TWI446400B - Fluorescent lamp with lamp cleaning method - Google Patents

Description

Fluorescent lamp cleaning method

The invention relates to a method for cleaning a glass tube, which is used for a fluorescent lamp, in particular for a backlight.

Application of alkali-containing tellurite glass (especially borosilicate glass) to gas discharge lamps - gas discharge lamps such as cold cathode fluorescent lamps (CCFL) or external electrode fluorescent lamps (EEFL) -- It is a known technology. The main components of such glasses are SiO ₂ , B ₂ O ₃ , alkali metal oxides, and alkaline earth metal oxides. Since the B ₂ O ₃ content of the glass substrate is relatively high (for example, 10% to 20% by weight), such glasses have relatively poor chemical stability to acids and bases, and are also poor in stability to hydrolysis.

Another known fact is that the glass tube needs to go through a cleaning procedure before the lamp is manufactured. On the one hand, this washing procedure is to remove dirt inside the lamp tube or outside the lamp tube (for example, dirt deposited during transportation), and on the other hand to remove possible glass fragments. In addition, if the lamp tube is coated with a scratch-resistant layer that prevents the lamp from being scratched during transportation or storage, it can also be removed in whole or in part via this cleaning procedure.

This common cleaning procedure has a number of disadvantages: due to the poor chemical stability of the glass, the glass surface may chemically react with the cleaning solution, such as leaching, during the cleaning process. This may cause the glass to decompose, that is, the glass may be completely or partially broken down, causing the glass component to enter the cleaning solution. Although the glass is only partially decomposed under standard conditions (room temperature and neutral pH), the shape and characteristics of the glass are still altered. In addition, ion exchange may occur on the surface of the glass, for example, alkali metal ions leave the glass and enter the cleaning solution, and exchange with protons (H ⁺ ), and B ₂ O ₃ may also be eluted from the glass substrate.

The negative effects of the chemical reaction of the cleaning solution with the glass will not manifest until further processing of the glass: in the subsequent processing, for example in the so-called "baking procedure" (maximum temperature range is approximately 500 ° C to In the heating step of about 750 ° C, usually 600 ° C to 600 ° C), the fluorescent layer is imprinted on the inner surface of the tube via heating, which causes the tube to shrink ("Shrinkage") and / or tight ("Compaction" ). In the present invention, the term "tightening" refers to an irreversible local compression, which corresponds to a shrinkage of the material at the molecular level. The reason is that the dissolution of the glass substrate (for example, alkali metal ions or B ₂ O ₃ ) causes the crystal lattice to become "rough mesh" to some extent, resulting in lattice shrinkage when the lamp is heated.

This tightness can cause the lamp to deform, especially the length of the lamp. The length is shortened to a degree of between about 0.5% and 10%. This means that in the worst case, the lamp will become unusable due to the shortened length and will therefore be classified as scrap.

It is therefore an object of the present invention to provide a cleaning method which does not react with the surface of the glass to reduce or completely avoid shrinkage caused by the reaction, resulting in a shortening of the length of the lamp during subsequent heat treatment. . An important object of the invention is to make the "contraction" dispersion width small, that is to say to make the length variation of a large number of lamps as uniform as possible. In addition to this, the cleaning method of the present invention must of course also be able to satisfy the requirement of making the glass surface clean.

The above object can be achieved by using a glass lamp cleaning method using the fluorescent lamp (especially the backlight fluorescent lamp) proposed by the present invention. The cleaning method is as follows: The glass tube is cleaned with an aqueous cleaning agent in a neutral to strong alkaline (pH between 7 and 12) at a temperature between about 0 ° C and about 90 ° C, or preferably above 20 ° C. To less than 80 ° C.

One surprising finding is that as long as the cleaning procedure is performed under specific conditions, the adverse effects (shrinkage) can be reduced to a very low or no degree of shrinkage. The key conditions are the pH of the cleaning agent and the cleaning temperature. The cleaning time (that is, the time the glass tube is in contact with the cleaning agent) is not of importance. As long as the requirements of the key conditions are met, the amount of waste caused by the cleaning process can be reduced and the output of the glass tube can be increased, which is very advantageous for the economic benefits pursued by the industry in which a large number of production methods are employed.

The cleaning agent is an aqueous detergent. The main component of the clearing agent is water, and the content is 50% or more, 60% or more, 70% or more, or preferably 80% or more. The cleaning agent is preferably an aqueous solution.

One boundary condition that should be maintained during the cleaning process is to adjust the pH of the cleaning agent to a neutral to strong alkaline range. The pH of the cleaning agent should be between 7 and 12, or preferably between 7 and 9 or 9 to 12. It has been experimentally confirmed that the advantage of adjusting the pH of the cleaning agent to this range is that the surface of the glass is not attacked by the cleaning agent or is eroded to a lesser extent. The advantage of a pH between 7 and 9 is that the cleaning agent is less aggressive (labor safe, environmentally friendly), but the cleaning effect is weak. The advantage of a pH between 9 and 12 is that the cleaning action is very strong, especially for cases where the glass tube is heavily soiled. Glass tube The dirt that is present is usually organic contaminants, such as oil or grease-like contaminants that are contaminated by finger touches. This type of contaminant is more easily removed by alkaline solutions, but is not easily removed by acidic solutions.

According to the invention, it is advantageous if the pH remains constant throughout the cleaning process. This can be achieved, for example, by continuously testing the pH and adding additives such as weak acids and/or bases as necessary. Another possibility is that the cleaning agent can be replaced or occasionally replaced during the cleaning process to restore or maintain the initial pH.

Another possibility is to add a pH buffer system to the cleaning agent to maintain the pH at the set pH value, ie to allow the pH to vary only to a small extent. For example, consider the following buffer system: KH ₂ PO ₄ /NaOH (pH 5.8 to 8.0), KH ₂ PO ₄ /Na ₂ HPO ₄ (pH 5.4 to 7.8), Na ₂ HPO ₄ /NaOH (pH 10.9) To 12.0), Tris buffer (eg Tris/HCL, pH 7.0 to 9.0), Borax buffer (eg Borax/HCL, pH 9.2 to 10.8), carbonate-carbonate buffer (pH 6.2 to 11.0), And many other buffer systems known to those skilled in the art. By adjusting the proportion of the components of the buffer solution, the pH can be brought to the desired range. For example, the following examples are listed in the following table:

In addition, another surprising finding is that the cleaning temperature should be kept as low as possible. It is advantageous to maintain the cleaning temperature between about 0 ° C and about 90 ° C and at about 20 ° C. Above to less than 80 ° C, maintained between about 20 ° C or more and less than 70 ° C, or preferably between about 25 ° C and above and less than 75 ° C. This so-called "about" means that the index value can vary within a range of up to 10% (or preferably up and down 20%). All intermediate values for each of the above temperature ranges should also follow this upper and lower range.

As long as it is cleaned within the above temperature range, the glass surface will not be eroded (or will only be slightly eroded).

Contrary to this, an unanticipated finding was that the cleaning time had only a minimal effect on the shrinkage of the glass tube due to heat treatment. Therefore, in order to achieve a good cleaning effect at the same time and to minimize the degree of shrinkage, an advantageous method is to wash at a lower temperature for a longer period of time, or to clean at a higher temperature for a shorter period of time, in which The former is better (cleaning at a lower temperature for a longer period of time). The so-called "lower temperature" refers to the temperature mentioned above. The temperature range in the range closer to the lower limit, and the so-called "higher temperature" refers to the temperature range closer to the upper limit in the aforementioned temperature range.

A particularly advantageous way is to add one or several compounds which aid in the cleaning of the glass to the cleaning agent. For example, Tenside is a compound that helps clean glass, including cationic Tenside, anionic Tenside, nonionic Tenside, and amphoteric Tenside.

Examples of cationic Tenside include alkylbenzene sulfonates, alkane sulfonates, aliphatic alcohol sulfates, aliphatic alcohol sulfates, alkyl phosphates, alkyl phosphates. Soap is also a cationic Tenside, and is a fatty acid with a high sodium and potassium content.

Examples of nonionic Tenside include, for example, aliphatic alcohol ethoxylates, alkylphenol ethoxylates, aliphatic aminoethoxylates, fatty acid ester ethoxylates, alcohol amines, ammonium oxide.

Examples of the anionic Tenside include, for example, an alkylammonium compound and an imidazole compound.

Examples of zwitterionic Tenside include sulfonate inner salts and taurine.

The most desirable Tenside is a neutral or weakly alkaline Tenside, such as soap.

The Tenside is present in an amount from about 0.1% to about 20% by weight, from about 0.5% to about 10% by weight, or preferably from about 1% to about 5% by weight.

In addition, an advantageous way is to add a complexing agent such as dissolved ions (such as alkali metals and alkaline earth metals) to the cleaning agent to produce complexation. The reaction is carried out and the reaction with the glass and/or detergent components is inhibited. Suitable complexing agents include EDTA, poly(hydroxycarboxylates), crown ethers, or other complexing agents, as described in the chemical literature.

According to a further advantageous embodiment of the invention, a neutral salt can additionally be added to the cleaning agent to increase the ion concentration. Any neutral salt that does not react with the components of the glass and the cleaning agent can be used. For example, NaCl, Na ₂ SO ₄ , CaCl ₂ , KCl, K ₂ SO ₄ , KBr, and the like.

For example, the cleaning agent of the present invention may have the following ingredients:

Of course, when selecting additives such as Tenside, buffer systems, salts, complexing agents, etc., a basic principle is that these additives do not adversely react with each other, so as to avoid the cleaning method of the present invention. Causes adverse effects.

The cleaning method of the present invention does not particularly restrict the glass of the glass tube, but is most suitable for the main component of borosilicate glass or calcium-hydrogen hydroxide. Sodium glass glass tube. The cleaning method of the present invention is applicable to all known glasses.

For example, glasses which are particularly suitable for cleaning by the method of the invention have the following glass components:

And oxides of elements such as Rh, Hf, Ta, W, Re, Os, Ir, Pt, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. 0%-5% (% by weight).

In addition, calcium-sodium hydroxide glass with the following glass components is also very suitable: Wherein Li ₂ O+Na ₂ O+K ₂ O accounts for 3%-20% by weight Among them, MgO+CaO+SrO+BaO accounts for 3%-20% (% by weight)

And oxides of elements such as Rh, Hf, Ta, W, Re, Os, Ir, Pt, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. 0% to 5% by weight, and if necessary, an appropriate amount of refining agent, for example. Chloride, sulfate, As ₂ O ₃ and/or Sb ₂ O ₃ . When refining a high temperature we are preferably used as the refining agent SnO _2.

An advantageous way is to simultaneously contain cerium oxide and tin oxide in the glass component. The advantage of this is that tin oxide prevents discoloration of the glass due to excessive cerium oxide content.

The cleaning method of the present invention does not particularly limit the shape of the glass tube. Glass tubes of any cross-sectional shape can be cleaned using the cleaning method of the present invention. The shape of the tube is usually adapted to the spatial conditions, such as the spatial conditions of the lamp for backlighting. Suitable lamp cross-sectional shapes include circular, circular, rectangular, and/or flat rectangular (eg, Planon® lamps manufactured by OSRAM). A lamp having a flat rectangular cross section is particularly suitable for a backlight lamp.

The glass tube cleaned by the cleaning method of the present invention is preferably an outer casing glass which is further processed into a fluorescent lamp, especially a casing glass of a micro fluorescent lamp. The processing is preferably carried out by first cleaning with the cleaning method of the present invention and then performing heat treatment. For example, a heating step in a so-called "baking procedure" (maximum temperature range from about 500 ° C to about 750 ° C, usually from 600 ° C to 600 ° C) Heat treatment is performed to imprint a phosphor layer on the inner surface of the tube.

Fluorescent lamps that can be fabricated from glass tubes can be used for backlighting, such as flat panel displays (so-called backlights, especially LCD displays). For this application, the size of this type of fluorescent lamp must be made very small, so the thickness of the lamp glass is also very thin. For example, the glass tube can be made into a circular tube having a diameter of <1.0 cm, <0.8 cm, <0.7 cm, or preferably <0.5 cm. The wall thickness of the round tubular outer casing glass is <1 mm, or preferably <0.7 mm. According to a possible variant, flat glass having a thickness of <1 cm can be used as a glass tube for the luminaire. The most suitable display and screen for the application is the so-called flat panel display, which is mainly used in laptop computers, especially flat panel backlights.

It is best to make the fluorescent lamp into a miniature fluorescent lamp. The lamps can be arranged in a transparent central portion, and preferably form the outer casing glass, while having two terminals with connecting wires, such as connecting wires made of metal or metal alloy wires that protrude into the lamp. One possible way is to combine the metal or metal alloy wire with the outer casing glass in one heating step. The metal or metal alloy wire is used as an electrode lead-out joint and/or electrode. The electrode lead is preferably made of tungsten, molybdenum or kovar. The linear expansion (CTE) of the outer casing glass is preferably the same as the linear expansion (CTE) of the electrode lead, so that the portion of the electrode lead is free from stress or only the stress defined/designed beforehand. The most desirable backlight is an external electrode fluorescent lamp (EEFL) without an electrode lead, because the coupling of the EEFL backlight without electrodes is via an electric field. Another known lamp is a cold cathode fluorescent lamp (CCFL) which ignites the plasma via electrodes within the band lamp.

The contents and theory of the present invention will be described below by way of an embodiment, but This embodiment does not impose any limitation on the scope of the present invention.

Glass tubes are made from the following borosilicate glass compositions:

The geometry of the glass tube is as follows: Outer diameter: 3.4mm

Inner diameter: 2.4mm

Wall thickness: 0.5mm

Tube length: 500mm

Figure 1 shows the cleaning of the glass tube in an environment of pH = 4.5. This pH value is not within the pH range suggested by the present invention, that is, the acidity is too strong, so that the shrinkage amount is markedly large at a higher temperature range. It can be seen from the figure that when the temperature is higher than 45 °C, obvious adverse effects can be observed on the glass tube, that is, the glass tube is deformed, and this deformation can cause the glass tube to be used in the backlighting lamp. in.

Fig. 2 shows the case where the glass tube was cleaned by the cleaning method of the present invention in an environment of pH = 7. The range of the different shrinkage amounts shown in Fig. 1 is very open to each other, so heat treatment can be performed at temperatures below 70 °C.

Fig. 3 shows the case where the glass tube was cleaned by the cleaning method of the present invention in an environment of pH = 9. As shown in Figure 3, a pH between 8 and 9 is very advantageous. As can be seen from Fig. 3, until the temperature exceeds 70 ° C, even if the treatment time is as long as 120 minutes, the amount of shrinkage is kept to a small extent, so that the glass to be cleaned does not actually have any deformation.

Figure 4 shows an example of the temperature-time curve of the "baking program". Of course, this is just an example. In fact, other different temperature-time curves can be adjusted as needed.

The method of the present invention is the first method of cleaning glass tubes that can substantially reduce shrinkage or shrinkage at all, particularly for cleaning glass tubes made of borosilicate glass or calcium-sodium hydroxide glass. Therefore, in the manufacture of the glass tube, the cleaning method of the present invention contributes to reducing the amount of waste of the glass tube, thereby lowering the cost and improving the economic efficiency.

The glass tube having the above composition and size was cleaned by the cleaning method of the present invention, and the relationship between the shrinkage amount (unit: mm) of the glass tube and the cleaning time and the cleaning temperature in different pH environments was investigated. The results of the study are shown in Figures 1 to 3, wherein: Figure 1: Relationship between shrinkage (unit: mm) of the glass tube and cleaning time and cleaning temperature in an environment of pH = 4.5.

Figure 2: Relationship between shrinkage (unit: mm) of glass tube and cleaning time and cleaning temperature in an environment of pH=7.

Figure 3: Relationship between shrinkage (unit: mm) of glass tube and cleaning time and cleaning temperature in an environment of pH=9.

Figure 4: An example of a temperature-time curve for the "baking program".

Claims (35)

A method for cleaning a glass tube for a fluorescent lamp, in particular a glass tube for a fluorescent lamp for backlighting, characterized in that the cleaning method is characterized by an aqueous cleaning agent at a pH between 7 and 12. The glass tube is cleaned in a strong to alkaline environment and the cleaning temperature is between about 0 ° C and about 90 ° C. The method of claim 1, wherein the cleaning temperature is between 20 ° C or more and less than 80 ° C. The method of claim 1, wherein the glass tube is cleaned with an aqueous cleaning agent at a pH between 7 and 9. The method of claim 1, wherein the glass tube is cleaned with an aqueous cleaning agent at a pH between 9 and 12. The method of claim 2, wherein the cleaning temperature is maintained between about 20 ° C or more and less than 70 ° C. The method of claim 2, wherein the cleaning temperature is maintained between about 25 ° C and less and less than 75 ° C. The method of any one of claims 1 to 6, wherein the pH remains constant throughout the cleaning process. The method of any one of claims 1 to 6, wherein the pH is continuously checked during the cleaning process. The method of claim 1, wherein: adding a weak acid or base to increase or decrease the pH value changed during the cleaning process. The method of claim 1, wherein the cleaning agent is replaced or occasionally replaced during the cleaning process to restore or maintain the initial pH. The method of claim 1, wherein: a pH buffering system is added to the cleaning agent. The method of claim 11, wherein the phosphate buffer, Tris buffer, Borax buffer, carbonate-carbonate buffer, ammonia buffer, or other similar buffer is selected. The method of claim 1, wherein the cleaning time is from about 10 minutes to about 120 minutes. The method of claim 1, wherein the cleaning agent is added with one or more compounds which aid in cleaning the glass. The method of claim 14, wherein: Tenside is added as a compound which contributes to cleaning the glass, in particular to a cationic Tenside, an anionic Tenside, a nonionic Tenside, or an amphoteric Tenside. The method of claim 1, wherein one or more neutral salts are added to the cleaning agent to increase the ion concentration. The method of claim 1, wherein one or more complexing agents are added to the cleaning agent. The method of claim 1, wherein the cleaning combines a lower temperature and a longer cleaning time or combines a higher temperature and a shorter cleaning time. The method of claim 1, wherein the aqueous solution is used as a cleaning agent. The method of claim 1, wherein the content of water in the clearing agent is 50% or more. The method of claim 20, wherein: the water is in the clearing agent The content is 60% or more. The method of claim 21, wherein the content of water in the clearing agent is 70% or more. The method of claim 22, wherein the content of water in the clearing agent is 80% or more. The method of claim 14, wherein the content of Tenside is from about 0.1% to about 20% by weight. The method of claim 24, wherein the content of Tenside is from about 0.5% to about 10% by weight. The method of claim 25, wherein the content of Tenside is from about 1% to about 5% by weight. The method of claim 1, wherein the cleaning agent comprises the following components or consists of the following components: The method of claim 27, wherein the one or more Tensides are from about 1% to 5% by weight. The method of claim 1, wherein the glass bulb is made of borosilicate glass or calcium-sodium hydroxide glass. The method of claim 1, wherein the borosilicate glass containing the following glass components is used: Wherein Li ₂ O+Na ₂ O+K ₂ O accounts for 3%-15% (by weight) And oxides of elements such as Rh, Hf, Ta, W, Re, Os, Ir, Pt, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. 0% to 5% (by weight), and if necessary, a refining agent containing an appropriate amount, such as chlorides, sulfates, As ₂ O ₃ and / or Sb ₂ O _3. The method of claim 30, wherein the TiO ₂ is > 0.5% to 10% by weight. The method of claim 31, wherein the TiO ₂ is >0.5% to 5% by weight. The method of claim 1, wherein the calcium-sodium hydroxide glass containing the following glass components is used: Wherein Li ₂ O+Na ₂ O+K ₂ O accounts for 3%-20% by weight Wherein MgO+CaO+SrO+BaO accounts for 3%-20% by weight of TiO ₂ 0%-10%, >0.5%-10%, or preferably And oxides of elements such as Rh, Hf, Ta, W, Re, Os, Ir, Pt, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. 0%-5% (% by weight). The method of claim 1, wherein the cross-sectional shape of the lamp tube is circular, elliptical, rectangular, and/or flat rectangular. The method of claim 1, wherein the cleaned glass tube is further processed into a fluorescent lamp, especially a miniature fluorescent lamp for backlighting.