JPS61267227A - Formation of fluorescent screen in fluorescent character display tube - Google Patents

Abstract

PURPOSE:To automate formation of fluorescent screen by flying the fluorescent particles electrostatically through facing electrodes and feeding to the segment electrode formed on the substrate. CONSTITUTION:Upon application of voltage onto a facing electrode 14 and a segment electrode row 2, the fluorescent particles in hopper 13 are charged positively. The charged particles are attracted electrostatically to the substrate side in accordance to the electrical field formed between the facing electrode and the segment electrode and adhered to the exposed section 2b to form a fluorescent screen 17. The thickness of the fluorescent screen 17 is regulated to desired level by setting the strength of applying voltage and the moving speed of belt carrying means 15.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for forming a phosphor screen in a fluorescent display tube.

(Prior Art) In a fluorescent display tube, a fluorescent screen is formed on a large number of segment electrodes arranged in one or more rows in one direction, and the fluorescent screen is sealed together with a hot cathode in a vacuum container.

While generating thermoelectrons from the hot cathode, a positive voltage is selectively applied to the segment electrodes depending on the information to be displayed, attracting thermoelectrons to the selected segment electrodes, and these thermoelectrons collide with the phosphor screen. Information is displayed by the fluorescence emitted when the display is done, and it is already well known as a barcode display tube and a phosphor dot array tube.

First, referring to FIG. 12, an outline of a fluorescent display tube will be explained using a fluorescent dot array tube as an example.

In FIG. 12, reference numeral 70 indicates glass, ceramic,
A substrate made of resin or the like is shown. A series of segment electrodes 71 are arranged on the substrate 70 in the longitudinal direction of the substrate, and each segment electrode 71 has a phosphor screen 72.
is formed. The size of each phosphor screen is 4
The size of the phosphor screen is extremely small, ranging from 0 x 40 μM to 50 x 50 μM, but in FIG. 12, the dimensions of the phosphor screen are shown larger than the other members.

On both sides of the phosphor screen array of the substrate 70, an insulating layer 73.7 is provided.
3 are formed along the longitudinal direction of the substrate, and on these,
Grid electrodes 74 and 74 are formed, respectively.

In FIG. 12, reference numeral 75 indicates a tungsten wire as a hot cathode stretched in the longitudinal direction of the substrate, the surface of which is coated with an electron emissive substance such as Ba5rO. Further, reference numeral 76 is a face member made of a transparent material such as glass, and is integrated with the substrate side as shown in FIG. 13.

Thus, the substrate 70, the insulator layers 73, 73, the grid electrodes 74, 74, and the face member 76 form a closed space, and within this space, the segment electrode 71, the phosphor screen 72 made of the phosphor layer, and the hot cathode 75 are formed. ,75 are trapped. The closed space is highly evacuated.

When a suitable voltage is applied to the grid electrodes 74, 74 and an alternating current of several tens of milliamps is passed through the hot cathode 75.75, the hot cathode 75.75 is heated by Joule heat and emits thermoelectrons. In this state, when a positive voltage is applied to one of the segment electrodes 71 to make it a positive potential, the thermoelectrons are attracted to the electrode portion of the segment electrode at a positive potential, and when sucked into the electrode portion, the phosphor screen 72 excites the energy state of the fluorescent substance. The excited fluorescent substance emits fluorescence when returning to the ground state. This fluorescence is observed through the face member 76.

Such a phosphor dot array tube is used as a part of the optical system of an optical printer or as a bar code display tube.

One of the methods for forming a phosphor screen is an electrodeposition method using electrophoresis. In this method, in the electrode formation step, a segment electrode array consisting of strip-shaped electrodes is formed on the substrate by photoetching, and in the insulating layer formation step, a part of the electrode is exposed by screen printing, and the A layer of thick film insulating glass is formed on the surface of the substrate including the electrodes, and this is fired.

Next, only a portion of the exposed electrode is exposed, and the surface of the substrate including the electrode is covered with a resist layer. Then, in the phosphor screen forming process, the above substrate is formed.

It is immersed in a dispersion liquid in which phosphor particles are dispersed, facing a counter electrode at a predetermined distance, and a voltage is applied between the segment electrode array and the counter electrode. The phosphor particles in the dispersion liquid move toward the segment electrodes due to the electric field formed between the two electrodes, and adhere to the exposed electrode portions to form a phosphor screen. After drying and fixing this phosphor screen, the resist layer is removed.

By the way, in the above-mentioned electrodeposition method, it takes 2 minutes to 2 minutes for the phosphor particles to adhere to the segment electrodes in a predetermined amount (predetermined film thickness).
There was a problem in that it took a long time of 10 minutes.

In addition, it is necessary to immerse the substrate in the dispersion liquid and lift it out, and it also requires relatively high-precision positioning between the segment electrodes and the counter electrode, resulting in high costs. be. Furthermore, if the conductivity of the phosphor particles forming the phosphor screen is low, sufficient luminance cannot be obtained.
There is also a problem.

(Objective) The first object of the present invention is to reduce manufacturing costs and to automate the manufacturing process. A second object of the present invention is to provide a novel method for forming a phosphor screen in a vacuum fluorescent display tube, and a second object of the present invention is to provide a method for forming a phosphor screen in a vacuum fluorescent display tube, which can reduce manufacturing costs, automate the process, and obtain sufficient luminance. It is provided by.

(Structure) In the phosphor screen forming step, the present invention applies a predetermined charge to the segment electrode rows, brings a counter electrode close to the exposed segment electrode rows, and at the same time applies a predetermined charge to the segment electrode rows. The fluorescent screen is formed by supplying phosphor particles to the surface of the substrate and electrostatically adhering the phosphor particles to the exposed segment electrode rows while applying a charge with a polarity opposite to that of the substrate. A method for forming a phosphor screen in a fluorescent display tube, comprising: applying a liquid containing trivalent aluminum ions to at least the exposed portion of the segment electrode array or the phosphor screen before or after forming the phosphor screen. It is in the surface formation method.

The present invention will be explained in detail below.

FIG. 1 shows the steps of the present invention, including an electrode forming step in which at least one row of electrodes made of a conductive material is provided on a substrate, and a substrate containing the electrodes in order to avoid contact between the grid electrode and the electrode. an insulating layer forming step of forming a segment electrode row by forming an insulating layer on the surface to expose a part of the electrodes along the electrode arrangement direction; and covering the insulating layer and the segment electrode row with a photoresist layer. Thereafter, a resist layer forming step is performed in which only the photoresist layer on each segment electrode constituting the segment electrode row is removed to expose the segment electrode row, and a predetermined charge is applied to the exposed segment electrode. A counter electrode is placed in close proximity to the exposed segment electrodes, and a charge having a polarity opposite to that of the segment electrode array is applied to the exposed segment electrodes, while supplying phosphor particles to the substrate, A phosphor screen forming step of attaching phosphor particles to the phosphor screen to form a phosphor screen, and applying a liquid containing trivalent aluminum ions to the exposed portion of the segment electrode array or the formed phosphor screen before or after forming the phosphor screen. The method consists of a phosphor screen forming step in which the photoresist layer is coated, and a photoresist layer removal step in which the photoresist layer is removed.

Each step will be explained in detail below.

Electrode Formation Step An electrode made of aluminum is formed on one surface of a substrate 1 made of, for example, a glass plate, as shown in FIG. 2(1), as indicated by reference numeral 2 in FIG. 2(2), by photoetching. As shown in FIG. 7, this electrode 2 has a width of approximately 50 μm.
m strips, and are formed in a line in the longitudinal direction of the substrate with an interval of about 35 μm between adjacent electrodes, and lead portions 2a of each electrode are drawn out to the left and right side edges of the substrate every other time.

Insulating layer forming process As shown in FIG. 2 (3), the substrate 1 including the strip-shaped electrodes 2 is made of, for example, lead glass and carbon and has a thickness of 10.
Cover with an insulating layer 3 of about 20 μm.

This insulating layer 3 is formed by a screen printing method and then
As shown in FIG. 7, the substrate 1
The electrode part located at the center in the width direction (hereinafter referred to as "
(referred to as an exposed portion 2bJ) and the end of the lead portion 2a are exposed. The exposed portions 2b are arranged in rows in the longitudinal direction of the substrate, and segment electrode rows are formed here.

Photoresist layer forming step As shown in FIG. 2(4), the insulating layers 3, the segment electrode array 2, and the substrate 1 are entirely coated with a photoresist layer 4. As the photoresist layer 4, for example, a negative type photoresist OMR-85r for fine processing is used.
A positive type photoresist for microfabrication 0FPR-80Or (cutting product name J) is used.

The photoresist layer 4 is prebaked at 85°C to 95°C for about 30 minutes.

Next, as shown in FIGS. 2(5) and 3, the photoresist layer 4 on the exposed portion 2b of each segment electrode is
As shown in a, it is removed in dots to expose the segment electrode array (center portion of the exposed portion 2b) again. dot 4
The width of a is controlled to 40 to 50 .mu.m, and an example of a method for forming such dots will be explained with reference to FIGS. 4 and 5.

In FIG. 4, the laser beam generated by the laser beam generator 5 is
The focused laser beam is guided to the scanning optical system 7 via the polarizer 6, and the photoresist layer 4 is exposed by spot scanning at the electrode arrangement pitch in a direction perpendicular to the arrangement direction of the segment electrodes. . Thereafter, this layer is developed and rinsed to remove the layer in dots to form dots 4a. In this case, a positive type photoresist is used as the photoresist layer 4, and the portions hit by the laser beam are removed to expose the electrode array to the dot-shaped segments 1. In addition, in FIG. 4, a method of sliding a mirror or the like may be adopted without using the polarizer 6. Furthermore, in FIG. 4, a laser beam generator 5
An adjusting means for adjusting the beam power may be provided between the polarizer 6 and the polarizer 6. The shape of the dot 4a is not limited to the exact square shown in the figure, but may be circular or oval.

FIG. 5 shows a substrate 1 coated with a photoresist layer 4;
There is a method in which a mask 8 on which a dot array pattern 8a having the same pitch as the electrodes 2 is formed is polymerized, and then the photoresist layer is removed in dots by applying light from a light source 9 having an emission wavelength such as ultraviolet light. It is shown. When the photoresist layer 4 is a positive type photoresist, a positive mask is used and the exposed portion is removed by development and rinsing to obtain the dots 4a. When the photoresist layer 4 is a negative type photoresist, a negative mask is used and the unexposed portions are removed by development and rinsing to obtain the dots 4a. Note that the photoresist layer 4 is formed in a dot shape.
The width of the exposed portion may be regulated by removing the layer in the form of a slit in the same direction as the arrangement direction of the segment electrodes to expose the exposed portion of the segment electrode array.

Phosphor screen forming process As shown in FIG.
It is attached to the phosphor particle supply means 10 shown in the figure.

The phosphor particle supply means 10 includes a tank 12 containing phosphor particles 11, a discharge hopper 13 disposed below the tank, and a counter electrode whose pointed end 14a protrudes from a discharge port 13a of the hopper 13. 14, a belt conveying means 15 that holds the substrate 1 and moves in the direction of the arrow while bringing the exposed portion 2b of the substrate close to the inner electrode 14; and a DC power supply 16 that applies a negative potential to.

tank] 2 is connected to the hopper 1 via the replenishment rotating body 12a.
3, the phosphor particles 11 are supplied. The discharge port 13a of the hopper 13 is formed in such a shape and opening area that it discharges the phosphor particles only when some external force acts on the phosphor particles. Although the illustrated counter electrode 14 is a conductive wire electrode having a pointed end, the electrode may be another type of electrode that does not have a pointed end. An electric field concentration effect can be expected from a counter electrode having a tip. The belt conveying means 15 is rotated at a predetermined speed in the direction of the arrow by a driving means (not shown), and as shown in FIG. 2(5) and FIG. The center of the exposed portion 2b of the segment electrode is the counter electrode 14.
The position is set so that the vehicle passes approximately directly under the vehicle at a predetermined interval. As shown in FIG. 8, when the substrate 1 is transported in a direction perpendicular to its longitudinal direction, the hopper 13 is extended to a length approximately equal to the length of the segment electrode array in a direction perpendicular to the plane of the paper. It is provided. Moreover, the counter electrodes 14 are preferably provided at substantially the same pitch as the arrangement pitch of the exposed portions 2b. The voltage is applied to the counter electrode 14 at intermittent timing synchronized with the moving speed of the segment electrode 2. Unlike the example shown in FIG. 8, when the substrate 1 is supported by the belt without any interval, the voltage may be continuously applied to the opposing electrode. In addition, in Fig. 8,
The insulating layer 3 and photoresist layer 4 on the substrate 1 are not shown.

Then, when a voltage is applied to the counter electrode 14 and the segment electrode array 2, the phosphor particles in the hopper 13 are positively charged. These charged phosphor particles are electrostatically attracted to the substrate side according to the electric field formed between the counter electrode and the segment electrode, and adhere to the exposed portion 2b, as shown in FIG. 2 (6).
Then, as shown in FIG. 6, a fluorescent screen 17 is formed. At this time, phosphor particles slightly adhere to the surface of the photoresist layer 4 in the portion covering the segment electrode row 2, but in FIGS. 2(6) and 6, phosphor particles adhere to the exposed portion. Only the phosphors that were used are shown.

The thickness of the phosphor screen 17 is adjusted to a desired thickness by appropriately setting the strength of the applied voltage, the moving speed of the belt conveying means 15, and the like.

FIG. 9 shows separate phosphor particle supply means. In the example shown in FIG. 9, a phosphor particle supply plate 21 is arranged below a tank 20, phosphor particles 11 are continuously flowed onto the plate, and the counter electrode 22 provided at the edge of the supply plate fluoresces. This method charges body particles. The supply plate 21, as shown in FIG.
It has a trough-like shape with a partition 21a, and needle-shaped counter electrodes 22, 22, . . . are provided protruding from the edges thereof. Although FIG. 10 shows the opposed electrodes 22 having a large mutual interval, it is preferable that they are arranged at substantially the same pitch as the arrangement pitch of the segment electrodes. The counter electrode 22 is connected to the positive electrode of the DC power supply 16. The belt conveyance means 15 is moved in a direction in which the substrate 1 held thereon is directly opposed to the counter electrode 22 . The segment electrode array of the substrate 1 being transported is connected to the negative electrode of the DC power supply 16 . tanri 20
is provided with a discharge rotating body 20a, and a supply plate 2
The amount of phosphor particles flowing out is controlled so that a sufficient amount of phosphor particles are present on the surface of the phosphor particles. The phosphor particles on the supply plate flow toward the opposing electrode due to the inclination of the plate or vibrations caused by an appropriate vibration mechanism (not shown), and fall from the edge of the plate. The fallen phosphor particles are recovered by a recovery device (not shown) and then returned to the tank 20.

Then, when the substrate 1 is conveyed in the direction of the indicated arrow, when a voltage is applied to the counter electrode 22, the phosphor particles present near the edge of the supply plate 21 are positively charged, and the counter electrode and the segment According to the electric field formed between the electrode and the exposed part 2
a, and electrostatically adheres to it, forming a fluorescent screen 17.
(See FIG. 2 (6)).

The substrate on which the phosphor screen has been formed by the method described in FIGS. 8 and 9 proceeds to the next step.

FIG. 11 shows a second invention. A feature of the present invention is that a liquid containing trivalent aluminum ions is applied before or after the phosphor particles are supplied to the exposed portion 2b. A liquid application means 30 is arranged upstream of the counter electrode 14 in the moving direction of the belt conveyance means 15 . This liquid application means consists of aluminum nitrate (A
A tank 32 stores a liquid 31 obtained by dissolving l(No, )3.9H20) in isopropyl alcohol ((c H3)2CHOH), and a rotating coating impregnated with the liquid 31 is placed below this tank. It consists of a roller 33. Note that instead of using a coating roller as the liquid coating means, the liquid may be supplied directly from a tank as a shower to the substrate, or may be sprayed and coated using a pump and a nozzle. The axial length of the application roller 33 is formed to be approximately equal to the length of the segment electrode array when the substrate 1 is conveyed in a direction perpendicular to the segment electrode array.

When the substrate is conveyed in the same direction as the longitudinal direction, the application roller only needs to have at least the width of the exposed portion 2b.

The phosphor particles 11 are stored in a tank 34, and are caused to fly toward the substrate 1 in response to voltage application to the counter electrode 14, and are electrostatically attached to the exposed portion 2b. At this time, trivalent aluminum ions A13+ are present in the haze portion 2b.
The applied phosphor particles have their electrical conductivity increased because the liquid containing the phosphor particles is applied thereto. Of course, the means for supplying the phosphor particles may be of the type shown in FIG. 8 or 9.

Although FIG. 11 shows an example in which the liquid 31 is applied before supplying the phosphor particles, the liquid may be applied after the particles are supplied to form the phosphor screen. In this case, it is more advantageous to use a non-contact shower method or a low-pressure spray method for the liquid 31 than to use a roller application method because the phosphor screen will not be disturbed.

The substrate having the phosphor screen formed by the method described in FIG. 11 is subjected to the next step after the phosphor screen is dried and the liquid component is removed.

Photoresist Layer Removal Step As shown in FIGS. 2(6) and 6, the substrate 1 on which the phosphor screen 17 is formed is fired with, for example, oxygen plasma to peel and remove the photoresist layer. When the photoresist layer 4 is removed, as shown in FIG. 2 (7) and FIG.
Segment electrode array 2 is exposed. At this time, the phosphor particles adhering to the photoresist layer 4 are also removed as the layer is peeled off. Therefore, on each segment electrode 2, a phosphor screen 17 having the same size as the dot 4a is formed. And this regarding board 1 lol
As it turns out, the phosphor screens 17 are arranged in an orderly dot pattern.

(Effects) As described above, according to the present invention, the phosphor particles are electrostatically ejected by the counter electrode and are supplied to the segment electrodes formed on the substrate, so that the formation of a phosphor screen is facilitated. It can be automated and the manufacturing cost of phosphor dot array tubes can be significantly reduced.

Furthermore, since a liquid containing trivalent aluminum ions is applied before or after forming the phosphor screen, the electrical conductivity of the phosphor particles increases, suppressing deterioration of the phosphor screen over time and stabilizing its brightness.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing the steps of the phosphor screen forming method of the present invention;
FIG. 2 is a process diagram showing a specific example of the above in a cross-sectional view, FIG. 3 is a partial plan view for explaining the photoresist layer forming process, and FIGS. 4 and 5 show a method for removing the photoresist layer. Block diagrams showing different examples, FIG. 6 is a partial plan view showing a state in which a phosphor screen is formed and the photoresist layer is not removed, and FIG. 7 is a partial plan view showing a state in which the photoresist layer is removed. FIG. 8 is a schematic sectional view showing an example of a phosphor particle supply means for implementing the phosphor screen forming method of the first invention, FIG. 9 is a schematic sectional view showing another example of the phosphor particle supply means, and FIG. 1O is a partial perspective view showing an example of a phosphor particle supply plate, FIG. 11 is a schematic sectional view showing an example of a phosphor particle supply means for carrying out the second invention, and FIG. 12 is a diagram of a fluorescent display tube. FIG. 13 is an exploded perspective view showing a phosphor dot array tube as an example, and a cross-sectional view of the same. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Segment electrode, 3... Insulating layer, 4... Photoresist layer, 4a... Dot, 1
1... Phosphor particles, 16... DC power supply, 17...
Fluorescent screen, 14.22...Counter electrode, 31...Liquid.

Claims (2)

[Claims] (1) In a fluorescent display tube, in the electrode forming step, at least one row of electrodes made of a conductive material is provided on the substrate, and in the insulating layer forming step, the electrodes are formed on the substrate surface including the electrodes along the direction in which the electrodes are arranged. forming a segment electrode array by forming an insulating layer that exposes a part of the segment electrode array, and in a photoresist layer forming step, the insulating layer and the segment electrode array are covered with a photoresist layer, and then the segment electrode array is formed. Only the photoresist layer on each segment electrode is removed to expose the segment electrode row, and in the phosphor screen forming step, a predetermined charge is applied to the segment electrode row, and the segment electrode row is placed opposite to the exposed segment electrode row. While placing electrodes in close proximity to each other and applying a charge having a polarity opposite to that of the segment electrode row to the electrodes, phosphor particles are supplied to the surface of the substrate to inject the phosphor particles into the exposed segment electrode row. A method for forming a phosphor screen, comprising: depositing the photoresist layer to form a phosphor screen, and removing the photoresist layer in a photoresist layer removal step to form a phosphor dot array. (2) In a fluorescent display tube, in the electrode forming step, at least one row of electrodes made of a conductive material is provided on the substrate, and in the insulating layer forming step, the electrodes are formed on the substrate surface including the electrodes along the direction in which the electrodes are arranged. forming a segment electrode array by forming an insulating layer that exposes a part of the segment electrode array, and in a photoresist layer forming step, the insulating layer and the segment electrode array are covered with a photoresist layer, and then the segment electrode array is formed. Only the photoresist layer on each segment electrode is removed to expose the segment electrode row, and in the phosphor screen forming step, a predetermined charge is applied to the segment electrode row, and the segment electrode row is placed opposite to the exposed segment electrode row. While placing electrodes in close proximity to each other and applying a charge having a polarity opposite to that of the segment electrode row to the electrodes, phosphor particles are supplied to the surface of the substrate to inject the phosphor particles into the exposed segment electrode row. Before or after the phosphor particles are deposited to form a phosphor screen, the substrate surface including at least the exposed segment electrode array or the formed phosphor screen contains trivalent aluminum ions. A method for forming a phosphor screen, comprising applying a liquid and removing the photoresist layer in a photoresist layer removal step to form a phosphor dot array.