JP2002296560A - Bonding method for liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to surely observe alignment marks within the surface of a panel, independently of kind of liquid crystal to be used, and to perform positioning with high precision. SOLUTION: When at least two liquid crystal panels 10 and 20 are bonded by an adhesive in between, in each liquid crystal panel 10 and 20, alignment marks 13 (24), 14 (23) consisting of transparent electrodes are provided in non- display areas within the surface of the panels and terminals 132, 142, 134, 144, 232, 242, 234 and 244 for lighting marks are formed at terminal parts 111, 121, 211 and 221 and prescribed voltage is applied to the terminals for lighting marks to light the alignment mark 13 (24) and 14 (23).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for bonding liquid crystal panels, and more particularly, to a positioning technique suitable for bonding a liquid crystal panel having a chiral nematic liquid crystal.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device using a chiral nematic liquid crystal, which forms a cholesteric phase at room temperature by adding a chiral material to a nematic liquid crystal, has attracted attention as a liquid crystal display device having a memory property.

This liquid crystal display element has a memory function of maintaining a stable state between a focal conic state and a planar state when no voltage is applied. In this chiral nematic liquid crystal, display is performed by changing the liquid crystal layer between a focal conic state and a planar state depending on how a voltage is applied. In the planar state, the liquid crystal molecules have a helical structure, and selectively reflect a wavelength corresponding to the product of the average refractive index of the cholesteric phase and the helical pitch with a circularly polarized light component that matches the helix direction.

According to the liquid crystal display device having the chiral nematic liquid crystal, the R, G,
A full-color display can be obtained by fabricating three liquid crystal panels having selective reflection of each color B and laminating them.
Although not a full-color display, multi-color display is possible by stacking two liquid crystal panels.

In any case, when stacking (bonding) the liquid crystal panels, it is required to precisely align the display patterns of the liquid crystal panels so that the display colors are not mixed or the display state is not deteriorated. You.

[0006]

As one of the techniques for aligning two or more panels, there is known an alignment method using end face matching based on the external dimensions of the panel. Is within ± 0.2 mm, this does not guarantee high-precision alignment as described above.

As another method, there is a method in which alignment marks are provided in a terminal portion of each liquid crystal panel or in a panel surface for alignment, and the alignment mark is provided in the terminal portion depending on the panel shape. May not be able to overlap the terminals.

On the other hand, if alignment marks for positioning are provided in the panel surface, the alignment marks can be overlapped with each other. However, no voltage is applied to the liquid crystal, such as a chiral nematic liquid crystal or a polymer dispersed liquid crystal. When a material exhibiting selective reflection and scattering properties is used in the above condition, the alignment marks in the panel surface cannot be seen and the superposition cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to ensure that alignment marks on a panel surface can be visually recognized irrespective of the type of liquid crystal used. It is an object of the present invention to provide a method for bonding liquid crystal panels, in which a plurality of liquid crystal panels are aligned and then bonded.

[0010]

In order to achieve the above-mentioned object, the present invention provides a method for bonding at least two liquid crystal panels via an adhesive, wherein each of the liquid crystal panels has a non-display area within its panel surface. An alignment mark made of a transparent electrode is provided in the region, and a mark lighting terminal for energizing the alignment mark is formed in the terminal portion, and a predetermined voltage is applied to the mark lighting terminal to light the alignment mark. The liquid crystal panels are aligned.

When a chiral nematic liquid crystal is used as the liquid crystal, an alignment mark is displayed by selective reflection of the planar by applying a predetermined voltage at which the chiral nematic liquid crystal enters a planar state to a mark lighting terminal.

It is preferable to use chiral nematic liquid crystals having different central wavelengths of selective reflection for each liquid crystal panel. According to this, the alignment marks of each liquid crystal panel are displayed in different colors, so that alignment is performed. Easier to do.

Further, if a predetermined voltage at which the chiral nematic liquid crystal is brought into a homeotropic state is applied to the mark lighting terminal, the liquid crystal layer has no scattering property and the shape of the alignment mark can be clearly observed. become able to.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is shown in FIG.
The liquid crystal panel 10 of FIG. 2C and the liquid crystal panel 20 of FIG.
Discloses a case where two liquid crystal panels are positioned and bonded.

One liquid crystal panel 10 has a first transparent electrode substrate 11 shown in FIG. 1A and a second transparent electrode substrate 1 shown in FIG.
2 as well as the other liquid crystal panel 20 in FIG.
The first transparent electrode substrate 21 shown in FIG. 2A and the second transparent electrode substrate 22 shown in FIG. 2B are included.

As the transparent electrode substrates 11 and 12, a glass substrate or a plastic substrate on which a transparent conductive film such as ITO is formed by a sputtering method or a vapor deposition method is used (the same applies to the transparent electrode substrates 21 and 22).

The transparent electrode substrates 11 and 12 are provided with terminal portions 111 and 121, respectively, but their drawing directions are relatively different by 90 °. Transparent electrode substrates 21 and 22
Similarly, the drawing directions of the terminal portions 211 and 221 are different from each other by 90 °.

In this embodiment, the liquid crystal panels 10, 20
Since both display full dots, the first transparent electrode substrate 1
For example, the scanning electrodes 112,
212 are patterned in stripes, and, for example, data electrodes 122 and 222 are patterned in stripes on the second transparent electrode substrates 12 and 22 side in the X direction.

It should be noted that if the second transparent electrode substrates 12 and 22 are to be superimposed on the first transparent electrode substrates 11 and 21, the data electrodes 122 and 222 are shown in the drawing as the second transparent electrode substrates 12 and 22. Will be formed on the back surface side.

When forming the electrodes, alignment marks are simultaneously formed in the non-display area of each transparent electrode substrate. The non-display area refers to the scan electrodes 112 (21
2) and the data electrode 122 (222) are located outside the display area where display dots are formed facing each other.

According to this embodiment, "serpentine" alignment marks 13 and 14 are provided at two positions at diagonal positions on the liquid crystal panel 10 side, and are also provided at two positions at diagonal positions on the liquid crystal panel 20 side. "Circular dots" that match the snake's eyes
Alignment marks 23 and 24 are provided.

Alignment mark 1 on liquid crystal panel 10
3 and 14, mark elements 131 and 141 patterned on the first transparent electrode substrate 11 side and mark elements 133 and 143 patterned on the second transparent electrode substrate 12 side are shown.
, Respectively.

In the terminal section 111 on the first transparent electrode substrate 11 side, mark lighting terminals 132 and 142 connected to the mark elements 131 and 141 are formed. Also, mark lighting terminals 134 and 144 connected to the mark elements 133 and 143 are formed on the terminal portion 121 on the second transparent electrode substrate 12 side.

Alignment mark 2 on liquid crystal panel 20
Mark elements 231 and 241 patterned on the first transparent electrode substrate 21 side and mark elements 233 and 243 patterned on the second transparent electrode substrate 22 side
, Respectively.

In the terminal section 211 on the first transparent electrode substrate 21 side, mark lighting terminals 232 and 242 connected to the mark elements 231 and 241 are formed. Further, mark lighting terminals 234 and 244 connected to the mark elements 233 and 243 are also formed on the terminal portion 221 on the second transparent electrode substrate 22 side.

Next, after an insulating film and an orientation control film are formed on the first transparent electrode substrate 11 (21) and the second transparent electrode substrate 12 (22), the two transparent electrode substrates 11 (21), 1
2 (22) is thermocompression-bonded via the peripheral sealing material. Then, a liquid crystal material is sealed in the cell gap.

In this manner, the liquid crystal panel 10 having the alignment marks 13 and 14 on the inner surface of the panel shown in FIG. 1C and the alignment mark 23 on the inner surface of the panel also shown in FIG. , 24 are obtained. In this embodiment, the liquid crystal panels 10 and 20 use chiral nematic liquid crystal.

When the two liquid crystal panels 10 and 20 are bonded to each other, alignment is first performed. In this embodiment, the alignment includes two steps of a temporary alignment step and a final alignment step.

First, in the temporary alignment step, the liquid crystal panel 1
Preferably, a thermosetting resin-based adhesive such as an epoxy-based thermosetting resin or an ultraviolet-curing resin is applied to any one of the bonding surfaces 0 and 20 by a screen printing method, a transfer method, a dispenser dropping method, preferably a screen. Apply by printing method,
The liquid crystal panel 10 and the liquid crystal panel 20 are overlaid to form a laminated panel P shown in FIG. In this case, the liquid crystal panel 1
The terminal portions 111 and 121 on the 0 side and the terminal portions 211 and 221 on the liquid crystal panel 20 are prevented from overlapping in position.

For example, assuming that the liquid crystal panel 20 is superimposed on the liquid crystal panel 10 as a reference, first, the liquid crystal panel 20 is turned upside down in the state of FIG. Position. Then, the liquid crystal panel 20 is rotated clockwise by 90 °. As a result, FIG.
As shown in (1), the alignment marks 13 and 24 form a pair, and the alignment marks 14 and 23 form a pair.

In the final alignment step, the alignment apparatus 30 shown in FIG. 4 is used. The positioning device 30 includes a lower movable table 310 and a pressing table 320 disposed above the lower movable table 310.

The movable table 310 is removably supported on an actuator 330 which can move in the X-axis direction, the Y-axis direction, and the Z-axis direction, and can also rotate in the θ direction about the Z-axis. The holding table 320 is also detachably supported by an opening / closing drive unit (not shown). Although not shown, the movable table 31
Both the 0 and the holding table 320 have a negative pressure suction hole connected to a negative pressure source.

The alignment device 30 is provided with alignment marks 13 provided at diagonal positions of the laminated panel P.
Two CCDs for reading (24) and 14 (23)
Cameras 341, 342 and their monitors 343, 344
It has. The holding table 320 is provided with a through-hole (not shown) for allowing the CCD cameras 341 and 342 to image the alignment mark.

Although not shown, the positioning device 30 is provided with a probe for applying a voltage to each of the mark lighting terminals. The contact means for the mark lighting terminal includes a pin probe, a conductive tape, a conductive rubber, and the like, and a pin probe is preferably used.

As a preparatory work, the pad 3 as a pad is placed on each of the movable table 310 and the holding table 320.
50 and 350 are attached respectively. In this embodiment, the pad 350 is formed by attaching a silicone rubber sheet 352 to a stainless steel plate 351, and the stainless steel plate 351 side is sucked and held by each of the tables 310 and 320.

In positioning, after the laminated panel P is disposed between the pads 350 and 350 and the holding table 320 is closed, the movable table 310 is pushed up by the actuator 330 in the Z-axis direction, and the holding table 3 is pressed.
Press firmly on the 20 side.

Then, a voltage (for example, about 30 V) for bringing the chiral nematic liquid crystal into a planar state is applied from the probe to each mark lighting terminal to light the alignment marks 13 (24) and 14 (23).

Further, by applying a voltage (for example, about 40 V) for bringing the chiral nematic liquid crystal into a homeotropic state, the scattering property of the liquid crystal may be eliminated, and the alignment mark formed on the substrate may be observed. .

The alignment marks 13 (24), 1
4 (23) is imaged by the CCD cameras 341 and 342,
While observing the screens of the monitors 343 and 344, the actuator 330 is moved so that the alignment marks overlap, and the alignment is completed when the alignment marks overlap.

Then, in order to fix this alignment, the fixing screws (not shown) are inserted through, for example, the four corners of the movable table 310 and the holding table 320 and firmly tightened. Then, the adhesive is fully cured by a heating means such as an oven (not shown). Note that a mark lighting terminal is not used in a product.

According to the present invention, three liquid crystal panels can be bonded together. In this case, there are two methods, a method of bonding three liquid crystal panels at the same time, and a method of bonding two liquid crystal panels first and then bonding a third liquid crystal panel. The easier way is the latter method.

FIG. 5 is a table showing two examples of the shape of an alignment mark applied to bonding three liquid crystal panels. The mark described in the upper part is composed of a typical circular fitting combination and has an advantage that it is easy to design with a simple shape, but it cannot be denied that the overall size becomes large.

On the other hand, the marks described in the lower part are inset puzzles, and three marks are incorporated in a fixed area. Therefore, the marks can be created without increasing the overall size. Therefore, it is effective for a panel having a small non-display area.

The application of the present invention is not limited to the bonding of a liquid crystal panel having a chiral nematic liquid crystal. For example, a two-layer STN composed of a driving STN and a reverse twisted STN for optical phase compensation is used. It is also applicable to bonding.

[0045]

Example 1 An alignment mark (with an inner diameter of 0.1 mm) as shown in FIG. 1 was formed on a glass substrate having a thickness of 0.4 mm, on which an ITO conductive film was formed by a sputtering method.
A first liquid crystal panel having a 3 mm snake pattern having an outer diameter of 0.5 mm and a second liquid crystal panel having alignment marks (a circular dot pattern having an outer diameter of 0.3 mm) as shown in FIG. 2 were prepared. A chiral nematic liquid crystal having a central wavelength of selective reflection of 570 nm (yellow) was injected into the first liquid crystal panel, and a chiral nematic liquid crystal having a central wavelength of selective reflection of 450 nm (blue) was injected into the second liquid crystal panel. And on the bonding surface of one liquid crystal panel,
An adhesive prepared by mixing a main agent ME-106 manufactured by Nippon Pernox Co. and a curing agent XH-1885 at a ratio of 10: 4 as an epoxy-based thermosetting resin was applied by a screen printing method and bonded. The laminated panel is set on the alignment device shown in FIG. 4 and a voltage of 40 V is applied from the mark lighting terminal to the alignment mark so that the liquid crystal layer is in a homeotropic state. Positioning was performed while doing so. At this time, since the liquid crystal in the alignment mark portion was oriented substantially perpendicular to the panel surface by the application of the voltage, the liquid crystal layer had no scattering property and the shape of the alignment mark could be clearly observed. In addition, the liquid crystal molecules were substantially vertically aligned around the alignment mark under the influence of the wraparound voltage, and the edge portion of the alignment mark could be clearly observed. afterwards,
The adhesive was cured by thermocompression bonding at 70 ° C. for 30 minutes at 0.2 kg / cm ² to produce a laminated panel. When the display was observed, a favorable display without pattern shift was obtained.

[0046]

As described above, according to the present invention,
When bonding at least two liquid crystal panels via an adhesive, an alignment mark made of a transparent electrode is provided in a non-display area in the panel surface of each liquid crystal panel, and a mark lighting terminal is formed in a terminal portion. And
A predetermined voltage is applied to the mark lighting terminal to turn on the alignment mark, and the alignment mark on the panel surface can be reliably observed regardless of the type of liquid crystal used, thereby performing high-accuracy alignment. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating the configuration of one liquid crystal panel to be bonded according to the present invention.

FIG. 2 is a schematic view illustrating the configuration of another liquid crystal panel to be bonded according to the present invention.

FIG. 3 is a plan view of a laminated panel formed by superposing the above-mentioned liquid crystal panels.

FIG. 4 is a schematic view showing an embodiment of a positioning device used in the present invention.

FIG. 5 is an explanatory diagram showing two examples of alignment marks applied to bonding three liquid crystal panels in a table format.

[Explanation of symbols]

10, 20 Liquid crystal panel 11, 21 First transparent electrode substrate 12, 22 Second transparent electrode substrate 111, 121, 211, 221 Terminal portion 13, 14, 23, 24 Alignment mark 132, 142, 134, 144, 232, 242 , 2
34,244 Mark lighting terminal 30 Alignment device 310 Movable table 320 Holding table 330 Actuator 341,342 CCD camera 343,344 Monitor 350 Pad P Laminated panel

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2H088 FA01 FA03 FA04 FA16 GA02 GA17 HA02 HA16 JA10 JA13 MA20 2H089 MA04Y NA38 NA41 NA42 NA44 QA12 RA08 RA10 TA02 TA14

Claims (4)

[Claims] When bonding at least two liquid crystal panels via an adhesive, an alignment mark made of a transparent electrode is provided in a non-display area in the panel surface of each of the liquid crystal panels, and a terminal portion is provided. Forming a mark lighting terminal that is energized with respect to the alignment mark, applying a predetermined voltage to the mark lighting terminal to light the alignment mark, and aligning each of the liquid crystal panels; How to attach liquid crystal panels. 2. A chiral nematic liquid crystal is used for each of the liquid crystal panels. A predetermined voltage at which the chiral nematic liquid crystal enters a planar state is applied to the mark lighting terminal, and the alignment mark is reflected by the planar selective reflection. The method for bonding liquid crystal panels according to claim 1, wherein the display is performed. 3. The liquid crystal panel according to claim 1, wherein a chiral nematic liquid crystal is used for each of the liquid crystal panels, and a predetermined voltage is applied to the mark lighting terminals so that the chiral nematic liquid crystal is in a homeotropic state. Matching method. 4. The method for bonding liquid crystal panels according to claim 2, wherein chiral nematic liquid crystals having different central wavelengths of selective reflection are used for each of the liquid crystal panels.