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Researchers Submit Patent Application, "Optical Film, Polarizing Plate, Liquid Crystal Display, and Method of Manufacturing Optical Film", for...

July 22, 2014



Researchers Submit Patent Application, "Optical Film, Polarizing Plate, Liquid Crystal Display, and Method of Manufacturing Optical Film", for Approval

By a News Reporter-Staff News Editor at China Weekly News -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors SATO, Hiroshi (Kanagawa, JP); SAITOH, Yukito (Kanagawa, JP); ICHIHASHI, Mitsuyoshi (Kanagawa, JP), filed on December 26, 2013, was made available online on July 10, 2014.

The patent's assignee is FUJIFILM Corporation.

News editors obtained the following quote from the background information supplied by the inventors: "A Known liquid crystal display includes a liquid crystal cell, a polarizing film, and an optical film for optical compensation (also referred to as an optically-compensatory film or retardation film).

"A transparent liquid crystal display includes two polarizing films on both surfaces of a liquid crystal cell, and one or more optically-compensatory films between the liquid crystal cell and the polarizing films. A reflective liquid crystal display has, in sequence, a reflector, a liquid crystal cell, an optically-compensatory film, and a polarizing film. A liquid crystal cell consists of rod-like liquid crystal molecules, two substrates encapsulating the molecules, and electrode layers for applying voltage to the molecules. Liquid crystal cells are categorized into various display modes by the alignment states of their rod-like liquid crystal molecules. For instance, transparent displays are present in various display modes, such as twisted nematic (TN), in-plane switching (IPS), ferroelectric liquid crystal (FLC), optically compensatory bend (OCB), super twisted nematic (STN), vertically aligned (VA), and electrically controlled birefringence (ECB) modes. Reflective displays are present in TN cells, hybrid aligned nematic (HAN) and guest-host (GH) modes.

"Optically-compensatory films are used in various liquid crystal displays to avoid coloring of images or increase the viewing angles. Traditional optically-compensatory films include stretched birefringent polymer films. As an alternative for an optical compensatory film composed of a stretched birefringent film, optically-compensatory films are currently proposed which include an optically anisotropic layer consisting of a support coated with an aligned liquid crystal compound. Liquid crystal compounds have a variety of alignment states and thus can provide optical properties that cannot be accomplished by traditional stretched birefringent polymer films.

"The optical properties of an optically-compensatory film depend on the optical properties or display mode of the liquid crystal cell. The use of a liquid crystal compound allows for the manufacture of an optically-compensatory film having different optical properties suitable for various display modes of the liquid crystal cell. Examples of such an optically-compensatory film include a laminate of two optically anisotropic layers, which is disclosed in Japanese Unexamined Patent Application Publication No. 2000-304930.

"In particular, Japanese Unexamined Patent Application Publication No. 2000-304930 discloses an optically-compensatory film in FIG. 6 including, in sequence, a support 1', a rubbed first alignment film 2', a first optically anisotropic layer 3', a rubbed second alignment film 2', and a second optically anisotropic layer 4', the second alignment film 2' being on the first optically anisotropic layer 3' and aligning liquid crystal compounds in the second optically anisotropic layer 4'."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Technical Problem

"A laminate of two or more optically anisotropic layers in Japanese Unexamined Patent Application Publication No. 2000-304930 is formed by laminating, in sequence, a first optically anisotropic layer, an alignment film, and a second optically anisotropic layer, resulting in increases in laminated layers and thus low productivity.

"FIG. 7 illustrates another optically-compensatory film including, in sequence, a support 1', a rubbed first alignment film 2', a first optically anisotropic layer 3', and a second optically anisotropic layer 4', the first optically anisotropic layer 3' having a rubbed surface, the second optically anisotropic layer 4' containing an aligned liquid crystal compound. The second optically anisotropic layer 4' is provided directly on the surface of the first optically anisotropic layer 3'. Rubbing the surface of the first optically anisotropic layer 3' leaves rubbing debris that increase the risks of repelling, bright dots, and irregularity in the resulting optical film.

"An object of the present invention, which has been made to solve such problems, is to provide an optical film including two or more optically anisotropic layers which is resistant to repelling, bright dots, and irregularity.

"Solution to Problem

"The inventors have studied to solve the problems and found that an optical film can be formed which includes a first optically anisotropic layer and a second optically anisotropic layer on a surface of the first optically anisotropic layer, wherein the surface tilt angle in the first optically anisotropic layer is in the range of 5.degree. to -80.degree. so that a liquid crystal compound in the second optically anisotropic layer can be aligned without an alignment film or rubbing.

"The problems were solved by the configuration , preferably by configurations to below.

" An optical film comprising: a first optically anisotropic layer; and a second optically anisotropic layer on the surface of the first optically anisotropic layer, wherein the first optically anisotropic layer is a layer of liquid crystal compounds which are aligned and fixed by polymerization, and the surface tilt angle of the liquid crystal compounds is in a range of 5.degree. to 80.degree. at a site in contact with the second optically anisotropic layer.

" The optical film according to , wherein a slow axis of the first optically anisotropic layer and a slow axis of the second optically anisotropic layer are orthogonal to each other.

" The optical film according to or , wherein a surfactant is eccentrically-located at a side of the surface of the first optically anisotropic layer, the surface being in contact with the second optically anisotropic layer.

" The optical film according to any one of to , wherein the first optically anisotropic layer contains rod-like liquid crystal compounds and the second optically anisotropic layer contains discotic liquid crystal compounds; or wherein the first optically anisotropic layer contains discotic liquid crystal compounds and the second optically anisotropic layer contains rod-like liquid crystal compounds.

" The optical film according to any one of to , the optical film being intended for use in a birefringent-mode liquid crystal display.

" The optical film according to any one of to , wherein the sum of an Re value of the first optically anisotropic layer and an Re value of the second optically anisotropic layer is in a range of -75 nm to 25 nm, each Re value indicating an in-plane retardation at a wavelength of 550 nm and being measured with reference to a slow axis of the first optically anisotropic layer.

" A hpolarizing plate comprising: a polarizing film; and protective films on both surfaces of the polarizing film, at least one of the protective films comprising the optical film according to any one of to .

" The polarizing plate according to , wherein at least one of the protective films is the optical film according to any one of to , and the polarizing film is bonded to an alignment film or an optically anisotropic layer through an adhesive layer.

" The polarizing plate according to , wherein at least one of the protective films is the optical film according to any one of to , the optical film comprising, in sequence, the polarizing film, a support, an alignment film, the first optically anisotropic layer, and the second optically anisotropic layer.

" A liquid crystal display comprising the optical film according to any one of to or the polarizing plate according to any one of to .

" A liquid crystal display comprising: a pair of polarizing plates; and a TN-mode liquid crystal cell between the pair of polarizing plates, wherein at least one of the pair of polarizing plates is the polarizing plate according to any one of to and comprises the second optically anisotropic layer near to the TN-mode liquid crystal cell.

" A liquid crystal display comprising: a pair of polarizing plates disposed in a birefringent mode; and a TN-mode liquid crystal cell between the pair of polarizing plates, wherein at least one of the pair of polarizing plates is the polarizing plate according to any one of to and the second optically anisotropic layer is disposed so as to be near to the TN-mode liquid crystal cell, and the sum of an Re value of the first optically anisotropic layer and an Re value of the second optically anisotropic layer is in a range of -75 nm to 25 nm, each Re value having a negative or positive sign, the negative sign corresponding to the direction of a director of liquid crystal molecules at a site in contact with a surface of the substrate near to the liquid crystal cell, the positive sign corresponding to a direction orthogonal to the direction of the director of the liquid crystal molecules.

" A method of manufacturing the optical film according to any one of to , comprising forming a second optically anisotropic layer by directly coating an unrubbed surface of the first optically anisotropic layer with a composition containing liquid crystal compounds, and aligning and fixing the liquid crystal compounds by polymerization.

" The method of manufacturing the optical film according to , comprising forming the first optically anisotropic layer by coating of a composition comprising liquid crystal compounds and a surfactant, and aligning and fixing the liquid crystal compounds by polymerization.

"The present invention provides an optical film including two or more optically anisotropic layers which is resistant to repelling, bright dots, and irregularity.

BRIEF DESCRIPTION OF DRAWINGS

"FIG. 1 is a schematic cross-sectional view illustrating an example optical film of the invention.

"FIG. 2 is a schematic cross-sectional view illustrating an example polarizing plate of the invention.

"FIG. 3 is a schematic cross-sectional view illustrating an example polarizing plate of the invention.

"FIG. 4 is a schematic cross-sectional view illustrating an example liquid crystal display of the invention.

"FIG. 5 is a schematic cross-sectional view illustrating an example liquid crystal display of the invention.

"FIG. 6 is a schematic cross-sectional view illustrating an example conventional optical film.

"FIG. 7 is a schematic cross-sectional view illustrating an example optical film."

For additional information on this patent application, see: SATO, Hiroshi; SAITOH, Yukito; ICHIHASHI, Mitsuyoshi. Optical Film, Polarizing Plate, Liquid Crystal Display, and Method of Manufacturing Optical Film. Filed December 26, 2013 and posted July 10, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4934&p=99&f=G&l=50&d=PG01&S1=20140703.PD.&OS=PD/20140703&RS=PD/20140703

Keywords for this news article include: Asia, FUJIFILM Corporation.

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Source: China Weekly News


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