JP2016177165A - Optical laminate, manufacturing method therefor and image display unit using the optical laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin optical laminate suppressing a curl and having a circular polarization function or an elliptic polarization function.SOLUTION: An optical laminate includes a polarizer, a retardation layer arranged on one side of the polarizer and a protective layer arranged on the other side of the polarizer. The retardation layer has a function of converting linear polarization to circular polarization or elliptic polarization. In the optical laminate, the difference between a heating size change rate in a first direction and a heating size change rate in a second direction substantially orthogonal to the first direction is 1.0% or lower.SELECTED DRAWING: Figure 1

Description

  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, image display devices such as mobile phones, smartphones, tablet personal computers (PCs), car navigation systems, digital signage, and window displays have been increasingly used under strong external light. When the image display device is used outdoors as described above, when the viewer views the image display device wearing polarized sunglasses, the transmission axis direction of the polarized sunglasses and the emission of the image display device depend on the viewing angle. As a result, the screen becomes black and the display image may not be visually recognized. In order to solve such a problem, a technique has been proposed in which a circularly polarizing plate (polarizing sunglasses-compatible polarizing plate) is disposed on the viewing-side surface of the image display device.

  Incidentally, there is an increasing demand for thinning of the image display device, and accordingly, there is an increasing demand for thinning the optical member used in the image display device. However, when trying to reduce the thickness of the polarizing plate for polarizing sunglasses as described above, there is a problem that curling (particularly, curling in the diagonal direction of the polarizing plate) is remarkable.

JP 2014-16425 A

  The present invention has been made in order to solve the above-described conventional problems, and an object of the present invention is to provide an optical laminate having a circular polarization function or an elliptical polarization function that is thin and curled. There is to do.

The optical layered body of the present invention includes a polarizer, a retardation layer disposed on one side of the polarizer, and a protective layer disposed on the other side of the polarizer. The retardation layer has a function of converting linearly polarized light into circularly polarized light or elliptically polarized light. In this optical layered body, 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 is 1.0% or less.
In one embodiment, the first direction is a slow axis direction or a fast axis direction of the retardation layer, and the second direction is a fast axis direction or a slow axis direction of the retardation layer. It is.
In one embodiment, the angle formed by the absorption axis of the polarizer and the slow axis of the retardation layer is 35 ° to 55 °.
In one embodiment, the optical layered body has a long shape, and the angle formed between the slow axis of the retardation layer and the long direction is 35 ° to 55 °.
In one embodiment, the optical layered body further includes a hard coat layer on the side of the retardation layer opposite to the polarizer.
In one embodiment, the polarizer, the retardation layer, and the protective layer are bonded together with 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. The image display device includes the optical layered body on the viewing side, and the retardation layer is disposed on the viewing side.

  According to an embodiment of the present invention, in an optical laminate including a polarizer, a retardation layer having a circular polarization function or an elliptical polarization function, and a protective layer, the heating dimensional change rate in the first direction and the first direction By controlling the difference with the heating dimensional change rate in the second direction substantially orthogonal to the optical laminate, it is possible to realize an optical laminate that is very thin but curled. In particular, suppression of curling in the diagonal direction is remarkable.

It is a schematic sectional drawing of the optical laminated body by one Embodiment of this invention. 4 is a graph showing a profile of a dimensional change rate in a slow axis direction and a fast axis direction with respect to temperature in Example 1. 6 is a graph showing a profile of a dimensional change rate in a slow axis direction and a fast axis direction with respect to temperature in Comparative Example 1; It is a graph which shows the profile of the dimensional change rate of the slow axis direction with respect to the temperature in the comparative example 2, and a fast axis direction. 2 is a photograph showing a curled state of the optical layered body of Example 1. FIG. 6 is a photograph showing a curled state of the optical layered body of Comparative Example 1. 6 is a photograph showing a curled state of the optical layered body of Comparative Example 2.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

(Definition of terms and symbols)
The definitions of terms and symbols in this specification are as follows.
(1) Refractive index (nx, ny, nz)
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximum (ie, the slow axis direction), and “ny” is the direction orthogonal to the slow axis in the plane (ie, the fast axis direction). “Nz” is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
“Re (λ)” is the in-plane retardation of the film measured with light having a wavelength of λ nm at 23 ° C. For example, “Re (450)” is the in-plane retardation of the film measured with light having a wavelength of 450 nm at 23 ° C. Re (λ) is determined by the formula: Re = (nx−ny) × d, where d (nm) is the thickness of the film.
(3) Thickness direction retardation (Rth)
“Rth (λ)” is a retardation in the thickness direction of the film measured with light having a wavelength of 550 nm at 23 ° C. For example, “Rth (450)” is the retardation in the thickness direction of the film measured with light having a wavelength of 450 nm at 23 ° C. Rth (λ) is determined by the formula: Rth = (nx−nz) × d, where d (nm) is the thickness of the film.
(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 between the two directions is 90 ° ± 10 °, preferably 90 ° ± 7 °. And more preferably 90 ° ± 5 °. The expressions “substantially parallel” and “substantially parallel” include the case where the angle between two directions is 0 ° ± 10 °, preferably 0 ° ± 7 °, more preferably 0 ° ± 5 °. Further, in the present specification, the term “orthogonal” or “parallel” may include a substantially orthogonal state or a substantially parallel state.
(6) Angle When referring to an angle in this specification, unless otherwise specified, the angle includes angles in both clockwise and counterclockwise directions.
(7) Long shape “Long shape” means an elongated shape having a sufficiently long length with respect to the width. For example, the elongated shape has a length of 10 times or more, preferably 20 times or more with respect to the width. Includes shape.

A. FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical layered body 100 of the present embodiment includes a polarizer 10, a retardation layer 20 disposed on one side of the polarizer 10, and a protective layer 30 disposed on the other side of the polarizer 10. Prepare. The retardation layer 20 has a function of converting linearly polarized light into circularly polarized light or elliptically polarized light. Therefore, the optical laminate 100 can typically be a circularly polarizing plate or an elliptically polarizing plate. The optical laminate 100 is typically arranged on the viewing side of the image display device. In this case, it arrange | positions so that the phase difference layer 20 may become a visual recognition side. With the configuration as described above, excellent visibility can be realized even when the display screen is viewed through a polarizing lens such as polarized sunglasses. Therefore, the optical laminate 100 can be suitably applied to an image display device that can be used outdoors.

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

  In the optical layered body 100, 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 is 1.0% or less, preferably It is 0.8% or less, More preferably, it is 0.6% or less, More preferably, it is 0.4% or less. According to the embodiment of the present invention, by controlling the heating dimensional change rate in two directions substantially orthogonal to each other, it is possible to realize an optical laminate that is very thin and curled. Typically, the first direction is the slow axis direction or the fast axis direction of the retardation layer 20, and the second direction is the fast axis direction or the slow axis direction of the retardation 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 polarizer 10 and the retardation layer 20 are laminated so that the absorption axis of the polarizer 10 and the slow axis of the retardation layer 20 form a predetermined angle. The angle formed by the absorption axis of the polarizer 10 and the slow axis of the retardation layer 20 is preferably 35 ° to 55 °, more preferably 38 ° to 52 °, and still more preferably 40 ° to 50 °. Particularly preferably, the angle is 42 ° to 48 °, and particularly preferably around 45 °. By arranging the retardation layer 20 on the viewing side with respect to the polarizer 10 in such an axial relationship, excellent visibility can be realized even when the display screen is viewed through a polarizing lens such as polarized sunglasses. it can. Therefore, the optical laminate according to the embodiment of the present invention can be suitably applied to an image display device that can be used outdoors.

  The optical layered body 100 may be a single wafer shape or a long shape (for example, a roll shape). When the optical laminated body 100 is long, the absorption axis direction of the long polarizer may be the long direction or the width direction. Preferably, the absorption axis direction of the polarizer is a long direction. This is because the polarizer can be easily manufactured, and as a result, the manufacturing efficiency of the optical laminate is excellent. When the optical layered body is long, the angle θ formed between the slow axis of the retardation layer 20 and the long direction is preferably 35 ° to 55 °, more preferably 38 ° to 52 °, and further The angle is preferably 40 ° to 50 °, particularly preferably 42 ° to 48 °, and particularly preferably around 45 °. As will be described later, by forming the retardation film constituting the retardation layer by oblique stretching, a long retardation film (retardation layer) having a slow axis in the oblique direction can be formed. As described above, a long optical laminated body can be realized. Since such a long optical laminate can be produced by roll-to-roll, productivity is remarkably improved.

  The total 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 in which curling is satisfactorily suppressed while having such a very thin thickness. The total thickness of the optical laminate means the total thickness of the polarizer, the retardation layer, the protective layer, the hard coat layer if present, and the adhesive layer for laminating them.

  Hereinafter, each layer which comprises the optical laminated body by embodiment of this invention is demonstrated.

A-1. Polarizer Any appropriate polarizer may be adopted as the polarizer 10. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

  Specific examples of polarizers composed of a single layer resin film include high hydrophilicity such as polyvinyl alcohol (PVA) resin film, partially formalized PVA resin film, ethylene / vinyl acetate copolymer partially saponified film, etc. Examples of molecular films that have been dyed and stretched with dichroic substances such as iodine and dichroic dyes, polyene-based oriented films such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products It is done. Preferably, a polarizer obtained by dyeing a PVA resin film with iodine and uniaxially stretching is used because of excellent optical properties.

  The dyeing with iodine is performed, for example, by immersing a PVA resin film in an iodine aqueous solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment or may be performed while dyeing. Moreover, you may dye | stain after extending | stretching. If necessary, the PVA-based resin film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA resin film in water and washing it before dyeing, the PVA resin film surface can be cleaned of stains and anti-blocking agents, and the PVA resin film can be swollen and dyed. Unevenness can be prevented.

  As a specific example of a polarizer obtained by using a laminate, a laminate of a resin substrate and a PVA resin layer (PVA resin film) laminated on the resin substrate, or a resin substrate and the resin Examples thereof include a polarizer obtained by using a laminate with a PVA resin layer applied and formed on a substrate. For example, a polarizer obtained by using a laminate of a resin base material and a PVA resin layer applied and formed on the resin base material may be obtained by, for example, applying a PVA resin solution to a resin base material and drying it. A PVA-based resin layer is formed thereon to obtain a laminate of a resin base material and a PVA-based resin layer; the laminate is stretched and dyed to make the PVA-based resin layer a polarizer; obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, the stretching may further include, if necessary, stretching the laminate in the air at a high temperature (for example, 95 ° C. or higher) before stretching in the aqueous boric acid solution. The obtained resin base material / polarizer laminate may be used as it is (that is, the resin base material may be used as a protective layer of the polarizer), and the resin base material is peeled from the resin base material / polarizer laminate. Any appropriate protective layer according to the purpose may be laminated on the release surface. Details of a method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. This publication is incorporated herein by reference in its entirety.

  The thickness of the polarizer is preferably 15 μm or less, more preferably 13 μm or less, still more preferably 10 μm, and particularly preferably 8 μm or less. The lower limit of the polarizer thickness is 2 μm in one embodiment and 3 μm in another embodiment. According to the embodiment of the present invention, even when the thickness of the polarizer is very thin, curling when the optical laminate is heated can be satisfactorily suppressed.

  The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is preferably 44.0% to 45.5%, more preferably 44.5% to 45.0%. According to the present invention, it is possible to realize an optical laminated body that is extremely thin and curl-suppressed, and further, it is possible to realize the excellent single transmittance as described above in such an optical laminated body.

  As described above, the degree of polarization of the polarizer 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 an optical laminated body that is very thin and curl-suppressed, and further, in such an optical laminated body, an excellent degree of polarization as described above can be realized.

A-2. Retardation Layer The retardation layer 20 has a function of converting linearly polarized light into circularly polarized light or elliptically polarized light as described above. That is, the retardation layer 20 typically has a relationship in which the refractive index characteristic is nx> ny. The in-plane retardation Re (550) of the retardation film is preferably 80 nm to 160 nm, more preferably 90 nm to 120 nm. When the in-plane retardation is in such a range, a retardation film having appropriate elliptical polarization performance can be obtained with excellent productivity and reasonable cost. As a result, an optical laminate that can ensure good visibility even when the display screen is viewed through a polarizing lens such as polarized sunglasses can be obtained with excellent productivity and reasonable cost.

  The retardation layer 20 exhibits any appropriate refractive index ellipsoid as long as it has a relationship of nx> ny. Preferably, the refractive index ellipsoid of the retardation layer exhibits a relationship of nx> ny ≧ nz. The Nz coefficient of the retardation layer is preferably 1 to 2, more preferably 1 to 1.5, and still more preferably 1 to 1.3.

  The retardation layer 20 is composed of any appropriate retardation film that can satisfy the optical characteristics as described above. A typical example of the resin forming the retardation film is a cellulose ester resin (hereinafter, also simply referred to as a cellulose ester).

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

  The cellulose ester is an acyl group such as an acetyl group or a propionyl group in part or all of the free hydroxyl groups (hydroxyl groups) at the 2nd, 3rd and 6th positions in the glucose unit constituting the cellulose with β-1,4-glycoside bonds. It is a polymer esterified by (polymer). Here, the “acyl group substitution degree” represents the total of the ratio of hydroxyl groups esterified with respect to the 2nd, 3rd and 6th positions of glucose as a repeating unit. Specifically, the degree of substitution is 1 when the hydroxyl groups at the 2-position, 3-position and 6-position of cellulose are each 100% esterified. Therefore, when all of the 2nd, 3rd and 6th positions of cellulose are 100% esterified, the degree of substitution is 3 at the maximum. The “average acyl group substitution degree” refers to an acyl group substitution degree in which the acyl group substitution degree of a plurality of glucose units constituting the cellulose ester resin is expressed as an average value per unit. The degree of acyl group substitution can be measured according to ASTM-D817-96.

  Examples of the acyl group include acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, and isobutanoyl. Group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group.

In one embodiment, when the acetyl group substitution degree of the cellulose ester resin is X and the propionyl group substitution degree is Y, X and Y preferably satisfy the following formulas (1) and (2).
Formula (1): 2.0 ≦ (X + Y) ≦ 2.8
Formula (2): 0 ≦ Y ≦ 1.0
More preferably, the cellulose ester resin satisfying the above formulas (1) and (2) includes a cellulose ester resin satisfying the following formula (1a) and the above formula (2), and a cellulose ester resin satisfying the following formula (1b): , Containing.
Formula (1a): 2.0 ≦ (X + Y) <2.5
Formula (1b): 2.5 ≦ (X + Y) ≦ 2.8
Note that “acetyl group substitution degree” and “propionyl group substitution degree” are more specific indicators of the above acyl group substitution degree, and “acetyl group substitution degree” refers to the 2nd and 3rd positions of glucose of the repeating unit. And the 6-position, the total of the proportion of hydroxyl groups esterified by acetyl groups, and “propionyl group substitution degree” means that the hydroxyl group is acetylated at the 2nd, 3rd and 6th positions of glucose of the repeating unit. The total of the ratio esterified by group is represented.

  The cellulose ester resin preferably has a molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of 1.5 to 5.5, more preferably 2.0 to 5.0, and even more preferably 2.5. It is -5.0, Most preferably, it is 3.0-5.0.

  Arbitrary appropriate cellulose can be used as a cellulose of the raw material of a cellulose ester resin. Specific examples include cotton linters, wood pulp, and kenaf. A cellulose ester resin obtained from different raw materials may be used in combination.

  The cellulose ester resin can be produced by any appropriate method. Representative examples include methods comprising the following procedures: raw cellulose, certain organic acids (eg, acetic acid, propionic acid), acid anhydrides (eg, acetic anhydride, propionic anhydride), and catalysts (eg, Sulfuric acid) is mixed to esterify the cellulose, and the reaction proceeds until a cellulose triester is obtained. In cellulose triester, the three hydroxyl groups (hydroxyl groups) of the glucose unit are substituted with an acyl acid of an organic acid. When two types of organic acids are used at the same time, a mixed ester type cellulose ester (for example, cellulose acetate propionate, cellulose acetate butyrate) can be prepared. Next, a cellulose ester having a desired degree of acyl group substitution is synthesized by hydrolyzing the cellulose triester. Thereafter, a cellulose ester resin can be obtained through steps such as filtration, precipitation, washing with water, dehydration, and drying.

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

  Arbitrary appropriate methods may be employ | adopted as a formation method of a resin film. For example, a melt extrusion method (for example, a T-die molding method), a cast coating method (for example, a casting method), a calendar molding method, a hot press method, a co-extrusion method, a co-melting method, a multilayer extrusion method, an inflation molding method, etc. It is done. Preferably, a T-die molding method, a casting method, and an inflation molding method are used.

  The thickness of the resin film (unstretched film) can be set to any appropriate value depending on desired optical characteristics, stretching conditions described later, and the like. Preferably they are 50 micrometers-300 micrometers, More preferably, they are 80 micrometers-250 micrometers.

  Any appropriate stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching direction) can be adopted for the stretching. Specifically, various stretching methods such as free end stretching, fixed end stretching / free end contraction, and fixed end contraction can be used singly or simultaneously or sequentially. The stretching direction can also be performed in various directions and dimensions such as a horizontal direction, a vertical direction, a thickness direction, and a diagonal direction. The stretching temperature is preferably in the range of glass transition temperature (Tg) ± 20 ° C. of the resin film.

  By appropriately selecting the stretching method and stretching conditions, a retardation film (resulting in a retardation layer) having the desired optical properties (for example, refractive index ellipsoid, in-plane retardation, Nz coefficient) is obtained. Can do.

  In one embodiment, the phase difference layer 20 is produced by uniaxially stretching a resin film or uniaxially stretching a fixed end. As a specific example of uniaxial stretching, there is a method of stretching in the longitudinal direction (longitudinal direction) while running the resin film in the longitudinal direction. Another specific example of the uniaxial stretching includes a method of stretching in the transverse direction using a tenter. The draw ratio is preferably 10% to 500%.

  In another embodiment, the retardation layer 20 is produced by continuously and obliquely stretching a long resin film in the direction of an angle θ with respect to the long direction. By adopting oblique stretching, a long stretched film having an orientation angle of an angle θ with respect to the long direction of the film can be obtained. Can be simplified. The angle θ is as described above.

  Examples of the stretching machine used for the oblique stretching include a tenter-type stretching machine that can apply a feeding force, a pulling force, or a pulling force at different speeds in the lateral and / or longitudinal direction. The tenter type stretching machine includes a horizontal uniaxial stretching machine, a simultaneous biaxial stretching machine, and the like, but any suitable stretching machine can be used as long as a long resin film can be continuously stretched obliquely.

  Examples of the oblique stretching method include, for example, JP-A-50-83482, JP-A-2-113920, JP-A-3-182701, JP-A-2000-9912, JP-A-2002-86554, Examples include the method described in JP-A-2002-22944.

  The thickness of the stretched film (as a result, the retardation layer) is preferably 20 μm to 80 μm, 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 a commercially available film may be used after being subjected to secondary processing (for example, stretching treatment, surface treatment).

  The surface of the retardation layer 20 on the side of the polarizer 10 may be subjected to surface treatment. Examples of the surface treatment include corona treatment, plasma treatment, flame treatment, primer coating treatment, and saponification treatment. Examples of the corona treatment include a method in which discharge is performed in normal pressure air by a corona treatment machine. As the plasma treatment, for example, a method of discharging in a normal pressure air by a plasma discharge machine can be mentioned. An example of the frame treatment is a method in which a flame is brought into direct contact with the film surface. Examples of the primer coating treatment include a method of diluting an isocyanate compound, a silane coupling agent or the like with a solvent and coating the diluted solution thinly. Examples of the saponification treatment include a method of immersing in a sodium hydroxide aqueous solution. Corona treatment and plasma treatment are preferable.

A-3. Protective layer The protective layer 30 is formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material that is the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based materials. And transparent resins such as polystyrene, polynorbornene, polyolefin, (meth) acryl, and acetate. Further, thermosetting resins such as (meth) acrylic, urethane-based, (meth) acrylurethane-based, epoxy-based, and silicone-based or ultraviolet curable resins are also included. In addition to this, for example, a glassy polymer such as a siloxane polymer is also included. Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in the side chain For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the resin composition.

  As said (meth) acrylic-type resin, Tg (glass transition temperature) becomes like this. Preferably it is 115 degreeC or more, More preferably, it is 120 degreeC or more, More preferably, it is 125 degreeC or more, Most preferably, it is 130 degreeC or more. It is because it can be excellent in durability. Although the upper limit of Tg of the said (meth) acrylic-type resin is not specifically limited, From viewpoints of a moldability etc., Preferably it is 170 degrees C or less.

As said (meth) acrylic-type resin, arbitrary appropriate (meth) acrylic-type resins can be employ | adopted within the range which does not impair the effect of this invention. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester -(Meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer) And methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, poly (meth) acrylic acid C _1-6 alkyl such as poly (meth) acrylate methyl is used. More preferably, a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

  Specific examples of the (meth) acrylic resin include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. Examples of the resin include high Tg (meth) acrylic resins obtained by intramolecular crosslinking or intramolecular cyclization reaction.

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

  Examples of the (meth) acrylic resin having the lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. Examples thereof include (meth) acrylic resins having a lactone ring structure described in JP-A-146084.

  The (meth) acrylic resin having the lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, and still more preferably 10,000 to 500,000. Preferably it is 50000-500000.

  The (meth) acrylic resin having a lactone ring structure has a Tg (glass transition temperature) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, still more preferably 130 ° C. or higher, particularly preferably 135 ° C., most preferably. Is 140 ° C. or higher. It is because it can be excellent in durability. The upper limit of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, but is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  In the present specification, “(meth) acrylic” refers to acrylic and / or methacrylic.

  The protective layer 30 is preferably optically isotropic. In this specification, “optically isotropic” means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is −10 nm to +10 nm. Say.

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

A-4. Hard Coat Layer The hard coat layer 40 has a function of imparting chemical resistance, scratch resistance and surface smoothness to the optical layered body and improving dimensional stability under high temperature and high humidity. Any appropriate configuration may be adopted as the hard coat layer 40. The hard coat layer is, for example, a cured layer of any appropriate ultraviolet curable resin. Examples of the ultraviolet curable resin include acrylic resins, silicone 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. If it is such a range, the optical laminated body which is excellent in the dimensional stability under high temperature can be obtained. The hard coat layer may contain any appropriate additive as required. Representative examples of the additive 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 Application Laid-Open No. 2007-171943, and the description thereof is incorporated herein by reference.

A-5. Adhesive layer Arbitrary appropriate adhesive layers (not shown) are used for bonding each layer which comprises the optical laminated body by embodiment of this invention. The adhesive layer may be a pressure-sensitive adhesive layer or an adhesive layer. Typically, the polarizer 10, the retardation layer 20, and the protective layer 30 are bonded together with an aqueous adhesive. Any appropriate aqueous adhesive can be adopted as the aqueous adhesive. Preferably, an aqueous adhesive containing a PVA resin is used. The average degree of polymerization of the PVA resin contained in the aqueous adhesive is preferably about 100 to 5500, more preferably 1000 to 4500, from the viewpoint of adhesiveness. The average saponification degree is preferably about 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, from the viewpoint of adhesiveness.

  The PVA resin contained in the aqueous adhesive preferably contains an acetoacetyl group. This is because the adhesion between the polarizer, the retardation layer and the protective layer is excellent, and the durability can be excellent. The acetoacetyl group-containing PVA resin can be obtained, for example, by reacting a PVA resin and diketene by an arbitrary method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA resin is typically 0.1 mol% or more, preferably about 0.1 mol% to 40 mol%, more preferably 1 mol% to 20 mol. %, Particularly preferably 1 mol% to 7 mol%. The degree of acetoacetyl group modification is a value measured by NMR.

  The solid content concentration 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 solid content concentration is such a range, there exists an advantage that the dimensional control rate of a polarizing plate is easy to control. When the solid content concentration is too low, the water content of the obtained optical laminate is increased, and the dimensional change may be increased depending on the drying conditions. If the solid content concentration is too high, the viscosity of the adhesive increases, and the productivity of the optical laminate may become insufficient.

  The thickness of the adhesive 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 cannot be obtained, and the adhesive strength may not be obtained. If the thickness of the adhesive layer is too thick, the optical laminate may not satisfy the durability.

A-6. Others In one embodiment, an easily bonding layer (not shown) may be provided on the surface of the retardation layer 20 on the polarizer 10 side. When providing an easily bonding layer, the phase difference layer 20 may or may not be subjected to the surface treatment described above. Preferably, the retardation layer 20 is subjected to a surface treatment. By combining the easy-adhesion layer and the surface treatment, realization of a desired adhesive force between the polarizer 10 and the retardation layer 20 can be promoted. The easy-adhesion layer preferably contains a silane having a reactive functional group. By providing such an easy-adhesion layer, realization of a desired adhesive force between the polarizer 10 and the retardation layer 20 can be promoted. Details of the easy-adhesion layer are described in, for example, JP-A-2006-171707.

  Practically, an adhesive layer (not shown) may be provided on the protective layer 30 side of the optical layered body. By providing the pressure-sensitive adhesive layer in advance, it can be easily bonded to another optical member (for example, a liquid crystal cell or an organic EL panel). In addition, it is preferable that the peeling film is bonded together on the surface of this adhesive layer until it uses.

B. Method for Producing Optical Laminate A characteristic part of an example of a method for producing an optical laminate according to an embodiment of the present invention will be briefly described. This manufacturing method produces the laminated body which has the phase difference layer 20 arrange | positioned on the one side of the polarizer 10 and the polarizer 10, and the protective layer 30 arrange | positioned on the other side of the polarizer 10, And the said laminated body is heated at the temperature of 85 degreeC or more, for example (henceforth a high temperature heating may be included hereafter). The heating temperature of the high temperature heating is preferably 86 ° C. or higher. The upper limit of the heating temperature of the high temperature heating is, for example, 100 ° C. The heating time of the high temperature heating is preferably 3 minutes to 10 minutes, more preferably 3 minutes to 6 minutes. You may heat a laminated body at the temperature below 85 degreeC (low temperature heating) before and / or after high temperature heating. The heating temperature and heating time of the low-frequency heating can be appropriately set according to the purpose and desired characteristics of the obtained optical laminate. High temperature heating and / or low temperature heating may also serve as a drying treatment of the adhesive in the lamination of the polarizer, the retardation layer (retardation film) and the protective layer (protective film). In addition, as for the formation method of a polarizer, a phase difference layer (retardation film), and a protective layer (protective film), any appropriate method as described above can be adopted. Arbitrary appropriate methods can also be employ | adopted for the lamination | stacking method of a polarizer, retardation layer (retardation film), and a protective layer (protective 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. The optical laminate is the optical laminate according to the embodiment of the present invention described in the above sections A and B. The optical layered body is arranged so that the retardation layer is on the viewing side. Typical examples of the image display device include a liquid crystal display device and an organic electroluminescence (EL) display device. Such an image display device can realize excellent visibility even when the display screen is viewed through a polarizing lens such as polarized sunglasses by providing the optical layered body on the viewing side. Therefore, such an image display device can be suitably used even outdoors.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this 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 laminates obtained in the examples and comparative examples were cut into 4 mm × 50 mm along the slow axis direction and the fast axis direction, respectively, and used as measurement sample sets. About each measurement sample, it chucked with the metal jig so that the length of a measurement part might be set to 20 mm, it injected into the heating furnace in that state, and the dimensional change rate with respect to a temperature change was measured. Specifically, using a thermal analysis system (manufactured by Hitachi High-Tech Science Co., TMA7100), the temperature was changed from 30 ° C. to 90 ° C. at a temperature rising rate of 1.5 ° C./min, and the dimensional change of each measurement sample. The rate was measured. Within the measurement temperature range (30 ° C. to 90 ° C.), at the temperature at which the difference in the dimensional change rate between the measurement sample cut out along the slow axis direction and the measurement sample cut out along the fast axis direction is the largest. The difference was defined as the heating dimensional change rate difference. The dimensional change rate profiles in the slow axis direction and in the fast axis direction with respect to temperature in Example 1 and Comparative Examples 1 and 2 are shown in FIGS.
(2) Length in curl direction The optical laminates obtained in Examples and Comparative Examples were cut into 112 mm × 65 mm (5 inch size) so that the absorption axis direction of the polarizer was the long side. When the cut-out optical laminate was curled, the length of the optical laminate in the curl direction was measured. The larger the measured length, the smaller the curl amount and the better the handleability.

[Example 1]
(Production of polarizer)
A PVA resin film having a polymerization degree of 2400, a saponification degree of 99.9 mol%, and a thickness of 30 μm is immersed in warm water at 30 ° C. and swollen while the length of the PVA resin film is 2.0 times the original length. Uniaxial stretching was performed so that Next, the mixture is immersed in an aqueous solution (dye bath) having a concentration of a mixture of iodine and potassium iodide (weight ratio 0.5: 8) of 0.3% by weight, and the length of the PVA resin film is 3.0, the original length. It dye | stained, uniaxially stretching so that it might become double. Then, while being immersed in an aqueous solution (crosslinking bath 1) of 5% by weight of boric acid and 3% by weight of potassium iodide, the PVA resin film was stretched so that its length was 3.7 times the original length. In an aqueous solution of 4% by weight boric acid and 5% by weight potassium iodide (crosslinking bath 2) at 60 ° C., the length of the PVA resin film was stretched to 6 times the original length. Further, after an iodine ion impregnation treatment with an aqueous solution (iodine impregnation bath) of 3% by weight of potassium iodide, it was dried in an oven at 60 ° C. for 4 minutes to obtain a long (roll-shaped) polarizer. The thickness of the obtained polarizer was 12 μm. The absorption axis of the polarizer was parallel to the longitudinal direction.
(Retardation film)
A long triacetyl cellulose (TAC) film that was obliquely stretched and further formed with a hard coat layer was used. The thickness of the TAC film was 40 μm, and the thickness of the hard coat layer was 5 μm. The in-plane retardation Re (550) of the TAC film was 105 nm, and the angle formed between the slow axis and the long direction was 45 °.
(Protective film)
A long lactonized polymethylmethacrylate film (thickness 30 μm) was used.

(Production of optical laminate)
The above polarizer, a protective film and a retardation film are bonded to each other by roll-to-roll through a polyvinyl alcohol-based adhesive (solid content concentration 5.6 wt%, thickness after drying 0.08 μm), and a hard coat layer A laminate having a configuration of / retardation layer / polarizer / protective layer was produced. Then, the produced laminated body was dried at 66 degreeC for 4 minutes, and 86 degreeC for 4 minutes, and the optical laminated body was obtained. In the obtained optical layered body, the absorption axis direction of the polarizer was parallel to the long direction, and the angle formed between the slow axis of the retardation layer and the long direction was 45 °. Moreover, the total thickness of the obtained optical laminated body was 97 micrometers. Furthermore, when the obtained optical laminate was subjected to the evaluations (1) and (2) above, 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.

[Comparative Example 1]
An optical laminate was obtained in the same manner as in Example 1 except that the drying condition of the laminate was changed to 66 ° C. for 4 minutes, 70 ° C. for 2 minutes, and 80 ° C. for 2 minutes. The obtained optical laminate had a heating dimensional change rate difference of 1.03% and a curl direction length of 42 mm. The state of curling is shown in FIG.

[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 obtained optical layered body had a heating dimensional change rate difference of 1.10% and a curl length of 38 mm. The curled state is shown in FIG.

[Evaluation]
As is apparent from FIGS. 5 to 7, the optical layered body of the example of the present invention has a total thickness of 97 μm by controlling the difference in heating dimensional change rate between the slow axis direction and the fast axis direction. It can be seen that curling can be well suppressed while being thin.

  The optical layered body according to the embodiment of the present invention is suitably used for an image display device, and can be particularly suitably used for an image display device that visually recognizes a display screen through a polarized lens such as polarized sunglasses.

DESCRIPTION OF SYMBOLS 10 Polarizer 20 Retardation layer 30 Protective layer 40 Hard-coat layer 100 Optical laminated body

Claims (7)

A polarizer, a retardation layer disposed on one side of the polarizer, and a protective layer disposed on the other side of the polarizer,
The retardation layer has a 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 and the heating dimensional change rate in the second direction substantially orthogonal to the first direction is 1.0% or less.
Optical laminate.   The first direction is a slow axis direction or a fast axis direction of the retardation layer, and the second direction is a fast axis direction or a slow axis direction of the retardation layer. The optical laminated body as described.   3. The optical laminate according to claim 1, wherein an angle formed between an absorption axis of the polarizer and a slow axis of the retardation layer is 35 ° to 55 °.   The optical laminate according to any one of claims 1 to 3, wherein the optical laminate has a long shape, and an angle formed between a slow axis of the retardation layer and a long direction is 35 ° to 55 °.   The optical laminated body in any one of Claim 1 to 4 further equipped with the hard-coat layer on the opposite side to the said polarizer of the said phase difference layer.   The optical laminate according to any one of claims 1 to 5, wherein the polarizer, the retardation layer, and the protective layer are bonded together with an aqueous adhesive having a solid content concentration of 6 wt% or less. An image display device comprising the optical layered body according to claim 1 on the viewing side, wherein the retardation layer is disposed on the viewing side.