JPS5889760A - Insulation defect detecting method at frit sealing section of cathode ray tube - Google Patents

Abstract

PURPOSE:To detect the insulation defect at the frit sealing section by applying the high voltage pulse repeatedly between an inner conductive film and an electrode contacted tightly to the outercircumference of the frit sealing section then analyzing the accumulated result of the current waveform. CONSTITUTION:A contact electrode 5 is contacted with an anode terminal 3 penetrating through a funnel glass wall 2 and conducting with an inner conductive film 4 on the tube inner wall face, while a current detecting electrode 6 is contacted tightly with the outercircumference of the frit sealing section. When a pulse signal 20 is applied from a processor 18, a switch 8 will function to apply a high voltage pulse of the voltage level Eo on a measuring circuit. The measuring current on the electrode 6 is provided through a level converting circuit 14 to a current extraction circuit 15. The circuit 15 is provided with the extraction signals 9a-9c with predetermined interval from a device 18 and the extracted current level is A/D converted 16 then stored in a memory 17. Said level is compared with the normal level prestored in the device 18 and the analized result is indicated on a display 19. In such a manner the insulation defect at the CRT frit sealing section can be detected easily and reliably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to improve the internal conductive film and the external conductive film of cathode ray tubes, which are caused by frit sealing parts that are relatively prone to insulation defects due to internal air bubbles or residual surface contamination. This invention relates to a method for easily and reliably detecting insulation defects between surfaces.

For negative TI and IS tubes, especially color tubes that require a process of exposure using a large mask to form a fluorescent surface, the panel that has undergone the process of forming a fluorescent surface on the inner surface of the bulb panel is placed at the large-diameter opening end of the funnel. It must be sealed using a frit (low melting point glass powder).

In the frit sealing part, internal KjL bubbles may occur, contamination may remain on the end faces of the panel or funnel, and contaminants may be mixed in during the process of applying 7-lit as a paste, so when the cathode ray tube is put into use, - When a high DC voltage that continuously accelerates the cathode rays is applied between the inner and outer surfaces of the glass wall of the cathode ray tube bulb, this frit seal becomes a weak point in electrical insulation and the insulation breaks down. There is a relatively high rate of failures in which a large amount of current flows through the capacitor. Therefore, as shown in Figure 1, funnel glass i! An anode terminal 3 that passes through the tube 2 and is electrically connected to the internal conductive film 4 on the inner wall surface of the tube is brought into contact with the anode terminal 3, and the anode of the DC high voltage power source 7 is connected via the switch 8. A current detection electrode 6 is brought into close contact with the frit-sealed portion, and the value of the current j (flowing through the frit-sealed portion is measured by a current detector 6a, thereby testing the insulation of the frit-sealed portion.

However, in the inspection method shown in FIG. 1, if the outer surface of the funnel glass 112 is contaminated, a relatively large leakage current i1 flows directly on the outer surface from the contact electrode 5 to the detection electrode 6. However, if a moving coil type galvanometer with a large moment of inertia is used, it will not be possible to measure the charging current waveform immediately after voltage application, or any disturbances in the current waveform due to insulation defects in the frit sealing part. There were five problems in that it was difficult to accurately determine whether there was an insulation defect in the bonded area.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for simply and reliably detecting the presence or absence of an insulation defect in a frit-sealed portion without the above-mentioned problems.

In order to achieve the above object, in the present invention, high voltage pulses are repeatedly applied between the internal conductive film of the cathode ray tube and the electrode that is in close contact with the outer periphery of the frit sealing part. Insulation defects in the frit sealing area were detected by analyzing the accumulated results of repeated measurements of the current waveform. The present inventor used an electronic measuring device to observe the current waveform immediately after applying voltage to the frit-sealed part, and found that if there is a defect in the frit-sealed part, the capacitance using the conductive film as an electrode It has been found that even in the process where the peak of the charging current increases and then decreases exponentially from that peak, the exponential process may be disrupted and a transient protrusion may occur. Small peaks due to irregular fluctuations observed in the process of decreasing from the peak have a high probability of appearing immediately after voltage application, and it is better to repeatedly apply high voltage pulses than to apply high voltage continuously for a relatively long time. This is because it was observed during fusion. The insulation defect detection device was made electronic to enable high-speed observation, and the observation results were converted into digital data, making it easy to accumulate repeated observation values and perform calculations for analysis. In order to obtain accurate and accurate observation results, the leakage current on the outer surface of the cathode ray tube must be
A guard electrode was also used to prevent the insulating current from entering the lit sealing area.

First, with reference to FIG. 2, we will explain the outline of the conventional detection path (which is basically the same in the case of the present invention), including the frit sealing part that is the object of measurement and the leakage current path that causes errors. . As can be seen from the figure, the current between the contact electrode 5 and the current detection electrode 6 consists of i flowing through the frit sealing part 1 and leakage current i1 flowing through the tube outer surface (effective resistance r s ). The internal conductive film 4 having a capacitance Cf is included in the path. Although il and j can be easily separated by using the well-known guard electrode as described above, the insulation properties of the frit sealing part In the past, there were some points that were not always clear, and it was not easy to accurately determine whether the product was good or bad in the mass production process.
exists, so the following equations (1), (21, and (3) hold true. However, t is time, q is the charge accumulated in Cf,
r( is the resistance of the frit welded part 1.

q(t)=Cf-Es(1-e'fCf) (2
The jf value i4 when one voltage is applied (t=o) is i(1=B
o/r((51 Also, the time constant t, = r(+1 value f after C1 has elapsed is "
"""/ e, r ((61). In these formulas, rf and Cf are considered constants, but
Actually, if there is an insulation defect in the frit sealing part 1, r(
fluctuates and decreases irregularly, and Cf becomes thicker. Conventionally, a 6m movable ring type galvanometer with a large moment of inertia was used.
Therefore, it was difficult to observe the current waveform. Note that the value of the total current II flowing through the galvanometer is, of course, Io=i(+iB).

FIG. 3 is a block diagram of one embodiment of the present invention.

When the pulse signal 2o is applied from the processing device 18, the switch 8 is actuated in response, and a high voltage pulse of voltage value Bo is repeatedly applied to the measurement circuit, for example, 20m5 on and 20m5 off, for a total of 10 seconds. The measurement is performed from the processing device.When the 'h extraction signal (pulse) 9a is given after the voltage is applied, the peak current of the current during the signal period is measured.The 'fs extraction signal is measured after the voltage is applied and after 11 hours have elapsed. When 9b is given, the peak value of the current during that period is determined, and at time t when e-1t becomes sufficiently small as time passes, when 11 extraction signal 9c is given, the peak value of the current during that period is determined. Extract. In this embodiment, the current flowing into the electrode 6 is I
, = t, ten times l, of which i (as mentioned above, if the frit sealing part is normal, it will change exponentially with time, and if there is an insulation defect in the sealing part, it will change irregularly. The line marked E indicates the voltage application state.
closes and high voltage pulse Eo (for example, constant anode voltage 28
35 kv@degrees) is repeatedly applied to the tube of kv. The line indicated by I, indicates I, = Sheng(+il), and 10
g shows an example in which there is no defect in the 7-lit sealed portion. The next line marked 'fm' is the peak value 1 of Io during the period of the signal 9a, extracted by the extraction circuit 15 based on the extraction signal 9a.
It shows Cape 1a, and although it is named Todoroki f, it includes Il.

The next line marked 'fm' shows the peak value of Io after the time constant t1=rf-Cf (the maximum value during the period of the pulsed kf, extraction signal 9b), 128, etc., when l19C is given. 1. It shows an extracted value of 13all), which is labeled Il but also includes if which has been greatly reduced. If there is a defect in the 7-lit sealing part, L*'f1 e'fm #e1, etc. are 10b, llb, 12b, respectively.

13b etc. i.e. exponentially 10
In the process of decreasing, irregular disturbances and small peaks may appear. Furthermore, such small peaks often appear shortly after voltage application.

This is why it is easier to detect defects by repeatedly applying high voltage pulses than by simply continuously applying the same high voltage. For convenience, Figure 4 shows the current when the sealed part is normal during the first voltage application, and the current when there is a defect in the sealed part during the second voltage application. Generally, the electric current t becomes as shown by 10b from the first application of the high voltage pulse. Note that in the case of a defect, the first peak, ie, llb, is generally higher than the normal lla even if no small peak appears during the drop. Now, returning to FIG. 3, the current value extracted by the extraction circuit 15 as described above is digitized by the A/D converter 16, stored in the memory 17, and used for analysis and calculation by the processing device 18. The calculation results are displayed on display 4119. If the sealing part is normal and defective, if
, f, may be compared with normal values for which a large amount of data has already been stored. Of course, the value of r(4)ct can also be calculated, and the cause of M* can also be estimated as to whether it is normal or abnormal.

In order to separate the surface leakage current, the 11 values described in connection with FIG. 4 were directly measured. I, subtracted from octopus.
However, as shown in FIG. 5, a guard electrode 21 may be provided around the contact electrode 5. In this case, the memory capacity is smaller and the processing time is generally shortened.

As described above, according to the present invention, insulation defects in the cathode ray tube frit sealing portion can be easily and reliably detected.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the conventional detection method, Fig. 2 is a schematic explanatory diagram of the detection circuit, Fig. 3 is a block diagram of an embodiment of the present invention, and Fig. 4 is an extraction current m-diagram of the above embodiment. FIG. 5 is an explanatory diagram of the guard electrode. DESCRIPTION OF SYMBOLS 1...Frit sealing part, 2...Funnel glass attachment, 3...Anode terminal, 4...Interior conductive film, 9a...
IO extraction signal, 9 b...' tl, extraction signal, 10
g, 10b”-I6 waveform, 1117k + l l
b"・'b extracted value, 12a. 12b...'fm extracted value, 14... Level conversion circuit, 15... Current extraction path, 16... λ/D converter,
17...Memory, 1B...Processing device, 19...Display device, 21...Guard electrode, 11...Frit sealing part current, il...Surface leakage current, Eo... DC high voltage, r (... frit sealing part resistance, Cf...'j
l Capacity in path.

Claims (1)

[Claims] High-voltage pulses are repeatedly applied between the internal conductive film and the electrodes that are in close contact with the outer periphery of the frit sealing part of the cathode ray tube, and the accumulated values are obtained by repeatedly measuring the current waveform that flows in response to the voltage application. A method for detecting insulation defects in a cathode ray tube frit sealing part, characterized in that insulation defects in a frit sealing part are detected by analysis.