CN110346861A - Optical laminate and image display device - Google Patents

Abstract

The present invention provides a kind of optical laminate, and it includes polarizing film and the optical film being laminated in one face, which projects after rectilinearly polarized light is transformed to elliptically polarized light, meets following formula: (1) 100nm≤R_e(590)≤180nm, (2) 0.5 < R_th(590)/R_e(590)≤0.8、(3)0.85≤R_e(450)/R_e(550) < 1.00 and (4) 1.00 < R_e(630)/R_e(550)≤1.1, in formula, R_e(590)、R_e(450)、R_e(550)、R_e(630) phase difference value in face when respectively indicating measurement wavelength 590nm, 450nm, 550nm, 630nm, R_th(590) thickness direction phase difference value when measurement wavelength 590nm is indicated, further, it would be desirable to provide the image display devices for having used the optical laminate.

Description

Optical laminate and image display device

This application is a divisional application of the application submitted by the applicant with the application number 201580027106.3 and the title of the invention "Optical laminate and image display device". The filing date of the parent case is May 8, 2015, and the priority date is May 23, 2014.

technical field

The present invention relates to an optical laminate including a polarizing plate, and an image display device using the optical laminate.

Background technique

Image display devices typified by liquid crystal display devices are installed in many mobile devices such as mobile phones, smartphones, tablet information terminals, portable televisions, digital cameras, and navigators. For example, when such a mobile device is used outdoors, the screen of the image display device may be observed while wearing polarized sunglasses. In this case, the image display device is required to have excellent visibility even when viewing the screen through polarized sunglasses.

Conventionally, several methods for improving the visibility when viewing a screen through polarized sunglasses have been proposed (Patent Documents 1 to 10).

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2009-122454

Patent Document 2: Japanese Unexamined Patent Publication No. 2011-107198

Patent Document 3: Japanese Patent Laid-Open No. 2011-215646

Patent Document 4: Japanese Unexamined Patent Publication No. 2012-230390

Patent Document 5: Japanese Patent Application Laid-Open No. 03-174512

Patent Document 6: Japanese Unexamined Patent Publication No. 2013-231761

Patent Document 7: Japanese Patent Laid-Open No. 2011-113018

Patent Document 8: Japanese Patent Laid-Open No. 2013-182162

Patent Document 9: Japanese Unexamined Patent Publication No. 2013-200445

Patent Document 10: Japanese Patent Laid-Open No. 2010-091655

Contents of the invention

The problem to be solved by the invention

Conventional methods for improving viewing performance when viewing a screen through polarized sunglasses can be roughly divided into: arranging a polarizing plate on the viewing side of an image display element such as a liquid crystal cell; A method for converting the linearly polarized light emitted from the polarizing plate into an elliptical (or circular) polarized light retardation plate (such as a λ/4 wavelength plate) (patent documents 1 to 9); and for disposing on the observation side of the above-mentioned polarizing plate A method for converting the linearly polarized light into non-polarized light with a polarization canceling layer (Patent Document 10).

However, the above-mentioned methods proposed in the prior art are all methods related to the technology for suppressing the brightness of the screen when viewing through polarized sunglasses depends on the absorption axis and the polarizing plate arranged on the viewing side of the image display element. The angles formed by the absorption axes of polarized sunglasses vary, not a technique related to the technique of suppressing changes in color tone (color smell) when the screen is viewed from various directions (azimuth angle and polar angle).

The object of the present invention is to provide an optical layered body of an image display device that can realize a small change in color tone when the screen is viewed from various directions (azimuth and polar angles) through polarized sunglasses, and the observability using the optical layered body. Good image display device.

method used to solve the problem

The present invention provides the following optical laminate and image display device.

[1] An optical laminate comprising a polarizing plate and an optical film laminated on one surface thereof,

The optical film converts linearly polarized light into elliptically polarized light and emits it, and satisfies the following formula:

(1) 100nm≤R _e (590)≤180nm,

(2) 0.5<R _th (590)/R _e (590)≤0.8,

(3) 0.85≤R _e (450)/R _e (550)<1.00, and

(4) 1.00<R _e (630)/R _e (550)≤1.1

In the formula, _Re (590), _Re (450), _Re (550), and _Re (630) respectively represent the in-plane retardation values when measuring wavelengths of 590nm, 450nm, 550nm, and 630nm, and R _th (590) Indicates the retardation value in the thickness direction at the measurement wavelength of 590 nm.

[2] The optical laminate according to [1], wherein the angle formed by the slow axis of the optical film and the absorption axis of the polarizer is 45±20° or 135±20°.

[3] The optical laminate according to [1] or [2], wherein the optical film contains a cyclic polyolefin-based resin, a polycarbonate-based resin, a cellulose-based resin, a polyester-based resin, or (a base) acrylic resin.

[4] The optical laminate according to any one of [1] to [3], wherein the optical film is laminated on the polarizing plate with a first pressure-sensitive adhesive layer or an adhesive layer interposed therebetween.

[5] The optical laminate according to any one of [1] to [4], further comprising a second pressure-sensitive adhesive layer laminated on the surface of the polarizer opposite to the optical film .

[6] The optical laminate according to any one of [1] to [4], further comprising a thermoplastic resin film laminated on the surface of the polarizing plate opposite to the optical film.

[7] The optical laminate according to [6], wherein the thermoplastic resin film is a retardation film.

[8] The optical laminate according to [6] or [7], further comprising a third pressure-sensitive adhesive layer laminated on the surface of the thermoplastic resin film opposite to the polarizing plate.

[9] An image display device comprising an image display element and the optical laminate according to any one of [1] to [8],

The optical laminate is arranged such that the polarizing plate is on the image display element side.

Invention effect

According to the present invention, it is possible to provide an optical laminate capable of realizing an image display device with a small change in color tone when the screen is viewed from various directions (azimuth angle and polar angle) through polarized sunglasses, and an image display device using the same.

Description of drawings

FIG. 1 is a schematic cross-sectional view showing an example of the layer constitution of the optical laminate of the present invention.

Fig. 2 is a schematic cross-sectional view showing another example of the layer constitution of the optical laminate of the present invention.

3 is a schematic cross-sectional view showing another example of the layer constitution of the optical laminate of the present invention.

4 is a schematic cross-sectional view showing another example of the layer constitution of the optical laminate of the present invention.

5 is a schematic diagram illustrating an azimuth angle and a polar angle indicating a direction in which a screen of an image display device is viewed.

FIG. 6 is a diagram illustrating an angle θ formed by a slow axis of an optical film and an absorption axis of a polarizing plate.

7 is a schematic cross-sectional view showing an example of the layer configuration of the liquid crystal display device of the present invention.

Fig. 8 is a side view and an exploded perspective view schematically showing a measurement system for color tone change.

FIG. 9 is an xy chromaticity diagram obtained for the optical laminate of Example 1. FIG.

FIG. 10 is an xy chromaticity diagram obtained for the optical laminate of Example 2. FIG.

FIG. 11 is an xy chromaticity diagram obtained for the optical laminate of Example 3. FIG.

FIG. 12 is an xy chromaticity diagram obtained for the optical laminate of Comparative Example 1. FIG.

FIG. 13 is an xy chromaticity diagram obtained for the optical laminate of Comparative Example 2. FIG.

FIG. 14 is an xy chromaticity diagram obtained for the optical laminate of Comparative Example 3. FIG.

FIG. 15 is an xy chromaticity diagram obtained for the optical laminate of Comparative Example 4. FIG.

FIG. 16 is an xy chromaticity diagram obtained for the optical laminate of Comparative Example 5. FIG.

FIG. 17 is an xy chromaticity diagram obtained for the optical laminate of Comparative Example 6. FIG.

Detailed ways

Hereinafter, the optical laminate and the image display device of the present invention will be described in detail by giving embodiments.

＜Optical laminates＞

[a] Layer composition of the optical laminate

The optical laminate of the present invention includes a polarizing plate and an optical film laminated on one surface thereof. An example of the layer constitution of the optical laminate of the present invention is shown in FIG. 1 . The optical laminate 1 shown in FIG. 1 includes a polarizing plate 10 and an optical film 20 laminated on one surface of the polarizing plate 10 with a first pressure-sensitive adhesive layer or an adhesive layer 25 interposed therebetween. In the optical laminate of the present invention, the optical film 20 is an optical element disposed on one side of the polarizing plate 10, and has the function of converting the linearly polarized light emitted from the polarizing plate 10 to the optical film 20 into elliptically polarized light (including circularly polarized light). case) and the function of injection.

Not limited to the example in FIG. 1 , the optical laminate of the present invention may further include another layer laminated on the surface of the polarizing plate 10 opposite to the optical film 20 . Examples of optical laminates including other layers are shown in FIGS. 2 and 3 . The optical laminate 2 shown in FIG. 2 includes a polarizing plate 10; an optical film 20 laminated on one side of the polarizing plate 10 via a first adhesive layer or an adhesive layer 25; The second adhesive layer 30 on the side opposite to the 20.

The optical laminate 3 shown in FIG. 3 comprises a polarizing plate 10; an optical film 20 laminated on one side of the polarizing plate 10 via a first adhesive layer or an adhesive layer 25; Or the adhesive layer 45 is laminated on the first thermoplastic resin film 40 on the side opposite to the optical film 20 of the polarizing plate 10; Three adhesive layers 50 . In the optical laminate 3, the third pressure-sensitive adhesive layer 50 may also be omitted.

The 2nd adhesive layer 30 or the 3rd adhesive layer 50 arrange|positioned at the outermost side of an optical laminated body can be used for bonding an optical laminated body to another optical member, such as an image display element, for example.

Moreover, like the optical laminated body 4 shown in FIG. 4, the 2nd thermoplastic resin film 60 may be interposed between the polarizing plate 10 and the optical film 20. The second thermoplastic resin film 60 can be bonded to the polarizing plate 10 via the adhesive layer 65 , for example.

〔b〕Polarizer

The polarizer 10 may be an optical element having a property of absorbing linearly polarized light having a vibration plane parallel to the optical axis (absorption axis) and transmitting linearly polarized light having a vibration plane perpendicular to the optical axis. Specifically, it may be An optical element in which a dichroic dye (iodine or a dichroic organic dye) is adsorbed and aligned on a polyvinyl alcohol-based resin film is suitably used.

The polyvinyl alcohol-based resin constituting the polarizing plate 10 can be obtained by saponifying polyvinyl acetate-based resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers that can be copolymerized therewith, and the like can be exemplified. Examples of other monomers to be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group. The saponification degree of polyvinyl alcohol-type resin is about 85-100 mol% normally, Preferably it is 98 mol% or more. The polyvinyl alcohol-based resin may be further modified. For example, polyvinyl formal and polyvinyl acetal modified with aldehydes may be used.

In addition, "(meth)acrylic acid" in this specification means at least one selected from acrylic acid and methacrylic acid. The same applies when referring to "(meth)acryloyl" and the like.

The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. Examples of specific polyvinyl alcohol-based resins or dichroic dyes include those exemplified in JP-A-2012-159778.

A film obtained by forming the above-mentioned polyvinyl alcohol-based resin into a film can be used as a raw material film of the polarizing plate 10 . The polyvinyl alcohol-based resin can be formed into a film by a known method. The thickness of the raw material film containing polyvinyl alcohol-type resin is about 1-150 micrometers, for example. In consideration of easiness of stretching, etc., the thickness is preferably 10 μm or more.

The polarizing plate 10 can be manufactured, for example, through the steps of uniaxially stretching the above-mentioned polyvinyl alcohol-based resin film; A step of dyeing the dye to adsorb the dichroic dye; a step of treating the polyvinyl alcohol-based resin film having the dichroic dye adsorbed thereon with an aqueous solution of boric acid; a step of washing with water after the treatment with the aqueous solution of boric acid; and drying process. The thickness of the polarizing plate 10 is usually about 2 to 40 μm, preferably about 3 to 30 μm.

The polarizing plate 10 can be manufactured according to the method described in Unexamined-Japanese-Patent No. 2012-159778, for example. In the method described in this document, instead of using the raw material film containing the above-mentioned polyvinyl alcohol-based resin, a polyvinyl alcohol-based resin layer is formed by coating the polyvinyl alcohol-based resin on the base film, and then stretched. After stretching and dyeing to form a polarizer layer (polarizer 10), a thermoplastic resin film such as a protective film is bonded.

〔c〕Optical film

The optical film 20 laminated on one face of the polarizing plate 10 is a film satisfying the following formula:

(1) 100nm≤R _e (590)≤180nm,

(2) 0.5<R _th (590)/R _e (590)≤0.8,

(3) 0.85≤R _e (450)/R _e (550)<1.00, and

(4) 1.00<R _e (630)/R _e (550)≦1.1.

In the formula, _Re (590), _Re (450), _Re (550), and _Re (630) respectively represent the in-plane retardation values when measuring wavelengths of 590nm, 450nm, 550nm, and 630nm, and R _th (590) Indicates the retardation value in the thickness direction at the measurement wavelength of 590 nm. These in-plane retardation values and thickness direction retardation values were measured in an environment with a temperature of 23° C. and a relative humidity of 55%.

Regarding the in-plane retardation value _Re and the thickness direction retardation value _Rth of the optical film 20, when the refractive index in the in-plane slow axis direction is _nx , and the in-plane fast axis direction (positive to the in-plane slow axis direction) When the refractive index in the intersecting direction is _ny , the refractive index in the thickness direction is _nz , and the thickness of the optical film 20 is d, it is defined by the following formula:

R _e = (n _x - n _y ) × d

_Rth ＝[{(n _x +n _y )/2}－n _z ]×d

According to the optical layered body in which the optical film 20 exhibiting the phase difference characteristics and wavelength dispersion characteristics of the above formulas (1) to (4) is laminated on one surface of the polarizing plate 10, when applied to an image display device ( More specifically, when the viewing side of the image display element is used as a polarizing plate configured so that the polarizing plate 10 is on the image display device side), it is possible to maintain viewing angles from various directions (azimuth angles) across polarized sunglasses. And polar angle) brightness when watching the picture, effectively suppress the color tone change, can improve the observability of the image display device. On the other hand, when any one or more of the above formulas (1) to (4) is not satisfied, the balance between the maintenance of brightness and the suppression of color tone change becomes insufficient.

As shown in FIG. 5( a ), the azimuth angle is an angle corresponding to the longitude, and the polar angle is an angle corresponding to the latitude. In FIG. 5( b ), an observation position (target position) when the azimuth angle is 0° and the polar angle is 40° is shown as an example.

From the viewpoint of maintaining the brightness when watching the screen through polarized sunglasses, R _e (590) in the formula (1) is preferably 105 to 170 nm. R _th (590)/R _e (590) is preferably 0.75 or less, Re _{(450)/R e (} 550) in formula (3) is preferably 0.86 to 0.98, and _Re (630) in formula (4) /R _e (550) is preferably 1.01 to 1.06.

The optical film 20 is a kind of retardation film having the function of converting the linearly polarized light emitted from the polarizer 10 to the optical film 20 into elliptically polarized light (including the case of circularly polarized light) and then emitting it. In order to reflect this function, refer to 6 , the optical film 20 is laminated on the polarizer 10 such that the angle θ formed by the slow axis 20a and the absorption axis 10a of the polarizer 10 is 45±20° or 135±20°. When the angle θ is out of this range, it is difficult to obtain the function of converting linearly polarized light into elliptically polarized light and emitting it. As a result, the brightness of the screen tends to decrease when viewed through polarized sunglasses. The angle θ is preferably 45±10° or 135±10°, more preferably 45±5° or 135±5°.

The optical film 20 may be a film containing a light-transmitting (preferably optically transparent) thermoplastic resin. Examples of thermoplastic resins include polyolefin-based resins such as chain polyolefin-based resins (polypropylene-based resins, etc.), cyclic polyolefin-based resins (norbornene-based resins, etc.); cellulose triacetate Cellulose-based resins such as cellulose ester-based resins such as cellulose diacetate; polyester-based resins; polycarbonate-based resins; (meth)acrylic-based resins; polystyrene-based resins; or mixtures thereof , copolymers, etc.

Examples of the chain polyolefin resin include not only homopolymers of chain olefins such as polyethylene resins and polypropylene resins, but also copolymers containing two or more types of chain olefins.

Cyclic polyolefin-based resins are a general term for resins polymerized with cyclic olefins as polymerization units. Specific examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, and combinations of cyclic olefins and chain olefins such as ethylene and propylene. Copolymers (typically random copolymers), graft polymers modified with unsaturated carboxylic acids or derivatives thereof, hydrogenated products thereof, and the like. Among them, norbornene-based resins using norbornene-based monomers such as norbornene and condensed-ring norbornene-based monomers as cyclic olefins are preferably used.

Cellulose ester-based resins are esters of cellulose and fatty acids. Specific examples of cellulose ester-based resins include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. In addition, copolymers thereof and resins in which a part of hydroxyl groups are modified with other substituents can also be used. Among them, cellulose triacetate (triacetylcellulose: TAC) is particularly preferable.

A polyester-based resin is a resin other than a cellulose ester-based resin having an ester bond, and is generally a resin composed of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. Dibasic dicarboxylic acids or derivatives thereof can be used as polycarboxylic acids or derivatives thereof, for example, terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl naphthalene dicarboxylate, etc. . Dihydric diols can be used as the polyhydric alcohol, and examples thereof include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexanedimethanol.

Specific examples of polyester-based resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyterephthalate Propylene glycol formate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, polycyclohexanedimethyl naphthalate.

The polycarbonate-based resin is composed of a polymer in which monomer units are bonded via carbonate groups. The polycarbonate-based resin may be a resin called a modified polycarbonate in which a polymer skeleton is modified, a copolycarbonate, or the like.

The (meth)acrylic resin is a resin having a compound having a (meth)acryloyl group as a main constituent monomer. Specific examples of (meth)acrylic resins include, for example, poly(meth)acrylates such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-( Meth)acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; (meth)methyl acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate with Copolymers of alicyclic hydrocarbon-based compounds (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.). It is preferable to use a poly(meth)acrylate C _1-6 alkyl ester as a main component polymer such as poly(methyl)acrylate, more preferably to use methyl methacrylate as a main component (50 to 100 % by weight, preferably 70 to 100% by weight) of methyl methacrylate resin.

The optical film 20 can be produced by stretching a film containing the above-mentioned thermoplastic resin, or coating a film containing the above-mentioned thermoplastic resin with a phase difference expressing substance such as a liquid crystal material capable of expressing a phase difference to form a phase difference layer. Examples of the stretching treatment include uniaxial stretching, biaxial stretching, and the like. Examples of the stretching direction include the mechanical flow direction (MD) of the unstretched film, the direction (TD) perpendicular thereto, the direction oblique to the mechanical flow direction (MD), and the like. The biaxial stretching may be simultaneous biaxial stretching in which two stretching directions are simultaneously stretched, or sequential biaxial stretching in which stretching is performed in another direction after stretching in a given direction. The stretching treatment can be carried out, for example, by stretching in the longitudinal direction (machine flow direction: MD) using two or more pairs of nip rolls with increased peripheral speeds on the exit side, or by gripping with a chuck. The unstretched film is stretched in the direction (TD) perpendicular to the direction of the mechanical flow while holding both sides of the unstretched film. At this time, by adjusting the thickness of the film or adjusting the draw ratio, the retardation value can be controlled within the range of the above formulas (1) to (2). In addition, by adding a wavelength dispersion adjuster to the resin, the wavelength dispersion value can be controlled within the range of the above formulas (3) to (4).

The thickness d of the optical film 20 is not particularly limited as long as it satisfies the above formulas (1) to (4). However, from the viewpoint of thinning the optical laminated body, it is preferably 90 μm or less, more preferably 60 μm or less. From the viewpoint of the handleability of the film 20, it is preferably 5 μm or more, and more preferably 10 μm or more.

The optical film 20 may contain one or more additives such as lubricants, plasticizers, dispersants, thermal stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, and antioxidants.

In addition, in order to impart desired optical characteristics or other characteristics, a coating layer (surface treatment layer) may be provided on the outer surface of the optical film 20 . Specific examples of the coating layer include a hard coat layer, an antiglare layer, an antireflection layer, an antistatic interference layer, and an antifouling layer. The method for forming the coating layer is not particularly limited, and known methods can be used.

[d] thermoplastic resin film

For the first thermoplastic resin film 40 (refer to FIG. 3 ) that can be laminated on the surface of the polarizer 10 opposite to the optical film 20, the second thermoplastic resin film that can be interposed between the polarizer 10 and the optical film 20 60 (see FIG. 4 ), specific examples of thermoplastic resins constituting films that can be used as these films may be the same as those exemplified above for the optical film 20 . When having both the first thermoplastic resin film 40 and the second thermoplastic resin film 60, both may be composed of the same kind of thermoplastic resin, or may be composed of different kinds of thermoplastic resin.

The first thermoplastic resin film 40 and the second thermoplastic resin film 60 may be protective films that only serve to protect the polarizer 10, and especially the first thermoplastic resin film 40 disposed on the image display element side of the polarizer 10 may also serve as a protective film. A protective film that has an optical function as a retardation film. For example, by stretching a film containing the above-mentioned thermoplastic resin, or coating a film containing the above-mentioned thermoplastic resin with a phase difference expressing substance such as a liquid crystal material that can express a phase difference to form a phase difference layer, it can be made to be endowed with any The retardation film of the retardation value.

The respective thicknesses of the first thermoplastic resin film 40 and the second thermoplastic resin film 60 are preferably 90 μm or less from the viewpoint of thinning the optical laminate, more preferably 60 μm or less, and preferably 60 μm or less from the viewpoint of handleability. 5 μm or more, more preferably 10 μm or more.

[e] Adhesive layer and adhesive layer

For the first adhesive layer of the first adhesive layer or the adhesive layer 25 (refer to FIGS. layer 30 (see FIG. 2 ), a third adhesive layer 50 (see FIG. 3 ), a fourth adhesive layer, or an adhesive that may be laminated on the surface of the first thermoplastic resin film 40 opposite to the polarizing plate 10. The fourth adhesive layer (refer to FIG. 3 ) of the layer 45, as an adhesive to form an adhesive layer that can be used as these adhesive layers, for example, may be (meth)acrylic adhesive, urethane, etc. Ester-based adhesives, silicone-based adhesives, polyester-based adhesives, polyamide-based adhesives, polyether-based adhesives, fluorine-based adhesives, rubber-based adhesives, etc., among them, From the viewpoints of transparency, adhesive force, reliability, reworkability, etc., it is preferable to use a (meth)acrylic adhesive. When the optical laminate has a plurality of pressure-sensitive adhesive layers, the pressure-sensitive adhesive compositions constituting these pressure-sensitive adhesive layers may have the same composition or different compositions.

(Meth)acrylic adhesives generally consist of (meth)acrylic resins as base polymers to which crosslinking agents such as isocyanate compounds, epoxy compounds, and aziridine compounds are added. Composition. Fine particles may be contained in the pressure-sensitive adhesive composition to form a light-scattering pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer is usually 1 to 40 μm, preferably 3 to 25 μm.

The adhesive layer can be provided by, for example, using an adhesive in the form of an organic solvent solution, applying it on the adhesive layer forming surface, and drying it, or using It is provided by the method of transferring the sheet-shaped adhesive on the molded plastic film (referred to as a separator film) to the adhesive layer forming surface.

As the adhesive layer forming the first adhesive layer or adhesive layer 25 (refer to FIGS. 1 to 4 ), the fourth adhesive layer or adhesive layer 45 (refer to FIG. 3 ), the adhesive layer 65 (refer to FIG. 4 ) adhesive, for example, a water-based adhesive or an active energy ray-curable adhesive can be used. Examples of the water-based adhesive include an adhesive containing a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, and the like. In particular, when one of the films to be bonded is a cellulose ester-based resin film subjected to surface treatment (hydrophilization treatment) by saponification or the like, it is preferable to use a water-based adhesive containing an aqueous solution of polyvinyl alcohol-based resin.

As the polyvinyl alcohol-based resin, in addition to a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, vinyl acetate and a compound that can be copolymerized with it can also be used. Polyvinyl alcohol-based copolymers obtained by saponifying copolymers of other monomers, modified polyvinyl alcohol-based polymers obtained by partially modifying their hydroxyl groups, and the like. The water-based adhesive may contain additives such as polyaldehydes, water-soluble epoxy compounds, melamine-based compounds, zirconium dioxide compounds, and zinc compounds.

A water-based adhesive is applied to at least one of the bonding surfaces of the two films to be bonded, and these films are bonded with the adhesive layer interposed therebetween, preferably by applying pressure using a bonding roller or the like to make them close together. . The coating method of the water-based adhesive (the same applies to the active energy ray-curable adhesive described later) is not particularly limited, and casting, Meyer rod coating, gravure coating, comma coating, and doctor blade can be used. Conventionally known methods such as method, die coating method, dip coating method, spray method, etc.

In the case of using a water-based adhesive, it is preferable to dry the film in order to remove water contained in the water-based adhesive after the above-mentioned lamination. Drying can be performed, for example, by introducing the film into a drying oven. The drying temperature (temperature of the drying oven) is preferably 30 to 90°C. If it is lower than 30 degreeC, adhesiveness will become insufficient easily. In addition, if the drying temperature is higher than 90° C., there is a possibility that the polarizing performance of the polarizing plate 10 may be deteriorated due to heat.

After the drying step, an aging step may be performed at room temperature or a temperature slightly higher than room temperature, for example, at a temperature of about 20 to 45° C. for about 12 to 600 hours. The aging temperature is usually set lower than the drying temperature.

The active energy ray-curable adhesive refers to an adhesive that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. In this case, the adhesive layer is a cured product layer of an active energy ray-curable adhesive. The active energy ray-curable adhesive is preferably a photocurable adhesive, more preferably an ultraviolet curable adhesive.

Examples of photocurable adhesives include adhesives containing a polymerizable compound and a photopolymerization initiator, adhesives containing a photoreactive resin, adhesives containing a binder resin and a photoreactive crosslinking agent, and the like. Examples of polymerizable compounds include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, photocurable urethane monomers, or photopolymerizable monomeric oligomers. Examples of the photopolymerization initiator include those containing a substance that generates active species such as neutral radicals, anion radicals, and cationic radicals by irradiation with light such as ultraviolet rays. As the photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.

In the case of using an active energy ray-curable adhesive, after the above lamination, a drying process is performed as necessary (when the active energy ray-curable adhesive contains a solvent, etc.), and then an active energy ray such as ultraviolet ray is irradiated. And the curing step of curing the active energy ray-curable adhesive. The active energy rays to be irradiated are not particularly limited, but are preferably ultraviolet rays having a luminescence distribution at a wavelength of 400 nm or less. Specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, chemical lamps, and black light lamps are preferably used as light sources. , Microwave excited mercury lamps, metal halide lamps, etc.

When laminating the film, for at least one film bonding surface, in order to improve the adhesiveness, surface treatments such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment can be carried out (easy to glue) Viscosity treatment), wherein, preferably plasma treatment, corona treatment or saponification treatment. For example, when one film to be bonded contains a cyclic polyolefin-based resin, plasma treatment or corona treatment may be performed. Moreover, when containing a cellulose ester resin, you may perform saponification process. As a saponification process, the method of immersing in alkali aqueous solution, such as sodium hydroxide and potassium hydroxide, is mentioned.

＜Image Display Device＞

The image display device of the present invention is a device in which the above-mentioned optical laminate of the present invention is disposed on the viewing side of the image display device such that the polarizing plate of the optical laminate is on the image display device side. The image display element may be a non-self-luminous element such as a liquid crystal cell, or may be a self-luminous element such as an organic EL display element. The liquid crystal cell is an element capable of displaying by sandwiching a liquid crystal layer between two transparent substrates and controlling the alignment state of the liquid crystal layer by voltage application, and a well-known liquid crystal cell in the field of liquid crystal display can be used. The organic EL display element is an element in which a light-emitting body containing an organic light-emitting material is sandwiched between a pair of electrodes, and well-known organic EL display elements in this field can still be used.

An example of a liquid crystal display device using a liquid crystal cell 70 as an image display element is shown in FIG. 7 . In this example, the optical laminated body 2 shown in FIG. 2 was applied, but it is not limited thereto as long as the image display device includes the optical laminated body of the present invention. As shown in FIG. 7 , the optical laminate can be attached to an image display element using an adhesive layer or the like. In the liquid crystal display device, the polarizing plate 80 is disposed on the backlight 90 side of the liquid crystal cell 70 , and the polarizing plate 80 may be attached to an image display element using an adhesive layer 85 or the like. As the polarizing plate 80 and the backlight 90 on the backlight side, conventionally known components can be used.

In the image display device of the present invention, the optical laminate is arranged on the image display element so that the optical film 20 is arranged on the viewing side of the polarizing plate 10 (so that the polarizing plate 10 is on the image display element side). The image display device including the optical laminate of the present invention has good brightness when viewing the screen from various directions (azimuth angle and polar angle) through polarizing sunglasses, has little change in color tone, and is excellent in visibility.

Example

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to these examples.

<Example 1>

(1) Production of polarizers

A polyvinyl alcohol film with a thickness of 75 μm (the average degree of polymerization is about 2400, and the degree of saponification is more than 99.9 mol%) is uniaxially stretched to about 5 times by dry stretching, and then kept under tension in pure water at 60°C After immersion for 1 minute, it was immersed for 60 seconds in the aqueous solution of 28 degreeC whose weight ratio of iodine/potassium iodide/water was 0.05/5/100. Thereafter, it was immersed for 300 seconds in a 72° C. aqueous solution having a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100. Next, after washing with pure water at 26° C. for 20 seconds, it was dried at 65° C. to obtain a polarizing plate with a thickness of 28 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

(2) Production of polarizing plate

Dissolve 3 parts by weight of carboxy-modified polyvinyl alcohol [trade name "KL-318" purchased from Kuraray Co., Ltd.] with respect to 100 parts by weight of water, and add a polyamide ring as a water-soluble epoxy resin to the aqueous solution. Oxygen-based additives [trade name "Sumirez Resin 650 (30)" purchased from Taoka Chemical Industry Co., Ltd., aqueous solution with a solid content concentration of 30% by weight] 1.5 parts by weight to prepare a water-based adhesive. This adhesive was coated on one side of the polarizing plate obtained in the above (1), and a 40 μm thick triacetyl cellulose (TAC) film [manufactured by Konica Minolta Opto Co., Ltd. Named "KC4UY"], the adhesive layer was dried to obtain a polarizing plate having a layer composition of TAC film/adhesive layer/polarizer.

(3) Fabrication of optical laminates

On the TAC film surface of the polarizing plate obtained in (2) above, the optical film A [Teijin Chemicals ( Co., Ltd.) polycarbonate film, trade name "PURE-ACE RM", thickness 53 μm] to obtain an optical laminated body. The angle θ formed by the slow axis of the optical film A and the absorption axis of the polarizing plate was set to 45°.

<Examples 2-3, Comparative Examples 1-6>

Except having used the following optical film instead of the optical film A, it carried out similarly to Example 1, and produced the optical laminated body.

Example 2: Optical film B [TAC film, thickness 43 μm]

Example 3: Optical film C [polycarbonate film manufactured by Teijin Chemicals Co., Ltd., trade name "PURE-ACE WR", thickness 53 μm]

Comparative example 1: Optical film D [Cyclic polyolefin film manufactured by Zeon Co., Ltd., trade name "Zeonor Film ZF35-Film #140", thickness 28 μm]

Comparative example 2: Optical film E [Cyclic polyolefin film manufactured by Japan Zeon Co., Ltd., trade name "Zeonor Film ZF35-Film #110", thickness 28 μm]

Comparative example 3: Optical film F [film made of cyclic polyolefin, thickness 20 μm]

Comparative Example 4: Optical film G [Cyclic polyolefin film manufactured by Zeon Co., Ltd., trade name "Zeonor Film ZD12", thickness 33 μm]

Comparative example 5: Optical film H [polycarbonate film manufactured by Kaneka Co., Ltd., trade name "RB-Film #130", thickness 25 μm]

Comparative Example 6: Optical film I [polyester film manufactured by Toray Co., Ltd., trade name "Lumirror 4ZY004", thickness 5 μm].

(Measurement of retardation characteristics and wavelength dispersion characteristics of optical films)

In an environment with a temperature of 23°C and a relative humidity of 55%, the R values of the optical films A to I used in Examples and Comparative Examples were measured using an automatic birefringence meter (KOBRA-WPR) manufactured by Oji Scientific Instruments Co., Ltd. _e (590), R _th (590), _Re (450), _Re (550), _Re (630), and calculate R _th (590)/R _e (590), _Re (450)/R _e (550), R _e (630)/R _e (550). The results are shown in Table 1.

(evaluation of hue change)

Referring to Fig. 8(a) and Fig. 8(b) which schematically show the measurement system of color tone change, at first, the polarizer surface and the glass plate of the optical laminate composed of the polarizer and the optical film are sandwiched by a sheet-shaped film with a thickness of 25 μm. Adhesive [Lintec Co., Ltd. product name "#7"] was bonded together to obtain a sample for evaluation. Then, this sample for evaluation was set in a viewing angle characteristic measurement and evaluation device [trade name "EZContrast" manufactured by ELDIM Corporation]. At this time, the samples for evaluation were arranged in the order of a light source (cold cathode ray), a glass plate, a polarizing plate, an optical film, and a light receiving unit (camera). In addition, between the optical film of the optical laminate and the light-receiving part, a polarizing plate assumed to be polarized sunglasses is arranged so that the absorption axis of the polarized plate of the optical laminated body and the absorption axis of the polarized plate assumed to be polarized sunglasses form an orthogonal Nylon. Cole Prism. In any of the Examples and Comparative Examples, the polarizing plate produced in Example 1 (the same polarizing plate as that included in the optical laminate) was used as the polarizing plate assumed to be polarized sunglasses.

The azimuth angle 0 at polar angles of 0, 10, 20, 30, 40, 50, 60, 70, and 80° was measured as the (x, y) value of the CIE-XYZ colorimetric system using the above-mentioned viewing angle characteristic measurement and evaluation device. , 45, 90, 135, 180, 225, 270, 315 degrees of chromaticity (a total of 9 × 8 = 72 points). Thereafter, the difference Δx between the maximum value and the minimum value of x and the difference Δy between the maximum value and the minimum value of y were obtained for these 72 points, and based on their total value Δx+Δy, the following evaluation criteria were used to evaluate The color tone change when viewing the picture from various directions (azimuth and polar angles) through polarized sunglasses. The results are shown in Table 1. In addition, the xy chromaticity diagram obtained about each Example and a comparative example is shown in FIGS. 9-17.

A: Δx+Δy is less than 0.065

B: Δx+Δy is 0.065 or more and less than 0.100

C: Δx+Δy is 0.100 or more.

[Table 1]

Explanation of symbols

1, 2, 3, 4 optical stacks,

10 polarizers,

10a The absorption axis of the polarizer,

20 optical films,

20a slow axis of optical film,

25 a first layer of adhesive or adhesive,

30 second adhesive layer,

40 first thermoplastic resin film,

45 fourth layer of adhesive or adhesive,

50 third adhesive layer,

60 second thermoplastic resin film,

65 adhesive layer,

70 LCD units,

80 polarizing plate,

85 adhesive layer,

90 backlight

Claims (10)

1. a kind of optical laminate, it includes polarizing film and the optical film being laminated in one face,

The optical film projects after rectilinearly polarized light is transformed to elliptically polarized light, and meets following formula:

(1)100nm≤R_e(590)≤180nm、

(2) 0.5 < R_th(590)/R_e(590)≤0.8、

(3)0.85≤R_e(450)/R_e(550) < 1.00 and

(4) 1.00 < R_e(630)/R_e(550)≤1.1

In formula, R_e(590)、R_e(450)、R_e(550)、R_e(630) measurement wavelength 590nm, 450nm, 550nm, 630nm are respectively indicated When face in phase difference value, R_th(590) thickness direction phase difference value when measurement wavelength 590nm is indicated,

In the outer surface of optical film setting hard conating, antiglare layer, anti-reflection layer or stain-proofing layer.

2. a kind of optical laminate it includes polarizing film and presss from both sides the optical film being laminated on layer by layer in one face across adhesive,

The optical film projects after rectilinearly polarized light is transformed to elliptically polarized light, and meets following formula:

(1)100nm≤R_e(590)≤180nm、

(2) 0.5 < R_th(590)/R_e(590)≤0.8、

(3)0.85≤R_e(450)/R_e(550) < 1.00 and

(4) 1.00 < R_e(630)/R_e(550)≤1.1

In formula, R_e(590)、R_e(450)、R_e(550)、R_e(630) measurement wavelength 590nm, 450nm, 550nm, 630nm are respectively indicated When face in phase difference value, R_th(590) thickness direction phase difference value when measurement wavelength 590nm is indicated,

The adhesive for forming the gluing oxidant layer is active energy ray-curable adhesive.

3. optical laminate according to claim 1 or 2, wherein

The absorption axiss angulation of the slow axis of the optical film and the polarizing film is 45 ± 20 ° or 135 ± 20 °.

4. optical laminate according to claim 1 or 2, wherein

The optical film contain cyclic polyolefin hydrocarbon system resin, polycarbonate-based resin, cellulose-based resin, polyester based resin or (methyl) acrylic resin.

5. optical laminate according to claim 1, wherein

The optical film is pressed from both sides to be laminated on the polarizing film layer by layer across first adhesive phase or adhesive.

6. optical laminate according to claim 1 or 2, wherein

The also second adhesive phase comprising being laminated on the face with the optical film opposite side of the polarizing film.

7. optical laminate according to claim 1 or 2, wherein

The also thermoplastic resin film comprising being laminated on the face with the optical film opposite side of the polarizing film.

8. optical laminate according to claim 7, wherein

The thermoplastic resin film is phase difference film.

9. optical laminate according to claim 7, wherein

The also third adhesive phase comprising being laminated on the face with the polarizing film opposite side of the thermoplastic resin film.

10. a kind of image display device has image-displaying member and optical laminate of any of claims 1 or 2,

It is image-displaying member side that the optical laminate, which is configured as the polarizing film,.