JP2001083531A - Sealant composition for liquid crystal display device and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain complete hardening of the sealant for adhesion of substrates with only ultraviolet rays irradiation or only with heating and to solve problems caused by defective adhesion of the sealant by using the specified sealant composition. SOLUTION: The sealant composition contains an ultraviolet ray setting acrylic resin composition comprising a photo radical initiator and an acrylate ester resin, an ultraviolet ray setting epoxy resin composition comprising a photo cationic initiator and an epoxy resin, an organic peroxide and talc particles in a hybrid state in which atoms on the surface of the talc particle are bonded with an epoxy compound in the molecular level so as to make the surface of the talc particle be covered with the epoxy compound and is provided with binary ultraviolet ray setting and thermosetting property. In this case the added amount of the talc particles in the hybrid state is preferably 10-70 wt.% in the binary setting sealant. Also for the purpose of improving the adhesive property of the binary setting sealant an epoxy acrylate is preferably used as the acrylate ester resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition which is completely cured by ultraviolet rays and completely cured by heating.
1. Field of the Invention The present invention relates to a primary curable sealant composition for a liquid crystal display device, and a liquid crystal display device which prevents deterioration of the adhesive strength of a sealant by bonding a pair of substrates using the sealant.

[0002]

2. Description of the Related Art In a liquid crystal display device using a TN (Twisted Nematic) liquid crystal, techniques for improving the viewing angle and the aperture ratio have been actively researched and developed.

For example, an active matrix type liquid crystal display device (hereinafter, referred to as an “IPS panel”) using a horizontal electric field parallel to a substrate for widening the field of view has been proposed. A liquid crystal display device (hereinafter referred to as a “transmissive pixel flat panel”) provided on a driving element
Has been proposed.

Each of these liquid crystal display devices has a 1 μm
In addition to having an organic film with a thickness of about or greater than that, in the case of large-sized liquid crystal displays such as liquid crystal displays for notebook PCs and monitors, UV-curable A sealant composition composed of two components, a resin and a thermosetting resin, is used. UV curable resin and heat curable resin 2
A method of manufacturing a liquid crystal display device by bonding and sealing two substrates by ultraviolet irradiation and heating with a sealant composition composed of components is disclosed in, for example, JP-A-53-22753.
JP-A-55-41488, JP-A-55-41488,
No. 105124. Also, the organic layer,
Bonding and sealing a substrate covered with a ceramic layer or a chrome layer with a UV-curable sealant composition,
JP-A-5-127175, JP-A-8-23421
No. 4, JP-A-10-96936.

[0005]

The problems of the prior art will be described below using an IPS panel as an example.

FIG. 14 is a cross-sectional view of an IPS panel using a thermosetting epoxy sealant for bonding substrates. Horizontal direction (parallel to glass substrate) on glass substrate 101
A switching element 102 for generating an electric field and an alignment control film 103 for controlling an alignment direction of liquid crystal molecules are formed. In addition, the glass substrate 10 facing the glass substrate 101
Reference numeral 4 denotes a black mask 105 made of a chromium material, a color filter 106, an overcoat film 107 made of an acrylic material and functioning as a protective film, and an orientation control film 1.
08 is formed. The glass substrate 101 and the glass substrate 104 are bonded to each other with a thermosetting epoxy sealant 109 with a gap of about 4 μm, and the gap is filled with liquid crystal. The mixed spacer 110 inside the thermosetting epoxy sealant 109 is used.
And the diameter of the spacer 111 in the display area are adjusted so that the gap amount between the substrates 101 and 104 can be made substantially equal.

[0007] In the process of manufacturing such an IPS panel, the peeling failure frequently occurred between the glass substrate 101 and the glass substrate 104. The inventor of the present application analyzed the cause of the peeling and found the phenomenon shown in FIG. Predicted. Specifically, in the manufacturing process of the IPS panel, there is a process of applying a force in the direction of arrow J shown in FIG. 15 to the device driving terminal around the glass substrate 101, and peeling occurs in this process. It is thought that there is. Then, the separated I
Observation of the PS panel revealed that the surface of the peeled portion 113 occurred at the interface between the overcoat film 107 and the black mask 105.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. A first object of the present invention is to completely remove the substrate by using only ultraviolet light in order to eliminate the peeling of the substrate which occurs during the manufacturing process of the liquid crystal display device. The present invention is intended to obtain a dual-curable sealant composition for a liquid crystal display device that cures completely and is completely cured only by heating.

A second object of the present invention is to use the above-mentioned sealant composition to completely cure the sealant for bonding the substrate by only ultraviolet rays or only by heating, thereby preventing poor adhesion of the sealant. It is another object of the present invention to provide a liquid crystal display device in which the problem caused by the liquid crystal display device is eliminated.

[0010]

Means for Solving the Problems A sealant composition for a liquid crystal display device, which is one of the inventions of the present application, comprises (1) an ultraviolet curable acrylic resin composition comprising a photoradical initiator and an acrylate resin. (2) an ultraviolet curable epoxy resin composition comprising a photocationic initiator and an epoxy resin, (3) an organic peroxide, and (4) atoms on the surface of the talc particles are bonded to the epoxy compound at a molecular level. And talc particles in a hybrid state whose surface is covered with an epoxy compound, and has dual curability of ultraviolet light and heating.

A liquid crystal display device according to another invention of the present application is a light-shielding wiring terminal group including a plurality of wiring terminals provided on a peripheral portion of a first glass substrate, and straddles the surface of the first glass substrate. Formed on the wiring terminal group as described above and having both ultraviolet curability and heat curability, a second glass substrate facing the first glass substrate via the sealant, a second glass substrate, What is claimed is: 1. A liquid crystal display device comprising a light-shielding film disposed between a glass substrate and a sealant for shielding the entire surface of the sealant from light, wherein the sealant composition comprises (1) a photoradical initiator and an acrylate resin. An ultraviolet-curable acrylic resin composition, (2) an ultraviolet-curable epoxy resin composition comprising a photocationic initiator and an epoxy resin,
It is characterized by containing (3) an organic peroxide and (4) hybrid talc particles whose surface is covered with an epoxy compound.

Here, an organic film may be provided between the light shielding film and the sealant or between the wiring terminal group and the sealant.

The material of the wiring terminal group is, for example, chromium metal or aluminum metal.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (Understanding Problems of Thermosetting Sealant) Numerical calculation (simulation) of a residual stress between a sealant and a substrate generated in a curing process of a sealant was performed. FIG. 1 shows a numerical calculation model. In order to reduce the calculation load, a two-dimensional simplified model was adopted in which a gap of about 4 μm was formed between the pair of glass substrates 1 and 2 facing each other, and the sealant 3 was interposed in the gap. The physical property data of the glass substrates 1 and 2 used in the calculation include a longitudinal elastic modulus (7450 kgf / mm
² ) The linear expansion coefficient (48 × 10 ⁻⁷ / ° C.) and the thickness of the substrate (1.1 mm) are adopted.

The longitudinal elastic modulus, linear expansion coefficient and thickness of the glass substrates 1 and 2 are Eg, αg and hg, respectively.
Are Es, α, respectively.
Assuming that s and hs, and the difference between the temperature at the time of curing the sealant 3 and the room temperature is Δt, the theoretical formula for calculating the residual stress is as follows. In the case of curing the sealant 3 s = 2 (αg−αs) Δt · hg · Es · Eg / (2Eg · hg + Es · hs) Equation (1) After the sealant 3 is cured, return to room temperature (cooling) Case σs = 2 (αg−αs) (− Δt) · hg · Es · Eg / (2Eg · hg + Es · hs) Equation (2)

Here, the curing process of the thermosetting sealant and the ultraviolet curable sealant will be described with reference to Table 1.

[0017]

[Table 1]

First, the curing process of a thermosetting epoxy sealant is roughly classified into the following steps.

(Step 1): A step of applying pressure and heat in order to obtain a predetermined thickness of the sealant (described in Table 1 as “this cure”).

(Step 2): A step of applying heat to the sealant for a time during which the thickness of the sealant does not change even after the pressure load is released (generally referred to as “tack-free”). ").

(Step 3): After releasing the pressure, a step of applying heat to completely cure the material (in Table 1,
Described as "After Cure").

On the other hand, the curing process of the ultraviolet-curable sealant is roughly classified into the following steps.

(Step 1): UV irradiation (6000 mJ /
cm ² ) about 80% of the material is cured and tack free.

(Step 2): After Cure (120 ° C.)
Completely curing the material.

When the residual stress in the sealant is calculated based on the above-described curing process, the total residual stress value (about 1.22 kgf / mm ² ) of the thermosetting sealant is calculated as follows. Total residual stress value (−0.018
kgf / mm ² ).
Therefore, in the case of a thermosetting sealant, compared to an ultraviolet-curable sealant, the residual stress generated in the sealant during the curing process increases, and there is a concern that the adhesiveness of the sealant may be adversely affected. The present inventor has considered.

The above calculation results are considered to be appropriate based on the following considerations.

In the case of a thermosetting epoxy sealant (FIG. 2), if the temperature of the sealant 3 does not reach 150.degree.
Since the curing of the sealing agent 3 is not promoted, the sealing agent 3 adhered to the glass substrates 1 and 2 follows the distortion (extension) of the glass substrates 1 and 2 until the temperature of the sealing agent 3 reaches this temperature. It can be freely deformed (FIG. 2A). In such a state, since both the glass substrates 1 and 2 and the sealant 3 can be freely deformed, no stress energy is stored inside the glass substrates 1 and 2 or inside the sealant 3. However, once the curing of the thermosetting sealing agent 3 is completed at a temperature of 150 ° C. of the sealing agent 3, the sealing agent 3 is solidified, and the sealing agent 3 and the glass substrates 1 and 2 are bonded. (FIG. 2B). Therefore, when the glass substrates 1 and 2 are returned to room temperature, the degree of shrinkage of the glass substrates 1 and 2 and the degree of shrinkage of the sealing agent 3 are different due to the difference in the coefficient of thermal expansion between the two, so that they are bonded and fixed to each other. A stress (stress in the width direction of the sealing agent 3) is generated between the sealing agent 3 and the glass substrates 1 and 2. It is considered that this stress is stored in the sealant 3 and the insides 1 and 2 of the glass substrate as residual stress (FIG. 2).
(C)). The arrows in the figure indicate the direction of the force received by each unit.

On the other hand, in the case of an ultraviolet-curable sealant (FIG. 3), about 80% of the sealant 3 is cured by ultraviolet irradiation before the sealant 3 is heated (FIG. 3).
(A)). Thereby, after ultraviolet irradiation, the sealant 3
Is solidified to some extent, and the glass substrate is adhered to the sealant 3 (FIG. 3B). Therefore, even if the glass substrates 1 and 2 are subsequently heated and cooled, the expansion and contraction of the sealant 3 at least in the portion where the sealant 3 is applied follows the expansion and cooling of the glass substrates 1 and 2. This means
Even if the glass substrates 1 and 2 are heated and cooled, if the temperature of the glass substrates 1 and 2 is finally set to the initial temperature, the bonding state between the glass substrates 1 and 2 and the sealant 3 is changed to the initial state before heating. Because there is no factor that causes stress between the two,
It is considered that the residual stress is not preserved inside the glass substrates 1 and 2 and inside the sealant 3 (FIG. 3C).

(Grasp of Problems of Ultraviolet Curable Sealant)
As described above, the use of an ultraviolet-curable sealant can significantly reduce the residual stress generated during the curing process, and therefore should improve the peeling failure of the liquid crystal display device. Thought.

However, when a commercially available ultraviolet curable sealant was used, the following problems became apparent.

In a notebook-type personal computer, there is a demand for narrowing the width of a frame that does not contribute to display around the display section (this is referred to as narrowing of the frame). A design was made in which the ultraviolet-curable sealant 3 was arranged on the wiring terminals 6 and below the peripheral black mask 5 of the color filter substrate (see FIG. 4). Therefore, on the color filter substrate side,
Since the entire surface of the ultraviolet curable sealant is shielded from light by the black mask 5 made of chromium (Cr) or aluminum (Al) metal, it is necessary to irradiate light from the TFT substrate side to cure the ultraviolet curable sealant 3. . However, on the other hand, since the wiring terminals 6 formed on the TFT substrate also have a light shielding function,
Light irradiation is not performed on the sealant formed on the wiring terminal 6.

This problem will be described in more detail with reference to a sectional perspective view (FIG. 5) of a portion taken along line VV shown in FIG. In order to supply a voltage, a wiring terminal group including a plurality of wiring terminals 6 is provided. The material of the wiring terminal group is a metal thin film of chromium (Cr) or aluminum (Al), which has a light shielding property. Have. Although a commercially available UV-curable sealant has a certain degree of heat-curing action, if this sealant 3
Is not completely cured only by heating, the wiring terminals 6
As for the sealant 3 provided above, the photocuring is not promoted because the light is not irradiated, and the promotion of thermal curing cannot be expected. This not only causes poor adhesion of the substrate, but also causes problems such as liquid crystal material contamination and alignment film contamination due to dissolution of the uncured sealant 3 in the liquid crystal. Therefore, it was concluded that a dual-curable sealant that can be completely cured only by ultraviolet irradiation and completely cured only by heating should be developed. In FIG. 5, the sealant 3
An organic film 7 is provided between the black mask 5 and the organic film 7.

The feature of the dual-curable sealant of the present invention is to solve this problem, the organic peroxide in the sealant composition generates radicals by heating to generate cations of the photocationic initiator. And accelerates heat curing of the epoxy compound. Hereinafter, the configuration and physical properties will be described in detail.

(Constitution and Physical Properties of Dual Curable Sealant) Hybrid talc particles in which atoms on the surface of talc particles are bonded to an epoxy compound at the molecular level and the surface is covered with the epoxy compound, JP-A-10-95
The talc surface is activated by applying physical energy to the talc surface by a mechanochemical method disclosed in Japanese Patent No. 901 (eg, heat treatment, stirring treatment, ball mill treatment, shredder treatment, ultrasonic treatment), and strongly bonded. Refers to particles coated with the epoxy compound. Preferred examples include trade names of Epikote 828 (Yukai Shell Co., Ltd.), Epikote 807 (Yukai Shell Co., Ltd.), H
A hybridized product of an epoxy compound such as BE100 (Shin Nippon Rika Co., Ltd.) and talc particles can be used.

By using such talc particles in a hybrid state in which the talc particles are covered with an epoxy compound, the dual-curable sealant of the present invention has flexibility and toughness and a small compression set. Further, since the surface of the talc particles is covered with a non-hydrophilic epoxy compound, the water resistance and moisture resistance of the binary curable sealant are dramatically improved. Furthermore, since the surface is not modified with a silane coupling agent or the like unlike the conventional filler, display defects caused by elution of the silane coupling agent or the like and contamination of the liquid crystal material are not caused. The added amount of the talc particles in the hybrid state is preferably 10 to 70% by weight in the binary curable sealant. If the amount is less than 10% by weight, the above-mentioned properties such as toughness cannot be imparted to the sealing agent. If the amount exceeds 70% by weight, the viscosity of the sealing agent becomes high, and it becomes difficult to apply the sealing agent to a thin line. is there.

The UV-curable acrylic resin composition may be any known UV-curable composition containing an acrylate resin and a photoradical initiator. Such a composition is described in detail, for example, in the above-mentioned JP-A-55-41488. In the present invention, the raw material or composition of the ultraviolet-curable acrylic resin composition is not particularly limited, but preferred acrylate resins include epoxy acrylates having a chemical structure having a hydroxy group in the molecule. This is because epoxy acrylate generally has higher adhesive strength than other acrylate resins.

The UV-curable epoxy resin composition may be any known UV-curable epoxy resin composition containing a compound having an epoxy group and a photocationic initiator represented by an onium salt or the like. Such a composition is described in JP-A-61-233719 and JP-A-61-510.
No. 24 discloses this in detail. In the present invention, the raw material or composition of the ultraviolet-curable epoxy resin composition is not particularly limited. Preferred onium salts include diazonium salts, iodonium salts, sulfonium salts and the like, and it can be said that onium salts that are compatible with the epoxy compound used are preferred. The mixing ratio between the ultraviolet-curable epoxy resin composition and the ultraviolet-curable acrylic resin composition is preferably from 6: 4 to 8.5: 1.5. This is because the physical properties of the sealing layer described later can be obtained in such a range of the mixing ratio.

The organic peroxide may be any known organic peroxide, and the present invention is not limited to a specific organic peroxide. In the dual-curable sealant of the present invention, this organic peroxide exhibits a unique action and effect.

Organic peroxides are generally considered as initiators of radical polymerization, and can be used for heat curing of acrylic resin compositions, but have not been used for heat curing of epoxy resin compositions. However, it has been found that the organic peroxide has an effect of lowering the curing temperature and increasing the curing speed of the ultraviolet-curable epoxy resin composition in the heating step after the irradiation of ultraviolet rays. This effect is presumed to be because the radical of the organic peroxide has some effect on the cation generation of the onium salt. The amount of organic peroxide added is
0.1 to 10% by weight in the sealant composition is preferred. 0.
If the amount is less than 1% by weight, the cation formation of the above-mentioned onium salt is not promoted, and if it exceeds 10% by weight, the storage stability of the sealant composition is impaired.

The dual-curing sealant having the above-described composition has a larger amount of UV-irradiation than a conventional UV-curable acrylic resin composition and a heat-curable epoxy resin composition. It can be completely cured, and can be completely cured only by heating. Even if there is a shaded portion through which ultraviolet light does not pass, the sealant can be completely and completely cured in a short time at a low heating temperature, and there is no fear that uncured components are eluted into the liquid crystal material. Furthermore, the cured seal layer is a tough elastic body, has a high peel strength, has a small compression set, and has a high water resistance, and thus exhibits excellent durability.

The physical properties of the dual-curing sealant were as follows: 1) The viscosity at 25 ° C. before curing was 50,000 to 80,000.
00mPa · s 2) The thixotropic property before curing is from 1.5 to 1.5 in a viscosity ratio at a rotation speed of 1 rpm and a rotation speed of 10 rpm of a rotational viscosity type.
3.0 3) Volume shrinkage at the time of curing is 3% or less 4) Curing temperature is low and curing time is shortened 5) Young's modulus after curing is adjusted to be 1000 to 3000 MPa.

In order to make the physical properties of the dual-curable sealant as described above, the dual-curable sealant is composed of a mixed system of an ultraviolet-curable acrylic resin composition and an ultraviolet-curable epoxy resin composition, and the mixing ratio is 6: 4. ８8.5: 1.5. It is preferable to use epoxy acrylate as the acrylate resin in order to increase the adhesive strength of the binary curable sealant. In addition, the composition was made ultraviolet curable to obtain a low curing temperature and a high curing rate, and the curability was further improved by adding an organic peroxide as described above.

Table 2 shows a formulation example of the binary curable sealant composition of the present invention.

[0044]

[Table 2]

(Results of Strength Test of Dual-Curable Sealant) FIG.
3 shows the strength test results of the original curable sealant. In the figure, A indicates the dual-curing sealant of the present invention, B indicates the conventional UV-curable sealant 1, and C indicates the fracture toughness of the conventional UV-curable sealant 2. As is clear from FIG. 6, the fracture toughness value of the strength of the dual-curable sealant is higher than that of the conventional ultraviolet-curable sealant, and the difference in the fracture toughness value between the two over time increases. It is getting bigger. The strength test was performed under conditions having a large effect on the degree of adhesion, specifically, under high-temperature and high-humidity environmental conditions of a temperature of 60 ° C. and a humidity of 90% RH (hereinafter referred to as “moisture resistance test”). The test sample was manufactured by curing the sealant between a pair of glass substrates of the liquid crystal display device. FIG.
The horizontal axis indicates the elapsed time (time from the time of curing and bonding of the substrate), and the vertical axis indicates the fracture toughness value after the high-temperature and high-humidity treatment (hereinafter, referred to as “moisture resistance”).

The dual-curing sealant has a high moisture resistance in the initial state (a state where the elapsed time is zero), and does not deteriorate with time. In comparison,
Although the conventional ultraviolet-curable sealant has a high moisture resistance in the initial state, the moisture resistance deteriorates with time. For example, the moisture resistance of each of the two types of UV-curable sealants after 500 hours,
It was about 1/5 of the moisture resistance strength in the initial state. If there is no moisture resistance of about 0.15 kgf / mm ^2/3 or more,
Despite hindering the production yield of liquid crystal display devices and the reliability of products, it is difficult for conventional UV-curable sealants to satisfy this condition.

From the above strength test results, it was clarified that the dual curable sealant of the present invention can improve the moisture resistance of the liquid crystal display device.

Embodiment 2 A method for testing the strength of a liquid crystal display device will be described with reference to FIGS.

FIG. 7 is a conceptual diagram for explaining that a sample for a strength test is cut from a liquid crystal display device. As shown in FIG. 7, a rectangular sample 8 is cut from the edge of the substrate of the liquid crystal display device 4. Regarding the size of this sample 8,
Its length in the longitudinal direction is 100 mm and its length in the width direction is 25 m
m and thickness were unified to 10 mm. The sample 8 is fixed to an aluminum jig 18 as shown in FIG.
The aluminum jig 18 is pulled in a direction in which the substrates are peeled from each other (the direction of the arrow in the figure).

The conditions of this tensile test are a test temperature (environmental temperature) of 25 ° C. and a tensile speed of 1 mm / min.

This test method is based on a DCB (Double Cantilever Beam) test widely used in the field of fracture mechanics. Considering the configuration of the liquid crystal display device,
Since the thickness of the glass substrate is sufficiently large with respect to the gap between the substrates, it is considered possible to evaluate the gap between the substrates as a kind of crack, and the fracture toughness (Fracture Toughness) is used as a parameter for evaluating the crack. It was used. The fracture toughness value is derived by stress calculation using the breaking strength (actually measured value) obtained from this strength test.

According to this test method, the strength of the liquid crystal display device can be quantified and the strength evaluation can be made objective.

Note that the measured value of the DCB test and the observation of the destruction state of the liquid crystal display device indicate that the measured value of the DCB test is equal to 0.
When it is 15 kgf / mm ^2/3 or more, it has been found that there is no practical problem in the manufacturing process and the product.

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific example of a strength test will be described below with reference to the drawings.

1. Configuration of Liquid Crystal Display Device FIG. 9 is a cross-sectional view of an IPS panel in which an organic film is provided on a color filter substrate, and FIG. 10 is a cross-sectional view of a pixel flat panel in which an organic film is provided on a TFT substrate.

First, the configuration of the IPS panel shown in FIG. 9 will be described.

FIG. 9 is a sectional view of an IPS panel for applying an electric field in a parallel direction (lateral direction) to a substrate.

In the glass substrate 1, a switching element 9 for generating a lateral electric field is formed on the substrate 1,
An alignment control film 10 is formed on the element 9. On the other hand, on the glass substrate 2 facing the glass substrate 1 via the liquid crystal (not shown), the black mask 11
And a color filter 12, and an overcoat film 13 is provided so as to cover the black mask 11 and the color filter 12. Then, similarly to the substrate 1, the orientation control film 10 is formed on the switching element 9 of the substrate 2. Here, as the material of the black mask 11, for example, a metal film having a light shielding property or a pigment having a light shielding property is used. As a material of the overcoat film 13, for example, an organic film such as an acrylic resin or an epoxy resin that is cured by heat or light is used.

The substrates 1 and 2 are mutually about 4-5 μm.
They are arranged facing each other with a gap of m maintained. The amount of this gap is uniquely determined by the diameter of the in-display spacer 14 arranged in the display area and the diameter of the in-seal spacer 15 arranged inside the sealant 3 around the substrates 1 and 2. . Here, the material of the sealant 3 is a thermosetting sealant or the above-mentioned dual-curable sealant of the present invention, and is formed by applying this in a ring shape on the substrate 1 by a screen printing method or a dispenser method. I do. After that, the substrate 1 and the substrate 2 are held while maintaining a gap of about 4 μm,
After the sealant 3 is cured, liquid crystal is injected into the gap region to complete the liquid crystal display.

Next, the configuration of the pixel flat panel shown in FIG. 10 will be described.

FIG. 10 is a sectional view of a pixel flat panel in which pixel electrodes are flattened by an organic film. However,
Descriptions of portions having the same configuration as the liquid crystal display device of FIG. 9 are omitted.

In order to flatten an ITO film (not shown) functioning as a transparent pixel electrode, a pixel flattening film 16 having a thickness of about 10 μm is formed on the substrate 1. As a material of the pixel flattening film 16, for example, an organic film such as a photosensitive acrylic resin is used. In order to generate a vertical electric field in the substrate 1, an ITO film (not shown) is provided on the pixel flattening film 16 on the substrate 1 side.
An ITO film 17 is also provided on the substrate 2 side. And
Since the ITO film 17 also has a function as a protective film, it is not necessary to separately form an overcoat film on the substrate 2. That is, the sealing agent 3 is the black mask 1
In direct contact with 1.

2. Sample measurement Regarding the IPS panel and the pixel flat panel,
The fracture toughness value of the liquid crystal display device was measured using the primary curable sealant. Further, in order to compare with the technical effect of the dual-curable sealant, a measured value of a fracture toughness value of a liquid crystal display device using a thermosetting sealant (for example, an epoxy-based sealant) is also shown. Table 1 shows the physical property values and curing conditions of each of the dual-curing sealant and the thermosetting sealant. Specifically, in the curing of the thermosetting sealant, after the main curing at 150 ° C. for 10 minutes,
After-cure at 150 ° C. for 60 minutes. In the curing of the binary curable sealant, after-curing is performed at 120 ° C. for 60 minutes after irradiating 6000 mJ / cm ² with ultraviolet rays.

FIG. 11 shows the measurement results of the fracture toughness value of the liquid crystal display device. In the fracture toughness value data shown in FIG. 11, ten IPS panels and ten pixel flattened panels are prepared, and a predetermined rectangular shape (length in the longitudinal direction is 100 mm and length in the width direction is defined from the ends of these panels). (25 mm, thickness 10 mm) A sample was cut out, and the results of measuring the strength of each of the 10 cut samples were compared with the average value and the minimum value of the data.

In the figure, D indicates the average value, E indicates the minimum value, and F to
I shows the case of the combination of the panel structure and the sealant.
F and G are the IPS panel shown in FIG. 9, H and I are the pixel flattening panels shown in FIG. 10, F and H are thermosetting sealing materials,
G and I show the combination of the binary hardening type sealant.

3. Evaluation of Measurement Results Based on the measurement results, the following results (1) to (4) could be obtained.

(1) When a binary curable sealant is used,
In both the IPS panel (FIG. 9) and the pixel flattened panel (FIG. 10), the average value of the fracture toughness value is constant, and the value is the fracture toughness value of the product specification (0.15 kgf / m).
m ^2/3 ).

(2) When a binary curable sealant is used,
In both the IPS panel and the pixel flattened panel, the average value and the minimum value of their fracture toughness values almost match, and there is almost no variation in the fracture toughness value between samples.

(3) When a thermosetting sealant is used,
The average value of the fracture toughness value of the PS panel was high, but the minimum value was low. That is, the variation in the fracture toughness value is large.

(4) When a thermosetting sealant was used, the average value of the fracture toughness of the pixel flat panel was low. That is, it was found that the fracture toughness value of the panel manufactured using the thermosetting sealant was considerably inferior to that obtained using the dual-curable sealant.

In order to clarify the phenomenon of the above experimental results, a cross section of the fracture surface was observed.

FIG. 12 shows an I-type using a thermosetting sealant.
It is a figure explaining the destruction situation of the sample with a low fracture toughness value in a PS panel.

FIG. 13 is a view for explaining the destruction state of the sample in the IPS panel using the dual-curable sealant, which is compared with the destruction state of FIG.

Here, FIGS. 12A and 13A are cross-sectional views of a substrate on which a color filter is formed (hereinafter, this substrate is referred to as a “color filter substrate”), and FIG. FIG. 13B shows a substrate on which switching elements are formed (hereinafter, this substrate is referred to as an “array substrate”).
Is shown).

According to FIGS. 12A and 12B, the separation of the array substrate 1 and the color filter substrate 2 is caused by the surface of the overcoat film 13 on the sealant 3 in the region where the sealant 3 is formed. And along the boundary of the surface of the black mask 5 (hereinafter, this peeling phenomenon is referred to as “interface destruction”). Then, the overcoat film 13 was observed on the sealant 3 on the array substrate 1 side (FIG. 12).
(B)).

On the other hand, FIG.
According to (b), since the sealant 3 is observed on both the array substrate 1 side and the color filter substrate 2 side, it is inferred that peeling of the array substrate 1 and the color filter substrate 2 occurred inside the sealant 3. (Hereinafter, this peeling phenomenon is referred to as “cohesive failure”).

That is, the interface between the organic film such as the overcoat film 13 and the inorganic film such as the black mask 5 has a weak adhesive force, and when a thermosetting sealant is used, the interface is along the interface. It is considered that peeling occurred.

Similarly to the IPS panel and the pixel flattening panel, the panel using the thermosetting sealing agent and having the lowest fracture toughness is the same as the overcoat film 13 (organic film). Interfacial fracture was observed at the boundary surface of the black mask 5 (inorganic film), and cohesive failure occurred in the panel having a large fracture toughness value. In addition,
About 20% of all samples were interfacial fractures.

From the above experimental results, the inventor of the present application has obtained the following knowledge based on the difference in the sealant.

(1) In the sample of the thermosetting sealant,
Interface destruction of the organic film (overcoat film) and the inorganic film (black mask) occurs. On the other hand, such interfacial destruction is not observed in the dual-curing sealant. Therefore,
It is considered that an adhesion problem occurs at the interface between the organic film and the inorganic film during the heating process of the sealant.

(2) With the dual-curing sealant, no interface breakage occurs in any of the samples. Therefore, in a liquid crystal display device using an organic film (overcoat film), the dual-curable sealant is selected. It is essential.

These findings are consistent with the fact that, for a liquid crystal display device without using an organic film, there is no problem with bonding with a thermosetting sealant.
This finding also confirmed the validity of the numerical calculation that the residual stress of the thermosetting sealant was larger than that of the dual-curing sealant (therefore, the thermosetting sealant is not preferable).

[0083]

The sealant composition of the present invention is characterized in that it can be completely cured by irradiation with ultraviolet rays, but is cured in a short time at a low heating temperature even if there is a shade portion which is not permeable to ultraviolet rays. On the point.

Therefore, according to the sealant composition according to the first aspect of the present invention, a sealant for a liquid crystal display device having a strong peeling strength, a high peel strength, a small compression set and a high water resistance after curing is obtained. Obtainable.

According to the liquid crystal display device of the second to fifth aspects of the present invention, even if the seal portion between the substrates is provided around the substrate where the wiring terminal group for shielding ultraviolet rays and the light shielding film coexist, By using the agent composition, the sealant composition can be completely cured in a short time with low irradiation of ultraviolet light and low heating temperature.

Further, according to the liquid crystal display device according to the second to fifth aspects of the present invention, since the internal stress generated in the sealing layer can be reduced, a liquid crystal display device having high adhesion reliability and high durability can be obtained. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a model for numerical calculation.

FIG. 2 is a conceptual cross-sectional view illustrating a process of generating residual stress inside a sealant and inside a substrate when a thermosetting sealant is used for bonding a substrate.

FIG. 3 is a conceptual cross-sectional view for explaining that generation of residual stress can be avoided when an ultraviolet-curable sealant is used for bonding a substrate.

FIG. 4 is a conceptual plan view of a liquid crystal display device.

FIG. 5 is a sectional perspective view taken along a line VV shown in FIG. 4;

FIG. 6 is a view showing a strength test result of a binary curable sealant.

FIG. 7 is a conceptual diagram illustrating sample cutting.

FIG. 8 is a conceptual diagram illustrating a sample tensile test.

FIG. 9 is a cross-sectional view of an IPS panel in which an organic film is provided on a color filter substrate.

FIG. 10 is a cross-sectional view of a pixel flat panel in which an organic film is provided on a TFT substrate.

FIG. 11 is a view showing a measurement result of a fracture toughness value of a liquid crystal display device.

FIG. 12 is a conceptual cross-sectional view illustrating a state of interface destruction of the liquid crystal display device.

FIG. 13 is a conceptual cross-sectional view illustrating a state of cohesive failure of a liquid crystal display device.

FIG. 14 is a sectional view of a liquid crystal display device in which a substrate is bonded with a thermosetting epoxy sealant.

FIG. 15 is a diagram illustrating a problem of adhesiveness of a thermosetting epoxy sealant in a liquid crystal display device.

[Explanation of symbols]

 1, 2, 101, 104 Glass substrate 3 Sealant 4 Liquid crystal display device 6 Wiring terminal 7 Organic film 8 Sample 9, 102 Switching element 16 Pixel flattening film 17 ITO film 18 Jig 10, 103, 108 Alignment control film 5, 11, 105 Black mask 12, 106 Color filter 13, 107 Overcoat film 109 Thermosetting epoxy sealant 14, 15, 110, 111 Spacer

Continued on the front page (72) Inventor Hidefumi Akasaka 1456, Hazama-cho, Hachioji-shi, Tokyo Within Three Bond Co., Ltd. (72) Inventor Kenichi Horie 1456, Hazama-cho, Hachioji-shi, Tokyo F-term in F Bond (reference) 2H089 MA03Y MA07Y QA07 QA16 TA02 TA03 TA12 TA13

Claims (5)

[Claims] 1. An ultraviolet-curable acrylic resin composition having dual curability by ultraviolet light and heat, comprising (1) a photo-radical initiator and an acrylate resin, (2) a photo-cationic initiator and an epoxy An ultraviolet-curable epoxy resin composition composed of a resin, (3) an organic peroxide, and (4) atoms on the surface of the talc particles bonded to the epoxy compound at a molecular level, and the surface was covered with the epoxy compound. A sealant composition for a liquid crystal display device, comprising talc particles in a hybrid state. 2. A light-shielding wiring terminal group comprising a plurality of wiring terminals provided on a peripheral portion of a first glass substrate;
A sealant formed on the wiring terminal group so as to straddle the surface of the glass substrate and having both ultraviolet curability and heat curability, and a second facing the first glass substrate via the sealant. A liquid crystal display device comprising a glass substrate, a light-shielding film disposed between the second glass substrate and the sealant, and shielding the entire surface of the sealant from light, wherein the sealant composition comprises: An ultraviolet-curable acrylic resin composition comprising an initiator and an acrylate resin,
(2) an ultraviolet-curable epoxy resin composition comprising a photocationic initiator and an epoxy resin, (3) an organic peroxide,
(4) A liquid crystal display device comprising: talc particles in a hybrid state whose surface is covered with an epoxy compound. 3. The liquid crystal display device according to claim 2, wherein an organic film is provided between said light shielding film and said sealant. 4. The liquid crystal display device according to claim 2, wherein an organic film is provided between the wiring terminal group and the sealant. 5. The liquid crystal display device according to claim 2, wherein said wiring terminal group or said light shielding film is made of chromium metal or aluminum metal.