JP2005196220A - Optical retardation compensated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing peeling at the interface of a glass cell and an optical retardation compensated film, in a liquid crystal display. <P>SOLUTION: This optical retardation compensated film comprises a thermoplastic saturated norbornene-based resin, having a moisture permeability of 200 g/m<SP>2</SP>24 hr or lower, in environmental conditions of 60°C, 95% RH. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a retardation compensation film. More specifically, the present invention relates to a retardation compensation film capable of constituting a liquid crystal display device having excellent durability in which peeling of the retardation compensation film does not occur even under conditions of high temperature and high humidity.

  In recent years, liquid crystal display devices (LCDs) are frequently used together with cathode ray tube CRTs in display devices such as computers.

  As a typical liquid crystal display device, a glass cell in which electrodes encapsulating liquid crystal molecules are incorporated, a retardation compensation film via a transparent adhesive, and a polarizing plate laminated thereon via an adhesive It has become.

  The retardation compensation film exhibits the function of compensating for the phase shift of the light that has passed through the liquid crystal molecules in the liquid crystal display device, but the polarizing plate and the retardation compensation film are firmly bonded. The glass cell and the retardation compensation film are not necessarily firmly bonded because re-peelability is required for process reasons.

  When a liquid crystal display device is exposed to a high-temperature and high-humidity atmosphere for a long time, water vapor in the atmosphere passes through the polarizing plate and the retardation compensation film and accumulates at the interface between the glass cell and the retardation compensation film. The adhered retardation compensation film is easily peeled off.

  In particular, since the polarizing plate has a large shrinkage property, the retardation compensation film firmly adhered to the polarizing plate tends to be peeled off from the glass cell as the polarizing plate shrinks.

  Conventionally, in order to solve this problem, the pressure-sensitive adhesive used mainly for adhesion between the retardation compensation film and the glass cell has been improved, and the molecular weight of the pressure-sensitive adhesive, the molecular weight distribution, the blending of various additives, etc. have been studied. It was.

  However, since the pressure-sensitive adhesive used for adhesion between the retardation compensation film and the glass cell is also required to have re-peelability due to the convenience of the production process of the liquid crystal display device, a method for reconciling re-peelability and strong adhesiveness is I haven't found it yet.

  Further, as a method for preventing the peeling, there is a method of imparting a water repellency to the polarizing plate. For example, in JP-A-6-308327, a fluorine-containing silane compound is adsorbed on the surface of the polarizing plate to form a water repellent layer. A forming method and the like are disclosed.

  However, the above method also increases the number of steps for forming the water repellent layer in the polarizing plate production step, and is not a preferable solution from the viewpoint of productivity.

  In view of the above-mentioned viewpoints, the present inventor prevents peeling at the glass cell-retardation compensation film interface, which is the weakest interface, from a viewpoint different from the viewpoint of improvement by the conventional adhesive or water repellent treatment. As a result of intensive research on the method for achieving the above, when a retardation compensation film having a specific moisture permeability is used, the above-mentioned problem is surprisingly solved, and both excellent durability against peeling and re-peelability are achieved. As a result, the present invention has been completed.

  The present invention provides a retardation compensation film capable of preventing peeling of the film at the glass cell-retardation compensation film interface without impairing the re-peelability required in the liquid crystal display device production process. With the goal.

That is, the present invention is made of a thermoplastic saturated norbornene resin, has a moisture permeability of 200 g / m ² · 24 hr or less under an environmental condition of 60 ° C. and 95% RH, and has a removability on the surface to be bonded to the glass cell. The present invention provides a phase difference compensation film characterized by being used in a liquid crystal display device comprising an adhesive layer.

  Hereinafter, the configuration of the present invention will be described in detail.

In the present invention, the moisture permeability is a moisture permeability as defined in Japanese Industrial Standard “JIS Z 0208”, and means the amount of water vapor that passes through a film-like substance of a unit area in a certain time. That is, the retardation compensation film of the present invention has a retardation compensation film as a boundary surface at 60 ° C., the relative humidity of air on one side is 95% RH, and the air on the other side is kept dry by a hygroscopic agent. The mass of water vapor passing through the retardation compensation film in 24 hours must be 200 g or less per 1 m ² .

  The method for measuring moisture permeability is a method defined in Japanese Industrial Standard “JIS Z 0208”. The condition of 60 ° C. and 95% RH is in consideration of the environment in which the actual liquid crystal panel is used, and the thickness of the retardation compensation film that satisfies the above moisture permeability is the thickness when mounting an actual liquid crystal display or the like. To do.

  The thickness of the retardation compensation film of the present invention is preferably 30 to 80 μm, more preferably 40 to 60 μm, in view of workability and retardation development.

  The retardation compensation film of the present invention is a film made of a transparent thermoplastic resin, and must exhibit a retardation by stretching. The transparency is preferably 80% or more, more preferably 90% or more in terms of total light transmittance in order to increase the light utilization efficiency of the liquid crystal display device. The haze is preferably 1% or less.

  The specific molecular structure of the retardation compensation film of the present invention that satisfies the above moisture permeability must be a structure that blocks water permeation. Search for various polymer resins by examining retardation development and transparency. As a result, the thermoplastic saturated norbornene resin was the most preferred resin in the present invention.

  The thermoplastic saturated norbornene-based resin is a known resin disclosed in, for example, Japanese Patent Laid-Open Nos. 3-14882 and 3-122137. In the present invention, these conventionally known thermoplastic saturated norbornene resins are used. Series resins can be used preferably.

  Examples of the monomer constituting the thermoplastic saturated norbornene resin include, for example, norbornene, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-cyano-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene, 5-phenyl-2-norbornene, 5- Phenyl-5-methyl-2-norbornene, 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1, 4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4: , 8-Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano-1,4,4a, 5,6,7 , 8,8a-octahydronaphthalene, 6-cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4 : 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5,8-dimethano-1,4,4a, 5 6,7,8,8a-octahydronaphthalene, 1,4-methano-1,4,4a, 4b, 5,8,8a, 9a-octahydrofluorene, 5,8-methano-1,2,3 4,4a, 5,8,8a-Octahydro-2.3-cyclopentadienonaphthalene 4,9: 5,8-dimethano-3a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoindene, 4,11: 5,10: 6,9-trimethano-3a, 4 , 4a, 5, 5a, 6, 9, 9a, 10, 10a, 11, 11a-dodecahydro-1H-cyclopentanthracene and the like.

  The thermoplastic saturated norbornene resin is, for example, (i) a ring-opening polymer or ring-opening copolymer of a norbornene monomer, which is subjected to hydrogenation after modification such as maleic acid addition or cyclopentadiene addition as necessary. (B) a resin obtained by addition polymerization of a norbornene monomer, (c) a resin obtained by addition polymerization with a norbornene monomer and an olefin monomer such as ethylene or α-olefin, (d) a norbornene monomer and cyclopentene, cyclohexane Examples thereof include resins obtained by addition polymerization with cyclic olefin monomers such as octene and 5,6-dihydrodicyclopentadiene, and modified products of these resins.

The polymerization is carried out by using, for example, a hydrated salt of Ir, Os, or Ru as a polymerization medium, MoCl ₅ , WCl ₆ , ReCl ₅ , (C ₂ H ₅ ) ₃ Al, (C ₂ H ₅ ) ₃ Al / TiCl. ₄ , (π-C ₄ H ₇ ) ₄ Mo / TiCl ₄ , (π-C ₄ H ₇ ) ₄ W / TiCl ₄ , (π-C ₃ H ₅ ) ₃ Cr / WCl _6, etc. Can be performed.

  The thermoplastic saturated norbornene resins are marketed by ZEON Corporation under the trade names “ZEONOR” and “ZEONEEX”, and by JSR Corporation under the trade name “ARTON”. In the present invention, “ZEONOR” and “ZEONEX” are preferable.

  When the number average molecular weight of the thermoplastic saturated norbornene resin decreases, the moisture resistance decreases and moisture permeability increases, and when the number average molecular weight increases, the film formability deteriorates. Therefore, the number average molecular weight is measured by gel permeation chromatography using a toluene solvent. And 25,000 to 100,000 are preferable, and more preferably 30,000 to 80,000.

  The retardation compensation film of the present invention can be produced by any known method using the above-described thermoplastic saturated norbornene-based resin, and examples thereof include a solution casting method and a melt molding method, and the solution casting method is preferable. .

  In order to form a film by the solution casting method, first, for example, a high boiling point solvent such as toluene, xylene, ethylbenzene, chlorobenzene, triethylbenzene, diethylbenzene, isopropylbenzene or the like, and these high boiling point solvents and cyclohexane, benzene, tetrahydrofuran, hexane, octane. Preferably, the thermoplastic saturated norbornene resin is dissolved in a mixed solvent of a low boiling point solvent such as 5 to 60% by weight to obtain a resin solution.

  Next, the obtained resin solution is cast on a heat-resistant film such as polyethylene terephthalate, a steel belt, a metal foil or the like by using a bar coater, a doctor knife, a Meir bar, a roll, a T die, and the like, and is dried by heating. .

  In order to improve the heat resistance, ultraviolet resistance, smoothness, etc. of the film within the range satisfying the moisture permeability required for the present invention, the retardation compensation film is an anti-aging agent such as phenolic or phosphorus-based, phenolic Anti-aging agents such as amines, antistatic agents such as amines, lubricants such as esters of aliphatic alcohols and partial esters of polyhydric alcohols, UV absorbers such as benzophenone and benzotriazole may be added. .

  The retardation compensation film of the present invention expresses a retardation by being uniformly stretched after a thermoplastic saturated norbornene resin or the like is formed by a known casting method such as a solution casting method or an extrusion method. . The stretching method is not particularly limited as long as the retardation of liquid crystal molecules can be compensated. In general, it is often used in a range where the retardation upon entering 550 nm is 100 to 800 nm.

  The retardation compensation film thus obtained is bonded to a constituent such as a polarizing plate on one side and a glass cell or the like through a transparent adhesive, and a liquid crystal display device can be produced by a conventional method. At that time, the pressure-sensitive adhesive that adheres to the glass cell surface is required to have re-peelability so that it can be peeled off immediately in case of a bonding mistake. However, when the retardation compensation film of the present invention is used, the pressure-sensitive adhesive has re-peelability. Even if an agent is used, peeling does not occur, and a liquid crystal display device having excellent durability can be manufactured.

  For example, a cross-linked acrylic pressure-sensitive adhesive is usually used as a transparent pressure-sensitive adhesive. Since this pressure-sensitive adhesive is provided with removability, the adhesive strength with a glass cell is weak, and the retardation compensation film of the present invention Otherwise, when the liquid crystal display device is placed under a high temperature and high humidity condition, the phase difference compensation film peels off.

  According to the present invention, there is provided a retardation compensation film capable of preventing peeling of the film at the glass cell-retardation compensation film interface even when the liquid crystal display device is placed under high temperature and high humidity. Can do.

  When the retardation compensation film of the present invention is used, the releasability can be improved while using a conventionally used pressure-sensitive adhesive, so that the releasability of the retardation compensation film required in the liquid crystal display device production process may be impaired. Furthermore, there is no inconvenience that the number of steps for forming the water repellent layer in the polarizing plate production process is increased.

〔Example〕
The present invention will be described more specifically with reference to the following examples. The present invention is not limited only to the following examples.

(1) Transparent resin for retardation compensation film The transparent resin used for the retardation compensation film as an example of the present invention is ZEONEX # 480 (manufactured by Nippon Zeon Co., Ltd .: 6-methyl-1,4: 5,8-dimethano- 1,4,4a, 5,6,7,8,8a-ringohydronaphthalene ring-opening polymerization, thermoplastic saturated norbornene resin obtained by hydrogenation reaction) was used. As a comparative example, a polycarbonate retardation compensation film “RPT384F” made of a Fuji resin and made of a polycarbonate resin was used.

(2) Casting / stretching The resin was diluted with xylene to 50% by weight, and cast on a metal belt so that the thickness after drying was 80 μm. Subsequently, the film was stretched by 200% in the length direction in an atmosphere of 140 ° C. to obtain a retardation compensation film having a retardation value of about 300 nm (at 550 nm light incident). At that time, the total light transmittance was 92.7%, and the haze was 0.2%.

(3) Measurement of moisture permeability The moisture permeability in a 60 ° C 95% RH atmosphere was measured based on JIS Z 0208. As a result, the water vapor permeability of the retardation compensation film as an example is 105 g / m ² · 24 hr (thickness 51 μm), which satisfies the water vapor permeability which is the condition of the present invention, and is an example of the present invention. It was confirmed.
Further, the moisture permeability of the polycarbonate retardation compensation film as a comparative example was 340 g / m ² · 24 hr (thickness 62 μm), and it was confirmed that this was not the retardation compensation film of the present invention.

(4) Peelability evaluation The peelability was evaluated by comparing the polarizing plate LLC2-9218 manufactured by Sanlitz Co., Ltd. with an acrylic adhesive so that the axial direction of the polarizing plate and the retardation compensation film was 45 °. The same pressure-sensitive adhesive was applied to the surface of the retardation compensation film in a state of being bonded to a compensation film to form an elliptical polarizing plate, cut to 150 mm square, and then bonded to a glass cell, and then autoclaved at 50 ° C., 5 kgf / cm ^2. Degassing was performed for 20 minutes under the conditions to remove bubbles, and then the degree of peeling was confirmed by exposing to 100 ° C. in an atmosphere of 60 ° C. and 95% RH.

(5) Result The structure using the retardation compensation film of the example could not confirm peeling.
The structure using the polycarbonate retardation compensation film of the comparative example was confirmed to be peeled off by about 20 mm from the end.
From the above results, the retardation compensation film of the present invention does not peel even when an adhesive having removability is used, and a liquid crystal display device having excellent durability can be produced.

Claims (1)

It consists of a thermoplastic saturated norbornene-based resin, has a water vapor transmission rate of 200 g / m ² · 24 hr or less under an environmental condition of 60 ° C. and 95% RH, and has a re-peelable pressure-sensitive adhesive layer on the surface to be bonded to the glass cell. A retardation compensation film used for a liquid crystal display device.