KR20120038445A - Light diffusion film and liquid crystal display device comprising same - Google Patents

Abstract

The present invention provides a light diffusing film having a high front contrast and a wide viewing angle without generating scintillation including a base film, light transmitting particles dispersed in the light transmitting resin and the light transmitting resin, and having a light diffusing layer having a flat surface. Has an average particle diameter of 0.5 µm or more and less than 20 µm, the content of the light-transmitting fine particles is 25 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the light-transmitting resin, and the refractive index of the light-transmitting fine particles is larger than that of the light-transmissive resin, The difference between the refractive index of the translucent microparticles and the refractive index of the translucent resin is 0.04 or more and 0.2 or less, and the thickness of the light diffusing layer is one or more and three times or less of the average particle diameter of the translucent microparticles. Moreover, it is a liquid crystal display device with which the said light-diffusion film is attached.

Description

LIGHT DIFFUSION FILM AND LIQUID CRYSTAL DISPLAY DEVICE COMPRISING SAME

The present invention relates to a light diffusing film and a liquid crystal display device including the same.

Background Art In recent years, the development of the liquid crystal display device is rapidly progressing, and has been used in mobile phones, personal computer monitors, televisions, liquid crystal projectors, and the like.

In general, the liquid crystal display device operates the liquid crystal in display modes such as twisted nematic (TN) mode, vertical alignment (VA) mode, and in-plane switching (IPS) mode, and electrically controls the light passing through the liquid crystal. By displaying the difference of contrast on a screen, it is a liquid crystal display device which expresses a character or an image.

The liquid crystal display has a problem of viewing angle dependence that, when the display screen is viewed in an oblique direction, deterioration of display characteristics due to a decrease in contrast or a gradation inversion phenomenon in which brightness is reversed in gradation display occurs.

In order to solve the said problem, the method of conventionally providing a light-diffusion means, for example, a light-diffusion layer, and improving the problem of viewing angle dependency is proposed.

A light diffusion film having a high haze light diffusion layer cured by coating a resin containing fine particles on a transparent substrate is used to widen the viewing angle (for example, JP2007-94369-A and JP2000-352607-A). However, in such a light-diffusion film, since light diffusivity is too strong, the contrast of a display image falls.

Light-diffusion films containing fine particles in the resin coating layer and having fine irregularities on the surface of the resin coating layer are also known (for example, JP2008-152268-A and JP2000-121809-A). However, in such a light-diffusion film, light diffusivity is weak and it cannot fully widen a viewing angle.

An object of the present invention is to provide a light diffusion film having a high front contrast and a wide viewing angle without generating scintillation, and a display device on which the light diffusion film is mounted.

[ Measures to solve the problem ]

The present invention includes the following.

[1] A light-diffusion film comprising a base film, light-transmitting fine particles dispersed in the light-transmissive resin and the light-transmissive resin, and having a light-diffusion layer having a flat surface,

The average particle diameter of the said translucent microparticles is 0.5 micrometer or more and less than 20 micrometers,

The content of the light-transmitting fine particles is 25 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the light-transmissive resin,

The refractive index of the light-transmitting fine particles is larger than that of the light-transmissive resin,

The difference between the refractive index of the translucent microparticles and the refractive index of the translucent resin is 0.04 or more and 0.2 or less,

The thickness of the said light-diffusion layer is a light-diffusion film which is 1 times or more and 3 times or less of the average particle diameter of the said translucent microparticles | fine-particles.

[2] The light-diffusion film according to [1], wherein the total haze is 40% or more and 70% or less, the internal haze is 40% or more and 70% or less, and the external haze is less than 1%.

[3] The light diffusing film according to [1] or [2], further comprising an antireflection layer on the side opposite to the base film of the light diffusing layer.

[4] A backlight device, a light deflecting means, a first polarizing plate, a liquid crystal cell in which a liquid crystal layer is provided between a pair of substrates, a second polarizing plate, and a light diffusion film are arranged in this order, and the first polarizing plate is A 2nd polarizing plate is a liquid crystal display device arrange | positioned so that these transmission axes may become a relationship of orthogonal Nicole, The said light-diffusion film is a light-diffusion film in any one of [1]-[3].

[5] The liquid crystal display device according to [4], wherein the light diffusion layer in the light diffusion film is disposed so as to be a light exit side than the base film.

[6] The optical deflecting means has two prism films each provided with a plurality of linear prism portions having ridges on the light exit side at predetermined intervals, and one prism film has a direction in which the ridge lines of the linear prism portions [4] arranged so that the prism film is substantially parallel to the transmission axis of the first polarizing plate, and the other prism film is arranged such that the direction of the ridge line of the linear prism is substantially parallel to the transmission axis of the second polarizing plate. Or the liquid crystal display device as described in [5].

[7] The liquid crystal display device according to any one of [4] to [6], wherein a vertex angle of a vertex corresponding to the ridge line in a vertical cross section perpendicular to the ridge line of the linear prism portion is 90 to 110 degrees.

[8] The liquid crystal display device according to any one of [4] to [7], further comprising a light diffusing means between the backlight device and the light deflecting means.

In addition, in this invention, the average particle diameter of translucent microparticles | fine-particles is a weight average particle diameter which can be stopped also by a Coulter multisizer (made by Beckman Coulter) based on the Coulter principle (pore electrical resistance method). In addition, the "light emission side" is a side (opposite side of a light source) which light incident from light sources, such as a backlight, is emitted when a light-diffusion film etc. are installed in a liquid crystal display device, and is a side near a viewer. On the contrary, the side where light enters from light sources, such as a backlight, may be called "light incidence side."

In addition, "substantially parallel to the transmission axis of a 1st polarizing plate" means an angle (for example, 15 degrees or less with respect to the said transmission axis in the case where it is parallel to the transmission axis of a 1st polarizing plate, and in the range which does not impair the effect of this invention). It is the meaning including the case of having (), and the case where it is parallel is the most preferable. Similarly, "substantially parallel to the transmission axis of the second polarizing plate" means an angle (for example, 15 degrees or less with respect to the transmission axis in the case where it is parallel to the transmission axis of the second polarizing plate and in a range that does not impair the effects of the present invention). It is the meaning including the case which has), and the case where it is parallel is the most preferable.

1 is a schematic view showing an example of a light diffusing film according to the present invention.
2 is a schematic view showing another example of the light diffusing film according to the present invention.
It is a schematic diagram which shows an example of the polarizing plate using the light-diffusion film of this invention.
4 is a schematic view showing an example of a liquid crystal display device according to the present invention.
5 is a schematic view showing an arrangement example of a prism film and a polarizing plate.
6 is a schematic view showing another example of a liquid crystal display according to the present invention.

Hereinafter, although the light-diffusion film and liquid crystal display device which concern on this invention are demonstrated based on drawing, this invention is not limited to these embodiment at all.

One embodiment of the light-diffusion film which concerns on this invention is described using FIG. The light-diffusion film 7 of FIG. 1 is made of the light-transmitting resin 721 and the light-transmitting fine particles 722 dispersed in the light-transmitting resin on one side of the base film 71, and has a light-diffusion layer 72 having a flat surface. It is laminated.

The translucent microparticles | fine-particles 722 used here are 0.5 micrometer-20 micrometers in average particle diameter, and the compounding quantity to the translucent resin 721 is 25 weight part or more and 60 weight part or less with respect to 100 weight part of light transmitting resins. By making the average particle diameter and compounding quantity of the translucent resin 721 into the said range, the outstanding light-diffusion property can be obtained without causing the fall of a front contrast. In addition, high transmission image clarity can be obtained. The preferable average particle diameter of the translucent microparticles 722 is 4-8 micrometers, and a preferable compounding quantity is 30-40 weight part.

The light-transmitting fine particles 722 used in the present invention are not particularly limited as long as they have the above average particle diameter and light-transmitting property, and conventionally known ones can be used. Examples thereof include organic fine particles such as acrylic resin, melamine resin, polyethylene, polystyrene, organic silicone resin, acrylic-styrene copolymer, and calcium carbonate, silica, aluminum oxide, barium carbonate, barium sulfate, titanium oxide, glass, and the like. Inorganic fine particles and the like. Each of these 1 type may be used independently, and may be used in mixture with other 1 or more types. Moreover, the balloon of an organic polymer, and glass hollow beads can also be used. The shape of the light-transmitting fine particles may be any of spherical shape, flat shape, plate shape and needle shape, but spherical shape is particularly preferable.

In addition, the refractive index of the translucent microparticles | fine-particles 722 is set larger than the refractive index of the translucent resin 721, The difference is 0.04 or more and 0.2 or less, and the range of 0.04-0.15 is preferable. By setting the difference between the refractive indices of the light-transmitting fine particles 722 and the light-transmitting resin 721 in the above range, the inside according to the difference in the refractive indices of the light-transmitting fine particles 722 and the light-transmitting resin 721 with respect to the light incident on the light diffusing layer 72. Scattering can be expressed and the occurrence of scintillation can be suppressed.

The light-transmissive resin 721 used in the present invention is not particularly limited as long as it is light-transmissive. For example, ionizing radiation curable resins such as ultraviolet curable resins and electron beam curable resins, thermosetting resins, thermoplastic resins, metal alkoxides, and the like can be used. Can be. Among these, it is used as it is about plastic resin, about curable resin, such as ionizing radiation curable resin, such as an ultraviolet curable resin, electron beam curable resin, and thermosetting resin, about a metal alkoxide by ionizing radiation, heat, etc., The metal alkoxide is used after hydrolysis, dehydration condensation, etc., respectively to convert the cured product into a cured product. Among these, an ionizing radiation curable resin is suitably used from the viewpoint of having a high hardness and providing sufficient scratch resistance to the light-diffusion film provided on the display surface.

Examples of the ionizing radiation curable resins are polyfunctional urethanes synthesized from polyfunctional acrylates such as acrylic acid esters or methacrylic acid esters of polyhydric alcohols, and diisocyanates and polyhydric alcohols and hydroxy esters of acrylic acid or methacrylic acid. Acrylates. In addition to these, polyether resins having a acrylate functional group, polyester resins, epoxy resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiolpolyene resins, and the like can also be used.

In the ionizing radiation curable resin, when using an ultraviolet curable resin, a photopolymerization initiator is added. It is preferable to use what existed in resin to use for a photoinitiator. As a photoinitiator (radical polymerization initiator), benzoin, such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl methyl ketal, its alkyl ether, etc. are used. The usage-amount of a photoinitiator is 0.5-20 mass parts with respect to 100 mass parts of resin normally. Preferably it is 1-5 mass parts.

In addition, examples of thermosetting resins include thermosetting urethane resins containing acrylic polyols and isocyanate prepolymers, phenol resins, urea melamine resins, epoxy resins, unsaturated polyester resins, and silicone resins.

Examples of the thermoplastic resin include cellulose derivatives such as acetyl cellulose, nitrocellulose, acetylbutyl cellulose, ethyl cellulose and methyl cellulose, vinyl acetate and its copolymers, vinyl chloride and its copolymers, vinylidene chloride and its copolymers Acetal resins such as polyvinyl formal, polyvinyl butyral, acrylic resins and copolymers thereof, acrylic resins such as methacryl resins and copolymers thereof, polystyrene resins, polyamide resins, linear polyester resins, polycarbonate resins, and the like. Can be used.

As a metal alkoxide, the silicon oxide type matrix etc. which use the silicon alkoxide system material as a raw material can be used. Specifically, tetramethoxysilane and tetraethoxysilane can be illustrated, and it can be set as the hardened | cured material in which the inorganic type or organic-inorganic composite type matrix was formed by hydrolysis and dehydration condensation.

When the ionizing radiation curable resin is used as the light transmitting resin 721, ionizing radiation such as ultraviolet rays or electron beams needs to be applied to the base film 71 after application and drying. In addition, when using thermosetting resin, a metal alkoxide, etc. as translucent resin 721, heating may be needed, for example, after apply | coating and drying to the base film 71. FIG.

In addition, the layer thickness of the light-diffusion layer 72 is 1 times or more and 3 times or less with respect to the average particle diameter of the translucent fine particle 722. When the layer thickness of the light diffusing layer 72 is thinner than 1 times the average particle diameter of the light transmitting fine particles 722, the texture of the light diffusing film 7 obtained becomes rough, scintillation is likely to occur, and the visibility of the display surface is lowered. do. In addition, when the layer thickness of the light diffusion layer 72 is thicker than three times the average particle diameter of the light-transmitting fine particles 722, the light diffusion becomes too strong and the contrast is lowered, so that the display quality is lowered.

As a layer thickness of the light-diffusion layer 72, 5-25 micrometers is preferable normally. If the layer thickness of the light diffusion layer 72 is thinner than 5 μm, sufficient scratch resistance may not be obtained as much as that which can be provided on the display surface, while if the layer thickness of the light diffusion layer 72 is thicker than 25 μm, The degree of curl of the produced light-diffusion film 7 may become large, and the handleability may worsen.

As a base film 71 used by this invention, what is necessary is just a light transmissive thing, For example, glass, a plastic film, etc. can be used. As a plastic film, what is necessary is just to have suitable transparency and mechanical strength. Examples thereof include cellulose acetate-based resins such as TAC (triacetyl cellulose) and polyester-based resins such as acrylic resins, polycarbonate resins and polyethylene terephthalates.

The light-diffusion film 7 of this invention can be produced as follows, for example.

A solvent solution (hereinafter sometimes referred to as a resin solution), such as ionizing radiation curable resin, thermosetting resin, thermoplastic resin, and metal alkoxide, in which the light-transmitting fine particles 722 are dispersed, is applied onto the base film 71. Then, the coating film thickness is adjusted so that the light-transmitting fine particles 722 do not appear on the coating film surface, so that the light diffusion layer 72 having a flat surface is formed on the surface of the base film 71. In this case, the dispersion of the light transmitting fine particles 722 in the resin liquid is preferably isotropic dispersion. In addition, when the ionizing radiation curable resin or the thermosetting resin is a liquid type having fluidity, and is capable of isotropically dispersing the light-transmitting fine particles 722, the resin may be used as it is without adding a solvent. In addition, in order to form the light-diffusion layer 72 which has a flat surface, in the manufacturing process of the light-diffusion layer 72, the method etc. which surface-treat the light-diffusion layer 72 using the roll which has a specular mold surface are used, etc. are used. Can be. The degree of flatness of the light diffusing layer 72 can be represented by an external haze, preferably 1% or less, and more preferably 0.5% or less.

Examples of the solvent used for the resin solution include alcohols such as ethanol, glycol ethers such as propylene glycol monomethyl ether, esters such as ethyl acetate and propylene glycol monomethyl ether acetate, ketones such as methyl ethyl ketone, and toluene Hydrocarbons such as these and alkyl halides such as methylene chloride.

The base film 71 may be subjected to a surface treatment prior to the application of the resin liquid for the purpose of improving the coatability and the adhesiveness with the light diffusing layer. Specific examples of the surface treatment include corona discharge treatment, glow discharge treatment, acid treatment, alkali treatment, ultraviolet irradiation treatment, and the like.

In addition, when using the light-diffusion film 7 of this invention as a support film of the polarizing plate mentioned later (shown in FIG. 3), the base film 71 and the polarizer 61 (shown in FIG. 3) are effectively adhere | attached. It is preferable to hydrophilize the base film 71 by an acid treatment or an alkali treatment from a viewpoint to make it.

There is no limitation on the method of applying the resin liquid on the base film 71. For example, the gravure coating method, the microgravure coating method, the roll coating method, the rod coating method, the knife coating method, the air knife coating method, the kiss coating method, The die coat method and the like can be used.

After apply | coating a resin liquid on the base film 71 directly or through another layer, it heats as needed and a solvent is dried. In the case of using ionizing radiation curable resins, thermosetting resins, metal alkoxides, or the like, the coating film is further cured by ionizing radiation and / or heat.

The ionizing radiation species can be appropriately selected from ultraviolet rays, electron beams, near ultraviolet rays, visible light, near infrared rays, infrared rays, X rays, and the like depending on the type of the translucent resin 721, and ultraviolet rays and electron beams are preferable, and are particularly easy to handle. Ultraviolet is preferable at the point that high energy is obtained easily.

As a light source of ultraviolet-ray which photopolymerizes an ultraviolet curable resin, any light source which generate | occur | produces an ultraviolet-ray can be used. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used. Moreover, ArF excimer laser, KrF excimer laser, an excimer lamp, a synchrotron radiation, etc. can also be used. Among these, an ultra high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, carbon arc, xenon arc, and a metal halide lamp can be used preferably.

Moreover, an electron beam can also be used similarly. As an electron beam, it is normally 50-1000 keV emitted from various electron beam accelerators, such as Cockcroft-Walton type | mold, a bander graph type | mold, a resonance transformer type, an insulation core transformer type | mold, a linear type | mold dynatron type | mold, and a high frequency type | mold. For example, the electron beam which has an energy of 100-300 keV can be mentioned.

In addition, in this invention, in order to manufacture the light-diffusion film 7 continuously using curable resins, such as an ionizing radiation curable resin and an electron beam curable resin, the process of continuously sending out the rolled base film 71 image. The manufacturing method which has the process of apply | coating and drying the resin solution which disperse | distributed the translucent microparticles | fine-particles 722, the process of hardening a coating film, and the process of winding up the light-diffusion film 7 in which the hardened light-diffusion layer 72 was formed It is preferable to use.

Other embodiment of the light-diffusion film of this invention is shown in FIG. In the light-diffusion film 7 shown in FIG. 2, the light-transmissive resin layer 73 is further laminated | stacked on the light-diffusion layer 72 which disperse | distributed and mixed the light-transmitting microparticles 722 in the light-transmissive resin 721. FIG.

It is preferable that the light-diffusion film of this invention has an antireflection layer further on the opposite side to the base film of a light-diffusion layer. An antireflection layer is a layer which is given a function by controlling the refractive index and the layer thickness of each layer, such as making the hard coat layer high refractive index and providing a low refractive index thin film thereon. You can prevent the outside of the object.

Next, an example of the polarizing plate using the light-diffusion film of this invention is shown in FIG. Although the general polarizing plate has the structure which the support film 62 was bonded to both surfaces of the polarizer 61, the polarizing plate shown in FIG. 3 used the light-diffusion film 7 of this invention as one support film, and is polarized It is a multifunctional film having a function and an antiglare (light diffusion) function. That is, the support film 62 is adhere | attached on one surface of the polarizer 61, and the light-diffusion film 7 which formed the light-diffusion layer 72 on the base film 71 is adhere | attached on the other surface, have. When attaching the polarizing plate of such a structure to a liquid crystal display device, it sticks to the glass substrate of a liquid crystal display panel, etc. so that the light-diffusion film 7 may be a light emission side. In addition, although bonding of the base film 71 and the polarizer 61 may be bonded through an adhesive bond layer, it is preferable to bond directly, without interposing an adhesive bond layer.

Next, a liquid crystal display device according to the present invention will be described. 4 is a schematic view showing an example of a liquid crystal display device according to the present invention. The liquid crystal display of FIG. 4 is a TN type liquid crystal display device of a normal white mode, and is a backlight device 2, the light-diffusion plate 3, two prism films 4a and 4b as a light deflection means, and a 1st polarizing plate (5), the liquid crystal cell 1 in which the liquid crystal layer 12 is provided between a pair of transparent substrates 11a and 11b, the 2nd polarizing plate 6, and the light-diffusion film 7 are arrange | positioned in this order, Is done.

As shown in FIG. 5, the 1st polarizing plate 5 and the 2nd polarizing plate 6 are arrange | positioned so that these transmission axes may become a relationship of orthogonal Nicole. In addition, the two prism films 4a and 4b have flat surfaces on the light incidence side, respectively, and a plurality of linear prism portions 41a and 41b are formed in parallel on the surface on the light exit side, and the linear prism portions ( 41a and 41b have ridge lines 42a and 42b on the light exit side. And the prism film 4a is arrange | positioned so that the ridgeline of the linear prism part 41a may become substantially parallel to the transmission axis direction of the 1st polarizing plate 5, and the prism film 4b is the linear prism part ( 41b) is arrange | positioned so that it may become substantially parallel with the transmission axis direction of the 2nd polarizing plate 6.

In FIG. 5, the cross-sectional shape in the vertical cross section orthogonal to the ridges of the linear prism portions 41a and 41b is a triangle, and the vertex angle θ of the vertex corresponding to the ridgeline among the vertices of the triangle is 90 ° to 110 °. It is preferable that it is the range of. The triangle may be any of the sides of the sides and the sides of the triangle, and when the light is to be focused in the front direction (normal direction of the display surface of the liquid crystal display), it is preferable that the two sides of the light exit side are the same isosceles triangle. .

The prism films 4a and 4b are arranged in such a manner that a plurality of linear prism portions 41a and 42a having such an isosceles triangular cross section are sequentially arranged so that the bottom sides corresponding to the vertex angles of the triangles are adjacent to each other. It is preferable to have a structure arranged such that the ridges 42a and 42b of the prism portions 41a and 42a are substantially parallel to each other. In this case, as long as the condensing ability is not significantly reduced, the triangles of the cross-sectional shape of the linear prism portions 41a and 42a may be curved or the like. The distance between each vertex is usually in the range of 10 µm to 500 µm, and preferably in the range of 30 µm to 200 µm.

In the liquid crystal display device having such a configuration, as shown in FIG. 4, the light emitted from the backlight device 2 is diffused by the light diffusion plate 3 and then enters the prism film 4a.

In a vertical cross section orthogonal to the transmission axis direction of the first polarizing plate 5, the light incident at an angle to the lower surface of the prism film 4a changes its path in the front direction and exits. Next, in the prism film 4b, in the vertical cross section orthogonal to the transmission axis direction of the second polarizing plate 6, the light incident at an angle to the lower surface of the prism film 4b is in the front direction as described above. Career changed course and exits. Therefore, the light which passed the two prism films 4a and 4b is condensed in the front direction also in any vertical cross section, and the brightness of a front direction improves.

The light imparted with directivity in the front direction is linearly polarized from circularly polarized light by the first polarizing plate 5 and enters the liquid crystal cell 1. Light incident on the liquid crystal cell 1 is emitted from the liquid crystal cell 1 by controlling the polarization plane for each pixel according to the orientation of the liquid crystal layer 12 controlled by the electric field. And the light radiate | emitted from the liquid crystal cell 1 is imaged by the 2nd polarizing plate 6, and is emitted to the display surface side via the light-diffusion film 7. The light-diffusion film is arrange | positioned so that a light-diffusion layer may be a light emission side rather than a base film.

Thus, in the liquid crystal display device of this invention, the directivity to the front direction of the light which injects into the liquid crystal cell 1 by the two prism films 4a and 4b becomes higher than before. As a result, the luminance in the front direction is improved as compared with the conventional apparatus. In addition, since the light diffusing film 7 described above is used, excellent light diffusivity and high transmission image clarity can be obtained without causing a decrease in front contrast.

Hereinafter, each member of the liquid crystal display device of the present invention will be described. First, the liquid crystal cell 1 used in the present invention is provided between a pair of transparent substrates 11a and 11b which are arranged to face each other at a predetermined distance by a spacer (not shown) and the pair of transparent substrates 11a and 11b. The liquid crystal layer 12 formed by enclosing a liquid crystal is provided. Although not shown in this figure, transparent electrodes and alignment films are laminated on the pair of transparent substrates 11a and 11b, respectively, and the liquid crystal is aligned by applying a voltage based on display data between the transparent electrodes. Although the display method of the liquid crystal cell 1 is a TN method here, you may employ | adopt display methods, such as an IPS system and a VA system.

The backlight device 2 includes a rectangular parallelepiped case 21 having an upper surface opening, and a cold cathode tube 22 as a linear light source arranged in parallel in a plurality of cases 21. It is preferable that the case 21 is formed from a resin material or a metal material, and at least the case inner circumferential surface is white or silver from the viewpoint of reflecting light emitted from the cold cathode tube 22 from the inner circumferential surface of the case. As a light source, in addition to a cold cathode tube, a hot cathode tube, an LED arranged linearly, etc. can also be used. In the case of using a linear light source, the number of linear light sources to be disposed is not particularly limited, but from the viewpoint of suppressing luminance unevenness of the light emitting surface, it is preferable that the distance between the centers of adjacent linear light sources is in a range of 15 to 150 mm. Do. In addition, the backlight device 2 used by this invention is not limited to the thing of the direct type | mold shown in FIG. 4, The side light type which arrange | positioned the linear light source or the point light source in the side surface of the light guide plate, or the plane which the light source itself is planar type Conventionally well-known things, such as a light source type, can be used.

The light-diffusion plate 3 is made by dispersing and dispersing a dispersant in a substrate, and examples of the substrate include polycarbonate, methacryl resin, methyl methacrylate-styrene copolymer resin, acrylonitrile-styrene copolymer resin, and methacryl. Polyolefins such as acid-styrene copolymer resins, polystyrene, polyvinyl chloride, polypropylene, polymethylpentene, polyester resins such as cyclic polyolefins, polyethylene terephthalates, polybutylene terephthalates, polyethylene naphthalates, and polyamide resins , Polyarylate, polyimide and the like can be used. In addition, as a diffusing agent to mix and disperse | distribute to a base material, it is microparticles which consist of a material from which the base material differs from a refractive index, In a specific example, acrylic resin, melamine resin, polyethylene, polystyrene, organic silicone resin different from the material of a base material And organic fine particles such as an acryl-styrene copolymer, and inorganic fine particles such as calcium carbonate, silica, aluminum oxide, barium carbonate, barium sulfate, titanium oxide, and glass, and the like, each of which may be used alone, or Used by mixing with one or more other types. In addition, a balloon or an organic hollow bead of an organic polymer can also be used as the diffusing agent. The range of 0.5-30 micrometers is suitable for the average particle diameter of a diffusing agent. The shape of the diffusing agent may be not only spherical but also flat, plate, needle and the like.

As for the prism films 4a and 4b, the light incidence surface side is a flat surface, and the linear prism of a triangular cross section is formed in parallel on the light emission surface side. As the material of the prism films 4a and 4b, for example, polycarbonate resin, ABS resin, methacryl resin, methyl methacrylate-styrene copolymer resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene and polypropylene And ionizing radiation curable resins such as polyolefin resins or ultraviolet curable resins and electron beam curable resins. As a manufacturing method of a prism film, it can manufacture by well-known methods, such as a release extrusion method, a press molding method, an injection molding method, a roll transfer method, a laser ablation method, a mechanical cutting method, a mechanical grinding method, and a photopolymer-process method. These methods may be used independently, respectively, or may combine 2 or more types of methods. In addition, you may disperse | distribute a light-diffusion agent to these prism sheets. As thickness of the prism films 4a and 4b, it is 0.1-15 mm normally, Preferably it is 0.5-10 mm.

As the 1st polarizing plate 5 and the 2nd polarizing plate 6 used by this invention, what bonded the support film on both surfaces of the polarizer is used normally. Examples of the polarizer include those in which a dichroic dye or iodine is adsorbed on a polarizer substrate such as polyvinyl alcohol-based resin, polyvinyl acetate resin, ethylene / vinyl acetate (EVA) resin, polyamide resin, polyester resin, and the like; and Among the molecularly oriented polyvinyl alcohol films, polyvinyl alcohol / polyvinylene copolymers containing oriented molecular chains of dichroic dehydration products of polyvinyl alcohol (polyvinylene) are included. In particular, what adsorbed the dichroic dye or iodine on the polarizer substrate of polyvinyl alcohol-type resin is used suitably as a polarizer.

Although there is no limitation in particular in the thickness of a polarizer, 100 micrometers or less are preferable for the purpose of thickness reduction of a polarizing plate, etc., More preferably, it is 10-50 micrometers, More preferably, it is 25-35 micrometers.

As a support film which supports and protects a polarizer, the film which consists of a polymer which is low birefringence and is excellent in transparency, mechanical strength, heat stability, water shielding property, etc. is preferable. Examples of such a film include cellulose acetate-based resins such as TAC (triacetyl cellulose), fluorine-based resins such as acrylic resins and tetrafluoroethylene / hexafluoropropylene copolymers, polyester-based resins such as polycarbonate resins and polyethylene terephthalate. Molded resin of polyimide resin, polysulfone resin, polyether sulfone resin, polystyrene resin, polyvinyl alcohol resin, polyvinyl chloride resin, polyolefin resin, polyamide resin, etc. It includes. Among these, a triacetyl cellulose film or a norbornene-based thermoplastic resin film obtained by saponifying a surface with an alkali or the like can be preferably used in terms of polarization characteristics, durability, and the like. Since a norbornene-type thermoplastic resin film becomes a favorable barrier from heat and wet heat, durability of a polarizing plate improves drastically, and since there is little moisture absorption rate, dimensional stability greatly improves and can be used especially suitably. The shaping | molding process to a film form can use the conventionally well-known method of the casting method, the calender method, and the extrusion method. Although there is no limitation in thickness of a support film, From a viewpoint of thickness reduction of a polarizing plate, etc., 500 micrometers or less are preferable normally, More preferably, it is 5-300 micrometers, More preferably, it is 5-150 micrometers.

6 shows another embodiment of the liquid crystal display device of the present invention. 6 differs from the liquid crystal display of FIG. 4 in that the phase difference plate 8 is disposed between the first polarizing plate 5 and the liquid crystal cell 1. The retardation plate 8 has a phase difference of almost zero in a direction perpendicular to the surface of the liquid crystal cell 1, and exhibits a phase difference when viewed obliquely without any optical action from the front surface. This is to compensate for the phase difference generated in (1). As a result, a wider viewing angle can be obtained, and better display quality and color reproducibility can be obtained. The retardation plate 8 can be disposed between one or both of the first polarizing plate 5 and the liquid crystal cell 1 and between the second polarizing plate 6 and the liquid crystal cell 1.

Examples of the retardation plate 8 include polycarbonate resins and cyclic olefin polymer resins as films, biaxially stretched films, and immobilized molecular arrangements of the liquid crystalline monomers by a photopolymerization reaction. Since the retardation plate 8 optically compensates for the arrangement of the liquid crystal, one having a refractive index characteristic opposite to that of the liquid crystal arrangement is used. Specifically, in the liquid crystal display cell of the TN mode, for example, "WV film" (manufactured by Fujifilm Co., Ltd.), and in the liquid crystal display cell of the STN mode, "LC film" (manufactured by Shin-Nippon Corporation), IPS, for example. In the liquid crystal cell of the mode, for example, a biaxial retardation film, in the VA mode liquid crystal cell, for example, a retardation plate in which an A plate and a C-plate are combined, a biaxial retardation film, and a liquid crystal cell of the? Cell mode, for example, "WV film for OBC". (Manufactured by FUJIFILM CORPORATION), etc. can be used suitably.

<Examples>

Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1

(1) Production of mirror mold

Industrial chromium plating was performed on the surface of the iron roll (STKM13A according to JIS) having a diameter of 200 mm, and the surface of the mold was then mirror polished using this iron roll to produce a mirror die. The Vickers hardness of the chrome plating surface of the obtained metal mold | die was 1000. In addition, the Vickers hardness was measured based on JIS Z 2244 using the ultrasonic durometer MIC10 (made by Krautkramer) (the Vickers hardness measurement method is the same also in the following example).

(2) Preparation of light-diffusion film containing light-diffusion layer and base film

Pentaerythritol triacrylate (60 parts by mass) and polyfunctional urethane acrylate (reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate, 40 parts by mass) were mixed in a propylene glycol monomethyl ether solution to give a solid content of 60 It adjusted to mass% and obtained the ultraviolet curable resin composition. In addition, the refractive index of the hardened | cured material after removing propylene glycol monomethyl ether from the said composition and UV-curing was 1.53.

Next, with respect to 100 mass parts of solid content of the said ultraviolet curable resin composition, 30 mass parts of polystyrene-type particle | grains (SBX-12 by Sekisui Chemical Co., Ltd. SBX-12) which have a weight average particle diameter of 12.0 micrometers as a translucent microparticles | fine-particles, a photoinitiator 5 parts by mass of phosphorus "Lucirine TPO" (manufactured by BASF Corporation, chemical name: 2,4,6-trimethylbenzoyldiphenylphosphine oxide) was added thereto, and diluted with propylene glycol monomethyl ether to obtain a solid content of 60% by mass. The coating liquid was prepared.

This coating liquid was apply | coated on the triacetyl cellulose (TAC) film (base film) of thickness 80micrometer, and it dried for 1 minute in the dryer set to 80 degreeC. The base film after drying was pressed against the mirror surface of the metal mold | die produced by said (1) by the rubber roll so that the ultraviolet curable resin composition layer might become a metal mold | die side, and it adhered closely. In this state, light from a high-pressure mercury lamp having an intensity of 20 mW / cm 2 is irradiated so as to be 300 mJ / cm 2 in the amount of h-line converted light, the ultraviolet curable resin composition layer is cured, and a light diffusion layer having a flat surface. The light-diffusion film of the structure shown in FIG. 1 which consists of a base film was produced.

Example 2

A light-diffusion film was produced in the same manner as in Example 1 except that 35 parts by mass of polystyrene-based particles (SBX-6, manufactured by Sekisui Seiko Co., Ltd.) having a weight average particle diameter of 6.0 µm were used as the light-transmitting fine particles.

Comparative Example 1

A light-diffusion film was produced in the same manner as in Example 1 except that 10 parts by mass of polystyrene-based particles (SBX-6, manufactured by Sekisui Seiko Co., Ltd.) having a weight average particle diameter of 6.0 µm were used as the light-transmitting fine particles.

Comparative Example 2

A light-diffusion film was produced in the same manner as in Example 1 except that 80 parts by mass of polystyrene-based particles (SBX-6, manufactured by Sekisui Seiko Co., Ltd.) having a weight average particle diameter of 6.0 µm were used as the light-transmitting fine particles.

Comparative Example 3

A light-diffusion film was produced in the same manner as in Example 1 except that 40 parts by mass of styrene-methyl methacrylate copolymer particles (manufactured by Sekisuka Seiking Co., Ltd.) having a weight average particle diameter of 6.0 µm were used as the light-transmitting fine particles. It was.

[Weight Average Particle Size of Translucent Particles]

The weight average particle diameter of the translucent microparticles | fine-particles used in Examples 1, 2 and Comparative Examples 1-3 was measured using the Coulter multisizer (made by Beckman Coulter) based on the Coulter principle (pore electrical resistance method).

[Film Thickness of Light Diffusion Layer]

The layer thicknesses of the light-diffusion films obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were measured using DIGIMICRO MH-15 (main body) and ZC-101 (counter) manufactured by NIKON Corporation, and the substrate thickness 80 was determined from this layer thickness. The film thickness of the light diffusion layer was obtained by subtracting the thickness.

[Measurement of haze value]

Haze value was measured about the light-diffusion film obtained in Examples 1 and 2 and Comparative Examples 1-3. The measurement results are shown in Table 1. In addition, from the ratio of the total light transmittance (Tt) representing the total amount of light transmitted by irradiating light to the film and the diffused light transmittance (Td) diffused and transmitted by the film, the following formula (1):

Haze (%) = (Td / Tt) × 100 (1)

The haze value is obtained according to. Here, the total light transmittance Tt is the sum of the parallel light transmittance Tp and the diffuse light transmittance Td transmitted while being coaxial with the incident light. The total light transmittance (Tt) and the diffused light transmittance (Td) were measured using a haze transmittance meter (HM-150, manufactured by MURAMAKAMISKI SAKI, Ltd.), in accordance with JIS K 7361.

In order to prevent curvature of a sample, it bonded to the glass substrate so that a 2nd light-diffusion layer might become a surface using an optically transparent adhesive, and the whole haze was measured in that state.

The internal haze was measured in the same manner as the measurement of the total haze by adhering a triacetyl cellulose film having almost zero haze to the film surface with glycerin and eliminating the influence on the outside of the film.

External haze was calculated | required according to the following formula from the measured value of the said whole haze and internal haze.

External haze (%) = Total haze (%)-Internal haze (%)

[Evaluation in Liquid Crystal Display Device]

In the backlight device of 32 type liquid crystal television "VIERA TH-32LZ85" (made by Panasonic Corporation) of IPS mode, the light-diffusion plate which has 10% of luminance values in 70 degree direction with respect to a front direction (normal direction of a display surface), and Two prism films each having a linear prism portion having a vertex angle of 95 ° corresponding to a ridge line in a vertical cross section perpendicular to the ridge line, and one prism film has the direction of the ridge line of the linear prism of the first polarizing plate. It was arrange | positioned so that it might be substantially parallel to a transmission axis, and the other prism film was arrange | positioned so that the direction of the ridgeline of the linear prism may be substantially parallel to the transmission axis of a 2nd polarizing plate. And the polarizing plate of the light emission surface side of a liquid crystal cell was peeled off, and the oxo type normal polarizing plate "TRW842AP7" (made by Sumitomo Chemical Co., Ltd.) was bonded so that it might become cross nicol, and the Example 1, 2, and a comparative example thereon The light-diffusion film produced by 1-3 was bonded together and the liquid crystal display device was produced.

About the produced liquid crystal display, front contrast was measured using the luminance meter "BM5A" type made from Topcon Corporation. Moreover, evaluation of the display quality seen from the direction whose viewing angle (angle formed with the front direction of a liquid crystal display device) is 40 degrees, 50 degrees, and 60 degrees was performed. In Table 2, the evaluation result of a viewing angle is shown in Table 2, and the measurement result of the front contrast with respect to the liquid crystal display device using each light-diffusion film of Examples 1, 2 and Comparative Examples 1-3.

As shown in Tables 2 and 3, the front contrast of the liquid crystal display device using the light diffusing films of Examples 1 and 2 does not decrease much compared with Comparative Examples 1 and 3 and is said to be almost equivalent. All of them had a wide viewing angle of 60 ° or more, while maintaining the level.

In contrast, in Comparative Example 1, since the blending amount of the translucent particles in the light diffusion layer is small, the light diffusion property is weak and the front contrast is high, but the viewing angle is narrow. In addition, in the comparative example 2, since the compounding quantity of the translucent particle | grains in a light-diffusion layer is too large, light diffusivity is too strong and a viewing angle is wide, but front contrast is falling large. In the comparative example 3, since the refractive index difference between the translucent resin and the translucent particle used for the light-diffusion layer is small, the light diffusivity is weak and the front contrast is high, but the viewing angle is narrow.

The liquid crystal display device including the light-diffusion film of the present invention has high front contrast and a wide viewing angle with little generation of scintillation.

1: liquid crystal cell, 11a, 11b transparent substrate,
12: liquid crystal layer,
2: backlight device,
21: case,
22: cold cathode tube,
3: light diffusion plate (light diffusion means),
4a, 4b: prism film (light deflection means),
41a, 41b: linear prism section,
42a, 42b: ridge,
5: first polarizer,
6: second polarizer,
7: light diffusion film,
71: base film,
72: light diffusing layer,
721: light transmitting resin,
722: translucent particulates,
73: a light-transmissive resin layer,
8: retarder

Claims (8)

As a light-diffusion film containing a base film, translucent microparticles disperse | distributed in translucent resin, and translucent resin, and having a light-diffusion layer with a flat surface,
The average particle diameter of the said translucent microparticles is 0.5 micrometer or more and less than 20 micrometers,
The content of the light-transmitting fine particles is 25 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the light-transmissive resin,
The refractive index of the light-transmitting fine particles is larger than that of the light-transmissive resin,
The difference between the refractive index of the translucent microparticles and the refractive index of the translucent resin is 0.04 or more and 0.2 or less,
The thickness of the said light-diffusion layer is a light-diffusion film which is 1 times or more and 3 times or less of the average particle diameter of the said translucent microparticles | fine-particles. The light-diffusion film of Claim 1 whose total haze is 40% or more and 70% or less, internal haze is 40% or more and 70% or less, and external haze is less than 1%. The light-diffusion film of Claim 1 or 2 which further has an anti-reflective layer on the opposite side to the base film of the said light-diffusion layer. The liquid crystal cell in which a liquid crystal layer is provided between a backlight device, a light deflection means, a 1st polarizing plate, and a pair of board | substrates, a 2nd polarizing plate, and a light-diffusion film are arrange | positioned in this order, and a 1st polarizing plate and a 2nd polarizing plate Silver is a liquid crystal display device arranged such that their transmission axes are in a relationship of orthogonal nicol,
The said light-diffusion film is a liquid crystal display device which is the light-diffusion film in any one of Claims 1-3. The liquid crystal display device according to claim 4, wherein the light diffusion layer in the light diffusion film is arranged so as to be a light exit side than the base film. The said optical deflection means has two prism films provided with two or more linear prism parts which have a ridgeline on a light output side at predetermined intervals on a light output side,
One prism film is arrange | positioned so that the direction of the ridge line of the linear prism part may become substantially parallel with respect to the transmission axis of the said 1st polarizing plate, and the other prism film has the direction of the ridge line of the linear prism of a 2nd polarizing plate. A liquid crystal display device arranged to be substantially parallel to the transmission axis. The liquid crystal display device according to any one of claims 4 to 6, wherein a vertex angle of a vertex corresponding to the ridge line in the vertical cross section perpendicular to the ridge line of the linear prism portion is 90 to 110 degrees. The liquid crystal display device according to any one of claims 4 to 7, further comprising a light diffusing means between the backlight device and the light deflecting means.

Images