JP2006235269A - Light diffusing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusing film which is excellent in a light diffusing property and a light condensing property and has high luminance and which hardly produces a curl even when thickness of a plastic film is <75μm. <P>SOLUTION: In the light diffusing film where a light diffusing layer consisting of a resin and resin particulates is formed on one surface of the plastic film, the resin particulate has a rugby ball shape, wherein maximum height is (x), maximum width is (y) and maximum thickness is (z), and satisfies following conditions A: x>y≥z, B: x:y:z=1.2 to 3:1:0.5 to 1, C: 1μm≤x≤20μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light diffusing film, and more particularly to a light diffusing film that has higher brightness than a conventional light diffusing film and is particularly useful when used for a backlight of a liquid crystal display.

Conventionally, a light diffusing film in which a light diffusing layer made of resin and resin fine particles is formed on one surface of a plastic film is known.
In Patent Document 1, a resin layer (light diffusion layer) in which beads for light diffusion film (resin fine particles) having a two-layer structure of a high refractive index resin core and a low refractive index resin shell are dispersed is formed on the surface of a plastic film. A light diffusing film is described.
Examples of the shape of the beads include a spherical shape, a spheroid shape, a confetti shape, a thin plate shape, and a needle shape.
However, the shape of the beads for light diffusing film which are generally used in practice is spherical, particularly true spherical.
This is because the conventional light diffusing film is required to have a uniform brightness throughout the light diffusing film even at the expense of some brightness improvement. In other words, it was desirable to use spherical resin fine particles with excellent properties that can diffuse and reflect light uniformly in various directions instead of reflecting light in a biased direction. This is due to two reasons that a production method for stably supplying a large amount of resin fine particles having a shape other than a true spherical shape has not been established.
The thickness of the plastic film is preferably 75 to 200 μm (100 μm in the examples) in view of curling of the light diffusion film and brightness, and the resin of the resin layer includes polyester polyol, acrylic resin, melamine It describes that a general resin such as a resin is used.
JP-A-11-109113

However, the conventional light diffusion film has the following drawbacks.
1. The light diffusing film is placed on the light guide plate of the backlight with the plastic film facing the light guide plate, and the light transmitted through the light guide plate passes through the plastic film and is reflected by the beads for the light diffusing film in the resin layer. Diffusely reflected in various directions.
At this time, if the light reflected by the beads is uniformly diffusely reflected in various directions, the entire light diffusing film has a uniform brightness, but if the ratio of the light that is diffusely reflected increases, the light that travels straight, that is, the light diffusing film becomes light. The proportion of light traveling in the orthogonal direction decreases, while the proportion of light that diffusely reflects decreases as the proportion of light traveling straight increases.
However, the light diffusing film has a good balance between the two properties of light diffusivity, which allows the light reflected by the beads to be diffusely reflected uniformly in various directions, and the light condensing property, in which light travels straight without being diffusely reflected. In order to do so, conventionally, it has been dealt with by using beads having a two-layer structure as described in Patent Document 1 or beads having an uneven surface.
Recently, brighter liquid crystal displays have been desired for liquid crystal displays used in LCD TVs and mobile phone displays, and in order to meet this demand, the light diffusion film used in the backlights of liquid crystal displays has been further increased. Brightness is required.
However, the light diffusing film beads used in conventional light diffusing films have a true spherical shape as described above, so that while maintaining the light diffusing property or improving the light diffusing property, the light collecting property is also improved. Therefore, there is a limit to the improvement of the image quality. Therefore, there is a problem that it is not possible to meet the demand for a light-diffusion film with higher brightness and excellent light diffusibility.
More specifically, the light diffusivity is based on the haze value of the light diffusing film, and the light condensing property is based on the total light transmittance value of the light diffusing film. A light diffusing film having a transmittance of 80% or more is desired, but there is no light diffusing film that satisfies both of them.
2. The plastic film reduces the brightness of the light diffusing film due to the effect of the type of resin used in the plastic film and the lubricant that is mixed in the plastic film, so the thickness of the plastic film is the brightness of the light diffusing film. From the viewpoint of improvement, a thinner one is preferable, but since the resin used in the resin layer in which the beads for the light diffusion film are dispersed is a general resin, if the thickness of the plastic film is less than 75 μm, the light diffusion film As a result, when the light diffusion film is incorporated into the liquid crystal backlight unit, there is a problem that the handling is bad and the productivity is lowered.

  The present invention eliminates all the above-mentioned drawbacks, and provides a light diffusing film that is excellent in light diffusibility and light condensing property, has high brightness, and does not easily curl even when the thickness of the plastic film is less than 75 μm. To do.

[1] The present invention relates to a light diffusion film in which a light diffusion layer made of resin and resin fine particles is formed on one side of a plastic film. The resin fine particles have a maximum height of x, a maximum width of y, and a maximum thickness. A light diffusing film characterized by being rugby ball-shaped resin fine particles having a thickness of z and resin fine particles satisfying the following conditions.
A. x> y ≧ z
B. x: y: z = 1.2-3: 1: 0.5-1
C. 1μm ≦ x ≦ 20μm
[2] The present invention provides a light diffusion film in which a light diffusion layer comprising a resin and resin fine particles is formed on one side of a plastic film, wherein the resin fine particles are the rugby ball-shaped resin fine particles according to the above [1]. The light diffusing film is a mixture of spherical resin fine particles.
[3] The present invention is the light diffusing film according to the above [1] or [2], wherein a moire prevention layer comprising a resin and inorganic or organic fine particles is formed on the other surface of the plastic film. .

(1) The light diffusing film of the present invention is a light diffusing film in which a light diffusing layer composed of a resin and resin fine particles is formed on one surface of a plastic film. A rugby ball-shaped resin fine particle having a large y and a maximum thickness z; x> y ≧ z, B.I. x: y: z = 1.2-3: 1: 0.5-1, C.I. Since the resin fine particles satisfy all three conditions of 1 μm ≦ x ≦ 20 μm, the light diffusibility and the light condensing property are excellent and the brightness is higher than that of the conventional light diffusion film using the spherical resin fine particles.
Specifically, the light diffusing film of the present invention has a haze of 80 or more, which is one of the indexes indicating the light diffusibility of the light diffusing film, and one of the indexes indicating the light collecting property. Is 80% or more, and is excellent in both light diffusibility and light condensing property, resulting in high luminance.
Furthermore, if the mixing amount of the resin fine particles in the light diffusing layer is 80 to 200% by weight with respect to the resin, it is more complete from the viewpoint of light diffusibility and light condensing property.
Further, if the resin fine particles are a mixture of rugby ball-shaped resin fine particles and true spherical resin fine particles and the weight ratio is rugby ball-shaped resin fine particles: true spherical resin fine particles = 9: 1 to 4: 6, It is preferable because the light collecting property can be obtained more stably.
(2) If the resin of the light diffusion layer is a resin that satisfies all the conditions of a glass transition temperature of 35 to 60 ° C., a molecular weight of 10,000 to 30,000, and a hydroxyl value of 15 to 25 mg KOH / g, the thickness of the plastic film Of course, when the thickness is 75 μm or more, it is preferable that the thickness is less than 75 μm because curling hardly occurs in the light diffusion film.
In particular, an acrylic resin that satisfies all of the above conditions is satisfactory.

  As the plastic film used in the light diffusion film of the present invention, a conventionally known plastic film such as a polyester film such as a polyethylene terephthalate film, a triacetate film, a norbornene film, a polycarbonate film, a vinyl chloride film, a polypropylene film, or an acrylic film can be used. Polyester films such as polyethylene terephthalate film are particularly preferred from the viewpoint of processability when producing a light diffusion film.

The thickness of the plastic film is preferably 25 to 150 μm, more preferably 25 to 75 μm.
If the thickness is less than 25 μm, it is not preferable because wrinkles are generated during processing of the light diffusing film, and the workability is deteriorated in some cases.
If the thickness is larger than 150 μm, the transparency is deteriorated and the improvement of the luminance is hindered, and the smoothness of the plastic film due to uneven thickness and sagging is deteriorated, and the light diffusion layer is hardly formed uniformly.
In addition, when the thickness of the plastic film is in the range of 25 μm or more and less than 75 μm, when a general resin described later is used as the resin of the light diffusion layer, the light diffusion film tends to be curled. Resin satisfying all the conditions of glass transition temperature of 35 to 60 ° C., molecular weight of 10,000 to 30,000, and hydroxyl value of 15 to 25 mgKOH / g, even if the thickness is in the range of 25 μm or more and less than 75 μm In this case, not only immediately after the light diffusing film is manufactured, but also when it is left for a long period of time in a high temperature and high humidity environment, it is preferable because curling hardly occurs in the light diffusing film.

  The light diffusing layer of the light diffusing film of the present invention is formed on one side of a plastic film and is composed of a resin and resin fine particles.

The resin fine particles are rugby ball-shaped resin fine particles having a maximum height of x, a maximum width of y, and a maximum thickness of z. x> y ≧ z, B.I. x: y: z = 1.2-3: 1: 0.5-1, C.I. It is preferable to use resin fine particles that satisfy all three conditions of 1 μm ≦ x ≦ 20 μm.
The height of the rugby ball-shaped resin fine particles means the length of the straight line connecting the top and bottom of the resin fine particles (the longest direction among the particle diameters of the resin fine particles). The width and the thickness mean the vertical length and the horizontal length of the cross-sectional shape of the resin fine particles in a plane orthogonal to the straight line connecting the top and bottom of the resin fine particles.
The maximum height x is the length of a straight line connecting the top and bottom of the rugby ball-shaped resin fine particles, and the maximum width y and the maximum thickness z are straight lines connecting the top and bottom of the resin fine particles. It is the maximum value of each of the vertical length and the horizontal length of the cross-sectional shape of the resin fine particles in a plane orthogonal to each other.
In addition, considering the light diffusibility and the light condensing property, the cross-sectional shape of the resin fine particles in a plane perpendicular to the straight line connecting the top and bottom of the rugby ball-shaped resin fine particles is not changed in the height direction of the resin fine particles. Therefore, among the above three conditions, the relationship between y and z (y ≧ z, y: z = 1: 0.5 to 1) is preferably maintained at any position in the height direction.
Therefore, the cross-sectional shape is a circle when y = z, and an ellipse when y> z, and the overall shape of the resin fine particles is a rugby ball shape when y = z and y> z. The rugby ball is compressed in the thickness direction, that is, has a thick oval shape.
Of course, a resin particle having a shape obtained by compressing the rugby ball in the thickness direction, that is, a thick oval-shaped resin particle is also included in the rugby ball-shaped resin particle in the present invention.
In order to further improve the light diffusibility and the light collecting property, resin fine particles having a rugby ball shape or a shape close to a rugby ball, in which the cross-sectional shape is a circle or a shape close to a circle (y = z or y≈z) are preferable. .

As described above, the rugby ball-shaped resin fine particles have a maximum height x, a maximum width y, and a maximum thickness z. x> y ≧ z, B.I. x: y: z = 1.2-3: 1: 0.5-1, C.I. All three conditions of 1 μm ≦ x ≦ 20 μm are satisfied. By making rugby ball-shaped resin fine particles satisfying all the above three conditions, excellent light diffusibility and light collecting property can be obtained. As a result, the light diffusion film has high brightness.
Therefore, the rugby ball-shaped resin fine particles that do not satisfy the above three conditions cannot be expected to improve the luminance as compared with the conventional spherical resin fine particles.
Furthermore, in order for the light diffusing film of the present invention to have high brightness, it is necessary to sufficiently exhibit the excellent light diffusibility and light condensing property of the rugby ball-shaped resin fine particles. In addition to using rugby ball-shaped resin fine particles that satisfy the above conditions, the resin fine particles are in an upright state, that is, the height direction of the resin fine particles is oriented in a direction perpendicular to the light diffusion film plane. It is preferable.
Therefore, the rugby ball-shaped resin fine particles are in an inclined state or a horizontal state, that is, the height direction of the resin fine particles is considerably inclined from the direction orthogonal to the light diffusion film plane or the light diffusion film plane. On the other hand, if it is in a parallel direction, the excellent light diffusibility and light condensing property of the rugby ball-shaped resin fine particles are not sufficiently exhibited, and as a result, the light diffusion film of the present invention has high brightness. It becomes difficult to become.

  Conventionally known general resins such as acrylic resin, styrene resin, silicon resin, and fluorine resin can be used as the type of resin used for the resin fine particles, but in particular, light resistance, transparency, and hardness. To acrylic resins are particularly preferred.

The resin used for the light diffusing layer serves as a binder for holding the resin fine particles in the light diffusing layer on the plastic film, such as acrylic resin, polyester resin, vinyl chloride vinyl acetate copolymer resin, fluorine resin, etc. Among them, acrylic resins are preferable from the viewpoints of transparency, uniform dispersibility of resin fine particles, and suitability during coating processing.
In particular, a plastic film having a thickness of 25 μm or more and less than 75 μm was used as a resin satisfying all the conditions of a glass transition temperature of 35 to 60 ° C., a molecular weight of 10,000 to 30,000 and a hydroxyl value of 15 to 25 mg KOH / g. Even when the light diffusing film is manufactured, it is difficult to curl the light diffusing film even when it is left for a long period of time in a high temperature and high humidity environment. It is more preferable to use a resin.
Above all, if an acrylic resin satisfying the above conditions is used, it is perfect in terms of optical characteristics and coating characteristics in addition to curling prevention.

The mixing amount of the rugby ball-shaped resin fine particles in the light diffusion layer is preferably 80 to 200% by weight, more preferably 100 to 150% by weight with respect to the resin.
If the mixing amount of the rugby ball-shaped resin fine particles is less than 80% by weight, the amount of the resin fine particles is small, so that the light diffusely reflected is reduced and the light diffusibility is lowered. Tends to be in a state of being sideways, that is, the height direction of the resin fine particles tends to be considerably inclined from a direction orthogonal to the light diffusion film plane or in a direction parallel to the light diffusion film plane. Since the light property is also lowered, it is difficult to obtain a uniform luminance of the light diffusion film as a result.
In addition, since the rugby ball-shaped resin fine particles are less likely to be inclined and easily stand up as the mixing amount increases, the excellent light diffusibility and light condensing property of the resin fine particles are easily exhibited. If the amount is too high, the resin as the binder cannot completely fix the rugby ball-shaped resin fine particles, and the resin fine particles are likely to be detached. This is not preferable because the light diffusion film cannot easily exhibit high brightness and light condensing performance, and as a result, the light diffusion film is unlikely to have high brightness.
Accordingly, the mixing amount of the rugby ball-shaped resin fine particles in the light diffusion layer is preferably 80 to 200% by weight with respect to the resin. This is perfect from the viewpoint of preventing the resin fine particles from being detached.

Alternatively, the resin fine particles may be a mixture of the rugby ball-shaped resin fine particles and the spherical resin fine particles, and the ratio may be rugby ball-shaped resin fine particles: true spherical resin fine particles = 9: 1 to 4: 6.
By doing so, the spherical resin fine particles are prevented from being in an inclined state or a horizontal state, and as a result, the rugby ball-shaped resin fine particles are compared with the case where they are used alone. The ball-shaped resin fine particles are apt to stand upright, that is, the height direction of the resin fine particles is likely to be in a direction perpendicular to the light diffusion film plane, and light diffusibility and light condensing properties can be obtained more stably. Therefore, it is preferable.
The particle size of the spherical resin fine particles is preferably 8 to 30 μm.
Further, the total mixing amount of the rugby ball-shaped resin fine particles and the spherical resin fine particles is preferably 50 to 200% by weight with respect to the resin.
As described above, the mixing amount when the rugby ball-shaped resin fine particles are used alone is 80 to 200% by weight with respect to the resin, whereas the total amount when the rugby ball-shaped resin fine particles and the spherical resin fine particles are mixed. As described above, the amount of mixing is 50 to 200% by weight, and excellent light diffusibility and light collecting properties can be obtained even with a small amount of mixing compared with the case where rugby ball-shaped resin fine particles are used alone. This is because the resin fine particles are easy to make the rugby ball-shaped resin fine particles stand upright.

  As a method for forming the light diffusion layer, conventionally known methods such as a reverse coating method, a die coating method, a gravure coating method, and a micro gravure coating method can be used.

  As described above, the light diffusing film of the present invention is excellent in light diffusibility and light condensing property, and as a result, has high brightness. Specifically, the light diffusing film of the present invention is a light diffusing film. The haze, which is one of the indices representing the light, is 80 or more, and the total light transmittance, which is one of the indices representing the light condensing property, is 80% or more, so it is excellent in both light diffusibility and light condensing properties. The brightness becomes high.

A resin obtained by graft-polymerizing an antistatic agent such as a phosphate ester or a quaternary ammonium salt to a resin such as an acrylic resin on the light diffusion layer of the light diffusing film of the present invention, or phosphoric acid. An antistatic layer made of a resin mixed with an antistatic agent such as an ester or a quaternary ammonium salt may be formed.
It is preferable to form an antistatic layer since dust or the like hardly adheres to static electricity when handling the light diffusing film or placing the light diffusing film on the light guide plate.

In the light diffusing film of the present invention, a moire preventing layer composed of a resin and inorganic or organic fine particles may be formed on the other surface of the plastic film on which the light diffusing layer is formed.
The moiré preventing layer prevents so-called moiré that occurs when the light diffusion film of the present invention is placed on the light guide plate of the backlight.

  The resin used for the anti-moire layer is not particularly limited as long as the purpose of the anti-moire layer can be achieved. Acrylic resin, polyester resin, vinyl chloride resin, vinyl chloride vinyl acetate copolymer resin, fluorine resin Resins such as resin, melamine resin, epoxy resin, and polypropylene resin can be used.

  Silica, smectite, zinc oxide, titanium oxide, fluororesin fine particles, styrene resin fine particles and the like can be used as the inorganic or organic fine particles used in the moire preventing layer.

As for the thickness of a moire prevention layer, 1-5 micrometers is preferable.
Even if it is thinner than 1 μm or thicker than 5 μm, it is difficult to prevent the occurrence of moire, which is not preferable.

Further, for the purpose of antistatic, an antistatic agent such as phosphate ester or quaternary ammonium salt may be mixed in the moire preventing layer.
By adding an antistatic agent to the moiré prevention layer, it is difficult for static electricity to adhere to dust when handling the light diffusing film or placing the light diffusing film on the light guide plate. Use in combination with a layer is preferable because the antistatic property is further improved.

  A conventionally known method such as reverse coating method, die coating method, gravure coating method, or micro gravure coating method can be used as a method for forming the moire preventing layer.

Here, the light diffusing film according to the present invention and the rugby ball-shaped resin fine particles used in the light diffusing film according to the present invention will be described with reference to the drawings.
FIG. 1 is a partially enlarged sectional view showing an example of a light diffusing film according to the present invention. A light diffusing layer 2 is provided on one side of a plastic film 1 and a moire preventing layer 3 is provided on the other side of the plastic film 1. In the light diffusion layer 2, the rugby ball-shaped resin fine particles 40 are mixed in an upright state, that is, in a state where the height direction of the fine particles is oriented in a direction perpendicular to the light diffusion film plane.
FIG. 2 is a partially enlarged sectional view showing an example of the light diffusing film according to the present invention. The light diffusing layer 2 is provided on one side of the plastic film 1 and the moire preventing layer 3 is provided on the other side of the plastic film 1. In the light diffusion layer 2, the spherical resin fine particles 50 and the rugby ball-shaped resin fine particles 40 are mixed and mixed, and the rugby ball-shaped resin fine particles 40 are upright, that is, the height direction of the fine particles is the light diffusion film plane. It is in a state facing in a direction orthogonal to the direction.
FIG. 3 is three enlarged views showing examples of rugby ball-shaped resin fine particles used in the light diffusion film according to the present invention.
[3a] is a view of a rugby ball-shaped resin fine particle having a maximum height x, a maximum width y, and a relationship of x> y as viewed from the side upright.
[3b] is a view of the rugby ball-shaped resin fine particles having the maximum width y and the maximum thickness z and having a relationship of y = z upright and viewed from directly above.
[3c] is a view of the rugby ball-shaped resin fine particles having a maximum width y and a maximum thickness z and having a relationship of y> z as viewed from directly above.

[Example 1]
Rugby ball-shaped resin with a maximum height x = 3.6-6 μm, a maximum width y = 3 μm, a maximum thickness z = 3 μm and various heights on one side of a 50 μm thick polyethylene terephthalate film 11.3 parts by weight of fine particles (Techpolymer manufactured by Sekisui Chemical Co., Ltd.) is an acrylic resin (Olyster manufactured by Mitsui Chemicals, Inc.) which is a binder resin and has a glass transition temperature of 43 ° C., a molecular weight of 20000, and a hydroxyl value of 20 mgKOH / g. Q193) A coating material mixed in 10 parts by weight and 1.3 parts by weight of isocyanate (Coronate HL manufactured by Nippon Polyurethane Co., Ltd.) was coated by a microgravure coating method to form a light diffusion layer.
In addition, the mixing amount of the rugby ball-shaped resin fine particles in the light diffusion layer was 100% by weight with respect to the resin.
Further, on the other side of the polyethylene terephthalate film, 20 parts by weight of acrylic resin (VMD medium manufactured by Dainichi Seika Co., Ltd.), 3 parts by weight of isocyanate (Takenate D110N manufactured by Takeda Chemical Co., Ltd.), and acrylic resin fine particles (Gantz Pearl manufactured by Guntsu Kasei Co., Ltd.) GB05) A coating composed of 0.23 parts by weight and 0.1 part by weight of a phosphoric ester-based antistatic agent (Shobaku 110 manufactured by Showa Ink Co., Ltd.) is coated by a reverse coating method to form a moire prevention layer. An inventive light diffusing film was obtained.

[Example 2]
Rugby having a maximum height x = 3.6 to 6 μm, a maximum width y = 3 μm, a maximum thickness z = 3 μm and various heights instead of the rugby ball-shaped resin fine particles of the light diffusion layer of Example 1. A mixture of 8 parts by weight of ball-shaped resin fine particles (Techpolymer manufactured by Sekisui Chemical Co., Ltd.) and 2 parts by weight of spherical resin fine particles having a particle diameter of 20 μm (Gantz Pearl GM 2004 manufactured by Guntoo Kasei) (rugby ball-shaped resin fine particles and true spherical shape) A light diffusing film of the present invention was obtained in the same manner as in Example 1 except that the weight ratio of resin fine particles was 8: 2).
The total amount of the rugby ball-shaped resin particles and the spherical resin particles in the light diffusion layer was 88% by weight with respect to the resin.

Comparative example

[Comparative Example 1]
In the same manner as in Example 1, except that 10 parts by weight of spherical resin fine particles (MBX20 manufactured by Sekisui Chemical Co., Ltd.) having a particle diameter of 20 μm were mixed instead of the rugby ball-shaped resin fine particles of the light diffusion layer of Example 1, A diffusion film was obtained.
In addition, the mixing amount of the spherical resin fine particles in the light diffusion layer was 88% by weight with respect to the resin.

[Comparative Example 2]
In the same manner as in Example 1, except that 10 parts by weight of spherical resin fine particles (MBX10 manufactured by Sekisui Chemical Co., Ltd.) having a particle diameter of 15 μm were mixed instead of the rugby ball-shaped resin fine particles of the light diffusion layer of Example 1, A diffusion film was obtained.
In addition, the mixing amount of the spherical resin fine particles in the light diffusion layer was 88% by weight with respect to the resin.

[Comparative Example 3]
In the same manner as in Example 1, except that 10 parts by weight of spherical resin fine particles (MBX5 manufactured by Sekisui Chemical Co., Ltd.) having a particle diameter of 5 μm were mixed instead of the rugby ball-shaped resin fine particles of the light diffusion layer of Example 1, A diffusion film was obtained.
In addition, the mixing amount of the spherical resin fine particles in the light diffusion layer was 88% by weight with respect to the resin.

  About the light-diffusion film of this invention obtained in Example 1, 2, and the light-diffusion film obtained in Comparative Examples 1-3, the following test was done and the performance as a light-diffusion film was compared.

1. Total light transmittance (measurement sample) Each of the light diffusion films of the present invention obtained in Examples 1 and 2 and the light diffusion films obtained in Comparative Examples 1 to 3 were prepared and used as samples.
(Measurement method) Measured according to JIS-K-7105 using a haze meter (NDH-300A manufactured by Nippon Denshoku).
(Measurement results) Table 1

2. Haze (Measurement Sample) Each of the light diffusion films of the present invention obtained in Examples 1 and 2 and the light diffusion films obtained in Comparative Examples 1 to 3 were prepared and used as samples.
(Measurement method) Measured according to JIS-K-7105 using a haze meter (NDH-300A manufactured by Nippon Denshoku).
(Measurement results) Table 1

3. Luminance Brightness generally varies depending on the number of light diffusing films, the types and number of prism sheets to be combined, the type of light guide plate, etc., so it cannot be expressed in absolute values. Compare with the values measured under the same conditions. It can only be expressed as a relative value.
Therefore, four patterns of samples were prepared by changing the number of light diffusion films or the number of prism sheets to be combined, and the light diffusion films of the present invention obtained in Examples 1 and 2 and Comparative Examples 1-3. We decided to compare the brightness of the light diffusing films obtained in (1).
(Measurement sample) Prepare the light diffusion films of the present invention obtained in Examples 1 and 2 and the light diffusion films obtained in Comparative Examples 1 to 5 respectively, and prepare samples of the following four patterns. Produced.
(A) The light diffusing film of the present invention obtained in Examples 1 and 2 or the light diffusing film obtained in Comparative Examples 1 to 3 was used as a sample. (B) Obtained in Examples 1 and 2. Each of the light diffusing films of the present invention or the light diffusing films obtained in Comparative Examples 1 to 3 was used as a sample.
At this time, the light diffusion layer surface side of the light diffusion film of the present invention obtained in Examples 1 and 2 on the lower side or the light diffusion film obtained in Comparative Examples 1 to 3 is the Example 1 and 2 on the upper side. The obtained light diffusing film of the present invention or the light diffusing film obtained in Comparative Examples 1 to 3 was laminated so as to be in contact with the moire preventing layer surface side.
(C) The prism surface of the prism sheet (BEF manufactured by Sumitomo 3M Limited) is respectively formed on the light diffusion film of the present invention obtained in Examples 1 and 2 or the light diffusion film obtained in Comparative Examples 1 to 3. The samples were stacked so as to be on top.
(D) Two prism sheets (BEF manufactured by Sumitomo 3M Co.) are stacked on the light diffusion films of the present invention obtained in Examples 1 and 2 or the light diffusion films obtained in Comparative Examples 1 to 3, respectively. And used as a sample.
The two prism sheets were overlapped so that the prism surfaces were on top, and the prism direction of the upper prism sheet was overlapped so as to be orthogonal to the prism direction of the lower prism sheet.
(Measurement method) Each sample of (A) to (D) is placed on a light guide plate of a backlight (manufactured by Hitachi, Ltd.) so that the moire prevention layer surface side is in contact with the light guide plate, and a cathode ray tube having a thickness of 5 mm. Was measured with a luminance meter (SL110 manufactured by Minolta Camera Co., Ltd.) fixed at a position 30 cm away from the sample.
(Measurement results) Table 1

It is a partially expanded sectional view which shows an example of the light-diffusion film which concerns on this invention. It is a partially expanded sectional view which shows an example of the light-diffusion film which concerns on this invention. It is three enlarged views which show an example of the resin particle of the rugby ball shape used for the light-diffusion film which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plastic film 2 Light-diffusion layer 3 Moire prevention layer 40 Rugby ball-shaped resin particle 50 True spherical resin particle x Maximum height of rugby ball-shaped resin particle y Maximum width of rugby ball-shaped resin particle z Maximum thickness of rugby ball-shaped resin particle The

Claims (3)

In a light diffusion film in which a light diffusion layer made of resin and resin fine particles is formed on one surface of a plastic film, the resin fine particles have a maximum height x, a maximum width y, and a maximum thickness z. A light diffusing film characterized by being fine resin particles and satisfying the following conditions.
A. x> y ≧ z
B. x: y: z = 1.2-3: 1: 0.5-1
C. 1μm ≦ x ≦ 20μm   In the light diffusion film in which a light diffusion layer composed of resin and resin fine particles is formed on one surface of a plastic film, the resin fine particles are a mixture of the rugby ball-shaped resin fine particles according to claim 1 and true spherical resin fine particles. A light diffusing film characterized by being a thing.   The light diffusing film according to claim 1 or 2, wherein a moire preventing layer made of a resin and inorganic or organic fine particles is formed on the other surface of the plastic film.

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