Patent Publication Number: US-6656231-B2

Title: Dyeing method of dyeing plastic lens

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a dyeing method of dyeing a plastic lens. 
     2. Description of Related Art 
     Conventionally, a dip dyeing method has been adopted in most cases as one of dyeing methods of dyeing plastic lenses for spectacles. This dip dyeing method includes: preparing a dyeing solution by mixing disperse dyes of primary colors of red, blue, and yellow and dispersing the mixture in water; heating the dyeing solution to about 90° C.; and dipping a plastic lens into the heated solution, thereby dyeing the lens. 
     As an alternative to the dip dyeing method, there has been proposed a vapor-deposition dyeing method. This method includes heating sublimatable solid dye under vacuum to sublimate and vapor-deposit the sublimated dye onto a plastic lens which is heated simultaneously under vacuum, thereby dyeing the lens. 
     The conventional dip dyeing method and vapor-deposition dyeing method, however, has the disadvantages that it is difficult to provide a stably dyed lens. In particular, it is difficult to dye a lens of low dyeability or to dye a lens in deep colors, or in colors of high density. Furthermore, it is desired to more easily and effectively dye a lens. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a dyeing method capable of easily and effectively dyeing a plastic lens and also stably dyeing various lenses in various colors. 
     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. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     To achieve the purpose of the invention, there is provided a dyeing method of dyeing a plastic lens, including: a step of placing the lens in a predetermined position in a vacuum vapor-deposition device; a step of placing a base body to be used for a dyeing operation in the vapor-deposition device, the base body being applied with dyeing solutions each containing a dissolved or fine-grained dispersed sublimatable dye to form a dye application area on the base body, and the base body being arranged so that the dye application area faces the lens without contact therewith; a step of heating the base body under vacuum in the vapor-deposition device, thereby sublimating the dye of the dye application area to vapor-deposit the sublimated dye on the lens; and a step of heating the lens on which the dye has been vapor-deposited at changing heating temperatures, thereby fixing the dye on the lens. 
     According to another aspect of the present invention, there is provided a dyeing method of dyeing a plastic lens, including: a step of adding a dyeing auxiliary agent for enhancing fixation of the dye to the lens; a step of placing the lens to which the dyeing auxiliary agent has been added in a predetermined position in a vacuum vapor-deposition device; a step of placing a base body to be used for a dyeing operation in the vapor-deposition device, the base body being applied with dyeing solutions each containing a dissolved or fine-grained dispersed sublimatable dye to form a dye application area on the base body, and the base body being arranged so that the dye application area faces the lens without contact therewith; a step of heating the base body under vacuum in the vapor-deposition device, thereby sublimating the dye of the dye application area to vapor-deposit the sublimated dye on the lens; and a step of heating the lens on which the dye has been vapor-deposited, thereby fixing the dye on the lens. 
     According to another aspect of the present invention, there is provided a dyeing method of dyeing a plastic lens, including: a step of placing the lens in a predetermined position in a vacuum vapor-deposition device; a step of placing a base body to be used for a dyeing operation in the vapor-deposition device, the base body being applied with dyeing solutions each containing a dissolved or fine-grained dispersed sublimatable dye to form a dye application area on the base body, and the base body being arranged so that the dye application area faces the lens without contact therewith; a step of heating the base body under vacuum in the vapor-deposition device, thereby sublimating the dye of the dye application area to vapor-deposit the sublimated dye on the lens; and a step of heating the lens on which the dye has been vapor-deposited at a heating temperature in a range of 90° C. to 150° C., thereby fixing the dye on the lens. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate an embodiment of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. 
     In the drawings, 
     FIG. 1 is a schematic view of a system for dyeing a plastic lens in an embodiment according to the present invention; 
     FIG. 2A is a back view of a print base body in the embodiment; 
     FIG. 2B is a front view of the print base body; 
     FIG. 2C is a sectional view of the print base body; 
     FIG. 3 is a schematic structural view of the inside of a vacuum vapor-deposition device used in the embodiment; 
     FIG. 4 is a partially enlarged sectional view of a dyeing jig disposed in the device shown in FIG. 3; and 
     FIG. 5 is a flow chart showing a routine of the dyeing method in the embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detailed description of a preferred embodiment of a dyeing method embodying the present invention will now be given referring to the accompanying drawings. 
     FIG. 1 is a schematic diagram of a dyeing system for dyeing a plastic lens in the present embodiment. FIG. 5 is a flow chart showing a routine of the dyeing method. 
     (1) Production of a Print Base Body (a Base Body to be Used for a Dyeing Operation) 
     At first, a print base body  10  to be used for dyeing a plastic lens  22  (hereinafter, simply referred to as a lens) is produced. On the body  10 , a sublimatable dye (a dyeing solution) is printed or applied. 
     As the sublimatable dye (which contains a dissolved or fine-grained dispersed sublimatable dye), there are used four dispersion dye inks of red, blue, yellow, and black, each being water-base ink, which are made by Upepo Kabushiki Kaisha. These inks are separately filled in commercially available ink cartridges for an ink jet printer. The cartridges are mounted in an ink jet printer  2 . This printer  2  in the present embodiment is a commercially available printer (MJ-520C of EPSON Kabusiki Kaisha). 
     Prior to the use of such printer  2  to produce the base body  10  on which the dye of a desired color, an available personal computer (hereinafter, referred to as PC)  1  is used to regulate the hue and density to be printed. The regulation of the hue and others is handled by a drawing software, a CCM (computer color matching), or the like, on the PC  1 . Accordingly, data on the desired color can be stored in the PC  1  so that the base body  10  with the same color quality can be repeatedly produced as needed. A color tint (ex. gradation pattern) is also controlled in digital form, which makes it possible to repeatedly reproduce the base body  10  in the same color density as required. 
     A print sheet  11  which forms the base body  10  is set in the printer  2 . The PC  1  is then operated to carry out printing based on the preset data on the desired hue and density. On the front face of the print sheet  11  (the base body  10 ), circular colored layers  12  which are areas applied with the dye are printed as shown in FIG.  2 B. In the present embodiment, two colored layers  12  are printed on one print sheet  11 . This is because the previous formation of the colored layers in pairs is more convenient for dyeing a pair of spectacle lenses; right and left lenses. Furthermore, the diameter of the colored layer  12  is preferably determined to be larger than the diameter of the lens  22  to be dyed. If the diameter of the colored layer  12  is shorter than that of the lens  22  to be dyed, there is a possibility that the entire surface of the lens  22  facing the colored layer  12  could not be sufficiently dyed. For preventing such inconvenience, the diameter of the colored layer  12  is designed in the above manner. 
     In the present embodiment, the print sheet  11  used for the production of the print base body  10  is a sheet having an entirely black-colored back face, on which no colored layer is printed, as shown in FIG.  2 A. As such sheet  11  having a black-colored face, a commercially available one may be used, alternatively, a sheet of which both faces are white may be used if only one of the white faces is colored black. Using the sheet  11  having a black-colored face is to efficiently absorb heat generated by a heating source, whereby to help rapid sublimation of the dye printed on the sheet  11  in a dyeing operation of the lens  22 . 
     In the present embodiment, the print sheet  11  having a black face is used to produce the print base body  10  for the above reason, but not limited thereto. For example, any print sheet may be used if only it has a back face that includes a predetermined region (a part or entire region) which is applied (painted or coated) with a color or material having a good or high coefficient of heat absorption (coefficient of infrared light absorption), for example, a color close to black or chrome. Furthermore, at least the predetermined region of such print sheet may be made of a material having a good or high heat conductivity, such as aluminum, so that more rapid sublimation of dyes can be effected. Alternatively, the print sheet itself may be made of an aluminum plate. In the use of paper for the sheet  11 , any paper usable in the printer  2  may be used and, preferably, a thin paper which is good or high in heat conductivity is used. The front face of the print sheet  11 , on which the colored layer  12  will be printed, may have the same color as that of the back face, but it is preferably white for facilitating visual observation of a print condition of the print base body  10  produced. 
     The size of the print sheet  11  used for production of the base body  10  is not limited, and any sized-sheet usable in the printer  2  may be used. The sheet size used in the present embodiment is A5-size. This sheet is roughly cut out after output from the printer  2  to remove the needless margin so that the cut sheet is fit into a dyeing jig  30  mentioned later. In the present embodiment, the shape of the colored layer  12  is circular, but it is not limited thereto. Any size and shape may be adopted if only the dye can be diffused evenly over the area of the lens  22  desired to be dyed. 
     It is also preferable that the back face of the sheet  11  is entirely or partially applied with a coating for preventing sublimation of the dye from the back face. This allows sublimation of the dye from only the front face of the base body  10  when heated. FIG. 2C is a schematic enlarged sectional view of the base body  10 . A coating layer  13  is therefore formed in advance on the back face of the print sheet  11  for preventing the passage of air therethrough. The material of the coating layer  13  may be selected from any materials which can prevent the passage of air and have enough heat-resistance not to melt at temperatures up to about 200° C., preferably about 270° C., and does not adsorb the sublimatable dye. For example, an olefinic resin, polyethylene glycol, or the like may be used. In this manner, the provision of the coating layer  13  makes it possible to prevent sublimation of the dye from the back face of the base body  10 , efficiently dyeing the lens, thereby facilitating dyeing of the lens in colors of high density. 
     The above mentioned almost black-colored coating region for preventing sublimation may be formed on the back face of the sheet  11  by, for example, coating a mixture composed of carbon and polyethylene glycol or a mixture composed of an olefinic resin and a pigment on the back face. 
     (2) Dyeing of a Plastic Lens 
     FIG. 3 shows a schematic view of the inside of a vacuum vapor-deposition device (hereinafter, referred to as a vapor-deposition device)  20  as viewed from its front, which is used for dyeing the plastic lens  22  in the present embodiment. 
     The vapor-deposition device  20  is provided at its front with a door not shown which is opened/closed for insertion/removal of the plastic lens  22 , the print base body  10 , and others. In the device  20 , fourteen heating lamps  21  in total used as heating sources to heat the base body  10  to thereby sublimate the dye are provided so that seven lamps are disposed at an upper position in the device  20  and seven lamps at a lower position. In this way, the lamps  21  are arranged in the positions opposite to the lens  22  with respect to the base bodies  10 , respectively. The lamps  21  in the present embodiment are halogen lamps, but not limited thereto. Any lamps or the like capable of heating the base body  10  in noncontact relation therewith may be used. 
     In the vapor-deposition device  20 , a shelf  23  is provided for holding thereon a dyeing jig  30  used to dye the plastic lens  22 . The shelf  23  is formed with a plurality of rectangular holes  23   a  in each of which the dyeing jig  30  is fit. The dyeing jig  30  is thus held (placed) at a middle position in the device  20 . 
     In the dyeing jig  30 , the base bodies  10  are placed above and below the lens  22 , or in opposite positions to each other with respect to the lens  22 , so that the colored layers  12  face the concave and convex surfaces of the lens  22  respectively without contact therewith. When the base bodies  10  arranged as above are heated by the lamps  21  lit up, the concave and convex surfaces of the lens  22  can therefore be dyed at a time. 
     If the distance between the base body  10  and the lamps  21  is too small, a heating temperature with respect to the base body  10  may be different depending on portions of the base body  10 , which causes nonuniform sublimation of the dye (the colored layer  12 ) provided on the base body  10 , resulting in an unevenly dyed lens  22 . If the distance is too large, on the other hand, producing only a low thermal effect, sublimation of the dye may take much time. Therefore, the distance between the base body  10  and the lamps  21  is preferably set in a range of about 50 mm to 500 mm, more preferably, about 150 mm to 300 mm. 
     Reference numeral  24  is a rotary pump which is used to produce an almost vacuum in the device  20 . Reference numeral  25  is a leak valve which is opened to take air into the device  20  maintained under vacuum, thereby to return it to an atmospheric pressure. 
     FIG. 4 is a sectional front view of the dyeing jig  30 . Reference numeral  31  is a box-like container which is fittable in the hole  23   a . This container  31  has the same shape as that of the hole  23   a  and is formed with a peripheral flange  31   a  which is allowed to hitch on the shelf  23  to prevent the container  31  from coming off the shelf  23 . Therefore, the container  31  can be held in the shelf  23  with the flange  31   a  engaged therewith. The container  31  also has a bottom  31   b  formed with two circular openings  31   c  each having a sufficiently larger diameter than that of the colored layer  12  formed on the base body  10 . When the base body  10  is put on the bottom  31   b  of the container  31 , the colored layers  12  of the base body  10  are positioned in a one-to-one correspondence with the openings  31   c . The two openings  31   c  are arranged in a line in a direction perpendicular to the drawing sheet, and only one of them is illustrated in FIG.  4 . 
     With such configuration, when the lamps  21  disposed at the lower position in the vapor-deposition device  20  are allowed to emit light, or are lit up, the light will directly impinge on the back face of the lower base body  10  through the openings  31   c , thereby easily causing sublimation of the dye from the colored layers  12 . 
     In the container  31 , space adjusting rings  32  are disposed on the base body  10  in a one-to-one relation with the two colored layers  12  formed on the body  10 . Each of the rings  32  has a cylindrical shape and a diameter larger than that of the colored layer  12  to enclose it. This ring  32  is used to adjust the distance (space) between the lens  22  and the base body  10  placed on the bottom side in the container  31 , while holding the base body  10  against dislocation. Changing the height of the ring  32 , or replacing the ring  32  with another having a different height, enables adjustment of the distance between the lens  22  and the base body  10 . This makes it possible to control the color density of the lens  22  to be dyed. 
     As shown in FIG. 4, a lens holder  34  for holding the lens  22  is put on the ring  32 . A space adjusting ring  33  is further placed on the lens holder  34  to adjust the distance (space) between the lens  22  and the base body  10  placed on the upper side in the container  31 . The lens holder  34  has a cylindrical shape provided with an internal shoulder  34   a  for supporting the lens  22  as shown in FIG.  4 . With this shoulder  34   a , the lens  22  can be set in the holder  34  without falling down. 
     The lens holder  34  is put on the ring  32 , and the lens  22  is set in the holder  34  so that the peripheral portion of the lens  22  is positioned on the shoulder  34   a . Thus, the lens  22  can be held in place above the opening  31   c.    
     Reference number  35  is a retainer for holding the base body  10  with respect to the ring  33 . This retainer  35  is formed at its upper face with two openings  35   a  as with the bottom  31   b  of the container  31  (only one of the openings is shown in FIG.  4 ). Through the openings  35   a , the light emitted from the lamps  21  (when lit up) disposed at the upper position in the vapor-deposition device  20  to directly impinge on the back face of the upper base body  10 . 
     Each height of the rings  32  and  33  may be determined depending on a desired dyeing condition. However, if the base body  10  makes contact with the lens  22 , the contact portion of the lens  22  will be dyed in a different color density and hue from the noncontact portion, thus irregularly coloring the lens  22 . To the contrary, if the base body  10  is too apart from the surface of the lens  22  to be dyed, the lens  22  can not be dyed in high density. Furthermore, particles of the dye tend to gather together without uniformly dispersing in a vapor phase and therefore unevenly deposit on the dyeing surface of the lens  22 . In view of this, the distance from the base body  10  to the geometrical center of the dyeing surface of the lens  22  is preferably set in a range of about 1 mm to 30 mm for the convex surface side and about 1 mm to 30 mm for the concave surface side. 
     The material of the lens  22  to be dyed is selected from a polycarbonate resin (e.g., diethylene glycol bisallyl carbonate polymer (CR-39)), a polyurethane resin, an allyl resin (e.g., allyl diglycol carbonate and its copolymer, and diallyl phthalate and its copolymer), a fumaric acid resin (e.g., benzyl fumarate copolymer), a styrene resin, a polymethyl acrylate resin, a fiber resin (e.g., cellulose propionate). Furthermore, a material with a high refractive index such as a thiourethane type, a thioepoxy type, and the like, and other materials with a high refractive index which have conventionally been regarded as having low (poor) dyeability may be used. 
     With the vapor-deposition device  20  having the above construction, the following operations take place to dye the lens  22 . 
     The unillustrated door of the device  20  is opened, and the container  31  is set in the holes  23   a  of the shelf  23 . Sequentially, the base bodies  10  produced in the above process (1) and the lens  22  are set in the dyeing jig  30  as shown in FIG.  4 . 
     Then, the door of the device  20  is airtightly closed. The pump  24  is then driven to produce a vacuum in the device  20 . This vacuum is produced by reducing the pressure in the device  20  to about 0.1 to 5 kPa. The vacuum may be below 0.1 kPa, but it will require a high-powered exhauster. On the other hand, the higher the pressure in the device  20 , the higher the temperature is required for sublimation of the dye. Therefore, the upper limit of the pressure is preferably up to about 5 kPa, more preferably in a range of about 1 to 3 kPa. 
     When the pressure in the device  20  is reduced to a predetermined value, the lamps  21  disposed at the upper and lower positions in the device  20  are lit up. The dye of the colored layer  12  can not be sublimated at temperatures of 100° C. or below. It is therefore preferable to increase the heating temperature to as high as possible in the shortest time. The reason why the heating temperature is thus increased to as high as possible is to enhance the productivity by shortening the time needed for completing the sublimation. The reason why the heating time is minimized is to prevent the occurrence of a defective condition that, if the time needed for increasing the heating temperature is too long, the temperature of the lens  22  itself will rise, makingit difficult to stick the sublimated dye to the lens. 
     In the present embodiment, the base body  10  (print sheet  11 ) has a black-colored back face as mentioned above, so that the base body  10  can absorb heat rapidly, increasing the rate of temperature thereof and easily raising the temperature to high. Therefore, the sublimation of the dye from the base body  10  can be completed in a short time, and the production efficiency can be enhanced. The completion of sublimation in a short time can also suppress the rise in temperature of the lens  22  itself. 
     The lamps  21  disposed at the upper position in the vapor-deposition device  20  are lit up to heat the base body  10  placed in the dyeing jig  30  at the upper portion thereof. On the other hand, the lamps  21  disposed at the lower position in the device  20  are lit up to heat the base body  10  placed in the jig  30  at the lower (bottom) portion thereof. Thus, both surfaces of the lens  22  are dyed at the same time. The higher density can therefore be obtained in one process as compared with the density obtained by a dyeing operation on only a single surface. 
     Furthermore, the concave surface and the convex surface of the lens  22  are dyed by use of individual print base bodies  10 , so that the lens  22  may be dyed with different colors and materials between the concave surface and the convex surface. 
     After completion of the heating by the lamps  21 , the leak valve  25  is opened to return the pressure in the device  20  to normal atmospheric pressure. Then, the door of the device  20  is opened and the lens  22  is taken out. On this lens  22 , the sublimated dye has been vapor-deposited, but it is liable to come off in this state. Therefore, the lens  22  is heated in an oven  3  (see FIG. 1) under normal atmospheric pressure to fix the deposited dye onto the lens  22 . This fixation process is carried out in the following steps; raising the temperature in the oven  3  to a temperature as high as possible below a resistible temperature of the lens  22 ; heating the lens  22  for a predetermined time needed for producing a desired hue and density; and after a lapse of the predetermined time, taking the lens  22  out of the oven  3 . If the heating temperature in the oven  3  is below 90° C., the color can not sufficiently develop. If it exceeds 150° C., the lens may be easily deformed. Therefore, the heating temperature is preferably set in a range of about 90° C. to 150° C. and, more preferably, about 110° C. to 130° C. The heating temperature may be increased up to about 170° C. according to the type of lens. If the heating time is shorter than 30 minutes, the color can not sufficiently develop. If it exceeds 3 hours, the dye may change in quality, which makes it impossible to provide a desired hue. For preventing those inconveniences, the heating time is preferably set in a range of 30 minutes to 3 hours and, more preferably, 30 minutes to 2 hours. 
     Furthermore, the heating temperature in the oven  3  may be changed so as to decrease continuously or in multiple steps. Alternatively, a constant heating temperature and a changing heating temperature may be combined. For instance, the lens is heated at a temperature of 140° C. for 1.5 hours (or at 150° C. for 1 hour); the temperature is gradually reduced from 140° C. (or 150° C.) to 80° C. in 2 hours; the lens is heated at 80° C. for 1 hour; the temperature is gradually reduced from 80° C. to 40° C. in 2 hours; and the heating is completed at the time when the temperature becomes 40° C. (in this case, the heating time may exceed 3 hours). It is to be noted that a preferable changing range of the heating temperature is from about 30° C. to 170° C. and a preferable heating time is up to about 7 hours. Under these conditions, the color can sufficiently develop and the deformation of the lens can be suppressed. 
     As mentioned above, by dyeing the lens from both sides thereof at one time, the lens can be dyed in color of high density in a short time. As compared with the conventional dip dyeing method, the dyeing method performed in the vapor-deposition according to the present invention can sufficiently dye even lenses made of materials with a high refractive index and low dyeability. 
     Moreover, a predetermined pretreatment for helping or enhancing the fixation of the dye may be applied to the lens  22  itself before the dye is sublimated from the base body  10  to be vapor-deposited onto the lens. This pretreatment can shorten the fixation time in the oven  3 . In the pretreatment, a dyeing auxiliary agent called a carrier, such as a phenyl phenol type, a naphthalene type, a chlorobenzene type, or the like, is used. An example of the pretreatment before dyeing of the lens  22  is performed by dipping the lens  22  itself in a carrier solution which is prepared by dissolving a dyeing auxiliary agent (DK-C of Daiwa Kagaku Kogyo Kabushiki Kaisha) in water and then washing the lens  22  by a washer. In this case, the carrier solution preferably contains the dyeing auxiliary agent at the ratio of about 0.1% to 5% to the total amount of the solution; the water temperature is preferably in a range of 60° C. to 100° C., more preferably, 80° C. to 90° C.; and the dipping time is preferably in a range of 1 to 3 minutes. 
     EXAMPLE 1 
     In this example 1, a lens of CR-39 is used. As a sublimatable ink, a disperse dye (water-base) made by Upepo Kabushiki Kaisha is used. By using a drawing software in the PC  1 , the hue (U) is set to 160, the saturation (S) is set to 255, and the lightness (V) is set to 153. Based on this color data, two circular layers  12  each having a diameter of 90 mm are printed on a print sheet  11  having a white front face (printing face) and a black back face (on which a coating treatment for preventing the passage of air has been applied). Sequentially, the sheet  11  is cut to remove the needless margin so as to fit into the dyeing jig  30  shown in FIG.  4 . The base body  10  is produced in the above manner. In this example, two base bodies  10  are produced for one dyeing jig  30 . 
     Next, the jig  30  is mounted on the shelf  23  in the vapor-deposition device  20  (see FIG.  3 ). The lens  22  and the two base bodies  10  are placed in the jig  30 . The pump  24  is driven to reduce the pressure in the device  20  to 1 kPa. When the pressure becomes 1 kPa, the upper and lower lamps (halogen lamps in this example)  21  are lit up to sublimate the dye from the base bodies  10 . The distance between the lamps  21  and each base body  10  is set to 200 mm. 
     A temperature rising state of the base body  10  during the heating is shown in Table 1. Temperature changes are measured by a thermocouple which is brought into contact with the back face (black side) of the base body  10 . 
     As a result, the dye (the colored layer  12 ) on the base body  10  was completely sublimated in about 45 seconds from light-up of the lamps  21 . 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Light-up 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 duration 
               
               
                 (sec.) 
                 0 
                 10 
                 20 
                 30 
                 40 
                 50 
                 60 
                 70 
                 80 
                 90 
                 100 
                 110 
                 120 
               
               
                   
               
             
            
               
                 Temp. of 
                 15 
                 54 
                 95 
                 128 
                 162 
                 186 
                 206 
                 226 
                 240 
                 253 
                 264 
                 274 
                 282 
               
               
                 base body 
               
               
                 (° C.) 
               
               
                   
               
            
           
         
       
     
     Comparison 1 
     This comparison 1 uses the same conditions as those in the example 1, except that a print sheet  11  having both white faces is used to produce a base body  10 . A temperature rising state of the base body  10  in this comparison is shown in Table 2. 
     The result is that the dye (the colored layer  12 ) on the base body  10  was merely partially sublimated even after a lapse of about 45 seconds from light-up of the lamps  21 . Complete sublimation of the dye took 120 seconds or more from the light-up of the lamps  21 . 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Light-up 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 duration 
               
               
                 (sec.) 
                 0 
                 10 
                 20 
                 30 
                 40 
                 50 
                 60 
                 70 
                 80 
                 90 
                 100 
                 110 
                 120 
               
               
                   
               
             
            
               
                 Temp. of 
                 15 
                 34 
                 51 
                 69 
                 88 
                 101 
                 113 
                 124 
                 134 
                 143 
                 145 
                 147 
                 151 
               
               
                 base body 
               
               
                 (° C.) 
               
               
                   
               
            
           
         
       
     
     EXAMPLE 2 
     Under the same conditions as in the example 1, the dyeing operation is performed on the convex and concave surfaces of the lens  22  (double-sided dyeing). With the lamps  21  lit up, the base body  10  is continuously heated until its temperature is raised to 250° C. After the completion of heating, the dyed lens  22  is taken out and then heated in the oven  3  at a temperature of 125° C. for about 60 min. to fix the color of the lens  22 . The chromaticity data is shown in Table 3. The color measurement is made using a spectroscopic photometer (DOT-3 made by Kabushiki Kaisha Murakami Sikisai Gijutsu Kenkyusho (Murakami color technical institute) using a D65 light source and 10 visual field. 
     In Table 3, Y indicates visual sensitivity transmittance; and L*, a*, and b* indicate CIE (Commission International d&#39;Eclairage) color specification values. 
     In the result of the visual observation that was made after the fixation process to check whether the produced color was in agreement with the desired color without appearance failure, color unevenness, and color missing portions, no particular deficiencies were found. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Y 
                 L* 
                 a* 
                 b* 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Double-sided 
                 21.57 
                 53.57 
                 −10.73 
                 42.64 
               
               
                   
                 dyeing 
               
               
                   
                   
               
            
           
         
       
     
     As seen in Table 3, by dyeing the both surfaces of the lens  22  at a time, the lens  22  could be dyed in the color density of approximately 80% in one dyeing work. 
     Comparison 2 
     Under the same conditions as in the example 1, the dyeing operation is carried out on only the concave surface of the lens  22  (single-side dyeing). Only the lamps  21  disposed at the upper position are lit up to continuously heat the base body  10  until its temperature rises to 250° C. After the completion of heating, the lens dyed is taken out and then heated in the oven  3  at a temperature of 125° C. for about 60 min. to fix the color of the lens  22 . The chromaticity data is shown in Table 4. 
     In the visual observation that was also made after the fixation process to check whether the produced color was in agreement with the desired color without appearance failure, color unevenness, and color missing portions, no particular deficiencies were found. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 Y 
                 L* 
                 a* 
                 b* 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Single-sided 
                 47.21 
                 74.32 
                 −10.39 
                 35.76 
               
               
                   
                 dyeing 
               
               
                   
                   
               
            
           
         
       
     
     As seen in Table 4, by dyeing only the single surface of the lens  22 , the lens  22  could merely be dyed in the color density of about 50% in one dyeing work. 
     EXAMPLE 3 
     The dyeing operation in this example uses a lens  22  made of a thioepoxy type material with a high refractive index (1.74) and a disperse dye (water-base) made by Upepo Kabushiki Kaisha as a sublimatable ink. With use of a drawing software in the PC  1 , the hue (U) is set to 120, the saturation (S) is set to 170, and the lightness (V) is set to 150. Based on this color data, two circular layers  12  each having a diameter of 90 mm are printed on a print sheet  11  having a white front face (printing face) and a black back face. Sequentially, the sheet  11  is cut to remove the needless margin so as to fit into the dyeing jig  30  shown in FIG.  4 . The base body  10  is thus produced. 
     Next, in the same manner as in the example 1, the vapor-deposition device  20  and the jig  30  are used to execute the dyeing operation on the lens  22 . This dyeing operation is performed on only the concave surface of the lens  22 , not both surfaces. The pressure in the device  20  is reduced to 1 kPa. Only the upper lamps  21  are lit up to continuously heat the base body  10  until its temperature rises to 250° C. After the completion of heating, the dyed lens  22  is taken out and subjected again to the same process to sublimate and vapor-deposit the dye twice onto the concave surface of the lens  22 . Then, the lens  22  is heated in the oven  3  under different heating conditions to fix the color of the dyed lens  22 . The heating conditions of the oven  3  are set to four types: 1 hour at a temperature of 125° C.; 1 hour at 135° C.; 2 hours at 135° C.; and 2 hours at 150° C. 
     The dyeing results of the lens  22  after the fixation process is shown in Table 5. The color measurement is made using aspectroscopic photometer as in the case of the example 2. 
     In Table 5, Y indicates visual sensitivity transmittance; and L*, a*, and b* indicate CIE color specification values. 
     In the visual observation that was made after the fixation process to check whether the produced color was in agreement with the desired color without appearance failure, color unevenness, and color missing portions, no particular deficiencies were found. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 Coloring 
                   
                   
                   
                   
               
               
                 conditions 
                 Y 
                 L* 
                 a* 
                 b* 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 125° C. - 1 Hr 
                 72.79 
                 88.35 
                 −7.51 
                 5.27 
               
               
                 135° C. - 1 Hr 
                 57.95 
                 80.71 
                 −15.43 
                 7.46 
               
               
                 135° C. - 2 Hr 
                 56.99 
                 80.18 
                 −13.92 
                 5.68 
               
               
                 150° C. - 2 Hr 
                 41.14 
                 70.28 
                 −23.49 
                 8.73 
               
               
                   
               
            
           
         
       
     
     As seen in Table 5, even the material with high refractive index which has been considered as having low (poor) dyeability could be dyed in high color density without any deficiency by the dyeing method of the present invention. 
     In another dyeing operation, a lens  22  itself is dipped in a 0.2% carrier solution (DK-C of Daiwa Kagaku Kogyo Kabushiki Kaisha) for pretreatment at a temperature of 80° C. for about 2 min. Then, the dyeing operation is executed under the above conditions (the coloring conditions in Table 5). 
     As a result, the same visual sensitivity transmittance as in the case of the above conditions could be obtained in half of the heating time (duration) in all the conditions. 
     Comparison 3 
     The same lens  22  as in the example 3 is dyed by the dip dyeing method. A dyeing solution containing disperse dyes of red: 1 g/l, yellow: 1 g/l, and blue: 4 g/l is prepared. The dyeing solution is heated to about 90° C. The lens  22  is dipped into the heated solution for 30 min. Sequentially, the dyed lens  22  is heated in the oven  3  for 1 hour at a temperature of 115° C., then completing the dyeing operation. A dyeing result is shown in Table 6. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 Coloring 
                   
                   
                   
                   
               
               
                 conditions 
                 Y 
                 L* 
                 a* 
                 b* 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 115° C. - 1 Hr 
                 85.04 
                 93.90 
                 −0.79 
                 0.87 
               
               
                   
               
            
           
         
       
     
     As shown in Table 6, the dyeing for 30 min. could produce only the color of about 15% density. In addition, the dipping time (duration) and the heating time (duration) in the oven  3  were extended, but no change was found in the result. 
     As described above, according to the present invention, the plastic lens can be easily and efficiently dyed. Furthermore, various lenses can be stably dyed in various colors. 
     The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiment chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.