Optical: systems and elements – Polarization without modulation – With color filter
Reexamination Certificate
2003-01-31
2004-06-29
Juba, Jr., John (Department: 2872)
Optical: systems and elements
Polarization without modulation
With color filter
C359S490020, C264S001340, C264S001350, C252S585000
Reexamination Certificate
active
06757102
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process of producing a polarizer and a polarizer obtained by the process concerned. And the present invention relates to a polarizing plate using the polarizer concerned. Furthermore, a visual display, such as a liquid crystal display, an organic EL display, a PDP (plasma display panel), using the polarizing plate concerned.
2. Description of the Prior Art
As a polarizing plate conventionally used for image viewing displays, such as liquid crystal display, in general, an iodine treated polarizing film in which iodine is adsorbed in a polyvinyl alcohol based film and then the film is oriented, and a dyestuff treated polarizing film in which dichromatic dyes are adsorbed in the polyvinyl alcohol base film and then the film is oriented are known as a polarizer and they are commonly used. In these polarizing plates, since a polarizing plate using an iodine treated polarizing film as a polarizer gives contrast higher than a polarizing plate using dyestuff treated polarizing film as a polarizer, they are suitably used. Besides, a polarizer processed by potassium iodide gives a polarizer that has a little coloring, and demonstrates approximately constant absorbance over approximately all wavelength regions of visible light to demonstrate neutral gray. The polarizer concerned is usually used as a polarizing plate with which protective films, such as triacetyl cellulose film, are adhered on one side or both sides.
However, in recent years, in plenty of cases, image viewing displays, such as liquid crystal displays, are used under high temperature conditions etc. for a long period of time as applicable field becomes wider, and as a result, requirements for polarizing plates (polarizers) becomes severe, and image viewing displays having characteristics suitable for usages are now on demands. In connection with the circumstance, optical durability under heated conditions, especially characteristics of giving no hue change is also required for polarizing plates.
An object of the present invention is to provide a polarizer comprising a polyvinyl alcohol based film controlling coloring and satisfying high durability under conditions of high temperature.
And other object of the present invention is to provide a polarizing plate utilizing the polarizer and further a visual display utilizing the polarizing plate.
SUMMARY OF THE INVENTION
As a result of repeated examinations carried out wholeheartedly by the present inventors to solve the above-mentioned problems, a process of producing a polarizer shown below was found out and the present invention was completed.
The present invention relates to a polarizer comprising a polyvinyl alcohol based film being dyed by iodine and treated with potassium iodide,
wherein an element content ratio (K/I) of iodine (I) and potassium (K) is 0.05 through 0.24.
In the above described present invention, in a polarizer comprising polyvinyl alcohol based film that is dyed by iodine, and is treated by potassium iodide etc., and whose coloring is suppressed, polarization function and hue of the polarizer are determined based on a state of a complex of iodine, but when iodine or potassium not participating in polarizing function and hue exists, it is assumed that adverse influence demonstrated under high temperature gives change of transmittance, polarizing degree, and hue, and thereby durability under high temperature is improved by controlling content of iodine and potassium in the above described polarizer to necessary minimum.
When an element content ratio (K/I) of iodine (I) and potassium (K) is controlled to 0.24 or less, a polarizer may be obtained in which coloring is suppressed, change of transmittance and polarizing degree, etc. at high temperature is small, superior in durability, and moreover polarizing degree is high. When the element content ratio (K/I) is more than 0.24, it is not preferable because optical characteristics when being heated at high temperature fall.
As for an element content ratio (K/I), it is preferable that an optimal element content ratio (K/I) may be selected according to usage. That is, in the case of semitransparent and reflective type liquid crystal modules, external light transmits a polarizing plate once, and a reflective plate then reflects it, and again it transmits into the polarizing plate, and thereby influence of hue of the polarizing plate is greatly demonstrated. Since a large element content ratio (K/I) enlarges a b value of a polarizing plate and the polarizing plate tends to look yellowish in response to influence of hue, the element content ratio (K/I), is preferably set to 0.05 through 0.18. In the case of liquid crystal modules for transmission type high definition displays, such as monitor of notebook type personal computer, and liquid crystal TV, since light from a backlight transmits a polarizing plate only once, an element content ratio (K/I) is preferably set to 0.10 through 0.24. Element percentage of iodine (I) and potassium (K) in a polarizer is determined from an element content analyzed by a fluorescent X-ray analysis etc.
And the present invention relates to a polarizing plate with which a transparent protective layer is prepared at least in one side of the above described polarizer.
In the above-mentioned polarizing plate, comprising at least one of a retardation plate, a viewing angle compensation film, a reflective plate, a transflective plate and a brightness enhancement film, is used.
Furthermore, the present invention relates to a visual display using the above-described polarizing plate.
DETAILD DESCRIPTION OF THE INVENTION
Polyvinyl alcohols or derivatives thereof are used for a material of a non-stretched film in a process of producing a polarizer of the present invention. As derivatives of polyvinyl alcohol, in addition to polyvinyl formals, polyvinyl acetals, etc. may be mentioned, and derivatives modified with olefins, such as ethylene and propylene; unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, and crotonic acid; alkyl esters of the above described unsaturated carboxylic acids and acrylamide etc. may be mentioned. Generally, polyvinyl alcohol with approximately 1000 to 10000 of degree of polymerization and approximately 80 to 100 mol % of degree of saponification is used.
In addition, additives, such as plasticizers, may also be contained in the above described polyvinyl alcohol film. As plasticizers, polyols and condensates thereof, etc., for example, glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, polyethylene glycols, etc. may be mentioned. Although an amount of the plasticizers used is not especially limited, it is preferable to be set no more than 20% by weight in the non-stretched film.
A uniaxial stretching processing and a dyeing processing by iodine are given to the above described polyvinyl alcohol based film (unstretched film), according to conventional methods, and further a processing by boric acid is conducted. Besides, a processing by potassium iodide is conducted to the polyvinyl alcohol based film (unstretched film). A processing by potassium iodide can be carried out by making potassium iodide included in a processing liquid concerned during a dyeing processing by iodine and a processing by boric acid, and in addition, it can be carried out, separately with the above described processing, by conducting an impregnation processing by a potassium iodide solution. The polyvinyl alcohol based film (stretched film) with the above described processing conducted thereto is dried by a conventional method, and a polarizer is obtained.
Besides, in preparation of a polarizer comprising a polyvinyl alcohol based film (stretched film), conditions, such as dipping temperature and dipping period in the above described each processing, and concentration of each processing liquid, are controlled so that an element content ratio (K/I) of iodine (I) and potassium (K) in the polarizer concerned may give a value in a range of 0.05 through 0.24.
In addition, co
Kondo Seiji
Nishida Akihiro
Tsuchimoto Kazuki
Jr. John Juba
Nitto Denko Corporation
Westerman Hattori Daniels & Adrian LLP
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