A display apparatus and a method for making the same

Abstract: A display apparatus has two plates (11), and an intermediate member (12) disposed between the two plates (11). The two plates (11) are bonded by way of the intermediate member (12). A liquid is sealed in a gap or space defined by the blades (11) and the intermediate member (12). The two plates (11) are bonded by means of a fluorocarbon resin or a fluorine contained resin having an alkoxide as a reaction group.

Description: BACKGROUND OF THE INVENTION This invention relates to a display apparatus and a method for making the same. In particular, this invention relates to a bubble type display apparatus for use as an inclination angle measuring device in which a liquid and a bubble are sealedly contained in a container so that the bubble is allowed to move depending on an angle of inclination of the container and a method for making the same. Also, this invention relates to a liquid crystal type display apparatus in which a liquid crystal is sealedly contained between two base plates equipped with electrodes and a method for making the same. PRIOR ART A circular bubble tube or bar-shaped bubble tube type display apparatus is known as an inclination angle measuring device in which a liquid and a bubble are sealedly contained in a tube-like container so that the bubble is allowed to move depending on an angle of inclination of the container. Such bubble tube type display apparatuses include a bubble tube constituted, for example, of a tube-shaped container and a top plate. The top plate is a disk-shaped glass plate whose inner surface is made concave at a given curvature. The sensitivity of the bubble tube is determined depending on the curvature. In general, the sensitivity, S, of the bubble tube is indicated in the following manner. For instance, when the quantity of movement of the bubble is taken as X, the curvature radius of the concave surface as R and the angle of inclination of the bubble tube as T, the relationship of X/R = tan T should be established. In the case where X is 1 mm and T is 2, R is calculated from 1 (mm)/R (mm) = tan 2 . Thus, R is equal to approximately 1719 mm. The curvature radius of the concave surface is determined as such. The container and the top plate are usually fusion-bonded with a low melting glass. Subsequently, an appropriate amount of a liquid is charged into the container through a port provided in position, and the port is then sealed. A wide variety of liquids are used for this purpose, including alcohols, ethers and mixtures thereof. For the fusion bonding between the container and the top plate, it is necessary to heat them up to at least approximately 550 o C. Also, there is known a bubble tube of the type wherein the behavior of the bubble is electrooptically read. In such a type bubble tube, illumination light is applied from the lower side of the bubble tube. The angle of inclination is detected by measuring a variation in quantity of the light accompanied by the movement of the bubble by means of a detector. In this type of bubble tube, a charging port is provided at a side of the container, and the container is closed at the bottom thereof with a bottom plate. In this case, the container and the top plate and the container and the bottom plate are, respectively, fusion-bonded with a low melting glass. In the above-stated conventional bubble tubes, in which the top and bottom plates are fusion-bonded to the container, the concave surface of the top plate suffers deformation by application of heat. Consequently, bubble tubes with high precision could not be obtained. On the other hand, conventional liquid crystal type display apparatuses include two base plates between which a liquid crystal is sealedly contained. Thermosetting type or ultraviolet hardening type sealing materials are used as an intermediate member for the sealing purpose. In case of the thermosetting type sealing materials, the intermediate member is pressed between and by the two base plates in a vertical direction while it is heated, whereby the intermediate member is hardened so as to bond the base plates. In case of the ultraviolet hardening type sealing materials, the intermediate member is hardened by illuminating ultraviolet on it through the two base plates, so as to bond them by way of the intermediate member. However, in case of the thermosetting type sealing materials, the intermediate member must be heated at a high temperature between 100 o C and 200 o C. In the case, when it is cooled after the sealing thereof, some thermal strain cannot be prevented from remaining. In case of the ultraviolet hardening type sealing materials, the intermediate member is apt to be dissolved by the liquid crystal sealed in the container. Thus, life time is shortened. In the prior art display apparatuses, for instance, liquid crystal type display apparatuses, the difference of solubility parameter between liquid crystals such as thermotropic or lyotropic liquid crystals and the conventional ultraviolet hardening type sealing materials ranges between 0.2 [cal/cm 3 ] 1/2 and 5.5 [cal/cm 3 ] 1/2 . The solubility to each other is so large that they are apt to be dissolved. US-A-3 990 781 discloses a liquid crystal display comprising a glass envelope having portions thereof bonded together by seal means comprised of a sealant material. The sealant material is composed of a fluorocarbon material together with a cooperational organosilane coupling agent material. The fluorocarbon material is a mixture of a vinylidene fluoride resin dispersion together with a vinylidene fluoride powder. The components are mixed and heated initially up to 600°F followed by a 15 minute 500°F heat treatment. The polyvinylidene fluoride is coupled to the coupling agent via intermolecular force bonds. Those intermolecular force bonds are hydrogen bonds between a fluorine atom of the polyvinylidene fluoride and a hydrogen atom of the organosilane coupling agent. SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal type display apparatus and a method of making the same in which a sealed portion is not substantially affected by liquid crystals such as thermotropic or lyotropic liquid crystals, high heat and ultraviolet so that leakage due to secular change can be avoided so as to increase the reliability of liquid crystal sealing. It is another object of the present invention to provide a bubble type display apparatus and a method of making it in which high precision can be obtained without limitation of the type of liquid being sealed and with which satisfactory airtightness can be maintained. According to the present invention, a display apparatus comprises two members, means for bonding said two members, a liquid sealed in a gap or space defined by said members, said bonding means being an adhesive made of a fluorocarbon resin of the formula (OR) 3 SiOF 2 C-(CF 2 CF 2 ) n -CF 2 OSi(OR) 3 , wherein R is an alkyl group, said resin having an alkoxide as a reaction group. The alkoxide reaction group is subject to hydrolysis by water followed by a three-dimensional polycondensation reaction in the hardening step, which can take place at room temperature. The fluorocarbon chain is connected to the silicon atom having the alkoxide reaction group via a covalent C-O-bond. A covalent bond is much stronger than a intramolecular force bond like a hydrogen bond. With that covalent bond it is not necessary to perform high temperature and high pressure for proper bonding. In one mode of the present invention, for instance, in case the display apparatus is a liquid crystal type display apparatus, the intermediate member itself functions as an adhesive for bonding the two plates. In this case, it is not necessary to provide any other intermediate member although it can be provided, if desired, within the scope of the present invention. In another mode of the present invention, for instance, the display apparatus is a bubble type display apparatus or an inclination angle measuring apparatus, the intermediate member is a container, and an adhesive is disposed between the plate and at least one open end of the container. In any case, the fluorocarbon resin of the invention is used for the bonding purpose. Because the fluorocarbon resin of the invention can be hardened at room temperature, the plates can be bonded without affects of heat. The fluorocarbon resin, before hardening, is a liquid or a soluble resin and can therefore be used as a liquid adhesive. In addition, the liquid crystal is not chemically affected by the fluorocarbon resin for a long time of period while a liquid crystal type display apparatus is used. For example, the difference of solubility parameter between the liquid crystal and the fluorocarbon resin is approximately from 6 [cal/cm 3 ] 1/2 to 9 [cal/cm 3 ] 1/2 . Thus, the solubility of the hardened fluorocarbon resin to the liquid crystal is extremely small so that the fluorocarbon resin is not dissolved by the liquid crystal. Therefore, the plate can be bonded with precision. A good bonding condition can be maintained without leakage for a long time of period so that sealing reliability can be increased. A good sealing condition can be obtained regardless of any type liquid. Because the plate can be bonded without thermal strain, a high precision can be obtained. Any liquid crystal type display apparatus can be freely designed through simple production steps. Preferred modes of the present invention are described in the dependant claims 2 to 7. According to another mode of the present invention, a method for making a display apparatus is described in claims 8 to 12. BRIEF DESCRIPTION OF THE DRAWINGS Plural preferred embodiments of the present invention will be explained with reference to the accompanying drawings in which: Fig. 1 is an explanatory view showing how to assemble a liquid crystal type display apparatus according to the present invention; Fig. 2 is a sectional view schematically showing a method for making the liquid crystal type display apparatus shown in Fig. 1 according to a first embodiment of the present invention; Fig. 3 is a sectional view schematically showing a method for making the liquid crystal type display apparatus shown in Fig. 1 according to a second embodiment of the present invention; Fig. 4 is a sectional view schematically showing a third embodiment of the present invention; Fig. 5 is a sectional view schematically showing the liquid crystal type display apparatus of Figs. 1 to 4 in an assembled condition thereof; Fig. 6 is a sectional view showing a bubble tube type display apparatus according to a fourth embodiment of the invention; Fig. 7 is a top view of the bubble tube type display apparatus of Fig. 6; Fig. 8 is a sectional view showing a bubble tube type display apparatus according to a fifth embodiment of the invention; and Fig. 9 is a top view of the bubble tube type display apparatus of Fig. 8. DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be explained referring to Figs. 1 and 2. A liquid crystal type display apparatus 10 for the picture image display purpose is assembled as schematically shown in Fig. 1. In a well-known manner, two base plates 11 are equipped with plural electrodes. Also, picture elements for the picture image display purpose and thin film transistor elements constituting switching elements are formed on a surface of the base plates 11 by means of photo-lithography or the like. The electrodes for the image signal scanning or signal output purposes are arranged along the peripheral edge of a scope of the liquid crystal type display apparatus. Also, orientation films are provided so as to cover the scope. They are not shown for the simplifying purpose. In Fig. 1, a sealing intermediate member 12 made of the fluorocarbon resin of the present invention is arranged on a surface of one of the base plates 11 in a predetermined pattern. The sealing intermediate member 12 has a port 13 for charging a liquid crystal therethrough. Many well-known spacers 16 are placed between the base plates 11 within the sealing intermediate member 12. The spacers 16 have such a predetermined size that the base plates 11 can be maintained with a desired distance so as to form a gap or space 14 between the base plates 11 which has a desired distance. The base plates 11 are pressed in the directions of the arrows in order to bond the base plates 11 as shown in Fig. 1. Referring to Fig. 2, a method of producing the liquid crystal type display apparatus of Fig. 1 will be explained by way of example. Two base plates 11 are aligned with precision so as to be superposed with a gap while the sealing intermediate member 12 is placed between them. The base plates 11 are held between and by two holding plates 21 made of a stainless steel. The holding plates 21 are larger in size than the base plates 11. A rectangular ring shape of elastic or resilient member 22 is positioned along the peripheral edge of the holding plates 21 and held between the holding plates 21 in a sealing manner. The base plates 11 are enclosed by the resilient member 22. A space or gap 30 defined by the two holding plates 21 and the resilient member 22 is sealed. When the two base plates 11 are in a superposed condition, a pressure is equally applied to the two base plates 11 by clamping means or the like so that they are bonded by way of the sealing intermediate member 12. For instance, as shown in Fig. 2, the two holding plates 21 are clamped by means of plural supporting bolts 17 and nuts 18 together with compression springs 19 so as to press the base plates 11 toward each other while the spacers 16 are disposed between them. In such a condition, the fluorocarbon resin of the sealing intermediate member 12 is hardened at a room temperature. By establishing a vacuum in a chamber in which the two base plates 11 and the sealing intermediate member 12 are arranged as shown in Fig. 2, the pressure in the gap or space 14 is decreased so that a liquid crystal such as thermotropic or lyotropic liquid crystals is charged into the gap 14 by way of the port 13. When the gap 14 becomes filled with the liquid crystal, a sealing element made of the fluorocarbon resin of the invention is set in the port 13 so as to close it whereby the liquid crystal is sealed within the gap 14. As a result, a liquid crystal type display apparatus 10 shown in Fig. 5 can be obtained. With reference to Fig. 3, a further method of producing the liquid crystal type display apparatus will be explained. Two base plates 11 are aligned with precision so as to be superposed with a gap while the sealing intermediate member 12 is placed between them. The base plates 11 are held between and by two holding plates 21 made of a stainless steel. The holding plates 21 are larger than the base plates 11. A rectangular ring shape of elastic or resilient member 22 is positioned along the peripheral edge of the holding plates 21 and held between the holding plates 21 in a sealing manner. The base plates 11 are enclosed by the resilient member 22. A space or gap 30 defined by the two holding plates 21 and the resilient member 22 is sealed. One end of a tube or pipe 24 is connected to the space 30, and the other end of the tube 24 is connected to a vacuum pump 23 equipped with a controller. A pressure gage 25 is placed at an intermediate portion of the tube 24 so as to detect a pressure in the tube 24. A valve 27 is also provided at an intermediate portion of the tube 24 between the gage 25 and the vacuum pump 23 so as to be connected to a liquid crystal supply source 26. In operation, the valve 27 is adjusted in a desired position so as to connect the space 30 with the vacuum pump 23. When the vacuum pump 23 starts, the pressure in the space 30 is reduced, and then the holding plates 21 are pressed by means of the atmospheric pressure. Thus, the base plates 11 are equally pressed until the gap or space 14 is adjusted so as to have a predetermined width or distance such as 5 microns corresponding to the size of the spacers 16. In such a condition, the distance between the holding plates is adjusted so as to be about 2.2 mm, for instance. While the gap 14 is in a vacuum condition, the sealing intermediate member 12 made of the fluorocarbon resin is hardened at a room temperature. As a result, the two base plates 11 are bonded by way of the sealing intermediate member 12 in a sealed manner. Next, the valve 27 is opened or reset in another position so as to connect the space 30 with the liquid crystal supply source 26. Because the gap 14 is in a vacuum condition, a liquid crystal is automatically fed from the liquid crystal supply source 26 into the gap 14 by way of the tube 24, the space 30 and the port 13. In another mode, the gap 14 can be filled with a liquid crystal by immersing the two base plates 11 into a liquid crystal container. After the gap 14 becomes filled with the liquid crystal, a sealing element is set in the port 13 so as to close the port 13 whereby the liquid crystal is sealed. As a result, the liquid crystal type display apparatus of Fig. 5 can be obtained. During the pumping step, the gap 14 and the space or chamber 30 are equally pumped because they are connected by way of the port 13 of the sealing intermediate member 12. The base plates 11 are pressed under a negative or reduced pressure while the intermediate member 12 is disposed between them. In this condition, there remains no air in sealed portions of the base plates 11 and the intermediate member 12. Therefore, the base plates 11 can be properly bonded to the intermediate member 12 without any small air therebetween. With reference to Fig. 4, another method of producing the liquid crystal type display apparatus will be explained. In the embodiment of Fig. 4, an elastic or resilient member 32 encloses the outer periphery of two base plates 11 between which many spacers 16 are placed within a ring-shaped sealing intermediate member 12 so as to have a predetermined distance between the two base plates 11. It is important that the inner periphery of the elastic member 32 engages the outer periphery of the base plates 11 in a sealing manner. One end of a tube 24 is inserted into an opening of the elastic member 32 and positioned near a port 13 formed in the sealing intermediate member 12. The other end of the tube 24 is connected to a vacuum pump 23. A pressure gage 25 is placed at an intermediate portion of the tube 24. When the vacuum pump 23 starts, the gap 14 is pumped. As a result, the base plates 11 are pressed by the atmospheric pressure. For instance, the maximum pressure of about 1 kgf/cm 2 can be applied onto the outer surface of the base plates 11. In this condition, the two base plates 11 are maintained with a predetermined distance by means of the spacers 16. In the embodiment of Fig. 4, because the base plates 11 are bonded by way of the sealing intermediate member 12 under a negative or reduced pressure, there remains no air in the sealed portions between the base plates 11 and the intermediate member 12 so as to obtain an excellent sealing condition. In particular, the embodiment of Fig. 4 is preferable in order to produce a large size of liquid crystal type display apparatus. In order to increase production efficiency, first, a very large liquid crystal type display apparatus is formed, and thereafter it is cut into a plurality of small liquid crystal type display apparatuses each having a desired small size. Fig. 5 shows the liquid crystal type display apparatus produced by the methods shown in Figs. 2 to 4. The reference numeral 15 designates the liquid crystal which the gap 14 is filled with. There remain substantially no air in the sealed portions between the base plates 11 and the intermediate member 12. In the above-stated embodiments of the present invention, the solvent-soluble fluorocarbon resin has an adhesive functional group so as to obtain a bonding force of several 10 2 kg in the form of a covalent bond, which can break glass by means of tensile force. By contrast, an epoxy resin adhesive which is conventionally used in a liquid crystal type display apparatus has only a bonding force of several 10 kg. For such a reason, the epoxy resin adhesive is apt to be gradually dissolved by the liquid crystal sealed in the display apparatus so that a good sealing condition cannot be maintained for a long time of period. In the embodiments of Figs. 3 and 4, because the base plates 11 are bonded while the gap 14 therebetween is in a vacuum condition, there remains no air at joint portions thereof so that excellent sealing and bonding conditions can be obtained. Also, because the base plates 11 are equally pressed by means of the atmospheric pressure, a mechanical strain can be reduced to the minimum value, and the base plates can be bonded with precision. Accordingly, a high quality of display apparatus can be produced. The embodiment of Fig. 4 is preferable for a method of producing a large size of liquid crystal display apparatus with a high quality and a high efficiency. The present invention is not limited to the above-stated embodiments only. For example, a plurality of base plates can be placed in a parallel or series form between two holding plates 21 so as to form a plurality of liquid crystal display apparatuses at the same time. A fourth embodiment of the present invention will be explained with reference to Figs. 6 and 7. Fig. 6 is a sectional view of a bubble type display apparatus according to a preferred embodiment, and Fig. 7 is a top view thereof. A bubble tube 100 is constituted of a top plate 101, a container 102 and a bottom plate 106. The top plate 101 is made of a glass disk which has a flat outer surface. An inner surface A is a concave surface which has a predetermined curvature radius. The container 102 is made of a metal cylinder such as, for example, a stainless steel cylinder. The bottom plate is also made of a glass disk similar to the top plate and has both flat inner and outer surfaces. The container 102 has a small through-hole 107 at one side thereof in order to permit a liquid 103 to be poured therethrough. The small through-hole 107 has a diameter of about 1 mm, for example. The top plate 101 is bonded to the container 102 at one end thereof and the bottom plate 106 is also bonded to the container 102 at the other end, both through the solvent-soluble fluorocarbon resin of the invention 105 having an adhesive functional group. The fluorocarbon resin 105 preferably has an adhesive functional group. After completion of the bonding, a predetermined amount of the liquid 103 is poured through the small through-hole 107 so that an appropriate size of a bubble 104 is left in the container. Subsequently, the through-hole 107 is plugged with a tapered pin 108. Thus, a bubble tube type display apparatus 100 can be obtained. The liquid 103 to be poured is preferably a mixture of methanol which is an alcohol having great polarity and diethyl ether which is an ether solvent, or a saturated hydrocarbon solvent typical of which is n-hexane. A mixture of an alcohol and an ether is placed in the container in such a way as stated hereinabove and subjected to an airtightness test at a high temperature of, for example 60 o C. As a result, it is recognized that the airtightness can be maintained over one year or longer even at a high temperature of 60°C. For comparison, an epoxy resin is used, in place of the soluble fluorocarbon resin, for bonding between the container and the top and bottom plates, thereby obtaining a bubble tube for comparison. When this bubble tube is kept at 60°C, the airtightness is lost in about one week. In the fourth embodiment of the invention, the bonding is made using the soluble fluorocarbon resin having an adhesive functional group. As a result, a covalent bond with a bonding force of several hundred kilograms is formed, thus ensuring such a long life as set out above. The bonding force is so great that, when bonded glass is pulled, it breaks. In contrast, with the bonding through the epoxy resin used for comparison, the bonding is made through an intramolecular force of only several kilograms. Accordingly, the airtightness cannot be kept over a long time. A fifth embodiment of the invention will be described with reference to Figs. 8 and 9. In the embodiment of Figs. 8 and 9, a container 201 is in the form of an elongated pipe and is slightly curved as a whole. The container 201 is made of glass. The container 201 has disk-shaped side plates 202, 204 bonded at opposite sides of the container 201 with a soluble fluorocarbon resin 205. A small through-hole 207 is formed at one side plate 202. The side plates 202, 204 are made of a stainless steel. Other arrangement is similar to that of the bubble tube type display apparatus 100, i.e. a liquid 203 is contained within the container together with a bubble 204'. In a bubble tube type display apparatus according to the above-stated embodiments of the invention, the container and the first and second members are bonded with the soluble fluorocarbon resin of the invention, so that satisfactory airtightness is ensured irrespective of the type of liquid being poured. In addition, the resultant bubble tube can have high precision. In a method for making a bubble tube type display apparatus according to the above-stated embodiments of the invention, the container and the first and second members are bonded in the first and second steps by means of the soluble fluorocarbon resin. Accordingly, little limitation is placed on the type of liquid being poured, resulting in a greater freedom in fabrication of the bubble tube. Thus, a bubble with high precision can be made by a simple procedure. The fluorocarbon resin of the present invention is a product sold by the Japanese company Asahi Class Co. Ltd under "CYTOP". The structure and mechanism of this fluorocarbon resin is as follows (OR) 3 SiOF 2 C-(CF 2 CF 2 ) n -CF 2 OSi(OR) 3 with R = alkyl group. The alkoxide reaction group is subjected to hydrolysis by water: The OH-groups resulting from the hydrolysis can undergo a polycondensation reaction, forming a three-dimensional fluorocarbon polymer matrix in the hardening step:

Claims: A display apparatus comprising two members, means for bonding said two members, a liquid sealed in a gap or space (14) defined by said members, said bonding means being an adhesive made of a fluorocarbon resin, characterised in that said fluorocarbon resin is of the formula (OR) 3 SiOF 2 C-(CF 2 CF 2 ) n -CF 2 OSi(OR) 3 , wherein R is an alkyl group, said resin having an alkoxide as a reaction group. The display apparatus according to claim 1, characterized in that said two members are two plates (11; 101, 106) immediately bonded to one another via said adhesive. The display apparatus according to claim 2, characterized by an intermediate member (12; 102; 201) disposed between said two plates (11; 101, 106; 202, 204), said intermediate member being bonded by means of said adhesive to the two plates. The display apparatus according to anyone of claims 1 - 3, characterized in that the display apparatus is a liquid crystal type display apparatus (10). The display apparatus according to claim 4, characterized by two base plates (11) equipped with electrodes and a liquid crystal sealed in the gap (14) between said two base plates (11). The display apparatus according to claim 1, characterized in that the display apparatus is a bubble type display apparatus (100, 200) for use as an inclination angle measuring apparatus, and the intermediate member is a container (102, 201), and said adhesive is disposed between the members and the container (102, 201). The display apparatus according to claim 6, characterized by a tube-like container (102, 201) having two open ends, said members serving to close the open ends of said container (102, 201), said container (102, 201) being sealedly filled with a liquid (103, 203) with a bubble (104, 204') so that said bubble (104, 204) is movable depending on an angle of inclination of said container. A method of making the display apparatus according to claim 1 comprising the step of bonding two members by means of a fluorocarbon resin of the formula (OR) 3 SiOF 2 C-(CF 2 CF 2 ) n -CF 2 OSi(OR) 3 , wherein R is an alkyl group, said resin having an alkoxide as a reaction group, and thereafter charging a liquid into a space or gap defined by said members. A method of making the display apparatus according to claim 5, wherein a liquid crystal is sealed between two base plates equipped with electrodes, comprising the steps of bonding said two base plates by means of a fluorocarbon resin resin of the formula (OR) 3 SiOF 2 C-(CF 2 CF 2 ) n -CF 2 OSi(OR) 3 , wherein R is an alkyl group, said resin having an alkoxide as a reaction group, and thereafter charging a liquid crystal into a gap between said two base plates. The method according to claim 9, wherein said adhesive is provided onto one of said two base plates as an intermediate member for a sealing purpose, said two base plates are superposed with a gap and said two base plates are bonded by way of said intermediate member. A method of making the display apparatus according to claims 6 or 7, comprising the first step of closing one of two open ends of a container with a first member, the second step of closing the other open end of said container with a second member, and the third step of sealedly filling a liquid and a bubble in said container, said container and said first member and said second member being bonded in the first step and the second step respectively with a fluorocarbon resin of the formula (OR) 3 SiOF 2 C-(CF 2 CF 2 ) n -CF 2 OSi(OR) 3 , wherein, R is an alkyl group, said resin having an alkoxide as a reaction group. The method according to anyone of claims 8 - 11, wherein, when said two members or plates are bonded, they are in a vacuum condition.

Inventors: SAITO SUSUMU, TAKAHASHI TAKASHI, SAITO, SUSUMU, TAKAHASHI, TAKASHI, Saito, Susumu, c/o K.K. Topcon, Takahashi, Takashi, c/o K.K. Topcon
Applicants: TOPCON CORP, KABUSHIKI KAISHA TOPCON
Application year: 1993
Main classification: G02F1
IPC codes: G02F1