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Researchers Submit Patent Application, "Die Structure, Transfer Molding Apparatus, Transfer Molding Method, Optical Member, Area Light Source Device,...

May 29, 2014



Researchers Submit Patent Application, "Die Structure, Transfer Molding Apparatus, Transfer Molding Method, Optical Member, Area Light Source Device, Liquid Crystal Display Device, and Mobile Device",

By a News Reporter-Staff News Editor at Politics & Government Week -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Takemura, Koichi (Shiga, JP); Shibata, Tomofusa (Kyoto, JP); Yamanaka, Yoshihisa (Shiga, JP); Kaneko, Kazutaka (Saitama, JP); Fujie, Yuzuru (Saitama, JP); Hashimoto, Naoki (Saitama, JP); Suzuki, Taichi (Shiga, JP); Kojima, Masayuki (Shiga, JP), filed on February 8, 2013, was made available online on May 15, 2014.

The patent's assignee is OMRON Corporation.

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to a transfer-molding die structure, a transfer molding apparatus, a transfer molding method, an optical member, an area light source device, a liquid crystal display device, and a mobile device.

"Conventionally, for example, Japanese Unexamined Patent Publication No. 2005-310286 discloses a transfer-molding die structure, which is incorporated in an optical-product transfer molding apparatus. The optical-product transfer molding apparatus heats and pressurizes a resin film between a first die and a second die using a transfer plate to perform the transfer molding of a finely irregular pattern. The optical-product transfer molding apparatus includes: the transfer plate that includes a transfer surface used to perform the transfer molding to a transferred portion of the resin film; an elastic plate that presses a peripheral portion located around the transferred portion of the resin film; and a transfer-plate heating mechanism and a transfer-plate cooling mechanism, which are provided in at least one of the first die and the second die.

"However, in the conventional die structure, it takes a long time to remove a bubble generated in the transfer molding. Particularly, in the case that a projecting portion is formed in the surface of the resin sheet, a large amount of air remains in a recess, which is provided in the transfer plate (a transfer member) in order to form the projecting portion, and it takes a longer time to remove a residual air, which degrades productivity.

"As illustrated in FIG. 8A, in the case that plural arc regions (a bold dotted line) including tapered surfaces are continuously arrayed in an inner edge portion of the recess of the transfer member, a flow rate of a molten resin is not homogenized. Therefore, a region of fast flow rate of the molten resin differs from a region of slow flow rate of the molten resin in a deformation amount of the residual air (a bold solid line), and the residual air is deformed from an even width to different shapes (FIGS. 8B to 8E). As a result, as illustrated in FIG. 8F, a boundary bubble that is generated by separating part of the residual air remains in a molding product to degrade a yield ratio."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "One or more embodiments of the present invention provides a die structure, a transfer molding apparatus, and a transfer molding method, in which the residual air generated during the transfer molding can surely and rapidly removed, and an optical member, an area light source device, a liquid crystal display device, and a mobile device, which are produced by the transfer molding method. A light guide plate and a prism sheet can be cited as an example of the optical member.

"In accordance with one or more embodiments of the present invention, a die structure includes: a first die; a second die that can relatively be separated from and brought into contact with the first die; and a transfer member that is provided in at least one of the first and second dies, the transfer member performing transfer molding while bringing a transfer surface into contact with a resin sheet supplied between the first and second dies, wherein the transfer member includes a recess that is formed in the transfer surface and at least one groove portion that is connected to the recess.

"Accordingly, the residual air, which is generated when the transfer surface of the transfer member is brought into contact with the resin sheet to perform the transfer molding, can surely and rapidly be exhausted through the groove portion.

"The groove portion may have a shape in which the groove portion is directly connected to the recess. The groove portion may be connected to the outside, or not connected to the outside. There is no practical issue when a portion molded in the groove portion is removed in grinding work after the molding.

"In the die structure in accordance with one or more embodiments of the present invention, the groove portion may have a depth greater than or equal to that of the recess.

"Accordingly, the residual air is hardly trapped in the inner surface of the recess, and the residual air can surely and rapidly be exhausted through the groove portion.

"In the die structure in accordance with one or more embodiments of the present invention, the groove portion may be connected to an outside of the transfer member.

"Accordingly, the residual air can further surely and rapidly be exhausted to the outside.

"In the die structure in accordance with one or more embodiments of the present invention, the groove portion may be formed to intersect the recess formed in the transfer surface.

"Accordingly, a degree of freedom of design of the groove portion is increased to facilitate the design.

"In the die structure in accordance with one or more embodiments of the present invention, the transfer member may include an auxiliary groove portion that is formed to be connected to the recess, and the groove portion may be connected to the recess through the auxiliary groove portion.

"Accordingly, the residual air temporarily collected in the auxiliary groove portion is surely and rapidly exhausted through the groove portion, so that the residual air can further surely and rapidly be exhausted.

"In the die structure in accordance with one or more embodiments of the present invention, each groove portion may have a sectional area of a folding-fan-shaped flow path in which a pressure of a molten resin flowing from the recess is substantially equalized.

"Accordingly, the residual air is equally exhausted from each groove portion, the residual air can further rapidly be exhausted.

"In the die structure in accordance with one or more embodiments of the present invention, each groove portion may be disposed in a position where a flow rate of the molten resin is substantially equalized.

"Accordingly, the flow of the molten resin is homogenized to simultaneously and evenly exhaust the residual air, so that productivity can be improved.

"In accordance with one or more embodiments of the present invention, a transfer molding apparatus includes the die structure described above.

"Accordingly, one or more embodiments of the present invention provides the transfer molding apparatus in which the residual air, which is generated when the transfer surface of the transfer member is brought into contact with the resin sheet to perform the transfer molding, can surely and rapidly be exhausted through the groove portion.

"In accordance with one or more embodiments of the present invention, a transfer molding method includes: an insertion step of inserting a resin sheet between a first die and a second die, which are disposed opposite each other; a sandwiching step of sandwiching the resin sheet between the first and second dies while a transfer surface of a transfer member is brought into contact with at least one of surfaces of the resin sheet; and a transfer molding step of heating at least one of the first and second dies to melt at least a surface portion of the resin sheet with which the transfer surface of the transfer member is brought into contact, and exhausting residual air remaining in a recess through a groove portion connected to the recess when a thick portion is formed by the recess formed in the transfer surface.

"Accordingly, one or more embodiments of the present invention provides the residual air, which is generated when the transfer surface of the transfer member is brought into contact with the resin sheet to perform the transfer molding, can surely and rapidly be exhausted through the groove portion.

"In the transfer molding method in accordance with one or more embodiments of the present invention, the groove portion may have a depth greater than or equal to that of the recess.

"Accordingly, the residual air is hardly trapped by the inner surface of the recess, and the transfer molding method in which the residual air can surely and rapidly be exhausted through the groove portion is obtained.

"In the transfer molding method in accordance with one or more embodiments of the present invention, a molten resin may be caused to flow partially to the groove portion in which a nonproductive portion is molded in the transfer molding step.

"Accordingly, the residual air can surely be exhausted to improve the yield ratio. There is no practical problem when the nonproductive portion is removed in the grinding work after the molding.

"In accordance with one or more embodiments of the present invention, an optical member is molded by the above transfer molding method.

"Accordingly, the residual air can surely and rapidly be exhausted, and the high-productivity, good-yield-ratio optical member is obtained.

"In accordance with one or more embodiments of the present invention, an area light source device includes: the optical member in accordance with one or more embodiments of the present invention; and a light source that is disposed in at least one end face of the optical member, wherein light incident from the light source to the optical member is output through a light exit surface of the optical member.

"Accordingly, the residual air can surely and rapidly be exhausted, and the high-productivity, good-yield-ratio area light source device is obtained.

"In accordance with one or more embodiments of the present invention, a liquid crystal display device includes: the area light source device in accordance with one or more embodiments of the present invention; and a liquid crystal panel.

"Accordingly, the residual air can surely and rapidly be exhausted, and the high-productivity, good-yield-ratio liquid crystal display device is obtained.

"In accordance with one or more embodiments of the present invention, a mobile device includes the area light source device in accordance with one or more embodiments of the present invention.

"Accordingly, the residual air can surely and rapidly be exhausted, and the high-productivity, good-yield-ratio mobile device is obtained.

"According to one or more embodiments of the present invention, advantageously the residual air, which is generated during the transfer molding in which the transfer surface of the transfer member is transferred to the resin sheet, can surely and rapidly be removed.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a schematic diagram illustrating an optical member forming apparatus according to one or more embodiments of the present invention;

"FIG. 2 is a partially one or more exploded perspective view schematically illustrating a transfer molding apparatus in FIG. 1;

"FIG. 3A is a partial bottom view of an upper-die transfer plate in FIG. 2, FIG. 3B is a partially schematic sectional view of a die portion in FIG. 2, and FIG. 3C is a partially enlarged sectional view of the die portion in FIG. 2;

"FIGS. 4A and 4B are partial plan views illustrating first and second modifications of one or more of the embodiments;

"FIGS. 5A, 5B, 5C, and 5D are partial plan views illustrating third, fourth, fifth, and sixth modifications of one or more of the embodiments;

"FIGS. 6A and 6B are a graph and an evaluation table illustrating an analysis result, which is performed to obtain an optimum slit width dimension removing a residual bubble;

"FIGS. 7A and 7B illustrate a measurement position and a graph of a measurement result when a flow rate of a molten resin changed depending on existence or non-existence of a slit is measured;

"FIG. 8 is a view illustrating a flow rate of the molten resin in one or more of the embodiments, FIG. 8A is a partially enlarged view of the flow rate of the molten resin, and FIGS. 8B, 8C, 8D, 8E, and 8F are schematic diagrams illustrating deformation and split processes of a long and thin residual air;

"FIG. 9A is an explanatory view illustrating a positional relationship between a half-finished plate and a cutting tool, and FIG. 9B is a sectional view illustrating a state in which a half-finished product is cut, and FIG. 9C is a sectional view illustrating a state immediately after the half-finished product is cut; and

"FIG. 10 is a sectional view illustrating a liquid crystal display device in which a light guide plate and a prism sheet, which are optical members of one or more of the embodiments, is incorporated."

For additional information on this patent application, see: Takemura, Koichi; Shibata, Tomofusa; Yamanaka, Yoshihisa; Kaneko, Kazutaka; Fujie, Yuzuru; Hashimoto, Naoki; Suzuki, Taichi; Kojima, Masayuki. Die Structure, Transfer Molding Apparatus, Transfer Molding Method, Optical Member, Area Light Source Device, Liquid Crystal Display Device, and Mobile Device. Filed February 8, 2013 and posted May 15, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4305&p=87&f=G&l=50&d=PG01&S1=20140508.PD.&OS=PD/20140508&RS=PD/20140508

Keywords for this news article include: OMRON Corporation.

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