JPH04278983A - Method for sealing display panel - Google Patents

Abstract

PURPOSE:To improve the hermetic property of the sealing part of an insulating substrate and a sealing plate and to enhance a sealing effect at the time of sealing the display part of a display panel by the sealing plate form the rear side of the insulating substrate. CONSTITUTION:An insulating film 50 is attached onto the leads 21a led out to the peripheral edge of the insulating substrate 10 from the display part 20 and a metallic film 60 of an annular pattern enclosing the display part 20 is provided thereon. In addition, the metallic film of the pattern corresponding to the insulating substrate 10 side is placed on the sealing plate 40 and thereafter, the metallic films on the insulating substrate 40 side and the sealing plate side are joined to each other by using a low melting metal 70 at a low temp.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a sealing method for protecting a display panel from the influence of outside air, and the present invention is a sealing method for protecting a display panel from the influence of outside air, in which a display section incorporated on a transparent insulating substrate is sealed by a sealing method disposed on the back side of the panel. This invention relates to a method of sealing with a plate.

0002

[Prior art] Electroluminescent type (hereinafter referred to as EL)
), liquid crystal type, plasma type, and other so-called flat display panels incorporate a thin film laminated structure as a display part on a transparent insulating substrate, but the display panel has a sufficient display area so that it is not affected by moisture or pollutants in the outside air. It is necessary to seal the area before use.

The simplest way to seal such a display panel is to apply a coating of resin or the like to the back side of the display panel, but in order to obtain a high protection effect against the outside air, it is possible to seal the display panel using a highly airtight glass or metal coating. The most reliable method is to completely confine the display section, which is susceptible to outside air, between the sealing plate and the insulating substrate. The present invention relates to a display panel sealing method using this sealing plate, and a typical example of the prior art will be briefly explained with reference to FIG. 4.

[0004] The display panel 30 shown in FIG. 4 is an EL display panel, and is constructed by incorporating a display section 20 having a thin film laminated structure on an insulating substrate 10 made of transparent glass. As is well known, the EL display section 20 includes a transparent electrode film 21 and a front insulating film 22 in a striped pattern elongated in the front and back direction of the figure.
, an EL light-emitting film 23, a backside insulating film 24, and a backside electrode film 2 with a striped pattern elongated in the horizontal direction of the figure.
5 are laminated, and display light emitted by EL is extracted from the insulating substrate 10 side by using a portion of the EL light emitting film 23 corresponding to the intersection of the transparent electrode film 21 and the back side electrode film 25 as each pixel. .

As the sealing plate 40, the same glass plate as the insulating substrate 10 is usually used, and as shown in the figure, this glass plate is disposed on the back side of the display panel 30, and its periphery is connected to the insulating substrate 10 through a sealing material 90. By sealing, the display section 20 is confined and sealed between the insulating substrate 10 and the sealing plate 40. A resin adhesive such as epoxy, glass powder, or frit is used as the sealing material 90, and the former is placed between the insulating substrate 10 and the sealing plate 40 and then under moderate pressure conditions.
Cured by heating at 0 to 180 °C, the latter at 400 to 80 °C
Heat and melt at 0°C.

[0006] In order to connect the display section 20 to the outside, leads are led to the outside through the above-mentioned sealing section. In the example of FIG. 4, the extended portion of the back side electrode film 25 is used as the lead 25c. The leads 25c are normally led out alternately on the left and right sides, but the cross section of the figure shows a case where they are led out on the right side. Of course, the transparent electrode film 21 also requires a lead, so the transparent electrode film 21 is similarly extended alternately in the front-rear direction in the figure through the sealed portion by the sealing material 90 to form a lead.

[0007]

[Problems to be Solved by the Invention] In the method of sealing the display panel 30 explained in FIG. 4, the glass insulating substrate 10 has very high airtightness, and the sealing plate 40 can also be made of a material with sufficiently high airtightness. However, there is a problem in that the airtightness of the sealed portion by the sealing material 90 is not necessarily sufficient, and this sealed portion has traditionally been a weak point in sealing the display panel.

[0008] When a resin adhesive such as epoxy is used as the sealing material 90, the insulating substrate 10, the sealing plate 40, and the leads 25
Although both of c. have good adhesion and high airtightness of the sealed surface, the resin itself has some air permeability, so the display characteristics may deteriorate during long-term use of the display panel. In addition, in the case of glass sealing materials, although the material itself has high airtightness,
There is a problem with the airtightness of the sealing surface. One reason for this is that defects are likely to occur on the bonding surface of the lead to the metal when glass frit or the like is heated and melted to seal it. Also, connect a narrow lead of, for example, 0.2 mm to 0.4 m from the sealing part.
Another reason is that the sealing tends to be incomplete at the corners of the finely uneven surface because they are lined up and guided at a narrow pitch of about m. Although such sealing problems can be slightly improved by increasing the heating and melting temperature of the glass, it is likely to have an adverse effect on the display section, such as deterioration of display characteristics.

Based on the current situation, an object of the present invention is to improve the airtightness of the sealing portion, which has been a weak point in the past, and to more completely seal the display panel.

0010

[Means for Solving the Problems] According to the present invention, the display portion incorporated on the transparent insulating substrate of the display panel is sealed from the back side of the panel using a sealing plate as described at the beginning. To do this, the leads led out from the display part at the peripheral edge of the insulating substrate are sequentially coated with an insulating film and a metal film in an annular pattern surrounding the display part, with the external connection parts exposed to the outside, and a sealing plate is placed on the lead. A metal film is coated on the peripheral edge of the side at a position corresponding to the metal film on the insulating substrate side, and then the metal film on the insulating substrate side and the metal film on the sealing plate side are coated at a low temperature via a low melting point metal. This is accomplished by bonding them together under heat.

The above-mentioned sealing method according to the present invention can be applied to display panels in general such as EL type, liquid crystal type, plasma type, electrochromic type, etc. In any case, the sealing plate has a material similar to the insulating substrate of the display panel. It is desirable to use a material such as glass in order to maintain a high sealing effect over a long period of time.

In implementing the method of the present invention, it is particularly advantageous to incorporate the insulating film and metal film on the insulating substrate side of the display panel in the above structure using the same material as that for the display part and in the same process as that for the display part. be. At this time, an insulating film is simultaneously formed in a pattern continuous with the display part and a pattern separated from it, and at least part of the metal film is made of the same material as the metal electrode film for the display part, for example, in the case of an EL display panel, it is made of the same material as the metal electrode film for the back side electrode film. It is advantageous to use aluminum and simultaneously form a pattern separated from the display section. Further, it is advantageous that the metal film on the sealing plate side is made of the same material and formed in the same pattern as that on the insulating substrate side.

[0013] It is preferable to use solder, especially eutectic alloy solder, as the low melting point metal for bonding the metal films on the insulating substrate side and the sealing plate side to each other, and prior to bonding, this low melting point metal is electrolytically plated. It is advantageous to pre-apply it in the form of a film or foil to one side of the insulating substrate and the sealing plate, in particular on the latter. The thickness of such a plating film or foil of a low melting point metal is preferably several tens of micrometers, preferably 20 to 80 micrometers, and the width is several mm or less, preferably 1 to 3 mm. Bonding is 180 to 25 depending on the type of low melting point metal.
The heating method at this time is to use a hot plate to heat the entire insulating substrate and sealing plate, but the metal film is heated by irradiation with an infrared ray or laser beam. It is more preferable to locally heat the low melting point metal through the heating process.

Furthermore, it is advantageous that both the metal films on the insulating substrate side and the sealing plate side are composite films coated with a metal that is easily compatible with a low melting point metal. For example, when using aluminum for the display part as the main body of the metal film, a thin film of nickel, copper, gold, etc., which is compatible with low melting point metals such as solder, is coated on top by sputter deposition or electroless plating. Advantageously, it is a coated composite metal membrane.

[0015]

[Operation] The method of the present invention focuses on the fact that metals are superior to resins and glass, which have been conventionally used as sealing materials, in terms of the airtightness of the metal itself and of the bond between metals. We succeeded in solving the above-mentioned problems by using a low-melting point metal that can be easily bonded at low temperatures, and by having an insulating film take on the role of sealing the lead-out part of the lead, where sealing defects are likely to occur. It is.

That is, in the method of the present invention, as described in the configuration in the previous section, an insulating film is first coated on the lead-out portion of the lead at the peripheral edge of the insulating substrate, and the uneven surface including the lead and the insulating substrate surface is sealed. It also serves as an insulator for the leads. Of course, this insulating film is coated so as to expose the external connection portions of the leads to the outside, and thereby the uneven surface caused by the leads is considerably flattened. Next, a metal film is coated on the insulating film in an annular pattern surrounding the display area for bonding with the low melting point metal film, and the insulating film is brought into close contact with the insulating film and flattened as described above. Seal the surface.

On the other hand, the sealing plate side is coated with a metal film in the same manner at a position corresponding to the metal film on the insulating substrate side at the peripheral edge thereof, and then the metal film on the insulating substrate side and the sealing plate side is coated. By bonding them to each other via a low melting point metal under low temperature heating, the space between the insulating substrate and the sealing plate is sealed with a highly airtight metal. At this time, the unevenness caused by the leads on the insulating substrate side is flattened by the insulating film as described above, and then further flattened by the metal film, so the metal film surface on the insulating substrate side is almost completely flattened. Of course, the metal film surface on the sealing plate side is also flat, so
The flat surfaces of both metal films can be easily bonded together at low temperatures using a low melting point metal and sealed with high airtightness.

[0018]

[Embodiments] Hereinafter, embodiments of the sealing method according to the present invention will be described with reference to the drawings. Figures 1 and 2 illustrate the present invention, respectively.
A first embodiment and a second embodiment applied to a display panel are shown, and parts corresponding to those in FIG. 4 described above are given the same reference numerals.

In the first embodiment shown in FIG.
4 is a cross-sectional view of the display panel 30 taken in the same direction as in FIG. 4, and FIG. 4B is a cross-sectional view taken in a direction perpendicular to this. Further, for reference, FIG. 3 shows a pattern of a portion related to the first embodiment in a plan view of the main part.

For the display section 20 of the display panel 30 in FIG. 1, a transparent electrode film 21 made of ITO (indium tin oxide) or the like is formed on the insulating substrate 10 to a thickness of about 2000 Å. In this example, when patterning into stripes as shown in 3(a), the lead 2
1a and 21b are formed simultaneously. Lead 21 as shown
The lead a is formed in a pattern separated from the transparent electrode film 21, and the lead 21b is formed in a pattern continuous with the transparent electrode film 21. Furthermore, at this time, in order to make the surface of the metal film 60 shown in FIG. 1 on the insulating substrate 10 side as flat as possible, spacer patterns 21c and 21d are appropriately formed between the leads 21a as shown in FIG. 3(a). It is preferable to form it.

Next, a front insulating film 22 of alumina or silicon nitride for the display section 20 is formed to a thickness of, for example, 4000 Å by sputtering using a metal mask, and about 0.5% Mn is deposited thereon. The EL light emitting film 23 made of doped ZnS or the like is deposited to a thickness of 4000 to 8000 Å by electron beam evaporation or the like.
The film was deposited to a film thickness of 500 to 700 °C as usual.
Heat treatment is performed for about 1 to 2 hours. For the back side insulating film 24 on the upper side, alumina or the like is formed to the same thickness as the front side insulating film 22, but by forming the film on the entire surface and photo-etching, it is possible to form the lead 21a at the same time as the back side insulating film 24.
An insulating film 50 is formed to cover the layers 21b and 21b. As shown in FIG. 3(b), in this embodiment, the upper and lower portions and left and right extending portions of the back side insulating film 24 are used as the insulating film 50.

The back side electrode film 26 of the display section 20 is formed by photo-etching a metal coated on the entire surface to a thickness of 0.5 to 1 μm by sputtering or the like to form a striped pattern as shown in FIG. 3(c). At this time, the metal film 60 used in the present invention and the metal for the external connection parts 25a, 25b of the leads 21a, 21b in this embodiment are simultaneously formed in the pattern shown. The metal film 60 surrounds the display section 20 from 1 to 3.
It is formed into a frame-like pattern with a narrow width of mm.

In this embodiment, solder is used as the low melting point metal for sealing, so the metal for the metal film 60 is a metal suitable for the back electrode film 26, for example, on the lower electrode film 61 of aluminum, which is compatible with the solder. A composite film structure is used in which thin upper electrode films 62 of good quality, for example, nickel are stacked. For the upper electrode film 62, copper, gold, etc. can be used instead of or in addition to this nickel. In particular, gold can be layered very thinly on nickel by electroless plating or electrolytic plating to improve solderability. It is advantageous to do so.

The material of the sealing plate 40 does not need to be an insulator as long as it has high airtightness, but in reality, it is best to use a glass plate similar to the insulating substrate 10 in order to make the thermal expansion coefficients the same. Preferably, the metal film 60 provided on the peripheral edge of the metal film 60 for the method of the present invention should have the same composite film structure as the insulating substrate 10 side, and of course needs to be formed in the same pattern as the insulating substrate 10 side. This metal film 60 is the insulating substrate 1
Similarly to the 0 side, it is formed by photo-etching the metal that is completely deposited on the sealing plate 40, or because the pattern is simple, it is deposited in a frame-like pattern by sputtering using a metal mask or the like.

The low melting point metal 70 for sealing includes lead and tin.
For example, a foil or film with a thickness of 20 to 80 μm may be used on the insulating substrate 1.
0 and the sealing plate 40, preferably the latter, with soldering flux or the like. Since the solder foil is very thin, it is convenient to carry it on a mount in advance and transfer it to the sealing plate 40 by a so-called transfer method. Alternatively, low melting point metal 7 can be formed by electrolytic plating.
A thin film of 0 may be grown on the metal film 60 on the sealing plate 40 side.

Insulating substrate 10 via this low melting point metal 70
The sealing by joining the metal film 60 on the side and the sealing plate 40 side is 1
It is carried out at a temperature of 80 to 250°C, approximately 200°C in this example. For this purpose, the insulating substrate 10 and the sealing plate 40 are superimposed and positioned in a suitable metal jig, and the jig is placed on a hot plate to melt the low melting point metal 70 for a short time of about 1 minute. The joining can be completed within 24 hours. Alternatively, the low melting point metal 70 may be locally heated through the metal film 60 by irradiation with an infrared ray or laser beam.

Note that this bonding is performed between the insulating substrate 10 and the sealing plate 4.
In order to keep the space that confines the display unit 20 between 0 and 0 clean, it is best to do this in an atmosphere filled with a well-dried inert gas such as nitrogen. It is advantageous to join the parts in the same state. After the low melting point metal 70 is heated and melted to complete the bonding, the small holes 41 of the sealing plate 40 shown in FIG.
The sealing is completed.

Display panel 3 sealed as described above
0, the insulating film 50 is in close contact with the leads 21a, 21b and the surface of the insulating substrate 10 between them, and seals the uneven surface with high airtightness. Further, the metal film 60 deposited by sputtering or the like is in close contact with the surfaces of the insulating film 50 and the sealing plate 40, thereby airtightly sealing the space between them. Insulating substrate 10
The fine irregularities on the surface of the insulating substrate 10 caused by the leads 21a and 21b are flattened by the insulating film 50 and the metal film 60, and the bonding surface of the metal film 60 becomes almost completely flat.
Low melting point metal 70 between the metal film 60 on the side and the sealing plate 40 side
Bonding or soldering by heating and melting can be easily and reliably performed, and a highly airtight seal can be reliably obtained.

According to this first embodiment, 150x220
The result of sealing the display panel 30 with dimensions of mm is as follows:
A high bonding strength of 6 kg was obtained between the insulating substrate 10 and the sealing plate 40. Moreover, in the internal space of this display panel 30,
Testing for leakage by filling the chamber with helium at atmospheric pressure showed that there was no detectable leakage, and airtightness was significantly higher than in the past.

Next, a second embodiment of the method of the present invention will be described with reference to FIG. 2A and 2B are cross-sectional views of the display panel 30 taken in directions corresponding to FIGS. 1A and 1B, respectively. The difference between this embodiment and the first embodiment is that the back electrode film 25 of the display section 20 is replaced by a protective film 26.
The insulating film 80 is formed by covering the metal film 60 with a metal film 60 and extending it to the underside of the metal film 60 . For the protective film 26 and the insulating film 80, it is desirable to use, for example, silicon nitride, which has a dense film quality and is particularly excellent in airtightness, and is preferably formed to a thickness of 0.5 to 1 μm by a plasma CVD method or the like. .

Further, in this embodiment, the metal film 60 provided on the upper side of the insulating film 80 needs to be formed separately from the metal for the back side electrode film 25. Therefore, for example, the metal film 60 on the sealing plate 40 side It is advantageous to use a metal such as copper that has good compatibility with the low melting point metal 70 for this metal film 60, separately from that for the back electrode film 25, since it is deposited using the same metal mask as that used for the metal film 60. Of course, if necessary, a thin nickel film or the like can be superimposed on this to form a composite film as shown in the figure. Furthermore, as shown in FIG. 2(a), the display section 20 of FIG.
Instead of the lead 21a made of ITO or the like for the transparent electrode film 21, a metal for the back side electrode film 25 is extended and the lead 21a is made of ITO or the like.
5c and its external connection.

As can be seen from the above, in this second embodiment, the number of steps required to form the insulating film 80 and the metal film 60 on the insulating substrate 10 is slightly increased compared to the first embodiment.
The sealing effect can be further enhanced by doubly sealing 0 with the protective film 26 and the sealing plate 40, and using a metal most suitable for bonding to the low melting point metal 70 for the metal film 60.

As can be seen from the above description, the present invention is not limited to the embodiments described above, but can be implemented in various forms. The materials and dimensions of the above-mentioned sealing insulating film and metal film are merely examples, and should be appropriately selected depending on necessity or circumstances. Furthermore, various choices can be made regarding the specific structure and pattern when these are used in common with the electrode film and insulating film of the display section.

[0034]

[Effects of the Invention] As explained above, in the method of the present invention, when sealing the display part incorporated on the insulating substrate of the display panel with the sealing plate from the back side of the panel, An insulating film and a metal film in an annular pattern surrounding the display area are sequentially coated on the lead-out leads so as to expose their external connection parts to the outside, and the insulating substrate side of the periphery is coated on the sealing plate side. The following effects can be achieved by coating a metal film with a pattern corresponding to the metal film and bonding the metal films on the insulating substrate side and the sealing plate side via a low melting point metal under low temperature heating.

(a) Since the insulating substrate and the sealing plate are sealed with a metal with high airtightness, there is almost no risk of outside air entering through the sealed portion, and compared to conventional sealing methods, especially resin sealing methods. The sealing effect is extremely high.

(b) Since the fine irregularities on the sealing surface caused by leading the leads to the outside through the sealing part are filled with an insulating film for sealing, there is a risk that sealing defects may occur at the corners of the irregular surface. The reliability of sealing can be improved by reducing the amount of damage. Furthermore, since the uneven surface is flattened by the insulating film, the reliability of metal sealing is also improved.

(c) Since the insulating substrate and the sealing plate are sealed by low-temperature bonding using a low-melting point metal as the sealing material, workability is good and reliability of sealing is improved. Also, 400
Since the sealing temperature may be lower than that required for glass sealing which requires a high temperature of .degree. C. or higher, there is no risk that the display characteristics of the display panel will deteriorate due to high temperatures.

(d) Since the sealing is performed by intermetallic bonding between the metal film and the low melting point metal, there are fewer defects on the sealing surface compared to glass sealing, and the reliability of the sealing is improved.

(e) Since the insulating substrate and the sealing plate are sealed by metal bonding, the strength of the sealing or adhesion between the two plates is extremely high, and the resistance to impact force is also high, so the mechanical strength of the display panel can be greatly increased. can be improved.

(f) Metal sealing has higher heat resistance than resin sealing, and there is no risk of the sealing effect being degraded by thermal stress during use of the display panel compared to glass sealing.

As described above, the present invention facilitates the sealing work while enhancing the sealing effect, reduces defects that are likely to occur in the seal or the sealing surface, improves the reliability of the seal, and achieves high sealing. It has the effect of stably maintaining the effect over a long period of time, and is expected to contribute to preventing deterioration of the display characteristics of the display panel.

[Brief explanation of the drawing]

FIGS. 1A and 1B are cross-sectional views of a display panel, each showing a first embodiment of the display panel sealing method according to the present invention, taken in a direction perpendicular to each other; FIGS.

FIG. 2 is a cross-sectional view of a display panel showing a second embodiment of the display panel sealing method according to the present invention, taken in a direction perpendicular to each other in FIGS.

[Fig. 3] The planar pattern of the main parts related to sealing of the display panel according to the first embodiment is shown in Fig. 3(a).
FIG. 4 is a plan view showing the insulating film shown in FIG. 12(b) and the metal film shown in FIG. 10(c), respectively.

FIG. 4 is a sectional view of a display panel showing a conventional sealing method.

[Explanation of symbols]

10 Insulating substrate 20 Display section of display panel 21a Lead 21b Lead 25a　　　External connection part of the lead 25b External connection part of lead 25c lead 30 Display panel 40 Sealing plate 50 Insulating film 60 Metal film 70 Low melting point metal 80 Insulating film

Claims (3)

[Claims] Claim 1: A method for sealing a display section incorporated on a transparent insulating substrate of a display panel with a sealing plate disposed on the back side of the panel, the method comprising: The lead-out leads are sequentially coated with an insulating film so as to expose their external connection parts to the outside, and a metal film with an annular pattern surrounding the display part is coated on the sealing plate side. A display panel characterized in that the metal film is coated with a pattern corresponding to the metal film, and the metal film on the insulating substrate side and the metal film on the sealing plate side are bonded to each other under low-temperature heating via a low melting point metal. Sealing method. 2. The method according to claim 1, wherein the insulating film is made of the same material as the insulating film for the display section and is formed at the same time by a common process. Method. 3. The method according to claim 1, wherein at least a part of the metal film on the insulating substrate side is made of the same material as the electrode film for the display section, and is separated from it by a common process. A method for sealing a display panel, characterized in that a pattern is formed at the same time.