Patent Publication Number: US-6339286-B1

Title: Cathode ray tube with a nonglare multi-layered film

Description:
RELATED APPLICATION 
     This application is a continuation application of application U.S. Ser. No. 08/068,170 filed May 28, 1993, now abandoned which is a continuation-in-part application of U.S. Ser. No. 07/891,034 filed Jun. 1, 1992, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cathode ray tube (CRT) for use in a terminal display for a computer, a TV set, etc., and more particularly to a nonglare film and a method of forming a nonglare film on a display surface of a display. 
     2. Description of the Related Art 
     In recent years, there has been an increased need to prevent the glare due to the reflection of external light on a display surface of a terminal display for a computer, a TV set, etc. To meet this need, various glare-proof means have been used with CRTs. For example, a panel formed with a metal multi-layer antireflection film has been attached to the front surface of a CRT. Another means employs a rough surface that has been formed by chemical etching directly onto the front panel of a CRT in order to scatter external light. Yet another utilizes a coating film formed on a surface of the front panel to exhibit a glare-proof effect. These means are found, for example, in Japanese Patent Laid-open Publication Nos. 60-109134, 60-129778, 60-14685, and 63-80451, and U.S. Pat. No. 4,563,612. In particular, the &#39;612 patent discloses a cathode ray tube comprising an antistatic, glare-reducing coating having a silicate material and a metallic compound. 
     However, the above-mentioned related art glare-proof means have the following drawbacks. As for the nonglare means the panel formed with the metal multi-layer antireflection film attached to the front surface of a CRT, the cost is greatly increased, and therefore such a CRT is not suitable for general users. As for the glare-proof means using a CRT with a rough surface directly formed on the front panel itself, the cost can be reduced, but a problem remains with resolution. Further, in the nonglare means utilizing a coating film formed on the surface of the front, there is a possibility that the quality of a reproduced image will be lowered when applying the glare-proof means to a high-definition type CRT, such as a graphic display. That is, enhancement of a glare-proof effect causes an increase in scattered light. As a result, the surface of the front panel looks whitish in bright places, consequently reducing the sharpness of the reproduced image. 
     Moreover, there is a further need to reduce the accumulation of dust on the CRT front panel. A known technique is to form an antistatic film on the surface of the front panel in order to prevent deposition of dust on the surface of the front panel (for example, Japanese Patent Laid-open Publication Nos. 61-16452, 1-251545, 1-276534, and U.S. Pat. No. 4,563,612). 
     Accordingly, there is a demand for a high definition type CRT capable of exhibiting an antistatic effect as well as the above-mentioned nonglare effect. 
     SUMMARY OF THE INVENTION 
     It is the primary object of the present invention to provide a cathode ray tube which can exhibit a nonglare effect and antistatic effect without lowering the quality of a reproduced image. 
     In accordance with the present invention, there is provided a cathode ray tube comprising a front panel coated with a nonglare film having a multi-layered structure. The multi-layered structure comprises at least a visible light absorbing layer containing a black dye, and an antistatic layer containing an inorganic metal compound as a conductive agent. 
     In a preferred embodiment, the cathode ray tube includes a visible light absorbing layer formed between the front panel and the antistatic layer. 
     Further, the nonglare film may be formed by using a water absorbing solvent selected from the group consisting of ethylene glycol, glycerol, diethylene glycol, propylene glycol, triethylene glycol, and hexylene glycol. 
     In accordance with the another aspect of the present invention, there is provided a method of manufacturing a cathode ray tube having a front panel coated with a nonglare film comprising: cleaning the front panel, heating the front panel for drying, forming a visible light-absorbing layer on the front panel by spraying a first ethyl silicate solution which contains 0.1-0.5 wt % black dye and 1-10 wt % SiO 2 , forming an antistatic layer on the front panel by spraying a second ethylsilicate solution which contains 40-60 wt % inorganic metal as a conductive agent in a solid content and 1-10 wt % SiO 2 , and baking the front panel to harden the nonglare film completely. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view, partially in section, of a cathode ray tube according to a first preferred embodiment of the present invention; 
     FIG. 2A is a front elevation of a front panel of a cathode ray tube according to second, third, fourth, fifth, and sixth preferred embodiments of the present invention, illustrating a luminance distribution; 
     FIGS. 2B and 2C are graphs illustrating a coating quantity distribution in relation to the luminance distribution shown in FIG. 2A; 
     FIG. 3A is a side and plan view of the layer having an irregular surface to be formed on a front panel by depositing a coating liquid and drying rapidly; 
     FIG. 3B is a side and plan view of the layer having a smooth surface to be formed on the front panel by depositing a coating liquid; 
     FIG. 4 is a side view of a nonglare film formed on a front panel according to a fifth preferred embodiment of the present invention; 
     FIG. 5 is an illustrative schematic sectional view showing a method of spraying a coating liquid with compressed air to coat on a surface of a front panel uniformly; 
     FIG. 6 is a perspective view of a painting robot which forms a nonglare film; 
     FIG. 7 is a plan view showing a scanning application system which employs a painting robot; 
     FIG. 8 is a graph showing a dependence of the gloss on a temperature of a panel before coating; 
     FIG. 9 is a graph illustrating a relation between the haze and the gloss; 
     FIG. 10 is a graph illustrating a relation between the gloss and the spraying time. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     There will now be described some preferred embodiments of the present invention with reference to the drawings. 
     FIG. 1 is a side view, partially in section, of a cathode ray tube (CRT) according to a first preferred embodiment of the present invention. The CRT illustrated is of a high-definition type to be applied to terminal display for a computer, for example. While a known electron gun or the like (not shown) is provided in the CRT, the detailed explanation thereof will be omitted because it is not directly related to the scope of the present invention. 
     Referring to FIG. 1, reference numeral  1  denotes a front panel of the CRT, and reference numeral  2  denotes a nonglare film formed on the front panel  1  by a method to be hereinafter described. The nonglare film  2  serves to prevent the glare due to scattered light. The nonglare film  2  has a double-layered structure consisting of a visible light absorbing layer  2   a  formed on the front panel  1  and an antistatic layer  2   b  formed on the visible light absorbing layer  2   a.  The visible light absorbing layer  2   a  contains a black dye to prevent the front panel  1  from appearing whitish in bright places, and the antistatic layer  2   b  contains an inorganic metal compound to prevent deposition of dust or the like, electrical shock, etc., due to static electricity. 
     A method for forming the nonglare film  2  will now be described. First, the front panel  1  of the CRT constructed by an ordinary process, is heated for drying at 100° C. or lower, preferably 30-60° C. Then, an ethyl silicate solution containing 0.1-0.5 wt % of a black dye, which is primarily composed of C.I. solvent Black 5, and 1-10 wt % of SiO 2  for scattering of light is sprayed onto a surface of the front panel  1  at a flow rate of 0.2-0.5 ml/sec. 
     Thus, the surface of the front panel  1  is subjected to glare-proof treatment so that a surface roughness becomes Rmax≦0.3 μm and Rz≦0.2 μm, and the visible light absorptivity due to the black dye becomes 10-30% (assuming that the absorptivity is 0% in the absence of the black dye). In this way, the visible light absorbing layer  2   a  is formed. 
     In the next step, an ethyl silicate solution containing 40-60 wt % of an inorganic metal compound, such as metal oxide, including at least a metal selected from the group consisting of tin, gold, palladium, platinum, iron, titanium, and aluminum as a conductive agent in a solid content and 1-10 wt % of powder of SiO 2  is sprayed onto the visible light absorbing layer  2   a  formed on the surface of the front panel  1  at a flow rate of 0.2-0.5 ml/sec. The particle size of the metal oxide is preferably smaller than 0.01 μm. If the particle size is larger than 0.01 μm, the surface roughness becomes too large. In this way, the antistatic layer  2   b  is formed. 
     A concentration of SiO 2  in the ethyl silicate solution is preferably about seven wt %. This is due to the fact that if the concentration of SiO 2  is too small, the required increase in the number of coatings reduces production efficiency, while if the concentration of SiO 2  is too large, a coating film becomes nonuniform. 
     In the next step, the coating film is baked at 150-200° C. for 10-30 minutes to vaporize an ethyl component of the coating liquid, thus completing a nonglare film  2  having a double-layered structure. A thickness of the nonglare film  2  (i.e., a total thickness of the visible light absorbing layer  2   a  and the antistatic layer  2   b ) is preferably about 0.5 μm. 
     An example of the above forming method for the nonglare film  2  will now be described more specifically. First, the surface of the front panel  1  of a 20-inch CRT is cleaned, and it is then preheated at 45° C. for 10 minutes. 
     Then, an ethyl silicate solution is sprayed onto the surface of the front panel  1  to form the nonglare film  2 . In this case, each of the visible light absorbing layer  2   a  and the antistatic layer  2   b  is formed by spraying the ethyl silicate solution for 50 seconds with a distance between the surface of the front panel  1  and a spray nozzle (not shown) set to 23 cm. 
     The ethyl silicate solution used to form the visible light absorbing layer  2   a  contains 0.3 wt % of a black dye and 5 wt % of SiO 2 , while the ethyl silicate solution used to form the antistatic layer  2   b  contains 50 wt % of metal oxide as a conductive agent in a solid content and 3 wt % of SiO 2 . 
     Thereafter, the coating film is baked at 170° C. for 20 minutes to form the nonglare film  2  having a fine surface roughness. Both the visible light absorbing layer  2   a  and the antistatic layer  2   b  has a thickness of about 0.25 μm. Further, a visible light absorptivity of the nonglare film  2  is about 30%. 
     According to this embodiment, it has been found that the CRT in has a resolution of 60 lines/cm or more, thus resolution is maintained. 
     There will now be described second through sixth preferred embodiments of the present invention relating to a coating liquid and a coating method therefor applied to the nonglare treatment of a front panel of a CRT, with reference to FIG.  2  and FIG.  3 . 
     In the second preferred embodiment, there is employed an already completed CRT having a front panel with a certain luminance distribution. That is, as shown in FIG. 2A, a front panel  21  of the CRT has a luminance distribution shown by contour lines such that luminance is high at a central portion and low at a peripheral portion. In a first step of the nonglare treatment of the front panel  11  of the CRT, a surface of the front panel  11  is polished with cerium oxide, and the cerium oxide is then removed to thereby clean the surface of the front panel  21 . 
     Then, the front panel  21  is preheated to about 40° C. for about 10 minutes. Such a preheating step is carried out for the purpose of slowing the drying rate of a coating liquid to be applied later to the front panel  21 . The temperature of 40° C. is a temperature which can be more easily maintained through all seasons of the year. If the drying rate of the coating liquid is excessively slow, the coating liquid flows and thereby becomes scaly so that it cannot be put into practical use. For these reasons, the temperature of about 40° C. is an optimum temperature for preheating of the front panel  21 . 
     In the next step, a coating liquid is sprayed onto the surface of the front panel by using a spray coating device of a two-fluid air atomizing type. The coating liquid is an ethyl silicate solution containing 0.3 wt % of a black dye (C.I. solvent Black 5), 3.0 wt % of silica, and 4.0 wt % of ethylene glycol. 
     In this embodiment, the coating conditions include: a spray air pressure of 1.5 kg/cm 2 -3.5 kg/cm 2 , an average particle size of the atomized liquid of 20 μm, a standard deviation of the particle size of 5 μm, a spraying rate of 0.4 ml/sec., a spraying time of 50 sec. for the entire surface of the front surface of a 20-inch CRT, and a distance of 30 cm between a nozzle of the spray coating device and the surface of the front panel  21 . 
     Further, the coating speed is controlled as shown in FIGS. 2B and 2C so that the coating quantity distribution is related to the luminance distribution of the front panel  21  shown in FIG.  2 A. In such a manner, the coating quantity is increased at the central portion having a high luminance and is decreased at the peripheral portion having a low luminance. 
     Thereafter another coating liquid is sprayed onto the first layer to form a second layer. The coating liquid for forming the second layer does not contain a dye but contains 50 wt % of a conductive agent in a solid content. The other components of the coating liquid are the same as those of the coating liquid for forming the first layer. The coating conditions of the coating liquid for the second layer are substantially the same as those of the coating liquid for the first layer, but a temperature of the surface of the front panel  21  is lowered to about 25 degrees C. by the coating liquid for the first layer. 
     After spraying the coating liquid for the second layer, the CRT is heated by radiation until a temperature of the surface of the front panel  21  becomes about 140° C., thus drying the coating liquid sprayed onto the surface of the front panel  21  to form a nonglare film. 
     In the CRT manufactured according to the second preferred embodiment, a density of the black dye contained in the nonglare film formed on the front panel  21  is high at the central portion of the front panel  21  and is low at the peripheral portion thereof. Such a difference in density of the black dye causes a difference in light transmittance. This difference in light transmittance and the difference in luminence shown in FIG. 2A counterbalance each other, so that both luminance and contrast become uniform throughout the front panel  21 . Further, since silica is contained in the coating liquid, fine roughness is formed on a surface of the nonglare film, so that the film exhibits a nonglare effect such that reflection of background light on the front panel  21  is suppressed. 
     The water absorbing solvent according to the present invention is not limited to ethylene glycol. For example, the water absorbing solvent may include glycerol, diethylene glycol, propylene glycol, triethylene glycol, and hexylene glycol. 
     Further, the coating film formed on the surface of the front panel  21  has an electrical resistance of 1×10 9 -5×10 9  Ω. That is, the coating film has a conductivity which exhibits an antistatic effect. Further, the nonglare film has a glossiness (gloss value) of 90 in case of an incident angle of 60° C. 
     Next, the third preferred embodiment will be described. In the third preferred embodiment, the coating liquid for the second layer is substantially the same as in the second preferred embodiment with the exception that ethylene glycol is not used. Furthermore, the coating conditions of the coating liquid for the second layer are substantially the same as those in the second preferred embodiment with the exception that the spray air pressure is set to 3.5 kg/cm 2 . 
     In the CRT manufactured according to the third preferred embodiment, the electrical resistance of the nonglare film formed on the surface of the front panel  21  is the same as that in the third preferred embodiment. However, the glossiness in case of the incident angle of 60° is lowered to 50, but a resolution of 65 lines/cm or higher is obtained. 
     Next, the fourth preferred embodiment will be described. In the fourth preferred embodiment, the coating film consisting of the first and second layers is formed in the same method as that in the second preferred embodiment with the exception that the drying condition of the coating liquid after sprayed for forming the first and second layers is set to about 170° C. for about 20 minutes. 
     In the second and fourth preferred embodiments mentioned above, the coating liquid for the second layer contains ethylene glycol in addition to the conductive agent and the silica. The relation between the content of ethylene glycol and the quality of the glare-proof effect as well as the clearness shown in Table 1, in which o represents good quality, and x represents poor quality. As Table 1 makes apparent, the content of ethylene glycol is preferably 1.0-8.0 wt %. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 7-inch 
                   
               
               
                 Content (wt %) 
                 Flat Panel 
                 14-inch Panel  
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 0.25 
                 x 
                 x 
               
               
                 0.5 
                 ∘ 
                 x 
               
               
                 1.0 
                 ∘ 
                 ∘ 
               
               
                 2.0 
                 ∘ 
                 ∘ 
               
               
                 4.0 
                 ∘ 
                 ∘ 
               
               
                 8.0 
                 ∘ 
                 ∘ 
               
               
                 10.0 
                 x 
                 x  
               
               
                   
               
            
           
         
       
     
     Further, the relation between the content of ethylene glycol and the glossiness in a 29-inch CRT is shown in Table 2. As apparent from Table 2, there is a large difference in glossiness between the cases where ethelyne glycol is present and the case where it is absent. However, there is not a large difference in glossiness when ethelyne glycol is present. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Glossiness 
               
               
                   
                 Content (wt %) 
                 (Gloss Value)  
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 0 
                 80.4 
               
               
                   
                 1.0 
                 87.2 
               
               
                   
                 2.0 
                 88.3 
               
               
                   
                 4.0 
                 86.4 
               
               
                   
                 8.0 
                 87.1  
               
               
                   
                   
               
            
           
         
       
     
     A method of fabricating the CRT in the fifth embodiment, shown in FIG. 4, will be described hereinafter. In FIG. 4, the reference numerals  41 ,  42 ,  43  and  44  denote incident light, diffused light, reflected light, and transmitted light, respectively. 
     The shape of the antistatic layer  45   a,  i.e., the first layer, containing an inorganic metal compound, employed in the fifth preferred embodiment is the same as that of the film shown in FIG.  3 A. The antistatic layer  45   a  is formed by depositing droplets of the coating liquid onto a panel  46  and drying the droplets rapidly so that the film serving as the antistatic layer  45   a  has an irregular surface with circular pits formed by the impinging droplets of the coating liquid. The shape of the visible light absorbing layer  45   b  containing black dye (ie. the second layer) is the same as that of the film shown in FIG.  3 B. 
     The visible light absorbing layer  45   b  is formed by depositing droplets of a liquid coating material onto the panel  46 , and then drying the liquid coating material after allowing the droplets of the liquid coating material to collapse. The visible light absorbing layer  45   b  is formed in a smooth, matte surface having a plurality of circular pits and elliptic pits. 
     A semifinished CRT, namely, a CRT having all its components except the nonglare film  45 , was completed through steps of processes shown in Table 3. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
             
            
               
                   
                 1 
                 Processes 
               
               
                   
                 2 
                 Setting of the semifinished CRT for coating 
               
               
                   
                 3 
                 Cleaning of the front panel 
               
               
                   
                 4 
                 Preheating 
               
               
                   
                 5 
                 Forming the first layer 
               
               
                   
                 6 
                 Forming the second layer 
               
               
                   
                 7 
                 Heating for hardening 
               
               
                   
                 8 
                 Delivery 
               
               
                   
                 9 
                 Details and conditions of the processes 
               
               
                   
                 10 
                 Grinding and cleaning of the surface of the 
               
               
                   
                   
                 panel 
               
               
                   
                 11 
                 Heating the panel at 40° C. for ten minutes to 
               
               
                   
                   
                 stabilize the panel for coating 
               
               
                   
                 12 
                 Spraying an antistatic liquid containing an 
               
               
                   
                   
                 ethyl silicate solution as binder over the 
               
               
                   
                   
                 surface of the panel to form the first layer 
               
               
                   
                   
                 having minute pits formed by impinging 
               
               
                   
                   
                 droplets of the antistatic liquid 
               
               
                   
                 13 
                 Spraying an ethyl silicate solution 
               
               
                   
                   
                 containing a black dye over the first layer 
               
               
                   
                   
                 to form the second layer for coloring and 
               
               
                   
                   
                 smoothing the surface of the first layer 
               
               
                   
                 14 
                 Heating the panel at 160° C. for twenty 
               
               
                   
                   
                 minutes to harden the nonglare film 
               
               
                   
                   
                 completely 
               
               
                   
                 15 
                 Cooling the CRT  
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Composition of the First Coating Liquid: 
                   
               
               
                   
                 (First layer) 
               
               
                   
                 Tin protoxide (SnO) powder: 
                 50% by weight 
               
               
                   
                 Solid ethyl silicate: 
                 2.0% by weight 
               
               
                   
                 Coating Conditions 
               
               
                   
                 Pressure of compressed air for spraying: 
                 2.5 kg/cm 2   
               
               
                   
                 Surface resistivity: 
                 2 × 10 9  Ω 
               
               
                   
                 Composition of the Second Coating Liquid: 
               
               
                   
                 (Second layer) 
               
               
                   
                 Black dye: 
                 0.3% by weight 
               
               
                   
                 Ethyl silicate: 
                 2.0% by weight 
               
               
                   
                 Coating Conditions 
               
               
                   
                 Pressure of compressed air for spraying: 
                 2.0 kg/cm 3   
               
               
                   
                 Light transmittance: 
                 85 to 90% 
               
               
                   
                 Haze: 
                 ≈3% 
               
               
                   
                 Gloss G (60°): 
                 80 to 85  
               
               
                   
                   
               
            
           
         
       
     
     When coating the surface of the panel with the coating liquid, the surface of the panel of the CRT  51  is scanned by the spray nozzle  54  to spray the coating liquid  52  with compressed air  53  to coat the surface of the panel uniformly with the coating liquid as shown in FIG.  5 . 
     The nonglare film  45  consisting of the antistatic layer  45   a  (i.e., the first layer) and the visible light absorbing layer  45   b  (ie., the second layer) coats the surface of the panel of the CRT, diffuses light, prevents the electrification of the panel, suppresses the reflected light  43  (the reflection of the ambient scenery on the panel) and improves the contrast of pictures displayed on the CRT. 
     In this specification, the gloss is defined as follows: 
     Reference Gloss 
     When light of a specified intensity is projected at an angle of incidence θ onto the surface of a reference block formed of glass having a refractive index of 1.567, the intensity of reflected light reflected at an angle of reflection θ is defined as having a value of 100. Gloss is dependent on the angle θ. In this embodiment, gloss is indicated by Gloss (60°) or G(60°), in which the angle θ=60°. 
     Haze indicates the degree of cloudiness of a surface and is indicated by a value obtained by calculation using the following expression. 
     
       
         Haze={(Luminous diffuse transmittance)/(Total ray transmittance)}×100 (%)  
       
     
     Sixth Embodiment 
     The surfaces of the front panels of the CRTs in the sixth embodiment is coated with the nonglare film by the same processes under the following different process conditions: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Preheating temperature: 
                 40° C. 
               
               
                   
                 Content of conductive agent: 
                 55 wt %/solids 
               
               
                   
                 Content of silica: 
                 0.6 wt % 
               
               
                   
                 Content of denatured ethyl alcohol: 
                 90 wt % 
               
               
                   
                 Content of pure water: 
                 8 wt % 
               
               
                   
                 Spraying rate: 
                 0.4 ml/sec (40 sec) 
               
               
                   
                 Spraying distance (Panel-Nozzle): 
                 23 cm 
               
               
                   
                 Content of black dye: 
                 0.13 wt % 
               
               
                   
                 Content of silica: 
                 1.5 wt % 
               
               
                   
                 Content of denatured ethyl alcohol: 
                 58 wt% 
               
               
                   
                 Content of pure water: 
                 40 wt % 
               
               
                   
                 Spraying rate: 
                 0.4 ml/sec (50 sec) 
               
               
                   
                 Spraying distance (Panel-Nozzle): 
                 25 cm  
               
               
                   
                   
               
            
           
         
       
     
     The characteristics of the surfaces of the front panel of the CRTs in the sixth embodiment were the same as those of the surface of the front panel of the CRT in the fifth embodiment. 
     The surfaces of the front panels of the CRTs embodying the present invention may be coated with the antistatic layer and the visible light absorbing layer by painting robots  62  as shown in FIG.  6 . For example, in the fifth embodiment the first layer and second layer of the CRT are formed on the front panel  61  by using one painting robot for the first layer and three painting robots  62  for the second layer. Each of the painting robots is provided with three spraying nozzles  62   a.    
     FIG. 7 shows a scanning application system employing a painting robot applying a film onto a CRT front panel  71 . Such a film formed by spraying must be dried evenly to form a uniform optical thin film over the surface of the panel of the CRT  71 . The film is deposited by moving the nozzles in the same directions for each layer. Further, the nozzles are moved over an area greater than the application area, i.e., the area of the panel of the CRT. Accordingly, the scanning application system is capable of uniformly forming the first layer (ie., the antistatic layer) and the second layer (ie. the visible light absorbing layer) over the entire surface of the panel. 
     FIG. 8 shows the dependence of the gloss on the temperature of the panel before coating. The following coating conditions were used: 
     Coating Conditions 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Ambient temperature: 
                 28° C. 
               
               
                   
                 Spraying pressure: 
                 1.5 kg/cm 2   
               
               
                   
                 Scanning speed (Painting robot): 
                 400 mm/sec 
               
               
                   
                 Spraying distance (Panel-Nozzle): 
                 300 mm 
               
               
                   
                 Number of coats: 
                 Three (Coloring liquid: 
               
               
                   
                   
                 Only the black dye)  
               
               
                   
                   
               
            
           
         
       
     
     As is obvious from FIG. 8, the higher the temperature of the panel, the shorter the film drying time and hence the lower the gloss. 
     FIG. 9 shows the relation between haze and the gloss. In FIG. 9, the mark ▪ denotes a coating liquid including 0.47 wt % of conductive agent and black dye, the mark  denotes a coating liquid including 0.47 wt % of black dye, and the mark ▴ denotes a coating liquid including 0.24 wt % of black dye. 
     As is obvious from FIG. 9, the coating liquid ( 1 ) containing the conductive agent forms a film having a haze higher than those of films formed of the coating liquids ( 2 ) and ( 3 ). The haze of a film formed of the coating liquid ( 2 ), which has a black dye content greater than that of the coating liquid ( 3 ), is higher than that of a film formed of the coating liquid ( 3 ). 
     FIG. 10 shows the relation between the gloss and the spraying time. 
     Coating Conditions 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Ambient temperature: 
                 28° C. 
               
               
                   
                 Humidity: 
                 58 to 64% 
               
               
                   
                 Temperature of the panel: 
                 30° C. 
               
               
                   
                 Spraying pressure: 
                 1.5 kg/cm 2   
               
               
                   
                 Scanning speed: 
                 400 mm/sec 
               
               
                   
                 Spraying distance (Panel-Nozzle): 
                 300 mm 
               
               
                   
                 Number of coats: 
                 Three (Coloring liquid)  
               
               
                   
                   
               
            
           
         
       
     
     As is obvious from FIG. 10, the gloss (before baking) increases with an increase of spraying time and saturates at a certain spraying time. 
     According to these embodiments mentioned above, a part of light to be scattered by the nonglare film having the above-mentioned surface roughness is absorbed by the visible light absorbing layer. Accordingly, even when the CRT is used at a bright place exposed to a large quantity of external light, the surface of the front panel  1  does not look whitish, thereby preventing a reduction in sharpness of a reproduced image. 
     Furthermore, static electricity generated on the front panel during operation of the CRT can be reduced by the antistatic layer, thereby preventing deposition of dust, electrical shock, etc. due to charging of the front panel. 
     While 40-60 wt % of metal oxide is contained in a solid content of the antistatic layer, the nonglare film has a strength durable enough for long-term usage since it has a multi-layered structure. 
     The nonglare film of the present invention provides a CRT surface panel which is more pleasing to view. This surface suppresses haze which arises from the use of a silicon coating having strong external light diffusing properties and which produces interference colors caused by the interference of light of certain wavelengths. It also suppresses haze produced by an antireflection coating which may be caused by surface color variation dependent on viewing angle. 
     Although the invention has been described in its preferred form with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be used otherwise than as specifically described herein without departing from the scope and spirit thereof.