JP2004226765A - Method for manufacturing optical layered body, and elliptically polarizing plate, circularly polarizing plate and liquid crystal display device comprising the layered body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for layering an optical element comprising a liquid crystal substance layer having no supporting substrate film. <P>SOLUTION: The optical layered body is manufactured in the following processes. They are: a first process of obtaining a layered body (A) consisting of a removable substrate 1/adhesive layer 1/liquid crystal substance layer 1; a second process of obtaining a layered body (B) consisting of an adhesive layer 2/liquid crystal substance layer 2/adhesive layer 2'/removable substrate 2'; a third process of stripping the removable substrate 1 before or after laminating a polarizing plate and the layered body (A) via a sticker/adhesive layer to obtain a layered body (C) consisting of the polarizing plate/sticker(adhesive) layer/adhesive layer 1/liquid crystal substance layer 1 or a layered body (D) consisting of the polarizing plate/sticker (adhesive) layer/liquid crystal substance layer 1/adhesive layer 1; and a fourth process of stripping the removable substrate 2' before or after laminating the layered body (C) or (D) and the layered body (B) via a sticker/adhesive (adhesive) layer. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing an optical laminate useful for various optical elements. In addition, the present invention relates to an elliptically polarizing plate or a circularly polarizing plate comprising the optical laminate obtained by such a manufacturing method, and further relates to a liquid crystal display device including the elliptically polarizing plate or the circularly polarizing plate.
[0002]
[Prior art]
Thin films (films) composed of an alignment layer of a liquid crystal compound, especially films composed of a liquid crystal material having a fixed nematic structure, twisted nematic structure, or nematic hybrid structure, are used as elements for color compensation and viewing angle compensation for liquid crystal display devices. Also, it has excellent performance as an optical rotatory optical element and the like, and contributes to high performance and light weight of various display elements. As a method for producing these films, a method has been proposed in which a layer made of a liquid crystal substance formed on an alignment substrate is transferred onto a light-transmitting substrate also serving as a support substrate (for example, Patent Document 1, Patent Document 1). 2). In addition, as a measure to withstand the severe durability test required for liquid crystal display elements, and for further thinning and weight reduction, a method of manufacturing an optical element made of a liquid crystal material without using a support substrate film has also been proposed. It has been proposed (for example, see Patent Document 3). According to such a manufacturing method, after the layer made of the liquid crystal substance aligned on the alignment substrate is once transferred to the removable substrate via the adhesive, the removable substrate is separated. It has become possible to manufacture an optical element comprising a liquid crystal material layer without a supporting substrate film.
[0003]
On the other hand, in recent years, optical films used for various display devices including liquid crystal display devices have been required to have higher-performance optical performance, and the use of only one optical film cannot satisfy the requirements. In many cases, they are used in layers. For example, lamination of a polymer stretched film typified by polycarbonate in a color compensation retardation film of an STN liquid crystal display device, a 板 wavelength plate and a 波長 wavelength plate in a circularly polarizing plate for a transflective liquid crystal display device. Or a broadband circularly polarizing plate obtained by laminating cholesteric films having different selected wavelength regions. On the other hand, while the functions are enhanced by the lamination of such optical films, the demand for thinner and lighter weights is also increasing very much, as represented by mobile phones and portable information terminal devices that have been widely spread in recent years. . Along with this, thinning and lightening of optical films used for display devices are also desired. For this reason, attempts have been made to produce thinner polymer stretched films, etc., but there are limits to thinning polymer stretched films due to optical characteristics and restrictions in the manufacturing process. There was a problem that the thickness was large.
In order to solve such a problem, it is considered effective to use an optical element made of a liquid crystal material without using a supporting substrate film as disclosed in Patent Document 3 described above. However, an industrial method for laminating the optical elements is considered. The manufacturing method has not been established.
[0004]
[Patent Document 1]
JP-A-4-57017 [Patent Document 2]
JP-A-4-177216 [Patent Document 3]
JP-A-8-278491
[Problems to be solved by the invention]
An object of the present invention is to achieve both high functionality of an optical characteristic surface and significant thinning, which were difficult with only a polymer stretched film. In other words, focusing on an optical film composed of a liquid crystal material layer capable of exhibiting an excellent optical function with a thinner wall, and as a result of earnestly examining a manufacturing method for laminating an optical element composed of a liquid crystal material layer without a supporting substrate film, finally, the present invention has been completed. The invention has been completed.
[0006]
[Means for Solving the Problems]
That is, the first aspect of the present invention is (1) after bonding a liquid crystal material layer 1 formed on an alignment substrate and having a fixed liquid crystal alignment to a removable substrate 1 via an adhesive layer 1, A first step of removing the alignment substrate, transferring the liquid crystal material layer 1 to the removable substrate 1, and obtaining a laminate (A) composed of the removable substrate 1 / the adhesive layer 1 / the liquid crystal material layer 1; After the liquid crystal material layer 2 having the liquid crystal alignment fixed thereon formed on the alignment substrate is adhered to the removable substrate 2 via the adhesive layer 2, the alignment substrate is peeled off to remove the liquid crystal material layer 2. The image is transferred to the removable substrate 2, and then the removable substrate 2 ′ and the liquid crystal material layer 2 are adhered to each other via the adhesive layer 2 ′. Step (3) of obtaining a laminate (B) composed of an adhesive layer 2 / liquid crystal material layer 2 / adhesive layer 2 '/ removable substrate 2' transferred to the substrate. Before or after laminating the laminate (A) with the polarizing plate via the adhesive / adhesive layer, the removable substrate 1 is peeled off, and the polarizing plate / adhesive (adhesive) layer / adhesion Third Step of Obtaining a Laminate (C) Consisting of Agent Layer 1 / Liquid Crystal Material Layer 1 or Laminate (D) Consisting of Polarizer / Adhesive (Adhesive) Layer / Liquid Crystal Material Layer 1 / Adhesive Layer 1 And (4) before or after laminating the laminate (C) or (D) and the laminate (B) via the adhesive / adhesive layer, the re-peelable substrate 2 ′ The present invention relates to a method for producing an optical laminate, which includes at least each of a fourth step of peeling.
[0007]
The second aspect of the present invention relates to the above-mentioned method for producing an optical laminate, wherein the liquid crystal material layer 1 and the liquid crystal material layer 2 have the same or different optical parameters.
A third aspect of the present invention is that at least one of the liquid crystal material layer 1 and the liquid crystal material layer 2 is made of a liquid crystal material layer in which a liquid crystal material having optically positive uniaxiality is formed in a liquid crystal state and in which a nematic alignment is fixed. The present invention relates to a method for producing the optical laminate described above.
A fourth aspect of the present invention relates to an elliptically polarizing plate comprising the optical laminate obtained by the above-described manufacturing method.
A fifth aspect of the present invention relates to a circularly polarizing plate comprising the optical laminate obtained by the above-described manufacturing method.
A sixth aspect of the present invention relates to a display device including at least the elliptically polarizing plate or the circularly polarizing plate described above.
In the above description, “/” indicates the interface between the layers, and will be similarly described below.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The liquid crystal material layer in which the alignment of the liquid crystal used in the present invention is fixed is a layer fixed by using a means for fixing a liquid crystal material in an aligned state. In the case of a liquid crystal material, a method of quenching from an alignment state to fix it in a vitrified state, orienting a low-molecular or high-molecular liquid crystal material having a reactive functional group, and then reacting the functional group (curing, crosslinking, etc. ) Immobilization method and the like.
Examples of the reactive functional group include a vinyl group, a (meth) acryloyl group, a vinyloxy group, an epoxy group, an oxetanyl group, a carboxyl group, a hydroxyl group, an amino group, an isocyanate group, and an acid anhydride. The reaction takes place in a suitable manner.
[0009]
The liquid crystal material that can be used in the liquid crystal material layer can be selected from a wide range, regardless of the low-molecular liquid crystal material or the high-molecular liquid crystal material, depending on the intended use and manufacturing method of the liquid crystal film. Substances are preferred. Further, the molecular shape of the liquid crystal substance may be rod-shaped or disk-shaped. For example, a discotic liquid crystal compound exhibiting discotic nematic liquid crystal properties can also be used.
Examples of the liquid crystal phase of the liquid crystal material layer before immobilization include a nematic phase, a twisted nematic phase, a cholesteric phase, a hybrid nematic phase, a hybrid twisted nematic phase, a discotic nematic phase, a smectic phase, and the like.
[0010]
As the polymer liquid crystal material, various kinds of main chain polymer liquid crystal materials, side chain polymer liquid crystal materials, or a mixture thereof can be used. As the main chain type polymer liquid crystal substance, polyester, polyamide, polycarbonate, polyimide, polyurethane, polybenzimidazole, polybenzoxazole, polybenzthiazole, polyazomethine, polyesteramide, polyester carbonate , Polyesterimide-based high-molecular liquid crystal materials, and mixtures thereof. In addition, as the side chain type polymer liquid crystal substance, a substance having a linear or cyclic structure skeleton chain such as polyacrylate, polymethacrylate, polyvinyl, polysiloxane, polyether, polymalonate, and polyester is used. And a mixture thereof having a mesogen group as a side chain. Of these, polyesters of a main chain type polymer liquid crystal material are preferred from the viewpoint of ease of synthesis and orientation.
[0011]
Low-molecular liquid crystal substances include saturated benzene carboxylic acids, unsaturated benzene carboxylic acids, biphenyl carboxylic acids, aromatic oxycarboxylic acids, Schiff bases, bisazomethine compounds, azo compounds, azoxy compounds, cyclohexane ester compounds And sterol compounds and the like, which have the above-mentioned reactive functional groups introduced into the terminals and exhibit liquid crystallinity, and among the above compounds, compositions in which a crosslinkable compound is added to a compound exhibiting liquid crystallinity. Examples of the discotic liquid crystal compound include a triphenylene-based compound and a tolcene-based compound.
Furthermore, various compounds having a functional group or site capable of reacting by heat or photocrosslinking reaction or the like in the liquid crystal material may be blended as long as the expression of liquid crystallinity is not hindered. Examples of the functional group capable of performing a cross-linking reaction include the various reactive functional groups described above.
[0012]
A liquid crystal material layer in which the orientation of liquid crystal is fixed, a method of applying a composition containing the liquid crystal material or various compounds to be added as needed on an alignment substrate in a molten state, or a solution of the composition. The coating film formed on the alignment substrate by the method of coating on the alignment substrate and the like is subjected to drying, heat treatment (liquid crystal alignment), and, if necessary, light irradiation and / or heat treatment (polymerization / crosslinking). It is formed by fixing the orientation by using a means for fixing the orientation.
[0013]
The solvent used for preparing the solution is not particularly limited as long as it can dissolve the liquid crystal substance or the composition used in the present invention and can be distilled off under appropriate conditions. Generally, acetone, methyl ethyl ketone, isophorone, and the like are used. Ketones, butoxyethyl alcohol, hexyloxyethyl alcohol, ether alcohols such as methoxy-2-propanol, ethylene glycol dimethyl ether, glycol ethers such as diethylene glycol dimethyl ether, ethyl acetate, methoxypropyl acetate, ester lactate such as ethyl lactate, Phenols such as phenol and chlorophenol, amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, chloroform, tetrachloroethane, dichlorobenzene What halogenated hydrocarbons such or a mixture of these systems are preferably used. Further, in order to form a uniform coating film on the alignment substrate, a surfactant, an antifoaming agent, a leveling agent, and the like may be added to the solution. Further, a dichroic dye, a normal dye, a pigment, or the like may be added for the purpose of coloring within a range that does not hinder the development of liquid crystallinity.
[0014]
The application method is not particularly limited as long as uniformity of the coating film is ensured, and a known method can be employed. For example, a roll coating method, a die coating method, a dip coating method, a curtain coating method, a spin coating method, and the like can be used. After the application, a solvent removing (drying) step by a method such as a heater or hot air blowing may be included. The thickness of the applied film in a dry state is 0.1 μm to 50 μm, preferably 0.2 μm to 20 μm, and more preferably 0.3 μm to 10 μm. Outside this range, the optical performance of the obtained liquid crystal material layer becomes insufficient, and the orientation of the liquid crystal material becomes insufficient.
[0015]
Subsequently, if necessary, after the orientation of the liquid crystal is formed by heat treatment or the like, the orientation is fixed. In the heat treatment, the liquid crystal is oriented by the self-orienting ability inherent to the liquid crystal material by heating to a liquid crystal phase manifestation temperature range. The conditions of the heat treatment cannot be unconditionally determined because the optimum conditions and the limit values are different depending on the liquid crystal phase behavior temperature (transition temperature) of the liquid crystal substance to be used, but it is usually in the range of 10 to 300 ° C., preferably 30 to 250 ° C. . At a very low temperature, the alignment of the liquid crystal may not proceed sufficiently, and at a high temperature, the liquid crystal substance may be decomposed or adversely affect the alignment substrate. Further, the heat treatment time is usually in a range of 3 seconds to 60 minutes, preferably 10 seconds to 30 minutes. If the heat treatment time is shorter than 3 seconds, the orientation of the liquid crystal may not be sufficiently completed, and if the heat treatment time is longer than 60 minutes, the productivity is extremely deteriorated. After the alignment of the liquid crystal is completed by heat treatment or the like of the liquid crystal material, the liquid crystal material layer on the alignment substrate is fixed as it is by using means suitable for the liquid crystal material used.
[0016]
As the alignment substrate, polyimide, polyamide, polyamide imide, polyphenylene sulfide, polyphenylene oxide, polyether ketone, polyether ether ketone, polyether sulfone, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyarylate, triacetyl cellulose, epoxy Films such as resin and phenolic resin can be exemplified.
[0017]
Depending on the production method, some of these films show a sufficient alignment ability for the liquid crystal substance used in the present invention without a treatment for expressing the alignment ability again, but the alignment ability is insufficient, or In the case of not showing the orientation ability, these films are stretched under appropriate heating, so-called rubbing treatment in which the film surface is rubbed in one direction with a rayon cloth or the like, polyimide, polyvinyl alcohol, silane cup A rubbing treatment may be performed by providing an alignment film made of a known alignment agent such as a ring agent, a film obliquely vapor-deposited with silicon oxide or the like, or a film in which the alignment ability is developed by appropriately combining them.
In addition, as the alignment substrate, a metal plate such as aluminum, iron, or copper provided with a large number of regular fine grooves on the surface, various glass plates, or the like can be used.
[0018]
Here, the direction of the orientation treatment of the oriented substrate film is not particularly limited, and can be appropriately selected by performing each of the above treatments in any direction. In particular, when handling a liquid crystal film formed on a long alignment substrate, a predetermined angle is selected with respect to the MD direction of the long continuous film, and the liquid crystal is aligned in an oblique direction as necessary. It is desirable. When the liquid crystal films are laminated in an axial arrangement such that optimal optical characteristics can be exhibited by performing orientation treatment in a predetermined angle direction, lamination in a state where MDs of long films are aligned (so-called roll-to-roll lamination) This is extremely advantageous in that it is possible to increase the efficiency of product pick-up.
[0019]
The liquid crystal material layer formed on the alignment substrate is then bonded to the removable substrate via an adhesive layer.
The adhesive has a sufficient adhesive strength to the liquid crystal material layer and the removable substrate, and is capable of peeling the removable substrate in a later step. If it does not impair, there is no particular limitation, for example, acrylic resin-based, methacrylic resin-based, epoxy resin-based, ethylene-vinyl acetate copolymer-based, rubber-based, urethane-based, polyvinyl ether-based and mixtures thereof and , A thermosetting type and / or a photocuring type, and an electron beam curing type. These adhesives include those having the function of a transparent protective layer for protecting the liquid crystal material layer. Note that an adhesive can be used as the adhesive.
[0020]
Since the reaction (curing) conditions of the above-mentioned reactive substances vary depending on the components constituting the adhesive, the viscosity, the reaction temperature, and the like, conditions suitable for each may be selected. For example, in the case of a photocuring type, preferably, various known photoinitiators are added, and light from a light source such as a metal halide lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, a xenon lamp, an arc lamp, a laser, or a synchrotron radiation light source is used. Irradiation and reaction may be performed. The irradiation amount per unit area (1 square centimeter) is usually 1 to 2000 mJ, preferably 10 to 1000 mJ as an integrated irradiation amount. However, this is not the case when the absorption region of the photoinitiator is significantly different from the spectrum of the light source, or when the reactive compound itself has the ability to absorb the light source wavelength. In these cases, an appropriate photosensitizer or a method of using a mixture of two or more photoinitiators having different absorption wavelengths can be employed. The acceleration voltage in the case of the electron beam curing type is usually 10 kV to 200 kV, preferably 50 kV to 100 kV.
[0021]
As described above, the thickness of the adhesive layer varies depending on the components constituting the adhesive, the strength of the adhesive, the operating temperature, and the like, but is usually 1 to 50 μm, preferably 2 to 30 μm, and more preferably 3 to 10 μm. Outside this range, the adhesive strength is insufficient, and bleeding from the end is undesirably caused.
[0022]
These adhesives may be added with various fine particles or the like or a surface modifier for the purpose of controlling optical characteristics or controlling the releasability or erosion of the substrate as long as the characteristics are not impaired.
Examples of the fine particles include fine particles having a different refractive index from the compound constituting the adhesive, conductive fine particles for improving antistatic performance without impairing transparency, and fine particles for improving abrasion resistance. Specifically, fine silica, fine alumina, ITO (Indium Tin Oxide) fine particles, silver fine particles, various synthetic resin fine particles and the like can be mentioned.
[0023]
The surface modifier is not particularly limited as long as it has good compatibility with the adhesive and does not affect the curability of the adhesive or the optical performance after curing. Surfactants, oil-soluble surfactants, polymer surfactants, fluorosurfactants, organometallic surfactants such as silicone, and reactive surfactants can be used. In particular, fluorine-based surfactants such as perfluoroalkyl compounds and perfluoropolyether compounds, and organometallic surfactants such as silicone are particularly preferable because of their large surface modifying effect. The amount of the surface modifier added is preferably in the range of 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, and even more preferably 0.1 to 3% by mass, based on the adhesive. If the addition amount is less than this range, the effect of addition becomes insufficient, while if it is too large, adverse effects such as an excessive decrease in the adhesive strength may occur. The surface modifier may be used alone or in combination of two or more as needed.
Further, various additives such as an antioxidant and an ultraviolet absorber may be added as long as the effects of the present invention are not impaired.
[0024]
As the removable substrate used in the present invention, polyethylene, polypropylene, olefin-based resins such as 4-methylpentene-1 resin, polyamide, polyimide, polyamideimide, polyetherimide, polyetherketone, polyetheretherketone, Polyether sulfone, polyketone sulfide, polysulfone, polystyrene, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyarylate, polyacetal, uniaxially stretched polyester, polycarbonate, polyvinyl alcohol, polymethyl methacrylate, polyarylate, amorphous polyolefin, norbornene A film of resin, triacetyl cellulose, epoxy resin or the like can be used.
[0025]
Above all, as a transparent and optically isotropic film excellent in inspecting optical defects, 4-methylpentene-1, polymethyl methacrylate, polystyrene, polycarbonate, polyether sulfone, polyarylate, amorphous polyolefin, norbornene Examples of such films include a base resin, triacetyl cellulose, and an epoxy resin.
[0026]
These plastic films may be coated in advance with silicone or have an organic thin film or an inorganic thin film formed thereon in order to have a proper removability. For the same purpose, the surface of the plastic film may be subjected to a chemical treatment such as a saponification treatment or a physical treatment such as a corona treatment.
[0027]
Further, in order to adjust the releasability of the removable substrate, the above plastic film may contain a lubricant or a surface modifier. The type and amount of the lubricant are not particularly limited as long as they do not adversely affect the testability and peelability of optical defects. Specific examples of the lubricant include fine silica, fine alumina, and the like. An index of the addition amount may be such that the haze value of the removable substrate is usually 50% or less, preferably 30% or less. If the addition amount is too small, the effect of addition is not recognized. On the other hand, if it is too large, the testability of optical defects deteriorates, which is not preferable.
Further, if necessary, other known various additives such as an antiblocking agent, an antioxidant, an antistatic agent, a heat stabilizer, and an impact resistance improver may be contained.
[0028]
Regarding the peeling force of the removable substrate, even if the removable substrate is manufactured from the same material, it cannot be determined unconditionally because it changes depending on the manufacturing method, the surface state, the wettability with the adhesive used, and the like. The peeling force at the interface with the adhesive (180 ° peeling, peeling speed 30 cm / min, measured at room temperature) is usually 0.38 to 12 N / m, preferably 0.38 to 8.0 N / m. Is desirable. If the peeling force is lower than this value, after peeling the alignment substrate after bonding the liquid crystal material layer on the alignment substrate to the removable substrate, the peeling force is too low, and the peelable substrate may float. When a good peeling state at the desired interface is not obtained, the transfer of the liquid crystal material layer to the removable substrate becomes insufficient, and when the peeling force is too high, when the removable substrate is peeled off, This is not preferable because the liquid crystal material layer is broken or peeling cannot be performed at the interface with the desired layer.
[0029]
In addition, the thickness of the re-peelable substrate may also affect the releasability, and is preferably 16 to 100 μm, particularly preferably 25 to 50 μm. If the thickness is too large, the release point may not be stable and the releasability may be deteriorated. On the other hand, if the thickness is too small, the mechanical strength of the film may not be maintained, and a problem such as tearing during production may occur.
[0030]
The polarizing plate used in the present invention is not particularly limited as long as the object of the present invention can be achieved, and a polarizing plate usually used in a liquid crystal display device can be appropriately used. A thin film type is preferred. Specifically, iodine and / or dichroism are applied to a PVA-based polarizing film such as polyvinyl alcohol (PVA) or partially acetalized PVA, or a hydrophilic polymer film made of a partially saponified ethylene-vinyl acetate copolymer. A polarizing film formed by adsorbing a dye and stretching the film, a polarizing film composed of a polyene oriented film such as a dehydrated PVA product or a dehydrochlorinated polyvinyl chloride product, and the like can be used. Further, a reflective polarizing film can also be used.
[0031]
The polarizing plate may be used alone or a polarizing film provided with a transparent protective layer or the like on one or both sides of the polarizing film for the purpose of improving strength, improving moisture resistance, improving heat resistance, and the like. Is also good. Examples of the transparent protective layer include those obtained by laminating a transparent plastic film such as polyester or triacetyl cellulose directly or via an adhesive layer, a resin coating layer, and a photocurable resin layer such as an acrylic or epoxy resin. Can be When these transparent protective layers are coated on both sides of the polarizing film, the same transparent protective layer may be provided on both sides, or different transparent protective layers may be provided.
[0032]
Next, the method for producing the optical laminate of the present invention will be described in detail.
The method for producing the liquid crystal material layer is not particularly limited, but for example, the liquid crystal material layer can be produced by the following method.
First, a liquid crystal material coating film is formed on an alignment substrate by an appropriate method, a solvent or the like is removed as necessary, and liquid crystal alignment is completed by heating or the like. Fix the orientation of the material layer. Next, an adhesive layer is formed on the liquid crystal material layer in which the orientation is fixed, and the liquid crystal material layer and the removable substrate are brought into close contact with each other via the adhesive layer, and then the adhesive layer is reacted (cured) if necessary. After that, the alignment substrate is peeled off. In this manner, the liquid crystal material layer having the fixed orientation can be transferred to the removable substrate. Thus, a liquid crystal substance layer bonded to the removable substrate via the adhesive layer can be obtained.
[0033]
In the obtained liquid crystal material layer, a transparent protective layer may be provided on the exposed liquid crystal material layer, or a surface protective film may be bonded for protecting the surface of the liquid crystal material layer. Here, the transparent protective layer can be selected from the above-mentioned adhesives.
That is, the layer structure of the liquid crystal material layer (hereinafter, referred to as a laminate (A)) formed on the removable substrate of the present invention via an adhesive layer includes:
(1) Removable substrate 1 / adhesive layer 1 / liquid crystal material layer 1
(2) Removable substrate 1 / adhesive layer 1 / liquid crystal material layer 1 / adhesive layer 1 '
And the like.
In the above description, “/” indicates the interface between the layers, and will be similarly described below.
[0034]
Next, as a second step, after forming a liquid crystal material layer 2 formed on the alignment substrate and having the liquid crystal alignment fixed thereon in the same manner as in the first step, it is bonded to the removable substrate 2 via the adhesive 2. Then, the alignment substrate is peeled off, the liquid crystal material layer 2 is transferred to the removable substrate 2, and then the removable substrate 2 ′ and the liquid crystal material layer 2 are adhered to each other via an adhesive 2 ′. Adhesive layer 2 / liquid crystal material layer 2 / adhesive 2 ′ / removable substrate 2 ′ by peeling the non-conductive substrate 2 and transferring it to the removable substrate 2 ′
To obtain a laminate (B) consisting of
[0035]
The liquid crystal material layer 1 and the liquid crystal material layer 2 may have the same or different optical parameters. That is, a combination of liquid crystal material layers required from the viewpoint of optical characteristics and the like can be selected. The optical parameters include the thickness of the liquid crystal material layer, intrinsic or apparent birefringence of the liquid crystal material, retardation, alignment fixed state, presence or absence of twist, twist angle, and the like. Also, the removable substrates 1, 2, 2 'or the adhesive layers 1, 1', 2, 2 'can be arbitrarily selected according to the releasability and required characteristics, and may be the same or different.
[0036]
Next, in a third step, the releasable substrate 1 is peeled off before or after laminating the laminate (A) with a polarizing plate via a tacky / adhesive (adhesive or adhesive) layer. Laminate (C) composed of a polarizing plate / adhesive (adhesive) layer / adhesive layer 1 / liquid crystal material layer 1 or a polarizing plate / adhesive (adhesive) layer / liquid crystal material layer 1 / adhesive layer To obtain a laminate (D).
Next, in a fourth step, the laminate (C) or (D) and the laminate (B) are bonded to each other via a sticky / adhesive layer before or after the lamination (2). By peeling off ', the optical laminate of the present invention can be obtained.
[0037]
Thus, although not particularly limited, an optical laminate having the following configuration can be obtained through at least the above steps.
(1) Polarizing plate / adhesive (adhesive) layer / adhesive layer 1 / liquid crystal material layer 1 / adhesive (adhesive) layer / adhesive layer 2 / liquid crystal material layer 2 / adhesive layer 2 '
{Circle around (2)} polarizing plate / adhesive (adhesive) layer / adhesive layer 1 / liquid crystal material layer 1 / adhesive (adhesive) layer / adhesive layer 2 '/ liquid crystal material layer 2 / adhesive layer 2
{Circle around (3)} Polarizing plate / adhesive (adhesive) layer / liquid crystal material layer 1 / adhesive layer 1 / adhesive (adhesive) layer / adhesive layer 2 / liquid crystal material layer 2 / adhesive layer 2 '
{Circle around (4)} Polarizing plate / adhesive (adhesive) layer / liquid crystal material layer 1 / adhesive layer 1 / adhesive (adhesive) layer / adhesive layer 2 '/ liquid crystal material layer 2 / adhesive layer 2
[0038]
Further, in the present invention, the liquid crystal material layer in which the alignment is fixed on the alignment substrate or the liquid crystal material layer transferred onto the removable substrate is repeatedly laminated via the adhesive layer. Can also be stacked in plural.
Further, during the manufacturing process of the present invention, in a form in which the oriented substrate and the removable substrate are left on one side, an adhesive with a release film is attached to the opposite surface of the oriented substrate or the opposite surface of the removable substrate. By peeling off the alignment substrate or the removable substrate, the release film of the pressure-sensitive adhesive can be treated as a new removable substrate. If this method is used, the pressure-sensitive adhesive can be used not only as a pressure-sensitive adhesive for laminating the optical laminate of the present invention, or for laminating with a liquid crystal cell or other optical members, but also for arbitrarily bonding the bonding surface. It can be turned upside down, further expanding the degree of freedom in manufacturing.
[0039]
Further, in the present invention, by using a releasable substrate having a releasable substrate formed in advance on the releasable substrate surface, the release layer can be formed between the liquid crystal material layer and another layer. It is also possible to form. By forming the release layer, it is possible to obtain a stress blocking effect for suppressing a change in appearance (for example, waving) of the thin liquid crystal material layer at the time of manufacturing or an environmental test. Here, the release layer is not particularly limited, but is preferably an optically isotropic transparent layer, and examples thereof include polymers such as acrylic, methacrylic, nitrocellulose, and epoxy compounds, and mixtures thereof. be able to. The thickness of the release layer is 0.3 μm to 40 μm, preferably 0.5 μm to 10 μm, and the glass transition point (Tg) is 20 ° C. or higher, preferably 50 ° C. or higher. The material is not particularly limited as long as it is a transparent layer and does not significantly impair the optical characteristics of the liquid crystal material layer. If the film thickness and the glass transition point are out of these ranges, the effect is insufficient, and it is not preferable because the purpose of thinning which is a part of the object of the present invention is not met.
[0040]
In addition, physical properties of the release layer may be controlled by partial crosslinking by adding a crosslinking component, addition of a plasticizer, addition of a lubricant, and the like.
Further, the method of forming the release layer is not particularly limited, for example, polyethylene, polypropylene, a material to be a release layer having the above film thickness in advance on a removable substrate film such as polyethylene terephthalate, coating , Extrusion, etc., and a transfer method in which this layer is adhered through a sticky / adhesive layer or a transparent protective layer, and then the removable substrate film is peeled off.
[0041]
The optical laminate of the present invention may include one or more layers of an antireflection layer, an antiglare treatment layer, a hard coat layer, and a light diffusion layer, in addition to the polarizing plate and the liquid crystal material layer. The adhesive or the like used for laminating or bonding to the polarizing plate is not particularly limited as long as it is an optical grade, and for example, a suitable one from the above-mentioned adhesives can be used.
The total thickness of the optical laminate of the present invention produced as described above is 450 μm or less, preferably 350 μm or less, more preferably 300 μm or less. Outside this range, it is not preferable because it does not meet the purpose of thinning, which is one of the objects of the present invention.
[0042]
The optical laminate of the present invention can function as a compensation member, an elliptically polarizing plate, and a circularly polarizing plate for various liquid crystal display devices according to the optical parameters of the liquid crystal material layer.
That is, the liquid crystal material layer constituting the optical laminate is, for example, a liquid crystal material layer in which the nematic alignment and the twisted nematic alignment are fixed functions as a retardation plate. The body can be used as a compensating plate of a transmissive or reflective liquid crystal display device of STN type, TN type, OCB type, HAN type and the like.
[0043]
In addition, the liquid crystal material layer in which the nematic hybrid alignment is fixed can be used as a retardation film or a wave plate using retardation when viewed from the front, and the direction of the retardation value (in the film thickness direction) It can also be used as a viewing angle improving member of a TN type liquid crystal display device by making use of the asymmetry caused by the tilt of the molecular axis).
[0044]
A liquid crystal material layer having a quarter-wave plate function can be used as a circularly polarizing plate, a reflection-type liquid crystal display device, an antireflection filter of an EL display device, or the like by being combined with a polarizing plate as in the present invention. In particular, in order to obtain a wide-band quarter-wave plate that functions over a wide band in the visible light region, a quarter-wave plate whose birefringent light has a phase difference of approximately 1/4 wavelength in a monochromatic light of 550 nm and a wavelength of 550 nm. It is generally known that it is effective to stack a half-wave plate having a birefringent light having a phase difference of approximately half a wavelength as a monochromatic light with their slow axes crossing each other. It is actually widely used in reflection type liquid crystal display devices and the like. That is, if a technique for obtaining a thin optical laminate as in the production method of the present invention is used, a thin broadband quarter-wave plate, which has been difficult only with a conventional stretched polymer film, can be obtained. Here, the retardation value of the 波長 wavelength plate is usually in the range of 70 nm to 180 nm, preferably 90 nm to 160 nm, particularly preferably 120 nm to 150 nm. The retardation value of the half-wave plate is usually in the range of 180 nm to 320 nm, preferably 200 nm to 300 nm, particularly preferably 220 nm to 280 nm. When the retardation ranges of the ４ wavelength plate and the 波長 wavelength plate deviate from the above, unnecessary coloring may occur in the liquid crystal display device. The retardation value represents the product of the birefringence Δn and the film thickness d.
[0045]
Further, in the optical laminate of the present invention, if the liquid crystal material layer constituting the laminate has a fixed cholesteric or smectic orientation, a polarizing reflection film for improving luminance, a reflection type color filter, a selective reflection It can be used for various anti-counterfeiting elements and decorative films utilizing the color change of the reflected light due to the viewing angle due to the ability.
[0046]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, taking the production of a circularly polarizing plate as an example, but the present invention is not limited thereto. The retardation (product of birefringence Δn and film thickness d) in this example is a value at a wavelength of 550 nm unless otherwise specified.
[0047]
[Preparation example]
Using 50 mmol of terephthalic acid, 50 mmol of 2,6-naphthalenedicarboxylic acid, 40 mmol of methylhydroquinone diacetate, 60 mmol of catechol diacetate and 60 mg of N-methylimidazole, polycondensation was performed at 270 ° C. for 12 hours under a nitrogen atmosphere. Next, the obtained reaction product was dissolved in tetrachloroethane, followed by reprecipitation with methanol for purification to obtain 14.6 g of a liquid crystalline polyester. This liquid crystalline polyester (polymer 1) has a logarithmic viscosity (phenol / tetrachloroethane (6/4 mass ratio) mixed solvent: 30 ° C.) of 0.16 dl / g, has a nematic phase as a liquid crystal phase, and isotropic phase−liquid crystal phase. The transition temperature was 250 ° C. or higher, and the glass transition temperature measured by a differential scanning calorimeter (DSC) was 112 ° C.
20 g of Polymer 1 was dissolved in 80 g of N-methyl-2-pyrrolidone to prepare a solution. This solution was applied on a polyimide film (trade name “Kapton”, manufactured by DuPont) rubbed with rayon cloth using a spinner, and the solvent was dried and removed, followed by heat treatment at 210 ° C. for 20 minutes to nematic alignment. A structure was formed. After the heat treatment, the liquid crystal material was cooled to room temperature to fix the nematic alignment structure, and a liquid crystal material layer (liquid crystal material layer 1) having an actual film thickness of 1.4 μm and having a uniform thickness was obtained on the polyimide film. The actual film thickness was measured using a stylus-type film thickness meter.
Next, by changing only the thickness at the time of coating with a spinner under the same conditions as above, a liquid crystal material layer having a uniform thickness of 0.7 μm and an actual film thickness of 0.7 μm, in which the nematic alignment structure of polymer 1 is fixed on a polyimide film. (Liquid crystal material layer 2) was obtained.
[0048]
[Example 1]
A commercially available UV-curable adhesive (UV-3400, manufactured by Toagosei Co., Ltd.) was applied on the liquid crystal material layer 1 (the surface opposite to the polyimide film) obtained in the preparation example to a thickness of 5 μm. 1 and a 25 μm-thick polyethylene terephthalate (PET) film 1 (S10, manufactured by Toray Industries, Inc.), which is a removable substrate, is laminated thereon. The adhesive layer 1 is irradiated with UV light of about 600 mJ. Cured. Thereafter, the polyimide film is peeled off from the laminate in which the PET film 1 / the adhesive layer 1 / the liquid crystal material layer 1 / the polyimide film are integrated, so that the liquid crystal material layer 1 is placed on the PET film 1 which is a removable substrate. Transfer was performed to obtain a laminate (A) composed of a PET film, an adhesive layer, and a liquid crystal material layer. Here, Δnd of the laminate (A) when the PET film 1 was peeled was 280 nm.
[0049]
Next, a commercially available UV-curable adhesive (UV-3400) is applied to the liquid crystal material layer 2 obtained in the preparation example (the surface opposite to the polyimide film) to a thickness of 5 μm as the adhesive layer 2, In the same manner as in the laminate (A), a laminate composed of a PET film 2, an adhesive layer 2, and a liquid crystal material layer 2 was obtained. Further, a commercially available UV-curable adhesive (UV-3400) is applied as a 5 μm thick adhesive layer 2 ′ on the liquid crystal material layer 2, and a 25 μm thick PET film 2 (S10, Toray (Made by Co., Ltd.), and the adhesive layer 2 ′ is cured by UV irradiation of about 600 mJ. Then, the PET film 2 is peeled off, and the adhesive layer 2 / the liquid crystal material layer 2 / the adhesive layer 2 ′ are formed. / A laminate (B) composed of the PET film 2 'was obtained. Here, Δnd of the laminate (B) when the PET film 2 ′ was peeled was 140 nm.
[0050]
A polarizing plate (thickness: about 180 μm; SQW-862 manufactured by Sumitomo Chemical Co., Ltd.) having a 25 μm-thick pressure-sensitive adhesive layer formed on one side in advance on the surface of the liquid crystal material layer 1 of the laminate (A), By peeling off the PET film 1, a laminate composed of the polarizing plate / adhesive layer / liquid crystal material layer / adhesive layer 1 was obtained.
After laminating the laminate and a liquid crystal film (B) in which a 25 μm-thick adhesive was previously formed on the surface of the adhesive layer 2, the PET film 2 ′ was peeled off to obtain a polarizing plate / adhesive layer / liquid crystal substance. A circularly polarizing plate of the present invention comprising layer 1 / adhesive layer 1 / adhesive layer / adhesive layer 2 / liquid crystal material layer 2 / adhesive layer 2 'was obtained. The total thickness of the circularly polarizing plate was 248 μm.
[0051]
[Example 2]
The circularly polarizing plate obtained in Example 1 was adhered to the upper and lower sides of a liquid crystal cell of a commercially available transflective TFT liquid crystal display device using an adhesive, and the display characteristics were evaluated. The display was good in both the mode and the transmission mode. In addition, when the display device was subjected to two types of durability tests, (1) 500 hours at 60 ° C. and 90% RH, and (2) 500 hours at 80 ° C. and dry, any abnormal appearance such as peeling or cracking was found. Was not recognized at all.
[0052]
[Comparative Example 1]
A commercially available uniaxially stretched polycarbonate film 1 (thickness: 60 μm, Δnd 135 nm) and a polycarbonate film 2 (thickness: 60 μm, Δnd 270 nm) are bonded to each other using a 25 μm adhesive, and are composed of a polycarbonate film 1 / an adhesive layer / a polycarbonate film 2. A laminate was obtained.
A polarizing plate (thickness: about 180 μm; SQW-862 manufactured by Sumitomo Chemical Co., Ltd.) in which a 25 μm pressure-sensitive adhesive layer was previously formed on one surface of two sides of the polycarbonate of the laminate was laminated, and the polarizing plate / pressure-sensitive adhesive layer / A circularly polarizing plate comprising polycarbonate film 2 / adhesive layer / polycarbonate film 1 was obtained. The total thickness of the circularly polarizing plate was as thick as 350 μm.
[0053]
[Comparative Example 2]
One side of a commercially available uniaxially stretched norbornene-based film 1 (thickness: 80 μm, Δnd 275 nm; Arton manufactured by JSR Corporation) was bonded to a 25 μm-thick adhesive layer previously formed on a silicone-treated PET film. Subsequently, a polarizing plate (thickness: about 180 μm; SQW-862 manufactured by Sumitomo Chemical Co., Ltd.) having a 25 μm-thick pressure-sensitive adhesive layer formed on one side in advance on the surface of the film on which the pressure-sensitive adhesive is not bonded, is bonded. Thus, a laminate comprising a polarizing plate / adhesive layer / norbornene-based film 1 / adhesive layer / silicone-treated PET film was obtained.
The silicone-treated PET film of the laminate is peeled off, and a commercially available uniaxially-stretched norbornene-based film 2 (thickness: 80 μm, Δnd: 130 nm; Arton manufactured by JSR Corporation) is bonded to form a polarizing plate / adhesive layer / norbornene. A circularly polarizing plate composed of a base film 1 / adhesive layer / norbornene film 2 was obtained. The total thickness of the circularly polarizing plate was 390 μm.
[0054]
【The invention's effect】
According to the present invention, it is possible to establish an industrial manufacturing method for laminating a liquid crystal material layer without a supporting substrate film, and to enhance the optical properties of the surface, which was conventionally difficult only with a laminate of a polymer stretched film alone. Thus, a new optical laminate realizing both of the above and a significant reduction in thickness can be obtained, and has extremely high industrial value.

Claims (6)

(1) The liquid crystal material layer 1 having the liquid crystal alignment fixed thereon formed on the alignment substrate is bonded to the removable substrate 1 via the adhesive layer 1, and then the alignment substrate is peeled off to remove the liquid crystal material layer. 1 is transferred to the removable substrate 1 to obtain a laminate (A) composed of the removable substrate 1 / the adhesive layer 1 / the liquid crystal material layer 1;
(2) The liquid crystal material layer 2 having the liquid crystal alignment fixed thereon formed on the alignment substrate is adhered to the removable substrate 2 via the adhesive layer 2, and then the alignment substrate is peeled off to remove the liquid crystal material layer. 2 is transferred to the removable substrate 2, and then the removable substrate 2 ′ and the liquid crystal material layer 2 are adhered to each other via the adhesive layer 2 ′. A second step of obtaining a laminate (B) consisting of the adhesive layer 2 / liquid crystal material layer 2 / adhesive layer 2 '/ removable substrate 2' transferred to 2 ',
(3) Before or after laminating the laminate (A) with a polarizing plate via a viscous / adhesive layer, the removable substrate 1 is peeled off, and the polarizing plate / adhesive (adhesive) A laminate (C) consisting of a layer / adhesive layer 1 / liquid crystal material layer 1 or a laminate (D) consisting of a polarizing plate / adhesive (adhesive) layer / liquid crystal material layer 1 / adhesive layer 1 is obtained. The third step,
And (4) peeling the releasable substrate 2 ′ before or after laminating the laminate (C) or (D) with the laminate (B) via the adhesive / adhesive layer. The fourth step,
A production method of an optical laminated body, characterized by at least passing through each of the steps. 2. The method according to claim 1, wherein the liquid crystal material layer 1 and the liquid crystal material layer 2 have the same or different optical parameters. At least one of the liquid crystal material layer 1 and the liquid crystal material layer 2 is composed of a liquid crystal material layer in which a liquid crystal material having optically positive uniaxiality is formed in a liquid crystal state and in which a nematic alignment is fixed. The method for producing an optical laminate according to claim 1. An elliptically polarizing plate comprising an optical laminate obtained by the method according to claim 1. A circularly polarizing plate comprising an optical laminate obtained by the production method according to claim 1. A liquid crystal display device comprising at least the elliptically polarizing plate or the circularly polarizing plate according to claim 4.