JP3992324B2 - Liquid crystal display device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technology for connecting a liquid crystal display panel and an external mother substrate in a liquid crystal display device.
[0002]
[Prior art]
A mother board (provided with circuits and electrodes for driving and controlling the liquid crystal display panel) equipped with a large number of display electrode terminal groups provided at the edge of the glass substrate of the liquid crystal display panel and an external circuit for supplying display information and power The connector structure is used almost without exception for the connection with the electrode group provided on the printed circuit board).
[0003]
Main examples of commonly used connector structures are: (1) zebra rubber (a prismatic structure in which a number of insulating and conductive rubbers are alternately stacked in the longitudinal direction) and the electrode terminal surface on the bottom surface of the liquid crystal display panel. A structure in which the electrodes are pressed together with the electrodes on the upper surface of the mother board, and the corresponding electrodes are connected by elastic contact of the conductive rubber part.
(2) One edge of a flexible sheet substrate (multiple lead wiring is formed between both ends on a thin and flexible substrate surface made of polyimide resin or polyester resin) is anisotropic. A structure in which a conductive sheet (ACF) is used as an intermediate to heat-press the electrode terminal surface of the liquid crystal display panel or apply a silver paste to solidify by heating, and connect the other edge to the electrode group of the mother substrate. Etc.
[0004]
These conventional techniques have the following problems. In the conventional example (1), the connector is flexible and easily deformed, and a metal plate or a resin frame-like member (requiring a molding die) is used to maintain the shape and the crimping force. Takes time. In the conventional example (2), the FPC or the like is punched with a mold, and the liquid crystal display panel must also be supported with another structure. That is, in any of the conventional examples, a connector and a frame part are required in addition to the display panel body, and a die is involved, which is expensive.
[0005]
In designing the entire liquid crystal display device, we are in charge of the design of the liquid crystal display panel and connectors, as well as the set manufacturer who is responsible for the design of the entire device including the motherboard, in consideration of the selection of connectors and the support method of the liquid crystal display panel. Consultation with LCD panel parts manufacturers is also necessary. Therefore, the design around the display is heavy in design and load (large time cost), high customizability for each set, and it is difficult to standardize the shape and specifications of parts, which is extremely desirable for parts manufacturers. It was difficult to reduce the cost because of the large number of points and inferior processing and assembly.
[0006]
Other electronic components are naturally mounted on the mother board, but they are usually SMD (surface mounted device) and can be easily automated using a robot and a solder reflow furnace. However, since the heat resistance of the liquid crystal panel is poor, in the conventional technique using a connector, such a method cannot be connected by individual soldering as a step ahead. The fact that the connection of the liquid crystal display panel cannot be mounted on the mother substrate at the same time as mounting of other elements or by a method according to other elements has hindered improvement in productivity and cost reduction of the display device.
[0007]
In addition, the liquid crystal display device includes functional elements having a close relationship with the liquid crystal display panel, such as a backlight element that illuminates a display that is an LED lamp element or an EL panel, or a detection element for a touch switch that is a touch panel or a touch sensor. In many cases, however, these functional elements cannot be directly connected to the liquid crystal display panel using solder, conductive adhesive or the like, mainly because the liquid crystal panel has poor heat resistance.
[0008]
Japanese Patent Laid-Open No. 3-282419 “Liquid Crystal Display” is a conventional example proposed. In this conventional example, as shown in FIG. 1, an EL backlight panel is disposed on the back surface of a liquid crystal display panel, and both edges thereof are inserted into concave grooves of a connector and held. As another conventional example, there is Japanese Patent Application No. 9-44903 filed by the present applicant and not yet published. This discloses a structure in which an electrical connection of a light emitting element for illumination to a mother substrate is made through a connector fixed to a liquid crystal display panel.
[0009]
In these conventional examples, there is an advance as a structure for holding and connecting a functional element attached to the liquid crystal display panel, and there is an advantage that other constituent members for holding and connecting can be omitted. Since this is done, a connector is essential, and the disadvantages associated with the cost and design cost of the connector cannot be overcome.
[0010]
[Problems to be solved by the invention]
The object of the present invention is to eliminate the connector structure associated with the liquid crystal display device, and to enable the liquid crystal display panel to be directly connected to the mother board by soldering or by using a thermosetting conductive adhesive. It is to provide a technique for constructing a liquid crystal display device that has a reduced structure and significantly reduced manufacturing costs and time costs.
[0011]
The liquid crystal display device of the present invention has the following feature (1) or (2).
(1) Of the upper glass substrate and the lower glass substrate having a substantially rectangular planar shape constituting the liquid crystal display panel, the side surfaces of both short sides of the lower glass substrate protruding greatly on both sides in the longitudinal direction of the upper glass substrate Has a plurality of through-holes that are divided after being provided through the lower glass substrate, covers the inner side surfaces of the divided through-holes, and is located away from the outer edge of the upper glass substrate A silver palladium electrode individually connected to the transparent electrode for display on the upper surface of the lower glass substrate is formed by coating and firing, and the liquid crystal panel is placed so that the lower glass substrate is in contact with the mother substrate, solder and individual display driving electrode on the mother substrate, and the individual silver-palladium electrodes of the inner side surface of the divided through holes are exposed on the outer peripheral side surface of said liquid crystal display panel It has direct connection Te.
( 2 ) In (1), a polarizing plate having a polyimide resin as a base material is fixed to the surface of an upper glass substrate or a lower glass substrate constituting the liquid crystal display panel.
The manufacturing method of the liquid crystal display device of the present invention has the following feature (3).
(3) preparing a large glass substrate included in an aligned state of the upper glass substrate or the lower glass substrate constituting the liquid crystal display panel, forming a transparent electrode on the large glass substrate, and aligning on the transparent electrode A step of forming a layer, and a step of drilling through holes so that the large glass substrate is linearly arranged at positions that are both short sides of the lower glass substrate that is larger in the longitudinal direction than the upper glass substrate. And a conductive paste containing silver palladium so that the transparent electrode partially overlaps with the upper and lower surfaces of the large glass substrate and the inner surface of the through-hole, and the overlapping position is separated from the position serving as the outer edge of the upper glass. A step of forming a silver-palladium electrode by baking the conductive paste at about 500 ° C., and a sealing material for creating a liquid crystal injection space on a large glass substrate A step of printing, a step of laminating two large glass substrates so that the upper glass substrate and the lower glass substrate overlap, a step of injecting and sealing liquid crystal, and a cutting line passing through the center of the through-hole row On the mother substrate so that the lower glass side is in contact with the liquid crystal display panel, the step of attaching a polarizing plate whose base material is a polyimide resin to the liquid crystal display panel, The display drive electrode on the mother substrate and the divided through hole arranged on the outer edge in the longitudinal direction of the liquid crystal display panel are overlapped, and the display drive electrode and silver palladium on the inner surface of the divided through hole are overlapped. And soldering the electrodes.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1A is a plan view of a liquid crystal display panel in one example of an embodiment of the present invention, and FIG. In the figure, 1 is an upper glass substrate of a liquid crystal display panel, and 2 is a lower glass substrate, and a liquid crystal material (not shown) is held in the gap. Reference numeral 3 denotes a lower ITO electrode (transparent conductive film) formed on the upper surface of the lower glass substrate 2. Reference numeral 4 denotes a through-hole that is opened before being cut into the lower glass substrate, and 5 is a silver-palladium electrode. The lower glass substrate 2 overlaps with the inner wall of the through-hole 4 so as to partially overlap the lower ITO electrode. A large number of them are formed at a predetermined pitch in the vicinity of both end faces. Reference numeral 6 denotes an upper polarizing plate attached to the upper surface of the upper glass 1.
[0013]
The connection state of the liquid crystal display panel will be described below with reference to the cross-sectional view of (b). The mother board and the like are drawn with dotted lines (instead of imaginary lines). 7 is a mother substrate, and 8 is a mother substrate electrode formed on the upper surface thereof, which is a general copper foil pattern. The planar arrangement of the portion overlapping the liquid crystal display panel is the same pitch and coincides with the silver palladium electrode 5. Are arranged to be. Reference numeral 9 denotes solder, which connects one silver palladium electrode 5 and one mother substrate electrode 8 formed on the inner wall surface of the through hole 4 one by one.
[0014]
Of the elements constituting the liquid crystal display panel, the upper polarizing plate 6 and the lower polarizing plate (not shown) are usually low in heat resistance except for the liquid crystal material. In order to improve this, the base material of a polarizing plate can be made into the polyimide resin which is a material with high heat resistance. Although the translucency of the polyimide resin is slightly inferior, it can be solved by reducing the thickness to about several tens of μm.
[0015]
FIG. 2 is a main manufacturing process diagram of a glass substrate used for an example of an embodiment of the present invention, FIG. 3 is a plan view of a large glass substrate in a state where up to step 3 is performed, and FIG. 5A is a plan view of the large glass substrate, FIG. 5A is a cross-sectional view of the through-hole portion of the large glass substrate in which the step 5 is performed, and FIG.
[0016]
A large number of upper and lower glass substrates are simultaneously formed on the surface of a large glass substrate having a size of 250 mm × 200 mm, for example, and finally separated individually. In FIGS. 3 and 4, the upper glass substrate and the lower glass substrate are drawn together in one large glass substrate, but this is for convenience of explanation. The yield will be better if only the glass substrate is made.
[0017]
In FIG. 2, step 1, ITO electrodes are deposited on the surface of the large glass substrate, and in step 2, they are etched into a required pattern. In step 3, an alignment layer for aligning liquid crystals is processed and formed. The state at the end of this step is shown in FIG. In FIG. 3, reference numeral 10 denotes a large glass substrate, in which the predetermined outlines of the upper glass substrate 1 and the lower glass substrate 2 to be finally cut and separated are indicated by thin solid lines. Reference numeral 3 denotes a patterned ITO electrode, but the portion related to display is not shown, and only the portion that becomes the lead line is shown by a thin solid line.
[0018]
In step 4 of FIG. 2, a number of through holes are drilled using a drill. The hole diameter is 0.3 mm or more, for example 0.5 mm. (In this case, the pitch of the hole rows, that is, the distance between the display lead terminals is 0.6 mm or more and 1.5 mm or less, for example, about 0.8-1 mm, although it depends on the hole diameter. This is enough for a display device that has a simple display pattern or LCD driver IC mounted on the liquid crystal display panel to reduce the number of input / output terminals to the liquid crystal display panel. This is shown in FIG.
[0019]
In step 5 of FIG. 2, a conductive paste containing silver palladium is applied around the through hole 4 on the upper surface of the large glass substrate by screen printing. At this time, vacuum suction is performed from the lower surface of the large glass substrate 10 so that the conductive paste covers the inner wall surface of the through hole. This state is shown in FIG. Since the conductive paste around the hole is partially overlapped with the lower ITO electrode 3, they both conduct, and the silver-palladium electrode 5 becomes a terminal of the display lead line after completion. Next, when the same operation is performed on the lower surface of the large glass substrate 10 in step 6, the conductive paste completely covers the inner wall surface of the through hole 4. This state is shown in FIG.
[0020]
In step 7 of FIG. 2, the applied conductive paste is baked to complete the silver palladium electrode 5. The firing temperature is about 500 ° C. which is lower than the transition temperature (Tg) of about 560 ° C. of the glass material for liquid crystal display panels. The firing temperature of silver palladium has been 700-750 ° C. in the past, but the recent development of materials for low temperature firing has also enabled the present invention.
[0021]
Since it is the same as the prior art, a brief description will be given below. In FIG. 2, step 8 is a sealant printing for creating a liquid crystal injection space, a step 9 is printing a common electrode, and a step 10 is bonding a large glass substrate (an upper glass substrate planned portion and a lower glass substrate on different large glass substrates). In step 11, liquid crystal is injected and sealed, in step 12, cut and separated into a single liquid crystal display panel is performed, and in step 13, upper and lower polarizing plates are pasted, A finished liquid crystal display panel is obtained.
[0022]
Cutting is performed using a slicer or the like, but the predetermined cutting line passes through the center of the through hole 4, so each through hole is divided into two parts, and the silver-palladium electrode formed on the inner wall surface is separated as shown in FIG. A terminal electrode group which is exposed on the side surface of the liquid crystal display panel and can be soldered according to the present invention is obtained.
[0023]
Next, although not shown, a soldering process between the completed liquid crystal display panel and the mother substrate will be described. Soldering is preferably done by positioning and placing the LCD panel on the mother board 9 and through a solder reflow furnace if the entire LCD panel allows heat resistance, but if the heat resistance is still severe, use an air gun or the like by hand. You can also solder quickly. In order to prevent the glass from cracking or cracking, it may be preheated to a heat resistant temperature of the liquid crystal, for example, 100 to 120 ° C., or may be subjected to solder plating on the silver palladium electrode. Further, only the silver-palladium electrode turned to the lower surface of the lower glass substrate by controlling the amount of solder may be connected to the mother substrate electrode.
[0024]
Next, another embodiment of the present invention will be described. Regarding the material of the metal film used as the terminal electrode, there may be a material other than silver palladium. In addition, as a method of manufacturing a terminal electrode group that can be soldered, a straight long hole is drilled instead of a through-hole array on the smooth side surface of the upper or lower glass substrate that has been cut in advance without using a small hole through-hole. A metal film may be formed on the smooth inner wall surface of the long hole of the large glass substrate in the state (through side). For example, a silver paste is transferred and printed in stripes aligned in the plate surface direction, fired, and further subjected to a base plating such as copper or nickel, followed by solder plating. In short, it is only necessary to form a metal film having the necessary heat resistance and strength near the side surface of the glass substrate. Further, the connection between the mother substrate and the liquid crystal display panel is not limited to soldering, and a thermosetting conductive adhesive may be used, or a low melting point alloy other than the solder material may be used for bonding. The scope of application of the present invention is not limited to the previously described embodiments.
[0025]
【The invention's effect】
In the present invention, since the technology capable of directly connecting the liquid crystal display panel and the mother substrate has been achieved, the following effects can be obtained.
(1) The liquid crystal display panel can be supported and connected to the mother substrate without using a connector or a connecting member, and the configuration of the display device is remarkably simplified.
(2) As a result, a significant cost reduction of the display device is achieved.
(3) Both the set maker and the parts maker reduce the design load and shorten the delivery time.
(4) Since there is no connector and no support frame for the liquid crystal display panel is required, an ultra-thin display body structure is possible.
(5) The technology of the present invention has a wide range of applications, and can be applied to a structure in which functional elements such as illumination elements and touch detection elements are directly mounted on a liquid crystal display panel, and in that case also a structure that is extremely simplified Can be realized.
[Brief description of the drawings]
1A is a plan view of an example of an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG.
FIG. 2 is a manufacturing process diagram of the liquid crystal display panel in the embodiment.
FIG. 3 is a plan view of a large glass substrate after a third step in the manufacturing process.
FIG. 4 is a partial plan view of a large glass substrate after the fourth step in the manufacturing process.
5A is a cross-sectional view of a large glass substrate after the fifth step and FIG. 5B after the sixth step during the manufacturing process.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Upper glass substrate 2 Lower glass substrate 3 Lower ITO electrode 4 Through hole 5 Silver palladium electrode 6 Upper polarizing plate 7 Mother substrate 8 Mother substrate electrode 9 Solder 10 Large glass substrate

Claims (3)

Among the upper glass substrate and the lower glass substrate having a substantially rectangular planar shape constituting the liquid crystal display panel, the side surfaces of both short sides of the lower glass substrate protruding greatly on both sides in the longitudinal direction of the upper glass substrate are A plurality of through-holes divided after being provided through the lower glass substrate are covered, and each of the divided through-holes covers the inner side surface of the divided through-hole and is separated from the outer edge of the upper glass substrate. A silver-palladium electrode individually connected to the transparent electrode for display on the upper surface of the glass substrate is formed by coating and baking, and the liquid crystal panel is placed so that the lower glass substrate is in contact with the mother substrate, and the mother substrate straight and individual display driving electrodes of the upper and the individual silver-palladium electrodes of the inner side surface of the divided through holes are exposed on the outer peripheral side surface of said liquid crystal display panel by soldering The liquid crystal display device, characterized in that connected.   The liquid crystal display device according to claim 1, wherein a polarizing plate based on a polyimide resin is fixed to a surface of an upper glass substrate or a lower glass substrate constituting the liquid crystal display panel. Preparing a large glass substrate included in an aligned state of an upper glass substrate or a lower glass substrate constituting a liquid crystal display panel, forming a transparent electrode on the large glass substrate, and forming an alignment layer on the transparent electrode And a step of drilling through holes so as to be linearly arranged at positions that are both short sides of the lower glass substrate that is larger in the longitudinal direction than the upper glass substrate in the large glass substrate, and A conductive paste containing silver palladium is applied so that the transparent electrode partially overlaps the upper and lower surfaces of the large glass substrate and the inner surface of the through hole, and the overlapping position is separated from the position of the outer edge of the upper glass. Printing a sealing material for forming a liquid crystal injection space on a large glass substrate, a step of baking the conductive paste at about 500 ° C. to form a silver palladium electrode, and A process, a process of laminating two large glass substrates so that the upper glass substrate and the lower glass substrate overlap, a step of injecting and sealing liquid crystal, and a cutting line passing through the center of the through-hole row. A process of dividing the liquid crystal display panel into a liquid crystal display panel, a process of attaching a polarizing plate whose base material is a polyimide resin to the liquid crystal display panel, and a liquid crystal display panel with a polarizing plate mounted on the mother substrate so that the lower glass side is in contact And the display drive electrode on the mother substrate and the divided through hole arranged on the outer edge in the longitudinal direction of the liquid crystal display panel are overlapped, and the display drive electrode and the silver palladium electrode on the inner surface of the divided through hole, And a method of manufacturing a liquid crystal display device.

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