Method of preparing the screen of a colour television picture tube and device performing the method

Claim 2

In the method of preparing the screen of a color television picture tube provided with fluorescent dots having a smaller area than the area Of holes of the shadow mask of the tube wherein light from a spot light source is projected through a hole of the shadow mask onto a panel bearing a photosensitive layer in such manner that an integrated quantity of light projected on the photosensitive layer produces a developable image of a dot having an area smaller than the hole of the shadow mask, the improvement in forming such developable image which comprises: using a stationary light source for projection of light through a hole of the shadow mask onto the panel on which there is to be formed the screen for the picture tube, interposing a tapered prism in the path of the projected light between the light source and the shadow mask, and rotating the prism in its longitudinal plane eccentrically to revolve the light image projected upon the panel through the hole in the shadow mask.

Claim 3

The method of claim 1 wherein the panel is coated with a layer of photosensitive polyvinyl alcohol resin and the panel after being subjected to the light projection is developed to wash away that portion of the layer in which developable images are not formed by the light projection.

Claim 4

In a device for preparing the screen of a color television picture tube provided with fluorescent dots having a smaller area than the area of holes of the shadow mask of the tube provided with an optical system for projecting light from a spot light source onto a panel bearing a photosensitive layer in such manner that an integrated quantity of light projected on the photosensitive layer produces a developable image of a dot having an area smaller than the hole of the shadow mask, the improvement which comprises: a stationary spot light source for projecting light through a hole of the shadow mask onto the panel on which there is to be formed the screen of the picture tube, a tapered prism interposed between said spot light source and the hole of the shadow mask to intercept the path of light from said source to the hole, and means for rotating said tapered prism in its longitudinal plane eccentrically to revolve the light image projected upon the panel through the hole in the shadow mask.

Claim 5

In a device for preparing the screen of a color television picture tube provided with fluorescent dots having a smaller area than the area of holes of the shadow mask of the tube provided with an optical system for projecting light from a spot light source onto a panel bearing a photosensitive layer in such manner that an integrated quantity of light projected on the photosensitive layer produces a developable image of a dot having an area smaller than the hole of the shadow mask, the improvement which comprises: a stationary spot light source for projecting light through a hole of the shadow mask onto the panel on which there is to be formed the screen of the picture tube, a tapered prism interposed between said spot light source and the hole of the shadow mask to intercept the path of light from said source to the hole, and means for rotating said tapered prism in its longitudinal plane eccentrically to revolve the light image projected upon the panel through the hole in the shadow mask.

Claim 6

The device of claim 3 wherein the optical system comprises a second tapered prism adjacent said tapered prism and means to adjust the angle between said prisms.

Claim 7

The device of claim 3 wherein said means to rotate said tapered prism comprises a metal frame for supporting at least one prism, a plurality of rollers abutting against the perifery of said frame to impart rotating motion to the prism, a base plate upon which said rollers are fitted, said plate having an opening therethrough at the portion of the plate that faces said prism and bearings carried by said base plate upon which the prism is supported for rotation.