In a conventional liquid crystal device, a pair of substrates is bonded with resin, and liquid crystal is injected from an injection port into the space formed by the substrates and the resin, and then sealed to form a liquid crystal cell. Since, in the construction in which a liquid crystal layer is held between substrates with the resin as a seal material, the resin has no moisture proof property, water tends to permeate through it into liquid crystal layer. Also, the liquid crystal in contact with the seal material and the residual resin that is not polymerized at the time of hardening of the resin tends to co-solve in each other, especially at high temperature. Thus, the resin may elute in the liquid crystal layer, and may lead to the problem of degradation of the characteristics of the liquid crystal due to alignment defects of liquid crystal molecules, or deterioration of specific electrical resistivity, etc.
In particular, in a spatial light modulation devices used for optical communication, high durability in an environment of high temperature and high relative humidity is demanded. In MEMS, in order to incorporate liquid crystal device that has the advantage of no mechanical moving part, it is essential to improve durability of liquid crystal device in an environment of high temperature and high relative humidity. Thus, a liquid crystal device has been proposed which uses inorganic material as a seal material in place of resin (see Patent Document 1).
FIG. 32 is a view useful for explaining a conventional liquid crystal device.
As shown in FIG. 32, a liquid crystal device 600 comprises a liquid crystal layer 650 sandwiched between a pair of substrates 610, 620 disposed in opposition to each other. The device substrate 610 and the opposing substrate 620 are bonded at the seal portion of the upper surface 680a of the frame part 680 enclosing the liquid layer 650. The seal portion is formed by direct joining of the frame part 680 integrally formed on the inner surface of the opposing substrate 620 and the contact surface of the device substrate 610 opposed to the frame part 680 in vacuum after surface activation treatment.
Therefore, the frame part 680 forming the liquid crystal layer between substrates is formed not from conventional resin but of same inorganic material as the opposing substrate 620, and is directly joined to the device substrate 610 by surface activation treatment, so that it is of highly moisture proof and can prevent permeation of water into the liquid crystal layer. Thus, it is possible to provide a highly durable liquid crystal device that can prevent deterioration of liquid crystal characteristics.
FIG. 33 is a view useful for explaining other conventional liquid crystal device.
As shown in FIG. 33, it is possible to subject the device 710 and the lid 720 to surface activation treatment and to join them directly (see Patent Document 2). In order to join the device 710 and the lid 720, a gold soldering film 730 of 1 μm or greater in thickness is formed as joint part on the joining surface of the device 710. On the joining surface of the lid 720, a gold thin film 740 is formed by sputtering or flash soldering. The thick gold soldering film 730 and gold thin film 740 may be formed on the contrary surfaces. After surface activation treatment is performed on the gold surface of the device 710 and the lid 720 by etching with Ar plasma in a vacuum chamber of a wafer joining apparatus, the device 710 and the lid 720 are brought into contact with each other, and pressurized to achieve joining.
FIG. 34 is a view useful for explaining still another conventional liquid crystal device.
As shown in FIG. 34, a liquid crystal display apparatus is proposed in which two plates 810, 820 are disposed in opposition to each other, and are pressurized in reduced pressure with a frame member 830 sandwiched therebetween to join the two plates in air tight manner via the frame member 830 (see Patent Document 3). Two plates are assembled together by joining of the plate 820 and the frame member 830 joined with frit glass 831 in advance with an adhesive 840 disposed on the plate 820.
Also, before joining, surface activation treatment is performed on the surface of the frame member 830 and the adhesive 840. Although the frame member is constructed from glass, it may be constructed from metal.