JP2003270657A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the packaging reliability of a drive IC against the bending deflection of a casing. <P>SOLUTION: The drive IC 5 has a rectangular shape, and is installed so that the long side direction (b) of the tabular casing 1 in which the casing 1 tends to be bent is orthogonal to the long side direction (a) of the IC 5. Furthermore, the plastic liquid crystal cell of a plastic substrate is adopted or polymer-dispersed liquid crystal is used as a liquid crystal cell, thereby the liquid crystal display device which is thinner and resistant to the bending deflection is obtained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device in which a liquid crystal cell is mounted in a flat case such as an IC card, and more particularly to the arrangement structure of each member and the liquid crystal cell configuration, and more specifically to the case. And a layout structure of a liquid crystal cell and an integrated circuit (hereinafter referred to as a driving IC) for driving the liquid crystal cell,
It relates to a liquid crystal cell configuration.

[0002]

2. Description of the Related Art IC in which an IC is mounted in a card-shaped housing
With the spread of cards, it has been required to equip an IC card with a display function. Since the housing of the IC card is thin and flat and made of resin, it easily bends, and a thin and flexible display body is required as a display body having a display function. By the way, the thickness of the IC card is about 0.8 mm, so the total thickness of the case is about 0.4 mm.
In this case, the total thickness of the liquid crystal cell mounting circuit board and the liquid crystal cell is about 0.4 mm.

A driving IC is required to drive a liquid crystal cell. However, it is necessary to incorporate a driving circuit required for the driving IC of the liquid crystal cell into the main IC of the IC card in the design, evaluation process and manufacturing process. This leads to a cost increase such as a long period of time and an increase in IC area, and causes many adverse effects. Therefore, the main IC of the IC card and the driving IC of the liquid crystal cell are separated. In addition to the electrode driving circuit of the liquid crystal cell, this driving IC has functions necessary for driving the liquid crystal cell, such as a Zener diode for limiting the high voltage, a power source for driving the liquid crystal cell, and an oscillation circuit.

While the driving IC needs to have a small area, it requires a large number of terminals for driving each pixel. Therefore, in order to secure a large number of places for arranging the connection terminals with respect to the area, the outer shape of the driving IC is often flat and rectangular. In the driving IC, bumps are formed on the connection terminals, the bump surface and the circuit board are opposed to each other, and electrical continuity is established via an anisotropic conductive film (also called ACF, anisotropic conductive film).

[0005]

As described above, the housing of the IC card is thin and flat, and is made of resin, so that it is easily bent. If this bending is large, the driving IC
Also, a force is applied to the drive IC, and the drive IC is largely deformed, causing a problem that the drive IC is peeled off or damaged from the circuit board. It is an object of the present invention to solve such problems and improve the mounting reliability of the driving IC against bending deformation of the housing.

[0006]

A liquid crystal display device in which a liquid crystal cell and a driving IC for driving the liquid crystal cell are mounted inside a flat housing, and the driving IC is also flat.
The driving IC is installed so that the longitudinal direction of the housing and the longitudinal direction of the driving IC are substantially orthogonal to each other. Further, the liquid crystal cell is also rectangular, the longitudinal direction of the liquid crystal cell and the longitudinal direction of the housing are substantially parallel, and the longitudinal direction of the liquid crystal cell and the longitudinal direction of the driving IC are orthogonal to each other.

The substrate of the liquid crystal cell is preferably plastic, and the liquid crystal of the liquid crystal cell is preferably a polymer dispersion type liquid crystal. Further, it is preferable that the display area of the liquid crystal cell is a matrix type liquid crystal cell divided into upper and lower parts, and electrode connection terminals for connecting to a driving IC are provided on the long side of the liquid crystal cell.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A flat housing, which has a rectangular parallelepiped shape when viewed from the top, has a characteristic of bending in the longitudinal direction in a flexible housing. Since the driving IC does not have flexibility, if the longitudinal direction of the driving IC is set in the same direction as the longitudinal direction of the housing, that is, if the longitudinal direction of the driving IC is bent, the housing is bent and the longitudinal direction of the driving IC is also increased. The driving IC was peeled from the circuit board due to the applied force, and the driving IC was damaged. However, the longitudinal direction of the driving IC, that is, the long side of the driving IC is perpendicular to the longitudinal direction of the housing. If it is installed on the drive IC, it is possible to prevent an excessive force from being applied to the driving IC. That is, the direction in which the housing easily bends and the drive I
By disposing the short sides of C in parallel, it is possible to prevent deformation of the driving IC.

Further, when a liquid crystal cell of a glass substrate is adopted as a display member provided in a flexible housing, the glass substrate has almost no flexibility, so that it is weak in bending deformation and easily damaged. Therefore, it is effective to use a liquid crystal cell (hereinafter referred to as a plastic liquid crystal cell) using a film-shaped plastic substrate having flexibility because the substrate has flexibility. Further, the plastic liquid crystal cell is suitable for an IC card or the like having a limited thickness because it can be easily made thinner than a liquid crystal cell using a glass substrate.

Further, a general twist nematic (hereinafter referred to as TN) type liquid crystal cell requires a polarizing plate.
A liquid crystal cell that does not use a polarizing plate is preferable for application to an IC card having a limited thickness. Guest-host type liquid crystal cells and cholesteric liquid crystal cells have long been known as such liquid crystal cells, but in recent years, polymer network liquid crystal (also called polymer dispersed liquid crystal,
A cell referred to as PN liquid crystal hereinafter) has been put to practical use. PN
The liquid crystal has a scattering mode and a transmission mode, becomes pure white in the scattering mode, can display a color tone similar to paper, and can obtain good display quality. Therefore, it can be said that the liquid crystal cell using the PN liquid crystal is suitable for an IC card having a limited thickness.

[0011]

EXAMPLE 1 The structure of the present invention will be described with reference to FIGS. 1 and 2. In FIG. 1, (a) is a plan view of the housing,
(B) is a perspective view of a disassembled case. FIG. 2 is a circuit diagram of the liquid crystal cell and the driving IC.

In this embodiment, a plastic liquid crystal cell is used as the liquid crystal cell and a PN liquid crystal is used as the liquid crystal. Figure 1
(A) is a plan view of the housing, and is installed so that the plastic liquid crystal cell 4 can be seen. FIG. 1B is a perspective view in which a housing, which is an integrally molded product of resin, is disassembled into an upper side 1 and a lower side 7. Here, the thickness of the internal circuit board 3 is ignored. A rectangular window 2 is opened on the upper side 1 of the housing so that the plastic liquid crystal cell 4 can be seen. On the circuit board 3,
A plastic liquid crystal cell 4, a driving IC 5, and a main IC 6 that mainly performs logical processing of an IC card are mounted. The lower side 7 of the housing is a flat plate.

In addition to the plastic liquid crystal cell 4, the driving IC 5 and the IC 6, electronic components such as capacitors and diodes are mounted on the circuit board 3 of FIG. 1 (not shown).
The outer shapes of the circuit board 3 and the upper side 1 of the housing are rectangular and have substantially the same shape. The circuit board 3 is a resin film. IC card is I
Since power and signals are exchanged magnetically with the read / write device of the C card, the circuit board 3 has an antenna (not shown) instead of a connector.

The features of the arrangement of the members will be described. The short side of the rectangular drive IC 5 is parallel to the long side of the housing. That is, the driving IC 5 is installed so that the longitudinal direction a of the driving IC 5 and the longitudinal direction b of the housing are orthogonal to each other. The long side of the plastic liquid crystal cell 4 and the long side of the circuit board 3 are parallel to each other, and the short side of the plastic liquid crystal cell 4 and the driving IC 5 are
The long sides of are parallel and close.

The circuit and structure relating to the plastic liquid crystal cell 4 will be described with reference to FIG. FIG. 2A is a circuit diagram when the liquid crystal cell 4 has 18 pixels. The input terminal 201 of the driving IC 5 is an input terminal for a signal output from a power supply terminal or a central processing circuit (hereinafter referred to as CPU) installed in the IC 6 of FIG. The 18 output terminals of the driving IC 5 are connected to the plastic liquid crystal cell 4 via the wiring 203.
Signal electrode (not shown), and one output terminal of the driving IC 5 is connected to the common electrode (not shown) via the wiring 202.
To the connection terminal 208. In the display area 207, the intersection of the signal electrode and the common electrode is a pixel. The display area 207 is filled with PN liquid crystal.

The wirings 202 and 203 are formed of ITO on the back surface of the upper substrate of the plastic liquid crystal cell 4 and are connected to each other through an anisotropic conductive film. Wiring 202
Is connected to the common electrode on the lower substrate 205 in the seal 206 via the connection terminal 208 in the upper right corner. In the static driving method in which each pixel is driven individually, the signal electrode of each pixel needs to be drawn out to the outer peripheral portion of the plastic liquid crystal cell 4. Therefore, assuming a case where the number of pixels is large, a connection terminal is provided to facilitate drawing. 208 are arranged on the upper and lower long sides of the plastic liquid crystal cell.

The driving IC 5 will be described in more detail with reference to FIG. When the magnetic flux B1 changes, the antenna A1 generates a voltage, and this voltage is rectified by the diode D1 and the capacitor C1 in the driving IC 5 to obtain the high voltage VEE. The Zener diode D2 is for limiting the electromotive force of the antenna A1 so as not to become too high. Driving IC
Within 5, the regulator circuit 212 creates a stable low voltage VDD from the voltage VEE. Capacitor C
Reference numeral 2 is for stabilization, and the plastic liquid crystal cell can be driven for a while even if the change in the magnetic field B1 disappears. The voltage VDD is the oscillation circuit OSC and the control circuit 210.
It can be used as a power source for the main IC 6 of FIG. The control circuit 210 creates drive waveforms for the signal electrode and the common electrode from the display data received from the CPU and the clock signal input from the oscillation circuit OSC. This drive waveform is converted into a square wave having the maximum value of the voltage VEE by the voltage conversion circuit 211, and each signal electrode seg and the common electrode c are converted.
output to om.

FIG. 2C shows the output waveform of the voltage conversion circuit 211. Regarding the common electrode drive waveform COM, the signal electrode waveform SEGon of the ON display pixel, and the signal electrode waveform SEGoff of the OFF display pixel, the highest value is the voltage VEE and the lowest value is the voltage 0.
It is a square wave of V (ground level). Signal electrode waveform SEGon of ON display pixel with respect to common electrode drive waveform COM
Are in reverse phase. At this time, a large voltage (effective value) is applied to the pixel to turn it on. On the contrary, with respect to the common electrode drive waveform COM, the signal electrode waveform SEGof of the off display pixel
f is in phase. At this time, the pixel voltage (effective value)
Is not applied and the display is turned off. In the case of a PN liquid crystal, it is general that it is turned on at about 5 V or more, but if it is desired to increase the whiteness at the time of turning off, it is necessary to thicken the liquid crystal layer, and therefore it is necessary to turn on at a high voltage. High voltage
It can be relatively easily obtained by increasing the number of windings of the antenna A1.

Since the plate-like housing is rectangular, it is easy to bend in the long side direction and difficult to bend in the short side direction. Since the direction in which the housing is easily bent and the short side of the driving IC 5 are parallel to each other, the driving IC 5 is hardly deformed even when the housing is largely bent in the long side direction. On the other hand, the rectangular driving IC 5 is easily bent on the long side, but since this direction is parallel to the short side of the housing, I
It is difficult to deform as a whole C card. In addition, since the short side of the plastic liquid crystal cell 4 is also strong against bending, the driving IC 5 adjacent thereto is also protected by the plastic liquid crystal cell 4 from bending due to external force.

(Embodiment 2) An embodiment in which the long side of the plastic liquid crystal cell and the short side of the housing are installed in parallel in FIG. 3 will be described. FIG. 3 is a plan view of the circuit board inside the housing, in which the driving IC 302 and the driving IC 302 are provided on the circuit board 300.
Plastic liquid crystal cell 303 and the main I of the IC card
C304 is installed. Further, a reinforcing member 301 is arranged on the upper side of the circuit board 300. Circuit board 300
The outer shape of the housing (not shown) is substantially the same as that of the first embodiment, and the long side of the plastic liquid crystal cell 303, that is, the longitudinal direction and the short side of the housing are parallel. That is, the plastic liquid crystal cell 303 is installed so that the longitudinal direction of the housing and the longitudinal direction of the plastic liquid crystal cell 303 are perpendicular to each other.

However, the longitudinal direction of the housing and the driving IC 30
The longitudinal direction of 2 is installed vertically. The short side direction of the housing is harder to bend than the long side, and is further hard to bend by the reinforcing member 301. Therefore, when an external force is applied to the IC card, the long side direction of the housing bends to absorb the external force, and the long side of the driving IC 302 is protected from bending deformation.

[0022]

As is clear from the above description, when a flexible liquid crystal cell is mounted in a flexible flat plate-like casing, the driving IC is formed in a rectangular shape and the casing is easily bent. If the short sides of this drive IC are made parallel, the drive IC
Becomes less susceptible to the bending deformation of the housing. Therefore, the driving IC is less likely to be peeled off or broken, and therefore the present invention has an effect of improving the mounting reliability of the driving IC against bending deformation of the housing. Also, by using PN liquid crystal as the liquid crystal cell or by using a liquid crystal cell of a plastic substrate, the total thickness of the circuit board for mounting the liquid crystal cell and the liquid crystal cell can be suppressed to about 0.4 mm, and the total housing If the thickness is about 0.4 mm, the thickness of the IC card is about 0.8.
It can be mm.

[Brief description of drawings]

1A is a plan view of a housing according to the present invention, and FIG. 1B is a perspective view of an exploded housing.

FIG. 2 is a circuit diagram around a plastic liquid crystal cell and a driving IC adopted in the present invention.

FIG. 3 is a plan view of a housing according to the present invention.

[Explanation of symbols]

1 Upper side of the housing 2 windows 3 circuit board 4 plastic liquid crystal cell 5 Driving IC 6 IC

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09F 9/00 346 G09F 9/30 310 5G435 9/30 310 9/35 9/35 G06K 19/00 J F term (reference) 2H089 HA04 HA40 JA10 KA17 NA58 QA02 QA16 TA01 TA02 TA07 UA09 2H090 JB03 JC04 JD13 KA11 LA01 LA04 2H092 GA48 GA50 NA11 PA01 PA06 QA15 5B035 AA08 BA05 BB09 CA03 CA06 CA07 5C094 AA15 AA36 AA48 AA56 BA43 BA48 DA06 DA20 DB10 FA01 HA10 5G435 AA07 AA18 BB13 EE32 EE37 EE40 LL00

Claims (5)

[Claims] 1. In a liquid crystal display device in which a liquid crystal cell and a driving IC for driving the liquid crystal cell are mounted inside a flat housing, the driving IC has a rectangular shape and a longitudinal direction in the housing. A liquid crystal display device, wherein the driving IC is installed such that a longitudinal direction of the driving IC and a longitudinal direction of the driving IC are substantially orthogonal to each other. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal cell is a plastic liquid crystal cell whose substrate is plastic. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal of the liquid crystal cell is a polymer dispersion type liquid crystal. 4. The liquid crystal display device according to claim 1, wherein the housing is an IC card. 5. The liquid crystal display device according to claim 1, wherein a reinforcing material is provided on a short side of the housing.