JP2010044238A - Reflection film for liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection film for a liquid crystal display device, obtaining high luminance when being used as a reflector in a backlight type backlight unit of a liquid crystal display device by restraining specular reflection on the film surface to cause diffuse reflection. <P>SOLUTION: The reflection film for the liquid crystal display device includes a white film and transparent projections 3-50 μm high, which are provided on the surface of the white film, wherein the coverage of the transparent projections to the white film surface is 50-100%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reflective film for a liquid crystal display device used as a reflective film in a backlight unit of a liquid crystal display device.

  The backlight unit of a liquid crystal display device can be broadly divided into a backlight method in which a light source is placed on the back of the display and a sidelight method in which a light source is placed on the side surface. In order to prevent escape to the back of the camera, a reflective film is installed on the back. This reflective film is required to have a thin and high reflectance. As a reflective film, a white polyester film containing fine bubbles inside the film is known and widely used.

  In recent years, with the spread of liquid crystal televisions and the like, a backlight system in which a light source is placed on the back of a display, in particular, requires a high-brightness backlight. However, there is a limit to only improving the reflectance of the reflective film.

JP 63-62104 A Japanese Patent Publication No. 8-16175 JP 2000-37835 A JP 2005-125700 A JP 2004-50479 A

  In the backlight method, if the reflective film is highly specularly reflected, the reflected light returns to the light source located on the reflective film, and the light does not reach the display surface, causing a loss of light and causing a decrease in luminance. become. When the present invention is used as a reflective film in a backlight unit of a backlight system of a liquid crystal display device by suppressing specular reflection by the film and providing reflected light with directivity that avoids a light source directly above. It is an object of the present invention to provide a reflective film for a liquid crystal display device that can obtain high luminance.

  That is, the present invention comprises a white film and a transparent protrusion having a height of 3 to 50 μm provided on the surface of the white film, and the coverage by the transparent protrusion on the surface of the white film is 50 to 100%. A reflective film for a liquid crystal display device.

  ADVANTAGE OF THE INVENTION According to this invention, the reflection film for liquid crystal display devices which can obtain high brightness | luminance when it uses as a reflection film for the backlight system backlight unit of a liquid crystal display device can be provided.

Hereinafter, the present invention will be described in detail.
[White film]
The white film in the present invention is a film made of a thermoplastic resin and having a white colorant or a void-forming substance contained in the film so as to exhibit a white color. As the colorant or void forming substance, for example, inorganic particles and organic particles can be used.

  The light reflectance of the white film is preferably 95% or more, more preferably 96% or more, and particularly preferably 97% or more as the reflectance at a wavelength of 550 nm. The white film may be a single layer film or a laminated film. From the viewpoint of obtaining high light reflectance and mechanical strength, a laminated film composed of a layer containing a relatively large amount of voids and a layer containing a relatively small amount of voids or no voids is preferable. Examples of the thermoplastic resin constituting the film include polyester, polyolefin, and polystyrene. Polyester is preferred from the viewpoint of achieving both mechanical properties and thermal stability.

[polyester]
When using polyester as a thermoplastic resin of a white film, polyester which consists of a dicarboxylic acid component and a diol component is used as polyester. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, adipic acid, and sebacic acid. Examples of the diol component include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,6-hexanediol.

  Among these polyesters, aromatic polyesters are preferable, and polyethylene terephthalate is particularly preferable. Polyethylene terephthalate may be a homopolymer, but a copolymer is preferred. In particular, when a laminated film composed of a layer containing a relatively large amount of voids and a layer containing a relatively small amount of voids or no voids is used as a white film, it is used for a layer containing a relatively large amount of voids. The polyester is preferably a copolymerized polymer. In that case, the ratio of the copolymerization component is, for example, 3 to 20 mol%, preferably 4 to 15 mol%, more preferably 5 to 13 mol%, based on the total dicarboxylic acid component. By setting the proportion of the copolymer component within this range, excellent film forming properties can be obtained even for a layer containing a relatively large amount of voids, and a laminated film having excellent thermal dimensional stability can be obtained.

  When inorganic particles are used as the colorant or void forming substance, white inorganic particles are preferred as the inorganic particles. Examples of the white inorganic particles include barium sulfate, titanium dioxide, silicon dioxide, and calcium carbonate particles. The average particle diameter of the inorganic particles is, for example, 0.2 to 3.0 μm, preferably 0.3 to 2.5 μm, and more preferably 0.4 to 2.0 μm. By using inorganic particles in this range, it can be dispersed moderately in the polyester, the particles are less likely to aggregate, and a film without coarse protrusions can be obtained, and at the same time, the film surface is not too rough, Glossiness can be controlled within an appropriate range. The inorganic particles may have any particle shape, for example, a plate shape or a spherical shape. The inorganic particles may be subjected to a surface treatment for improving dispersibility.

  When organic particles are used as the colorant or void forming substance, resin particles that are incompatible with polyester are used as the organic particles. As the organic particles, silicone resin particles and polytetrafluoroethylene particles are preferable. The average particle diameter of the organic particles is, for example, 0.2 to 10 μm, preferably 0.3 to 8.0 μm, and more preferably 0.4 to 6.0 μm. By using the organic particles in this range, it is possible to obtain a film that can be appropriately dispersed in the polyester, that the particles do not easily aggregate, and that does not have coarse protrusions.

[Transparent protrusion]
The reflective film for a liquid crystal display device of the present invention comprises a white film and a transparent protrusion having a height of 3 to 50 μm provided on the surface of the film. Transparent protrusions may be provided continuously or discontinuously.

  In the present invention, the coverage by the transparent protrusions on the white film surface is 50 to 100%. If the coverage is less than 50%, the directivity of light that avoids the light source directly above is impaired, and an increase in luminance cannot be expected. This ratio is preferably 60% or more, more preferably 70% or more, and particularly preferably 80% or more.

  In the present invention, the coverage is measured with respect to a measurement area having a total length of 6 mm in each of the measurement areas having a length of 3 mm in two orthogonal directions in the film plane. Is defined as the percentage that is.

Specifically, using a microtome, a section is cut out so that the thickness direction of the film becomes a cut surface, and this section sample is made 3000 times using a Hitachi S-4700 field emission scanning electron microscope. And observe the measurement area with a total length of 6 mm of the measurement area with a length of 3 mm in each of the two orthogonal directions in the film plane, and add up the length of the part not covered with transparent protrusions in the measurement area And calculated by the following formula.
Coverage rate = (6 mm− (cumulative length of the portion not covered with the transparent protrusion)) / 6 mm × 100 (%)

In addition, when the largest diameter part of a transparent protrusion has come out outside the coating-film surface, it is considered that the part covered with the maximum diameter of a transparent particle is coat | covered with the transparent protrusion.
As long as the transparent protrusion is formed of a transparent substance, the transparent protrusion may be formed of an organic substance or an inorganic substance. Further, both may be mixed or combined to form the protrusion. The light transmittance of the substance forming the transparent protrusions is 50% or more, preferably 60% or more, and more preferably 70% or more. In order to prevent coloring, the thing which does not absorb light in a visible region is good.

  As an organic substance that forms transparent protrusions, for example, acrylic, silicone, styrene, and urethane can be used. Acrylic and styrene are preferred because they hardly absorb light in the visible light region. Glass can be preferably used as the inorganic substance. Among organic substances, for example, a UV curable resin or a thermosetting resin can be used.

Transparent protrusions may be formed by transparent particles. When forming transparent protrusions with transparent particles, the transparent protrusions are preferably composed of a binder and transparent particles.
In this case, the shape of the transparent particles can be, for example, a spherical shape, a rugby ball shape, or a convex lens shape. In order to collect light and increase the luminance, the aspect ratio is 1.0 to 3. Particles having a shape at 0 are preferred, and spherical particles are particularly preferred. The spectrum ratio is the major axis / minor axis of the particle.

  In this case, the size of the transparent particles is preferably 5 to 50 μm, more preferably 7 to 45 μm, particularly preferably 8 to 40 μm, and most preferably 10 to 30 μm in terms of average particle diameter. By having an average particle size within this range, aggregation is unlikely to occur and the directivity of light is easy to control, and it is difficult to cause streaky coating defects during particle removal or coating. Can do.

  As the binder, for example, an acrylic resin, a polyester resin, a polyurethane resin, a polyesteramide resin, a polyolefin resin, a copolymer or a blend thereof can be used. The binder may be crosslinked by blending an isocyanate-based, melamine-based, or epoxy-based crosslinking agent.

  In the present invention, the transparent protrusion may have any shape, but preferably has a dome shape or a pyramid shape, and particularly preferably has a dome shape. The dome-shaped protrusion may be a protrusion having a smooth convex surface, and is preferably a hemispherical surface or a part of a spheroid surface, particularly preferably a hemispherical surface. The hemispherical surface does not necessarily have to be half of a sphere, and corresponds to a dome-shaped protrusion if a part of the sphere protrudes to the surface in a convex shape.

  The transparent protrusion may be formed, for example, by placing a curable resin filled in a mold on a film and curing it. When a UV curable resin is used as the cured back resin, a reactive group-containing compound such as a (meth) acryloyl group, vinyl group or epoxy group is reacted with the aforementioned reactive group-containing compound by irradiation with UV light or the like. What mixed the compound which generate | occur | produces active species, such as a possible radical and a cation, can be used.

  From the viewpoint of curing speed, a combination of a reactive group-containing compound (monomer) containing an unsaturated group such as a (meth) acryloyl group or a vinyl group and a radical photopolymerization initiator that generates a radical by UV light is preferable.

  Examples of the (meth) acryloyl group compound include phenoxyethyl (meth) acrylate, phenoxy-2-methylethyl (meth) acrylate, phenoxyethoxyethyl (meth) acrylate, 3-phenoxy-2-hydroxypropyl (meth) acrylate, 2-phenylphenoxyethyl (meth) acrylate, 4-phenylphenoxyethyl (meth) acrylate, 3- (2-phenylphenyl) -2-hydroxypropyl (meth) acrylate, and p-cumylphenol reacted with ethylene oxide ( (Meth) acrylate, ethylene oxide-added bisphenol A (meth) acrylate, propylene oxide-added bisphenol A (meth) acrylate, bisphenol A diglycidyl ether and (meth) acrylate Bisphenol A epoxy (meth) acrylate obtained by epoxy ring opening with acid, bisphenol F epoxy (meth) acrylate obtained by epoxy ring opening reaction of bisphenol F diglycidyl ether and (meth) acrylic acid can be mentioned. .

  The height of the transparent protrusion in the present invention is 3 to 50 μm. If the height is less than 3 μm, the effect of directivity of light will not be exhibited, and if it exceeds 50 μm, the projection will drop off or the effect of imparting directivity to reflected light will vary greatly depending on the design of the position of the light source of the backlight Concerns arise.

  When a transparent protrusion is dome shape, it is preferable that the average diameter of the bottom face of each dome is 5-50 micrometers. By setting the average diameter in this range, it is preferable that the protrusions can be prevented from dropping without impairing the effect of imparting directivity to the reflected light. In the case of a dome shape, the most preferable shape is a hemisphere.

  When the transparent protrusion has a pyramid shape, the length of one side of the bottom surface of each pyramid is preferably 5 to 50 μm. By setting the length of one side in this range, it is preferable to prevent the protrusions from dropping without impairing the effect of imparting directivity to the reflected light.

[Production method]
Hereinafter, an example of the method for producing the reflective film of the present invention will be described. In this example, a laminated film is used as the white film. In addition, as this white film, the film marketed by the name of Teijin Tetron UX02-225 (made by Teijin DuPont Film) can be used, for example.

  The raw material polyester used for the film is filtered using a non-woven fabric type filter having an average opening of 10 to 100 μm, preferably an average opening of 20 to 50 μm made of fine stainless steel wire having a wire diameter of 15 μm or less. By performing this filtration, it is possible to suppress agglomeration of particles that are usually agglomerated and become coarse agglomerated particles, and to obtain a laminated film with few coarse foreign matters.

The filtered polyester composition is extruded from a die to a multilayer state by a simultaneous multilayer extrusion method using a feed block in a molten state to produce a laminated unstretched sheet.
The laminated unstretched sheet extruded from the die is cooled and solidified by a casting drum to form a laminated unstretched film. This laminated unstretched film is heated by roll heating, infrared heating or the like, and stretched in the longitudinal direction to obtain a laminated longitudinally stretched film. This stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls. The stretching is preferably performed at a temperature equal to or higher than the glass transition point (Tg) of the polyester. The draw ratio is preferably 2.2 to 4.0 times, more preferably 2.3 to 3.9 times in both the longitudinal direction and the direction orthogonal to the longitudinal direction (hereinafter referred to as the transverse direction). If it is less than 2.2 times, the thickness unevenness of the film is deteriorated and a good film cannot be obtained, and if it exceeds 4.0 times, breakage tends to occur during film formation, which is not preferable.

  Subsequently, the laminated film after the longitudinal stretching is sequentially subjected to lateral stretching, heat setting, and thermal relaxation to form a laminated biaxially oriented film. These processes are performed while the film is running. The transverse stretching process starts from a temperature higher than the glass transition point (Tg) of the polyester. Although the temperature rise in the transverse stretching process may be continuous or stepwise (sequential), the temperature is usually raised sequentially. For example, the transverse stretching zone of the tenter is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium having a predetermined temperature for each zone. The transverse stretching ratio is preferably 2.5 to 4.5 times, more preferably 2.8 to 3.9 times, although it depends on the required characteristics of this application. If it is less than 2.5 times, the thickness unevenness of the film is deteriorated and a good film cannot be obtained, and if it exceeds 4.5 times, breakage tends to occur during film formation. Hereinafter, the melting point is abbreviated as Tm.

The film after transverse stretching is preferably heat treated with a constant width or a width reduction of 10% or less while holding both ends (Tm-20 ° C.) to (Tm-100 ° C.) to reduce the thermal shrinkage. When the heat treatment temperature is higher than (Tm−20 ° C.), the flatness of the film is deteriorated and the thickness unevenness is increased, which is not preferable. If it is lower than (Tm-100) ° C., the heat shrinkage rate may increase, which is not preferable. Further, in order to adjust the heat shrinkage, both ends of the film being held can be cut off, the take-up speed in the film vertical direction can be adjusted, and the film can be relaxed in the vertical direction. As a means for relaxing, the speed of the roll group on the tenter exit side is adjusted. As the rate of relaxation, the speed of the roll group is reduced with respect to the film line speed of the tenter, preferably 0.1 to 2.5%, more preferably 0.2 to 2.3%, particularly preferably 0.3. The film is relaxed by performing a speed reduction of ˜2.0% (this value is referred to as “relaxation rate”), and the longitudinal heat shrinkage rate is adjusted by controlling the relaxation rate. Further, the width of the film in the horizontal direction can be reduced in the process until both ends are cut off, and a desired heat shrinkage rate can be obtained.
The white film itself can be prepared, for example, in this way.

Next, a transparent protrusion is formed on the white film.
When forming transparent protrusions using transparent particles, dissolve or disperse the binder and apply a predetermined amount of the coating agent with the transparent particles dispersed using a die coating device or gravure roll coating device. For example, it can be obtained by drying in an oven set in steps to 120 ° C.

  When forming transparent protrusions without using transparent particles, after forming protrusions of a desired shape on the film with a predetermined mold using a curable resin that gives a transparent cured product, Transparent protrusions can be formed by curing the curable resin with ultraviolet rays (UV light).

Hereinafter, the present invention will be described in detail by way of examples. Each characteristic value was measured by the following method.
(1) Reflectance An integrating sphere was attached to a spectrophotometer (Shimadzu Corporation UV-3101PC), and the light reflectance when a BaSO ₄ white plate was 100% was measured at a wavelength of 550 nm, and this value was defined as the reflectance.

(2) Relative luminance The luminance of the display device when used as a reflector in a liquid crystal display device was evaluated. Remove the reflective film from the backlight of Sony's 32-inch TV (BRAVIA KDL-32V2500), install the film to be evaluated, and use a luminance meter (Model MC-940, manufactured by Otsuka Electronics) The luminance was measured at a measurement distance of 500 mm from the center in front. The relative luminance is a relative value of luminance calculated based on the luminance of the reflective film of Comparative Example 1 in which the transparent particle coating layer is not provided.
Relative brightness = (Brightness of reflection film) / (Brightness of reflection film of Comparative Example 1) × 100 (%)

(3) Average particle size of inorganic particles and organic particles of white film The particle size distribution of the particles was obtained with a particle size distribution meter (LA-950, manufactured by Horiba, Ltd.), and the particle size at d50 was defined as the average particle size.

(4) Average particle diameter of transparent particles used for formation of protrusions Using a S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd., arbitrarily adding 100 particles before being added to the resin (film) at a magnification of 1000 times The average particle size was determined. When the particles were not spherical, (major axis + minor axis) / 2 was defined as the average particle size.

(5) Aspect ratio of particles used for formation of protrusions Using an S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd., arbitrarily observing 30 exposed particles at a magnification of 500 times, the values of major axis and minor axis From the following formula, the average value was calculated.
Aspect ratio = major axis / minor axis

(6) Coverage of film by transparent protrusions A sample was cut out using a microtome so that the thickness direction of the film was a cut surface. The slice sample was observed at a magnification of 3000 times using a Hitachi S-4700 field emission scanning electron microscope. The measurement area of 3 mm in length in each of the two orthogonal directions in the film plane is observed for the total measurement area of 6 mm, and the lengths of the portions not covered by the transparent protrusions in the measurement area are integrated. It calculated | required by the type | formula (refer FIG. 5).
Coverage rate = (6 mm− (cumulative length of the portion not covered with the transparent protrusion)) / 6 mm × 100 (%)

(7) Height of transparent protrusions The height of the transparent protrusions is obtained by arbitrarily determining the height of the protrusions that are transparent in the vertical direction from the film surface (or the binder surface when particles are buried with a binder) at 20 points. The average value was defined as the height of the transparent protrusion.

(8) Thickness of the coating film A cross section of the film sample was taken with a digital microscope (HIROX Co. Ltd.,
(HI-SCOPE Advanced KH-3000) was observed and photographed at a magnification of 5 times, the thickness of the binder was determined from the photograph, 10 points were arbitrarily measured, and the average value was obtained.

[Example 1]
Reflection of a white film (Teijin Tetron UX02-225 made by Teijin DuPont Films) consisting of two layers, a reflective layer composed of a polyester composition containing barium sulfate particles as a void-forming agent and a support layer composed of polyester On top of the layer (reflectance 98.5%), after applying a coating solution having the composition shown in the following preparation recipe at a coating amount of a wet thickness of 20 g / m ² in a die coating apparatus, And dried to obtain a reflective film.
Preparation recipe 1)
-Protrusion forming material: Sekisui Plastics Industry MBX-20SS (38 wt%)
-Acrylic binder: Nippon Shokubai U Double S2740 (20% by weight)
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (2% by weight)
Organic solvent: butyl acetate (40% by weight)
Table 1 shows the physical properties of the obtained reflective film.

[Example 2]
A reflective film was obtained in the same manner as in Example 1 except that the coating liquid was changed to the coating liquid having the composition shown in the following preparation recipe and the coating liquid was applied at a wet thickness of 10 g / m ² .
Preparation recipe 2)
Protrusion forming material: Sekisui Plastics Industry MBX-10SS (30% by weight)
-Acrylic binder: Nippon Shokubai U Double S2740 (28 wt%)
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (2% by weight)
Organic solvent: ethyl acetate (40% by weight)
Table 1 shows the physical properties of the obtained reflective film.

[Example 3]
A reflective film was obtained in the same manner as in Example 1 except that the coating liquid was changed to the coating liquid having the composition shown in the following preparation recipe and was applied at a coating amount of a wet thickness of 25 g / m ² .
Preparation recipe 3)
-Protrusion forming material: Sekisui Plastics Industry MBX-30SS (32% by weight)
-Acrylic binder: DIC ACRYDIC A807BA (25% by weight)
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (3 wt%)
Organic solvent: methyl ethyl ketone (40% by weight)
Table 1 shows the physical properties of the obtained reflective film.

[Example 4]
A reflective film was obtained in the same manner as in Example 1 except that the coating liquid was changed to the coating liquid having the composition shown in the following preparation recipe and the coating liquid was applied at a coating thickness of 30 g / m ^{2 in} wet thickness.
Preparation recipe 4)
Protrusion-forming substance particles: Sekisui Plastics Industry MBX-50SS (25% by weight)
-Acrylic binder: Nippon Shokubai U Double S2740 (38 wt%)
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (3 wt%)
Organic solvent: ethyl acetate (34% by weight)
Table 1 shows the physical properties of the obtained reflective film.

[Example 5]
A reflective film was obtained in the same manner as in Example 1 except that the coating liquid was changed to the coating liquid having the composition shown in the following preparation recipe and was applied at an application amount of wet thickness of 15 g / m ² .
Preparation recipe 5)
Protrusion forming material: Sekisui Plastics Industry MBX-15SS (19% by weight)
-Acrylic binder: Nippon Shokubai U Double S2740 (37% by weight)
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (4% by weight)
Organic solvent: butyl acetate (40% by weight)
Table 1 shows the physical properties of the obtained reflective film.

[Example 6]
On the reflection layer of the white film, a quadrangular pyramidal protrusion was formed on the entire surface without any gap. That is, a coating liquid having the composition shown in the following preparation recipe is poured into a SUS mold so as to form a quadrangular pyramid, and a white film is adhered to the SUS mold, and UV is applied with a high-pressure mercury lamp (Toscurer manufactured by Harrison Toshiba Lighting). The coating liquid was cured by irradiating light and dried in an oven at 100 ° C. to form a quadrangular pyramid on the entire reflective surface of the white film to obtain a reflective film. The size of the reflective film was adjusted to the size of the reflective film of the backlight of a 32-inch television (BRAVIA KDL-32V2500) manufactured by Sony Corporation used for evaluation of relative luminance. FIG. 1 shows a schematic diagram of the square thrust portion of the mold used for forming the square thrust projection.
Preparation recipe 6) UV curable resin, EB3700 made by Daicel UC
(Bisphenol A type epoxy acrylate) (25% by weight)
・ BPE200 made by Shin-Nakamura Chemical
(Ethylene oxide-added bisphenol A methacrylic ester) (8% by weight)
-BR-31 made by Daiichi Pharmaceutical
(Tribromophenoxyethyl acrylate) (42% by weight)
・ Toa Gosei M-110
((Meth) acrylate of p-cumylphenol reacted with ethylene oxide)
(8% by weight)
LR8883 (radical generator) manufactured by BASF (1% by weight)
・ Methyl ethyl ketone (16% by weight)
Table 1 shows the physical properties of the obtained reflective film.

[Example 7]
A coating solution having the composition of the preparation recipe 6 in Example 6 is applied on a white film at a coating amount of 15 g / m ² using a die coating apparatus, and the coating surface of the film is shown in FIG. With a nip roller provided with prismatic unevenness, the coating layer is uneven and cured by irradiating with UV light with a high-pressure mercury lamp (Harrison Toshiba Lighting, Inc.) and drying in an oven at 100 ° C. To create a prism shape.
In the measurement of relative luminance in this example, a reflective film was installed so that the flow direction of the prism was parallel to the cold cathode tube of the light source of the backlight.

[Comparative Example 1]
The film was evaluated without coating the coating solution on the white film.

[Comparative Example 2]
A reflective film was obtained in the same manner as in Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe and was applied at an application amount of a wet thickness of 40 g / m ² .
Preparation recipe 7)
-Acrylic binder: Nippon Shokubai U Double S2740 (57 wt%)
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (3% by weight)
Organic solvent: butyl acetate (40% by weight)

[Comparative Example 3]
A reflective film was obtained in the same manner as in Example 1 except that the coating liquid was changed to the coating liquid having the composition shown in the following preparation recipe and the coating liquid was applied at a coating thickness of 2 g / m ^{2 in} wet thickness.
Preparation recipe 8)
Protrusion forming material: Soken Chemical MX-150 (30% by weight)
-Acrylic binder: Nippon Shokubai U Double S2740 (27% by weight)
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (3% by weight)
Organic solvent: butyl acetate (40% by weight)
Table 1 shows the physical properties of the obtained reflective film.

[Comparative Example 4]
A reflective film was obtained in the same manner as in Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe and was applied at an application amount of wet thickness of 80 g / m ² .
Preparation recipe 8)
・ Protrusions: Potters-Ballotini Co Ltd. J-120 (30% by weight)
-Acrylic binder: Nippon Shokubai U Double S2740 (27% by weight)
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (3% by weight)
Organic solvent: butyl acetate (40% by weight)
Table 1 shows the physical properties of the obtained reflective film.

[Comparative Example 5]
A reflective film was obtained in the same manner as in Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe and was applied at an application amount of a wet thickness of 40 g / m ² .
Preparation recipe 9)
-Protrusion forming material: Sekisui Plastics Industry MBX-50 (3 wt%)
-Acrylic binder: DIC ACRYDIC A807BA (50% by weight)
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (3% by weight)
Organic solvent: butyl acetate (44% by weight)
Table 1 shows the physical properties of the obtained reflective film.

[Comparative Example 6]
A reflective film provided with a prism of the reflective layer was obtained in the same manner as in Example 6 except that the shape of the prism provided on the reflective layer of the white film was changed to the shape shown in FIG.
Table 1 shows the physical properties of the obtained reflective film.

[Comparative Example 7]
A film was obtained by processing the surface in the same manner as in Example 7 except that the shape of the prism provided on the reflective layer of the white film was changed to the shape shown in FIG.
Table 1 shows the physical properties of the obtained reflective film.

In this invention, the example of sectional drawing of the reflective film for liquid crystal display devices which formed the transparent protrusion on the white film with the transparent particle is shown in FIG. By diffusing and reflecting the light from the light source placed above the reflective film with directivity in a direction that avoids the light source, the loss of light due to returning to the light source is reduced, and the amount of light reaching the display surface is reduced. Can do a lot.
The reflective film for a liquid crystal display device of the present invention can be suitably used as a reflective film incorporated in a backlight unit of a liquid crystal display device.

In Example 6, it is a schematic diagram of the square thrust part of the metal mold | die used for formation of the square thrust type protrusion. In Example 7, it is the shape of the prism-shaped unevenness formed on the coating layer when the unevenness is formed on the coating layer using the nip roller provided with the prism-shaped unevenness. FIG. 10 is a schematic view of a square thrust portion of a mold used for forming a square thrust projection in Comparative Example 6. It is the shape of the prism-shaped unevenness | corrugation formed in a coating layer, when forming an unevenness | corrugation in a coating layer using the nip roller which provided the prism-shaped unevenness | corrugation in the comparative example 7. FIG. It is a schematic diagram of the range of length 3mm of the measurement area | region of each measurement direction among the cut surfaces of the film cut | disconnected using the microtome in the measurement of the coverage by a transparent protrusion. It is an example of sectional drawing of the reflective film for liquid crystal display devices of this invention which formed the transparent protrusion on the white film with the transparent particle.

Claims (1)

  A liquid crystal display device comprising a white film and a transparent protrusion having a height of 3 to 50 μm provided on the surface of the white film, wherein the coverage by the transparent protrusion on the surface of the white film is 50 to 100% Reflective film.