TWI683749B - Optical layered body, manufacturing method thereof, and image display device using the optical layered body - Google Patents

Abstract

The present invention provides a thin optical laminate with circular polarization function or elliptical polarization function that suppresses curling.

The optical layered body according to the embodiment of the present invention includes a polarizing element, a phase difference layer disposed on one side of the polarizing element, and a protective layer disposed on the other side of the polarizing element. The phase difference layer has the function of converting linear polarized light into circular polarized light or elliptical polarized light. The difference between the heating dimensional change rate in the first direction of the optical laminate and the heating dimensional change rate in the second direction substantially orthogonal to the first direction is 1.0% or less.

Description

Optical layered body, manufacturing method thereof, and image display device using the optical layered body

The present invention relates to an optical laminate, a method for manufacturing the same, and an image display device using the optical laminate.

In recent years, as mobile phones, smart phones, tablet personal computers (PCs), navigation systems, digital signage, window displays, etc., the opportunities for using image display devices under strong outside light have increased. In the case of using the image display device outdoors in this way, when the viewer wears polarized sunglasses to view the image display device, the transmission axis direction of the polarized sunglasses and the image display device may vary depending on the viewing angle of the viewer The direction of the transmission axis on the exit side becomes a crossed Nicols state. As a result, the screen may become black and the displayed image may not be recognized. In order to solve such a problem, a technique of arranging a circular polarizing plate (a polarizing plate for polarized sunglasses) on the viewing side surface of the image display device is proposed.

However, the requirements for thinning of image display devices are becoming stronger and stronger. Accompanyingly, the requirements for thinning of optical members used in image display devices are becoming stronger and stronger. However, if an attempt is made to reduce the thickness of the polarizing plate of the polarized sunglasses as described above, there is a significant problem of curling (especially curling of the polarizing plate in the diagonal direction).

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-16425

The present invention has been completed to solve the aforementioned problems, and an object thereof is to provide a thin optical laminate having a circular polarizing function or an elliptical polarizing function that suppresses curling.

The optical laminate of the present invention includes a polarizing element, a phase difference layer disposed on one side of the polarizing element, and a protective layer disposed on the other side of the polarizing element. The phase difference layer has the function of converting linearly polarized light into circularly polarized light or elliptically polarized light. The difference between the heating dimensional change rate in the first direction of the optical laminate and the heating dimensional change rate in the second direction substantially orthogonal to the first direction is 1.0% or less.

In one embodiment, the first direction is the late phase axis direction or the advance phase axis direction of the phase difference layer, and the second direction is the phase advance axis direction or the late phase axis direction of the phase difference layer.

In one embodiment, the angle formed by the absorption axis of the polarizing element and the slow phase axis of the phase difference layer is 35° to 55°.

In one embodiment, the optical layered body is elongated, and the angle formed by the retardation axis of the phase difference layer and the longitudinal direction is 35° to 55°.

In one embodiment, the optical layered body further includes a hard coat layer on the opposite side of the phase difference layer from the polarizing element.

In one embodiment, the polarizing element, the phase difference layer, and the protective layer are bonded using an aqueous adhesive having a solid content concentration of 6% by weight or less.

According to another aspect of the present invention, an image display device is provided. This image display device includes the above-mentioned optical laminate on the viewing side, and the phase difference layer is disposed on the viewing side.

According to an embodiment of the present invention, a polarizing element, a circularly polarizing function or In the optical laminate of the elliptically polarized phase difference layer and the protective layer, by controlling the difference between the heating dimensional change rate in the first direction and the heating dimensional change rate in the second direction substantially orthogonal to the first direction , A very thin optical laminate with suppressed curling can be realized. In particular, the suppression of diagonal curl is obvious.

10‧‧‧Polarizing element

20‧‧‧ phase difference layer

30‧‧‧Protective layer

40‧‧‧hard coating

100‧‧‧Optical laminate

FIG. 1 is a schematic cross-sectional view of an optical laminate according to an embodiment of the present invention.

FIG. 2 is a graph showing the dimensional change rates of the late phase axis direction and the advance phase axis direction with respect to temperature in Example 1. FIG.

FIG. 3 is a graph showing the curves of the dimensional change rate with respect to temperature in the direction of the late phase axis and the direction of the advance phase axis in Comparative Example 1. FIG.

4 is a graph showing the curve of the dimensional change rate with respect to temperature in the direction of the late phase axis and the direction of the advance phase axis in Comparative Example 2. FIG.

5 is a photograph showing a curled state of the optical laminate of Example 1. FIG.

6 is a photograph showing the curled state of the optical laminate of Comparative Example 1. FIG.

7 is a photograph showing the curled state of the optical laminate of Comparative Example 2. FIG.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)

The definitions of terms and symbols in this manual are as follows.

(1) Refractive index (nx, ny, nz)

"Nx" is the refractive index in the direction where the refractive index in the plane becomes maximum (ie, the direction of the slow phase axis), and "ny" is the refractive index in the direction orthogonal to the slow phase axis (that is, the direction of the phase axis) , "Nz" is the refractive index in the thickness direction.

(2) In-plane phase difference (Re)

"Re(λ)" is the in-plane phase of the film measured using light of wavelength λ nm at 23°C difference. For example, "Re(450)" is the in-plane retardation of the film measured using light with a wavelength of 450 nm at 23°C. Re(λ) is obtained by using the formula: Re=(nx-ny)×d when the thickness of the film is d (nm).

(3) Phase difference in thickness direction (Rth)

"Rth(λ)" is the phase difference in the thickness direction of the film measured at 23°C using light with a wavelength of 550 nm. For example, "Rth(450)" refers to the phase difference in the thickness direction of the film measured with light having a wavelength of 450 nm at 23°C. Rth(λ) is obtained by using the formula: Rth=(nx-nz)×d when the thickness of the film is d (nm).

(4) Nz coefficient

The Nz coefficient is obtained by Nz=Rth/Re.

(5) Substantially orthogonal or parallel

The expressions "substantially orthogonal" and "substantially orthogonal" include the case where the angle formed by the two directions is 90°±10°, preferably 90°±7°, more preferably 90°±5°. The expressions "substantially parallel" and "substantially parallel" include the case where the angle formed by the two directions is 0°±10°, preferably 0°±7°, and more preferably 0°±5°. Furthermore, when simply referred to as "orthogonal" or "parallel" in this specification, it may include a state of being substantially orthogonal or substantially parallel.

(6) Angle

When an angle is mentioned in this specification, the angle includes clockwise and counterclockwise angles unless otherwise specified.

(7) Long strip

The "long shape" refers to an elongated shape with a sufficiently long length relative to the width, and includes, for example, an elongated shape with a length of 10 times or more, preferably 20 times or more.

A. The overall composition of the optical laminate

FIG. 1 is a schematic cross-sectional view of an optical laminate according to an embodiment of the present invention. The optical layered body 100 of this embodiment includes a polarizing element 10 and a polarizing element 10 disposed on one side of the polarizing element 10 The phase difference layer 20 and the protective layer 30 disposed on the other side of the polarizing element 10. The phase difference layer 20 has a function of converting linear polarized light into circular polarized light or elliptical polarized light. Therefore, the optical laminate 100 may be typically a circular polarizing plate or an elliptical polarizing plate. The optical laminate 100 is typically arranged on the viewing side of the image display device. In this case, the phase difference layer 20 is arranged so as to be the viewing side. With the above-described configuration, even when the display screen is viewed through polarized lenses such as polarized sunglasses, excellent visibility can be achieved. Therefore, the optical laminate 100 can be preferably applied to an image display device that can be used outdoors.

The optical layered body 100 may be further provided with a hard coat layer 40 on the opposite side of the phase difference layer 20 from the polarizing element 10 as needed. Furthermore, the optical layered body 100 may include another phase difference layer (not shown). The number, arrangement position, optical characteristics (for example, refractive index ellipsoid, in-plane phase difference, thickness direction phase difference, wavelength dispersion characteristics), mechanical characteristics, etc. of other phase difference layers can be appropriately set according to purposes.

The difference between the heating dimensional change rate in the first direction of the optical laminate 100 and the heating dimensional change rate in the second direction substantially orthogonal to the first direction is 1.0% or less, preferably 0.8% or less, more preferably It is 0.6% or less, and further preferably 0.4% or less. According to the embodiment of the present invention, by controlling the heating dimensional change rate in two directions that are substantially orthogonal, a very thin optical laminate with reduced curl can be realized. Typically, the first direction is the direction of the slow phase axis or the phase advance axis of the phase difference layer 20, and the second direction is the direction of the phase advance axis or the direction of the slow phase axis of the phase difference layer. By controlling the heating dimensional change rate in these two specific directions, curling can be further suppressed in a very thin optical laminate.

The polarizing element 10 and the phase difference layer 20 are laminated so that the absorption axis of the polarizing element 10 and the slow phase axis of the phase difference layer 20 form a specific angle. The angle formed by the absorption axis of the polarizing element 10 and the retardation axis of the phase difference layer 20 is preferably 35° to 55°, more preferably 38° to 52°, and further preferably 40° to 50°, particularly preferably 42°~48°, especially about 45°. By arranging the phase difference layer 20 on the viewing side of the polarizing element 10 with such an axial relationship, even when the display screen is viewed through polarizing lenses such as polarized sunglasses, excellent visibility can be achieved. because Furthermore, the optical laminate according to the embodiment of the present invention can be preferably applied to an image display device that can be used outdoors.

The optical layered body 100 may be in the form of a single piece or a long shape (for example, a roll shape). When the optical laminate 100 is elongated, the absorption axis direction of the elongated polarizing element may be either the longitudinal direction or the width direction. Preferably, the absorption axis direction of the polarizing element is the longitudinal direction. The reason is that the polarizing element is easy to manufacture, and as a result, the manufacturing efficiency of the optical laminate is excellent. When the optical laminate is elongated, the angle θ formed by the retardation axis of the retardation layer 20 and the longitudinal direction is preferably 35° to 55°, more preferably 38° to 52°, and further preferably 40°~50°, especially good is 42°~48°, especially good is about 45°. By forming the retardation film constituting the retardation layer by oblique extension as described later, it can be formed in an oblong retardation film (retardation layer) having a retardation axis obliquely, and as a result, a long strip can be realized Shaped optical laminate. Since such an elongated optical layered body can be produced by roll-to-roll, the production characteristics are excellent.

The overall thickness of the optical laminate is typically 40 μm to 300 μm, preferably 60 μm to 160 μm, more preferably 80 μm to 140 μm, and still more preferably 100 μm to 120 μm. According to the embodiment of the present invention, it is possible to obtain an optical laminate whose thickness is very thin as described above and curling is suppressed satisfactorily. In addition, the total thickness of the optical layered body refers to the total thickness of the polarizing element, the retardation layer, the protective layer, the hard coat layer in the presence of the hard coat layer, and the subsequent layers used to laminate these layers.

Hereinafter, each layer constituting the optical laminate according to the embodiment of the present invention will be described.

A-1. Polarizing element

As the polarizing element 10, any suitable polarizing element may be used. For example, the resin film forming the polarizing element may be a single-layer resin film or a laminate of two or more layers.

Specific examples of the polarizing element composed of a single-layer resin film include a polyvinyl alcohol (PVA) resin film, a partially methylated PVA resin film, and ethylene-vinyl acetate Copolymer-based partially saponified membranes and other hydrophilic polymer membranes are subjected to dyeing treatment and extension treatment with dichroic substances such as iodine or dichroic dyes, dehydration treatment of PVA or dehydrochlorination treatment of polyvinyl chloride, etc. Polyene-based alignment film, etc. In terms of excellent optical characteristics, it is preferable to use a polarizing element obtained by dyeing a PVA-based resin film with iodine and uniaxially stretching.

The above dyeing with iodine is performed, for example, by immersing the PVA-based resin film in an aqueous iodine solution. The extension ratio of the uniaxial extension is preferably 3 to 7 times. Elongation can be carried out after dyeing, or it can be carried out while dyeing. In addition, it may be dyed after stretching. If necessary, the PVA-based resin film is subjected to swelling treatment, cross-linking treatment, cleaning treatment, drying treatment, and the like. For example, by immersing the PVA-based resin film in water for washing before dyeing, not only can the dirt or anti-blocking agent on the surface of the PVA-based resin film be cleaned, but also the PVA-based resin film can be swollen to prevent uneven dyeing.

As a specific example of the polarizing element obtained using the laminate, a laminate using a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and a coating formed thereon A polarizing element obtained from a laminate of a resin substrate and a PVA-based resin layer. A polarizing element obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it Then, a PVA-based resin layer is formed on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to make the PVA-based resin layer into a polarizing element. In the present embodiment, extending typically includes immersing the laminate in a boric acid aqueous solution and extending. Furthermore, the stretching may be carried out in the air before the stretching in the boric acid aqueous solution, if necessary, further including a laminate at a high temperature (for example, 95° C. or higher). The resulting resin substrate/polarizer laminated body can be used directly (that is, the resin substrate can be used as a protective layer of the polarizing element), or the resin substrate can be peeled from the resin substrate/polarizer laminated body. Use any suitable protective layer according to the purpose. Details of the manufacturing method of such a polarizing element are described in Japanese Patent Laid-Open No. 2012-73580, for example. The entire contents of this gazette are cited as a reference to this specification in.

The thickness of the polarizing element is preferably 15 μm or less, more preferably 13 μm or less, still more preferably 10 μm, particularly preferably 8 μm or less. The thickness of the polarizing element is limited to 2 μm in one embodiment and 3 μm in other embodiments. According to the embodiment of the present invention, although the thickness of the polarizing element is so thin, curling when the optical laminate is heated can be suppressed well.

The polarizing element preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing element is preferably 44.0% to 45.5%, and more preferably 44.5% to 45.0%. According to the present invention, it is possible to realize a very thin optical layered body in which curling is suppressed, and further, in such an optical layered body, an excellent monomer transmittance as described above can be achieved.

As described above, the polarization degree of the polarizing element is 98% or more, preferably 98.5% or more, and more preferably 99% or more. According to the present invention, it is possible to realize a very thin optical layered body in which curling is suppressed, and further, in such an optical layered body, the excellent polarization degree as described above can be achieved.

A-2. Phase difference layer

As described above, the phase difference layer 20 has a function of converting linearly polarized light into circularly polarized light or elliptically polarized light. That is, the phase difference layer 20 typically has a refractive index characteristic showing a relationship of nx>ny. The in-plane retardation Re(550) of the retardation film is preferably 80 nm to 160 nm, and more preferably 90 nm to 120 nm. If the in-plane retardation is within such a range, a retardation film having suitable elliptically polarizing performance can be obtained with excellent productivity and reasonable cost. As a result, it is possible to obtain an optical laminate that can ensure good visibility even when the display screen is viewed through polarizing lenses such as polarized sunglasses with excellent productivity and reasonable cost.

The phase difference layer 20 only needs to have a relationship of nx>ny, and displays any suitable refractive index ellipsoid. Preferably, the refractive index ellipsoid of the phase difference layer shows the relationship of nx>ny≧nz. The Nz coefficient of the phase difference layer is preferably 1 to 2, more preferably 1 to 1.5, and further preferably 1 to 1.3.

The retardation layer 20 is composed of any suitable retardation film that can satisfy the optical characteristics as described above. As the resin for forming the retardation film, a cellulose ester resin (hereinafter also simply referred to as cellulose ester) is typically mentioned.

Specific examples of cellulose esters include cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate , Cellulose acetate phthalate, cellulose phthalate. Preferred are cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate. The cellulose ester may be used alone or in combination.

Cellulose esters use β-1,4-glycosidic bonds to form part or all of the free hydroxyl groups (hydroxy) at the 2nd, 3rd and 6th positions in the glucose unit of cellulose, using acetyl groups such as acetyl and propyl groups Esterified polymer. Here, the "acyl group substitution degree" means the total ratio of the esterification rate of the hydroxyl group at the 2, 3, and 6 positions of the glucose in the repeating unit. Specifically, the degree of substitution of each of the hydroxyl groups at the 2nd, 3rd, and 6th positions of cellulose is 100% esterified. Therefore, when 100% esterification occurs at the 2nd, 3rd, and 6th positions of cellulose, the degree of substitution is the maximum of 3. In addition, the "average degree of substitution of acyl group" refers to a degree of substitution of the acyl group that represents the degree of substitution of a plurality of glucose units constituting the cellulose ester resin in the form of the average value of each unit. The degree of substitution of the acetyl group can be determined in accordance with ASTM-D817-96.

Examples of the acetyl group include acetyl group, propyl group, butyl group, heptyl group, hexyl group, octyl group, decyl group, dodecyl group, tridecyl group, tetradecyl group, and decyl group. Hexacarbon acetyl, octadecyl acetyl, isobutyl acetyl, third butyl acetyl, cyclohexane carbonyl, oleoyl, benzoyl, naphthyl carbonyl, cinnamyl acetyl.

In one embodiment, when the acetyl group substitution degree of the cellulose ester resin is X and the propyl group substitution degree is Y, X and Y preferably satisfy the following formula (1) and formula (2) ).

Formula (1): 2.0≦(X+Y)≦2.8

Formula (2): 0≦Y≦1.0

More preferably, the cellulose ester resin satisfying the above formula (1) and formula (2) contains a cellulose ester resin satisfying the following formula (1a) and the above formula (2), and cellulose satisfying the following formula (1b) Ester resin.

Formula (1a): 2.0≦(X+Y)<2.5

Formula (1b): 2.5≦(X+Y)≦2.8

In addition, the "degree of acetyl substitution" and "degree of propyl substitution" are more specific indicators of the degree of substitution of acetyl groups mentioned above. The so-called "degree of substitution of acetyl groups" means the 2nd and 3rd positions of glucose in the repeating unit. The total ratio of the hydroxyl groups at the 6-position and the 6-position is esterified with an acetyl group. The so-called "propionyl substitution degree" refers to the ratio at which the hydroxyl groups at the 2nd, 3rd, and 6th positions of the glucose of the repeating unit are esterified by the acetyl group. Total.

The molecular weight distribution (weight average molecular weight Mw/number average molecular weight Mn) of the cellulose ester resin is preferably 1.5 to 5.5, more preferably 2.0 to 5.0, further preferably 2.5 to 5.0, and particularly preferably 3.0 to 5.0.

As the raw material cellulose of the cellulose ester resin, any suitable cellulose can be used. Specific examples include cottonseed, wood pulp, and kenaf. The cellulose ester resin obtained from different raw materials can also be used in combination.

The cellulose ester resin can be manufactured by any suitable method. As a representative example, a method including the following procedures may be mentioned: mixing cellulose of a raw material, a specific organic acid (for example, acetic acid, propionic acid), an anhydride (for example, acetic anhydride, propionic anhydride), and a catalyst (for example, sulfuric acid), mixing Cellulose is esterified and the reaction is carried out until cellulose triester is obtained. In the cellulose triester, the three hydroxy groups of the glucose unit are replaced by the carboxylic acid of the organic acid. If two organic acids are used at the same time, cellulose esters of mixed ester type (eg cellulose acetate propionate, cellulose acetate butyrate) can be made. Then, the cellulose triester is hydrolyzed, thereby synthesizing the cellulose ester having the desired degree of substitution of the acyl group. After that, the cellulose ester resin can be obtained through the steps of filtration, precipitation, water washing, dehydration, and drying.

The retardation layer 20 (retardation film) is typically produced by extending a resin film formed of the resin as described above in at least one direction.

As a method of forming the resin film, any appropriate method can be adopted. For example, melt extrusion method (e.g. T-die forming method), casting coating method (e.g. casting method), calendering method, hot pressing method, co-extrusion method, co-melting method, multilayer extrusion, inflation molding Law etc. Preferably, a T-die forming method, a casting method, and an inflation forming method are used.

The thickness of the resin film (unstretched film) can be set to any appropriate value according to the required optical characteristics, the stretching conditions described below, and the like. It is preferably 50 μm to 300 μm, and more preferably 80 μm to 250 μm.

Any suitable stretching method and stretching conditions (eg, stretching temperature, stretching ratio, stretching direction) can be used for the above stretching. Specifically, various extension methods such as free-end extension, fixed-end extension/free-end contraction, and fixed-end contraction can be used alone, or they can be used simultaneously or sequentially. Regarding the extending direction, it can be performed in various directions or dimensions such as a horizontal direction, a vertical direction, a thickness direction, and a diagonal direction. The extension temperature is preferably within a range of ±20°C of the glass transition temperature (Tg) of the resin film.

By appropriately selecting the above stretching method and stretching conditions, a retardation film (resulting in a retardation layer) having the desired optical characteristics (for example, refractive index ellipsoid, in-plane retardation, and Nz coefficient) can be obtained.

In one embodiment, the retardation layer 20 is produced by uniaxially extending the resin film or uniaxially extending the fixed end. As a specific example of uniaxial stretching, a method of extending the resin film in the longitudinal direction and extending in the longitudinal direction (longitudinal direction) can be cited. As another specific example of uniaxial stretching, a method of stretching in a transverse direction using a tenter can be cited. The extension magnification is preferably 10% to 500%.

In another embodiment, the retardation layer 20 is produced by continuously extending the elongated resin film diagonally in a direction with an angle θ with respect to the longitudinal direction. By adopting oblique extension, a long strip with an alignment angle of angle θ relative to the longitudinal direction of the film can be obtained The stretched film in the shape can realize roll-to-roll when laminating with the polarizing element, which can simplify the manufacturing steps. The angle θ is as described above.

As a stretching machine used for diagonal stretching, for example, a tenter-type stretching machine that can apply a feed force, an extension force, or a drawing force at different speeds in the lateral direction and/or the longitudinal direction can be applied. Tenter-type stretching machines include transverse uniaxial stretching machines, simultaneous biaxial stretching machines, etc., as long as the elongated resin film can be continuously stretched obliquely, any suitable stretching machine can be used.

Examples of the method of diagonally extending include Japanese Patent Laid-Open No. 50-83482, Japanese Patent Laid-Open No. 2-113920, Japanese Patent Laid-Open No. 3-182701, Japanese Patent Laid-Open No. 2000-9912 , Japanese Patent Laid-Open No. 2002-86554, Japanese Patent Laid-Open No. 2002-22944, etc.

The thickness of the stretched film (resulting in a phase difference layer) is preferably 20 μm to 80 μm, and more preferably 30 μm to 60 μm.

As the retardation film constituting the retardation layer 20, a commercially available film may be used as it is, or the commercially available film may be subjected to secondary processing (for example, stretching treatment, surface treatment) according to the purpose and used.

The surface of the phase difference layer 20 on the polarizing element 10 side may be subjected to surface treatment. Examples of the surface treatment include corona treatment, plasma treatment, flame treatment, primer coating treatment, and saponification treatment. As the corona treatment, for example, a method in which a corona treatment machine performs discharge in atmospheric air is used. Plasma treatment may include, for example, a method in which a plasma discharge machine performs discharge in atmospheric air. The flame treatment may include, for example, a method of directly contacting the flame with the film surface. The primer coating treatment includes, for example, a method of diluting an isocyanate compound, a silane coupling agent, etc. with a solvent and thinly applying the diluted solution. Saponification treatment can be exemplified by immersion in an aqueous solution of sodium hydroxide. Corona treatment and plasma treatment are preferred.

A-3. Protective layer

烯系、聚烯烴系、(甲基)丙烯酸系、乙酸酯系等之透明樹脂等。又，亦可列舉(甲基)丙烯酸系、胺基甲酸酯系、(甲基)丙烯酸胺基甲酸酯系、環氧系、聚矽氧系等之熱硬化型樹脂或紫外線硬化型樹脂等。除此以外，例如亦可列舉矽氧烷系聚合物等玻璃質系聚合物。又，亦可使用日本專利特開2001-343529號公報(WO01/37007)中記載之聚合物膜。作為該膜之材料，例如可使用含有側鏈具有經取代或未經取代之醯亞胺基之熱塑性樹脂、及側鏈具有經取代或未經取代之苯基以及腈基之熱塑性樹脂的樹脂組合物，例如可列舉具有包含異丁烯與N-甲基馬來醯亞胺之交替共聚物、及丙烯腈-苯乙烯共聚物之樹脂組合物。該聚合物膜例如可為上述樹脂組合物之擠出成形物。 The protective layer 30 is formed of any suitable film that can be used as a protective layer of the polarizing element. Specific examples of the material that becomes the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), or polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, and Acetyl imide series, polyether sock series, poly sock series, polystyrene series, poly urethane

Transparent resins such as olefin-based, polyolefin-based, (meth)acrylic-based, and acetate-based. In addition, thermosetting resins such as (meth)acrylic acid-based, urethane-based, (meth)acrylic acid-based urethane-based, epoxy-based, and polysiloxane-based resins or ultraviolet-curable resins can also be mentioned. Wait. In addition to this, for example, vitreous-based polymers such as siloxane-based polymers can be cited. Alternatively, the polymer film described in Japanese Patent Laid-Open No. 2001-343529 (WO01/37007) may be used. As the material of the film, for example, a resin combination containing a thermoplastic resin having a substituted or unsubstituted amide imide group in the side chain, and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used Examples of the material include resin compositions having an alternating copolymer containing isobutylene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extruded product of the above resin composition.

As the (meth)acrylic resin, Tg (glass transition temperature) is preferably 115°C or higher, more preferably 120°C or higher, even more preferably 125°C or higher, and particularly preferably 130°C or higher. The reason is that it is excellent in durability. The upper limit of the Tg of the (meth)acrylic resin is not particularly limited, but from the viewpoint of moldability and the like, it is preferably 170°C or lower.

酯共聚物等)。較佳為列舉聚(甲基)丙烯酸甲酯等聚(甲基)丙烯酸C_1-6烷基酯。更佳為列舉以甲基丙烯酸甲酯作為主成分(50~100重量%、較佳為70~100重量%)之甲基丙烯酸甲酯系樹脂。 As the above-mentioned (meth)acrylic resin, any suitable (meth)acrylic resin can be used as long as the effect of the present invention is not impaired. For example, poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth)acrylate copolymer, methacrylic acid Methyl ester-acrylate-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS (methyl methacrylate-styrene) resin, etc.), polymers with alicyclic hydrocarbon groups (such as methyl Methyl acrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylic acid

Ester copolymer, etc.). Preferably, poly(meth)acrylic acid C _1-6 alkyl esters, such as polymethyl (meth)acrylate, are mentioned. More preferably, a methyl methacrylate-based resin having methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is cited.

Specific examples of the (meth)acrylic resin include Acrypet VH or Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and (meth) having a ring structure in the molecule described in Japanese Patent Laid-Open No. 2004-70296 Acrylic resin, high Tg (meth)acrylic resin obtained by intramolecular crosslinking or intramolecular cyclization reaction.

As the (meth)acrylic resin, the (meth)acrylic resin having a lactone ring structure is particularly preferable in terms of having high heat resistance, high transparency, and high mechanical strength. .

Examples of the (meth)acrylic resin having a lactone ring structure include Japanese Patent Laid-Open No. 2000-230016, Japanese Patent Laid-Open No. 2001-151814, Japanese Patent Laid-Open No. 2002-120326, and Japanese Patent (Meth)acrylic resin having a lactone ring structure described in Japanese Patent Laid-Open No. 2002-254544, Japanese Patent Laid-Open No. 2005-146084, and the like.

The mass average molecular weight (sometimes referred to as weight average molecular weight) of the (meth)acrylic resin having a lactone ring structure is preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, and still more preferably 10,000 to 500,000. Especially good is 50000~500,000.

The Tg (glass transition temperature) of the (meth)acrylic resin having a lactone ring structure is preferably 115°C or higher, more preferably 125°C or higher, further preferably 130°C or higher, particularly preferably 135°C, and most Preferably, it is above 140°C. The reason is that it is excellent in durability. The upper limit of the Tg of the (meth)acrylic resin having a lactone ring structure is not particularly limited, but from the viewpoint of moldability and the like, it is preferably 170°C or lower.

In addition, the "(meth)acrylic system" in this specification means an acrylic system and/or a methacrylic system.

The protective layer 30 is preferably optically isotropic. The "optical isotropy" in this specification means that the in-plane phase difference Re (550) is 0 nm to 10 nm, and the thickness direction phase difference Rth (550) is -10 nm to +10 nm.

The thickness of the inner protective film is preferably 20 μm to 80 μm, more preferably 30 μm to 60 μm.

A-4. Hard coating

The hard coat layer 40 has the functions of imparting chemical resistance, scratch resistance, and surface smoothness to the optical laminate, and improving dimensional stability under high temperature and high humidity. As the hard coat layer 40, any suitable configuration may be adopted. The hard coat layer is, for example, a hardened layer of any suitable ultraviolet-curable resin. Examples of the ultraviolet curing resins include acrylic resins, polysiloxane resins, polyester resins, urethane resins, amide resins, and epoxy resins. The glass transition temperature of the resin constituting the hard coat layer is preferably 120°C to 300°C, more preferably 130°C to 250°C. Within this range, an optical laminate with excellent dimensional stability at high temperatures can be obtained. The hard coat layer may also contain any suitable additives as needed. Representative examples of such additives include inorganic fine particles and/or organic fine particles.

The thickness of the hard coat layer 40 is preferably 10 μm or less, more preferably 1 μm to 8 μm, and still more preferably 3 μm to 7 μm.

The details of the hard coat layer are described in, for example, Japanese Patent Laid-Open No. 2007-171943, and this description is incorporated by reference in this specification.

A-5. Then layer

Any suitable adhesive layer (not shown) is used for bonding of the layers constituting the optical laminate according to the embodiment of the present invention. The subsequent layer may be an adhesive layer or an adhesive layer. Typically, the polarizing element 10, the retardation layer 20, and the protective layer 30 are bonded using an aqueous adhesive. As the water-based adhesive, any suitable water-based adhesive can be used. It is preferable to use an aqueous adhesive containing a PVA-based resin. The average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably about 100 to 5500 in terms of adhesiveness, and more preferably 1,000 to 4500. The average saponification degree is preferably about 85 mol% to 100 mol% in terms of adhesiveness, and more preferably 90 mol% to 100 mol%.

The PVA-based resin contained in the water-based adhesive preferably contains an acetyl group. The reason is that it can be excellent in the adhesion of the polarizing element to the retardation layer and the protective layer, 面Excellent. The PVA-based resin containing an acetoacetyl group can be obtained, for example, by reacting the PVA-based resin with diketene by any method. The modification degree of the acetyl acetyl group of the PVA-based resin containing acetyl acetyl group is typically 0.1 mol% or more, preferably about 0.1 mol% to 40 mol %, and more preferably 1 mol Ear% ~ 20 mol%, especially good for 1 mol% ~ 7 mol%. In addition, the degree of modification of the acetylacetonyl group is a value measured by NMR (Nuclear Magnetic Resonance).

The concentration of the solid content of the water-based adhesive is preferably 6% by weight or less, more preferably 0.1% by weight to 6% by weight, and further preferably 0.5% by weight to 6% by weight. If the solid component concentration is within this range, it has the advantage of easily controlling the size control rate of the polarizing plate. If the concentration of the solid component is too low, the moisture content of the resulting optical laminate becomes large, and the size change may become larger depending on the drying conditions. If the concentration of the solid component is too high, the viscosity of the adhesive becomes high, and the productivity of the optical laminate may be insufficient.

The thickness of the next layer is preferably 0.01 μm to 7 μm, more preferably 0.01 μm to 5 μm, still more preferably 0.01 μm to 2 μm, and particularly preferably 0.01 μm to 1 μm. If the thickness of the adhesive layer is too thin, the cohesive force of the adhesive itself may not be obtained and the adhesive strength may not be obtained. If the thickness of the adhesive layer is too thick, the optical laminate may fail to meet the durability.

A-6. Other

In one embodiment, an easy adhesion layer (not shown) may be provided on the surface of the phase difference layer 20 on the polarizing element 10 side. In the case of providing an easy adhesion layer, the above-mentioned surface treatment may be applied to the phase difference layer 20 or not. It is preferable to perform surface treatment on the phase difference layer 20. By combining the easy adhesion layer and the surface treatment, the realization of the required adhesion between the polarizing element 10 and the phase difference layer 20 can be promoted. The easy-adhesion layer preferably contains silane having a reactive functional group. By providing such an easy adhesion layer, the realization of the required adhesion between the polarizing element 10 and the retardation layer 20 can be promoted. The details of the easy adhesion layer are described in Japanese Patent Laid-Open No. 2006-171707, for example.

In practical use, an adhesive layer (not shown) may also be provided on the protective layer 30 side of the optical laminate Show). By providing an adhesive layer in advance, it can be easily attached to other optical members (for example, liquid crystal cells and organic EL (Electroluminescence) panels). Furthermore, it is preferable that a release film is attached to the surface of the adhesive layer before being used.

B. Manufacturing method of optical laminate

An example of the method for manufacturing the optical laminate according to the embodiment of the present invention will be described only for characteristic parts. The manufacturing method includes: manufacturing a laminate having a polarizing element 10, a phase difference layer 20 disposed on one side of the polarizing element 10, and a protective layer 30 disposed on the other side of the polarizing element 10; Heating at a temperature above ℃ (hereinafter sometimes referred to as high-temperature heating). The heating temperature of high-temperature heating is preferably 86°C or higher. The upper limit of the heating temperature for high-temperature heating is, for example, 100°C. The heating time for high-temperature heating is preferably 3 minutes to 10 minutes, more preferably 3 minutes to 6 minutes. Before and/or after high-temperature heating, the laminate may be heated at a temperature less than 85°C (low-temperature heating). The heating temperature and heating time of bass heating can be appropriately set according to the purpose and the required characteristics of the obtained optical laminate. The high-temperature heating and/or low-temperature heating can also be used as a drying treatment for the adhesive in the build-up of the polarizing element, retardation layer (retardation film), and protective layer (protective film). In addition, the method of forming the polarizing element, the retardation layer (retardation film) and the protective layer (protection film) is as described above, or any suitable method may be used. In addition, any suitable method may be used for the lamination method of the polarizing element, the retardation layer (retardation film), and the protective layer (protection film).

C. Image display device

An image display device according to an embodiment of the present invention includes an optical laminate on the viewing side. Optical layering system The optical layered body according to the embodiment of the present invention described in the above items A and B. The optical build-up system is arranged so that the phase difference layer becomes the viewing side. Representative examples of image display devices include liquid crystal display devices and organic electroluminescence (EL) display devices. Since such an image display device includes the above-mentioned optical layered body on the viewing side, even when a display screen is viewed through a polarizing lens such as polarized sunglasses, excellent visibility can be achieved. Therefore, such an image display device can be preferably used outdoors.

[Example]

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples. In addition, the evaluation items in the examples are as follows.

(1) Difference in heating dimensional change rate

The optical layered bodies obtained in Examples and Comparative Examples were cut out in the direction of the slow phase axis and the direction of the phase advance axis to 4 mm×50 mm, respectively, and used as a measurement sample group. Each measurement sample was clamped with a metal jig so that the length of the measurement portion became 20 mm, and was put into the heating furnace in this state, and the dimensional change rate with respect to temperature change was measured. Specifically, using a thermal analysis system (Hitachi High-Tech Science Co., Ltd., TMA7100), the temperature was changed from 30°C to 90°C at a heating rate of 1.5°C/min, and the dimensional change rate of each measurement sample was measured. Within the range of the measurement temperature (30°C to 90°C), the temperature at which the difference in the dimensional change rate of the measurement sample cut along the direction of the late phase axis and the measurement sample cut along the direction of the advanced phase axis reaches the maximum The difference below is the difference in heating dimensional change rate. Furthermore, the curves of the dimensional change rate with respect to temperature in the direction of the slow phase axis and the direction of the progressive phase axis in Example 1 and Comparative Examples 1 and 2 are shown in FIGS. 2 to 4, respectively.

(2) Length in curling direction

The optical laminates obtained in Examples and Comparative Examples were cut out to 112 mm×65 mm (5 inch size) so that the absorption axis direction of the polarizing element became the long side. When the cut optical laminate is curled, the length of the optical laminate in the curl direction is measured. The larger the measured length, the smaller the amount of curling, indicating that the handleability is more excellent.

[Example 1]

(Manufacture of polarizing elements)

The PVA-based resin film with a polymerization degree of 2400, a saponification degree of 99.9 mol%, and a thickness of 30 μm was immersed in warm water at 30° C. to swell it while making the length of the PVA-based resin film 2.0 times the original length. The shaft extends. Then, immersed in an aqueous solution (dyeing bath) with a concentration of 0.3% by weight in a mixture of iodine and potassium iodide (weight ratio 0.5:8), on one side to make PVA The length of the resin film is 3.0 times the original length, and uniaxially stretched for dyeing. Then, after being immersed in an aqueous solution (crosslinking bath 1) of 5 wt% boric acid and 3 wt% potassium iodide, the length of the PVA resin film was extended to 3.7 times the original length, then boric acid at 60°C In an aqueous solution of 4% by weight and 5% by weight of potassium iodide (crosslinking bath 2), the length of the PVA-based resin film was extended so as to be 6 times the original length. Furthermore, after performing an iodine ion impregnation treatment with an aqueous solution of 3% by weight of potassium iodide (iodine impregnation bath), it was dried in an oven at 60° C. for 4 minutes to obtain a long polarized element (roll shape). The thickness of the obtained polarizing element was 12 μm. The absorption axis of the polarizing element is parallel to the longitudinal direction.

(Retardation film)

A long strip of triacetyl cellulose (TAC) film stretched diagonally to form a hard coat layer was used. The thickness of the TAC film is 40 μm, and the thickness of the hard coat layer is 5 μm. In addition, the in-plane phase difference Re (550) of the TAC film was 105 nm, and the angle formed by the slow phase axis and the longitudinal direction was 45°.

(Protection film)

A long strip of lactonized polymethyl methacrylate film (thickness 30 μm) was used.

(Fabrication of optical laminate)

The above-mentioned polarizing element, protective film and retardation film were laminated by roll-to-roll via a polyvinyl alcohol-based adhesive (solid content concentration 5.6% by weight, thickness after drying 0.08 μm) to produce a hard coating/ A layered body composed of a phase difference layer/polarizing element/protective layer. Thereafter, the produced laminate was dried at 66°C for 4 minutes and at 86°C for 4 minutes to obtain an optical laminate. The absorption axis direction of the polarizing element of the obtained optical laminate is parallel to the longitudinal direction, and the angle formed by the retardation axis of the retardation layer and the longitudinal direction is 45°. In addition, the total thickness of the obtained optical laminate was 97 μm. Furthermore, the obtained optical layered body was subjected to the evaluations of (1) and (2) above. As a result, the difference in heating dimensional change rate was 0.32%, and the length in the curl direction was 102 mm. The state of curling is shown in Fig. 5.

[Comparative Example 1]

An optical laminate was obtained in the same manner as in Example 1, except that the drying conditions of the laminate were changed to 66°C for 4 minutes, 70°C for 2 minutes, and 80°C for 2 minutes. The difference in heating dimensional change rate of the obtained optical laminate was 1.03%, and the length in the curling direction was 42 mm. The state of curling is shown in Fig. 6.

[Comparative Example 2]

An optical laminate was obtained in the same manner as in Example 1, except that the drying conditions of the laminate were changed to 66°C for 4 minutes, 70°C for 17 seconds, and 80°C for 17 seconds. The difference in heating dimensional change rate of the obtained optical laminate is 1.10%, and the length in the curling direction is 38 mm. The state of curling is shown in Fig. 7.

[Evaluation]

It is clear from FIGS. 5 to 7 that the optical laminate according to the embodiment of the present invention can control the difference in the heating dimensional change rate between the direction of the slow phase axis and the direction of the phase advance axis to achieve a very thin total thickness of 97 μm. And it suppresses curl well.

[Industry availability]

The optical layered body according to the embodiment of the present invention can be preferably used for an image display device, and in particular, can be preferably used for an image display device for viewing a display screen through a polarizing lens such as polarized sunglasses.

10‧‧‧Polarizing element

20‧‧‧ phase difference layer

30‧‧‧Protective layer

40‧‧‧hard coating

100‧‧‧Optical laminate

Claims (7)

An optical laminate including a polarizing element, a phase difference layer disposed on one side of the polarizing element, and a protective layer disposed on the other side of the polarizing element, the phase difference layer has a function of converting linearly polarized light into circularly polarized light or The function of elliptically polarized light, the difference between the heating dimension change rate in the first direction of the optical laminate and the heating dimension change rate in the second direction substantially orthogonal to the first direction is 1.0% or less, and the phase difference The in-plane phase difference of the layer is 80nm~160nm. The optical layered body according to claim 1, wherein the first direction is the slow phase axis direction or the progressive axis direction of the phase difference layer, and the second direction is the phase advance axis direction or the slow phase axis direction of the phase difference layer. The optical laminate as claimed in claim 1, wherein the angle formed by the absorption axis of the polarizing element and the slow phase axis of the phase difference layer is 35° to 55°. The optical layered body according to claim 1 is elongated, and the angle formed by the retardation axis of the phase difference layer and the longitudinal direction is 35° to 55°. The optical laminate according to claim 1, further comprising a hard coat layer on the opposite side of the phase difference layer from the polarizing element. The optical layered body according to claim 1, wherein the polarizer and the retardation layer and the protective layer are bonded with an aqueous adhesive having a solid component concentration of 6% by weight or less. An image display device includes an optical layered body as described in claim 1 on a viewing side, and the phase difference layer is disposed on the viewing side.

Images