JP3020221B2 - Light diffusion film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusion film applied to a backlight panel of a liquid crystal display.

[0002]

2. Description of the Related Art In a liquid crystal display device, an illumination panel is disposed behind the liquid crystal display panel so that the displayed image can be easily viewed, and light from the backlight illumination panel is transmitted from the rear to the front of the liquid crystal display panel. It is known to cause. FIGS. 1 and 2 show structural examples of such a backlight illumination panel. 1 shows a cross-sectional view of a side-lamp type lighting panel in which a lamp is provided on one side end of a light guide plate, and FIG. 2 shows a lamp provided on both side ends of a light guide plate. 1 shows a cross-sectional configuration diagram of a side lamp type lighting panel. In these figures, 1 is a light guide plate, which is made of a transparent plastic plate such as an acrylic plate,
A white dot pattern 2 for reflection is printed on the back surface. Reference numeral 3 denotes a lamp, and reference numeral 4 denotes a lamp cover. A reflection sheet 6 is laminated on the inner surface of the lamp cover. 5
Is a reflection plate, and 7 is a light diffusion film. In the lighting panel having such a structure, the light from the lamp 3 is
The light enters the light guide plate 1, passes through the light diffusion film 7 disposed on the surface thereof, and is led out toward the liquid crystal panel disposed in front of the light diffusion film 7.

Conventionally, as a light diffusion film 7 applied to such a lighting panel, conventionally, a plastic film having a solid fine particle layer formed on both surfaces or a fine uneven surface by embossing the surface of the film. What laminated | stacked the formed plastic film was used. In particular, when a higher luminance is required for a lighting panel, a plurality of these films are used in a laminated state. However, when a plurality of films are stacked and used as described above, there is a problem that the cost is increased due to complexity of the manufacturing process, mixing of dust or lamination failure.

[0004]

SUMMARY OF THE INVENTION The present invention solves the problems of structural complexity and high cost found in a conventional light diffusion film made of a plastic film, and a light diffusion film made of a single plastic film. An object is to provide an excellent light diffusion film.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, a solid fine particle layer having an average particle size of 10 μm or less is provided on the surface of a transparent plastic film, and a spherical particle layer made of a polyolefin resin having an average particle size of 30 μm or less is provided on the back surface of the plastic film. A light diffusing film applied to a backlight illumination panel in a liquid crystal display device, characterized by having a structure in which is disposed.

The transparent plastic film used in the present invention includes polycarbonate, polyester, nylon, polyacrylate, polyvinyl chloride, polyolefin and the like. In the present invention, it is particularly preferable to use a plastic having a refractive index in the range of 1.46 to 1.70. Further, the thickness of the plastic film is 0.1 mm.
05-0.5 mm, preferably 0.075-0.3 mm
It is. It is not particularly necessary to perform embossing on the front and back surfaces of the plastic film, but fine irregularities having a center line average roughness of 0.1 to 6 μm can be formed as necessary.

To obtain the light diffusing film of the present invention,
Solid fine particle layer (A) on the surface side of plastic film
Form. This solid fine particle layer (A) covers solid fine particles.
Disperse in the inner resin solution and emboss
Formed by applying to the surface of the engineered film and drying
can do. As binder resin liquid, Vine
Solution of binder resin in a solvent or binder resin
(Emulsion) in which is dispersed in a solvent is used
It is. As the binder resin, a thermoplastic resin or a thermosetting resin
A curable resin, a photocurable resin or the like is used. With solid particulates
For this purpose, organic and inorganic fine particles are used. Organic
Examples of the system fine particles include synthetic resin fine particles (crosslinked steel).
Len polymer beads, Acrylic resin polymer beads
Etc.) and formalin resin. Inorganic fine particles
As, silica, alumina, zirconia, titania,
Zeolite, kaolin, clay, calcium carbonate, sulfuric acid
Barium, magnesium hydroxide, calcium carbonate, phosphorus
Calcium acid and the like. Average particle size of solid fine particles
Is 10 μm or less, preferably 1 to 7 μm. Ma
The solid fine particles and the binder in the solid fine particle layer (A)
-The weight ratio with the resin is 1/10 to 4/1, preferably 1
/ 5 to 2/1. Thickness of solid fine particle layer (A)
Is 1 to 30 μm, preferably 3 to 20 μm. Solid
The center line average roughness of the body fine particle layer (A) is 0.2 to 5.0.
μm, preferably 0.3 to 3.0 μm, in this range
Deviates to obtain a film having good light diffusion properties
Can not do.

In the present invention, a spherical particle layer (B) made of a polyolefin resin is formed on the back side of the plastic film. This spherical particle layer (B) can be formed by dispersing spherical particles of a polyolefin-based resin in a binder resin, applying the dispersion to the back surface of the film, and drying. As the binder resin liquid, a solution in which the binder resin is dissolved in a solvent,
A dispersion (emulsion) in which a binder resin is dispersed in a solvent is used. As the binder resin, a thermoplastic resin, a thermosetting resin, a photocurable resin, or the like is used. As the spherical particles of the polyolefin-based resin, spherical particles made of a polymer or copolymer mainly composed of an olefin such as polyethylene, polypropylene, polybutylene, and ethylene / propylene copolymer are used. The average particle size of the spherical particles is 30 μm or less, preferably 5 to 20 μm.
m. The weight ratio between the spherical particles and the binder resin in the spherical particle layer (B) is 0.1 / 1 to 4 /
1, preferably 0.6 / 1 to 2/1. The thickness of the spherical particle layer (B) is 2 to 30 μm, preferably 5 to 20 μm
And the center line average roughness of the surface is 0.2 to
2.0, preferably 0.5 to 1.5.

In the light diffusion film of the present invention, the solid fine particle layer (A) formed on the surface side is preferably a spherical particle layer made of a formalin resin. in this case,
Formalin resin means a resin containing formalin as a condensation reaction component. Examples of such a formalin resin include benzoguanamine / formaldehyde condensate, melamine / formaldehyde condensate, and benzoguanamine / melamine / formaldehyde condensate. Among these resins, benzoguanamine / melamine / formaldehyde condensates show particularly excellent light diffusion effects.
The average particle diameter of the spherical particles of the formalin resin is 10 μm or less, preferably 1 to 8 μm, more preferably 2.2 to 5 μm.
μm.

The benzoguanamine / melamine / formaldehyde condensate (hereinafter also referred to as BMF resin) is a resin represented by the following formula.

Embedded image (In the formula, n and m each represent an integer of 1 or more.)

The average particle size of the BMF resin used in the present invention is 1 to 8 μm, preferably 2.2 to 5 μm. Further, the particle range is usually 0.5 to 8 μm. BMF resins provide films with better light diffusion properties than other formalin resins such as benzoguanamine / formaldehyde condensates and melamine / formaldehyde condensates.

The light diffusion film having the spherical particle layer (A) made of the above-mentioned formaldehyde resin can be obtained by applying a coating liquid containing the resin particles and a binder resin to the surface side of the film and drying the coating liquid. . In this case, the weight ratio of the formaldehyde resin to the binder resin is 0.7 to 2.0, preferably 1 to 1.5.
If the ratio deviates from this range, the light diffusibility of the obtained film is deteriorated. The thickness of the formaldehyde resin particle layer (A) is 2 to 30 μm, preferably 3 to 2 μm.
0 μm, and the center line average roughness is 0.2 to 5 μm.
m, preferably 0.3 to 1.5 μm.

[0013]

Next, the present invention will be described in more detail with reference to examples. In addition, all the parts and% shown below are based on weight.

Example 1 A polyethylene terephthalate film having a thickness of 75 μm was used as a base film. The following synthetic silica dispersion is applied to the surface side of the substrate film, and dried at 130 ° C. for 3 minutes to form a synthetic silica layer (A) having a center line average roughness of 0.52 μm (thickness: 15 μm). Formed. (Synthetic silica dispersion) Synthetic silica: 8.0 parts (Syloid 244, manufactured by Fuji Devison Chemical Co., Ltd., average particle size: 1.8 μm) Water: 50 parts Nonionic surfactant: 0.1 parts 5 wt% ammonia water: 0.9 part Cross-linked acrylic emulsion: 66 parts Next, a dispersion of white polyolefin-based resin particles shown below was applied to the back side of the base film, and the dispersion was applied at 110 ° C.
For 5 minutes to form a polyolefin-based resin particle layer (B) having a center line average roughness of 0.96 μm (thickness: 12 μm). (Polyolefin-based resin particle dispersion) Chemipearl W-800: 35.6 parts Ethanol: 20.0 parts Nonionic surfactant: 0.12 parts Melamine resin: 13.2 parts Self-crosslinking acrylic emulsion: 55.2 parts Modified poval: 4.0 parts Ammonium chloride: 0.12 parts Funnel oil: 2.8 parts The above-mentioned Chemipearl W-800 (manufactured by Mitsui Petrochemical Co., Ltd.)
Is an aqueous dispersion of spherical particles composed of low molecular weight polyolefin having an average particle diameter of 7 μm (softening point of 130 ° C.) and having a solid content concentration of 40%.

(Measurement of Performance of Light Diffusion Film) The light diffusion film obtained above is mounted on the light guide plate 1 of the lighting panel having the structure shown in FIG. In this case, the light diffusion film is placed so that the back side (the side having the spherical particle layer made of polyolefin resin) is in contact with the light guide plate. next,
Set the luminance meter in the direction perpendicular to the light guide plate. Next, the lamp is turned on and the brightness of the light transmitted through the diffusion film is measured. Table 1 shows the results. For comparison, the performance of a conventional light diffusion film was measured in the same manner. Table 1 shows the results. As the light diffusion film of the conventional product, one obtained by laminating one light diffusion film (F-300HS, manufactured by Somar Co., Ltd.) and the embossed base film shown in Example 1 (conventional product A),
Further, a laminate (conventional product B) of two light diffusing films A and a substrate film embossed with the same light was used. As shown in Table 1, the brightness of the conventional product A is not sufficient as compared with the product of the present invention. Also, in the case of the conventional product B, the luminance was sufficient, but the number of laminated films was three,
Work efficiency deteriorates remarkably. On the other hand, the product of the present invention has sufficient luminance, requires only one film, and has very good work efficiency.

[0016]

[Table 1]

Example 2 A polyethylene terephthalate film having a thickness of 75 μm was used as a base film. On the surface side of this base film, a dispersion containing BMF resin particles shown below is applied,
After drying at 130 ° C. for 3 minutes, center line average roughness 0.1 μm
BMF resin particle layer (A) (thickness: 5 μm) was formed.
Then, in the same manner as in Example 1, a spherical particle layer (B) made of a polyolefin resin is formed on the back surface of the film.
Was formed to obtain a light diffusion film. (BMF resin particle dispersion) BMF resin particles: 8.0 parts (average particle size: about 3 μm) Nonionic surfactant: 0.4 parts 5 wt% aqueous ammonia: 3.0 parts Melamine resin: 6.1 parts Self-crosslinking Acrylic emulsion: 23 parts Ammonium chloride: 0.24 parts Funnel oil: 5.0 parts Water: 23.4 parts

Example 3 In Example 2, a benzoguanamine / formaldehyde condensate (average particle diameter: about 2) was used in place of the BMF resin particles.
μm) to obtain a light diffusion film in the same manner.

Example 4 In Example 2, a melamine / formaldehyde condensate (average particle diameter: about 1.2 μm) was used instead of the BMF resin particles.
A light diffusing film was obtained in the same manner except that m) was used.

(Measurement of Performance of Light Diffusion Film) Each of the light diffusion films obtained above is placed on the light guide plate 1 of the lighting panel having the structure shown in FIG. 1 so that the back surface thereof is in contact with the light guide plate. . Next, a luminance meter is set in a direction perpendicular to the light guide plate. Next, the lamp is turned on and the brightness of the light transmitted through the diffusion film is measured. Table 2 shows the results. For comparison, the performance of a conventional light diffusion film was measured in the same manner. Table 2 shows the results.
As the light diffusion film of the conventional product, one obtained by laminating one light diffusion film (F-300HS, manufactured by Somar Co., Ltd.) and the embossed base film shown in Example 1 (conventional product A), What laminated | stacked the light-diffusion film A and the base film which carried out the same emboss processing (conventional product B) was used. As shown in Table 2, the luminance of the conventional product A is not sufficient as compared with the product of the present invention. In the case of the conventional product B, the luminance was sufficient, but the number of films to be laminated was three, and the working efficiency was significantly deteriorated. On the other hand, the product of the present invention has sufficient luminance, requires only one film, and has very good work efficiency.

[0021]

[Table 2]

[0022]

The light diffusing film of the present invention is excellent in its light diffusing effect and transmits light derived from the surface of the light guide plate with high luminance in the direction of the liquid crystal display panel. Therefore, a liquid crystal display device having a backlight using an illumination panel to which the light diffusion film of the present invention is applied has a high luminance and allows a displayed image to be easily viewed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a side-lamp-type lighting panel in which a lamp is provided at one side end of a light guide plate.

FIG. 2 is a cross-sectional configuration diagram of a side-lamp-type lighting panel in which lamps are provided at both ends of a light guide plate.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light guide plate 2 white dot pattern 3 lamp 4 lamp cover 5 reflector 6 reflector sheet 7 light diffusion film

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-350821 (JP, A) JP-A-4-258901 (JP, A) JP-A-4-88039 (JP, A) 173201 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 5/02 B32B 27/14 G02F 1/1335 530 G02F 9/00

Claims (3)

(57) [Claims] 1. A solid fine particle layer having an average particle size of 10 μm or less is provided on the surface of a transparent plastic film, and a spherical particle layer made of a polyolefin resin having an average particle size of 30 μm or less is provided on the back surface of the plastic film. A light diffusing film applied to a backlight illumination panel in a liquid crystal display device having a structure as described above. 2. A spherical particle layer comprising a formalin resin having an average particle size of 10 μm or less is provided on the surface of a transparent plastic film, and a spherical particle comprising a polyolefin resin having an average particle size of 30 μm or less is provided on the back surface of the plastic film. A light diffusion film applied to a backlight illumination panel in a liquid crystal display device having a structure in which layers are provided. 3. A benzoguanamine / melamine / average particle having an average particle size of 2.2 to 5 μm on a surface of a transparent plastic film.
Arranging a spherical particle layer made of formaldehyde condensate,
A light diffusion film applied to a backlight illumination panel in a liquid crystal display device, having a structure in which a spherical particle layer made of a polyolefin resin having an average particle diameter of 30 μm or less is provided on the back surface of the plastic film.