JPH112706A - Diffusion film and display device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sharply display data on the liquid crystal display device by uniform surface light emission without any decrease in lightness. SOLUTION: A film which has a dispersion phase dispersed at a >1 mean aspect ratio in a continuous phase composed of resin on a plane or flank of the film is used as a diffusion plate of the liquid crystal device. A transmission display device has a diffusion film, having a dispersion phase dispersed at a >=3 mean aspect ratio uniaxially when viewed from the plane of the film, arranged as a diffusion plate 3 for a back light between a display module 5 and a fluorescent tube 1. A reflection display device, on the other hand, has a diffusion film, having a dispersion phase dispersed at a >=3 aspect ratio when viewed from, the flank of the film, arranged for front scattering on a display module. The resin of the diffusion film includes olefine resin, acrylic resin, styrene resin, polyester resin, polyamide resin, polycarbonate resin, etc., and the refractive index difference between the resin of the continuous resin and the dispersion phase is >=0.001 (approximately 0.01 to 0.3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffusion film effective for uniformly emitting light in a backlight or a forward diffusion of a surface display or lighting device, for example, a liquid crystal display device, and a display device using the same.

[0002]

2. Description of the Related Art In a surface illumination device such as a liquid crystal display device, a diffusion sheet is disposed on an upper surface of a light guide plate to diffuse light from the light guide plate to make luminance uniform. Examples of such a diffusion sheet include a diffusion film in which a transparent and heat-resistant polycarbonate film or polyester film is coated with refractive fine particles (resin beads) or a light-transmitting inorganic fine particle, and the film has refractive fine particles (resin). (Diabeads) and diffusion films containing translucent inorganic fine particles.

[0003] In recent years, the demand for these diffusion sheets has been increasing especially as a diffusion sheet for a backlight of a liquid crystal display device. The backlight is usually provided between the cold-cathode tube and the liquid crystal layer, and makes the light emitted from the cold-cathode tube uniform. However, if the light diffusion is too large, there is a problem that sufficient light emission luminance cannot be obtained. Therefore, by providing an optical element such as a prism lens between the diffusion plate and the liquid crystal layer, the luminance is improved as a light beam as perpendicular to the liquid crystal display surface as possible.

As shown in FIG. 1, a backlight of a surface-type display device (ie, a display device having a flat display area) has a structure in which a surface-type display module (particularly, a transmission-type liquid crystal module) is illuminated from the back side. A plurality of fluorescent discharge tubes (cold-cathode tubes) 1, a reflector 2 disposed on the back side of the fluorescent discharge tube 1, and a diffuser 3 for uniformly illuminating by light diffusion. It is composed of a prism sheet 4 laminated on the diffusion plate and a surface display module 5 laminated on the prism sheet. The surface type display module 5 includes a first polarizing film 6a, a first glass substrate 7a, a first electrode 8a formed on the glass substrate, and a first The first alignment film 9a, the liquid crystal layer 10, the second alignment film 9b, the second
The electrode 8b, the color filter 11, the second glass substrate 7b, and the second polarizing film 6b are sequentially laminated. In such a structure, the display module can be directly illuminated from the back by the built-in fluorescent tube (cold cathode tube) 2.

[0005] The structure of the backlight of the flat panel display device is as shown in FIG.
Light guide plate 24 interposed between the light guide plate and the diffusion plate 23, a fluorescent tube (cold cathode tube) 21 disposed on a side of the light guide plate, and a reflecting member 25 disposed on a side of the fluorescent tube. Also known is a structure with As described above, the prism sheet and the display module are arranged on the diffusion plate 23. In such a structure, the display module can be illuminated by emitting light from the fluorescent tube (cold-cathode tube) 21 to the surface of the diffusion plate 23 through the light guide plate 24. In the structure of FIG. 2, by devising the shape of the light guide plate 24, it is possible to perform surface light emission more uniformly than in the structure of FIG. 1.

However, as shown in FIG. 3, the width of the light emission distribution (luminance distribution) in the longitudinal (axial) direction x of the fluorescent tubes (cold cathode tubes) 1 and 21 has the light emission distribution (luminance distribution) in the direction y perpendicular to the longitudinal direction. Luminance distribution) width. As described above, in the ordinary backlight structure, there is anisotropy in the light emission distribution (luminance distribution) width in the arrangement direction of the fluorescent tubes. on the other hand,
In a normal diffusion film containing the fine particles, since the light diffusing ability is isotropic, light is diffused more than necessary in a specific direction, resulting in a decrease in luminance.

Japanese Patent Application Laid-Open No. Hei 7-261171 discloses a pair of glass substrates, electrodes formed on opposing surfaces of these glass substrates, liquid crystal sealed between these electrodes, In the reflection type liquid crystal display device including the polarizing film laminated on the outer surface, a light scattering layer in which two or more resins having different refractive indexes are mixed and dispersed in a phase separated state is provided on the polarizing film. It has been proposed. This document describes that two or more resins are mixed in a solvent and applied or printed on a polarizing film to form a light scattering layer.

Further, as a display module of a reflection type display device, a module having a structure shown in FIG. 4 is also known. That is, the display module includes a pair of glass substrates 31a and 31b, electrodes 32a and 32b formed on opposing surfaces of the glass substrates, and a liquid crystal 33 interposed between the pair of electrodes. Electrode 3 on lower glass substrate 31a
2a is formed as a reflector and a pixel electrode,
A color filter 34 is interposed between the other glass substrate 31b and the electrode 32b. Further, a polarizing layer 35, a retardation layer 36, and a diffusion plate 37 are sequentially laminated on the upper glass substrate 31b. In such a reflective display device, one polarizing layer 35 is located on the entire surface side of the liquid crystal cell, and unlike a transmissive display device with a built-in lamp, incident light (external light) is diffused by the diffusion plate 37. Then, the light enters the liquid crystal cell, is reflected by the reflection plate in the liquid crystal cell, and is diffused through the diffusion plate 37. Therefore, the display data by the display module can be clearly recognized from any angle without using a lamp or reducing the brightness using external light.

However, in the reflection type display device, when the light diffusing ability of the diffusion plate is increased, the external light incident on the diffusion plate from the external light source is largely diffused, and the reflection light from the reflection plate is also irregularly reflected. The light is emitted from the diffusion plate. for that reason,
The clarity of display data may be reduced.

[0010]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a diffusion film useful for clearly displaying data on a display device and a display device (particularly, a liquid crystal display device) having the same. is there. It is another object of the present invention to provide a diffusion film capable of emitting light evenly without reducing the brightness of a backlight in a transmissive display device, and a display device (particularly, a liquid crystal display device) including the same. . Still another object of the present invention is to provide a diffusion film which can uniformly emit light by a simple operation of adjusting the disposing direction even if the emission distribution (luminance distribution) width from the tubular light source has anisotropy. (Especially, a liquid crystal display device) provided with the display device. It is another object of the present invention to provide a diffusion film capable of displaying display data brightly and clearly in a reflective display device, and a display device including the same.

[0011]

The diffusion film of the present invention can be used for both a transmission type display device and a reflection type display device, and is a film in which a dispersed phase is dispersed in a continuous phase composed of a resin. On the plane or side of the film (ie when viewed from the plane or side of the film)
The dispersed phase is dispersed with an average aspect ratio exceeding 1.
As the diffusion film of the transmissive display device, in the plane of the film, a diffusion film in which a dispersed phase is uniaxially dispersed in a continuous phase with an average aspect ratio of 3 or more,
As the diffusion film of the reflection type display device, a diffusion film in which a dispersed phase is dispersed in a continuous phase at an average aspect ratio of 3 or more on a side surface of the film is preferable. The difference in refractive index between the resin constituting the continuous phase and the dispersed phase is at least 0.0
01 or more. Such a diffusion film is selected from an olefin resin, an acrylic resin, a styrene resin, a polyester resin, a polyamide resin, a polycarbonate resin, and the like, and has a refractive index difference of 0.01 to 0.3.
And a diffusion film having an average aspect ratio of the dispersed phase of 3 to 100. Such a diffusion film is useful for a backlight of a transmissive display device and for forward scattering of a reflective display device. According to the present invention, there is provided a display device (a transmissive display device with a built-in lamp) in which a light diffusion transmission unit is disposed between a display module and a light projection unit, wherein the light diffusion transmission unit includes:
The dispersion film is composed of a diffusion film in which a dispersed phase is uniaxially dispersed with an average aspect ratio exceeding 1 in a continuous phase composed of a resin, and the long axis direction of the dispersed phase of the diffusion film is the axial direction of the fluorescent tube. (Display device) arranged along the line. Also, a display device (reflection type display device) in which light diffusion / transmission means is provided on a reflection type display module, wherein the light diffusion / transmission means has a diffused phase dispersed with an average aspect ratio exceeding 1 is provided. A display device composed of a film is also included.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The diffusion film of the present invention in which the average aspect ratio of the disperse phase exceeds 1 is (a) in the plane (longitudinal or widthwise plane) of the film (that is, when viewed from the plane of the film). A film having an average aspect ratio exceeding 1; and (b) a film having an average aspect ratio exceeding 1 on the side surface (surface in the thickness direction) of the film (that is, when viewed from the side surface of the film). it can. Such diffusion films (a) and (b)
Each of them is suitable as a diffusion film of a reflection type display device. Among the diffusion films (a), a film in which a dispersed phase is uniaxially dispersed in a continuous phase is suitable as a light diffusion transmission means of a transmission type display device.

As the resin constituting the diffusion film, any of a thermoplastic resin and a thermosetting resin (epoxy resin, unsaturated polyester resin, diallyl phthalate resin, silicone resin, etc.) can be used. Preferred resins are thermoplastic resins. Examples of thermoplastic resins include olefin-based resins (polyethylene, polypropylene, etc.),
Vinyl chloride resin (polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, etc.), vinyl acetate resin (polyvinyl acetate, ethylene-vinyl acetate copolymer, etc.), polyvinyl alcohol resin (polyvinyl alcohol, ethylene-vinyl) Alcohol copolymers), acrylic resins (polymethyl methacrylate, methyl methacrylate)
Acrylic ester copolymer, etc.), styrene resin (homopolymer or copolymer such as polystyrene, styrene-methyl methacrylate copolymer, styrene-maleic anhydride copolymer, modified polymer, rubber modified styrene resin, etc.) , Polyester resin (homopolymer such as polyalkylene terephthalate, copolyester,
Examples thereof include modified polyesters, polyamide resins (homopolymers such as nylon 6, nylon 66, nylon 610, and nylon 612, copolymers and modified polyamides), and polycarbonate resins.

In order to form a continuous phase, at least one of these resins is used, and a plurality of resins may form a continuous phase and a dispersed phase, and at least one resin and a filler may form a continuous phase. And a dispersed phase may be formed. In the present specification, a resin in which a dispersed phase is dispersed in a continuous phase, such as a styrene-butadiene copolymer (SB resin) and an acrylonitrile-butadiene-styrene copolymer (ABS resin), is also referred to as “a plurality of resins. "In the category,
Such a resin may be used alone. Preferred resins for forming the continuous phase and the dispersed phase include a combination of a plurality of resins selected from olefin resins, acrylic resins, styrene resins, polyester resins, polyamide resins, and polycarbonate resins. The combination of these resins and fillers is also preferable.

As the filler, an organic or inorganic filler having the above-mentioned aspect ratio can be used. For example, fibrous fillers (inorganic fibers such as glass fiber, silica fiber, alumina fiber and zirconia fiber, and heat-resistant organic materials such as aramid fiber) can be used. And flaky fillers (such as mica).

The combination of a plurality of resins and the combination of a resin and a filler are not particularly limited as long as they form a morphology in which a dispersed phase is dispersed in a continuous phase and provide light diffusivity. The difference in refractive index between the resin and the filler forming the phase is 0.001 or more (for example, 0.01
To about 0.3), preferably about 0.01 to 0.2 (e.g., 0.01 to 0.1).

The combination of a plurality of resins giving such a refractive index difference includes, for example, the following combinations. (1) Combination of olefin resin and at least one selected from acrylic resin, styrene resin, polyester resin, polyamide resin, and polycarbonate resin (2) Styrene resin and polyester resin, polyamide (3) Combination of polyester resin with at least one selected from polyamide resin and polycarbonate resin, etc. The resin constituting the continuous phase And the resin or filler constituting the dispersed phase are usually incompatible or hardly compatible with each other.

The ratio of the resin constituting the continuous phase to the resin or filler constituting the dispersed phase is not particularly limited. Usually, the ratio of the continuous phase / dispersed phase depends on the type of resin, melt viscosity, and desired degree of light diffusion. = 95/5 to 30/70 (% by weight), preferably about 90/10 to 40/60 (% by weight), and more preferably about 80/20 to 50/50 (% by weight).

A compatibilizer may be used in combination with the resin composition. The compatibilizer can be selected from conventional compatibilizers according to the types of the continuous phase and the dispersed phase. Examples thereof include oxazoline compounds and modified resins (for example, carboxyl groups, acid anhydride groups, epoxy groups, oxazoline groups, and the like). A modified resin modified with at least one selected modifying group), a rubber-modified resin (acrylonitrile-butadiene-
Styrene copolymer (ABS resin), hydrogenated styrene-butadiene (SB) block copolymer, hydrogenated styrene
Butadiene-styrene block copolymer (SEBS),
Examples include hydrogenated (styrene-ethylene / butylene-styrene) block copolymers, epoxy-modified styrene-butadiene (SB) block copolymers, and the like. As the compatibilizer, a block or graft copolymer having the same components as the polymer blend-based constituent resin, a block or graft copolymer containing a component that can be mixed with the polymer blend-based constituent resin, and the like are usually used. . The amount of the compatibilizer used is, for example, 0.1 to 20 of the entire resin composition.
% By weight, preferably from 0.5 to 15% by weight, more preferably from about 1 to 10% by weight.

The diffusion film is made of a conventional additive, for example,
Stabilizers such as antioxidants, UV absorbers, heat stabilizers,
It may contain a plasticizer, an antistatic agent, a flame retardant, a filler, and the like.

The thickness of the diffusion film of the present invention is not particularly limited as long as uniform light diffusion can be ensured according to the average size and aspect ratio of the dispersed phase.
μm, preferably 10-200 μm, especially 20-100
It is about μm.

The feature of the diffusion film of the present invention is that, when viewed from the plane or side of the film, the average aspect ratio of the dispersed phase exceeds 1, especially 3 or more (for example, 3 to 100,
It is preferably 5 to 75, more preferably about 10 to 60, and especially about 20 to 50). In such a diffusion film, the average aspect ratio of the dispersed phase dispersed in the continuous phase is not 1, and the light diffusing ability differs depending on the orientation direction of the dispersed phase.

The aspect ratio is a ratio L of the length L of the dispersed phase in the major axis direction to the minimum width W of the dispersed phase in the minor axis direction.
/ W, and the length L of the dispersed phase in the major axis direction is usually
0.1 to 200 μm (for example, 1 to 100 μm), preferably about 1 to 150 μm (for example, 1 to 80 μm), particularly about 2 to 100 μm (for example, 2 to 50 μm),
Usually, it is about 30 to 100 μm). The dispersed phase may be fibrous, and the aspect ratio of the fibrous dispersed phase L
/ W may be infinite.

As shown in FIG. 5, (a) in the film 41 in which the dispersed phase is uniaxially dispersed with an average aspect ratio exceeding 1 on the plane of the film, when light is incident, the length of the dispersed phase d1 is increased. The diffusivity in the direction orthogonal to the long axis of the dispersed phase (Y-axis direction) is higher than that in the axial direction (X-axis direction). Therefore, of the incident light from the backlight, the direction in which the diffusion capability of the film is large is diffused in the direction in which the luminance distribution width is small, and the direction in which the diffusion capability of the film is small in the direction in which the luminance distribution width is large. By arranging the film, unnecessary light scattering does not occur. That is, in a transmissive display device with a built-in lamp, the long axis of the disperse phase with respect to the axial direction (longitudinal direction) of the light source (especially the fluorescent tube) as the light projecting means according to the scattering angle and scattering intensity of the diffusion film By disposing the diffusion film along (especially in parallel), the surface light can be uniformly emitted to the display panel without significantly lowering the overall luminance.

Among the diffusion films of the present invention, the film (a) in which the disperse phase is uniformly dispersed in the uniaxial direction can be used as a film light source (tube light source) such as a fluorescent discharge tube as described above. Utilizing the optical anisotropy of the above, surface light can be uniformly emitted from the diffusion film. Therefore, surface display devices,
For example, it is useful as a diffusion film (light diffusion transmission sheet) for a transmission type liquid crystal display device with a built-in light source (particularly, a liquid crystal display device using a tubular fluorescent tube as a light source).

The flat panel display device (particularly a liquid crystal display device) of the present invention has a structure similar to the backlight structure shown in FIGS. Therefore, the details of the apparatus shown in FIGS. 1 and 2 are omitted. The light diffusing plates (light diffusing and transmitting means) 3 and 37 are each made of the above-mentioned diffusing film. In addition, since the light is uniformly emitted from the light diffusion plates 3 and 37 by the diffused light to illuminate the surface display module by utilizing the optical anisotropy of the diffusion film, the long axis of the dispersed phase of the diffusion film is used. The direction (direction in which the diffusion film is taken or stretched) is disposed along the axial direction of the fluorescent tube.

The above-mentioned surface type display module is usually
It is a transmissive module, and the display area of the module is not limited to the same plane and may be curved. The light source may be constituted by a single fluorescent tube, or may be constituted by a plurality of fluorescent tubes as shown in FIG. Even when a plurality of light sources are installed side by side, the brightness distribution width becomes wide in the direction in which the fluorescent tubes are installed (direction orthogonal to the axial direction of the fluorescent tubes). Surface light emission. In addition, as long as the display module can be uniformly illuminated from the back surface side in the arrangement of the diffusion film, the major axis of the dispersed phase may not completely coincide with the axial direction of the tubular fluorescent tube. (In the range of about 20 °).

On the other hand, (b) a film in which a dispersed phase is dispersed with an average aspect ratio exceeding 1 on the side of the film,
Light incident on the disperse phase from the perpendicular direction is effectively used as reflected light without being scattered much. on the other hand,
Light incident from an oblique direction is irregularly reflected at a large angle by the disperse phase. That is, the film exhibits isotropic properties with respect to incident light perpendicular to the film surface, and exhibits anisotropy with respect to light incident obliquely with respect to the film surface. Therefore, even in the case of a reflective display device (especially a reflective liquid crystal display device), display data from the display module can be displayed brightly and clearly. Therefore, the diffusion film (b) is useful as a diffusion film for a reflective display device (particularly, a reflective liquid crystal display device).

In the diffusion film (b), it is sufficient that the dispersed phase is dispersed in the above-described form on the side surface of the film, and the orientation direction in the plane direction is not particularly limited. May be oriented. The form of the dispersed phase may be a flat plate, a Soloban sphere, a rugby ball, a prism, a fiber, or the like. In order to effectively diffuse light from oblique directions without lowering the light intensity, A combination of these disperse phases (for example, a combination of a Soroban spherical disperse phase and a fibrous disperse phase) may be used. The diffusion film is, for example, as shown in FIG. 6, the diffusion film 42 in which the disk-shaped dispersed phase d2 is oriented or dispersed parallel to the thickness direction as viewed from a plane, and as shown in FIG. 7, the diffusion film is elliptical as viewed from a plane. And a diffusion film 43 in which the dispersed phase d3 is randomly oriented or dispersed in the plane of the film, and a film 41 in which the dispersed phase d1 is uniaxially oriented as shown in FIG. Among the diffusion films (b), when viewed from the side of the film, a film in which a dispersed phase is randomly dispersed in the aspect ratio can diffuse light incident from any angle, so that a double reflection of a display image and an external light source Can be reliably prevented, and data can be clearly displayed.

Such a diffusion film (b) is useful for forward scattering in a display module of a reflection type display device (particularly, a reflection type liquid crystal display device). That is, it is useful to use the diffusion film (b) as the light diffusion transmission means provided on the display module of the reflection type display device. In a reflective display device, as shown in FIG. 4, the reflective display device is usually laminated directly or via an adhesive on a deflection layer 34 or a film of a display module. In the display module shown in FIG.
4. The phase difference plate 36 is not always necessary. The electrode 32a of the lower glass substrate 31a can be formed of an electrode material having high reflectivity and high conductivity (such as aluminum).

The diffusion film is formed by a conventional film forming method,
For example, the above components are blended by a conventional method (melt blending method, tumbler method, etc.), and the obtained polymer blend is melt-kneaded, and is extruded from a T die or a ring die to obtain a film or sheet by an extrusion molding method. Can be. Alternatively, a diffusion film can be obtained by solution blending the above components and forming a film by a casting method or the like. In order to adjust the aspect ratio and the characteristics of the film, the film or sheet may be vertically and / or vertically adjusted as necessary.
Alternatively, they may be stretched in the lateral direction by about 1.2 to 10 times. The film having a flat dispersed phase in the diffusion film (b) may be obtained, for example, by flattening the dispersed phase by heating and pressing a sheet containing the dispersed phase.

The transmissive display module of the display device can be composed of a liquid crystal cell or the like composed of a pair of transparent substrates and liquid crystal injected between the substrates. In the display device, the operation of the liquid crystal cell (element) can be controlled by the control circuit. The display device may include another element, for example, a deflecting plate, and the surface of the display module may be subjected to an anti-glare treatment using a non-glare film or the like. The surface display device of the present invention can be used as a display device connected to a computer, a touch panel device capable of inputting and outputting data, and the like.

[0033]

According to the diffusion film of the present invention, since the dispersed phase is dispersed in the continuous phase at an average aspect ratio exceeding 1, it is useful for clearly displaying data on a display device. For example, when a diffusion film in which the dispersed phase is uniaxially oriented is used for a transmission type display device (especially a transmission type liquid crystal display device), the brightness of the backlight is not reduced,
The display module can be illuminated from behind by emitting light from the surface uniformly, and the display module can clearly display data, images, and the like. In particular, emission distribution (luminance distribution) from a tubular light source
Even if the width has anisotropy, uniform surface emission can be achieved by a simple operation of adjusting the arrangement direction of the film. Furthermore, when applied to a reflective display device (especially a reflective liquid crystal display device), display data can be clearly displayed even when external light is incident from an oblique direction.

[0034]

EXAMPLES The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 38% by weight of polystyrene (PS: Daicel Styrol 51, manufactured by Daicel Chemical Industries, Ltd.) and polyethylene (P
E: Mitsubishi Chemical Corporation, Novatec LF405M) 57
Dry blend at a ratio of 5% by weight, hydrogenated styrene-butadiene-styrene block copolymer (SEBS: Claiton G1652 manufactured by Shell Chemical Co., Ltd.), and melt-blending at 200 ° C. using a twin-screw extruder. Thus, a blend resin pellet was prepared. The obtained resin pellets,
The film was supplied to an extruder equipped with a T-die and extruded to obtain a film having a thickness of 50 μm.

Incidentally, when 100 dispersed phases on the surface of the film were randomly observed by a micrograph, the average length in the major axis direction of the dispersed phase was 80 μm, and the average aspect ratio was 40.

When a laser beam was incident on the obtained film and the scattering intensity was measured, as shown in FIG.
In the stretching direction of the film, the scattering angle was about 2 °, while as shown in FIG. 5, the scattering angle was about 4 ° in the direction perpendicular to the stretching direction, and the anisotropy was apparent in the diffusivity. Was done.

In the apparatus shown in FIG. 1, when the long axis direction of the dispersed phase of the diffusion film was arranged in a direction orthogonal to the axial direction of the fluorescent tube, the backlight for the display module was non-uniform. . On the other hand, when the long axis direction of the dispersed phase of the diffusion film was disposed along (parallel to) the axial direction of the fluorescent tube, a uniform light emitting surface was obtained.

Example 2 A light diffusing film was obtained in the same manner as in Example 1 except that nylon 6 (NY: Ube Nylon 1013B, manufactured by Ube Industries, Ltd.) was used instead of polyethylene and the extrusion temperature was 250 ° C. . When the dispersed phase was observed in the same manner as in Example 1, the average length in the major axis direction of the dispersed phase was 70 μm.
m, and the average aspect ratio was 30.

Example 3 Nylon 6 (NY: Ube Nylon 1013B, manufactured by Ube Industries, Ltd.) was used instead of polyethylene, and polybutylene terephthalate (PBT: Polyplastics Co., Ltd., Duranex 600F) was used instead of polystyrene.
Using P), a light diffusing film was obtained in the same manner as in Example 1 except that the extrusion temperature was changed to 250 ° C. Example 1
Observation of the dispersed phase in the same manner as in Example 1 showed that the average length of the dispersed phase in the major axis direction was 75 μm and the average aspect ratio was 35.

Example 4 Polymethyl methacrylate (PMM) was used instead of polyethylene.
A: Sumitomo Chemical Co., Ltd., Sumipec), and a light diffusion film was obtained in the same manner as in Example 1 except that the extrusion temperature was 250 ° C. When the dispersed phase was observed in the same manner as in Example 1, the average length in the major axis direction of the dispersed phase was 70 μm, and the average aspect ratio was 30.

In the apparatus shown in FIG. 1, when the long axis direction of the dispersed phase of the diffusion films of Examples 2 to 4 is arranged in a direction orthogonal to the axial direction of the fluorescent tube, the backlight for the display module is obtained. Was non-uniform. On the other hand, when the long axis direction of the dispersed phase of the diffusion films of Examples 2 to 4 was arranged along (parallel to) the axial direction of the fluorescent tube, a uniform light emitting surface was obtained.

[Brief description of the drawings]

FIG. 1 is a main part schematic diagram showing an example of the structure of a transmission type display device.

FIG. 2 is a main part schematic diagram showing another example of the structure of the backlight of the display device.

FIG. 3 is a schematic perspective view showing the fluorescent discharge tube of FIGS. 1 and 2;

FIG. 4 is a schematic sectional view showing an example of a reflective display module.

FIG. 5 is a diagram showing a relationship between a diffusion film and a light diffusion intensity distribution.

FIG. 6 is an enlarged schematic perspective view showing another example of the diffusion film.

FIG. 7 is an enlarged schematic perspective view showing still another example of the diffusion film.

FIG. 8 is a graph showing the results of measuring the scattering intensity (stretching direction) of the diffusion film obtained in Example 1.

FIG. 9 is a graph showing the measurement results of the scattering strength (in the direction perpendicular to the stretching direction) of the diffusion film obtained in Example 1.

[Explanation of symbols]

 1,21 ... Fluorescent tube 2,22 ... Reflection plate 3,37 ... Diffusion plate 24 ... Light guide plate 41,42,43 ... Diffusion film

Claims (7)

[Claims] 1. A diffusion film in which a dispersed phase is dispersed in a continuous phase composed of a resin, wherein the dispersed phase is dispersed with an average aspect ratio exceeding 1 on a plane or side surface of the film. 2. In the plane of the film, in a continuous phase,
The diffusion film according to claim 1, wherein the dispersed phase is uniaxially dispersed at an average aspect ratio of 3 or more. 3. On the side of the film, during the continuous phase:
The diffusion film according to claim 1, wherein the dispersed phase is dispersed at an average aspect ratio of 3 or more. 4. The diffusion film according to claim 1, wherein the difference in the refractive index between the resin constituting the continuous phase and the dispersed phase is at least 0.001. 5. A plurality of resins selected from an olefin resin, an acrylic resin, a styrene resin, a polyester resin, a polyamide resin, and a polycarbonate resin and having a refractive index difference of 0.01 to 0.3. 2. The diffusion film according to claim 1, wherein the diffusion film has a mean aspect ratio of 3 to 100. 6. A display device in which a light diffusing / transmitting means is provided between a display module and a light projecting means, wherein the light diffusing / transmitting means is arranged in a continuous plane on a plane of a film.
A display device comprising a diffusion film in which a dispersed phase is dispersed in a uniaxial direction with an average aspect ratio exceeding 1.0, and a major axis direction of the dispersed phase of the diffused film is disposed along an axial direction of the fluorescent tube. 7. A display device in which light diffusion and transmission means is provided on a reflective display module, wherein the light diffusion and transmission means is constituted by the diffusion film according to claim 1.