JP2004020927A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a miniature high-definition liquid crystal display, with a lowered rejection rate during manufacture, in which groups of opposite terminals are connected to each other by way of an anisotropic electrically conductive layer containing electrically conductive particles dispersed in a resin, stable electric conductivity is ensured between the opposite terminals, a resistance change, a capacitance change and a short circuit are suppressed between the adjacent terminals even when the interval between the terminals is narrowed, and actuation is stabilized. <P>SOLUTION: The particle diameter D of the electrically conductive particles 1 is adjusted to 1 μm to 1/3 of the interval Ws between adjacent ones of groups 18B, 18C of terminals. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device using an anisotropic conductive material for connection between opposing terminals and capable of obtaining stable electric characteristics.
[0002]
[Prior art]
2. Description of the Related Art A liquid crystal display device is often used for a display unit of a video device, a personal computer, a portable information terminal, or the like. Conventionally, in these liquid crystal display devices, a conductive rubber is used as a means for connecting a large number of liquid crystal terminals arranged adjacently to the periphery of a liquid crystal substrate at a fine interval and a driving terminal facing the liquid crystal terminals on a one-to-one basis. Many connectors and film connectors have been used, but in recent years conflicting demands have been made for further refinement of the liquid crystal display, a larger screen and a smaller and thinner device, or more efficient manufacturing operations. In order to satisfy demands such as cost reduction and cost reduction, a COG (Chip on glass) or an FPC (Flexible Print Circuit) in which a liquid crystal driving IC is mounted on a tape carrier is connected to the terminal group as a connection means between the terminals. Technologies such as TCP (Tape Carrier Package) have rapidly spread. On the other hand, in the configuration of the liquid crystal display unit, the size of the liquid crystal layer is increased and reduced due to demands such as miniaturization of equipment, improvement of space efficiency, reduction of the number of driving ICs, rationalization of mounting work, and cost reduction. A system in which circuit terminals of both substrates are concentrated on only one of the liquid crystal substrates has begun to be adopted. In this case, there is a need for a technique for directly connecting terminal groups provided opposite to both substrates separated by a predetermined gap formed by a liquid crystal seal while maintaining the gap. Anisotropic conductive materials are often used as a means for connecting a large number of terminals arranged adjacent to one another at a fine interval in a vertical direction and maintaining the insulation with high reliability between adjacent terminals. ing.
[0003]
FIG. 8 schematically shows a configuration of a terminal connecting portion using a conventional anisotropic conductive material. In FIG. 8, terminal groups 103,..., 104. Adjacent terminals on each substrate are arranged at a terminal interval Ws so as not to contact each other. This terminal interval Ws is usually set to about 1/2 of the terminal pitch P. An anisotropic conductive layer 105 is interposed between the two substrates 101 and 102. In the anisotropic conductive layer 105, conductive particles 107 are dispersed in an adhesive resin base material 106 at an appropriate ratio. When the anisotropic conductive layer 105 is pressed from above and below while being sandwiched between the two substrates 101 and 102, the conductive particles 107a sandwiched between the opposing terminals 103 and 104 among the conductive particles 107. The terminals 103 and 104 are crimped to the upper and lower terminals to electrically connect the terminals 103 and 104 facing each other. At this time, the conductive particles 107a are compressed by the upper and lower terminals and slightly deformed as shown in FIG. 8, or the conductive particles press the contact surface of the terminal to partially press-fit the terminal surface, or By both, the contact area with the terminal is increased, and substantial conduction is achieved. On the other hand, the conductive particles 107b dispersed in the portion of the terminal interval Ws are electrically isolated because they are not in contact with each other and do not contact the terminals. In other words, when the anisotropic conductive layer 105 is compressed by being sandwiched between conductors, it becomes conductive in the direction of the terminal (vertical direction) facing the terminal, but becomes non-conductive in the direction of the adjacent terminal (horizontal direction). is there. This technique is simple and highly reliable as a means for directly connecting a large number of terminal groups arranged at close intervals directly and collectively, and is widely applied to connection of various terminal groups of a liquid crystal display device.
[0004]
For example, Japanese Patent Application Laid-Open No. Hei 1-237520 uses an anisotropic conductive layer for connection between a power supply terminal group of a liquid crystal substrate and an FPC on which a driving IC is mounted. Japanese Patent Application Laid-Open No. Hei 5-249483 discloses a method for preventing a problem such as poor connection between terminals from being caused by a variation in the particle size of conductive particles or a variation in conditions at the time of pressure bonding. It has been proposed to use an anisotropic conductive material in which conductive particles and non-conductive spacers are mixed when performing a so-called common transition in which the electrode wiring is transferred from one side of the substrate to the other side. Further, International Publication WO99 / 52011 proposes the use of an anisotropic conductive material containing conductive particles as a part of a liquid crystal seal provided around a liquid crystal layer when performing the common transition.
[0005]
[Problems to be solved by the invention]
However, as the liquid crystal display screen becomes more color, higher definition, and larger screen, and it becomes necessary to arrange a large number of circuit terminals in a limited space, a fine pitch of the terminal row is inevitably required. As a result, the width of the terminal indicated by the symbol Wt in FIG. 8 and the distance between adjacent terminals indicated by the symbol Ws are greatly reduced as compared with the conventional art, and accordingly, various problems occur in the conventional anisotropic conductive material. Was. That is, as seen in recent high-definition color liquid crystal display devices, when the terminal pitch indicated by reference symbol P in FIG. 8 is reduced to about 10 μm to about 50 μm, the dispersed state of the conductive particles 107 in the anisotropic conductive layer 105 is changed. Even if it is slightly deviated, the number of conductive particles 107 sandwiched between the upper and lower terminals and contributing to conduction greatly changes between adjacent terminals, as schematically shown in state A of FIG. In some cases, the conductive resistance varies between the 104 terminals, and as shown in the state B, the conductive particles are not substantially distributed between the upper and lower terminals, and the conductive particles become nonconductive or have high resistance. Further, as shown in the state C, the conductive particles protruding from the terminal side end substantially narrow the terminal interval Ws as shown by the symbol Wr, and change the electric resistance and the capacitance between the adjacent terminals. In some cases, as shown by D, the conductive particles were connected in a chain and caused a short circuit between adjacent terminals. In particular, in a multi-tone color matrix liquid crystal display, since a drive waveform containing an extremely high frequency component is applied to each pixel electrode, there is a small amount of continuity between upper and lower terminals, insulation resistance between adjacent terminals, capacitance, and the like. The change has made the operation of the liquid crystal display device unstable, resulting in a defective product, which has been a cause of lowering the production yield. Further, when this anisotropic conductive layer 105 is used as a liquid crystal seal, the conductive particles 107c also serving as spacers of the liquid crystal seal expand in response to a change in temperature due to a change in environmental temperature, for example, as shown in a state E of FIG. Or, when the contraction occurs, the gap G of the liquid crystal layer 108 expands or contracts, and in any case, the operation of the liquid crystal display unit becomes unstable.
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and accordingly, it is an object of the present invention to obtain a stable connection even when the arrangement of the terminal groups is reduced, with respect to the connection of the terminal groups using an anisotropic conductive material. It is to provide a liquid crystal display device.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention is a liquid crystal display device in which opposing terminal groups are connected to each other via an anisotropic conductive layer in which conductive particles are dispersed in a resin, Provided is a liquid crystal display device in which a particle diameter is 1/3 or less of an interval between adjacent terminals and 1 μm or more.
[0007]
If the particle size of the conductive particles is set to be 1/3 or less of the distance between adjacent terminals, even if the dispersed state of the conductive particles is biased to some extent, the conductive particles are sandwiched between the opposing terminals and contribute to conduction. Does not change at a large ratio, so that the variation of the conduction resistance between the opposite terminals is reduced. In addition, since the conductive particles protrude from the terminals, the gap between the adjacent terminals is substantially narrowed, so that the possibility of changing the electric resistance or capacitance or the possibility of short-circuiting the adjacent terminals in a chain is greatly reduced. Further, when the anisotropic conductive layer is used as a spacer of the liquid crystal display, the possibility that the gap fluctuates due to temperature fluctuation or the like and the operation of the liquid crystal display becomes unstable is minimized. However, when the particle size of the conductive particles is less than 1 μm, the conductive particles are buried in the terminal surface due to the concave portions caused by the roughness of the terminal surface or the terminal surface being depressed by the conductive particles, thereby making connection. Substantial effects as an anisotropic conductive layer are lost, such as loss of function and difficulty in producing the particles themselves.
[0008]
It is preferable that the compounding ratio of the conductive particles dispersed in the anisotropic conductive layer is in the range of 0.5% by weight to 3.5% by weight.
When the mixing ratio is within the above range, a sufficient amount of the conductive particles is distributed between the opposed terminals, and practical conduction is achieved. In particular, there is no possibility that the conductive particles are not distributed between the opposing terminals and become non-conductive. If the conductive particles are less than 0.5% by weight, the average number of particles distributed between the opposed terminals decreases, and the conduction resistance increases and the irregularity of the conduction resistance increases. If the content exceeds 3.5% by weight, chains of particles are likely to occur in the plane direction, lowering the insulation resistance between adjacent terminals, increasing the capacitance, and sometimes causing a short circuit, which is not preferable.
[0009]
The anisotropic conductive layer may contain a non-conductive spacer. In this case, the particle size of the conductive particles is preferably larger than the particle size of the spacer in the range of 0.02 μm to 0.5 μm.
If the anisotropic conductive layer contains a non-conductive spacer, when the anisotropic conductive material is sandwiched between the opposing terminals and pressed, a certain thickness corresponding to the particle size of the spacer is applied between the terminals. As a result, the electrical characteristics and the temperature characteristics between the terminals are stabilized. In particular, when performing a common transition in a liquid crystal display portion, when the anisotropic conductive layer is used as at least a part of a liquid crystal seal provided between two opposing liquid crystal substrates surrounding the liquid crystal layer, the spacer becomes This defines the gap between the two liquid crystal substrates. At this time, since a material having a small expansion and contraction due to a temperature change can be selected as the spacer, a stable liquid crystal display unit with a small gap fluctuation even when the temperature changes can be obtained. If the particle size of the conductive particles is set to be larger than the particle size of the spacer in the range of 0.02 μm to 0.5 μm, the conductive particles are pressed flat within the width of the gap defined by the spacer, or The conductive particles are pressed into the surface of the terminal or both of them, so that the contact area with the terminal can be increased and good conduction can be secured. If the difference in particle size between the conductive particles and the spacer is less than 0.02 μm, the contact area between the terminal and the conductive particles may not be sufficiently secured. Large, the conductive particles may define the gap width, and the spacer may not be able to define the gap width.
[0010]
In the liquid crystal display device of the present invention, one of the opposed terminal groups may be formed on a liquid crystal substrate and the other may be formed on an external substrate. Further, each of the opposing terminal groups may be formed on an inner surface of a liquid crystal substrate opposing the liquid crystal layer.
That is, one of the opposing terminal groups is a terminal group extending from a pixel electrode formed on the liquid crystal substrate of the liquid crystal display portion, and the other is, for example, a terminal group formed on an FPC mounted with a liquid crystal driving IC. May be. Also, for example, when performing a common transition in the liquid crystal display portion, opposing terminal groups are formed on the inner surface of the liquid crystal substrate that opposes the liquid crystal layer, and a spacer is preferably included between these terminal groups. By interposing the anisotropic conductive layer, the anisotropic conductive layer also serves as a liquid crystal seal while ensuring conduction between the opposing terminal groups.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to specific examples, but these specific examples do not limit the present invention at all. Also, the accompanying drawings are for explaining the idea of the present invention, and elements unnecessary for the description of the present invention are omitted, and the shapes, dimensional ratios, numbers, etc. of the illustrated elements are not necessarily the actual ones. Not a match.
[0012]
(Embodiment 1)
1 is a plan view showing a liquid crystal display unit according to the present embodiment, FIG. 2 is a plan view showing an enlarged view of a portion P in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. It is. In the liquid crystal display device of the present embodiment, the wiring of the liquid crystal display portion is concentratedly arranged on one liquid crystal substrate by common transition. In the liquid crystal display section 10, a liquid crystal layer 14 is formed between two transparent liquid crystal substrates, that is, a common substrate 11 and a segment substrate 12, and a liquid crystal layer 14 is provided around the liquid crystal layer 14 so that liquid crystal does not leak. A liquid crystal seal 13 having a predetermined thickness G is formed so as to keep the gap, that is, the gap between the substrate 11 and the segment substrate 12 constant. One side of the segment substrate 12 is extended to form a shelf-shaped terminal portion 17.
[0013]
Pixel electrodes 18 and 19 for driving the liquid crystal are arranged in a matrix on opposing inner surfaces of the common substrate 11 and the segment substrate 12, respectively. The wirings 18A and 19A extend around the inside of the liquid crystal seal 13 and the periphery of the liquid crystal layer 14 in a non-contact manner, and are arranged intensively on one side of the liquid crystal seal 13. The wires 18A formed on the common substrate 11 are inserted so that their terminals are parallel to the contact surface between the common substrate 11 and the liquid crystal seal 13 to form common terminals 18B. On the other hand, common lead terminals 18C are formed at positions on the segment substrate 12 opposite to the common terminals 18B with the liquid crystal seal 13 interposed therebetween, and the terminals extend to the terminal portions 17 of the segment substrate. The terminals of the wirings 19A formed on the segment substrate 12 pass through the liquid crystal seal 13 and extend to the terminal portions 17 of the segment substrate to form segment terminals 19B. The common terminal group 18B has a terminal width Wt of 20 μm, an interval Ws between adjacent terminals of 25 μm, and a terminal thickness of 0.2 μm.
[0014]
In the present embodiment, the liquid crystal seal 13 is made of an anisotropic conductive material. The liquid crystal seal 13 is formed by uniformly dispersing the conductive particles 1 in the adhesive resin 3. The mixing ratio of the conductive particles 1 dispersed in the liquid crystal seal 13 is 2.5% by weight. The resin 3 is made of an epoxy resin, and the conductive particles 1 are made of a gold-plated resin. The particle diameter D of the conductive particles 1 is 7 μm, which is about 1 / 3.5 times the terminal interval Ws (25 μm) in the common terminal group 18B.
[0015]
As shown in FIG. 3, in the portion of the liquid crystal seal 13 interposed between the opposed common terminal 18B and the common lead terminal 18C, the conductive particles 1 are formed between the common terminal 18B and the common lead terminal 18C during manufacturing. The terminal 18B, 18C is pressed by receiving the pinching pressure and deforms flat, or as described in the first embodiment, the conductive particles 1 press the upper and lower terminals 18B, 18C and partially press-fit the terminals 18B, 18C. The contact area with the conductive particles 1 is increased, and conduction between the upper and lower terminals via the conductive particles 1 is ensured.
[0016]
On the other hand, the conductive particles existing in the gap Ws between the adjacent terminals do not come into contact with any of the terminals, and are electrically isolated in the resin 3. As a result, the liquid crystal seal 13 in the present embodiment realizes anisotropy that conducts only between the opposing terminals. At the same time, the conductive particles 1 in the liquid crystal seal 13 also play a role as a spacer for defining a gap G between the common substrate 11 and the segment substrate 12. Among the conductive particles 1 in the liquid crystal seal 13, the particles sandwiched between the upper and lower terminals are pressed as described above and deform flat, but as shown in FIG. Has no terminals, the particle size of the conductive particles 1... Distributed in portions where no terminals are formed substantially forms a gap G between the common substrate 11 and the segment substrate 12.
[0017]
Thus, in the liquid crystal display device of the present embodiment, a stable gap is secured in the liquid crystal layer 14 and the terminals of all the pixel electrodes are aligned on the surface of the terminal portion 17 by the common transition. A configuration using an anisotropic conductive layer can be applied to connection between these terminal groups and, for example, the terminal group of a liquid crystal driving FPC.
[0018]
(Test Example 1)
Regarding the liquid crystal seal 13 of the present embodiment, the ratio (D / Ws) between the particle diameter D of the conductive particles 1 and the terminal interval Ws, and the mixing ratio (% by weight) of the conductive particles 1 dispersed in the liquid crystal seal 13 are shown. With various changes, the rate of occurrence of gap unevenness in each case was measured. FIG. 4 shows the results.
As shown in FIG. 4, when the ratio (D / Ws) between the particle diameter D and the terminal interval Ws is set to 1/3 (0.33) or less, the practical mixing ratio of the conductive particles, that is, the upper and lower opposed particles The occurrence rate of gap unevenness can be suppressed within an allowable range of 0.5% or less within a range (0.5% by weight to 3.5% by weight) within which sufficient conduction between terminals can be obtained.
[0019]
(Embodiment 2)
FIG. 5 is a plan view showing a liquid crystal display unit according to the present embodiment, and FIG. 6 is a cross-sectional view taken along line CC of FIG. The liquid crystal display of this embodiment is substantially the same as that of the first embodiment except that the configuration of the liquid crystal seal 13 is different. Therefore, here, only the configuration of the liquid crystal seal 13 in the present embodiment will be described in detail.
[0020]
In the liquid crystal seal 13 of this embodiment, the conductive particles 1 and the spacers 2 are uniformly dispersed in the adhesive resin 3. The conductive particles 1 are made of gold-plated resin, and the compounding ratio of the conductive particles 1 dispersed in the liquid crystal seal 13 is 2.5% by weight. The particle diameter D of the conductive particles 1 is 7 μm, which is about 1 / 3.5 times the terminal interval Ws (25 μm) in the common terminal group 18B.
[0021]
As shown in an enlarged perspective view of FIG. 5, the spacer 2 of the present embodiment is made of a cut piece of glass fiber or an inorganic bead having a defined cross-sectional diameter, and a liquid crystal seal 13 is provided between the common substrate 11 and the segment substrate 12. When formed, the cross-sectional diameter of the spacer 2 defines the gap G of the liquid crystal layer 14. In the liquid crystal seal 13 of the present embodiment, the particle diameter D of the conductive particles 1 is larger than the cross-sectional diameter of the spacer 2 by 0.35 μm. Therefore, in the portion where the liquid crystal seal 13 is sandwiched between the common terminal 18B and the common lead terminal 18C, the conductive particles 1 are flattened by the difference between the particle size and the cross-sectional diameter of the spacer 2, and the contact area with the upper and lower terminals is reduced. To ensure sufficient conductivity. Since the spacer 2 is made of a glass fiber which is hard and has a small coefficient of thermal expansion, even if the spacer 2 is pressed between the common substrate 11 and the segment substrate 12, the cross-sectional diameter does not substantially change due to a temperature change. The gap G of the liquid crystal layer 14 is kept constant. The thickness of each of the common terminal 18B and the common lead terminal 18C is 0.2 μm, which is extremely smaller than the gap G of the liquid crystal layer 14, so that the difference in thickness between the terminal portion and the non-terminal portion of the liquid crystal seal is practically ignored. be able to.
[0022]
(Test Example 2)
Regarding the liquid crystal seal 13 of Embodiment 2, the particle diameter D of the conductive particles, the cross-sectional diameter of the spacer, and the mixing ratio of the conductive particles and the spacer are not changed, and only the terminal interval Ws of the adjacent terminal is variously changed. The short-circuit occurrence rate of the adjacent terminal was measured. FIG. 7 shows the results. In FIG. 7, the horizontal axis represents the magnification of the terminal interval Ws with respect to the particle diameter D of the conductive particles (Ws / D, that is, the reciprocal of D / Ws).
As can be seen from FIG. 7, if the magnification of the terminal interval Ws with respect to the particle diameter D is 3 times or more (that is, D / Ws ≦）), the adjacent terminals at the mixing ratio at which sufficient conduction can be obtained between the upper and lower terminals. Can be suppressed within the allowable range of 0.1% or less.
[0023]
By using the liquid crystal seal of the present embodiment, sufficient conductivity between the upper and lower terminals in the common transition can be ensured, and resistance change, capacitance change and short circuit between adjacent terminals can be effectively suppressed, and temperature change Thus, a liquid crystal display device in which the gap of the liquid crystal layer is stable can be obtained.
[0024]
【The invention's effect】
In the liquid crystal display device of the present invention, since the particle size of the conductive particles in the anisotropic conductive layer sandwiched between the terminal groups arranged to face each other is set to 1/3 or less of the distance between adjacent terminals. In addition, while ensuring stable conductivity between opposing terminals, resistance change, capacitance change, and short-circuit between adjacent terminals are effectively suppressed, and at the time of common transition, fluctuation of the gap of the liquid crystal layer due to temperature change, etc. Is effectively suppressed, and a small and high-definition liquid crystal display device with a stable operation and a reduced defect occurrence rate during manufacturing can be obtained.
[Brief description of the drawings]
FIG. 1 is a plan view showing a liquid crystal display unit according to an embodiment of the present invention.
FIG. 2 is an enlarged plan view showing a portion P in FIG. 1;
FIG. 3 is a sectional view taken along line BB of FIG. 2;
FIG. 4 is a graph showing the relationship between the particle size of conductive particles and the rate of occurrence of gap unevenness.
FIG. 5 is a plan view showing a liquid crystal display section according to another embodiment of the present invention.
FIG. 6 is a sectional view taken along line CC of FIG. 5;
FIG. 7 is a graph showing the relationship between the particle size of conductive particles and the short-circuit occurrence rate of adjacent terminals.
FIG. 8 is a cross-sectional view illustrating a configuration of a terminal connecting portion using a conventional anisotropic conductive material.
FIG. 9 is a cross-sectional view showing various states of conductive particles in a conventional anisotropic conductive layer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Conductive particle 2 ... Spacer 3 ... Resin 10 ... Liquid crystal display part 11 ... Common substrate 12 ... Segment substrate 13 ... Liquid crystal seal 14 ... Liquid crystal layer 17 ... Terminal part 18 ... Pixel electrode, 18A ... Wiring, 18B ... Common terminal 18C: Common lead terminal 19: Pixel electrode

Claims (5)

A liquid crystal display device in which terminal groups facing each other are connected to each other via an anisotropic conductive layer in which conductive particles are dispersed in a resin,
A liquid crystal display device, wherein the particle size of the conductive particles is 1/3 or less of the distance between adjacent terminals and 1 μm or more. The liquid crystal display device according to claim 1, wherein the compounding ratio of the conductive particles dispersed in the anisotropic conductive layer is in a range of 0.5% by weight to 3.5% by weight. . The said anisotropic conductive layer contains a non-conductive spacer, and the particle diameter of the said conductive particle is larger than the particle diameter of the said spacer in the range of 0.02 micrometer-0.5 micrometer, The Claims characterized by the above-mentioned. The liquid crystal display device according to claim 1. 4. The liquid crystal display device according to claim 1, wherein one of the opposed terminal groups is formed on a liquid crystal substrate, and the other is formed on an external substrate. 5. 4. The liquid crystal display device according to claim 1, wherein each of the terminal groups facing each other is formed on an inner surface of a liquid crystal substrate facing each other with a liquid crystal layer interposed therebetween. 5.

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