KR20120131703A - Low Melting Temperature Glass Compositions for Laser-Based Sealing - Google Patents

Abstract

PURPOSE: A low-melting point glass composition for laser sealing with excellent adhesive strength and water resistance is provided to fuse at low temperature by easily absorbing laser light to seal OLED(Organic Light Emitting Diode). CONSTITUTION: A low-melting point glass composition includes 10-30wt% of P2O5, 30wt% or less of V2O5, 5-30 wt% of ZnO, 10-20 wt% of Sb2O3, and 1-15wt% of one of TiO2 and Fe2O3. The low-melting point glass composition additionally includes crystalline ceramic powder as filler. The crystalline ceramic powder is more than one or two kinds selected from beta-eucryptite, zirconium tungsten phosphate (Zr2WP2O12) and zirconium tungsten oxides (ZrW2O8). The crystalline ceramic powder is 30 wt% or less based on the whole composition. [Reference numerals] (AA) Embodiment 1; (BB) Filler; (C1,C2) Embodiment; (DD) Substrate glass; (EE) Temperature

Description

Low Melting Temperature Glass Compositions for Laser-Based Sealing

The present invention relates to a low melting glass composition, specifically, a display panel, a fluorescent display tube, a back light unit, and in particular, a low melting glass composition capable of melting at low temperature by absorbing laser light for encapsulating an OLED. will be.

Organic Light Emitting Diodes (OLEDs), also called organic ELs, are considered the most promising candidates to challenge the shudders of LCDs, which are currently leading the flat panel display market. OLEDs can be applied not only to displays but also to lighting, which has great market potential.

The emission principle of OLED is to utilize the phenomenon that light of a specific wavelength is generated by combining electrons and holes injected from both electrodes in a light emitting layer made of an organic compound. When a voltage is applied to the electrode, holes move from the anode, electrons move from the cathode to the organic thin film, and when electrons and holes meet and recombine, an energy level with high energy is generated. When light is relaxed to a low ground state, light of a specific wavelength is generated. At this time, visible light of wavelengths corresponding to red, green, and blue is emitted depending on the type of organic materials and the additives constituting the emission layer. OLEDs can be driven at low voltages, can be made thin, and have a wide range of applications, including displays, lighting, and sensors, with a wide viewing angle and fast response speed.

When manufacturing a display device or an illumination light source using OLED, a sealing technology is needed to protect organic materials that are vulnerable to moisture and air, and sealing technology is the most important point of OLED long life technology issues.

Generally, the sealing method used is a method of fixing using a photocurable resin, the resin can not guarantee 100% moisture resistance. Attaching a desiccant to the inside is not suitable for a high resolution display or a transparent display method. This problem can be solved by using glass frit as a sealing material.However, in the case of a general low melting glass sealing material, the sealing should be performed by applying heat of 450 ° C. or higher to the entire device. Electronic components in the device deteriorate and ultimately lead to instrument defects.

In order to solve this problem, the glass frit part uses a low temperature local heating sealing method using an infrared laser so that the temperature of the AMOLED pixel, which is 1 to 2 mm away from the sealing part, is maintained at 100 ° C or less while receiving sufficient heat. Should apply.

Therefore, the infrared absorption glass frit for low temperature localized heat bonding with low glass transition point, low thermal expansion coefficient of 4 ~ 8ppm / ℃, excellent infrared absorption characteristics, etc. is essential to be suitable for low temperature localized heat sealing method using infrared laser. .

As a conventional sealing glass composition, a material in which refractory ceramic powder or the like is added to a glass powder containing a lead component has been used, but recently, it is sealed at low temperature without containing harmful components such as lead component for environmental reasons. A glass composition capable of doing is proposed.

Among the glass compositions, phosphate glass, borosilicate glass, alkali glass and bismuth glass are known as low melting point glasses which do not contain lead components. Among them, bismuth glass has a great interest because it can be calcined at a low temperature and has excellent chemical resistance But the price of bismuth is 8 times higher than that of lead.

In general, phosphate glass is widely used as a low melting point glass composition for sealing, and the phosphate glass has a thermal expansion coefficient of about 110 to about 70 ~ 80 × 10 ⁻⁷ / ° C. which is much higher than that required for sealing PDP, VFD, and BLU. Since it has a thermal expansion coefficient of about 120 × 10 ⁻⁷ / ° C., low-expansion ceramic powder is used as a filler in phosphate glass to match the difference in thermal expansion coefficient.

However, in order to seal the OLED, a coefficient of thermal expansion of about 30 to 40 × 10 ⁻⁷ / ° C. is required, so that in order to match the difference in the coefficient of thermal expansion, more low-expansion ceramics are added than the addition amount of the low-expansion ceramic powder used in PDP and the like. Powder should be used. For this reason, the sealing property of the glass composition is lowered at the time of sealing, so that sealing is not easy, and in order to solve this problem, there is a problem of working at a higher temperature.

Therefore, the thermal expansion coefficient of the glass composition is 90 × 10 ⁻⁷ / ° C. or lower without containing lead, and the thermal expansion coefficient is 55 × 10 ⁻⁷ / ° C. or lower, even if the low expansion ceramic powder is not excessively added. There is still a need for the development of a glass composition having excellent sealing properties even at a relatively low temperature (low laser output) because the absorption of the laser wavelength is more than 80% and the glass transition temperature is 350 to 400 ° C.

The present invention has been proposed in the above technical background, and an object thereof is that the coefficient of thermal expansion is small in order to easily seal the OLED without containing a lead component, and in particular, the laser light for encapsulating the OLED is easily absorbed at low temperature. It is to provide a low melting point glass composition capable of melting.

Another object of the present invention is to mix the crystalline ceramic powder into the glass composition as a filler to enable a sufficient sealing while maintaining the ambient temperature below 150 ℃ by laser light irradiation, and to provide a glass composition having excellent adhesion strength and excellent water resistance To provide.

In order to achieve the above object, according to the present invention, in weight%, P ₂ O ₅ 10-30%, V ₂ O ₅ 30% or less, ZnO 5-30%, Sb ₂ O ₃ 10-20%, and A low melting glass composition comprising at least one of two components, such as TiO ₂ and Fe ₂ O ₃ , in 1 to 15% is provided.

In the present invention, the low melting point glass composition may further comprise a low-expansion crystalline ceramic powder as a filler (Filler), such crystalline ceramic powder, for example, beta-eucryptite (β-eucryptite), zirconium tungsten One kind or two or more kinds may be selected and used from phosphate (Zr ₂ WP ₂ O ₁₂ ) and zirconium tungsten oxide (ZrW ₂ O ₈ ).

In addition, the crystalline ceramic powder is preferably added to 30% by weight or less based on the total glass composition.

Use of the glass composition of the present invention provides the following advantages over the technique using conventional organic adhesives.

First, OLED sealing does not require a separate desiccant.

Second, the conventional UV-treated organic adhesive is degraded by moisture, but using the glass composition of the present invention can prevent this phenomenon.

Third, conventional UV treated organic adhesives typically require long post-treatment in a furnace, but the glass compositions of the present invention can substantially reduce the processing time of a given component.

Fourth, using the glass composition of the present invention can have a longer life than conventional epoxy-sealed OLED is low resistance to moisture penetration of the OLED.

1 is a graph showing the results of XRD analysis of the glass prepared according to the present invention with a conventional example.
Figure 2 is a graph showing the thermal expansion behavior with the addition of a ceramic filler (beta-eucryptite) to the glass composition of the present invention.
3 is a graph showing the thermal expansion behavior of the addition of a ceramic filler (zirconium tungsten phosphate) to the glass composition of the present invention.

In the present invention, the term "low melting point" glass refers to glass having a glass transition temperature of 400 ° C or less. In addition, the "low expansion ceramic filler" refers to a ceramic filler having a negative mean coefficient of thermal expansion.

In the present invention, low melting point glass having sufficient fluidity even by maintaining a short time of 5 to 30 minutes at a relatively low temperature of 400 to 550 ° C. has a composition range as follows by weight%.

P ₂ O ₅ is a material that forms glass, which lowers the coefficient of thermal expansion of the glass composition and may not be vitrified when the content is less than 10%. On the other hand, when the content exceeds 30%, the glass after sealing There exists a possibility that the water resistance of a composition may fall rapidly. Therefore, P ₂ O ₅ is preferably included in the glass composition at 10 to 30%.

V ₂ O ₅ is a component that improves the flow characteristics and improves the laser absorption ability, when the content exceeds 30% there is a fear that the glass composition is unstable and devitrified during melting. Therefore, V ₂ O ₅ is preferably included in the glass composition at 30% or less.

ZnO is used for the purpose of improving the water resistance of the glass composition, lowering the coefficient of thermal expansion, and improving the flow characteristics of the glass composition, and when the content is less than 5%, it is difficult to substantially achieve the addition effect, and the content is 30%. If it exceeds, there is a fear that the fluidity is drastically lowered by crystallization. Therefore, ZnO is preferably included in the glass composition at 5 to 30%.

Sb ₂ O ₃ is generally added to improve the water resistance of the phosphate-based glass, but if the content exceeds 20%, there is a concern that the glass softening point is increased, so that the sealing may not be performed at a temperature of 550 ° C. or less. Therefore, Sb ₂ O ₃ is 20% or less, preferably 10 to 20% is preferably included in the glass composition.

In the present invention, unlike a common heat source, the glass composition is made of a transition metal oxide such as Fe ₂ O ₃ or TiO ₂ to improve absorption characteristics in the wavelength range (about 800 nm) of the laser beam by using a laser as a heat source. One feature. TiO ₂ and Fe ₂ O ₃ is a fear that is used in order to improve the laser absorption, the flowability of the crystallization during the sealing of the glass composition decreases when the amount of TiO ₂ added in excess of 15%, Fe ₂ O _When the content of ₃ degrees exceeds 15%, the softening point of the glass composition is high, and there is a fear that sealing may not occur at a temperature of 550 ° C. or lower. Therefore, TiO ₂ and Fe ₂ O ₃ are each preferably included in the glass composition at 15% or less, particularly 1 to 15%. And each of these components can be added not only individually but also together, In that case, it is good that the total amount does not exceed the above upper limit.

When using the glass composition of this invention for sealing OLED, crystalline ceramic powder is mixed with the above-mentioned powdery glass composition with a filler, and is manufactured as a glass mixture. The reason for mixing the crystalline ceramic powder with the glass powder is to lower the coefficient of thermal expansion and to improve the sealing strength after sealing. However, when the content of the refractory ceramic powder to be added is more than 30% by weight, the airtightness of the sealing portion is deteriorated due to the rapid decrease in fluidity of the glass mixture, so it is preferable to add it at 30% by weight or less.

Refractory ceramic powder used as a filler in the present invention is a beta-eucryptite (β-Eucryptite), zirconium tungsten Phosphate (Zrconium Tungsten Phosphate; Zr ₂ WP ₂ O ₁₂ ) or zirconium tungsten oxide (ZrW ₂ O ₈ ) and the like Can be mentioned.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely provided to explain the present invention in more detail, and the technical scope of the present invention is not limited by these examples.

(Example)

First, the composition as shown in Table 1 was prepared, and then the glass powder and the glass mixture were prepared in the order given below and the physical properties were measured.

1) The composition contained in the range of the glass composition was designed as shown in Table 1 to accurately weigh the composition raw materials.

2) The lead-free glass composition for OLED encapsulation shown in Table 1 was mixed with sufficient time so that all the compositions were completely mixed through a gravity-free mixer.

3) After the mixing of the glass composition is added to the alumina crucible, it is preferable to proceed the melting operation at a temperature of 1100 to 1300 ℃, more preferably 1200 to 1250 ℃. In addition, the melting time is maintained for 10 to 60 minutes (min) to allow the glass composition to be uniformly mixed in the molten state. If the melting temperature is less than 1100 ℃ high melt viscosity may occur when each component is not evenly mixed. The lead-free glass composition melted in the melting step was quenched through air cooling and water cooling quenching.

4) The quenched glass melt was ground into fine particles through a first coarse grinding operation via a ball mill.

5) The first coarse ground glass melt was ground to a fine powder through a second milling process, in which the grinding was carried out in a wet manner, and glass powder was obtained by a second milling process through a ball mill.

6) The pulverized lead-free glass powder was classified to prepare a powder having a particle size (Dmax.) Of 15.0 μm or less. The particle size of the refractory ceramic powder used as the filler was also made into a powder having a particle size (Dmax.) Of 15.0 µm or less. The low melting point glass powder and the low expansion refractory ceramic powder were mixed at the weight% shown in Table 1, and finally, the glass mixture for OLED sealing was manufactured.

7) In order to investigate the thermal properties of the low melting point glass composition, the molten glass was taken and processed into specimens, and then the coefficient of thermal expansion (CTE) and glass transition temperature (Tg) were measured using a dilatometer (NETZSCH, DIL 402 PC, Korea). ) Was measured. The glass transition temperature is preferably 400 ° C. or lower, the thermal expansion coefficient of the glass powder is preferably 90 × 10 ⁻⁷ / ° C. or lower, and the thermal expansion coefficient of the glass mixture is preferably about 40 to 50 × 10 ⁻⁷ / ° C.

8) In the water resistance test, the sealing glass mixture was molded to have a width / length of 10 mm × 10 mm and a height of 5 mm, and then immersed in 95 ° C. water for 720 minutes, and then measured the loss weight of the sealing glass mixture.

Example 1 Comparative Example 1 Comparative Example 2 Example 2 Comparative Example 3 Glass composition (wt%) P ₂ O ₅ 30 55 - 30 30 ZnO 20 20 20 20 20 V ₂ O ₅ 25 - 55 20 25 Sb ₂ O ₃ 10 10 10 10 - B ₂ O ₃ - - - - 10 Fe ₂ O ₃ 15 15 15 - - TiO ₂ - - - 15 15 Glass transition temperature, Tg (℃) 367.0 407.2 - 373.4 361.2 Glass availability ○ ○ × ○ ○ Thermal expansion coefficient (x10 ^-7 / ℃) 81.4 97.1 67.9 83.3 69.7 Water resistance (g / m ² / day) 3.448 × 10 ^-8 7.054 × 10 ^-5 8.25 × 10 ^-6 7.845 × 10 ^-7 1.365 × 10 ^-4 Laser wavelength (810 nm) Absorption rate (%) 98 98 98 84 32 Sealable Laser Power
(Laser irradiation speed = 10mm / s) 18 W Measure
Never Measure
Never 20W Measure
Never

Example 3 Same as the composition of Example 1 P ₂ O ₅ 30 ZnO 20 V ₂ O ₅ 25 Sb ₂ O ₃ 10 B ₂ O ₃ - Fe ₂ O ₃ 15 TiO ₂ - Glass
mixture Glass composition (wt%) 80 80 Ceramic filler (wt%) β-eucryptite 20 - Zr ₂ WP ₂ O ₁₂ - 20 Thermal expansion coefficient (× 10 ^-7 / ℃) 55.2 45.4 Sealed laser power (watt) 30 25

From Table 1, the sealing glass mixtures of Examples 1 and 2 exhibited excellent flow characteristics at relatively low temperatures of 400 ° C or lower without containing lead. Particularly, in the case of Example 1, the thermal expansion coefficient of 81.4 × 10 ⁻⁷ / ° C. and the water resistance of 3.448 × 10 ⁻⁸ g / m ² / day were shown, and good sealing was achieved when the laser power was irradiated at 18 Watts. Able to know.

On the other hand, in Comparative Example 1 in which the content of P ₂ O ₅ is 55%, the coefficient of thermal expansion is excessively large due to the excessive addition of P ₂ O ₅ , and the water resistance is reduced. In Comparative Example 2, the resultant obtained when the content of V ₃ O ₅ was too high at 55% was in a crystallized state, and glass was not obtained, and it was also found that the water resistance was significantly reduced.

As can be seen from Example 1 and Comparative Examples 1 and 2, a combination of P ₂ O ₅ and V ₂ O ₅ is required to obtain the desired low glass transition temperature, thermal expansion coefficient, and water resistance, and any of these components It can be seen that a satisfactory characteristic is not obtained in the glass composition containing an excessively large amount.

On the other hand, the glass composition of Comparative Example 3 contains TiO ₂ to seal through laser absorption, but it can also be confirmed that when B ₂ O ₃ is added instead of Sb ₂ O ₃ , a great decrease in water resistance is obtained. From these results, it can be seen that when B ₂ O ₃ is added, the water resistance is dropped and the object of the present invention cannot be achieved.

In addition, Example 3 of the present invention is a ceramic filler in the glass composition of Example 1 in order to minimize the occurrence of thermal stress due to thermal expansion matching with the OLED substrate (44 × 10 ^-7 / ° C.) Conium tungsten phosphate was added to 20% by weight, respectively, to evaluate the properties, and the results are shown in Table 2.

As shown in Table 2, especially when zirconium tungsten phosphate was added, the thermal expansion rate of the OLED substrate was almost similar. From these results, when the low-expansion ceramic filler is added to the glass composition, the laser output value required for sealing increases, but there is an advantage that the generation of thermal stress after sealing can be minimized due to the reduction of the coefficient of thermal expansion.

1 is a graph showing the results of XRD analysis of the glass prepared according to the present invention with a conventional example. As shown in FIG. 1, it can be seen that crystallization does not occur in all cases except that Comparative Example 2, in which the peak appears by crystallization at the time of cooling after melting of the glass composition, shows that glass is satisfactorily produced.

2 is a graph showing the coefficient of thermal expansion according to the addition of a ceramic filler (beta-eucryptite) to the glass composition of the present invention. As shown in FIG. 2, as the beta-eucryptite is added to the glass composition of Example 1 of the present invention by 10% and 20%, the thermal expansion rate is controlled to a level close to that of the substrate glass. It can be seen.

3 is a graph showing the coefficient of thermal expansion according to the addition of a ceramic filler (zirconium tungsten phosphate) to the glass composition of the present invention. As shown in Figure 3, the zirconium tungsten phosphate is added to the glass composition of Example 1 of the present invention 10%, 20%, respectively, it is understood that the effect of controlling the thermal expansion rate close to the thermal expansion rate of the substrate glass Can be.

In view of the above, according to the present invention, it has excellent flow characteristics at a relatively low temperature of 500 ° C. or less without containing a lead component, and a laser absorption rate of up to 98% can be obtained with excellent thermal expansion characteristics, and at the same time good water resistance ( 3.448 × 10 ⁻⁸ g / m ² / day).

Furthermore, when the low-expansion ceramic filler is added at 20%, the coefficient of thermal expansion can be adjusted to 49.4 × 10 ^-7 / ° C., similar to that of the OLED substrate (44 × 10 ^-7 / ° C.), and sealed using a heat source laser. It was confirmed that the bonding is possible at a speed of 10mm / s at 25W power.

In the above, the present invention has been illustrated and described by way of specific preferred embodiments, but the present invention is not limited to the above-described embodiments, and the general knowledge in the technical field to which the present invention pertains falls within the scope of the present invention. Various changes and modifications will be possible by those who have

The present invention can be usefully used for a display panel, a fluorescent display tube, a back light unit, or, in particular, for sealing an OLED using laser light.

Claims (4)

By weight, at least one of the two components: P ₂ O ₅ 10-30%, V ₂ O ₅ 30% or less, ZnO 5-30%, Sb ₂ O ₃ 10-20%, and TiO ₂ and Fe ₂ O ₃ Low melting glass composition comprising 1 to 15% of the species. The method of claim 1,
The low melting point glass composition further comprises a crystalline ceramic powder as a filler (Filler). The method of claim 2,
The crystalline ceramic powder is one or two or more selected from beta-eucryptite (β-eucryptite), zirconium tungsten phosphate (Zr ₂ WP ₂ O ₁₂ ) and zirconium tungsten oxide (ZrW ₂ O ₈ ) Melting point glass composition. The method of claim 2,
The crystalline ceramic powder is a low melting point glass composition, characterized in that less than 30% by weight based on the total composition.

Images