KR100948414B1 - Manufacturing Method of Electrode of Cold Cathode Fluorescent Lamp - Google Patents

Abstract

The present invention comprises a kneading step of kneading a metal powder comprising molybdenum and nickel and a thermoplastic binder to produce a feedstock for injection molding; An injection molding step of injecting the feedstock into an injection molding machine; A degreasing step for removing the thermoplastic binder from the injection molding result generated in the injection molding step; It comprises a sintering step for densification of the resultant to remove the thermoplastic binder, wherein the molybdenum is 97 ~ 99 parts by weight and the nickel is 1 to 3 parts by weight based on the weight of the metal powder The present invention relates to a method for producing an electrode for a cathode fluorescent lamp and an electrode for a cold cathode fluorescent lamp.

Cold Cathode Fluorescent Lamp Electrode

Description

Manufacturing Method of Electrode for Cold Cathode Fluorescent Lamp {Manufacturing Method of Electrode of Cold Cathode Fluorescent Lamp}

The present invention relates to an electrode for a cold cathode fluorescent lamp and a method of manufacturing the same, and more particularly to a method for manufacturing a cold cathode fluorescent lamp electrode (CCFL) used in the backlight of the liquid crystal display by a metal powder injection molding method and the like It relates to an electrode for a cold cathode fluorescent lamp produced by.

1 is a view showing the structure of a cold cathode fluorescent lamp, in which a cold cathode fluorescent lamp (CCFL) has electrodes 3 disposed at both ends of the glass tube 1, and the electrode 3 is connected to a terminal 2 through the terminal 2. It is configured to be connected to the outside. Cold-cathode fluorescent lamps are used in scanners, copiers, panel displays, decorative light sources, PC monitors, back light of liquid crystal display (LCD) displays, and the like. Its core component consists of a cylindrical shape with an open bottom at one end to achieve the Hollow Cathode effect.

Cold-cathode fluorescent lamps are fluorescent lamps that are turned on at low temperatures without heating the filament, and have electrodes 3 at both ends of the glass tube, and the inside of the lamp 5 contains a certain amount of mixed gas such as neon, mercury, and argon. (4) has a structure similar to that of a general fluorescent lamp coated with a phosphor. However, while ordinary fluorescent lamps start emitting electrons by heating, cold cathode fluorescent lamps emit electrons by a high voltage electric field applied to two electrodes 3. When the electron emission starts, mercury is excited to emit ultraviolet rays, and the ultraviolet rays collide with the phosphor of the inner wall 4 of the glass tube to emit visible light.

That is, when a high voltage is applied between the electrodes 3 at the start-up, electrons existing in the tube are attracted to both electrodes 3 to move at high speed, collide with the electrodes 3, and secondary electrons are released to discharge. Electrons flowing by the discharge collide with mercury atoms in the tube to generate ultraviolet rays. The ultraviolet rays excite the fluorescent material to emit visible light.

Cold cathode fluorescent lamps with this principle of operation require the following demanding performance conditions. (1) high brightness, (2) long life, (3) low power consumption, (4) low current driving capability, (5) customs (thin), (6) low heat generation, (7) low UV radiation, (8 Excellence in brightness and chromatic uniformity and (9) endure frequent flashing.

In order to satisfy such demanding requirements, the cold cathode fluorescent lamp needs to be miniaturized according to the demand for high brightness. In addition, the electrode for cold cathode fluorescent lamps must be made of (1) materials with excellent discharge characteristics, and (2) In order to guarantee a long service life, a stable material should be applied even if the discharge amount is large. (3) A material having a low cathode drop voltage should be applied to achieve low power consumption and low power driving. In addition, the electrode for cold cathode fluorescent lamps should be further miniaturized for (4) customs properties, and (5) should be able to have the same function as the components even in mass production.

However, the conventional manufacturing method of the electrode for cold cathode fluorescent lamps and the electrode produced thereby have a problem that does not satisfy all of these requirements.

First, powder metallurgy (PM) method through uniaxial press molding is mentioned as one of the manufacturing methods of the electrode for conventional cold cathode fluorescent lamps. This method is a manufacturing method which press-forms a raw material powder with a press and sinters the molded object. Powder metallurgy through press molding mixes the molding lubricant into the metal powder prior to molding for the fluidity of the metal powder and the lubricity of the contact between the metal powder and the mold during molding. Since the post-degreasing process is simple and the overall process is relatively simple, it has been widely applied as an electrode manufacturing method for cold cathode fluorescent lamps.

However, in the powder metallurgy method through press molding, filling is performed into a mold by dropping a metal powder from a metal powder supplying device into a space composed of a mold and a press during molding. There was a problem that the deviation of the density could not be solved. Furthermore, in the case of manufacturing an electrode for a cold cathode fluorescent lamp, which is a small and thin product which is sensitive to small changes in the molded packing density, the deviation is a big disadvantage and there is a problem that causes a huge defective rate in production.

Accordingly, in order to solve this problem of powder metallurgy through press molding, a few μm of fine metal powder was introduced, but in this case, due to the increase in viscosity, the flowability of the metal powder during molding was sharply lowered and the filling was poor, resulting in mass production. It was difficult to supply stable metal powders at the same time, and the defect rate by unmolding increased greatly. In addition, above all, powder metallurgy through press molding has a big disadvantage in that surface roughness, shape freedom, and productivity are inferior.

In addition, there is also a method of manufacturing the electrode through a mechanical cutting process, which is basically only one product per machine can be processed, the productivity is very low, and inevitably waste more than half of the raw materials during processing Therefore, there was a problem that caused the price increase due to the excessive use of raw materials.

In addition, there was also a method of manufacturing electrodes by casting, which was subject to limitations due to problems such as airtightness and difficulty in dimensional control, surface roughness and mechanical properties. In addition, the forging electrode manufacturing method has great advantages such as productivity and inexpensiveness. However, this method is suitable for the manufacture of a relatively simple shape, and thus is not suitable for the manufacture of electrodes for cold cathode fluorescent lamps, which are small and thin products. There was also a problem that the post-processing is relatively high compared to other manufacturing techniques.

Therefore, the technical problem to be achieved by the present invention is to satisfy the overall product performance required for the electrode for cold cathode fluorescent lamps, to be suitable for the production of small and thin products, to provide a relatively uniform physical properties even in mass production The present invention provides a method of manufacturing an electrode for a cathode fluorescent lamp and an electrode thereof.

In order to achieve the above technical problem, the present invention provides a method for manufacturing an electrode for a cold cathode fluorescent lamp, the kneading step of kneading a metal powder and a thermoplastic binder containing molybdenum and nickel to produce a feedstock for injection molding; An injection molding step of injecting the feedstock into an injection molding machine; A degreasing step for removing the thermoplastic binder from the injection molding result generated in the injection molding step; It comprises a sintering step for densification of the resultant to remove the thermoplastic binder, wherein the molybdenum is 97 ~ 99 parts by weight and the nickel is 1 to 3 parts by weight based on the weight of the metal powder Provided is a method of manufacturing an electrode for a cathode fluorescent lamp.

In the present invention, the thermoplastic binder preferably includes a wax-based binder.

In the present invention, the metal powder is preferably kneaded at a rate of 50 to 60% by volume based on the volume of the feedstock.

In the present invention, the powder particle diameter of the metal powder is preferably 2 ~ 8㎛ and tap density is 2 ~ 4 g / cc.

In the present invention, the kneading temperature in the kneading step is 150 ~ 170 ℃ and the kneading time is preferably 1.5 to 3 hours (hr).

In the present invention, the cold cathode fluorescent lamp electrode by the sintering step is preferably densified to a relative density of 93 ~ 97%.

In the present invention, the sintering step preferably includes a step of maintaining the sintering maximum temperature conditions in the range of 1390 ~ 1410 ℃ for 1 to 2 hours (hr).

In the present invention, the thermoplastic binder comprises a wax-based binder, the degreasing step is made by a pyrolysis method, the degreasing step is to maintain a maximum temperature condition of 600 ~ 900 ℃ range for 1 to 2 hours (hr) It is preferable to include a process.

In addition, the present invention is a cold cathode fluorescent lamp electrode composed of molybdenum and nickel, wherein the molybdenum of the total composition comprises 97 ~ 99 parts by weight of the cold cathode, characterized in that contains 1 to 3 parts by weight of nickel Provided are electrodes for fluorescent lamps.

In the present invention, the relative density of the cold cathode fluorescent lamp electrode is preferably 93 to 97%.

According to the manufacturing method of the electrode for cold cathode fluorescent lamp according to the present invention, it is possible to form a high aspect ratio product through the metal powder injection molding, it is possible to improve the productivity as well as to produce an electrode product with excellent precision and homogeneous physical properties Do. In addition, the manufacturing method of the electrode for a cold cathode fluorescent lamp according to the present invention can induce a ripple effect to replace the conventional manufacturing method, excellent mass productivity, easy to secure the assembly properties and physical properties control through the dimensional control It also has the effect of maximizing economic profit creation.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and the scope of protection of the present invention is not limited by these examples.

The metal powder injection molding method is a new manufacturing technology that combines the advantages of the metal powder sintering technology developed in the powder metallurgy industry with the injection molding technology that has been applied for a long time in the high quality plastic industry. In other words, due to the limited fluidity of the powder and the difficulty of transferring the compressive force, a new molded product can be obtained by using the same molding principle as that of plastic injection molding for parts of complex shape which cannot be obtained by a conventional powder metallurgy (PM) process. It is a molding method. In the metal powder injection molding method, a fine metal powder is mixed with a binder which is a polymer binder which is the main agent of injection molding, injection molded into a mold, and then degreased to remove the binder from the injection molded product. It consists of a series of processes to achieve densification.

The metal powder injection molding method has attracted attention as a next-generation flagship manufacturing method because complex shaped parts produced by metal powder injection molding can be mass-produced with excellent mechanical properties and dimensional accuracy. When the metal powder injection molding method is applied, not only the effect of product shape complexity, low price and high performance can be obtained, but also the preliminary dimensions of the final product can be predicted, thereby reducing post-processing of the final product. Low metals can save raw materials economically. The mechanical equipments and molds of this process can be designed by computer programs that have already been applied to injection molding of existing thermoplastic resin products, and the main equipment price is relatively cheap compared to that of other molding technologies. Furthermore, the surface of the final product is very good.

With the development of powder manufacturing technology, raw material mixing technology, molding technology and sintering technology in the metal powder injection molding process, low cost can be realized. Recently, ornaments such as mobile phone parts, high-quality watch bands, medical parts, industrial machine parts, military parts Its use is being expanded to complex shaped parts such as automobile parts.

The advantages of the metal injection molding process can be summarized as: (1) mass production of complex shaped products, (2) high dimensional accuracy, (3) beautiful surface finish, (4) waste reduction through recycling of raw materials, and (5) Easy property control.

Referring to the manufacturing method of the electrode for a cold cathode fluorescent lamp according to an embodiment of the present invention.

The method for manufacturing an electrode for a cold cathode fluorescent lamp according to the present embodiment includes a kneading step of kneading a metal powder containing molybdenum and nickel and a thermoplastic binder to produce a feedstock suitable for injection molding; An injection molding step of injecting the feedstock into an injection molding machine; A degreasing step for removing the thermoplastic binder from the injection molding result generated in the injection molding step; It comprises a sintering step for densification of the result of removing the thermoplastic binder. In this embodiment, it is necessary to maintain optimum conditions for each process, that is, metal powder selection, binder selection, raw material blending technology, mold design, injection molding conditions, degreasing schedule, and sintering schedule, so as to satisfy the required physical properties of the electrode. In the above description, feed stock refers to a mixture of metal powder and a thermoplastic binder.

Hereinafter, the present embodiment will be described in detail for each step.

1. Metal powder and thermoplastic binder selection

1) Metal grade selection

Recently, a material having a lower cathode drop voltage, heat resistance and corrosion resistance has been required as an electrode material for a cold cathode fluorescent lamp. In this embodiment, molybdenum (melting point 2620 ° C.), a high melting point metal having a low work function and being difficult to sputter, is applied under such a requirement. More specifically, in the present embodiment, 97 to 99 parts by weight of molybdenum and 1 to 3 parts by weight of nickel are included with respect to the metal contained in the electrode. Molybdenum can satisfy the demanding performance of cold cathode fluorescent lamps because of its higher melting point and better discharge characteristics than nickel.

2) Metal powder selection

In order to satisfy the function of the electrode for cold cathode fluorescent lamp, it is very important to select the optimum metal powder by understanding the characteristics of the metal powder before injection. The ideal metal powder should have a low surface energy for mixing and injection molding and a high surface energy for sintering. Therefore, spherical powders are suitable for mixing and injection molding, and irregular powders having a large surface area are suitable for sintering. In order to meet these two requirements at the same time, it is very important to refine the spherical powder.

When the powder of irregular shape is used in the metal powder injection molding process, the strength of the molded body is increased after the removal of the binder, but the packing density is decreased. On the other hand, the use of spherical powder can reduce the amount of binder because the packing density increases, it is possible to minimize the dimensional change after sintering. In addition, the spherical powder is preferable in the metal powder injection molding process because the molded body strength can be increased at a high packing density. As the metal powder applied to this embodiment, spherical and fine powders are used as shown in Table 1.

Metal powder Grade Powder shape Tap density Powder particle size Mo (97 to 99 parts by weight) -Ni (1 to 3 parts by weight)  rectangle 2 ~ 4g / cc 2 ~ 8㎛

3) Thermoplastic Binder Selection

As the thermoplastic binder, a binder suitable for a fine spherical molybdenum base metal powder used as a material for an electrode for cold cathode fluorescent lamps is applied. In the injection molding process, a binder, which is an intermediate medium which uniformly fills the feedstock to the desired shape and maintains the injection molded shape until sintering is started, is hardly present in the final product, but the kneading process, the injection molding process, the degreasing process, It is an indispensable factor in the temperature raising process at low temperature before the diffusion of metal powder in the sintering process.

Considering the basic requirements of the binder, i) the thermoplastic binder must be well wetted with the metal powder in the kneading process so that the liquid mixing is uniform, and ii) the powder mixed in the mold space flows well in the injection molding process, and iii In the degreasing process after injection molding, it should be easy to remove from the injection molded body.

In addition, one of the most important roles of the binder is to form an internal bond between the binder and the metal powder to reduce the viscosity of the mixed feedstock, thereby improving the fluidity during injection molding and solid loading (volume fraction of the metal powder). This increases the shrinkage rate during sintering to improve sinterability and facilitates dimensional control of the product. In addition, in order for the feedstock to be effectively mixed and formed without defects, various flow characteristics must be satisfied. The flow characteristics depend on the type of thermoplastic binder, the temperature during injection molding, the strain rate, the solid phase rate, the metal powder properties, and the like.

A feedstock having a low viscosity at a constant solid phase content can be secured by applying a binder having a low viscosity, that is, a binder having a relatively low molecular weight, and such a binder includes a wax-based binder. For this reason, in the present embodiment, a wax-based binder using paraffin wax or the like is applied, but in general, only a pure wax-based binder has insufficient role of the binder so that polyoxymethylene (POM), polyethylene ( Polymer materials such as polyethylene and PE) are optionally added in an amount of 30 to 40% by volume based on the total volume of the thermoplastic binder. That is, in the present embodiment, as the thermoplastic binder, a binder in which the polymer material is added thereto is used as a main binder component of 60-70% by volume of the wax-based binder based on the total binder volume.

2. Raw material kneading process

One of the most important factors among the various parameters of feedstock used as a charging material for injection molding is the raw material kneading technique that determines the composition of metal powder and thermoplastic binder. If the solidity rate is excessively high, injection molding is drastically deteriorated due to the high viscosity. In other words, when the amount of the thermoplastic binder decreases, the viscosity increases, so that the flowability of the feedstock in the mold decreases, and pores are formed in the feedstock. On the other hand, excessively low solid phase rate leads to a long degreasing process due to a relatively large amount of binders, and loses its shape retaining ability before being sintered because particles suddenly sink or move in an excessive amount of binder as the temperature rises. The molded body is broken, and the shrinkage rate increases during the sintering process, which greatly exceeds the expected shrinkage rate during mold design, causing many problems in dimensional control. In addition, the extra binder separates the metal powder particles during the injection molding, thereby forming a non-uniform injection molding part, which causes problems in the dimensional control.

Therefore, the most ideal combination of feedstock is a state in which metal powders are point-bonded and no pore is present in the binder. In this embodiment, the following kneading conditions are required for the production of such ideal feedstock and for forming a defect-free product. Specifically, in order to set the feedstock produced through the kneading process in the mixing process of the Mo-Ni metal powder and the thermoplastic binder to have an optimum solid filling amount having fluidity suitable for the injection molding process, the volume of the powder at a specific temperature The change in torque during kneading with percentage addition was investigated.

In the critical condition where the torque value is rapidly increased, the content of the liquid organic binder starts to be deficient, so that the lubricity is significantly lowered and the injection property is not secured. In the present embodiment, the Mo-Ni metal powder is 50 ~ based on the volume of the feedstock. Proper injection property is ensured by kneading at a rate of 60% by volume.

In addition, an experiment was conducted to determine the proper injection temperature by examining the torque change according to the temperature change during kneading (Torque (N * m) Vs Temp. (℃)). 160-210 degreeC shown was computed.

As described above, appropriate kneading conditions for producing a feedstock having characteristics suitable for an injection molding process or the like were calculated, as shown in Table 2.

Kneading conditions Working variables Kneading speed Kneading temperature Kneading time Condition 700 ~ 900 RPM 150 ~ 170 ℃ 1 hour 30 minutes to 3 hours

3. Pelletizing

When a well-formed feedstock comes out of the kneader, it must be cooled to form a small granular mass. Before injection molding, the purpose of pelletizing feedstock from kneading is largely used. (1) It has a certain size so that it can be charged in a uniform amount in the injection molding machine and can be moved while being melted uniformly. And (2) recycled materials can be used again in the injection molding process. The metal powder injection molding process is economically advantageous due to such recycling. In this embodiment, the pellet size is 7 to 9mm * 4 to 6mm in diameter uniformly produced.

Table 3 summarizes the pelletizing conditions as described above.

Pelletizing Condition Working variables Screw speed Cutter speed Heater temperature Condition 60 ~ 65RPM 10 ~ 15RPM 80 ~ 85 ℃

4. Injection molding process

The purpose of the injection molding process is to obtain an injection molded body in which metal powder is uniformly dispersed in a desired product shape without pores or other defects. In order to meet this purpose, first, the feedstock manufactured through the kneading process is put into the injection molding machine in granule form, and the temperature in the heating cylinder of the injection molding machine is increased so that the wax-based binder included in the feedstock has fluidity. Raise the barrel temperature. In the injection molding process, the injection temperature and the injection pressure are important variables of injection molding along with thickness, diameter, length, etc. of sprue, runner, and gate in the mold.

Injection molding begins with the melting of pelletized feedstock in the barrel of the injection molding machine. The screw reciprocating in the barrel fills and homogenizes the loaded feedstock and pressurizes the mixture. That is, the injection step is performed by moving the screw in the barrel forward to push the molten feedstock into the mold. Since the mold is colder than the feedstock that just enters the cavity of the mold and is filled, the temperature decreases and the viscosity increases. Therefore, in addition to maintaining a constant mold temperature to compensate for the viscosity, the pressure (injection pressure, holding pressure) must be continuously increased until the feedstock is filled. After the filling is completed and the molding is completed, the heat of the feedstock is discharged through the mold. In order to maintain the shape of the injection molding when the mold is opened to take out the injection molding which has been cooled to some extent, the temperature during the ejection should be lower than the critical flow temperature of the feedstock.

The inventor of the present invention has invested a lot of time and effort to investigate the optimum injection conditions for eliminating the density gradient of the injection molding and to eliminate bubbles during injection molding, and to control the mixing of raw materials before injection revolution. High solid phase increases the viscosity and requires high injection pressure during injection molding. High injection pressures change viscosity and separate metal powder and binder. In addition, since viscosity is sensitive to temperature and strain, the fluidity of the mold geometry changes continuously. Incomplete injection conditions will cause the feedstock to fill with a density gradient in the mold, leading to dimensional deformation in the final sintering process.

Therefore, in the present embodiment, in order to obtain a uniform filling density and the effect of bubble prevention, the optimum solid phase rate, injection temperature, injection pressure, mold structure (particularly sprue, runner, gate size, degassing) and humidity are selected. Care was taken to the management. The barrel temperature suitable for the injection operation was found to be in the range of about 160-210 ° C., and the injection conditions are set as shown in Table 4 below.

Proper Injection Condition Control variable Injection speed Injection pressure Pressure Mold temperature Cycle time Input value 30 ~ 40mm / s 1000 ~ 2500kgf 1000 ~ 2000kgf 40 ° C 20-40 sec

5. Degreasing process

The injection molded product as described above is subjected to a degreasing process to remove the binder, this degreasing process is a factor that greatly affects the quality of the finished product after sintering. In this embodiment, the thermogravimetric analysis (TGA, Thermal Gravimetric Analysis) and the differential thermal analysis (DTA) of the binder was performed on the injection molded product, and the degreasing schedule as shown in FIG. 2 was completed according to the result.

The degreasing process is a process that requires special attention to shape retention as the binder in the injection molded product is pulled out. Therefore, the degreasing process should be carefully scheduled in consideration of the characteristics of the thermoplastic binder and the metal powder characteristics. If the degreasing process is not completed before sintering, since the binder filled with 40-50% by volume of the feedstock is pulled out, defects are easily generated in the weakened molded body. Degreasing is one of the very difficult techniques, as it must go through several very delicate steps to get out.

In this embodiment, a degreasing process is used to remove the binder by thermal decomposition. The pyrolysis degreasing step is a method in which an injection molded product charged into a degreasing furnace is gradually heated to vaporize and evaporate a binder through pyrolysis. In this embodiment, hydrogen is selected as an atmosphere gas to a degreasing furnace which carries a vaporized binder to the outside and serves to prevent the oxidation of the molded body. Considering the degreasing capacity and the size and quantity of electrode products, the flow rate of hydrogen gas is 30-50 liters per minute (see Table 5). In the pyrolysis method, it is important to squeeze the degreasing schedule well by understanding the characteristics of the binder and the metal powder, but the role of the carrier gas to quickly escape the vaporized binder to the degreasing furnace without filling or backflowing is also very important.

In the pyrolysis method, when the binder is heated, the relationship of the amount of vaporization with the heating temperature is linearly increased, and several binder components are mixed and used to have this ideal relationship. During the degreasing process, the various components in the binder gradually exit, while the remaining binder components are held in place while the components removed in the relatively low temperature phase are sufficiently released to maintain the shape of the molded body. In general, when the binder of the first composition is removed, if the volume change is small, deformation of the molded body can be minimized.

When the binder is released from the molded body in two forms, the binder may be divided into two phases: the binder moves from the inside to the surface in the liquid phase and then evaporates from the surface to the gas and from the inside to the gas. The wax binder belongs to the former and the resin binder belongs to the latter. In the case of applying a wax-based binder, since the vaporization is generated on or near the surface of the molded article, even if the evaporation rate is high, there is an advantage that the molded article is destroyed.

In the present embodiment, as described above, the thermoplastic binder is configured to include a wax-based binder, and the degreasing time is kept long before and after the temperature at which the phase transformation of the binder starts using a pyrolysis curve, and the temperature increase rate is started from the temperature at which the weight change starts. Slowly to prevent deformation or defect of electrode product due to abrupt separation of binder. Accordingly, the optimum process conditions for the maximum temperature holding conditions, gas atmosphere, gas flow rate, total degreasing time and degreasing rate in the degreasing process were derived as shown in Table 5 below.

Degreasing process condition and degreasing rate Control variable Maximum Temperature * Holding Time Gas atmosphere  Gas flow rate Total degreasing time Degreasing rate Input value (600 ~ 900) ℃ * (1 ~ 2) hr Hydrogen 30 ~ 50 L / min 36-48hr over 90

6. Sintering process

De member in this embodiment passed through the degreasing process is isolated by performing a sintering process according to the sintering schedule as pores (closed pore) generated reducing relative density of 93-97% produced a high-density electrode parts as the shown in Figure 6 Is possible.

Here, the relative density refers to the density of the sintered body compared to the theoretical density, where the theoretical density (theoretical density) refers to the density when there are no defects such as pores inside the metal at all. Indicates. That is, since the pores exist inside the sintered body after the sintering process, the relative density is used to indicate the density of the sintered body compared with the theoretical density.

Sintering is the diffusion process of thermally activated powders at the atomic level, and consequently reduces the specific surface area of the powder particles. As a result, the contact area between the metal powder particles increases, densification occurs, and the pore area generated by degreasing decreases due to sintering, so that the product shrinks and densification occurs.

The main purpose of the sintering in this embodiment is to make an electrode product for cold cathode fluorescent lamp of the required physical properties by densifying the porous degreasing body through sintering. The sintering conditions are optimally selected in consideration of the grade of the metal powder, the particle size, shape and particle size distribution of the powder, and the various processes to manufacture the molded body.

Particularly, in order to achieve the highest density of the relative density of 93 to 97%, which is the maximum purpose of the sintering process in this embodiment, the particle size, the temperature increase rate of sintering, temperature, time, sintering atmosphere, etc. are important parameters. In addition, in the sintering process, more than 14% of shrinkage occurs compared to the injection molded product for densification, so that the sintering in the temperature rising rate, holding time, and sintering temperature range can be maintained in order to maintain uniform densification of the electrode parts and high reproducibility of the entire batch. It is also important to closely examine the temperature distribution in the furnace to determine the interval at which the products are placed.

When only molybdenum powder, which is a high melting point element, is applied, a sintering temperature of 1800 ° C. or more is required to secure a relative density of 90% or more. However, when the molybdenum is composed of 97 parts by weight to 99 parts by weight and 1 to 3 parts by weight of nickel as in the present embodiment, the relative density of 93 to 97% is maintained under conditions maintained for 1 to 2 hours at the highest sintering temperature of 1390 to 1410 ° C. Can be achieved, thereby ensuring excellent production capacity. In this example, the sintering conditions were set as shown in Table 6.

Sintering Process Conditions and Relative Density Control variable Maximum Temperature * Holding Time Gas atmosphere  Gas flow rate Total sintering time Relative density Input value (1390 ~ 1410) ℃ * (1 ~ 2) hr Hydrogen  6 ~ 10 L / min 10-20hr 93-97%

As described above, according to the embodiment according to the present invention, a kneading process of kneading a metal powder and a thermoplastic binder to generate a feedstock, an injection molding process of injection molding the feedstock, and a thermoplastic in the injection molding result. A high density cold cathode fluorescent lamp electrode can be manufactured through a degreasing process for removing the binder and a sintering process for increasing the density of the electrode. According to the present embodiment, the metal powder injection molding is capable of forming a high aspect ratio product, and it is possible to produce an electrode product having excellent precision and homogeneous physical properties as well as improving productivity. In addition, the manufacturing method of the electrode for a cold cathode fluorescent lamp according to the present embodiment can induce a ripple effect to replace the conventional manufacturing method, excellent mass productivity, easy to secure the assembly properties and control the physical properties through the dimensional control and economical It is effective to maximize profit generation.

1 is a cross-sectional view showing the structure of a cold cathode fluorescent lamp.

Figure 2 shows a degreasing schedule in the method of manufacturing an electrode for a cold cathode fluorescent lamp according to an embodiment of the present invention.

Figure 3 illustrates a sintering schedule in the method of manufacturing an electrode for a cold cathode fluorescent lamp according to an embodiment of the present invention.

Claims (11)

In the manufacturing method of the electrode for cold cathode fluorescent lamps, A kneading step of kneading the metal powder containing molybdenum and nickel and the thermoplastic binder to produce a feedstock for injection molding; An injection molding step of injecting the feedstock into an injection molding machine; A degreasing step for removing the thermoplastic binder from the injection molding result generated in the injection molding step; It comprises a sintering step for densification of the result of removing the thermoplastic binder, The molybdenum is 97 to 99 parts by weight and the nickel is 1 to 3 parts by weight based on the weight of the metal powder, In the kneading step, the kneading temperature is 150 ~ 170 ℃ and the kneading time is 1.5 ~ 3 hours (hr), In the injection molding step, the injection speed is 30 ~ 40mm / s and the injection pressure is 1000 ~ 2500kgf, The degreasing step is performed by a pyrolysis method, and includes a step of maintaining a maximum temperature condition in the range of 600 to 900 ° C. for 1 to 2 hours (hr), The sintering step is a method of manufacturing an electrode for a cold cathode fluorescent lamp, characterized in that it comprises a step of maintaining the sintering maximum temperature conditions in the range of 1390 ~ 1410 ℃ for 1 to 2 hours (hr). The method of claim 1, The thermoplastic binder is a manufacturing method of the electrode for cold cathode fluorescent lamps, characterized in that it comprises a wax-based binder. The method of claim 1, The metal powder is a method of manufacturing an electrode for a cold cathode fluorescent lamp, characterized in that the kneading at a rate of 50 to 60% by volume based on the volume of the feedstock. The method of claim 3, wherein The metal powder has a powder particle diameter of 2 to 8 µm and a tap density of 2 to 4 g / cc. delete The method of claim 1, The cold cathode fluorescent lamp electrode by the sintering step is a manufacturing method of the electrode for cold cathode fluorescent lamp, characterized in that the density is increased to a relative density of 93 ~ 97%. delete delete delete delete delete

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