JP3096383B2 - Reflective liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
More particularly, the present invention relates to a reflective liquid crystal display device suitably used for an electronic desk calculator, an electronic organizer, and the like.

[0002]

2. Description of the Related Art A conventional reflection type liquid crystal display device is a so-called twisted nematic (hereinafter referred to as "T") formed by twisting a nematic liquid crystal composition having a positive dielectric anisotropy.
N ") is arranged between a pair of polarizing plates. This TN type liquid crystal display element has a feature of low power consumption, and is used for a relatively small liquid crystal display device such as an electronic desk calculator and a digital clock.

However, as described above, the TN type liquid crystal display element requires two polarizing plates, and therefore, when used as a reflection type liquid crystal display element, the light intensity is only about 1/4 of that of natural light. I can't get it. Therefore, sufficient contrast between bright display and dark display cannot be obtained at the time of display, and the display becomes unclear.

In order to solve such a problem, Japanese Patent Laid-Open No.
In the liquid crystal display device disclosed in 5-70817, 1
By disposing a TN-type liquid crystal display element between one polarizing plate and a 波長 wavelength plate, the number of polarizing plates is reduced and the contrast is improved.

[0005]

However, Japanese Patent Application Laid-Open No. 55-70817 merely describes the display driving principle of the liquid crystal display device constructed as described above, and actually manufactures the liquid crystal display device. In this case, there is no description of various conditions, for example, conditions for determining the display quality, such as the value of the product d · Δn of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn of the liquid crystal molecules. This is because, in 1980, a thin-film quarter-wave plate had not been realized, and no attempt was made to actually manufacture a liquid crystal display device using the quarter-wave plate. . Even today, a quarter-wave plate is used only slightly in a projection type projection device, and has not been adopted in a thin and lightweight liquid crystal display device.

An object of the present invention is to provide a thin and lightweight reflective liquid crystal display device which improves display quality without impairing the advantage of low power consumption of a TN type liquid crystal display element.

[0007]

According to the present invention, there is provided a liquid crystal display device comprising a pair of substrates and a nematic liquid crystal layer in which liquid crystal molecules are twisted by about 45 ° between the substrates, and a liquid crystal display device. A polarizing plate disposed on one surface side, a reflection unit disposed on the other surface side of the liquid crystal display element, and a liquid crystal display element disposed between the reflection unit and the plurality of polymer stretched films are laminated. A quarter-wave plate having the configuration,
The angle between the absorption axis direction of the polarizing plate and the major axis direction of the liquid crystal molecules closest to the surface of the substrate close to the polarizing plate is 85 ° or more.
The reflection type liquid crystal display device is characterized in that the angle d is 95 ° and the product d · Δn of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn of the liquid crystal molecules is selected to be 500 nm to 700 nm.

[0008]

According to the present invention, a liquid crystal display element formed between a pair of substrates by interposing a nematic liquid crystal layer in which liquid crystal molecules are twisted by about 45 ° between the substrates, a polarizing plate, a reflecting means, The reflection type liquid crystal display device is configured to include the 波長 wavelength plate. Here, the angle formed between the direction of the absorption axis of the polarizing plate and the major axis direction of the liquid crystal molecules closest to the surface of the substrate close to the polarizing plate, the thickness d of the liquid crystal layer and the refractive index anisotropy Δn of the liquid crystal molecules.
With the product d · Δn. With this optimization,
It was confirmed that the contrast between the bright display and the dark display was good and a display close to achromatic was obtained. Further, according to the present invention, the quarter-wave plate has a configuration in which a plurality of stretched polymer films are laminated, and therefore, it is possible to realize a preferable dark display having a good contrast in a wide wavelength region.

[0009]

FIG. 1 is a sectional view of a reflection type liquid crystal display device 1 which is the basis of the present invention. A reflective liquid crystal display device is a liquid crystal display device that can uniformly illuminate the entire display surface with ambient light by arranging a reflector on a back surface opposite to a display surface on which an observer views an image. . In the reflection type liquid crystal display device 1, the liquid crystal display element 2 is generally disposed between the polarizing plate 3 and the reflection plate 4 serving as reflection means, and the liquid crystal display element 2 is disposed between the liquid crystal display element 2 and the reflection plate 4. The four-wavelength plate 5 is arranged and configured. The polarizing plate 3 is made of a stretched polyvinyl alcohol film, and the quarter-wave plate 5 is made of a stretched polymer film such as polycarbonate. The reflector 4 is realized by a non-directional aluminum reflector. The liquid crystal display element 2 includes a liquid crystal layer 6 interposed between an upper substrate 7 and a lower substrate 8. The upper substrate 7 is formed by forming at least a transparent electrode 10 and an alignment film 11 on one surface of a translucent substrate 9. The lower substrate 8 is formed by forming at least a transparent electrode 13 and an alignment film 12 on one surface of a translucent substrate 14. The upper substrate 7 and the lower substrate 8 are arranged such that the one surfaces face each other.

The liquid crystal layer 6 is made of a nematic liquid crystal material having a positive dielectric anisotropy, and liquid crystal molecules forming the liquid crystal layer 6 are twisted about 45 ° between the upper substrate 7 and the lower substrate 8. It is oriented in a state. The light-transmitting substrates 9 and 14 are made of a light-transmitting material such as glass. Translucent substrate 9,
For example, ITO (IndiumTin)
Oxide) transparent electrodes 10 and 13 formed of a film are formed in a plurality of strips, respectively, so as to be parallel to each other, and translucent substrates 9 and 14 such that the transparent electrodes 10 and 13 are orthogonal to each other. Is arranged. Alignment films 11 and 12
Is realized by, for example, a polyimide resin, the surface of which has been subjected to an orientation treatment such as a rubbing treatment,
Controls the alignment state of liquid crystal molecules.

FIG. 2 is a diagram showing the arrangement conditions of the components of the reflection type liquid crystal display device 1. As shown in FIG. Arrow 16 indicates the absorption axis direction of the polarizing plate 3, arrow 17 indicates the long axis direction of the liquid crystal molecules closest to the upper substrate 9, and arrow 18 indicates the long axis direction of the liquid crystal molecules closest to the lower substrate 8. And arrow 19 is 1/4
The slow axis direction of the wave plate 5 is shown.

In the reflection type liquid crystal display device 1, the angle between the arrow 16 and the arrow 17 is α, the angle between the arrow 17 and the arrow 18, ie, the twist angle of the liquid crystal molecules is φ, and the angle between the arrow 18 and 18 is The angle formed by the arrow 19 is β, and the angle α is α = 85 ° to 95
°, hopefully α = 90 °, angle φ is φ = 45 °, angle β
So that β = −5 ° to 5 °, and hopefully β = 0 °,
The polarizing plate 3 and the quarter-wave plate 5 are arranged.

The single transmittance and the degree of polarization of the polarizing plate 3 are desired to be 46% or more and 95% or more, respectively. The single transmittance and the degree of polarization of the polarizing plate 3 used in the liquid crystal display device 1 are 46.5% and 95.0%, respectively.
And the twist angle φ of the liquid crystal molecules is 45 °, and d · Δn
Is 600 nm (d = 6 μm, Δn = 0.1).

FIG. 3 is a diagram for explaining the display principle of the reflection type liquid crystal display device 1. As shown in FIG. As the liquid crystal material forming the liquid crystal layer 6, a 45 ° twisted nematic liquid crystal material having a positive dielectric anisotropy is used. The direction of the absorption axis of the polarizing plate 3 indicated by the arrow 23 is orthogonal to the direction of the long axis of the liquid crystal molecules 22 closest to the upper substrate 7 indicated by the arrow 24. Further, the slow axis direction of the quarter-wave plate 5 indicated by an arrow 25 and the long axis direction of the liquid crystal molecules 23 closest to the lower substrate 8 indicated by an arrow 26 are made to coincide.

Referring to FIG. 3A, transparent electrodes 10 and 13 are used.
Will be described when a bright display is performed in a non-energized state. Since no electric field is generated between the transparent electrodes 10 and 13, the liquid crystal molecules 22 are oriented in the liquid crystal layer 6 by twisting by 45 °. Natural light 27
Is the absorption axis direction 2 of the polarizing plate 3
The incident light 28a vibrates in a direction orthogonal to the direction 3. The incident light 28a has a vibration direction of 4 as it passes through the liquid crystal layer 6.
The light 28 b is twisted by 5 ° and vibrates in the same direction as the slow axis direction 25 of the 波長 wavelength plate 5. Since the vibration direction of the light 28b incident on the 波長 wavelength plate 5 and the slow axis direction 25 of the 波長 wavelength plate 5 are the same direction, the light 28b is １ ／ wavelength without changing its vibration direction. The light passes through the plate 5 and is reflected by the reflection plate 4 to become reflected light 29a.

The vibration direction of the reflected light 29a and the quarter-wave plate 5
Is in the same direction as the slow axis direction 25 of the
a transmits through the quarter-wave plate 5 without changing its vibration direction. The reflected light 29a transmitted through the 波長 wavelength plate 5 is twisted by 45 ° as it passes through the liquid crystal layer 6, and becomes light 29b vibrating in a direction orthogonal to the absorption axis direction 23 of the polarizing plate 3. Therefore, the light 29b can pass through the polarizing plate 3. In this way, bright display is realized.

Next, referring to FIG.
The case where dark display is performed in the state where 0 and 13 are energized will be described. The liquid crystal molecules 22 are oriented in the direction of the electric field generated by energization, as indicated by the arrow 30. The natural light 27 becomes incident light 28 a that vibrates in a direction orthogonal to the absorption axis direction 23 of the polarizing plate 3 as it passes through the polarizing plate 3. Incident light 28a
Since the optical rotation of the liquid crystal molecules 22 disappears when the transparent electrodes 10 and 13 are energized, the light passes through the liquid crystal layer 6 without changing the vibration direction. The oscillation direction of the incident light 28a and the slow axis direction 25 of the 波長 wavelength plate 5 are 45
The incident light 28a becomes a right-handed circularly polarized light 28c as it passes through the quarter-wave plate 5 because of the angle of °. The right-handed circularly polarized light 28c is reflected by the reflector 4 and becomes a left-handed circularly polarized light 29c. The left-handed circularly polarized light 29c becomes light 29d that vibrates in a direction perpendicular to the vibration direction of the incident light 28a as it passes through the quarter-wave plate 5. Light 29d
Pass through the liquid crystal layer 6 without changing its vibration direction. Vibration direction of light 29d and absorption axis direction 23 of polarizing plate 3
Is consistent with Therefore, the light 29d cannot pass through the polarizing plate 3. Thus, dark display is realized.

FIG. 4 is a side view showing the structure of the reflection type liquid crystal display device 41 according to the first embodiment of the present invention. Since the reflection type liquid crystal display device 41 has a similar configuration to the reflection type liquid crystal display device 1, the same components are denoted by the same reference numerals. This embodiment is characterized in that the quarter-wave plate 5 is made of two polymer stretched films 4 having different retardation values.
2 and 43 are laminated. The retardation value of each film is 100 nm to 320 nm, respectively.
Is appropriately selected within the range. In this example, the retardation value of the film 42 was 270 nm, and the retardation value of the film 43 was 140 nm.

FIG. 5 is a diagram showing the arrangement conditions of the reflection type liquid crystal display device 41. 5, the same reference numerals are used for the same conditions as in FIG. Stretched polymer film 4
The slow axis direction of No. 2 is indicated by an alternate long and short dash line arrow 44, and the slow axis direction of the stretched polymer film 43 is indicated by a broken arrow 45.
The angle between the arrow 18 and the arrow 44 is ε, and the angle between the arrow 18 and the arrow 45 is ζ.

In this embodiment, the angle ε is ε = −20 ° to −20 °.
35 °, hopefully −27.5 °, and angle ζ = 20
The stretched polymer films 42 and 43 are arranged so that the angle is 45 ° to 45 °, preferably 35 °. The range of angles α and φ is
Same as above.

FIG. 6 is a side view showing the structure of a reflective liquid crystal display device 51 according to a second embodiment of the present invention. Since the reflection type liquid crystal display device 51 has a configuration similar to that of the reflection type liquid crystal display device 41, the same reference numerals are used for the same components. This embodiment is characterized in that the quarter-wave plate 5 is formed by laminating three polymer stretched films 42, 43, and 52. The retardation value of each film is appropriately selected in the range of 100 nm to 320 nm. In the present embodiment, the retardation values of the polymer stretched films 42, 43, and 52 were set to 270 nm, 140 nm, and 2 nm, respectively.
70 nm.

FIG. 7 is a diagram showing an arrangement condition of the reflection type liquid crystal display device 51. As shown in FIG. 7, the same reference numerals are used for the same conditions as in FIG. The slow axis direction of the polymer stretched film 52 is indicated by a dashed arrow 53 and an arrow 5
The angle between 3 and the arrow 18 is δ.

In this embodiment, the angle ε is ε = −3.5 ° or more.
-18.5 °, hopefully -11.0 °, and angle ζ is ζ = 35 ° to 75 °, hopefully 55 °, and angle δ
Are arranged such that δ = −30 ° to −45 °, and preferably −38.5 °.

FIG. 8 is a side view showing the structure of a reflective liquid crystal display device 61 according to a third embodiment of the present invention. Since the reflection type liquid crystal display device 61 has a configuration similar to that of the reflection type liquid crystal display device 41, the same reference numerals are used for the same components. This embodiment is characterized in that a stretched polymer film 62 is disposed between the lower substrate 8 and the quarter-wave plate 5. The retardation value of the stretched polymer film 62 is selected from the range of 70 nm to 90 nm. In this embodiment, the thickness is set to 80 nm.

FIG. 9 is a diagram showing an arrangement condition of the reflection type liquid crystal display device 61. 9, the same reference numerals are used for the same conditions as in FIG. The slow axis direction of the stretched polymer film 62 is indicated by a two-dot chain line arrow 63, and the angle formed between the arrow 63 and the arrow 18 is represented by γ.

In this embodiment, the angle γ is γ = 85 ° -95.
°, and hopefully 90 °.

FIG. 10 is a graph showing the polarization state of outgoing light transmitted through the liquid crystal layer 6 during bright display. D · of the liquid crystal layer 6
When the Δn value was changed stepwise from 300 nm to 1000 nm, 450 nm and 550 nm transmitted through the liquid crystal layer 6 were used.
The change in the polarization state of the outgoing light of each wavelength light of m and 650 nm is indicated by the ellipticity. When the value of d · Δn increases, the thickness of the liquid crystal layer 6 increases. Therefore, in order to realize a thin and lightweight reflective liquid crystal display device, it is necessary to set the value of d · Δn as small as possible. .

The horizontal axis represents d · Δn, and the vertical axis represents ellipticity.
The changes in the ellipticity of the outgoing elliptically polarized light when the light of each wavelength of 50 nm, 550 nm, and 650 nm are incident are shown by a broken line 71, a solid line 72, and a chain line 73, respectively. 450 nm,
550 nm wavelength light is d · Δn ≧ 400 nm, and
It can be seen that the 650 nm wavelength light has a d · Δn ≧ 500 nm and the ellipticity of the outgoing elliptically polarized light falls within a relatively low value of about 0.1%. Judging from this result, the lower limit of d · Δn is set to 500 nm.

FIG. 11 is a graph showing the polarization state of outgoing light passing through the liquid crystal layer 6 during dark display. D · of the liquid crystal layer 6
When the Δn value is changed stepwise from 300 nm to 1000 nm, the change of the emission azimuth when the light of 550 nm wavelength passes through the liquid crystal layer 6 is shown. The emission azimuth is an angle formed between the vibration direction of the linearly polarized light that is the incident light and the vibration direction of the linearly polarized light that is the outgoing light. If the emission azimuth is large, the compensation by the 1/4 wavelength plate becomes incomplete, and good contrast cannot be obtained due to light leakage.
It is necessary to set the emission azimuth as small as possible.

The horizontal axis indicates d · Δn and the vertical axis indicates the emission azimuth, and the change in the emission azimuth when light having a wavelength of 550 nm is transmitted is indicated by a broken line 81. The output azimuth angle is d · Δn = 30.
Within 10 nm in the range of 0 nm to 700 nm, d ·
It can be seen that when Δn exceeds 700 nm, it sharply increases. Judging from this result, the upper limit of d · Δn is 700
nm.

Therefore, judging from FIGS. 10 and 11, the appropriate range of the d.Δn value of the liquid crystal layer 6 in the present invention is set to d.Δn = 500 nm to 700 nm.

FIG. 12 is a view showing the polarization state of the outgoing light transmitted through the stretched polymer film constituting the quarter-wave plate 5. Each of the 450 nm, 550 nm, and 650 nm wavelength light was applied to the stretched polymer film 4 used in each of Examples 1, 2, and 3.
The polarization shapes of the respective outgoing lights when passing through 2, 43 and 52 are shown. FIG. 12A shows the polarization shape of the outgoing light of each wavelength light when only the film 42 is used.
(B) shows the polarization shape of the outgoing light of each wavelength light when the films 42 and 43 are overlaid, and FIG. 12 (c) shows the polarization of the outgoing light of each wavelength light when the films 42, 43 and 52 are overlaid. Show the shape. 12 (a), 12 (b),
In FIG. 12C, the polarization shape of the emitted light of 450 nm wavelength light is indicated by a solid line 91, the polarization shape of the emitted light of 550 nm wavelength light is indicated by a broken line 92, and the polarization shape of the emitted light of 650 nm wavelength light is indicated by a one-dot chain line 93. Shown respectively. The incident vibration direction of each wavelength light is shown by a solid line 94.

With reference to FIG. 12A, the polarization shape of the emitted light of each wavelength in the case of using only the film 42 will be described. 45 transmitted through the film 42 which is a 波長 wavelength plate
The polarization shape of the outgoing light having the wavelength of 0 nm is elliptically polarized light whose major axis is the incident vibration direction 94 as shown by the solid line 91. The polarization shape of the outgoing light having the wavelength of 550 nm is substantially circularly polarized as indicated by the broken line 92. In addition, 6
The polarization shape of the emitted light having the wavelength of 50 nm is elliptically polarized light whose minor axis is the incident vibration direction 94, as indicated by the one-dot chain line 93. As described above, the polarization shape of the emitted light of each wavelength light transmitted through the 波長 wavelength plate realized by one stretched polymer film is not perfect circularly polarized light and does not match.
The realization of a preferred dark display with good contrast is inadequate.

Referring to FIG. 12B, the films 42, 4
Next, a description will be given of the polarization shape of the outgoing light of each wavelength light when 3 is superimposed. The polarization shape of the outgoing light of each wavelength light transmitted through the polymer stretched films 42 and 43 is substantially circularly polarized, and substantially coincides. As described above, in the combination of the two stretched polymer films 42 and 43, the shapes of the outgoing elliptically polarized lights of the respective wavelengths are almost the same, so that a dark display having a good contrast can be realized.

Referring to FIG. 12C, the films 42, 4
The polarization shape of the outgoing light of each wavelength light when 3 and 52 are overlapped will be described. Polymer stretched films 42, 43, 52
The shape of the polarization of the outgoing light of each wavelength light that has passed through is substantially circularly polarized and coincides with each other. As described above, in the combination of the three stretched polymer films 42, 43, and 52, the polarization shapes of the emitted lights of the respective wavelengths are circularly polarized and coincide with each other. Can be realized.

As described above, by laminating a plurality of stretched polymer films, a good dark display can be obtained in a wide wavelength region. That is, in dark display at the time of energization, each wavelength light transmitted through the １ ／ wavelength plate is
Since the light is emitted in a state close to the circularly polarized light and with the same azimuth angle, it is possible to realize a dark display without coloring and a better contrast.

FIG. 13 shows the state of each embodiment at the time of dark display.
It is a figure which shows the polarization | polarized-light shape of the emitted light when each wavelength light of 450 nm, 550 nm, and 650 nm penetrates the 45 degree twisted nematic liquid crystal layer of d * (DELTA) n = 600nm. When a voltage is applied between the transparent electrodes 10 and 13, the liquid crystal molecules 22
Are oriented along the direction of the electric field, but the liquid crystal molecules 22 actually have a twist component. As a result, the linearly polarized light transmitted through the liquid crystal layer 6 when energized becomes elliptically polarized light.

The polarization shape of outgoing light of 450 nm wavelength light transmitted through the liquid crystal layer 6 is indicated by a solid line 101, the polarization shape of outgoing light of 550 nm wavelength light is indicated by a broken line 102, and the polarization shape of outgoing light of 650 nm wavelength light is indicated by a one-dot chain line. 103, and the incident vibration direction of each wavelength light is shown by a solid line 104. Judging from the outgoing elliptically polarized light 101, 102, 103 of each wavelength light, it can be said that the twist of the liquid crystal molecules 22 has been substantially eliminated. Therefore, a dark display having a good contrast can be obtained by combination with a stretched polymer film.

FIG. 14 shows that the liquid crystal display element 2 and the stretched polymer film 62
It is a figure which shows the polarization shape of the emitted light when each wavelength light of 50 nm, 550 nm, and 650 nm transmits. The stretched polymer film 62 is provided to suppress the ellipticity of the outgoing elliptically polarized light 101, 102, 103 caused by the above-described torsional component of the liquid crystal molecules 22. The polymer stretched film 62 is
The liquid crystal molecules 22 are arranged so that their slow axes are 90 ° counterclockwise with respect to the major axis direction of the liquid crystal molecules 22 closest to the lower substrate 8, and have a retardation value of 80 nm.

450 transmitted through the stretched polymer film 62
The polarization shape of the outgoing light of nm wavelength light is 550 with a solid line 111.
The polarization shape of the outgoing light of nm wavelength light is represented by a broken line 112 at 650.
The polarization shape of the outgoing light of nm wavelength light is indicated by a one-dot chain line 113, and the incident vibration direction of each wavelength light is indicated by a solid line 114.
Indicated by Outgoing elliptically polarized light 111, 112, 11 of each wavelength light
3 is the outgoing elliptically polarized light 101, 10 in FIG.
It can be seen that the ellipticity is remarkably suppressed as compared with 2,103. That is, while the residual ellipticity of each wavelength light transmitted through the liquid crystal layer 6 is about 0.3, the residual ellipticity of each wavelength light transmitted through the liquid crystal layer 6 and the stretched polymer film 62 is It was able to be suppressed to 0.2 or less.

Therefore, by using the stretched polymer film 62, it is possible to obtain a dark display having a better contrast.

FIG. 15 is a side view showing the structure of a reflective liquid crystal display device 121 as a comparative example of the present invention. Since the reflective liquid crystal display device 121 has a similar configuration to the reflective liquid crystal display device 1, the same components are denoted by the same reference numerals. The reflection type liquid crystal display device 121 has a configuration in which the polarizing plate 122 is disposed between the liquid crystal display element 2 and the reflection plate 4 in place of the quarter wavelength plate 5 in the reflection type liquid crystal display device 1. . That is, the liquid crystal display element 2 is configured to be sandwiched between the two polarizing plates 3 and 122. Each of the polarizing plates 3 and 122 has a single transmittance of 44.5% and a degree of polarization of 96.5%. Further, the reflection type liquid crystal display device 121
The torsion angle in the major axis direction of the liquid crystal molecules used for
・ Δn is 636 nm.

FIG. 16 shows the reflection type liquid crystal display device 121.
It is a figure which shows the arrangement condition of. The arrow 16 indicates the direction of the absorption axis of the polarizing plate 3, the arrow 17 indicates the long axis direction of the liquid crystal molecules closest to the upper substrate 7, and the arrow 18 indicates the long axis direction of the liquid crystal molecules closest to the lower substrate 8. And the arrow 131 indicates the polarizing plate 1
22 shows the direction of the absorption axis 22.

At this time, the angle between the arrows 16 and 17 is α, the angle between the arrows 18 and 131 is η, the twist angle of the liquid crystal molecules is φ, and α = 5 °, η = 5 °, φ = 90
The polarizing plates 1 and 122 are arranged so as to make the angle?.

Table 1 shows the measurement results of brightness, lightness index, color tone, and saturation in the comparative example and the first, second, and third examples. The comparative example and each example will be described. .

[0046]

[Table 1]

The brightness is a value when the comparative example is set to 100.0. The larger the value, the brighter the display. The brightness is remarkably increased in each example as compared with the comparative example. This is because two polarizing plates are used in the comparative example, whereas only one polarizing plate is used in the first, second, and third embodiments, so that light is transmitted through the polarizing plate. It is considered that the decrease in the brightness of the ambient light was suppressed. The lightness index L * is an index obtained by the following equation (1).

L * = 10Y ^1/2 (where 0 <Y <100) (1) The lightness index L * is an index that changes only by the value of Y in the CIE chromaticity coordinates.

The color tone indicates the degree of coloring at the time of bright display and dark display, and the values of a * and b * indicating the color tone are obtained by the following equations (2) and (3), and the target value “0” is obtained.
The closer to, the more achromatic color is displayed. In addition, it is reddish when a *> 0, and greenish when a * <0. When b *> 0, it is yellowish, and when b * <0, it is blueish. X, Y, Z
Is a value on the CIE chromaticity coordinates.

A * = 17.5 (1.02X−Y) / Y ^1/2 (2) b * = 7.0 (Y−0.847Z) / Y ^1/2 (3) Indicates color tone The values of a * and b * are very close to the target values in the third embodiment in both bright display and dark display. This indicates that the color tone was significantly improved in Example 3.

The saturation C * indicates the vividness of the display, and is obtained by the following equation (4). As the value of C * approaches 0, better black and white display is realized.

C * = (a * ² + b * ² ) ^1/2 (4) The value of C * is significantly reduced in each of the examples in the bright display as compared with the comparative example. It can be seen that a bright display close to white was obtained. In the dark display,
Although the C * value is higher in the second example than in the comparative example, the C * value is lower in the third example than in the comparative example. It can be seen that a dark display close to was obtained.

From the above experimental results, the display quality was improved in each of the examples.
It was confirmed that an extremely good display quality was obtained.

In the present invention, the value of d · Δn is 500n
Outside the range of m to 700 nm, bright display is colored and brightness is reduced, and dark display is not sufficiently displayed in black. As a result, good contrast cannot be obtained.

Further, the single transmittance of the polarizing plate is 46% or less,
The polarization degree becomes 95% or less, α = 85 ° to 95 °, β =
If the angle is out of the range of -5 ° to 5 °, both bright display and dark display will be colored.

Further, if a substrate made of a polymer film such as polycarbonate is used instead of glass as the translucent substrate on which the transparent electrode is formed, a clearer display can be obtained.

[0057]

As described above, according to the present invention, the major axis direction of the liquid crystal molecules, the absorption axis direction of the polarizing plate, the slow axis direction of the quarter wavelength plate, and the value of d · Δn are determined. Since the optimization is performed, it is possible to obtain a display in which the color tone is achromatic and the contrast is good. In particular, according to the present invention, the quarter-wave plate has a configuration in which a plurality of stretched polymer films are laminated, and thereby it is possible to realize a preferable dark display having a good contrast in a wide wavelength region. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a reflective liquid crystal display device 1 which is a basis of the present invention.

FIG. 2 is a diagram showing an arrangement condition of components of the reflection type liquid crystal display device 1.

FIG. 3 is a diagram for explaining the display principle of the reflective liquid crystal display device 1.

FIG. 4 is a side view showing the configuration of the reflection type liquid crystal display device 41 according to the first embodiment of the present invention.

FIG. 5 is a diagram showing an arrangement condition of components of the reflection type liquid crystal display device 41.

FIG. 6 is a side view showing a configuration of a reflection type liquid crystal display device 51 according to a second embodiment of the present invention.

FIG. 7 is a view showing an arrangement condition of components of the reflection type liquid crystal display device 51.

FIG. 8 is a side view showing a configuration of a reflective liquid crystal display device 61 according to a third embodiment of the present invention.

FIG. 9 is a view showing an arrangement condition of components of the reflection type liquid crystal display device 61.

FIG. 10 shows 450 nm and 550 n transmitted through the liquid crystal layer 6.
It is a figure which shows the change of the ellipticity of the emitted light of each wavelength of m and 650nm.

FIG. 11 is a diagram showing a change in an emission azimuth of light having a wavelength of 550 nm transmitted through a liquid crystal layer 6;

FIG. 12 is a diagram showing polarization shapes of emitted lights of wavelengths of 450 nm, 550 nm, and 650 nm transmitted through polymer stretched films 42, 43, and 52.

FIG. 13 is a diagram showing the polarization shape of outgoing light when light of each wavelength of 450 nm, 550 nm, and 650 nm is transmitted through a 45 ° twisted nematic liquid crystal layer with d · Δn = 600 nm.

FIG. 14 shows a liquid crystal display element 2 and a stretched polymer film 6
FIG. 2 is a diagram showing the polarization shape of outgoing light when each wavelength light of 450 nm, 550 nm, and 650 nm is transmitted.

FIG. 15 is a reflective liquid crystal display device 1 according to a comparative example of the present invention.
FIG. 21 is a side view showing the configuration of FIG.

FIG. 16 is a diagram showing an arrangement condition of components of the reflection type liquid crystal display device 121.

[Explanation of symbols]

 1, 41, 51, 61 Reflective liquid crystal display device 2 Liquid crystal display element 3 Polarizer 4 Reflector 5 1/4 wavelength plate 6 Liquid crystal layer 7 Upper substrate 8 Lower substrate 9, 14 Translucent substrate 10, 13 Transparent electrode 42,43,52,62 Polymer stretched film

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-55-70817 (JP, A) JP-A-3-223715 (JP, A) JP-A-2-154226 (JP, A) JP-A-1- 217316 (JP, A) JP-A-4-116515 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13363 G02F 1/1335 510 G02F 1/1335 520

Claims (1)

(57) [Claims] 1. A liquid crystal display element formed between a pair of substrates by interposing a nematic liquid crystal layer in which liquid crystal molecules are twisted by about 45 ° between the substrates, and a polarized light disposed on one surface side of the liquid crystal display element.反射 wavelength plate having a configuration in which a plurality of polymer stretched films are stacked between a liquid crystal display element and a reflection means, and a reflection means disposed on the other surface side of the liquid crystal display element; The angle between the absorption axis direction of the polarizing plate and the major axis direction of the liquid crystal molecules closest to the surface of the substrate adjacent to the polarizing plate is 85 ° or more.
95 °, the product d of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn of the liquid crystal molecules
-A reflective liquid crystal display device wherein Δn is selected from 500 nm to 700 nm.