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Patent Application Titled "Liquid Crystal Display Panel and Liquid Crystal Display Device Including Same" Published Online

February 12, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventor Matsukizono, Hiroshi (Osaka-shi, JP), filed on April 2, 2012, was made available online on January 30, 2014.

The assignee for this patent application is Sharp Kabushiki Kaisha.

Reporters obtained the following quote from the background information supplied by the inventors: "In recent years, a TFT that uses an oxide semiconductor for its channel layer has been receiving attention. This thin film made of an oxide semiconductor (hereinafter, also referred to as an 'oxide semiconductor film') has high mobility and high visible light transmission properties, and thus, is used for applications of liquid crystal display devices, etc. For the oxide semiconductor film, there is known, for example, an oxide semiconductor film made of InGaZnO.sub.x (hereinafter, referred to as 'IGZO') which is an oxide semiconductor using indium (In), gallium (Ga), zinc (Zn), and oxygen (O) as its main components.

"Meanwhile, a liquid crystal display panel has a problem that due to entry of light into a channel layer of a TFT, changes in the threshold of the TFT occur. It is known that in a TFT using IGZO for its channel layer (which may be hereinafter referred to as an 'IGZO-TFT') in particular, the electrical conductivity level changes on the short wavelength side of visible light due to optical absorption (see, for example, Patent Document 1). Specifically, in a TFT that uses IGZO for its channel layer, changes in threshold occur due to entry of short-wavelength visible light into the channel layer. This causes a reduction in the reliability of the liquid crystal display panel.

"In connection with the invention of the present application, Patent Document 2 discloses a liquid crystal display panel in which a red color filter pattern which absorbs short-wavelength light most is disposed in a position on a color filter substrate that faces a TFT on an array substrate. According to such a configuration, since short-wavelength light can be prevented from entering the channel layers of the TFTs, changes in the thresholds of the TFTs can be suppressed."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventor's summary information for this patent application: "Problems to be Solved by the Invention

"However, in the liquid crystal display panel described in Patent Document 2, red color filter patterns are disposed in positions facing TFTs in blue and green subpixel formation portions. That is, color filters of different colors are provided close to each other. Hence, red light having leaked from the neighborhood of the TFTs is mixed in blue or green display. As a result, red is mixed in the blue or green display, degrading display quality.

"An object of the present invention is therefore to provide a liquid crystal display panel that improves the reliability of thin film transistors while suppressing a degradation in display quality, and a liquid crystal display device including the liquid crystal display panel.

"Solution to the Problems

"A first aspect of the present invention is directed to a liquid crystal display panel for displaying a color image based on a predetermined number of primary colors, the liquid crystal display panel comprising:

"a first substrate and a second substrate facing each other;

"a liquid crystal layer sandwiched between the first substrate and the second substrate;

"a plurality of video signal lines and a plurality of scanning signal lines disposed to intersect each other on the first substrate;

"a plurality of pixel formation portions disposed in a matrix form along the plurality of video signal lines and the plurality of scanning signal lines; and

"coloring layers of the predetermined number of primary colors, wherein

"each pixel formation portion includes a plurality of subpixel formation portions associated with the predetermined number of primary colors, respectively,

"each subpixel formation portion includes: a thin film transistor having a channel layer made of an oxide semiconductor, and disposed for a corresponding video signal line and a corresponding scanning signal line disposed along the subpixel formation portion; and a pixel electrode connected to the thin film transistor and facing a corresponding coloring layer of a primary color associated with the subpixel formation portion,

"in each pixel formation portion, the pixel electrodes of the plurality of subpixel formation portions are arranged in a predetermined direction,

"a thin film transistor connected to one of pixel electrodes adjacent in the predetermined direction to a pixel electrode facing a coloring layer of a primary color with a shortest wavelength among the predetermined number of primary colors is disposed on an opposite side of the one of the pixel electrodes from the pixel electrode facing the coloring layer of the primary color with the shortest wavelength,

"a distance between a thin film transistor connected to the pixel electrode facing the coloring layer of the primary color with the shortest wavelength and the pixel electrode facing the coloring layer of the primary color with the shortest wavelength is greater than a distance between the thin film transistor connected to the one of the pixel electrodes and the one of the pixel electrodes, and

"a distance between a thin film transistor connected to an other one of the pixel electrodes adjacent in the predetermined direction to the pixel electrode facing the coloring layer of the primary color with the shortest wavelength and the pixel electrode facing the coloring layer of the primary color with the shortest wavelength is greater than or equal to a distance between the thin film transistor connected to the pixel electrode facing the coloring layer of the primary color with the shortest wavelength and the pixel electrode facing the coloring layer of the primary color with the shortest wavelength.

"In a second aspect of the present invention, based on the first aspect of the invention, the predetermined direction is an extension direction of the plurality of scanning signal lines, and

"a distance between a thin film transistor connected to an other one of pixel electrodes adjacent in the extension direction of the plurality of scanning signal lines to the pixel electrode facing the coloring layer of the primary color with the shortest wavelength and the pixel electrode facing the coloring layer of the primary color with the shortest wavelength is greater than a distance between a thin film transistor connected to the pixel electrode facing the coloring layer of the primary color with the shortest wavelength and the pixel electrode facing the coloring layer of the primary color with the shortest wavelength.

"In a third aspect of the present invention, based on the second aspect of the invention, the thin film transistor connected to the pixel electrode facing the coloring layer of the primary color with the shortest wavelength and the thin film transistor connected to the other one of the pixel electrodes are disposed in positions facing each other with corresponding video signal lines sandwiched therebetween, the corresponding video signal lines being connected to the thin film transistors, respectively.

"In a fourth aspect of the present invention, based on the first aspect of the invention, the predetermined direction is an extension direction of the plurality of video signal lines, and

"a distance between a thin film transistor connected to an other one of pixel electrodes adjacent in the extension direction of the plurality of video signal lines to the pixel electrode facing the coloring layer of the primary color with the shortest wavelength and the pixel electrode facing the coloring layer of the primary color with the shortest wavelength is equal to a distance between a thin film transistor connected to the pixel electrode facing the coloring layer of the primary color with the shortest wavelength and the pixel electrode facing the coloring layer of the primary color with the shortest wavelength.

"In a fifth aspect of the present invention, based on the first aspect of the invention, a light-shielding layer is disposed in a position facing each thin film transistor.

"In a sixth aspect of the present invention, based on the first aspect of the invention, the coloring layers are disposed on the second substrate.

"In a seventh aspect of the present invention, based on the first aspect of the invention, each coloring layer is disposed on a pixel electrode facing the coloring layer.

"In a eighth aspect of the present invention, based on the first aspect of the invention, the primary color with the shortest wavelength is blue.

"In a ninth aspect of the present invention, based on the eighth aspect of the invention, the color image is displayed based on red, green, and blue.

"In a tenth aspect of the present invention, based on the eighth aspect of the invention, the color image is displayed based on red, green, blue, and yellow.

"A eleventh aspect of the present invention is directed to a liquid crystal display device comprising a liquid crystal display panel according to any one of the first to tenth aspects of the inventions.

"Effects of the Invention

"According to the first aspect of the present invention, in a liquid crystal display panel for displaying a color image based on a predetermined number of primary colors, a thin film transistor in a subpixel formation portion associated with a primary color with the shortest wavelength among the plurality of number of primary colors is disposed in a position further away from a coloring layer of the primary color with the shortest wavelength than in the conventional case. Furthermore, of thin film transistors disposed between a pixel electrode facing a coloring layer of a first primary color and a pixel electrode facing a coloring layer of a second primary color which are arranged consecutively in a predetermined direction, a thin film transistor other than the thin film transistor in the subpixel formation portion associated with the primary color with the shortest wavelength is also disposed in a position further away from the coloring layer of the primary color with the shortest wavelength than in the conventional case. As a result, entry of light of the primary color with the shortest wavelength into a thin film transistor in a subpixel formation portion associated with the primary color with the shortest wavelength and into a thin film transistor other than the thin film transistor in the subpixel formation portion associated with the primary color with the shortest wavelength among thin film transistors disposed between a pixel electrode facing a coloring layer of the first primary color and a pixel electrode facing a coloring layer of the second primary color which are arranged consecutively in the predetermined direction is suppressed, reducing threshold shifts in these thin film transistors. Therefore, the reliability of the thin film transistors in the liquid crystal display panel can be improved. Note that since a configuration such as that in the above-described Patent Document 2 in which color filters of different primary colors are provided in positions close to each other is not adopted, a degradation in display quality caused by the mixing of other primary colors in display in a subpixel formation portion is suppressed.

"According to the second or third aspect of the present invention, in a liquid crystal display panel in which coloring layers are formed in a stripe pattern in an extension direction of a plurality of scanning signal lines, the same effects as those brought about in the first aspect of the present invention can be brought about.

"According to the fourth aspect of the present invention, in a liquid crystal display panel in which coloring layers are formed in a stripe pattern in an extension direction of a plurality of video signal lines, the same effects as those brought about in the first aspect of the present invention can be brought about.

"According to the fifth aspect of the present invention, since entry of light into each thin film transistor is suppressed, a threshold shift in the thin film transistor decreases. By this, the reliability of the thin film transistors in the liquid crystal display panel can be further improved.

"According to the sixth aspect of the present invention, in a liquid crystal display panel in which coloring layers are disposed on the second substrate side, the same effects as those brought about in the first aspect of the present invention can be brought about.

"According to the seventh aspect of the present invention, in a liquid crystal display panel in which coloring layers are disposed on the first substrate side, the same effects as those brought about in the first aspect of the present invention can be brought about.

"According to the eighth aspect of the present invention, entry of blue light into a thin film transistor for blue and a thin film transistor other than a thin film transistor in a subpixel formation portion for blue among thin film transistors disposed between a pixel electrode facing a coloring layer of the first primary color and a pixel electrode facing a coloring layer of the second primary color which are arranged consecutively in the predetermined direction is suppressed, reducing threshold shifts in these thin film transistors. Therefore, the reliability of the thin film transistors in the liquid crystal display panel can be improved.

"According to the ninth aspect of the present invention, in a liquid crystal display panel for displaying a color image based on three primary colors, red, green, and blue, the same effect as that brought about in the eighth aspect of the present invention can be brought about.

"According to the tenth aspect of the present invention, in a liquid crystal display panel for displaying a color image based on four primary colors, red, green, blue, and yellow, the same effect as that brought about in the eighth aspect of the present invention can be brought about.

"According to the eleventh aspect of the present invention, in a liquid crystal display device, the same effect (s) as those brought about in any of the first to tenth aspects of the present invention can be brought about.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a block diagram showing a configuration of a liquid crystal display device including a liquid crystal display panel according to a first embodiment of the present invention.

"FIG. 2 is a circuit diagram showing an electrical configuration of a pixel formation portion in the first embodiment.

"FIG. 3 is a plan view showing a structure of a part of the liquid crystal display panel according to the first embodiment.

"FIG. 4 is a cross-sectional view of A-A' line of FIG. 3.

"FIG. 5 is a plan view showing a structure of a part of a liquid crystal display panel according to a variant of the first embodiment.

"FIG. 6 is a cross-sectional view showing a structure of a part of a liquid crystal display panel according to a second embodiment of the present invention.

"FIG. 7 is a circuit diagram showing an electrical configuration of a pixel formation portion in a third embodiment of the present invention.

"FIG. 8 is a plan view showing a structure of a part of a liquid crystal display panel according to the third embodiment.

"FIG. 9 is a plan view showing a structure of a part of a liquid crystal display panel according to a fourth embodiment of the present invention.

"FIG. 10 is a plan view showing a structure of a part of a liquid crystal display panel according to a variant of the fourth embodiment.

"FIG. 11 is a cross-sectional view showing a configuration of a TFT in the basic consideration of the present invention.

"FIG. 12 is a diagram showing experiment results in the basic consideration.

"FIG. 13 is a plan view showing a structure of a part of a conventional liquid crystal display panel in the basic consideration.

"FIG. 14 is a cross-sectional view of B-B' line of FIG. 13."

For more information, see this patent application: Matsukizono, Hiroshi. Liquid Crystal Display Panel and Liquid Crystal Display Device Including Same. Filed April 2, 2012 and posted January 30, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=3800&p=76&f=G&l=50&d=PG01&S1=20140123.PD.&OS=PD/20140123&RS=PD/20140123

Keywords for this news article include: Electronics, Semiconductor, Sharp Kabushiki Kaisha.

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Source: Electronics Newsweekly


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