WO2023054471A1 - 異方性光拡散フィルム及び異方性光拡散フィルムを備える表示装置 - Google Patents
異方性光拡散フィルム及び異方性光拡散フィルムを備える表示装置 Download PDFInfo
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- WO2023054471A1 WO2023054471A1 PCT/JP2022/036175 JP2022036175W WO2023054471A1 WO 2023054471 A1 WO2023054471 A1 WO 2023054471A1 JP 2022036175 W JP2022036175 W JP 2022036175W WO 2023054471 A1 WO2023054471 A1 WO 2023054471A1
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- Prior art keywords
- anisotropic light
- light diffusion
- needle
- filler
- film
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- FKTHNVSLHLHISI-UHFFFAOYSA-N 1,2-bis(isocyanatomethyl)benzene Chemical class O=C=NCC1=CC=CC=C1CN=C=O FKTHNVSLHLHISI-UHFFFAOYSA-N 0.000 description 1
- CDMDQYCEEKCBGR-UHFFFAOYSA-N 1,4-diisocyanatocyclohexane Chemical compound O=C=NC1CCC(N=C=O)CC1 CDMDQYCEEKCBGR-UHFFFAOYSA-N 0.000 description 1
- JIABEENURMZTTI-UHFFFAOYSA-N 1-isocyanato-2-[(2-isocyanatophenyl)methyl]benzene Chemical compound O=C=NC1=CC=CC=C1CC1=CC=CC=C1N=C=O JIABEENURMZTTI-UHFFFAOYSA-N 0.000 description 1
- NOWKCMXCCJGMRR-UHFFFAOYSA-N Aziridine Chemical compound C1CN1 NOWKCMXCCJGMRR-UHFFFAOYSA-N 0.000 description 1
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- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
- G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
- G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
Definitions
- the present invention relates to an anisotropic light-diffusing film and a display device comprising the anisotropic light-diffusing film.
- Patent Document 1 discloses a method for producing a transmitted light scattering control film in which the conditions for uniaxially stretching a thermoplastic polymer resin film are controlled to form grooves extending in a direction perpendicular to the stretching direction on the film surface. is disclosed.
- an object of the present invention is to provide an anisotropic light diffusion film that has a viewing angle widening effect with an excellent balance between the contrast ratio in the front direction and the oblique direction.
- the present inventors conducted intensive research, found that the above problems could be solved by an anisotropic light diffusion film satisfying specific physical properties, and completed the present invention.
- the present invention An anisotropic light diffusion film having an anisotropic light diffusion layer containing an isotropic transparent resin matrix and a needle-like filler, and a transparent substrate,
- the needle-like filler is unidirectionally oriented and dispersed in the isotropic transparent resin matrix,
- the degree of orientation of the anisotropic light diffusion film is 8 or more
- the anisotropic light diffusion layer has a thickness of 5 ⁇ m to 20 ⁇ m
- the angle difference between the alignment axis of the needle-like filler and the absorption axis of the upper polarizing plate of the liquid crystal display device is within ⁇ 5°, and the filler is laminated on the viewing side of the upper polarizing plate. It is an anisotropic light diffusion film.
- the degree of orientation of the anisotropic light-diffusing film can be measured by the following method.
- Method for measuring degree of orientation A laminate 1 is prepared by laminating a TAC film on the anisotropic light-diffusing layer side of an anisotropic light-diffusing film via a transparent adhesive layer having a thickness of 25 ⁇ m. Between the two polarizing plates having a structure in which the absorption axes are different from each other by 90° (crossed Nicols), the absorption axis of one of the polarizing plates and the orientation axis of the needle-like filler in the anisotropic light diffusion layer in the laminate 1 are parallel. , the laminate 1 is laminated to form a laminate 2 .
- the total light transmittance of the laminate 2 is measured according to JIS K 7361.
- the light from the light source is irradiated from one polarizing plate side, and the other polarizing plate side (the polarizing plate where the absorption axis of the polarizing plate and the orientation axis of the needle-like filler in the anisotropic light diffusion layer are not parallel) side.
- the haze value (total haze value) of the laminate 1 is measured according to JIS K 7136. From the obtained total light transmittance, [the haze value of the laminate 1]/[the total light transmittance of the laminate 2] is calculated, and the obtained value is taken as the degree of orientation.
- the needle-like filler preferably has a minor axis of 0.1 ⁇ m to 10 ⁇ m, a major axis of 2 ⁇ m to 1000 ⁇ m, and an aspect ratio of 10 to 100.
- the isotropic transparent resin matrix is preferably an acrylic resin having a glass transition temperature of 40°C to 160°C. It is preferable that the difference in absolute value between the refractive index of the needle-like filler in the longitudinal direction and the refractive index of the isotropic transparent resin matrix is 0.03 or less.
- the thickness of the film is preferably 6 ⁇ m to 520 ⁇ m.
- the anisotropic light-diffusing film is provided on the viewing side of the upper polarizing plate of the liquid crystal display device, and the angle difference between the orientation axis of the needle-like filler in the anisotropic light-diffusing film and the absorption axis of the upper polarizing plate is is within ⁇ 5°, and the viewing side of the upper polarizing plate is laminated so as to be the transparent substrate.
- an anisotropic light diffusion film that has a viewing angle widening effect with an excellent balance between the contrast ratio in the front direction and the oblique direction.
- FIG. 1 is a diagram plotting the measurement results of front and 60° direction contrast ratios for Examples and Comparative Examples.
- the present invention is not limited to these.
- the present invention may be applied not only to an anisotropic light diffusion film, but also to an anisotropic light diffusion layer constituting an anisotropic light diffusion film, a paint for obtaining an anisotropic light diffusion layer, or the anisotropic light diffusion layer.
- a display device to which an anisotropic light diffusion film is applied, or a manufacturing method thereof may be used.
- the present invention can also be a laminate containing an anisotropic light-diffusing film and other predetermined layers (base material, protective layer, pressure-sensitive adhesive layer, optical function layer, etc.).
- each component of the paint that is the raw material for manufacturing the anisotropic light diffusion layer each component of the uncured anisotropic light diffusion layer (composition) at the stage of applying and drying the paint, and after curing
- each component of a certain anisotropic light diffusion layer may be described without particular distinction.
- An anisotropic light-diffusing film has an anisotropic light-diffusing layer and a transparent substrate.
- anisotropic light diffusion layer contains an isotropic transparent resin matrix and needle-like fillers. Also, the anisotropic light diffusion layer may contain other components.
- the isotropic transparent resin matrix material is not particularly limited, but a polymer resin having high optical transparency and physical strength as an anisotropic light diffusion film can be used. In addition, this polymer resin is required to have high adhesion to the transparent base material. Specific examples of polymer resins that can be used include acrylic resins, styrene resins, styrene-acrylic copolymers, polyurethane resins, polyester resins, epoxy resins, cellulose resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymers.
- polyvinyl butyral resins polyvinyl butyral resins, cycloolefin resins, norbornene resins, and the like, and these can be used alone or in mixture.
- These polymer resins are usually used by dissolving them in an organic solvent, but it is also possible to introduce a thermosetting or photo-curing system, or to use non-solvent materials.
- the polymer resin preferably has a glass transition temperature of 40°C to 160°C, more preferably 50°C to 100°C, even more preferably 50°C to 80°C.
- the glass transition temperature can be measured by a known method, and a known measuring method can be used.
- the isotropic transparent resin matrix preferably has a refractive index of 1.45 to 1.55.
- the refractive index of the isotropic transparent resin matrix can be measured by a method conforming to Method A described in JIS K-7142 (1996).
- the needle-like filler is unidirectionally oriented and dispersed in the isotropic transparent resin matrix of the anisotropic light diffusion layer.
- the needle-like filler is not particularly limited as long as it is a needle-like (including fibrous) filler with a high aspect ratio. Colorless or white is preferred for cleaning.
- metal oxides such as titanium oxide, zirconium oxide and zinc oxide, metal compounds such as boehmite, aluminum borate, calcium silicate, basic magnesium sulfate, calcium carbonate and potassium titanate, glass, synthetic resins, etc.
- a needle-like or fibrous material consisting of is preferably used.
- the needle-like filler is preferably calcium carbonate.
- the short diameter of the needle-like filler is preferably 0.1 ⁇ m to 3 ⁇ m, more preferably 0.3 ⁇ m to 2 ⁇ m, even more preferably 0.5 ⁇ m to 1 ⁇ m.
- the major diameter (length) of the needle-like filler is preferably 5 ⁇ m to 50 ⁇ m, more preferably 7 ⁇ m to 40 ⁇ m, and even more preferably 10 ⁇ m to 30 ⁇ m.
- the aspect ratio (major axis/minor axis) of the needle-like filler is preferably 1.5-500, more preferably 3.5-135, even more preferably 10-60.
- the needle-like filler preferably has a refractive index of 1.45 to 1.55 in the longitudinal direction.
- the absolute value of the difference between the refractive index in the major axis direction of the needle-like filler and the refractive index of the isotropic transparent resin matrix is preferably 0.03 or less, more preferably 0.02 or less. , is more preferably 0.01 or less.
- the refractive index in the long axis direction of the needle-like filler or the difference between the refractive index in the long axis direction of the needle-like filler and the refractive index of the isotropic transparent resin matrix to such a range, it is possible to widen the viewing angle. Therefore, the light diffused by the needle-like filler in the anisotropic light-diffusing layer can be efficiently utilized in the direction to be diffused, and the effect of widening the viewing angle of the anisotropic light-diffusing film can be enhanced.
- the needle-like filler preferably has a refractive index of 1.60 to 1.70 in the minor axis direction.
- the content of the needle-like filler is preferably 1 part by weight or more, 5 parts by weight or more, 10 parts by weight or more, or 15 parts by weight or more when the total solid content of the anisotropic light diffusion layer is 100 parts by weight. It is preferably not more than 40 parts by weight, not more than 30 parts by weight, or not more than 20 parts by weight.
- An anisotropic light diffusing layer may be produced by curing a coating containing a curing agent.
- the curing agent is not particularly limited as long as it does not impair the effects of the present invention, and for example, isocyanate curing agents, aziridine curing agents, epoxy curing agents, metal chelate curing agents and the like can be used. These can be used singly or in combination. Among these, the isocyanate-based curing agent has suitable reactivity and is preferable from the viewpoint of productivity.
- the isocyanate-based curing agent is not particularly limited as long as it does not impede the effects of the present invention.
- Aromatic polyisocyanates such as; hexamethylene diisocyanate (HDI), isophorone diisocyanate, aliphatic polyisocyanates such as dicyclohexamethane diisocyanate; cyclohexane 1,4-diisocyanate, isophorone diisocyanate (IPDI), hydrogenated xylylene diisocyanate, hydrogenated Alicyclic polyisocyanates such as bis(isocyanatophenyl)methane and bicycloheptane triisocyanate; isocyanurate compounds; buret type compounds; These can be used singly or in combination.
- HDI hexamethylene diisocyanate
- isophorone diisocyanate aliphatic polyisocyanates such as dicyclohexamethane diisocyanate
- the anisotropic light-diffusing layer can contain other components.
- Other components are not particularly limited as long as they do not inhibit the effects of the present invention.
- Various additives commonly used in the field of light diffusion films such as ultraviolet absorbers, antioxidants, light stabilizers and surfactants, may be contained.
- ultraviolet absorbers such as ultraviolet absorbers, antioxidants, light stabilizers and surfactants
- conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed description thereof will be omitted.
- the thickness of the anisotropic light diffusion layer is 5 ⁇ m to 20 ⁇ m, more preferably 5 ⁇ m to 15 ⁇ m, even more preferably 5 ⁇ m to 10 ⁇ m.
- the anisotropic light diffusion layer of the present invention can be coated or laminated on a transparent substrate.
- the transparent substrate that can be used is not particularly limited, but the higher the transparency, the better. % or more is more preferable.
- the haze value of the transparent substrate is preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.
- the total light transmittance of the transparent substrate can be measured by a method conforming to JIS K7361, and the haze value of the transparent substrate can be measured by a method conforming to JIS K7136.
- a transparent plastic film, a glass plate, or the like can be used as the transparent substrate, but a plastic film is preferable because it is thin, light, hard to crack, and excellent in productivity.
- PET polyethylene terephthalate
- PEN polyethylene naphthalate
- TAC triacetylcellulose
- PC polycarbonate
- PI polyimide
- PS polysulfone
- PES polyethersulfone
- cellophane polyethylene
- PE polypropylene
- PVA polyvinyl alcohol
- cycloolefin resin etc.
- the transparent substrate a laminate of a plurality of substrates made of the same or different materials can be used as the transparent substrate.
- the thickness of the transparent base material is preferably 1 ⁇ m to 500 ⁇ m, more preferably 25 ⁇ m to 250 ⁇ m, even more preferably 40 ⁇ m to 150 ⁇ m, in consideration of usage and productivity.
- a laminate 1 is prepared by laminating a TAC film on the anisotropic light diffusion layer side of an anisotropic light diffusion film via a 25 ⁇ m-thick transparent adhesive layer (transparent and sticky at room temperature).
- the transparent adhesive layer has, for example, a haze value of 1% and a total light transmittance of 90%, and the TAC film is, for example, FUJITAC TG60UL manufactured by Fujifilm Corporation.
- the laminate 1 is laminated to form a laminate 2 .
- the total light transmittance of the laminate 2 is measured using a haze meter (NDH7000 manufactured by Nippon Denshoku Industries Co., Ltd.).
- the light from the light source is irradiated from one polarizing plate side, and the other polarizing plate side (the polarizing plate where the absorption axis of the polarizing plate and the orientation axis of the needle-like filler in the anisotropic light diffusion layer are not parallel) side.
- Measure the total light transmittance of Also, the haze value (total haze value) of the laminate 1 is measured according to JIS K 7136. From the obtained total light transmittance, [haze value of laminate 1]/[total light transmittance of laminate 2] is calculated, and the obtained value is taken as the degree of orientation.
- the degree of orientation is preferably as high as possible, preferably 8 or more, more preferably 9 or more, even more preferably 10 or more.
- the haze value (total haze value) of the laminate 1 is preferably 15-75, more preferably 20-70.
- the total light transmittance of the laminate 2 is preferably 10% or less, more preferably 9% or less, and even more preferably 5% or less.
- the degree of orientation can be adjusted by the viscosity of the paint, the coating thickness of the paint, the coating speed, and the type of resin and needle-like filler in the paint.
- the thickness of the anisotropic light-diffusing film is preferably 6 ⁇ m to 520 ⁇ m, more preferably 30 ⁇ m to 265 ⁇ m.
- a paint is prepared by stirring a solution containing the components constituting the anisotropic light diffusion layer described above and, if necessary, a volatile solvent. Subsequently, after coating the paint on the transparent substrate described above, the solvent is removed by drying to form a composition (uncured anisotropic light diffusion layer).
- An anisotropic light-diffusing film comprising a transparent substrate and an anisotropic light-diffusing layer can be produced by curing for about 1 day to 2 weeks in a temperature environment of about 60°C.
- the degree of orientation of the needle-like filler can be adjusted by adjusting the size of the needle-like filler, the viscosity of the paint containing the needle-like filler, the coating method, the coating speed, and so on. Also, the thickness of the anisotropic light diffusion layer to be formed can be adjusted by the amount of solvent in the paint.
- the anisotropic light-diffusing film is laminated on the viewing-side polarizing plate (upper polarizing plate) of the liquid crystal display device, and an optical functional layer such as a hard coat layer can be attached to the anisotropic light-diffusing film.
- the anisotropic light-diffusing film is arranged so that the angle difference between the orientation axis of the needle-like filler in the anisotropic light-diffusing layer of the anisotropic light-diffusing film and the absorption axis of the upper polarizing plate of the liquid crystal display device is within ⁇ 5°. It is preferably used by being laminated on the viewing side of the upper polarizing plate of the liquid crystal display device. With such a structure, a display device having an excellent effect of widening the viewing angle can be obtained.
- ⁇ Preparation of anisotropic light diffusion film>> ⁇ Example 1> 72 parts by weight of solid content of acrylic resin 1 (solid content concentration 40%, solvent: ethyl acetate) of Tg 60 ° C., calcium carbonate whiskers (long diameter 10 ⁇ m to 30 ⁇ m, short diameter 0.5 ⁇ m to 1.0 ⁇ m, long diameter 1.49) in ethyl acetate at a concentration of 50 wt%, 26 parts by weight of a needle-like filler (calcium carbonate whisker) and 2 parts by weight of hexamethylene diisocyanate as a curing agent are mixed, and the viscosity is Paint 1 was produced, which had a viscosity of 850 mPa ⁇ s.
- the absolute value of the refractive index difference between the acryl resin and the needle-like filler in the longitudinal direction was zero.
- the paint 1 was applied on a TAC film having a thickness of 60 ⁇ m using an applicator, dried at 100° C. for 3 minutes, and the anisotropic light diffusion film of Example 1 having the anisotropic light diffusion layer 1 on the TAC film got 1.
- the thickness of the anisotropic light diffusion layer 1 was 10 ⁇ m.
- Example 2 The viscosity is 880 mPa s by the same manufacturing method as the anisotropic light diffusion film 1 except that the amount of the solid content of the acrylic resin 1 is 83 parts by weight and the amount of the needle-like filler is 15 parts by weight.
- a paint 2 was prepared. At this time, the absolute value of the refractive index difference between the acryl resin and the needle-like filler in the longitudinal direction was zero. Subsequently, the paint 2 was applied and dried in the same manner as in Example 1 to obtain an anisotropic light diffusion film 2 of Example 2 having an anisotropic light diffusion layer 2 on a TAC film. The thickness of the anisotropic light diffusion layer 2 was 10 ⁇ m.
- Example 3 A manufacturing method similar to that of the anisotropic light diffusion film 1 except that the added amount of the solid content of the acrylic resin 1 was 62 parts by weight, the added amount of the needle-like filler was 37 parts by weight, and the added amount of the curing agent was 1 part by weight.
- a paint 3 having a viscosity of 820 mPa ⁇ s was prepared by the above. At this time, the absolute value of the refractive index difference between the acryl resin and the needle-like filler in the longitudinal direction was zero. Subsequently, the paint 3 was applied and dried in the same manner as in Example 1 to obtain an anisotropic light diffusion film 3 of Example 3 having an anisotropic light diffusion layer 3 on a TAC film. The thickness of the anisotropic light diffusion layer 3 was 10 ⁇ m.
- Example 4 The anisotropic light diffusion layer 4 is formed on the TAC film by the same manufacturing method as the anisotropic light diffusion film 1, except that the paint 1 is applied using an applicator so that the anisotropic light diffusion layer has a thickness of 5 ⁇ m. Anisotropic light diffusion film 4 of Example 4 was obtained. The thickness of the anisotropic light diffusion layer 4 was 5 ⁇ m.
- the anisotropic light diffusion layer 5 is formed on the TAC film by the same manufacturing method as the anisotropic light diffusion film 1, except that the paint 1 is applied using an applicator so that the thickness of the anisotropic light diffusion layer is 20 ⁇ m.
- Anisotropic light diffusion film 5 of Example 5 was obtained.
- the thickness of the anisotropic light diffusion layer 5 was 20 ⁇ m.
- Anisotropic Light Diffusion Film 1 was manufactured by the same method as in the preparation of the anisotropic light diffusion film 1, except that the amount of the needle-like filler added was changed to 26 parts by weight from the dispersion obtained by dispersing the calcium carbonate whiskers of Example 1 in ethyl acetate at a concentration of 60 wt%. , and a viscosity of 1000 mPa ⁇ s. At this time, the absolute value of the refractive index difference between the acryl resin and the needle-like filler in the longitudinal direction was zero.
- Example 6 the paint 4 was applied and dried in the same manner as in Example 1 to obtain an anisotropic light diffusion film 6 of Example 6 having an anisotropic light diffusion layer 6 on a TAC film.
- the thickness of the anisotropic light diffusion layer 6 was 10 ⁇ m.
- Anisotropic Light Diffusion Film 1 was manufactured by the same manufacturing method as in the preparation of the anisotropic light diffusion film 1, except that the amount of the needle-like filler added was changed to 26 parts by weight from the dispersion liquid in which the calcium carbonate whiskers of Example 1 were dispersed in ethyl acetate at a concentration of 20 wt%. , and a viscosity of 230 mPa ⁇ s was prepared. At this time, the absolute value of the refractive index difference between the acryl resin and the needle-like filler in the longitudinal direction was zero.
- Example 2 the paint a was applied and dried in the same manner as in Example 1 to obtain an anisotropic light-diffusing film a of Comparative Example 1 having an anisotropic light-diffusing layer a on a TAC film.
- the thickness of the anisotropic light diffusion layer a was 10 ⁇ m.
- the anisotropic light diffusion layer b is formed on the TAC film by the same manufacturing method as the anisotropic light diffusion film 1, except that the paint 1 is applied using an applicator so that the thickness of the anisotropic light diffusion layer is 25 ⁇ m.
- An anisotropic light diffusion film b of Comparative Example 2 was obtained. The thickness of the anisotropic light diffusion layer b was 25 ⁇ m.
- the laminate 1 was laminated to produce a laminate 2 . Subsequently, based on JIS K 7361, the total light transmittance of the laminate 2 was measured using a haze meter (NDH7000 manufactured by Nippon Denshoku Industries Co., Ltd.).
- the light from the light source is irradiated from one polarizing plate side, and the other polarizing plate side (the polarizing plate where the absorption axis of the polarizing plate and the orientation axis of the needle-like filler in the anisotropic light diffusion layer are not parallel) side.
- the haze value (total haze value) of the laminate 1 was measured according to JIS K 7136. From the obtained total light transmittance, [haze value of laminate 1]/[total light transmittance of laminate 2] was calculated, and the value was taken as the degree of orientation.
- Table 1 shows the total light transmittance of the laminate 2, the haze value of the laminate 1, and the degree of orientation in each example and comparative example. It was evaluated that the larger the value of the degree of orientation, the better the orientation of the needle-like filler.
- the absorption axis of the upper polarizing plate (visible side) of the liquid crystal display and the alignment axis of the needle-like filler of the anisotropic light-diffusing layer of each anisotropic light-diffusing film of Examples and Comparative Examples were made parallel, Each anisotropic light-diffusing film was laminated via the transparent adhesive layer on the anisotropic light-diffusing layer. From the viewing side of the liquid crystal display with an anisotropic light diffusion film, using a brightness viewing angle measuring device (manufactured by TEM Co., CONOMETER 80), -80 ° to +80 ° in the direction perpendicular to the orientation direction of the needle-like filler.
- a brightness viewing angle measuring device manufactured by TEM Co., CONOMETER 80
- the brightness in white display and the brightness in black display were measured in the range of .
- the contrast ratio (white luminance / black luminance) from the measured values of white luminance and black luminance at each angle
- the front direction contrast ratio ((contrast ratio at 0 °) / (contrast ratio at 0 ° of the liquid crystal display) ) ⁇ 100
- 60° direction contrast ratio ((contrast ratio at 60°)/(contrast ratio at 0° of liquid crystal display)) ⁇ 100.
- Table 1 shows the front direction contrast ratio and the 60° direction contrast ratio in each example and comparative example.
- the relationship between the contrast ratios in each direction was graphed with the 60° direction contrast ratio on the X axis and the front direction contrast ratio on the Y axis, and shown in FIG.
- the anisotropic light-diffusing film of each example had a field-enlarging effect with an excellent balance between the front direction contrast ratio and the 60° direction contrast ratio.
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Abstract
Description
等方性透明樹脂マトリックス及び針状フィラーを含有する異方性光拡散層と、透明基材と、を有する異方性光拡散フィルムであって、
前記針状フィラーは、前記等方性透明樹脂マトリックス内で一方向に配向して分散しており、
前記異方性光拡散フィルムの配向度が8以上であり、
前記異方性光拡散層の厚みが5μm~20μmであり、
前記針状フィラーの配向軸と、液晶表示装置の上偏光板の吸収軸との角度差が±5°以内で、かつ、前記上偏光板の視認側に積層して用いられることを特徴とする異方性光拡散フィルムである。
異方性光拡散フィルムの配向度は、以下の方法によって測定することができる。
(配向度の測定方法)
異方性光拡散フィルムの異方性光拡散層側に、25μmの厚みの透明粘着層を介してTACフィルムを貼合した積層体1を作製する。
吸収軸が互いに90°異なる(クロスニコル)構成2枚の偏光板間に、一方の偏光板の吸収軸と、積層体1内異方性光拡散層針状フィラーの配向軸とが平行となるように、積層体1を積層して積層体2とする。
続いて、JIS K 7361に準拠して積層体2の全光線透過率の測定を行う。このとき光源からの光の照射は、一方の偏光板側より照射し、他方の偏光板(偏光板の吸収軸と、異方性光拡散層の針状フィラーの配向軸とが平行でない偏光板)側の全光線透過率を測定する。
また、JIS K 7136に準拠して積層体1のヘイズ値(全ヘイズ値)を測定する。
得られた全光線透過率より、[積層体1のヘイズ値]/[積層体2の全光線透過率]を算出し、その値を配向度とする。
前記等方性透明樹脂マトリックスは、ガラス転移温度が40℃~160℃であるアクリル樹脂であることが好ましい。
前記針状フィラーの長径方向の屈折率と、前記等方性透明樹脂マトリックスの屈折率との絶対値差が0.03以下であることが好ましい。
フィルムの厚みが6μm~520μmであることが好ましい。
異方性光拡散フィルムは、異方性光拡散層と、透明基材と、を有する。
異方性光拡散層は、等方性透明樹脂マトリックスと、針状フィラーと、を含有する。また、異方性光拡散層は、その他の成分を含んでいてもよい。
<等方性透明樹脂マトリックス>
等方性透明樹脂マトリックス材料は、特に限定されないが、光学的透明性が高く、異方性光拡散フィルムとしての物理的強度を有する高分子樹脂が使用可能である。また、この高分子樹脂には透明基材との高い密着性が求められる。使用可能な高分子樹脂の具体例としては、アクリル樹脂、スチレン樹脂、スチレン-アクリル共重合体、ポリウレタン樹脂、ポリエステル樹脂、エポキシ樹脂、セルロース系樹脂、酢酸ビニル系樹脂、塩ビ-酢ビ共重合体、ポリビニルブチラール樹脂、シクロオレフィン樹脂、ノルボルネン樹脂等が挙げられ、これらの単独もしくは混合物を利用することができる。これらの高分子樹脂は、通常有機溶剤に溶解して使用されるが、熱硬化や光硬化のシステムを導入したり、無溶剤系の材料を使用することも可能である。
ガラス転移温度は、公知の方法で測定することができ、公知の測定方法を用いることができ、例えば、JIS K7121-1987「プラスチックの転移温度測定方法」に準拠する方法により測定することができる。
等方性透明樹脂マトリックスの屈折率は、JIS K-7142(1996)に記載のA法に準拠する方法により測定することができる。
針状フィラーは、異方性光拡散層の等方性透明樹脂マトリックス内で一方向に配向して分散している。
針状フィラーは、針状(繊維状を含む)を呈する高アスペクト比のフィラーであれば特に限定されないが、本発明の異方性光拡散フィルムを液晶表示装置等に用いる場合、透過光の着色を防ぐために、無色又は白色のものが好ましい。
針状フィラーの短径は、0.1μm~3μmであることが好ましく、0.3μm~2μmであることがより好ましく、0.5μm~1μmであることが更に好ましい。
針状フィラーのアスペクト比をこのような範囲とすることで、異方性光拡散層内の針状フィラーの配向度を高めることが可能である。
針状フィラーは、長径方向の屈折率が、1.45~1.55であることが好ましい。
針状フィラーの含有量は、異方性光拡散層の全固形分を100重量部としたとき、1重量部以上、5重量部以上、10重量部以上又は15重量部以上とすることが好ましく、50重量部以下、40重量部以下、30重量部以下又は20重量部以下であることが好ましい。
針状フィラーの含有量をこのような範囲とすることで、異方性光拡散層内の針状フィラーによる光の拡散が最適となり、異方性光拡散フィルムの視野角拡大効果を高めることが可能である。
異方性光拡散層は、硬化剤を含む塗料を硬化させることで製造されてもよい。
硬化剤は本発明の効果を阻害しない限りにおいて特に限定されず、例えば、イソシアネート系硬化剤、アジリジン系硬化剤、エポキシ系硬化剤、金属キレート型硬化剤等を用いることができる。これらは、単独で、又は、複数を組み合わせて用いることができる。これらのうち、イソシアネート系硬化剤が適当な反応性を有しており、生産性の観点で好ましい。
異方性光拡散層は、その他の成分を含むことができる。その他の成分としては、本発明の効果を阻害しない限りにおいて特に限定されず、例えば、カップリング剤、レベリング剤、架橋助剤、可塑剤、軟化剤、充填剤、帯電防止剤、老化防止剤、紫外線吸収剤、酸化防止剤、光安定剤、界面活性剤等の、光拡散フィルムの分野において一般的な各種の添加剤を含有してもよい。このような各種添加剤については、従来公知のものを常法により使用することができ、特に本発明を特徴づけるものではないので、詳細な説明は省略する。
異方性光拡散層の厚みは、5μm~20μmであり、5μm~15μmであることがより好ましく、5μm~10μmであることが更に好ましい。異方性光拡散層の厚みをこのような範囲とすることで、異方性光拡散層内の針状フィラーの配向度を高めることが可能である。
本発明の異方性光拡散層は、透明基材上に塗工、または積層することができる。使用可能な透明基材としては、特に限定されないが、透明性が高いもの程良好であって、全光線透過率が80%以上であることが好ましく、85%以上であることがより好ましく、90%以上であることが更に好ましい。また、透明基材のヘイズ値は、3.0%以下であることが好ましく、1.0%以下であることがより好ましく、0.5%以下であることが更に好ましい。
透明基材の全光線透過率は、JIS K7361に準拠する方法により測定することができ、また、透明基材のヘイズ値は、JIS K7136に準拠する方法により測定することができる。
透明基材は、透明なプラスチックフィルムやガラス板等が使用可能であるが、薄く、軽く、割れ難く、生産性に優れる点でプラスチックフィルムが好適である。具体的にはポリエチレンテレフタレート(PET)、ポリエチレンナフタレート(PEN)、トリアセチルセルロース(TAC)、ポリカーボネート(PC)、ポリアリレート、ポリイミド(PI)、芳香族ポリアミド、ポリスルホン(PS)、ポリエーテルスルホン(PES)、セロファン、ポリエチレン(PE)、ポリプロピレン(PP)、ポリビニルアルコール(PVA)、シクロオレフィン樹脂等が挙げられ、これらの単独又は混合の材質とすることができる。更には、透明基材としては、同一又は異なる材質からなる基材を複数積層したものを用いることができる。
透明基材の厚みは、用途や生産性を考慮すると1μm~500μmであることが好ましく、25μm~250μmであることがより好ましく、40μm~150μmであることが更に好ましい。
<<針状フィラーの配向度>>
針状フィラーは、異方性光拡散層内で一方向に配向して分散している。
ここで、本発明においては、以下の方法によって算出される[積層体1のヘイズ値]/[積層体2の全光線透過率]を、配向性の指標である「配向度」と称すこととする。
異方性光拡散フィルムの異方性光拡散層側に25μmの厚みの透明粘着層(透明であり、常温で粘着性を有するもの)を介してTACフィルムを貼合した積層体1を作製する。なお、透明粘着層は、例えば、ヘイズ値1%、全光線透過率90%のものであり、TACフィルムは、例えば、富士フィルム社製のフジタックTG60ULである。
吸収軸が互いに90°異なる(クロスニコル構成)2枚の偏光板間に、一方の偏光板の吸収軸と、積層体1内異方性光拡散層針状フィラーの配向軸とが平行となるように、積層体1を積層して積層体2とする。
続いて、JIS K 7361に準拠し、ヘイズメーター(日本電色工業社製、NDH7000)を用いて積層体2の全光線透過率の測定を行う。このとき光源からの光の照射は、一方の偏光板側より照射し、他方の偏光板(偏光板の吸収軸と、異方性光拡散層の針状フィラーの配向軸とが平行でない偏光板)側の全光線透過率を測定する。
また、JIS K 7136に準拠して、積層体1のヘイズ値(全ヘイズ値)を測定する。
得られた全光線透過率より、[積層体1のヘイズ値]/[積層体2の全光線透過率]を算出し、その値を配向度とする。
このとき、配向度が大きい程、二枚の偏光板の透過軸が互いに90°の関係(クロスニコル)となっていることに対する異方性光拡散フィルムの影響が少ない、つまり、針状フィラーの配向性が良好であることを示すこととなる。配向度は大きい方が好ましく、8以上であることが好ましく、9以上であることがより好ましく、10以上であることが更に好ましい。
配向度をこのような範囲とすることで、異方性光拡散層内の針状フィラーによる光の拡散が最適となり、異方性光拡散フィルムの視野角拡大効果を高めることが可能である。
異方性光拡散フィルムの厚みは、6μm~520μmであることが好ましく、30μm~265μmであることがより好ましい。
以下、異方性光拡散フィルムの製造方法の一例を示す。
続いて塗料を上述した透明基材上に塗工した後、溶剤を乾燥除去して組成物(未硬化異方性光拡散層)とし、さらに必要に応じて組成物の硬化のために、室温又は30℃~60℃程度の温度環境下で1日~2週間程度養生することにより、透明基材と異方性光拡散層よりなる異方性光拡散フィルムを製造できる。
異方性光拡散フィルムは、液晶表示装置の視認側偏光板(上偏光板)上に積層され、更に、異方性光拡散フィルムには、ハードコート層等の光学機能層を貼り合わせることができる。
<実施例1>
Tg=60℃のアクリル樹脂1(固形分濃度40%、溶剤:酢酸エチル)の固形分72重量部と、炭酸カルシウムウィスカー(長径10μm~30μm、短径0.5μm~1.0μm、長径方向屈折率1.49)を酢酸エチルに50wt%の濃度で分散させた分散液より、針状フィラー(炭酸カルシウムウィスカー)26重量部と、硬化剤としてヘキサメチレンジイソシアネート2重量部とを混合し、粘度が850mPa・sである、塗料1を作製した。このとき、アクリル樹脂と、針状フィラー長径方向との屈折率差の絶対値は0であった。
続いて塗料1を、60μmの厚みのTACフィルム上にアプリケーターを用いて塗工した後、100℃で3分間乾燥し、TACフィルム上に異方性光拡散層1を有する実施例1の異方性光拡散フィルム1を得た。なお、異方性光拡散層1の厚みは10μmであった。
アクリル樹脂1の固形分の添加量を83重量部、針状フィラーの添加量を15重量部とした他は、異方性光拡散フィルム1の作製と同様の製法により、粘度が880mPa・sである、塗料2を作製した。このとき、アクリル樹脂と、針状フィラー長径方向との屈折率差の絶対値は0であった。
続いて塗料2を、実施例1と同様に塗工、乾燥し、TACフィルム上に異方性光拡散層2を有する実施例2の異方性光拡散フィルム2を得た。なお、異方性光拡散層2の厚みは10μmであった。
アクリル樹脂1の固形分の添加量を62重量部、針状フィラーの添加量を37重量部、硬化剤の添加量を1重量部とした他は、異方性光拡散フィルム1の作製と同様の製法により、粘度が820mPa・sである、塗料3を作製した。このとき、アクリル樹脂と、針状フィラー長径方向との屈折率差の絶対値は0であった。
続いて塗料3を、実施例1と同様に塗工、乾燥し、TACフィルム上に異方性光拡散層3を有する実施例3の異方性光拡散フィルム3を得た。なお、異方性光拡散層3の厚みは10μmであった。
塗料1を、異方性光拡散層の厚みが5μmとなるようにアプリケーターを用いて塗工した他は、異方性光拡散フィルム1の作製と同様の製法により、TACフィルム上に異方性光拡散層4を有する実施例4の異方性光拡散フィルム4を得た。なお、異方性光拡散層4の厚みは5μmであった。
塗料1を、異方性光拡散層の厚みが20μmとなるようにアプリケーターを用いて塗工した他は、異方性光拡散フィルム1の作製と同様の製法により、TACフィルム上に異方性光拡散層5を有する実施例5の異方性光拡散フィルム5を得た。なお、異方性光拡散層5の厚みは20μmであった。
実施例1の炭酸カルシウムウィスカーを酢酸エチルに60wt%の濃度で分散させた分散液より、針状フィラーの添加量を26重量部とした他は、異方性光拡散フィルム1の作製と同様の製法により、粘度が1000mPa・sである、塗料6を作製した。このとき、アクリル樹脂と、針状フィラー長径方向との屈折率差の絶対値は0であった。
続いて塗料4を、実施例1と同様に塗工、乾燥し、TACフィルム上に異方性光拡散層6を有する実施例6の異方性光拡散フィルム6を得た。なお、異方性光拡散層6の厚みは10μmであった。
実施例1の炭酸カルシウムウィスカーを酢酸エチルに20wt%の濃度で分散させた分散液より、針状フィラーの添加量を26重量部とした他は、異方性光拡散フィルム1の作製と同様の製法により、粘度が230mPa・sである、塗料aを作製した。このとき、アクリル樹脂と、針状フィラー長径方向との屈折率差の絶対値は0であった。
続いて塗料aを、実施例1と同様に塗工、乾燥し、TACフィルム上に異方性光拡散層aを有する比較例1の異方性光拡散フィルムaを得た。なお、異方性光拡散層aの厚みは10μmであった。
塗料1を、異方性光拡散層の厚みが25μmとなるようにアプリケーターを用いて塗工した他は、異方性光拡散フィルム1の作製と同様の製法により、TACフィルム上に異方性光拡散層bを有する比較例2の異方性光拡散フィルムbを得た。なお、異方性光拡散層bの厚みは25μmであった。
上記で得られた実施例1~6及び比較例1、2の異方性光拡散フィルムに対し、以下評価を実施し、結果を表1及び図1に示した。
本評価は、実施例及び比較例の合計8種の異方性光拡散フィルムに対し、個別に下記評価を合計8回行った。
実施例及び比較例の異方性光拡散フィルムの異方性光拡散層側に25μmの厚みの透明粘着層(ヘイズ値1%、全光線透過率90%)を介してTACフィルム(富士フィルム社製、フジタックTG60UL)を貼合した積層体1を作製した。
吸収軸が互いに90°異なる(クロスニコル構成)2枚の偏光板間に、一方の偏光板の吸収軸と、積層体1内異方性光拡散層針状フィラーの配向軸とが平行となるように、積層体1を積層して積層体2を作製した。
続いて、JIS K 7361に準拠し、ヘイズメーター(日本電色工業社製、NDH7000)を用いて積層体2の全光線透過率の測定を行った。このとき光源からの光の照射は、一方の偏光板側より照射し、他方の偏光板(偏光板の吸収軸と、異方性光拡散層の針状フィラーの配向軸とが平行でない偏光板)側の全光線透過率を測定した。
また、JIS K 7136に準拠して、積層体1のヘイズ値(全ヘイズ値)を測定した。
得られた全光線透過率より、[積層体1のヘイズ値]/[積層体2の全光線透過率]を算出し、その値を配向度とした。各実施例及び比較例における、積層体2の全光線透過率、積層体1のヘイズ値、配向度を表1に示した。
なお、配向度の値が大きい程、針状フィラーの配向性が優れているものと評価した。
実施例及び比較例の各異方性光拡散フィルムの異方性光拡散層側に25μmの厚みの透明粘着層(ヘイズ値1%、全光線透過率90%)を貼合し、VA方式の液晶ディスプレイの画面表面に、液晶ディスプレイの上偏光板(視認側)の吸収軸と、実施例及び比較例の各異方性光拡散フィルムの異方性光拡散層の針状フィラーの配向軸とが平行となるようにして、異方性光拡散層上の透明粘着層を介して各異方性光拡散フィルムを積層した。
異方性光拡散フィルム付液晶ディスプレイの視認側より、輝度視野角測定器(ティー・イー・エム社製、CONOMETER 80)を用いて、針状フィラーの配向方向に直行する方向の-80°~+80°の範囲における、白表示での輝度と、黒表示での輝度とを測定した。
各角度における白輝度と黒輝度の測定値よりコントラスト比(白輝度/黒輝度)を算出した後、正面方向コントラスト比:((0°におけるコントラスト比)/(液晶ディスプレイの0°におけるコントラスト比))×100、60°方向コントラスト比:((60°におけるコントラスト比)/(液晶ディスプレイ0°におけるコントラスト比))×100、として算出した。各実施例及び比較例における、正面方向コントラスト比、60°方向コントラスト比を表1に示した。
更に、各方向コントラスト比の関係を、60°方向コントラスト比をX軸、正面方向コントラスト比をY軸としてグラフ化し、図1に示した。
図1に示されるように、各実施例の異方性光拡散フィルムは、正面方向コントラスト比及び60°方向コントラスト比のバランスに優れた視野拡大効果を有していた。
Claims (6)
- 等方性透明樹脂マトリックス及び針状フィラーを含有する異方性光拡散層と、透明基材と、を有する異方性光拡散フィルムであって、
前記針状フィラーは、前記等方性透明樹脂マトリックス内で一方向に配向して分散しており、
前記異方性光拡散フィルムの配向度が8以上であり、
前記異方性光拡散層の厚みが5μm~20μmであり、
前記針状フィラーの配向軸と、液晶表示装置の上偏光板の吸収軸との角度差が±5°以内で、かつ、前記上偏光板の視認側に積層して用いられることを特徴とする異方性光拡散フィルム。 - 前記針状フィラーは、短径が0.1μm~10μmであり、長径が2μm~1000μmであり、アスペクト比が10~100であることを特徴とする請求項1に記載の異方性光拡散フィルム。
- 前記等方性透明樹脂マトリックスは、ガラス転移温度が40℃~160℃であるアクリル樹脂であることを特徴とする請求項1又は2に記載の異方性光拡散フィルム。
- 前記針状フィラーの長径方向の屈折率と、前記等方性透明樹脂マトリックスの屈折率との絶対値差が0.03以下であることを特徴とする請求項1~3のいずれか1項に記載の異方性光拡散フィルム。
- フィルムの厚みが6μm~520μmであることを特徴とする請求項1~4のいずれか1項に記載の異方性光拡散フィルム。
- 液晶表示装置の上偏光板の視認側に、請求項1~5のいずれか1項に記載の異方性光拡散フィルムが、前記異方性光拡散フィルム中の前記針状フィラーの配向軸と、前記上偏光板の吸収軸との角度差が±5°以内で積層されていることを特徴とする表示装置。
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Publication number | Priority date | Publication date | Assignee | Title |
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JP2004184860A (ja) * | 2002-12-05 | 2004-07-02 | Fuji Photo Film Co Ltd | 偏光板、および液晶表示装置 |
JP2008158462A (ja) * | 2006-12-26 | 2008-07-10 | Tomoegawa Paper Co Ltd | 拡散偏光子及びそれを含む光学素子 |
JP2010117497A (ja) * | 2008-11-12 | 2010-05-27 | Tosoh Corp | 光学フィルム |
JP2015127819A (ja) * | 2015-02-05 | 2015-07-09 | 株式会社巴川製紙所 | 表示装置 |
US20200348557A1 (en) * | 2019-04-30 | 2020-11-05 | Samsung Display Co., Ltd. | Optical film for display device and display device having the same |
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JP2004184860A (ja) * | 2002-12-05 | 2004-07-02 | Fuji Photo Film Co Ltd | 偏光板、および液晶表示装置 |
JP2008158462A (ja) * | 2006-12-26 | 2008-07-10 | Tomoegawa Paper Co Ltd | 拡散偏光子及びそれを含む光学素子 |
JP2010117497A (ja) * | 2008-11-12 | 2010-05-27 | Tosoh Corp | 光学フィルム |
JP2015127819A (ja) * | 2015-02-05 | 2015-07-09 | 株式会社巴川製紙所 | 表示装置 |
US20200348557A1 (en) * | 2019-04-30 | 2020-11-05 | Samsung Display Co., Ltd. | Optical film for display device and display device having the same |
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