US3628429A - Exposure device for manufacturing color picture tubes - Google Patents

Exposure device for manufacturing color picture tubes Download PDF

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Publication number
US3628429A
US3628429A US881464A US3628429DA US3628429A US 3628429 A US3628429 A US 3628429A US 881464 A US881464 A US 881464A US 3628429D A US3628429D A US 3628429DA US 3628429 A US3628429 A US 3628429A
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United States
Prior art keywords
light source
lens
mask
light
center
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Expired - Lifetime
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US881464A
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English (en)
Inventor
Piet Gerard Joseph Barten
Johannes Cornelis Adria Vannes
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US Philips Corp
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US Philips Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/20—Manufacture of screens on or from which an image or pattern is formed, picked up, converted or stored; Applying coatings to the vessel
    • H01J9/22—Applying luminescent coatings
    • H01J9/227—Applying luminescent coatings with luminescent material discontinuously arranged, e.g. in dots or lines
    • H01J9/2271—Applying luminescent coatings with luminescent material discontinuously arranged, e.g. in dots or lines by photographic processes
    • H01J9/2272—Devices for carrying out the processes, e.g. light houses

Definitions

  • the dimensions of the light source G03b are increased to compensate for any loss in brightness from 95/l the lens.
  • ⁇ H is PATENTEnnEc21 Ian 352 ,4 5
  • the invention relates to an exposure device for manufacturing image screens for cathode-ray tubes for displaying colored images, which device is provided with a light source by which a pattern of apertures in a mask is optically projected onto a photosensitive binder provided on a support, the path of light from the light source to the support passing through a substantially rotation-symmetrical negative lens, the light intensity 13 from the light source to a point on the edge of the support satisfying the condition:
  • B is the angle between the line of connection between the center C, of the light source and the center C of the support and the line of connection between C, and the point on the edge of the support; and la is the light intensity of the light source at an angle a with C,C,,, wherein a is given by the relation: 7
  • the said support is generally a transparent cover glass which forms part of the future picture screen for the said cathode-ray tube.
  • a support (and a layer possibly provided thereon) of a future picture screen is sometimes also called face plate.
  • the cathode-ray tube mentioned in the preamble is, for example, a color television display tube; it may be, however, alternatively a tube in which colors are made visible on the screen for other purposes.
  • the light source is, for example, a primary light source having a given light distribution such as a lamp having an internal reflector, or it is a secondary light source.
  • a primary light source having a given light distribution such as a lamp having an internal reflector
  • a secondary light source such as a lamp having an internal reflector
  • An example of the latter type is weakly matted disc irradiated by a projector.
  • a further example of the latter type is a tip of a conelike light conductor, whereby the lower side of the cone receives light.
  • a cathode-ray tube for displaying colored images generally includes a system of electrodes which supplies a few electron beams the electrons of which move along different paths through the apertures in a mask towards the screen for generating the so-called primary colors. These are generally the colors green, red and blue.
  • a very large number of dots (or stripes) is generally provided in the screen a number of which comprises a luminescent substance which radiates light of one of theprimary colors (for example, green) upon electron incidence; other dots on the screen comprise a luminescent substance which radiates light of one of the other primary colors (for example, red) upon electron incidence.
  • a third group of dots may comprise, for example, a blue luminescent substance.
  • the said screen generally includes a collection of a very large number of groups of dots.
  • One group of dots consists of a combination of dots of different composition.
  • each electron beam covers (through the mask) only the dots of one and the same composition.
  • This new layer is now exposed at such areas that the new dots" will come at the areas to be impinged upon later by the second electron beam.
  • the latter dots thus are not located at the same areas as the previously provided dots. If necessary this process may be repeated for a third layer, etc.
  • the exposure" is always effected by means of radiation to which the photosensitive binder reacts. This may be, for example, visible radiation or, for example, ultraviolet light. It is alternatively possible to expose a layer which comprises the photosensitive binder only and to provide the luminescent substance only at a later stage.
  • Iy 10cos wherein I7 is the light intensity in a direction which forms an angle 7 with the above-mentioned line of connection and I0 is the light intensity in the direction which substantially coincides with the direction of the mentioned line of connection.
  • a different formulation of this condition is that the brightness of a surface element of the light source (that is to say, of an element of the tip of the cone in the case of the patent specification referred to) will be smaller for larger angles with the vertical.
  • a drawback of the mentioned known device is that additional auxiliary means are usually necessary to maintain the ratio between the illumination value at the area of the center of the support (the screen) and at the area of the edge of the support below an acceptable limit.
  • additional auxiliary means are usually necessary to maintain the ratio between the illumination value at the area of the center of the support (the screen) and at the area of the edge of the support below an acceptable limit.
  • the ratio between the illumination value at the area of the center of the support the screen
  • the edge of the edge of the support below an acceptable limit.
  • a known auxiliary means for obtaining a better illumination distribution on the screen is the use of a filter layer in the light path from the light source to the screen, the permeability of the filter layer being smaller for rays towards the center of the screen than for rays towards the edges.
  • a filter causes loss of light which is at the expense of the exposure time.
  • a further proposed auxiliary means for enhancing the light intensity distribution on the support consists in using a slightly tilted lens between the light source and the support. This, however, has the drawback of an asymmetry in the illumination distribution on the screen.
  • An exposure device for manufacturing image screens for cathode-ray tubes for displaying colored images, which device is provided with a light source by which a pattern of apertures in a mask is optically projected onto a photosensitive binder provided on a support, and in which the light path from the light source to the support passes through a substantially rotation-symmetrical negative lens and in which the light intensity 113 from the light source to a point on the edge of the support satisfies the condition:
  • An advantage of this exposure device is that due to the comparatively great divergence of the beam of light from the light source the possibility is created to enlarge the transverse dimensions of the light source. It is true that the spread of the beam of light, which in itself results in an improvement of the center-toedge ratio of the illumination on the screen, sometimes goes at the expense of the overall quantity of light which is projected onto the screen. However, by simultaneously choosing the transverse dimensions of the light source to be larger, and to at least maintain the brightness thereof, the quantity of light radiated by that source to the screen is increased. This has a compensating effect on the sometimes partially detrimental influence of the above-mentioned divergence. In addition the larger transverse dimension of the light source compensates the reduction of the image from that source which image is obtained with the negative lens. The maximum admissible transverse dimension of the light source is detennined inter alia by the properties of the photosensitive layer, the distance between the. light source and the screen, the size of the apertures of the mask, etc.
  • the negative lens in the embodiment of this U.S. patent specification referred to is arranged in such a position and has such a refraction that the reduction of the tip of the cone as viewed from the screen is negligibly small. This lens also serves for completely different purposes.
  • the reduction factor is smaller than three-fourths in the case of the present invention. This may be explained as follows:
  • a cone tip having a transverse dimension D is used which projects light through a negative lens onto a support which is provided with a photosensitive binder.
  • the light distribution of the tip of the cone of dimension D is assumed to be the same as that of the tip of the cone of dimension d. Furthermore it is assumed that D d and D/d).
  • the light intensity is I, and l,,,,, respectively.
  • the light absorption (in a transmission filter) used for obtaining the correct illumination-distribution on the support can be reduced on its path from C l to C
  • the photosensitive binder consists of a photoresist which is soluble in water and which contains a bichromate salt as a sensitizer
  • the dimensions of the light source in mm. transverse to the connection from C to C are preferably at least equal to:
  • L is the distance in mm. between C and C and Q is the distance in mm. between the central part of the mask and the central part (C of the support.
  • An advantage of this preferred solution is that a possible loss of light due to the divergence of the beam is compensated for at least for the greater part by the choice of comparatively large transverse dimensions of the light source.
  • the reference C is the diameter of a luminous surface element which is provided at a distance P from a mask M, the distance between mask M and a screen S being denoted by 0.
  • An aperture in the mask is circular and has a diameter B.
  • the diameter between the limit of the half-shadow at S and the unexposed parts is indicated by D max.
  • the cone bounded by the circumference of the aperture of the mask of diameter B and the center of C as atip terminates on S in a circle of diameter Do.
  • D max/D0 Acceptable values for D max/D0 are D max/D0 s 1.6.
  • CQ/LB s 0.6 that is to say, Cs 0.6 LB/Q.
  • the lens of an exposure device has preferably a concave boundary surface facing the light source wherein the center of curvature of the boundary surface lies on the line of connection between the light source and the center of the lens and wherein the second boundary surface of the lens is part of a convex surface, the center of this convex surface being located on a straight line through the light source and the center of the lens, the second boundary surface having a convex shape and the conditions:
  • v is the distance in mm. between the center C and the lens
  • n is the relative refractive index of the material of the lens for the wavelength range of the light from the light source
  • R is the radius of curvature in mm. of the second boundary surface
  • t is the thickness in mm. of the central part of the lens.
  • the optical system is aplanatic.
  • a light ray then impinges upon the second boundary surface of the lens at a straight angle.
  • FIG. 1 shows a figure already described and relating to the course of the light rays from a luminous surface element having a diameter C, 7
  • FIG. 2 is a diagrammatical cross section of an exposure device according to the invention.
  • FIG. 3 shows a few details of the exposure device of FIG. 2 at an enlarged scale
  • FIG. .4 shows a light distribution of a tip of a light conductor of the exposure device of FIG. 2.
  • the reference numeral 1 denotes a substantially closed container of approximately 1 m. height.
  • the reference numeral 2 denotes a cover for this container.
  • This cover 2 is provided with an aperture 3.
  • Three or more stops 4 (one of which is visible in FIG. 2) and a positioning notch 5 are provided near the aperture 3.
  • a screen 6 is urged against the stops 4 with the aid of a notch 5. This serves to have the screen 6 occupy a given position.
  • the screen 6 is a future 25-inch image screen of a color television display tube.
  • a mask 7 which is provided with a plurality of holes 8, 8 etc. is provided at a short distance from this screen.
  • the container 1 contains a secondary light source 9 which is formed by the tip of a conelike light conductor 10.
  • the source 9 radiates light via a negative lens 11 (according to the invention) and via a correction lens 12 through the apertures 8, 8 etc. of the mask 7 onto the screen 6.
  • a photosensitive layer provided on the side of screen 6 facing the cone 9 is then exposed. This layer consists of a photoresist which is soluble in water and contains a bichromate salt as a sensitizer.
  • the correction lens 12 serves for adaptation of the direction of the light rays to the direction of the deflected electron beam (in the tube to be manufactured).
  • a filter layer 12a whose permeability increases from its center towards the edge is provided on the lens 12.
  • the reference numerals l3 and 14 denote two electric wires which serve to supply an electric discharge lamp which projects light onto the base plane of the cone 10.
  • This lamp and the cone are mounted in an auxiliary member 15 which is supported by a few vertical consoles l6 and 17.
  • the distance between the center C of the tip of the cone and the lens 11 was 25 mm. in a certain embodiment.
  • the distance between C and a point C, which represents the center of screen 6, was then 352 mm.
  • An aperture of the mask near the point C had a diameter of approximately 0.29 mm.
  • the central portion of the lens 11 had a thickness of approximately 3 mm.
  • the tip 9 of the cone had a diameter which was approximately 1.5 times larger than is common practice, namely 6 mm.
  • the lens 11 and the tip 9 of the cone of FIG. 2 are shown at an enlarged scale.
  • the reference I-l represents the centerline through the center of the tip C of the cone and the center of the lens 11.
  • the reference 0 is a point of intersection of this centerline H with the lens 11.
  • the reference K denotes the center of curvature of the first boundary surface and K, denotes the center of curvature of the second boundary surface of the lens 11.
  • the reference C JG denotes the course of a ray of light from the tip of the cone through the lens 11 to the screen 6. This ray of light intersects the second boundary surface at a straight angle.
  • the radius of curvature of the first boundary surface was 10 mm. in the relevant case and it was 19.8 mm. for the second boundary surface.
  • the refractive index n of the lens was 1.48 for the light from the lamp.
  • the reduction M of the tip 9 of the cone by the lens 11 is approximately 0.68, that is to say, it is less than three-fourths so that f 3v is satisfied.
  • the reference C denotes the central point of the previously mentioned cone 10.
  • the reference I in this Figure denotes the light intensity into the direction of the point C,.
  • the reference TB denotes the light intensity of the tip of the cone into the direction of a point on the edge of the support.
  • the magnitude of the light intensity into other directions is denoted by the curve 21 in FIG. 4. This curve shows that the light intensity is smaller at a greater angle with C C
  • the lens 11 see FIGS. 2 and 3
  • the ratio between the light intensities towards C and into the direction [3 is improved, however. This is apparent, for example, from FIG. 3.
  • the light intensity into the direction B is generated by a ray of light which is radiated by the cone 10 at an angle a, that is to say, at a smaller angle.
  • the quantity of light actually radiated by the cone 10 in combination with the lens 11 into the direction [3 is denoted by I in FIG. 4.
  • This light intensity I is greater than the light intensity IB. In the relevant embodiment a was approximately 2840.
  • the filter layer which is generally applied on the lens 12 may be less thick in the center of this lens.
  • the light absorption in the center of the lens 12 was only approximately 2.5 times that of the edge of the lens 12.
  • less loss of light occurs in the filter layer.
  • the lens is an aplanatic lens as is apparent from the mentioned radii of curvature and distances, at least the point C, is displayed on the screen 6 without error. This is advantageous for obtaining phosphor dots of the desired shape on the screen.
  • An exposure device for projecting aperture patterns from a substantially planar mask onto a photosensitive layer on a picture screen for cathode-ray tubes comprising a conical light source having a longitudinal axis orthogonal to the plane of said mask, and a substantially rotationally symmetrical negative lens between said light source and said mask, the focal length f in mm. of said lens satisfying the condition:
  • v is the distance in mm. between the center of the light source and the lens, said lens diverging the light radiated from said light source to enlarge the transverse dimensions of said light source as viewed from said mask, and wherein the light intensity I, from said light source to a point on the edge of said mask satisfies the condition:
  • said photosensitive layer comprises a photoresist that is soluble in IOIOIS 0079 water and contains a bichromate salt as a sensitizer, and the dimensions of said light source in mm. are at least equal to 0.7-LB/Q wherein: B is the diameter in mm. of an aperture in the central part of said mask, L is the distance in mm. between the centers of said light source and said mask, and Q is the distance in mm. between the centers of said mask and said screen.
  • An exposure device as claimed in claim 1 further comprising a corrective lens between said lens and mask for adapting the direction of said light radiated from said light source to the direction of deflected electron beams, said corrective lens having a filter layer, the permeability of said filter layer increasing from its center towards its edges.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
US881464A 1968-12-04 1969-12-02 Exposure device for manufacturing color picture tubes Expired - Lifetime US3628429A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6817330A NL6817330A (enrdf_load_stackoverflow) 1968-12-04 1968-12-04

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US3628429A true US3628429A (en) 1971-12-21

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US881464A Expired - Lifetime US3628429A (en) 1968-12-04 1969-12-02 Exposure device for manufacturing color picture tubes

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US (1) US3628429A (enrdf_load_stackoverflow)
JP (1) JPS4944307B1 (enrdf_load_stackoverflow)
BE (1) BE742548A (enrdf_load_stackoverflow)
BR (1) BR6914676D0 (enrdf_load_stackoverflow)
DE (1) DE1958521A1 (enrdf_load_stackoverflow)
ES (1) ES374156A1 (enrdf_load_stackoverflow)
FR (1) FR2025237A1 (enrdf_load_stackoverflow)
GB (1) GB1245325A (enrdf_load_stackoverflow)
NL (1) NL6817330A (enrdf_load_stackoverflow)
SE (1) SE344847B (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4078239A (en) * 1976-07-02 1978-03-07 Zenith Radio Corporation Method and apparatus for screening slot-mask, stripe screen color cathode ray tubes
US4516841A (en) * 1983-08-19 1985-05-14 Rca Corporation Method for screening line screen slit mask color picture tubes
US4568162A (en) * 1983-08-19 1986-02-04 Rca Corporation Method for screening line screen slit mask color picture tubes
US5946519A (en) * 1997-08-18 1999-08-31 Chunghwa Picture Tubes, Ltd. Light source for forming phosphor elements on CRT display screen

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58134779A (ja) * 1982-02-04 1983-08-11 Toshiba Corp サ−マルプリンタ
JPS63254078A (ja) * 1987-04-13 1988-10-20 Fujitsu Ltd ワイヤドツトプリンタのプラテン機構
KR920007032A (ko) * 1990-09-22 1992-04-28 김정배 칼라브라운관의 노광장치

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2936682A (en) * 1956-07-02 1960-05-17 Sylvania Electric Prod Device for use in processing discrete screen patterns for cathode ray tubes
US2942099A (en) * 1958-04-11 1960-06-21 Rca Corp Optical projection system
US3420150A (en) * 1965-05-10 1969-01-07 Rauland Corp Lighthouse intensity exposure control lens

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2936682A (en) * 1956-07-02 1960-05-17 Sylvania Electric Prod Device for use in processing discrete screen patterns for cathode ray tubes
US2942099A (en) * 1958-04-11 1960-06-21 Rca Corp Optical projection system
US3420150A (en) * 1965-05-10 1969-01-07 Rauland Corp Lighthouse intensity exposure control lens

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4078239A (en) * 1976-07-02 1978-03-07 Zenith Radio Corporation Method and apparatus for screening slot-mask, stripe screen color cathode ray tubes
US4516841A (en) * 1983-08-19 1985-05-14 Rca Corporation Method for screening line screen slit mask color picture tubes
US4568162A (en) * 1983-08-19 1986-02-04 Rca Corporation Method for screening line screen slit mask color picture tubes
US5946519A (en) * 1997-08-18 1999-08-31 Chunghwa Picture Tubes, Ltd. Light source for forming phosphor elements on CRT display screen

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Publication number Publication date
GB1245325A (en) 1971-09-08
BE742548A (enrdf_load_stackoverflow) 1970-06-02
DE1958521A1 (de) 1970-06-18
JPS4944307B1 (enrdf_load_stackoverflow) 1974-11-27
BR6914676D0 (pt) 1973-04-19
FR2025237A1 (enrdf_load_stackoverflow) 1970-09-04
NL6817330A (enrdf_load_stackoverflow) 1970-06-08
SE344847B (enrdf_load_stackoverflow) 1972-05-02
ES374156A1 (es) 1971-12-16

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