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AssigneeNitto Denko Corporation
InventorsKazuki Tsuchimoto, Seiji Kondou, Akihiro Nishida
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The present invention provides a polarizing film having a high polarization degree and high transmittance, a process for producing the polarizing film, and a polarizing plate using the polarizing film, and an optical member. In the process for producing the polarizing film, a polyvinyl alcohol-based film is dry-stretched uniaxially, relaxed in an aqueous solution containing iodine or a dichroic dyestuff, and further stretched in an aqueous solution containing a PVA crossling agent. It is preferable that the polyvinyl alcohol-based film has a dry-stretch ratio of at least 2, the film after relaxation has a stretch ratio of at least 1.02, and the total stretch ratio is at most 6.5. It is also preferable that the relaxation rate is at most 10% of the dry-stretch ratio.
A process for producing a polarizing film, comprising:
A polarizing film obtained by uniaxially dry-stretching a polyvinyl alcohol-based film, relaxing the film in an aqueous solution containing at least one component selected from the group consisting of iodine and a dichroic dyestuff, and further stretching the relaxed film in an aqueous solution containing a PVA crosslinking agent;
A polarizing plate comprising a polarizing film and a protective film bonded to at least one surface of the polarizing film, wherein the polarizing film is produced by uniaxially dry-stretching a polyvinyl alcohol-based film, relaxing the film in an aqueous solution containing a component selected from the group consisting of iodine and a dichroic dyestuff, and further stretching the relaxed film in an aqueous solution containing a PVA crosslinking agent.
An optical member comprising a polarizing film and a plate laminated on the polarizing film, the plate is selected from the group consisting of a reflecter and a transflecter, wherein the polarizing film is produced by uniaxially dry-stretching a polyvinyl alcohol-based film, relaxing the film in an aqueous solution containing a component selected from the group consisting of iodine and a dichroic dyestuff, and further stretching the relaxed film in an aqueous solution containing a PVA crosslinking agent.
An optical member comprising a polarizing film and a plate laminated on the polarizing film, the plate is selected from the group consisting of a retardation plate and a λ plate, wherein the polarizing film is produced by uniaxially dry-stretching a polyvinyl alcohol-based film, relaxing the film in an aqueous solution containing a component selected from the group consisting of iodine and a dichroic dyestuff, and further stretching the relaxed film in an aqueous solution containing a PVA crosslinking agent.
An optical member comprising a polarizing film and an optical compensating film laminated on the polarizing film, wherein the polarizing film is produced by uniaxially dry-stretching a polyvinyl alcohol-based film, relaxing the film in an aqueous solution containing a component selected from the group consisting of iodine and a dichroic dyestuff, and further stretching the relaxed film in an aqueous solution containing a PVA crosslinking agent.
An optical member comprising a polarizing film and a brightness enhancement film laminated on the polarizing film, wherein the polarizing film is produced by uniaxially dry-stretching a polyvinyl alcohol-based film, relaxing the film in an aqueous solution containing a component selected from the group consisting of iodine and a dichroic dyestuff, and further stretching the relaxed film in an aqueous solution containing a PVA crosslinking agent.
A liquid crystal display comprising a liquid crystal cell and a polarizing film applied to at least one surface of the liquid crystal cell, wherein the polarizing film is produced by uniaxially dry-stretching a polyvinyl alcohol-based film, relaxing the film in an aqueous solution containing a component selected from the group consisting of iodine and a dichroic dyestuff, and further stretching the relaxed film in an aqueous solution containing a PVA crosslinking agent.
Dependencies are inferred from the claim text.
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Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state: in the form of a thin…
Of plates or sheets: uniaxial, e.g. oblique
Producing flat articles, e.g. films or sheets: films or sheets
After-treatment of articles without altering their shape; Apparatus therefor: for changing orientation
Term end not estimated
The present invention relates to an optical compensating film that drastically improves contrast, display colors and other visual properties of a liquid crystal display (hereinafter this term can be abbreviated as LCD) and also having higher durability and excellent handling properties in a liquid crystal display, an elliptically polarizing plate, and a liquid crystal display using the optical compensating film and the elliptically polarizing plate.
Liquid crystal displays have been used for desk-top electronic calculators, electronic clocks, personal computers, word processors, and meters of automobiles and other machines, and such LCDs comprise polarizing plates. A polarizing plate is produced, for example, by laminating protective films such as triacetylcellulose on both surfaces of a polarizing film of a polyvinyl alcohol-based (PVA) film in which iodine or a dichroic dyestuff is adsorb-oriented. Recently, such films have been required to have a high polarization degree and high transmittance.
A polarizing film can be produced, for example, by adsorbing either iodine or a dichroic dyestuff in a non-oriented polyvinyl alcohol-based film before stretching, or by adsorbing iodine or a dichroic dyestuff in a polyvinyl alcohol-based film that has been stretched and oriented. A polyvinyl alcohol-based film lacks a process stability, and thus it is difficult to stretch uniformly because hydrogen bonds among the molecules are disconnected by moisture during a wet stretch. For producing a film having a high polarization degree and high transmittance, various processes have been proposed. For example, JP-08 (1996)-240715 A describes a process of adsorb-orienting iodine or the like in a polyvinyl alcohol-based film subsequent to a dry uniaxial stretching of the film, and then dipping the film in an aqueous solution containing boric acid at a temperature ranging from 70° C. to 85° C. JP-10 (1998)-288709 A describes a process of dry uniaxial stretching of a polyvinyl alcohol-based film, dyeing, and further stretching of the film at least 1.5 times in a boron compound. JP-11 (1999)-49878 A describes a process of dry uniaxial stretching of a polyvinyl alcohol-based film, dyeing, and stretching of the film from 1.1 to 1.8 times while dipping in an aqueous solution of boric acid.
A polyvinyl alcohol (PVA) film having an average polymerization degree of 2400 and a film thickness of 75 μm (a product by Kuraray, trade name: 9×75RS) were stretched 3 times in an oven at 100° C. Later, the film was dipped for one minute in a 30° C. iodine bath (concentration: 0.04 wt %) while being relaxed (relaxation rate is 20%, which corresponds to 6.7% of a dry-stretch ratio). The film was further dipped for one minute in a 30° C. boric acid bath (concentration: 5 wt %) while being stretched 1.5 times, and washed in 25° C. pure water, dried for 4 minutes at 60° C., so that a polarizing film was obtained.
A PVA film as described in Example 1 was applied with tension backwards while being contacted with a surface of a heating roller at 100° C. so as to stretch 4 times. Later, the film was dipped for one minute in a 30° C. iodine bath (concentration: 0.04 wt %) while being relaxed (relaxation rate is 20%, which corresponds to 5% of a dry stretch ratio). The film was further dipped for one minute in a 30° C. boric acid bath (concentration: 5 wt %) while being stretched 1.3 times, and washed in 25° C. pure water, dried for 4 minutes at 60° C., so that a polarizing film was obtained.
A PVA film as described in Example 1 was stretched 4 times in an oven at 100° C. Later, the film was dipped for one minute while being relaxed in a 30° C. iodine bath (concentration: 0.04 wt %) (relaxation rate is 25%, which corresponds to 6.3% of a dry-stretch ratio). The film was further dipped for one minute in a 30° C. boric acid bath (concentration: 5 wt %) while being stretched 1.3 times, and washed in 25° C. pure water, dried for 4 minutes at 60° C., so that a polarizing film was obtained.