JPH0611711A - Reflection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display device having a good display grade and high fineness by disposing an optical phase compensation member between a polarizer and a liquid crystal element. CONSTITUTION:Large projections 4 and small projections 5 consisting of a synthetic resin material are formed on a glass substrate 2. The diameters in the bottoms of the large projections 4 and the small projections 5 are respectively determined at 5mum and 3mum as an example and the intervals therebetween are determined at least at >=2mum as an example. A smoothing film 6 is formed to coat these projections 4, 5 and fill the recessed part between the projections 4, 5. A metallic reflection film 7 consisting of a metallic material, such as aluminum, is formed on this smoothing film 6. This metallic reflection film 7 is formed in plural arrays to a longitudinal band shape. The projections 4, 5, the smoothing film 6 and the metallic reflection film 6 constitute a reflection plate 8 on the glass substrate 2. An oriented film 9 is formed on the metallic reflection film 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device which does not use a direct-view backlight, and more specifically, it is an office automation device such as a word processor or a so-called notebook personal computer, and various video and game devices. In particular, the present invention relates to a reflection type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, the application of liquid crystal display devices to word processors, laptop personal computers, portable television receivers called pocket televisions, etc. has been rapidly developing. In particular, among liquid crystal display devices, a reflective liquid crystal display device that reflects light incident from the outside to display an image does not require a backlight as a light source and thus consumes less power and can be thin and lightweight. ,
Attention has been paid.

Conventionally, the reflective liquid crystal display device has a TN.
(Twisted nematic) method and STN (super twisted nematic) method are used. In the TN method, a liquid crystal display element including a pair of glass substrates, a transparent electrode formed on the surface of each glass substrate, and a liquid crystal layer sealed between the glass substrates is arranged between a pair of polarizing plates, Black and white display is performed by utilizing the optical properties of the liquid crystal display element, that is, the optical rotation characteristic when no voltage is applied and the optical rotation elimination characteristic when a voltage is applied.

Regarding color display, a color filter for each color such as red, blue, and green is provided in the liquid crystal display element to utilize the optical switching characteristics of the liquid crystal display element when no voltage is applied or when no voltage is applied. However, multi-color display in which relatively few colors are displayed by additive color mixing, or full-color display capable of displaying basically any color is realized. Such a reflective liquid crystal display device currently uses an active matrix driving system or a simple matrix driving system as a driving system, and is adopted as a portable display device for a so-called pocket liquid crystal television receiver as an example.

In a display system widely adopted as a display device in office automation equipment such as a word processor, a liquid crystal has a liquid crystal display principle similar to the liquid crystal of the TN system, and a twist angle of liquid crystal molecules is set to 180 to 270 degrees. The STN method to be set may be mentioned. This STN system is characterized by increasing the twist angle of the liquid crystal molecules to 90 degrees or more and optimizing the set angle of the transmission axis of the polarizing plate with respect to the elliptically polarized light generated by the birefringence effect of the liquid crystal display element. The accompanying rapid molecular orientation deformation is made to correspond to the change in the birefringence of the liquid crystal, and the optical characteristics exhibiting a sharp optical change above the threshold value are used for display. Therefore, it is suitable for high-multiplex drive of the simple matrix drive system.

On the other hand, a disadvantage of this STN method is that it exhibits yellow green or dark blue coloring as a display background color due to birefringence of the liquid crystal. As a measure to improve this coloring phenomenon,
Proposing a liquid crystal display device that enables color display by superimposing a liquid crystal display device for optical compensation and a retardation plate made of a polymer such as polycarbonate on the STN liquid crystal display device for display to achieve color display close to black and white. Has been done.
A liquid crystal display element configured to perform such color compensation is used as a so-called paper white liquid crystal display device. The detailed operation principle of the TN and STN liquid crystal display devices is described in "Liquid Crystal Device Handbook" 1989, p. 329, edited by Japan Society for the Promotion of Science, 142nd Committee.
It is described on page 346 and is a well-known technique.

When these TN type or STN type liquid crystal display elements are to be applied as a reflection type liquid crystal display device, in view of the principle of the display method, the liquid crystal display element is sandwiched between a pair of polarizing plates and is reflected to the outside. It is necessary to install a board. Therefore, due to the thickness of the glass substrate used for the liquid crystal display device, it depends on the angle at which the user views the glass substrate, that is, the angle between the normal direction of the glass substrate and the direction at which the user views the liquid crystal display device. There is a problem that parallax occurs and the display is double recognized.

In the conventional TN method or STN method, when the birefringence of liquid crystal is controlled by an electric field to perform display by utilizing an optical shutter function, a polarizing plate is used in a liquid crystal display device of such a display method. In the case of using one sheet, it is impossible to realize a display with contrast, that is, a monochrome display, in principle as the reflection type liquid crystal display device described above.

A reflection type TN (45 degree twist type) liquid crystal display device using one polarizing plate and a quarter wavelength plate is disclosed in Japanese Patent Laid-Open No. 55-48733. In this prior art, a liquid crystal layer twisted by 45 degrees is used, and by controlling the applied electric field, the polarization plane of the incident linearly polarized light is divided into a state parallel to the optical axis of the quarter wavelength plate and a state twisted by 45 degrees. Realizes two states and displays in black and white. The configuration of the liquid crystal display element is, from the incident light side, a polarizer, a 45 ° twist liquid crystal display element, a quarter wavelength plate and a reflector. US Pat. No. 4,701,028 discloses a reflective vertical alignment liquid crystal display device in which one polarizing plate, one wavelength plate and a vertical alignment liquid crystal display element are combined.

[0010]

However, in the liquid crystal display device described in JP-A-55-48733, it is necessary to dispose a quarter reflector between the liquid crystal layer and the reflector. In addition, a reflective film cannot be formed inside the liquid crystal display element. Therefore, there is a problem that it is difficult to simplify and downsize the configuration. Further, since the basic principle regarding display is the same as that of the TN method, the steepness of the electro-optical characteristics is similar to that of the TN method. That is, there is a problem that it is difficult to improve the contrast in terms of display quality and the steepness of the electro-optical characteristics described above.

Further, the vertical alignment type liquid crystal display device described in US Pat. No. 4,701,028 has the following problems.

The vertical alignment of the liquid crystal layer, in particular the tilted vertical alignment, is extremely difficult to control with respect to the posture of the molecule, and the structure for realizing such control becomes complicated, which is not suitable for mass production. The vertical alignment has a weak alignment regulating force and a slow response speed. When the vertical alignment is used, dynamic scattering may occur during driving, which causes a problem in reliability of display operation.

An object of the present invention is to solve the above-mentioned technical problems and to provide a reflection type liquid crystal display device having no parallax, high definition and high display quality.

[0014]

According to the present invention, in a reflective liquid crystal display device in which a polarizer is arranged on the light incident side of a liquid crystal element, the liquid crystal element is an insulating substrate having at least a transparent electrode formed thereon. A surface having a smooth unevenness, a light-reflecting surface is formed on the one surface, and a mirror-like light-reflecting member having a counter electrode for display driving in cooperation with the transparent electrode, and the insulating substrate. And enclosed between the reflective member and
A reflection type liquid crystal comprising a liquid crystal layer in which the alignment of liquid crystal molecules is selected from either parallel alignment or twist alignment, and an optical phase compensation member is disposed between the polarizer and the liquid crystal element. It is a display device.

In the present invention, the retardation Δn ₁ d ₁ (Δn ₁ ; optical anisotropy of the liquid crystal layer, d ₁ ; layer thickness of the liquid crystal layer) of the liquid crystal element and the retardation Δn ₂ of the optical phase compensating member. d ₂ (Δn ₂ ; optical anisotropy of the optical phase compensation member,
d ₂ ; the thickness of the optical phase compensation member) is the wavelength λ of light in the range of 400 to 700 nm when the voltage V1 is applied,

[0016]

## EQU3 ## When | Δn ₁ d ₁ −Δn ₂ d ₂ | /λ=m/2±0.1 (m = 0, 1, 2, ...)
For wavelength λ of light in the range of ~ 700 nm,

[0017]

[Expression 4] | Δn ₁ d ₁ −Δn ₂ d ₂ | /λ=0.25+m/2±0.1 (m = 0,1,2, ...) Depending on the electric field applied to the liquid crystal layer, a numerical value | Δn ₁ d ₁ −Δn ₂ d ₂ | / λ
It is characterized by changing the.

Further, according to the present invention, the retardation Δn ₁ d _{1 of the} liquid crystal element and the retardation Δn ₂ d _{2 of the} optical phase compensation member are 400 to 700 nm when no voltage is applied.
Is selected so as to satisfy the third expression, and the numerical value | Δn ₁ d ₁ −Δn ₂ d ₂ | / λ is changed by the electric field applied to the liquid crystal layer. It is characterized by doing so.

In the present invention, the retardation Δn ₁ d _{1 of the} liquid crystal element and the retardation Δn ₂ d _{2 of the} optical phase compensation member are 400 to 700 nm when no voltage is applied.
For the wavelength λ of light in the range of, the numerical value | Δn ₁ d ₁ −Δn ₂ d ₂ | / λ is changed by the electric field applied to the liquid crystal layer. It is characterized by doing so.

The present invention is also characterized in that the light reflecting film forming the light reflecting surface of the light reflecting member faces the liquid crystal layer side.

Further, the invention is characterized in that the light reflecting surface is defined as an electrode surface facing a transparent electrode formed on the insulating substrate.

In the present invention, the optical phase compensation member is
A liquid crystal element comprising a pair of transparent substrates, transparent electrodes formed on each transparent substrate, and a liquid crystal layer sealed between the transparent substrates.

In the present invention, the optical phase compensation member is
It is a polymer stretched film.

According to the present invention, a transparent flattening layer that absorbs irregularities formed on the surface of the light reflecting member is provided on the light reflecting surface, and a transparent electrode is formed on the flattening layer. ,
It is characterized in that the transparent electrode is defined as an electrode facing the transparent electrode formed on the insulating substrate.

Further, the present invention is characterized in that a color filter layer is formed on either the insulating substrate or a transparent electrode formed on the insulating substrate.

[0026]

The display principle of the reflective liquid crystal display device of the present invention will be described below. Incident light to the reflective liquid crystal display device of the present invention reaches the reflecting member via the polarizer, the optical phase compensating member and the liquid crystal layer, and is reflected by the reflecting member to pass through the liquid crystal layer, the optical phase compensating member and the polarizer. Exit through. Here, the linearly polarized light emitted from the polarizer becomes elliptically polarized light after passing through the optical compensation member and the liquid crystal layer, and the phase difference δ of the elliptically polarized light at this time is

[0027]

[Expression 5] δ = (2π / λ) (Δn ₁ d ₁ −Δn ₂ d ₂ ) Where the symbol λ is the wavelength of light and the symbol Δ
n ₁ d ₁ is the retardation of the liquid crystal layer, the symbol Δn ₂ d ₂ is the retardation of the optical phase compensation member, and the symbols Δn ₁ and Δn ₂
Is the optical anisotropy (birefringence) of the liquid crystal layer and the optical phase compensation member, and the symbols d ₁ and d ₂ are the thicknesses of the liquid crystal layer and the optical phase compensation member, respectively.

When the value δ of the above equation 5 is set to the so-called 1/4 wavelength condition and the 3/4 wavelength condition, the incident light is blocked. That is, the condition is generally expressed by the formula shown in the fourth formula, | Δn ₁ d ₁ −Δn ₂ d ₂ | /λ=0.25+m
/ 2 is established. Considering the wavelength dispersion of the retardation of the liquid crystal layer, the wavelength range is 400 nm to 700.
The characteristics of the optical phase compensating member may be set so as to generally satisfy the fourth expression in the range of nm, that is, in the visible wavelength range.

The linearly polarized light from the polarizer which has entered the optical phase compensating member passes through the optical phase compensating member and the liquid crystal layer satisfying the above-mentioned formula 4, and becomes, for example, clockwise circularly polarized light, and becomes the reflecting member. It is reflected at and becomes counterclockwise circularly polarized light. On the other hand, when the light passes through the liquid crystal layer and becomes a left-handed circularly polarized light, it is reflected by the reflecting member to become a right-handed circularly polarized light.

As a result, the reflected light from the reflecting member passes through the liquid crystal layer and the optical compensating member again to become linearly polarized light which is orthogonal to the linearly polarized light before passing through the liquid crystal layer at the time of incidence and is shielded by the polarizer. It

Further, the third equation | Δn ₁ d ₁ −Δn ₂ d ₂ |
When the optical phase compensating member satisfies the conditions of the optical anisotropy Δn ₂ and the thickness d ₂ so as to satisfy / λ = m / 2, the light passes through the polarizer and enters the optical phase compensating member. The linearly polarized light remains linearly polarized light having parallel polarization directions even after passing through the optical phase compensation member and the liquid crystal layer. Therefore, after being reflected by the reflecting member or the reflected light passes through the liquid crystal layer and the optical reflecting member again. After that, the polarization state of linearly polarized light whose polarization directions are parallel is maintained. Therefore, the emitted light passes through the polarizer. It is possible to perform display by utilizing these light blocking state and light passing state.

In the case of such a display principle, when the light reflecting member does not maintain the polarization property, the conversion from the clockwise circularly polarized light to the counterclockwise circularly polarized light as described above or vice versa is efficient. And the contrast is reduced.

A flat specular reflection member is used as the reflection member for maintaining the polarization, but this makes it difficult to see the display because an external object is reflected as it is. The applicant has already filed a patent application as a method for producing a reflector. In this patent application, a substrate is coated with a photosensitive resin to form a pattern, and then heat treatment is performed to deform the convex portion into a smooth shape, and then a reflecting surface is formed thereon. According to this method, the convex portion can be formed smoothly, so that a multiple reflection is less and a bright reflecting surface that retains the polarization property can be obtained. By using such a reflecting member, it is possible to obtain a reflecting plate having both specularity, that is, light polarization maintaining and diffusing properties.

[0034]

1 is a cross-sectional view of a reflection type liquid crystal display device (hereinafter abbreviated as liquid crystal display device) 1 according to one embodiment of the present invention, and FIG. 2 is a plan view of a glass substrate 2 in the liquid crystal display device 1. is there. The liquid crystal display device 1 of this embodiment is of a simple matrix system as an example. The liquid crystal display device 1 includes a pair of transparent glass substrates 2 and 3, and a large number of large protrusions 4 and small protrusions 5 made of a synthetic resin material described below are formed on the glass substrate 2. Bottom diameter D1 of large protrusion 4 and small protrusion 5
D2 is set to 5 μm and 3 μm, respectively, as an example, and the distance D3 is set to at least 2 μm or more as an example.

These protrusions 4 and 5 are covered to form protrusions 4 and 5.
The smoothing film 6 is formed by filling the recesses between. The surface of the smoothing film 6 is affected by the projections 4 and 5 and is formed into a smooth curved surface. A reflective metal film 7 made of a metal material such as aluminum, nickel, chromium or silver is formed on the smoothing film 6. As shown in FIG. 2, the reflective metal film 7 is formed in a strip shape that is long in the left-right direction of FIG. The projections 4, 5, the smoothing film 6, and the reflective metal film 7 on the glass substrate 2 constitute a reflector plate 8 as a light reflecting member. An alignment layer 9 is formed on the reflective metal layer 7.

A glass substrate 3 facing the glass substrate 2
A transparent electrode 10 made of ITO (indium tin oxide) or the like is formed in a plurality of rows on the surface of the transparent metal film 7 in the direction perpendicular to the longitudinal direction of the reflective metal film 7. The reflective metal film 7 and the transparent electrode 10 form a matrix electrode structure. An alignment film 11 is formed so as to cover the glass substrate 3 on which the transparent electrode 10 is formed, and the peripheral portions of the glass substrates 2 and 3 facing each other have a sealing material 1 described later.
It is sealed with 2. Between the alignment films 9 and 11, for example, a liquid crystal material having a positive dielectric anisotropy Δε, for example, manufactured by Merck,
A liquid crystal layer 13 such as a product name ZLI4792 is enclosed.

On the opposite side of the glass substrate 3 from the liquid crystal layer 13, a stretched film made of polycarbonate (optical anisotropy Δ
n ₂ and thickness d ₂ ), an optical compensating plate 14 which is an optical phase compensating member is provided, and further, as an example, a single transmittance 4 is provided.
An 8% polarizing plate 15 is arranged.

One of the scanning circuit 16 and the data circuit 17 is connected to the reflective metal film 7 and the transparent electrode 10, respectively. The scanning circuit 16 and the data circuit 17 are
By the control of the control circuit 18 such as a microprocessor,
Based on the display data corresponding to the display content, the reflective metal film 7
While scanning the transparent electrode 10, the display voltage V1 or the non-display voltage V2 from the voltage generation circuit 19 is applied to realize the display.

FIG. 3 is a diagram showing an optical configuration of the polarizing plate 15, the optical compensation plate 14 and the liquid crystal layer 13. That is, the angle θ1 formed by the axial direction L2 of the slow axis of the optical compensation plate 14 in the clockwise direction with respect to the axial direction L1 of the absorption axis or the transmission axis of the polarizing plate 15 is set to 45 degrees, for example. On the other hand, the alignment direction L of the liquid crystal molecules 20 shown in FIG.
3 is a counterclockwise angle θ with respect to the axial direction L1.
2 is set to 45 degrees as an example.

FIG. 4 is a sectional view for explaining the manufacturing process of the reflector 8 shown in FIG. As shown in FIG. 4 (1), the thickness t1 (the glass substrate of 1.1 mm ² Examples 2 (Corning In this example, trade name 7059) is used. On the glass substrate 2, Tokyo examples Made by Oka, product name OFP
A photosensitive resin material such as R-800 is used at 500 rpm to 3
The resist layer 21 is formed by spin coating at 000 rpm. In this embodiment, spin coating is preferably performed at 2500 rpm for 30 seconds to form a resist film 21 having a thickness t2 (1.5 μm as an example).

Next, the glass substrate 2 having the resist film 21 formed thereon is baked at 90 ° C. for 30 minutes, and as shown in FIG. 4B, a large number of large and small circular patterns to be described later are formed. The exposed photomask 22 is arranged and exposed, and as an example, development is performed with a developer consisting of a 2.38% solution of NMD-3 under the trade name of Tokyo Ohka Co., Ltd., and glass is used as shown in FIG. 4 (3). Large protrusions 23 and small protrusions 24 having different heights were formed on the surface of the substrate 2. As you can see, two different heights
The reason for forming more than one type of protrusion is to prevent coloring of the reflected light due to interference of the light reflected at the crests and valleys of the protrusion.

The photomask 22 has a diameter D1 (for example, 5 μm) and a diameter D as shown in the arrangement of the large protrusions 4 and the small protrusions 5 formed by the photomask 22.
Two (for example, 3 μm) circles are randomly arranged, and an interval D3 between the circles is selected to be at least 2 μm or more. The pattern of the photomask 22 is not limited to this. The glass substrate 2 in the manufacturing stage of FIG. 4C is heated at 200 ° C. for 1 hour,
As shown in (4), the tops of the projections 23 and 24 were slightly melted to form an arc shape. Further, as shown in FIG. 4 (5), the same material as the photosensitive resin material is applied on the glass substrate 2 in the manufacturing stage of FIG. 4 (4) at 1000 rpm to 30 rpm.
Spin coat at 00 rpm. In this embodiment, spin coating is preferably performed at 2000 rpm. As a result, the recess between the protrusions 23 and 24 is filled, and the surface of the smoothing film 6 thus formed can be formed into a relatively gentle and smooth curved surface.

Further, a metal thin film of aluminum, nickel, chromium, silver or the like is formed on the surface of the smoothing film 6 to a film thickness t3 (for example, 0.01 to 1.0 μm). In this embodiment, aluminum is sputtered,
The reflective metal film 7 is formed.

A polyimide resin film is formed on each glass substrate 2 and 3 and baked at 200 ° C. for 1 hour. Then, a rubbing process for aligning the liquid crystal molecules 20 is performed.
As a result, the alignment films 9 and 11 are formed. The sealing material 12 for sealing between the glass substrates 2 and 3 is formed by screen-printing an adhesive sealing material mixed with a spacer having a diameter of 6 μm as an example.

When the reflection plate 8 thus formed and the glass substrate 3 on which the transparent electrode 10 and the alignment film 11 are formed are combined, spacers having a diameter of 5.5 μm are scattered between the glass substrates 2 and 3. Then, the layer thickness of the liquid crystal layer is regulated. The liquid crystal layer 13 is sealed by facing the glass substrates 2 and 3 and pasting them together with the sealing material 12 and then degassing in vacuum. The liquid crystal layer 13 has a refractive index anisotropy Δn ₁ of 0.094 and a layer thickness d ₁ of 5.
Since it is 5 μm, the retardation Δn ₁ d ₁ of this liquid crystal layer 13 is 517 nm.

FIG. 5 is a graph showing the voltage / reflectance characteristic of the liquid crystal display device 1 of this embodiment. Wavelength λ is 550 nm
Value (Δn ₁ d ₁ −Δn ₂ d ₂ ) when the light of
The retardations Δn ₂ d ₂ of the optical compensation plate 14 were selected so that /λ=0.25, 0.3, and 0.5. Characteristic curves 25 and 2 of FIG.
6,27 are obtained. That is, the characteristic curve 25 corresponds to the case where m = 0 in the fourth equation, and the characteristic curve 27
Corresponds to the case where m = 1 in the third equation.

Since the characteristic curve 26 does not satisfy both the third and fourth equations, the reflected light from the reflecting plate 8 or the characteristic curve 27 emitted from the liquid crystal display device 1 or the reflected light is output when no voltage is applied. An intermediate state in the case of the characteristic curve 25 that is shielded is shown, one of the third and fourth equations is satisfied at the voltage V1, and the third and fourth equations are satisfied at the voltage V2.
The other of the expressions is satisfied, and at this time, a preferable display quality is realized. That is, in this embodiment, the optical compensating plate 14 or the liquid crystal layer 1 is provided so that the third and fourth expressions are satisfied.
It is understood that high display quality can be realized by selecting the retardation of 3.

According to the experiments conducted by the present inventors regarding this embodiment, when a voltage is applied, the reflectance in the normal direction to the light incident from the direction inclined by an angle of 30 degrees with respect to the normal direction of the liquid crystal display device 1. Was about 45% at maximum and the maximum contrast ratio was 7. A standard white plate of magnesium oxide MgO was used as a reference member for determining the contrast ratio at this time. It should be noted that in the graph of FIG. 5, the reflectance becomes small because of the numerical value (Δn ₁ d ₁ −Δn
₂ d ₂ ) / λ is ± 0.25, and when the reflectance is maximum, the numerical value (Δn ₁ d ₁ −Δn ₂ d ₂ ) / λ is 0.5. By using these two states, monochrome display can be realized.

In this embodiment, only the case where m = 1 in the third equation and m = 0 in the fourth equation is shown, but it was confirmed that the same effect is exhibited even when the variable m is another numerical value. . In addition, here, both the third formula and the fourth formula show that the effect appears when the difference in retardation between the liquid crystal layer and the film shows a certain specific value. This value changes due to variations in layer thickness and film layer thickness. Therefore, when this value fluctuates, it is examined how much it affects the contrast. In both the third and fourth formulas, within a range of ± 0.1 or less, a large influence does not appear and it can be practically used. I knew that.

FIG. 6 is a diagram for explaining the operation of the liquid crystal display device 1 of this embodiment. For convenience of explanation, the liquid crystal display device 1 is shown.
Is disassembled and shown. In the light-shielding operation shown in FIG. 6A, when the incident light 28 passes through the polarizing plate 15, it becomes a linearly polarized light 29 parallel to the axial direction L1 of the polarizing plate 15. Linearly polarized light 29
However, the light passes through the optical compensation plate 14 and the liquid crystal layer 13 that satisfy the above-mentioned second expression, and becomes, for example, clockwise circularly polarized light 30.
This circularly polarized light 30 is reflected by the reflection plate 8 and is left-handed circularly polarized light 31.
Becomes When the circularly polarized light 31 passes through the liquid crystal layer 13 and the optical compensator 14 each having a retardation satisfying the fourth expression, the linearly polarized light having a polarization plane orthogonal to the direction of the linearly polarized light 29 at the time of incidence is obtained. 32. The linearly polarized light 32 is blocked by the polarizing plate 15. That is, the reflected light from the reflector 8 is blocked.

On the other hand, when the light passes through the liquid crystal layer 13 and becomes clockwise circularly polarized light, the circularly polarized light becomes counterclockwise circularly polarized light when reflected by the reflector 8.

On the other hand, during the light transmitting operation shown in FIG. 6B, the retardations Δn ₂ d ₂ and Δn ₁ d ₁ of the optical compensating member 14 and the liquid crystal layer 13 are set so as to satisfy the above-mentioned third equation. To be elected. At this time, when the incident light 28 passes through the polarizing plate 15, it becomes a linearly polarized light 29 parallel to the axial direction L1.
The linearly polarized light 29 retains the same polarization state even when passing through the optical compensating plate 14 and the liquid crystal layer 13 which are defined so as to satisfy the third expression. Even if the linearly polarized light 29 that has passed through the liquid crystal layer 13 is reflected by the reflection plate 8, the same linearly polarized state is maintained, and the same holds even after passing through the liquid crystal layer 13 and the optical compensation plate 14. Therefore, this reflected light passes through the polarizing plate 15 and is emitted.

In this embodiment, a stretched film made of polycarbonate was used as the optical compensation plate 14, but the present invention is not limited to this, and examples thereof include polyvinyl alcohol (PVA) or polymethylmethacrylate (PMMA). Stretched films of can also be used. Further, a liquid crystal element in which an alignment film is formed on the surfaces of a pair of glass substrates and a liquid crystal layer is enclosed between the alignment films for parallel alignment can also be used as the optical phase compensation plate. The retardation of the liquid crystal layer in this case is also a value defined by the above-mentioned third and fourth expressions. The liquid crystal molecules are arranged so as to be orthogonal to the liquid crystal molecules of the display element.

In the reflection type liquid crystal display device 1 of the present embodiment, the surface of the reflection plate 8 on which the reflection metal film 7 is formed is arranged on the liquid crystal layer 13 side, so that the parallax when observing the liquid crystal display device 1 is reduced. It is eliminated and a good display screen is obtained. Furthermore, when the liquid crystal display device 1 is configured to be driven by active matrix, it may be used as a pixel electrode connected to a thin film transistor used as a switching element or a non-linear element having a MIM (metal-insulation film-metal) structure. As mentioned above, it has been confirmed that good display quality can be realized.

Further, in order to increase the steepness of the electro-optical characteristics, it is desirable that the retardation Δn ₁ d ₁ of the liquid crystal layer 13 is uniform regardless of the location. Strictly speaking, when the reflection plate 8 has irregularities due to the projections 4 and 5 described above, the film thickness of the liquid crystal layer 13 is different between the tops of the projections 4 and 5 and the bottoms between the projections 4 and 5, and as a result, The retardation is also different. Therefore, the inventor of the present invention adds a planarizing layer made of acrylic resin as an example to fill the surface irregularities of the reflective metal film 7 and planarize it on the reflective metal film 7 of the reflector 8 shown in FIG. Then, a transparent electrode made of ITO or the like was further formed thereon in a shape similar to that of the reflective metal film 7 to form a display electrode. With this, the height difference of the protrusions on the surface of the flattening layer can be set to 0.1 μm.

By doing so, it was confirmed that the steepness of the electro-optical characteristics can be remarkably improved. In this case, regardless of whether it is an inorganic material or an organic material for the flattening layer, a transparent film having a flattening ability can be used regardless of the material. As a result, it was confirmed that simple multiplex driving of 100 scanning lines or more is possible.

Further, it has been confirmed that the same effect can be exhibited by an opaque substrate such as a silicon substrate instead of the glass substrate 2 in this embodiment. When such a silicon substrate is used as the glass substrate 2 in the above-described embodiment, the circuit elements such as the scanning circuit 16, the data circuit 17, the control circuit 18, and the voltage generating circuit 19 described above are integrated on the silicon substrate. It has the advantage that it can be formed.

As another embodiment of the present invention, a nematic liquid crystal twisted by 240 degrees between the glass substrates 2 and 3 (for example, manufactured by Chisso Corporation, trade name SD-4107).
There is a case where is used as the liquid crystal layer 13. In this embodiment, a stretched film made of polycarbonate is used as the optical compensation plate 14 in the structure shown in FIG. 1, and the liquid crystal layer 13 is formed so as to satisfy the conditions of the third and fourth formulas.
And the retardation Δn ₁ d ₁ , Δ of the optical compensator 14.
The n ₂ d ₂ was adjusted. The other components have the same configurations as those shown in FIG. According to such a configuration, according to the experiment by the present inventor, the display contrast was 6 in the case of 1/200 duty driving, and good display characteristics without parallax were realized.

In this embodiment, the liquid crystal twisted by 240 degrees is used for the liquid crystal layer 13, but the present invention is not limited to this, and any twist angle liquid crystal material or twisted liquid crystal can be used. Any liquid crystal material that does not have a property that retardation can be controlled by an electric field can be applied to the present invention. Moreover, even if a retardation can be set as the optical compensator 14 and such a retardation is optimally set so as to satisfy the conditions of the third and fourth formulas, the present invention is also possible. Will be feasible.

The present invention is not limited to the above embodiments, but can be applied to a wider range of reflection type light control devices. Further, by forming a color filter layer on one substrate, multi-color or full-color display is possible.

[0061]

As described above, according to the present invention, the incident light reaches the reflecting member via the polarizer, the optical phase compensating member and the liquid crystal layer, and is reflected by the reflecting member to be reflected by the liquid crystal layer and the optical phase compensating member. The light was emitted through the member and the polarizer.
Here, the linearly polarized light emitted from the polarizer becomes elliptically polarized light after passing through the optical compensation member and the liquid crystal layer, and the phase difference δ of this elliptically polarized light is determined by the third formula.

Numerical value (Δn ₁ d ₁ −Δn) in the third equation
_The optical switching operation can be realized by adjusting ₂ d ₂ ) / λ with the electric field applied to the liquid crystal layer. That is, since the light reflection member can be formed inside the liquid crystal element and the projections on the unevenness of the reflection surface of the light reflection member can be formed smoothly, a multiple reflection is less and a bright reflection surface that retains the polarization property can be obtained. it can. By using such a reflecting member, it is possible to obtain a reflecting plate having both the polarization property of light and the diffusivity. That is, it is possible to eliminate the parallax and realize a reflective liquid crystal display device having high definition and high display quality.

Further, by providing the liquid crystal molecules in parallel alignment or twist alignment, it is possible to realize a reflective liquid crystal display device which has a high response speed, high reliability of display operation, and which is suitable for mass production.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal display device 1 according to an embodiment of the present invention.

FIG. 2 is a plan view of a glass substrate 2.

FIG. 3 is a diagram illustrating optical characteristics of the liquid crystal display device 1.

FIG. 4 is a cross-sectional view illustrating a manufacturing process of the reflection plate 8.

FIG. 5 is a graph illustrating the voltage-reflectance characteristic of the liquid crystal display device 1.

FIG. 6 is a diagram illustrating a display operation of the liquid crystal display device 1 of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2,3 Glass substrate 4,5 Protrusion 6 Smoothing film 7 Reflective metal film 8 Reflector 9,11 Alignment film 10 Transparent electrode 13 Liquid crystal layer 14 Optical compensation plate 15 Polarizing plate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kozo Nakamura 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Naofumi Kimura 22-22 22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within the corporation

Claims (10)

[Claims] 1. A reflection type liquid crystal display device comprising a polarizer disposed on the light incident side of a liquid crystal element, wherein the liquid crystal element has an insulating substrate having at least a transparent electrode and one surface of which has smooth irregularities. Between the insulating substrate and the reflecting member, and the specular light reflecting member having the light reflecting surface formed on the one surface and the counter electrode for display driving in cooperation with the transparent electrode. And a liquid crystal layer in which the orientation of liquid crystal molecules is selected to be either parallel orientation or twist orientation, and an optical phase compensation member is disposed between the polarizer and the liquid crystal element. Reflective liquid crystal display device. 2. A retardation Δn _{1 of the} liquid crystal element.
d ₁ (Δn ₁ ; optical anisotropy of liquid crystal layer, d ₁ ; layer thickness of liquid crystal layer) and retardation Δn ₂ d _{2 of} optical phase compensation member
(Δn ₂ ; optical anisotropy of the optical phase compensating member, d ₂ ; thickness of the optical phase compensating member) is 400 to 400 when the voltage V1 is applied.
For the wavelength λ of the light in the range of 700 nm, when | Δn ₁ d ₁ −Δn ₂ d ₂ | /λ=m/2±0.1 (m = 0, 1, 2, ...) Light transmission state, and a wavelength of 400 when voltage V2 is applied.
˜Δn ₁ d ₁ −Δn ₂ d ₂ | /λ=0.25+m/2±0.1 (m = 0,1,2, ...) ), A value of | Δn ₁ d ₁ −Δn ₂ d ₂ | / λ is selected depending on the electric field applied to the liquid crystal layer.
The reflective liquid crystal display device according to claim 1, wherein the reflection type liquid crystal display device is changed. 3. A retardation Δn _{1 of the} liquid crystal element.
d ₁ and the retardation of the optical phase compensation member Δn ₂ d ₂
Are selected so as to satisfy the first expression with respect to the wavelength λ of light in the range of 400 to 700 nm when no voltage is applied, and the numerical value | Δn ₁ is determined by the electric field applied to the liquid crystal layer.
The reflective liquid crystal display device according to claim _1, wherein d ₁ −Δn ₂ d ₂ | / λ is changed. 4. The retardation Δn _{1 of the} liquid crystal element.
d ₁ and the retardation of the optical phase compensation member Δn ₂ d ₂
Are selected so as to satisfy the second equation with respect to the wavelength λ of light in the range of 400 to 700 nm when no voltage is applied, and the numerical value | Δn _{1 is set} by the electric field applied to the liquid crystal layer.
The reflective liquid crystal display device according to claim _1, wherein d ₁ −Δn ₂ d ₂ | / λ is changed. 5. The reflective liquid crystal display device according to claim 1, wherein a light reflecting film forming a light reflecting surface of the light reflecting member faces the liquid crystal layer side. . 6. The reflective liquid crystal display device according to claim 1, wherein the light reflecting surface is defined as an electrode surface facing a transparent electrode formed on the insulating substrate. 7. The liquid crystal element, wherein the optical phase compensating member comprises a pair of transparent substrates, transparent electrodes formed on the respective transparent substrates, and a liquid crystal layer enclosed between the respective transparent substrates. The reflective liquid crystal display device according to claim 1. 8. The reflective liquid crystal display device according to claim 1, wherein the optical phase compensation member is a polymer stretched film. 9. A transparent flattening layer that absorbs irregularities formed on the surface of the light reflecting member is provided on the light reflecting surface, and a transparent electrode is formed on the flattening layer. The reflective liquid crystal display device according to claim 1, wherein the electrode is defined as an electrode facing a transparent electrode formed on the insulating substrate. 10. The reflective liquid crystal display device according to claim 1, wherein a color filter layer is formed on either the insulating substrate or a transparent electrode formed on the insulating substrate.