Abstract:
A beam index type cathode ray tube having an improved alignment of index stripes, phosphor stripes and matrix stripes. An alignment of the index stripes, the color stripes and the matrix stripes is confirmed during an exposure processing state of the index stripes by using confirming points formed in the screen. An exposed state of the screen is determined by optically testing an alignment of the confirming points and a master screen. On determining that a misalignment exists, the relative positions of the screen and the master screen are adjusted to remove the misalignment.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the benefit of Korean Application No. 00-12506 filed Mar. 13, 2000, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a beam index type cathode ray tube, and more particularly, to a beam index type cathode ray tube in which a process of forming a screen on an inner surface of a panel is improved.  
           [0004]    2. Description of the Related Art  
           [0005]    A beam index type cathode ray tube is designed to reduce problems of a general cathode ray tube. The beam index type tube senses index signals generated by an electron beam and synchronizes the sensed index signals with color signals, such that the electron beam always arrives at a phosphor material at a desired location on a screen to obtain an image.  
           [0006]    The beam index type cathode ray tube forms index stripes generating index light from the screen which is formed on an inner surface of the panel, and the index stripes are generally formed on an aluminum film of the screen with a predetermined interval.  
           [0007]    A method of forming the index stripes is realized by applying a slurry for index stripes on an aluminum film, and exposing the slurries to cleaning after evaporating the aluminum film in the procedure of manufacturing the screen. The index stripes are patterned by using a master glass pattern mask in the exposing process.  
           [0008]    That is, the master glass pattern mask serves as a shadow mask for exposing, which is used in the procedure of manufacturing a screen of a general cathode ray tube, wherein location and width of the index stripes are determined according to an actual mounting state of the master glass pattern mask when setting exposing areas, and therefore, the mounting state of the master glass pattern mask is important to form an excellent screen.  
           [0009]    The cathode ray tube is formed with a glass tube which maintains an inner atmosphere in a high vacuum state, but it is possible to know a state of a screen, which is realized in the screen, only after completing the final manufacturing process. Therefore, it is desirable to prevent the loss of manufacturing costs by checking the screen for defects in an initial state.  
           [0010]    Accordingly, in the process of manufacturing a general cathode ray tube, the manufacturing defects have been prevented by continuously checking an exposed state of the screen with a microscope or other sensors which sense light released outside from a panel through a light source of an exposed stand in the exposing process.  
           [0011]    While in the process of manufacturing the beam index type cathode ray tube, it is impossible to confirm the exposed state of the index stripes by confirming light released outside from the panel through a light source, since the light beams cannot be released from the panel due to an aluminum film, which is formed under the index stripes. Therefore, the exposed state of the index stripes has been confirmed not in an initial stage but in a screen test stage for determining the quality of color reproduction after completing the manufacturing.  
           [0012]    The related art method for manufacturing the beam index type cathode ray tube has disadvantages that manufacturing cost is wasted or increased for confirming the exposed state. Even though the index stripes are exposed in an erroneous mounting state of the master glass pattern mask, such a mistake may be detected or rectified not in the initial stage but only after finishing the manufacturing process.  
         SUMMARY OF THE INVENTION  
         [0013]    Therefore, an object of the present invention is to resolve the above disadvantages and problems of the related art and to provide a beam index type cathode ray tube, in which an exposed state of an index strip may be promptly checked during an exposing process so that manufacturing defects due to exposure errors may be prevented.  
           [0014]    Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention.  
           [0015]    In order to achieve the above and other objects of the present invention, a beam index type cathode ray tube includes a tube, the inside of which is maintained in a vacuum state. A screen is formed at one side in the tube, the screen comprising phosphor stripes, a black matrix, an aluminum film and index stripes. An electron gun is installed in the tube toward the screen and a deflection unit is installed in the tube to deflect an electron beam emitted by the electron gun to the screen. A detector is installed in the tube to sense light emitted by the index stripe and confirming points are formed in the screen for confirming an exposed state of the screen.  
           [0016]    The confirming points are preferably formed in an ineffective area of the screen. The conforming points are formed free of the aluminum film and preferably in a similar manner as the phosphor stripes and the black matrix. In the process of exposing a photosensitive slurry to form the index stripes, the alignment of a master mask and the black matrix is controlled by observing light passing through both the master mask and the confirming points or by observing light emitted by the phosphor stripes of the confirming points. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    The above object other objects of the present invention will become more apparent by describing in detail embodiments thereof with reference to the attached drawings in which:  
         [0018]    [0018]FIG. 1 is a side cross-sectional view of a beam index type cathode ray tube according to the present invention;  
         [0019]    [0019]FIG. 2 is a front view of a beam index type cathode ray tube for explaining a structure of a screen part according to the present invention;  
         [0020]    [0020]FIG. 3 is a partial cross-sectional view for explaining the structure of the screen part according to the present invention;  
         [0021]    [0021]FIG. 4 is a detailed view of a part A of FIG. 2;  
         [0022]    [0022]FIG. 5 is a detailed view of a part B of FIG. 2;  
         [0023]    [0023]FIG. 6 is a cross-sectional view for explaining an exposing process of index stripes according to the present invention;  
         [0024]    [0024]FIG. 7 is a conceptional view for showing a false exposure toward an R phosphor stripe; and  
         [0025]    [0025]FIG. 8 is a conceptional view for showing a false exposure toward a G phosphor stripe.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    Reference will now be made in detail to the embodiment of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.  
         [0027]    [0027]FIG. 1 is a perspective view of a beam index type cathode ray tube according to the present invention and FIG. 2 is a front view of an inner panel for explaining a screen part according to the present invention. Referring now to FIGS. 1 and 2, a cathode ray tube  20  is formed with a panel  21   a  forming a front glass, a funnel  21   b  formed contiguous to a rear part of the panel  21   a , and a neck  21   c  contiguous to the rear part of the funnel  21   b . A vacuum state is maintained inside the cathode ray tube  20 .  
         [0028]    On the inside of the panel  21   a  of the tube  20 , a screen  23  including red R, green G and blue B phosphor stripes  23   a  is formed, a black matrix  23   b  is arranged between the phosphor stripes  23   a , and an aluminum film  23   c  is formed on the phosphor stripes  23   a  and the black matrix  23   b , so that color reproduction is generated by the electron beam scanned to the screen  23 .  
         [0029]    Further, in the screen  23 , index stripes  23   d  which generate index signals are formed on the aluminum film  23   c  at corresponding positions where the black matrix  23   b  is arranged.  
         [0030]    An electron gun  25  is installed in the neck  21   c  and emits the electron beam toward the screen  23 , a deflection unit  27  deflects the electron beam emitted from the electron gun  25  and a detector  29 , senses light emitted from the index stripes  23   d  to transmit the light to an indexing circuit part (not shown) as electric signals. The deflection unit  27  and the detector  29  are installed on an outer periphery of the funnel  21   b.    
         [0031]    Confirming points  31  which confirm an exposure state, are formed in the screen  23  in the manufacturing process of the screen  23 . See FIGS. 1 and 3.  
         [0032]    The confirming points  31  are formed to confirm the exposure state of the index stripes  23   d , are arranged in a non-effective screen area  23   e  of the screen  23  as shown in FIG. 2 and are formed with R, G and B phosphors  31   a  and a black matrix  31   b  arranged therebetween as one set as shown in FIGS. 4 and 5.  
         [0033]    At least one confirming point  31  is formed in longer and/or shorter axial directions of the screen  23  within the non-effective screen area  23   e  of the screen  23 , wherein the confirming points  31  are formed in four positions A, A 1 ,B and B 1  of the screen  23  as shown in FIG. 2.  
         [0034]    [0034]FIG. 4 and FIG. 5 are detailed views of confirming points  31  which are located in positions A and B of FIG. 2, respectively, wherein the confirming points  31  are formed on a same layer with the phosphor stripes  23   a  and the black matrix  23   b , which are formed in an effective screen  23   f , corresponding to the phosphor stripes  23   a  and the black matrix  23   b . The confirming points  31  are offset a predetermined distance from the effective screen area  23   f  of the screen  23  as shown in FIG. 2.  
         [0035]    That is, the confirming points  31  are formed with construction elements of the screen  23  when manufacturing the screen  23  during the manufacturing process of the beam index cathode ray tube.  
         [0036]    For a more detailed description, the manufacture of the screen  23  starts from forming the black matrix  23   b , wherein a photoresistive material for a photoresist layer is deposited over an inner surface of the panel  21   a , an exposure operation of the photoresist layer is performed on exposure areas, and a developing operation is completed for the photoresist layer, so that the photoresist layer is formed with a predetermined pitch on the inner surface of the panel  21   a.    
         [0037]    Also, a light absorptive material for a light absorptive layer is deposited over the inner surface of the panel  23   a  on the photoresist layer, an etching operation is performed on the photoresist layer, and a cleaning operation is completed for the light absorptive layer, so that the black matrix  23   b  is formed with a predetermined pitch on the inner surface of the panel  21   a.    
         [0038]    Afterwards, a phosphor slurry is applied on the black matrix  23   b , an exposure operation is performed on exposure areas, and a developing operation is completed, so that the phosphor stripes  23   a  are formed between the black matrix  23   b . Such procedures are serially performed according to the R, G and B phosphors.  
         [0039]    The above procedures are performed according to a general method except that the black matrix  23   b  and the phosphor stripes  23   a  are patterned to be formed as the black matrix  31   b  and the phosphors  31   a  with the confirming points  31  in the above positions. For this patterning, a suitable master glass pattern mask is provided.  
         [0040]    After the above processes, the aluminum film  23   c  is formed by a vacuum evaporation with a predetermined thickness on the black matrix  23   b  and the phosphor stripes  23   a , however as shown in FIG. 3, the aluminum film  23   c  is not formed on the confirming points  31 .  
         [0041]    A shielding plate (not shown) is arranged on the confirming point  31  to prevent the evaporation of the aluminum film on the confirming points  31 , when evaporating the aluminum film  23   c . Such an operation is more easily achieved where the confirming points  31  are arranged in the non-effective screen  23   e.    
         [0042]    Referring now to FIG. 6, the process of forming the index stripes  23   d  is continued. A slurry  23   d   1  for forming the index stripes is applied on the aluminum film  23   c  and an exposure operation is carried out over an exposure area, so that light, which is emitted toward the panel  21   a  from a light source  40   a  of an exposure fixture  40 , arrive at the slurry for index stripe positions corresponding to the black matrix  23   b . Where an operator can not observe light from light source  40   a  passing through the confirming points  31  when the operator watches the panel  21   a  on an outside surface  21   d  of the panel  21   a , this means that the exposure procedure is properly carried out with relation to the index stripes  23   d , and that a master glass pattern mask  40   b  is mounted with respect to the exposure area in the right position and in the proper state.  
         [0043]    However, if the master glass pattern mask  40   b  is not mounted at the right position, the exposure operation becomes poorly performed, which may be confirmed using the confirming points  31  during the procedure.  
         [0044]    If the exposure process is poorly performed, it is possible to observe that the light beams emitted from the light source  40   a  become deviated from the black matrix  3  lb and partially slanted toward the fluorescent stripes  31   a , as shown in FIG. 7 and FIG. 8, where the operator or a false exposure sensor  40   c  observes the inside of the panel  21   a  through the confirming points  31 . Accordingly, the operator and the false exposure sensor  40   c  can sense the light beams which come from the phosphor stripes  31   a  and determine a poor exposure state of the index stripes  23   d . For reference, FIG. 7 shows a false exposure toward an R phosphor strip  31   a   1  and FIG. 8 shows a false exposure toward a G phosphor stripe  31   a   2 .  
         [0045]    If the exposure process of the index stripes  23   d , as described above, is badly carried out, the process is temporarily interrupted and continued after adjusting the exposure position of the index stripes  23   d . During the interruption, the false exposure sensor  40   c  transmits a corresponding electric signal to a control part  42  as the false exposure sensor  40   c  senses the above incorrect exposure state. The control part  42  adjusts the relative positions of the panel  21   a  and the master glass pattern mask  40   b  to correct the false exposure position precisely and then continues the exposure operation.  
         [0046]    As described above, in the beam index type cathode ray tube according to the present invention, the exposure processing state of the index stripes is checked while manufacturing the screen part before manufacturing of the cathode ray tube is completed. Thereby, a defective exposure process of the index stripes and loss of manufacturing costs are effectively prevented.  
         [0047]    Although an embodiment of the present invention has been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.