Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2002-07-17
2003-11-25
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S619000, C359S626000, C359S599000, C264S002700, C349S112000
Reexamination Certificate
active
06654176
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the art of fields necessary for controlling light through convergence, diffusion, reflection, diffraction and the like, e.g. the art of fields such as of display, illumination, medical treatment, optical communication, computers and the like, which require microlenses. More specifically, the invention relates to a microlens array employed for the manufacture of a reflection-type liquid crystal display device and a diffuse reflector plate of a solar cell requiring a high efficiency, a method for making a transfer master pattern for a microlens array, a concave and convex pattern obtained from the transfer master pattern, a laminate for transfer, and a liquid crystal display device.
DESCRIPTION OF THE RELATED ART
A microlens array has been used for forming a diffraction grating filter, optical parts for optical communication or a focussing glass of camera parts. The microlens array takes a round or circular form having a diameter of approximately 10 to 30 &mgr;m with a depth of 0.6 to 50 &mgr;m. Usually, the microlens array is designed in a spherical form which is axially symmetrical with respect to the center thereof. For the measure of manufacturing a microlens, an indentation system set out in Japanese Unexamined Patent Publication Nos. Hei 9-327860 and Hei 11-42649 and a photolithographic system (hereinafter referred to merely as photolitho system) as proposed in Japanese Unexamined Patent Publication No. Hei 6-194502 wherein etching is performed after exposure to light are known. A fly cutting system, in which a lens face is rotationally cut while rotating a cutting tool, is known.
An instance of a lens array where microlenses are arranged at equal pitches includes a diffraction grating filter used as an optical part or an optical communication part. On the other hand, an instance of a microlens array of the type wherein microlenses are arranged at uneven pitches includes a reflector plate for preventing iridescent reflection and reflecting white light or a reflection electrode member for a reflection-type liquid crystal. For this purpose, it is necessary that several millions to several tens of millions of microlenses be formed.
For the processing of spherically designed microlenses, such microlenses are frequently formed according to the photolitho method. As a measure of mechanically controlling the processing dimension of a microlens, an indentation technique and a fly cutting technique using rotary cutting are used, respectively.
A liquid crystal display (hereinafter abbreviated as LCD) makes use of such features as to be thin, small in size and low in consumption power and has now been in use as a display unit of watches, desk-top calculators, TV sets, personal computers and the like. Further, in recent years, color LCD has been developed and started to be employed in various fields including, aside from those of OA devices and AV devices, those of navigation systems, view finders, monitors of personal computers and the like. Thus, it has been expected that its market will be drastically extended. Especially, attention has been paid to reflection-type LCD, in which light incident from outside is reflected for display, for application to a portable end instrument from the standpoint that back light is unnecessary with small consumption power, and thus, thinning and weight saving are enabled. For conventional reflection-type LCD, a twisted nematic system and a super twisted nematic system have been adopted. These systems become dark in display because ½ of incident light is not utilized for the display by the influence of linear polarizers. To avoid this, the display mode of a system wherein the polarizer is reduced to one in number and is combined with a phase plate or a phase transfer guest or host system has been proposed.
In order to obtain a bright display by efficiently utilizing external light in reflection-type LCD, it is necessary that the intensity of light scattered in directions vertical to a display face be increased with respect to incident light from all angles. To this end, a reflection film on a reflector plate should be so controlled as to impart appropriate reflection characteristics thereto.
A method of forming a diffuse reflector plate has been proposed in Japanese Unexamined Patent Publication No. Hei 4-243226, in which a photosensitive resin is coated onto a substrate and patterned by use of a photomask to form fine irregularities, each with a size of several micrometers, and a metal thin film is formed thereon.
Further, Japanese Unexamined Patent Publication No. Hei 11-42649 proposes a method of making a transfer master pattern wherein an indentater having a spherical tip is pressed thereby continuously forming concave configurations and also a method of making a reflector plate by transferring the pattern to a reflector substrate.
Moreover, a method of forming, on a substrate, a film made of fine particles dispersed in a resin so as to control diffusability in Japanese Unexamined Patent Publication No. Hei 7-110476.
Where a microlens array is formed according to a photolitho method, this process is carried out through chemical reaction, making it difficult to control the shape or configuration of individual microlens faces. Especially, in a reflector plate of the type wherein microlenses are arranged at irregular or uneven pitches, the sizes of adjacent microlenses differ from each other with a problem on the control of depth, so that the control of the configuration becomes difficult. As a result, the arrangement of axially symmetric spheres is difficult.
FIG. 20
is a perspective view of an indentation tool and an indentation master block showing a method of forming microlenses by an indentation system. In order that an axially symmetric spherical configuration is formed in the indentation system shown in the figure, it is necessary to avail a tool having a spherical form. For the tool, a diamond indentater
60
is usually employed. If the diamond indentater
60
can be constituted of a single crystal, a tool having a completely spherical face can be obtained. Diamond has a harder face and a softer face depending on the crystal orientation, so that it is difficult to finish the tool as having a complete sphere. Strictly speaking, the configuration of the tool has anisotropy. Especially, if an aspheric surface configuration in an axially symmetric form is desired, it is very difficult to obtain an intended configuration profile. In this sense, a difficulty is involved in forming a microlens
62
of a desired configuration in an indentation matrix
63
by means of the diamond indentater
60
. Although such a tool is available when using a super hard material with which an intended tool shape is liable to obtain, the tool made of a polycrystal material is disadvantageous in that not only the surface roughness at the tip thereof becomes poor, but also durability is not good when a great number of indentations are formed. Moreover, the indentation method has the problem that with the irregular pitches ascribed to the plastic flow of material, the configurations differ depending on the density of the irregular pitches.
With the fly cutting using rotary cutting, the profile accuracy of a tool is two-dimensionally controlled, making it possible to process the tool as having a configuration of high accuracy. In order to obtain an axially symmetric microlens, it is necessary to set the radius of cutting edge of a tool and the position of a rotation center in high accuracy, under which where the diameter of a microlens is at about 10 &mgr;m or below, it is very difficult to determine the center of rotation. In addition, the axially symmetric configuration of an aspheric face is difficult to process.
In the method set forth in Japanese Unexamined Patent Publication No. Hei 4-243226, the formation of concave and convex configurations includes the steps of exposing every substrate to light through a photomask and developing, so that the procedure is complicated, and thus, is neither low in cost or hig
Ishizawa Isao
Maeda Yukio
Ohta Tomohisa
Satoh Makoto
Taya Masato
Epps Georgia
Hasan M.
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