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Researchers Submit Patent Application, "Luminance Enhancement Film, Backlight Module and Liquid Crystal Display Device", for Approval

June 5, 2014



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 TYAN, Yi-Long (TAOYUAN, TW); CHEN, Chia-Yi (TAOYUAN, TW); JUAN, Yu-Mei (TAOYUAN, TW); HSIN, Lung-Pin (TAOYUAN, TW); CHEN, Hui-Yong Paul (TAOYUAN, TW), filed on February 14, 2013, was made available online on May 22, 2014.

The patent's assignee is Ubright Optronics Corporation.

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to an optical film with a reinforced layer, particularly to the optical film with superior in thermal stability, dimensional stability and anti-deformation ability.

"With the advancement of technology, in order to meet people's needs for light, thin, short and small electronic digital products, it prompted the development of the thickness of liquid crystal display panel to become thinner and more lightweight so as to achieve a lightweight and thin electronic digital products which are easy to carry. An efficient way to achieve this goal is to make the backlight module thinner.

"The fundamental structure of a common backlight module except the light source includes (from bottom to top): reflective sheet, light guiding plate, lower diffusion sheet, lower luminance enhancement film, upper luminance enhancement film and upper diffusion sheet. In order to reduce the thickness of the backlight module, the existing methods in the industry are as follow: (1) using a multi-functional composite sheet material, i.e., integrating parts of the optical films mentioned above into one composite sheet, for example, combining the upper diffusion sheet with upper luminance enhancement film into one upper luminance enhancement composite sheet; (2) reducing the thickness of each optical film, and thus achieving the purpose of reducing the total thickness thereof, for example, changing the luminance enhancement film used for notebook computers from the original substrate whose thickness is 125 .mu.m into the replaced substrate whose thickness is 100 .mu.m, or even 75 .mu.m.

"However, in adopting the above-mentioned method (2), particularly using the substrate with thinner thickness, there would be the following problem. When, using a substrate with, a large area to produce a large-size panel, the rigidity of the substrate will become insufficient and thus easily cause deformation. In addition, when the light source of the backlight module is of edge light, the heat is easy to concentrate on the specific location at the edge of the backlight module, causing that the temperature at the edge of the backlight module would be higher than that in other portion of the backlight module and then making the edge of the substrate easily deform due to the high temperature, thereby re-suiting in some problems, such as warp, corrugation, unevenness. This problem would be more apparent on the substrate with thinner thickness.

"As to prior arts about applying coating layer on the specific layer of the backlight module to achieve unique purposes, there are some examples as follows.

"First, U.S. Pat. No. 5,995,288 (hereinafter, referred to as 'PD1') discloses an optical sheet in which a resin coating layer is disposed on a side of the substrate opposite to the side forming unit prisms. The coating layer has a thickness in the range from 2 .mu.m to 20 .mu.m and contains particles whose particle diameter is in the range from 1 .mu.m to 10 .mu.m, whereas the ratio of the refractive index of the particles to the refractive index of the resin forming the coating layer is in the range from 0.9 to 1.1. With this structure, a purpose for preventing the Newton's rings can be achieved.

"In addition, U.S. Pat. No. 6,280,063 (hereinafter, referred to as 'PD2') discloses a brightness enhancement article in which a first major surface of the substrate forms an array of prisms while a second major surface of the substrate forms a light scattering layer. This light scattering layer has a thickness in the range from 1 to 50 .mu.m and contains a plurality of components projecting from the second major surface. Additionally, the haze value of this brightness enhancement article is in the range from 20 to 60% and transmittance is not greater than 94%, whereby the brightness enhancement article can maintain a brightness enhancement characteristic and an extinction characteristic as well.

"Furthermore, US 2008/0151549 (hereinafter, referred to as 'PD3') discloses a scratch-resistant optical film in which a hard coating layer is provided on the surface of the reflective substrate as a scratch-resistant layer. The scratch-resistant, layer has a surface resistivity in the range from 10.sup.8.OMEGA./.quadrature. to 10.sup.12.OMEGA./.quadrature., a thickness in the range from 1 .mu.m to 20 .mu.m; and contains organic particles whose particle diameter is in the range from 0.1 .mu.m to 10 .mu.m. Based on this structure, the reflective substrate has low shrinkage ability, hardly warps and has a good antistatic and high hardness, wherein the reflective substrate may have excellent scratch resistance due to the high hardness."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Although above-mentioned PD1 and PD2 disclose the relevant technique that a coating layer containing specific particles are formed on the back surface of a luminance enhancement layer, they pay attention to preventing the Newton's rings or imparting extinction, characteristic but do not do study on improving the rigidity and dimensional stability of the luminance enhancement film itself. In addition, although PD3 discloses that the hard coating layer is disposed on the surface of the reflective substrate to prevent the reflective substrate from warping and enhance its hardness thereby providing excellent scratch resistance, it mainly makes the improvement on reflective layer of the backlight unit but not on the luminance enhancement film.

"In summary, existing technique does not effectively solve the problem encountered when adopting the thinner luminance enhancement film to the display with a larger size. Therefore, in the market, an effective method is urgently needed to reinforce the stability of the luminance enhancement film so as to meet the requirement of stability of the luminance enhancement film used in backlight module.

"In consideration of the subject mentioned above, the purpose of the present invention is to provide a luminance enhancement film in which a prism row structure is formed on a surface of the substrate and a reinforced layer is formed on another surface of the substrate. Said reinforced layer has a glass transition temperature (Tg) in the range from 80.degree. C. to 250.degree. C. and a thickness in the range from 3 .mu.m to 50 .mu.m.

"Further, the present invention, also provides a backlight module using the luminance enhancement film mentioned above and a liquid crystal display with this backlight module.

"According to the present invention, the thermal stability, dimensional stability and anti-deformation ability can be improved because the reinforced layer with high glass transition, temperature (Tg) and suitable thickness is provided on the luminance enhancement film so that the luminance enhancement will not appear warp, corrugation and unevenness after being lightened and then overheated. At the same time, the rigidity of the luminance enhancement film will be raised and thus the luminance enhancement film can be used in the panel with a larger size, and the problem generally encountered, such as deformation and bad thermal stability, can be solved.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a perspective view of an embodiment of a luminance enhancement film according to the invention;

"FIG. 2 is a perspective view of another embodiment of a luminance enhancement film according to the invention;

"FIG. 3 is a schematic diagram of an example of a reinforced layer forming a special structure according to the invention;

"FIG. 4 is a schematic diagram of another example of a reinforced layer forming a special structure according to the invention;

"FIG. 5A is a schematic diagram showing an observation on whether a part of the luminance enhancement film warps or not;

"FIG. 5B is a schematic diagram showing an observation on whether a part of the luminance enhancement film appears corrugation or not;

"FIG. 6A is a diagram showing that the corrugations appear after the luminance enhancement film of Comparative Example 3 assembled in 12-inch backlight module is lightened for ten minutes;

"FIG. 6B is a diagram showing that the corrugation appears after the luminance enhancement film of Example 3 assembled in 12-inch backlight module is lightened for ten minutes;

"FIG. 7A is a diagram showing that the corrugations appear after the luminance enhancement film of Comparative Example 4 assembled in 14-inch backlight module is lightened for ten minutes;

"FIG. 7B is a diagram showing that the corrugation appears after the luminance enhancement film of Example 4 assembled in 14-inch backlight, module is lightened for ten minutes;"

For additional information on this patent application, see: TYAN, Yi-Long; CHEN, Chia-Yi; JUAN, Yu-Mei; HSIN, Lung-Pin; CHEN, Hui-Yong Paul. Luminance Enhancement Film, Backlight Module and Liquid Crystal Display Device. Filed February 14, 2013 and posted May 22, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4171&p=84&f=G&l=50&d=PG01&S1=20140515.PD.&OS=PD/20140515&RS=PD/20140515

Keywords for this news article include: Ubright Optronics Corporation.

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