Asahi Glass Company, Limited

Kara Yoshida

Yuriko Kaida

Hiromichi Nagayama

Hiroshi Kumai

Tomoki Gunjima

Nobuhiko Takeshita

Hiromasa Sato

Hiroki Hotaka

Yuzuru Tanabe

Mizuho Ishida

To provide a liquid crystal optical modulation element which is excellent in durability against blue laser and which can maintain the characteristics for a long period of time. A liquid crystal optical modulation element to modulate a laser beam having a wavelength of at most 500 nm, which comprises a layer of a polymer liquid crystal composition sandwiched between a pair of transparent substrates facing each other, characterized in that

Liquid crystal optical modulation element and optical head device

An optical head device having a broadband phase plate of transforming at least three linearly polarized light beams having different wavelengths into circularly polarized light beams, is obtained. A broadband phase plate comprising two phase platesA andB laminated with e.g. an adhesive agent so that their optical axes are crossed, wherein provided that wavelengths of linearly polarized incident light beams are &#x3bb;, &#x3bb;and &#x3bb;(&#x3bb;&#x3c;&#x3bb;&#x3c;&#x3bb;), at least one or both of the two phase plates has such a phase difference characteristics that a ratioR(&#x3bb;)/R(&#x3bb;)and a ratioR(&#x3bb;)/R(&#x3bb;)between retardation values of the wavelengths are smaller than 1 andR(&#x3bb;)/R(&#x3bb;)is smaller thanR(&#x3bb;)/R(&#x3bb;), is integrated in the optical head device.

Optical head device

In the production of a glass substrate for magnetic disk, the present invention provides a method for producing a glass substrate for magnetic disk including a step of polishing a main surface of a circular glass substrate using a polishing pad made of a foamed resin while feeding a polishing liquid containing an abrasive, in which a polishing pad made of a foamed resin having an international rubber hardness of 45 IRHD or less, the hardness being measured at a dry state before contact with a slurry by the M method defined in JIS K6253, is used as a starting polishing pad and polishing is started after a polishing surface of the starting polishing pad is subjected to a dressing treatment to adjust the pad so that an open pore area ratio is 8% or more and an average circle equivalent diameter of open pores is 10 &#x3bc;m or more, in order to suppress an increase in roll-off in the polishing step of the main surface of the circular glass plate.

Method for producing glass substrate for magnetic disk

A liquid crystal compound represented by the formulaCH&#x2550;CR&#x2014;COO-(L)-E-E-E-E-Rwherein R: a hydrogen atom or a methyl group; R: a Calkyl group; k: 0 or 1; L: &#x2014;(CH)O&#x2014; or &#x2014;(CH)&#x2014; (wherein each of p and q which are independent of each other, is an integer of from 2 to 8); E: a 1,4-phenylene group; E, E, E: each independently a 1,4-phenylene group or a trans-1,4-cyclohexylene group and at least one of Eand Eis a trans-1,4-cyclohexylene group, provided that the 1,4-phenylene group and trans-1,4-cyclohexylene group in Eto Emay be such that a hydrogen atom bonded to a carbon atom in each group may be substituted by a fluorine atom, a chlorine atom or a methyl group. To provide a novel liquid crystal compound for preparing an optical element which can exhibit a proper Rd value depending upon usable wavelength and application and which is excellent in durability against a blue laser beam.

Polymerizable liquid crystal compound, liquid crystal composition, optical anisotropic material and optical element

To provide optical elements such as a phase plate suitably used in a broadband range and a polarizing diffraction element excellent in diffraction efficiency, a polymerizable liquid crystal composition to be used for them, and an optical head device using them. A polymerizable liquid crystal composition containing a polymerizable compound having a mesogen structure comprising the following condensed benzene ring group (A) and the following 6-membered cyclic group (B) bonded to at least one bond in the group (A) directly or via a connecting group &#x2014;OCO&#x2014; or &#x2014;COO&#x2014;, and a monovalent terminal group bonded to each of both terminals of the mesogen structure, at least one of the terminal groups being a monovalent organic group having a polymerizable moiety:

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Tokyo, Japan

Kara Yoshida