Field of the invention
The present invention relates to a universal exposure apparatus for use in black matrix exposure machines. More particularly, the present invention relates to a universal exposure apparatus for use in manufacture of both color picture tubes and color display tubes incorporating an improved lighthouse device. Background of the invention
Generally, when manufacturing a cathode ray tube, an exposure apparatus is used for forming both a black matrix and a fluorescent layer on an inner surface of a panel. The panel of the cathode ray tube is exposed to light by the exposure apparatus in either stripe type or dot type according to a shape of an aperture of a shadow mask.
The exposure apparatus comprises an exposure pedestal on which a panel having a shadow mask is disposed, a body connected to a lower portion of the exposure pedestal, a light source mounted inside the body, for irradiating a light to an inner surface of the panel, and a correction lens and a filter for refracting or diffusing the light emitted from the light source.
The conventional exposure apparatus forms a black matrix having a certain shape on the inner surface of the panel by exposing photosensitive resin deposited on the inner surface of the panel of the cathode ray tube or forms a fluorescent surface by exposing fluorescent material deposited on an inner surface of the panel.
The screen forming device employed in exposing the sensitized screening material for color cathode ray tubes of the above described type, is conventionally known in the art as a "lighthouse." This structure contains an optical system comprising a light permeable refractive medium or corrective lens and a conjunctive light means relatively positioned to provide the required amount of radiant or actinic energy for proper exposure activation of the light-sensitive coating disposed on the viewing area of the panel. For example, to produce the desired pattern of both the matrix and the phosphor elements of the screen structure, the components of the optical system are oriented or aligned relative to an optical axis in a manner to radiate light over the whole of the multi-apertured mask. Thus, the actinic energy traverses the apertures therein to expose discrete areas, be they matrix windows or the subsequently disposed phosphor dots or stripes, on the respectively sensitized screen material therebehind to thereby produce a patterned array of defined configurations having exactness in accordance with the registration requirements of subsequent electron beam impingement in the finished tube. Several factors determine the optimum setup of the exposure optical system, whereupon the screen-lens-light-means distance relationships are altered depending upon variables such as: the size and shape of the screen, the sensitivity of the photoresist material, and the size and shape of the mask apertures.
A lamp house (also referred to in the art as a light house) forms a critical part of the picture tube manufacturing process. The method of using a lamp house generally comprises of coating a photoresist on to a
panel which ultimately is converted to the display or picture tube, loading the photoresist coated panel on the lamp house, and then commencing the exposure process.
Traditionally, the manufacture of color picture tubes and color display tubes has required different lamp houses due to the very specific respective exposure parameters. A lamp house used for the exposure of a color picture tube cannot be used as such in exposure of a color display tube.
In a conventional exposure process for color picture tubes, the light source moves with a defined amplitude, frequency and time at three defined positions - red blue and green. The movement of the lamp house from one defined position to the other is achieved by mechanical means such as a cam arrangement. Since different panels of different products have different requirements of exposure, the amplitude is determined and set manually. Frequency, time and sequence of movement of the lamp source for different types of panels of different color picture tube panels is generally determined based on a programmable logic controller provided in the lamp house.
Conventional exposure process for color display tubes on the other hand requires that the lamp source move in a predefined path in order to create an aperture on the panel screen. The path followed by the lamp source is dependant on the specific requirements of the batch of color display tube panels being exposed. For example, in some cases, the exposure is achieved by rotating the lamp source in an eccentric manner.
As can be understood, one of the most significant problems in the use of lamp source is that different lamp sources are required for color picture tubes and color display tubes because of process complications due to different path requirements. Even if the industry is dedicated to manufacture of only color picture tubes, the very specific requirements of each type of panels result in requirement of different lamp sources. This problem is particularly aggravated if the industry is involved in the manufacture of both color picture and color display tubes. Some of the attendant problems of the use of multiple lamp sources include high floor space requirements resulting in wastage of space, high inventory and maintenance costs, non-standardization of design parameters, loss of time in shut down and re-setting and stabilization time.
Conventional systems for both color picture and color display tubes use a six layer optical system. However, there is no single exposure system for both color picture and color display tubes.
Lighthouses and their use for preparing screen structures for cathode-ray tubes are described in the prior art, such as in U.S. Pat.
Epstein et al and elsewhere. Such lighthouses may include a lens assembly comprised of one or more optical elements and means for projecting a light field from a substantially point light source through the lens assembly and then incident upon a layer of light-sensitive material on the surface of the support for the screen structure.
The prior art notes that the light intensity across the light field at the light-sensitive layer is not uniform due to causes which may be
inherent in the geometry of the optical system or may be due to
imperfections in parts of the optical system. It has also been found
desirable to provide a tailored gradation in brightness in the light field.
It has been proposed to correct nonuniformities in the light field and to
provide a tailored gradation of brightness by interposing in the lens
assembly a intensity-correction filter. Harry
R. Frey discloses such a filter prepared, for example, by positioning a photosensitive layer containing light-attenuation material in the lens assembly, exposing the layer to the light field from the light source until the layer, upon development, produces a light-attenuating filter which is a negative of the intensity variations in the light field. By employing a dodger or similar expedient, the filter may also provide a tailored gradation of brightness in the light field. After development, this light-intensity-correction filter is returned to its position in the lighthouse where it is used in combination with the particular light source and lens assembly with which it was made.
As can be seen, however, no prior art exists for manufacture of a lighthouse which has universal applicability for both color picture tubes and color display tubes. Objects of the invention
The main object of the invention is to provide a universal exposure system with applicability in manufacture of both color picture tubes and color display tubes.
It is another object of the invention to provide a universal exposure system wherein automated alteration of exposure parameters
Is achievable by a preset programme logic dependant on the type of panel being treated in any batch, without requiring shut down and replacement of the lighthouse itself.
Another object of the present invention to provide a universal exposure system for use in forming phosphor dots on the inner surface of the glass faceplate of a color CRT in a manner which provides a high degree of color purity and white uniformity.
Summary of the inventionAccordingly, the present invention provides an universal exposure apparatus for use in the manufacture of both color picture tubes and color display tubes, said exposure apparatus comprising a light source and an optical device for transmitting the light from the light source to the panel required to be exposed, characterised in that said optical device is provided with adaptable lens positions and contours dependent on the panel being exposed, said optical device being provided with an onboard controller communicating with an external controller, said external controller being provided with a programme logic means, said programme logic means being provided with data storage means to store data and information relevant to specific pathways for specific batches of panels, retrieval means to retrieve such information on request from the optical device and transmit path related information thereto, said optical system being alterable depending on the information receiyed from said external controller such that light of required intensity, frequency and characteristics is impinged on the panel.
In one embodiment of the invention, the exposure apparatus comprises modification in lens positions and lens contours dependant on requirements of the panel to be exposed.
In yet another embodiment of the invention, the path followed for a color display tube is sinusoidal closed loop. This specially applied path of the light source makes perfect the round dot in case of display screen.
In another embodiment of the invention, the frequency, amplitude and time for a color picture tube is determined using preset values stored in the programme logic of said external controller.
In a further embodiment of the invention, the apparatus is enabled to trace the desired red, blue and green positions with predefined frequency, amplitude and time for a color picture tube. Brief description of the accompanying drawings
Figure 1 is a flow chart of the operation of the process of the invention.
Figure 2 is a line diagram of the lamp house optical system of the invention.
Figure 3 is a block diagram of the apparatus of the invention. Detailed description of the invention
The present invention therefore provides a universal exposure apparatus for use in the manufacture of both color picture tubes and color display tubes. The exposure apparatus comprises a light source and an optical device for transmitting the light from the light source to the panel required to be exposed. The optical device is provided with an onboard controller communicating with an external controller. The external controller is provided with a programme logic means provided with means to store data and information relevant to specific pathways
for specific batches of panels, means to retrieve such information on request from the optical device and transmit path related information thereto. The optical device is alterable depending on the information received from the external controller such that light of required intensity, frequency and characteristics is impinged on the panel.
The exposure apparatus comprises modification in lens positions and lens contours dependant on requirements of the panel to be exposed. The path followed for a color display tube is sinusoidal closed loop. This specially applied path of the light source makes perfect the round dot in case of display screen. The frequency, amplitude and time for a color picture tube is determined using preset values stored in the programme logic of said external controller. The apparatus is enabled to trace the desired red, blue and green positions with pre-defined frequency, amplitude and time for a color picture tube.
The invention will now be described with reference to the accompanying drawings.
Figure 1 is a flow chart of the operation of the process of the invention. The panel to be exposed is set (11) and the clampers (12) are then set. The rotary cover plate rotation is started in step 3 (13) following which the auto start (14) command is given. The panel is subjected to green xposure (15), blue colour exposure (16) and red colour exposure (17), After verification of completion of exposure (18), the panel is unloaded in step 9 (19). The standard exposure time for all three colour exposures is in the range of 6 to 14 seconds and the time taken to transfer for all colours is about 22 seconds. The total exposure
time for all three colours is in the range of 40 to 62 seconds. The panel type used as an example for the process depicted in Figure 1 comprised a 22" SSP, a 21" super flat, a 17" cathode display tube and a 15" cathode display tube. This process flow sheet clearly proved the universality of the exposure system of the invention.
The three-axis exposure system is a sub-system in the lamp house. The function of this exposure system is to expose the panel for the required period of exposure. The machine PLC identifies the product positions and issues commands to adjust the lens system to the required positions. The signal for exposure is thereafter passed on to the three-axis system. This positions the lamp to the required coordinates and opens the shutter. The lamp house is then moved along a predefined path and at a predetermined speed and time. After the determined period of exposure, the three-axis system issues a signal through its controller to further process the panel by unloading it from the system.
Referring now to Figure 2, a line diagram of lamp house optical system of the invention is given. The lamp house optical system consists of the following: a seal line (21) connected operatively to a shield plate (22); a rotary cover glass (23) provided between the shield plate (22) and the main lens (24). A wedge lens (25) is provided connected to the main lens (24) on one side and to a sub lens/cover glass (26) on the other side. The light from the lamp house (28) is passed on to the cover glass/sub lens (26) through a rotary filter (27).
Referring now to Figure 3, a power supply (31) is provided connected to a power box (32) which is in turn connected to the control means (33). The control means is connected on the other side thereof to an equipment terminal block (34) and to a voltage regulator (35). The voltage regulator is connected to a leakage transformer (36) which is then further connected to a lamp intensity control system (37) which controls the intensity of the lamp house (not shown) through the lamp house controls (38). The equipment terminal block (34) is connected to the motor, a fan, a sensor means a CNC system and other ancillary equipment.
After the panel is coated with the photoresist, it is loaded onto the lighthouse. The product is sensed and the appropriate data values recovered from the programme logic by the onboard controller of the lighthouse. The light source itself is an ultraviolet lamp. The path for color picture tubes is oscillation in linear axis at three positions. In the case of color display tubes, the path is sinusoidal closed loop in the form of a sleeping 8 at three positions.
The lighthouse selects the appropriate programme from the external controller depending on the panel to be exposed. For example, if the panel is a color picture tube, specific frequency, amplitude and time parameters for all of red, blue and green positions are chosen from a predetermined set of valued stored in the programme logic of the external controller. This value is loaded onto the onboard controller, which then initiates functioning of the apparatus. After the signal for the red position is received, the x-axis starts oscillating with defined
amplitude, frequency and time. Shutter for the exposure opens only after oscillation starts and closes before the stop of the oscillation. The same cycle is repeated for both the blue and the green positions by positioning the y-axis at green and blue respectively.
In the case of a color display tube, the x, y and z - axes are first positioned at preset values. After initiation of operation of the apparatus, the lamphouse first moves in a sinusoidal closed loop with defined amplitude, frequency and time due to the interpolation of the x and the y - axes. After start, the shutter is opened and closed before stop of oscillation. This cycle is repeated for the other colors, by changing the y axis from green and blue.
What is described above and illustrated in the figures accompanying this specification is illustrative of the invention, it will be understood that various modifications are possible to the system of the invention without departing from the scope of the invention in any manner.

We Claim
1. An universal exposure apparatus for use in the manufacture of color picture tubes and color display tubes, said exposure apparatus comprising a light source, a optical device for transmitting the light from the light source to the panel required to be exposed, and being provided with adaptable lens positions and lens contour dependent on the panel being exposed, said optical device being provided with an onboard controller communicating with an external controller, said external controller being provided with a programme logic means, said programme logic means being provided with data storage means to store data and information relevant to specific pathways for specific batches of panels, retrieval means to retrieve such information on request from the optical device and transmit path related information thereto, said optical device being changeable depending on the information received from said external controller for impinging light of required intensity, frequency and characteristics on the panel.
2. An apparatus as claimed in claim 1 wherein the path followed for a color display tube is sinusoidal closed loop.
3. An apparatus as claimed in claim 1 wherein the said programme logic means /or determining the frequency, amplitude, and time for a colour picture tube based on such preset values and is provided with a memory means to store preset values.
4. An universal exposure apparatus for use in the manufacture of color picture tubes and color display tubes substantially as described herein before and with reference to the accompanying drawings.