JP2002365644A - Manufacturing method and manufacturing apparatus of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of an alignment defect in consequence of exertion of a locally excessive pressure to substrates to be aligned in a manufacturing method and manufactured apparatus for liquid crystal display devices. SOLUTION: Flat planar buffer materials 31 and 32 are stuck to the outside surfaces of upper and lower surface plates (stages) 11 and 12 of a rigid body plate press 1 having an alignment mechanism to perform panel alignment by aligning the array substrate 21 and the counter substrate 22. The materials which are <=70 deg. in JIS A hardness (the hardness by the A-shaped spring type hardness tester stipulated in JIS K 6301) and is <=50 μm in the variation of thicknesses (the difference between the maximum value and minimum value in one sheet of the buffer material) are used as the buffer materials 31 and 32.

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 and a manufacturing apparatus used for the method.

[0002]

2. Description of the Related Art Display panel (liquid crystal cell) of a liquid crystal display device
Is a liquid crystal material sandwiched between a pair of insulating substrates, and four circumferences of the liquid crystal material layer are sealed with a sealing material. An alignment film made of polyimide or the like for aligning the liquid crystal material is provided on a surface of each insulating substrate in contact with the liquid crystal material. At least one of the pair of insulating substrates is transparent and forms a liquid crystal display surface. The sealant holds the liquid crystal material from four sides and prevents moisture and the like from entering the liquid crystal material.

[0003] A large number of spacers are arranged between a pair of insulating substrates forming a display panel to keep the distance between the substrates constant. As a method of arranging the spacers, in addition to a method of uniformly dispersing spheres having a uniform diameter on one of the substrates, a heat-sealing layer is provided on the surface of such a spherical spacer and fixed by heating. Or a method of forming a columnar spacer on one of the substrates by patterning.

[0004] Assembling of a display panel is usually performed as follows. First, a seal material pattern having a mouth shape surrounding a display area is formed along the four circumferences on one insulating substrate by screen printing or by applying a seal material by a dispenser of a movable nozzle type. This is combined by the other insulating substrate being positioned and pressed. After the sealing material is cured by heating or the like, surrounding unnecessary areas are scribe-removed.
In the case of multi-paneling in which a plurality of display panels are cut out from one original substrate, the display panels are cut into predetermined areas and separated.

[0005] When applying the sealing material, a short cut is provided near the midpoint of one side of the substantially rectangular shape of the sealing material pattern, and after the sealing material is cured, the liquid crystal material is injected from the cut (injection port). You. After the injection is completed, the injection port is closed, and the assembly of the liquid crystal cell is completed.

The distance between the two substrates in the display panel body assembled in this manner is a predetermined value (predetermined gap value) determined by the dimensions of the spacer in substantially the entire region including the region of the sealing material. Becomes

In general, the steps of aligning and bonding a pair of insulating substrates and pressing are performed in a state where each insulating substrate is held by upper and lower platens (stages) made of a rigid material such as stainless steel. It is performed continuously. By using a plate made of such a rigid material, the positioning accuracy can be realized, and stable clamping can be performed even under a considerable gauge pressure. In particular, uniform pressure is applied to the entire insulating substrate by giving sufficient accuracy to the parallelism between the upper and lower platens.

[0008]

However, as a result of the present inventors' intensive studies on the above-mentioned bonding and press-fitting according to the prior art, a local alignment defect in the alignment film occurs due to this process. It was known. That is, in spite of the fact that no defective alignment was observed when the inspection was performed after the substrate alignment step, a part of the defective alignment was often found on the substrate after the bonding step.

The inventors of the present application have further studied the cause of the defective alignment film, and as shown schematically in FIG. 3, foreign matter 4 (dust) adhering to the substrates 21 and 22 It has been found that the local application of a large pressure (local eccentric load) between the and the surface plates 11 and 12 is the main cause of the occurrence of local orientation failure. In addition, regarding the mechanism of the occurrence of local misalignment due to the local uneven load, when the pressure is clamped while foreign matter is sandwiched,
It was considered that the substrate was undulated by the influence of the foreign matter, and the alignment film on the substrate was disturbed by contact with the alignment film or structure on the other substrate.

[0010] In addition, there has been a case where the alignment film is continuously disturbed at the same location. It has been known that this is caused when a projection is formed on the stage by foreign matter.

The present invention provides a method and an apparatus for manufacturing a liquid crystal display device which can prevent or reduce local defects in an alignment film.

[0012]

According to a method of manufacturing a liquid crystal display device of the present invention, an alignment film is formed on one main surface of each of a pair of first and second substrates; A step of applying a sealing material to a predetermined region of the alignment film forming surface of the two substrates, and holding the first and second substrates with a pair of rigid disks with the alignment film forming surfaces facing each other. A method for manufacturing a liquid crystal display device, comprising: a registration / positioning step of performing positioning and overlapping with each other, and a pressing step of pressing the first and second substrates together after the registration / positioning step. In the pressing step, a flat cushioning material having a JIS A hardness of 70 degrees or less and a thickness variation of 50 μm or less is provided between the first and second substrates and the rigid board. Characterized by being distributed .

According to the above configuration, it is possible to prevent the occurrence of poor alignment caused by locally applying excessive pressure to the substrates to be bonded.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method of manufacturing a liquid crystal display device according to the present invention, when a pair of substrates are bonded and clamped via a sealing material and a spacer, a pair of substrates and a pair of substrates are clamped together. A flat cushioning material is arranged between the board and the stage.

The cushioning material has a hardness (JIS-A hardness) measured by an A-type spring hardness tester specified in JIS K 6301 of 70 degrees or less and a thickness variation of 50 μm or less.

If the JIS-A hardness of the cushioning material exceeds 70 degrees, it is difficult to sufficiently absorb the protrusion due to the foreign matter when the foreign matter is caught between the substrate and the surface plate, and the local uneven load is generated. Cannot be sufficiently prevented. J of cushioning material
The IS-A hardness is preferably 5 to 70 degrees, more preferably 5 to 60 degrees, and still more preferably 10 to 50 degrees.

The variation in the thickness is the difference between the maximum value and the minimum value of the thickness of one cushioning material, and can be measured by, for example, an optical method of scanning a laser beam distance meter. If the thickness variation exceeds 50 μm, the variation in pressure distribution in the substrate surface becomes too large, and there is a possibility that local uneven load due to foreign matter cannot be sufficiently absorbed.

The range of thickness variation is preferably 40
μm or less, and more preferably 30 μm or less.
As will be described later, when a groove or the like for separating from the substrate is provided in the cushioning material, this groove portion is not included in the variation in thickness.

As the cushioning material, various materials can be used as long as they do not contaminate the substrate and have a certain level of durability, toughness, deformation recovery, and the like. . The cushioning material is made of, for example, a rubber material selected from silicone rubber, fluorine rubber, polyester elastomer, and polyurethane elastomer. However, in some cases, a porous material such as a foamed product of ABS resin can be used. It is also possible to use a nonwoven fabric made of fine fibers, a fine-woven or knitted fabric, or an artificial suede.

The thickness of the cushioning material is preferably 0.3 to 10
mm, more preferably 0.5 to 5 mm, and still more preferably 1.0 to 3.5 mm. The thickness of the cushioning material is 0.3m
If it is smaller than m, when a relatively large foreign substance is caught, the protrusion due to the foreign substance cannot be covered, and a local eccentric load occurs. On the other hand, if the thickness of the cushioning material exceeds 10 mm, the positioning accuracy between the pair of substrates is adversely affected.

The cushioning material is preferably provided with a net-like groove or the like in order to improve the releasability from the substrate after pressing is completed. For example, when forming into a flat plate shape, nylon taffeta may be formed on the surface on the substrate side. Preferably, the width of the groove is 100 μm (0.1 mm) or less, and the depth of the groove is 50 μm or less.

If the surface of the cushioning material is coated with an anti-adhesion material such as a fluorine-based resin, sufficient releasability from the substrate can be realized without providing such grooves.

It is preferable that a part or all of the buffer material has conductivity in order to prevent generation of static electricity. It is common to mix conductive particles in the entire resin material when forming the cushioning material.However, kneading a conductive polymer or forming a conductive portion continuous in the thickness direction at predetermined intervals It can also be provided. It is also possible to composite with a conductive fiber material.

When the cushioning material is non-conductive, it is desirable to provide a conductive coating for the purpose of preventing static electricity. Examples of the conductive coating include a coating in which carbon fine particles are dispersed.

When the cushioning material is a material that is easily cut in contact with the edge of the substrate material such as glass, it is desirable to apply a protective coating. For example, a material such as silicon-epoxy or silicon-urethane can be coated. Also, conductivity can be imparted to this protective coating at the same time.

Further, instead of these coatings, a suitable resin film layer functioning as a protective layer or a conductive layer may be attached.

The cushioning material can be attached to the surface plate of the substrate bonding apparatus. For example, when the surface plate is provided with a vacuum chuck mechanism, it is held from the surface plate by the vacuum chuck mechanism at the time of bonding. By doing so, it is possible to appropriately perform inspection and replacement of thickness variations and the like. When the substrate is held by the vacuum chuck mechanism provided on the surface plate, a large number of small-diameter through-holes having a suitable diameter are provided in a flat buffer material, and the substrate is sucked and held through these through-holes. Can be The through holes can be formed at the same time when the cushioning material is molded, or can be formed by punching, laser processing, or water jet processing after molding.

When the substrate and the buffer are held on the surface plate by the vacuum chuck mechanism, the buffer may be adsorbed and then the substrate may be adsorbed, or the substrate and the buffer may be brought in and adsorbed simultaneously. good. At this time, by devising the distribution of the through holes provided in the cushioning material, a part of the suction port of the vacuum chuck can be used exclusively for absorbing and holding the cushioning material. For example, a region where the through holes are omitted at predetermined intervals may be provided in the cushioning material so that the buffering material is adsorbed at this location.

The platen is a rigid plate made of a rigid material such as stainless steel, metal aluminum, an aluminum alloy, a magnesium alloy, and a ceramic plate.

At least one of the upper and lower platens is provided with a vertical movement / pressing mechanism such as a hydraulic cylinder for overlapping and pressing the two substrates.

In order to align the two substrates, the substrate bonding apparatus places the substrates in the vertical direction, the horizontal direction, and the rotational direction (X, Y,
θ), and an alignment state detection mechanism for detecting and confirming the alignment state using an alignment (alignment) mark or the like of the substrate.

In the embodiments described below, the liquid crystal display device is of an active matrix type in which switch elements are arranged for each display pixel, and an array substrate on which the switch elements are arranged and a counter substrate are provided with a sealing material and a spacer. Combined through. In particular, the present invention is a transmissive liquid crystal display device in which a switch element for each pixel is formed of a thin film transistor (hereinafter abbreviated as TFT) and requires backlight.

On the electrode forming surface of the array substrate, a plurality of signal lines and scanning lines are arranged in a grid on a transparent insulating substrate such as glass or quartz, and amorphous silicon (hereinafter a-Si) is provided at each intersection. : Abbreviated as H) is connected. The gate electrode of the TFT is electrically connected to the scanning line, the drain electrode is electrically connected to the signal line, and the source electrode is electrically connected to a transparent conductive material constituting the pixel electrode, for example, ITO (Indium-Tin-Oxide). Have been.

On the electrode forming surface of the opposing substrate, an opposing electrode made of ITO is disposed on a transparent insulating substrate such as glass, so as to shield a color filter layer for realizing color display and a TFT portion on the array substrate. A light-shielding layer is provided for the purpose.

On the uppermost layer of the electrode formation surface of the array substrate and the counter substrate, an alignment film is provided by subjecting an organic resin film such as polyimide to a rubbing treatment or the like.

The substrate bonding apparatus and the substrate bonding step of the embodiment will be described below with reference to FIGS.

FIG. 1 is a longitudinal sectional view showing a substrate bonding apparatus 1.
Is schematically shown.

The upper and lower platens 11 and 12 are stainless plates such as SUS304, and have vacuum chucks 15 and 16. A flat cushioning material 31 held on the upper and lower stools 11 and 12 by the vacuum chuck 15, respectively.
32 is a 2 mm thick rubber plate made of FB658N manufactured by Kureha Elastomer Co., Ltd. The JIS A hardness was measured to be 50 to 60, and the thickness variation was 60 μm.
It was below.

The surfaces of the cushioning members 31 and 32 are formed with a checkerboard-like groove provided by nylon taffeta. The groove width is about 50 μm, and the groove depth is about 40 μm.
m. The dimension of each side of the substantially square portion defined by these grooves is about 1 mm. Furthermore, a coating layer of polythiophene, which is a conductive polymer, is formed on the surfaces of the buffer materials 31 and 32.

The array substrate 21 and the opposing substrate 22 are held by the vacuum chuck 16 on the upper and lower stools 11 and 12, respectively. A large number of through holes 33 penetrating through the cushioning materials 31 and 32 so as to correspond to the suction ports of the vacuum chuck 16.
Is provided.

The upper surface plate 11 is attached to the lower surface of a horizontally movable block 13 movable in each of the X, Y and θ directions. On the other hand, the lower platen 12 is attached to the upper end of a hydraulic cylinder 14, and the hydraulic cylinder 14 performs vertical movement and upward pressurization.

If a specific example of the dimensional configuration and the like is shown, the array substrate 21 and the opposing substrate 22 bonded by the bonding apparatus 1 are large original substrates made of 550 mm × 650 mm glass (third stage line). . After the original substrates 21 and 22 are combined with each other via a sealing material, the substrates are cut and scribed into four empty cells corresponding to four 15-inch diagonal liquid crystal display devices, that is, display panels before liquid crystal injection. Separated. That is, the display panel of 15 inches diagonal is "four-chamfered".

Hereinafter, the array substrate 21 in the embodiment will be described.
The step of bonding the substrate and the counter substrate 22 will be briefly described.

(1) A seal material is discharged from a nozzle of a syringe driven by a robot arm, and a pattern of the seal material is applied along four circumferences of each area corresponding to each display panel to be cut out, and then a solvent contained therein is applied. Is removed.

(2) The vacuum chucks 15 attach and hold the cushioning materials 31 and 32 on the upper and lower platens (stages) 11 and 12.

(3) The vacuum chuck 16 attaches and holds the array substrate 21 to the upper platen 11 via the buffer material 31, and attaches the opposing substrate 22 to the lower platen 12 via the buffer material 32. And hold.

(4) The upper horizontal movable block 13 is horizontally moved or rotated to perform rough positioning before bonding. In addition, the surface plate 1 is driven by driving the hydraulic cylinder 14.
2, the array substrate and the opposing substrates 21 and 22 are attached to each other, and then precise alignment is performed while checking the degree of overlap between the alignment marks on both substrates with a microscope. In particular, this is performed by an automatic alignment mechanism provided with a control device.

(5) At room temperature of about 25 ° C., gradually increase the pressing pressure to apply 1.0 mm to the array substrate and the opposing substrates 21 and 22.
A pressure of kgf / cm ² (about 0.1 MPa) is applied.

(6) The positional displacement between the two substrates 21 and 22 is prevented by a spot-shaped photocurable resin or the like, and in this state, the substrate is transferred to a thermosetting seal curing device.

(7) The temperature is raised while being kept in a pressed state between the heating plates of the seal hardening device, and the hardening of the seal material is completed by heating at 150 ° C. for 1 hour, for example.

(8) Thereafter, the presence or absence of a defect in the alignment film is inspected by a polarizing device.

FIG. 2 shows the frequency of misalignment obtained in the above example together with a comparative example. In the comparative example, the bonding was performed in exactly the same manner as in the example except that the cushioning materials 31 and 32 were not used.

As can be seen from FIG. 2, according to the embodiment, the occurrence of defective orientation was significantly reduced. In particular, no jump in the frequency of misalignment as seen in the comparative example was observed, and the frequency did not exceed 0.5 frequencies per pair of original substrates. Since this degree of misalignment is considered to be caused by a cause different from the local eccentric load, it is considered that this embodiment completely prevented the misalignment caused by the local eccentric load. .

On the other hand, in the apparatus of the embodiment, the diameter is 0.8
mm-sized metal-based foreign material 4 of 1.0 mmf / cm ² (approximately 0.1 MPa) is sandwiched between a glass substrate and a cushioning material.
The pressure was clamped to a), and in this state, the pressure distribution in the substrate surface was measured by a tactile sensor (pressure distribution measuring device). As a result, it was known that no noticeable increase in pressure was observed even at the location of the metallic foreign matter, and that the occurrence of local uneven load was prevented.

As described above, according to the substrate bonding apparatus and the substrate bonding process of the embodiment, it is possible to prevent the occurrence of a local uneven load due to the foreign matter adhering to the substrate surface. In addition, it is possible to prevent the occurrence of local misalignment. Moreover, there is no increase in equipment load or process load other than disposing the cushioning material between the substrate and the surface plate.

In the description of the above embodiment, the transmission type amorphous silicon TFT is used as the liquid crystal display device.
Although the type is described as an example, the same applies to a reflection type and a polycrystalline silicon type.

[0057]

According to the method and the apparatus for manufacturing a liquid crystal display device, it is possible to prevent the occurrence of defective alignment due to locally applying an excessive pressure to the substrates to be bonded.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a substrate bonding apparatus according to an embodiment.

FIG. 2 is a graph showing a decrease in poor orientation when the substrate bonding apparatus of the example is used.

FIG. 3 is a longitudinal sectional view corresponding to FIG. 1, showing a problem of the substrate bonding apparatus according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laminating apparatus 11,12 Upper and lower surface plate (stage) 13 Horizontal movable block 14 Hydraulic cylinder 15,16 Vacuum chuck 21,22 Array substrate and counter substrate 31,32 Buffer material 33 Buffer material through hole 4 Foreign material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H089 LA41 NA22 NA32 NA38 NA39 NA45 NA49 QA12 QA15 TA04

Claims (6)

[Claims] 1. A step of forming an alignment film on one main surface of each of a pair of first and second substrates, and applying a sealing material to a predetermined region of an alignment film forming surface of the first substrate or the second substrate. And a superposition / positioning step of performing the positioning while holding the first and second substrates with a pair of rigid disks in a state where the surfaces on which the alignment films are formed face each other. A method of manufacturing a liquid crystal display device, comprising: a pressing step of pressing the first and second substrates together after the overlapping / positioning step; A method for manufacturing a liquid crystal display device, wherein a flat cushioning material having a JISA hardness of 70 degrees or less and a thickness variation of 50 μm or less is disposed between a substrate and the rigid board. 2. The method of manufacturing a liquid crystal display device according to claim 1, wherein said cushioning material is provided with mesh-like fine grooves on a surface. 3. The method for manufacturing a liquid crystal display device according to claim 1, wherein said buffer material is one whose surface is coated with a conductive material or a protective layer. 4. The method of manufacturing a liquid crystal display device according to claim 1, wherein said buffering material is held by a vacuum mechanism provided on said rigid board in said overlapping / positioning step. 5. The method according to claim 1, wherein said cushioning material is made of a rubber material selected from silicone rubber, fluorine rubber, polyester elastomer, and polyurethane elastomer. 6. A bonding mechanism for holding and positioning the first and second substrates by a pair of rigid disks, respectively, and then bonding the substrates, and a pressing mechanism for pressing between the pair of rigid disks. In a manufacturing apparatus of a liquid crystal display device including a rigid disk press provided with: JIS A hardness is 70 degrees or less on an outer surface of the rigid disk,
An apparatus for manufacturing a liquid crystal display device, wherein a flat buffer material having a thickness variation of 50 μm or less is provided.