JP2000214445A - Liquid crystal device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of effectively preventing reflection of a background without impairing display brightness and high contrast in a liquid crystal device. SOLUTION: In this liquid crystal device comprising a liquid crystal layer 30 held between a pair of substrates (an active matrix substrate 10, a counter substrate 20), a light reflection means (pixel electrodes 15) is formed on one substrate out of a pair of the substrates and diffraction gratings DG (the diffraction grating DG1, the diffraction grating DG2), having characteristics due to superposition of at least two waveforms with different periods, are provided on the substrate on the liquid crystal layer side rather than on the light reflection means side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device or an electronic apparatus used for a display of a notebook computer or a portable game machine.

[0002]

2. Description of the Related Art A reflection type liquid crystal device is constructed such that a light reflecting layer provided inside a display device reflects external light to provide a display which can be viewed, so that a backlight device is unnecessary. This has the advantage that power consumption can be kept low.

Various modes of a reflection type liquid crystal device have been developed. For example, an OCB mode (SID'9) has been developed.
5, p.599) and reflection TN mode (AM-LCD'95, p.329, SID'9
0, p.145).

However, since the reflection type liquid crystal device depends on the intensity of external light, the display tends to be dark inside a room or the like, and the contrast cannot be sufficiently secured. .

For this reason, the field to which the reflection type liquid crystal device can be applied is limited to some fields such as calculators, various display panels, small game machines, and the like. Since a member such as a filter is required, light transmittance is reduced, and it is difficult to secure sufficient brightness due to reflection of external light, so that the contrast is further reduced.

Therefore, in order to improve the reflection luminance of the reflection type liquid crystal device and secure sufficient display brightness, the following liquid crystal device has been developed (SID'97 Digest, p.102).
3).

For example, a so-called polymer-dispersed liquid crystal has a state in which a polymer and a liquid crystal material are mixed, and changes the refractive index difference between the polymer and the liquid crystal depending on the presence or absence of an applied voltage, thereby causing light scattering. The display is performed by increasing or decreasing the amount.

That is, by eliminating the difference in refractive index between the polymer and the liquid crystal, light is specularly reflected to obtain a black display. Also, by generating a refractive index difference between the polymer and the liquid crystal,
Light is scattered to obtain a white display.

According to the method using such a polymer-dispersed liquid crystal, display can be performed without using a polarizing plate, so that there is no loss of light amount due to the polarizing plate. Accordingly, sufficient display brightness can be ensured even in a reflective liquid crystal device.

[0010]

However, in the conventional liquid crystal device, it is necessary to improve the reflectance in the light transmitting state in order to secure the brightness of the display. However, in this case, it has been found that the reflection of the background becomes a problem in the light transmission state of the liquid crystal device because the surface of the reflection layer is a mirror surface.

[0011] The reflection of the background affects the visibility in addition to the contrast and the brightness of the display, and has a disadvantage of deteriorating the display quality.

One of the measures for preventing the reflection of the background is to roughen the surface of the reflective layer so that the reflective layer itself has a scattering effect. In other words, the mirror effect of the reflection layer is eliminated by the scattering effect, but processing to have scattering characteristics in the first place lowers the reflectance. Therefore, lowering the reflectance leads to lowering of the brightness of the display, which is the end of the game.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to effectively prevent the reflection of the background without impairing the brightness and contrast of the display in a liquid crystal device. The main purpose is to provide technologies that can be used.

[0014]

In order to achieve the above object, the present invention provides a liquid crystal device having a liquid crystal layer sandwiched between a pair of substrates. And a diffraction grating having a characteristic in which at least two waveforms having different periods are superimposed is formed on the liquid crystal layer side of the light reflecting means.

According to this, the incident light is guided by the diffraction grating having a characteristic in which at least two waveforms having different periods are superimposed so as to have a uniform diffraction intensity distribution. Therefore, the incident light modulated by the diffraction grating is incident on the liquid crystal layer, and is again modulated by the diffraction grating when reflected by the light reflecting means and emitted from the liquid crystal layer again, so that the background or the like can be projected as it is. It is prevented and visibility can be improved.

In a liquid crystal device in which a liquid crystal layer is sandwiched between a pair of substrates, one of the pair of substrates is provided with a light reflecting means, and the other substrate has a light reflection means. May be provided with diffraction gratings having characteristics in which at least two waveforms having different periods are superimposed on different sides. Also in this case, a diffraction grating provided on a side of the other substrate different from the liquid crystal layer side,
The incident light is introduced in a state modulated so as to have a uniform diffraction intensity distribution. Therefore, the incident light modulated by the diffraction grating is incident on the liquid crystal layer, and is again modulated by the diffraction grating when reflected by the light reflecting means and emitted from the liquid crystal layer again, so that the background or the like can be projected as it is. It is prevented and visibility can be improved.

In a liquid crystal device having a liquid crystal layer sandwiched between a pair of substrates, a light reflecting means is formed on one of the pair of substrates, and the other substrate has a light reflecting means on the liquid crystal layer side. Alternatively, a diffraction grating having a characteristic in which at least two waveforms having different periods are superimposed may be formed. Also in this case, the incident light is guided by the diffraction grating provided on the liquid crystal layer side of the other substrate so as to be modulated so as to have a uniform diffraction intensity distribution. Therefore, the incident light modulated by the diffraction grating is incident on the liquid crystal layer, and is again modulated by the diffraction grating when reflected by the light reflecting means and emitted from the liquid crystal layer again, so that the background or the like can be projected as it is. It is prevented and visibility can be improved.

Note that the diffraction grating reduces the luminance factor,
It is preferable to have a characteristic of lowering the glossiness and making the diffraction intensity distribution uniform.
4, and the glossiness is desirably 1,000 or less. This is because reflection can be effectively prevented.

Further, the diffraction grating can be configured as a light modulation element in which a wavefront in which at least two waveforms having different periods are superimposed is formed on the surface of the sheet member.

Further, the diffraction grating may be a light modulation element in which a refractive index distribution having a waveform in which at least two waveforms having different periods are superimposed is formed inside a sheet-shaped member made of a translucent material.

Further, the diffraction grating may have an internal refractive index distribution for suppressing generation of scattered light or higher-order diffracted light.

Further, the liquid crystal layer may be a composite layer comprising a liquid crystal and a polymer.

The liquid crystal layer may be a nematic liquid crystal layer, and the polarizing means may be provided only on the other substrate.

Further, the diffraction grating may be arranged on the liquid crystal layer side of the light reflecting means.

With these configurations, the amount of backscattered light due to the surface shape or internal structure can be reduced, and the distribution of forward scattered light can be appropriately controlled, which does not contribute to display brightness and hinders visibility. Since the generation of useless light can be suppressed, the reflection of the background can be effectively prevented without sacrificing the brightness and contrast of the display.

Further, by using a liquid crystal device equipped with the diffraction grating as a display device in an electronic device, the reflection of the background can be reduced without sacrificing the brightness and contrast of the display in the display devices of various electronic devices. It is possible to provide a display that can be effectively prevented and is easy to see.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of the liquid crystal device according to the first embodiment, and FIG. 2 is a partially enlarged cross-sectional view taken along line AA ′.

In the drawing, reference numeral 10 denotes an active matrix substrate.

The active matrix substrate 10 is formed of glass, and a liquid crystal device is formed by the opposing substrate 20. A plurality of pixel electrodes 15 are formed on the active matrix substrate 10, and a sealing material 50 is formed around a pixel region (a region where the alignment state of the liquid crystal layer 30 changes) by the pixel electrodes 15. Note that the sealing material 50 is made of a photocurable resin.

A light-shielding peripheral parting layer 51 is provided along the inner periphery of the sealing material 50.

When the active matrix substrate 10 is set in a light-shielding case in which an opening is formed corresponding to a pixel region, the peripheral parting layer 51 is formed at the edge of the opening of the case due to a manufacturing error or the like. It is formed of a band-shaped light-shielding material having a width of about 500 μm to 1 mm around the pixel area so as not to be hidden by, for example, to allow about 100 μm as a deviation from the case of the substrate. Such a light-shielding peripheral parting layer 51
Is, for example, Cr (chromium), Ni (nickel), Al
The counter substrate 20 is formed by sputtering, photolithography, and etching using a metal material such as (aluminum). Instead of the metal material, the peripheral parting layer 51 may be formed of a material such as resin black in which carbon or Ti (titanium) is dispersed in a photoresist.

A peripheral circuit (scanning line drive circuit) 52 and a pad 53 as an external terminal are provided along the lower side of the pixel region in a region outside the sealing material 50, and are provided on both sides of the pixel region (left and right in FIG. A peripheral circuit (signal line driving circuit) 54 is provided along the side. Further, a wiring 55 for electrically connecting the peripheral circuits 54 provided on both sides of the pixel region is provided on the upper side of the pixel region.
Columns 56 made of a conductive material for establishing electrical continuity between the active matrix substrate 10 and the counter substrate 20 are provided at the four corners of the sealing material 50. The opposing substrate 20 having substantially the same contour as the sealing material 50 is formed by the sealing material 50 on the active matrix substrate 1.
The liquid crystal device P is fixed to 0.

In FIG. 2, a thin film transistor (hereinafter, referred to as a TFT element) 60 connected to the pixel electrode 15 formed of ITO (indium tin oxide) is formed on the active matrix substrate 10.

The TFT element 60 as a switching element
Are a gate electrode 11 formed of, for example, a molybdenum-tantalum alloy, a gate insulating film 12 formed of silicon nitride, an active semiconductor layer 13 formed of amorphous silicon doped with phosphorus, and a source electrode formed of aluminum. 14, and a drain electrode 16.
The pixel electrode 15 is a drain electrode 16 of the TFT element 60.
Is electrically connected to

The TFT element 60 is configured to apply a potential to the pixel electrode 15 according to a driving potential supplied from a wiring layer (not shown).

The pixel electrode 15 also functions as a reflection layer for reflecting light incident from the outside.

The TFT element 60 and the pixel electrode 1
An alignment film 17 made of a polyimide resin is formed on 5 and rubbed in a predetermined direction.

On the other hand, a transparent counter electrode 21 made of ITO (indium tin oxide) is formed on the surface of the counter substrate 20 made of glass. In addition, the counter electrode 21
An alignment film 22 is formed on the surface of the substrate, and a rubbing process is performed.

Between the active matrix substrate 10 and the opposing substrate 20, a liquid crystal having dielectric anisotropy and a refractive index anisotropy, and a polymer having a relationship between the liquid crystal and a predetermined refractive index are interposed. The liquid mixture 30a dispersed and dispersed is injected to form the liquid crystal layer 30.

When a composite layer composed of such a liquid crystal and a polymer is used as the liquid crystal layer 30, the refractive index of the polymer and the liquid crystal molecules (with the exception of the active matrix substrate 10 or When the refractive indices in the direction perpendicular to the counter substrate 20 are substantially the same, they become optically transparent. When the refractive indices of the polymer and the liquid crystal molecules are different, the incident light is scattered. Become like

On the other hand, the pixel electrode 15 is
When a voltage is applied between the liquid crystal molecules having dielectric anisotropy and the counter electrode 21, the orientation direction of the liquid crystal molecules having dielectric anisotropy changes in the direction of the electric field due to the electric field caused by the voltage. A difference occurs between the refractive index in the direction perpendicular to the substrates 10 and 20 and the refractive index of the polymer. Therefore,
A light scattering state is obtained.

When no electric field is applied, the refractive index of the polymer in the direction perpendicular to the substrate surface is substantially the same as the refractive index of the liquid crystal molecules, and the liquid crystal layer 30 is in a light transmitting state.

On the other hand, when an electric field is applied, a change in the refractive index of the liquid crystal molecules causes a difference in the refractive index from the refractive index of the polymer, and the liquid crystal layer 30 is in a light scattering state.

When no electric field is applied, the refractive index of the polymer is different from the refractive index of the liquid crystal molecules, resulting in a light scattering state. It can also be set in advance so that the refractive index of the liquid crystal molecules is substantially the same as that of the liquid crystal molecules, and the liquid crystal molecules are in a light transmitting state.

On the outer surface 20a of the counter substrate 20, a phase modulation type diffraction grating DG is adhered.

The diffraction grating DG can be formed as a surface shape of a waveform in which at least two waveforms having different periods are superimposed (diffraction grating DG1), or at least two waveforms having different periods are provided inside the translucent member. Can be configured as a refractive index distribution having a waveform in which is superimposed (diffraction grating DG2).

FIG. 3 is a partially enlarged sectional view according to the second embodiment. The plan view is the same as FIG. 1 described above. The difference from the configuration according to the first embodiment is that the switching element formed on the active matrix substrate 10 is an MIM.

The configuration will be described below.

In FIG. 3, reference numeral 10 denotes an active matrix substrate formed of glass. On the active matrix substrate 10, a wiring layer (not shown) made of Ta is formed. The electrode part 112 is formed integrally.

An anodic oxide film 113 is formed on the surface of the first electrode portion 112.
By sputtering and patterning r,
The second electrode part 114 is formed integrally with the pixel electrode 115.

The first electrode portion 112 and the anodic oxide film 113
And the second electrode unit 114 is a MIM made of a non-linear element.
A (metal-insulator-metal) element is configured to apply a potential to the pixel electrode 115 according to a drive potential supplied from a wiring layer (not shown).

The pixel electrode 115 also functions as a reflection layer for reflecting light incident from the outside.

The MIM element and the pixel electrode 115
On top of this, an alignment film 116 made of a polyimide resin is formed, and rubbing is performed in a predetermined direction.

On the other hand, a plurality of transparent opposing electrodes 121 made of ITO (indium tin oxide) are formed on the surface of the opposing substrate 20 made of glass in a stripe shape.

The alignment film 1 is provided on the surface of the counter electrode 121.
A rubbing process is performed in the same direction as the orientation film 116, for example.

On the outer surface 20a of the counter substrate 20, a phase modulation type diffraction grating DG is adhered.

This diffraction grating DG can be configured as a surface shape of a waveform in which at least two waveforms having different periods are superimposed (diffraction grating DG1). Alternatively, it can be configured as a refractive index distribution having a waveform in which at least two waveforms having different periods are superimposed inside the translucent member (diffraction grating DG2). A waveform in which at least two waveforms having different periods as described above are superimposed. (1) controlling the spatial intensity distribution of the transmitted light of the light (for example, ceiling light or sunlight) incident on the liquid crystal device, and (2) controlling the transmitted light as described above. The effect based on the light modulation action of controlling the spatial intensity distribution of the light reflected by the pixel electrode 115 can be obtained.

Here, the characteristics and specific configuration required for the phase modulation type diffraction grating DG according to the present invention will be described with reference to the drawings.

First, FIG. 8 is a graph showing characteristics of a liquid crystal device in which a composite layer composed of liquid crystal and a polymer is interposed as a liquid crystal layer. An outline of characteristics of the liquid crystal device will be described.

In FIG. 8, OFF indicates a state in which no voltage is applied to the liquid crystal, and ON indicates a state in which a voltage is applied.

The light reflectance on the vertical axis indicates a relative value when the value of the standard diffuser (BaSO ₄ ) is 100. The measurement was performed with the azimuth of the liquid crystal display surface set to 0 ° and the light incident direction set to −30 °.

Referring to FIG. 8, it can be seen that the reflectivity sharply increases near the measurement angle of 20 to 40 ° when the voltage is turned off, and becomes higher than the state when the voltage is turned on. this is,
This shows that when a user looks at the liquid crystal device with the naked eye, the background is more intense when the viewing angle is 20 to 40 ° in a state where no voltage is applied to the liquid crystal.

FIG. 9 is a graph showing the relationship between the contrast and the viewing angle. In FIG. 9, the specular reflection direction (+30)
°), it can be seen that in the vicinity of the angle region, the reflection by the built-in reflection layer is strong and the contrast is extremely low (（4 or less).
In this specification, the specular reflection direction (+30
°) A nearby angle region is referred to as an “invalid region”.
In a liquid crystal device, this invalid area cannot be used for display, so that the invalid area is desirably as small as possible in order to use a large display area.

Here, considering the index for evaluating the performance of the liquid crystal device from the viewpoint of the reflection of the background, the luminance ratio and the glossiness can be raised.

FIG. 10 schematically shows a standard method of measuring the luminance factor. For example, white light (C) collimated at an angle of 45 ° with respect to a normal line n of a liquid crystal device P as a measurement sample. (Light source), and the intensity of the reflected light is measured by the photodetector 100 arranged in the normal direction.

Then, the measured value is used as a standard reference sample (BaS
The value obtained by dividing the measured value for O ₄ ) is defined as the luminance ratio (J
IS-Z8722).

FIG. 11 shows an outline of a standard measuring method of glossiness. For example, white light (C) collimated at an angle of 45 ° with respect to a normal line n of a liquid crystal device P as a measurement sample. (A light source) is incident, and the intensity of the reflected light is measured by a photodetector 101 arranged at a reflection angle (45 °). The definition of glossiness is detailed in JIS-Z8741.

The degree of gloss has a correlation with the intensity of specular reflection and the sharpness of the reflected image.

FIG. 12 shows a voltage O in a conventional liquid crystal device.
It is a graph which shows the glossiness at the time of N and at the time of OFF,
The amounts attributable to the built-in reflection layer and the amounts attributable to the glass substrate surface are shown.

Here, two factors for determining the glossiness are the built-in reflection layer and the surface of the glass substrate.

That is, when the voltage is ON, the light is scattered by the liquid crystal layer, and at this time, the reflection on the glass surface mainly affects the glossiness. However, the absolute value of the glossiness is as small as 200%.

On the other hand, when the voltage is OFF, the liquid crystal layer is transparent, and most of the light is reflected by the built-in reflection layer, so that the specular reflection greatly affects the glossiness. The absolute value of the size is 1
It can be seen that the voltage reaches 200%, which is about six times that when the voltage is ON.

In the liquid crystal device, the following three conditions are required for the phase modulation type diffraction grating DG in order to prevent the reflection of the background.

(1) The amount of backscattering is small. That is, since backscattering has an adverse effect of increasing unnecessary luminance when the voltage is turned off and lowering contrast, it is necessary to reduce backscattering inherent to the diffraction grating DG. . The degree of backscattering can be evaluated by the magnitude of the luminance factor.

(2) The glossiness is low. That is, since the glossiness has a correlation with the sharpness of the reflected image, it is necessary to reduce the glossiness due to the reflection on the built-in reflection layer and the glass surface.

(3) Narrow forward scattering distribution In other words, the wider the forward scattering distribution, the wider the ineffective area described above and the narrower the visual field, so that while satisfying the above conditions (1) and (2), It is necessary to make the forward scattering distribution unique to the diffraction grating DG as narrow as possible.

In the present embodiment, the following two types of diffraction gratings are used as the phase modulation type diffraction grating DG satisfying such conditions.

(A) A diffraction grating having, as a surface shape, a waveform in which at least two waveforms having different periods are superimposed on the surface of the translucent member. (B) At least two waveforms having different periods are superimposed inside the translucent member. In the present embodiment, as a specific example of the diffraction grating according to the above (a), a diffraction grating DG1 having a light diffusion plate function shown in FIG.
FIG. 14 illustrates a volume type diffraction element DG2 as a specific example of the diffraction grating according to the above (b).

FIG. 13 is a cross-sectional view schematically showing a schematic configuration of a diffraction grating DG1 having, as a surface shape, a waveform in which at least two waveforms having different periods are superimposed on the surface of the translucent member.

The diffraction grating DG1 has a light diffusion characteristic. For example, a predetermined period (for example, 25.5 × 32.5 μm) is formed on the surface of a sheet-like transparent member 200 made of, for example, PMMA (polymethyl methacrylate) or glass. And the sine wave of
A waveform W1 of a superimposed wave formed by superimposing a sine wave having a triple cycle thereof is formed by engraving by photolithography and dry etching.

The average size of the waveform W1 of the superimposed wave is preferably about 10 μm or more, and the average height is preferably about 1 μm.
μm or more.

The size of the waveform W1 of the superposed wave is preferably smaller than the pixel size. For example, when the pixel size is several tens to several hundreds of μm square, the length of one cycle of the waveform W1 of the superposed wave is longer. It is desirable that the height is about 20 μm in the plane direction.

On the other hand, FIG. 14 is a cross-sectional view schematically showing a schematic configuration of a volume type diffraction element DG2 having, as a refractive index distribution, a waveform in which at least two waveforms having different periods are superimposed inside a translucent member. FIG.

The volume type diffraction element DG2 is, for example, a PMM.
A sine wave of a predetermined period (for example, 25.5 × 32.5 μm) is provided inside a polished sheet-like transparent substrate 201 made of A (polymethyl methacrylate), glass, or the like.
A superimposed wave-like refractive index distribution W2 formed by superimposing a double-period sine wave is formed by introducing a substance such as a predetermined metal by ion implantation, plasma processing, chemical reaction, or the like.

The waveform W1 of the superimposed wave of the diffraction grating DG1
And the period of the refractive index distribution W2 in the form of a superimposed wave of the diffraction element DG2 is determined in consideration of the number of diffracted lights to be applied to a predetermined angle range and the size of the moiré fringes. Is determined such that the sum of the amounts of diffracted light applied to a predetermined angle range is maximized.

That is, assuming that the grating period (determined from the number of diffracted lights to be injected into a predetermined angle area (viewing area)) is p, the predetermined angle area is ± θ, and the maximum diffraction order is N, these relations are as follows. Is given by the following equation.

Sin θ = Nλ / p (1) However, in consideration of the periodicity of the liquid crystal panel, it is necessary to select a grating period so that moire fringes do not occur (are not visually recognized).

As for the grating depth, the light energy input into a predetermined angle range -θ to + θ, that is, (2N +
1) the sum of the ^two diffracted light intensity is determined to be maximum.

Here, _assuming that the sum of the diffracted light intensities is Ση _n , the lattice depth is h, and the optimal depth is h _opt , Ση _n (h _opt ) → max. ... Equation 2

If the grating period is p _g and the pixel period of the liquid crystal panel is p _LC , the period p _{M of the} moire fringes to be visually recognized is given by the following equation.

1 / p _M = | 1 / _pg −n / p _LC |; n is a positive integer Expression 3 In the above embodiment, a case where two sine waves having different periods are superimposed is described. However, the present invention is not limited to this, and three or more sine waves having different periods may be superimposed, and the waveform to be superimposed is not limited to the sine wave.

Next, the characteristics of the diffraction grating DG1 and the volume type diffraction element DG2 according to the present embodiment with respect to the reflection of the background will be described. For comparison, a conventional simple sine wave (period) shown in FIG. Is, for example, 25.5 × 32.5
A transmitted light scattering intensity distribution was measured using a diffraction grating (referred to as a simple grating) having a waveform W ′ of μm) formed on the surface.

FIG. 16 shows the transmitted light scattering intensity distributions (light scattering characteristics) of the surface irregular type diffraction grating DG1 and volume type distributed refractive index type diffraction element DG2 and the conventional simple grating according to the present embodiment. FIG. 16 (b) is an enlarged view of a part of the angle range (± 5 °) of FIG. 16 (a).

In FIG. 16, broken lines indicate light scattering characteristics of the simple grating, and solid lines indicate light scattering characteristics of the diffraction gratings DG1 and DG2 according to the present embodiment.

According to the measurement result of the transmitted light scattering intensity distribution in FIG. 16, the angle range (± 5 °) which contributes to the visibility of the liquid crystal device is obtained.
It can be seen that, while the change in the scattered light intensity is relatively large in the simple grating, the distribution of the scattered light intensity changes relatively smoothly in the diffraction grating DG1 and the diffraction element DG2, and the change is small. This indicates that visibility can be improved in a liquid crystal device using the diffraction grating DG1 or the diffraction element DG2.

It is considered that such improvement in visibility is caused by the difference between the diffraction pattern of the conventional simple grating and the diffraction pattern of the diffraction grating having the superposed wave structure of the present invention.

That is, as shown in FIG. 17, in the simple grating, five main diffracted lights (0 order, ± 1 order, ± 2 order) are converted into ± 1 order.
In contrast to the case where the light is injected into the angle range of 5 °, in the case of a superimposed grating such as the diffraction grating DG1 or the diffraction element DG2, FIG.
As shown in FIG. 8, the eleven main diffracted lights (0th order, ± 1
, ± 2, ± 3, ± 4, ± 5) within the angle range of ± 5 °.

Further, in addition to the quantitative evaluation based on the above measurement, the diffraction grating DG1 and the diffraction element DG2 as the diffraction grating having the superimposed wave structure according to the present embodiment, and the simple grating are arranged on the liquid crystal panel, An evaluation test was conducted on the specularity (the degree of reflection of the background), contrast, blurring of the image, and moire fringes.

The results are as follows.

(1) Regarding the mirror feeling and contrast,
No remarkable difference was found between the diffraction grating DG1 and the diffraction element DG2 and the simple grating.

(2) Regarding visibility, it was felt that the diffraction grating DG1 and the diffraction element DG2 had higher visibility than the simple grating.

Note that no moiré fringes were observed in any case. From the above evaluation results, the diffraction grating D as the diffraction grating having the superimposed wave structure according to the present embodiment is comprehensively obtained.
It was confirmed that G1 and the diffraction grating DG2 were more effective in improving the visibility of the liquid crystal device than the simple grating.

Next, the diffraction grating DG1 and the diffraction element DG2 according to the present embodiment were mounted on a liquid crystal device, and the luminance factor and the glossiness were measured by the measurement methods shown in FIGS.

As a result, a graph showing the relationship between diffuse reflectance and gloss as shown in FIG. 19 was obtained. In the graph of FIG. 19, Δ represents the characteristic of the diffraction grating DG1, and ○ represents the diffraction element D.
It is a plot of the characteristics of G2.

From the viewpoint of preventing the reflection of the background, the region surrounded by the dotted line in the drawing is a desirable region, and the luminance ratio is 0.4%.
Below, the glossiness is in the range of 1000 or less.

This is because, for example, the contrast of the liquid crystal device alone without using the diffraction grating DG1 or the diffraction element DG2 is ９9.
At 0, when the luminance factor with the diffraction grating DG1 or the diffraction element DG2 mounted is ０．４0.4 or more, the contrast of the display device is reduced to ５5 or less, and when the luminance factor is ０．３0.3. , The contrast is up to 7.0, and the luminance ratio is up to 0.2.
In this case, the contrast is と 8.0. Then, from the result of the visibility evaluation, it is determined that a contrast of ５5 or less is not acceptable.

Therefore, the target value of the luminance factor is determined to be 0.4 or less.

Further, regarding the glossiness, when the glossiness is 1000 or more, the target value is set to 1000 or less in consideration of the fact that more and more viewers answered that "mirror feeling is not sufficiently removed". It is defined.

From the graph of FIG. 19, it can be seen that both the diffraction grating DG1 and the diffraction element DG2 are within the desired region indicated by the dotted line, and are effective in reducing the reflection of the background.

The contrast of the liquid crystal display device without using the diffraction gratings DG1 and DG2 was up to 9.0, whereas the contrast in the case of using the diffraction grating DG1 was up to 8.0. , And 7.0 when the diffraction grating DG2 was used, and it was confirmed that the contrast was in a practically sufficient level in both cases.

The glossiness (the degree of reflection of the background, the degree of specularity) is shown in FIG. 20 when the diffraction gratings DG1 and DG2 as the superposition grating according to the present embodiment are mounted when the voltage is turned off. And the case where neither was mounted are shown in the graph.

According to FIG. 20, when neither the diffraction grating DG1 nor the diffraction grating DG2 is mounted, the gloss is about 1
200%, about 600% when using the diffraction grating DG1, and about 40% when using the diffraction grating DG2.
The glossiness could be suppressed to 0% and 1000% or less.

In particular, when the diffraction grating DG1 is used,
The gloss component due to the surface reflection of the glass could be almost completely removed.

Here, the diffraction grating DG according to the above embodiment is described.
A mechanism for improving the visibility of the liquid crystal display device by using the diffraction grating 1 and the diffraction grating DG2 will be described.

According to the first and second embodiments shown in FIGS. 1 to 3, the incident light passes through the diffraction grating DG1 or DG2 and is modulated (scattered or diffracted). The light passes through the substrate 20 and is transmitted or scattered by the liquid crystal layer 30 in accordance with the state of each pixel (ON / OFF of the electric field).

The transmitted light is applied to the pixel electrode 1 also serving as a reflection layer.
The light is reflected by the liquid crystal layer 5, 115 and passes through the liquid crystal layer 30, the counter substrate 20, and the diffraction grating DG1 or DG2, and is visually recognized again.

At this time, most of the light scattered by the liquid crystal layer 30 passes through the diffraction grating DG1 or DG2 and is directly visually recognized, and part of the light is reflected by the pixel electrode 15 and indirectly reflected. It is visually recognized.

In the above-described liquid crystal device, the reflection of the background becomes a problem in the pixels in the transmission state.

In the conventional liquid crystal device, in the transmission state, the higher the transmittance of the liquid crystal layer 30 is, the more the pixel electrodes 15 and 115 function as a reflection layer. It was reflected on the screen and visibility was impaired.

However, according to the liquid crystal devices according to the first and second embodiments, the special diffraction grating DG1 or DG2 having the above-described characteristics is provided on the surface of the counter substrate 20. The incident light is modulated by the diffraction grating DG1 or DG2 and enters the inside of the liquid crystal layer 30, is reflected by the pixel electrodes 15 and 115, passes through the diffraction grating DG1 or DG2 again, and again. After being modulated, it reaches the eyes of the viewer. As described above, in the present embodiment, the light is modulated by the diffraction grating DG1 or DG2 at the time of light incidence and at the time of light emission, so that the background or the like is suppressed from being visually recognized as in the related art. The problem of the reflection of the background can be solved.

In particular, in the liquid crystal device, the image is in the vicinity of the diffraction grating DG1 or DG2 (up to 1 mm or less).
, And the background is located relatively far (up to 200 mm). Therefore, by designing, manufacturing and using the diffraction gratings DG1 and DG2 in consideration of these conditions, the image quality is almost affected. Without this, the reflection of the background can be effectively prevented.

Incidentally, the diffraction grating DG1 or the diffraction grating DG
2, the amount of irregular reflection on the surface can be reduced by designing the superimposed wave waveform or the internal refractive index distribution on the surface so that unnecessary scattered light is not generated. In this case, a decrease in contrast and a decrease in visibility due to unnecessary scattered light can be suppressed.

Next, another embodiment of the liquid crystal device will be described with reference to FIGS.

In the liquid crystal device shown in FIG. 4, a reflective layer 19 made of a metal thin film is formed on the surface of an active matrix substrate 10.
And the diffraction grating DG1 or DG2 is disposed between the liquid crystal layer 30 and the reflection layer 19. A transparent pixel electrode 17 made of ITO is formed between the diffraction grating DG1 or DG2 and the liquid crystal layer 30.

According to this embodiment, the external light is the diffraction grating D
After being modulated by passing through G1 or the diffraction grating DG2, the light is reflected by the reflection layer 19, so that reflection of the background can be prevented.

Further, in the present embodiment, depending on the state of the liquid crystal layer 30, the displayed image is modulated by the diffraction grating DG1 or DG2 only on the return path of light, and is not modulated on the outward path. In addition, it is possible to reduce the deterioration of the quality of the display image due to the influence of the modulation.

In the liquid crystal device shown in FIG. 5, a diffraction grating DG1 or a diffraction grating DG is provided between the counter substrate 20 and the liquid crystal layer 30.
2 and the diffraction grating DG1 or DG2
The counter electrode 21 was formed on the surface of.

On the active matrix substrate 10, the pixel electrode 15 also serving as a reflection layer for reflecting light incident from the outside is provided.
(115) is formed.

According to this embodiment, the diffraction grating DG1 or DG2 can be arranged in the vicinity of the liquid crystal layer 30, so that the influence of the light modulation on the display quality is reduced and the reflection of the background is reduced. Can be effectively prevented.

In the embodiment shown in FIG. 6, the diffraction grating DG1
Alternatively, a reflective layer 19 made of a metal thin film is formed on the surface of an active matrix substrate 18 having the same function as the diffraction grating DG2.

Specifically, the active matrix substrate 18 forms a waveform in which sine waves having different periods are superimposed on the surface thereof (equivalent to the diffraction grating DG1), or sine waves having different periods are superimposed inside the substrate. It is formed by forming a refractive index distribution (equivalent to the diffraction grating DG2).

On the other hand, on the surface of a counter substrate 20 made of glass, a transparent counter electrode 21 made of ITO (indium tin oxide) is formed on the entire surface of the substrate or in a stripe shape.

A liquid crystal layer 30 is interposed between the active matrix substrate 18 and the counter substrate 20.

In addition, the active matrix substrate 18
A transparent pixel electrode 17 made of ITO is formed between the pixel electrode and the liquid crystal layer 30.

According to this embodiment, since external light is modulated by passing through the active matrix substrate 10 (also modify the drawing) and reflected by the reflective layer 19, it is possible to prevent the reflection of the background. Can be.

It is to be noted that, depending on the state of the liquid crystal layer 30, the displayed image is modulated by the active matrix substrate 10 only on the backward path of light, and is not modulated on the outward path. Quality deterioration can be reduced.

Further, according to the present embodiment, since the active matrix substrate 18 itself has a function of modulating light, there is no need to separately provide a diffraction grating DG1 or DG2, and these are attached to the substrate. Therefore, the manufacturing process can be simplified and the manufacturing cost can be reduced.

In the embodiment shown in FIG. 7, the diffraction grating DG1
Alternatively, the counter electrode 21 was formed on the surface of the counter substrate 23 using the counter substrate 23 having the same function as the diffraction grating DG2.

On the active matrix substrate 10, a pixel electrode 15 also serving as a reflection layer for reflecting light incident from the outside is provided.
(115) is formed.

According to this embodiment, it is possible to effectively prevent the reflection of the background while reducing the influence on the display quality due to the influence of the light modulation.

Further, according to the present embodiment, the opposing substrate 2
3 itself has the function of modulating light, so there is no need to provide a separate diffraction grating DG1 or DG2,
Since the step of attaching these to the substrate can be omitted, the manufacturing process can be simplified and the manufacturing cost can be reduced.

FIG. 21 is an external view showing an example of an electronic apparatus using the reflection type liquid crystal device according to the present invention.

FIG. 21A is a perspective view showing a mobile phone. 1000 denotes a mobile phone body, of which 10
Reference numeral 01 denotes a liquid crystal display unit using the reflection type liquid crystal device according to the present invention.

FIG. 21B is a diagram showing a wristwatch-type electronic device. 1100 is a perspective view showing the watch main body.
Reference numeral 1101 denotes a liquid crystal display unit using the reflection type liquid crystal device according to the present invention. Since it has high-definition pixels with less reflection of the background as compared with the conventional clock display unit, it is possible to display television images, and a wristwatch-type television can be realized.

FIG. 21C shows a portable information processing apparatus such as a word processor or a personal computer. Reference numeral 1200 denotes an information processing apparatus; 1202, an input unit such as a keyboard;
Reference numeral 206 denotes a liquid crystal display unit using the reflection type liquid crystal device according to the present invention, and 1204 denotes an information processing apparatus main body. In this device, high-definition display with little reflection of the background can be realized.

Since each of the above electronic devices is an electronic device driven by a battery, the life of the battery can be extended by using a reflection type liquid crystal device having no light source lamp.

The present invention is not limited by the above-described embodiment. In addition, a polarizing element is provided only on one substrate side, and a reflection type liquid crystal using a nematic liquid crystal is used as a liquid crystal layer. Also in the device, a phase modulation type diffraction grating (diffraction grating DG1 or DG2, etc.) according to the present invention in which at least two waveforms having different periods are superimposed is applied without sacrificing display brightness and contrast. The reflection of the background can be prevented.

Furthermore, the present invention is not limited to a liquid crystal device, but may be applied to a display device having a reflective layer, for example, an electro-optical device formed of an organic EL device.
And the diffraction grating DG2) can prevent the background from being reflected without sacrificing display brightness or contrast.

[Brief description of the drawings]

FIG. 1 is a plan view illustrating a schematic configuration of a first embodiment of a liquid crystal device according to the present invention.

FIG. 2 is a partially enlarged longitudinal sectional view showing a schematic configuration of the first embodiment of the liquid crystal device according to the present invention.

FIG. 3 is a partially enlarged longitudinal sectional view illustrating a schematic configuration of a liquid crystal device according to a second embodiment of the present invention.

FIG. 4 is a schematic longitudinal sectional view showing another embodiment of the liquid crystal device according to the present invention.

FIG. 5 is a schematic longitudinal sectional view showing another embodiment of the liquid crystal device according to the present invention.

FIG. 6 is a schematic longitudinal sectional view showing another embodiment of the liquid crystal device according to the present invention.

FIG. 7 is a schematic longitudinal sectional view showing another embodiment of the liquid crystal device according to the present invention.

FIG. 8 is an explanatory diagram showing the reflection characteristics of the reflection type liquid crystal device.

FIG. 9 is an explanatory diagram showing a relationship between a contrast and a viewing zone.

FIG. 10 is an explanatory diagram showing a method of measuring a luminance factor.

FIG. 11 is an explanatory diagram showing a measurement method of glossiness.

FIG. 12 is an explanatory diagram showing glossiness of a conventional reflection type liquid crystal display device.

FIG. 13 is a cross-sectional view illustrating a configuration example of a diffraction grating DG1 as a superimposed grating according to the embodiment of the present invention.

FIG. 14 is a cross-sectional view illustrating a configuration example of a diffraction grating DG2 as a superposition grating according to the embodiment of the present invention.

FIG. 15 is a cross-sectional view illustrating a configuration example of a conventional simple grating.

FIG. 16 is a graph showing forward scattering characteristics of the diffraction gratings DG1 and DG2.

FIG. 17 is an explanatory view showing a diffraction pattern and a cross-sectional profile of a conventional simple grating.

FIG. 18 is an explanatory diagram showing diffraction patterns and cross-sectional profiles of the diffraction gratings DG1 and DG2.

FIG. 19 is a graph showing the relationship between diffuse reflectance and glossiness of the diffraction gratings DG1 and DG2.

FIG. 20 is a graph showing a comparison between gloss levels of the diffraction gratings DG1 and DG2.

FIGS. 21 (a), (b), and (c) are external views each showing an example of an electronic apparatus using the liquid crystal display device according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 active matrix substrate 11 gate electrode 12 gate insulating film 13 active semiconductor layer 14 source electrode 15 pixel electrode 16 drain electrode 17 alignment film 20 counter substrate 21 counter electrode 23 counter substrate also serving as diffraction grating 30 liquid crystal layer 30 a liquid crystal molecule 50 sealing material 51 Peripheral parting layer 52 Peripheral circuit 53 Pad 54 Peripheral circuit 55 Wiring 56 Column 60 TFT element 100 Photodetector 101 Photodetector 112 First electrode unit 113 Anodized film 114 Second electrode unit 115 Pixel electrode 116 Alignment film 117 Pixel electrode 118 Active matrix substrate also serving as diffraction grating 121 Counter electrode 200 Transparent member 201 Transparent substrate DG Phase modulation type diffraction grating DG1 Diffraction grating DG2 Diffraction grating W1, W2 Waveform of superimposed wave

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H089 HA04 KA06 LA22 LA28 MA04Y RA04 SA02 TA09 TA11 TA17 2H091 FA14Y FA19X FB02 FC10 FC27 FD06 FD14 GA13 HA06 JA01 KA01 LA16 5G435 AA01 BB12 BB16 CC09 DD12 FF01 FF06 H03

Claims (13)

[Claims] 1. A liquid crystal device having a liquid crystal layer sandwiched between a pair of substrates, wherein a light reflecting means is formed on one of the pair of substrates, the liquid crystal layer being closer to the liquid crystal layer than the light reflecting means. A diffraction grating having a characteristic in which at least two waveforms having different periods are superimposed on each other. 2. A liquid crystal device in which a liquid crystal layer is sandwiched between a pair of substrates, wherein one of the pair of substrates is provided with a light reflecting means, and the other substrate is provided with a light reflecting means. Wherein a diffraction grating having a characteristic of superimposing at least two waveforms having different periods is provided on different sides. 3. A liquid crystal device in which a liquid crystal layer is sandwiched between a pair of substrates, wherein a light reflecting means is formed on one of the pair of substrates, and the other substrate has a light reflecting means on the liquid crystal layer side. And a diffraction grating having a characteristic in which at least two waveforms having different periods are superimposed. 4. The diffraction grating according to claim 1, wherein the diffraction grating has characteristics of reducing the luminance factor, reducing the glossiness, and making the diffraction intensity distribution uniform. A liquid crystal device according to any one of the above. 5. The liquid crystal device according to claim 4, wherein the luminance factor is 0.4 or less, and the glossiness is 1000 or less. 6. The optical modulator according to claim 1, wherein the diffraction grating is a light modulation element having a wavefront formed by superimposing at least two waveforms having different periods on the surface of the sheet member. The liquid crystal device according to the above. 7. The diffraction grating is a light modulation element having a refractive index distribution formed inside a sheet member made of a translucent material, wherein the refractive index distribution is obtained by superimposing at least two waveforms having different periods. The liquid crystal device according to any one of claims 1 to 5, wherein the liquid crystal device has characteristics. 8. The liquid crystal device according to claim 1, wherein the diffraction grating has a surface shape for suppressing generation of scattered light or higher-order diffracted light. 9. The method according to claim 1, wherein the diffraction grating has an internal refractive index distribution for suppressing generation of scattered light or higher-order diffracted light. Liquid crystal devices. 10. The liquid crystal layer according to claim 1, wherein the liquid crystal layer is a composite layer composed of a liquid crystal and a polymer.
The liquid crystal device according to any one of the above. 11. The liquid crystal device according to claim 1, wherein the liquid crystal layer is a nematic liquid crystal layer, and a polarizing means is provided only on the other substrate. 12. The diffraction grating according to claim 1, wherein the diffraction grating is arranged on the liquid crystal layer side of the light reflecting means.
A liquid crystal device according to claim 1. 13. An electronic apparatus using a liquid crystal device equipped with the diffraction grating as a display device.