JPH11281985A - Spacer discharging method and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately arrange spacers by using the ink-jet method and to manufacture a liquid crystal display element with a good productivity by using an ink mixed with a solvent having a boiling point of a specific value or higher and spacers, and heating a substrate temperature to a specific temperature or above. SOLUTION: This method for discharging granular spacers by using an ink-jet head 1 on a substrate 3, an ink prepared by mixing a solvent having a boiling point of >=100 deg.C and the spacers is used, and the spacers are scattered while heating the substrate to >=60 deg.C. By defining the boiling point of the solvent as >=100 deg.C the possibility of spacer discharge failure caused by volatilization and the reduction of the solvent near an ink-jet head nozzle is extremely reduced. As a result, stable discharge becomes possible for a long time. Moreover, the heating temperature of the substrate should be 60 deg.C or higher, and the effect is large if the substrate is heated to -40 deg.C to 130 deg.C higher than the boiling point of the solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a spacer discharging method for discharging a spacer onto a substrate using an ink jet device, and a liquid crystal display device manufactured using the same.

[0002]

2. Description of the Related Art In a display element such as a liquid crystal display element, a spherical or fibrous spacer is arranged between substrates in order to keep a constant gap between the substrates. Conventionally, this spacer is dispersed by dispersing the spacer in a solvent and spraying on a substrate by a spray method or the like using a spacer spraying device such as spraying, or spraying while preventing aggregation by imparting static electricity to the spacer. The dry method was known. The spacers scattered in this manner have a problem that aggregation and scattering unevenness are apt to occur, and display unevenness is easily caused.

For this reason, there has been a tendency to spray more than necessary in order to keep the gap between the substrates even if there is unevenness in the spraying. However, when a large number of spacers are scattered, the amount of light leakage increases, and in particular, when a large amount of spacers are agglomerated, they become conspicuous and display quality deteriorates.

In addition, there has been proposed a method of arranging spacers at predetermined positions by a printing method such as screen printing or flexographic printing. According to this method, since the arrangement position of the spacer can be specified, the required minimum amount of the spacer is sufficient, and problems such as aggregation of the spacer do not occur. However, since the printing methods are all contact methods, the printing plate comes into direct contact with the surface subjected to the alignment treatment, which tends to cause a problem of causing poor alignment. Further, since there is a high tendency to use a solvent having a high viscosity, there is also a problem that the solvent is difficult to volatilize.

Therefore, as a method of arranging the spacer at a predetermined position, it has been proposed to supply the spacer to a specific position using a dispenser or an ink jet device. In that case, the liquid crystal itself or a solvent used in a conventional wet method was used as it is as a solvent for inkjet.

[0006]

However, when a liquid crystal is used, a high degree of control is required for impurities and the viscosity is high, so that it is necessary to finely control the temperature of the ink jet head. Further, the liquid crystal is supplied into the ink jet head and its piping, and it is necessary to clean the contents every time the liquid crystal of the liquid crystal cell to be used changes, and the amount of wasted liquid crystal is considerably increased. Had also.

When the solvent used in the conventional wet method is used as it is, it is generally quick-drying with a boiling point of less than 100 ° C., mainly of isopropyl alcohol and chlorofluorocarbon, and has a surface tension of 20 dyn / at room temperature. cm or less of solvent was used. In that case, the drying speed becomes faster around the nozzles of the inkjet head, and it is easy to cause a spacer to adhere around the nozzles or to cause a shift in the ejection direction.

Further, when the liquid is discharged onto the alignment film that has been subjected to the alignment treatment, the liquid tends to spread greatly after the landing of the spacer because the surface tension is small, and the accuracy of the landing position tends to be deteriorated due to the flow of the spacer. In the case of a color liquid crystal display device, since a light-shielding film is provided between pixels, it is preferable that a spacer can be disposed in the light-shielding film portion. However, the ratio of the spacer protruding from the light-shielding film portion tends to increase.

For this reason, it is conceivable to arrange the spacers one by one at equal intervals also in supplying the spacers by the ink jet method. However, since the required number of spacers is determined by the target liquid crystal display element, a large number of spacers are also arranged in the pixel region for displaying.

Therefore, in the spacer discharge method by the ink jet method, there is a demand for a spacer discharge method in which the ink jet discharge characteristics are improved and the landing position accuracy of the spacer is improved so that the alignment performance of the alignment film is not adversely affected. Was.

An object of the present invention is to solve these problems and to accurately arrange spacers by using an ink-jet method to manufacture a liquid crystal display device having high display quality with high productivity.

[0012]

According to the present invention, there is provided a spacer discharging method for discharging granular spacers onto a substrate by using an ink jet apparatus, the method comprising using an ink obtained by mixing a solvent having a boiling point of 100 ° C. or more with a spacer. A spacer discharging method characterized in that the spacers are sprayed while the substrate temperature for spraying is heated to 60 ° C. or higher.

Further, a spacer discharging method for heating the substrate temperature to −40 ° C. to 130 ° C. with respect to the boiling point of the solvent used for the ink jet, and the surface tension of the ink used for the ink jet at room temperature is 35 dyn. / C
Provided is a method of ejecting a spacer using an ink of m to 50 dyn / cm.

Further, in a liquid crystal display device in which a pair of alignment-treated substrates are opposed to each other and a liquid crystal and a granular spacer are interposed therebetween, the spacer is supplied by an ink-jet method. I will provide a.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a substrate is heated when a granular spacer for adjusting a substrate gap of a liquid crystal display element is discharged onto the substrate using an ink jet device. Accordingly, since a solvent having a high surface tension can be used, the solvent is not unnecessarily quickly volatilized at the time of discharging by the ink jet, thereby making it difficult to cause a discharge failure. Further, after the ink has landed on the substrate, the ink is quickly volatilized by the heated substrate.

FIG. 1 is a front view of a typical example of a spacer discharging device used in the present invention. In FIG. 1, reference numeral 1 denotes an ink jet head, 2 denotes a guide rail on which the ink jet head 1 moves, 3 denotes a substrate, 4 denotes a slide table on which the substrate 3 is mounted, and 5 denotes a base on which the slide table is mounted.
In the present invention, the substrate 3 is heated by a heating unit (not shown).

In the apparatus shown in FIG. 1, the ink jet head 1 moves on the guide rail 2. That is, the spacer is discharged while moving in the left-right direction in the figure. On the other hand, the slide table 4 moves in the depth direction in the figure. This allows
The spacer can be discharged to an arbitrary position on the substrate. The positioning of the ejection position is not limited to this example, and the inkjet head itself may be movable in two directions, left, right, and depth, and the slide table itself may be movable in two directions, left, right, and depth. Good.

The spacer discharging device is used for various purposes, and is particularly preferably used for a spacer discharging device of a liquid crystal display element. In a liquid crystal display device, a spacer is arranged between two substrates in order to keep a constant gap between the two substrates. This is used regardless of whether it is an STN type liquid crystal display element or a TFT type liquid crystal display element.

The ink jet head used in the present invention may have a known structure such as a head driven by a piezoelectric element or a head driven by evaporating a solution by heating. In the present invention, unlike a normal colored ink, a large-diameter spacer, that is, a type driven by a piezoelectric element is preferably used in order to discharge a solid substance.

The number of nozzles of the ink jet head may be one, or several tens or more nozzles may be used. Since the discharge from each nozzle can be controlled in the ink jet head, it is usually preferable to arrange the spacers using an ink jet head having a large number of nozzles from the viewpoint of productivity.

As the spacer used in the present invention, any spacer can be used as long as the spacer can be discharged from the nozzle of the ink jet head. Although the diameter of the spacer varies depending on the purpose of use, it is usually about 2 to 20 μm for a liquid crystal display element. The material of the spacer is typically made of plastic, but glass or ceramic can be used as long as it is granular. As the spacer in the present invention, a spherical spacer, a cylindrical spacer having substantially the same diameter and height, and the like can be used.

In the present invention, one spacer may be discharged in one discharge, or two or more spacers may be used. When two or more ink droplets are ejected, it is particularly preferable that the ink is ejected so as to be arranged on a light shielding film arranged between pixels.

FIG. 2 is a plan view showing a state where spacers are ideally arranged on a substrate by the method of the present invention. In FIG. 2, reference numeral 11 denotes a pixel, 12 denotes a light-shielding film that fills a gap between pixels that become a non-display portion, and 13 denotes a spacer.

In the present invention, it is preferable that the spacer is basically arranged in a non-display portion other than a pixel used for display. This is because it is difficult to completely prevent some of the spacers from entering the pixels used for display because the spacers are ejected by the inkjet method and the line width of the light shielding film is narrow. . It is most preferable that the spacers can be arranged only in non-display portions other than the pixels used for display. However, if 80% or more of the spacers are arranged in the non-display portions, the deterioration of display quality is small. .

The pixel used for the display means a portion where the electrodes face each other and the display is intentionally changed depending on the voltage application state. In the case of display using a normal dot matrix, pixels are rectangular and a non-display portion is formed so as to surround the periphery. If there is an active element such as a TFT, that part is also usually used as a non-display part. In some cases, spacers are not arranged in the active element part to prevent damage to the active element due to pressurization.In such a case, the spacer is arranged in the non-display part and in the part without the active element. Become.

This non-display portion is preferably covered with a light-shielding film in order to increase the display contrast ratio. In the present invention, even if two or more spacers are simultaneously ejected and the spacers are aggregated and arranged, it is preferable that the light-shielding film is provided in the non-display portion because light leakage due to aggregation is not seen.
In the following description, it is assumed that the non-display portion has a light shielding film.

Color STNLCD and color TFTLCD
In FIG. 2, as shown in FIG. 2, a large number of RGB three-color pixels are arranged surrounded by a light-shielding film. In the present invention, this light shielding film 1
It is preferable that the spacers are ejected such that the spacers 13 are located on the upper surface 2. This pixel usually has a short side of 50 to 150 μm.
It is formed with m pitches. This is determined by the display area and the number of pixels arranged therein. In the case of RGB three-color pixels, generally, three rectangular pixels collectively constitute a substantially square display area.

For example, in the case of SVGA display at 2.1 inches, the pitch on the short side is about 102 μm, and the pitch on the long side is about 306 μm. A light-shielding film 12 is formed in a portion surrounding the pixel 11. The light-shielding film is patterned in consideration of the patterning accuracy of the electrodes and the positioning accuracy of the two substrates. If the accuracy is reduced, the width of the light-shielding film is increased, the aperture ratio of the pixels is reduced, and the display becomes dark. Therefore, it is better that the width of the light-shielding film is as narrow as possible. Therefore, the width of the light shielding film is generally set to about 10 to 25 μm.

When no active element is provided in STNLCD,
The pitch on the short side is about 102 μm, and the pitch on the long side is about 3
06 μm and the width of the light shielding film is 20 μm,
The shape of each pixel is 82 × 286 μm, and the aperture ratio is about 7
5%. In the present invention, a spacer is discharged to a portion where the light shielding film is provided.

In this case, it is preferable to discharge a spacer at a portion where the light shielding film crosses in a T-shape or a cross shape. In the example of FIG. 2, rectangular pixels are repeatedly arranged vertically, horizontally, and vertically. That is, the lines of the light-shielding film are provided in the form of a lattice in a straight line at the top, bottom, left and right. It is preferable that a spacer is disposed at a portion where the light shielding films cross in a cross shape. If the ink jet method is used, it is easy to control the arrangement of the spacer near this portion.

In the case of FIG. 2, taking the above-mentioned STNLCD as an example, if the inkjet head scans in the left-right direction of FIG. 2, the nozzle pitch of the inkjet head may be 306 μm. Therefore, the spacers can be arranged with a small number of nozzles, and the productivity is good. When the number of nozzles is small, the possibility of occurrence of ejection failure is reduced, and the yield is improved.

That is, an inkjet head having a nozzle pitch of 306 μm is used as an inkjet head, and the inkjet head can be scanned in the short side direction of the pixel, that is, in the horizontal direction in FIG. 2 to discharge the spacer.

In this case, an ink jet head having a fixed nozzle pitch of 306 μm may be used as the ink jet head, and an ink jet head having a pitch longer than that may be used, and the ink jet head may be inclined with respect to the scanning direction. Scanning.

In the present invention, the substrate is heated to 60 ° C. or higher when discharging the spacer. This is because a solvent having a high boiling point and not drying very quickly can be used as a solvent of a discharge liquid used for discharging the spacer by the inkjet method. By heating the substrate,
The ejected ink containing the spacer dries quickly even if the solvent used has a high boiling point. In addition, there is little danger that the solvent may be reduced near the nozzles of the ink jet head to cause defective spacer ejection.

In the present invention, since a solvent ink having a boiling point of 100 ° C. or higher is used, the heating temperature of the substrate is set to 60 ° C. or higher. In the case of a mixed solvent, the boiling points of all the solvents are, in principle, 100 ° C. or higher.
However, a very small amount, for example, less than 5 wt% of the ink, or a substance used as an additive may include a substance having a boiling point of less than 100 ° C.

In the present invention, by setting the boiling point of the solvent to 100 ° C. or higher, the possibility of spacer discharge failure due to the evaporation and reduction of the solvent near the nozzle of the ink jet head is greatly reduced. For this reason, stable ejection for a long time becomes possible.

Further, the heating temperature of the substrate is 60 ° C. or higher, and the effect is greater if the substrate is heated to −40 ° C. to 130 ° C. with respect to the boiling point of each solvent used in the ink jet. Further, as the ink, an ink having a surface tension of 35 to 50 dyn / cm at normal temperature is used.
It is preferable in view of the stability of the ink jet at normal temperature. Thereby, even if ejection is continued for a long time, ejection failure is unlikely to occur, and productivity is high.

The surface tension of the ink at room temperature is 35 to
By setting it in the range of 50 dyn / cm, a more stable ejection time can be extended as compared with a case where the boiling point of the solvent is simply set to 100 ° C. or higher.

As the solvent, any solvent can be used as long as it satisfies the above-mentioned characteristics. As the organic solvent, for example, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether and the like are preferably exemplified. When a plurality of solvents are used in combination, those having a boiling point of all solvents of 100 ° C. or higher are used.

In the present invention, this ink can be used only with an organic solvent, but it is basically preferable to use water as a base, and water is used by mixing such an organic solvent. Water / organic solvent weight ratio is water / organic solvent =
The ratio may be determined experimentally as appropriate at about 95/5: 50/50 in consideration of the drying speed and the dischargeability.

The ratio between the spacer and the other inks is
What is necessary is just to set suitably within the range which can be discharged from the nozzle of an inkjet head. This varies depending on the diameter of the spacer, but is usually about 0.05 to 5% by weight.

The ink mixed with the spacer contains, in addition to the spacer, the organic solvent and water, an adhesive used for bonding the spacer to the substrate surface, a dispersant for improving dispersibility, and the like. Is also good. When these are mixed, it is preferable that the surface tension of the mixed solvent be 35 to 50 dyn / cm. The term ink used in the present invention refers to a material ejected by an ink-jet method as ink, and it does not matter whether a colorant is mixed in the composition.

The spacer discharging method of the present invention is used for dispersing spacers and can be used for various display elements, touch switches, etc., but is suitable for liquid crystal display elements.
In particular, it is suitable for manufacturing a liquid crystal display element in which a light-shielding film is arranged between pixels. Hereinafter, an example applied to the manufacture of a liquid crystal display element will be described.

As a substrate of the liquid crystal display element, a substrate having only electrodes provided thereon, a substrate having an alignment film formed thereon,
A substrate on which a color filter or a light-shielding film is formed, a substrate on which an active element such as a TFT is formed, and a substrate formed by combining these members can be used.

In the case of a liquid crystal display element, a non-hydrophilic organic resin-based alignment film represented by polyimide is often used. In this case, it is preferable that the solution combined with the spacer contains as much water as possible with a high surface tension.

The liquid crystal display element is formed by stacking two substrates. For this reason, the spacer of the present invention is usually arranged on one substrate by an inkjet method. Then, a liquid crystal display element is manufactured by being overlapped with the other substrate. The substrate on which the spacer is discharged is preferably the substrate on the side on which the light-shielding film is formed, from the viewpoint of alignment.

[0047]

EXAMPLES Examples 1 to 3 (Examples and Comparative Examples) As an apparatus for discharging spacers, an apparatus as shown in FIG. 1 was used, and a CCD camera and a fiberscope light source were provided for monitoring the apparatus. As a substrate, a color filter substrate of 12.1 inch SVGA size was prepared. This color filter substrate is formed by forming a chromium-based light-shielding film and color filter on a glass substrate, forming a resin insulating film, patterning a transparent conductive film of ITO, and forming a polyimide alignment film thereon. And

Water / ethylene glycol monobutyl ether (EGMBE) = 90/10 (weight ratio) was used as the ink with spacers ejected by the inkjet method. The boiling point of water was 100 ° C, and the boiling point of ethylene glycol monobutyl ether was 171 ° C. The surface tension of this mixed solvent was 45.4 dyn / cm.

In this solvent, 0.5 wt% of a plastic spherical spacer having a diameter of 4 μm is mixed to form an ink, and five spacers are respectively attached to the vicinity of the intersection of the light shielding films as shown in FIG. Discharge was performed. At this time, the substrate was discharged at 170 ° C. (Example 1), 100 ° C. (Example 2), and normal temperature (Example 3). The stability of this discharge was such that discharge was possible for a long time regardless of the substrate temperature. The ejection life (time during which stable ejection continues) is described in Example 1,
Examples 2 and 3 are equivalent because the inks are the same, and Table 1 shows Example 1 as a representative.

As a substrate opposed to the color filter substrate, a transparent conductive film made of ITO was patterned on a glass substrate, and an alignment film of polyimide was formed on the transparent conductive film. These two substrates were arranged so that the alignment film sides face each other, the periphery was sealed with a sealing material, and liquid crystal was injected to produce a color STNLCD. Table 2 shows the results of measuring the specific resistance of the liquid crystal when a liquid crystal display element was formed by using the substrate at a different heating temperature. In Table 2,
“O” indicates a specific resistance of 10 ⁻¹⁰ Ωcm or more, “Δ” indicates a specific resistance of the order of 10 ⁻⁹ Ωcm, and “X” indicates a specific resistance of less than 10 ⁻⁹ Ωcm.

As a result, in the example where the substrate is held at room temperature,
The specific resistance is considerably low, and when observed with a microscope, it is about 6
The diameter was about 0 μm, and the appearance was uneven.
This is probably because the evaporation of the solvent was delayed and the alignment film was contaminated or had an adverse effect on the alignment state.

Examples 4 to 10 (Examples and Comparative Examples) Table 1 shows the results of measuring the ejection stability and the ejection life (time) by changing the ink composition (other than the spacer). Table 1
In Table 1, the meanings of the abbreviations of the solvents in the ink composition are as follows, and the surface tension is the surface tension of the ink composition (dyn / c).
m). The surfactant (dodecylbenzenesulfonic acid) in the ink compositions of Examples 8 and 9 is not a solvent,
It is an additive used for the purpose of adjusting the surface tension.

IPA: isopropyl alcohol (boiling point 8
2.3 ° C) EG: Ethylene glycol (boiling point 197 ° C) EGMBE: Ethylene glycol monobutyl ether (boiling point 171 ° C) EGMME: Ethylene glycol monomethyether (boiling point 124 ° C)

As is clear from the results, the temperature was 100 ° C.
By using the ink using the above solvent, the ejection life is prolonged and the productivity is improved. In particular, by using an ink having a surface tension of 35 to 50 dyn / cm at normal temperature, the surface tension can be significantly increased.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

According to the spacer discharging method of the present invention, the spacer is sprayed while the substrate temperature on which the spacer is sprayed is heated to 60 ° C. or higher using an ink obtained by mixing a solvent having a boiling point of 100 ° C. or higher with the spacer. Therefore, the ejection lifetime of the spacer by the ink jet method, that is, the continuous production time can be lengthened, and the productivity is increased.

Nevertheless, since the substrate is heated, the solvent is quickly volatilized, and the adverse effect on the alignment film and the like of the liquid crystal display element is small. In particular, the viscosity is high,
By using the ink having a specific surface tension, the ejected spacer is hard to move, and the spacer is easily arranged at a predetermined position.

As a result, a large number of spacers can be arranged in the light-shielding film portion on the substrate, and since almost no spacers are arranged in the pixels used for display, light leakage is reduced and the contrast ratio is improved. The present invention can be applied to various applications within a range that does not impair the effects of the present invention.

[Brief description of the drawings]

FIG. 1 is a front view of a representative example of a spacer discharge device used in the present invention.

FIG. 2 is a plan view of a substrate on which a spacer is discharged according to the present invention.

[Explanation of symbols]

 1: Inkjet head 2: Guide rail 3: Substrate 4: Slide table 5: Base 11: Pixel 12: Light shielding film 13: Spacer

Claims (4)

[Claims] 1. A spacer discharging method for discharging granular spacers on a substrate by using an ink jet apparatus, wherein a substrate having a boiling point of 100.degree. A spacer discharging method characterized by spraying spacers while heating as described above. 2. The method according to claim 1, wherein the substrate is heated to a temperature of −40 ° C. to 130 ° C. with respect to the boiling point of the solvent used for the ink jet. 3. The method according to claim 1, wherein the ink used in the inkjet has a surface tension at room temperature of 35 to 50 dyn / cm. 4. A liquid crystal display device in which a pair of alignment-treated substrates are opposed to each other and a liquid crystal and a granular spacer are interposed therebetween, wherein the spacer is supplied by an ink-jet method according to any one of claims 1 to 3. A liquid crystal display device, comprising: