1. Field of the Invention
This invention relates to a molded optical panel for use in, such as, for example, a back light or front light panel of liquid crystal display, an edge light panel of various kinds of face illuminators and illumination boards, and a light diffusing panel and a mold for forming the optical panel.
2. Description of the Related Art
In Applicants"" co-pending Japanese Patent Application Hei 11(1999)-267686, there is proposed an optical panel for use in an edge light panel on one face of which is formed integrally a light guiding pattern by making use of a mold provided with a mold base and a molded pattern formed indirectly on the mold base by charging a heat-resistant resin forming a light guiding element into a porous pattern film obtained by exposing and developing a negative-type photosensitive resin by a photoresist method.
The co-pending Japanese application has advantages in that it is possible to produce a mold relatively easily for an extremely short amount of time, namely, half a day to a day, as compared with the conventional method of making the mold by an electrical discharging process, etching process and the like which requires a working time of several days to one week. Accordingly, it becomes possible to respond properly to requests for short-run productions and deliveries of a small amount of various types of flat panel illuminators such as the optical panel for edge light panel or liquid crystal backlights. Further, the co-pending application has advantages of making it possible to form the light guiding pattern of higher precision and higher density as compared with the optical panel for the edge light panel molded by using the conventional mold, and to obtain the optical panel for the edge light panel exhibiting high luminance and high uniformity while preventing the see-through pattern.
However, since the molded pattern is formed indirectly of heat-resistant resin by the use of a negative-type photosensitive resin, it is necessary to supply the heat-resistant resin forming the light guiding element to a porous pattern film via a screen mesh and the like after forming the porous pattern film of the negative-type photosensitive resin. Accordingly, the co-pending Japanese application has disadvantages in that a process for producing the mold is still complicated and precise charging of the heat-resistant resin into the porous pattern becomes gradually difficult due to inclusion of air and the like. As the light guiding element comprising a dot or a line or the like is minute, there is a tendency of creating a failure in the molded pattern resulting from insufficient charging of the heat-resistant resin.
Accordingly, a first problem to be solved by this invention is to propose a molded optical panel having high luminance and high uniformity or a molded optical panel having excellent light diffusing properties, either type of panel being suitable for short-run production and delivery in small numbers by facilitating the production of the mold and shortening the working time. A second problem to be solved by this invention is to propose the mold used for molding these optical panels.
The present inventor has been developed to address the first and second problems as described above, wherein the following facts were determined:
(1) Since the molded pattern can be formed directly on the mold base by a photosensitive heat-resistant resin, wherein the molded pattern is formed on the mold base using a photoresist method via the pattern film by making use of the photosensitive heat-resistant resin, the problems resulting from charging of the heat-resistant resin when the molded pattern is formed indirectly can be solved. Moreover, it is possible to simplify the process of the production of the mold and shorten the working time.
(2) When the molded pattern is formed by making use of the photoresist method using, for example, a pattern designed by CAD as a positive or negative pattern film depending on an application of the optical panel, the molded pattern corresponding to the designed pattern can be reproduced exactly. Accordingly, the optical pattern as a reversal pattern of the molded pattern can be obtained. The optical pattern thus formed exhibits a high luminance and high uniformity corresponding exactly to the designed pattern.
(3) Further, direct formation of the molded pattern by the photoresist method permits forming a suitable molded pattern which is capable of controlling light. For example, the molded pattern having a wide range of density can be formed with example, the molded pattern having a wide range of density can be formed with extremely high degree of precision covering from the conventional limit of density of approximately 25 lines to 50 lines per inch (25.4 mm) in terms of line density, namely, 0.5 mm to 1 mm in terms of space between each of two pattern elements to fine pattern of maximum high density and still performing guide of incident light effectively, for example, high density of 0.05 mm or less in terms of space. The molded pattern is reversed to obtain the corresponding light guiding pattern.
(4) By maximizing the space between each of two pattern elements, the optical pattern of fine precision and high density corresponding to the reversed pattern of the molded pattern can be formed. Accordingly, the optical panel for an edge light panel of high performance exhibiting a high luminance and high degree of uniformity and eliminating the pattern see-through can be obtained.
(5) Further, it is possible to apply the optical panel of the present invention to the light diffusing panel which diffuses light from a light emitting apparatus, such as, a backlight panel of liquid crystal display, placed immediately below the light diffusing panel and to utilize diffused light so as to illuminate uniformly through the light diffusing panel. A fine pattern and high density of the optical pattern can be formed on the light diffusing panel to obtain a high degree of uniformity of the light diffusing panel.
According to one aspect of this invention, there is provided an optical panel at least on one surface of which is formed integrally an optical pattern. The optical pattern is directly formed by making use of a mold and a molded pattern of a photosensitive heat-resistant resin formed by the use of a photoresist method via a pattern film. The photoresistant resin is a positive type and the pattern film is a optical pattern elements. In an alternative form of the present invention, the film, thereby the optical pattern is formed as a concave pattern having photosensitive heat-resistant resin is a positive type and the pattern film is a negative film, thereby the optical pattern is formed as a projected pattern having projected optical pattern elements. The photosensitive heat-resistant resin may be negative type and the pattern film may be a positive film, thereby the optical pattern is formed as a projected pattern having projected optical pattern elements. Further, the photosensitive resin may be negative type and the pattern film may be a negative film, thereby the optical pattern is formed as a concave pattern having concave pattern elements. The optical pattern includes the optical pattern elements each of which is more than 1 xcexcm and less than 300 xcexcm in diameter or side length having space of more than 5 xcexcm and less than 1 mm between each two optical pattern elements. The optical pattern acts as a light guiding pattern and is formed by changing non-stepwise diameter and/or density of the optical pattern element comprising dots or lines so as to perform light guiding inversely proportional to an amount of incident light from a light incident edge face of the optical panel toward a position distant from the light incident edge face to perform light guiding control. The optical panel of the present invention can be used for a light diffusing panel using the optical pattern as a light diffusing pattern. The photoresist method used herein implies a method used for semiconductors or other similar device and is defined as a method in which a photoresist film is formed on a mold base, exposed to light and developed to transfer a pattern from pattern film used in the light exposure.
The molded optical panel of the present invention can simplify the production of the mold, and shorten significantly the working time to approximately a few hours, and can be adapted properly to the short-run production and delivery of a small amount of various kinds of the optical panels, such as, the edge light panels and the light diffusing panel. Further, the molded optical panel of the present invention can form the optical pattern corresponding exactly to the designed pattern, and ensure brightness and uniformity of the optical panel as designed, which results in performing the secondary illumination. Furthermore, the molded optical panel of the present invention can provide the fine optical pattern exhibiting high performance, utmost high fine precision and high density without see-through of the pattern. In addition, the molded optical panel of the present inventions can provide the preferable shape of the optical pattern, and makes the light guiding of, for example, an edge light panel high luminance and high uniformity either by forming the optical pattern high density or by controlling the light guiding of incident light in the direction distant from the light source. The same result can be obtained when the optical panel is used as a light diffusing panel.
According to another aspect of this invention, there is provided a mold for forming the optical pattern integrally at least on one surface of the optical panel. The mold comprises a mold base and a molded pattern of a photosensitive heat-resistant resin formed directly on the mold base by the use of a photoresist method via a pattern film. The photosensitive heat-resistant resin used in the mold is preferably a photosensitive polyimide resin.
The mold for a molded optical panel of the present invention can simplify the production of the mold, and significantly shorten the working time to a few hours, and can be adapted properly to the short-run production and delivery of a small amount of various kinds of the optical panels. Further, the mold for the molded optical panel of the present invention can form the molded pattern on the mold base corresponding exactly to the designed pattern having high adhesion to the mold base. Furthermore, the mold for the molded optical panel of the present invention can provide the mold having a high precision and durability for use in forming the optical pattern of the edge light panel or light diffusing pane. In the mold of the present invention, it is preferably to use a photosensitive heat-resistant resin which makes the direct production of the molded pattern by the photoresist method easy and can provide the mold having excellent transference at the time of molding of the optical panel.