JPH05127175A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve the workability and mechanical strength of the structure to adhere a liquid crystal panel. CONSTITUTION:The liquid crystal panel has the structure constitute by sticking a color filter substrate 1 and an element substrate 2 by a sealing material 3 and sealing a liquid crystal layer 4 between these two substrates. An acrylic UV curing type resin is used as the sealing material 3. An acrylic resin layer 13 is utilized for the adhesion boundary on the color filter 1 side and a silicon oxide material layer, for example, PSG phosphorus-doped glass layer 10, is used as the boundary on the element substrate 2 side. An epoxy UV curing type resin may be utilized as well in place of the acrylic UV curing type resin. A transparent electrode 14 is utilized in place of the acrylic resin layer 13 as the adhesion boundary on the color filter substrate 1 side in such a case.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a seal structure for a pair of substrates which are arranged to face each other.

[0002]

2. Description of the Related Art A flat panel type liquid crystal display device generally has a structure in which a pair of substrates having electrodes formed thereon are adhered by a sealing material along a peripheral portion with a predetermined gap. A liquid crystal is enclosed in this gap, and a character or a figure is displayed by applying a voltage between the opposing electrodes and utilizing the optical change of the liquid crystal layer at that time. The thickness of the liquid crystal layer is usually about 5 μm to 15 μm and is regulated by the size of the gap between the pair of substrates. If this gap is not uniformly maintained, color unevenness may occur on the display surface or the response time of the liquid crystal may vary, resulting in deterioration of display quality.

Usually, in order to assemble a liquid crystal display device or a liquid crystal cell, a sealing material is printed on one of a pair of substrates with a predetermined width and a predetermined height, and then the other substrate is laminated and adhered. A thermosetting adhesive resin such as a thermosetting epoxy resin has been used as the sealing material. The pair of substrates are adhered by curing the sealing material under heating and pressure. Therefore, the substrate gap size is determined immediately after heating and pressurizing. However, in a liquid crystal cell having a relatively large display area or a liquid crystal cell that requires high definition and high density, even if the gap size immediately after heating and pressurization is uniform, the heat between the substrate material and the seal material is Due to the difference in expansion coefficient and the like, there is a defect that the gap size changes and becomes non-uniform in the cooling process, or a pattern pitch shift occurs between the upper and lower substrates. In order to solve this drawback, for example, Japanese Patent Application Laid-Open No. 57-94271 proposes a method of controlling the cooling rate after heating and pressurizing to remove thermal strain. However, heat treatment is inevitable as long as a thermosetting sealing material is used, and it is difficult to maintain the overlay accuracy of the upper and lower substrates even if various measures are taken.

[0004]

In view of the drawbacks of the thermosetting sealing material, recently, a method of using an ultraviolet curing resin as a sealing material has been proposed. This kind of sealing material can be cured at a relatively low temperature by irradiation of ultraviolet rays, and the problem of thermal distortion does not occur originally. However, the adhesive strength is more difficult than that of the thermosetting resin, and there is a problem or problem that sufficient mechanical strength cannot be obtained depending on the material and surface condition of the adhesive interface. For example, an alignment control film for liquid crystal molecules is generally formed on the surface of the substrate. If the membrane is composed of a relatively chemically inert material,
The bonding reaction to the interface of the ultraviolet curable resin becomes difficult to occur, and the adhesive strength decreases. Alternatively, in the type in which the drive elements are integratedly formed on the surface of the substrate, the surface of the substrate may be covered with a protective film such as a silicon nitride film.
Since the silicon nitride film is relatively inactive, it is not possible to obtain sufficient strength when using an ultraviolet curable adhesive.
Therefore, when the ultraviolet curable sealant is used, stable adhesive strength cannot be obtained, and serious defects including peeling of the flat panel may occur.

In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide an adhesive interface structure capable of guaranteeing sufficient adhesive strength with respect to the ultraviolet curable sealing material. The present invention can be applied to all kinds of flat panel type liquid crystal display devices, but is particularly effective for assembling an active matrix type color liquid crystal display device. This type of device is obtained by arranging and adhering one substrate on which a color filter is formed and the other substrate on which a liquid crystal driving element is formed so as to face each other.

[0006]

Means for solving the problems of the above-mentioned conventional techniques and achieving the objects of the present invention are as follows. That is, in a liquid crystal display device in which a pair of substrates each having a transparent electrode on the opposite surface are arranged to face each other along a peripheral portion thereof with a sealing material interposed therebetween, an ultraviolet curable resin is used as the sealing material and A solution was taken to form a silicon oxide based material layer at the interface between the curable resin and one of the substrates.

As one embodiment of the present invention, an active matrix color display device can be given. In this device, a liquid crystal driving element is mounted on an insulating base material, and a peripheral portion of the first substrate is covered with a silicon oxide-based material layer, and a color filter is provided on a glass base material. It is composed of a second substrate covered with a resin layer. The pair of substrates are arranged to face each other along the peripheral portion with a sealing material made of an acrylic ultraviolet curing resin interposed therebetween, and are fixed by adhesion. A liquid crystal layer is sealed in the gap between the two substrates that are bonded together. In some cases, an epoxy UV curable resin, which is characterized by a stronger adhesive strength, can be used as a sealant instead of a general acrylic UV curable resin. In this case, the transparent electrode may be interposed between the acrylic resin layer and the sealing material made of the epoxy-based ultraviolet curing resin. Finally, the above-mentioned silicon oxide-based material layer is formed of, for example, phosphorus-doped glass (PS).
G) Membranes can be used.

[0008]

In the present invention, the ultraviolet curable resin is used as the sealing material, and the surface treatment is performed by coating the peripheral surface of at least one of the substrates with the silicon oxide type material layer. The ultraviolet curable resin has excellent adhesiveness to the silicon oxide-based material layer, and a liquid crystal panel structure having sufficient mechanical strength can be obtained. Such an adhesive structure is particularly effective when an active matrix type liquid crystal display panel is produced by bonding a color filter substrate and an element substrate together. In this case, the surface of the peripheral portion on the element substrate side is covered with the silicon oxide based material layer. PSG used as a protective film or a passivation film is most suitable as this material. On the other hand, an acrylic resin layer is provided on the peripheral surface of the color filter substrate. Since this material also has excellent adhesiveness to the UV curable resin, a seal structure having sufficient mechanical strength can be obtained. The acrylic resin layer is particularly preferable because it can also serve as a protective film for the color filter thin film.

As the ultraviolet curable resin, a general acrylic resin and an epoxy resin having particularly excellent adhesive strength characteristics can be used. When an acrylic ultraviolet curable resin is used, it has compatibility with each other because it has a composition chemically similar to that of the above-mentioned acrylic resin layer, and thus is preferable. Further, even when the epoxy-based UV-curable resin is used, since it has excellent adhesion performance, sufficient peeling resistance can be assured even for the acrylic resin layer. However, in the case of an epoxy type, it has excellent adhesiveness not only to the acrylic resin layer but also to a transparent electrode made of ITO or the like. Therefore, depending on the structure of the liquid crystal panel, a transparent electrode may be provided on the color filter substrate side at the interface between the acrylic resin layer and the sealing material made of the epoxy-based ultraviolet curing resin.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic partial sectional view showing a first embodiment when the present invention is applied to the assembly of an active matrix type liquid crystal display device. The active matrix type liquid crystal display device is configured by adhering a color filter substrate 1 and an element substrate 2 with a sealing material 3 interposed therebetween, and enclosing a liquid crystal layer 4 in a gap between both substrates.

Pixel electrodes 5 arranged in a matrix are formed on the inner surface of the element substrate 2. The pixel electrode 5 can be formed by depositing a polycrystalline silicon film on an insulating base material 6 such as quartz and then performing selective etching. A drive element 7 is formed corresponding to each pixel electrode 5.
The drive element 7 is formed by making full use of semiconductor manufacturing technology for the above-mentioned polycrystalline silicon film, and is composed of, for example, a field effect type thin film transistor (TFT). The drain electrode of the TFT is connected to the pixel electrode 5, and the source electrode is connected to the aluminum wiring 8. These electrodes and aluminum wiring are formed on the interlayer insulating film made of the lower PSG layer 9. Further, the surface of the drive element array is covered with a protective film or passivation film made of the upper PSG layer 10.

On the other hand, the color filter substrate 1 is a glass base material 1.
1 and the color filter film 12 of RGB three primary colors is patterned on the inner surface thereof. The color filter film 12 is provided corresponding to the pixel electrode 5 and is also protectively covered with a top coat made of an acrylic resin layer 13. In addition, the transparent electrode 14 made of ITO or the like is patterned on the top coat. The transparent electrode 14 substantially covers the entire display screen.

Color filter substrate 1 through a predetermined gap
Also, an acrylic UV-curable resin is used as the sealing material 3 for attaching the element substrates 2 to each other. The sealing material 3 is applied along the peripheral portion of one of the substrates by screen printing or the like, and then cured by irradiation with ultraviolet rays. The surface of the peripheral portion of the element substrate 2 is previously coated with the PSG layer 10 to form an adhesive interface. This bonding interface is the driving element 7
It consists of an extension of the passivation film deposited on top. However, instead of this, the PSG layer 10 may be separately formed only in the peripheral portion to serve as an adhesive interface. The PSG layer 10, which is a silicon oxide-based material, is compatible with the acrylic UV-curable resin and constitutes an excellent adhesive interface. On the other hand, an acrylic resin layer 13 is previously arranged on the surface of the peripheral portion of the color filter substrate 1 and constitutes the other adhesive interface. This adhesive interface is an extended portion of the top coat that covers the color filter film 12. However, instead of this, an acrylic resin layer may be separately provided for the adhesive interface in a separate step. The acrylic resin layer is also compatible with the acrylic ultraviolet curable resin and constitutes an excellent adhesive interface.

Acrylate or methacrylate is generally used as the acrylic UV-curable resin and has a structure represented by the following chemical formula 1.

[Chemical 1] In the above structural formula, X and Y are appropriately selected according to the required characteristics of the resin. This type of ultraviolet curable resin is commercially available and can be obtained from, for example, Sony Chemical Company. A radical type polymerization initiator is generally used.

FIG. 2 is a schematic partial sectional view showing a second embodiment. Similar to the first embodiment, the color filter substrate 1 and the element substrate 2 are attached to each other with the sealing material 3 to form an active matrix type liquid crystal display device. The difference from the first embodiment is that an epoxy-based ultraviolet curable resin is used as the sealing material 3. Many of these resins generally have a structure called bisphenol A type,
For example, it has a molecular structure represented by the following chemical formula 2.
In addition, X in the molecular formula is appropriately selected according to the required characteristics of the resin. Epoxy resins are superior in adhesiveness to the above-mentioned acrylic resins and are a relatively new material for ultraviolet curing. For example, it is available from Sony Chemicals. As the polymerization initiator, either a radical type or an ionic type can be used.

[Chemical 2]

As the adhesive interface on the element substrate 2 side, the PSG layer 10 is used as in the first embodiment. On the other hand, as the adhesive interface on the color filter substrate 1 side, the transparent electrode 14 is used unlike the first embodiment. That is, the transparent electrode 14 is interposed between the sealing material 3 and the acrylic resin layer 13. Since the epoxy-based UV-curable resin has more excellent adhesiveness, it firmly adheres also to the transparent electrode 14 made of ITO or the like. In this embodiment, the transparent electrode 14 is formed over the entire surface of the color filter substrate 1.
Since it is allowed to form, there is an advantage that the manufacturing process can be simplified without the need of patterning.

FIG. 3 shows a third embodiment of the present invention. As in the case of the second embodiment, an epoxy-based ultraviolet curable resin is used as the sealing material 3. The difference from the second embodiment is that the SiO ₂ layer 20 is used instead of the PSG layer 10 as the bonding interface on the element substrate 2 side. The SiO ₂ layer 20 is formed on the entire surface of the element substrate 2 or along the peripheral portion thereof by a vacuum deposition method,
It is formed by using a sputtering method or a chemical vapor deposition method. The epoxy-based UV-curable resin is compatible with the SiO ₂ layer and has excellent adhesive strength. Si
The O ₂ layer has a merit that it is easier to form a film than the PSG layer.

On the other hand, as the adhesive interface on the color filter substrate 1 side, the acrylic resin layer 13 is used as in the first embodiment. Epoxy UV curable resins are compatible with acrylic resins having different compositions, and excellent adhesive strength can be obtained.

FIG. 4 shows a fourth embodiment of the present invention. As in the case of the third embodiment, an epoxy-based ultraviolet curable resin is used as the sealing material 3. The difference from the third embodiment is that the transparent electrode 14 is used as an adhesive interface on the color filter substrate 1 side. That is, the transparent electrode 14 is interposed between the acrylic resin layer 13 and the sealing material 3. Since this portion has the same layer structure as that of the second embodiment, sufficient fixing strength can be obtained as already described.
Epoxy-based UV-curable resin is characterized by being superior in adhesiveness to acrylic-based resins. Therefore, the epoxy type can use the silicon oxide type material layers having various compositions as an adhesive interface. In addition to PSG and SiO ₂ which have already been exemplified, quartz and the like constituting the insulating base material 6 are included in this. Further, the epoxy type is compatible with a transparent electrode such as ITO in addition to the acrylic resin layer. On the other hand, the acrylic type has a relatively narrow selection range of the adhesive interface and, for example, good adhesive strength can be obtained for the PSG layer and the acrylic resin layer.

FIG. 5 is a schematic partial sectional view showing a comparative example with respect to the present invention. Similar to the embodiment, the sealing material 3 made of an ultraviolet curable resin is used to bond the color filter substrate 1 and the element substrate 2 together. However,
The difference is that the SiN layer 30 is used as an adhesive interface on the element substrate 2 side. This SiN layer is chemically inactive compared to, for example, a SiO ₂ layer. The surface of the SiO ₂ layer is covered with active groups such as OH groups that contribute to chemical bonding, whereas the SiN layer has almost no such active groups.
Therefore, the ultraviolet curable resin does not firmly adhere to the SiN layer. The SiN layer is used as a passivation film for semiconductor devices because of its denseness and chemical inertness.

Next, the manufacturing method of the embodiment shown in FIGS. 1 to 4 will be described with reference to FIG. In step S1, a color filter substrate is created. That is, the glass substrate 11
After the RGB color filter film 12 is formed on the surface of, the top coat is applied with an acrylic resin and the transparent electrode 14 is patterned thereon. At the same time, a desired adhesive interface is formed along the periphery of the color filter substrate 1.

Next, in step S2, an ultraviolet curable resin is applied by printing on the peripheral portion of the color filter substrate where an adhesive interface is formed by screen printing or the like.

On the other hand, in step S3, an element substrate is prepared. This step is performed by using ordinary thin film processing technology and semiconductor integrated circuit technology.

Then, in step S4, a silicon oxide-based material which becomes an adhesive interface is coated along the periphery of the element substrate. Note that this step may be performed as a part of the element substrate forming step.

In step S5, the color filter substrate and the element substrate, which have been formed respectively, are superimposed and pressed to temporarily fix them. This pressure fixing is performed using, for example, a press.

Subsequently, in step S6, ultraviolet rays are radiated through the substrate surface using an ultraviolet lamp or the like to cure the sealing material. The curing time by UV irradiation is about tens of seconds to several minutes, and the tact time can be greatly shortened as compared with the conventional heat curing treatment.

Finally, in step S7, the bonded substrates are divided into individual cells. Subsequently, a liquid crystal is sealed in the spaces between the individual cells to obtain a display panel. In this way, generally, a multi-cavity method is adopted in order to efficiently manufacture the panel. In this case, instead of the above example, the cell division may be performed after enclosing the liquid crystal.
Further, particularly in the case of manufacturing an active matrix type liquid crystal panel, a single-cavity method may be adopted from the beginning.

FIG. 7 shows an example of an active matrix type color liquid crystal display device thus obtained. The glass base material 11 and the insulating base material 6 are opposed to each other, and the liquid crystal 4 is sealed in the gap. On the lower insulating base material 6, the data lines 41 and the scanning lines 42 arranged in a matrix, and the driving elements 7 and the pixel electrodes 5 arranged at their intersections are arranged. A common electrode or transparent electrode 14 and RGB color filter films 12 corresponding to the respective pixel electrodes 5 are arranged on the upper glass substrate 11. When such a laminated structure is sandwiched between two polarizing plates 43 and 44 and white light is made incident, a transmission type color display device is obtained.

Although the above-mentioned embodiments are all related to the active matrix type color liquid crystal display device, the present invention is not limited to this, and can be applied to bonding and assembling various kinds of liquid crystal display panels. .. For example, it can be applied to a simple matrix type liquid crystal panel or a mono-color liquid crystal display panel.

FIG. 8 shows a test sample for evaluation.
This sample is prepared for each of the first to fourth embodiments and the comparative example, and the element substrate 1 and the color filter substrate 2 are bonded together according to the process chart shown in FIG. In order to evaluate the adhesive strength, the portion A of the element substrate 1 was fixed and a force in the peeling direction as indicated by an arrow was applied to the color filter substrate 2. As a result, with respect to the samples of the first to fourth examples, peeling did not occur and the glass substrate was broken. Therefore, the adhesive strength is 3kg, which is the measurement limit.
It turned out that it was above. On the other hand, in the case of the sample of the comparative example shown in FIG. 5, peeling occurred with a force of 2.0 to 2.3 kg. From the above results, it became clear that the liquid crystal panels according to the first to fourth examples have practically sufficient mechanical strength. In other words, it can be seen that the adhesive interface shown in FIGS. 1 to 4 is extremely effective for the sealing material made of the ultraviolet curable resin.

[0031]

As described above, according to the present invention, by appropriately setting the structure of the adhesive interface, it becomes possible to put the ultraviolet curable resin excellent in workability into practical use, and the tact time is the same as that of the conventional thermosetting resin. There is an effect that it can be greatly improved as compared with the case of using a resin. In addition, even if the ultraviolet curable resin is used as the sealing material, the mechanical strength equivalent to the conventional one can be obtained, and the practically sufficient reliability can be guaranteed.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view showing a first embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the same.

FIG. 3 is a sectional view showing a third embodiment of the same.

FIG. 4 is a sectional view showing a fourth embodiment of the same.

FIG. 5 is a cross-sectional view showing a comparative example.

FIG. 6 is a process drawing showing a manufacturing process of a liquid crystal display device according to the present invention.

FIG. 7 is a schematic view showing a structure of an active matrix type color liquid crystal display device.

FIG. 8 is a perspective view showing the shape of an evaluation sample of the present invention.

[Explanation of symbols]

1 Color Filter Substrate 2 Element Substrate 3 Sealing Material 4 Liquid Crystal Layer 5 Pixel Electrode 6 Insulating Base Material 7 Driving Element 8 Aluminum Wiring 9 PSG Layer 10 PSG Layer 11 Glass Base Material 12 Color Filter Film 13 Acrylic Resin Layer 14 Transparent Electrode 20 SiO ₂ layer

Claims (5)

[Claims] 1. A liquid crystal display device in which a pair of substrates each having a transparent electrode on its opposite surface are arranged to face each other along a peripheral portion thereof with a sealing material interposed therebetween, wherein the sealing material is made of an ultraviolet curable resin. At the same time, a liquid crystal display device characterized in that a silicon oxide-based material layer is formed at the interface between the ultraviolet curable resin and one of the substrates. 2. A first substrate having a liquid crystal driving element mounted on an insulating base material, the peripheral portion of which is covered with a silicon oxide-based material layer, and a color filter on a glass base material, the peripheral portion of which is A second substrate covered with an acrylic resin layer is arranged along the peripheral portion so as to face each other via a sealing material made of an acrylic UV-curable resin, and is bonded and fixed.
A liquid crystal display device having a structure in which a liquid crystal layer is enclosed between both substrates. 3. A first substrate having a liquid crystal driving element mounted on an insulating base material, the peripheral portion of which is covered with a silicon oxide-based material layer, and a color filter on a glass base material, the peripheral portion of which is A liquid crystal display having a structure in which a second substrate covered with an acrylic resin layer is arranged to face each other with a sealing material made of an epoxy-based ultraviolet curable resin and is adhesively fixed, and a liquid crystal layer is sealed between both substrates. apparatus. 4. The liquid crystal display device according to claim 3, wherein a transparent electrode is interposed between the acrylic resin layer and the sealing material made of an epoxy-based ultraviolet curable resin. 5. The liquid crystal display device according to claim 2, wherein the silicon oxide based material layer is made of phosphorus-doped glass.