KR19980070411A - Evaporative Getter Devices with Reduced Active Time - Google Patents

Abstract

The present invention is directed to an evaporable getter device configured for use in conventional television tubes or flat displays with reduced barium evaporation time, in addition to BaAl ₄ alloy and nickel powders used in known devices, iron, aluminum, titanium or A third component powder selected from these alloys is included.

Description

Evaporative Getter Devices with Reduced Active Time

The present invention relates to an evaporative getter device with reduced activation time.

As is known, evaporative getter materials have been used to maintain vacuum in the inner surface of water tubes and computer screens for television sets. While significant improvements have now been made, the use of evaporable getter materials on the inside of flat displays is under study.

A getter material commonly used in water tubes is metal barium deposited in the form of a thin film on the inner wall of the tube. To obtain such a film, a device as known in the art of evaporable getter devices introduced into a tube during manufacture is used. These devices are formed of an open metal container comprising a barium and aluminum compound BaAl ₄ having a particle size of about 250 μm or less and a nickel powder having a particle size of 60 μm or less in a weight ratio of about 1: 1. These devices are well known in the art, for example in US Pat. No. 5,118,988. Barium also causes evaporation by heating the device by means of coils at the outer surface of the water tube in the activation process, defined as 'flash', when the temperature of the powder reaches a value in the range of 800 to 850 ° C. The following reactions occur.

BaAl ₄ + 4Ni → Ba + 4NiAl (Ⅰ)

This reaction is a strong exothermic reaction and raises the temperature of the powder to about 1200 ° C. at which temperature barium evaporates and deposits onto the tube wall to form a metal film.

The time required to evaporate all the barium contained within the device is measured starting from the moment the device is powered by the coil means, but in this field the term 'total time' to be used as TT in the description and claims herein. Will be prescribed. For example, to obtain about 300 mg of barium film required by a large sized color tube, for example, the TT required for a conventional getter device is 40-45 seconds. However, this time will be followed by slower steps in the existing line of manufacturing electron tubes, requiring manufacturers to have a device capable of emitting barium at low TT values.

To achieve this result, the power supplied by the coil may generally be increased or an increase in powder reactivity may be obtained by reducing the particle size.

However, it is impossible to increase coil power in commercially available getter devices. In fact, by doing this, the powder container does not have enough time to raise its temperature very rapidly and even out the diffusion in the packet of thermal powder and raises the melting of the container.

In addition, it is not possible to reduce the size of the powder particles, which is due to the regionally increased reaction rate between BaAl ₄ and Ni as the packets of the powder are inflated continuously and the material is released from the powder as much as possible. .

It is an object of the present invention to provide a vaporizable getter device which overcomes the disadvantages of the prior art and has reduced active time.

This object is according to the present invention,

a) BaAl ₄ compound powder,

b) with nickel powder, and

c) an evaporable getter device comprising a metal container provided with a mixture comprising a third component selected from aluminum, iron, titanium and alloy powders thereof in the range of 0.3% to 5% of the total weight of the mixture and having reduced activation time. Is achieved.

The amount of the mixture of the third component in the powder mixture depends on the component actually used and generally ranges from about 0.3% to 5%. In particular, the percentage of the third component is preferably 0.8% to 2% for aluminum, 0.3% to 1.2% for iron and 0.5% to 5% for titanium. If the amount of the third component is lower than indicated, no intended action of reducing the barium evaporation time is obtained. On the other hand, when the third component is operated larger than the above-mentioned amount, the barium flash is not easy to control while exhibiting an intensifying characteristic. The weight ratio between nickel and BaAl ₄ and nickel is generally 1: 1, which is the same as that of the prior art device, and in particular, a getter device having a ratio of 5.3: 4.7 between nickel and BaAl ₄ is widely used.

In order to achieve the object of the present invention, the third component does not require particularly high purity and generally industrial metals or alloys having a purity of about 98-99% can be used. The particle size of the powder of the third component useful for the purposes of the present invention is 80 μm or less and preferably about 55 μm or less.

The powders of compound BaAl ₄ and nickel used in the getter device of the present invention are the same as those used in the prior art devices. In the case of nickel, powders having a particle size of 60 μm or less are generally used, whereas compound BaAl ₄ is used. In the case of powder, powder having a particle size of 250 mu m or less is generally used.

The metal container can be made of various metals such as nickel plated iron or constantan, and it is preferable to use steel AISI 304 or AISI 305 which shows not only good resistance to oxidation and heat treatment but also excellent cooling working ability. The metal container can take any form and in particular any of the forms known and used in the art, such as devices according to US Pat. Nos. 4,127,361, 4,323,818, 4,486,686, 4,504,765, 4,642,516, 4,961,040 and 5,118,988.

It is also possible in accordance with the present invention to obtain an evaporable getter device with reduced frittable activation time, in which the getter device can withstand an oxidizing atmosphere at a temperature of about 450 ° C. for a duration of up to 2 hours. These conditions are that these devices must be used in some processes of manufacturing the water pipes. During evaporation of the barium from the fritable getter device, more calories are produced than in conventional getter devices, making it more difficult to maintain the powder packet in the container. Fritable getter devices equipped with evaporable barium in amounts of up to 200 mg are already manufactured and commercially available. On the contrary, fritable getter devices capable of evaporating larger amounts of barium, in particular greater than about 300 mg, need to employ specific solutions in view of their greater reactivity. The patent application entitled 'Fritable getter device capable of obtaining barium in high yield' filed with the same patent application as this patent application adds an element which delays heat diffusion in the circumferential direction in the powder packet and in the same packet. A method of making a fritable getter device obtained by adding a metal element discontinuously in an essentially flat state is described. By adding a third component to a fritable getter device of either a conventional type or a high yield type, it is possible to obtain a fritable getter device having barium emission equivalent properties only during reduced evaporation times.

The invention will be further illustrated by the following examples. These examples are not intended to be limiting but have described how to practice the invention and some embodiments have been described so that the invention may be applied in an optimal fashion.

Excuse me 1

A plurality of all identical same getter devices were placed at the bottom of a container made of steel AISI 304 having a ridge of 1 mm height and having a diameter of 20 mm and a height of 4 mm as described in US Pat. No. 5,118,988, incorporated herein by reference. For each of the provided. 767 mg BaAl ₄ powder with particle size less than 250 μm, 866 mg nickel powder with particle size less than 60 μm, and 99% purity 18 mg iron with particle size less than 80 μm for each sample The homogeneous mixture containing the powder uniformly is poured into the container. The powder mixture is then compressed on the inner side of the container with a suitable punch. The samples were connected to a pumping device, placed in an hourly glass measuring chamber, emptied the chamber and tested by performing a barium evaporation test by the following method as described in standard ASTM F 111-72. Each test is heated by a high frequency means having a power that causes evaporation to begin 12 s after the start of heating, and this test is for the total time of heating which is to be changed in various tests in the range of 35 to 45 s. Are different. The amount of barium evaporated at the end of each test was explored. The TT required to evaporate 300 mg of barium from the device is reported in Table 1.

Excuse me 2

Multiple getter devices, all identical to each other, were provided using a container as described in the first example for it. In this vessel a net of steel AISI 304 with a 1.5 mm wide mesh placed on the floor height was placed. 767 mg BaAl ₄ powder with particle size less than 250 μm, 866 mg nickel powder with particle size less than 60 μm, and 99% purity 18 mg iron with particle size less than 50 μm for each sample A homogeneous mixture containing the powder uniformly was poured into the container. The mixture of powder was pressed on the inner side of the container using a punch in the form to form four radial recesses at the pocket surface. The samples thus obtained were treated at 450 ° C. for 1 hour in air to simulate frit sealing conditions. The barium evaporation test was then carried out on each and all samples similarly according to the first example. Also in this case, each device is heated by high frequency means having a power that causes evaporation to begin 12 s after heating is started, while heating is maintained during the TT, which varies from sample to sample and varies from 35 to 45 s. Then, the TT value required to evaporate the barium amount of 300 mg from the device is searched.

The results of this test are reported in Table 1.

(Comparative) Example 3

Same as Example 1, but with no powdered iron, heating the device at high frequency at a power level that allows evaporation to begin 12 s after heating begins and using a series of samples using another TT that can be varied between 35 and 45 s The test of Example 1 was repeated.

(Comparative) Example 4

The series of tests of Example 2 was repeated by using the same getter device as Example 1, except that aluminum powder was used. The TT to evaporate 300 mg of barium from these samples is reported in Table 1.

excuse % Third Ingredient Total time (s) One 1.09 (Fe) 35 2 1.09 (Al) 35 3 0 45 4 0 40

As can be seen from the table, it is possible to achieve 300 mg barium yield with a TT of 35 s using the device according to the invention, which is 5 or 10 s time to achieve the same yield in the sample using the prior art. Should be taken more.

The present invention overcomes the disadvantages of the prior art and provides an evaporative getter device with reduced activation time.

Claims (11)

A vaporizable getter device for reducing the activation time, a) BaAl ₄ compound powder, b) with nickel powder, and c) An evaporable getter device comprising a mixture comprising a third component selected from aluminum, iron, titanium and alloy powders thereof in the range of 0.3% to 5% of the total weight of the mixture and a metal container provided therein. The evaporable getter device of claim 1, wherein when the third component is aluminum, its weight percentage in the mixture is between 0.8% and 2%. The evaporable getter device of claim 1, wherein when the third component is iron, its weight percentage in the mixture is 0.3% to 1.2%. 2. The vaporizable getter device of claim 1 wherein when the third component is titanium, its weight percentage in the mixture is from 0.5% to 5%. The evaporable getter device of claim 1, wherein a weight ratio between the nickel and BaAl ₄ is 1: 1. The evaporable getter device of claim 1, wherein a weight ratio between the nickel and the BaAl ₄ is 5.3: 4.7. The evaporable getter device of claim 1, wherein the powder of the third component has a particle size of 80 μm or less. 8. An evaporable getter device according to claim 7, wherein said third component powder has a particle size of 55 [mu] m or less. The evaporable getter device of claim 1, wherein the nickel powder has a particle size of 60 μm or less. The evaporable getter device of claim 1, wherein the BaAl ₄ powder has a particle size of 250 μm. An evaporative getter device in which the activation time is reduced and made fritable, a) a top openable metal container, b) provided in a container in the form of a packet on an upper surface on which a radial recess is formed, comprising a third component selected from BaAl, nickel, and aluminum, iron, titanium and their alloys, wherein the third component is A mixture provided in an amount of 0.3% to 5% based on the total weight of the mixture, and c) a discontinuous metal element that is flat in shape and parallel to the bottom of the container and immersed in the powder packet at a location spaced from the bottom of the container such that the free surface of the packet itself is not exposed; Evaporative getter device.