JPH0243519A - Method for assembling display panel - Google Patents

Abstract

PURPOSE:To easily control working and to reduce the generation of display defects or unevenness by containing a spacer material into a volatile liquid, spraying and sticking the liquid to the surface of a substrate by an electrostatic spraying method, mutually bonding the peripheral edge parts of the substrates with a prescribed gap, and then sealing a display medium into the gap between both the substrates. CONSTITUTION:When the spacer material 10 is previously sprayed to the surface of a substrate 10 by the electrostatic spraying method and stuck to the substrate 10 by electrostatic force, both the bonding agent and display medium 90 can be stuck or sealed as pure states containing no spacer material 40. When the spacer material contained in the volatile liquid 50 is electrostatically sprayed, the spray density of the spacer material 40 on the substrate can be controlled to a required value in accordance with the contents of the spacer material 40 in the volatile liquid. Consequently, the spacer material 40 can be uniformly sprayed to the substrate, so that unevenness on the display face can be removed and the failure of assembling work can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a method for assembling display panels, typically liquid crystal display panels, in which a pair of substrates of a display panel are separated from each other by a predetermined gap, and the peripheral edges thereof are assembled. The present invention relates to an assembly method in which a display medium is sealed in a gap between both substrates after the substrates are bonded to each other.

[Conventional technology]

A display panel generally includes a pair of substrates as described above, and when assembling them, first the two substrates are adhered to each other at the periphery with a predetermined gap between them, and then the two substrates are bonded to each other in the gap between the substrates surrounded by the adhesive layer. The display medium is enclosed, but in order to improve the clarity of the display, it is generally necessary to narrow the gap between the substrates, for example, in the case of a liquid crystal display panel, it is necessary to narrow the gap to about 5 to 10 -, and to make the display uniform within the panel surface. In order to achieve this, it is necessary to minimize the in-plane variation in this gap size.

Therefore, when assembling the display panel, the gap between the substrates can be reduced to about the number mentioned above by gluing the two substrates together with a spacer material such as a very small glass bead, glass fiber, or plastic bead sandwiched between them. Conventionally, it has been managed to maintain a constant value. This procedure will be explained with reference to FIGS. 2 and 3.

A pair of substrates 10 and 20 constituting a display panel is illustrated in FIG. 2(a) and FIG. Same figure (
The substrate 10 in a) is a so-called active matrix substrate for a liquid crystal display panel, and has a large number of rectangular pixel electrodes 11 arranged in rows and columns on a transparent glass plate, and a scanning voltage is applied to the pixel electrodes arranged in the row direction in the figure. Horizontally elongated scanning electrode 1
2, and a driving element 13, which is a two-terminal element such as a diode in this example, connected between each pixel electrode 11 and the scanning type 1i12. ! The I element electrode 11 and the scanning electrode 12 are formed from a very thin transparent conductive film, which is usually less than 0.1, and the end portions of the scanning electrode 12 are formed as connecting portions 12a alternately on the left and right sides as shown. The drive element 13 may be a three-terminal element such as a transistor, but in any case, the thickness is 21! m
These are the front and rear thin film elements.

In the substrate 20 of FIG. 5), a large number of vertically elongated data electrodes 21 are provided on a similar glass plate so as to face the pixel electrodes 11 arranged in the column direction on the active matrix substrate IO side, and the ends thereof are As it is, the upper and lower portions are alternately used as connection portions 21a. This data electrode 21 is also formed from a very thin transparent conductive film in the same way as above.

FIG. 3 shows a conventional method for assembling a pair of 1&temporary 10 and 20 as described above into a display panel. Since both substrates must be adhered to each other with the above-mentioned predetermined gap, First, by applying an adhesive such as epoxy containing the spacer material 40 described above to one substrate, for example 10, by means of screen printing or the like, the adhesive layer 30 is formed into a frame-shaped pattern having a population 31 as shown in the figure. Next, the other substrate 20 is superimposed on it as shown in the figure.
The front substrates 10 and 20 are bonded together with the adhesive layer 30 under pressure and heat, and then the adhesive layer 30 is sufficiently cured by heating.

Since the adhesive layer 30 is once melted and then solidified under pressure and heat during bonding, the gap between the two plates is regulated by the dimensions of the spacer material 40 mixed in the adhesive and is set to a predetermined value. It is said that

Next, a display medium 90 such as a liquid crystal is sealed in the gap between the front substrates 10 and 20 surrounded by the hardened adhesive layer 30, but only the periphery of the front substrate is bonded with the frame-shaped adhesive layer 30. Since it is not possible to keep the internal gaps uniform, display medium 90 with spacer material 40 mixed in advance is used.
Insert into the gap. For this purpose, the entrance 3 of the adhesive layer 30 is
After evacuating the gap between the boards sufficiently from step 1,
The display medium 90 is sucked together with the spacer material 40 into the gap surrounded by the adhesive layer 30 as shown by the arrow in the figure. After this enclosing step is completed, the entrance 31 is closed with an adhesive and the adhesive is cured, thereby completing the assembly of the display panel.

[Problem to be solved by the invention]

However, the conventional method described above is difficult to assemble,
There are problems such as uneven distribution of spacer material within the display surface.

The first cause of the problem is that a spacer material is mixed into the adhesive, and during screen printing, the screen tends to become knotted, causing the coating pattern of the adhesive layer to collapse, and if the degree of collapse is large. Since the display medium is likely to leak, the screen must be frequently cleaned, making work management very difficult.

The second cause is that the display medium contains a spacer material, which deteriorates the flow when the display medium is enclosed and tends to cause uneven distribution of the spacer material, as shown in Figure 3. Sometimes the driving element 13 protrudes from the substrate lO side.
The spacer material 40 tends to get caught in the flow of the highly viscous display medium 90 such as liquid crystal, resulting in incomplete sealing and air bubbles remaining behind the drive element or in the corners of the sealed space. 40 concentrates in the range A near the entrance 31 during enclosing, and it becomes difficult to reach the range B further away. Air bubbles naturally cause display defects, and if the distribution of the spacer material is uneven, the gaps between the substrates will also become uneven, which tends to cause uneven display.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a display panel assembly method that facilitates work management and reduces display defects and unevenness.

(Means for Solving Problem 11) In the present invention, when assembling a display panel in which a display medium is enclosed between a pair of substrates whose peripheral portions are bonded to each other with a predetermined gap as described above, An insulating spacer material that regulates the gap between the substrates is contained in a volatile liquid, and the volatile liquid is dispersed using an electrostatic spraying method while the spacer material is charged and placed on one substrate, for example. By distributing and adhering the adhesive layer uniformly to the substrate, for example, placing the other substrate on which an adhesive layer has been applied in advance, the two substrates are combined with a spacer material interposed between them, and the periphery is After the two substrates are bonded to each other, the display medium is encapsulated within the gap defined by the spacer material and surrounded by the adhesive layer, thereby successfully achieving the object.

The density of spacer material on the board is 20 per square meter.
The most appropriate number is ~30. # It is preferable to use a highly volatile liquid with a boiling point near room temperature, such as Freon, as the volatile liquid for electrostatic spraying, and it is best to use electrostatic spraying with the substrate held in a vertical position. desirable.

[Effect]

In the method of the present invention, instead of mixing the spacer material into the adhesive or including it in the display medium as in the past, the spacer material is sprayed onto the substrate in advance by electrostatic spraying as in the above structure, and then By applying electrical power, both the adhesive and the display medium can be applied or encapsulated in their pure form, containing no spacer material.
It succeeded in solving 11 problems by eliminating the causes of conventional problems.

Although it is possible to electrostatically spray the spacer material alone, in the method of the present invention, by electrostatically spraying the spacer material in a volatile liquid, it is possible to reduce the volatility of the spacer material. The dispersion density on the substrate can be controlled to a desired value depending on the content in the liquid. Spacer material particles are strongly charged in a DC electric field due to the DC voltage for electrostatic spraying and scattering due to evaporation of volatile liquid, are uniformly dispersed due to mutual repulsion, and are efficiently attached to the substrate due to electrostatic attraction. (This allows the spacer material to be uniformly spread over the substrate, and also minimizes the loss of expensive spacer material. Also, if the spacer material is Since it is insulating, each of the charged particles scattered on the substrate strongly adheres to the electric bridge made of the conductive film of the substrate due to electrostatic attraction.As a result,
It is possible to stably maintain a uniform distribution of the spacer material during the assembly work of the display panel.

However, if the volatile liquid that is sprayed together with the spacer material adheres to the substrate, it will easily contaminate the substrate and will be detrimental to the stable adhesion of the spacer material particles. Disperse it as much as possible through evaporation before doing so. For this purpose, it is desirable to move the spray nozzle away from the substrate, but in the method of the present invention, the use of electrostatic spraying allows the scattering loss of the spacer material to be minimized even if the spraying distance is sufficiently large.

〔Example〕

Hereinafter, an embodiment of a method for assembling a display panel according to the present invention will be described in detail with reference to FIG.

This figure shows the main steps in this example.

Figure (a) schematically shows the electrostatic spraying process of the spacer material. As the spacer material 40, the above-mentioned glass or plastic beads with a diameter of 5 to 110 l1 or glass fibers with a similar diameter and a length of several tens of inches are used, depending on the desired gap between the substrates of the display panel. A suitable amount of this is contained in a volatile liquid 50, for example, fluorocarbon, and the mixture is charged into a stirring container 60 having a closed structure shown at the lower right of the figure. A stirring rod 61 made of a magnetic material is placed in the bottom of the container 60, and this stirring rod is rotated by an electromagnetic stirrer 62 to keep the spacer material 40 well dispersed in the volatile liquid 50 at all times.

The stirring container 60 is equipped with an inlet pipe 60a and an outlet pipe 60b. For example, nitrogen gas N is supplied to the inlet pipe 60a through a valve 63.
is applied to the liquid level of the volatile liquid 50, and the outlet pipe 60b is
The spacer material 40 is extruded together with the volatile liquid 50. In the piping from this stirring container to the spray nozzle 70 is an electromagnetic on-off valve 6 for starting and stopping spraying.
5 is installed, and in this example, nitrogen gas is supplied to the nozzle 70 via a regulating valve 64. This supply of nitrogen gas to the spray nozzle is useful for finely adjusting the spray amount and promoting scattering of the sprayed volatile liquid. The spray nozzle 70 is supported in a spray chamber, which is simply indicated by a dashed line in the figure, via an insulator 72, and a valve 64 is connected to the spray nozzle 70.
and 65 are connected with insulating piping.

In this example, the substrate on which the spacer material is spread is, for example, the active matrix substrate IO shown in FIG.
The part a is sandwiched between metal jigs 73, and the spraying chamber 7
1, in this embodiment is supported in a vertical position as shown and is also placed at ground potential. The reason why the substrate 1O is placed in a vertical position is to prevent even if some volatile liquid drips from the nozzle 70 after closing the on-off valve 65 at the end of spraying, it will not stick to the substrate 10. The spraying method has the advantage of being able to spray the spacer material regardless of the orientation of the substrate.

Note that an infrared lamp 74 is installed in the spraying chamber 71 as shown in the figure.
A heating means, such as It is desirable to apply a negative high voltage V of, for example, about 30 kll to the spray nozzle 70 from a high voltage power source 80 as usual.

During the spraying work, the regulating valve 64 is adjusted to an appropriate opening degree to blow out nitrogen gas from the nozzle 70, and with a predetermined voltage applied to the nozzle 70, the electromagnetic on-off valve 65 is opened for a predetermined time. The spacer material 40 may be blown out from the stirring container 6G together with the volatile liquid 50 from the nozzle 70. After the volatile liquid 50 is blown out from the nozzle, it is almost scattered by the time it reaches the substrate 10, and the charged insulating spacer material is Only 40 are attracted towards the substrate 10 by electrostatic attraction and are electrostatically deposited on the substrate 10 in a uniform distribution due to mutual repulsion. The scattering density of the spacer material 40 on the substrate 10 is 20 per square as described above.
The opening time of the electromagnetic on-off valve 65 is controlled so that the number of openings is 30. In the case of this electrostatic spraying method, the utilization efficiency of the spacer material can be increased to 70% or more.

The same figure (b) shows the process of combining the substrates 10 and 20 and adhering them to each other, and shows the substrate 1 on which the spacer material 40 is spread
0 into the recess of the assembly base plate heated to an appropriate temperature by heater H, and on top of it, the other base ti2, on which the adhesive layer 30 was previously applied in the form of a frame using the screen printing method etc. on the same keyaki as before.
0 using an appropriate jig as shown in the figure, and applying an appropriate pressure P, the adhesive layer 30 is melted and solidified. As a result, both substrates 10 and 20 are bonded to each other with a uniform gap determined by the particle size of the spacer material 40. After completing this bonding step, the adhesive is completely cured at a predetermined temperature under slight pressure in a constant temperature bath. Due to slight contraction of the adhesive resin when the adhesive layer 30 hardens, the gap between the two substrates is regulated to a predetermined value with a slight pressure being applied to the spacer material 40, and the spacer material 40 is also sandwiched between the two substrates. In the case of the present invention, the adhesive layer 30 in this adhesive step is of course a pure form of adhesive without spacer material.

The same figure (C) shows the process of enclosing the display medium 90. In the present invention, this display medium 90 does not contain a spacer agent unlike the conventional case, but the inside of the gap is sufficiently evacuated from the entrance 31 of the adhesive layer 30 in the same manner as in the conventional case. After pulling the display medium 90 from the entrance 31
Since the 0 display medium 90, which is sealed in the space surrounded by the adhesive layer 30 between both substrates by inhaling it, does not include a spacer material, the flow at the time of sealing is considerably improved compared to the conventional one, and the sealing time is shorter than the conventional one. The spacer material sandwiched between the two substrates will not move and its distribution will not change during this encapsulation process. After this encapsulation process, the inlet 31 should be closed with adhesive and cured. The assembly of the display panel is completed.

In the display panel assembled as a prototype using the method described above, no air bubbles were observed in the enclosed display medium, and display test results showed that there was no unevenness in display brightness due to uneven gaps between the substrates. I was not able to admit. Note that, as is the case with the conventional art, after the display medium is enclosed, the presence of the spacer material within the display surface is no longer recognized.

〔Effect of the invention〕

As explained above, in the present invention, when assembling a display panel in which a display medium is enclosed between a pair of substrates whose peripheries are bonded to each other with a predetermined gap between them, an insulator is used to regulate the gap between the substrates. The spacer material is contained in a volatile liquid, and the volatile liquid is scattered using an electrostatic spraying method, and the spacer material is electrically charged. By combining both substrates with a spacer material interposed between them and adhering them to each other at the periphery, the display medium is enclosed within the gap regulated by the spacer material between the front substrates. By eliminating the need to mix a spacer material into the adhesive layer or display medium, it becomes easier and more reliable to apply the adhesive layer by screen printing and to seal the display medium into the gap between the plates. At the same time, conventional problems such as leakage of the display medium from the adhesive layer, air bubbles being mixed into the display medium, and non-uniform dispersion of the spacer material can be virtually eliminated.

In this way, the method of the present invention not only reduces display panel manufacturing costs by eliminating defects during assembly work, but also
It has the feature of improving the performance of display panels by eliminating display defects caused by the inclusion of air bubbles and in-plane display unevenness caused by uneven gaps between substrates. Practical application and further dissemination 1
It is expected that it will contribute to development.

[Brief explanation of the drawing]

1 and 2 relate to the present invention, and FIG. 1 is a block diagram of an electrostatic spraying device showing an embodiment of the display panel assembly method according to the present invention for each main process, and a cross-sectional view and a plan view of the display panel. , FIG. 2 is a plan view illustrating a substrate to be assembled into a display panel by the method of the present invention. FIG. 3 is a plan view of a display panel for explaining a conventional display panel assembly method. In FIG. 0, 10F is one substrate or active matrix substrate, 11:ii! Elementary electrode, 12: Scanning electrode, 12a: Connection section, 13: Drive element, 20; Other 1s temporary, 21: Data electrode, 21a: Connection section, 30: Adhesive layer, 31: Inlet for enclosure, 40+ Spacer material, 50; volatile liquid, 60:t
j1 stirring container, 60a + inlet pipe, 60b: outlet pipe, 61:
ljl stirring bar, 62: electromagnetic stirrer, 63: valve, 64F11
Valve regulator, 65X electromagnetic shut-off valve, 70; Spray nozzle, 71i spray chamber, 72: Insulator, 73: Jig, 74: Infrared lamp, 80: High voltage power supply, 90: Display medium or liquid crystal, A
, 8F display medium enclosure range, Ej ground, point, H: heater, N: nitrogen gas, P: pressurizing force, V: high voltage for electrostatic spraying,
M% 3θ 〃

Claims (1)

[Claims] A method for assembling a display panel in which a display medium is sealed between a pair of substrates whose peripheries are adhered to each other with a predetermined gap between them, the insulating spacer material regulating the gap between the substrates being volatile. After containing it in a liquid, it was sprayed and adhered to the substrate with a charged spacer material while scattering a volatile liquid using an electrostatic spraying method, and the spacer material was interposed between both substrates. A method for assembling a display panel, characterized in that the two substrates are assembled together in a state that they are adhered to each other at their peripheral edges, and a display medium is enclosed within a gap regulated by a spacer material between both substrates.