JP2004309723A - Ferroelectric liquid crystal display and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that when a conductive medium connecting a transparent electrode of an upper substrate and an electrode of a circuit substrate is to be connected by forming a hole with laser light in a ferroelectric liquid crystal display, because the hole is formed in the conductive medium, the gas produced by laser irradiation remains in the hole and may corrode and peel the contact face between the transparent electrode and the conductive medium. <P>SOLUTION: A ferroelectric liquid crystal display element having a pair of substrate disposed in offset positions, a transparent electrode formed on the upper substrate, pixel electrodes formed on the lower substrate, and a ferroelectric liquid crystal held between the pair of substrates is mounted on a circuit board. The transparent electrode on the upper substrate and the electrode of the circuit board opposing to the transparent electrode are connected with a conductive medium to constitute the ferroelectric liquid crystal display. In this liquid crystal display, a gas bent hole is formed by using a laser to penetrate the transparent electrode of the upper substrate and the conductive medium. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ferroelectric liquid crystal display device and a method for manufacturing the same.
[0002]
[Prior art]
2. Description of the Related Art Liquid crystal display devices have become widespread as substitutes for cathode ray tubes, and have been further improved because they can be made thinner and lighter and can be used with low power consumption. The reaction speed was slower than that of a cathode-ray tube, and there was a problem that flickers occurred. However, the ferroelectric liquid crystal was developed as a liquid crystal having a high reaction speed, and its practical use has been promoted.
[0003]
In ferroelectric liquid crystal display devices, the distance between the upper substrate and the lower substrate in the liquid crystal display device must be about 1 μm, and mass production technology has not yet been established. Small ferroelectric liquid crystal display devices have begun to be mass-produced.
[0004]
FIG. 1 is a sectional view of a conventional ferroelectric liquid crystal display device. The ferroelectric liquid crystal display device is composed of a ferroelectric liquid crystal 5 sandwiched between an upper substrate 1 and a lower substrate 2. A transparent electrode 3 (for example, ITO or SnO2) is formed on the upper substrate 1 and a lower substrate 2 is formed. Is formed with a pixel electrode 4. The ferroelectric liquid crystal display element is fixed to a circuit board 6 (for example, with a double-sided tape), and an electrode 7 formed on the circuit board 6 and a transparent electrode 3 formed on the upper substrate 1 are connected by a conductive medium (for example, conductive paste) 8. Have been. Since the reliability of the electrical connection between the transparent electrode 3 and the conductive medium 8 is poor, the transparent electrode 3 and the conductive medium 8 are welded by the laser 9. Reference numeral 10 denotes a hole formed by irradiating the laser 9.
[0005]
A technology has been disclosed in which a contact block is provided between an electrode on an upper substrate and an electrode on a lower substrate of a liquid crystal display element, and the electrodes are electrically connected by calcining with a laser beam to electrically connect the electrodes. FIG. 2 is a sectional view of a conventional liquid crystal display device. The liquid crystal display element is composed of a liquid crystal 15 sandwiched between an upper substrate 11 and a lower substrate 12. An ITO 13 is formed on the upper substrate 11, and an electrode 14 is formed on the lower substrate 12. Further, a passivation film 16 is formed on the electrode 14. A contact block (silver paste block) 17 is provided between the passivation film 16 formed on the lower substrate 12 and the ITO 13 formed on the upper substrate 11. Irradiation with a laser beam 19 forms a hole 18 in the passivation film 16. At this time, a hole is also formed in one place of the electrode 14. In this way, by forming the holes by calcination, the electrical contact between the electrode made of ITO 13 and the electrode 14 can be kept good. (For example, see Patent Document 1)
[0006]
[Patent Document 1]
JP-A-7-72495 (page 3, FIG. 3)
[0007]
[Problems to be solved by the invention]
As shown in FIG. 1, when a conductive medium for connecting the transparent electrode on the upper substrate and the electrode on the circuit board is connected by making a hole with a laser, the hole is formed in the conductive medium. There is a possibility that the contact surface between the transparent electrode and the conductive medium is eroded and peeled off. An object of the present invention is to solve the above problems.
[0008]
[Means for Solving the Problems]
A pair of substrates are offset, a transparent electrode is formed on the upper substrate, a pixel electrode is formed on the lower substrate, and a ferroelectric liquid crystal display element sandwiching ferroelectric liquid crystal between the pair of substrates is mounted on a circuit board, In a ferroelectric liquid crystal display device in which an electrode of a circuit board facing a transparent electrode of an upper substrate is connected with a conductive medium, a ferroelectric liquid crystal display device provided with a gas vent hole through the transparent electrode of the upper substrate and the conductive medium with a laser. And
[0009]
The conductive medium has a small-diameter portion between the upper substrate and the circuit board, and the gas vent hole is a ferroelectric liquid crystal display device provided on the outer periphery of the small-diameter portion.
[0010]
The gas vent hole is a ferroelectric liquid crystal display device provided obliquely to the plane of the upper substrate.
[0011]
A ferroelectric liquid crystal display device provided with a plurality of the gas vent holes is provided.
[0012]
At least, a step of fixing the ferroelectric liquid crystal display element to the circuit board, a step of applying a conductive medium between the electrodes of the circuit board and the transparent electrode of the upper substrate, a curing step of curing the conductive medium, and a laser of the upper substrate. A method for manufacturing a ferroelectric liquid crystal display device includes a step of providing a gas vent hole penetrating a transparent electrode and a conductive medium.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 3 is a sectional view showing an embodiment of the ferroelectric liquid crystal device according to the present invention. The same reference numerals are used for the same components as in the prior art. In the present embodiment, the electrode pads 7 ′ formed on the circuit board 6 and the end portions 3 ′ of the transparent electrodes 3 formed on the upper substrate 1 are in a shifted positional relationship. The conductive medium 8 is, for example, a conductive paste and is applied so as not to protrude from the electrode pad 7 ′, and is applied to the transparent electrode 3 so as to spread appropriately. As shown in the figure, a conductive paste 8 is applied so that a small-diameter portion 8 ′ is formed between the upper substrate 1 and the circuit board 6. This can be easily realized by adjusting the viscosity of the conductive paste 8.
[0014]
The laser 9 irradiates vertically from the upper portion of the upper substrate 1 to a position that passes through the large diameter portion of the conductive paste 8 and does not cover the small diameter portion 8 ′. Thereby, a gas vent hole 10 ′ penetrating the transparent electrode 3 and the conductive paste (conductive medium) 8 of the upper substrate 1 can be provided.
[0015]
FIG. 4 is a top view of the ferroelectric liquid crystal display device shown in FIG. Providing three through holes 10 'enhances reliability.
[0016]
FIG. 5 shows another embodiment of the present invention, in which the arrangement is such that the end face of the upper substrate 1 (that is, the end 3 'of the transparent electrode 3) and the end face 7'a of the electrode pad 7' of the circuit board are substantially opposed to each other. 3 is a cross-sectional view of the ferroelectric liquid crystal display device of FIG. This is an example in which a laser 9 is irradiated from the upper left of the conductive paste 8, and a gas vent hole 10 ′ penetrating the transparent electrode 3 of the upper substrate 1 and the conductive paste (conductive medium) 8 is opened diagonally as shown in the figure. Can be In this structure, a gas vent hole 10 ′ penetrating the transparent electrode 3 of the upper substrate 1 and the conductive paste (conductive medium) 8 can be provided without forming a small diameter portion in the conductive paste 8.
[0017]
Next, the manufacturing process of the ferroelectric liquid crystal display device according to the present invention will be described.
1. A ferroelectric liquid crystal display element is fixed to a circuit board. For fixing, an adhesive, a double-sided tape, or the like is used.
2. A conductive paste is applied between the electrodes on the circuit board and the transparent electrodes on the upper board. The conductive pad formed on the circuit board is easily adhered with the conductive paste, and the circuit board is preferably set on a surface to which the conductive paste is not easily attached to prevent the conductive paste from protruding. First, a conductive paste is applied to the conductive pad, and then applied directly to the transparent electrode on the upper substrate. In general, a dispenser is used for applying the conductive paste, but it is preferable to adjust the viscosity so that the conductive paste can be easily applied as described above.
3. Cure to cure the conductive medium. The curing temperature is determined in consideration of the heat resistance of the ferroelectric liquid crystal.
4. A gas vent hole is provided for penetrating the transparent electrode and the conductive paste on the upper substrate with a laser. The focal point of the laser beam is preferably at the position of the transparent electrode, and the spot diameter is preferably as small as possible.
[0018]
In this specification, a gas vent hole penetrates the transparent electrode and the conductive paste. However, since the transparent electrode is transparent, there are cases where holes are opened and cases where holes are not opened. A gas vent hole penetrating the transparent electrode and the conductive paste is included in any case.
[0019]
【The invention's effect】
According to the present invention, since a gas vent hole penetrating the transparent electrode of the upper substrate and the conductive medium is provided, gas generated by laser irradiation in the conductive medium accumulates, and the contact surface between the transparent electrode and the conductive medium is eroded. Can be prevented.
[0020]
By providing a small diameter portion in the conductive medium or irradiating the laser obliquely, a gas vent hole penetrating the transparent electrode of the upper substrate and the conductive medium can be easily formed.
[0021]
The reliability of conduction can be improved by forming a plurality of gas vent holes.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a conventional ferroelectric liquid crystal display device. FIG. 2 is a cross-sectional view of a conventional liquid crystal display device. FIG. 3 is a cross-sectional view showing one embodiment of a ferroelectric liquid crystal device according to the present invention. FIG. 5 is a top view of the ferroelectric liquid crystal display device shown in FIG. 3; FIG. 5 is another embodiment of the present invention, in which an end surface of an upper substrate 1 (ie, an end 3 ′ of a transparent electrode 3) and an electrode pad of a circuit substrate; Sectional view of a ferroelectric liquid crystal display device having an arrangement structure in which end faces 7'a of 7 'are substantially opposed to each other.
DESCRIPTION OF SYMBOLS 1 Upper substrate 2 Lower substrate 3 Transparent electrode 3 'Transparent electrode end 4 Pixel electrode 5 Ferroelectric liquid crystal 6 Circuit board 7 Electrode 7' Electrode pad 7'a End face 8 of electrode pad 7 'Conductive medium (conductive paste)
8 'small diameter part 9 laser 10 hole 10' hole 11 upper substrate 12 lower substrate 13 ITO
14 electrode 15 liquid crystal 16 immobilization film 17 contact block (silver paste block)
18 hole 19 laser beam

Claims (6)

A pair of substrates are offset, a transparent electrode is formed on the upper substrate, a pixel electrode is formed on the lower substrate, and a ferroelectric liquid crystal display element holding a ferroelectric liquid crystal between the pair of substrates is mounted on a circuit board, In a ferroelectric liquid crystal display device in which an electrode of a circuit board opposed to a transparent electrode of an upper substrate is connected by a conductive medium, a gas vent hole is provided through the transparent electrode of the upper substrate and the conductive medium by a laser. Ferroelectric liquid crystal display. 2. The ferroelectric liquid crystal display device according to claim 1, wherein the conductive medium has a small-diameter portion between the upper substrate and the circuit board, and the vent hole is provided on the outer periphery of the small-diameter portion. 2. The ferroelectric liquid crystal display device according to claim 1, wherein the gas vent hole is provided obliquely with respect to the plane of the upper substrate. 4. The ferroelectric liquid crystal display device according to claim 1, wherein an end face of the upper substrate and an end face of the electrode of the circuit board substantially face each other. 5. The ferroelectric liquid crystal display device according to claim 1, wherein a plurality of gas vent holes are provided. At least, a step of fixing a ferroelectric liquid crystal display element to a circuit board, a step of applying a conductive medium between an electrode of the circuit board and a transparent electrode of the upper substrate, a curing step of curing the conductive medium, and a laser of the upper substrate. A method for manufacturing a ferroelectric liquid crystal display device, comprising a step of providing a gas vent hole penetrating a transparent electrode and a conductive medium.

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