JP2905498B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a liquid crystal display device (TFT-L) using a projection type or a transmission type thin film transistor using a backlight.
CD), which relates to a light shielding structure for protecting a TFT from light incident on a liquid crystal display panel and preventing characteristic deterioration.

<Prior Art> FIG. 6 shows a sectional view of a TFT-LCD panel. Conventional TFT
The LCD seals the TFT substrate 66 on which the TFT 62 and the transparent display electrode 63 are formed, the light shielding film 65 for preventing light from entering the TFT, and the opposing substrate 64 on which the transparent opposing electrode is formed. The structure is such that a liquid crystal layer is held in a gap between both substrates by bonding with a resin 61. The sealing resin is usually an epoxy resin in which a filler is dispersed, and is transparent or translucent.
FIG. 7 shows a plan view of the panel viewed from the counter substrate side. 71
Is a TFT array substrate, and 72 is a counter substrate. In FIG. 7, an electrode terminal of a gate electrode line is provided around the TFT substrate,
The electrode terminals of the source electrode lines are drawn out of the screen. A flexible board on which an LSI is mounted is connected to these signal lines to transmit electric signals from the drive circuit.
Such a TFT-LCD is attached to the optical system shown in FIG. 3 to produce a projection type liquid crystal display device. Normally, a TFT-LCD uses a twisted nematic mode, and polarizers are arranged before and after the panel. In this case, the inventors of the present invention have clarified that the better display characteristics can be obtained when the light from the light source is incident from the counter substrate side of the TFT-LCD panel.

<Problems to be solved by the invention> However, when the above-described optical system is adopted,
Since the sealing resin 61 (silicon resin or epoxy resin in which filler is dispersed) shown in FIG. 6 is conventionally translucent or white, light incident on the sealing resin is scattered in the sealing resin and As shown in FIG. 8, the light penetrates into the panel and enters the TFT. For this reason, there is a drawback that photoconduction occurs in the semiconductor film of the TFT and the switching characteristics of the TFT deteriorate due to scattered light of the sealing resin.

<Means for Solving the Problems> The present invention includes a light source and a liquid crystal display panel in which a sealing resin for holding two transparent substrates and holding a liquid crystal is provided, and a thin film transistor is provided on one of the transparent substrates. In the liquid crystal display device, a light shielding portion for preventing the thin film transistor from being deteriorated is provided on a light incident side of the liquid crystal display panel in a region covering an end portion of the sealing resin and the transparent substrate outside the sealing resin. It is characterized by having.

<Operation> According to the present invention, light scattering in the sealing resin can be prevented, whereby deterioration of switching characteristics due to light indirectly incident on the TFT is eliminated, and as a result, a transmission type or projection type liquid crystal display device is obtained. It is possible to prevent the display characteristics from deteriorating.

<Embodiment> FIG. 1 is a plan view of a liquid crystal display device according to a first embodiment of the present invention as viewed from a counter substrate side. In the first embodiment, a light-shielding frame 11 is provided which is in close contact with the light incident side surface of the liquid crystal display panel and covers the entire sealing resin of the liquid crystal display panel. As the material of the light-shielding frame, a material obtained by laminating a polyimide film on an aluminum foil was used. Similar effects can be obtained even if the material of the light-shielding frame 11 is another metal plate, metal foil, colored polymer plate or film, or colored paper. In FIG. 1, 12 is a TFT array substrate, 13 is a counter substrate, and 14 is a sealing resin. FIG. 2 shows the liquid crystal display device shown in FIG. 1 without the light-shielding frame. Reference numeral 21 denotes a TFT array substrate, and reference numeral 22 denotes a counter substrate. At the periphery of the TFT substrate, the electrode terminals of the gate electrode lines and the electrode terminals of the source electrode lines are drawn out of the screen, and LSIs 251, 252, and 253 are used to transmit electric signals from the drive circuit to these signal lines. Are connected to flexible boards 261, 262, and 263. FIG. 3 shows a projection type liquid crystal display device using this liquid crystal display device. In FIG. 3, 31 is a condenser mirror, 32 is a lamp of a light source, 33 and 34 are first and second condenser lenses, 35 is a heat ray and ultraviolet cut filter, and 36 is a TFT-L.
A CD panel, 37 is a projection lens, and 38 is a screen. Normally, a TFT-LCD uses a twisted nematic mode, and polarizers are arranged before and after the panel. When a display experiment was conducted using the projection optical system shown in FIG. 3, good display was obtained without deterioration in image quality due to deterioration of TFT characteristics caused by scattered light due to the conventional sealing resin. As a material of the light-shielding frame, a metal plate such as an aluminum plate, colored paper, a colored plastic plate, a colored polymer film, or a composite material thereof can be used, and the same effect is obtained.

FIG. 4 shows a sectional view of a liquid crystal display device as a reference example.
A coloring agent was mixed with the epoxy resin 406 as a sealing resin of the liquid crystal display panel shown in FIG. Carbon black was used as a coloring agent. Also, in FIG.
In the TFT, a gate insulating film 405, a silicon layer 400, and an n + silicon layer 401 are laminated on a gate electrode 402, and a source electrode 40
3 and a transistor having a structure in which a drain electrode 404 is formed. The TFT-LCD utilizes the switching action of the TFT to sequentially transmit a signal voltage to a number of pixel electrodes 407 in the screen, and a liquid crystal layer 4 sealed between the pixel electrode and the counter electrode 410.
This is a device that displays an image by applying a voltage to 13 and holding the voltage. Reference numeral 408 denotes a passivation film for protecting a TFT or the like, and 412 denotes an alignment film for aligning liquid crystal molecules. 409, 411 are insulating substrates such as glass,
Reference numeral 410 denotes a passivation film for the counter electrode. Also, 414
Reference numeral denotes a light-shielding film for preventing light from entering the TFT. Using this liquid crystal display device, a display experiment was conducted with the projection optical system shown in FIG. Obtained. In addition, the same effect was obtained by blending each of red, green, and blue pigments to make them black.
In this case, red pigment, chrome green (green), and ultramarine (blue) were used as pigments. In this case, the sealing resin is not limited to the epoxy resin, and it is needless to say that the same effect can be obtained by using an adhesive such as a silicone resin or an acrylic resin. Further, the pigment is not limited to the experimental example, and the same effect can be obtained even with a resin colored with a dye.

FIG. 5 shows a second embodiment of the present invention. In the liquid crystal display panel shown in FIG. 5, reference numeral 51 denotes a sealing resin. In the second embodiment, a mounting plate 52 for mounting the liquid crystal display panel to the projection device is provided on the light incident side with respect to the panel, and the opening of the mounting plate covers the entire sealing resin portion S of the panel. That is, the sealing resin is shielded from light by making it slightly larger by a margin d for positioning the liquid crystal display panel and the mounting plate 52 so as not to cover the display area D. Using this liquid crystal display device, a display experiment was conducted with the projection optical system shown in FIG. 3, and a good display without deterioration in image quality due to deterioration of TFT characteristics caused by scattered light by the conventional sealing resin was obtained. Was done.

<Effect of the Invention> As described above, according to the present invention, a light source and a liquid crystal display panel in which a sealing resin that holds two transparent substrates together to hold liquid crystal is provided and a thin film transistor is provided on one of the transparent substrates are provided. In the provided liquid crystal display device, since a light shielding portion for preventing deterioration of the thin film transistor is provided on the light incident side of the liquid crystal display panel in a region covering an outer end portion of the sealing resin and the sealing resin of the transparent substrate, It is possible to prevent light scattered by the sealing resin from being incident on the thin film transistor and prevent deterioration of the thin film transistor characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 3 and FIG. 5 are views showing an embodiment of the present invention, FIG. 4 is a sectional view showing the structure of a TFT-LCD in a reference example, and FIG. FIG. 7 is an explanatory view showing a conventional example, and FIG. 8 is an explanatory view showing a conventional problem. 406: Black sealing resin, 711, 712, 713: Driver
LSI, 714, 715, 716: Flexible board with driver LSI mounted, 77: Frame for mounting liquid crystal display panel, 78: Mounting hole for mounting liquid crystal display panel, 80: Incident light, 81: Scattered light, 31 …… Mirror,
32 ... Light source lamp, 33,34 ... First and second condenser lenses, 35 ... Heat ray and ultraviolet cut filter, 36 ... TFT-LCD panel, 37 ... Projection lens, 38 ...
screen

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takao Nomura 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Masahiro Adachi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor Eiichi Takahashi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Shuhei Yasuda 22-22 Nagaike-cho, Abeno-ku, Osaka-shi Osaka Prefecture Inside Sharp Corporation (56) JP-A-62-299889 (JP, A) JP-A-60-133493 (JP, A)

Claims (1)

(57) [Claims] 1. A liquid crystal display device comprising a light source and a liquid crystal display panel provided with a sealing resin for bonding two transparent substrates to hold liquid crystal and having a thin film transistor provided on one of the transparent substrates. A liquid crystal display, comprising: a light-blocking portion for preventing deterioration of the thin-film transistor on a light incident side of the liquid crystal display panel in a region covering an end portion of the transparent resin and the sealing substrate outside the sealing resin. apparatus.