JPS6037637A - Formation of metal back of cathode-ray tube - Google Patents

Abstract

PURPOSE:To prevent a blistering phenomenon of a metal reflecting film by specifying a temperature gradient condition of a baking process. CONSTITUTION:In the baking process for forming a metal reflecting film for metal back, a heating gradient in the large region of a weight decreasing rate on the thermal weight analytical curve of an intermediate film is set up to be remarkably slow compared with the starting time. The heating gradient is made to be 2 deg.C/min in the region of 250-290 deg.C, in which thermal decomposition of a sensitive bonding agent is accelerated, and in the region of 335-405 deg.C, in which the thermal decomposition of an intermediate film is accelerated. The temperature gradient condition can be made slower or a heating curve, in which constant temperature heating is performed for a fixed time in the region showing sudden thermal decomposition while intermittently raising temperature after diffusion of evaporation gas, can be adopted. Thereby, a blistering phenomenon of the metal reflecting film due to sudden evaporation of the intermediate film can be prevented.

Description

[Detailed description of the invention] (b) Industrial application field A cathode ray tube with a metal back.

(b) Prior Art It is well known that the brightness of a cathode ray tube can be improved by forming a metal back made of aluminum or the like on the fluorescent surface of the cathode ray tube. This metal reflective film is generally formed by vapor deposition. At this time, since there are irregularities and voids on the fluorescent surface to which the fluorescent particles are attached, an intermediate film (organic film) that can be thermally decomposed and volatilized is formed on the fluorescent surface in order to smooth the vapor deposition surface. are doing. This process is generally called filming. After this filming step, a metal is deposited on the organic coating,
Thereafter, a baking process is performed to burn off all unnecessary organic matter. During this baking process, organic substances are thermally decomposed, gasified, and released into the atmosphere, so if the metal reflective film does not have appropriate porosity, the metal reflective film will move. ``Yu 1 Ga #1 Power;
On the other hand, the metal reflective film needs to be smoother in order to act as a highly reflective mirror surface for the light emitted by the phosphor. The organic film underlying the metal reflective film must be formed to create a metal reflective film that is smoother and has appropriate porosity.

In order to obtain an organic film with these contradictory properties, a method generally referred to as an emulsion method in which an aqueous emulsion of an organic polymer is applied and dried is employed. When the film formed from the above-mentioned emulsion is dried above the minimum film formation temperature, it becomes a continuous film, and when it is below the minimum film formation temperature, it does not become a continuous film, but the polymer particles form independent shapes and dry and adhere to each other. It has this property. Taking advantage of the properties of
If the temperature and polymer temperature are properly controlled, an organic film having the above-mentioned contradictory properties will be formed. (Refer to Special Ship No. 56-76896) In such a conventional example, in the baking process, the heating curve as shown in Fig. 1 (i.e., heating up to 420°C with a temperature increase gradient (10°C/1 minute), approx. 4
Heated at constant temperature for 70 minutes at 20℃, cooled for 20 minutes after cooling)
was adopted.

However, in such conventional methods, metal backs cannot be formed even after undergoing the fc manufacturing process, which is controlled with high precision in order to satisfy the mutually exclusive requirements of having porosity and ensuring high flatness. It has been found that a decrease in yield due to the occurrence of blistering in the metal reflective film forming the metal bank cannot be avoided. To realize a high-quality cathode ray tube with high yield and improved brightness by making it possible to form an interlayer film that prevents the problem from occurring and has high flatness.

2) Structure of the Invention In the baking process for forming the metal reflective film for the metal back after the formation of the fluorescent surface, the weight loss rate on the thermogravimetric analysis curve of the intermediate film deposited with good flatness is large. The heating gradient in the region is set to be significantly slower than at the start-up time to prevent blistering of the metal reflective film due to rapid volatilization of the intermediate film.

fJ→Example Below For examples of the present invention, FIG. 2 shows a cross-sectional view of the main part of the fluorescent surface upon completion of metal reflective film deposition, FIG. 3 shows a thermogravimetric analysis curve of the intermediate film (organic film), This will be explained with reference to FIG. 4, which shows the thermogravimetric analysis curve of the photosensitive binder, and FIG. 5, which shows the heating curve in the baking process.

In this embodiment as well, the steps from forming the phosphor film on the face plate to depositing the metal reflective film follow the conventional example, but will be briefly explained below with reference to FIG.

First, a face plate provided with black stripes (not shown) separating the stripe patterns of each primary color (R, G, B) is prepared.

Next, a slurry is prepared in which a phosphor (for example, L powder) to be photoprinted in the process is suspended in a photosensitive binder, which is a mixture of polyviny-I real alcohol and N1 chromic acid solution, and the slurry is washed. Let the process finish. Next, the coated and dried R color phosphor is exposed to ultraviolet light using a shadow mask having a predetermined transmission pattern, and only the irradiated pattern is cured. After that, develop and remove unexposed areas and wash.
Then, a desired pattern of R color phosphor film α0) is formed on the face plate (1). In Figure 2, 0υ
The figure shows the phosphor particles and the photosensitive binder is shown enlarged. By sequentially carrying out this exposure and development process for each of the other G and B color phosphors, desired film surfaces of the G, G and B phosphors are formed.

The phosphor film surface 00) formed as described above [see (b) Prior Art section] is not a mirror surface but has irregularities of several tens of μm (2
) cannot be avoided. Therefore, if a metal reflective film is deposited directly on it, a metal back film is formed directly on it (for example, aluminum).

(ram) enters the concave portions of the phosphor surface and the vapor-deposited surface becomes a similar uneven surface, which significantly deteriorates the smoothness of the metal back surface and reduces its specularity, resulting in a decrease in the brightness of the phosphor surface.

UIS7J-Lmm+/e+lu1mMf+ to 8 Ift
'6++-#-J-,)m An intermediate film (3) is formed by filming with an organic substance that can be volatilized by decomposition and removed in a later process, such as an acrylic emulsion, and the unevenness of the phosphor film (10) is formed. Adopt a method of leveling the surface to improve its flatness.

If a metal reflective film (5) is deposited on this intermediate film (3), a metal back film with good reflection efficiency should be formed.

However, it is essential that the metal back film thus formed has some degree of porosity in order to allow the interlayer material volatilized during the subsequent baking process to escape.

The metal reflective film (5) can be made microscopically porous to a certain extent by making the film thinner.However, if the film thickness is made thinner, the reflection efficiency decreases, and the effect of improving brightness due to the metal back is reduced. drop down. Taking these points into consideration, the above-mentioned interlayer film has a two-layer structure, with the first layer filling in and leveling the unevenness of the fluorescent surface, and the second layer controlling the degree of porosity caused by pinholes. It is also possible to form an organic material that can be used as a metal reflective film, inject vapor-deposited metal particles into the pinholes, and use the missing portions as pinholes in the metal reflective film.

However, with this method, the interlayer film (3) volatilizes unevenly in the subsequent baking process, and if concentrated at a particular time, the metal reflective film (5) may blister due to the pressure. This phenomenon occurs, and the yield rate of forming the metal back film is significantly reduced. Therefore, it is better to increase the degree of porosity of the metal reflective film (5) in order to improve the yield rate even at the expense of reflective efficiency. It's a win.

Rather, in the present invention, a metal reflective film is formed by vapor deposition to a thickness that can ensure sufficient reflection efficiency7, and the degree of porosity in that film thickness, the permeability of volatile substances in the baking process, and the thermogravimetric analysis of volatile substances are analyzed. Determine the heating curve for the shite baking process by considering the heating curve so that the material forming the interlayer film evaporates at a uniform rate without applying excessive pressure that may cause blisters on the metal reflective film. Make it.

Figures 6 and 4 respectively show the inside of the photosensitive binder to be removed by volatilization in the baking process (3).
The thermogravimetric analysis curve of In both figures, the horizontal axis shows the heating time after the start of baking, the vertical axis shows the weight and heating temperature of each substance, and the dotted line shows the heating curve.

According to this heating curve, each substance is heated at a constant heating gradient (1
0°C/min) to about 420°C, the weight of the photosensitive binder (2) changes as shown by the solid line in Figure 6, and the weight of the interlayer film (3) changes as shown by the solid line in Figure 4. . Referring to FIG. 6, the photosensitive binder gradually thermally decomposes at the start of heating and ends at about 420°C, but especially at 25°C.
Between 0°C and 290°C, that is, 5 minutes of heating time from 25 minutes to 60 minutes, the total weight decreased by 64.6%,
It shows an extremely high weight loss rate of 0.87 (at 57°C), and as shown in Figure 4, the intermediate model has a particularly high weight loss rate at 665°C.
to 405°C, a total mold plate reduction of 79.4% was observed during the heating time of 65 minutes to 41 minutes, and 1
．． Extremely high weight loss rate of 13%/°C (57°C
).

Based on these facts, both materials were baked by heating with a uniform heating gradient. In this case, the thermal decomposition of each material rapidly progresses during the above-mentioned specific time, so that the vaporized gas is absorbed by the metal reflective film (
5) The inventor of the present invention has conducted repeated experiments to simulate conditions in which both substances are thermally decomposed uniformly in the heated region and the generation of volatile gas is not concentrated in a specific time period. As shown in FIG. 5, in the region of 250°C to 290°C where the thermal decomposition of the photosensitive binder is accelerated, the heating temperature gradient is set to the conventional -, that is, (2°C/min), and the intermediate film is It has been found that in the region from 665°C to 405°C where thermal decomposition is accelerated, the heating gradient can be set to the conventional τ, ie (2°C/min). The temperature gradient condition is not limited to this value, but it may be made more gradual, or it may be heated at a constant temperature for a certain period of time in a region exhibiting rapid thermal decomposition, and then a heating curve may be created in which the temperature is increased intermittently after waiting for the vaporized gas to dissipate. May be adopted. Furthermore, since the time required for volatilization to be completed after reaching the constant temperature heating range around 420°C is shorter than in the conventional example, this constant temperature heating time can be greatly shortened and the temperature can be lowered at approximately the same temperature gradient as in the conventional example. This prevents damage to the fluorescent surface due to rapid cooling.

Effects of the Invention According to the method of the present invention, the volatilization temperature of the photosensitive binder and the intermediate film is made uniform during the baking process, and the gas pressure exerted on the metal reflective film is made low and uniform or below a certain value. This not only improves the yield in the process of forming a metal back including a fluorescent surface, but also prevents fire even when the thickness of the intermediate film is increased and pinnails are reduced. Since blistering can be suppressed, the specularity of the metal film is greatly improved, and reflection efficiency is improved, making it possible to actually use a cathode ray tube with higher brightness.

[Brief explanation of the drawing]

FIG. 1 shows a heating curve of a conventional example in a baking process. Figure 2 is an enlarged sectional view of the main part after the metal reflective film has been deposited, Figure 6 is the thermogravimetric analysis curve of the photosensitive binder, Figure 4 is the thermogravimetric analysis curve of the intermediate film, and Figure 5 is the invention of the present invention. This is the heating curve of the baking process. (1)...Face plate, Ql)...
・・Fluorescent particles, ′′ ・・・Photosensitive binder, (3
)...-Intermediate film, (5)...Metal reflective film. Figure 1 / Figure 8 Figure 2

Claims (2)

[Claims] (1) An intermediate film with a smooth surface made of a thermally decomposable material is provided on the fluorescent surface coated on the face plate, and a metal reflective film forming a metal back is deposited on this intermediate film, and then the mll interview is performed. In the baking process in which organic substances in the film are thermally decomposed and evaporated from the pinholes of the metal reflective film, the heating gradient in the region where the weight loss rate is large on the thermogravimetric analysis curve of the intermediate film is compared to that at the start-up stage. A method for forming a metal puncture in a cathode ray tube, characterized in that a heating curve set extremely slowly is used to prevent blistering of the metal reflective film due to rapid volatilization of the material. (2) The heating gradient in the region where the weight loss rate is large on the thermogravimetric analysis curve of the photosensitive binder in the fluorescent surface is similarly set to be slow.
L9Konoshima Rito1 肚SaMoe→) The method for forming a metal back of a cathode ray tube as described in Section 4 of Xiaokin Shiken.