WO2007029606A1

WO2007029606A1 - Light diffusion film and surface light source using same

Info

Publication number: WO2007029606A1
Application number: PCT/JP2006/317301
Authority: WO
Inventors: Akikazu Kikuchi; Hiromitsu Takahashi; Kozo Takahashi; Takayuki Kaneko
Original assignee: Toray Industries, Inc.
Priority date: 2005-09-06
Filing date: 2006-09-01
Publication date: 2007-03-15
Also published as: TW200717108A; KR20080042882A

Abstract

Disclosed is a light diffusion film comprising a base film which contains a light diffusion element inside. This light diffusion film is provided with a rough surface having a ratio between the maximum value Asmax and the minimum valum Asmin of the average aspect ratio, namely Asmax/Asmin (anisotropic degree) of not less than 1.1 on at least one side. This light diffusion film is excellent in luminance uniformity and high luminance characteristics.

Description

Specification

Light diffusion film and surface light source using the same

Technical field

TECHNICAL FIELD [0001] The present invention relates to a light diffusing film suitably used for a planar light source such as a planar light source (backlight), a light box, an electric signboard device, and a planar illumination of a liquid crystal display. More specifically, the present invention relates to a light diffusing film that is preferably used for mounting on a light emitting surface of a so-called direct type surface light source or side light type surface light source, a direct type surface light source and a side light type surface light source using the same.

Background art

In recent years, many displays using liquid crystals have been used as display devices for personal computers, televisions, mobile phones and the like. Since these liquid crystal displays are not themselves illuminants, they can be displayed by irradiating light using a backside surface light source. In addition, in order to meet the requirement that the entire surface of the surface light source must be evenly irradiated by simply irradiating light, the surface light source has a surface light source structure called a side light type surface light source or a direct type surface light source. It has been adopted.

[0003] At this time, if there is uneven luminance in the light emitted from the surface light source, the image quality of the display deteriorates, so that the entire screen is required to be irradiated uniformly.

[0004] In particular, a direct-type surface light source is preferably used for a surface light source applied to a television or the like. A direct type surface light source is a planar light source of a type in which a light source is disposed in a hollow casing and emitted light is emitted from the main plane of the casing (for example, Patent Document 1). That is, a structure in which a number of light sources such as cold cathode ray tubes are disposed immediately below the light emission surface.

[0005] For this reason, the direct type surface light source among various surface light sources has a large brightness difference between the position directly on the light source on the screen and the position other than the light source, and is easily recognized as uneven brightness. There's a problem. For this reason, in general, a translucent milky white plate (so-called light diffusing plate) having a very strong light diffusibility is used on the light exit surface (Fig. 2) to reduce luminance unevenness as much as possible. This light diffusing plate is a resin plate such as acrylic or polycarbonate having a thickness of several millimeters mixed with organic and inorganic fine particles (preferably silicone fine particles). Yes.

[0006] Furthermore, if the uniformity is still insufficient, a light shielding pattern is printed directly on the light diffusing plate, and the light transmitted from the upper part of the light source is partially blocked to uniform the brightness of the entire screen (for example, patent References 2) etc. have been proposed.

[0007] On the other hand, liquid crystal displays and the like are required to have higher screen luminance, and in response to this, techniques such as increasing the light emission intensity of the light source are employed. In this case, uneven brightness is more likely to occur. Therefore, increasing the thickness of the light diffusing plate or further increasing the amount of fine particles added increases the light diffusibility of the light diffusing plate, thereby reducing luminance unevenness. Elimination has been attempted.

Patent Document 1: JP-A-5-119311 (Claim 1, FIG. 1)

Patent Document 2: Japanese Patent Laid-Open No. 11 268211 (Claims 1 and 2, FIGS. 1 and 4) Disclosure of the Invention

Problems to be solved by the invention

However, simply increasing the light diffusibility of the light diffusing plate has a problem in that the light transmittance is decreased, and the brightness enhancement effect due to the increase in the light emission intensity of the light source is diminished.

Accordingly, in view of these points, an object of the present invention is to provide a novel light diffusing film capable of efficiently eliminating luminance unevenness and achieving both luminance uniformity on the screen and high luminance characteristics. A further object of the present invention is to provide a novel surface light source, particularly a direct type surface light source, having high brightness and high uniformity using this light diffusion film.

Means for solving the problem

In order to solve the above problems, the present invention has the following configuration. That is, the light diffusing film of the present invention has a base film containing a light diffusing element inside, and the ratio of the maximum aspect ratio Asmax to the minimum value Asmin on at least one surface Asma xZAsmin (anisotropic degree) ) Is a light diffusing film with a surface irregularity shape of 1.1 or more.

Moreover, the surface light source of this invention is a surface light source using the said light-diffusion film. The invention's effect

According to the light diffusing film of the present invention, there is provided a direct surface light source that is excellent in high front luminance characteristics and screen uniformity, illuminates a liquid crystal screen brightly, and makes a liquid crystal image clearer and easier to see. Can do.

Brief Description of Drawings

FIG. 1 is a perspective view for illustrating the structure of a surface light source using the light diffusion film of the present invention.

FIG. 2 is a perspective view for illustrating the structure of a planar light emitter.

FIG. 3 is a diagram for explaining how to obtain the surface unevenness aspect ratio of a light diffusion film.

FIG. 4 is a bird's-eye view (excluding a light diffusion film) for illustrating a linear light source structure.

FIG. 5 is a bird's-eye view (excluding a light diffusion film) for illustrating a linear light source structure.

FIG. 6 is a bird's-eye view (excluding a light diffusion film) for illustrating a linear light source structure.

FIG. 7 is a cross-sectional view for illustrating the relationship between the average distance a between the light sources of the direct type surface light source, the average distance between the light source of the direct type surface light source and the light diffusing film, and the angle Θ shown in Equation (1). is there.

FIG. 8 is a bird's-eye view (excluding the light diffusion film) for illustrating the positional relationship between the straight lines L1 to L10.

FIG. 9 is a bird's eye view for explaining a measurement system of B (−5) and B (+5).

FIG. 10 is an (X-Z) cross-sectional view of the mold used in Example 3-1.

FIG. 11 is an (x-z) cross-sectional view of the mold used in Example 3-2.

FIG. 12 is an (x-z) cross-sectional view of the mold used in Example 3-3.

Explanation of symbols

[0013] 1: Light reflecting film

2: Light source

3: Light diffusion plate

4: Floodlight

5: Incident light

6: Receiver 7: Light diffusion film

8: Mold

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] The light diffusing film of the present invention has a base film containing a light diffusing element inside, and at least one surface has a ratio of the maximum aspect ratio Asmax to the minimum value Asmin A smaxZAsmin ( It is necessary that the surface irregularity shape with an anisotropic degree of 1.1 or more is formed. By making the light diffusing film satisfying such conditions, it is possible to dramatically improve the luminance unevenness of the direct type surface light source and to dramatically improve the luminance characteristics.

[0015] First, the light diffusion film of the present invention needs to be composed of a base film containing a light diffusion element therein. Although light is diffused also by the fine surface irregularities described later, the light may not be sufficiently diffused by the surface irregularities alone. Therefore, light can be diffused more efficiently by including a light diffusing element in the base film.

Here, the light diffusing element preferably has a component force having a refractive index different from that of the main component constituting the base film. The greater the difference in refractive index, the greater the light diffusivity.

[0017] First, in the present invention, the resin constituting the base film is not particularly limited, but preferably has no absorption in the visible light region. Here, “having no absorption in the visible light region” means that when a film having a smooth surface of 200 μm thickness is formed only with these resins, the total light transmittance power of the film is ΟΟηπ. ! It means 70% or more in the whole area of ~ 700nm. Examples of resins satisfying such conditions include polyolefins (including cycloolefin copolymers), polycarbonates and polyesters. Among them, aromatic polyester is preferably used as a resin having good dimensional stability, mechanical properties, and handling properties (handleability).

[0018] Among aromatic polyesters, polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene 2, 6 naphthalene dicarboxylate, polypropylene terephthalate, polybutylene terephthalate, poly 1,4-cyclohexylene dimethylene having excellent productivity. It is more preferable to use terephthalate or the like. Among these, PET fat is Since it is cheap and easily available, it can be most preferably used.

[0019] These polyesters may be homopolymers or copolymers. Examples of the copolymer component in the case of a copolymer include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and diol components having 2 to 15 carbon atoms. Acids, adipic acid, sebacic acid, phthalic acid, sulfonic acid group-containing isophthalic acid, and their ester-forming compounds, diethylene glycol, triethylene glycol, neopentyl glycol, cyclohexane dimethanol, polyalkylene glycol, etc. Can be mentioned.

[0020] Various additives may be added to these polyester resins within a range that does not impair the effects of the present invention. These additives include optical brighteners, crosslinkers, heat stabilizers, oxidation stabilizers, UV absorbers, organic lubricants, organic and inorganic fine particles, fillers, light stabilizers, antistatic agents, nucleating agents, Examples include dyes, dispersants, and coupling agents.

[0021] Next, the type of the light diffusing element contained in the interior of the resin constituting the film as described above is not particularly limited, and various inorganic particles, organic particles, resin, and the like can be used. It is preferable that the light diffusing element has no significant absorption in the visible light region. The light diffusing element can be a single component or two or more components.

[0022] When a polyester-based resin (refractive index: 1.55 to L 6 5) is used as a main component constituting the light diffusing film, an example of an element suitably used as a light diffusing element is a polyolefin type Resin (refractive index 1.45-: L 55), silicone-based resin (refractive index 1.4-1.5), talyl-based resin (including copolymer) (refractive index 1.45-: L 55), methacrylic resin (including copolymer) (refractive index 1.45 ~: L55), bubbles (refractive index 1.0), silica (refractive index 1.45 ~: L6), sulfuric acid Examples thereof include barium (refractive index: 1.6 to 1.7), calcium carbonate (refractive index: 1.45: L 7), and titanium oxide (refractive index: 2.5 to 2.7).

[0023] Among them, fine particles composed of silicone-based resin, fine particles composed of acrylic-based resin, or fine particles composed of methacrylic resin have a low refractive index and visible light absorption. It is preferably used. Here, the fine particles refer to particles having an average particle diameter, which is an average value of sphere equivalent diameters, of 0.1 μm or more and 100 μm or less. The equivalent diameter of a sphere refers to the diameter of a sphere having the same volume as that of a sphere that has a shape other than a sphere. [0024] Further, when polyolefin resin is used as the light diffusing element, polymethylpentene (refractive index 1.45) can be preferably used because it has a low refractive index and little absorption in visible light. In addition, since polymethylpentene has a melting point of about 235 ° C., it has an advantage that it can be melt-extruded together with a polyester resin.

[0025] When the resin constituting the base film and the resin serving as the light diffusion element are melt-extruded together, the resin constituting the light diffusion element is dispersed in the resin constituting the base film. It will be. In this case, the average particle diameter of the light diffusing element can be obtained by taking the average of the sphere equivalent diameters of the resin dispersion to be the light diffusing element.

[0026] The average particle size of the light diffusing element is preferably 0.2 μm or more and 50 μm or less, more preferably 0.3 μm or more and 20 μm or less, and even more preferably 0.5 μm or more and 10 μm or less. m or less. By setting the particle size of the light diffusing element within the range where the light diffusion element is used, light can be diffused efficiently, and uneven brightness can be reduced. On the other hand, if it is less than 0 .: L m, the light transmitted through the film may be colored due to the Rayleigh scattering phenomenon. On the other hand, if it is 100 m or more, the light diffusing element is visually recognized, which may be unfavorable in appearance.

[0027] The above-mentioned refractive index is a typical value, and may vary depending on the copolymerization component, the degree of polymerization, the crystal structure, and the like.

In the light diffusing film of the present invention, the light diffusing element area occupancy ratio in a cross section perpendicular to the film surface is preferably 1% or more, more preferably 2% or more. When the light diffusing element area occupancy is 1% or more, the light diffusing property is improved more efficiently.

[0029] Although the upper limit is not particularly specified, if it exceeds 50%, the light diffusibility becomes too large, and the light incident on the film is scattered not only forward but also backward. The transmittance may decrease.

[0030] In the light diffusing film of the present invention, the number density of the light diffusing elements in a cross section perpendicular to the film surface is preferably 250 Zmm ² or more. More preferably 500 ZMM ^2. When the number density of the light diffusing elements is 250 Zmm ² or more, the light diffusing property is more efficiently obtained.

[0031] Incidentally, the upper limit is not particularly defined, it exceeds 100,000,000 ZMM ^2, only the light-diffusing property becomes too large, the light incident on the film in the rear as well as front only Due to scattering, the light transmittance may decrease.

[0032] Further, it is particularly preferable that the occupation ratio of the light diffusing elements in the cross section of the film is 1% or more and the number density of the light diffusing elements in the cross section of the film is 250 Zmm ² or more. In this case, light diffusivity is very efficiently increased.

[0033] In the light diffusing film of the present invention, it is preferable that the base film containing the light diffusing element is stretched beyond the -axis. More preferably, it is stretched biaxially. This is because at least the base film is stretched so that the entire light diffusion film can have excellent mechanical properties such as high strength.

Here, as a method for efficiently obtaining a stretched substrate film, for example, a method for producing a laminated film as described below can be mentioned.

[0035] First, thermoplastic resins A and B that satisfy the following formula (I) are prepared.

TA (° C)> TB (° C) (I)

Here, TA is the melting point of resin A, and TB is the melting point of resin B. Laminate resin A having a melting point higher than that of resin B on one or both sides of resin B. Here, the light diffusing element is dispersed in the resin B to obtain an unstretched laminated sheet.

[0036] Next, the laminated sheet is stretched uniaxially or more. At this time, along with stretching, separation may occur at the interface between the resin B and the light diffusing element, and voids called voids may be formed. When the generation of voids is small, the voids themselves are appropriate light diffusing elements. However, when a large amount of voids are formed, the transmittance of the laminated sheet decreases, and when used as a light diffusion film, the luminance characteristics may be inferior. In such a case, after stretching, the voids can be eliminated by heat treatment under conditions satisfying the following formula (Π).

TA (° C)> TH (° C)> TB (° C) (II)

Here, TH is a heat treatment temperature. That is, by performing a heat treatment at a temperature at which only the resin B is melted, the void between the resin B and the light diffusing element once generated can be eliminated.

[0037] In this way, a stretched substrate film can be obtained.

[0038] Here, the type of rosin used in sorghum A and B is not particularly limited, but polyethylene terephthalate is used as slab A, polyethylene terephthalate is used as sallow B, and isophthalic acid is cyclohexane. Preferred is rosin copolymerized with sandimethanol etc. to lower its melting point. Appropriately used.

Note that the light diffusing element used at this time is not particularly limited. For example, the above-described light diffusing element can be preferably used. In the case of using a resin having a low melting point obtained by copolymerizing polyethylene terephthalate in resin A, polyethylene terephthalate in resin B and isophthalic acid cyclohexane dimethanol, etc., fine particles composed of silicone-based resin, acrylic It is particularly preferable to use fine particles composed of a system resin, microparticles composed of a methacrylic resin, or polymethylpentene, refractive index and points of dispersibility in a resin.

[0040] Next, the light diffusing film of the present invention has at least one surface having a concave / convex shape having a ratio AsmaxZAsmin (anisotropy) of 1.1 or more as the ratio of the maximum value Asmax to the minimum value Asmin of the average aspect ratio. It is also necessary that the

[0041] Hereinafter, the uneven surface shape will be described in detail.

[0042] First, the shape of the surface irregularities formed on the film surface in the present invention is not particularly limited. However, at least one surface needs to have a surface irregularity shape in which the ratio AsmaxZAsmin (anisotropic degree) of the maximum value Asmax and the minimum value Asmin of the average aspect ratio is 1.1 or more.

Here, the average aspect ratio is obtained as follows.

(1) Cut the film perpendicular to the film surface so as not to crush it in the thickness direction, and observe the cross section. Here, in the film cross section, the film surface direction is defined as the X-axis direction (an arbitrary direction is defined as a positive direction), and the film thickness direction is defined as the y-axis direction.

(2) AO is an arbitrary point among the convex and concave parts (maximum points) of the surface irregularities. (See Figure 3)

(3) Next, let A1 be the nearest recess (minimum point in the thickness direction) in the positive X-axis direction with respect to AO.

(4) Measure the absolute value of the distance between AO and A1 in the X-axis direction, and let this be Axl. At this time, if the distance is less than 0.5 m, the local minimum point is not regarded as a recess, and the next closest recess in the X-axis plus direction is searched for, which is designated as A1.

(5) Measure the absolute value of the distance between AO and A1 in the y-axis direction and call this Ayl. At this time, the If the distance is less than 0.5 / zm, the local minimum point is not regarded as a recess, and the next nearest recess in the X-axis plus direction is searched for, which is designated as A1.

(6) Calculate Asl according to the following formula.

Asl = Ayl / Axl

(7) Therefore, let A1 be the nearest convex part (maximum point in the thickness direction) in the positive direction of the X axis with respect to A1!

(8) Measure the absolute value of the distance between A1 and A2 in the X-axis direction and call this Ax2. At this time, if the distance is less than 0.5 m, the local maximum point is not regarded as a convex part, and the next closest convex part in the X-axis plus direction is searched for, and is designated as A2.

(9) Measure the absolute value of the distance in the y-axis direction between A1 and A2, and call this Ay2. At this time, if the distance is less than 0.5 m, the local maximum point is not regarded as a convex part, and the next closest convex part in the X-axis plus direction is searched for, and is designated as A2.

(10) Find As2 according to the following formula.

As2 = Ay2 / Ax2

(11) Repeat steps (3) to (10) above to determine the concavo-convex parts corresponding to A3 to A100, and obtain As3 to AslOO.

(12) Asl force The simple average of AslOO is obtained, and this is defined as the aspect ratio As (0 °) of the surface shape. However, if the irregularity is only up to An, the simple average of Asl force Asn is obtained, and this is used as the aspect ratio As (0 °) of the surface irregularity. Here, n is an integer less than 100.

Further, the anisotropy of the aspect ratio in the film plane is determined as follows.

(13) Cut the film perpendicular to the film surface so that it is 15 ° clockwise with respect to the direction cut in (1) above.

(14) Perform steps (1) to (13) above, and set the aspect ratio of the obtained surface shape to As (15 °).

(15) Similarly, 30 °, 45 °, 60 °, 75 °, 90 °, 105 °, 120 °, 135 °, 150 in the clockwise direction with respect to the direction cut in (1) above in the film plane Cut the film perpendicularly to the film surface so that the directions are shifted by 165 ° and 165 °. 3), the aspect ratio of the obtained surface shape was set to As (30 °), As (45.), As (60.), As (75.) '-'As (165 °) To do.

(16) As (0.), As (15.), As (30.), As (45.), As (60.), As (75.) · · · Of Α s (165 °), The maximum value is Asmax and the minimum value is Asmin.

(17) The value obtained by dividing Asmax by Asmin (AsmaxZAsmin) is the degree of anisotropy. If Asmin is 0, the anisotropy is infinite. In addition, when all of As (n °) (n = 0 to 165 °) have the same value, the anisotropy is 1.

[0045] The light diffusion film of the present invention has an anisotropy of at least one surface unevenness of 1.

Must be 1 or more. The anisotropy is preferably 1.3 or more, more preferably 1.5 or more, and particularly preferably 2.0 or more. By setting the anisotropy of the surface irregularity to 1.1 or more, a light diffusion film having a high luminance unevenness improvement effect and a luminance improvement effect can be obtained.

[0046] Although the detailed reason why the above effect can be obtained by setting the anisotropy of the uneven surface shape to 1.1 or more is unknown, the present inventors consider as follows! /

[0047] The direct type surface light source in which the light diffusion film of the present invention is particularly used is a light source having a straight portion as shown in FIGS. 4, 5, and 6 (examples include a cold cathode tube, an organic EL, an inorganic EL, and an LED). In many cases, it is installed so that the straight portions thereof are substantially parallel to each other.

[0048] In such a case, in the direction orthogonal to the straight line portion of the light source (for example, the direction indicated by the broken line in FIG. 4), the light source and the portion where the light source does not exist appear alternately, and the luminance distribution has a very large deviation. have.

[0049] On the other hand, in the direction parallel to the linear portion of the light source, there can be (1) two turns on the light source and (2) a non-light source. First, (1) on the light source (for example, the direction indicated by the one-dot chain line in FIG. 4), the luminance distribution deviation is small because the luminance distribution of the light source is almost uniform. Next, (2) on the non-light source (for example, the direction indicated by the two-dot chain line in Fig. 4), since there is no light source, the absolute value of the luminance is low, but the deviation of the luminance distribution is small. Thus, the deviation of the luminance distribution in the direction parallel to the straight line portion of the light source is small.

In other words, the emitted light distribution (luminance distribution) of the light source power varies greatly depending on the direction to the light source. That is, there is a large anisotropy. Therefore, it is not necessary to diffuse light in the direction parallel to the linear direction of the light source, but diffuse light very strongly in the direction perpendicular to the linear direction of the light source. There is a need.

[0050] Here, it is presumed that the fine unevenness imparted to the film surface has a function of diffusing light. This light diffusivity does not need to be the same in the entire plane. In other words, it is necessary to diffuse light strongly in the direction perpendicular to the linear direction of the light source, but it is not necessary to diffuse light strongly in the direction parallel to the linear direction of the light source. . Rather, in the direction parallel to the linear direction of the light source, it is considered that it is not necessary to diffuse the light strongly so that the luminance is not lowered. As a result, by using the light diffusing film of the present invention, the light beam direction can be controlled efficiently, and the luminance characteristics are considered to be improved as compared with the conventional light diffusing plate.

[0051] Further, it is preferable that the in-plane angle indicating the minimum value Asmin is substantially orthogonal to the in-plane angle indicating the maximum value Asmax of the aspect ratio of the uneven surface shape. As described above, this is considered to be because the direction in which light should be strongly diffused in the direct type surface light source and the direction that does not require strong diffusion are orthogonal to each other. Here, “substantially orthogonal” means that the cut surface As (0 °), As (15.), '-' As (165.) in increments of 15 ° It means that the cut surface to be orthogonal. For example, when As (0 °) is Asmax and As (90 °) is Asmin, or As (105 °) is Asmax and As (15 °) is Asmin.

[0052] In the light diffusion film of the present invention, it is preferable that the unevenness formed on the surface should be fine.

[0053] The light diffusing film of the present invention can be suitably used for a liquid crystal display or the like. Since the display is observed by human eyes, the surface unevenness of the light diffusing film is visually recognized. This is because it is often preferable in terms of quality.

Therefore, in the present invention, “fine” means a case where the simple average Axav from Axl to AxlOO obtained in the cross section having Asmax is 1 mm or less. When Axav is 1 mm or less, the surface unevenness of the light diffusion film can be prevented from being visually recognized by a display observer, and a high-quality display or the like can be provided. [0055] Axav is preferably 0.5 mm or less, and more preferably 0.2 mm or less. The lower limit is not particularly specified, but it is 0.1 m or more. By setting Axav to 0.1 μm or more, it becomes possible to diffuse light incident on the surface irregularities geometrically and diffuse light more efficiently.

[0056] Further, in the present invention, Asmax is preferably 0.3 or more. More preferably, it is 0.5 or more, particularly preferably 0.7 or more, and most preferably 1.0 or more. When Asmax is 0.3 or more, excellent light diffusibility can be obtained, and screen uniformity and luminance characteristics can be improved. The upper limit is not particularly specified, but is preferably 10 or less. If it exceeds 10, the tendency of light rays to be emitted only in a specific direction becomes strong, and it may not contribute much to the brightness uniformity in the screen.

[0057] The shape of the surface irregularities is not particularly limited, and may be a regular shape or an irregular shape. Examples of regular shapes include quadratic curves and some or all of trigonometric functions.

[0058] The method for imparting such a fine surface irregularity shape to the substrate film is not particularly limited, but thermal imprinting and optical imprinting can be suitably used.

[0059] Thermal imprinting refers to heating a mold with a fine surface shape and a resin, pressing the mold against the resin, cooling the mold and the resin, and then releasing the mold. In this method, the shape on the mold surface is transferred to the resin. Here, the resin used for thermal imprinting may be a thermoplastic resin or a thermosetting resin, but a highly transparent resin is preferred. Examples of the resin suitable for thermal imprinting include acrylic resin, silicone resin, various olefin copolymers, polycarbonate, polystyrene, polyolefin, polyethylene terephthalate, and the like. Here, when polyethylene terephthalate is used, it is preferable to copolymerize isophthalic acid, cyclohexanedimethanol, naphthalate, spiroglycol, fluorene or the like in order to reduce crystallinity. This is because when the crystallinity is high, the film may crystallize and become white when heat imprinted.

[0060] On the other hand, optical imprinting is a method in which a photocurable resin is applied on a base film, a mold having a fine surface shape is pressed against a portion to which the photocurable resin is applied, The part is irradiated with light such as ultraviolet rays, the photocurable resin is cured, then released, and the shape applied to the mold surface It is a technique to transfer the shape to rosin. Examples of the resin suitable for optical imprint include acrylic resin.

The light transmittance of the light diffusion film of the present invention is preferably 40% or more. More preferably, it is 50% or more, particularly preferably 60% or more. This is because the luminance characteristics can be improved by setting the light transmittance to 40% or more.

[0061] The haze of the light diffusion film of the present invention is preferably 50% or more. More preferably, it is 65% or more, particularly preferably 80% or more. This is because when the haze is 50% or more, the screen uniformity when the light diffusion film is used as a surface light source can be improved.

[0062] The overall thickness of the light diffusion film of the present invention is preferably 1000 µm or less. Further, it is preferably 10 to 500 μm, particularly preferably 20 to 300 μm. Here, the “total thickness of the light diffusing film” is the thickness of the base film when the light diffusing film is composed only of the base film. In addition, when the light diffusing film has another resin layer laminated on the surface of the base film, the thickness is the combined thickness of the base film and the resin layer. When the total thickness is 1000 m or less, the light diffusing film can be reduced in weight, and handling properties can be improved. By reducing the weight, it is possible to reduce the load applied to the surface light source when the light diffusing film is actually mounted on the surface light source. In particular, when the total thickness is 300 m or less, the light diffusing film can be easily wound up in a roll shape, and handling properties and post-processing properties can be remarkably improved. On the other hand, when it exceeds 1000 / zm, when it is used as a light diffusing film for a liquid crystal display or the like, the thickness of the entire surface light source may increase, which may be preferable.

[0063] As described above, the light diffusion film is a plate-like material that is incorporated into a surface light source for light diffusion. Specifically, it is often used for a light diffusion plate of a direct type surface light source. Accordingly, it is preferable that the light diffusing film has an achromatic color or slightly bluish in terms of the color tone of the screen. In consideration of this point, it is also a preferred embodiment to add an appropriate amount of a fluorescent brightening agent to the light diffusion film. For example, commercially available fluorescent whitening agents can be used as appropriate. For example, UBITEC (R) (Ciba-Gaigi), OB-1 (Eastman), TBO (Sumitomo Seika), Keikoru. (R) (manufactured by Nippon Soda Co., Ltd.), Kyalite (R) (manufactured by Nippon Kayaku Co., Ltd.), Leukopua (R) EGM (manufactured by Client Japan), etc. can be used. [0064] The light diffusing film of the present invention is in the normal direction when light is incident on the light diffusing film in an angle range of 20 ° to 50 ° with respect to the normal direction of the film surface. It is preferable that the minimum value BI of the specific luminance of the transmitted light beam is 0.0013 or more. More preferably, it is 0.004 or more, and particularly preferably 0.008 or more.

[0065] By setting the minimum value BI of the specific brightness to 0.0013 or more, the brightness unevenness of the direct type surface light source can be drastically improved.

[0066] In the light diffusion film of the present invention, the maximum average specific luminance Bmax is preferably 0.002 or more, more preferably 0.005 or more, and particularly preferably 0.01 or more.

Here, the specific luminance is a value obtained by a measuring device called a go-off otometer. The specific measurement method is the force described in detail below. When a light beam is incident on the light diffusion film at an angle of 20 ° to 50 ° with respect to the normal direction of the surface of the light diffusion film (incident angle is assumed to be 0), The light intensity transmitted in the normal direction is divided by the light intensity of the incident light, and the value divided by cos Θ is the specific luminance. At this time, the tilt is not allowed (the tilt angle is 0 °).

[0068] The average specific luminance is the specific luminance of light transmitted in the normal direction when the light beam is incident on the light diffusion film at an angle of 20 ° to 50 ° with respect to the normal direction of the film surface. The maximum average specific brightness Bmax is the value that gives the maximum average specific brightness, taking into account the front and back of the film and the in-plane anisotropy of the film. Detailed measurement methods will be described later.

[0069] By setting the values of the minimum specific brightness BI and Z or the maximum average specific brightness Bmax within the above range, a light diffusion film having a high brightness unevenness improvement effect and a brightness improvement effect can be obtained. The upper limits of the specific luminance minimum value BI and the maximum average specific luminance Bmax are not particularly limited, but are preferably 0.5 or less. If it exceeds 0.5, light is transmitted only in a specific direction, which may be inferior in luminance unevenness improvement effect and luminance characteristics.

[0070] Further, the light diffusing film of a preferred embodiment of the present invention in which the specific luminance minimum values BI and Z or the maximum average specific luminance Bmax are within the above range is a direct-type surface light source having two or more linear light source portions. Particularly preferably used. Here, the two or more linear light source sections mean that a plurality of linear light sources as shown in FIG. 4 are arranged side by side, and two or more straight line sections as shown in FIGS. 5 and 6 are U-shaped. In some cases, it may be composed of Multiple light source It is preferable that the straight portions are parallel.

[0071] When two or more straight portions are configured in a U-shape or the like, if there are two or more straight portions, one light source is included in the light source portion having two or more straight portions.

[0072] The light diffusion film of the present invention is a method in which light is incident on the light diffusion film at an angle of 20 ° to 50 ° with respect to the normal direction of the film surface, and the film is rotated in-plane. It is preferable that the ratio Bmax × ZBmin of the maximum average specific luminance Bmax and the minimum average specific luminance Bmin of light transmitted in the line direction is 1.1 or more. More preferably, it is 1.3 or more, and particularly preferably 1.5 or more. When the BmaxZBmin of the light diffusing film is 1.1 or more, it is possible to obtain high luminance characteristics while efficiently equalizing the luminance in the screen.

Here, the minimum average specific luminance Bmin and BmaxZBmin are obtained by the method described below using a go-off otometer.

[0074] Hereinafter, the minimum value BI of the specific luminance, the maximum average specific luminance Bmax and the minimum average specific luminance Bmin, and the method for obtaining the ratio BmaxZBmin will be described in detail.

(1) The measurement is performed by transmission measurement, the tilt angle is 0 ° (no tilt), and a polarizing filter and a bandpass filter (such as a color filter) are not used! ,.

(2) Next, without setting anything on the sample stage, measure the light intensity with a light incident angle of 0 ° and a light receiving angle of 0 °, and the value at this time shall be KA.

(3) Both surfaces of the film to be measured are defined as a-side and b-side for convenience. Place the film to be measured on the sample stage so that the light incident surface is a-plane and without bending. Light incident angle Θ (normal direction of film surface) is 20 °, and light receiving angle is 0 °. Measure the luminous intensity KB (0 = 20 °).

(4) Calculate the relative luminance B using the following formula.

B (0 = 20 °) = (KB / KA) / cos Θ

(5) Θ = 25 °, 30 °, 35 °, 40 °, 45 °, 50 °, -20 °, -25 °, -30 °, -35 °, 40 °, 45 °, 50 ° [Same as above] [This brightness is obtained. Θ = 20 °, 25 °, 30 °, 35 °, 40 °, 45 °, 50 °, -20 °, -25 °, -30 °, -35 °, -40. Let 比 (φ = 0 °, a-plane) be the minimum value of the specific brightness of -45 ° and 150 °. Also, 0 = 20 °, 25 °, 30 °, 35 °, 40 °, 45 °, 50 °, 20 °, 25 °, 30 °, 35 °, The average specific luminance of specific luminances of −40 °, −45 °, and 150 ° is obtained, and this is defined as Β & ν (φ = 0 °, a plane). Here, φ indicates the in-plane rotation angle in the measurement (clockwise direction is the + direction).

(6) Rotate the film in the direction of 15 ° clockwise with respect to the direction measured in (3) to (5). That is, φ = 15. Become

(7) Perform steps (3) to (5) above to obtain ΒΜ (φ = 15 °, a-plane) and Β & ν (φ = 15 °, a-plane).

(8) 30 °, 45 °, 60 °, 75 °, 90 °, 105 °, 120 °, 135 °, 150 °, 165 ° clockwise with respect to the direction measured in (3) in the film plane Rotate the film in the direction of the film surface so that it is in the rotated direction. Then, the above operations (3) to (5) are performed at each rotational position, and ΒΜ (φ = 30 °, a surface), ΒΜ (φ = 45 °, a surface), ..., ΒΜ (φ = 165 , A surface), and Β & ν (φ = 30,, a surface), Bav (φ = 45,, a surface),…, Β & ν (φ = 165., A surface).

(9) Repeat the above steps (3) to (8) for the b-plane. それぞれ (φ = 0 °, b®), B Μ (= 15 °, b-plane), ..., ΒΜ (φ = 165 , B plane), and Bav (φ = —15,, b plane),..., Β & ν (φ = —165 °, b plane).

(10) The highest Bav obtained up to (9) above is taken as the maximum average specific luminance Bmax. Also, the BM at the surface and angle φ when Bmax is measured is defined as the minimum specific brightness value BI. In the present invention, when a surface irregularity shape having an anisotropic degree of 1.1 or more is formed on only one surface, the surface opposite to the surface usually has the maximum average specific luminance Bmax. become.

(11) On the surface taking the maximum average specific luminance Bmax, the smallest value among the Bavs obtained by the above measurement with the in-plane rotation angle φ varied is the minimum average specific luminance Bmin.

(12) Find the value obtained by dividing Bmax by Bmin (BmaxZBmin). When Bmin is 0, Bma xZBmin is infinite. BmaxZBmin is 1 when Bmax and Bmin are the same value.

Although the detailed reason why the above-mentioned effect can be obtained by setting BI, Bmax, and BmaxZmin within the above ranges is unknown, the present inventors consider as follows. Light diffusion of the present invention The direct type surface light source for which the film is preferably used has a light source having two or more straight portions as shown in FIGS. 4 to 6 and is installed so that the straight portions are substantially parallel to each other. Many. That is, there is a large anisotropy in the outgoing light distribution with the light source power.

[0076] Luminance unevenness is a phenomenon caused by the difference between the luminance directly above the light source and the luminance between the light sources due to the large anisotropy of the emitted light distribution of the strong light source power. When the direct type surface light source is observed from the front (when viewed from the normal direction with respect to the light emitting surface of the surface light source), the light source itself is a light emitter, and the brightness is very high. On the other hand, as a matter of course, there is no light emitter between the light sources, and the luminance is remarkably lower than that immediately above the light source. Here, the luminance between the light sources mainly depends on how much light incident on the light diffusing film is refracted and scattered in the direction of the observer, in addition to the light source power existing in the vicinity.

[0077] Therefore, when a light beam is incident on the light diffusion film at an angle of δ derived from the following formula (III), the amount of light emitted in the normal direction of the film surface is set to a certain level or more, so that The brightness of the light diffusing film in the portion located in the area increases. As a result, it is considered that the luminance unevenness is improved and high luminance characteristics are exhibited.

[0078] tan δ = (a / 2) / h · · · (III)

In the formula (III), a is the average distance between the light sources of the direct type surface light source, and b is the average distance between the light source of the direct type surface light source and the light reflection diffusion film. Here, the angle δ indicates the angle shown in FIG.

In Formula (III), a is a force that is the average distance between the light sources of the direct type surface light sources. This is obtained as follows.

(1) The long side direction of the surface light source is the L side, and the short side direction is the S side. If the surface light source is square, the L side and S side are determined for convenience. Next, divide one L side into 11 equal parts, and draw straight lines L1 to L10 perpendicular to the L side to the other L side as well (Fig. 8).

(2) If the straight line L1 intersects with two or more fluorescent tubes, the distance from the intersection of the straight line L1 and the first fluorescent tube (the intersection is the center of the fluorescent tube) to the next fluorescent tube Measure (distance between light sources). Similarly, the distance between all the light sources is measured, and the average of them is calculated. Let LA1 be the average distance between light sources obtained by this method. If the straight line L1 intersects only one or less fluorescent tubes, there is no data because there is no distance between light sources. (3) Repeat the same process for straight lines L2 to L10 to find LA2 to LA10.

(4) As for the S side, one S side is divided into 11 equal parts, and straight lines S1 to S 10 are drawn perpendicularly to the S side from the equally divided point to the other S side. Then, the same operation as (2) to (3) is performed to obtain SA1 to SA11 and SA.

(5) The average of LA1 to 10 and SA1 to 10 is defined as the average distance a between the surface light sources. Note that straight lines without data are not subject to average calculation.

[0080] On the other hand, in the above formula (III), b is an average distance between the direct type surface light source and the light diffusion film. This is obtained as follows.

(1) Numbers are assigned to each linear light source unit for convenience, such as linear light source unit 1, linear light source unit 2,..., Linear light source unit n.

(2) Measure the length of the linear light source section of the linear light source section 1 and divide the linear light source section 1 into 11 equal parts in the length direction.

(3) For the linear light source unit 1, measure the shortest distance from the radial center of the linear light source unit to the light source side surface of the light diffusion film at each equally divided point.

(4) Average the shortest distances at each equally divided point, and use the average value as the distance between the light diffusion films of the straight light source part of the straight light source part.

(5) For other linear light source units, the distance between the linear light source unit and one light diffusion film is obtained.

(6) Average the distance between the linear light source unit 1 light diffusion film from the linear light source unit 1 to the linear light source unit n obtained above, and let the average value be b.

[0081] Based on a and b obtained by the above method, the angle δ is derived from the above equation (III).

[0082] It should be noted that δ of a direct type surface light source used in a liquid crystal display or the like currently on the market is 30. Most of them are about 40 °.

[0083] In order to reduce luminance unevenness, in a direction perpendicular to the linear direction of the light source, light should be diffused very strongly, or a certain directivity should be given to the light emission direction. It is preferable to control. In other words, by using the light diffusion phenomenon or by providing a certain directivity in the light emission direction, light incident on the film surface at an angle of δ is observed in the front direction of the observer (normal to the film surface). Light emitted from the light source Large distribution anisotropy is eliminated. As a result, it is presumed that when the luminance unevenness is reduced or the luminance is increased, the effect appears.

[0084] From this, it is preferable that the light diffusion film of the present invention has a performance of emitting light incident in an angle range of 20 ° to 50 ° corresponding to δ in the normal direction of the film surface. Specifically, it is preferable that the minimum value 比 of the specific luminance is 0.0013 or more at the in-plane angle φ having the highest diffusibility or the highest directivity of the emitted light. In other words, the minimum value 比 of the specific luminance is incident within an angle range of 20 ° to 50 ° with respect to the film surface at the in-plane angle φ with the highest diffusibility or the highest directivity of the emitted light. It can be said that it is an index indicating the lower limit of the ability to emit light in the normal direction of the film surface.

[0085] Further, the maximum average luminance Bmax is obtained by measuring the incident light in the angle range of 20 ° to 50 ° with respect to the film surface at the in-plane angle φ having the highest diffusibility or the highest directivity of the emitted light. It can be said that this is an index indicating the average of the performance of emission in the normal direction of the film surface. The maximum average specific luminance Bmax is preferably 0.002 or more.

[0086] On the other hand, since it is considered unnecessary to diffuse light in a direction parallel to the linear direction of the light source, the film of the present invention can be applied to all in-planes (in other words, any φ However, it is estimated that the specific brightness minimum value BI and maximum average specific brightness Bmax are high and are not necessary. Rather, it is thought that it is not necessary to reduce the brightness if the light is not diffused strongly.

Therefore, it is considered that the light diffusing film of the present invention has an optical anisotropy in the film plane. Specifically, the ratio BmaxZBmin between the maximum average specific luminance ratio Bmax and the minimum average luminance ratio Bmin is 1. Desirably 1 or more.

[0087] As a result, the light diffusion film of the present invention efficiently controls the emission direction of the incident light, and the luminance characteristics are improved as compared with the conventional light diffusion film while reducing the luminance unevenness. It is considered a thing.

According to the study by the present inventors, it was impossible to obtain a light diffusion film having such an effect of improving luminance unevenness by any conventional method.

[0089] Although the details of the reason are unknown, it is considered that the conventional light diffusion plate is only intended to enhance the light diffusibility. Therefore, the light diffusion film intended for the present invention On the other hand, it has been unavoidable that improvement in luminance unevenness is insufficient.

[0090] Since commercially available liquid crystal displays often use direct-type surface light sources, these liquid crystal displays were disassembled, the light diffusion plate was taken out, and the specific luminance was measured. In the range of ˜50 °, the minimum specific brightness BI and the maximum average brightness Bmax were less than 0.0013, and BmaxZBmin was almost 1.0.

[0091] In addition, the light diffusion film of the present invention exhibits a high luminance unevenness improvement effect and luminance characteristics with a direct type surface light source having a δ force of 0 ° to 60 °. More preferably, it is 20 ° to 50 °, and further preferably 30 ° to 40 °.

If the δ force is greater than 0 °, the distance between the light sources becomes very large, and even if the specific luminance BI, Bmax, Bmax × ZBmin is set within a suitable range, the luminance unevenness may not be sufficiently eliminated. On the other hand, if the δ force is less than 0 °, the luminance characteristics may be inferior.

[0092] Further, in the light diffusion film of the present invention, the average specific luminance B (+5) satisfies the following formula (IV), or the average specific luminance B (-5) satisfies the following formula (V). Favored ,. More preferably, both the formulas (IV) and (V) are satisfied. Here, the average specific luminance B (+5) is transmitted in the direction of + 5 ° with respect to the normal direction when incident at an angle of 20 ° to 50 ° with respect to the normal direction of the film surface. It is the average specific luminance. The average specific brightness B (-5) is transmitted in the direction of 5 ° with respect to the normal direction when incident at an angle of 20 ° to 50 ° with respect to the normal direction of the film surface direction. It is the average specific luminance. The measurement of B (+5) and B (-5) shall be performed based on the measurement condition of Bmax. In other words, the Bmax value is first measured, and then the receiving angle of the receiver is set to + 5 ° or 5 ° from the normal direction of the film (Figure 9). However, the tilt angle shall be 0 ° (no tilting).

B (+ 5) /Bmax≥0.5 5 (IV)

B (-5) /Bmax≥0.5 · '· (ν).

[0093] When the diffusion film of the present invention satisfies the formula (IV) or (V), the improvement in luminance unevenness can be further enhanced. The details of the reason are currently under intensive analysis, but the present inventors consider as follows. That is, B (+ 5) ZBmax or B (− 5) ZBma X is small, which means that light with strong directivity is incident on incident light with a constant incident angle Θ. It means that a line is emitted. In other words, the light beam is emitted intensely only in a certain angle direction. Here, the light diffusing film has the role of leveling the luminance in the screen, but it is preferable that the light is emitted only in a specific angle direction like a prism. If a light beam is emitted strongly only in a specific angle direction, light is hardly emitted in the other direction, which may contribute little to luminance uniformity in the screen.

[0094] Here, as means for setting the minimum specific brightness BI to 0.0013 or more and the maximum average specific brightness Bmax to 0.002 or more, for example, the surface of the light diffusing film may have a fine uneven shape. For example, the maximum value of the aspect ratio Asmax should be 0.3 or more. Asmax is more preferably 0.5 or more, and particularly preferably 0.7 or more. By setting the aspect ratio Asmax to 0.3 or more, the specific luminance minimum value BI and specific luminance Bmax can be increased. The upper limit of Asmax is not particularly specified, but is preferably 10 or less. Beyond 10, there is a strong tendency for light to be emitted only in a specific direction, and B (+ 5) ZBmax and B (— 5) ZBmax may become small, which is not very good for luminance uniformity in the screen. This is because there are things.

[0095] In addition, the light diffusion film of the present invention has an anisotropy AsmaxZAsmin of 1.1 or more, but when AsmaxZAsmin is 1.1 or more, the value of BmaxZBmin can be increased. AsmaxZAsmin is more preferably 1.3 or more, particularly preferably 1.5 or more.

[0096] The light diffusing film of the present invention preferably has a surface irregularity shape with an anisotropic degree of 1.1 or more formed on the surface of the base film containing the light diffusing element therein (hereinafter referred to as the present invention). Preferred form I). Here, “the surface unevenness shape of 1.1 or more is formed on the surface of the base film containing the light diffusing element therein” means that the base film itself has an anisotropic degree of 1 A form in which one or more surface irregularities are formed, or a form in which a surface irregularity having a degree of anisotropy of 1. or more is formed in the coating layer applied to the base film. In other words, this is a form in which a light diffusing element is contained in one film and a surface uneven shape having an anisotropy of 1.1 or more is formed. In other words, a film that contains a light diffusing element inside and a film that has a surface with an irregularity of 1.1 or more on its surface are overlapped. It is not a form of overlapping different films.

[0097] The optical properties of the light diffusing film are preferably different in the preferred embodiment of the present invention from Form I and the form in which separate films are laminated. The power for which the details of this reason are under intensive study The present inventors consider as follows! / Speak.

That is, when the films are simply overlapped, an air layer exists between the films, and therefore, a critical angle exists when light passes through the air layer in the first film internal force. Light rays having an angle greater than the critical angle cannot be transmitted through the interface between the film and the air layer because of the total reflection phenomenon and are reflected 100%. Therefore, a light beam having a limited emission angle is emitted from the first film with a limited amount of light. In other words, only a limited amount of emitted light is incident on the second film.

[0099] On the other hand, in the preferred U, Form I of the present invention, the above phenomenon does not occur. First, when a surface irregularity shape having an anisotropy of 1.1 or more is formed on the surface of the substrate film itself, the critical angle does not exist and the light transmittance increases. In addition, even when a surface irregularity shape having an anisotropic degree of 1.1 or more is formed on the coating layer applied to the base film, if the refractive index of the base film is smaller than the refractive index of the substance constituting the coating layer After all, there is no critical angle and the light transmittance is high. Even if the refractive index of the base film is larger than the refractive index of the material constituting the coating layer, the critical angle is larger because the refractive index difference is smaller than the refractive index difference between the base film and air. As a result, the light transmittance is increased.

That is, in the preferred form I of the present invention, a light beam having a wide emission angle is incident on the surface uneven shape with a sufficient amount of light, and as a result, more light is anisotropically diffused by the surface uneven shape. Can be considered. Therefore, it is easy for the light diffusion film of the preferred form I of the present invention to have two effects of high luminance characteristics and luminance uniformity.

[0101] In addition, when the light diffusing film of the present invention is mounted on a surface light source, it is preferable that the surface provided with a surface irregularity shape having an anisotropy degree of 1.1 or more is positioned so as to be located in the viewer direction. . By mounting on the surface light source in this positional relationship, the in-plane luminance of the surface light source can be particularly improved, and the in-plane luminance uniformity can also be improved.

[0102] Further, in the surface light source equipped with the light diffusion film of the present invention, the light diffusion film and the light source It is preferred to have a fabric in between.

Here, the fabric is composed of fibers. The fibers constituting the light diffusing fabric include acrylic fibers such as poly (methyl methacrylate) and polyacrylonitrile, polyester fibers such as polyethylene terephthalate and poly (ethylene terephthalate), polyamide fibers such as nylon 6 and nylon 66, polyurethane fibers, polyethylene, Polyolefin fibers such as polypropylene, polyimide fibers, polyacetal fibers, polyether fibers, polystyrene fibers, polycarbonate fibers, polyesteramide fibers, polyphenylene sulfide fibers, polychlorinated bull fibers, polyether ester fibers, polyacetate bull fibers, Includes a variety of synthetic fibers such as polybulutyl fiber, poly (vinylidene fluoride) fiber, ethylene-butyl acetate copolymer fiber, fluorinated resin, and styrene-acrylic copolymer fiber ! / ヽ at best, made from one type of synthetic fibers, even I, then, two or more types of synthetic fibers force be configured even ヽ,. Polyester fibers, poly (sulfur sulfide) fibers, fluoro-resin fibers, etc. can be preferably used for moisture absorption stability and thermal stability, etc., but polyester fibers are also particularly preferably used for versatility and transparency. it can.

[0104] The fiber may be a spun yarn obtained by spinning a staple that has been crimped and cut to a predetermined length, or may be a filament yarn made of a continuous synthetic fiber. The number of single yarns to be formed may be one monofilament yarn or a multifilament yarn composed of two or more single yarns. It is preferable to use a filament yarn in view of high light transmittance.

[0105] The fabric may have any structure such as a woven fabric, a knitted fabric, a dry nonwoven fabric, and a wet nonwoven fabric. However, the fabric has good dimensional stability and small thickness unevenness when handling the fabric, and excellent mechanical strength. From the viewpoint, a woven fabric is particularly preferable. The weaving structure of the woven fabric is not particularly limited, and may be any structure such as plain weave, twill weave and satin weave.

[0106] Although such a fabric is generally lightweight, it itself has light diffusibility, and therefore, when combined with a light diffusing film, it is possible to further improve screen brightness uniformity and brightness. From such a viewpoint, the fabric preferably has a haze of 50% or more.

[0107] Furthermore, by spreading such a fabric and fixing it to the surface light source casing, it is possible to give the fabric a role as a support for an optical film such as a light diffusion film. is there. From this point of view, the fabric is preferably a woven fabric having excellent mechanical strength.

[0108] The color tone of the fabric and the fibers constituting it is preferably an achromatic color with no coloring. Among these, a transparent color or white color that does not absorb light is preferable. By using fabrics of these color tones, it is possible to reduce light loss and contribute to high luminance characteristics.

[0109] Further, while the light source of the surface light source of the liquid crystal display is turned on, the fabric may be exposed to ultraviolet rays contained in the light source, and yellowing and strength deterioration may occur, and the ultraviolet durability is sufficient. It may not be. When the fabric turns yellow, the color tone of the light transmitted through the yellowed fabric changes, and the color tone of the display screen may also change. Therefore, it is preferable that the fabric is subjected to UV resistance treatment. The term “ultraviolet resistant treatment” refers to reducing the occurrence of yellowing or deterioration of strength even when a cloth is exposed to ultraviolet rays by applying an ultraviolet absorbent or an antioxidant (hereinafter referred to as an ultraviolet absorbent) to the cloth. The application method is a method of spraying an ultraviolet absorber or the like, a pad curing method in which it is dried after being immersed in a bath containing an ultraviolet absorber, a method of applying to the fiber surface, such as a coating method or a printing method. May be exhausted inside the fiber! /.

Next, an example of the method for producing a light diffusion film of the present invention will be described, but the present invention is not limited to this example.

[0111] In a composite film-forming apparatus having a main extruder and a sub-extruder, a thermoplastic resin B chip (melting point TB) constituting the main layer of a base film that has been sufficiently vacuum-dried as necessary; A mixture of light diffusing elements is fed to a heated main extruder. The added light of the light diffusing element may be obtained by using a master chip prepared by uniformly melting and kneading in advance, or may be directly kneaded and supplied to an extruder. Further, in order to laminate a thermoplastic resin layer having a melting point TA, chips of thermoplastic resin A which has been sufficiently vacuum-dried as necessary are supplied to a heated sub-extruder.

[0112] In this way, the raw materials are supplied to each extruder, and laminated (AZB or AZBZA) so that the polymer of the sub-extruder comes to one side of the polymer of the main extruder in the T-die composite die. Co-extrusion molding is performed to obtain a melt-laminated sheet.

[0113] The molten laminated sheet is closely cooled and fixed on a cooled drum to produce an unstretched laminated film. At this time, in order to obtain a uniform film, static electricity is applied to close the drum. It is desirable to put it on. After that, a base material finem is obtained through a stretching process, a heat treatment process, and the like as necessary.

[0114] The stretching method is not particularly limited, but the sequential biaxial stretching method in which the stretching in the longitudinal direction and the stretching in the width direction are separated, or the simultaneous biaxial stretching in which the stretching in the longitudinal direction and the stretching in the width direction are performed simultaneously. There is a law.

[0115] As a method of sequential biaxial stretching, for example, the unstretched laminated film is guided to a heated roll group, stretched in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film), and then cooled roll group Cool with.

[0116] Subsequently, both ends of the film stretched in the longitudinal direction are guided to a heated tent while being held by clips, and can be stretched in a direction perpendicular to the longitudinal direction (lateral direction or width direction).

[0117] As a method of simultaneous biaxial stretching, for example, the both ends of the above-mentioned unstretched laminated film are guided to a heated tenter while being gripped with a clip, and stretched in the width direction and at the same time the clip traveling speed is accelerated. There is a method in which stretching in the longitudinal direction is performed simultaneously. This simultaneous biaxial stretching method has the advantage that the film surface does not come into contact with the heated roll, so that the film surface is not damaged as an optical defect.

[0118] In order to impart planar stability and dimensional stability to the biaxially stretched laminated film thus obtained, and to eliminate voids (voids) generated between the resin B and the light diffusing element as necessary. Next, heat treatment (heat setting) is performed in the tenter. Here, when the void is eliminated, it is desirable that the heat treatment temperature TA is a temperature satisfying the above-mentioned equation (iii). By adjusting the heat treatment temperature and the heat treatment time, it is possible to completely eliminate the voids or to leave some of the voids to act as light diffusing elements.

[0119] After the heat treatment, the substrate film is obtained by uniformly cooling and then cooling to near room temperature.

[0120] Next, a photocurable resin is coated on the base film using a known coating means. After coating, press a mold with an uneven surface with an aspect ratio of 1.1 or more and irradiate it with light. The light irradiation direction is not particularly limited. The light diffusing film of the present invention is obtained by releasing the mold after irradiating light and curing the photocurable resin. Can do.

Example

[0121] An evaluation method of the light diffusion film obtained in each example, comparative example, and reference example will be described.

[0122] [Characteristic measurement method and evaluation method]

(1) Maximum aspect ratio of surface irregularities Asmax, minimum value Asmin, anisotropy Asmax / Asmin

First, using a microtome, the light diffusion film is cut perpendicularly to the film surface direction without crushing it in the thickness direction. Next, the cut section is enlarged and observed with a scanning electron microscope such as S-2100A (Hitachi, Ltd.) at an appropriate magnification (500 to 10000 times as a guide), and in accordance with the method described above. Calculate the maximum value Asmax, the minimum value Asmin, and the degree of anisotropy AsmaxZAsmin of the aspect ratio of the surface irregularity shape. Note that the N number of samples measured in each of the examples, comparative examples, and reference examples is 1.

[0123] (2) Light transmittance, haze

Light transmittance and haze were measured using a direct reading haze computer HGM-2DP (for C light source) (manufactured by Suga Test Instruments Co., Ltd.). The total light transmittance and haze are obtained for both surfaces of the light diffusion film, and the values on the surface with higher light transmittance are the light transmittance and haze of the light diffusion film. The N number of samples measured for each example, comparative example, and reference example is 1.

[0124] (3) Area occupancy and average particle size of light diffusing element in cross section perpendicular to film surface First, a microtome is used to cut the light diffusing film perpendicularly to the film surface without crushing it in the thickness direction. . Next, the cut section was enlarged and observed with a scanning electron microscope such as S-2100A (Hitachi, Ltd.) at an appropriate magnification (500 to as a guide: LOOOO times). Calculate the area occupancy ratio of the light diffusing element in the cross section perpendicular to the surface. The N number of the sample measured for each example, comparative example, and reference example is 1.

[0125] The total thickness of the film is measured from the magnified image, and this is taken. Next, in the film cross section, the range of thickness direction LX film surface direction L is arbitrarily defined, and the range The total area of the light diffusing elements contained therein is calculated. The area occupancy of the light diffusing element is calculated by dividing the total area of the light diffusing element by the measurement range (ie, L ² ). The same operation is performed at 10 locations with different measurement ranges, and the average value is the area occupancy ratio of the light diffusing element in the film cross section.

[0126] The area of each light diffusing element can be obtained by tracing the shape of each light diffusing element on a transparent film or tracing paper from the cross-sectional image obtained above, and using this image analysis software. (For example, Toyobo Co., Ltd. Image Analyzer V10LAB or NanoHunter NS2K-Lt manufactured by Nanosystem Co., Ltd., which is the software successor), the area and sphere equivalent diameter of each light diffusing element are obtained. Here, those with a sphere equivalent diameter of 0 or less are not included in the total area of the light diffusing element.

[0127] The simple average of the sphere equivalent diameters of the respective light diffusing elements obtained above is defined as the average particle diameter of the light diffusing elements. Here, when calculating the average particle size of the light diffusing element, those with a sphere equivalent diameter of 0.1 μm or less are included in the average calculation.

[0128] If the film is formed by laminating two or more layers or a coating layer is formed, a light diffusing element is contained, and only the layer is selected and observed.

[0129] (4) Number density of light diffusing element in cross section perpendicular to film surface

First, using a microtome, the light diffusion film is cut perpendicular to the film surface without being crushed in the thickness direction. Next, the cut section was magnified and observed with a scanning electron microscope such as S-2100A (Hitachi Ltd.) at an appropriate magnification (500 to L0000 as a guide). Calculate the number density of light diffusing elements in the cross section perpendicular to the surface. The N number of samples measured for each example, comparative example, and reference example is 1.

[0130] The entire thickness of the film is measured from the magnified image, and this is taken. Next, in the film cross section, the range in the thickness direction LX film surface direction L is arbitrarily defined, and the number of light diffusing elements included in the range is calculated. Here, light diffusing elements having a sphere equivalent diameter of 0.1 μm or less are not included in the number of light diffusing elements. The number density of the light diffusing elements is calculated by dividing the number of the light diffusing elements by the measurement range (that is, L ² ). The same operation was performed at 10 locations with different measurement ranges, and the average value was calculated for the light diffusing element in the film cross section. Number density. Here, the unit of number density is [piece Zmm ² ].

[0131] In the case where the film is formed by laminating two or more layers or a coating layer is formed, a light diffusing element is contained! Only the layer is selected and observed.

[0132] (5) Front light source brightness and uniformity

A direct-type surface light source with 12 39W-long 4W linear fluorescent tubes installed. Each fluorescent tube is installed in parallel with the length direction of the fluorescent tube so that the distance between the fluorescent tubes (the distance between the centers of the fluorescent tubes) is 26 mm. The cross-sectional thickness (diameter) of the fluorescent tube is 2 mm. The direct type surface light source has a light-reflective film (# 188E60L, manufactured by Toray Industries, Inc.) with a rectangular shape (long side is 40cm, short side is 30cm). The distance between the light source center and the bottom of the reflector is 10mm. It is installed under the fluorescent tube.

[0133] Using this direct type surface light source, the shapes in Examples 1 1 to 1 17, 3— 1 to 3-4 and Comparative Examples 1 — 1 to 1-3, 3— 1 were rectangular (the long side was 40 cm) The light diffusing film with a short side of 30 cm was installed so that the distance between the center of the fluorescent tube and the surface of the light diffusing film in the observer direction was 10 mm. In this case, δ of the surface light source is 52 °.

[0134] In Examples 2-1 to 2-10, Comparative Examples 2-1 to 2-4, and Reference Examples 2-1 to 2-3, the shape is rectangular (the long side is 40 cm and the short side is 30 cm). The light diffusing film was installed so that the distance between the center of the fluorescent tube and the surface of the light diffusing film in the observer direction was 18.6 mm. In this case, δ of the surface light source is 35 °.

[0135] In any case, the light diffusion film was installed so that the direction in which the aspect ratio of the light diffusing film was maximum and the longitudinal direction of the fluorescent lamp were orthogonal to each other.

[0136] All fluorescent tubes were turned on, and luminance was measured according to the following method after 1 hour.

[0137] Luminance measurement was performed using EyeScale-3 of Eye 'system. The attached CCD camera was placed at a point lm from the center of the surface light source, facing the surface light source surface. Here, the center of the surface light source refers to the center of gravity of the surface of the light diffusion film.

The front luminance of the surface light source was an average luminance in the range of 10 cm × 10 cm at the center of the surface light source. In this evaluation method, it is satisfactory if the front luminance of the surface light source is 5500 cdZmm ² or more.

[0139] In addition, the uniformity is the maximum brightness in the range of 10cm x 10cm in the center of the surface light source. It was obtained by dividing. The uniformity is preferably 1.2 or less, more preferably 1

1 or less, more preferably 1.05 or less. If the degree of uniformity is large, it is difficult to see due to uneven brightness

This is because V may be a screen.

[0140] Each example, comparative example,

The N number of samples measured in this way is 1.

[0141] (6) Minimum value of specific brightness BI, maximum average specific brightness Bmax, minimum average specific brightness Bmin

Specific brightness is measured by Murakami Color Research Laboratory Co., Ltd.

The measurement conditions and method are shown below for measurement using P-200. In each example, comparative example, and reference example, the N number of the sample measured was 1.

(i) Measurement is performed by transmission measurement. The tilt angle is 0 ° (no tilt), the beam aperture scale value VS1 is set to 3.0, and the light receiving stop scale value VS3 is set to 2.0. Do not use polarizing filters or bandpass filters (such as color filters).

(ii) After making the above conditions, measure the light intensity with a light incident angle Θ of 0 ° and a light receiving angle of 0 °, without setting anything on the sample stage. At this time, adjust the HIGH VOLT ADJ. Knob so that the value displayed on the panel meter (output signal) is 90 to L10. At this time, the value of HIG H VOLT ADJ. Is HVA, and the value of the panel meter (output signal) is KAA. Even if the HIGH VOLT ADJ. Knob is adjusted, if the panel meter (output signal) numeric display power S 110 is exceeded, a neutral density filter is used. Two or more neutral density filters may be used. When using a neutral density filter, measure the attenuation factor GA in advance. The method for measuring the attenuation factor GA will be described later. The neutral density filter is a GP-200 type neutral density filter manufactured by Murakami Color Research Laboratory.

Therefore, the actual luminous intensity KA is

KA = (KAA / GA)

It becomes.

(iii) Both surfaces of the film to be measured are defined as a-side and b-side for convenience. Place the film to be measured on the sample stage so that the light incident surface is a-plane and there is no deflection. Measure the luminous intensity KB (Θ = 20 °) with a light incident angle Θ (normal to the film surface) of 20 ° and an acceptance angle of 0 ° (normal to the film surface).

In measurement, the HIGH VOLT ADJ. Value of the main body is HVA. Also panel If the value displayed on the meter (output signal) exceeds 110, use a neutral density filter. Two or more neutral density filters may be used. If a neutral density filter is used, measure the neutral density GB in advance. Dimming rate GB measurement method conforms to dimming rate GA measurement method. If the value displayed on the panel meter (output signal) does not exceed 110, the value shall be KBB.

Therefore, the actual luminous intensity KB is

• KB = (KBB / GB)

It becomes.

(iv) Based on the method described above, the minimum specific brightness value BI, maximum average specific brightness Bmax, and minimum average specific brightness Bmin are calculated.

[0142] (Measurement method of light attenuation GA)

The straight light transmittance was measured using a direct reading haze computer HGM-2DP (for C light source) (manufactured by Suga Test Instruments Co., Ltd.), and the measured value was defined as GA. When two or more neutral density filters are used, measure with the neutral density filters stacked. The straight light transmittance obtained as a result of the measurement is defined as the light attenuation rate. Note that the light attenuation rate when the neutral density filter is not used is 1.00.

[0143] (7) Difference between in-plane rotation angle indicating maximum average specific luminance Bmax and in-plane rotation angle indicating minimum average specific luminance Bmin Δ φ

When the in-plane rotation angle indicating the maximum average specific brightness Bmax obtained in (6) is φ max and the in-plane rotation angle indicating the minimum average specific brightness Bmin is φ πήη, the difference Δφ is obtained from the following equation: It was.

Δ = I max—φ mm |.

[Examples, comparative examples, reference examples]

[Example 1 1]

Pellets mixed with 99.93% by volume of polycarbonate as the main resin component of the light diffusing film and 0.07% by volume of anatase titanium oxide with an average particle diameter (diameter) of 1 μm as the light diffusing element. Supplied. Next, melt extrusion was performed, and a substrate film was prepared by cooling on a mirror-casting drum by an electrostatic application method.

[0145] An uneven shape was formed on one surface of this base film by the following method. Note that here The used mold is a nickel mold having a curved surface represented by the following formula.

• z = 5 X sin (0.0691 X x) +5 X sin (0.0628 X y)

Here, z indicates the mold thickness direction, and x and y indicate the mold surface direction. The unit is / zm.

[0146] First, the obtained base film and mold were heated to 180 ° C and held for 2 minutes. Next, the surface of the base film provided with the mold shape was pressed at a pressure of 10 MPa and held for 3 minutes. Thereafter, while maintaining the pressure, it was cooled to 130 ° C. and the pressure was released. The film with surface irregularities formed from the mold was released to obtain a light diffusion film.

[0147] Maximum value Asmax, minimum value Asmin, anisotropy of the aspect ratio of the surface shape in the obtained light diffusing film, number density of light diffusing elements in the film cross section, area occupancy, transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are values measured by making light rays incident from the surface on which the surface irregularity shape is formed.

[0148] This light diffusion film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source was 1.15, and the average front luminance was 5800 cdZm ² , indicating good performance.

[Example 1 2]

99.2% by volume of polyethylene terephthalate (hereinafter referred to as “SPG-PET”) in which 30 moles of spiroglycol as the main resin component of the light diffusing film is copolymerized in the extruder with 30 mol / ml of diol units. Pellets mixed with 0.8% by volume of polymethylpentene were supplied as elements. Next, melt extrusion was performed, and a substrate film was prepared by cooling on a mirror-casting drum by an electrostatic application method.

[0150] An uneven shape was formed on one surface of this base film in the same manner as in Example 11.

[0151] The maximum value Asmax, the minimum value Asmin, the anisotropy, the number density of the light diffusing element in the cross section of the film, the area occupancy, the transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 4 m.

[0152] In this light diffusion film, the surface on which the surface irregularities are formed is in the observer direction (surface irregularities The surface on which the shape is not formed is laid on the light source side). Uniformity of the surface light source 1. 10 average front luminance 5700CdZm ^2, showed a good performance.

[Example 1 3]

Pellets mixed with 98.8% by volume of SPG-PET as the main resin component constituting the light diffusion film and 1.2% by volume of polymethylpentene as the light diffusion element were supplied to the extruder. Next, melt extrusion was performed, and a substrate film was prepared by cooling on a mirror-casting drum by an electrostatic application method.

[0154] An uneven shape was formed on one surface of this base film in the same manner as in Example 11.

[0155] The maximum value Asmax, the minimum value Asmin, the anisotropy, the number density of the light diffusing element in the film cross section, the area occupancy, the transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size was 4.5 m.

[0156] This light diffusion film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source was 1.08, and the average front luminance was 5600 cdZm ² , indicating good performance.

[Example 1 4]

In the main extruder, the polyester resin obtained by copolymerizing 10 mol% of isophthalic acid component with respect to the acid unit and 10 mol% of cyclohexanedimethanol component with respect to the glycol unit as the main resin component constituting the light diffusion film. Pellets containing 97% by volume of fat (melting point TB: 225 ° C) (hereinafter referred to as “IC-PET”) and 3% by volume of polymethylpentene as a light diffusing element were supplied. Further, a sub-extruder was used separately from the main extruder, and PET (melting point TA: 265 ° C) pellets were supplied to the sub-extruder. Next, on both sides of the component layer supplied to the main extruder, the component layer supplied to the sub-extruder on the surface layer is the thickness ratio. Sub-extruder component layer: Main extruder component layer: Sub-extruder component layer = 1: Melting three-layer lamination coextrusion was carried out to 8: 1. The extruded resin was cooled on a mirror cast drum by the electrostatic application method to produce a three-layer laminated sheet. This laminated sheet was stretched by a factor of 3.2 in the longitudinal direction at a temperature of 87 ° C. The film was stretched 3.4 times in the width direction at 110 ° C through a 95 ° C preheating zone. Furthermore, a substrate film with a thickness of 280 μm was obtained by heat treatment at a heat treatment temperature TH of 235 ° C for 30 seconds.

[0158] An uneven shape was formed on one surface of this base film by the following method. The mold used here is a nickel mold having a curved surface represented by the following formula.

• z = 5 X sin (0.0691 X x) +5 X sin (0.0628 X y)

[0159] First, UV curing resin (Dainippon Ink & Chemicals Co., Ltd .: Unidic 15-829) and initiator (Ciba's Specialty Chemicals Co., Ltd .: Irgacure 907) were UV cured resin: initiator = 99: 1 was mixed at a mass ratio, mixed for 30 minutes with a mixer and stirred to obtain a coating solution. Next, the coating solution was applied to the surface of the mold provided with the surface shape so that the thickness of the coating film was 50 / zm. After the application, a base film was placed on the upper surface of the coating film and adhered. Thereafter, a total of 500 mjZW ultraviolet rays were irradiated from the base film surface side to the mold surface direction. After UV irradiation, it was heat-fixed at 40 ° C for 30 minutes. Thereafter, the mold was released to obtain a light diffusing film in which an ultraviolet curable resin layer having surface irregularities formed on one surface of the base film was laminated.

[0160] The maximum value Asmax, the minimum value Asmin, the anisotropy, the number density of the light diffusing element in the cross section of the film, the area occupancy, the transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 4.8 μm.

[0161] This light diffusing film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The surface light source had a uniformity of 1.06 and an average front luminance of 5400 cdZm ² , indicating good performance.

[0162] [Example 1 5]

The main extruder, as the main榭脂component constituting the light diffusing film IC- PET (melting point TB: 225 ° C) to 94 volume ^_0/0, pellets with a polymethylpentene as the light diffuser mixing 6 vol% Supplied. In addition to the main extruder, a sub-extruder is used. Point TA: 265 ° C.) Pellets were fed. Next, the component layers supplied to the sub-extruder on both side layers of the component layer supplied to the main extruder in the thickness ratio are sub-extruder component layer: main extruder component layer: sub-extruder component layer = 1: Melting three-layer lamination coextrusion was carried out to 8: 1. The extruded resin was cooled on a mirror cast drum by the electrostatic application method to produce a three-layer laminated sheet. This laminated sheet was stretched 3.2 times in the longitudinal direction at a temperature of 87 ° C, and then stretched 3.4 times in the width direction at 110 ° C through a preheating zone of 95 ° C with a tenter. Furthermore, the substrate film having a thickness of 180 μm was obtained by heat treatment at a heat treatment temperature TH of 235 ° C. for 30 seconds.

[0163] An uneven shape was formed on one surface of this base film in the same manner as in Example 14

[0164] The maximum value Asmax, the minimum value Asmin, the anisotropy, the number density of the light diffusing element in the cross section of the film, the area occupancy, the transmittance, the haze, The total thickness was as shown in Table 1. The transmittance and haze are values measured by making light rays incident from the surface provided with the uneven surface shape. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 5 / zm.

[0165] This light diffusing film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface not having the surface unevenness was the light source side). Uniformity of the surface light source is 1.0 5, the average front luminance 5400CdZm ^2, showed a good performance.

[Example 1 6]

A base film having a thickness of 120 μm was obtained in the same manner as in Example 1-5 except that the extrusion amounts of the main extruder and the sub-extruder were changed. The thickness ratio is: sub-extruder component layer: main extruder component layer: sub-extruder component layer = 1: 8: 1.

[0167] An uneven shape was formed on one surface of this base film in the same manner as in Example 14. However, the mold used was a nickel mold with a curved surface represented by the following formula. • Z = 5 X sin (0.104 X x) +5 X sin (0.0942 X y)

[0168] Maximum value Asmax, minimum value Asmin, anisotropy, number density of light diffusing elements in the film cross section, area occupancy, transmittance in the obtained light diffusion film Table 1 shows the haze and the total thickness. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 5 / zm.

[0169] This light diffusion film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source is 1

. 04, the average front luminance showed good performance and 5500CdZm ^2.

[Example 1 7]

[0171] An uneven shape was formed on one surface of this base film in the same manner as in Example 14.

. However, the mold used was a nickel mold with a curved surface represented by the following formula.

• z = 5 X sin (0.173 X x) +5 X sin (0.157 X y)

[0172] The maximum value Asmax, the minimum value Asmin, the anisotropy of the aspect ratio of the surface shape in the obtained light diffusion film, the number density of the light diffusion element, the area occupancy, the transmittance, the haze, The total thickness was as shown in Table 1. The transmittance and haze are values measured by making light rays incident from the surface on which the surface irregularity shape is formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 5 / zm.

[0173] This light diffusion film was laid so that the surface on which the surface irregularities were formed was in the observer direction (the surface on which the surface irregularities were not formed was on the light source side). The uniformity of this surface light source was 1.03 and the average front luminance was 5500 cdZm ² , indicating good performance.

[Example 1 8]

[0175] An uneven shape was formed on one surface of this base film in the same manner as in Example 14. However, the mold used was a nickel mold with a curved surface represented by the following formula. • z = 5 X sin (0.346 X x) +5 X sin (0.314 X y)

[0176] Maximum aspect ratio of surface shape in the obtained light diffusing film Asmax, minimum value Asmin, anisotropy, number density of light diffusing element in the film cross section, area occupancy, transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are values measured by making light rays incident from the surface on which the surface irregularity shape is formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 5 / zm.

[0177] This light diffusion film was laid so that the surface on which the surface irregularities were formed was in the observer direction (the surface on which the surface irregularities were not formed was on the light source side). The uniformity of this surface light source was 1.03 and the average front luminance was 5500 cdZm ² , indicating good performance.

[Example 1 9]

[0179] An uneven shape was formed on one surface of this base film in the same manner as in Example 14. However, the mold used was a nickel mold with a curved surface represented by the following formula.

• z = 5 X sin (0.518 X x) +5 X sin (0.471 X y)

[0180] Maximum aspect ratio of surface irregularities in the obtained light diffusion film Asmax, minimum value Asmin, anisotropy, number density of light diffusing elements in the film cross section, area occupancy, transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 5 / zm.

[0181] A powerful light diffusion film was laid so that the surface on which the surface irregularities were formed was in the observer direction (the surface on which the surface irregularities were not formed was on the light source side). The surface light source had a uniformity of 1.03 and an average front luminance of 5600 cdZm ² , indicating good performance.

[0182] [Example 1 10]

Except for changing the extrusion amounts of the main extruder and sub-extruder, the thickness was changed in the same manner as in Example 1-5. A 120 μm substrate film was obtained. The thickness ratio is: sub-extruder component layer: main extruder component layer: sub-extruder component layer = 1: 8: 1.

[0183] An uneven shape was formed on one surface of this base film in the same manner as in Example 14. However, the mold used was a nickel mold with a curved surface represented by the following formula.

• z = 5 X sin (0.0942 X x) +5 X sin (0.0628 X y)

[0184] The maximum value Asmax, the minimum value Asmin, the anisotropy, the number density of the light diffusing element in the film cross section, the area occupancy, the transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 5 / zm.

[0185] This light diffusion film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source was 1.02, and the average front luminance was 5500 cdZm ² , indicating good performance.

[Example 1 11]

[0187] An uneven shape was formed on one surface of this base film in the same manner as in Example 14. However, the mold used was a nickel mold with a curved surface represented by the following formula.

• z = 5 X sin (0.0942 X x) +5 X sin (0.0471 X y)

[0188] Maximum aspect ratio of surface shape in the obtained light diffusing film Asmax, minimum value Asmin, anisotropy, number density of light diffusing element in the film cross section, area occupancy, transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are values measured by making light rays incident from the surface on which the surface irregularity shape is formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 5 / zm.

[0189] In this light diffusion film, the surface on which the surface irregularities are formed is in the observer direction (surface irregularities The surface on which the shape is not formed is laid on the light source side). The uniformity of this surface light source was 1.01, and the average front luminance was 5500 cdZm ² , indicating good performance.

[0190] [Example 1 12]

The main extruder, as the main榭脂component constituting the light diffusing film IC- PET (melting point TB: 225 ° C) to 96 volume ^_0/0, acrylic having an average particle size of 4 mu m as a light diffusing element - styrene rack Pellets mixed with 4% by volume of bridge particles were supplied. In addition to the main extruder, a sub-extruder was used, and PET (melting point TA: 265 ° C) pellets were supplied to this sub-extruder. Next, the component layer supplied to the sub-extruder on the surface layer on both sides of the component layer supplied to the main extruder in the thickness ratio. Sub-extruder component layer: main extruder component layer: sub-extruder component layer = 1: 8 : Three-layer melt co-extrusion was performed so as to be 1. The extruded resin was cooled on a mirror cast drum by an electrostatic application method to prepare a three-layer laminated sheet. The laminated sheet was stretched 3.2 times in the longitudinal direction at a temperature of 87 ° C, and then stretched 3.4 times in the width direction at 110 ° C through a preheating zone of 95 ° C with a tenter. Further, a base film having a thickness of 120 μm was obtained by heat treatment at a heat treatment temperature TH of 235 ° C. for 30 seconds.

[0191] An uneven shape was formed on one surface of this base film in the same manner as in Example 14. However, the mold used was a nickel mold with a curved surface represented by the following formula. • z = 5 X sin (0.0942 X x) +5 X sin (0.0314 X y)

[0192] The maximum value Asmax, the minimum value Asmin, the anisotropy, the number density of the light diffusing element in the film cross section, the area occupancy, the transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed.

[0193] This light diffusing film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source was 1.00 and the average front luminance was 5500 cdZm ² , indicating good performance.

[Example 1 13]

Example 1 A substrate film having a thickness of 120 m was obtained in the same manner as in 12.

[0195] An uneven shape was formed on one surface of this base film in the same manner as in Example 14 . However, the mold used was a nickel mold with a curved surface represented by the following formula.

• z = 5 X sin (0.157 X x) +5 X sin (0.0628 X y)

[0196] Maximum value Asmax, minimum value Asmin, anisotropy of the aspect ratio of the surface irregularity shape in the obtained light diffusion film, number density of light diffusion elements in the film cross section, area occupancy, transmittance

Table 1 shows the haze and the total thickness. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed.

[0197] The light diffusing film was laid so that the surface on which the surface irregularities were formed was in the observer direction (the surface on which the surface irregularities were not formed was on the light source side). The uniformity of this surface light source is 1

01, the average front brightness was 5600cdZm ² and showed good performance.

[0198] [Example 1 14]

[0199] An uneven shape was formed on one surface of this base film in the same manner as in Example 14

• z = 5 X sin (0.314 X x) +5 X sin (0.126 X y)

[0200] Maximum aspect ratio of surface irregularities in the obtained light diffusing film Asmax, minimum value Asmin, anisotropy, number density of light diffusing elements in the film cross section, area occupancy, transmittance

[0201] This light diffusing film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source is 1

The average front brightness was 5600 cdZm ² , indicating good performance.

[0202] [Example 1 15]

[0203] An uneven shape was formed on one surface of this base film in the same manner as in Example 14

• z = 5 X sin (0.471 X x) +5 X sin (0.236 X y) Here, z indicates the mold thickness direction, and x and y indicate the mold surface direction. The unit is / zm.

[0204] Maximum value Asmax, minimum value Asmin, anisotropy, number density of light diffusing elements in cross section of film, area occupancy rate, transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed.

[0205] This light diffusion film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source was 1.00 and the average front luminance was 5600 cdZm ² , indicating good performance.

[Example 1 16]

The main extruder, mainly as榭脂component IC- PET (melting point TB: 225 ° C) constituting the light diffusing film 96 volume ^_0/0, pellets of a mixture of polymethylpentene 4 vol% light diffuser Supplied. A sub-extruder was used separately from the main extruder, and PET (melting point TA: 265 ° C) pellets were supplied to this sub-extruder. Next, the thickness of the component layer supplied to the sub-extruder on both side layers of the component layer supplied to the main extruder is as follows: Component layer of the sub-extruder: Component layer of the main extruder: Component layer of the sub-extruder = 1 The melted three-layer lamination coextrusion was performed so that the ratio was 8: 1. A three-layer laminate sheet was prepared by cooling on a mirror-casting drum by applying electrostatic force. This laminated sheet was stretched 3.2 times in the longitudinal direction at a temperature of 87 ° C, and subsequently stretched 3.4 times in the width direction at 110 ° C through a preheating zone of 95 ° C. Furthermore, the substrate film having a thickness of 120 μm was obtained by heat treatment at a heat treatment temperature TH of 235 ° C. for 30 seconds.

[0207] An uneven shape was formed on one surface of this base film in the same manner as in Example 14. However, the mold used was a nickel mold with a curved surface represented by the following formula. Z = 5 X sin (0.314 Xx)

[0208] Maximum aspect ratio of the surface shape in the obtained light diffusion film Asmax, minimum value

Asmin, anisotropy, number density, area occupancy, transmittance, haze and total thickness of the light diffusing element in the film cross section were as shown in Table 1. The transmittance and haze are values measured by making light rays incident from the surface on which the surface irregularity shape is formed.

[0209] In this light diffusion film, the surface on which the surface unevenness is formed is in the direction of the observer (surface unevenness The surface on which the shape is not formed is laid on the light source side). The uniformity of this surface light source was 1.01, and the average front luminance was 5700 cdZm ² , indicating good performance.

[0210] [Example 1 17]

The following fabrics were created and spread out, and double-sided adhesive tape (Nitto Denko Corporation N)

0. 500). On the fabric (the surface opposite to the side facing the fluorescent lamp), the surface of the light diffusing film obtained in Example 116, on which the surface unevenness is formed, is in the observer direction (the surface unevenness is The layers were formed so that the surface not formed was on the fabric side. Hitoshi Hitoshido of the surface light source is 1.00, the average front luminance showed good performance and 5900cdZm ^2. The support of the light diffusion film by the fabric was good with almost no sag of the fabric.

[0211] (Composition of fabric)

1. Yarn used: warp yarn (84dtex—72 filament, 100% polyester filament yarn), horizontal yarn (84dtex—72 filament, 100% polyester filament yarn)

2. Weaving organization: Plain weave

3. Weaving density: Vertical weaving density 110 Z-inch, horizontal weaving density 90 Z-inch.

[0212] The total light transmittance and haze of the fabric made with the above configuration were 51% and 90%, respectively.

[0213] [Comparative Example 1 1]

The main extruder, as the main榭脂component constituting the light diffusing film IC- PET (melting point TB: 225 ° C) to 92 volume ^_0/0, pellets with a polymethylpentene as the light diffuser mixing 8 vol% Supplied. A sub-extruder was used separately from the main extruder, and PET (melting point TA: 265 ° C) pellets were supplied to this sub-extruder. Next, the component layer supplied to the sub-extruder on both sides of the component layer supplied to the main extruder in the thickness ratio is the thickness ratio. Sub-extruder component layer: Main extruder component layer: Sub-extruder component layer = Melting three-layer lamination coextrusion was performed so that 1: 8: 1. A three-layer laminate sheet was prepared by cooling on a mirror-casting drum by applying electrostatic force. This laminated sheet was stretched 3.2 times in the longitudinal direction at a temperature of 87 ° C, and subsequently stretched 3.4 times in the width direction at 110 ° C through a preheating zone of 95 ° C. Further, a heat treatment temperature TH was set at 235 ° C. for 30 seconds to obtain a base film having a thickness of 150 μm.

[0214] The obtained base film was directly used as a light diffusion film. This light diffusion film Is flat on both sides, the number density, area occupancy, and transmittance of the light diffusing element in the film cross section

Table 1 shows the haze and the total thickness. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 5.2 m.

[0215] The uniformity of the surface light source on which this light diffusing film was laid was 1.42, and the average front luminance was 4800 cd / m (?).

[0216] [Comparative Example 1 2]

PET pellets were supplied to the extruder as the main resin component of the film. Next, melt extrusion was performed, and a single-layer sheet was prepared by cooling on a mirror-casting drum by an electrostatic application method. This single-layer sheet was stretched 3.2 times in the longitudinal direction at a temperature of 87 ° C, and then stretched 3.4 times in the width direction at 110 ° C through a 95 ° C preheating zone with a tenter. Furthermore, a base material Finolem with a thickness of 150 μm was obtained by heat treatment at a heat treatment temperature TH of 235 ° C for 30 seconds.

[0217] An uneven shape was formed on one surface of the obtained base film in the same manner as in Example 16.

[0218] As a result, the maximum value Asm ax, the minimum value Asmin, the anisotropy, the transmittance, the haze, and the total thickness of the aspect ratio of the surface shape in the obtained light diffusion film were as shown in Table 1. The transmittance and haze are numerical values measured by making light rays incident from the surface on which the surface irregularities are formed.

[0219] This light diffusing film was laid so that the surface on which the surface irregularities were formed was in the observer direction (the surface on which the surface irregularities were not formed was on the light source side). The uniformity of this surface light source is 1

68. The average front brightness was 5000 cdZm ² .

[0220] [Comparative Example 1 3]

[0221] An uneven shape was formed on one surface of this base film in the same manner as in Example 14

• z = 5 X sin (0.0942 X x) +5 X sin (0.0942 X y) Here, z indicates the mold thickness direction, and x and y indicate the mold surface direction. The unit is / zm.

[0222] The maximum value Asmax, the minimum value Asmin, the anisotropy, the number density of the light diffusing element in the cross section of the film, the area occupancy, the transmittance, haze, The total thickness was as shown in Table 1. The transmittance and haze are numerical values measured by making light incident from the surface on which the surface irregularities are formed. As a result of cross-sectional observation, polymethylpentene was dispersed in a spherical shape, and the average particle size (diameter) was 5 / zm.

[0223] This light diffusing film was laid such that the surface on which the surface irregularities were formed was in the observer direction (the surface on which the surface irregularities were not formed was on the light source side). The uniformity of this surface light source was 1.22, and the average front luminance was 5100 cdZm ² .

[0224] [Example 2-1]

In the main extruder, the polyester resin obtained by copolymerizing 10 mol% of the isophthalic acid component with respect to the acid unit and 10 mol% of the cyclohexanedimethanol component with respect to the glycol unit as the main resin component constituting the light diffusion film. fat (mp 225 ° C) (hereinafter, "IC- PET" say.) 98 volume ^_0/0, polymethylpentene supplying pellets were mixed 2 vol% as light diffuser, also, the main extrusion A sub-extruder was used separately from the machine, and PET (melting point 265 ° C) pellets were supplied to this sub-extruder. Next, the thickness of the component layer supplied to the sub-extruder on both side layers of the component layer supplied to the main extruder is as follows: Component ratio of sub-extruder: Component ratio of main extruder: Component ratio of sub-extruder = 1: Melting three-layer lamination coextrusion was carried out to 8: 1. The extruded resin was cooled on a mirror cast drum by an electrostatic application method to produce a three-layer laminated sheet. This laminated sheet was stretched 3.3 times in the longitudinal direction at a temperature of 88 ° C, and then stretched 3.5 times in the width direction at 115 ° C through a preheating zone of 95 ° C with a tenter. Furthermore, the substrate film having a thickness of 140 μm was obtained by heat treatment at 240 ° C. for 30 seconds.

[0225] An uneven shape was formed on one surface of this base film by the following method. The mold used here is a nickel mold having a curved surface represented by the following formula.

• z = 5 X sin (0.314 X x) +5 X sin (0.251 X y)

[0226] First, the UV curing resin (Dainippon Ink & Chemicals Co., Ltd .: Unidic 15-829) and the initiator (Ciba 'Specialty Chemicals Co., Ltd .: Irgacure 907) were UV cured. Fat: Initiator = Mixing at a ratio of 99: 1, mixing with a mixer for 30 minutes and stirring to obtain a coating solution. Next, the coating solution was applied to the surface of the mold provided with a surface shape so that the thickness of the coating film was 50 m. After the application, a base film was placed on the upper surface of the coating film and adhered. Thereafter, a total of 500 mjZW of ultraviolet rays was irradiated from the base film side to the mold surface direction. After UV irradiation, it was heat fixed at 40 ° C for 30 minutes. Thereafter, the mold was released to obtain a light diffusing film in which an ultraviolet curable resin layer having a surface irregularity formed on one surface of the base film was laminated.

[0227] The minimum specific brightness BI, maximum average specific brightness Bmax, minimum average specific brightness Bmin, ratio of maximum and minimum BmaxZBmin, in-plane rotation angle indicating maximum average specific brightness Bmax Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2. Here, the transmittance and haze are numerical values measured by incidence of light from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are numerical values obtained by measuring the incidence of light rays from the surface when the surface irregularities are formed.

[0228] This light diffusing film was laid so that the surface on which the surface irregularities were formed was in the observer direction (the surface on which the surface irregularities were not formed was on the light source side). The surface light source had a uniformity of 1.08 and an average front luminance of 5900 cdZm ² , indicating good performance.

[0229] [Example 2-2]

A base film having a thickness of 140 μm was obtained in the same manner as in Example 2-1. An uneven shape was formed on one surface of this base film in the same manner as in Example 2-1. However, the mold used was a nickel mold with a curved surface represented by the following formula.

• z = 5 X sin (0.314 X x) +5 X sin (0.188 X y)

[0230] The minimum specific brightness BI, maximum average specific brightness Bmax, minimum average specific brightness Bmin, maximum / minimum ratio BmaxZBmin, in-plane rotation angle indicating maximum average specific brightness Bmax Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δ φ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy ratio of maximum value to minimum value AsmaxZ Asm In, transmittance, haze, and total thickness were as shown in Table 2. Here, the transmittance and haze are numerical values measured by incidence of light from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are numerical values obtained by measuring the incidence of light from the surface when the surface irregularities are formed.

[0231] This light diffusing film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source was 1.06, and the average front luminance was 5800 cdZm ² , indicating good performance.

[0232] [Example 2-3]

A base film having a thickness of 140 μm was obtained in the same manner as in Example 2-1.

[0233] An uneven shape was formed on one surface of this base film in the same manner as in Example 2-1. However, the mold used was a nickel mold with a curved surface represented by the following formula. • z = 5 X sin (0.314 X x) +5 X sin (0.126 X y)

[0234] The in-plane rotation angle indicating the minimum specific value BI, maximum average specific luminance Bmax, minimum average specific luminance Bmin, maximum / minimum ratio BmaxZBmin, maximum average specific luminance Bmax of the obtained light diffusion film Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2. Here, the transmittance and haze are numerical values measured by incidence of light from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are numerical values obtained by measuring the incidence of light rays from the surface when the surface irregularities are formed.

[0235] This light diffusing film was laid so that the surface on which the surface irregularities were formed was in the viewer direction (the surface on which the surface irregularities were not formed was on the light source side). The uniformity of this surface light source was 1.04, and the average front luminance was 5700 cdZm ² , indicating good performance.

[0236] [Example 2-4]

[0237] An uneven shape was formed on one surface of this base film in the same manner as in Example 2-1. However, the mold used was a nickel mold with a curved surface represented by the following formula. Z = 5 X sin (0.251 Xx)

[0238] The in-plane rotation angle indicating the minimum specific brightness BI, maximum average specific brightness Bmax, minimum average specific brightness Bmin, maximum / minimum ratio BmaxZBmin, maximum average specific brightness Bmax of the obtained light diffusion film Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2. Here, the transmittance and haze are numerical values measured by incidence of light from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are numerical values obtained by measuring the incidence of light rays from the surface when the surface irregularities are formed.

[0239] This light diffusing film was laid so that the surface on which the surface irregularities were formed was in the observer direction (the surface on which the surface irregularities were not formed was on the light source side). Uniformity of the surface light source is 1.0 3, the average front luminance 5900CdZm ^2, showed a good performance.

[0240] [Example 2-5]

[0241] An uneven shape was formed on one surface of this base film in the same manner as in Example 2-1. However, the mold used was a nickel mold with a curved surface represented by the following formula. Z = 5 X sin (0.440 Xx)

[0242] The in-plane rotation angle indicating the minimum specific brightness BI, the maximum average specific brightness Bmax, the minimum average specific brightness Bmin, the maximum / minimum ratio BmaxZBmin, and the maximum average specific brightness Bmax of the obtained light diffusion film Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2. Here, the transmittance and haze are numerical values measured by incidence of light from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are numerical values obtained by measuring the incidence of light rays from the surface when the surface irregularities are formed.

[0243] The surface on which the uneven surface of the light diffusion film is formed is directed toward the viewer (the uneven surface) The surface where no is formed is laid on the light source side. The uniformity of this surface light source is 1.0

3. The average front brightness was 5800cdZm ² , showing good performance.

[Example 2-6]

[0245] An uneven shape was formed on one surface of this base film in the same manner as in Example 2-1.

Z = 5 X sin (0.628 X x)

[0246] The obtained light diffusion film has a minimum specific brightness BI, a maximum average specific brightness Bmax, a minimum average specific brightness Bmin, a ratio between the maximum and minimum values BmaxZBmin, an in-plane rotation angle indicating the maximum average specific brightness Bmax, and Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2. Here, the transmittance and haze are numerical values measured by incidence of light from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are numerical values obtained by measuring the incidence of light rays from the surface when the surface irregularities are formed.

[0247] This light diffusing film was laid so that the surface on which the surface irregularities were formed was in the observer direction (the surface on which the surface irregularities were not formed was on the light source side). The surface light source had a uniformity of 1.0 2 and an average front luminance of 5800 cdZm ² , indicating good performance.

[0248] [Example 2-7]

The diffusion film obtained in Example 2-3 was incorporated into a surface light source so that the distance between the center of the fluorescent tube and the light source side surface of the light diffusion film was 23.5 mm. The δ of this surface light source was calculated to be 30 °, but the uniformity was 1.03 and the average front luminance was 6000 cd / m ² , indicating good performance.

[Example 2—8]

The diffusion film obtained in Example 2-6 was incorporated into a surface light source so that the distance between the center of the fluorescent tube and the light source side surface of the light diffusion film was 23.5 mm. When the δ of the surface light source was calculated, but was 30 °, uniformity ratio 1.02, the average front luminance 5900cd / m ² der It showed good performance.

[0250] [Example 2-9]

The diffusion film obtained in Example 2-3 was incorporated into a surface light source so that the distance between the center of the fluorescent tube and the light source side surface of the light diffusion film was 15.5 mm. When the δ of this surface light source was calculated, the force uniformity of 40 ° was 1.05, and the average front brightness was 5600 cdZm ² , indicating good performance.

[0251] [Example 2-10]

The diffusion film obtained in Example 2-6 was incorporated into a surface light source so that the distance between the center of the fluorescent tube and the light source side surface of the light diffusion film was 15.5 mm. When the δ of this surface light source was calculated, the force uniformity of 40 ° was 1.03, and the average front brightness was 5700 cdZm ² , indicating good performance.

[0252] [Reference Example 2-1]

Polycarbonate pellets were supplied to the extruder as the main resin component constituting the light diffusion film. Next, melt extrusion was performed, and a single-layer sheet was prepared by cooling on a mirror-casting drum by an electrostatic application method.

[0253] An uneven shape was formed on one surface of this single-layer sheet by the following method. The mold used here is a nickel mold having a curved surface represented by the following formula.

• z = 5 X sin (0.0942 X x) +5 X sin (0.0942 X y)

[0254] First, the obtained single-layer sheet and mold were heated to 175 ° C and held for 2.5 minutes. Next, the surface of the single-layer sheet with the shape of the mold was pressed with a pressure of 12 MPa and held for 3 minutes. Thereafter, while maintaining the pressure, it was cooled to 125 ° C. and the pressure was released. The film on which the surface irregularities were formed was released from the mold to obtain a light diffusion film.

[0255] The in-plane rotation angle indicating the minimum specific brightness BI, maximum average specific brightness Bmax, minimum average specific brightness Bmin, maximum / minimum ratio BmaxZBmin, maximum average specific brightness Bmax of the obtained light diffusion film Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2. Where transmittance and haze are It is the numerical value which measured by making a light ray inject from the surface in which the surface uneven | corrugated shape was formed. BI, Bmax, and Bmin are numerical values obtained by measuring the incidence of light from the surface when the surface irregularities are formed.

[0256] This light diffusing film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source was 1.19 and the average front luminance was 6100 cdZm ² .

[0257] [Reference Example 2-2]

In the extruder, 99.8% by volume of a polyester resin obtained by copolymerizing 20 mol% of cyclohexanedimethanol component with glycol unit as a main resin component constituting the light diffusion film in the extruder, light diffusion element A pellet containing 0.2% by volume of polymethylpentene was supplied. Next, melt extrusion was carried out, and a single layer sheet was prepared by cooling on a mirror cast drum by an electrostatic application method.

An uneven shape was formed on one surface of this single layer sheet by the following method. The mold used here is a nickel mold having a curved surface represented by the following formula.

• z = 5 X sin (0.157 X x) +5 X sin (0.157 X y)

[0258] First, the obtained single-layer sheet and mold were heated to 135 ° C and held for 3 minutes. Next, the surface on which the mold shape was given to the single-layer sheet was pressed with a pressure of lOMPa, and held for 3 minutes. Thereafter, while maintaining the pressure, it was cooled to 65 ° C. and the pressure was released. The film on which the concave / convex shape was formed from the mold was released to obtain a light diffusion film.

[0259] The minimum specific brightness BI, the maximum average specific brightness Bmax, the minimum average specific brightness Bmin, the ratio between the maximum and minimum BmaxZBmin, the in-plane rotation angle indicating the maximum average specific brightness Bmax Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2. Here, the transmittance and haze are numerical values measured by incidence of light from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are numerical values obtained by measuring the incidence of light rays from the surface when the surface irregularities are formed. [0260] This light diffusion film was laid so that the surface on which the surface irregularities were formed was in the viewer direction (the surface on which the surface irregularities were not formed was on the light source side). Uniformity of the surface light source 1. 14 average front luminance was found to be 5800cdZm ^2.

[0261] [Reference Example 2-3]

In the main extruder, the polyester resin obtained by copolymerizing 10 mol% of isophthalic acid component with respect to the acid unit and 10 mol% of cyclohexanedimethanol component with respect to the glycol unit as the main resin component constituting the light diffusion film. fat (mp 225 ° C) (hereinafter, "IC- PET" say.) 98 volume ^_0/0, polymethylpentene supplying pellets were mixed 2 vol% as light diffuser, also, the main extrusion A sub-extruder was used separately from the machine, and PET (melting point 265 ° C) pellets were supplied to this sub-extruder. Next, the thickness of the component layer supplied to the sub-extruder on both side layers of the component layer supplied to the main extruder is as follows: Component ratio of sub-extruder: Component ratio of main extruder: Component ratio of sub-extruder = 1: Melting three-layer lamination coextrusion was carried out to 8: 1. A three-layer laminated sheet was prepared by cooling on a mirror-casting drum by electrostatic application. This laminated sheet was stretched 3.3 times in the longitudinal direction at a temperature of 88 ° C, and then stretched 3.5 times in the width direction at 115 ° C through a preheating zone of 95 ° C with a tenter. Further, a base film having a thickness of 390 μm was obtained by heat treatment at 240 ° C. for 30 seconds.

[0262] An uneven shape was formed on one surface of the base film by the following method. The mold used here is a nickel mold having a curved surface represented by the following formula.

• z = 5 X sin (0.314 X x) +5 X sin (0.314 X y)

[0263] First, an ultraviolet-curing resin (Dainippon Ink Chemical Co., Ltd .: Unidic 15-829) and an initiator (Ciba 'Specialty Chemicals Co., Ltd .: Irgacure 907) were UV-cured resin: initiator = 99: 1 The mixture was mixed for 30 minutes with a mixer and stirred to obtain a coating solution. Next, the coating solution was applied to the surface of the mold surface shape so that the thickness of the coating film was 50 / zm. After the application, a base film was placed on the upper surface of the coating film and adhered. Thereafter, a total of 500 mjZW of ultraviolet rays was irradiated from the base film side to the mold surface direction. After UV irradiation, it was heat fixed at 40 ° C for 30 minutes. After that, by releasing the mold, the light spreading in which the ultraviolet curable resin layer having the surface unevenness formed on one surface of the substrate film is laminated. A powder film was obtained.

[0264] The minimum specific brightness BI, maximum average specific brightness Bmax, minimum average specific brightness Bmin, ratio of maximum and minimum BmaxZBmin, in-plane rotation angle indicating maximum average specific brightness Bmax Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2. Here, the transmittance and haze are numerical values measured by incidence of light from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are numerical values obtained by measuring the incidence of light rays from the surface when the surface irregularities are formed.

[0265] This light diffusing film was laid so that the surface on which the surface irregularities were formed was in the viewer direction (the surface on which the surface irregularities were not formed was on the light source side). Uniformity of the surface light source 1. 1 0, the average front luminance was 5800cdZm ^2.

[0266] [Comparative Example 2-1]

The main extruder is supplied with pellets containing 90% by volume of IC-PET as the main resin component of the light diffusing film and 10% by volume of polymethylpentene as the light diffusing element. Using a sub-extruder, PET (melting point 265 ° C) pellets were fed to this sub-extruder. Next! The thickness of the component layer supplied to the sub-extruder on both sides of the component layer supplied to the main extruder in Bamboo. The component ratio of the sub-extruder: The component ratio of the main extruder: The component ratio of the sub-extruder = 1 The melted three-layer lamination coextrusion was performed so that the ratio was 8: 1. A three-layer laminate sheet was prepared by cooling on a mirror-cast cast drum by the electrostatic application method. This laminated sheet was stretched 3.3 times in the longitudinal direction at a temperature of 88 ° C, and then stretched 3.5 times in the width direction at 115 ° C through a preheating zone of 95 ° C with a tenter. Furthermore, the substrate film having a thickness of 140 μm was obtained by heat treatment at 240 ° C. for 30 seconds.

[0267] The obtained light diffusion film has a minimum specific brightness BI, a maximum average specific brightness Bmax, a minimum average specific brightness Bmin, a ratio between the maximum and minimum values BmaxZBmin, an in-plane rotation angle indicating the maximum average specific brightness Bmax, and Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2. [0268] This light diffusion film was incorporated into a surface light source. Uniformity of the surface light source 1. 24 average positive surface brightness was 4300cdZm ^2.

[0269] [Comparative Example 2-2]

The main extruder is supplied with pellets containing 98% by volume of IC-PET as the main resin component of the light diffusing film and 2% by volume of polymethylpentene as the light diffusing element. Using a sub-extruder, PET (melting point 265 ° C) pellets were fed to this sub-extruder. Next, the component layer supplied to the sub-extruder on both sides of the component layer supplied to the main extruder in the thickness is the thickness ratio. Sub-extruder component ratio: main extruder component ratio: sub-extruder component ratio = Melting three-layer lamination coextrusion was performed so that 1: 8: 1. A three-layer laminated sheet was prepared by cooling on a mirror-casting drum by electrostatic application. This laminated sheet was stretched 3.3 times in the longitudinal direction at a temperature of 88 ° C, and then stretched 3.5 times in the width direction at 115 ° C through a preheating zone of 95 ° C with a tenter. Further, the substrate film having a thickness of 140 μm was obtained by heat treatment at 240 ° C. for 30 seconds.

[0270] The in-plane rotation angle indicating the minimum specific value BI, maximum average specific luminance Bmax, minimum average specific luminance Bmin, maximum / minimum ratio BmaxZBmin, maximum average specific luminance Bmax of the obtained light diffusion film Difference in in-plane rotation angle indicating minimum average specific brightness Bmin Δφ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy as the ratio of maximum value to minimum value AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Table 2.

[0271] This light diffusion film was incorporated into a surface light source. Uniformity of the surface light source 1. 79 average positive surface brightness was found to be 5200cdZm ^2.

[0272] [Comparative Example 2-3]

The diffusion film obtained in Comparative Example 2-2 was incorporated into a surface light source so that the distance between the center of the fluorescent tube and the light source side surface of the light diffusion film was 23.5 mm. The δ of this surface light source was calculated and found to be 30 °. Uniformity 1. 73 average front luminance been filed in 5300cdZm ^2.

[0273] [Comparative Example 2-4]

The diffusion film obtained in Comparative Example 2-2 was incorporated into a surface light source so that the distance between the center of the fluorescent tube and the light source side surface of the light diffusion film was 15.5 mm. Calculating δ of this surface light source As a result, it was 40 °. Uniformity 1. 86 average front luminance been filed in 5000cdZm ^2.

[0274] [Example 3-1]

A base film having a thickness of 120 μm was obtained in the same manner as in Examples 1-16.

[0275] An uneven shape was formed on one surface of this base film in the same manner as in Example 14. However, the mold used was a nickel mold with a curved surface represented by the following formula. • {(x + n X 100 ) 2/50 2} + {z 2 /37.5 2} = 1

However, 50≤ (χ + η Χ 100) ≤50 (η = 0, ± 1, ± 2, ± 3 ···), z≤0.

Here, z indicates the mold thickness direction, and x and y indicate the mold surface direction. The unit is μm.

In other words, the cross-sectional shape of the mold is shown in FIG. 10, and the shape with unevenness in the y-axis direction is a strip lens column. In-plane rotation angle and minimum indicating the minimum specific brightness BI, maximum average specific brightness Bmax, minimum average specific brightness Bmin, ratio of maximum and minimum BmaxZBmin, maximum average specific brightness Bmax of the obtained light diffusion film Difference of in-plane rotation angle indicating average specific brightness Bmin ΔΦ, maximum aspect ratio of surface shape Asmax, minimum value Asmin, anisotropy ratio of maximum value to minimum value AsmaxZAsmin, transmittance, haze, total thickness Are shown in Tables 3 and 4. Here, the transmittance and haze are numerical values measured by entering light rays from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are values measured by incidence of light from a surface on which no surface irregularity is formed.

[0277] This light diffusing film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source was 1.01, and the average front luminance was 5700 cdZm ² , indicating good performance.

[0278] [Example 3-2]

[0279] An uneven shape was formed on one surface of this base film in the same manner as in Example 14. However, the mold used was shaped so that the A-side end and B-side end (A-END and B-END in Fig. 11) of the unit curved surface shown in Fig. 11 were joined continuously. This is a nickel mold. Here, z indicates the mold thickness direction, and x and y indicate the mold surface direction. In addition, the shape without unevenness in the y-axis direction is a stripe lens column. [0280] The minimum specific brightness BI, maximum average specific brightness Bmax, minimum average specific brightness Bmin, ratio between maximum and minimum BmaxZBmin, in-plane rotation angle indicating maximum average specific brightness Bmax Minimum average specific brightness Bmin in-plane rotation angle difference Δφ, surface shape aspect ratio maximum value Asmax, minimum value Asmin, ratio of maximum value to minimum value Anisotropy AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Tables 3 and 4. Here, the transmittance and haze are numerical values measured by making light rays incident from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are values measured by entering light from a surface on which no surface irregularity is formed.

[0281] This light diffusing film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source was 1.00, and the average front luminance was 5800 cdZm ² , indicating good performance.

[0282] [Example 3-3]

[0283] An uneven shape was formed on one surface of the base film in the same manner as in Example 14. However, the mold used was shaped so that the A-side end and B-side end (A-END and B-END in Fig. 12) of the unit curved surface shown in Fig. 12 were continuously joined. This is a nickel mold. Here, z indicates the mold thickness direction, and x and y indicate the mold surface direction. In addition, the shape without unevenness in the y-axis direction is a stripe lens column.

[0284] The obtained light diffusion film has a minimum specific brightness BI, maximum average specific brightness Bmax, minimum average specific brightness Bmin, ratio of maximum and minimum BmaxZBmin, in-plane rotation angle indicating maximum average specific brightness Bmax, and Minimum average specific brightness Bmin in-plane rotation angle difference Δφ, surface shape aspect ratio maximum value Asmax, minimum value Asmin, ratio of maximum value to minimum value Anisotropy AsmaxZ Asmin, transmittance, haze The total thickness was as shown in Tables 3 and 4. Here, the transmittance and haze are numerical values measured by making light rays incident from the surface on which the surface irregularities are formed. BI, Bmax, and Bmin are values measured by entering light from a surface on which no surface irregularity is formed.

[0285] This light diffusing film was laid so that the surface on which the surface unevenness was formed was in the observer direction (the surface on which the surface unevenness was not formed was on the light source side). The uniformity of this surface light source is 1 The average front brightness was 6000 cdZm ² , indicating good performance.

[0286] [Example 3-4]

The following fabrics were prepared and spread out, and fixed to the surface light source casing with double-sided adhesive tape (Nitto Denko Co., Ltd. No. 500). On the fabric (the surface opposite to the side facing the fluorescent lamp), the surface of the light diffusing film obtained in Example 32, on which the surface unevenness is formed, is the viewer direction (the surface unevenness is formed) When layered so that the unfinished surface is the fabric side), the uniformity is 1.0.

0. The average front luminance was 6000 cdZm ² , indicating good performance. The support of the light diffusing film by the fabric was good with almost no deflection of the fabric.

[0287] (Composition of fabric)

1. Yarn used: warp yarn (56dtex—18 filament, 100% polyester filament yarn), horizontal thread (84dtex—36 filament, 100% polyester filament yarn)

2. Weaving organization: Plain weave

3. Weaving density: Vertical weaving density 118 Z-inch, horizontal weaving density 92 Z-inch.

[0288] The total light transmittance and haze of the fabric made with the above composition were 55% and 91%, respectively. O

[0289] [Comparative Example 3-1]

The film obtained in Comparative Example 1-1 was laid on a surface light source, and further on it (observer direction), the surface of the film obtained in Comparative Example 12 was formed with a surface irregularity shape in the observer direction (front view). It was laid so that the surface on which the surface irregularities were not formed was the light source side). Table 4 shows the haze and transmittance. Here, the transmittance and haze were superimposed on the film obtained in Comparative Example 1-1 on the film obtained in Comparative Example 1-2 so that the surface with the surface irregularities formed on the outside. It is a numerical value measured by making a light ray incident from the surface on which the surface uneven shape of the film obtained in Comparative Example 12 was formed. The uniformity of this surface light source was 1.27 and the average front brightness was 5200.

[0290] [Table 1]

lO £ Ll £ / 900Zd / 13d 19 9096Z0 / .00Z OAV

s ^ 0292w Transmittance Haze Overall thickness Cloth ft Uniformity Brightness

[%] [%] [• im] [-] [cd / m ² ] Example 3— 1 72 93 160 None 1.01 5700

Example 3— 2 71 92 150 None 1.00 5800

Example 3—3 70 93 150 None 1.00 6000

Example 3—4 71 92 150 Yes 1.00 6000

Comparative Example 3— 1 68 93 300 None 1.27 5200 Industrial Applicability

The light diffusing film of the present invention is suitable and useful for a surface light source used in a display device such as a personal computer, a television or a mobile phone, particularly a flat display device such as a liquid crystal display device.

Claims

The scope of the claims

[I] It has a base film containing a light diffusing element inside, and the ratio AsmaxZAsmin (anisotropy) of the maximum aspect ratio of the average aspect ratio Asmax to the minimum value Asmin is 1.1 or more on at least one surface. A light diffusion film in which a certain surface uneven shape is formed.

[2] The light diffusing film according to [1], wherein the base film is stretched beyond the -axis.

[3] The light diffusing film according to [1], wherein an area occupancy of the light diffusing element in a cross section perpendicular to the film surface is 1% or more.

4. The light diffusing film according to claim 1, wherein the number density of the light diffusing elements in a cross section perpendicular to the film surface is 250 Zmm ² or more.

[5] The light diffusion finolem according to [1], wherein the maximum value Asmax of the average aspect ratio is 0.3 or more.

[6] The minimum value BI of the relative luminance of the light transmitted in the normal direction when the light is incident on the film in an angle range of 20 ° to 50 ° with respect to the normal direction of the film surface is 0. 2. The light diffusing film according to claim 1, which is as described above.

[7] When the light beam is incident on the film in an angle range of 20 ° to 50 ° with respect to the normal direction of the film surface, the maximum average specific luminance Bmax of the light beam transmitted in the normal direction is 0.00. 2. The light diffusion film according to claim 1, wherein the light diffusion film is 2 or more.

[8] Maximum average ratio of light rays transmitted in the normal direction when light rays are incident on the film at an angle of 20 ° to 50 ° with respect to the normal direction of the film surface and the film is rotated in the plane. The light diffusing film according to claim 1, wherein the ratio BmaxZBmin between the luminance Bmax and the minimum average specific luminance Bmin is 1.1 or more.

[9] The surface irregularity shape having an anisotropy of 1.1 or more was applied to the surface of the base material film itself containing the light diffusing element or the base film containing the light diffusing element inside. Formed on the coating layer! The light diffusing film according to claim 1.

[10] A surface light source using the light diffusion film according to any one of [1] to [9].

[II] The surface light source according to claim 10, wherein the light diffusing film is arranged such that a surface having a surface irregularity shape having an anisotropy of 1.1 or more is directed toward an observer.

12. The surface light source according to claim 11, further comprising a cloth between the light diffusion film and the light source. 13. The surface light source according to claim 12, wherein the light diffusion film is supported by the fabric.