LIQUID CRYSTAL DISPLAY UNIT

Abstract: An arrangement of a liquid crystal display unit includes a display panel (2) having a plurality of terminals (3), a plurality of flexible films (6) made of electrically non-conductive material and an LSI chip (4) carried on each flexible film (6). A plurality of electrodes are deposited on the film (6), and films (6) are provided in association with display panel (2) so as to electrically connect LSI chip (4) with terminals (3).

Description: The present invention relates to a liquid crystal display unit and, more particularly, to an arrangement and connection of IC chips that define a drive circuit for the display unit. Recently, pocket-size computers and portable computers have been developed. Such a computer has a liquid crystal display unit which is defined by a liquid crystal multi-dot display element and a drive circuit for driving the display element. The liquid crystal multi-dot display element has a plurality of dots aligned in a matrix format, enabling the display of various characters and symbols through on/off control of the dots. The drive circuit is formed by a plurality of IC chips, such as LSI chips. The liquid crystal multi-dot display element has very many terminals, such as in the order of hundreds, which are aligned along the side of the element with a predetermined narrow pitch. The drive circuit also has the same number of terminals which are electrically connected to the corresponding terminals on the element. According to the prior art, the LSI chips are mounted on a circuit board made of a non-flexible hard material and, therefore, it is necessary to provide a relatively large space to install the circuit board at a position neighboring the multi-dot display element. This will result in a bulky liquid crystal display unit. Furthermore, according to the prior art, the circuit board is provided with very many terminals which are aligned with a predetermined pitch so that when the circuit board is placed at its position adjacent the multi-dot display element, the terminals on the circuit board can be electrically connected to the corresponding terminals on the display element. However, since the terminals on the circuit board and display element are aligned with a narrow space, the positioning of the circuit board is very difficult. If the circuit board moves a little, the terminals on the circuit board may not be connected to the proper terminals on the display element. Moreover, according to the prior art, the terminals on the circuit board and those on the display element must be formed with high accuracy. Otherwise, some terminals may fail to connect with the corresponding terminals, even if the circuit board is positioned properly. The document DE-A-31 05 981 discloses an arrangement of a liquid crystal display unit comprising a display panel having a plurality of terminals, a flexible film, an IC-chip carried on the flexible film and means for electrically connecting said IC-chip with said terminals. It is an essential object of the present invention to provide a liquid crystal display unit and a method for producing it, wherein the IC chips for the driving circuit can be installed in a narrow space adjacent the display unit and which display unit is compact in size and can readily be manufactured at low cost and at higher reliability In accomplishing this object, a liquid crystal display unit according to the present invention comprises the features of claim 1. The object is solved furtheron by a method for proucing a liquid crystal display unit with the features of claim 8. These and other objects and features of the present invention will become apparent from the following description taken in conjunction with preferred embodiments thereof with reference to the accompanying drawings, throughout which like parts are designated by like reference numerals, and in which: Fig. 1 is an exploded perspective view of a liquid crystal display unit according to a first embodiment of the present invention; Fig. 2 is an exploded side elevational view of the liquid crystal display unit of Fig. 1; Fig. 3 is a circuit diagram of an electrode pattern employed in the liquid crystal display unit of Fig. 1; Fig. 4 is a top plan view of a printed circuit film employed for the first embodiment showing a pattern of electrodes extending from an LSI; Fig. 5 shows a pattern of common electrodes; Fig. 6 shows the pattern of Fig. 4 overlapped with that of Fig. 5 so as to effect the electric connection between certain terminals on the electrode pattern of Fig. 4 and those on the electrode pattern of Fig. 5; Fig. 7 is an exploded perspective view of a liquid crystal display unit according to a second embodiment of the present invention, but particularly showing parts which differ from those of Fig. 1; Fig. 8 is an exploded side elevational view of the liquid crystal display unit of Fig. 7; Fig. 9 is a circuit diagram of an electrode pattern employed in the liquid crystal display unit of Fig. 7; Fig. 10 is a perspective view of a liquid crystal display unit according to a third embodiment of the present invention, particularly showing the rear side thereof; and Fig. 11 is a cross-sectional view taken along a line XI-XI shown in Fig. 10. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 1, a liquid crystal display unit according to a first embodiment of the present invention is shown. The liquid crystal display unit has a liquid crystal multi-dot display panel 2 defined by two layers of transparent plates, such as glass plates, and a liquid crystal arrangement (not shown) sandwiched therebetween. Display panel 2 can be viewed in the direction indicated by an arrow. Extending from the liquid crystal arrangement are a plurality of terminals 3 which are aligned along a tiered edge. A drive circuit for driving the liquid crystal arrangement is formed by IC chips, such as LSI chips 4, each of which is carried by a flexible film 6. It is to be noted that each LSI chip 4 is a so-called film carrier type and is firmly carried on a separate sheet of film 6, through a known step, such as an inner bonding step. Thus, LSI chip 4 projects above and below the flexible film 6, as best shown in Fig. 2. Flexible films 6 are positioned side-by-side and located immediately under display panel 2. Each flexible film 6 has a predetermined pattern of electrodes 8 and 10 deposited thereon which are extending from LSI chip 4. Electrodes 8 are aligned along one side of film 6 and are provided for sending signals to the liquid crystal arrangement in a manner which will be described later. Electrodes 10 are deposited at different distances from LSI chip 4, and are provided for receiving electric power and various data signals from a bus structure described below. The bus structure, according to the first embodiment, is formed by three parallel line electrodes 12 deposited on an elongated flexible film 14. Each line electrode has widened places 12a disposed with a predetermined pitch. The widened places 12a on three lines 12 do not align with each other, but are in offset relation. Flexible film 14 is provided on the aligned flexible films 6 such that widened places 12a are electrically connected to electrodes 10 on films 6 through a suitable connecting means, such as bonding or soldering. Accordingly, short electrodes 10 on films 6 are connected to each other. Similarly, intermediate electrodes 10 and long electrodes 10 are also connected to each other, respectively. An elongated unidirectional conductive rubber sheet 16 is provided between an array of electrodes 3 on display panel 2 and an array of electrodes 8 on flexible film 6. Rubber sheet 16 has such a feature that it permits electric conduction only in its thickness direction T. Accordingly, electrodes 3 are electrically connected to corresponding electrodes 8. Provided under the flexible films 6 is a base plate 20 which has a groove 22 formed therein so as to receive the projecting portion of each LSI chip 4. Referring to Fig. 2, flexible films 6 provided with flexible film 14 and rubber sheet 16 are fixedly supported between panel 2 and base plate 20 by U-shaped holders 13 (only one is shown in Fig. 2) which are pressure fitted at opposite ends of the display unit. It is to be noted that the end portion of elongated flexible film 14, particularly the side deposited with electrodes 8, are uncovered, so as to permit the external electric connection to electrodes 8. The signals transmitted through electrodes 8 are applied to LSIs 4, each of which produces a particular signal for driving particular segment or segments. The signal produced from each LSI 4 is transmitted from terminals 8 through rubber sheet 16 to terminals 3 and further to the liquid crystal arrangement. Referring to Fig. 3, a circuit diagram of the electric connection between the bus structure and LSIs 4 is shown. As apparent from Fig. 3, the alignment of terminals A, B and C of LSI chips 4 is the same through all the LSI chips 4. Thus, the same type of LSIs 4 are employed. In the embodiment shown in Figs. 1 through 3, there are five terminals 8 extending from LSI chip 4 for connection with the liquid crystal arrangement, and three terminals 10 for connection with the bus lines. The number of the terminals is not limited to the above-described embodiment but can be any other number. For example, according to one model of LSI, there are sixty-four terminals 8 for connection with the liquid crystal arrangement and eight terminals 10 for connection with the bus lines. An electrode pattern on film 6 for the above-described model of LSI is shown in Fig. 4, and an electrode pattern on film 14 for the bus structure employed therefor is shown in Fig. 5. As indicated in Fig. 5, additional lines 13 are provided on film 14 for connection with the neighboring LSI chips. Fig. 6 shows a manner in which the electrode pattern of Fig. 4 is overlapped with the electrode pattern of Fig. 5. Furthermore, the flexible films, each carrying LSI chip 4, may be provided on the other side (not shown) of panel 2, in a manner similar to that shown in Fig. 10. Referring to Fig. 7, a liquid crystal display unit according to a second embodiment of the present invention is shown. When compared with the first embodiment, the electrode patterns for the electric connection between LSI chips 4 and the bus structure is different. Electrodes 10' are so aligned that, when films 6 are aligned to form an array of terminals 8, as shown in Fig. 7, the terminal portions 10', as well as the terminal portions 12', for effecting the electric connection, e.g., by the deposition of solder beads, are aligned in a straight line. This arrangement is accomplished by extending the bus lines in S-formation. When this arrangement is employed, films 6 can be arranged in a size smaller than that of the first embodiment shown in Fig. 1. Referring to Fig. 8, the liquid crystal display unit of the second embodiment is not provided with the base plate 20. Thus, U-shaped holders 13 are pressure fitted to hold film 6 and panel 2 with the unidirectional conductive rubber sheet 16 inserted therebetween. Referring to Fig. 9, a circuit diagram of the electric connection between the bus structure and LSIs 4 is shown. As apparent from Fig. 9, the alignment of terminals A, B and C of LSI chips 4 is either ABC or CBA and, therefore, two different types of LSIs 4 are employed. Referring to Fig. 10, a bottom view of a liquid crystal display unit according to a third embodiment of the present invention is shown. Fig. 11 shows a cross sectional view taken along a line XI-XI shown in Fig. 10. When compared with the previous embodiments, the bus structure is formed by a hard circuit board 14'. Furthermore, in this embodiment, instead of using the unidirectional conductive rubber and holder 13, electrodes 8 of films 6 are directly connected to electrodes 3 of panel 2 through a suitable known method, such as a heat seal method. Moreover, instead of soldering, electrodes 10 and electrodes 12 can be connected also through a heat seal method. According to the present invention, since the films 6 are separated from each other, the positioning of each film 6 can be accomplished easily so that terminals 8 on every film 6 can be properly connected to the corresponding terminals 3 on panel 2. Furthermore, since films 6 are formed by flexible material, they can be provided in the least necessary space, resulting in compact size of the display unit. According to the second embodiment, since the electric connection between electrodes 10 and electrodes 12 can be accomplished along a straight line, film 6 can be formed in a very small size. According to the third embodiment, since electrodes 8 and corresponding electrodes 3 are directly connected to each other, the electric connection therebetween can be accomplished with high reliability. Furthermore, when the electric connections are accomplished through heat seal method, there will be hardly any heat expansion or heat contraction of film 6, resulting in the simple positioning of the films 6. Although the present invention has been fully described with reference to several preferred embodiments, many modifications and variations thereof will now be apparent to those skilled in the art, and the scope of the present invention is therefore to be limited not by the details of the preferred embodiments described above, but only by the terms of the appended claims.

Claims: Liquid crystal display unit comprising a display panel (2) having a plurality of first terminals (3), aligned along one side of said display panel, a first flexible film (6) carrying at least one integrated circuit (4) and a circuit pattern for electrically connecting said integrated circuit (4) with said first terminals (3), said display panel and said first flexible film are arranged substantially parallel and mutually opposed, characterized in that further such flexible films (6) are provided, each said first and further flexible films carrying a LSI-chip (4) and a circuit pattern connected to said LSI-chip (4), each of said circuit patterns having second terminals (8) and third terminals (10) provided on opposite sides of the LSI-chip (4) said flexible films (6) are aligned in the same direction as the alignment of said first terminals (3), said second terminals (8) are directly electrically connected to said first terminals (3) by heat sealing, and a circuit board (14,14') is provided between said flexible films and said display panel which has a circuit pattern having bus line electrodes (12) extending in the same direction as the direction of alignment of said first terminals (3) for the electric connection of third terminals (10) of one flexible film (6) with the third terminals (10) of adjacent flexible films (6). Liquid crystal display unit as claimed in claim 1, wherein said third terminals (10) are electrically connected to bus line electrodes (12) of said circuit board (14,14') by heat sealing. Liquid crystal display unit as claimed in claim 1 or 2, wherein said third terminals (10) provided on one side of the LSI-chip (4) are disposed at different distances from said LSI-chip (4). Liquid crystal display unit as claimed in one of claims 1 to 3, wherein said third terminals (10) are aligned along a straight line. Liquid crystal display unit as claimed in one of claims 1 to 4, wherein said circuit board is provided by a flexible film (14). Liquid crystal display unit as claimed in one of claims 1 to 4, wherein said circuit board is provided by a hard circuit board (14'). Liquid crystal display unit as claimed in one of claims 1 to 6, further comprising a base plate (20) having a groove (22) formed therein receiving the projecting position of each aligned LSI-chip (4). Method for producing a liquid crystal display unit comprising a display panel (2) having a plurality of first terminals (3) aligned along one side of said display panel, and a first flexible film (6) for carrying at least one integrated circuit (4) and a circuit pattern for electrically connecting said integrated circuit (4) with said terminals (3), said display panel and said first flexible film are arranged substantially parallel and mutually opposed characterized by aligning said first and a plurality of further such flexible films (6) in the same direction as the alignment of said first terminals (3) of the display panel (2), providing each flexible film (6) with a circuit pattern and an LSI-chip (4), heat sealing the second terminals (8) of the flexible film (6) with said first terminals (3) for electrically connecting the terminals (3,8) and connecting third terminals (10) of one flexible film (6) with third terminals (10) of adjacent flexible films (16) by providing bus line electrodes (12) on a circuit board (14,14') extending in the same direction as the direction of alignment of first terminals (3). Method as claimed in claim 8, characterized by electrically connecting said third terminals (10) of the flexible film (6) with terminals (12) of the circuit pattern on the circuit board (14,14') by way of heat sealing.

Inventors: MASHIBA, TAMAKI, MORINO, MASUAKI, WASHIZUKA, ISAMU
Applicants: SHARP KABUSHIKI KAISHA
Application year: 1985
Main classification: G02F1
IPC codes: G02F1, G09F9