JP2002202514A - Liquid crystal panel, method for manufacturing the same, and apparatus for manufacturing the same - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To facilitate ultraviolet curing of a sealing material in a color reflective liquid crystal panel. SOLUTION: A step of bonding two opposing substrates 2-1 and 2-3 to form an ultraviolet-curable sealing material 2-8 for enclosing a liquid crystal 2-6, and a method of forming the sealing material 2-8. After aligning the formed substrate and the opposing substrate, bonding the two substrates, pressing the bonded substrates so as to have a predetermined gap, shielding the portions other than the seal portion from light, A liquid crystal panel comprising: a step of adjusting the temperature within a temperature range of 40 ° C. or more and 80 ° C. or less and irradiating a seal portion with ultraviolet rays; and a step of forming a liquid crystal cell by cutting and leaving a necessary terminal portion. Manufacturing method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a liquid crystal panel.

[0002]

2. Description of the Related Art With respect to a method of manufacturing a liquid crystal panel in which liquid crystal is sealed in a gap between two substrates with electrodes, one sealing material is used for bonding two substrates and sealing the liquid crystal. Liquid-type thermosetting epoxy resins (“Structobond XN-21-S” manufactured by Mitsui Toatsu Chemicals, Inc., and “World Lock 780-BB” manufactured by Kyoritsu Chemical Industries Co., Ltd.) are well known.

[0003] The sealing material containing the thermosetting epoxy resin as a component is subjected to a thermosetting process performed after the substrates are bonded together.
Since the viscosity of the sealing material decreases in the initial stage of the overheating, problems such as a decrease in the positioning accuracy of the substrate, breakage of the seal line, and gap failure due to the floating of the seal occur. In addition, since about one hour is required for thermosetting, the production efficiency is reduced, and the size of the thermosetting equipment is increased due to the increase in the size of the mother substrate.

In order to solve such a problem, a method using an ultraviolet-curable sealing material is considered. In general, there are two types of UV-curable sealing materials: cationic polymerization and radical polymerization. The former cationic polymerization is a curing mechanism of epoxy resin, and the radical polymerization is methacryl,
Or it is a curing mechanism of an acrylic resin. Here, the epoxy resin, which is a cationic polymerization, is excellent in adhesiveness and constitutional properties, but has low reliability in liquid crystal since a photoinitiator of high cationic ionicity is used. Therefore,
It is difficult to use an ultraviolet-curable sealant containing an epoxy resin that is a cationic polymerization as a component. In contrast to this UV-curable epoxy resin, UV-curable methacrylic and acrylic resins are radical polymers, and the ionicity of the photoinitiator used is low, so that they can be used in the dropping method. Therefore, in general, methacryl or acrylic resin of this radical polymer is used as an ultraviolet-curable sealing material.

With respect to a method of manufacturing a liquid crystal panel, an orientation film made of a polyimide resin is formed on a substrate on which a pair of electrodes are formed, and the orientation direction of the liquid crystal is determined by rubbing the surface of the orientation film with a cloth called rubbing. Is performed. The ultraviolet-curable sealing material is formed on the substrate subjected to the orientation treatment in a predetermined pattern by screen printing and drawing application using a dispenser. Then, a spacer material for forming a gap between the substrates is arranged on the other substrate. As the spacer material, resin beads are mainly used, but recently, resin pillars formed on a substrate are also used. The two substrates are aligned and bonded, and pressure is applied until a predetermined gap is formed between the two substrates. After that, an area other than the seal portion is shielded from light, and only the seal portion is irradiated with ultraviolet rays to cure the seal. Unnecessary portions are cut off between the two substrates bonded together to form a liquid crystal cell. In addition,
Before bonding the substrates, the required amount of the liquid crystal material is dropped and supplied into the area surrounded by the sealing material, and the two substrates are set to 0.8 Ton.
A dropping method of performing alignment and bonding under a reduced pressure of rr or less is also well known as a method of manufacturing a liquid crystal cell.

[0006]

In the case where an ultraviolet-curable sealing material has been used, the sealing portion must be irradiated with ultraviolet light. Therefore, the electrode part is inevitably I
In the case of a substrate formed of a transparent electrode such as TO, or a substrate formed with a color filter, it was not possible unless the panel had a seal formed on the outer periphery of the black matrix. At present, demands on the market are increasing because liquid crystal panels on which TFTs are formed can be manufactured at low cost. Also, with the diversification of uses of liquid crystal panels on which the TFTs are formed, the frame of the peripheral portion is usually narrowed. Further, in STN, there is an increasing demand for a color reflective liquid crystal panel as a portable power saving liquid crystal panel.
Among these needs for liquid crystal panels, TFT and ST
In an N-color reflection type liquid crystal panel, the electrodes are formed of Al, which completely shields ultraviolet rays. In addition, with the colorization and narrowing of the frame, the position where the seal is formed will be on the black matrix of the color filter. In such a liquid crystal panel configuration, it is very difficult to cure the sealant with ultraviolet light.

In this case, the sealing material must be cured by irradiating ultraviolet rays to the sealing portion from the Al electrode side. At present, the width of the Al electrode is about 50 μm to 100 μm, and the space between the electrodes is about 5 μm to 20 μm. UV irradiation conditions for sufficiently polymerizing the sealing material even in the shadow of the wiring under such a pattern,
And a sealing material is required.

The present invention relates to a method of manufacturing a liquid crystal panel using an ultraviolet-curable sealing material capable of improving the bonding accuracy of a substrate and the productivity, and relates to a color TFT liquid crystal panel having a narrow frame and a reflective TFT. It is an object of the present invention to provide a method of manufacturing a liquid crystal panel that can support a color STN panel.

[0009]

In order to solve the above-mentioned problems, in the method of manufacturing a liquid crystal panel of the present invention, the temperature of the substrate when irradiating ultraviolet rays is adjusted, particularly in the step of curing the sealing material with ultraviolet rays. Can be achieved by At this time, the temperature of the substrate is appropriately selected from 40 ° C. to 80 ° C. In general, the higher the substrate temperature during ultraviolet irradiation, the more the polymerization of the seal is promoted. However, when adopting the dripping method, if the temperature at the time of UV irradiation is high, the display quality is degraded due to the elution of the sealing composition from the sealing material that is not sufficiently cured into the liquid crystal, and the yield due to the gap height and the breakage of the seal is reduced. A drop occurs.

In this case, the temperature of the substrate is increased with time, or the stage is divided into two stages, the first stage is irradiated with ultraviolet rays at a low temperature to the seal, and the second stage is irradiated with ultraviolet rays at a high temperature. This can be solved by adopting a method in which the seal is sufficiently cured.

As a method of adjusting the temperature of the substrate during the irradiation of the ultraviolet rays, any of a hot plate, circulation of warm air, and an increase in the temperature of the mask substrate due to absorption of the ultraviolet rays may be employed.

Next, with respect to the ultraviolet-curing sealing material used under the above conditions, the resin component is mainly made of either methacryl or acrylic resin. It is desirable to use a component obtained by appropriately mixing an epoxy acrylate oligomer and a viscosity adjusting monomer. A photoinitiator is appropriately added to the main material in a range of 1 wt% to 3 wt%. Also, a thioxanthone-based photoinitiator is appropriately blended within a range of 1 wt% to 3 wt%. Here, as a photoinitiator, acetophenone type, benzoin type,
Any one of benzophenone-based photoinitiators may be selected, but a benzoin-based photoinitiator is particularly desirable. In addition, as for the sealing material, it is desirable to appropriately mix a filler material for adjusting the viscosity and a silane coupling material for improving the adhesion to the substrate.

In the method of manufacturing a liquid crystal panel according to the present invention, in a step of irradiating an ultraviolet curable methacrylic or acrylic sealing material with an ultraviolet ray, the temperature of the substrate at the time of irradiating the ultraviolet ray is adjusted, whereby a TFT liquid crystal panel having a narrow frame design can be obtained. Even a liquid crystal panel such as a reflective color STN panel whose electrode component is formed of a light-shielding material such as Al can cure the sealant with ultraviolet light, and the production of the liquid crystal panel can be performed without imposing a large burden on future panel design. It becomes possible.

Here, the substrate temperature when irradiating the sealing material with ultraviolet rays may be arbitrarily selected within a range of 40 ° C. to 80 ° C. Usually, if only the ultraviolet curing of the sealing material is performed, the curing of the sealing material is further promoted by setting the temperature of the substrate high. However, when the dropping method is adopted, if the substrate temperature at the time of irradiating the sealing material with ultraviolet rays exceeds 80 ° C., the temperature becomes higher than the phase transition temperature of the liquid crystal, the liquid crystal becomes an isotropic phase, and the solubility of the sealing material component increases. In addition, since the volume of the liquid crystal increases, the height of the sealing material also changes. Therefore, the temperature of the substrate at the time of ultraviolet irradiation is 8
It is desirably 0 degrees or less.

The ultraviolet light used for curing the seal is 31.
There is a need to cut wavelengths below 0 nm. This is to prevent the liquid crystal from being damaged by ultraviolet rays. Therefore, the ultraviolet light used for curing the seal has a wavelength range of 310 nm to 400 nm and an illuminance of 10 mw / c.
m ² or more, an integrated light amount of 3000 mJ / cm ² or more is required. In this condition range, the illuminance is the largest 30.
mw / cm ² in achieving irradiation time the accumulated quantity of light 3000 mJ / cm ² at is 100 seconds. At this time, the keeping time of the set substrate temperature is a time obtained by subtracting the time required for the substrate to rise from 100 seconds. The substrate area is about 250
000 mm ² to about 640000 mm ² , and when the thickness of the substrate is about 1 mm to about 0.5 mm, it is required that the ^two substrates are stacked and the temperature of the substrate reaches 80 ° C. for about 10 seconds to about 2 seconds.
Since it takes only 0 seconds, it is possible to sufficiently irradiate ultraviolet rays at a predetermined temperature.

As described above, the ultraviolet curing method for a seal material according to the present invention has high alignment accuracy and allows the seal material to be sufficiently cured even when the electrode portion is shielded from light, so that a liquid crystal panel with high display quality can be produced. A method for manufacturing a liquid crystal panel can be provided.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a liquid crystal panel according to the present invention is characterized in that a sealing material for enclosing liquid crystal and bonding two substrates is an ultraviolet curing type, and this sealing material is heated simultaneously with irradiation of ultraviolet light. It is.

The composition of the ultraviolet-curable sealing material used here will be described. The main components are epoxy acrylate oligomer and trifunctional acrylate monomer, talc and silica fine powder as filler material, silane coupling agent,
A photoinitiator containing 1 to 3 wt% of a benzoin compound was used.

The substrate may have an area of about 250,000 mm ² to about 640000 mm ² and a thickness of the substrate in a range of about 1 mm to about 0.5 mm. In this embodiment, the size of the substrate is 550 mm × 670 mm and the thickness of the substrate is 0.7 mm.

Next, an ultraviolet irradiation method for curing the sealant will be described with reference to the drawings.

FIG. 1 is a schematic view of the ultraviolet irradiation apparatus adopted this time. The lamp 1-1 uses a high-pressure mercury lamp,
Cutting was performed by inserting a glass 1-2 that cuts a size of nm or less. The wavelength range of the lamp is 310 nm
Illuminance in the range from to 400 nm is from 10 to 13 mw / c
m ² . And the irradiation time is 10 minutes,
In other words, the irradiation energy is 6000 to 7800 mJ
cm ² . Further, a mask 1-3 was inserted between the lamp 1 and the substrate 1-4 so that the clearance was 1 mm so that ultraviolet rays were not irradiated to portions other than the seal portion. The material of the mask 1-3 used is Tempax glass, and there is almost no illuminance loss in the ultraviolet region. Then, a hot plate 1-5 for adjusting the temperature was provided below the substrate.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention and comparative examples will be described below with reference to the drawings.

FIG. 2 is a sectional view of the liquid crystal panel prepared this time. Of the pair of substrates, the substrate 2-1 on the side irradiated with Ueno ultraviolet rays is provided with a multilayer Cr layer 2-2 in a slit shape. The lower substrate 2-3 has this multilayer C
r2-2 is not formed. A total of six types of slit patterns were prepared, two types of light shielding portions of 40 μm and 50 μm, and three types of space portions of 5 μm, 10 μm and 20 μm. Then, a transparent electrode 2-4 made of ITO is provided so as to face the upper and lower substrates. Then, a polyimide alignment film 2-5 on this electrode is formed. The alignment film 2-5 is subjected to an alignment process by rubbing so that the twist angle of the liquid crystal 2-6 becomes 90 degrees.
Further, spacer resin beads 2-7 for forming a gap between the two substrates are arranged. This time, the beads 2-7 have a particle size of 4.5 μm and a density of 100 beads / mm.
Arranged to be ² . Then, the liquid crystal 2-6 is sealed and 2
An acrylic UV-curable sealing material 2-8 for bonding two substrates is provided below the multilayer Cr.

Next, the evaluation result of the liquid crystal panel is shown in FIG. As the evaluation items, the width of the abnormal orientation of the sealing material and the voltage holding ratio representing the voltage holding of the liquid crystal when a pulse wave of 5 V and 30 Hz was applied to the liquid crystal were adopted.

First, as a conventional example 1, an epoxy thermosetting sealing material ("Stract Bond XN-21-S" manufactured by Mitsui Toatsu Chemicals, Inc.) was used. Using a material, the results are shown for the case where the temperature of the substrate during ultraviolet irradiation is 25 ° C., the temperature of the substrate is 40 ° C. for Example 1, 60 ° C. for Example 2, and 80 ° C. for Example 3. Set the temperature of the hot plate to the desired temperature and left it there, so the substrate was about 5 seconds at 40 ° C and about 10 seconds at 60 ° C.
Seconds, reaching 80 ° C. in about 15 seconds. Here, the holding time at the predetermined temperature is sufficiently equivalent.

From these results, in Comparative Example 1, the width of the abnormal orientation of the sealing material was 0.5 mm or more, and the voltage holding ratio was about 90%, which is lower than the conventional example. In particular, regarding the width of the orientation abnormality of the seal material, the active distance from the seal is reduced due to the liquid crystal panel configuration. If this distance is the shortest, it is about 0.1 mm. This is because a dummy pattern of a color filter is required, and the width is required to be about 0.1 mm. Therefore, the abnormal orientation width of the sealing material needs to be less than 0.1 mm. Next, with respect to the holding ratio, although the degree varies depending on the configuration of the liquid crystal panel, when the voltage holding ratio is 90% or less, display quality such as in-plane burn-in and flicker is adversely affected. Therefore, the voltage holding ratio needs to be 90% or more. Also, there is no problem with regard to in-plane luminance unevenness as long as it is 90% or more.

FIG. 3 shows the results of analysis by Raman spectroscopy on the degree of polymerization of the sealing material under the slit of the electrode with respect to each temperature at the time of ultraviolet irradiation. The method of calculating the degree of polymerization by Raman spectroscopy is based on “C
Assuming that the difference between the absorption of the “C = C” bonding portion and the absorption of the “C = C” bonding portion of the sealing material when the temperature at the time of ultraviolet irradiation is 80 ° C. and the irradiation energy is 6000 mJ / cm ² ,
The percentage of absorption at the "C = C" bonded portion of the seal material at each position was expressed as a percentage.

From this result, it can be seen that the part shaded by the wiring has a degree of polymerization of the seal of 20 compared to the space part.
%, But does not largely depend on the distance. However, although the degree of polymerization of the sealing material in the space decreases with respect to the temperature at the time of irradiation, the difference in the degree of polymerization of the sealing material between the wiring shadow and the space is not significantly affected. From the evaluation of the actual panel in Table 1, the degree of polymerization obtained by Raman spectroscopy shows that there is no problem in use if the polymerization degree is 60% or more.

Next, Table 2 shows that the illuminance of the ultraviolet lamp is 30 m.
The results of the abnormal orientation of the sealing material and the voltage holding ratio in the case of v / cm ² are shown. Here, the irradiation time was 200 seconds at a substrate temperature of 40 ° C. as Example 3 and Example 4, the irradiation time was 600 seconds at a substrate temperature of 40 ° C. as Example 5, and the irradiation time was 80 ° C. at Example 6 The results when the irradiation time is 200 seconds and the irradiation time is 600 seconds at 80 ° C. as Example 7 are shown. In addition, the irradiation time at 25 ° C. is 200 seconds as Comparative Example 2, and the irradiation time is 600 seconds at 25 ° C. as Comparative Example 3. Here, when the irradiation time is 200 seconds, the irradiation energy is 6000 mJ /
cm, 600 seconds, 18000 mJ / cm ² .

From this result, even when the substrate temperature is 40 ° C. for 200 seconds, there is no problem in the peripheral orientation state. However, when the substrate temperature is 25 ° C., if the irradiation time is long, some effects can be obtained, but the quality is not merely satisfied. Therefore, the temperature of the substrate at the time of ultraviolet irradiation has a great influence on the curing of the sealing material.

Further, when a liquid crystal panel is prepared by the dropping method, a problem when raising the substrate temperature during irradiation with ultraviolet rays is that the sealing material is brought into contact with a high-temperature liquid crystal in an insufficiently cured state. Therefore, Table 3 shows the results of the orientation of the sealing material of the liquid crystal panel and the voltage holding ratio when the temperature of the substrate is increased and the substrate is left at the time of ultraviolet irradiation. At this time, the conditions at the time of ultraviolet irradiation are as follows: the substrate temperature is 80 ° C., the illuminance of the ultraviolet lamp is 10 mw / cm ² , and the irradiation time is 60 minutes.
Performed at 0 seconds. In Example 8, the standing time from bonding of the substrate to the irradiation of the ultraviolet rays was 1 minute at room temperature. In Example 9, the leaving time was 2 minutes at room temperature. In Example 10, the substrate temperature was 40 ° C.
In Example 11, the substrate temperature was 60 ° C. for 1 minute. In Example 12, the substrate temperature was 80 ° C. for 1 minute. In Comparative Example 4, the substrate temperature was 100 ° C. for 1 minute. Since the actual temperature rise of the substrate is 80 ° C. and about 15 seconds from room temperature, one minute is a sufficiently long time.

As can be seen from Table 3, even in the dropping method, the display quality is not affected if the substrate temperature at the time of ultraviolet irradiation is up to 80 ° C. However, when the substrate temperature is 100 ° C., the width of the orientation abnormality in the sealing material is as poor as 0.5 mm. This is considered to be because the phase transition temperature of the liquid crystal material is 85 ° C., and at 100 ° C., the liquid crystal material becomes an isotropic phase to enhance the solubility of the sealing material. Since the phase transition temperature does not become lower than 80 ° C. in an actual liquid crystal material, sufficient curing of the sealing material can be obtained without any problem if the temperature of the substrate at the time of ultraviolet irradiation is up to 80 ° C. even in the case of the dropping method.

As described above, even in a liquid crystal panel having a wiring shadow on an electrode portion, the temperature of the substrate is set to 80 ° C. and the illuminance is set to 10 to 30 mw / cm.
^{2. If} the irradiation energy is 6000 mJ / cm ² or more, a liquid crystal panel having good display quality can be provided.

At this time, the UV-curable sealing material is mainly composed of methacrylic or acrylic resin, and acetophenone, benzophenone, or benzoin-based photoinitiator is compounded in a range of 1 wt% to 3 wt%. ,
It is necessary to use a thioxanthone-based photoinitiator in a range of 1% by weight or more and 3% by weight or less, and a filler for viscosity adjustment and a silane-based coupling agent.

Further, in the present embodiment, the wiring width of the electrode was examined up to 50 μm. However, from the result of Raman spectroscopy, it is possible to use even when the electrode width is 100 μm. There is no problem if the slit width is 5 μm or more.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

As described above, the present invention relates to a method of manufacturing a liquid crystal panel using a UV-curable sealing material capable of improving the bonding accuracy of a substrate and the productivity, and relates to a method for manufacturing a narrow frame. It is possible to provide a method of manufacturing a liquid crystal panel that can correspond to a color TFT liquid crystal panel or a reflection type color STN panel.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an ultraviolet irradiation method according to the present invention.

FIG. 2 is a sectional view of a liquid crystal panel used in the present embodiment.

FIG. 3 is a graph showing the degree of polymerization of a sealing material at the shadow of an electrode in Raman spectroscopy.

[Explanation of symbols]

 1-1 High-pressure mercury lamp 1-2 Glass that cuts a wavelength of 310 nm or less 1-3 Light-shielding mask 1-4 Liquid crystal panel 1-5 Hot plate 2-1 Substrate with multilayer Cr slit 2-2 Multilayer Cr slit 2-3 Substrate 2-4 Transparent electrode 2-5 Alignment film 2-6 Liquid crystal 2-7 Resin beads 2-8 Acrylic UV curable sealing material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Matsukawa 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H089 MA04Y MA05Y NA22 NA24 NA37 NA44 QA12 RA10 TA01 TA09 TA12 TA13 TA17 2H091 FA02Y FA14Z FA34Y HA10 LA12 5G435 AA17 BB12 CC09 CC12 EE09 KK02 KK05 KK10

Claims (4)

[Claims] 1. A method of manufacturing a liquid crystal panel, wherein at least one of the electrodes of the substrate is formed of a material having a light-shielding property, and the other substrate is provided with a color filter and a black matrix. A step of bonding two substrates to each other to form an ultraviolet-curable sealing material for enclosing liquid crystal, and after positioning the substrate facing the sealing material and two substrates, Bonding the substrates, pressing the bonded substrates so as to have a predetermined gap, and shielding the portions other than the seal portion from light, and adjusting the substrate temperature within a temperature range of 40 ° C. or more and 80 ° C. or less. A method for manufacturing a liquid crystal panel, comprising: a step of irradiating an ultraviolet ray to a seal portion; and a step of forming a liquid crystal cell by cutting while leaving a necessary terminal portion. 2. The method for manufacturing a liquid crystal panel according to claim 1, wherein a step of supplying liquid crystal dropwise is performed between the step of forming the sealing material and the step of bonding the two substrates. A method for manufacturing a liquid crystal panel, comprising: 3. The ultraviolet-curable sealing material is composed of methacrylic or acrylic resin, and the photoinitiator component is any one of acetophenone-based, benzoin-based, and benzophenone-based. Is 1wt
The method according to claim 1, wherein the photoinitiator is a thioxanthone-based photoinitiator and the compounding ratio thereof is 1 wt% or more and 3 wt% or less. 4. Wherein the effective wavelength region of ultraviolet to be irradiated to the sealing is at 400nm inclusive 310 nm, illuminance at said wavelength range at ^{10mw / cm 2, 30mw / cm} 2 or less, integrated light quantity 3000 mJ / cm ² or more 10,000m
4. The method for manufacturing a liquid crystal panel according to claim 1, wherein J / cm ² is J / cm ² .