KR20070031904A - Anisotropic diffusion film - Google Patents

Abstract

The present invention relates to a novel anisotropic diffusion film having high brightness, high uniformity and high productivity, and more particularly, to anisotropic diffusion film suitable for surface light sources used in flat panel display devices such as liquid crystal display devices such as direct backlights. An anisotropic diffusion film in which a convex stripe-shaped lens is formed on one surface of a base film, wherein the cross-sectional shape in a plane perpendicular to the stripe direction satisfies the following A to C, and has an overall light transmittance of 70% or more. It is a film.

A. The contour of the convex part of the cross section is curved.

B. The aspect ratio of the convex part of the cross section is 1 or more and 3 or less.

C. The distance between the vertices of adjacent convex portions of the cross-sectional shape is between 10 µm and 100 µm.

Description

Anisotropic Diffusion Film {ANISOTROPIC DIFFUSION FILM}

TECHNICAL FIELD The present invention relates to an anisotropic diffusion film, and more particularly, to an anisotropic diffusion film suitable for a surface light source used in flat display devices such as liquid crystal display devices.

In this invention, an anisotropic diffused film means the film whose distribution of the diffused light which permeate | transmits a film is not isotropic when a light ray enters a film surface perpendicularly. That is, the distribution of diffused light in any plane including the axis of incident light (where any plane is perpendicular to the film plane), and the diffusion in a plane perpendicular to the plane and including the axis of incident light It refers to the film from which light distribution differs.

Recently, many displays using liquid crystals have been used as display devices for personal computers, televisions, and cellular phones.

Since these liquid crystal displays are not themselves light emitters, display is possible by irradiating light using a surface light source from the back side. In addition, in order to meet the demand that the surface light source not only irradiates light but also irradiates the entire screen uniformly, a structure having a surface light source called a side light type backlight or a direct type backlight is employed.

Among these, in the direct type backlight used for televisions etc., generally, the several lamp arrange | positioned in parallel, and the milky-white diffuser plate are provided in the upper surface side of a lamp, and the diffusion sheet, prism sheet, etc. are suitably arrange | positioned. As a milky-white diffuser plate, the diffuser plate which disperse | distributed dispersible particle | grains in acrylic resin etc. is typical, and has a function which reduces the image of the lamp installed in the back surface in a direct type | mold backlight, and improves uniformity.

On the other hand, the demand for making the surface light source brighter (requirement of high luminance) only increases, and there are methods such as increasing the number of lamps or increasing the output as a means thereof. It is also inefficient.

Moreover, the proposal regarding the anisotropic diffusion film is made | formed with respect to said request | requirement of high brightness. Concretely provided with cylindrical lens part in stripe shape (refer patent document 1), the thing which disperse | distributed rod-shaped bubble (refer patent document 2), or having a vertically divided spindle shape ( Patent Document 3) and the like have been proposed.

[Patent Document 1: Japanese Patent Laid-Open No. 2002-62528]

[Patent Document 2: Japanese Patent Laid-Open No. 2002-98810]

[Patent Document 3: Japanese Patent Laid-Open No. 2002-107510]

However, in any of the conventional milky white diffuser plates and the above-mentioned proposals, in particular, in the direct type backlight, it does not have sufficiently high brightness and uniformity, and it is a fact that productivity and cost cannot be made highly compatible.

It is an object of the present invention to provide a novel anisotropic diffusion film having high brightness, high degree of homogeneity and high productivity in view of these points.

In order to solve the said subject, the anisotropic diffusion film of this invention has the following structures.

That is, an anisotropic diffusion film composed of a convex stripe-shaped lens formed on one surface of the base film, the cross-sectional shape in the plane perpendicular to the stripe direction satisfies the following A to C, and has a total light transmittance of 70% or more. to be.

A. The contour of the convex part of the cross section is curved.

B. The aspect ratio of the convex part of the cross section is 1 or more and 3 or less.

C. The distance between the vertices of adjacent convex portions of the cross-sectional shape is between 10 µm and 100 µm.

According to the present invention, a novel anisotropic diffusion film having high brightness, high bactericidal agent and high productivity is obtained.

1 is a schematic cross-sectional perspective view of an anisotropic diffusion film according to an embodiment of the present invention.

FIG. 2 shows a schematic cross-sectional view of an anisotropic diffusion film according to the present invention, which is another embodiment different from the anisotropic diffusion film of FIG. 1.

<Description of Symbols for Main Parts of Drawings>

1: base material sheet

2: convex stripe lens

3: convex part of convex stripe lens

The anisotropic diffuser film of the present invention has a basic structure in which a convex stripe lens is formed on one surface of a base film. The convex stripe-shaped lens portion satisfies the following three requirements A, B, and C in a plane perpendicular to the direction of the stripe, and has a total light transmittance of 70% or more.

A. The contour of the convex part of the cross section is curved.

B. The aspect ratio of the convex part of the cross section is 1 or more and 3 or less.

C. The distance between the vertices of adjacent convex portions of the cross-sectional shape is 10 µm or more and 100 µm or less.

The schematic cross-sectional perspective view of the anisotropic diffusion film of this invention is shown in FIG. In Fig. 1, reference numeral 1 denotes a base sheet, and a convex stripe lens having a reference numeral 2 is formed thereon, and 3 is a convex portion of the convex stripe lens.

In the present invention, the aspect ratio of the convex portion of the cross section of the convex stripe-shaped lens component portion needs to be 1 or more and 3 or less.

Herein, the "convex stripe-shaped lens" has a plurality of convex portions lined up in a cross section thereof, and the outline of the convex portion basically forms a curved line, preferably a semicircular shape (arc shape) or a semi-elliptic curve. .

In addition, in this invention, an "aspect ratio" is the ratio (b / a) of the half gap (a) of the distance between the vertices of the convex part of a cross section, and the height b of the convex part. That is, the distance between the vertices of the convex portions of the cross section of the convex stripe-shaped lens component is twice as large as a, and the distance between the vertices is denoted by 2a in FIG. The aspect ratio is preferably 1.5 or more and 2.5 or less. By setting the aspect ratio to the above range, it is possible to provide sufficiently high luminance and uniformity in the direct backlight.

If the aspect ratio is less than 1, the effect of improving the leveling agent is insufficient, making it difficult to use as a direct type backlight member. If the aspect ratio is more than 3, the leakage of backscattered light and light to the side is increased, and the luminance is lowered, so that it is difficult to use as a direct backlight member.

In the present invention, the distance between the vertices 2a of the convex portion needs to be 10 µm or more and 100 µm or less, and preferably 20 µm or more and 50 µm or less.

When the distance 2a between the peaks of this convex part is smaller than 10 micrometers, generation of color deviation by spectroscopy and moire with a liquid crystal cell will arise easily, and it will become difficult to use as a backlight member. In addition, when the distance 2a between the peaks of the convex portions exceeds 100 µm, the thickness of the stripe lens becomes thicker than necessary, which causes deterioration of flatness due to warpage and curl of the film, low productivity, and high cost. Not.

In the present invention, the distance (c) of the flat portion between adjacent convex portions of the convex stripe lens illustrated in FIG. 2 is preferably 3 µm or less in terms of increasing the diffusion efficiency and obtaining a high uniformity, more preferably. Is 2 µm or less, and most preferably 1.5 µm or less. When the distance c is larger than 3 µm, the amount of light transmitted straight is increased, the diffusibility is lowered, and the performance of diffusing light as the diffusion film becomes smaller, which is not preferable depending on the application.

In addition, when there are flat portions between adjacent convex portions as shown in FIG. 2, the aspect ratio is a value expressed by {b / (a- (c / 2))}.

In the present invention, the anisotropic diffusion film may be a laminated structure composed of two layers A and B having different polymer skeletons, glass transition temperatures, melting points, etc., such as A / B and A / B / A. It is preferable to give a convex shape to any one of layer A or layer B in the configuration of / B. In the case of such a laminated structure, the above-described total light transmittance is a value obtained by measuring the entire laminated structure.

Although it does not specifically limit in the above-mentioned anisotropic diffusion film of this invention, Preferably, it consists of substantially polyester.

When forming the anisotropic diffusion film of this invention, the polyester used as a preferable is a general term of the high molecular compound which makes the main bond in a principal chain an ester bond, and can be obtained by polycondensation reaction of a dicarboxylic acid component and a glycol component normally. . As the dicarboxylic acid component, for example, telephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfondicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium Alicyclic dicarboxylic acid, such as sulfonic dicarboxylic acid, phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, aliphatic dicarboxylic acid, such as maleic acid and fumaric acid, cyclohexanedicarboxylic acid, etc. Oxycarboxylic acids, such as dicarboxylic acid and paraoxy benzoic acid, etc. are mentioned. As the glycol component, for example, aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol and neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol and polypropylene glycol, and cyclo Alicyclic glycols, such as hexane dimethanol, aromatic glycols, such as bisphenol A and bisphenol S, etc. are illustrated.

Moreover, the polyester copolymer which used 2 or more types of said dicarboxylic acid components and / or glycol components may be sufficient as the polyester used as a preferable thing when constructing the anisotropic diffusion film of this invention.

In the anisotropic diffusion film of the present invention, the base film is preferably substantially composed of polyester, but the proportion of polyester in the film is preferably 90% by mass or more, and more preferably 95% by mass or more. . When the ratio of polyester is 90 mass% or more, it can be said that it is a film excellent in heat resistance and long-term stability. Hereinafter, the film comprised substantially from these polyesters is only called polyester film.

In addition, when using a polyester film for a base film in order to control diffusivity auxiliary, the said polyester film may contain the other polymer, particle | grains, etc. Examples of the polymers and particles include thermoplastic resins such as organic silicone resins, polystyrene resins, polyolefin resins and polyester resins, and inorganic fine particles such as glass, silica, barium sulfate, titanium oxide, magnesium sulfate, magnesium carbonate and calcium carbonate. have.

In this invention, it is preferable to use a polyester film for a base film, and to add particle | grains to the said polyester film is preferable at the point which improves reactivity and blocking resistance, and as an particle | grain to add, an inorganic particle Or organic particles can be used.

As the inorganic particles, for example, silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate and the like can be used. It is preferable that the average particle diameter of the inorganic particle used is 0.005-5 micrometers, More preferably, it is 0.01-3 micrometers, Especially preferably, it is 0.02-2 micrometers. If the average particle diameter is less than 0.005 µm, the effect of the activity and blocking resistance may not be sufficiently expressed. In addition, when the average particle diameter exceeds 5 µm, it may be recognized as an optical defect, or unnecessary diffusion and a decrease in transmittance may occur.

When using a polyester film for a base film, it is preferable to use the polyester film which shows the glass transition temperature of 60 degreeC or more from a long-term stability etc. or a heat resistance point, and glass transition temperature is 70 degreeC or more more preferably. Especially preferably, what shows 80 degreeC or more is used. The reason for this is that when the glass transition temperature is less than 60 ° C., there may be a problem that the transmittance and anisotropy after long-term storage change and sufficient characteristics are not expressed. Moreover, it is preferable that glass transition temperature is 150 degrees C or less from the point of balance of the stretchability, productivity, heat resistance, and moldability of polyester.

Moreover, in this invention, it is preferable that resin which comprises a convex stripe-shaped lens is polyester at the point which employ | adopts productivity or a thermal imprint (thermal embossing) process.

Moreover, when an acrylic resin, an epoxy resin, a urethane resin, etc. are coat | covered on a base film as resin which comprises a convex stripe-shaped lens, optical imprint using ultraviolet rays (hardens resin by ultraviolet irradiation, carrying out metal mold transfer to coat resin). May be employed, or a method may be employed in which thermal imprint and optical imprint are combined.

As resin which comprises the said convex stripe-shaped lens, a transparent thing is preferable specifically, As resin, acrylic resin, such as polyester resin mentioned above, poly (meth) acrylic acid, poly (meth) acrylic acid ester, its copolymer, epoxy It is preferable to consist of any of epoxy resins, such as a copolymer, an epoxyurethane resin, an urethane resin, or a mixed component thereof, and an ultraviolet curable type may be sufficient as it.

Although it does not specifically limit as a monomer of these transparent resins, or a copolymerization component, For example, polyhydric alcohol, a trimethol propane tri (meth) acrylate, a hexanediol (meth) acrylate, and a tripropylene glycol di (meth) acrylate , Diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanedioldi (meth) acrylate, neopentyl glycoldi (meth) Although an acrylate etc. exist, it is not limited to these.

Examples of the ultraviolet curable type include those in which a polymerizable unsaturated bond or a prepolymer, an oligomer, and / or a monomer having an epoxy group is appropriately mixed in the molecule. Examples of the prepolymer and oligomer in the ultraviolet curable resin composition include unsaturated polyesters such as condensates of unsaturated dicarboxylic acids and polyhydric alcohols, polyester methacrylates, polyether methacrylates, polyol methacrylates and melamine methacrylates. Examples of methacrylates such as methacrylates, polyester acrylates, epoxy acrylates, urethane acrylates, polyether acrylates, polyol acrylates and melamine acrylates, and cationic polymerization type epoxy compounds are exemplified. Especially, in this invention, the resin layer comprised from the at least 1 sort (s) or 2 or more sorts chosen from the group which consists of acrylic resin, an epoxy resin, and a urethane resin is preferably illustrated as resin which comprises ultraviolet curability.

Moreover, in the anisotropic diffusion film of this invention, various shapes can also be provided also to the surface on the opposite side to the surface which comprises a convex stripe-shaped lens, and when providing fine shape to both surfaces in this way, the thermal imprint method is used as one method. It is preferable to employ.

Since the anisotropic diffusion film of this invention is equipped and used for a liquid crystal display, even if it exposes for a long time to the heat which the lamp | ramp of a liquid crystal display emits, it is preferable that a total light transmittance hardly changes. Therefore, in this invention, it is preferable that the change rate of the total light transmittance after hot air processing at 80 degreeC and 500 hours is 3% or less, More preferably, it is 2% or less. Here, the said change rate is a value calculated | required as (| Tb-Ta |) / Tb * 100 (%), making Tb the total light transmittance before a process, and Ta as the total light transmittance after a process.

In order to make the rate of change of the total light transmittance after the hot air treatment at 80 ° C. and 500 hours below 3%, when the resin constituting the convex stripe lens is polyester, the glass transition temperature is preferably 80 ° C. or higher. Preferably it is 90 degreeC or more, Especially preferably, it is 100 degreeC or more. In addition, the intrinsic viscosity of 0.7 dl / g or more is preferable because it can suppress the decrease in the transmittance of the resin due to the crystallization progress and can also be exposed to heat for a long time to suppress the embrittlement of the resin. The intrinsic viscosity is more preferably 0.8 dl / g or more and 1.2 dl / g or less.

In the present invention, the thickness of the anisotropic diffusion film is preferably 75 to 500 µm, more preferably 150 to 400 µm, particularly preferably 200 to 350 µm in terms of elasticity and processability of the film.

In addition, when polyester is used for the anisotropic diffusion film of this invention, in the said polyester, various additives, for example, antioxidant, a heat stabilizer, a weather stabilizer, a ultraviolet absorber, organic in the range which does not impair the effect of this invention. Lubricating agent, pigment, dye, filler, antistatic agent and nucleating agent may be blended.

Moreover, when using a polyester film for the anisotropic diffusion film of this invention, it is preferable that permeation b value is 1.5 or less, More preferably, it is 1.0 or less. If the b value exceeds 1.5, the film looks yellow, and if such a film is attached to the surface of the display device, the film is deteriorated or discolored, and if such a film is provided inside the display device, It is not preferable because there is a possibility of impairing the balance of the color tone. Moreover, it is preferable that this permeation b value is -0.5 or more. This means that the film appears darker when the transmission b value is less than -0.5, and it gives a dark impression when such a film is attached to the surface of the display device. Also, when the film is provided inside the display device, the color tone or luminance is balanced. It is not recommended because it may be damaged. The color tone of the film can be adjusted within the range in which the film forming process is stable depending on the color tone of the raw material itself, the type of the laminated film formed on the film surface layer, or the film thickness, but the temperature setting during melt extrusion of the polyester is as low as possible. Therefore, it is important to minimize the temperature deviation.

In addition, the anisotropic diffusion film of the present invention needs to have a total light transmittance of 70% or more. The total light transmittance is preferably 80% or more, and more preferably 85% or more. Here, total light transmittance is the value at the time of making it enter from the surface provided with the convex cross section. Moreover, in order to make total light transmittance into this range, it is important to reduce and control the bubble and particle | grains which generate backscattering.

In the present invention, a method of forming a convex shape on the surface of the film in a stripe shape in one direction is performed by heating the film as necessary to transfer the film from the mold and the flat plate, or by applying a pressure between the mold roll and the roll. Method and the like are preferred. In this method, high productivity and reliability are obtained by the substrate being a film substantially polyester.

Moreover, an acrylic resin, an epoxy resin, a urethane resin, etc. are coat | covered on a base film as needed, and the optical imprint (curing resin by ultraviolet irradiation while mold-transferring to coat resin) using ultraviolet-ray can also be employ | adopted, and The method which combined thermal imprint and optical imprint can also be employ | adopted.

In the present invention, the surface roughness of the convex apex is preferably 1 µm or less in terms of improving the luminance and improving the uniformity (reducing the luminance deviation), and more preferably 0.5 µm or less.

Next, although the manufacturing method of the anisotropic diffusion film of this invention is described, this invention is not limited by this.

Co-polyester and polyethylene terephthalate containing the predetermined inorganic particles are set to an arbitrary lamination thickness ratio to perform melt two-layer coextrusion, and then cooled in a mirror cast drum by electrostatic application to obtain an unstretched two-layer laminated sheet. . The two-layer laminated sheet is biaxially stretched in the longitudinal direction and the width direction, and heat treated to obtain a polyester film. After heat-transfer-molding using a metal mold | die so that it may become a convex stripe-shaped lens on the copolyester layer side of the obtained polyester film, it can cool and can obtain an anisotropic diffusion film.

The anisotropic diffusion film of this invention is used suitably for a display, especially the diffusion sheet of a liquid crystal display, the screen of a projection television, etc.

<Example>

Hereinafter, although an Example is given and described about this invention, this invention is not necessarily limited to these. In addition, the characteristic was measured and evaluated by the following method.

(1) glass transition temperature of polyester

After melt | dissolving the sample cut out from the polyester film, it was quenched, it measured with the differential scanning calorimeter (type DSC2 by Parkin Elmer company) at the temperature rise rate of 10 degree-C / min, and the melting | fusing point was calculated | required from the melting peak.

(2) intrinsic viscosity of polyester

The polyester was dissolved in orthochlorophenol and measured at 25 ° C.

(3) total light transmittance

The total light transmittance of the film thickness direction was measured using the fully automatic direct haze computer HGM-2DP (made by Sugashi Kenki Co., Ltd.). The measurement was performed about each sample which divided | segmented the film of A4 size into four, and calculated | required the average value of these four measured values. Here, the incident surface is a surface to which a convex cross section is provided.

(4) Transmission b value

It measured by the transmission method according to JIS-K-7105 using the spectrophotometer SE-2000 type (made by Nippon Denshoku Industries Co., Ltd.).

(5) brightness

An anisotropic diffusion film obtained on a transparent acrylic plate having a thickness of 1 mm was installed on a light source of a 17-inch 8-lamp direct type lamp (lamp diameter 3 mm) so that the stripe direction and the lamp direction were parallel to each other. On the other side, the diffusion film (GM3 by Kimoto KK) and the prism sheet (BEF by 3M company) were arrange | positioned on it.

After the cold cathode ray tube lamp was turned on for 60 minutes to stabilize the light source, luminance (mm / m 2) was measured using a color luminance meter BM-7fast (manufactured by Topcon Co., Ltd.).

The measurement was performed with respect to 9 points of the center point of each area | region which divided the backlight surface of the center part of 10 cm x 10 cm into 9 equal to 3x3 area | region, and made the average value into luminance.

In addition, the luminance deviation was evaluated based on the deviation of the measurement results of nine points.

Luminance deviation (%) = (maximum value of 9 points-minimum value of 9 points) / (average value of 9 points) x 100

(6) Measurement of the shape of the convex part

The microtome is used to cut the film without crushing in a plane perpendicular to the stripe direction. Subsequently, the cut section is magnified and observed at an appropriate magnification using a scanning electron microscope S-2100A type (Hitachi Seisakusho Co., Ltd.) to take a photograph. In five convex sections having continuous sections, the average value is obtained by analyzing the distance (a) of half the distance between the vertices of the convex portions, the height of the convex portions (b), and the distance (c) of the flat portions between adjacent convex portions. Obtain

This observation and photography are performed for arbitrary ten points of the film, and the average value of each value is obtained.

Example 1

Polyethylene terephthalate (SPG-PET, glass transition temperature 105 ° C., intrinsic viscosity 0.71 dl / g) copolymerized with 30 moles of spiroglycol containing 0.05% by mass of spherical silica having an average particle diameter of 0.3 μm from the sub-extruder was used as the main extruder. Polyethylene terephthalate (PET, glass transition temperature of 75 ° C.) containing 0.1% by mass of spherical silica having an average particle diameter of 0.3 μm was subjected to melt two-layer coextrusion so that the lamination thickness ratio was SPG-PET / PET = 1/2. Cooling was performed on the mirror cast drum by the electrostatic application method to produce a two-layer laminated sheet. The bilayer laminated sheet thus obtained was biaxially stretched three times in the longitudinal direction and the width direction at a temperature of 110 ° C, and then heat-treated at a temperature of 235 ° C for 15 seconds to obtain a polyester film having a total film thickness of 250 µm.

A convex stripe lens having an aspect ratio of 1.52 was transferred to a SPG-PET laminated surface of the obtained polyester film at a heating temperature of 130 ° C. and a cooling temperature of 20 ° C. using a mold of a corresponding shape. Here, the distance a of half of the distance between the vertices of the convex portion is 50 µm, and the height b of the convex portion is 75 µm. The distance c of the flat portions between the adjacent convex portions was 1 m.

An anisotropic diffusion film obtained on a transparent acrylic plate having a thickness of 1 mm was placed on a light source of a 17-inch 8-lamp direct type lamp (lamp diameter 3 mm) so that the stripe direction and the lamp direction were parallel (convex stripe-provided surface). On the opposite side to this light source), the diffusion film (GM3 by Kikimoto Co., Ltd.) and the prism sheet (BEF by 3M company) were arrange | positioned on it. The obtained front luminance was high at 500 Hz / m 2, and the luminance deviation was good at 1%. Moreover, the color tone of the screen was also good, with little yellowish taste.

Moreover, about the obtained anisotropic diffused film, when the change of the transmittance | permeability after processing for 500 hours at the temperature of 80 degreeC was confirmed, it was 1.5% and was favorable with almost no change with the total light transmittance of 84% of an initial film.

Example 2

Polyethylene terephthalate (SPG-PET, glass transition temperature 105 DEG C, intrinsic viscosity 0.64 dl / g) copolymerized with 30 moles of spiroglycol containing 0.05% by mass of spherical silica having an average particle diameter of 0.3 µm from the sub-extruder was used as the main extruder. Polyethylene terephthalate (PET, glass transition temperature of 75 ° C.) containing 0.1% by mass of spherical silica having an average particle diameter of 0.3 μm was subjected to melt two-layer coextrusion so that the lamination thickness ratio was SPG-PET / PET = 1/2. Cooling was performed on the mirror cast drum by the electrostatic application method to produce a two-layer laminated sheet. The bilayer laminated sheet thus obtained was biaxially stretched three times in the longitudinal direction and the width direction at a temperature of 110 ° C, and then heat-treated at a temperature of 235 ° C for 15 seconds to obtain a polyester film having a total film thickness of 300 µm.

A convex stripe-shaped lens having an aspect ratio of 2.04 was transferred to a SPG-PET laminated surface of the obtained polyester film at a heating temperature of 130 ° C. and a cooling temperature of 20 ° C. using a mold of a corresponding shape. Here, the distance a of half of the distance between the vertices of the convex portion is 50 µm, and the height b of the convex portion is 100 µm. Moreover, the distance c of the flat part between adjacent convex parts was 2 micrometers.

A transparent acrylic plate with a thickness of 1 mm is placed on a light source of a 17-inch 8-inch direct type lamp (lamp diameter 3 mm), and an anisotropic diffusion film obtained so that the stripe direction and the lamp direction are parallel to each other is provided (shape designation). The surface was opposite to the light source), and a diffuser film (GM3 manufactured by Kimoto Co., Ltd.) and a prism sheet (BEF, manufactured by 3M Corporation) were disposed thereon to produce a surface light source. The obtained surface light source had a high luminance of 540 Pa / m 2 and a luminance deviation of 0.5%. Moreover, the color tone of the screen also had little yellow taste and was favorable.

Moreover, about the obtained anisotropic diffused film, when the change of the transmittance | permeability after processing for 500 hours at the temperature of 80 degreeC was confirmed, it was 1.7% and was favorable with almost no change with the total light transmittance of 82% of an initial film.

Example 3

Polyethylene terephthalate (SPG-PET, glass transition temperature 105 ° C., intrinsic viscosity 0.71 dl / g) copolymerized with 30 moles of spiroglycol containing 0.05% by mass of spherical silica having an average particle diameter of 0.3 μm from the sub-extruder was used as the main extruder. Polyethylene terephthalate (PET, glass transition temperature of 75 ° C.) containing 0.1% by mass of spherical silica having an average particle diameter of 0.3 μm was subjected to melt two-layer coextrusion so that the lamination thickness ratio was SPG-PET / PET = 1/2. Cooling was performed on the mirror cast drum by the electrostatic application method to produce a two-layer laminated sheet. The bilayer laminated sheet thus obtained was biaxially stretched three times in the longitudinal direction and the width direction at a temperature of 110 ° C, and then heat-treated at a temperature of 235 ° C for 15 seconds to obtain a polyester film having a total film thickness of 250 µm.

A convex stripe-shaped lens having an aspect ratio of 1.55 was transferred to a SPG-PET laminated surface of the obtained polyester film at a heating temperature of 130 ° C. and a cooling temperature of 20 ° C. by using a mold of a corresponding shape. Here, the distance a of half of the distance between the vertices of the convex portion is 50 µm, and the height b of the convex portion is 75 µm. The distance c of the flat portions between the adjacent convex portions was 3.5 µm.

A transparent acrylic plate with a thickness of 1 mm is placed on a light source of a 17-inch 8-inch direct type lamp (lamp diameter 3 mm), and an anisotropic diffusion film obtained so that the stripe direction and the lamp direction are parallel to each other is provided (shape designation). The surface was opposite to the light source), and a diffuser film (GM3 manufactured by Kimoto Co., Ltd.) and a prism sheet (BEF, manufactured by 3M Corporation) were disposed thereon to produce a surface light source. The obtained surface light source had a front luminance of 500 mW / m 2, high luminance, and a luminance deviation of 1.8%. Moreover, the color tone of the screen also had little yellow taste and was favorable.

Moreover, about the obtained anisotropic diffused film, when the change of the transmittance | permeability after processing for 500 hours at the temperature of 80 degreeC was confirmed, it was 1.5% and was favorable with almost no change with the total light transmittance of 80% of an initial film.

Example 4

An acrylic ultraviolet curable monomer liquid mixture was coated on the article number U426 film which is a 188 micrometers optical polyester film made by Toray Industries. The metal mold | die was piled on the coat surface, and the coat | covered acrylic ultraviolet curable monomer mixture liquid was floated on the whole lens frame.

Subsequently, the ultraviolet-ray was irradiated for 45 second from the ultraviolet-ray lamp of 6.4 kPa of irradiation intensity 80W / cm arrange | positioned at the polyester film side, and the ultraviolet curable monomer liquid mixture was polymerized and hardened | cured. Subsequently, the mold was peeled from the coat surface to form a convex stripe lens having an aspect ratio of 1.52 made of an acrylic resin having a refractive index of 1.59. Here, the distance a of half of the distance between the vertices of the convex portion is 50 µm, and the height b of the convex portion is 75 µm. The distance c of the flat portions between the adjacent convex portions was 1 m.

An anisotropic diffusion film obtained on a transparent acrylic plate having a thickness of 1 mm was installed on a light source of a 17-inch 8-lamp direct type lamp (lamp diameter 3 mm) so that the stripe direction and the lamp direction were parallel to each other. On the other side, the diffusion film (GM3 by Kimoto KK) and the prism sheet (BEF by 3M company) were arrange | positioned on it. The obtained surface light source had a high luminance of 520 Pa / m 2 and a luminance deviation of 1.5%. Moreover, the color tone of the screen also had little yellow taste and was favorable.

Moreover, about the obtained anisotropic diffused film, when the change of the transmittance | permeability after processing for 500 hours at the temperature of 80 degreeC was confirmed, it was 1.5%, and was favorable with almost no change with 94% of the initial film total light transmittance.

Example 5

Polyethylene terephthalate (CHD-PET, glass transition temperature 75 ° C) obtained by copolymerizing cyclohexanedimethanol 23 moles from the sub-extruder, polyethylene terephthalate (PET) (glass transition temperature 75 ° C) from the main extruder, The melt two-layer coextrusion was performed so that CHD-PET / PET = 1/4, and it cooled on the mirror cast drum by the electrostatic application method, and produced the two-layer laminated sheet. The two-layer laminated sheet thus obtained was stretched 3.2 times in the longitudinal direction at a temperature of 95 ° C., followed by further corona discharge treatment in air to the uniaxially stretched film, and metallized the following coating solution on the treated surface. It applied by the bar coat method using a bar.

Both ends of the uniaxially stretched film coated with the coating liquid are guided in the tenter while holding with a clip, preheated to 110 ° C in a preheating zone, and stretched 3.3 times in the transverse direction in a stretching zone at 125 ° C, and then at a temperature of 235 ° C. The mixture was heat treated for 15 seconds at to obtain a polyester film having a total film thickness of 250 µm.

A convex stripe-shaped lens having an aspect ratio of 1.52 was transferred to a CHD-PET laminated surface of the obtained polyester film at a heating temperature of 110 ° C. and a cooling temperature of 20 ° C. using a mold of a corresponding shape. Here, the space | interval a of half of the distance between the vertices of a convex cross section is 50 micrometers, and convex height b is 75 micrometers. The distance c of the flat part between adjacent convex stripe-shaped lenses was 1 m.

An anisotropic diffusion film obtained on a transparent acrylic plate having a thickness of 1 mm was placed on a light source of a 21-inch 10-inch direct type lamp (lamp diameter 3 mm) so that the stripe direction and the lamp direction were parallel to each other. On the other side, a diffusion film (GM3 manufactured by Kimoto Co., Ltd.) and a prism sheet (BEF, manufactured by 3M Corporation) were disposed thereon. The obtained surface light source had a high luminance of 500 mW / m 2 and a luminance deviation per one inch of all directions (the difference between the maximum luminance and the minimum brightness divided by the average luminance) was 1%. Moreover, the color tone of the screen also had little yellow taste and was favorable.

Moreover, about the obtained anisotropic diffused film, when the change of the transmittance | permeability after processing for 500 hours at the temperature of 80 degreeC was confirmed, it was 2.8%, and it was favorable with the initial film total light transmittance of 91% largely without a change.

Coating layer formation coating liquid mixes the following antistatic agent (C) and binder resin (D) by antistatic agent (C) / binder resin (D) = 30/70 by solid mass ratio, dilutes with water, and solid content concentration is 4 mass. Made in%.

C. Antistatic agent: Polystyrene sulfonate lithium salt water dispersion (molecular weight = about 70,000)

D. binder resin: acrylic emulsion (acrylic component: methyl methacrylate / ethyl acrylate / acrylic acid / N-metholacrylamide = 60/38/1/1 (mass%) copolymer, glass transition temperature 60 ° C.)

(Comparative Example 1)

On a light source of a 17-inch 8-inch direct type lamp (lamp diameter 3 mm), a 2 mm acrylic milky plate with a transmittance of 58%, anisotropy 1, and haze of 93% was installed, and a diffusion film (manufactured by Kimoto, Ltd.) was placed thereon. GM3) and the prism sheet (BEF by 3M company) were arrange | positioned, and the surface light source was produced. Here, the distance of a lamp and an acrylic milky board was made the same as the distance of the lamp and a transparent acrylic board in Examples 1-3. The luminance deviation was 3% and the front luminance was lower than that of the example at 400 Hz / m 2.

(Comparative Example 2)

Polyethylene naphthalate (PET / I, glass transition temperature of 75 ° C., intrinsic viscosity of 0.59 dl / g) copolymerized with 17 moles of isophthalic acid containing 0.1% by mass of spherical silica having an average particle diameter of 0.3 μm from the sub-extruder was used as the main extruder. Melted two-layer coextrusion from polyethylene terephthalate (PET, glass transition temperature 75 ° C.) containing 0.1% by mass of spherical silica having an average particle diameter of 0.3 μm from the layer so that the lamination thickness ratio is (PET / I) / PET = 1/4 Was performed, and it cooled on the mirror cast drum by the electrostatic application method, and produced the 2-layer laminated sheet. The bilayer laminated sheet thus obtained was biaxially stretched three times in the longitudinal direction and the width direction at a temperature of 110 ° C, and then heat-treated at a temperature of 220 ° C for 15 seconds to obtain a polyester film having a total film thickness of 250 µm.

A convex stripe lens having an aspect ratio of 0.75 was transferred to a PET / I laminated surface of the obtained polyester film at a heating temperature of 110 ° C. and a cooling temperature of 20 ° C. using a mold of a corresponding shape. In this case, the distance a of half of the distance between the vertices of the convex portion is 50 µm, and the height b of the convex portion is 37.5 µm. The distance c of the flat portions between the adjacent convex stripe lenses was 0 mu m.

Anisotropic diffusion obtained on a transparent acrylic plate having a thickness of 1 mm was installed on a light source of a 17-inch 8-inch direct type lamp (lamp diameter 3 mm), and the stripe direction and the lamp direction were parallel. The film was provided (the shape-providing surface was opposite to the light source), and a diffusion film (GM3 manufactured by Kimoto Co., Ltd.) and a prism sheet (BEF, manufactured by 3M) were disposed thereon. The obtained surface light source had a high luminance of 420 Pa / m 2 and a luminance deviation of 5%.

In addition, the obtained anisotropic diffused film was confirmed that the transmittance change after hot air treatment at a temperature of 80 ° C. for 500 hours was 5%, and a large change was observed from the initial film.

The anisotropic diffusion film of this invention is a suitable anisotropic diffusion film for surface light sources used for display apparatuses, such as a personal computer, a television, or a mobile telephone, especially flat-panel display apparatuses, such as a liquid crystal display device, and is highly usable.

Claims (5)

An anisotropic diffusion film comprising a convex stripe-shaped lens formed on one surface of a base film, wherein the cross-sectional shape in a plane perpendicular to the stripe direction satisfies the following A to C, and has a total light transmittance of 70% or more. Anisotropic Diffusion Film. A. The contour of the convex part of the cross section is curved. B. The aspect ratio of the convex part of the cross section is 1 or more and 3 or less. C. The distance between the vertices of adjacent convex portions of the cross-sectional shape is 10 µm or more and 100 µm or less. The anisotropic diffusion film according to claim 1, wherein the base film is polyester. The anisotropic diffusion film according to claim 1, wherein a distance between the flat portions between adjacent convex portions having a cross-sectional shape is 3 µm or less. The anisotropic diffusion film according to claim 1, wherein the convex stripe lens is polyester. The anisotropic diffusion film according to claim 1, wherein the rate of change of the total light transmittance after hot air treatment at 80 ° C. and 500 hours is 3% or less.

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