JP2000284249A - Production of liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obviate the occurrence of a deviation between plastic substrates at the time of thermal compression bonding by correcting the dimensional change of the substrates generated by penetration of moisture and organic solvent at the time of washing of a plastic liquid crystal display element. SOLUTION: When the plastic substrates are used for the transparent electrode substrates of the liquid crystal display element, the one substrate (first plastic substrate) on the side to be sprayed with intra-surface spacers is subjected to a vacuum heat treatment between a washing stage after a rubbing treatment and a thermal compression bonding stage. The other substrate (second plastic substrate) on the side to be coated with a peripheral sealing material is subjected to the vacuum heat treatment between the washing stage after the rubbing treatment and a coating application stage for the peripheral sealing material. Both of the vacuum heat treatment conditions for the first and second plastic substrates are preferably <=100 Torr, >=60 deg.C and 1 to 24 hours of the treatment time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device using a transparent electrode substrate as a plastic substrate, and more particularly, to a liquid crystal display device in which no displacement occurs between substrates during thermocompression bonding of the substrates. And a method for producing the same.

[0002]

2. Description of the Related Art Plastic substrates have been adopted in the field of liquid crystal display devices because of their reputation for being lighter than glass substrates and more resistant to breakage, and are expected to be used in portable telephones and portable information terminal equipment in recent years. Has been sent.

[0003] In particular, in information terminal equipment, a large screen and high definition are being promoted in order to cope with an increase in the amount of information. As a matter of course, development of a liquid crystal display element using a plastic substrate is urgent.

[0004]

However, when a plastic substrate is used as the transparent electrode substrate, there are the following problems.

[0005] That is, since a plastic substrate is inherently easily permeated by moisture and an organic solvent, the moisture and the organic solvent are not allowed to pass through the inside of the plastic substrate while being left in the process or during a washing process with the water or the organic solvent. And accumulate on the surface, which can change the dimensions of the substrate,
Warpage has occurred and a problem has occurred in the cell forming process.

In particular, when two substrates are thermocompression-bonded via an organic peripheral sealing material, bubbles are generated in the peripheral sealing material because moisture and an organic solvent evaporate as gas due to the high heat. Or In addition, a displacement occurs between the substrates due to a change in the dimensions of the substrates.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a liquid crystal display device in which a plastic substrate is used as a transparent electrode substrate. Provided is a method of manufacturing a liquid crystal display element in which a substrate can be accurately thermocompression-bonded without causing a shift without causing a substrate to have a warp or a dimensional change, and bubbles and the like are not generated in a peripheral sealing material. is there.

According to the present invention, an object of the present invention is to clean the first and second plastic substrates with water or an organic solvent after rubbing the alignment film formed on the transparent electrode, and to apply the first and second plastic substrates to the first plastic substrate. Are spread and fixed by in-plane spacers, and after applying a peripheral sealing material to the second plastic substrate, the first plastic substrate and the second plastic substrate are thermocompression-bonded via the peripheral sealing material.
For the first plastic substrate, after the cleaning step, and
The first plastic substrate is subjected to heat treatment under reduced pressure before the step of bonding with the second plastic substrate, and the second plastic substrate is subjected to the second heat treatment after the cleaning step and before the peripheral sealing material coating step. This is achieved by subjecting the plastic substrate to heat treatment under reduced pressure.

The conditions of the reduced pressure heat treatment for the first and second plastic substrates depend on the material and thickness thereof, and the form of the reduced pressure treatment apparatus. According to a preferred embodiment of the present invention, the reduced pressure value is 100 torr or less. Especially 10 torr
The temperature is 60 ° C. or higher, preferably 100 ° C. or higher, and the upper limit temperature is in the range of Tg−20 ° C., where Tg is the glass transition point of the substrate material. The processing time is 1
The time is preferably not less than 24 hours and not more than 24 hours.

Even if the heat treatment under reduced pressure is performed under such conditions, the moisture or organic solvent contained in the air may permeate or adhere to the substrate again if left untreated. It is preferable that a peripheral sealing material is applied to the second plastic substrate within 12 hours, and both plastic substrates are thermocompression-bonded.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacture of a liquid crystal display element starts with the selection of a mother substrate for forming a plurality of liquid crystal display panels. In a plastic liquid crystal display device, two plastic substrates made of, for example, polycarbonate and having a thickness of about 0.1 to 0.4 mm are used as mother substrates. One is for F plate (front panel) and the other is for R
Used for boards (rear panels).

Usually, a hard coat layer, a gas barrier coat layer, an undercoat layer, and the like are sequentially formed on this kind of plastic substrate, and an ITO (i.
A transparent conductive film made of ndium tin oxide) is formed over the entire surface.

First, two mother boards (F board and R board)
The plates are washed together, and through respective steps of resist application, exposure, development, etching, and resist stripping, transparent electrodes are respectively formed in the display areas allocated in advance, and an alignment film is formed on the transparent electrodes. A rubbing process is performed.

After the cleaning, the in-plane spacers are sprayed on the F plate side, for example, and the fixing process is performed. On the R plate side, a peripheral sealing material made of epoxy resin is applied around each display area.

Thereafter, the F plate and the R plate are superimposed on each other with reference to their alignment marks and thermocompression-bonded.
In this way, a plurality of cells are formed simultaneously. next,
A stick substrate is cut out from the mother substrate in units of columns or rows, and after injecting liquid crystal into each cell, a liquid crystal display panel is cut out from the stick substrate individually.

The F plate and the R plate follow substantially the same process until cleaning after the rubbing treatment, but thereafter, go through a different process (history) to the thermocompression bonding process. As mentioned above, F
The plate is used for the process of spraying and fixing the in-plane spacer, whereas the R plate is used for the process of printing the peripheral seal material.

For this reason, when the thermocompression bonding step is performed, a geometrical error occurs between the two substrates due to warpage or dimensional change. Further, due to the high temperature at the time of thermocompression bonding, the moisture and the organic solvent that have permeated into the substrate at the time of cleaning become gas and evaporate, so that air bubbles may be generated in the peripheral sealing material.

Therefore, according to the present invention, the F plate and the R plate are each subjected to a heat treatment under reduced pressure before the thermocompression bonding step to remove moisture or an organic solvent penetrating into the substrate or adhering to the surface to thereby reduce the heat. At the time of pressure bonding, a shape error does not occur between both substrates. Also, air bubbles are not generated in the peripheral sealing material.

That is, regarding the F plate, the F plate is subjected to a reduced pressure heat treatment after the cleaning step after the rubbing treatment and before the thermocompression bonding step. Further, the R plate is subjected to a reduced pressure heat treatment after the cleaning step after the rubbing treatment and before the coating step of the peripheral sealing material.

It is preferable that the conditions for the heat treatment under reduced pressure of the F plate and the R plate are the same. The reduced pressure heating process involves a reduced pressure value, temperature and time.
It is preferably at most 00 torr, particularly preferably at most 10 torr.

The temperature is at least 60 ° C., preferably at least 100 ° C., the boiling point of water. The upper limit temperature is required to be within a range of Tg-20 ° C., where Tg is a glass transition point of the substrate material. Further, the processing time is 1 hour or more, and preferably 24 hours or less. More preferably, 8
~ 16 hours is good.

By performing the reduced pressure heat treatment under the same conditions as described above, it is possible to eliminate the shape error of the F plate and the R plate. It is preferable to apply a peripheral sealing material to the R plate within 12 hours after the heat treatment under reduced pressure, and thermocompression-bond both substrates, since there is a possibility that they will permeate or adhere to the substrate again.

[0023]

Example 1 An F plate and an R plate for a mother substrate have a hard coat layer, a gas barrier coat layer, and an undercoat layer, and a transparent conductive film made of ITO is formed on one surface thereof over the entire surface. Thickness 0.1mm
Two plastic substrates with an ITO transparent conductive film made of the above polycarbonate resin were prepared.

After each substrate is washed with water and washed with IPA (isopropyl alcohol), the motherboard on the F plate side includes a display area and a terminal portion connected to the display area to form one panel unit. Each time, the transparent conductive film was patterned to form a column electrode (for example, an X electrode) as a transparent electrode and an extraction electrode in a stripe shape. Then, a 400 ° -thick alignment film made of polyimide was formed in each display region except for the terminal portion, and rubbing treatment was performed.

On the motherboard on the R plate side, only a display area is set without providing a terminal portion, and the display area is set as one panel unit, a plurality of the display regions are allocated, and a transparent electrode is patterned for each panel unit. Electrodes (for example, Y electrodes) were formed in a stripe shape. Then, a 400 ° -thick alignment film made of polyimide was formed in each of the display regions, and a rubbing treatment was performed.

Next, both the F plate and the R plate were washed with IPA. And about 100 degreeC and 10 torr about R board
A heat treatment under reduced pressure for 12 hours was performed, and then a thermosetting epoxy resin-based peripheral sealing material was applied around the display area by printing.

On the other hand, with respect to the F plate, an in-plane spacer having an average particle size of 6.0 μm was sprayed, fixed at 90 ° C., and then heat-treated under reduced pressure at 100 ° C., 10 torr for 12 hours. Carried out.

In the peripheral sealing material on the side of the R plate, styrene-styrene is used as a conductive connecting material (transfer material) between the substrates.
Gold / resin beads made of divinylbenzene copolymer
2 wt% of conductive beads having an average particle diameter of 6.0 μm plated with two layers of nickel and 5 wt% of a conductive filler were mixed. Further, resin beads having a surface layer made of a thermoplastic resin and having a core of a styrene-divinylbenzene copolymer were used for the in-plane spacer.

Next, the F plate and the R plate were thermocompression-bonded with their respective display areas facing each other so that the twist angle of the liquid crystal molecules was 240 °. Then, a stick substrate having a plurality of cells belonging to the same column or the same row was cut out from the bonded mother substrate in a unit of a column or a row, and an injection port was taken out.

Thereafter, liquid crystal was injected into each cell from the injection port, and after sealing the injection port, each cell was cut out from the stick substrate to obtain a liquid crystal display panel.
Observation of the pattern on the F plate side and the pattern on the R plate side of the liquid crystal display panel manufactured in this way showed that the relative displacement accompanying the dimensional change of the substrate was 10 μm or less. Also, no air bubbles were found in the peripheral sealing material, and the sealing shape was good.

<Comparative Example 1> The same plastic substrate as in Example 1 was used as the F plate and the R plate, but the heat treatment under reduced pressure was not particularly performed. Otherwise, a liquid crystal display panel was manufactured in the same manner as in Example 1. In Comparative Example 1, the relative displacement between the pattern on the F plate side and the pattern on the R plate side due to the dimensional change of the substrate was 50 μm. Further, there were also some bubbles generated in the peripheral sealing material.

[0032]

As described above, according to the present invention,
In the case where a plastic substrate is used as the transparent electrode substrate of the liquid crystal display element, one of the substrates on which the in-plane spacers are scattered is subjected to a reduced pressure heat treatment between the cleaning step after the rubbing treatment and the thermocompression bonding step, The other substrate on the side to which the peripheral sealing material is applied is subjected to a reduced pressure heating process between the cleaning process after the rubbing process and the application process of the peripheral sealing material, so that the two plastic substrates are warped. As a result, the thermocompression bonding can be performed accurately without causing a displacement, and bubbles can be prevented from being generated in the peripheral sealing material.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Koji Fujimoto, Inventor 1-2-1 Kamisakabe, Amagasaki City, Hyogo Prefecture Opterex Amagasaki Plant F-term (reference) 2H088 EA22 FA03 FA10 FA16 FA21 FA26 HA01 HA03 KA11 LA08 MA20 2H089 HA30 LA07 LA19 LA46 MA04X MA06Y NA09 NA24 NA45 NA55 NA58 QA12 TA01 2H090 HB08Y JB03 JC08 JC12 JD15

Claims (3)

[Claims] The first and second plastic substrates after rubbing the alignment film formed on the transparent electrode are washed with water or an organic solvent, and an in-plane spacer is sprayed on the first plastic substrate. The method for manufacturing a liquid crystal display element, wherein the first plastic substrate is adhered to the second plastic substrate, and then the first plastic substrate and the second plastic substrate are thermocompressed via the peripheral seal material. Is after the washing process, and
The first plastic substrate is subjected to heat treatment under reduced pressure before the step of bonding with the second plastic substrate, and the second plastic substrate is subjected to the second heat treatment after the cleaning step and before the peripheral sealing material coating step. A method for producing a liquid crystal display element, comprising subjecting a plastic substrate to heat treatment under reduced pressure. 2. The reduced pressure heat treatment conditions for the first and second plastic substrates are both 100 torr or less and 6
The method for producing a liquid crystal display device according to claim 1, wherein the temperature is 0 ° C or more and the treatment time is 1 to 24 hours. 3. Within 12 hours after the heat treatment under reduced pressure, the second
3. The method according to claim 1, wherein a peripheral sealing material is applied to the plastic substrate, and the first and second plastic substrates are thermocompression-bonded.