JPH09265094A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display element having an optical modulation layer having high backward scatterability of the optical modulation layer by laminating a first liquid crystal layer which is a first optical modulating means and a second liquid crystal layer which is a second optical modulating means. SOLUTION: Light is scattered by the refractive index difference between the ordinary ray refractive index of the liquid crystal material 105 in the first liquid crystal layer 101 and the refractive index of the constituting material of a translucent matrix and the most of the light is backward scattered. Part of the light not backward scattered is transmitted or forward scattered and is made incident on the second liquid crystal layer 102. Of the incident light on the second liquid crystal layer 102, nearly the half thereof is reflected by the reflection electrodes 112 disposed on the rear surface of the second liquid crystal layer 102 and is returned again to the first liquid crystal layer 101. The refractive indices of the transparent resin and the liquid crystals are both equal with respect to this polarized light and, therefore, the light is not scattered and is used all as the reflected light. Then, the most of the incident light is utilized as the reflected light and the bright display is obtd. in an off state.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display devices have the advantages of small size, thinness, and low power consumption. Therefore, display devices for personal computers, word processors, EWS, etc., display devices for calculators, electronic books, electronic notebooks, PDAs, It is used in various fields such as display devices such as mobile TVs, mobile phones, and portable facsimiles. In recent years, in particular, the use as a display device for portable information terminals is spreading.

Since the liquid crystal itself is a non-emissive type display element which does not emit light, some kind of light source is required to visually recognize the display.

A conventional liquid crystal display device is mainly of a transmissive type, that is, a flat type illumination device called a backlight is provided on the back surface of a liquid crystal panel. However, the backlight consumes a relatively large amount of power, which has been a major factor in hindering the low power operation which should be the original advantage of the liquid crystal display device.

A reflection type liquid crystal display device is a method in which a reflection plate for reflecting light is provided on the back surface of a liquid crystal panel and ambient light is reflected on the front surface to perform display. With this method, a backlight is not required, so that it is possible to significantly reduce power consumption.

Most of the liquid crystal display elements that have been put to practical use in the past are TN (Twisted Nematic) or STN (Super Twisted Nema).
tic) display mode is used. Each of the liquid crystal display elements of these display modes has two polarizing plates between two polarizing plates.
The liquid crystal layer sandwiched between the transparent substrates is sandwiched. In any of the display modes, a polarizing plate is used to display only the polarized light component in one direction, so that in principle 50% of the light source light is used.
Only less than% light is used.

When the light utilization efficiency of the liquid crystal display element is low, there is a problem that the transmissive liquid crystal display element requires high-luminance illumination and consumes a large amount of power. Further, the reflective liquid crystal display element has a problem that the display is dark and difficult to see. In particular, a display device for a portable information terminal is required to have low power consumption and a thin shape. Therefore, a reflective liquid crystal display device with improved display brightness is required.

Under these circumstances, a liquid crystal display element of the type in which liquid crystals are dispersed in a polymer matrix has been proposed as a liquid crystal display element that employs a display mode that does not use a polarizing plate in recent years.

These display modes are PDLC (Pol
ymer Dispersed Liquid Cry
stal, PNLC (Polymer Network)
k Liquid Crystal) or the like.

The liquid crystal display device adopting these display modes obtains contrast by controlling the scattering and transmission (non-scattering state) of incident light without using a polarizing plate. 6 and 7 show a PNLC type liquid crystal display device 600.
It is a figure which shows the structure of.

As the light modulation layer, a liquid crystal layer is sandwiched between substrates 603 having electrodes 604 formed of ITO or the like. The light modulation layer is composed of a light-transmitting polymer matrix 601 formed three-dimensionally in a mesh shape, and a liquid crystal composition 602 dispersed in this polymer matrix. Here, a liquid crystal having a positive dielectric anisotropy is used. Further, the minor axis direction of the refractive index of the liquid crystal material the refractive index of the polymer (ordinary refractive index) should fit the n _o.

FIG. 6 shows an OFF state (state in which no voltage is applied), in which liquid crystal molecules are distributed in a polymer matrix in a random orientation direction.

FIG. 7 shows the ON state (voltage application), in which the liquid crystal molecules rise to the homeotropic alignment state by the electric field formed in the direction perpendicular to the substrate surface.

In the OFF state (state in which no voltage is applied), the refractive index of the randomly oriented liquid crystal layer is approximately n in the minor axis direction.
3-dimensional average value of the refractive index n _e of _o and longitudinally (n _e +
2n _o ) / 3, which is deviated from the refractive index n _{o of the} polymer.
Therefore, the incident light is reflected or refracted at the interface between the polymer and the liquid crystal to be in a scattering state.

In the ON state, the liquid crystal molecules are in the homeotropic alignment state. Therefore, none of the polymer and the liquid crystal with respect to light incident on the liquid crystal cell from the vertical or near-vertical direction refractive index becomes n _o, reflection or refraction becomes transmissive (transparent) state does not occur.

By disposing a black light absorbing plate on the back surface of the liquid crystal display element, a reflective direct view type liquid crystal display element can be constructed.

A liquid crystal display element of the type which obtains contrast by controlling the scattering and transmission (non-scattering state) of incident light without using such a polarizing plate is a conventional TN type liquid crystal display element or STN type liquid crystal display. Compared to the device, it can display brighter and paper white.

In the reflection type direct-viewing type liquid crystal display element, transmitted light and forward scattered light are not used but back scattered light is used, so that a large scattering ability is required. In order to increase the backscattering, a liquid crystal material having a large refractive index anisotropy (n _e −n _o ) may be used, or the light modulation layer may be thickened. However, a practical liquid crystal material has a refractive index anisotropy of up to about 0.2, and if it is further increased, there is a problem that the reliability decreases.

Further, if the light modulation layer is thickened, the driving voltage becomes high. As a result, power consumption becomes large, the circuit scale becomes large and the display element becomes thick and large, and in the type driven by a non-linear switching element such as a thin film transistor, the element or wiring width becomes large and the aperture ratio decreases and the display becomes dark. I have a problem.

On the other hand, by disposing a prism sheet between the liquid crystal cell and the black light absorbing plate as seen in the lecture number 3C405 of the 20th Liquid Crystal Conference, the transmitted light and the forward scattered light are reused. However, a configuration that enhances the backscattering power has also been proposed. However, this configuration has a problem that the viewing angle is narrowed, and since the distance between the light modulation layer of the liquid crystal cell and the black light absorbing plate is large, double display due to parallax occurs and it is difficult to see.

In addition, for example, in the lecture number 3C405 of the 18th liquid crystal debate, a conventional PNLC type liquid crystal display device and a TN are shown.
There has been proposed a liquid crystal display element 500 in which a liquid crystal display element is combined (see FIG. 5). When a normally white TN type liquid crystal display element 501 with a reflector is arranged on the back surface of the PNLC type liquid crystal display element 600 and driven simultaneously, OF
At the time of F, a part of the total incident light is reflected back by the PNLC layer and transmitted and forward scattered, and half of this is reflected by the TN cell and returned to the PNLC layer, so that it becomes brighter than one layer of 5 PNLC. When turned on, the TN cell is in a dark state and has the same function as the black light absorbing plate. However, even with this method, only half of the transmitted and forward scattered light can be used.

As described above, in a liquid crystal display element of a display mode such as PDLC or PNLC, if an attempt is made to increase the backscattering ability of the light modulation layer to brighten the display, power consumption increases, and the liquid crystal display element becomes large and thick. There is a problem. Further, if the refractive index anisotropy of the liquid crystal is increased, there is a problem that the stability and reliability of the liquid crystal are deteriorated. further,
There are problems that the viewing angle becomes narrow and the display is doubled.

As described above, it is difficult to efficiently use the lost light such as the transmitted light and the forward scattered light.

[0024]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. That is,
An object of the present invention is to provide a liquid crystal display device including a light modulation layer having a high backscattering ability of the light modulation layer.

Another object of the present invention is to provide a liquid crystal display device having a high reflectance and a high contrast ratio.

[0026]

A liquid crystal display device of the present invention comprises a first liquid crystal layer having a homogeneous alignment, and a three-dimensional network transparent film formed so as to maintain the alignment in the first liquid crystal layer. A first light modulation means comprising a light matrix,
A first polarizing plate which is laminated with the first light modulating means and has a first light transmission axis, and a second deflecting plate which has a second transmission axis in a twisted relationship with the first transmission axis, A second light modulator having a first liquid crystal layer and a second liquid crystal layer which are twist-aligned in alignment with the first and second transmission axes is provided between the first and second polarizing plates.

Further, the liquid crystal display element of the present invention comprises a first liquid crystal layer and a three-dimensional mesh-like translucent matrix formed in the first liquid crystal layer so that the liquid crystal molecules are homogeneously aligned. A first light modulator having the first light modulator, a first polarizing plate having a first light transmission axis parallel to the long axis of the homogeneously aligned liquid crystal molecule, and a second polarizer having a twist relationship with the first transmission axis. Second light having a second polarizing plate having a transmission axis and a twist-arranged second liquid crystal layer formed to transmit light between the first polarizing plate and the second polarizing plate A modulator, a reflector disposed so as to face the first light modulator across the second light modulator, a first liquid crystal layer, and a second liquid crystal layer.
And a voltage applying means for applying a voltage to the liquid crystal layer to form a homeotropic alignment.

Further, the liquid crystal display element of the present invention is a liquid crystal display element in which a first liquid crystal layer which is a first light modulating means and a second liquid crystal layer which is a second light modulating means are laminated. A first light modulation including a first liquid crystal layer and a three-dimensional mesh-like translucent matrix formed in the first liquid crystal layer so that liquid crystal molecules constituting the liquid crystal layer are homogeneously aligned. Means and a second light modulating means twisted so as to be parallel to the major axis of the homogeneously aligned liquid crystal molecules of the first liquid crystal layer on the surface facing the first light modulating means, and the first light modulating means. A first polarizing plate which is disposed between the modulation means and the second light modulation means and which allows the transmitted light of the first light modulation means to enter the second light modulation means; and the second light modulation means. The second polarization modulator, which is arranged so as to face the first polarization plate with the light being sandwiched, transmits the light transmitted through the second light modulation means in parallel with the polarization plane. A second polarizing plate having a reflecting plate for reflecting the second polarizing plate transmitting light to the second polarizing plate side, the first
The light modulating means and the second light modulating means are provided with electrodes for applying a voltage.

The refractive index n _p of the translucent matrix forming the first liquid crystal layer is substantially the same as the uniaxial refractive index n _{o of} the liquid crystal molecules forming the first liquid crystal layer (ordinary refractive index). You may make it equal.

The transparent matrix may be made of a liquid crystalline polymer. This liquid crystalline polymer is, for example, a mixture of a liquid crystalline monomer having an ultraviolet curability and a liquid crystal composition forming the first liquid crystal layer, and the mixture is injected between substrates that have been rubbed so as to be homogeneously aligned and irradiated with ultraviolet rays. Then, the liquid crystalline monomer may be polymerized to be formed.

The angle formed by the light transmission axis of the first polarizing plate and the light transmission axis of the second polarizing plate may be set to 90 degrees. In this case, the second liquid crystal display element included in the second light modulator is a TN (Twisted Nematic) mode liquid crystal display element.

Further, the angle formed by the light transmission axis of the first polarizing plate and the light transmission axis of the second polarizing plate may be set to any one of 180 degrees to 360 degrees. In this case, the second liquid crystal display element included in the second light modulator is the STN
(Super Twisted Nematic) system liquid crystal display device. If the liquid crystal molecule orientation is the STN orientation, the response to the applied voltage becomes steeper. Further, when the liquid crystal layers forming the first light modulating means and the second light modulating means are driven by the pair of voltage applying means, the response characteristic of the second liquid crystal layer becomes steep and the first liquid crystal layer is formed. The partial voltage of the voltage applied to is also large. Therefore, by making the second liquid crystal layer have the STN orientation, the response characteristics of the liquid crystal display device as a whole including the first light modulating means and the second light modulating means are improved. (Effect, corresponding to high time-division simple matrix) That is, in the liquid crystal display element of the present invention, the light modulating means for controlling the incident light is composed of a homogeneously aligned liquid crystal material and a transparent solid substance that maintains the orientation of the liquid crystal material. A liquid crystal display device comprising two layers of a first light modulating means and a second light modulating means made of a liquid crystal material with twisted nematic alignment.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram schematically showing an example of the structure of a liquid crystal display device of the present invention.

In this liquid crystal display element 100, the first liquid crystal layer 101 constituting the first light modulating means and the second liquid crystal layer 102 constituting the second light modulating means are the liquid crystal driving means. First substrate 103 and second substrate 1 on which electrodes are formed
It is sandwiched between 04 and.

The first liquid crystal layer 101 constituting the first light modulating means comprises a homogeneously aligned liquid crystal material 105 and a three-dimensional mesh-like translucent matrix 1 dispersed in the liquid crystal.
06. The ordinary refractive index n _o of the liquid crystal material 105 and the refractive index n _m of the constituent material of the translucent matrix were set to be equal.

For the liquid crystal material 105, for example, nematic liquid crystal may be used. Translucent matrix 106
For example, the polymer may be formed into a network. The domains formed by the light-transmitting matrix 106 may be continuous or independent.

The second liquid crystal layer 102 constituting the second light modulating means is composed of a normally white type TN-aligned nematic liquid crystal material 107 twisted 90 degrees in the layer thickness direction. That is, in this example, the second liquid crystal layer 1
Reference numeral 02 denotes a TN mode liquid crystal display element. In the liquid crystal display element of the present invention, the second liquid crystal layer 102 is not limited to the TN mode, and the twist direction of liquid crystal molecules in the layer thickness direction is 180 degrees to 36 degrees.
It may be set to 0 degree. In this case, the second liquid crystal layer 102 is STN-based (STN mode, SBE mode,
It becomes a liquid crystal display element of OMI mode, etc.).

The second liquid crystal display element 102 is sandwiched between the first polarizing plate 108 and the second polarizing plate 109. The direction of the transmission axis of the first polarizing plate is arranged so as to be parallel to the long axis direction of the homogeneously aligned liquid crystal molecules of the first liquid crystal layer 101. In addition, the first polarizing plate 1
08 and the second polarizing plate 109 are arranged such that their transmission axes are aligned with the alignment direction of the liquid crystal molecules of the second liquid crystal display element 102 sandwiched therebetween.

That is, when the second liquid crystal layer 102 is in the TN mode, the transmission axis of the first polarizing plate 108 is homogeneously aligned in the direction of the transmission axis of the first polarizing plate. The direction of the transmission axis of the second polarizing plate is set to be parallel to the long axis direction of the liquid crystal molecules, and the first liquid crystal layer 10 is used.
It is arranged so as to be orthogonal to the long axis direction of the homogeneously aligned liquid crystal molecule 1.

When the second liquid crystal layer 102 is of STN type, the transmission axis of the second polarizing plate is brought into contact with the second liquid crystal layer 102.
It may be made to match the orientation of the liquid crystal.

A voltage for driving the first liquid crystal layer 101 and the second liquid crystal layer 102 is applied to the first substrate 103 and the second substrate 104 which sandwich the first and second light modulating means. Electrodes that are means are formed.

The first liquid crystal layer 101 of the first substrate 103
For example, ITO (Indium Tin Oxi
de) or the like, a transparent electrode 110 formed of a transparent conductive film is formed, and on the surface of the transparent electrode 110 on the side where the first liquid crystal layer 101 is sandwiched, an alignment film 111 that allows liquid crystal to be homogeneously aligned is formed. Has been formed.

The second liquid crystal layer 102 of the second substrate 104.
On the surface on the side of sandwiching, the reflection plate which is the reflection means for reflecting the incident light to the second liquid crystal layer 102 side, and the reflection electrode 112 which also serves as the voltage application means for the first and second liquid crystal layers. It is arranged.

The operation of the liquid crystal cell of the liquid crystal display device 100 of the present invention will be described below. Figure 1 shows the OF of this liquid crystal display device.
FIG. 2 shows an F (no voltage applied) state, and FIG. 2 shows an ON (voltage applied) state.

The light incident on the liquid crystal display element 100 is
The polarization component LE of the liquid crystal layer 101 in the major axis direction and the polarization component LO of the minor axis direction will be described separately.

In the OFF state, the light LE is scattered in the first liquid crystal layer due to the difference in refractive index between n _o and n _e , and most of the light is backscattered. A part of the light that has not been backscattered is transmitted or scattered forward and enters the second liquid crystal layer 102.
The TN layer of the second liquid crystal layer 102 is in a bright state, and the incident light is scattered and the polarization is disturbed. Almost half of the light that has entered the second liquid crystal layer 102 is reflected by the reflective electrode 112 disposed on the back surface of the second liquid crystal layer 102 and returns to the first liquid crystal layer 101 again. With respect to this polarized light, both the transparent resin and the liquid crystal have the same refractive index of n _o , so that they are all used as reflected light without being scattered.

On the other hand, the light LO of the polarization component in the minor axis direction of the first liquid crystal layer 101 has a refractive index n of both the constituent material of the transparent matrix 106 and the liquid crystal 105 in the first liquid crystal layer 101.
The second liquid crystal layer 10 transmits without being scattered because it is equal at _o.
2 is incident. All of the light incident on the second liquid crystal layer 102 is reflected by the reflective electrode 11 formed on the back surface of the second liquid crystal layer 102.
The light is reflected at 2, is transmitted through the first liquid crystal layer 101 again, and is all used as reflected light.

In the ON state, the first liquid crystal layer 101 and the second liquid crystal layer 101
The liquid crystal layer 102 is also homeotropically aligned.

In the first liquid crystal layer 101, the light transmissive matrix 106 and the liquid crystal 105 both have the same refractive index n _o for both LE and LO light. Therefore, the light LE, the light L
It is transmitted without being scattered together with O, and is incident on the second liquid crystal layer 102. The transmission axis of the first polarizing plate 108 and the second polarizing plate 10
Since the transmission axes of 9 are orthogonal and the second light modulation means is in the dark state, all incident light is absorbed and reflected light disappears.

Thus, the liquid crystal display device 100 of the present invention.
In the OFF state, most of the incident light is used as reflected light, and a bright display can be obtained. Further, in the ON state, there is no reflected light and a sufficiently black display can be obtained, and high contrast can be obtained.

In order to obtain homogeneous alignment in the first liquid crystal layer 101, for example, the 17th liquid crystal discussion meeting 4F
119, a mixture of an ultraviolet curable monomer and a liquid crystal material may be sandwiched between substrates that have been subjected to an alignment treatment by rubbing, and this may be irradiated with ultraviolet rays to polymerize the monomer to polymerize it. . At this time, if a liquid crystalline monomer that becomes a liquid crystalline polymer after polymerization is used, a better homogeneous alignment can be obtained,
The performance of the liquid crystal display device is further improved.

The first liquid crystal layer formed by using such a method and the first liquid crystal layer may be laminated.

The liquid crystal display device 10 of the present invention illustrated in FIG.
In No. 0, the first light modulating means and the second light modulating means are sandwiched between a pair of substrates on which electrodes are formed, but a laminated structure other than this may be adopted.

As a method of superimposing the first light modulating means and the second light modulating means, for example, a structure in which two individually produced cells are stacked as shown in FIG. 3, and two liquid crystal layers are formed as shown in FIG. A configuration in which one substrate is disposed so as to face each other, and FIG.
As shown in FIG. 2 and FIG.
In the liquid crystal display element illustrated in FIG. 3, the liquid crystal layer may be continuously formed without a substrate, and the reflective electrode 112 is divided into a transparent electrode 112b and a reflective plate 112c. Are arranged.

In the structure shown in FIG. 4, after the cell of the first or second liquid crystal layer is manufactured, this cell is used as one side of the substrate and
You may make it a cell of a layer. In the structure of FIG. 1, for example, after forming a mixed layer of a light-transmitting matrix and liquid crystal using one side as a peelable substrate, peeling the one side substrate and using this as the one side substrate, a TN cell of another layer is produced. Good.

As compared with FIG. 3, the liquid crystal display device having the structure shown in FIG. 4, and further shown in FIG. 1 or FIG. 2 has no parallax due to the layer thickness, and a better display can be obtained. In the above description, the second
The case where the TN layer of the liquid crystal layer of 90 degree TN orientation is shown.
In addition, for example, when the liquid crystal molecule orientation is a super twisted orientation in which the liquid crystal molecule orientation is in a range of 180 degrees to 360 degrees, a steeper response to voltage is obtained. In the configuration of FIG.
02, the voltage division to the first liquid crystal layer 101 increases, so that the liquid crystal display element 100 as a whole including the first liquid crystal layer 101 can obtain a steep response, and a high time division simple matrix can be obtained. It will be applicable to driving.

Means for applying an operating voltage to the liquid crystal layer include TFT (thin film transistor) and MIM (Metal).
Any of a method using a non-linear switching element such as an Insulator Metal), a simple matrix method, and a static method can be applied.

Although a method of combining a PNLC mode cell and a TN mode cell has been proposed so far, in this configuration, since the liquid crystal is randomly aligned in the PNLC layer, both the light LE and the light LO are (n) in the OFF state. _e + 2n
_Scatter based on the difference in refractive index between _o ) / 3 and n _o . Further, in the TN layer which is the second liquid crystal layer, half of the transmitted and forward scattered light is reflected and returned to the PNLC layer which is the first liquid crystal layer, but since it is scattered again, part of it is backscattered in the opposite direction. Will end up. On the other hand, in the liquid crystal display element of the present invention,
The larger the refractive index difference n _o and n _e to light LE, can be obtained a larger scattering. For example, n _o =
When 1.5 and n _e = 1.7, the reflectance at the first liquid crystal layer, which is the first light modulating means, that is, the interface of the light vertically incident on the interface between the translucent matrix and the liquid crystal is Conventional PN
The composition of the LC mode cell and the TN mode cell is about 0.05%, and the composition of the liquid crystal display device of the present invention is 0.39%, which is about 8 times higher than the conventional reflectance. You can Therefore, with the same layer thickness, the liquid crystal display device of the present invention can obtain much larger backscattering. Furthermore, since a part of the light LE and all of the light LO can be reflected without loss and used as outgoing light after passing through the second liquid crystal layer constituting the second light modulator, a brighter display can be obtained. Can be obtained. In addition, by increasing the refractive index anisotropy of the liquid crystal material as in the past,
It does not lower the reliability of the liquid crystal material.

In the liquid crystal display device of the present invention, the light modulating means is 2
Although it is a layer, since the utilization efficiency of incident light is high, it is not necessary to increase the layer thickness of the liquid crystal display element as a whole. Therefore, a high reflectance can be obtained without increasing the drive voltage. Further, high reflectance can be obtained without deteriorating the viewing angle as in the case of using the prism sheet.

Next, an example of the method of manufacturing the liquid crystal display element of the present invention will be described.

First, an alignment layer made of a polyimide resin is applied on two glass substrates having ITO transparent electrodes formed thereon, and a rubbing treatment is performed. These two glass substrates are combined with a resin sphere spacer of 10 μm sandwiched so that the rubbing directions are parallel to each other, and a material obtained by blending a nematic liquid crystal with a liquid crystalline monomer and a polymerization initiator is injected into the gap.

Then, ultraviolet rays are irradiated from the glass substrate side to polymerize the monomer. By doing so, the first liquid crystal layer, which is the first light modulating means, in which the liquid crystal is held in the homogeneous alignment between the fine structures (domains) of the three-dimensionally networked polymer matrix is formed.

On the other hand, two glass substrates are combined with a resin sphere spacer of 5 μm sandwiched so that the rubbing directions are orthogonal to each other, and a nematic liquid crystal containing a small amount of cholesteric liquid crystal is injected between them to form a second liquid crystal layer. To do. A polarizing plate is attached to the surface of the second liquid crystal layer on the side of the first substrate with the transmission axis aligned with the rubbing direction of the substrate on the side of the first liquid crystal layer of the second liquid crystal layer. Similarly, a polarizing plate with a reflection plate is attached to the surface of the second liquid crystal layer opposite to the first substrate side so that the rubbing direction of this surface coincides with the transmission axis. In this way, a reflective TN cell, which is the second light modulating means, is manufactured.

The two cells constituting the first light modulating means and the second light modulating means are connected to the alignment direction of the liquid crystal molecules of the first liquid crystal layer and the transmission axis of the polarizing plate above the second liquid crystal layer. The liquid crystal display device of the present invention having the structure illustrated in FIG. 3 can be produced by superimposing in the same direction.

As the liquid crystal material of the first liquid crystal layer which constitutes the first light modulating means, for example, TL203 manufactured by Merck may be used. The refractive index of this liquid crystal material is n
_e = 1.73, which is n _o = 1.53. As the monomer that is the material of the translucent matrix, for example, a biphenyl type diacrylate monomer may be used. The refractive index of the polymer formed by polymerizing this monomer is _nm = 1.53. In other words, equal to the refractive index n _o of the short axis direction of the liquid crystal material of the first liquid crystal layer.

As the liquid crystal material of the second liquid crystal layer constituting the second light modulating means, for example, MLC-60 manufactured by Merck & Co., Inc.
09 may be used.

On the other hand, a liquid crystal display device having a conventional structure as illustrated in FIG. 5 was prepared in the same manner as described above except that the two glass substrates of the first liquid crystal layer were not subjected to the alignment treatment, and a comparative example was prepared. It was set to A. In this liquid crystal display element, liquid crystal is randomly aligned between domains formed by a tough polymer matrix.

In addition, the two glass substrates of the first liquid crystal layer were not subjected to orientation treatment, and the resin ball spacer was set to 15 μm to match the layer thickness of two layers of the constitution of the liquid crystal display device of the present invention. A layered PNLC cell was prepared, a matt black-painted blackboard was placed on the back surface thereof, and a liquid crystal display device having a conventional structure was prepared to be Comparative Example B. The same material as in the present invention was used for the light-transmitting matrix and the liquid crystal material.

Further, a prism sheet BEF-90 manufactured by Sumitomo 3M was disposed between the PNLC cell of Comparative Example B and the blackboard to prepare a liquid crystal display element having a conventional structure, which was referred to as Comparative Example C.

For each of the liquid crystal display devices of Comparative Examples A to C described above, the reflectance R ₀ % when no voltage was applied and the value when the reflectance was saturated were measured using a color difference meter CR-200b manufactured by Minolta. Table 1 shows the results of comparative evaluation of Rsat, the applied voltage Vsat at this time, and the contrast ratio CR = R0 / Rsat.

[0071]

[Table 1] The same voltage was simultaneously applied to two liquid crystal display elements each having a structure in which a plurality of light modulation means were laminated. It can be seen that the liquid crystal display element of the present invention has an extremely high reflectance when no voltage is applied, as compared with the conventional liquid crystal display element. As a result, in the liquid crystal display device of the present invention, a much higher contrast ratio than the conventional one was obtained.

Further, the visual observability from each azimuth was compared by visual observation, but in the liquid crystal display element using the prism sheet (Comparative Example C), the reversal of the contrast was observed in the azimuth orthogonal to the groove of the prism sheet. The liquid crystal display device of the present invention did not have such a problem. Further, the liquid crystal display element of the present invention and the liquid crystal display elements A to C of the comparative example having the conventional configuration had the same driving voltage.

As described above, the liquid crystal display device of the present invention can obtain extremely high reflectance and contrast ratio as compared with the liquid crystal display devices A to C having the conventional structure.

Next, an example of a method for manufacturing the liquid crystal display device of the present invention illustrated in FIG. 1 will be described.

An alignment layer made of a polyimide resin was applied on one glass substrate having an ITO transparent electrode formed thereon and subjected to a rubbing treatment. Another substrate opposite to this substrate was used as a support to form a film-shaped substrate on which a polarizer having adsorbed iodine on a stretched PVA resin was formed on a peelable Teflon sheet. These two substrates were combined so that the rubbing direction and the PVA stretching direction were parallel to each other with a 10 μm resin ball spacer interposed therebetween, and a nematic liquid crystal material, a material curable with an ultraviolet curable monomer and a polymerization initiator were injected into the gap. Then, UV light was irradiated from the glass substrate side to UV-polymerize the monomer. In this way, a cell including a first liquid crystal layer constituting a first light modulating means in which liquid crystal molecules were held in a homogeneous alignment between fine structures (domains) formed by a three-dimensional network polymer matrix was formed. When the Teflon sheet of the cell including the first liquid crystal layer is peeled off, the first liquid crystal layer and the polarizer layer remain on the glass substrate. This is referred to as a substrate A here.

On the other hand, the surface of the glass substrate was treated with hydrofluoric acid (HF) to form fine irregularities, on which silver (Ag) was vapor-deposited as a reflection electrode which also serves as an electrode and a reflection plate, and further stretched PVA was formed thereon. A polarizer layer was formed by adsorbing iodine on a resin. This is referred to as a substrate B here.

Substrate A and substrate B are combined by sandwiching a resin sphere spacer forming a gap of 13 μm so that the PVA stretching directions are orthogonal to each other and the periphery is sealed, and a nematic liquid crystal in which a small amount of cholesteric liquid crystal is added to the gap is used. Injected.

Thus, the layer thickness 1 of the first liquid crystal layer, in which the two layers of light modulating means as illustrated in FIG.
A liquid crystal display element having a thickness of 0 μm and a thickness of the second liquid crystal layer of 5 μm was produced.

As the liquid crystal material of the first liquid crystal layer which constitutes the first light modulating means, for example, TL2 manufactured by Merck & Co., Inc.
03 may be used. The refractive index of this liquid crystal material is n _e = 1.73 and n _o = 1.53. As the monomer that is the material of the translucent matrix, for example, a biphenyl type diacrylate monomer may be used. The refractive index of the polymer formed by polymerizing this monomer is _nm = 1.53. That is, the first
_Is equal to the refractive index no of the liquid crystal material of the liquid crystal layer in the short axis direction.

The same measurement as in the example shown in Table 1 was performed on this liquid crystal display element. Table 2 shows the results.

[0081]

[Table 2] Compared with the characteristics of the liquid crystal display element of the present invention shown in Table 1, there is no loss due to reflection of the glass and the air layer between the first light modulating means and the second light modulating means, so that a higher contrast can be obtained. I was able to. Also, in the example of Table 1 (see FIG. 4),
Although a display bleeding phenomenon was observed when observed from an oblique direction, the bleeding was greatly improved in the liquid crystal display device of the present invention having the configuration of FIG.

Next, an example in which the liquid crystal display device of the present invention is applied to an active matrix type liquid crystal display device will be described.

Similar to a general TFT (thin film transistor) driving type liquid crystal display element that is currently put into practical use, a TFT element is formed by using amorphous silicon deposited by a plasma CVD method on a glass substrate. Data lines, gate lines, ITO pixel electrodes, etc. were formed to produce a 640 × 480 dot TFT array substrate. Here, an example in which a thin film transistor in which an active layer is formed of amorphous silicon is adopted has been described, but a thin film transistor in which an active layer is formed of non-single crystal silicon may be adopted. The structure of the thin film transistor may be a coplanar type or an inverted stagger type.

On the other hand, an ITO electrode was formed on a glass substrate to prepare a counter electrode. Then, the first light modulating means and the second light modulating means are laminated between the TFT array substrate and the counter electrode by using the same method as in the manufacturing example of the liquid crystal display element having the configuration illustrated in FIG. 1 described above. The manufactured liquid crystal display element was produced. This liquid crystal cell has a TAB (Tape Automat)
An active matrix type liquid crystal display device was manufactured by connecting a drive circuit using a driver IC of an ed bonding type.

When this liquid crystal display device was driven, the reflectance when white (OFF) was 46%, the reflectance when black (ON) was 2.1%, and the contrast ratio was 22: 1. Good display was obtained.

Further, the first light modulating means and the second light modulating means, which are STN mode liquid crystal layers in which the liquid crystal molecule orientation of the second liquid crystal layer of this liquid crystal display element is tearing by 270 degrees, are laminated. A liquid crystal display device was produced. As a result, the steepness of the reflectance change with respect to the applied voltage of the liquid crystal display element is improved,
An even higher contrast ratio of 30: 1 was obtained.

In the above example, static drive, TF
An example of T drive has been shown. The liquid crystal display element of the present invention is not limited to the conditions of these examples. For example, as the driving means for the liquid crystal layer, MIM other than TFT is used.
A method using a non-linear switching element such as (Metal-Insulator-Metal) or a simple matrix method may be applied. The second liquid crystal layer (TN layer) may have an STN structure in which a twist of 180 to 360 degrees is used instead of the 90 degree twist.

[0088]

As described above, the liquid crystal display device of the present invention is a liquid crystal display device provided with a light modulation layer having a high backscattering ability. Further, according to the liquid crystal display element of the present invention, it is possible to obtain extremely high reflectance and contrast ratio. According to the liquid crystal display element of the present invention, for example, PDLC mode, P
The use of a light modulation layer in which a transparent matrix is dispersed in a liquid crystal material such as NLC mode reduces the reliability of the liquid crystal material,
The reflectance and the contrast can be greatly improved and a good display can be obtained without causing problems such as an increase in the size of the driving circuit, an increase in power consumption, and a deterioration in the viewing angle. INDUSTRIAL APPLICABILITY The liquid crystal display element of the present invention is a liquid crystal display element which is suitable for a reflection type liquid crystal display element and which has a high light utilization rate and is bright and has high visibility.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an example of the configuration of a liquid crystal display element of the present invention.

FIG. 2 is a diagram schematically showing an example of the configuration of a liquid crystal display element of the present invention.

FIG. 3 is a diagram schematically showing another example of the configuration of the liquid crystal display element of the present invention.

FIG. 4 is a diagram schematically showing still another example of the configuration of the liquid crystal display element of the present invention.

FIG. 5 is a diagram schematically showing an example of the configuration of a conventional liquid crystal display element.

FIG. 6 is a diagram schematically showing the operation of a conventional PNLC-mode liquid crystal display element.

FIG. 7 is a diagram schematically showing the operation of a conventional PNLC-mode liquid crystal display element.

[Explanation of symbols]

100 ... Liquid crystal display element, 101 ... First liquid crystal layer, 1
02 ... second liquid crystal layer 103 ... first substrate, 104 ... second substrate, 105
...... Liquid crystal 106 ...... Transparent matrix, 107 ...... Nematic liquid crystal 108 ...... First polarizing plate, 109 ...... Second polarizing plate, 1
11 ... Alignment film 112 ... Reflective electrode, 112b ... Transparent electrode, 112c
...... Reflector 500 …… Liquid crystal display element, 600 …… Liquid crystal display element

Claims (6)

[Claims] 1. A first liquid crystal layer which is homogeneously aligned,
A first light modulating unit composed of a three-dimensional mesh-shaped light-transmitting matrix formed so as to maintain the orientation in the first liquid crystal layer, and the first light modulating unit are laminated to form a first light modulating unit. A first polarizing plate having a light transmission axis, a second deflecting plate having a second transmission axis in a twisted relationship with the first transmission axis, and a first and a second polarizing plate between the first and second polarizing plates. And a second light modulating unit having a second liquid crystal layer aligned in a twist alignment with the second transmission axis. 2. A first light modulating means having a first liquid crystal layer and a three-dimensional mesh-like translucent matrix formed in the first liquid crystal layer so that the liquid crystal molecules are homogeneously aligned. The first axis parallel to the long axis of the homogeneously aligned liquid crystal molecule
A first polarizing plate having a light transmission axis, a second polarizing plate having a second transmission axis in a twisted relationship with the first transmission axis, a first polarizing plate and a second polarizing plate. A second light modulating means having a twisted second liquid crystal layer formed so as to transmit light between the first light modulating means and the second light modulating means so as to face the first light modulating means. 2. A liquid crystal display device, comprising: a reflector disposed in the first liquid crystal layer; and a voltage applying unit that applies a voltage to the first liquid crystal layer and the second liquid crystal layer to form a homeotropic alignment. 3. The liquid crystal display according to claim 1, wherein the translucent matrix has a refractive index substantially equal to the refractive index n of the first liquid crystal in the uniaxial direction. element. 4. The liquid crystal display device according to claim 1, wherein the translucent matrix is made of a liquid crystalline polymer. 5. The liquid crystal according to claim 1, wherein an angle formed by the light transmission axis of the first polarizing plate and the light transmission axis of the second polarizing plate is 90 degrees. Display element. 6. The angle formed by the light transmission axis of the first polarizing plate and the light transmission axis of the second polarizing plate is any one of 180 degrees to 360 degrees. 3. The liquid crystal display element according to any one of 2.