Liquid crystal display apparatus

Abstract: A liquid crystal display apparatus is provided which needs a small, thin and compact area thereof for mounting semiconductor chips for driving liquid crystal and, accordingly, a reduced cost. Semiconductor chips (4) for driving liquid crystal are mounted on the surfaces (the first layers (1)) of multi-layer substrates in a face-down manner, each of the surfaces having input lines (5) to the chips (4) and output lines (8) from the chips. The input lines have lands (7) for connecting the multi-layer substrates to each other. At least one intermediate layer (2) is formed between the upper surface (1) and the reverse surface (3), the intermediate layer having bus lines (10). The bus lines and the input lines of the first layer are connected to one another via through holes (6). The output lines of the first layer and the terminals (13) of the third layer are connected to one another via through holes of the first, second and the third layers (9, 11, 12).

Description: The present invention relates to a liquid crystal display apparatus having a plurality of semiconductor chips for driving liquid crystal. Fig. 5 is a view which illustrates the structure of a conventional color liquid crystal display apparatus disclosed in JP-A-2-214826. In order to be adaptable to the increased number of the color display pixels, TCPs (Tape-Carrier-Packages) 50151 1 to 50151 3 are formed into three layers. TCPs 50151 1 to 50151 3 each comprise a semiconductor device 111 1 to 111 3 for driving liquid crystal which is mounted on a flexible wiring member in the so-called TAB method. Further, TCP output terminals disposed on one side of the respective TCP are connected to the terminal portion of a liquid crystal member 110 with an anisotropic conductive agent 115, while TCP input terminals are connected by soldering to a drive control circuit substrate 50155 disposed on the other side. Therefore, the number of required connections increases due to the rise in the pixel density. Hence, defects occurring in this connection cannot be prevented. What is worse, the structure, in which the TCPs are stacked, causes the semiconductor device to project in the direction of the thickness, resulting in a problem to rise in that the size of the apparatus cannot be reduced. The document JP-A-63-210914 discloses a color liquid crystal display panel according to the prior art portion of claim 1. In this prior art, the semiconductor devices are mounted directly on the first substrate. The second substrate is positioned between the semiconductor devices on the one hand and the terminals of the electrode groups of the liquid crystal panel on the other hand. This document does not disclose how power and control signals are supplied to the semicondutor devices. The present invention is directed to overcome the foregoing problems and therefore an object of the present invention is to provide a liquid crystal display apparatus capable of displaying precise and high density color images by a liquid crystal thereof while necessitating reduced cost and the size thereof. The features of the invention are set forth in appended claim 1. The structure of the liquid crystal display apparatus according to the present invention has an arrangement that bus lines and connection terminals are formed on the laminated substrate, and a plurality of the semiconductor devices are mounted to be connected to electrodes of the display device. As a result, the drive control circuit substrate can be omitted from the structure and the number of mutual connections between semiconductor devices can be decreased. Therefore, reliability can be improved and the size of the apparatus can be reduced. Other and further objects, features and advantages of the invention will be appear more fully from the following description. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross sectional view which illustrates the structure for mounting a semiconductor device and a state where it is connected to a display device according to an embodiment of the present invention; Fig. 2 is a plan view of the structure shown in Fig. 1; Fig. 3 is a circuit diagram of a connection portion according to an embodiment of the present invention; Fig. 4 is a circuit block diagram for a liquid crystal display apparatus according to an embodiment of the present invention; and Fig. 5 is a cross sectional view which illustrates a conventional structure for mounting a semiconductor device and a state where it is mounted on a display device. An embodiment of the invention will now be described with reference to Figs. 1 to 4. Fig. 1 is a cross sectional view which illustrates an embodiment of a mounting structure adapted to a liquid crystal display apparatus according to the present invention in which a semiconductor device mounted on a laminated substrate is connected to a liquid crystal display device. Fig. 2 is a plan view which illustrates the mounting structure shown in Fig. 1. Fig. 3 is a detailed plan view which illustrates the terminal connection portion of the foregoing liquid crystal display device. Fig. 4 is a block diagram which illustrates a color liquid crystal apparatus structured by using the foregoing mounting structure. Referring to Fig. 1, a liquid crystal display device 110 is a display substrate including a line electrode group, a column electrode group and a color filter. A liquid crystal composition is enclosed among the foregoing elements and electrode terminal group 113 is formed. Laminated substrates 112-1 and 112-2 shown in Figs. 1 and 2 have output lines P11 to P3n and bus lines formed by patterning to establish the vertical electrical connections between the substrate layers, the laminated substrates 112-1 and 112-2 being stacked. Semiconductor devices 111-1, 111-2 and 111-3 are ICs which drive liquid crystal and which have connection terminals in which bumps are formed. Each of the semiconductor devices 111 is connected to the connection terminals formed on the laminated substrate 112 in a face-down mounting manner. Although three semiconductor devices 111-1, 111-2 and 111-3 are mounted to correspond to three-color pixels in this embodiment, the number of the semiconductor devices may be determined to be adaptable to the number of the pixels. Each laminated substrate 112 has terminals for connecting each semiconductor device formed on the surface layer thereof, input/output line P11 of the semiconductor device 111-1 formed on the first layer thereof, input/output line P21 of the semiconductor device 111-2 on the second layer thereof, input/output line P31 of the semiconductor device 111-3 formed on the third layer thereof and bus lines formed on the surface of the third layer thereof. Although the laminated substrate 112 is formed into tree layers, the present invention is not limited to the number of layers if an efficient wiring pattern can be formed. Although this embodiment employs ceramic to make laminated substrate 112 depending upon consideration of expansion and contraction occurring due to thermal influence, a polyimide film or the like, which is a flexible substrate, may be used. As can be seen from Fig. 1, the structure for mounting a semiconductor device according to this embodiment has the arrangement that the lines for driving the liquid crystal display device 110 and the bus lines are formed on the substrate thereof. Therefore, the drive control circuit substrate can be omitted from the structure and, accordingly, the number of required elements can be decreased considerably. Therefore, the cost of the elements can be reduced significantly. Referring to Fig. 3, the laminated substrate 112-1 and the liquid crystal display device 110 are connected to each other such that alignment is established between the liquid crystal display device electrode terminal group 113 respectively pulled out for color pixel R (red) 131-1, G (green) 131-2 and B (blue) 131-3 and the laminated substrate terminal group 114 connected to the semiconductor devices 111-1 (for red), 111-2 (for green) and 111-3 (for blue) corresponding to each pixel and formed at the extensions of the liquid crystal driving output line P11 (the output from the semiconductor device 111-1), P21 (the output from the semiconductor device 111-2) and P31 (the output from the semiconductor device 111-3). Further, a pressing machine is used to press and connect them under pressing conditions: 180°C, 30 Kg/cm 2 and 20 seconds so that the connection is established. Color display suffers from a problem in that the contrast is unsatisfactory due to excessive cross talk as compared with white and black display because the drive method must bear a high duty. However, the connection method according to this embodiment is able to reduce the cross talk and, accordingly, a high-contrast display can be realized because individual output lines for semiconductor devices are connected for each color electrode and, therefore, a proper drive waveform can be supplied. Fig. 4 is a block diagram which illustrates an embodiment of a color liquid crystal display apparatus using the foregoing mounting structure according to this embodiment. A display device 10 is a 640 x 480 dots STN color liquid crystal display, and semiconductor devices 111-1 to 111-12 are segment drivers for driving liquid crystal having 160 outputs. Each of the laminated substrates 112-1 to 112-4 has semiconductor devices 111-1 to 111-12 for R (red), G (green) and B (blue) mounted thereon. The laminated substrates 112-1 to 112-4 are mounted in parallel on electrode terminals formed on the periphery of the liquid crystal display device 110. The laminated substrates 112-1 to 112-4, on which the semiconductor devices 111-1 to 111-12 are mounted, are mutually connected at four points for the purpose of supplying electric power and control signals. When a color liquid crystal display apparatus was manufactured by employing the foregoing mounting structure, a compact liquid crystal display apparatus was formed because the density of the structure for mounting the semiconductors was raised. Further, the number of connections required to connect the liquid crystal display devices could be reduced to 1/3 as compared with the conventional structure. Therefore, the connection reliability was improved. A liquid crystal display apparatus using the structure for mounting the semiconductor device according to this embodiment was manufactured and a reliability test was performed. As a result, satisfactory results were obtained in a TS test (between - 30°C and 80°C) in 1000 cycles and a TH test (at 60°C and 90%RH) for 1000 hours. Excellent connection reliability was realized.

Claims: A liquid crystal display apparatus having a line electrode group and a column electrode group formed on a first substrate said electrode groups forming a plurality of pixels for different colors, and drive means mounted on said first substrate for supplying display drive signals to said electrode groups to perform color pixel display, said drive means including a second substrate (112-1, 112-2) and at least one semiconductor device (111-1, 111-2, 111-3) for each of said colors, said second substrate (112-1, 112-2, 112-3, 112-4) having a plurality of layers laminated one upon the other and carrying for each of said colors a respective group of drive lines (P11, P21, P31 - P3n) for connecting output terminals of said semiconductor devices with terminals (113) of said electrode groups provided on said first substrate, wherein each group of drive lines (P11, P21, P31 - P3n) is arranged on a different one of said layers, characterized in that said second substrate (112-1, 112-2) has formed thereon bus lines arranged to supply electric power for driving the liquid crystal and control signals to all semiconductor devices (111-1, 111-2, 111-3), and connection terminals, and said semiconductor devices (111-1, 111-2, 111-3) are mounted on said second substrate (112-1, 112-2). The apparatus according to claim 1, wherein said semiconductor devices (111-1, 111-2, 111-3) have an elongated shape and are arrayed on said second substrate (112-1, 112-2) perpendicular to an edge of said first substrate with the longer sides of the semiconductor devices extending in parallel to that edge.

Inventors: FURUICHI KAZUAKI, KAMIMURA MASARU, MAEDA KINICHI, MURAMATSU EIJI, MURAYAMA KENICHI, SAKURA SEIICHI, UCHIYAMA KENJI, YAMADA SHIGETOSHI, FURUICHI, KAZUAKI, KAMIMURA, MASARU, MAEDA, KINICHI, MURAMATSU, EIJI, MURAYAMA, KENICHI, SAKURA, SEIICHI, UCHIYAMA, KENJI, YAMADA, SHIGETOSHI
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1993
Main classification: H01L23
IPC codes: G02F1, H01L23, H05K1, H05K3, H01L25