Color CRT shadow mask and method of making same

An improved method of making a color CRT shadow mask composed of a very thin steel foil material and having a pattern of apertures therein, such mask being highly susceptible to denting, creasing, scratching, tearing and other unacceptable handling-related mechanical defects attributable in large part to the fragility of the mask, the improved method resulting in significantly reduced losses from such handling-related mechanical defects and thus effecting substantial manufacturing economies, and a superior product as well, the method comprising:

• providing a plurality of shadow mask blanks each with a pattern of apertures photoetched therein, which blanks have been cut from a foil of steel, precision cold-rolled to a full hard condition with a thickness of about 6-8 mils, said foil being characterized by being composed of an interstitial free steel material;
• subjecting a stack of said blanks to an annealing operation, said annealing operation being characterized by being carried out at a relatively low maximum temperature and for a time material effective to cause said steel material to have a grain size between about 0.01-0.04 mm, said relatively low maximum temperature being effective to avoid sticking together of said blanks, thus avoiding any handling-related folding or creasing of the blanks normally associated with attempts to separate blanks stuck together in conventional high temperature annealing operations, said blanks being substantially free of wrinkles, dents, creases, scratches and other handling-related mechanical defects which would be expected if the conventional high temperature anneal were employed;
• and
• clamping and drawing each blank to form a dished shadow mask without the interposition of vibration or roller leveling operations and thereby avoiding undesirable creasing, roller marking, denting, tearing or work hardening of the blank normally associated with these operations,
• whereby the end product shadow mask, due to the use of full hard interstitial free steel material, and the obviation of a high temperature anneal and the necessary consequent vibration and roller leveling, is comparatively free of the aforesaid handling-related mechanical defects and is thus much less costly to manufacture than prior masks despite the high initial material cost, and
• whereby the end product shadow mask, due to the use of said interstitial free steel material, has an aperture pattern of improved definition as a result of more uniform stretching of the mask blank.

An improved method of making a color CRT shadow mask composed of a very thin steel foil material and having a pattern of apertures therein, such mask being highly susceptible to denting, creasing, scratching, tearing and other unacceptable handling-related mechanical defects attributable in large part to the fragility of the mask, the improved method resulting in significantly reduced losses from such handling-related mechanical defects and thus effecting substantial manufacturing economies, and a superior product as well, the method comprising:

• providing a plurality of shadow mask blanks each with a pattern of apertures photoetched therein, which blanks have been cut from a foil of steel, precision cold-rolled to a full hard condition with a thickness of about 6-8 mils, said foil being characterized by being composed of an interstitial free steel material;
• subjecting a stack of said blanks, unseparated by spacers, to a limited rapid annealing operation, said annealing operation being characterized by being carried out at a relatively low maximum temperature in the range of about 600.degree.-850.degree. C. and for time effective to achieve full recrystallization of the material and a grain size of about 0.025-0.035 millimeters, said relatively low maximum temperature being effective to substantially completely avoid any sticking together of said blanks, thus avoiding any handling-related folding or creasing of the blanks normally asssociated with attempts to separate blanks stuck together in conventional high temperature annealing operations, said blanks being substantially completely free of wrinkles, dents, creases, scratches and other handling-related mechanical defects which would be expected if the conventional high temperature anneal were employed;
• and
• clamping and drawing each blank to form a dished shadow mask without the interposition of vibration or roller leveling operations and thereby avoiding undesirable creasing, roller marking, denting, tearing or work hardening of the blank normally associated with these operations,
• whereby the end product shadow mask, due to the use of full hard interstitial free steel material, and the obviation of a high temperature anneal and the necessary consequent vibration and roller leveling, is comparatively free of the aforesaid handling-related mechanical defects and is thus much less costly to manufacture than prior masks despite the higher initial material cost, and
• whereby the end product shadow mask, due to the use of said interstitial free steel material, has an aperture pattern of improved definition as a result of more uniform stretching of the mask blank.

An improved method of making a color CRT slot-type shadow mask composed of a very thin steel foil material and having an aperture pattern in the form of parallel rows of aligned elongated slots separated by narrow tie-bars, such masks being highly susceptible to denting, creasing, scratching, tearing and other unacceptable handling-related mechanical defects attributable in large part to the fragility of the mask, the improved method resulting in significantly reduced losses from such handling-related mechanical defects and thus effecting substantial manufacturing economies, and a superior product as well, the method comprising:

• providing a plurality of shadow mask blanks each with a pattern of slots photoetched therein, which blanks have been cut from a foil of steel, precision cold-rolled to a full hard condition with a thickness of about 6-8 mils, said foil being characterized by being composed of an interstitial free steel material;
• subjecting a stack of said blanks, unseparated by spacers, to an annealing operation, said annealing operation being characterized by being carried out at a relatively low maximum temperature in the range of 600.degree.-850.degree. C. for a time effective to achieve full material and a grain size of about 0.025-0.035 millimeters said relatively low maximum temperature being effective to substantially completely avoid any sticking together of said blanks, thus avoiding any handling-related folding or creasing of the blanks normally associated with attempts to separate blanks stuck together in conventional high temperature annealing operations, said blanks being substantially completely free of wrinkles, dents, creases, scratches and other handling-related mechanical defects which would be expected if the conventional high temperature anneal were employed;
• and
• clamping and drawing each blank to form a dished shadow mask without the interposition of vibration or roller leveling operations and thereby avoiding undesirable creasing, roller marking, denting, tearing, or work hardening of the blank normally associated with these operations,
• whereby the end product shadow mask, due to the use of full hard interstitial free steel material, and the obviation of a high temperature anneal and the necessary consequent vibration and roller leveling, is comparatively free of the aforesaid handling-related mechanical defects and is thus much less costly to manufacture than prior masks despite the higher initial material cost, and
• whereby the end product shadow mask, due to the use of said interstitial free steel material, has a slot pattern of improved definition as a result of more uniform stretching of the mask blank, and has greater uniformity in shape from mask to mask due to the narrowness in the range of yield points within a given mask and from mask to mask.