Method and system for fabricating an electrooptical device

[0002] This application is a divisional of application Ser. No. 08/566,143, filed Dec. 1, 1995, now U.S. Pat. No. 5,929,161.

[0003] 1. Field of the Invention

[0004] The present invention relates to a method of fabricating liquid-crystal electrooptical devices using flexible film substrates and also to a system for fabricating such liquid-crystal electrooptical devices using flexible film substrates.

[0005] 2. Description of the Related Art

[0006] A liquid-crystal electrooptical device is known as a thin, small-sized, lightweight display device. The liquid-crystal electrooptical device comprises a pair of substrates spaced several micrometers from each other and a liquid crystal material held between the substrates. The substrates are required to transmit visible light and so glass substrates are generally used as the substrates. The glass substrates have the required optical characteristics. In addition, they are inexpensive.

[0007] The liquid-crystal electrooptical device must meet the following technical requirements: (1) It is small in size and lightweight; and (2) the cost of fabricating the liquid-crystal electrooptical device is reduced and its productivity is improved.

[0008] Of these requirements, the requirement (1) is that the liquid-crystal electrooptical device is made thinner and lighter in weight. A known configuration which satisfies these requirements uses resinous substrates (generally known also as plastic substrates) transmitting light.

[0009] Where resinous substrates are employed, reductions in size and weight can be accomplished. Since the substrates themselves have flexibility, a physical stress can be applied to them, or they can be used in a curved state. These kinds of usage can further extend the application of the liquid-crystal electro-optical device.

[0010] However, where resinous substrates are used, a reduction in fabrication cost and an improvement in the productivity are not accomplished.

[0011] It is an object of the present invention to provide techniques for fabricating liquid-crystal electrooptical devices, using flexible substrates, at low cost and with high productivity.

[0012] A system for fabricating liquid crystal cells according to the present invention comprises a first roll on which a first flexible substrate has been wound, a second roll on which a second flexible substrate has been wound, means for forming a liquid crystal material layer on the surface of the first substrate, and means for bonding together the first and second substrates 206,201.

[0013] A specific example of the structure of the above-describe ed system is shown in FIG. 1, where a first flexible substrate 206 has been wound on a first roll 119. A second flexible substrate 201 has been wound on a second roll 101. A dripping device 135 acts to drip a liquid crystal material onto the surface of the first substrate 206. A set of rolls, 137 and 138, is the means for bonding together the first and second substrates 206,201.

[0014] The flexible substrates can be made from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PES (poly-ethylene sulfite), polyimide, or PAR (polyarylate).

[0015] A method of fabricating liquid crystal cells according to the present invention consists of preparing a first flexible substrate wound on a first roll, preparing a second flexible substrate wound on a second roll, and squeezing a liquid crystal material between the first and second substrates to form an elongated liquid crystal cell.

[0016] Another method of fabricating liquid crystal cells according to the present invention consists of winding a flexible substrate on a roll, printing an orientation film on the substrate, orienting molecules of the orientation film, spraying spacers on the orientation film, and printing a sealing material. These manufacturing steps are effected successively.

[0017] A specific example of the above-described method is illustrated in FIG. 1. An orientation film 209 is formed on the flexible substrate 206 by rolls 127 and 128, the substrate 206 being wound on the roll 119. Spacers 211 are sprayed. A sealing material (not shown) is printed.

[0018] Other objects and features of the invention will appear in the course of the description thereof, which follows.

[0019] FIG. 1 is a schematic diagram of a system for fabricating liquid-crystal electrooptical devices according to the present invention.

[0020] The present example is a production system capable of producing liquid-crystal electrooptical devices in succession, each electrooptical device using flexible resinous substrates. This fabrication system is schematically shown in FIG. 1 and intended to produce the flexible resinous substrates wound on rolls 101 and 119, for constructing each liquid-crystal electrooptical device.

[0021] First, a manufacturing step regarding resinous substrates wound around the roll 119 is described. In this example, resinous substrate coiled around the roll 119 consist of film of PET (polyethylene terephthalate). A three-colored (R, G, and B) filter 203 is printed on the surface of the RET film 200 drawn out of the roll 112. This PET film acts as a base in forming the color filter 203. The color filter 203 is formed by means of three sets of rolls 113. Where the manufactured liquid crystal display is a monochrome display, these three sets of rolls are not necessary.

[0022] After forming the color filter 203, a protective film 205 wound on a roll 115 is formed so as to cover the color filter 203 previously formed. A self-adhesive film 204 wound on a roll 116 is stuck on the rear side of the base, i.e., on the opposite side of the surface on which the colored filter is formed. This series of manufacturing steps is performed, using a pair of pressure rolls, 117 and 118.

[0023] Then, another PET film 206 which is wound on the roll 119 and forms a base is stuck via the self-adhesive film 204 by means of a set of pressure rolls, 120 and 121. Subsequently, the protective film 205 is peeled off by a roll 123 and wound on a roll 122.

[0024] Thereafter, an overcoat film 207 is printed by a set of rolls, 123 and 124, to flatten the irregularities created by the formation of the color filter 203. This overcoat film 207 is made from a resinous material transparent to light.

[0025] A required electrode pattern 208 is printed, using a set of rolls, 125 and 126. The electrode pattern 208 is made from a conductive ink.

[0026] Then, an orientation film 209 is printed by the use of a set of rolls, 127 and 128. The orientation film 209 is passed through a heating furnace 129 to bake it. As a result, a solidified orientation film 210 is obtained.

[0027] The orientation film 210 is passed between rolls 130 and 131 to rub the surfaces of the orientation film 210. In this way, the molecules of the film are oriented. Then, spacers are sprayed from a spacer dispenser 132 to place the spacers 211 on the oriented film 210.

[0028] Thereafter, a sealing material (not shown) is printed to bond together opposite substrates and to prevent the liquid crystal material from leaking from the spacing between the substrates.

[0029] Subsequently, the liquid crystal material is dripped, using the liquid crystal material-dripping device 135, to form a liquid crystal material layer 212. In this manner, one substrate is completed. The manufacturing steps described thus far are successively carried out by rotating the various rolls.

[0030] The other substrate is manufactured in the manner described below. A desired electrode pattern 213 is formed on the PET film 201 drawn out of the roll 101 by a pair of rolls 102 and 103. Then, an orientation film 214 is printed through the use of a pair of rolls 104 and 105. The film is baked by a heating furnace 108, so that a solidified orientation film 215 is formed. Thereafter, the substrate is passed between a pair of rolls 109 and 110 and guided to the rolls 137 and 138 to form a cell.

[0031] The liquid crystal cell is formed on the PET film pair by the steps described thus far. This PET film pair is passed between a pair of rolls 137 and 138 to bond together the films, using a sealing material. Then,

[0032] Then, heating is done within a heating furnace 139 to cure the sealing material, thus completing bonding of the substrates. The resulting substrate assembly is cut into desired size with a cutter 150. In this way, a liquid crystal cell is completed.

[0033] The manufacturing steps described thus far are performed in succession by rotating the various rolls. By cutting the substrate assembly with the cutter 150, liquid crystal cells are successively fabricated.

[0034] In the present example, passive liquid crystal cells are manufactured. It is also possible to fabricate active liquid crystal cells by fabricating nonlinear devices and TFTs simultaneously by printing techniques.

[0035] In the present example, liquid crystal cells are formed on PET films which are industrially often used like magnetic tape. Besides PET, PEN (polyethylene naphthalate), PES (polyethylene sulfite), polyimide, and PAR (polyarylate) can be used.

[0036] Where PET or PES film is used, birefringence may take place, in which case the image displayed on the device may be adversely affected. On the other hand, neither PES film nor PAR film induces birefringence and they satisfy the optical characteristics which every display device must meet.

[0037] In the present invention, when flexible liquid crystal cells are manufactured, flexible substrates wound on rolls are used. Consequently, liquid crystal cells can be manufactured in succession.