, wherein the thermoplastic resin is at least one resin selected from a polyolefin resin and a polyester resin. 3. The liquid crystal display device according to claim 1, wherein the inorganic filler is at least one filler selected from barium sulfate, calcium carbonate, titanium oxide, alumina and magnesium hydroxide. Light reflector for backlight unit. 4. The thermoplastic resin is a polyolefin resin, and barium sulfate is 180 as an inorganic filler.
The light reflector for a backlight unit of a liquid crystal display device according to claim 1, wherein the light reflector is contained in an amount of ˜300 parts by weight. 5. A porous resin sheet as another additive,
With respect to 100 parts by weight of the thermoplastic resin, 0.
The light reflector for a backlight unit of a liquid crystal display device according to claim 1, comprising at least one kind of additive selected from 01 to 5 parts by weight and 1 to 30 parts by weight of titanium oxide. 6. The porosity of the porous resin sheet is 40 to 70.
%, The light reflector for a backlight unit of a liquid crystal display device according to claim 1. 7. The porous resin sheet has a thickness of 100 to 30.
The light reflector for a backlight unit of a liquid crystal display device according to claim 1, wherein the light reflector has a thickness of 0 μm.