Low melting point glass composition

Abstract

The invention provides a low-melting-point glass composition which is used for being sintered with fluorescent powder. The low melting point glass composition includes 5 wt% to 15 wt% of silica, 6 wt% to 26 wt% of diboron trioxide, 12 wt% to 25 wt% of zinc oxide, 1 wt% to 15 wt% of niobium pentoxide, and 7 wt% to 72 wt% of bismuth trioxide. Wherein the glass transition temperature of the low-melting-point glass composition is between 420 DEG C and 500 DEG C, so that the low-melting-point glass composition can be sintered with the fluorescent powder at a low temperature. Even if the red fluorescent powder with relatively low resistance to high temperature is sintered, the structure of the red fluorescent powder cannot be damaged, so that the situation that the fluorescent glass has different colors or is blackened can be avoided, and the luminous benefit of the fluorescent powder can be maintained.

Description

Technical Field

[0001] The present invention relates to a composition of glass, and particularly to a composition of low-melting-point glass. Background Art

[0002] Generally, a light-emitting device having a light-emitting diode (LED) is encapsulated with a material formed by mixing a phosphor and a polymer silicone. Under high-temperature and long-term use, the silicone material is prone to deterioration and yellowing, thereby reducing the light-emitting efficiency of the light-emitting device. Therefore, a method of replacing the silicone with a glass material has emerged on the market to avoid the aforementioned deterioration and yellowing conditions.

[0003] Currently, a glass material and a phosphor are co-sintered to form a fluorescent glass. However, the glass material and the phosphor must be sintered at a high temperature (e.g., 750 °C) for a long time to form the fluorescent glass. For some phosphors with special color temperatures or special compositions, such as red phosphors, the temperature tolerance is usually only 600 °C. If the sintering temperature exceeds 600 °C, the structure of the phosphor with a special color temperature or special composition will deteriorate, resulting in the fluorescent glass being discolored or blackened.

[0004] In addition, if a general low-melting-point glass material is used, it also has the disadvantage of being prone to failure in a high-temperature and high-humidity environment due to its internal structure. In addition, the coefficient of thermal expansion (CTE) of a general low-melting-point glass material is relatively high, and it is easy to react with the phosphor to damage the structure of the phosphor, thereby causing deterioration or discoloration of the fluorescent glass.

[0005] Therefore, there is an urgent need to find a novel low-melting-point glass material that can be co-sintered with phosphors having special color temperatures and special compositions without damaging the structure of the phosphors. Summary of the Invention

[0006] In view of the above problems, the main object of the present invention is to provide a composition of low-melting-point glass for sintering with a phosphor. By virtue of the specific components of the composition of low-melting-point glass, the glass transition temperature of the composition of low-melting-point glass can be between 420 °C and 500 °C, so as to solve the problem that the glass material sintered with the phosphor in the prior art must be melted at a high temperature, thereby damaging the structure of the phosphor.

[0007] To achieve the above object, the present invention provides a composition of low-melting-point glass for sintering with a phosphor. The composition of low-melting-point glass includes 5% to 15% by weight of silicon dioxide (SiO 2 ), 6% to 26% by weight of boron trioxide (B 2 O 3)), 12 wt% to 25 wt% zinc oxide (ZnO), 1 wt% to 15 wt% niobium pentoxide (Nb 2 O 5 ), and 7 wt% to 72 wt% bismuth trioxide (Bi 2 O 3 ). Among them, the glass transition temperature (Tg) of the low melting point glass composition is between 420 °C and 500 °C.

[0008] According to an embodiment of the present invention, the low melting point glass composition further includes 0.1 wt% to 28 wt% barium oxide (BaO).

[0009] According to an embodiment of the present invention, the low melting point glass composition is applied to sintering with a phosphor at a low temperature.

[0010] According to an embodiment of the present invention, the low temperature is between 500 °C and 600 °C.

[0011] According to an embodiment of the present invention, the phosphor includes a red phosphor.

[0012] According to an embodiment of the present invention, after the low melting point glass composition is sintered with the red phosphor, a fluorescent glass is formed, and the light output flux of the fluorescent glass is greater than 100 lumens.

[0013] According to an embodiment of the present invention, the low melting point glass composition does not contain an alkali metal oxide.

[0014] According to an embodiment of the present invention, the alkali metal oxide includes lithium oxide (Li 2 O), and sodium oxide (Na 2 O).

[0015] According to an embodiment of the present invention, the low melting point glass composition does not contain lead (Pb) components and tellurium (Te) components.

[0016] As described above, according to the low melting point glass composition of the present invention, it includes 5 wt% to 15 wt% silica, 6 wt% to 26 wt% boron trioxide, 12 wt% to 25 wt% zinc oxide, 1 wt% to 15 wt% niobium pentoxide, and 7 wt% to 72 wt% bismuth trioxide. With the foregoing components and ratios, the glass transition temperature of the low melting point glass composition can be between 420 °C and 500 °C, and thus it can be sintered with a phosphor at a low temperature. Therefore, even for a red phosphor with low tolerance to high temperatures, its structure will not be damaged during sintering, thereby avoiding the occurrence of color variation or blackening of the fluorescent glass and maintaining the luminous efficiency of the phosphor. Brief Description of the Drawings

[0017] None Detailed Description of the Embodiments

[0018] To better understand the technical content of the present invention, the following preferred specific embodiments are provided for illustration.

[0019] First, the low-melting glass composition of this embodiment can be sintered with a phosphor to jointly form a fluorescent glass. In other words, the low-melting glass composition of this embodiment is the raw material for manufacturing the fluorescent glass. Among them, the low-melting glass composition includes silicon dioxide (SiO 2 ), boron trioxide (B 2 O 3 ), zinc oxide (ZnO), niobium pentoxide (Nb 2 O 5 ), and bismuth trioxide (Bi 2 O 3 ). Among them, silicon dioxide is the main component of the glass network structure. Silicon dioxide has the effects of increasing the structural stability of the glass, reducing the thermal expansion coefficient, resisting thermal shock, improving chemical stability, and mechanical strength. However, if the content of silicon dioxide in the low-melting glass composition is too high, it is easy to increase the melting temperature (abbreviated as Tm) and viscosity, which is not conducive to the homogenization of the melting process and the subsequent processing of the fluorescent glass. To avoid the above-mentioned high melting temperature and high viscosity, the content of silicon dioxide in this embodiment is between 5 wt% and 15 wt%.

[0020] In this embodiment, boron trioxide can jointly form the network structure of the glass with silicon dioxide. In addition, boron trioxide can also be used as a flux for borosilicate glass to reduce the melting temperature and viscosity. The reduction of the melting temperature allows for sintering with the phosphor at a low temperature (to be further described later). However, if the content of boron trioxide is too high, it will reduce the weather resistance of the fluorescent glass. To avoid the above-mentioned reduction in weather resistance, the content of boron trioxide in this embodiment is between 6 wt% and 26 wt%.

[0021] In this embodiment, bismuth trioxide can also be used as the main component of the glass network structure. Therefore, the low-melting-point glass composition of this embodiment mainly consists of silica, boron trioxide, and bismuth trioxide. Among them, bismuth trioxide can reduce the melting temperature and the glass transition temperature (abbreviated as Tg). However, if the content of bismuth trioxide is too small, it cannot effectively reduce the melting temperature and the glass transition temperature. On the contrary, if the content of bismuth trioxide is too large, it is easy to crystallize and react with the phosphor, which will cause the produced fluorescent glass to have abnormal colors or turn black, and will affect the transmittance of the fluorescent glass. To avoid the above situation, the content of bismuth trioxide in this embodiment is between 7 wt% and 72 wt%.

[0022] In this embodiment, zinc oxide is used as a network modifier. Compared with alkali metal oxides and alkaline earth metal oxides, zinc oxide can increase the glass stability and improve the weather resistance. Among them, alkali metals include lithium, sodium, potassium, rubidium, cesium, and francium, and alkaline earth metals include beryllium, magnesium, calcium, strontium, barium, and radium. However, if the content of zinc oxide is too high, it will also increase the melting temperature and is prone to cause crystallization of the fluorescent glass. To avoid the above situation, the content of zinc oxide in this embodiment is between 12 wt% and 25 wt%.

[0023] In this embodiment, niobium pentoxide can also be used as a network modifier. Similar to the function of zinc oxide, compared with alkali metal oxides and alkaline earth metal oxides, niobium pentoxide can increase the glass stability and improve the weather resistance, and will not significantly increase the melting temperature and the glass transition temperature, and can reduce the coefficient of thermal expansion (abbreviated as CTE). Therefore, niobium pentoxide is superior to high-melting-point substances such as aluminum oxide (Al 2 O 3 ), zirconium dioxide (ZrO 2 ), and titanium dioxide (TiO 2 ) that can improve the weather resistance but will increase the melting temperature and the glass transition temperature. Therefore, the low-melting-point glass composition of this embodiment does not contain aluminum oxide, zirconium dioxide, and titanium dioxide. And the content of niobium pentoxide also has its limitations. When the content of niobium pentoxide is too high, it is easy to cause crystallization of the glass. To avoid crystallization, the content of niobium pentoxide in this embodiment is between 1 wt% and 15 wt%.

[0024] In addition, since both zinc oxide and niobium pentoxide in the low-melting-point glass composition of this embodiment can be used as network modifiers, preferably, the low-melting-point glass composition does not contain alkali metal oxides. Among them, alkali metal oxides can be, for example but not limited to, lithium oxide (Li 2 O), and sodium oxide (Na 2O). Additionally, alkali metals are also prone to reacting with the phosphor during sintering, which may further cause color deviation or blackening. Therefore, the low-melting-point glass composition of this embodiment does not contain alkali metal oxides, which can also avoid color deviation or blackening of the produced fluorescent glass.

[0025] Preferably, the low-melting-point glass composition of this embodiment may further include barium oxide (BaO). In this embodiment, barium oxide can also be used as a network modifier. Similar to the function of zinc oxide, it can increase the glass stability and improve the weather resistance. However, when the content of barium oxide is excessive, it will increase the melting point and thermal expansion coefficient of the glass, and it is also prone to crystallization. To avoid the above-mentioned situations, the content of barium oxide in this embodiment can be between 0.1 wt% and 28 wt%.

[0026] The components and proportions of the above low-melting-point glass composition are summarized in Table 1.

[0027] Table 1: Components and proportions of the low-melting-point glass composition of this embodiment.

[0028] Component <![CDATA[SiO 2 > <![CDATA[B 2 O 3 > ZnO <![CDATA[Nb 2 O 5 > <![CDATA[Bi 2 O 3 > BaO Wt% 5～15 6～26 12～25 1～15 7～72 0.1～28

[0029] In short, the low-melting-point glass composition of this embodiment includes 5 wt% to 15 wt% of silicon dioxide (SiO 2 ), 6 wt% to 26 wt% of boron trioxide (B 2 O 3 ), 12 wt% to 25 wt% of zinc oxide (ZnO), 1 wt% to 15 wt% of niobium pentoxide (Nb 2 O 5 ), and 7 wt% to 72 wt% of bismuth trioxide (Bi 2 O 3 ). Preferably, the low-melting-point glass composition may further include 0.1 wt% to 28 wt% of barium oxide (BaO).

[0030] With the composition and proportion of the aforementioned low-melting-point glass, the glass transition temperature (Tg) of the low-melting-point glass composition can be between 420°C and 500°C, and thus it can be sintered with phosphor at a low temperature. In other words, the low-melting-point glass composition of this embodiment can be sintered with phosphor at a low temperature. Among them, the low temperature can be a sintering temperature less than or equal to 600°C. In this embodiment, the low temperature is preferably between 500°C and 600°C. It should be noted that the low-melting-point glass composition of this embodiment can be sintered with any type of phosphor. For example, YAG yellow phosphor, silicon aluminum oxynitride (SiAlON) orange phosphor, LuAG green phosphor, and red phosphor, etc. Among them, YAG yellow phosphor, silicon aluminum oxynitride (SiAlON) orange phosphor, and LuAG green phosphor are relatively stable and have higher tolerance to high temperature. For example, they can withstand heat up to 800°C and their structures will not be damaged. The red phosphor is, for example, red phosphate phosphor, and its tolerance to temperature is usually only 600°C. However, it can be co-sintered with the low-melting-point glass composition of this embodiment at a temperature between 500°C and 600°C, thereby avoiding the destruction of the structure of the red phosphor and also avoiding the situation of the fluorescent glass generating abnormal color or blackening, so as to improve the yield of the fluorescent glass. Therefore, the low-melting-point glass composition of this embodiment can be used with any type of phosphor and will not damage the structure of phosphors with special color temperature or special composition (such as red phosphor).

[0031] Preferably, the low-melting-point glass composition of this embodiment does not contain lead (Pb) and tellurium (Te) components that have an impact on the environment. Specifically, lead monoxide (PbO) and tellurium dioxide (TeO2) are often used as the main components of low-melting-point glass. However, lead and tellurium are components that are toxic to the environment. The low-melting-point glass composition of this embodiment has a glass transition temperature between 420°C and 500°C with the composition ratio shown in Table 1, so as to avoid using lead components and tellurium components.

[0032] Experimental Example 1: Preparation of fluorescent glass.

[0033] First, Table 2 presents a list of seven low-melting-point glass compositions with different raw material ratios within the proportion range of the aforementioned low-melting-point glass composition. Table 3 is a list of four glass compositions with proportion ranges different from those of the aforementioned low-melting-point glass composition.

[0034] Table 2: Raw material ratios and characteristics of low-melting-point glass composition.

[0035]

[0036]

[0037] Table 3: Composition ratios and characteristics of glass composition.

[0038]

[0039] According to the ratios recorded in Table 2 and Table 3, after uniformly mixing the raw materials respectively, place them into a crucible. Then, place the crucible in an atmosphere furnace with normal air or nitrogen flowing through. Similarly, conduct heat treatment for 30 minutes to 60 minutes according to the melting temperature (Tm) listed in Table 2 and Table 3 to melt and obtain homogenized glass. Then, inject the molten homogenized glass into water for quenching to obtain glass sand.

[0040] Next, after grinding the glass sand into glass powder with a particle size less than 100 μm (micrometers), then mix the glass powder with the phosphor. Among them, the content of the glass powder can be between 60% by weight and 80% by weight, and the content of the phosphor is between 20% by weight and 40% by weight. For example, 70% by weight of glass powder and 30% of phosphor can be used. After forming the mixture of the glass powder and the phosphor into an ingot shape, conduct sintering for 30 minutes to 60 minutes according to the co-firing temperature listed in Table 2 and Table 3 to make fluorescent glass. It should be noted that the fluorescent glass made in Experimental Example 1 is the glass before grinding. Before applying it to the light-emitting device of the light-emitting diode, a grinding process can be carried out, which is further described in Experimental Example 2.

[0041] In addition, Table 2 and Table 3 also record the composition of each (low melting point) glass and the characteristics of the fluorescent glass made therefrom. For example, the melting temperature (Tm), glass transition temperature (Tg), coefficient of thermal expansion (CTE), co-firing temperature, and whether the fluorescent glass has color change (i.e., the last column of Table 2 and Table 3). The phosphor used in Experimental Example 1 is a red phosphor (i.e., red phosphate phosphor), and its tolerance to high temperature is relatively low, usually only 600 °C. Therefore, when the co-firing temperature exceeds 600 °C, the structure of the red phosphor may be damaged, resulting in color change such as color difference or blackening of the fluorescent glass.

[0042] Referring to Table 2, it can be seen that the glass transition temperatures (Tg) of the low melting point glass compositions numbered 1-1 to 1-7 are all between 420 °C and 500 °C, and the co-firing temperatures are between 500 °C and 600 °C. Therefore, the fluorescent glass made from the low melting point glass compositions numbered 1-1 to 1-7 also has no color change such as color difference or blackening. In short, the glass transition temperature (Tg) of the low melting point glass composition within the range of the raw material ratios defined in this disclosure is between 420 °C and 500 °C, and the low melting point glass composition can be applied to sinter with the phosphor at a low temperature (between 500 °C and 600 °C).

[0043] In addition, the silicon dioxide (SiO 2 ) and boric oxide (B 2 O 3) Zinc oxide (ZnO), niobium pentoxide (Nb 2 O 5 ), bismuth trioxide (Bi 2 O 3 ), and barium oxide (BaO) are all within the ranges defined in the foregoing embodiments. The glass transition temperatures (Tg) of No. 2-1 and No. 2-2 are both between 420 °C and 500 °C, and the co-firing temperature is 600 °C, which also belongs to the low melting point glass composition. However, the glass compositions of No. 2-1 and No. 2-2 are added with alkali metals that are prone to react with the phosphor, namely lithium oxide (Li 2 O) and sodium oxide (Na 2 O), so that the fluorescent glasses made of the low melting point glass compositions of No. 2-1 and No. 2-2 have color changes such as different colors or blackening.

[0044] The silica (SiO 2 ) in the glass compositions of No. 2-3 and No. 2-4 is different from the range defined in the foregoing embodiments (i.e., 5 wt% to 15 wt%), and thus the proportions of other raw materials are not within the ranges defined in the foregoing embodiments. Among them, the glass compositions of No. 2-3 and No. 2-4 do not add niobium pentoxide (Nb 2 O 5 ) and bismuth trioxide (Bi 2 O 3 ), but are replaced with titanium dioxide (TiO 2 ) and alumina (Al 2 O 3 ) that are commonly used in the art to improve weather resistance. As can be seen from Table 3, the glass transition temperatures (Tg) of No. 2-3 and No. 2-4 both exceed 500 °C, and the co-firing temperature exceeds 600 °C, and thus cannot be applied to sinter with the phosphor at low temperatures. As mentioned above, too high a co-firing temperature (for example, exceeding 600 °C) will cause the structure of the red phosphor to be damaged, and the fluorescent glasses made of the glass compositions of No. 2-3 and No. 2-4 do have color changes such as different colors or blackening.

[0045] It can be seen from Experimental Example 1 that each raw material and its proportion of the low melting point glass composition defined in the present disclosure have practical significance.

[0046] Experimental Example 2: Measuring the optical properties of the fluorescent glass.

[0047] Using the low-melting-point glass compositions numbered 1-2, 1-5, and 1-7 in Experimental Example 1, and the low-melting-point glass compositions numbered 2-3 and 2-4, respectively, and three different phosphors, fluorescent glasses were made according to the method described in Experimental Example 1. Among them, the three different phosphors are YAG yellow phosphor, silicon aluminum oxynitride (SiAlON) orange-yellow phosphor, and red phosphor.

[0048] The prepared fluorescent glass was cut and ground to a thickness between 50 μm and 200 μm, and the surface roughness was between 30 nm (nanometers) and 300 nm. Then, after cutting it into a size of 2 mm (millimeters) in both length and width, it was attached to a blue light chip. Among them, the blue light chip can emit light with a wavelength between 445 nm and 455 nm. The optical properties were measured with an operating current of 700 mA (milliamperes). For example, in this experimental example, the light output flux of the blue light chip was measured, and its unit is lumen (Im), as shown in Table IV.

[0049] Table IV: Light output flux of fluorescent glass applied to blue light chip.

[0050] Number 1-2 1-5 1-7 2-3 2-4 YAG 262 270 256 253 231 α-SiAlON 138 144 130 135 129 red phosphor 105 111 101 86 81

[0051] Regarding the fluorescent glass using YAG yellow phosphor or α-SiAlON orange-yellow phosphor, since the YAG yellow phosphor and α-SiAlON orange-yellow phosphor have higher tolerance to high temperature, compared with the light output flux of No. 1-2, No. 1-5, and No. 1-7, the light output flux of No. 2-3 has no significant difference, while the light output flux of No. 2-4 decreased slightly. Regarding the fluorescent glass using red phosphor, the light output flux of No. 2-3 and No. 2-4 is significantly lower than that of No. 1-2, No. 1-5, and No. 1-7, indicating that after sintering the glass used in No. 1-2, No. 1-5, and No. 1-7 with red phosphor, the red phosphor still maintains a certain luminous efficiency, while the fluorescent glass of No. 2-3 and No. 2-4 is more affected by heat and the luminous efficiency decreases. Specifically, when the fluorescent glass (such as No. 1-2, No. 1-5, and No. 1-7) sintered with the red phosphor with the composition ratio of the low-melting-point glass defined in this disclosure is applied to the blue light chip, its light output flux can still be greater than 100 lumens (Im). The light output flux remaining above 100 lumens (Im) indicates that the structure of the red phosphor is less affected, so its luminous efficiency can still be maintained. When the fluorescent glass (such as No. 2-3 and No. 2-4) sintered with the red phosphor with the composition ratio of the glass not defined in this disclosure is applied to the blue light chip, its light output flux drops below 100 lumens (Im). The light output flux less than 100 lumens (Im) indicates that the structure of the red phosphor is more damaged, resulting in a decrease in its luminous efficiency.

[0052] Therefore, as can be seen from Experimental Example 2 as well, each raw material and its proportion of the low-melting-point glass composition defined in the present disclosure have substantial significance.

[0053] In summary, according to the low-melting-point glass composition of the present invention, it includes 5 wt% to 15 wt% of silicon dioxide, 6 wt% to 26 wt% of boron trioxide, 12 wt% to 25 wt% of zinc oxide, 1 wt% to 15 wt% of niobium pentoxide, and 7 wt% to 72 wt% of bismuth trioxide. With the foregoing components and proportions, the glass transition temperature of the low-melting-point glass composition can be between 420°C and 500°C, and thus it can be sintered with a phosphor at a low temperature. Therefore, even for a red phosphor with low tolerance to high temperatures, its structure will not be damaged during sintering, thereby avoiding the occurrence of color variation or blackening of the fluorescent glass and maintaining the luminescence efficiency of the phosphor.

[0054] It should be noted that the above-mentioned numerous embodiments are examples for easy explanation, and the scope of protection claimed by the present invention should be subject to what is described in the scope of the claims, rather than being limited to the above embodiments.

Claims

1. A low melting point glass composition for sintering with a phosphor, characterized in that: The low melting point glass composition comprises: 5 to 15% by weight of silicon dioxide, 6 to 26 wt% of boron trioxide, 12 to 25% by weight of zinc oxide, 1 to 15 wt% of niobium pentoxide, and 7 to 72% by weight of bismuth trioxide; wherein, The glass transition temperature of the low melting point glass composition is between 420°C and 500°C.

2. The low melting point glass composition according to claim 1, characterized in that: The low melting point glass composition further includes 0.1 wt % to 28 wt % of barium oxide.

3. The low melting point glass composition according to claim 1, characterized in that: The low melting point glass composition is applied to be sintered with a phosphor at a low temperature.

4. The low melting point glass composition according to claim 2, characterized in that: The cryogenic temperature is between 500°C and 600°C.

5. The low melting point glass composition according to claim 2, characterized in that: The phosphor includes a red phosphor.

6. The low melting point glass composition according to claim 5, characterized in that: The low melting point glass composition and the red fluorescent powder are sintered to form a fluorescent glass, and the light output flux of the fluorescent glass is greater than 100 lumens.

7. The low melting point glass composition according to claim 1, characterized in that: The low melting point glass composition does not contain an alkali metal oxide.

8. The low melting point glass composition according to claim 1, characterized in that: The alkali metal oxide includes lithium oxide and sodium oxide.

9. The low melting point glass composition according to claim 1, characterized in that: The low melting point glass composition does not contain a lead component and a tellurium component.

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