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AssigneeMatsushita Electric Industrial Co., Ltd.
InventorKumao Ichinose
Estimating the term…
After forming a phosphor film on an inner face of a front panel, light exposure is performed with respect to the phosphor film by irradiating light from an exposure light source onto the phosphor film through an exposure lens. The exposure lens has a concave incidence surface on which light from the exposure light source is incident, and the incidence surface has an average radius of curvature of 100 mm to 500 mm. Thus, light to which peripheral portions are exposed can have a smaller incident angle with respect to the incidence surface of the exposure lens, thereby allowing the reflectance of the light to be decreased. As a result, even in light exposure with respect to a phosphor film of a color picture tube with a wide deflection angle, an amount of light for the light exposure can be secured in the peripheral portions.
An exposure lens that is used for light exposure with respect to a phosphor screen of a color picture tube, comprising:
A method of manufacturing a color picture tube, comprising the step of performing light exposure with respect to a phosphor film, in which after the phosphor film is formed on an inner face of a front panel, light from an exposure light source is irradiated onto the phosphor film through an exposure lens,
An exposure device that is used to perform light exposure with respect to a phosphor screen of a color picture tube, comprising:
Dependencies are inferred from the claim text.
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No related US applications are recorded in the indexed filing history.
Backward citations are indexed for grants only.
Devices for carrying out the processes, e.g. light houses: auxiliary lenses and filters
Electric discharge tubes or discharge lamps
Term end not estimated
1. Field of the Invention
The present invention relates to an exposure lens and an exposure device that are used to form a phosphor screen of a color picture tube and a method of manufacturing a color picture tube using the exposure lens.
2. Related Background Art
FIG. 1 is a cross sectional view of an exposure lens according to Embodiment 1 of the present invention.
FIG. 2 is a cross sectional view of an exposure lens according to Embodiment 2 of the present invention.
FIG. 3 is a sectional view along a diagonal line of a phosphor screen, showing a color picture tube.
The incidence surface of the exposure lens is formed of a concave curved surface, thereby attaining a smaller angle formed by an incident light beam and a normal of the incidence surface. For example, in the case of a color picture tube with a deflection angle of 120°, by the use of an exposure lens with a concave incidence surface having a radius of curvature of 500 mm in place of the conventional exposure lens with a flat incidence surface, an angle formed by an incident light beam and a normal of the incidence surface of the lens can be decreased from 60° to 54°. As a result, the reflectance on the incidence surface of the lens can be decreased from 19% to 14%, and thus a sufficient amount of light can be secured at peripheral portions of a phosphor screen.
With an average radius of curvature of less than 100 mm, a difference in the effect of decreasing the reflectance becomes insignificant. Further, the problem of lowered processing accuracy also may be caused due to the shape of a steeper concave curve. Thus, preferably, the average radius of curvature is not less than 100 mm.
Herein, the “average radius of curvature” is defined as a radius of a circle that has a center on a normal passing through a central point of an exposure lens and is drawn by passing through two points, which are the central point and a point in a peripheral portion (position in which a light beam is incident that is emitted from an exposure light source in a direction defined by a deflection half angle) of the exposure lens. Where a distance in a plane direction from the central point to the point in the peripheral portion is indicated as r, and a difference in a height direction between these two points is indicated as z, the average radius of curvature can be determined using an expression (r2+z2)/(2×z). In the case of an exposure lens with a non-spherical incidence surface, the average radius of curvature can be determined as a radius of an imaginary spherical surface passing through the two points, i.e. a central point and a point in a peripheral portion of the exposure lens.