TWI783087B - Optical laminate and production method therefor - Google Patents

Abstract

Provided is an optical laminate containing a protection film, a polarizing plate, a phase retardation layer, and a pressure sensitive adhesive layer in this order, where the protection film satisfies the formula: [First modulus of elasticity] - [Second modulus of elasticity]

300 MPa.

In the formula, the first modulus of elasticity refers a tensile modulus of elasticity in a direction orthogonal to an absorption axis of the polarizing plate measured at a temperature of 23℃ at a relative humidity of 55% RH, and the second modulus of elasticity refers a tensile modulus of elasticity in a direction parallel to the 10 absorption axis of the polarizing plate measured at a temperature of 23℃ at a relative humidity of 55% RH.

Description

Optical layered body and method for producing the optical layered body

The present invention relates to an optical laminate including a protective film, a polarizing plate, a retardation layer and an adhesive layer, and a method for manufacturing the optical laminate.

As for polarizers used in image display devices such as liquid crystal display devices and organic EL display devices, conventionally, polarizers made of polyvinyl alcohol-based resins are generally used to bond triethyl alcohol with an adhesive. Protective film made of acyl cellulose (TAC).

In recent years, protective films made of resins other than TAC have been used from the viewpoints of thinning, durability, cost, and productivity [for example, JP 2004-245925 A (Patent Document 1)].

A retardation layer and an adhesive layer are sometimes laminated on one side of the polarizing plate. Although it is required to reduce the thickness of the multilayer structure including such a polarizing plate, the sheet-like body of the multilayer structure obtained by cutting out a thin and inelastic multilayer structure, especially a long multilayer structure , prone to bow-like warping deformation. In this specification, this deformation|transformation is also called "warping."

A multilayer structure is generally made with a peelable protective film (also called a surface protective film) attached to the surface of the polarizer (the surface opposite to the side where the retardation layer and the adhesive layer are laminated) to protect the surface. The multi-layer structure with protective film is circulated in the market. In a multilayer structure with a protective film, there is also a tendency that "if it becomes thinner, it will easily warp when forming a sheet".

Hereinafter, the above-mentioned multilayer structure with a protective film including a protective film, a polarizing plate, a retardation layer, and an adhesive layer in this order is also simply referred to as an "optical laminate".

There are two types of warping in optical laminates: "positive warping" and "reverse warping". In the optical layered body, the so-called "normal warpage" is warpage in which the surface on the protective film side is concave, and the so-called "reverse warpage" is warpage in which the surface on the protective film side is convex.

If the reverse warpage occurs, when the sheet-shaped body of the optical laminate is bonded to image display elements such as liquid crystal cells and organic EL elements through the adhesive layer, it will become easy to cause bonding errors or cause The unfavorable situation that air bubbles are mixed at the interface between the adhesive layer and the image display element.

The object of the present invention is to provide an optical laminate with reverse warpage suppressed and its manufacturing method.

The present invention provides the optical layered body shown below and its manufacturing method.

[1] An optical laminate comprising in sequence: a protective film, a polarizing plate, one or more retardation layers, and an adhesive layer; the aforementioned protective film satisfies the following formula (I): 1st modulus of elasticity - 2nd Modulus of elasticity≧300MPa (I)

In the formula, the so-called first modulus of elasticity refers to the tensile modulus of elasticity in the direction perpendicular to the absorption axis of the polarizing plate at a temperature of 23°C and a relative humidity of 55%RH, and the so-called second modulus of elasticity refers to the modulus of elasticity at a temperature of 23°C. Tensile elastic modulus in a direction parallel to the absorption axis of the polarizing plate at ℃ and a relative humidity of 55%RH.

[2] The optical laminate according to item [1], wherein the polarizing plate has a thickness of 110 μm or less.

[3] The optical laminate described in [1] or [2], wherein the one or more retardation layers include a retardation layer made of a cured liquid crystal compound.

[4] A method of manufacturing an optical laminate, which is a method of manufacturing the optical laminate described in any one of items [1] to [3], which includes: the first step, comprising satisfying the following formula ( The protective film in the area of I) is laminated on one side of the polarizing plate; the second step is to laminate more than one retardation layer and adhesive layer on the opposite side of the aforementioned polarizing plate to the aforementioned single side; the third step The step is to cut out the aforementioned optical laminate from the aforementioned region; the first elastic modulus-the second elastic modulus≧300MPa (I)

In the formula, the so-called first elastic modulus refers to the tensile elastic modulus in the direction perpendicular to the absorption axis of the polarizing plate at a temperature of 23°C and a relative humidity of 55%RH, and the so-called second elastic modulus refers to a temperature of 23°C and a relative humidity of 55%RH. Tensile elastic modulus in a direction parallel to the absorption axis of the aforementioned polarizing plate at a relative humidity of 55%RH.

[5] The production method according to item [4], wherein the second step includes a step of peeling off the base film after laminating a laminated volume including a base film and a retardation layer on the opposite side.

According to the present invention, an optical layered body in which reverse warpage is suppressed, and a method for producing the optical layered body can be provided.

1‧‧‧Protective film

2, 2a, 2b‧‧‧polarizer

3‧‧‧The first retardation layer

3a‧‧‧The first bonding layer

4‧‧‧The second retardation layer

4a‧‧‧The second bonding layer

5‧‧‧1st adhesive layer

6‧‧‧Separation film

7‧‧‧Polarizing plate with protective film

8‧‧‧Laminating roller

10‧‧‧Polarizer

20‧‧‧The first thermoplastic resin film

30‧‧‧The second thermoplastic resin film

40‧‧‧Substrate film

50‧‧‧The second adhesive layer

60‧‧‧Elongated optical laminate

61‧‧‧Absorption axis of polarizer

70‧‧‧flaky body

80‧‧‧Flake horn

Fig. 1 is a schematic cross-sectional view showing an example of an optical laminate.

Fig. 2 is a schematic cross-sectional view showing an example of the layer structure of a polarizing plate.

Fig. 3 is a schematic cross-sectional view showing another example of the layer structure of a polarizing plate.

Fig. 4 is a flowchart showing a method of manufacturing an optical laminate.

Fig. 5 is a side view showing an example of the manufacturing step S101 of a polarizing plate with a protective film.

Fig. 6 is a schematic diagram showing a method of manufacturing a sheet-shaped body and explaining measurement points of MD warpage.

<Optical laminate>

The optical laminated system of the present invention comprises in order: a protective film, a polarizing plate, one or more retardation layers, and an adhesive layer (the first adhesive layer).

Hereinafter, the optical layered body will be described in detail.

(1) The structure of the optical laminate

Fig. 1 is a schematic cross-sectional view showing an example of the optical layered body of the present invention. The optical laminate shown in Fig. 1 includes in order: a protective film 1; a polarizing plate 2; a first bonding layer 3a; a first retardation layer 3; a second bonding layer 4a; a second retardation layer 4; agent layer 5; separation membrane 6.

The first adhesive layer 5 is defined as an adhesive layer disposed on the outermost side of the polarizing plate 2 opposite to the side on which the protective film 1 is laminated.

The protective film 1 is composed of a base film 40 and a second adhesive layer 50 laminated on the base film 40 .

When the protective film 1 is composed of a base film 40 and a second adhesive layer 50 laminated on the base film 40, the second adhesive layer 50 of the protective film 1 is superimposed so as to be in contact with the polarizing plate. 2 on one side.

According to the present invention, for example, in the optical layered body shown in FIG. 1 , the occurrence of reverse warpage that makes the surface on the protective film 1 side convex can be suppressed.

According to the optical layered body whose reverse warpage is suppressed, when it is bonded to the image display device through the first adhesive layer it has, it is possible to suppress the occurrence of bonding errors, or prevent the occurrence of bonding errors between the first adhesive layer and the image. The unfavorable situation of air bubbles mixed in the interface of the display element.

The optical laminate can be a strip or a sheet, but usually the problem of warping is likely to occur in the sheet, so the optical laminate is preferably a sheet.

In this specification, a "sheet-shaped body" is a film of a small size cut out from a film of a large size [for example, a strip-shaped (belt-shaped) film].

Here, the warping of the optical layered body is classified into two types of so-called "MD warping" and "TD warping" differently from the above-mentioned classification of "normal warping" and "reverse warping". The so-called "MD warping" refers to the warpage of the sheet-shaped optical laminated body due to the stress (shrinkage force, expansion force, etc.) in a direction parallel to the MD direction of the elongated optical laminated body from which the sheet-shaped body is cut out. song.

Specifically, the MD warpage can be obtained by cutting out a measurement sample (sheet) from the elongated optical layered body according to the description in the paragraphs of the examples described later, and placing the measurement sample on the concave side. When placed face up on a horizontal platform, among the two diagonals of the measurement sample, the two angles on the diagonal with the smaller angle to the absorption axis direction of the polarizing plate of the measurement sample form a The raised warpage (warpage in the direction of the absorption axis) is measured to measure its size. In a long polarizer with a protective film, when the absorption axis direction of the polarizer is parallel to the MD direction of the protective film, the MD warpage can be set as Among the two diagonals of the measurement sample, the two corners on the diagonal that have a smaller angle with the MD direction of the elongated optical layered body are warped in a raised shape.

The so-called "TD warpage" refers to the warping of the sheet-shaped body of the optical layered body due to the stress (shrinkage force, expansion force, etc.) in a direction parallel to the TD direction of the elongated optical layered body from which the sheet-shaped body is cut out. song.

In the present invention, attention is paid to MD warpage. The reverse warp that can be suppressed by the present invention refers to reverse warp belonging to MD warp.

The so-called MD direction means the mechanical movement direction of the film, that is, the long direction of the film, and the so-called TD direction means the direction perpendicular to the MD direction.

The layer structure of the optical laminate of the present invention is not limited to the structure shown in FIG. 1 as long as it includes a protective film, a polarizing plate, one or more retardation layers, and an adhesive layer in sequence, and may have, for example, the following layer structure.

[a] It is not necessary to have the first adhesive layer 3 a and the first retardation layer 3 , or the second adhesive layer 4 a and the second retardation layer 4 .

[b] The first retardation layer 3 can be directly formed on the surface of the polarizing plate 2 .

[c] It may further include retardation layers other than the first retardation layer 3 and the second retardation layer 4 .

[d] The separation film 6 may not be provided.

[e] The protective film 1 may have a single-layer structure.

The length of the elongated optical layered body is, for example, 100 to 20000 m, preferably 1000 to 10000 m. Also, the width of the elongated optical layered body is, for example, 0.5 to 3 m, preferably 1 to 2.5 m.

The size, shape and cutting angle of the sheet-shaped optical layered body are not particularly limited.

The sheet-shaped body of the optical laminate is preferably a square shape, more preferably a square shape having a long side and a short side. The square shape is preferably a rectangle.

When the shape of the sheet is rectangular, the length of the long side is, for example, 50 mm to 300 mm, preferably 70 mm to 150 mm. The length of the short side is, for example, 30mm to 200mm, preferably 40mm to 100mm.

Although there is no special limitation, when the shape of the sheet is rectangular, when the sheet is viewed from the side of the protective film 1, the direction of the absorption axis of the polarizer 2 can be 45 degrees relative to its long side and short side angle.

Alternatively, when the shape of the sheet is rectangular, when the sheet is viewed from the protective film 1 side, the direction of the absorption axis of the polarizer may be parallel to its long side, or may be at an angle of 90 degrees.

The optical layered body (preferably a sheet-shaped body of the optical layered body) preferably does not have reverse warpage, and the reverse warpage is measured according to the description in the paragraphs of the embodiments described later; more preferably, the amount of positive warpage is 20mm Below, or flat without warping; even more preferably, the positive warpage is less than 10mm, or flat without warping; especially preferred, flat without warping.

The optical layered body (preferably a sheet-shaped body of the optical layered body) is preferably a structure with a separation film 6 on the outside of the first adhesive layer 5, or a structure without a structure, and the state of warping is as described above; moreover Preferably, in the structure having at least the separation film 6, the warped state is as described above.

(2) Protective film

(2-1) Structure of protective film

The protective film 1 is a film for protecting the surface of the polarizing plate 2, and usually, when the second adhesive layer 50 is provided after bonding an optical laminate such as an image display element, the entire adhesive layer can be peeled off and removed. Therefore, the protective film 1 is attached to the above-mentioned surface of the polarizing plate 2 in a peelable manner.

As described above, the protective film 1 can be composed of the base film 40 and the second adhesive layer 50 laminated on the base film 40 .

The base film 40 can be a thermoplastic resin, such as polyolefin resins such as polyethylene resin, polypropylene resin, and cyclic polyolefin resin; polyethylene terephthalate, polyethylene naphthalate, etc. Ester resin; polycarbonate resin; (meth)acrylic resin, etc. The base film 40 may have a single-layer structure or a multi-layer structure.

The second adhesive layer 50 can be composed of a (meth)acrylic adhesive, an epoxy adhesive, a urethane adhesive, a silicone adhesive, or the like.

In addition, the protective film 1 may be a resin film having self-adhesive properties such as polypropylene-based resin and polyethylene-based resin. At this time, the protective film 1 does not have the second adhesive layer 50 .

The thickness of the protective film 1 may be, for example, 5 to 150 μm, preferably 10 to 100 μm, more preferably 20 to 75 μm, more preferably 25 to 70 μm (for example, less than 60 μm, and less than 55 μm). When the thickness of the protective film 1 is less than 5 μm, the protection of the polarizing plate 2 may become insufficient, and it is also disadvantageous in terms of handleability. When the thickness of the protective film 1 exceeds 150 μm, it is disadvantageous in terms of thinning the optical layered body and reworkability of the protective film.

(2-2) Elasticity of protective film

The protective film 1 included in the optical laminate satisfies the following formula (I): first modulus of elasticity - second modulus of elasticity≧300MPa (I).

In formula (I), the so-called first modulus of elasticity refers to the tensile modulus of elasticity (MPa) in the direction perpendicular to the absorption axis of the polarizing plate 2 at a temperature of 23°C and a relative humidity of 55%RH; the so-called second modulus of elasticity The rate is the tensile modulus (MPa) in the direction parallel to the absorption axis of the polarizing plate 2 at a temperature of 23° C. and a relative humidity of 55% RH.

According to the optical layered body provided with the protective film 1 satisfying the formula (I), it is possible to suppress the reverse warpage that makes the surface on the protective film 1 side convex.

The direction perpendicular to the absorption axis of the polarizing plate 2 has the same meaning as the TD direction of the protective film 1 and the polarizing plate 2 when the optical layered body is manufactured by, for example, a manufacturing method described later.

"Satisfying formula (I)" means that the first modulus of elasticity and the second modulus of elasticity satisfy formula (I) when the protective film is measured according to the description in the paragraphs of the examples described later.

From the viewpoint of suppressing reverse warpage of the optical layered body, the left side of the formula (I) is preferably at least 400 MPa, more preferably at least 500 MPa.

Generally speaking, the smaller the size, the easier it is for reverse warpage to occur in a sheet. Therefore, when the size of the sheet-shaped body is small, in order to sufficiently suppress reverse warpage, it may be preferable to make the left side of the formula (I) larger.

(3) Polarizer

(3-1) Structure of polarizer

The polarizing plate 2 is a polarizing element including at least a polarizer, and usually includes a thermoplastic resin film attached to one or both sides of the polarizing plate.

The thermoplastic resin film may be a protective film for protecting a polarizer or the like. When bonding a protective film (thermoplastic resin film) to the protective film 1 side of the polarizing plate 2, the protective film (thermoplastic resin film) may be a retardation film. Moreover, the following resin layers, such as an antireflection treatment layer, can be provided in the protective film 1 side of this protective film (thermoplastic resin film).

The thermoplastic resin film may also have a resin layer (for example, an optical layer) laminated on its surface. Examples of the resin layer are: hard coat layer, antiglare layer, antireflection layer, antistatic layer, antifouling layer, etc. The resin layer is particularly suitably used as a thermoplastic resin film on the protective film 1 side.

The thermoplastic resin film can be bonded to the polarizer through an adhesive layer or an adhesive layer.

The thickness of the polarizing plate 2 is usually 150 μm or less, preferably 110 μm or less, more preferably 80 μm or less, and more preferably 70 μm or less from the viewpoint of thinning the polarizing plate 2 . The smaller the thickness of the polarizing plate 2, the easier it is for the optical laminate to warp. It was found that reverse warping of the optical layered body can be effectively suppressed even when the thickness of the polarizing plate 2 is small.

The thickness of the polarizing plate 2 is usually 20 μm or more or 30 μm or more.

An example of the layer structure of the polarizing plate 2 will be described with reference to FIG. 2 and FIG. 3 , but the layer structure is not limited to these examples.

The polarizer 2a shown in FIG. 2 is provided with: a polarizer 10; a first thermoplastic resin film 20 bonded to one side of the polarizer 10; a second thermoplastic resin film 30 bonded to the other side of the polarizer 10. The first and second thermoplastic resin films 20 and 30 are, for example, protective films.

Like the polarizing plate 2b shown in FIG. 3, one of the first and second thermoplastic resin films 20, 30 may be omitted. In the polarizing plate 2b, the second thermoplastic resin film 30 is omitted. Such a polarizing plate having a thermoplastic resin film on only one side of the polarizing plate 10 is beneficial to thinning the polarizing plate.

Although not shown in Figures 2 and 3, it is preferable to use an adhesive to bond the polarizer 10 to the first and second thermoplastic resin films 20 and 30 .

(3-2) Polarizer

The polarizer 10 constituting the polarizer 2 is an absorption-type polarizer, which has "a linearly polarized light that will have a vibration plane parallel to its absorption axis, and that has a direction perpendicular to the absorption axis (with the The property of linearly polarized light penetration of the vibrating plane parallel to the transmission axis. An example of the polarizer 10 is a polarizer in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film. Such a polarizer 10 can be manufactured by, for example, a method including: a step of uniaxially stretching a polyvinyl alcohol-based resin film; dyeing the polyvinyl alcohol-based resin film with a dichroic dye to thereby adsorb two The step of dichroic dye; the step of treating the polyvinyl alcohol resin film adsorbed with dichroic dye with a cross-linking liquid such as boric acid aqueous solution; and the step of washing with water after being treated with the cross-linking liquid.

As the polyvinyl alcohol-based resin, saponified polyvinyl acetate-based resin can be used. Polyvinyl acetate-based resins include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers that can be copolymerized with vinyl acetate, etc. . Examples of other monomers that can be copolymerized with vinyl acetate include: unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides with ammonium groups.

In this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. The same applies to terms such as "(meth)acryl" and "(meth)acrylate".

The degree of saponification of polyvinyl alcohol-based resins is usually 85 to 100 mol%, preferably above 98 mol%. The polyvinyl alcohol resin can be modified, for example, polyvinylformal or polyvinylacetal modified by aldehydes can also be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually 1,000 to 10,000, preferably 1,500 to 5,000.

The degree of saponification and the average degree of polymerization of polyvinyl alcohol-based resins can be determined in accordance with JIS K 6726.

A film made of such a polyvinyl alcohol-based resin can be used as a raw film of the polarizer 10 . The film-forming method of polyvinyl alcohol-type resin is not specifically limited, A well-known method can be used. The thickness of the polyvinyl alcohol-based resin film is not particularly limited, but is, for example, about 10 to 150 μm, preferably 50 μm or less, more preferably 35 μm or less.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. When the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before or during the crosslinking treatment. Furthermore, uniaxial stretching can also be performed in these plural stages.

In the case of uniaxial stretching, uniaxial stretching can be performed between rolls with different rotating speeds, or uniaxial stretching can be performed using heated rolls. Furthermore, uniaxial extension can be done in the atmosphere The conventional stretching may be a wet stretching in which the polyvinyl alcohol-based resin film is stretched in a state in which the polyvinyl alcohol-based resin film is swollen using a solvent or water. The elongation ratio is usually 3 to 8 times.

As a method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing a dichroic dye can be employed. As the dichroic dye, iodine or a dichroic organic dye can be used. In addition, the polyvinyl alcohol-based resin film is preferably previously subjected to a treatment of immersion in water before the dyeing treatment.

The cross-linking treatment after dyeing with a dichroic dye is usually carried out by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid. When using iodine as a dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide.

The thickness of the polarizer 10 is generally about 2 to 40 μm. From the viewpoint of thinning the polarizing plate 2, the thickness of the polarizing plate 10 is preferably 20 μm or less, more preferably 15 μm or less, and more preferably 10 μm or less. The thicker the polarizer 10 is, the easier it is to warp the optical laminate. However, according to the present invention, even if the thickness of the polarizer 10 is, for example, 10 μm or more, furthermore, 15 μm or more, especially 20 μm or more, it can also suppress reverse Warped optical laminate.

(3-3) First and second thermoplastic resin films

The first and second thermoplastic resin films 20 and 30 are independently transparent thermoplastic resins, preferably films made of optically transparent thermoplastic resins. The thermoplastic resins constituting the first and second thermoplastic resin films 20, 30 can be, for example, polymers such as chain polyolefin resins (polypropylene resins, etc.), cyclic polyolefin resins (norbornene resins, etc.). Olefin-based resins; cellulose-based resins such as triacetyl cellulose and diacetyl cellulose; polyester-based resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate-based resins Resins; (meth)acrylic resins such as methyl methacrylate resins; polystyrene resins; polyvinyl chloride resins; acrylonitrile/butadiene/styrene resins; acrylonitrile/styrene resins ; Polyvinyl acetate resin; Polyvinylidene chloride resin; Polyamide resin; Polyacetal resin; Modified polyphenylene ether resin; Polyethylene resin; polyether resin; polyarylate resin; polyamideimide resin; polyimide resin, etc.

The chain polyolefin-based resin includes, in addition to homopolymers of chain olefins such as polyethylene resins and polypropylene resins, copolymers containing two or more kinds of chain olefins. More specific examples include: polypropylene-based resins (polypropylene resins belonging to homopolymers of propylene, copolymers mainly composed of propylene), polyethylene-based resins (polyethylene resins belonging to homopolymers of ethylene, ethylene-based host copolymer).

Cyclic polyolefin resin is a general term for resins polymerized with cyclic olefins as polymerization units. Specific examples of cyclic polyolefin resins include: ring-opening (co)polymers of cyclic olefins; addition polymers of cyclic olefins; copolymers of cyclic olefins and chain olefins such as ethylene and propylene ( Representatively, random copolymers), graft polymers modified with unsaturated carboxylic acids or their derivatives, and hydrogenated products thereof. Among them, it is preferable to use a norbornene-based resin in which a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer is used as a cyclic olefin.

The so-called cellulose-based resin refers to a part or all of the hydrogen atoms in the hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linter fibers and wood pulp (hardwood pulp, conifer pulp) through acetyl, Propyl and/or butyryl-substituted cellulose organic acid esters or cellulose mixed organic acid esters. Examples include cellulose acetate, propionate, butyrate, and their mixed esters. Among them, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferred.

Polyester-based resins are resins other than the above-mentioned cellulose-based resins having ester bonds, and are generally composed of polycondensates of polycarboxylic acids or their derivatives and polyhydric alcohols. Polycarboxylic acid or its derivatives can use divalent dicarboxylic acid or its derivatives, such as: terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl naphthalene dicarboxylate, etc. . The polyol system can use 2 bis Alcohols include, for example, ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, cyclohexanedimethanol, and the like. Examples of suitable polyester-based resins include polyethylene terephthalate.

Polycarbonate-based resins are engineering plastics composed of monomer units bonded through carbonate groups, and are resins with high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin may be a resin called modified polycarbonate in which a polymer skeleton is modified in order to lower the photoelastic coefficient, or a copolymerized polycarbonate with improved wavelength dependence.

A (meth)acrylic resin is a polymer containing a structural unit derived from a (meth)acrylic monomer. The polymer is typically a methacrylate containing polymer. It is preferable that the ratio of the structural unit derived from a methacrylate with respect to all structural units is a polymer containing 50 weight% or more. The (meth)acrylic resin may be a homopolymer of methacrylate or a copolymer containing a structural unit derived from another polymerizable monomer. In this case, the proportion of structural units derived from other polymerizable monomers is preferably 50% by weight or less relative to all structural units.

The methacrylate that can constitute the (meth)acrylic resin is preferably an alkyl methacrylate. Alkyl methacrylate can be for example: such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tertiary butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and 2-hydroxyethyl methacrylate are alkyl methacrylates whose alkyl groups have 1 to 8 carbon atoms. The carbon number of the alkyl group contained in the alkyl methacrylate is preferably 1-4. In a (meth)acrylic-type resin, methacrylate may be used individually by 1 type, and may use 2 or more types together.

Examples of the other polymerizable monomers that can constitute the (meth)acrylic resin include acrylate and other compounds having a polymerizable carbon-carbon double bond in the molecule. Other polymerizable monomers may be used alone or in combination of two or more. Acrylic esters are preferably alkyl acrylates. Alkyl acrylates include: methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tertiary butyl acrylate, propyl acrylate 2-Ethylhexyl enoate, cyclohexyl acrylate, alkyl acrylate having 1 to 8 carbon atoms in the alkyl group of 2-hydroxyethyl acrylate, and the like. The carbon number of the alkyl group contained in the alkyl acrylate is preferably 1-4. In the (meth)acrylic resin, only one type of acrylate may be used alone, or two or more types may be used in combination.

Other compounds having a polymerizable carbon-carbon double bond in the molecule include vinyl compounds such as ethylene, propylene, and styrene; vinyl cyanide compounds such as acrylonitrile. Other compounds having a polymerizable carbon-carbon double bond in the molecule may be used alone or in combination of two or more.

The first and second thermoplastic resin films 20 and 30 can be protective films laminated and pasted on one side of the polarizer 10 to protect the polarizer 10 . The first or second thermoplastic resin film 20, 30 may also be a protective film having optical functions such as retardation film and brightness enhancement film.

For example, by stretching (uniaxial stretching, biaxial stretching, etc.) a thermoplastic resin film made of the above-mentioned materials, it is possible to obtain a retardation film provided with an arbitrary retardation value. The first and/or second thermoplastic resin film 20, 30 may also have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer laminated on its surface. .

The thickness of the first and second thermoplastic resin films 20 and 30 is usually 1 to 100 μm, but from the viewpoint of strength and handleability, it is preferably 5 to 60 μm, more preferably 5 to 50 μm.

The thinner the thickness of the first thermoplastic resin film 20 or the second thermoplastic resin film 30, the more likely the polarizing plate with protective film is warped. However, according to the present invention, even the first thermoplastic resin film 20 can be provided. Alternatively, the thickness of the second thermoplastic resin film 30 is, for example, 40 μm or less, or even as thin as 30 μm or less, and an optical laminate that also suppresses reverse warpage.

Like the polarizing plate 2a shown in FIG. 2, when thermoplastic resin films are provided on both sides of the polarizing plate 10, these thermoplastic resin films may be made of the same kind of thermoplastic resin, or may be made of different kinds of thermoplastic resin. constitute. Also, the thickness may be the same or different. fit When the configurations of the thermoplastic resin films on both sides are different, the optical layered body tends to be warped, so in such a case, the present invention is particularly advantageous.

(3-4) Adhesive

As described above, the first and second thermoplastic resin films 20 and 30 can be bonded to the polarizer 10 via an adhesive layer, for example. The adhesive for forming the adhesive layer may be a water-based adhesive, an active energy ray-curable adhesive or a thermosetting adhesive, preferably a water-based adhesive or an active energy ray-curable adhesive.

Examples of water-based adhesives include adhesives containing polyvinyl alcohol-based resin aqueous solutions, water-based two-component urethane-based emulsion adhesives, and the like. Among them, a water-based adhesive containing an aqueous solution of a polyvinyl alcohol-based resin is particularly suitably used. Polyvinyl alcohol-based resins can be used in addition to vinyl alcohol homopolymers obtained by saponification of polyvinyl acetate, which is a homopolymer of vinyl acetate, by mixing vinyl acetate with other monomers that can be copolymerized with vinyl acetate. The polyvinyl alcohol-based copolymer obtained by saponifying the copolymer of the body, or the modified polyvinyl alcohol-based polymer whose hydroxyl group has been partially modified. The water-based adhesive may include cross-linking agents such as aldehyde compounds (glyoxal, etc.), epoxy compounds, melamine-based compounds, methylol compounds, isocyanate compounds, amine compounds, and polyvalent metal salts.

When using a water-based adhesive, it is preferable to carry out a drying step for removing water contained in the water-based adhesive after laminating the polarizer 10 and the first and second thermoplastic resin films 20 and 30 . After the drying step, there may also be an aging step of aging at a temperature of, for example, 20 to 45°C.

The so-called active energy ray-curable adhesive is an adhesive containing a curable compound cured by irradiation of active energy rays such as ultraviolet rays, visible light, electron rays, and X-rays, and is preferably an ultraviolet-curable adhesive.

The curable compound may be a cation polymerizable curable compound or a radical polymerizable curable compound. Cationic polymerizable hardening compounds can be, for example: epoxy series Compounds (compounds having 1 or more epoxy groups in the molecule), or oxetane-based compounds (compounds having 1 or more oxetane rings in the molecule), or a combination of these. Examples of radically polymerizable hardening compounds include (meth)acrylic compounds (compounds having one or more (meth)acryloxy groups in the molecule), or radically polymerizable Other vinyl compounds with double bonds, or combinations thereof. A cation polymerizable curable compound and a radical polymerizable curable compound may also be used together. The active energy ray-curable adhesive generally further includes a cationic polymerization initiator and/or a radical polymerization initiator for initiating the curing reaction of the curable compound.

When bonding the polarizer 10 and the first and second thermoplastic resin films 20 and 30 , in order to improve the adhesiveness, surface activation treatment may be applied to the bonding surface of at least any one of them. Surface activation treatment can be, for example: such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, free active ray treatment (ultraviolet treatment, electron beam treatment, etc.) Dry treatment; such as ultrasonic treatment using solvents such as water or acetone, saponification treatment, wet treatment of anchor coating treatment. These surface-activating treatments may be performed alone or in combination of two or more.

When bonding thermoplastic resin films on both sides of the polarizer 10, the adhesives used to bond these thermoplastic resin films may be the same type of adhesive or different types of adhesives.

(4) Phase difference layer

The optical laminate system includes one or more retardation layers (layers having retardation characteristics), and the retardation layers are laminated on the opposite side of the laminated protective film 1 of the polarizing plate 2 . Fig. 1 shows an example having two retardation layers.

When the optical laminate includes two or more retardation layers, the retardation layers may have slow axes in the same direction or slow axes in different directions.

The one or more retardation layers contained in the optical laminate are independent, and may be a retardation layer (retardation film) formed as a film, or may be formed by coating (coating) a composition for forming a retardation layer. The formed layer is preferably a layer formed by coating (coating).

An example of the retardation layer is a retardation layer composed of a cured product of a liquid crystal compound (liquid crystal cured retardation layer). In the retardation layer, the liquid crystal compound has liquid crystal alignment in a predetermined direction, which is fixed by hardening of the liquid crystal compound. The liquid crystal alignment in a predetermined direction can be adjusted by the alignment restriction force of the alignment layer described later.

As the liquid crystal compound constituting the retardation layer, it is preferable to use a polymerizable liquid crystal compound having a polymerizable group. The alignment state of the liquid crystal compound can be fixed by the polymerization reaction of the polymerizable liquid crystal compound. The polymerization reaction of the polymerizable liquid crystal compound may be a thermal polymerization reaction using a thermal polymerization initiator or a photopolymerization reaction using a photopolymerization initiator, but photopolymerization is preferred.

The alignment direction of the liquid crystal compound contained in the phase difference layer can be restricted by the alignment layer as described above, but in the case of using a polymerizable liquid crystal compound as the liquid crystal compound, it is also possible to make the polymerizable liquid crystal compound light by irradiating polarized light. Orientation is adjusted by making the orientation of the polymerizable liquid crystal compound manifest or improve.

The liquid crystal curable retardation layer can be formed using a known liquid crystal compound. The type of liquid crystal compound is not particularly limited, and a rod-shaped liquid crystal compound, a discotic liquid crystal compound, and a mixture thereof can be used.

One or more retardation layers included in the optical laminate can function independently, for example, as a 1/2 wavelength plate, a 1/4 wavelength plate, a positive C plate, a 1/4 wavelength plate with reverse wavelength dispersion, etc. .

When the optical laminate includes two retardation layers, combinations thereof include a combination of a 1/2 wavelength plate and a 1/4 wavelength plate, a combination of a positive C plate and a 1/4 wavelength plate with reverse wavelength dispersion.

The thickness of the retardation layer is usually 1 to 100 μm when it is a retardation film, but it is preferably 5 to 60 μm, more preferably 5 to 50 μm from the viewpoint of strength and handleability.

The thickness of the retardation layer is usually 0.1 to 10 μm, preferably 0.2 to 8 μm, more preferably 0.5 to 5 μm.

The retardation layer may be laminated directly adjacent to the adjacent layer, or may be laminated via an adhesive layer (for example, the first adhesive layer 3a and the second adhesive layer 4a of the optical laminate shown in FIG. 1).

The adhesive layer may be a layer formed of an adhesive or a layer formed of an adhesive.

Regarding the adhesive agent, the description in (3-4) above is cited. Regarding the adhesive (adhesive composition), the description in the following (5) is cited.

(5) The first adhesive layer

The first adhesive layer 5 is disposed on the opposite side of the laminated protective film 1 of the polarizing plate 2, on the outer side (the side away from the polarizing plate 2) than the above-mentioned one or more retardation layers, and as an optical laminate When multiple adhesive layers are included, it is the adhesive layer arranged on the outermost side.

The first adhesive layer 5 can be used to bond the optical laminate to an image display element or other optical members.

The first adhesive layer 5 is composed of an adhesive composition mainly composed of (meth)acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resins. Among them, an adhesive composition using a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a matrix polymer is suitable. The adhesive composition may be an active energy ray curing type or a thermosetting type.

As for the (meth)acrylic resin (matrix polymer) that can be used in the adhesive composition, for example: butyl (meth)acrylate, ethyl (meth)acrylate, (meth) 1 or 2 (meth)acrylates of isooctyl acrylate and 2-ethylhexyl (meth)acrylate A polymer or copolymer of more than one monomer. For the matrix polymer, it is preferred to copolymerize polar monomers. Examples of polar monomers include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, (meth)acrylic acid N,N -Dimethylaminoethyl ester, glycidyl (meth)acrylate monomers with carboxyl, hydroxyl, amido, amino, epoxy, etc.

The adhesive composition may also contain only the above-mentioned matrix polymer, but usually further contains a cross-linking agent. Examples of cross-linking agents include: metal ions with a valence of more than 2, which form a metal carboxylate salt with a carboxyl group; polyamine compounds, which form an amide bond with a carboxyl group; polyepoxide compounds or Polyols that form ester bonds with carboxyl groups; polyisocyanate compounds that form amide bonds with carboxyl groups. Among them, polyisocyanate compounds are preferred.

The so-called active energy ray-curable adhesive composition has the property of being hardened by irradiation with active energy rays such as ultraviolet rays or electron rays, and the adhesive composition has adhesiveness even before irradiation with active energy rays and can be The adherend adhered to the film etc. can be hardened by the irradiation of active energy rays and the properties of the adhesive force can be adjusted. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition. The active energy ray-curable adhesive composition further contains an active energy ray polymerizable compound in addition to a matrix polymer and a crosslinking agent. Furthermore, a photopolymerization initiator, a photosensitizer, etc. may be contained as needed.

The adhesive composition may contain: microparticles, particles (resin particles, glass particles, etc.), glass fibers, resins other than matrix polymers, antistatic agents, tackifiers, fillers (metal powders) for imparting light scattering properties. or other inorganic powders, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, anti-corrosion agents, photopolymerization initiators and other additives.

The first adhesive layer 5 can be formed by applying a dilute solution of the above-mentioned adhesive composition in an organic solvent on a base material and drying it. The base material may be a retardation layer constituting an optical laminate, a separator film (for example, the separator film 6 ), and the like. Active energy ray hardening adhesive composition In this case, the formed adhesive layer can be irradiated with active energy rays to obtain a hardened product having a desired degree of hardening.

The thickness of the first adhesive layer 5 is usually 1 to 40 μm, but is preferably 2 to 30 μm from the viewpoint of thinning the optical layered body and the like.

(6)Separation film

The separator film (peeling film) 6 is a film temporarily attached to protect the surface of the first adhesive layer 5 until the first adhesive layer 5 is attached to an image display element or another optical member. The separation film 6 is generally composed of a thermoplastic resin film that has been subjected to release treatment on one side with a silicone-based, fluorine-based, or other release agent, and the release-treated surface is bonded to the first adhesive layer 5 .

The thermoplastic resin constituting the separation film 6 may be, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester such as polyethylene terephthalate or polyethylene naphthalate. Department of resin, etc. The thickness of the separation film 6 is, for example, 10 to 50 μm.

<Manufacturing method of optical laminate>

With reference to Fig. 4, the manufacturing method of optical laminated body of the present invention comprises the following steps: the first step (manufacturing step of polarizing plate with protective film) S101 is to include the protection of the region that satisfies the formula (I) described later. The film is laminated on one side of the polarizing plate to obtain a polarizing plate with a protective film; and the optical laminate manufacturing step S102.

The optical laminate manufacturing step S102 preferably includes the following steps: The second step is to laminate one or more layers of retardation film on the surface of the obtained polarizing plate with a protective film on the opposite side to the above-mentioned single surface. layer and adhesive layer; and the third step is to cut out the aforementioned optical laminate from the aforementioned region.

Hereinafter, each step will be described in detail.

(1) Step 1

Referring to FIG. 5, the first step of laminating the polarizing plate 2 and the protective film 1 (the manufacturing step of the polarizing plate with protective film) S101 can be performed using a pair of rollers (laminating rollers) 8, 8, for example. From the viewpoint of production efficiency, this method is particularly advantageous when the polarizing plate 2 and the protective film 1 are elongated.

Therefore, it is preferable that both the polarizing plate 2 and the protective film 1 supplied to the manufacturing step S101 of the polarizing plate with a protective film are elongated.

The length of the strip-shaped polarizing plate 2 and the protective film 1 is, for example, 100 to 20000 m, preferably 1000 to 10000 m. Moreover, the width of the strip-shaped polarizing plate 2 and the protective film 1 is, for example, 0.5 to 3 m, preferably 1 to 2.5 m.

The protective film 1 supplied to the manufacturing step S101 of a polarizing plate with a protective film includes a region satisfying the following formula (I): first elastic modulus−second elastic modulus≧300 MPa (I).

This area may be the whole of the protective film 1 or a part thereof. Also, a long protective film usually has a first modulus of elasticity and a second modulus of elasticity which are different in the width direction, but show substantially the same value in the longitudinal direction.

In formula (I), the so-called first modulus of elasticity refers to the tensile modulus of elasticity (MPa) in the direction perpendicular to the absorption axis of the polarizing plate 2 at a temperature of 23°C and a relative humidity of 55%RH; the so-called second modulus of elasticity It is the tensile elastic modulus (MPa) in the direction parallel to the absorption axis of the polarizing plate 2 at a temperature of 23° C. and a relative humidity of 55% RH.

The so-called "satisfying the formula (I)" means that when the protective film is measured according to the description in the paragraphs of the examples described later, the first modulus of elasticity and the second modulus of elasticity satisfy the formula (I).

From the viewpoint of suppressing reverse warpage of the optical layered body, the left side of the formula (I) is preferably at least 400 MPa, more preferably at least 500 MPa. The left side of formula (I) is usually below 2000MPa, typically below 1500MPa.

As for the protective film 1 supplied to the manufacturing process S101 of the polarizing plate with a protective film, what is necessary is just to use what satisfies the formula (I) and the left side of formula (I) measured about the obtained protective film.

The lamination system of the polarizer 2 and the protective film 1 is, for example: continuously transport the long polarizer 2 and the long protective film 1 continuously, overlap the protective film 1 on one side of the polarizer 2 and pass through it. Sandwiched between a pair of laminating rollers 8 and 8, the polarizing plate 7 with a protective film can be manufactured by laminating the two films.

The MD direction (transportation direction) of the polarizing plate 2 and the MD direction (transportation direction) of the protective film 1 are generally parallel. The so-called parallel means that the angle formed by the MD direction of the polarizing plate 2 and the MD direction of the protective film 1 is 0°±5°, preferably 0°±2°.

From the viewpoint of suppressing the reverse warpage of the obtained optical layered body, it is preferable to bond both films so that the absorption axis of the polarizing plate 2 is parallel to the MD direction of the protective film 1 . The so-called parallel means that the angle formed by the absorption axis of the polarizing plate 2 and the MD direction of the protective film 1 is 0°±5°, preferably 0°±2°.

When the two films are bonded so that the absorption axis of the polarizer 2 is parallel to the MD direction of the protective film 1, the direction perpendicular to the absorption axis of the polarizer 2 has the same meaning as the TD direction of the protective film 1 and the polarizer 2.

By passing the laminated body of the polarizing plate 2 and the protective film 1 between the pair of bonding rollers 8, 8, the laminated body is pressed from top to bottom, so that the two films are adhered to each other.

The polarizer 2 has a transparent hard coat (the surface is a smooth hard coat) on its outermost surface. When the transparent hard coat is attached to the protective film 1, it is easy to improve the adhesion between the polarizer 2 and the protective film 1, This tends to easily obtain an optical layered body in which reverse warpage is suppressed. Therefore, it is preferable that the polarizing plate 2 has a transparent hard coat layer (the surface is a smooth hard coat layer) on its outermost surface.

When the protective film 1 is composed of the base film 40 and the second adhesive layer 50 laminated thereon, when the protective film 1 is overlapped on one side of the polarizing plate 2 and passed between a pair of bonding rollers 8, 8 , It is laminated so that the second adhesive layer 50 of the protective film 1 is connected to the above-mentioned one side of the polarizing plate 2 . Before laminating the protective film 1 and the polarizing plate 2, at least one of the bonding surface of the protective film 1 and the polarizing plate 2 can be subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification, etc. Surface activation treatment.

In the step of bonding by a pair of bonding rollers 8, 8, the pressure (nip pressure) applied to the laminate of the protective film 1 and the polarizing plate 2 is, for example, 0.01 to 0.5 MPa, or It can be 0.05 to 0.3MPa. As the bonding rollers 8 and 8, conventionally known ones such as those made of metal (containing alloys such as SUS) or rubber can be used on the surface.

In the polarizing plate with protective film manufacturing step S101, it is preferable to apply tension to the polarizing plate 2 and the protective film 1 while laminating the two films, and it is more preferable that the tension of the polarizing plate 2 before lamination is smaller than that of the protective film 1 Tension before lamination. Such tension control is advantageous in suppressing reverse warpage of the resulting optical layered body. Tension before bonding refers to the tension applied in the MD direction of the film before bonding the two films (the laminated body of the two films passes through a pair of bonding rollers 8, 8). To measure.

From the viewpoint of suppressing the reverse warpage of the obtained optical laminate, the tension before bonding in the MD direction of the polarizing plate 2 is preferably 250 N/m or less, more preferably 200 N/m or less.

From the same viewpoint, the tension before bonding in the MD direction of the protective film 1 is preferably 260 N/m or more, more preferably 300 N/m or more.

(2) Step 2

This step is a step of laminating one or more retardation layers and the first adhesive layer 5 on the side opposite to the side where the protective film 1 is laminated in the polarizing plate 2 of the polarizing plate with protective film 7 . A separator film 6 may be laminated on the outer surface of the first adhesive layer 5 .

The optical layered body obtained in this step is preferably elongated.

The length of the elongated optical layered body is, for example, 100 to 20000 m, preferably 1000 to 10000 m. Also, the width of the elongated optical layered body is, for example, 0.5 to 3 m, preferably 1 to 2.5 m.

The lamination method of the retardation layer of the polarizing plate 7 with a protective film may include a step of peeling the substrate film after laminating the laminate volume including the substrate film and the retardation layer on the opposite side. This method is advantageous when the phase difference layer is a layer formed by coating (coating) like a liquid crystal hardening type phase difference layer.

If the step of laminating the retardation layer includes the above-mentioned step of peeling the base film, reverse warpage is likely to occur in the obtained optical layered body, but according to the present invention, even when the step of peeling the base film is included, manufacturing Optical laminate with suppressed reverse warpage.

For example, the method of laminating the first retardation layer 3 which is a layer formed by coating on the polarizing plate 7 with a protective film includes a method including the following steps. The second retardation layer 4 can also be laminated in the same manner.

[a] The step of forming an alignment layer on the base film; [b] The step of forming the first retardation layer 3 on the alignment layer to obtain a laminate; The step of laminating on the polarizing plate 7 with a protective film; and [d] the step of peeling off the base film.

The alignment layer is not particularly limited as long as it can impart orientation properties such as horizontal alignment, vertical alignment, hybrid alignment, and oblique alignment to the liquid crystal compound contained in the retardation layer. The alignment layer can be, for example, an alignment film made of an alignment polymer, a photo alignment film using a photo alignment polymer, or a groove (groove) alignment film, etc., preferably a photo alignment film using a photo alignment polymer. membrane.

When the alignment layer is an alignment film formed of an alignment polymer, the alignment restriction force on the liquid crystal compound can be adjusted arbitrarily by the surface state and rubbing conditions. at this time, The alignment layer can be formed by applying a composition containing an alignment polymer and a solvent to a substrate film and removing the solvent, or applying the above-mentioned composition to a substrate film and removing the solvent, followed by a known rubbing treatment .

When the alignment layer is a photo-alignment film using a photo-alignment polymer, after applying a composition containing a polymer or a monomer with a photoreactive group and a solvent to the substrate film and removing the solvent, irradiating polarized light, by This obtains an orientation layer. Polarized light for irradiation is preferably polarized ultraviolet light.

The retardation layer system can be formed by applying a composition for forming a retardation layer containing a liquid crystal compound and a solvent on the alignment layer, removing the solvent, and then irradiating ultraviolet rays to align the liquid crystal compound in accordance with the alignment confining force of the alignment layer. Orientation is formed.

As the liquid crystal compound, it is preferable to use a polymerizable liquid crystal compound having a polymerizable group. The alignment state of the liquid crystal compound can be fixed by the polymerization reaction of the polymerizable liquid crystal compound.

The alignment direction of the liquid crystal compound contained in the phase difference layer can be restricted by the alignment layer as described above, but when a polymerizable liquid crystal compound is used as the liquid crystal compound, the polymerizable liquid crystal compound can also be photoaligned by polarized light irradiation , to be adjusted to show or improve the orientation of the polymerizable liquid crystal compound.

Thereafter, by performing steps [c] and [d], the retardation layer, which is a layer formed by coating, can be laminated on the polarizing plate 7 with a protective film.

On the other hand, when the retardation layer is a retardation film, it is preferable to prepare a long retardation film, and to bond the retardation film to the above-mentioned opposite side through an adhesive layer using a bonding roller.

After laminating one or more retardation layers on the opposite side of the polarizing plate 2 of the polarizing plate with protective film 7 to the side where the protective film 1 is laminated, the first adhesive layer 5 or the first adhesive layer 5 and the first adhesive layer 5 are further laminated. The laminated body of the separator film 6 was obtained as an optical laminated body.

(3) Step 3

When the optical layered body obtained in the second step is elongated, it is preferable to cut out a sheet-shaped body from the elongated optical layered body in this step.

Cutting out (cutting) can be performed using conventionally known cutting means such as a cutter for cutting.

Regarding the size, shape, and cutting angle of the sheet-shaped body, the description in the above-mentioned <optical layered body> (1) is cited.

[Example]

Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited to these examples.

In the following examples, the thickness of the polarizing plate and the film, the elastic modulus difference of the protective film, and the tension before lamination in the MD direction of the polarizing plate and the protective film were measured as follows.

(1) Thickness of polarizer and film

The measurement was performed using a digital micrometer "MH-15M" manufactured by NIKON Co., Ltd.

(2) The elastic modulus of the protective film is poor

The sample for elastic modulus measurement is clamped by the upper and lower grippers of the tensile testing machine [Autograph AG-Xplus testing machine manufactured by Shimadzu Corporation] so that the distance between the grippers is 5 cm. At both ends of the side direction, under the environment of 23°C and 55% relative humidity, the test sample is stretched toward the length direction of the test sample at a tensile speed of 1 mm/min. From the obtained stress-strain curve, 3 From the slope of the straight line to 6MPa, calculate the tensile modulus [MPa] at 23°C and 55% relative humidity. In this case, the thickness for calculating the stress is the thickness value of only biaxially stretched polyethylene terephthalate (base film).

The tensile modulus calculated from the measurement of the sample for measuring the first modulus of elasticity is the first modulus of elasticity, and the modulus of tensile elasticity calculated from the measurement of the sample for measuring the second modulus of elasticity is the second modulus of elasticity.

The first modulus of elasticity - the second modulus of elasticity were calculated from the obtained first modulus of elasticity and second modulus of elasticity.

Hereinafter, the first elastic modulus - the second elastic modulus are simply referred to as "elastic modulus difference".

(3) Tension before lamination of polarizing plate and protective film in MD direction

Measure the film tension [N/m] of the polarizing plate and the protective film by using the stress detection roll installed between the laminating roll and a pair of rolls closest to the laminating roll, and use it as the tension before lamination in the MD direction; the polarizing plate And the protective film travels between a pair of laminating rolls for laminating the polarizing plate and the protective film, and a pair of rolls on the upstream side of the pair of laminating rolls and closest to the laminating rolls.

<Examples 1 to 3, Comparative Examples 1 to 2>

(A) Production of polarizer

While continuously conveying long strips of polyvinyl alcohol film [average degree of polymerization: about 2400, degree of saponification: more than 99.9 mol%, thickness: 30 μm], while performing uniaxial stretching to about 4 times by dry method, and then maintaining the original tightness In a stretched state, soak in pure water at 40°C for 1 minute, and then immerse in an aqueous solution with a weight ratio of iodine/potassium iodide/water of 0.1/5/100 at 28°C for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 10.5/7.5/100 at 68° C. for 300 seconds. Then, after washing with pure water at 5° C. for 5 seconds, it was dried at 70° C. for 180 seconds to obtain a strip-shaped polarizer in which iodine was adsorbed and oriented on the uniaxially stretched polyvinyl alcohol film. The thickness of the polarizer is 13 μm.

(B) Production of polarizing plate

The elongated polarizer obtained in (A) above is continuously conveyed, and the elongated first thermoplastic resin film [transparent hard coat film manufactured by Nippon Paper Co., Ltd., trade name "COP25ST-HC" is continuously conveyed at the same time, A film that forms a transparent hard coat layer on a cyclic polyolefin-based resin film, thickness: 29 μm] and a long strip-shaped second thermoplastic resin film [Triathyl cellulose (TAC) film manufactured by Fuji Film Co., Ltd., commercial product Named "ZRG20SL", thickness: 20μm], inject water-based adhesive between the polarizer and the first thermoplastic resin film, and between the polarizer and the second thermoplastic resin film, while passing through a pair of bonding rollers In between, a laminated film composed of the first thermoplastic resin film/water-based adhesive layer/polarizer/water-based adhesive layer/second thermoplastic resin film is obtained.

Next, the obtained laminated film was transported, and heat-treated at 80° C. for 300 seconds by a hot-air dryer to dry the water-based adhesive layer to obtain a long polarizing plate.

The above-mentioned water-based adhesive used the following aqueous solution: the concentration obtained by dissolving polyvinyl alcohol powder [trade name "Gohsefimer" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average degree of polymerization: 1100] in hot water at 95°C: 3 wt. % of polyvinyl alcohol aqueous solution, the cross-linking agent [sodium glyoxylate manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] is mixed in a ratio of 1 part by weight to 10 parts by weight of polyvinyl alcohol powder. The thickness of the obtained polarizing plate was 62 μm.

(C) Manufacture of strip-shaped polarizing plate with protective film

Continuously transport the strip-shaped polarizing plate obtained in (B) above, and at the same time continuously transport the strip-shaped protective film [in biaxially stretched polyethylene terephthalate (thickness: 38 μm) Laminated with a (meth)acrylic adhesive layer (thickness: 15 μm), product name "AY-4212" manufactured by Fujimori Industrial Co., Ltd.], these are stacked and passed between a pair of bonding rollers, thereby Press the laminated body of the protective film and the polarizing plate from top to bottom to continuously manufacture the long polarizing plate with the protective film.

The protective film is bonded to the first thermoplastic resin film (transparent hard coat) surface of the polarizing plate via the adhesive layer.

In addition, the pressure (nipping pressure) applied to the laminate of the protective film and the polarizing plate by the bonding roller was 0.1 MPa. At this time, the tension before bonding in the MD direction of the polarizing plate was 151 N/m, and the tension before bonding in the MD direction of the protective film was 327 N/m.

The manufacturing methods of the elongated polarizing plates with protective films in Examples 1 to 3 and Comparative Examples 1 to 2 are the same except that the protective films used are different (they are the same product, but the batch numbers are different).

(D) Fabrication of strip-shaped optical laminates

On the surface of the polarizing plate with a protective film obtained in the above (C) opposite to the protective film in the polarizing plate, a (meth)acrylic adhesive layer with a thickness of 5 μm/a liquid crystal curing layer with a thickness of 2 μm is sequentially laminated type retardation layer/(meth)acrylic adhesive layer with a thickness of 5 μm/liquid crystal hardening type retardation layer with a thickness of 1 μm/(meth)acrylic adhesive layer with a thickness of 25 μm/made of polyethylene terephthalate The separation film constituted by the film is used to produce a long optical laminated body.

The lamination of the liquid crystal hardening type retardation layer with a thickness of 2 μm is carried out in the following manner: After forming the alignment layer and the liquid crystal hardening type retardation layer on the base film composed of triacetyl cellulose (TAC) film, the This laminate was bonded to the above-mentioned opposite surface through a (meth)acrylic adhesive layer having a thickness of 5 μm, and then the alignment layer and the base film were peeled off.

Similarly, lamination of a liquid crystal curable retardation layer with a thickness of 1 μm is performed by forming an alignment layer and a liquid crystal curable retardation layer on a substrate film made of a triacetyl cellulose (TAC) film. This laminate was bonded to the surface of a liquid crystal curable retardation layer with a thickness of 2 μm through a (meth)acrylic adhesive layer with a thickness of 5 μm, and then the alignment layer and the base film were peeled off.

Thereafter, a laminate of a (meth)acrylic adhesive layer with a thickness of 25 μm and a separator film composed of a polyethylene terephthalate film was bonded to the surface of a liquid crystal curable retardation layer with a thickness of 1 μm to produce Long optical laminated body.

The obtained elongated optical layered body (excluding the separator) had a thickness of 100 μm.

(E) Determination of the elastic modulus difference of the protective film

From the central portion in the width direction of the obtained elongated optical layered body, a small rectangular piece of 100 mm long side x 25 mm short side was cut out using a super cutter. Cutting out is carried out in such a way that the long side of the small piece is parallel to the TD direction of the elongated optical laminate, and the short side of the small piece is parallel to the MD direction of the long optical laminate. The protective film was peeled off from this small piece, and it was used as the sample for the measurement of the 1st elastic modulus.

Also, similarly, from the elongated optical layered body, a small rectangular piece of 100 mm long side x 25 mm short side was cut out using a super cutter. However, when cutting out, the long side of the small piece is parallel to the MD direction of the long optical laminate, and the short side of the small piece is parallel to the TD direction of the long optical laminate. way. Also, the cutting out of the small piece was carried out so that the position of the sample for measuring the first elastic modulus in the width direction of the elongated optical layered body was the same. The protective film was peeled off from this small piece, and it was used as the sample for the measurement of the 2nd elastic modulus.

Moreover, if the cutting positions in the width direction of each are the same, the first elastic modulus and the second elastic modulus of the elongated protective film are the same regardless of the cutting positions in the longitudinal direction.

For the sample for measuring the first modulus of elasticity and the sample for measuring the second modulus of elasticity, the first modulus of elasticity, the second modulus of elasticity, and the difference between the moduli of elasticity were obtained according to the method described above. The results are shown in Table 1.

(F) Fabrication of the sheet-shaped body of the optical laminate

As shown in FIG. 6, the elongated optical layered body 60 obtained from the above (D) is super- A cutter cuts out a rectangular sheet 70 (long side 140 mm×short side 70 mm) to obtain a sheet-like body of an optical laminate. The sheet-shaped body 70 is cut out from the central part in the width direction. Also, the first elastic modulus and the second elastic modulus of the protective film included in the sheet-shaped body 70 are respectively the first elastic modulus, the second elastic modulus when the measurement sample is cut out from the elongated optical layered body in the above-mentioned manner and measured. The second elastic rate has the same value.

(G) Measurement of the MD warpage of the sheet-shaped body of the optical laminate

About the sheet-shaped body 70 of the obtained optical layered body, the amount of MD warpage was measured by the following method. The results are shown in Table 1. Cutting out of the sheet-shaped body 70 was carried out in an environment of 23° C. and a relative humidity of 55% immediately after the elongated optical layered body was produced.

Place the sheet 70 on the reference plane (horizontal platform) with the concave side facing up. In this state, two angles 80 on the diagonal of the two diagonals of the sheet-shaped body 70 with the smaller angle to the direction of the absorption axis of the polarizer of the sheet-shaped body 70 are respectively measured from the reference plane. The height of the two corners 80 is calculated as the average of the height of the MD warpage [mm].

A state where the protective film side is concave is a state having normal warpage, and a state where the protective film side is convex is a state having reverse warpage.

In Table 1, when the value of the MD warpage amount is a positive value, it shows positive warpage, and when it is a negative value, it shows reverse warpage. The MD warpage amount of 0 mm means that the above-mentioned two corners 80 will not be raised regardless of whether the sheet-shaped body 70 faces upward on the protective film side or on the opposite side.

The sheet-like system of the optical layered bodies of Examples 1 to 3 having the protective film satisfying the formula (I) was suppressed in reverse warpage and had a flat state. After the separator film was peeled and removed from the sheet-like bodies of Examples 1 to 3, the amount of MD warpage was measured by the same method as in (G) above, but no reverse warpage was shown in any of them.

1‧‧‧Protective film

2‧‧‧Polarizer

3‧‧‧The first retardation layer

3a‧‧‧The first bonding layer

4‧‧‧The second retardation layer

4a‧‧‧The second bonding layer

5‧‧‧1st adhesive layer

6‧‧‧Separation film

40‧‧‧Substrate film

50‧‧‧The second adhesive layer

Claims (5)

An optical laminate comprising a protective film, a polarizing plate, more than one retardation layer, and an adhesive layer in sequence; the aforementioned protective film satisfies the following formula (I): 774MPa≧first elastic modulus-second elastic modulus ≧437MPa (I) In the formula, the so-called first elastic modulus refers to the tensile elastic modulus in the direction perpendicular to the absorption axis of the polarizing plate at a temperature of 23°C and a relative humidity of 55%RH; the so-called second elastic modulus refers to Tensile modulus in the direction parallel to the absorption axis of the polarizing plate at a temperature of 23°C and a relative humidity of 55%RH. The optical laminate according to claim 1, wherein the thickness of the polarizing plate is 110 μm or less. The optical layered product according to claim 1 or 2, wherein the one or more retardation layers include a retardation layer made of a cured liquid crystal compound. A method for manufacturing an optical laminate, which is a method for manufacturing the optical laminate described in any one of items 1 to 3 of the scope of the patent application, which includes: the first step is to include a region that satisfies the following formula (I) The protective film is laminated on one side of the polarizing plate; the second step is to laminate more than one retardation layer and adhesive layer on the opposite side of the aforementioned polarizing plate to the aforementioned single side; the third step is to start from The aforementioned region is cut out of the aforementioned optical laminate; 774MPa≧1st modulus of elasticity-2nd modulus of elasticity≧437MPa (I) In the formula, the so-called first modulus of elasticity refers to the tensile modulus of elasticity in the direction perpendicular to the absorption axis of the polarizing plate at a temperature of 23°C and a relative humidity of 55%RH; the so-called second modulus of elasticity refers to the modulus of elasticity at a temperature of 23°C, Tensile elastic modulus in a direction parallel to the absorption axis of the aforementioned polarizing plate at a relative humidity of 55% RH. The manufacturing method described in claim 4 of the patent application, wherein the second step includes: after layering a laminated volume including a base film and a retardation layer on the opposite side, and then peeling off the base film.

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