JP2002072184A - Liquid crystal display - Google Patents

Abstract

(57) [PROBLEMS] To reduce the display characteristics of a liquid crystal display panel and the operating characteristics of an input device in a liquid crystal display device having a transparent body such as a touch panel provided on the front surface, using a general-purpose material for the transparent body. Without interfacial reflection and good visibility. SOLUTION: Opposing rear substrate 12 and front substrate 14,
The liquid crystal 1 sandwiched between the rear substrate 12 and the front substrate 14
5, the phase difference plate 17 sequentially provided on the front surface of the front substrate 14
In the liquid crystal display panel 10 including the liquid crystal display panel 10 and the polarizing plate 18, and the ECB mode liquid crystal display device 1 including a transparent body such as the touch panel 2 provided on the front surface of the liquid crystal display panel 10, the front substrate 14 and the phase difference plate 17 An air layer 19 is provided therebetween, and the phase difference plate 17, the polarizing plate 18, and the transparent body 2 are laminated and adhered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ECB mode liquid crystal display device having a transparent body such as a touch panel and a protection plate provided on a front surface thereof.

[0002]

2. Description of the Related Art Reflective or transflective liquid crystal display devices have been used as display devices for mobile phones and personal digital assistants because of their excellent visibility in bright environments and can be driven with low power consumption.

When a liquid crystal display device is mounted on a display device such as a mobile phone or a portable information terminal, an input device typified by a touch panel and a transparent resin for protecting the liquid crystal display panel are provided on the front surface of the liquid crystal display panel. A transparent body such as a plate (protection plate) is provided. For example, as in a liquid crystal display device 1A shown in FIG. 2, a touch panel 2 is provided on a front surface of a liquid crystal display panel 10 in an ECB mode.

The liquid crystal display device 1A comprises a liquid crystal display cell 1 having a liquid crystal 15 sandwiched between a rear substrate 12 on which a reflective electrode 11 is provided and a front substrate 14 on which a transparent electrode 13 is provided.
6, a λ / 4 plate is attached as a retardation plate 17 on the front substrate 14 of the liquid crystal display cell 16, and a polarizing plate 18
To produce the liquid crystal display panel 10, and the touch panel 2 is arranged on the front surface of the liquid crystal panel 10 via the air layer 19.

[0005]

However, if a transparent body such as the touch panel 2 is provided on the front of the liquid crystal display panel, reflection and reflection of the image are caused by the interface reflection by the air layer 19 in the gap between the transparent body and the liquid crystal panel 10. Since the drop occurs, the visibility of the liquid crystal display device is significantly impaired.

Therefore, conventionally, an anti-reflection layer is provided on the front surface 10a of the liquid crystal display panel 10 or on the surface 2a of the transparent body (touch panel 2) facing the liquid crystal display panel 10 to prevent interfacial reflection. However, the formation of the antireflection layer causes an increase in the cost of the liquid crystal display device, and also causes a problem of coloring when the liquid crystal display device is viewed from an oblique direction.

In the case where the transparent body is an input device, there is a method of preventing the interface reflection by attaching the input device to the front of the liquid crystal display panel without placing an air layer (Japanese Patent Laid-Open No. 7-105).
No. 781). However, both the input device to be bonded and the liquid crystal panel are robust and have no flexibility, so that bonding is difficult. In addition, when the input device and the liquid crystal display panel are attached to each other, there is a problem that the image quality is greatly impaired due to the inclusion of bubbles at the time of attachment, and a press at the time of input with the input device is transmitted to the liquid crystal display panel, and the image fluctuates. The problem arises.

There is also a method of filling a transparent elastic body in the gap between the input device and the liquid crystal display panel (Japanese Patent Application Laid-Open No. 9-251159). According to this method, image fluctuation can be reduced. However, the difficulty of the operation of bonding the input device and the liquid crystal display panel has not been solved.

[0009] Even when the transparent body is a protective plate, the difficulty of the laminating operation and the problem of the inclusion of bubbles due to the lamination occur as in the case where the transparent body is an input device.

In order to facilitate the bonding of the transparent body and the liquid crystal display panel, it is conceivable to make the transparent body flexible. In this case, the original function of the protection plate to protect the liquid crystal panel is considered. Decrease.

On the other hand, as a method for improving the visibility while maintaining the gap between the transparent body and the liquid crystal display panel, when the transparent body is an input device, a polarizing plate constituting the liquid crystal display panel is attached to the front of the input device. According to this method, interface reflection can be suppressed. However, since the input device is formed of a transparent resin, usually,
Has birefringence. Therefore, according to this method, a decrease in contrast, coloring, or the like occurs, and on the contrary, the visibility decreases. Therefore, in this method, it is necessary to use a material having low birefringence as a constituent material of the input device. In addition, when the input device is a device requiring constant pressing, such as a resistance contact type touch panel, there is a problem that when a polarizing plate is attached to the front surface, operating characteristics such as operating force and linearity are reduced. .

A method has been proposed in which one of the pair of substrates constituting the input device serves as a phase difference plate so as not to lower the operating characteristics (Japanese Patent Laid-Open No. 11-13411).
No. 2). However, also in this case, it is necessary to use a material having low birefringence as a constituent material of the input device. Further, the input method of the input device is limited to a so-called resistance contact type touch panel.

In order to solve the problems of the prior art, the present invention uses an input device such as a touch panel, a liquid crystal display device provided with a transparent body such as a protective plate on the front surface, and uses a general-purpose material for the transparent body. The interface reflection is suppressed without deteriorating the display characteristics of the liquid crystal display panel and the operating characteristics of the input device at all,
The purpose is to obtain good visibility.

[0014]

SUMMARY OF THE INVENTION The present inventor has proposed a liquid crystal display device in which an input device such as a touch panel and a transparent body such as a protection plate are provided on the front surface of a liquid crystal panel. Is attached to the transparent body side instead of the liquid crystal cell, and an air layer is provided between the liquid crystal cell and the phase difference plate of the laminated body in which the retardation plate, the polarizing plate and the transparent body are laminated and adhered, and the air layer of the laminated body is provided. Reflection from the interface on the liquid crystal cell side and the interface on the air layer side of the liquid crystal cell can be significantly suppressed by the action of the retardation plate and the polarizing plate, and the presence of an air layer between the transparent body and the liquid crystal cell It has been found that the display characteristics of the liquid crystal display panel and the operation characteristics of the input device are not impaired.

That is, the present invention provides a liquid crystal display panel comprising a rear substrate and a front substrate facing each other, a liquid crystal sandwiched in a gap between the rear substrate and the front substrate, and a retardation plate and a polarizing plate sequentially provided on the front surface of the front substrate. , And a liquid crystal display device comprising a transparent body provided on the front surface of the liquid crystal display panel, wherein an air layer is provided between the front substrate and the retardation plate, the retardation plate, the polarizing plate, and the transparent body Provided is an ECB mode liquid crystal display device in which the layers are in close contact with each other.

Further, according to the present invention, a rear substrate and a front substrate are opposed to each other, and a liquid crystal is sandwiched between the two substrates to produce a liquid crystal display cell. A retardation plate, a polarizing plate, and a transparent body are laminated and adhered. A method for manufacturing an ECB mode liquid crystal display device, comprising the steps of: forming a laminate by the following steps: arranging the laminate so that the phase difference plate of the laminate faces the front substrate of the liquid crystal display cell via an air layer. I will provide a.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. In each of the drawings, the same reference numerals represent the same or equivalent components.

FIG. 1 is a cross-sectional view of a liquid crystal display device 1 according to one embodiment of the present invention provided with a touch panel 2 as a transparent body. In this liquid crystal display device 1, a rear substrate 12 on which a reflective electrode 11 is provided and a front substrate 14 on which a transparent electrode 13 is provided are opposed to each other, and a liquid crystal 15 is sandwiched between both substrates to produce a liquid crystal display cell 16. The process, the phase difference plate 17, the polarizing plate 18, and the touch panel 2 are laminated and adhered to each other to form a laminate 20.
And an ECB mode produced by a step of arranging the laminate 20 so that the retardation plate 17 of the laminate 20 faces the front substrate 14 of the liquid crystal display cell 16 via the air layer 19. The liquid crystal display device 1 is characterized in that an air layer 19 is provided between a liquid crystal display cell 16 and a laminate 20 including the touch panel 2.

Here, the liquid crystal display cell 16 itself is a known E
The liquid crystal display cell can be configured similarly to the liquid crystal display cell of the CB mode liquid crystal display device. For example, the liquid crystal layer forming the liquid crystal display cell 16 has approximately 1 /
It functions as a four-wavelength, zero-wave retardation plate, and is designed so that a phase difference of approximately λ / 2, 0 is generated during reciprocation of the liquid crystal layer.

The retardation plate 17 and the polarizing plate 18 are essential members for forming an image on the liquid crystal display panel 10, and constitute the liquid crystal display panel 10 together with the liquid crystal display cell 16. As the retardation plate 17 and the polarizing plate 18, those used in a known ECB mode liquid crystal display device can be used. For example, as the phase difference plate 17, the ellipticity of the elliptically polarized light emitted from the phase difference plate 17 is 0.7
A 波長 wavelength plate having a thickness of 1.0 or less can be used. More specifically, a polycarbonate, polyarylate, polysulfone, cycloolefin-based resin film is used as a raw material, and the retardation is 100 to 200 nm.
And a retardation plate having a retardation of 100 to 200 nm and a retardation plate having a retardation of 100 to 200 nm.
It may be composed of two 00 nm retardation plates.

The thickness of the air layer 19, that is, the gap between the phase difference plate 17 of the laminate 20 and the front substrate 14 depends on the size, thickness, rigidity and the like of the laminate 20, but is usually 0.3 mm. ~ 1.0
mm is preferable. In order to leave such a gap, for example, the phase difference plate 17 and the front substrate 14 may be bonded together with a double-sided adhesive tape having a predetermined thickness.

As the touch panel 2, for example, a resistance contact type touch panel, a capacitance type touch panel, an electromagnetic induction type touch panel and the like in which two transparent electrode substrates are opposed to each other via a spacer can be provided.

The liquid crystal display 1 has an external light L as shown by an arrow.
When 0 is incident, since the strongest interface reflection occurs at the interface with the air layer, strong interface reflection occurs at the interface between the phase difference plate 17 and the air layer 19 and at the interface between the front substrate 14 and the air layer 19. . By the way, the polarization direction when the reflected light L1 from the interface between the phase difference plate 17 and the air layer 19 is incident on the polarization plate 18 is determined by the action of the phase difference plate 17 when the external light L0 passes through the polarization plate 18. Are rotated by 90 ° with respect to the polarization direction of. Therefore, the reflected light L1 does not exit to the observer side, and does not impair the visibility and display characteristics of the liquid crystal display panel 10. Similarly, when the reflected light L 2 from the interface between the front substrate 14 and the air layer 19 is incident on the polarizing plate 18, the polarization direction of the reflected light L 2 is changed by the action of the retardation plate 17 to the external light L 0.
Is rotated by 90 ° with respect to the polarization direction when transmitted. Therefore, the reflected light L2 is not emitted to the observer side, and does not cause a decrease in visibility or a display.

When no voltage is applied, the liquid crystal layer becomes 1 /
Since this acts as a four-wavelength plate, when combined with the action of the retardation plate 17, of the external light L 0 incident on the liquid crystal display device 1, the light L 3 reflected on the reflection electrode 11 of the rear substrate 12
Means that the half-wave plate is reciprocally acted between the time when the light passes through the polarizing plate 18 and the time when the light enters the polarizing plate 18 again. After that, the polarization direction is not changed from that of the light incident on the polarizing plate 18 again, and the light incident on the polarizing plate 18 is emitted to the observer side, and white display is performed. On the other hand, when a voltage is applied, the liquid crystal layer does not function as a 波長 wavelength plate, and thus a black display is performed.

As described above, according to the liquid crystal display device 1, the strongest interface reflected light is prevented from being emitted to the observer side without forming an antireflection layer which increases the cost, and the visibility is improved. Can be improved. In addition, in the liquid crystal display device 1, since the interference of light is not used, unnecessary coloring from an oblique direction does not occur.
Furthermore, since a polarizing plate or a phase difference plate is not attached to the front surface of the touch panel 2, the influence of birefringence can be ignored, and the room for selecting materials for the touch panel 2 can be expanded.

The liquid crystal display device of the present invention can adopt various modes other than the mode shown in FIG. For example, as the transparent body, various members such as a touch panel and a protection plate made of a transparent material, which are not involved in the image forming mechanism of the liquid crystal display panel 10 itself, can be provided.

If necessary, a light-scattering layer may be formed, a light-scattering film may be adhered, an anti-glare treatment, etc. may be performed to provide a light scattering function between the layers or between the layers. Further, if necessary, an antireflection film may be formed on the front surface of the transparent body.

The liquid crystal display device of the present invention can be suitably applied to a liquid crystal display device using a reflection type liquid crystal display panel 10 in which a reflection electrode 11 is provided on a rear substrate 12 as shown in FIG. Alternatively, the present invention can be applied to a liquid crystal display device using a transflective liquid crystal display panel in which a transflective layer or a reflective layer with a transmissive window is provided on a rear substrate. In this case, a backlight may be provided behind the rear substrate.

Further, the liquid crystal display device of the present invention is particularly useful as a liquid crystal display device incorporated in a portable information terminal, a portable telephone, or the like. For example, as shown in FIG. 3, a mobile phone 30 having a display unit 31 formed of a liquid crystal panel, wherein a protective plate is provided on the liquid crystal display panel by a front case 32
And a portable information terminal 40 having a display section 41 with a touch panel as shown in FIG. The operation of the information terminal 40 itself and the control of optional devices such as a wireless telephone, a recording / reproducing function, and a digital camera function to be mounted on the portable information terminal 40 as necessary can be operated by the touch panel of the display unit 41. It is used as a liquid crystal display device of various devices such as a device.

[0030]

According to the present invention, in an input device such as a touch panel, a liquid crystal display device provided with a transparent body such as a protective plate on the front surface, a general-purpose material is used for the transparent body, and the display characteristics of the liquid crystal display panel can be improved. The interface reflection can be suppressed without deteriorating the operation characteristics of the input device at all, and good visibility can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal display device of the present invention.

FIG. 2 is a cross-sectional view of a conventional liquid crystal display device.

FIG. 3 is a perspective view of a mobile phone having a liquid crystal display panel with a protection plate.

FIG. 4 is a perspective view of a portable information terminal having a liquid crystal display panel with a touch panel.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... The liquid crystal display device of this invention, 2 ... Touch panel
0: liquid crystal display panel, 11: reflective electrode, 12: rear substrate, 13: transparent electrode, 14: front substrate, 15: liquid crystal, 16: liquid crystal display cell, 17: retardation plate, 18
... Polarizing plate, 19 ... Air layer, 20 ... Laminated body, 30 ... Mobile phone, 40 ... Portable information terminal

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 9/00 366 G09F 9/00 366A H04M 1/02 H04M 1/02 CA F term (Reference) 2H089 HA18 HA40 QA08 QA16 RA07 TA17 2H091 FA08X FA11X FA15Y FA31X FD06 HA09 LA03 LA16 5B087 AA02 AC15 CC02 CC12 CC13 CC14 CC33 5G435 AA01 BB12 BB15 DD11 FF01 FF03 FF05 GG21 HH02 LL07 5K023 AA07 BB07

Claims (6)

[Claims] 1. A liquid crystal display panel comprising a rear substrate and a front substrate facing each other, a liquid crystal sandwiched in a gap between the rear substrate and the front substrate, a retardation plate and a polarizing plate sequentially provided on the front surface of the front substrate, and the liquid crystal. A liquid crystal display device including a transparent body provided on a front surface of a display panel, wherein an air layer is provided between a front substrate and a retardation plate, and the retardation plate, the polarizing plate, and the transparent body are laminated and adhered. ECB mode liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein the transparent body is a touch panel or a protection plate. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal display panel is a transflective liquid crystal display panel in which a rear substrate has a transflective layer or a reflective layer with a transmissive window. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal display panel is a reflection type liquid crystal display panel having a rear substrate having a reflection electrode. 5. A process in which a rear substrate and a front substrate are opposed to each other and a liquid crystal is sandwiched between both substrates to produce a liquid crystal display cell, and a retardation plate, a polarizing plate, and a transparent body are laminated and adhered to form a laminate. A method for manufacturing an ECB mode liquid crystal display device, comprising: a manufacturing step; and a step of arranging a multi-layer body such that a phase difference plate of a laminate faces a front substrate of a liquid crystal display cell via an air layer. 6. The method for manufacturing a liquid crystal display device according to claim 5, wherein a touch panel or a protection plate is provided as the transparent body.