Liquid crystal device, method of manufacturing the same and electronic apparatus

Abstract: Described is liquid crystal device enabling a decrease in an area for mounting a liquid crystal driving IC thereon, and having high reliability, and a method of manufacturing the liquid crystal device. A driving IC (1) is face-down bonded to a substrate (2). The thickness (T) of the driving IC (1) is made larger than the thickness ( t ) of a opposing substrate (3) of a liquid crystal panel (50), and the upper surface (61) of the driving IC (1) is made higher than the upper surface (63) of the opposing substrate (3). The upper surface (61) of the driving IC (1) is heated and pressed by a bonding tool (4) to bond bumps (21) of the driving IC (1) to interconnecting lines (41) and (42), and bond the driving IC (1) to the substrate (2) with an adhesive (7). It is thus possible to sufficiently heat and press the driving IC (1) without contact between the bonding tool (4) and the opposing substrate (3), thereby permitting bonding with high reliability.

Description: The present invention relates to a liquid crystal device, a method of manufacturing the same, and an electronic apparatus, and particularly to a liquid crystal device comprising a semiconductor chip (referred to as driving IC hereinafter) COG (Chip on Glass)-mounted on a liquid crystal panel, for driving a liquid crystal, a method of manufacturing the same and an electronic apparatus comprising the liquid crystal device provided as a display device. In recent years, liquid crystal devices have been increasingly manufactured so as to have a COG structure in which a driving IC is mounted on a panel having higher definition and higher density. Such a COG structure is described in, for example, Fig. 1 of JP-A-4-319918. A conventional liquid crystal device having this COG structure will be described with reference to Fig. 14. A conventional liquid crystal device 300 comprises a liquid crystal panel 350 having a substrate 31, a opposing substrate 36 and a liquid crystal material 352 held between both substrates, and a driving IC 32. The driving IC 32 is connected to the substrate 31 by interconnecting lines 341 and 342 and bumps 33 to form the COG structure. The driving IC 32 is protected by a sealing resin 35. In this conventional liquid crystal device, the sealing resin 35 is higher than the upper surface 361 of the opposing substrate 36, but the upper surface 321 of the driving IC 32 is not higher than the upper surface 361 of the opposing substrate 36. When the driving IC 32 is bonded, the upper surface 321 of the driving IC 32 must be pressed by a bonding tool 304 before the sealing resin 35 is provided. However, if the driving IC 32 is close to the opposing substrate 36, since the bonding tool 304 is generally larger than the driving IC 32, the bonding tool 304 gets on the opposing substrate 36, or contacts the edge of the opposing substrate 36. As a result, the driving IC 32 cannot be sufficiently pressed, and the bumps 33 are not sufficiently connected to the interconnecting lines 341 and 342, thereby causing the problem of deteriorating the reliability. In order to prevent the bonding tool 304 from getting on the opposing substrate 36 or contacting the edge of the opposing substrate 36, it is necessary to mount the driving IC 32 on the substrate 31 at a distance from the opposing substrate 36 of the liquid panel 350. Therefore, a driving IC mounting area on the substrate 31 is increased, thereby causing the problem of inevitably increasing the size of the liquid device 300. The electronic apparatus equipped with the conventional liquid crystal device 300 also has the problem that an increase in an area for mounting the liquid crystal device makes it impossible to decrease the size and weight of the apparatus. JP-61-087133 A discloses a liquid crystal device similar to the one described above in which the driving element is mounted on a conductive rubber connector and the total thickness of that connector and the driving element from the surface of the second substrate (thrid main surface) exceeds that of the first substrate Accordingly, a main object of the present invention is to provide a liquid crystal device which enables a decrease in an area for mounting a liquid crystal driving IC thereon and having high reliability, and a method of manufacturing the same. Another object of the present invention is to provide an electronic apparatus which is equipped with a liquid crystal device and whose size and weight are decreased. These objects are achieved with a liquid crystal device as claimed in claim 1, a method as claimed in claims 10, and an electronic apparatus as claimed in claim 23. Preferred embodiments of the invention are subject-matter of the dependent claims. In the construction in accordance with Claim 1, since the upper surface of the driving element is higher than the upper surface (first main surface) of the first substrate, even when the driving element is COG-mounted on the second substrate of a compact liquid crystal panel with a narrow area in which the space between the driving element and the first substrate is decreased, the bonding tool for pressing the driving element does not contact the first substrate. Therefore, it is possible to perform face-down bonding using a large bonding tool. As a result, the bonding tool can easily be maintained parallel, and the heat capacity of the bonding tool can be increased, thereby permitting face-down bonding with more uniform load at more uniform temperature. It is thus possible to provided a liquid crystal device with high reliability in which bonding between the driving element and panel interconnecting lines is sufficiently ensured. Here, when the first substrate has a polarizing plate and other optical elements, which have previously been bonded thereto, the thickness of the first substrate represents the thickness of the first substrate including these optical elements. In this case, the upper surface of the driving element is higher than the upper surfaces of the optical elements, and the bonding tool is prevented from contacting the optical elements such as the polarizing plate, thereby exhibiting the above functions. In accordance with Claim 5, the distance between the first substrate and the driving element is 2 mm or less, particularly, 1 mm or less. In the manufacturing method in accordance with Claim 10, since the driving element is pressed from the upper side with the upper surface thereof higher than the upper surface (first main surface) of the first substrate, even when the driving element is COG-mounted on the second substrate of a compact liquid crystal panel with a narrow marginal area in which the space between the driving element and the first substrate is decreased, the bonding tool for pressing the driving element does not contact the first substrate. This permits face-down bonding by a large bonding tool. As a result, the bonding tool can easily be maintained in parallel, and the heat capacity of the bonding tool can be increased, thereby permitting face-down bonding with more uniform load at more uniform temperature. It is thus possible to produce a small liquid crystal device with high reliability in which bonding of the driving element and panel interconnecting lines is sufficiently ensured. Here, when the first substrate used has a polarizing plate and other optical elements which are bonded thereto, the thickness of the first substrate represents the thickness of the first substrate including these optical elements. In this case, the upper surface of the driving element is higher than the upper surfaces of the optical elements, and the bonding tool is prevented from contacting the optical elements such as the polarizing plate, thereby exhibiting the above functions. In accordance with Claim 14, the distance between the first substrate and the driving element is 2 mm or less, particularly, 1 mm or less. In accordance with Claim 15, the driving element is bonded directly to the panel interconnecting lines in the state wherein only the adhesive is present between the respective bumps, thereby less causing short-circuit between the bumps. It is thus possible to cope with high-fineness bump pitches. In accordance with Claim 16, bonding of the bumps and the interconnecting lines through the conductive paste can relieve variations in the thickness of the driving element and variations in flatness of the bonding tool, and thus improve the yield of the COG process and ensure high reliability. A silver paste is preferably used as the conductive paste. In accordance with Claim 17, the fixing member causes the conductive particles to take a part in connection, and can relieve variations in the thickness of driving IC and variations in flatness of the bonding tool, and thus improve the yield of the COG process and ensure high reliability. In accordance with the present invention, since the bonding tool for pressing the driving element does not contact the first substrate, as described above, face-down bonding can be performed by using a large bonding tool, and consequently the heat capacity of the bonding tool can be increased, thereby permitting face-down bonding at more uniform temperature. The present invention is particularly effective to heat the driving element by the bonding tool. It is preferable that the driving element is heated while being by the bonding tool to be bonded to the second substrate with the thermosetting adhesive, and is then cooled to a predetermined temperature by stopping heating by the bonding tool under pressing by the bonding tool, and pressing by the bonding tool is then stopped. In this bonding, since the viscosity (elastic modulus) increases with a decrease in temperature due to the correlation between the temperature and viscosity (elastic modulus), the driving element can securely be fixed and bonded. This is referred to as the hot-cold effect which improves the adhesive force of the adhesive used. In accordance with Claim 19, the adhesive can also be heated by light. In this case, visible light or ultraviolet light can be preferably used as light. As the second substrate, a transparent substrate is preferably used. In this case, light is preferably applied from the main surface side of the second substrate. In this case, it is also preferable that the thermosetting adhesive is heated by light while pressing the driving element by the bonding tool to fix the driving element to the second substrate with the adhesive, and is then cooled to a predetermined temperature by stopping heating by light while pressing the driving element by the bonding tool, and pressing by the bonding tool is then stopped. The adhesive force of the adhesive is improved by the hot-cold effect. In accordance with Claim 20, the bonding can maintain the temperature at a low temperature during cure bonding of the adhesive, and can thus decrease the heat effect on the panel. In this case, visible light or ultraviolet light is preferably used. As the second substrate, a transparent substrate is preferably used. In this case, light is preferably applied from the side of the fourth main surface of the second substrate. As the first and second substrates, transparent glass is preferably used but a transparent resin may also be used. Embodiments of the present invention will be described below with reference to the drawings. Fig. 1 is a schematic perspective view illustrating a liquid crystal device in accordance with first to eighth embodiments of the present invention. Fig. 2 is a sectional view illustrating a liquid crystal device in accordance with first to eighth embodiments of the present invention. Fig. 3 is a sectional view illustrating a liquid crystal device in accordance with first to eighth embodiments of the present invention. Fig. 4 is a sectional view illustrating a liquid crystal device in accordance with the second embodiment of the present invention. Fig. 5 is a sectional view illustrating the liquid crystal device in accordance with the second embodiment of the present invention. Fig. 6 is a sectional view illustrating a liquid crystal device in accordance with the third embodiment of the present invention. Fig. 7 is a sectional view illustrating a liquid crystal device in accordance with the fourth embodiment of the present invention. Fig. 8 is a sectional view illustrating the liquid crystal device in accordance with the fourth embodiment of the present invention. Fig. 9 is a sectional view illustrating a liquid crystal device in accordance with the fifth embodiment of the present invention. Fig. 10 is a sectional view illustrating the liquid crystal device in accordance with the fifth embodiment of the present invention. Fig. 11 is a sectional view illustrating a liquid crystal device in accordance with the sixth embodiment of the present invention. Fig. 12 is a sectional view illustrating a liquid crystal device in accordance with the seventh embodiment of the present invention. Fig. 13 is a sectional view illustrating a liquid crystal device in accordance with the ninth embodiment of the present invention. Fig. 14 is a sectional view illustrating a conventional liquid crystal device. Fig. 1 is a schematic perspective view illustrating a liquid crystal device in accordance with first to eighth embodiments of the present invention. A liquid crystal device 100 according to each of the embodiments comprises a liquid crystal panel 50 having a substrate 2, a opposing substrate 3 and a liquid crystal material (not shown) held between these substrates; a driving IC 1; and a flexible printed board 45. On the substrate 2 are provided interconnecting lines 41 for connecting to the output terminals of the driving IC 1, and interconnecting lines 42 for connecting to the input terminals of the driving IC 1, the driving IC 1 being connected to the interconnecting lines 41 and 42 and provided on the substrate 2. The flexible printed board 45 is connected to the interconnecting lines 42. (First Embodiment) Figs. 2 and 3 are sectional views illustrating a liquid crystal device in accordance with the first embodiment of the present invention. Referring Fig. 2, the liquid crystal device 100 comprises the liquid crystal panel 50 and the driving IC 1. A seal 51 is provided in the periphery between the substrate 2 and the opposing substrate 3 so that a liquid crystal material 52 is sealed between the substrate 2 and the opposing substrate 3 with the seal 51 therebetween. On the upper surface 62 of the substrate 2 are provided the interconnecting lines 41 for connecting to the output terminals of the driving IC 1 and the interconnecting lines 42 for connecting to the input terminals of the driving IC 1. The driving IC 1 is connected to the interconnecting lines 41 and 42 though bumps 21 to be bonded face down to the substrate 2. The driving IC 1 is bonded to the substrate with an adhesive 7. The thickness T of the driving IC 1 is larger than the thickness t of the opposing substrate 3 of the liquid crystal panel 50, and thus the upper surface 61 of the driving IC 1 becomes higher than the upper surface 63 of the opposing substrate 3 of the liquid crystal panel 50. The method of manufacturing the liquid crystal device 100 will be described below with reference to Fig. 3. First, the liquid crystal panel 50 having the liquid crystal material 52 sealed between the substrate 2 and the opposing substrate 3 with the seal 51 therebetween is prepared. Then, the adhesive 7 is provided on the substrate of the liquid crystal panel 50, and the input-output bumps 21 of the driving IC 1 are respectively aligned with the corresponding interconnecting lines 42 and 41. The upper surface of the driving IC 1 is then heated and pressed by a bonding tool 4 to respectively, electrically and mechanically bond the input/output bumps 21 of the driving IC 1 to the interconnecting lines 42 and 41, as well as bonding the driving IC 1 to the upper surface 62 of the substrate 2 with the adhesive 7. The adhesive 7 is a thermosetting epoxy adhesive, and bonding conditions include a temperature of 220°C, a pressure of 5 gf/mm 2 (0.05 N/mm 2 ), and a time of 20 seconds. The need for decreasing the mounting area of the driving IC 1 causes the need to decrease the distance between the driving IC 1 and the opposing substrate 3 of the liquid crystal panel 50. This distance is conventionally 1 mm or more, and generally about 2 to 3 mm, but the distance has recently been required to be decreased to about 0.5 mm. Therefore, as this distance decreases, the distance between the bonding tool 4 used for bonding the driving IC 1 and the opposing substrate 3 decreases. As shown in Fig. 3, the outer size of the bonding tool 4 is larger than the driving IC in order to securely bond it. In this case, the conventional bonding method causes interference between the bonding tool 4 and the opposing substrate 3, and is thus impossible to sufficiently bond the driving IC 1. In this embodiment, the thickness T of the driving IC 1 is 0.56 mm, and the thickness t of the opposing substrate 3 of the liquid crystal panel 50 is 0.4 mm (the thickness t strictly including the cell thickness of the panel, about 0.001 to 0.02 mm). The height of the upper surface 61 of the driving IC 1 from the upper surface 62 of the substrate 2 is 0.56 mm, and the height of the upper surface 63 of the opposing substrate 3 from the upper surface 62 of the substrate 2 is 0.4 mm. The material of the substrate 2 and the opposing substrate 3 is soda glass. The distance between the driving IC 1 and the opposing substrate 3 is 0.5 mm, the width W of the driving IC 1 is 2.02 mm, and the width w of the bonding tool 4 is 4.0 mm. In this embodiment, the thickness T of the driving IC 1 is 1.4 times the thickness t of the opposing substrate 3, and a gap of 0.16 mm is secured between the bonding tool 4 and the opposing substrate 3. However, it is considered based on the variations obtained from experimental results that, with a gap of about 0.08 mm at a minimum, the same effects as described above can be obtained. Hence, the thickness T of the driving IC 1 may be 1.17 times or more, i.e., about 1.2 times or more, the thickness t of the opposing substrate 3. In this embodiment, since the thickness of the driving IC 1 is made larger than the thickness of the opposing substrate 3 of the liquid crystal panel 50, a certain gap is secured between the bonding tool 4 and the opposing substrate 3 during bonding. It is thus possible to carry out face-down bonding by using a large bonding tool 4. Consequently, the bonding tool 4 can easily be maintained in parallel, and the heat capacity of the bonding tool 4 is increased, thereby permitting face-down bonding with more uniform load at more uniform temperature. Therefore, the driving IC 1 can sufficiently be heated and pressed without contact between the bonding tool 4 and the opposing substrate 3, thereby enabling bonding with high reliability. It is also possible to prevent breakage of the opposing substrate 3 and suppress the heat effect of the bonding tool 4 on the liquid crystal panel 50. Further, the direct bonding of the bumps 21 of the driving IC 1 to the interconnecting lines 41 and 42 with the adhesive 7 allows only the adhesive 7 to be present between the respective bumps 21. This prevents the occurrence of short-circuits between the bumps 21, and makes it possible to cope with very small bump pitches. (Second Embodiment) Figs. 4 and 5 are sectional views illustrating a liquid crystal device in accordance with the second embodiment of the present invention. Referring to Fig. 4, the liquid crystal device 100 differs from the first embodiment in the point that a polarizing plate 11 is provided on the upper surface 63 of the opposing substrate 3, and a polarizing plate 12 is provided on the lower surface of the substrate 2, but this embodiment is the same as the first embodiment in the other points. The liquid crystal device may be made a reflection type in which a reflecting plate is provided on the polarizing plate 12 on the lower surface of the substrate 2. In this embodiment, the thickness T of the driving IC 1 is larger than the total thickness t' of the thickness of the opposing substrate 3 of the liquid crystal panel 50 and the thickness of the polarizing plate 11, and the upper surface 61 of the driving IC 1 is higher than the upper surface 64 of the polarizing plate 11 provided on the opposing substrate 3 of the liquid crystal panel 50. The method of manufacturing the liquid crystal device 100 will be described below with reference to Fig. 5. In this embodiment, although the liquid crystal device 100 is manufactured by the same method as the first embodiment, the thickness T of the driving IC 1 is 0.56 mm, and the total thickness t' of the thickness (0.3 mm) of the opposing substrate 3 of the liquid crystal panel 50 and the thickness (0.18 mm) of the polarizing plate 11 is 0.48 mm (the thickness t' strictly including the cell thickness of the panel, about 0.001 to 0.02 mm). The height of the upper surface 61 of the driving IC 1 from the upper surface 62 of the substrate 2 is 0.56 mm, and the height of the upper surface 64 of the polarizing plate 11 on the opposing substrate 3 from the upper surface 62 of the substrate 2 is 0.48 mm. The distance between the driving IC 1 and the opposing substrate 3 is 0.5 mm, the width W of the driving IC 1 is 2.02 mm, and the width w of the bonding tool 4 is 4.0 mm. In this embodiment, the thickness T of the driving IC 1 is 1.17 times the total thickness t ' of the thickness of the opposing substrate 3 and the thickness of the polarizing plate 11, and a gap of 0.08 mm is secured between the bonding tool 4 and the opposing substrate 3. In this embodiment, since the thickness of the driving IC 1 is larger than the total thickness of the thickness of the opposing substrate 3 of the liquid crystal panel 50 and the thickness of the polarizing plate 11, a certain distance is secured between the bonding tool 4 and the polarizing plate 11 during bonding. It is thus possible to carry out face-down bonding by using a large bonding tool 4. Consequently, the bonding tool 4 can easily be maintained in parallel, and the heat capacity of the bonding tool 4 is increased, thereby permitting face-down bonding with more uniform load at more uniform temperature. Hence, the driving IC 1 can sufficiently be heated and pressed without contact between the bonding tool 4 and the polarizing plate 11, thereby enabling bonding with high reliability. Further, it is possible to prevent breakage of the opposing substrate 3 and the polarizing plate 11, and suppress the heat effect of the bonding tool 4 on the liquid crystal panel 50 to a low level. (Third Embodiment) Fig. 6 is a sectional view illustrating a liquid crystal device in accordance with the third embodiment of the present invention. The liquid crystal device 100 of this embodiment has the same structure as the liquid crystal device 100 of the first embodiment described above with reference to Fig. 2. As the adhesive 7, a thermosetting epoxy adhesive is used. The method of manufacturing the liquid crystal device 100 will be described below with reference to Fig. 6. First, the liquid crystal panel 50 comprising the liquid crystal material 52 sealed with the seal 51 between the substrate 2 and the opposing substrate 3 is prepared. The adhesive 7 is then provided on the substrate 2 of the liquid crystal panel 50, the input/output bumps 21 of the driving IC 1 are then respectively aligned with the corresponding interconnecting lines 42 and 41. Thereafter, the driving IC 1, the interconnecting lines 41 and 42, the bumps 21 and the adhesive 7 are heated by applying near infrared and/or visible light 13 generated by a xenon lamp or the like to the bonding surface of the driving IC 1 from the lower side of the pedestal 5 made of quartz glass while pressing the upper surface of the driving IC 1 by the bonding tool 4, to respectively, electrically and mechanically bond the input/output bumps 21 of the driving IC 1 and the interconnecting lines 42 and 41, as well as bonding the driving IC 1 to the upper surface 62 of the substrate 2 with the adhesive 7. The bonding conditions include a temperature of 220°C, a pressure of 5 gf/mm 2 (0.05 N/mm 2 ), and a time of 20 seconds, and the quantity of the light applied and the pressure are set so as to establish these conditions. Then, heating by the light 13 is stopped to decrease the temperature to 150°C under pressing by the bonding tool 4, and pressing by the bonding tool 4 is then stopped. This improves the adhesive force of the adhesive 7 due to the hot-cold effect. A pedestal 5 is made of quartz glass so that light can be applied to the adhesive 7 through the substrate 2. The bonding tool 4 may be heated by a heater or the like. In this case, the temperature of the bonding tool 4 may be 30 to 200°C lower than that in the first embodiment. In this embodiment, the thickness T of the driving IC 1 is 0.56 mm, and the thickness t of the opposing substrate 3 of the liquid crystal panel 50 is 0.4 mm (the thickness t strictly including the cell thickness of the panel of about 0.001 to 0.02 mm). The height of the upper surface 61 of the driving IC 1 from the upper surface 62 of the substrate 2 is 0.56 mm, and the height of the upper surface 63 of the opposing substrate 3 from the upper surface 62 of the substrate 2 is 0.4 mm. The material of the substrate 2 and the opposing substrate 3 is soda glass. The distance between the driving IC 1 and the opposing substrate 3 is 0.5 mm, the width W of the driving IC 1 is 2.02 mm, and the width w of the bonding tool 4 is 4.0 mm. In this embodiment, the thickness T of the driving IC 1 is 1.4 times the thickness t of the opposing substrate 3, and a gap of 0.16 mm is secured between the tool 4 and the opposing substrate 3. However, even in heating by the xenon lamp from the lower side of the pedestal 5, as in this embodiment, it is considered based on the variations obtained from experimental results that, with a gap of about 0.08 mm at a minimum, the same effects as described above can be obtained. Hence, the thickness T of the driving IC 1 may be 1.17 times or more, i.e., about 1.2 times or more, the thickness t of the opposing substrate 3. In this embodiment, since the thickness of the driving IC is larger than the thickness of the opposing substrate 3 of the liquid crystal panel 50, a certain distance is secured between the bonding tool 4 and the opposing substrate 3 during bonding. Thus, it is possible to carry out face-down bonding by using a large bonding tool 4, and consequently, the bonding tool 4 can easily be maintained in parallel, thereby permitting face-down bonding with more uniform load. Hence, the driving IC 1 can sufficiently be pressed without breakage of the opposing substrate 3 due to contact of the bonding tool 4 therewith, thereby enabling bonding with high reliability. In addition, the use of light irradiation permits a decrease in the temperature of the bonding tool 4, and can significantly decrease the heat effect on the liquid crystal panel 50. (Fourth Embodiment) Fig. 7 and 8 are sectional views illustrating a liquid crystal device in accordance with the fourth embodiment of the present invention. Referring to Fig. 7, the liquid crystal device 100 differs from the first embodiment in the point that the bumps 21 of the driving IC 1 are respectively bonded to the interconnecting lines 41 and 42 through a silver paste 8, but is the same as the first embodiment in the other points. In this embodiment, the thickness T of the driving IC 1 is larger than the thickness t of the opposing substrate 3 of the liquid crystal panel 50, and the upper surface 61 of the driving IC 1 is higher than the upper surface 63 of the opposing substrate 3 of the liquid crystal panel 50. In this embodiment, the thickness T of the driving IC 1 strictly includes the thickness of the driving IC 1, the thickness of the silver paste 8 and the thickness of the interconnecting lines 41 and 42. The method of manufacturing the liquid crystal device 100 will be described below with reference to Fig. 8. First the liquid crystal panel 50 comprising the liquid crystal material 52 sealed between the substrate 2 and the opposing substrate 3 with the seal 51 therebetween is prepared. Then, the silver paste 8 is adhered to the input/output bumps 21 of the driving IC 1. The adhesive 7 is then provided on the substrate 2 of the liquid crystal panel 50, and the input/output bumps 21 of the driving IC 1 are respectively aligned with the corresponding interconnecting lines 42 and 41. Thereafter, the upper surface 61 of the driving IC 1 is heated and pressed by the bonding tool 4 to respectively, electrically and mechanically bond the input/output bumps 21 of the driving IC 1 to the interconnecting lines 42 and 41 through the silver paste 8, as well as bonding the driving IC 1 to the upper surface 62 of the substrate 2 with the adhesive 7. The adhesive 7 is a thermosetting epoxy adhesive, and the bonding conditions include a temperature of 220°C, a pressure of 5 gf/mm 2 (0.05 N/mm 2 ), and a time of 20 seconds. In this embodiment, the thickness T of the driving IC is 0.56 mm, and the thickness t of the opposing substrate 3 of the liquid crystal panel 50 is 0.4 mm (the thickness 5 strictly including the cell thickness of the panel, about 0.001 to 0.2 mm). The height of the upper surface 61 of the driving IC 1 from the upper surface 62 of the substrate 2 is 0.56 mm, and the height of the upper surface 63 of the opposing substrate 3 from the upper surface 62 of the substrate 2 is 0.4 mm. The distance between the driving IC 1 and the opposing substrate 3 is 0.5 mm, the width W of the driving IC is 2.02 mm, and the width w of the bonding tool 4 is 4.0 mm. In this embodiment, the thickness T of the driving IC 1 is 1.4 times the thickness t of the opposing substrate 3, and a gap of 0.16 mm is secured between the bonding tool 4 and the opposing substrate. However, even when the input/output bumps 21 of the driving IC 1 are respectively bonded to the interconnecting lines 41 and 42 through the silver paste 7, as in this embodiment, it is considered based on the variations obtained from experimental results that, with a gap of about 0.08 mm at a minimum, the same effects as described above can be obtained. Therefore, the thickness T of the driving IC may be 1.17 times or more, i.e., about 1.2 times or more, the thickness t of the opposing substrate 3. In this embodiment, since the input/output bumps 21 of the driving IC 1 are respectively bonded to the interconnecting lines 41 and 42 through the silver paste 7, it is possible to relieve variations in the thicknesses of the driving IC 1 and the input/output bumps 21, and in the flatness of the bonding tool 4. (Fifth Embodiment) Figs. 9 and 10 are sectional views illustrating a liquid crystal device in accordance with the fifth embodiment of the present invention. Referring Fig. 9, the liquid crystal device 100 differs from the first embodiment in the point that the driving IC 1 is bonded to the upper surface 62 of the substrate 2 by using an anisotropic conductive film 10, but is the same as the first embodiment in the other points. The anisotropic conductive film 10 comprises conductive particles 9 comprising gold-plated resin balls dispersed in the epoxy adhesive 7 so that the bumps 21 of the driving IC 1 are respectively bonded to the interconnecting lines 41 and 42 through the conductive particles 9, and the driving IC 1 is bonded to the substrate 2 with the epoxy adhesive 7. In this embodiment, the thickness T of the driving IC 1 is larger than the thickness t of the opposing substrate 3 of the liquid crystal panel 50, and the upper surface 61 of the driving IC 1 is higher than the upper surface 63 of the opposing substrate of the liquid crystal panel 50. The thickness T of the driving IC 1 strictly includes the thickness of the driving IC 1, the thickness of the bumps 21, the thickness of the conductive particles 9 and the thickness of the interconnecting lines 41 and 42. The method of manufacturing the liquid crystal device 100 will be described below with reference to Fig. 10. First the liquid crystal panel 50 comprising the liquid crystal material 52 sealed between the substrate 2 and the opposing substrate 3 with the seal 51 therebetween is prepared. Then, the anisotropic conductive film 10 is provided on the substrate 2 of the liquid crystal panel 50, and the input/output bumps 21 of the driving IC 1 are respectively aligned with the corresponding interconnecting lines 42 and 41. Thereafter, the upper surface 61 of the driving IC 1 is heated and pressed by the bonding tool 4 to respectively, electrically and mechanically bond the input/output bumps 21 of the driving IC 1 to the interconnecting lines 42 and 41 through the conductive particles 9, as well as bonding the driving IC 1 to the upper surface 62 of the substrate 2 by the adhesive 7 in the anisotropic conductive film 10. The bonding conditions include a temperature of 220°C, a pressure of 5 gf/mm 2 (0.05 N/mm 2 ), and a time of 20 seconds. In this embodiment, the thickness T of the driving IC 1 is 0.56 mm, and the thickness t of the opposing substrate 3 of the liquid crystal panel 50 is 0.4 mm (the thickness t strictly including the cell thickness of the panel, about 0.001 to 0.02 mm). The height of the upper surface 61 of the driving IC 1 from the upper surface 62 of the substrate 2 is 0.56 mm, and the height of the upper surface 63 of the opposing substrate 3 from the upper surface 62 of the substrate 2 is 0.4 mm. The distance between the driving IC 1 and the opposing substrate 3 is 0.5 mm, the width W of the driving IC is 2.02 mm, and the width w of the bonding tool 4 is 4.0 mm. In this embodiment, the thickness T of the driving IC 1 is 1.4 times the thickness t of the opposing substrate 3, and the gap between the bonding tool 4 and the opposing substrate 3 is ensured at 0.16 mm. Even when the input/output bumps 21 of the driving IC 1 are respectively bonded to the interconnecting lines 41 and 42 through the conductive particles 9 of the anisotropic conductive film 10, as in this embodiment, it is considered based on the variations obtained from experimental results that, with a gap of about 0.08 mm at a minimum, the same effects as described above can be obtained. Therefore, the thickness T of the driving IC 1 may be 1.17 times or more, i.e., about 1.2 times or more, the thickness t of the opposing substrate 3. In this embodiment, since the input/output bumps 21 of the driving IC 1 are respectively bonded to the interconnecting lines 41 and 42 through the anisotropic conductive film 10, the conductive particles 9 of the anisotropic conductive film 10 are involved in bonding, and thus the variations in the thickness of the driving IC 1 and the input/output bumps 21 and in the flatness of the bonding tool 4 can be relieved. (Sixth Embodiment) Fig. 11 is a sectional view illustrating a liquid crystal device in accordance with the sixth embodiment of the present invention. The liquid crystal device 100 of this embodiment has the same structure as the liquid crystal device 100 of the fourth embodiment described with reference to Fig. 7. As the adhesive 7, a thermosetting epoxy adhesive is used. The method of manufacturing the liquid crystal device 100 will be described. First the liquid crystal 50 comprising the liquid crystal material 52 sealed between the substrate 2 and the opposing substrate 3 with the seal 51 therebetween is prepared. The silver paste 8 is adhered to the input/output bumps 21 of the driving IC 1. Then, the adhesive 7 is provided on the substrate 2 of the liquid crystal 50, and the input/output bumps 21 of the driving IC 1 are respectively aligned with the corresponding interconnecting lines 42 and 41. Thereafter, the driving IC 1, the interconnecting lines 41 and 42, the bumps 21, the silver paste 8 and the adhesive 7 are heated by applying near infrared and/or visible light 13 generated by a xenon lamp or the like from the lower side of the pedestal 5 made of quartz glass while pressing the upper surface 61 of the driving IC 1 by the bonding tool 4, to respectively, electrically and mechanically bond the input/output bumps 21 of the driving IC 1 to the interconnecting lines 42 and 41 through the silver paste 8, as well as bonding the driving IC 1 to the upper surface 62 of the substrate 2 with the adhesive 7. The bonding conditions include a temperature of 220°C, a pressure of 5 gf/mm2 (0.05 N/mm 2 ), and a time of 20 seconds, and the quantity of the light applied and the pressure are set to establish these conditions. Then, heating by the light 13 is stopped to decrease the temperature to 150°C under pressing by the bonding tool 4, and pressing by the bonding tool 4 is then stopped. This bonding improves the adhesive force of the adhesive 7 by the hot-cold effect. A pedestal 5 is made of quartz glass so that light can be applied to the adhesive 7 through the substrate 2. The bonding tool 4 may be heated by a heater or the like. In this case, the temperature of the bonding tool 4 is 30 to 200°C lower than that in the fourth embodiment. In this embodiment, the thickness T of the driving IC 1, the thickness t of the opposing substrate 3 of the liquid crystal panel 50, the height of the upper surface 61 of the driving IC 1 from the upper surface 62 of the substrate 2, the height of the upper surface 63 of the opposing substrate 3 from the upper surface of the substrate 2, the distance between the driving IC 1 and the opposing substrate 3, the width W of the driving IC 1 and the width w of the bonding tool 4 are the same as in the fourth embodiment. This embodiment is also the same as the fourth embodiment in that the gap between the bonding tool 4 and the opposing substrate 3 is about 0.08 mm at a minimum, and the thickness T of the driving IC 1 may be 1.17 or more times, i.e., about 1.2 or more times, the thickness t of the opposing substrate 3. (Seventh Embodiment) Fig. 12 is a sectional view illustrating a liquid crystal device in accordance with the seventh embodiment of the present invention. The liquid crystal device 100 of this embodiment has the same structure as the liquid crystal device 100 of the fifth embodiment described with reference to Fig. 9. The method of manufacturing the liquid crystal device 100 will be described below. First the liquid crystal panel 50 comprising the liquid crystal material 52 sealed between the substrate 2 and the opposing substrate 3 with the seal 51 therebetween is prepared. Then, the anisotropic conductive film 10 is provided on the substrate 2 of the liquid crystal panel 50, and the input/output bumps 21 of the driving IC 1 are respectively aligned with the corresponding interconnecting lines 42 and 41. Thereafter, the driving IC 1, the interconnecting lines 41 and 42, the bumps 21, and the anisotropic conductive film 10 are heated by applying near infrared and/or visible light 13 generated by a xenon lamp or the like from the lower side of the pedestal 5 made of quartz glass while pressing the upper surface 61 of the driving IC 1 by the bonding tool 4, to respectively, electrically and mechanically bond the input/output bumps 21 of the driving IC 1 to the interconnecting lines 42 and 41 through the conductive particles 9 of the anisotropic conductive film 10, as well as bonding the driving IC 1 to the upper surface 62 of the substrate 2 with the adhesive 7 of the anisotropic conductive film 10. The bonding conditions include a temperature 220°C, a pressure of 5 gf/mm 2 (0.05 N/mm 2 ), and a time of 20 seconds, and the quality of the light applied and the pressure are set so as to establish these conditions. Then, heating by the light 13 is stopped to decrease the temperature to 150°C under pressing by the bonding tool 4, and pressing by the bonding tool 4 is then stopped. This bonding improves the adhesive force of the adhesive 7 by the hot-cold effect. A pedestal 5 is made of quartz glass so that light can be applied to the adhesive 7 through the substrate 2. The bonding tool 4 may be heated by a heater or the like. In this case, the temperature of the bonding tool 4 may be 30 to 200°C lower than that in the fifth embodiment. In this embodiment, the thickness T of the driving IC 1, the thickness t of the opposing substrate 3 of the liquid crystal panel 50, the height of the upper surface 61 of the driving IC 1 from the upper surface 62 of the substrate 2, the height of the upper surface 63 of the opposing substrate 3 from the upper surface 62 of the substrate 2, the distance between the driving IC 1 and the opposing substrate 3, the width W of the driving IC 1, and the width w of the bonding tool 4 are the same as in the fifth embodiment. This embodiment is also the same as the fifth embodiment in that the gap between the bonding tool 4 and the opposing substrate 3 may be about 0.08 mm at a minimum, and the thickness T of the driving IC 1 may be 1.17 times or more, i.e., about 1.2 times or more, the thickness t of the opposing substrate 3. (Eighth Embodiment) A liquid crystal device in accordance with the eighth embodiment of the present invention is described with reference to Figs. 2 and 3. This embodiment differs from the first embodiment in the point that the substrate 2 and the opposing substrate 3 used comprise a transparent resin composed of polyether sulfone (PES) as a base material, and a blend-type adhesive containing epoxy-type adhesive and styrene- butadiene-styrene (SBS) type adhesive in a mixing ratio of about 8 : 2, but this embodiment is the same as the first embodiment in the other points. In this embodiment, the bonding conditions include a temperature of 130°C, a pressure of 4 gf/mm 2 (0.04 N/mm 2 ), and a time of 20 seconds. In this embodiment, the thickness T of the driving IC 1 is 0.56 m, and the thickness t of the opposing substrate 3 of the liquid crystal panel 50 is 0.12 mm (the thickness t strictly including the cell thickness of the panel of about 0.001 to 0.02 mm). The height of the upper surface 61 of the driving IC 1 from the upper surface 62 of the substrate 2 is 0.56 mm, and the height of the upper surface 63 of the opposing substrate 3 from the upper surface 62 of the substrate 2 is 0.12 mm. The distance between the driving IC 1 and the opposing substrate 3 is 0.5 mm, the width W of the driving IC 1 is 2.02 mm, and the width w of the bonding tool 4 is 4.0 mm. Here, the thickness T of the driving IC 1 is 4.7 times the thickness t of the opposing substrate 3, and a gap of 0.44 mm is secured between the bonding tool 4 and the opposing substrate 3. In this embodiment, since the thickness of the driving IC 1 is made sufficiently larger than the thickness of the opposing substrate 3 of the liquid crystal panel 50, a certain distance is ensured between the bonding tool 4 and the opposing substrate 3 during bonding, and the driving IC 1 can sufficiently be heated and pressed without contact of the bonding tool 4 with the opposing substrate 3, thereby permitting bonding with high reliability. It is also possible to prevent breakage of the opposing substrate, and suppress the heat effect of the bonding tool 4 on the liquid crystal panel 50 to a low level. The liquid crystal device 100 of each of the embodiments is a preferred embodiment, and the present invention is not limited to the liquid crystal device 100 and the manufacturing method therefor according to each embodiment. For example, the adhesive 7 is not limited to the adhesive used in each of the embodiments, and styrene-butadiene-styrene (SBS) type, epoxy type, acrylic type, polyester type, urethane type adhesives and the like may be used singly or in combination or compound of at least two of these adhesives. This is true for the adhesive 7 of the anisotropic conductive film 10. Although, in the third, sixth and seventh embodiments, the thermosetting adhesive is used as the adhesive 7 and is heated by applying infrared and/or visible light by the xenon lamp from the lower side of the pedestal 5, a photosetting adhesive may be used as the adhesive 7. In this case, the adhesive is cured by applying ultraviolet light by a mercury lamp from the lower side of the pedestal 5. This causes only a small temperature rise by light irradiation, and can thus cure the adhesive at a low temperature of room temperature to about 80°C. As the photosetting adhesive, an acrylic photosetting adhesive may preferably be used. Furthermore, in order to protect exposed portions of the panel such as the interconnecting lines portion from moisture, dust, contact, etc., a molding agent or a coating agent may be coated. As the conductive particles 9 used in the anisotropic conductive film 10, solder particles; particles of Ni, Au, Ag, Cu, Pd, Sn or the like; particles of a mixture or an alloy of some of these metals; composite metal particles obtained by plating; plastic particles (polystyrene, polycarbonate, acryl or the like) plated with at least one of Ni, Co, Pd, Au, Ag, Cu, Fe, Sn, Pb, etc; or carbon particles may be used. In addition, the material of the substrates 2 and 3 of the liquid crystal panel is not limited to the material used in each of the embodiments, and polycarbonate (PC), polyethylene terephthalate (PET), polyester (PS), polyether etherketone (PEEK), polyacrylate and the like may be used singly or as a composite resin comprising some of these resins. (Ninth Embodiment) Fig. 13 is a perspective view illustrating an electronic apparatus in accordance with a ninth embodiment of the present invention. In this embodiment, an electronic apparatus 22 is provided with the liquid crystal device 100 of the present invention as a display device. In this embodiment, the electronic apparatus 22 is a portable telephone which is required to be made small, lightweight and thin from the viewpoint of its functions, and is required to have a large display screen in order to make information easy to see. The liquid crystal device 100 of the present invention is compact and has a small area for mounting the driving IC 1, and thus enables an increase in the size of the screen without increase in the side of the liquid crystal device 100. Even in the portable telephone provided with the liquid crystal device 100, the area for mounting the liquid crystal device 100 can be decreased, and thus other electronic parts can efficiently be mounted. It is thus possible to provide a small product having a high degree of freedom in designing the product, a large display screen and a high value as a commercial product. In accordance with the present invention, even when a driving element is COG-mounted on a substrate of a compact liquid crystal panel having a narrow marginal area in which the distance between the driving element and the first substrate is decreased, the bonding tool for pressing the driving element does not contact the other opposing substrate of the liquid crystal panel. It is thus possible to carry out face-down bonding by using a large bonding tool. Consequently, the bonding tool can easily be maintained in parallel, and the heat capacity of the bonding tool is increased, thereby permitting face-down bonding with more uniform load at more uniform temperature. Thus, the present invention provides a small liquid crystal device with high reliability in which the bonding between the driving element and panel interconnecting lines is sufficiently ensured. When the liquid crystal device is mounted in an electronic apparatus, the electronic apparatus obtained is small, lightweight and thin and has high reliability.

Claims: A liquid crystal device comprising: a first substrate (3) having opposite first and second main surfaces; a second substrate (2) having opposite third and fourth main surfaces, the third main surface having first and second regions, and the first region being placed opposite to the second main surface of said first substrate (3); a liquid crystal material (52) provided between the second main surface of said first substrate (3) and the first region of the third main surface of said second substrate (2); interconnecting lines (41, 42) provided on the third main surface of said second substrate (2); and a driving element (1) provided on the second region of the third main surface of said second substrate (2) to be electrically connected to said interconnecting lines (41, 42), characterized in that the thickness of the driving element (1) is larger than the thickness of said first substrate (3). The device according to Claim 1, wherein the thickness of said driving element (1) is 0.08 mm or more larger than the thickness of said first substrate (3). The device according to Claim 1, wherein the thickness of said driving element (1) is 1.17 times or more the thickness of said first substrate (3). The device according to any one of Claims 1 to 3, wherein the thickness of said driving element (1) is 4.7 times or less the thickness of said first substrate (3). The device according to any one of Claims 1 to 4, wherein the distance between said first substrate (3) and said driving element (1) is 2 mm or less. The device according to any one of Claims 1 to 5, wherein said driving element (1) is face-down bonded to said second substrate (2). The device according to any one of Claims 1 to 6, wherein said driving element (1) is bonded to said interconnecting lines (41, 42) through bumps (21). The device according to any one of Claims 1 to 7, wherein said driving element (1) is fixed to said second substrate (2) with an adhesive (7), an adhesive and a conductive paste, or an anisotropic conductive film. The device according to claim 1, further comprising a polarizing plate (11) on the first main surface, the thickness of said driving element (1) being larger than a sum of the thickness of said first substrate (3) and the thickness of the polarizing plate (11). A method of manufacturing a liquid crystal device comprising the steps of: preparing a liquid crystal panel comprising: a first substrate (3) having opposite first and second main surfaces; a second substrate (2) having opposite third and fourth main surfaces, interconnecting lines (41, 42) being provided on the third main surface, the third main surface having first and second regions, and the first region being placed opposite to the second main surface of said first substrate (3); and a liquid crystal material (52) provided between the second main surface of said first substrate (3) and the first region of the third main surface of said second substrate (2); and pressing a driving element (1) having opposite fifth and sixth main surfaces and bumps (21) provided on the sixth main surface, by a bonding tool (4) from the fifth main surface thereof, to bond said bumps (21) to said interconnecting lines (41, 42) as well as fixing said driving element (1) to said second substrate (2) with a fixing member provided between the sixth main surface of said driving element (1) and the third main surface of said second substrate (2) in the state wherein the sixth main surface of said driving element (1) is placed opposite to the second region of the third main surface of said second substrate (2) characterized in that the thickness of said driving element (1) is larger than the thickness of said first substrate (3). The method according to Claim 10, wherein the thickness of said driving element (1) is 0.08 mm or more larger than the thickness of said first substrate (3). The method according to Claim 10, wherein the thickness of said driving element (1) is 1.17 times or more the thickness of said first substrate (3). The method according to any one of Claims 10 to 12, wherein the thickness of said driving element (1) is 4.7 times or less the thickness of said first substrate (3). The method according to any one of Claims 10 to 13, wherein said driving element (1) is fixed to said second substrate (2) with a distance of 2 mm or less between said first substrate (3) and said driving element (1). The method according to any one of Claims 10 to 14, wherein said fixing member is an adhesive (7). The method according to Claim 15, further comprising the step of adhering a conductive paste to the bumps (21) to bonding the bumps (21) with the interconnecting lines (41, 42) through the conductive paste, as well as fixing said driving element (1) to said second substrate (2) with the adhesive (7). The method according to any one of Claims 10 to 14, wherein the fixing member is an anisotropic conductive film comprising an adhesive (7) and conductive particles. The method according to any one of Claims 15 to 17, wherein the adhesive (7) is a thermosetting adhesive and said driving element (1) is heated while being pressed by the bonding tool to fix said driving element (1) to said second substrate (2) with the adhesive (7). The method according to any one of Claims 15 to 17, wherein the adhesive (7) is a thermosetting adhesive and the adhesive is heated by applying light to the adhesive while pressing said driving element (1) by the bonding tool to fix said driving element (1) to said second substrate (2) with the adhesive. The method according to any one of Claims 15 to 17, wherein the adhesive (7) is a photosetting adhesive and the adhesive is cured by applying light to the adhesive while pressing said driving element (1) by the bonding tool to fix said driving element (1) to said second substrate (2) with the adhesive. The method according to claim 10, wherein the bonding tool (4) that presses the fifth main surface overlaps said driving element (1) . The method according to claim 10, wherein the bonding tool presses the fifth main surface of said driving element (1) after providing a polarizing plate (11) on the first main surface so that the thickness of said driving element (1) is larger than the sum of the thickness of said first substrate (3) and the thickness of said polarizing plate (11). An electronic apparatus comprising a liquid crystal device of any one of Claims 1 to 8.

Inventors: ENDOU KOUGO, UCHIYAMA KENJI, ENDOU, KOUGO, UCHIYAMA, KENJI, Endou, Kougo, c/o Seiko Epson Corporation, Uchiyama, Kenji, c/o Seiko Epson Corporation
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1997
Main classification: G02F1
IPC codes: G02F1, G09F9