EP1868221A2 - Procédé de fabrication d'une cathode pour des tubes à rayons cathodiques - Google Patents

Procédé de fabrication d'une cathode pour des tubes à rayons cathodiques Download PDF

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Publication number
EP1868221A2
EP1868221A2 EP07106047A EP07106047A EP1868221A2 EP 1868221 A2 EP1868221 A2 EP 1868221A2 EP 07106047 A EP07106047 A EP 07106047A EP 07106047 A EP07106047 A EP 07106047A EP 1868221 A2 EP1868221 A2 EP 1868221A2
Authority
EP
European Patent Office
Prior art keywords
skirts
cathode
chemical attack
skirt
manufacturing according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07106047A
Other languages
German (de)
English (en)
Other versions
EP1868221A3 (fr
Inventor
Fabian Poret
Sandrine Belorgeot-Pierrat
Emmanuelle Robin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thomson Licensing SAS
Original Assignee
Thomson Licensing SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thomson Licensing SAS filed Critical Thomson Licensing SAS
Publication of EP1868221A2 publication Critical patent/EP1868221A2/fr
Publication of EP1868221A3 publication Critical patent/EP1868221A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H01J1/28—Dispenser-type cathodes, e.g. L-cathode

Definitions

  • the invention relates to a method for manufacturing cathodes for cathode ray tubes and an electron gun obtained by this method. It is notably applicable to low power cathodes in which the sleeve containing the heating filament and its cup are manufactured separately.
  • Cathodes for electron guns of cathode ray tubes comprise a skirt (or sleeve) designed to contain the heating filament of the cathode.
  • a cup designed to receive the emissive layer of the cathode is fitted on the skirt.
  • the skirts have a very low wall thickness.
  • the thickness for NiCr skirts can be less than 18 micrometres at the level of the small diameter of the skirts (cup fitting diameter).
  • these skirts during their manufacture by stamping and drawing out, are cold worked and have smooth outer surfaces that have a very low level of roughness.
  • the skirts After being shaped, the skirts are annealed at an approximate temperature of 1050°C.
  • the skirts are placed in bulk in a boat. They therefore tend to stick to one another through a mechanism of local sintering. Owing to the low thickness of their wall, it is therefore very difficult to separate them and there is a frequent risk of deforming or even piercing them.
  • the purpose of the invention is to resolve this problem.
  • the invention therefore relates to a method of manufacturing cathode skirts of electron guns comprising a thermal annealing step followed by an assembly step for each skirt of a cup designed to bear the electro-emissive zone of the cathode.
  • the method according to the invention comprises, before the said thermal annealing, a realisation step of surface irregularities on the outer face of each skirt.
  • This irregularity realisation step preferably comprises a chemical attack step.
  • this irregularity realisation step can also be carried out by an oxidation step of the outer face of each skirt.
  • this step is preferably performed collectively on a batch of skirts and the chemical attack step is followed by a rinsing step followed by a drying step.
  • the said chemical attack is realised using a solution of hydrochloric acid.
  • the concentration of the said solution in hydrochloric acid is advantageously between 30 and 37%.
  • the hydrochloric acid solution temperature is advantageously between 20°C and 40°C and can thus provide for the chemical attack step to be between 15 and 45 minutes.
  • the concentration in acid of the said solution of hydrochloric acid is 37%
  • the temperature of the acid solution is 22°C
  • the duration of the chemical attack is 30 minutes.
  • the said chemical attack can also be realised using a solution of acetic acid and nitric acid.
  • the following volume composition of the said solution can be provided:
  • the temperature of the acetic acid and nitric acid solution is between 80°C and 110°C, and that the duration of the chemical attack is between 15 and 45 minutes.
  • the temperature of the acetic acid and nitric acid solution is about 100°C and the duration of the chemical attack step is about 30 minutes.
  • the method according to the invention comprises the following steps:
  • the invention is also applicable to an electron gun for cathode ray tubes realised by means of the method thus described.
  • Figure 1a shows an example of a skirt of a cathode such as can be found in the art in the low power cathodes.
  • the skirt 1 comprises a widened part 11 for attaching the cathode to the electron gun and a shrunken part 10.
  • the top extremity of the shrunken part 10 is not closed.
  • a cup 2 is therefore provided which is placed on the extremity of the skirt 1 according to the direction of the arrow indicated in figure 1a. This cup is designed to receive the emissive material of the cathode.
  • the skirt 1 is manufactured by stamping and drawing out.
  • the diameter of the shrunken part 10 is typically in the order of a millimetre and the thickness of the wall of this part 10 is about 18 micrometres.
  • skirts thus manufactured is placed in bulk in a boat to undergo annealing at around 1000°C.
  • the skirts then tend to stick to one another.
  • the skirts Owing to the small thickness of the walls of the skirts, the skirts have a certain fragility.
  • the invention thus provides, after the realisation step of the skirts by stamping and before the annealing step, an attack step of the outer surface of the skirts enabling skirts to be obtained having an outer surface presenting sufficient roughness so that the number of contact points between the skirts is reduced when they are placed in bulk in the boat with a view to annealing.
  • This attack of the outer surface of the skirts can be carried out by oxidation, by sand blasting or by chemical attack.
  • Figure 2 shows the method of the invention using a chemical attack method.
  • the NiCr skirts undergo a chemical attack in a bath of acid for a duration comprising between 15 and 45 minutes.
  • the method then provides for a rinsing step in a current of deionised water at a temperature of between 60°C and 80°C for a duration of 10 to 30 minutes.
  • Cups such as the cup 2, are assembled on the extremities of the skirts (by laser welding for example).
  • the acid used is a hydrochloric acid.
  • the concentration is between 30 and 37% of hydrochloric acid.
  • the temperature of the acid bath in which the skirts are immersed can be between 20°C and 40°C, namely almost at ambient temperature.
  • the period of treatment in an acid bath is approximately between 15 and 45 minutes.
  • an HCl acid can be used at a concentration of about 37% and this chemical attack step will be carried out at a temperature close to 22°C for approximately 30 minutes.
  • a solution of glacial acetic acid, nitric acid and water is used.
  • the volume composition of this solution will be as follows:
  • the treatment will be carried out at a temperature of between 80°C and 110°C for 15 to 45 minutes.
  • the treatment will be carried out at around 100°C (103°C for example) for 30 minutes.
  • the measurement of the said roughness accounted for in the present invention is the statistical criterion R a that represents the arithmetical average deviation from the mean with respect to the mean line of the surface profile.
  • an Ra value of at least 0.25 ⁇ m will prevent the tendency that the skirts have to stick together when they are undergoing annealing when their surface is not treated.
  • composition of the acid baths, their temperature and the duration of the chemical attack must be optimised in accordance with the invention to prevent the roughnesses from being smoothed by an attack that is too powerful or too long.
  • the NiCr is reconstructed and the skirt matt and rough after attack becomes smooth and glossy after annealing.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • ing And Chemical Polishing (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
EP07106047A 2006-04-26 2007-04-12 Procédé de fabrication d'une cathode pour des tubes à rayons cathodiques Withdrawn EP1868221A3 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR0651486A FR2900500A1 (fr) 2006-04-26 2006-04-26 Procede de fabrication de cathode pour tube a rayons cathodiques

Publications (2)

Publication Number Publication Date
EP1868221A2 true EP1868221A2 (fr) 2007-12-19
EP1868221A3 EP1868221A3 (fr) 2008-03-05

Family

ID=37435393

Family Applications (1)

Application Number Title Priority Date Filing Date
EP07106047A Withdrawn EP1868221A3 (fr) 2006-04-26 2007-04-12 Procédé de fabrication d'une cathode pour des tubes à rayons cathodiques

Country Status (3)

Country Link
EP (1) EP1868221A3 (fr)
CN (1) CN101064231A (fr)
FR (1) FR2900500A1 (fr)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR792982A (fr) * 1934-08-10 1936-01-14 Thomson Houston Comp Francaise Perfectionnements aux électrodes émettrices
US4247377A (en) * 1979-02-21 1981-01-27 United Technologies Corporation Method for electrolytic etching
FR2818437A1 (fr) * 2000-12-15 2002-06-21 Thomson Tubes & Displays Structure de cathode a oxydes
FR2840450A1 (fr) * 2002-05-31 2003-12-05 Thomson Licensing Sa Corps cathodo-emissif pour cathode impregnee de tube electronique

Also Published As

Publication number Publication date
EP1868221A3 (fr) 2008-03-05
FR2900500A1 (fr) 2007-11-02
CN101064231A (zh) 2007-10-31

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