JPS59209256A - Glass paste for fluorescent character display tube - Google Patents

Abstract

PURPOSE:To improve the chemical resistance and the moisture resistance of a glass paste for a fluorescent character display tube by using ultrafine particles of a metal compound in the composition. CONSTITUTION:A lead-borosilicate-system low-melting-point glass 13 is mixed with a pigment 14, metallic compound particles having diameters of below 1mum and an organic medium 16 to make a paste. Many ultrafine particles of a metallic compound 15 adhere to the surface of low-melting-point glass 13 and the pigment 14. The organic medium 16 exists among the particles of the low-melting- point glass 13, the pigment 14 and the metallic compound 15 to disperse these particles. The low-melting-point glass 13 principally consists of not less than 50% of PbO and contains B2O3, ZnO, Al2O3, SiO2, CaO and the like. The thus obtained material, after being molten, is crushed so as to form particles of around 3.0mum diameters. The pigment 14 is a black pigment principally consisting of the oxide of a metal such as Cr, Fe, Co or the like.

Description

[Detailed Description of the Invention] The present invention is arranged on an anode substrate of a fluorescent display tube, and is used to shield wiring conductors, insulate wiring conductors from each other, and to improve visibility as a back of a display section. Regarding the glass paste that is mainly composed of low melting point frit glass, in particular, adding ultrafine particles of metal carbide or oxide,
The present invention relates to a glass paste for fluorescent display tubes that forms a glass insulating film in a matte state with low specular reflectance.

In general, a fluorescent display tube, as shown in FIG. 1, has a vacuum container composed of a substrate 1 and a front container 2.
A molded front type is formed of insulating glass or ceramics, and a flat-bottomed boat-shaped front container 2 of translucent glass is polymerized and sealed near the outer periphery of the substrate 1;
As shown in the figure, the vacuum container is an insulating glass substrate l,
There is an assembled front type container in which a front container 2 consisting of a translucent front plate 2a and a side plate 2b adhesively fixed to stand upright around the substrate 1 is sealed and sealed.

In either type of fluorescent display tube, an anode is formed on the substrate 1. For the anode, a wiring conductor 3 of A1 is provided on the substrate 1 by a font etching method, or a wiring conductor 3 made of Ag paste is provided by a thick film printing method. An insulating layer 4 mainly composed of low melting point glass is provided on the upper surface of this wiring conductor 3 by screen printing.

The insulating layer 4 has through holes 5 in which the insulating layer 4 is not coated at predetermined positions on the upper surface of the wiring conductor 3, as shown in FIG.
will be established. Furthermore, the through hole 5 is formed on the upper surface of the insulating layer 4.
An anode conductor 6 mainly composed of carbon is disposed on the upper surface of the anode conductor 6 . A phosphor layer 7 is deposited on the upper surface of this anode conductor 6 to constitute an anode. A mesh-like control electrode 8 is disposed above the phosphor layer 7 when necessary, facing the phosphor layer 7.
Furthermore, a filament-shaped cathode 9 is stretched above it. Reference numeral 10 denotes a terminal portion joined to the end portion of the wiring conductor 3.

The insulating layer 4 will be explained in more detail.

The insulating material forming the insulating layer 4 is in the form of a paste containing low melting point glass as a main component, and is therefore referred to as glass paste.

Conventional glass paste consists of the following materials:

It consisted of a low-melting glass, a pigment, and an organic medium. Among the above materials, the low melting point glass mainly contains pbo, and also contains B2O3, ZnO, Al2O3, 51
02CaQ etc. are mixed and melted, then cooled and pulverized to have an average particle size of about 3 μm.

The pigment (Pigmen 1-) is a black pigment whose main component is an oxide such as Cr, Fe, or Co.

The organic medium is called vehicle and is ethylcellulose.

It is a viscous solvent made by mixing methylcellulose with an organic solvent such as terpineol.

The above materials were mixed and made into a paste to form a glass paste.

This glass paste is applied to the upper surface of the wiring conductor 3 of the board 1 by screen printing method and baked to form an insulating layer 4. As shown in FIG. 4 is also one layer. Furthermore, if the display pattern is complex, the wiring conductors 3 need to be formed in two layers since a single layer of the wiring conductors 3 will result in intersecting parts. Therefore, as shown in FIG. 2, a first insulating layer 4 is formed on the upper surface of the first layer wiring conductor 3, and a second layer of disconnected conductor 3a is deposited on the upper surface of this insulating layer 4. As described above, there are examples in which the insulating layer is a single layer and multilayers having two or more layers. In any case, since it is necessary to accurately arrange the through holes 5 at the predetermined positions 3-, a glass paste with excellent printability is required. The insulating layer 4 deposited by the printing method is fired at the softening point of the low-melting glass, 540-550° C., to burn off the vehicle as an organic medium and melt and fix the low-melting glass and the pigment together. In this insulating layer 4, as shown in the enlarged cross-sectional view of FIG.
are in a dispersed state. The specific gravity of the pigment 12 is greater than the specific gravity of the glass 11, so the pigment 12 does not appear on the surface, and the surface of the insulating layer 4 is the same as the glass 1.
It is composed of one smooth surface.

Further, the insulating layer 4 is disposed on all the display parts other than the display segments so as to surround the peripheries of the display segments.

Therefore, the insulating layer as well as the display segments are visible to the eyes of an observer looking at the fluorescent display tube. In other words, it becomes the background of the display segment.

The color of this back may be black to create a contrast between the light-emitting segments and the back, or a white background where the back is the same color as the body color of the non-light-emitting segments. This will be explained using the case of the back.

One of the conditions for the insulating layer 4 as a backing is that it is not glossy. In other words, from the viewpoint of visibility, it is ideal that there is no phenomenon in which external light or light from a light emitting segment is specularly reflected on the surface of the insulating layer 4 as a back and appears to be emitted from the insulating layer 4.

However, since the conventional insulating layer 4 has a smooth surface made of glass as described above, light from outside the display tube and light emitting segments inside the display tube are reflected by the inner surface of the front case 2, causing the insulating layer 4 to It became easier to specularly reflect light directed toward the surface, and the specular reflectance accounted for most of the total reflectance.

Therefore, the viewer may notice that the light emitted by the light emitting segment and the external light that is specularly reflected by the back or the light that is reflected by the light emitting segment by the front container 2 and further reflected by the insulating layer 4 overlap, and therefore, the light emitted by the light emitting display segment is It will appear as if the area is emitting light. Therefore, there is a problem in that the true display and the false display of the reflected light on the insulating layer 4 overlap and appear double to the observer, resulting in poor visibility.

Therefore, the inventors discovered that by mixing a large amount of a pigment that does not deform even at the softening point of low-melting glass, the surface of the insulating layer 4 becomes uneven, causing more diffuse reflection and less specular reflection, resulting in a non-glossy surface. Therefore, only the display portion is reflected and does not appear on the insulating layer 4, but since the proportion of low-melting glass is reduced, the insulating layer 4 becomes porous and has many minute holes. It becomes easy to adsorb and absorb a large amount of gas into the through holes, and it is difficult to degas the adsorbed and absorbed gas during evacuation after sealing, and it gradually appears after evacuation and creating a vacuum state, which has a negative impact on the cathode. This also has the disadvantage that the life of the display tube is shortened, and furthermore, because it is porous, the insulating function is reduced.

Therefore, the present invention was made in view of the above-mentioned circumstances, and the insulating layer 4 is not porous, and minute irregularities are formed only on the surface of the insulating layer 4, resulting in many diffused reflections.
The object of the present invention is to provide a glass paste composition for a fluorescent display tube that can form an insulating layer with little specular reflection.

In order to achieve the object of the present invention, the present invention includes a wiring conductor disposed on a substrate, an insulating layer provided with a through hole on the wiring conductor, and an anode conductor connected to the wiring conductor via the through hole. In the glass space 1-, which forms an insulating layer of a fluorescent display tube that performs a light-emitting display by bombarding an anode consisting of a phosphor layer deposited on an anode conductor with electrons emitted from a cathode, a lead borosilicate-based low melting point material is used. Glass with pigment and particle size 1
It is characterized by a composition formed into a paste by mixing metal compound particles of μm or less and an organic medium. The present invention will be explained below with reference to an embodiment shown in one drawing.

FIG. 3A is an enlarged microscopic view of the glass paste for a fluorescent display tube of the present invention.

13 is a low melting point glass particle, and 14 is a pigment particle. A large number of 7- ultrafine particle metal compounds 15 are attached around the low melting point glass 13 and the pigment 14. The organic medium 16 exists between the particles of the low melting point glass 13, the pigment 14, the ultrafine metal compound 15, etc., and disperses the particles.

The low melting point glass 13 is composed of the following components.

The main component is lead oxide (pbo), which accounts for more than 50% of the total. In addition, silicon oxide (B203), zinc oxide (ZnO
), alumina (A1203), silica (Si02),
Contains calcium oxide (Cab), etc.

The above raw materials are melted and then ground to form particles with a particle size of about 3.0 μm.

Next, the pigment 14 is a black pigment, including Cr and F.
The main ingredients are oxides of metals such as CO. Iron oxide has a melting point of 1,550°C, while chromium oxide and cobalt oxide have a very high melting point of 1,900°C or higher. Chemical changes occur at firing humidity of <550°C. It is stable. Particle size is 0.5~3μ
It is m.

The ultrafine metal compound 15 is 5i02, Al2O3, T
It is at least one type of substance selected from metal oxides such as iO2 and metal compounds 8- such as SiC, and is ultrafine particles with a particle size of 1 μm or less. In the case of this example, an example using ultrafine particles of SiO□ (AERO5IL■ manufactured by Nippon Aerosil Co., Ltd.) will be described.

The ultrafine particles 5i02 are obtained by agglomerating SiO□ by hydrolyzing S i C14 in an oxyhydrogen flame.

2H2+ 02 + 5iCi41erte5i02 +
4HC1 5i02 synthesized by the above gas phase reaction forms ultrafine particles with an average particle size in the range of 10 to 20 μm. The 5i02 produced in this way is amorphous, has a wide specific surface area of approximately 220 rrr/g, and has a huge number of particles of 1017 per gram.

In addition, the ultrafine particles of Sj,02 have silal groups (
Since it has Sill(), the water molecules are approximately 40wt.
Up to % can be absorbed. However, this moisture is 510
Moisture can be easily released by heating 2.

The temperature range in which this physically adsorbed water is released starts from around 100°C and ends up being released up to about 200°C.

Furthermore, Sj,02 has the effect of adjusting the softening point of the low melting point glass by mixing it with the low melting point glass.

In other words, 5i has poor thermal conductivity on the surface of low melting point glass particles.
Because of the protective film 02, the temperature range from when it begins to soften to when it becomes completely uniformly vitrified is wider than that of conventional low melting point glasses, as shown in Figure 5.

It also has the effect of adjusting the fluidity of the low melting point glass by mixing it with the low melting point glass. Furthermore, when it is made into a paste form, it also has the effect of improving printing characteristics.

The organic medium contains 1 to 2 w of a cellulose binder such as ethyl cellulose, methyl cellulose, or nitrocellulose.
t% and 98 to 99 wt% of an alcohol, such as terpineol, which is a binder solvent.

Therefore, since it is a viscous solvent, it can be formed into a paste by mixing the low melting point glass and the like with this solvent. Furthermore, since this organic medium is made entirely of organic matter, it has the characteristic that it decomposes and evaporates when burned in the air.

A glass paste for a fluorescent display tube is formed using the materials described above.

The composition of glass paste for fluorescent display tubes is an important percentage: low melting point glass 51-75 pigment 4-19 ultrafine particles 5i0
2 0.5-5 organic medium 2
A black glass paste is formed by weighing out a predetermined amount at the above ratio and stirring and mixing thoroughly.

The mixing amount can be varied within the range described above. For example, by increasing the proportion of pigment, the black color of the glass paste can be deepened, and by increasing the proportion of ultrafine particles 5102, it is possible to lower the softening point and improve printability. As long as it is within the above range, a glass paste that can achieve the object of the present invention can be produced.

The glass paste for a fluorescent display tube thus formed contains 0.5 to 5% of ultrafine particles of a metal compound, such as silicon oxide (SiO2), so that the ultrafine 11-particle metal compound 15 forms the third As shown in Figure A, it adheres to the surface of the low melting point glass particles 13 and acts as a protective film for the low melting point glass particles 13. In addition, the ultrafine metal compound 15 of 5i02 also adheres to the surface of the pigment particles 14,
There are also ultrafine particles that are free and do not adhere anywhere.

Adhesive coating is applied around the low melting point glass particles 13,
The ultrafine particles 5i02 act as a protective film because they have the property of adsorbing moisture, and the moisture surrounding the low melting point glass particles [3] is adsorbed by the ultrafine particles 5i02.

Therefore, there is no direct contact with the low melting point glass, no hydrolysis reaction of the low melting point glass occurs, and there is an effect of preventing deterioration of the low melting point glass. In addition, since the moisture adsorbed on 5102 is easily released from SiO□ by heating during sealing, it can be prevented from remaining inside the envelope of the fluorescent display tube.

In addition, since it contains ultrafine particles of SiO□, the temperature range of the softening point when the glass paste is fired is 540 to 550°C, as shown in Figure 5, compared to the softening point of a conventional paste that does not contain ultrafine particles of S x O2. The product of this invention is 545-6001
The range of softening point becomes wider at 2-℃. That is, it begins to soften at approximately 545°C, and as the temperature rises, it gradually softens and the glass particles fuse together, and when the temperature reaches 600°C, they all melt uniformly to form a block of glass and become integrated. Since the softening point of conventional glass paste is 540 to 550°C, the temperature had to be controlled within a range of 10°C, but the glass paste 1- of the present invention has a range of 55°C. The control range of the heating temperature for obtaining the insulating layer 4 with the required degree of fusion becomes wider, and the control becomes easier.

Moreover, this ultrafine particle 5i02 has a silanol group (S
iOH), and these silanol groups tend to form hydrogen bridges and bond with each other. However, this hydrogen bridge bond.

Because they are weak bonds, just applying a slight external force will separate them again and break the molecular state. Therefore, since the molecular weight becomes low, the viscosity decreases. When the external force is removed and the product is left standing, bonds between SiO□ particles (hydrogen crosslinks) occur again.

This phenomenon is called the thixotropic effect and has the effect of improving printing characteristics. That is, when printing pastes 1 to 1 containing ultrafine particles S]0□, they are suppressed by the mesh of the screen by the squeegee. Therefore, as external force is applied to the paste by the squeegee, the bonds are broken and the viscosity decreases, resulting in improved fluidity, allowing it to pass through even fine meshes smoothly. However, once the paste passes through the screen and is printed on the substrate, it remains stationary, causing hydrogen bonds and increasing viscosity. Therefore, not only can printing be performed with high precision without the paste dripping or flowing out, but also there is an effect that the paste does not become porous due to its good fluidity.

Further, the chain-like bonded particles to which the ultrafine particles 5102 are bonded are bonded on the surface of the low-melting point glass particles to form a chain-like or network-like structure, as shown in FIG. 3B. In this state, it is heated to 545-600℃ through a sintering process.
When heated to a temperature of about 100 ml, some of the particles of low-melting glass bond together and the shape of the particles changes, but they do not become a single block of glass.

On the surface, a large number of ultrafine particles of SiO□ are bonded in a chain or network form and aggregated to form an aggregate. Since these aggregates adhere irregularly to the surfaces of the low-melting point glass particles and pigments, fine irregularities are formed on the surface of the insulating layer 4. Therefore, it is possible to form the surface of the insulating layer 4 in a matte state due to these three factors: the unevenness of the low melting point glass particles, the unevenness of the pigment particles, and the unevenness due to the aggregate of ultrafine SiO3 particles. .

FIG. 6 is a graph showing the total reflectance of an insulating layer formed using the glass paste for a fluorescent display tube of the present invention and an insulating layer formed using a conventional glass paste. The total reflectance is shown when the total reflectance of white alumina is taken as 100%. From this graph, it can be seen that the total reflectance of the glass paste of the present invention is higher than that of the conventional glass paste.

Moreover, FIG. 7 is a graph of the specular reflectance of the insulating layer of the conventional glass space 1- and the insulating layer of the product of the present invention.

The regular reflectance of each of the above is shown when the regular reflectance of white alumina is taken as 100%. It can be seen from this graph that the regular reflectance of the glass paste 1 of the present invention 15- is smaller than that of the conventional glass paste at any wavelength. That is, from the graphs of FIGS. 6 and 7, it can be inferred that the insulating layer made of the glass paste for a fluorescent display tube of the present invention has a high total reflectance but a low specular reflectance, and therefore a high diffuse reflectance. It can be seen from these graphs that when the regular reflectance is low and the diffuse reflectance is high, external light and reflected light from the light emitting segments are not reflected on the surface of the insulating layer.

The present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various changes without changing the gist thereof.

As explained above, according to the glass paste for fluorescent display tubes according to the present invention, since ultrafine particles of a metal compound are contained in the composition, a structure in which the ultrafine particles are attached to all the surfaces of the low melting point glass particles is created. Therefore, it acts as a protective layer for low-melting glass, and has the effect of providing a stable glass paste with strong chemical resistance and water resistance.

Furthermore, when the insulating layer 16- is formed using the glass paste of the present invention by a printing method, the printing characteristics are significantly improved due to the thixoropic effect, and the insulating layer is formed without becoming porous, with minute irregularities being formed on the surface. The specular reflectance is low, and the surface is matte, with no gloss, and there is no reflection of light-emitting display parts such as fluorescent display tubes, no double appearance caused by external light, and excellent visibility. It also has the effect of serving as an insulating layer for display tubes.

Furthermore, since the softening point of the glass paste is widened, it also has the effect of making it easier to control the temperature in the firing process after the insulating layer is deposited.

[Brief explanation of the drawing]

1 and 2 are longitudinal cross-sectional views of a general fluorescent display tube, FIG. 3A is an enlarged view showing the state before printing of the glass paste of the present invention, and FIG. 3B is a view of the glass paste of the present invention. Figure 4 is an enlarged view showing the state of the conventional glass paste after printing and firing, Figure 5 is the sintering temperature and combination of the conventional glass paste and the glass paste of the present invention. 6 and 7 are graphs showing the total reflectance and specular reflectance of the glass paste according to the present invention and the conventional glass paste. 1... Board 3... Wiring conductor 4
... Insulating layer 5 ... Through hole 6 ... Anode conductor 7 ... Phosphor layer 9
...Cathode 12 ...Pigment particle 1
3...Glass particles 14...Pigment particles 15...Metal compound particles 16...Organic medium patent applicant Futaba Electronics Co., Ltd. 19- Figure 1 Figure 2 Dg o o o“′ () 10 Dry mouth test Miku

Claims (1)

[Claims] A wiring conductor arranged on a substrate, an insulating layer with a through hole on the wiring conductor, an anode conductor connected to the wiring conductor via the through hole, and a phosphor coated on the anode conductor. In a glass paste for forming an insulating layer of a fluorescent display tube that performs luminescent display by the bombardment of electrons emitted from a cathode onto an anode consisting of a layer, a lead borosilicate-based low melting point glass is mixed with a pigment and a metal with a particle size of 1 μm or less. A glass paste for a fluorescent display tube, characterized in that it has a composition formed into a paste by mixing compound particles and an organic medium.