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HK1096160B - Liquid crystal display device of vertical alignment - Google Patents

Liquid crystal display device of vertical alignment Download PDF

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Publication number
HK1096160B
HK1096160B HK07103106.8A HK07103106A HK1096160B HK 1096160 B HK1096160 B HK 1096160B HK 07103106 A HK07103106 A HK 07103106A HK 1096160 B HK1096160 B HK 1096160B
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HK
Hong Kong
Prior art keywords
optical compensation
liquid crystal
plates
plate
plane
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HK07103106.8A
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Chinese (zh)
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HK1096160A1 (en
Inventor
君平 小林
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Ortus Technology Co., Ltd.
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Priority claimed from JP2005176971A external-priority patent/JP2006309105A/en
Application filed by Ortus Technology Co., Ltd. filed Critical Ortus Technology Co., Ltd.
Publication of HK1096160A1 publication Critical patent/HK1096160A1/en
Publication of HK1096160B publication Critical patent/HK1096160B/en

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Description

Vertical alignment type liquid crystal display element
Technical Field
The present invention relates to a vertical alignment type liquid crystal display device having a liquid crystal layer in which liquid crystal molecules are aligned vertically with respect to a pair of substrates between the substrates.
Background
In conventional liquid crystal displays, as liquid crystal display elements, a transmissive liquid crystal display element in which a backlight is provided on the back surface of the liquid crystal display element to illuminate, a transflective liquid crystal display element in which a reflective region is locally provided, and the like are widely used. Examples of the method of aligning the liquid crystal molecules of these liquid crystal display elements include TN (twisted nematic) type, homeotropic (homeotropic) type, and the like. In any of these modes, liquid crystal molecules are aligned substantially parallel to the main surface of the liquid crystal substrate in a state where no voltage is applied, and the long axis direction of the molecules is changed in a direction perpendicular to the main surface of the substrate by applying a voltage, whereby the liquid crystal layer is optically changed.
In the liquid crystal display element of the horizontal alignment type such as TN type as described above, the liquid crystal molecules are not perfectly perpendicular to the main surface of the substrate when a voltage is applied, due to an anchoring effect of the horizontal alignment film or the like. Therefore, when a voltage is applied, the birefringence in the normal direction of the main surface of the substrate cannot be 0, and the display quality (contrast) is degraded. Therefore, as an alignment method for realizing high transmittance and high contrast, a vertical alignment (va (vertical alignment)) mode in which the substrate is aligned in a vertical direction (birefringence is almost 0) with respect to the main surface of the substrate without voltage application and is aligned in a horizontal direction with voltage application has been attracting attention.
In the VA mode, when an electric field is applied to the liquid crystal layer, alignment control is performed so that the liquid crystal molecules in each pixel region are inverted in one direction, and although high contrast can be achieved as described above, the viewing angle characteristics are insufficient. Therefore, in order to improve the viewing angle characteristics, it has been proposed to control the alignment so that the liquid crystal molecules in each pixel region are inverted in a plurality of directions when a voltage is applied between the opposing electrodes by applying an oblique electric field to the electrodes in the pixel region while providing a gap or the like. However, in such a liquid crystal display element of the vertical alignment mode, since the tilt directions of the liquid crystal molecules are oriented in multiple directions by applying a voltage, when viewed from a direction perpendicular to the main surface of the substrate, the polarizing axis of the polarizing plate and the axis of the liquid crystal cannot extract light even in the same direction, and the transmittance is low.
As a liquid crystal display device in which a plurality of retardation plates are arranged in such a VA mode liquid crystal display element to improve the viewing angle dependence (color shift) of contrast and color tone, a liquid crystal display device in which a retardation layer having a retardation of approximately 1/2 or more and 3/4 or less with respect to visible light and a retardation layer having an optically negative anisotropic refractive index and a retardation of approximately 0 with respect to visible light are arranged in a vertical alignment type liquid crystal cell has been proposed (for example, patent document 1).
[ patent document 1]
Japanese laid-open patent publication No. 2003-015134
A liquid crystal display device in which a plurality of retardation plates are arranged is still insufficient in contrast and color shift, and sufficient transmittance of a liquid crystal display element cannot be obtained, and high contrast cannot be obtained in a sufficiently wide viewing angle range.
Disclosure of Invention
The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a vertical alignment mode liquid crystal display element having high transmittance and a wide viewing angle.
In order to achieve the above object, a liquid crystal display device according to claim 1 of the present invention includes: a substrate provided with a 1 st electrode;
another substrate arranged to face the first substrate, and having a 2 nd electrode provided on a surface facing the first substrate, the 2 nd electrode forming a pixel region through a region facing the 1 st electrode;
a vertical alignment film formed on the surfaces of the 1 st electrode and the 2 nd electrode facing each other;
a liquid crystal layer sealed between the substrates and having negative dielectric anisotropy;
a pair of polarizing plates disposed on outer surfaces of the one and the other substrates opposite to the surfaces thereof facing each other, respectively; and
and two optical compensation layers respectively disposed between the pair of substrates and the pair of polarizing plates, and giving a phase difference of a value substantially 1/4 of the wavelength λ to the transmitted visible light.
In such a liquid crystal display element, it is preferable that the two optical compensation layers are each composed of a 1 st optical compensation plate having a relationship that when a refractive index in a 1 st axis direction parallel to the main surfaces of the pair of substrates is Nx, a refractive index in a 2 nd axis direction parallel to the main surfaces of the substrates and perpendicular to the 1 st axis direction is Ny, and a refractive index in a 3 rd axis direction perpendicular to the main surfaces of the substrates is Nz, values of Nx, Ny, and Nz have a relationship of Nx > Ny > Nz, and an in-plane phase difference in a plane parallel to the main surfaces of the substrates has a value of 1/4 of a visible light wavelength λ.
Preferably, each of the optical compensation layers is composed of a 1 st optical compensation plate having a refractive index in a 1 st axis direction parallel to the main surfaces of the pair of substrates, a refractive index in a 2 nd axis direction parallel to the main surfaces of the substrates and perpendicular to the 1 st axis direction, a refractive index in a 3 rd axis direction perpendicular to the main surfaces of the substrates, and a thickness d, the values of Nx, Ny, and Nz have a relationship of Nx > Ny > Nz, the value of the in-plane phase difference R represented by (Nx-Ny) d is set in a range of 120nm to 160nm, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in a range of 50nm to 300 nm.
In this case, it is preferable that: the two sheets of the 1 st optical compensation plates are arranged so that an in-plane phase retardation axis in a direction in which a refractive index is maximum or an in-plane phase advance axis in a direction in which the refractive index is minimum in a plane parallel to the principal surface of the substrate are orthogonal to each other,
a pair of polarizing plates are arranged so that optical axes thereof are orthogonal to each other, and a polarizing axis of any one of the polarizing plates intersects the in-plane phase retardation axis or the in-plane phase advance axis of the adjacent optical compensation plate at an angle of 35 DEG to 55 deg.
Moreover, it is preferable that: between the two 1 st optical compensation plates disposed on both outer sides of the pair of substrates and the polarizing plates disposed on the respective outer sides, there are also disposed retardation plates having Nx, Ny, and Nz values in a relationship of Nx > Ny ≈ Nz, respectively, and a retardation R in a plane parallel to the main surface of the substrate has a value in a range of 240nm to 300 nm.
In this case, it is preferable that: the optical axes of a pair of polarizing plates are orthogonal to each other,
two pieces of the 1 st optical compensation plates disposed on both outer surfaces of the pair of substrates are disposed so that respective in-plane phase delay axes in a direction in which a refractive index is maximum or respective in-plane phase lead axes in a direction in which the refractive index is minimum in a plane parallel to the main surfaces of the substrates are orthogonal to each other, and the 1 st optical compensation plates are disposed in a direction intersecting with adjacent polarizing plates in a range of 5 ° to 25 ° or 65 ° to 85 °,
two phase difference plates provided outside the two 1 st optical compensation plates are arranged such that respective phase delay axes in a direction in which a refractive index is the largest in a plane parallel to a main surface of the substrate or respective phase lead axes in a direction in which a refractive index is the smallest are orthogonal to each other, and the phase difference plates are arranged in a direction intersecting with an in-plane phase delay axis or an in-plane phase lead axis of an adjacent 1 st optical compensation plate in a range of 50 ° to 70 °.
Moreover, it is preferable that: in addition to the retardation plate, another 2 nd optical compensation plate is disposed between the pair of polarizing plates, and the values of Nx, Ny and Nz of the optical compensation plate have a relationship of Nx > Ny > Nz, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300 nm.
In this case, it is preferable that: the optical axes of a pair of polarizing plates are orthogonal to each other,
the 2 nd optical compensation plates are respectively arranged between the two phase difference plates and the polarizing plates arranged outside the two phase difference plates, and are arranged so that the in-plane phase delay axes or the in-plane phase advance axes of the 2 nd optical compensation plates are parallel or orthogonal to each other and are parallel or orthogonal to the optical axes of the adjacent polarizing plates,
two pieces of the 1 st optical compensation plates arranged on both outer surfaces of the pair of substrates are arranged such that in-plane phase delay axes in a direction in which a refractive index is maximum or in-plane phase lead axes in a direction in which a refractive index is minimum in a plane parallel to the main surfaces of the substrates are orthogonal to each other, and the 1 st optical compensation plate is arranged in a direction intersecting with an optical axis of an adjacent polarizing plate in a range of 5 ° to 25 ° or 65 ° to 85 °,
two phase difference plates provided outside the two 1 st optical compensation plates are arranged such that respective phase delay axes in a direction in which a refractive index is the largest in a plane parallel to a main surface of the substrate or respective phase lead axes in a direction in which a refractive index is the smallest are orthogonal to each other, and the phase difference plates are arranged in a direction intersecting with an in-plane phase delay axis or an in-plane phase lead axis of an adjacent 1 st optical compensation plate in a range of 50 ° to 70 °.
In addition, when two sheets of the optical compensation plate and the retardation plate are provided, it is preferable to use a transflective liquid crystal panel in which a reflective film corresponding to a part of one of the 1 st electrode and the 2 nd electrode is formed, and a transmissive display region for controlling light transmitted through a pair of substrates facing each other and a reflective display region for controlling light reflected by the reflective film are formed in one pixel region formed by a region facing each of the electrodes.
In the liquid crystal display device in which the optical compensation plates are disposed on both outer surfaces of the pair of substrates, it is more preferable that: between a pair of polarizing plates, a 2 nd optical compensation plate different from the 1 st optical compensation plate is disposed, and the values of Nx, Ny and Nz of the optical compensation plate have a relationship of Nx > Ny > Nz, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300 nm.
In this case, it is preferable that: the optical axes of a pair of polarizing plates are orthogonal to each other,
two 1 st optical compensation plates disposed on both outer surfaces of the pair of substrates, the 1 st optical compensation plates being disposed so that in-plane phase delay axes in a direction in which a refractive index is maximum or in-plane phase lead axes in a direction in which the refractive index is minimum in a plane parallel to the principal surfaces of the substrates are orthogonal to each other, and the 1 st optical compensation plates being disposed so as to intersect optical axes of adjacent polarizing plates at an angle in the range of 35 DEG to 55 DEG,
the two 2 nd optical compensation plates provided outside the two 1 st optical compensation plates are arranged so that the in-plane phase retardation axes in the direction of the maximum refractive index and the in-plane phase advance axes in the direction of the minimum refractive index in a plane parallel to the principal surface of the substrate are parallel to or orthogonal to each other and the optical axes of the adjacent polarizing plates are parallel to or orthogonal to each other.
In the liquid crystal display element of the present invention, it is preferable that: a1 st optical compensation plate is disposed between an outer surface of one of a pair of substrates and one of polarizing plates of the pair of polarizing plates, and has a relationship of Nx > Ny > Nz in terms of Nx, Ny, and Nz values and a value of 1/4 in terms of visible light wavelength λ in a plane parallel to the main surface of the substrate, and a phase difference plate is disposed between an outer surface of the other of the pair of substrates and the other of the pair of polarizing plates, and has a relationship of Nx > Ny ≈ Nz in terms of Nx, Ny, and Nz values and a value of in-plane phase difference R in a plane parallel to the main surface of the substrate in terms of 120nm to 160 nm.
In this case, it is preferable that: the 1 st optical compensation plate and the phase difference plate are arranged so that an in-plane phase retardation axis in a direction in which a refractive index is maximum or an in-plane phase advancing axis in a direction in which the refractive index is minimum in a plane parallel to a main surface of the substrate are orthogonal to each other,
the pair of polarizing plates are arranged so that the optical axes thereof are orthogonal to each other, and are arranged in a direction in which the optical axis of each polarizing plate crosses the in-plane phase retardation axis or the in-plane phase advance axis of the 1 st optical compensation plate and the adjacent phase difference plate at 35 ° to 55 °.
Moreover, it is preferable that: between the pair of polarizing plates, another 2 nd optical compensation plate different from the 1 st optical compensation plate is further disposed, and the values of Nx, Ny and Nz of the other 2 nd optical compensation plate have a relationship of Nx > Ny > Nz, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300 nm.
In this case, it is preferable that: the 2 nd optical compensation plate is respectively arranged between the 1 st optical compensation plate and one polarizing plate and between the phase difference plate and the other polarizing plate and is parallel to or orthogonal to the optical axis of the adjacent polarizing plate,
the 1 st optical compensation plate and the phase difference plate are arranged so that an in-plane phase retardation axis in a direction in which a refractive index is maximum or an in-plane phase advancing axis in a direction in which the refractive index is minimum in a plane parallel to a main surface of the substrate are orthogonal to each other,
the pair of polarizing plates are arranged so that their optical axes are orthogonal to each other, and are arranged in a direction in which the polarizing axis of each polarizing plate crosses the in-plane phase retardation axis or the in-plane phase advance axis of the 1 st optical compensation plate and the adjacent retardation plate at 35 ° to 55 °.
In addition, these liquid crystal display elements may be provided with a member for aligning liquid crystals constituting the liquid crystal layer so that the director is directed in a plurality of directions by applying the electric field.
A liquid crystal display device according to claim 2 of the present invention includes:
a substrate provided with a transparent 1 st electrode;
another substrate which is arranged to face the first substrate and has a transparent 2 nd electrode formed on a surface thereof facing the first substrate, the transparent 2 nd electrode forming a pixel region for transmission type display through a region facing the 1 st electrode;
a vertical alignment film formed on the surfaces of the 1 st electrode and the 2 nd electrode facing each other;
a liquid crystal layer sealed between the substrates and having negative dielectric anisotropy;
a pair of polarizing plates disposed on outer surfaces of the one and the other substrates opposite to the surfaces thereof facing each other, respectively;
two pieces of 1 st optical compensation plates which are respectively arranged between the pair of substrates and the pair of polarizing plates, and which have a relationship that when a refractive index in a 1 st axis direction parallel to main surfaces of the pair of substrates is Nx, a refractive index in a 2 nd axis direction parallel to the main surfaces of the substrates and perpendicular to the 1 st axis direction is Ny, and a refractive index in a 3 rd axis direction perpendicular to the main surfaces of the substrates is Nz, values of Nx, Ny, and Nz have a relationship of Nx > Ny > Nz, and which give a phase difference of a value of 1/4 at a wavelength λ to transmitted light; and
the two 2 nd optical compensation plates are respectively arranged between the two 1 st optical compensation plates and the polarizing plates arranged outside the two 1 st optical compensation plates, the values of Nx, Ny and Nz respectively have a relationship of Nx > Ny > Nz, and the direction of an in-plane phase retardation axis having the largest in-plane refractive index parallel to the main surface of the substrate is orthogonal or parallel to the transmission axis of the adjacent polarizing plate.
In such a liquid crystal display element, it is preferable that: the optical axes of the pair of polarizing plates are orthogonal to each other,
the two 1 st optical compensation plates are arranged so that the in-plane retardation in a plane parallel to the principal surface of the substrate has a value of 1/4 which is the wavelength λ of visible light, and the direction of the in-plane retardation axis having the largest refractive index in a plane parallel to the principal surface of the substrate is at an angle of substantially 45 ° to the transmission axis of the adjacent polarizing plate.
A liquid crystal display device according to claim 3 of the present invention includes:
a substrate provided with a transparent 1 st electrode;
a second substrate having a reflective film provided on a surface thereof facing the first substrate, the reflective film facing a part of the first electrode 1, and a second electrode 2 disposed in a region including the reflective film, the second electrode being formed in a region facing the first electrode to form a pixel region including a reflective display region corresponding to the reflective film and a transmissive region other than the reflective display region;
a vertical alignment film formed on the surfaces of the 1 st electrode and the 2 nd electrode facing each other;
a liquid crystal layer sealed between the substrates, having negative dielectric anisotropy, giving a phase difference of substantially 1/2 from a wavelength of light transmitted through the transmissive display region of the pixel region, and having a layer thickness of substantially 1/2 from a layer thickness corresponding to the reflective region of the pixel region;
a pair of polarizing plates disposed on outer surfaces of the one and the other substrates opposite to the surfaces thereof facing each other, respectively;
two pieces of 1 st optical compensation plates, each of which is disposed between the pair of substrates and the pair of polarizing plates, wherein when a refractive index in a 1 st axis direction parallel to main surfaces of the pair of substrates is Nx, a refractive index in a 2 nd axis direction parallel to the main surfaces of the substrates and perpendicular to the 1 st axis direction is Ny, and a refractive index in a 3 rd axis direction perpendicular to the main surfaces of the substrates is Nz, values of Nx, Ny, and Nz have a relationship of Nx > Ny > Nz; and
two phase difference plates respectively arranged between the two 1 st optical compensation plates and the polarizing plates respectively arranged outside, the in-plane phase retardation axes of the 1 st optical compensation plate and the phase difference plate adjacent to each other, which have the maximum in-plane refractive index in a plane parallel to the main surface of the substrate, are substantially oriented to 45 DEG to each other, the values of Nx, Ny and Nz have a relationship of Nx > Ny ≈ Nz, and the value of the in-plane phase difference synthesized by the optical compensation plates and the phase difference plates adjacent to each other has a value of 1/4 in-plane phase difference which is substantially the wavelength of transmitted light.
In such a liquid crystal display element, it is preferable that: the optical axes of a pair of polarizing plates are orthogonal to each other,
two pieces of the 1 st optical compensation plates disposed on both outer surfaces of the pair of substrates are disposed so that in-plane phase retardation axes in a direction in which a refractive index is maximum in a plane parallel to the main surfaces of the substrates are orthogonal to each other, and the 1 st optical compensation plates are disposed in a direction intersecting with a transmission axis of an adjacent polarizing plate in a range of 5 ° to 25 ° or 65 ° to 85 °,
the two retardation plates provided outside the two 1 st optical compensation plates are arranged so that in-plane retardation axes in a direction in which an in-plane refractive index is maximum in a plane parallel to the principal surface of the substrate are orthogonal to each other.
According to the liquid crystal display device of claim 1 of the present invention, since the two optical compensation layers which give a phase difference of substantially 1/4 in wavelength λ to the transmitted visible light are disposed on both sides of the vertical alignment type liquid crystal cell, the transmittance is improved.
Further, since the optical compensation layer is formed of an optical compensation plate having a relationship of refractive index Nx, Ny, and Nz of Nx > Ny > Nz and a phase difference in a plane parallel to the principal surface of the substrate of 1/4 of the visible light wavelength λ, or an optical compensation plate having a relationship of Nx > Ny > Nz of Nx, Ny, and Nz, a value of in-plane phase difference R represented by (Nx-Ny) d is set in a range of 120nm to 160nm and a value of phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in a range of 50nm to 300nm, light incident on the liquid crystal display element can be converted into substantially circularly polarized light and incident on the liquid crystal cell, thereby improving transmittance.
Further, since the optical compensation layers are disposed on both sides of the liquid crystal cell, light polarized into linearly polarized light by the polarizing plates can be converted into circularly polarized light and incident on the liquid crystal cell, and the polarized light transmitted through the liquid crystal cell can be converted into substantially linearly polarized light again and incident on the polarizing plate on the emission side, whereby a liquid crystal display element having high transmittance and a wide viewing angle range can be realized.
In the liquid crystal display element in which the optical compensation plates are disposed on both sides of the liquid crystal cell, by further disposing a substantially uniaxial retardation plate having Nx, Ny, and Nz values in a relationship of Nx > Ny ≈ Nz between the optical compensation plate and the polarizing plates disposed outside the optical compensation plate, and having a retardation R in a plane parallel to the main surface of the substrate having a value in a range of 240nm to 300nm, it is possible to realize a transflective liquid crystal display element which has high transmittance, a wide range of viewing angles, and both of reflective display and transmissive display in which color shift is reduced.
In addition, in the liquid crystal display element in which the optical compensation plates are disposed on both sides of the liquid crystal cell, or in the liquid crystal display element in which the optical compensation plates and the retardation plates are disposed on both sides of the liquid crystal cell, respectively, by further disposing another optical compensation plate having a relationship of Nx > Ny > Nz and in which a value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in a range of 50nm to 300nm, the value of the phase difference Rz in the Z direction can be made extremely large, and the range of the viewing angle can be made extremely wide.
In the present invention, a liquid crystal display element having a high contrast ratio and a practically wide viewing angle can be obtained by disposing the optical compensation plate on one surface of a liquid crystal panel and disposing a uniaxial retardation plate having a relationship of Nx > Ny ≈ Nz and an in-plane retardation R having a value in a range of 120nm to 160nm on the other surface.
In this case, by arranging another optical compensation plate in which the value of the phase difference Rz in the Z direction is set in the range of 50nm to 300nm, the value of the phase difference Rz in the Z direction can be made extremely large, and the range of the viewing angle can be further widened.
Further, according to the liquid crystal display device of claim 2 of the present invention, two 1 st optical compensation plates made of a biaxial retardation plate for giving a retardation of 1/4, which is a value of the wavelength λ, to transmitted light are disposed on both sides of a vertical alignment type liquid crystal panel for performing transmission display, and two 2 nd optical compensation plates made of a biaxial retardation plate for making the direction of the in-plane retardation axis orthogonal or parallel to the transmission axis of the adjacent polarizing plate are disposed on the outer side thereof, so that the phase difference in the Z axis direction of these adjacent 1 st and 2 nd optical compensation plates is added, a large phase difference can be obtained in the Z axis direction, and the viewing angle characteristics are greatly improved.
Further, according to the liquid crystal display device of claim 3 of the present invention, since the optical compensation plates composed of the biaxial retardation plates and the uniaxial retardation plates in which the retardation axes are arranged to intersect the in-plane retardation axes of the biaxial retardation plates at 45 ° are arranged on both sides of the vertical alignment type liquid crystal panel which performs the transmissive display and the reflective display, and the value obtained by combining the in-plane phase differences of the optical compensation plates and the retardation plates adjacent to each other is substantially 1/4 of the wavelength of the transmitted light, these optical compensation plates and retardation plates function as a broad-band λ/4 plate, and have a high contrast, a substantially wide viewing angle, and a sufficiently improved viewing angle dependency of color tone.
Drawings
Fig. 1 is a diagram showing a structure of a liquid crystal display element according to embodiment 1 of the present invention.
Fig. 2A to 2C are diagrams for explaining the influence of the protrusions formed on the alignment film on the alignment of the liquid crystal molecules, fig. 2A is a diagram when the alignment of the liquid crystal is observed from the substrate side surface when no electric field is applied, fig. 2B is a diagram when the alignment of the liquid crystal is observed from the substrate side surface when an electric field is applied, and fig. 2C is a diagram when the alignment of the liquid crystal is observed from the substrate front direction when an electric field is applied.
Fig. 3 is a diagram for explaining the arrangement of the optical axes of the optical elements according to embodiment 1.
Fig. 4A and 4B show contrast distributions at viewing angles of liquid crystal display elements, where fig. 4A is a viewing angle characteristic diagram of embodiment 1, and fig. 4B is a viewing angle characteristic diagram of a comparative example.
Fig. 5 is a diagram showing the structure of a liquid crystal display element according to embodiment 2 of the present invention.
Fig. 6 is a diagram for explaining the arrangement of the optical axes of the optical elements according to embodiment 2 of the present invention.
Fig. 7 is a diagram for explaining the arrangement of the optical axes of the optical elements according to embodiment 3 of the present invention.
Fig. 8 is a diagram for explaining the arrangement of the optical axes of the optical elements according to embodiment 4 of the present invention.
Fig. 9 is a diagram showing a structure of a liquid crystal display element according to embodiment 5 of the present invention.
Fig. 10 is a diagram for explaining the arrangement of the optical axes of the optical elements according to embodiment 5 of the present invention.
Fig. 11 is a view angle characteristic diagram showing a contrast distribution with respect to a view angle of the liquid crystal display element of embodiment 5.
Fig. 12 is a diagram showing a structure of a liquid crystal display element according to embodiment 6 of the present invention.
Fig. 13 is a diagram for explaining the arrangement of the optical axes of the optical elements according to embodiment 6 of the present invention.
Fig. 14 is a diagram showing a structure of a modification of the optical compensation plate.
Detailed Description
(embodiment mode 1)
As shown in fig. 1, the liquid crystal display device of the present embodiment includes: a pair of substrates 1, 2; a pixel electrode 3 and a counter electrode 4 formed on the inner surfaces of the substrates facing each other; alignment films 5, 6 formed on the surfaces of these electrodes; a liquid crystal panel 70 including a liquid crystal layer 7 sealed between the pair of substrates; a pair of polarizing plates 8, 9 disposed on the outer sides of the pair of substrates 1, 2 of the liquid crystal panel 70 so as to sandwich the substrates; two optical compensation layers 12, 13 respectively disposed between the pair of polarizing plates 8, 9 on both sides of the liquid crystal panel 70; and a sealing material 21 for bonding the pair of substrates 1, 2.
The substrates 1 and 2 are transparent substrates made of glass or the like, for example, and are arranged to face each other with a liquid crystal layer 7 interposed therebetween.
The pixel electrode 3 and the counter electrode 4 are transparent electrodes made of an ito (indium Tin oxide) film or the like containing indium Tin oxide as a main component, and are formed on the opposing inner surfaces of the substrates 1 and 2, respectively. The liquid crystal display element is an active matrix type liquid crystal display element, and an active element 3a is connected to each pixel electrode 3, a counter electrode 4 is formed of a transparent conductive film covering the entire display region, and the pixel electrode 3 forms one pixel by a region facing the counter electrode 4.
Note that the liquid crystal display element is not limited to the active matrix type, and for example, in the case of the passive matrix type, a plurality of pixel electrodes 3 may be formed as signal electrodes extending in the 1 st direction in parallel with each other, and a plurality of counter electrodes 4 may be formed as scanning electrodes extending in the 2 nd direction orthogonal to the signal electrodes 3.
The alignment films 5 and 6 are formed of a polymer film of hexamethyldisiloxane or the like so as to cover the pixel electrode 3 and the counter electrode 4. The alignment films 5 and 6 are vertical alignment films having an alignment regulating force for vertically aligning the liquid crystal molecules 7a in the vicinity of the alignment film of the liquid crystal layer 7.
As shown in an enlarged cross-sectional view of fig. 2A, a minute protrusion 6a is formed at the center of each pixel region of the alignment film 5, and when a voltage is applied between the pixel electrode 3 and the counter electrode 4 to change the alignment state and turn over the liquid crystal molecules, the minute protrusion 6a is used to obtain the alignment stability of the liquid crystal molecules in each pixel region.
The liquid crystal layer 7 is made of a liquid crystal material exhibiting negative dielectric anisotropy, and is enclosed in a region made up of the substrates 1 and 2 and the sealing material 21.
When no voltage is applied between the opposing electrodes (when no voltage is applied), the liquid crystal layer 7 has liquid crystal molecules 7a aligned perpendicular to the main surfaces of the substrates as shown in fig. 1 by the alignment regulating force of the alignment films 5 and 6. When an electric field is applied, the liquid crystal molecules are turned over so as to be parallel to the main surfaces of the substrates due to the negative dielectric anisotropy, and when a sufficiently large voltage is applied, the liquid crystal molecules are aligned substantially parallel to the main surfaces of the substrates.
In this case, as shown in fig. 2A schematically showing a portion where the protrusion 6a of one pixel is formed, the liquid crystal molecules 7a near the protrusion 6a formed in the center portion of each pixel region of the alignment film 6 are aligned so as to be perpendicular to the surface of the protrusion 6a, and the liquid crystal molecules around the protrusion are tilted toward the center of the pixel. The tilt alignment of the liquid crystal molecules in the vicinity of the center of the pixel tends to cause the liquid crystal molecules 7a in the pixel to fall down toward the center of the pixel. Therefore, when a voltage is applied between the pixel electrode 3 and the counter electrode 4, the liquid crystal molecules in the pixel region are aligned by turning the long axes of the molecules radially around the protrusion 6a and turning over, as shown in fig. 2B and fig. 2C showing fig. 2B in a plan view. This makes it possible to obtain an alignment state in which the director (director) of the liquid crystal molecules is oriented in all directions in one pixel.
As described above, in the case where the projection 6a is provided in each pixel region, one orientation state centered on the projection 6a can be obtained in each pixel region. In addition, when a slit (slit) dividing the pixel region into a plurality of slits is provided in one electrode forming the pixel region and the protrusion 6a is formed substantially at the center of the region divided by the slit, a radial alignment state around the protrusion 6a may be obtained in each of the divided regions dividing one pixel region into a plurality of regions, and a plurality of domains (domains) may be formed in one pixel region.
Further, the liquid crystal layer 7 has a birefringence Δ n (extraordinary refractive index n) according to the liquid crystale-ordinary optical refractive index n0) And the gap (thickness of the liquid crystal layer 7) d, for example, are Δ nd ≈ 350nm ± 100nm (the value of Δ nd ranges from 250nm to 450 nm), and liquid crystal molecules are aligned vertically substantially in the same manner as the main surfaces of the substrates 1 and 2 when the liquid crystal layer 7 is not applied with a voltage.
The polarizing plates 8 and 9 disposed on both sides of the liquid crystal panel 70 are disposed on the outer surfaces of the substrates 1 and 2, respectively, as shown in fig. 1, and are disposed so that optical axes 8a and 9a, such as transmission axes and absorption axes, are orthogonal to each other (cross prisms) as shown in fig. 3.
The two optical compensation layers 12, 13 disposed on both sides of the liquid crystal panel 70 are constituted by optical compensation plates, the optical compensation plate is made of norbornene resin with small wavelength dependence of refractive index, the refractive index in the 1 st axis direction parallel to the main surfaces of the pair of substrates is Nx, a refractive index in a 2 nd axis direction parallel to the main surface of the substrate and perpendicular to the 1 st axis direction is Ny, when the refractive index in the 3 rd axis direction (film thickness direction) perpendicular to the main surface of the substrate is Nz and the thickness of the optical compensation layer is d, the refractive indices Nx, Ny and Nz in three directions orthogonal to each other have a relationship of Nx > Ny > Nz, the value of the in-plane retardation R represented by (Nx-Ny) d is set in the range of 120nm to 160nm, more preferably 140nm, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300 nm.
That is, a biaxial retardation plate in which the refractive index Nz in the 3 rd axis direction perpendicular to the main surface of the substrate in the thickness direction is smaller than the refractive index values in the other two axis directions is disposed between the pair of polarizing plates 8 and 9 on both sides of the liquid crystal panel 70, the in-plane retardation R of the biaxial retardation plate is set to a phase difference of substantially 1/4, which is the intermediate wavelength of the visible light band, and the phase difference Rz in the Z direction is set to a value that compensates for the phase difference of the liquid crystal layer 7 that changes with light obliquely incident on the liquid crystal panel.
As shown in fig. 3, the two optical compensation plates 12 and 13 are arranged such that in-plane phase retardation axes 12a and 13a in a direction in which the refractive index is the largest on a plane parallel to the plate surfaces thereof, or in-plane phase advancing axes in a direction in which the refractive index is the smallest orthogonal to the in-plane phase retardation axes 12a and 13a are orthogonal to each other, and that the in-plane phase retardation axes 12a and 13a or the in-plane phase advancing axes intersect the polarizing axes formed by the transmission axes 8a and 9a or the absorption axes of the adjacent polarizing plates 8 and 9 at an angle in the range of 35 ° to 55 °, substantially 45 °, that is, an allowable range of ± 10 ° (45 ° ± 10 °) with 45 ° as the center.
Next, the operation of the liquid crystal display device having the above-described structure will be described.
In the liquid crystal display element shown in fig. 1, in a state where no voltage is applied between the pixel electrode 3 and the counter electrode 4 (voltage-non-applied state), no electric field is generated between the pixel electrode 3 and the counter electrode 4, and the liquid crystal molecules 7a in the liquid crystal layer 7 are aligned perpendicular to the main surfaces of the substrates 1 and 2 as schematically shown in fig. 1. Therefore, the linearly polarized light transmitted through the inner polarizer 9 on the side opposite to the observation side is converted into circularly polarized light by the inner optical compensation plate 13 and is incident on the liquid crystal layer 7 of the liquid crystal panel 70, the circularly polarized light is transmitted without being subjected to the optical action of the liquid crystal layer 7 in which the liquid crystal molecules 7a are vertically aligned, and is returned to the original linearly polarized light by the observation side optical compensation plate 12, and is incident on the observation side polarizer 8 disposed on the cross prism as linearly polarized light having a polarization plane parallel to the absorption axis thereof, and is absorbed by the observation side polarizer 8 to be displayed in black (dark).
On the other hand, when a voltage corresponding to display data of a pixel is applied between the pixel electrode 3 and the counter electrode 4 (voltage applied state), an electric field is generated between these electrodes. The liquid crystal molecules 7a are inclined in accordance with the electric field intensity, and the liquid crystal molecules 7a in the liquid crystal layer 7 change their alignment state from a vertically aligned state in which they are aligned perpendicularly to the substrate main surfaces (main surfaces of the substrates 1 and 2) to a horizontally aligned state in which they are aligned parallel to the substrate main surfaces.
When a sufficiently high electric field is applied to the liquid crystal layer 7, the liquid crystal molecules 7a are aligned radially with the projection 6a at the center of the pixel as the center, substantially parallel to the substrate main surface. The linearly polarized light transmitted through the inner polarizing plate 9 positioned on the lower side in the drawing has an in-plane retardation of the inner optical compensation plate 13 substantially having a retardation of 1/4, which is the wavelength λ of visible light, and the in-plane retardation axis 13a or the phase lead axis crosses the transmission axis 9a of the polarizing plate 9 at an angle of substantially 45 °, so that the linearly polarized light is converted into circularly polarized light rotating in one rotational direction and is incident on the liquid crystal layer 7.
The linearly polarized light incident on the liquid crystal layer 7 is converted into circularly polarized light rotating in the opposite direction to the one direction by the substantial λ/2 phase difference of the liquid crystal layer 7, and is incident on the optical compensation plate 12 on the observation side. Since the optical compensation plate 12 on the observation side is also set so that the in-plane retardation thereof substantially has a retardation of 1/4 of the visible light wavelength λ and the phase retardation axis 12a or the phase advancing axis thereof is orthogonal to the phase retardation axis 12a or the phase advancing axis of the optical compensation plate 13 on the inner side, the circularly polarized light incident on the optical compensation plate 12 on the observation side in one direction is converted into linearly polarized light having a polarization plane orthogonal to the polarization plane of the linearly polarized light transmitted through the inner polarizing plate 9 and is incident on the polarizing plate 8 on the observation side, and the transmission axis 8a of the polarizing plate 8 on the observation side is arranged so as to be orthogonal to the polarization plane of the linearly polarized light transmitted through the inner polarizing plate 9Since the transmission axes 9a of the optical compensation plates 9 are orthogonal to each other, the linearly polarized light transmitted through the optical compensation plate 12 is transmitted through the polarizing plate 8 on the observation side, and white display (bright) is performed. The transmitted light intensity I in this case is λ at the wavelength of the light and I at the average intensity0The expression is shown in the following equation.
(equation 1)
I＝I0sin2(πΔnd/λ)
As shown in equation 1, since the transmitted light intensity I does not have the azimuth angle θ of the director of the liquid crystal molecules as a parameter, the light can be transmitted uniformly over the entire area of each pixel, and a high transmittance is obtained.
On the other hand, when there is no in-plane retardation in the optical compensation plates 12 and 13, the transmitted light intensity I is expressed by the following equation where θ is the angle formed by the polarization axes 8a and 9a and the liquid crystal director viewed from the normal direction of the principal surface of the substrate.
(equation 2)
I＝I0sin2(πΔnd/λ)sin2(2θ)
In equation 2, the transmission light intensity I has a maximum transmittance when θ is ± 45 °, and I is 0 when θ is 0 °. In the case of a liquid crystal display element in which liquid crystal molecules 7a are aligned in a radiation-like manner in each pixel when an electric field is applied to the liquid crystal layer 7, the transmittance I is 0 in a region of the liquid crystal molecules 7a which is turned over in substantially the same direction (θ is 0 °) as the optical axes 8a and 9a of the polarizers 8 and 9, and a dark portion occurs in each pixel in a radiation-like manner when viewed from the normal direction of the principal surface of the substrate, resulting in a low transmittance.
In addition, the abnormal light refractive index of the liquid crystal layer 7 is n, the phase difference in the liquid crystal layer 7 in the oblique direction when no voltage is applied is in the oblique directioneThe ordinary optical refractive index of the liquid crystal is n0When the angle of inclination from the substrate normal direction to the substrate horizontal plane is φ, the following equation is used for simplicity.
(equation 3)
Δnd(φ)＝{nen0/(ne 2cos2φ+n0 2sin2φ)-1/2-n0}×(d/cosφ)
As shown in equation 3, the larger the angle φ inclined from the substrate normal direction to the substrate horizontal plane, the larger the Δ nd(φ)The larger the value of (c).
On the other hand, the retardation Rz in the thickness direction of the optical compensation layers 12 and 13 is expressed by the following equation when the thickness of the optical compensation layers 12 and 13 is d.
(equation 4)
Rz＝{(Nx+Ny)/2-Nz}×d
Therefore, the value of the phase difference Rz in the Z direction of the optical compensation layers 12 and 13 is set so as to cancel the increased portion of the phase difference in the substrate normal direction of the predetermined angle Φ inclined from the substrate normal. In the present embodiment, the value of the phase difference Rz in the Z direction of the optical compensation layers 12 and 13 is set within the range of 50 to 300nm, and the changes in contrast and luminance when viewed from a direction inclined with respect to the substrate normal direction are reduced by the optical compensation layers 12 and 13, the range of the viewing angle is expanded, and the inversion of the color tone due to the viewing angle Φ is compensated.
As described above, in the liquid crystal display device of the present embodiment, since the value of the in-plane retardation R of the optical compensation layers 12 and 13 having the relationship of Nx > Ny > Nz is substantially set to λ/4, a dark portion does not occur in a display pixel which becomes a problem when white display is performed by applying a voltage between the pixel electrode 3 and the counter electrode 4, and high transmittance is obtained, and further, since the value of the Z-direction retardation Rz of the optical compensation layers 12 and 13 is set to a range of 50nm to 300nm, the range of the viewing angle can be widened, and the inversion of the color tone can be suppressed.
Fig. 4A shows a viewing angle and a contrast distribution of the liquid crystal display element of the present embodiment having the optical compensation layer, and fig. 4B shows a contrast distribution of an angle (viewing angle) with respect to an observation direction with respect to a substrate normal direction in the liquid crystal display element as a comparative example without the optical compensation layer. As shown in the figure, in the comparative examples without the optical compensation layers 12 and 13, the region having a contrast of 10 or more is in the range of about 30 ° to 40 ° as shown by a solid line, and the range of the viewing angle is very narrow. In contrast, in the case of the liquid crystal display element of the present embodiment provided with the optical compensation layers 12 and 13, the region having a contrast of 10 or more is enlarged to the range of 160 ° in the vertical and horizontal directions as shown by the solid lines.
As described above, according to the liquid crystal display element of the present embodiment, by providing the liquid crystal panel in which the projection 6a is provided at the center of the pixel and the liquid crystal molecules 7a are oriented radially from the center of the pixel in the va (vertical alignment) mode, and providing the optical compensation plates 12 and 13 on both sides of the liquid crystal panel, which have a relationship of Nx > Ny > Nz in terms of the values of Nx, Ny, and Nz, and in which the phase difference in the plane parallel to the main surfaces of the substrates 1 and 2 has the value of 1/4 of the visible light wavelength λ, it is possible to perform display with high transmittance and high contrast, and by using the optical compensation plates 12 and 13 in which the value of the phase difference Rz in the Z direction is in the range of 50nm to 300nm, it is possible to perform display with a wide viewing angle.
(embodiment mode 2)
In embodiment 1, the liquid crystal display element in which one optical compensation plate 12, 13 is disposed on each side of the liquid crystal panel 70 is shown, but as shown in fig. 5, another optical compensation plate 14, 15 different from the optical compensation plates 12, 13 is additionally disposed on each side of the liquid crystal panel 70, and the object of the present invention can be achieved. By disposing two other optical compensation plates 14 and 15 on both sides of the liquid crystal panel 70 in this way, the value of the phase difference Rz in the Z direction can be made sufficiently large, and the viewing angle dependence of the contrast can be sufficiently compensated. The liquid crystal display device according to embodiment 2 is similar to that of embodiment 1 except that the liquid crystal display device of fig. 1 additionally includes another optical compensation layer 14, 15 on each side of the liquid crystal panel 70, and therefore the same members are given the same reference numerals and the description thereof is omitted.
As shown in fig. 5, the liquid crystal display device of this embodiment includes: a liquid crystal panel 70; a 1 st optical compensation layer 12 disposed on the viewing side of the liquid crystal panel 70; and a 2 nd optical compensation plate 14 disposed further on the observation side, further comprising: a 1 st optical compensation plate 13 disposed on the side opposite to the observation side of the liquid crystal panel 70; and a 2 nd optical compensation plate 15 disposed further inside.
The 2 nd optical compensation layers 14 and 15 are optical compensation plates 14 and 15 in which the refractive indices Nx, Ny, and Nz have a relationship of Nx > Ny > Nz, the phase difference Rz in the Z direction is set to a value in the range of 50nm to 300nm, and the in-plane phase difference R may be absent or present, and may have any value.
That is, on the observation side of the liquid crystal panel 70, the 1 st optical compensation plate 12 on the observation side as in embodiment 1 is disposed such that the in-plane retardation axis 12a thereof is oriented at 45 ° with respect to the horizontal direction (horizontal direction) when the liquid crystal display element is observed, the polarizing plate 8 closest to the observation side is disposed such that the transmission axis 8a thereof is parallel to the horizontal direction, and the 2 nd optical compensation plate 14 on the observation side is disposed such that the in-plane retardation axis 14a thereof is parallel to the transmission axis 8a of the polarizing plate 8 on the observation side between the 1 st optical compensation plate 12 on the observation side and the polarizing plate 8 on the observation side.
As shown in fig. 6, on the side opposite to the viewing side of the liquid crystal panel 70, the inner 1 st optical compensation plate 13 similar to embodiment 1 is disposed such that the in-plane phase retardation axis 13a thereof is oriented in a direction of 135 ° with respect to the horizontal direction (horizontal direction) when viewing the liquid crystal display element, the innermost polarizing plate 9 is disposed such that the transmission axis 9a thereof is orthogonal to the horizontal direction, and the inner 2 nd optical compensation plate 15 is disposed such that the in-plane phase retardation axis 15a thereof is orthogonal to the transmission axis 9a of the inner polarizing plate 9 between the inner 1 st optical compensation plate 13 and the inner polarizing plate 9.
In this way, the 2 nd optical compensation plates 14 and 15 are disposed so that the in-plane retardation axes 14a and 15a thereof are parallel to or orthogonal to the transmission axes 8a and 9a of the adjacent polarizing plates 8 and 9, respectively, and the arrangement of these optical axes prevents optical effects from occurring with respect to linearly polarized light having a polarization plane parallel to the transmission axes 8a and 9a or the absorption axes of the respective polarizing plates 8 and 9, and therefore the 1 st optical compensation plates 12 and 13 and the 2 nd optical compensation plates 14 and 15 disposed on both sides of the liquid crystal panel 70 function as one optical compensation plate in which the values of the phase difference Rz in the Z direction are added between the respective adjacent optical compensation plates.
In the liquid crystal display device of embodiment 2, similarly to embodiment 1, in a no-voltage state in which no voltage is applied to the pixel electrode 3 and the counter electrode 4, the linearly polarized light transmitted through the inner polarizing plate 9 is converted into circularly polarized light by the inner 2 nd optical compensation plate 15 and the inner 1 st optical compensation plate 13 and is incident on the liquid crystal layer 7 of the liquid crystal panel 70, and the circularly polarized light is transmitted through the liquid crystal layer 7 as it is, and then returned to the original linearly polarized light again by the 1 st optical compensation plate 12 and the 2 nd optical compensation plate 14 on the observation side, and is absorbed by the polarizing plate 8 disposed on the observation side of the cross prism, and is displayed in black (dark).
In a state where a sufficiently high voltage is applied between the pixel electrode 3 and the counter electrode 4, the linearly polarized light transmitted through the inner polarizing plate 9 is converted into circularly polarized light by the inner 2 nd and 1 st optical compensation plates 15 and 13 and is incident on the liquid crystal layer 7 of the liquid crystal panel 70, the circularly polarized light is converted into circularly polarized light of opposite rotation by the liquid crystal layer 7 oriented so as to have a phase difference of λ/2, the linearly polarized light whose polarization plane is rotated by 90 ° with respect to the polarization plane of the linearly polarized light transmitted through the inner polarizing plate 9 is converted by the 1 st and 2 nd optical compensation plates 12 and 14 on the observation side, and the linearly polarized light is transmitted through the polarizing plate 8 on the observation side arranged on the cross prism and is displayed in white (bright).
Further, since the phase difference between the 1 st and 2 nd optical compensation plates is increased by changing the inclination angle of light incident in a direction inclined from the normal line of the liquid crystal display element in accordance with the inclination angle of the light, the change in the phase difference caused by the oblique incidence to the liquid crystal layer 7 can be compensated by the change in the phase difference between the 1 st and 2 nd optical compensation plates, and the range of the viewing angle can be widened.
As described above, in embodiment 2, the 1 st optical compensation plate and the 2 nd optical compensation plate are disposed on both sides of the liquid crystal panel 70, so that the value of the phase difference Rz in the Z direction can be sufficiently increased, and the viewing angle dependence of the contrast can be sufficiently compensated.
(embodiment mode 3)
In embodiment 1, the liquid crystal display element in which the optical compensation plates 12 and 13 are disposed on both sides of the liquid crystal panel is shown, but the present invention is not limited thereto, and in fig. 1, the optical compensation element 13 on the side opposite to the observation side of the liquid crystal panel 70 may be replaced with another optical compensation plate layer (optical compensation plate 16) having different optical characteristics. The liquid crystal display device of embodiment 3 is the same as that of embodiment 1 except that one optical compensation layer disposed on one side of the liquid crystal panel 70 is replaced with another optical compensation layer having different optical characteristics, and therefore the same members are assigned the same reference numerals and the description thereof is omitted.
As shown in fig. 7, the liquid crystal display device of this embodiment includes: a liquid crystal panel 70; a 1 st optical compensation layer 12 disposed on the viewing side of the liquid crystal panel 70; another optical compensation plate 16 disposed on the inner side opposite to the observation side of the liquid crystal panel 70; and a pair of polarizing plates 8 and 9 disposed so as to sandwich the liquid crystal panel 70, the 1 st optical compensation layer 12, and the other optical compensation plate 16.
The other optical compensation plate is constituted by a retardation plate 16 in which Nx, Ny, and Nz have a relationship of Nx > Ny ≈ Nz (Ny and Nz are substantially equal, Nx is larger than Ny), and an in-plane retardation R in a plane parallel to the main surface of the substrate has a value in a range of 120nm to 160 nm.
The 1 st optical compensation plate 12 and the phase difference plate 16 are arranged such that in-plane phase retardation axes 12a and 16a in a direction in which a refractive index is maximum in a plane parallel to a main surface of the substrate or in-plane phase advancing axes in a direction in which the refractive index is minimum are orthogonal to each other, the pair of polarizing plates 8 and 9 are arranged such that optical axes 8a and 9a thereof are orthogonal to each other, and polarizing axes 8a and 9a of the respective polarizing plates 8 and 9 are arranged such that they intersect phase retardation axes 12a and 16a or phase advancing axes of the 1 st optical compensation plate 12 and the phase difference plate 16 adjacent thereto at an angle of 35 ° to 55 ° and substantially 45 °.
In this liquid crystal display device, when a sufficiently high electric field is applied to the liquid crystal layer 7, as in embodiment 1, since the in-plane retardation of the 1 st optical compensation plate 12 disposed on the liquid crystal plate 70 side is substantially λ/4 of transmitted light, the in-plane retardation of the phase difference plate 16 disposed inside the liquid crystal plate is also substantially λ/4, the in-plane retardation axis 12a of the 1 st optical compensation plate 12 and the retardation axis 16a of the phase difference plate 16 are arranged so as to be orthogonal to each other, and the in-plane retardation axis is substantially 45 ° to the transmission axes 8a, 9a of the adjacent polarizing plates 8, 9, the linearly polarized light transmitted through the inner polarizing plate 9 is converted by the phase difference plate 16 into circularly polarized light rotated in one rotational direction and is incident on the liquid crystal layer 7, and the liquid crystal layer 7 is converted into circularly polarized light rotated in the opposite direction to the one rotational direction, the light enters the 1 st optical compensation plate 12 on the observation side, is converted by the optical compensation plate 12 on the observation side into linearly polarized light whose polarization plane is rotated by 90 ° with respect to the polarization plane of the linearly polarized light when the light enters the retardation plate 16, enters the polarizing plate 8 on the observation side, and is transmitted through the polarization plane 8 to be displayed brightly.
Therefore, high transmittance is obtained and brightness is obtained, and the contrast becomes high.
Further, since the 1 st optical compensation layer 12 is disposed on the observation side of the liquid crystal panel 70, the phase difference Rz in the Z direction of the 1 st optical compensation layer 12 partially cancels the phase difference increase in the substrate normal direction at the angle Φ inclined from the substrate normal, and the region with a contrast of 10 or more is widened to a range of 140 °, thereby improving the viewing angle characteristics.
(embodiment mode 4)
In embodiment 3, the liquid crystal display element in which one 1 st optical compensation layer 12 is disposed on one side of the liquid crystal panel 70 and the retardation plate 16 composed of the other optical compensation layer having different optical characteristics is disposed on the other side is shown, but as shown in fig. 8, one additional optical compensation plate may be additionally disposed on each of the outer sides of the 1 st optical compensation layer 12 and the other optical compensation layer (retardation plate 16) disposed on both sides of the liquid crystal panel 70. By disposing two further optical compensation plates 17 and 18 on both sides of the liquid crystal panel 70 in this manner, the value of the phase difference Rz in the Z direction can be made sufficiently large, and the viewing angle dependence of the contrast can be sufficiently compensated for. The liquid crystal display device according to embodiment 4 has the same configuration as that of embodiment 3 except that the liquid crystal display device of fig. 7 additionally includes the other optical compensation layers 17 and 18 on both sides of the liquid crystal panel 70, and therefore the same members are given the same reference numerals and the description thereof is omitted.
As shown in fig. 8, the liquid crystal display device of this embodiment includes: a liquid crystal panel 70; a 1 st optical compensation layer 12 disposed on the viewing side of the liquid crystal panel 70; and a 2 nd optical compensation plate 17 disposed further on the observation side, further comprising: a phase difference plate 16 disposed on the inner side opposite to the observation side of the liquid crystal panel 70; and a 2 nd optical compensation plate 18 disposed further inside.
The 2 nd optical compensation layers 17 and 18 are optical compensation plates in which the refractive indices Nx, Ny, and Nz have a relationship of Nx > Ny > Nz, and the value of the phase difference Rz in the Z direction is set in the range of 50nm to 300nm, and the in-plane phase difference R may be absent or present, and may have any value.
That is, on the observation side of the liquid crystal panel 70, the optical compensation plate 12 on the observation side as in embodiment 3 is disposed such that the in-plane retardation axis 12a thereof is oriented in a direction of 45 ° with respect to the horizontal direction (horizontal direction) when the liquid crystal display element is observed, the polarizing plate 8 closest to the observation side is disposed such that the transmission axis 8a thereof is parallel to the horizontal direction, and the 2 nd optical compensation plate 17 on the observation side is disposed such that the in-plane retardation axis 17a thereof is parallel to the transmission axis 8a of the polarizing plate 8 on the observation side between the 1 st optical compensation plate 12 on the observation side and the polarizing plate 8 on the observation side.
On the inner side opposite to the observation side of the liquid crystal panel 70, the retardation plate 16 similar to embodiment 3 is disposed such that the in-plane retardation axis 16a thereof is oriented in a direction of 135 ° with respect to the horizontal direction (horizontal direction) when the liquid crystal display element is observed, the innermost polarizing plate 9 is disposed such that the transmission axis 9a thereof is orthogonal to the horizontal direction, and the inner 2 nd optical compensation plate 18 is disposed such that the in-plane retardation axis 18a thereof is orthogonal to the transmission axis 9a of the inner polarizing plate 9 between the inner retardation plate 16 and the inner polarizing plate 9.
In this way, since the 2 nd optical compensation plates 17 and 18 are disposed so that the in-plane retardation axes 17a and 18a thereof are parallel to or orthogonal to the transmission axes 8a and 9a of the adjacent polarizing plates 8 and 9, respectively, and the arrangement of these optical axes does not cause an optical effect on linearly polarized light having a polarization plane parallel to the transmission axes 8a and 9a or the absorption axes of the respective polarizing plates 8 and 9, the 1 st optical compensation plate 12 and the 2 nd optical compensation plate 17 disposed on the observation side of the liquid crystal panel 70 function as one optical compensation plate that adds up the values of the phase difference Rz in the Z direction, respectively.
In the liquid crystal display element according to embodiment 4, as in embodiment 3, with respect to incident light from the inside substantially parallel to the normal direction of the liquid crystal display element, in a no-voltage state in which no voltage is applied to the pixel electrode 3 and the counter electrode 4, linearly polarized light transmitted through the inner polarizing plate 9 is transmitted through the inner 2 nd optical compensation plate 18 without being optically affected, enters the phase difference plate 16, is converted into circularly polarized light by the phase difference plate 16, is incident on the liquid crystal layer 7 of the liquid crystal panel 70, passes through the liquid crystal layer 7 as it is, is returned to the original linearly polarized light by the 1 st optical compensation plate 12 on the observation side, and is incident on the 2 nd optical compensation plate 17, the 2 nd optical compensation plate 17 transmits without being optically affected, and is absorbed by the polarizing plate 8 on the observation side disposed on the cross prism, thereby displaying black (dark).
In a state where a sufficiently high voltage is applied between the pixel electrode 3 and the counter electrode 4, linearly polarized light of the inner polarizing plate 9 is transmitted, the inner 2 nd optical compensation plate 18 is transmitted without optical action and enters the phase difference plate, is converted into circular polarization by the phase difference plate 16 and enters the liquid crystal layer 7 of the liquid crystal panel 70, is converted into circular polarization rotating in opposite direction by the liquid crystal layer 7 having the phase difference orientation of lambda/2, is converted into linear polarization having a polarization plane rotated by 90 DEG with respect to the polarization plane of the linear polarization transmitted through the inner polarizing plate 9 by the 1 st optical compensation plate 12 on the observation side and enters the 2 nd optical compensation plate 17, the 2 nd optical compensation plate 17 is not optically transmitted, and transmits through the polarizing plate 8 on the observation side arranged on the cross prism to display white (bright).
Further, since the phase difference between the 1 st and 2 nd optical compensation plates is increased by changing the inclination angle of light entering from an oblique direction with respect to the normal line of the liquid crystal display element, the change in the phase difference caused by the oblique incidence to the liquid crystal layer 7 can be compensated by the change in the phase difference between the 1 st and 2 nd optical compensation plates, and the range of the viewing angle is widened.
As described above, in embodiment 4, the 1 st optical compensation plate 12 and the 2 nd optical compensation plate 17 are disposed on one side of the liquid crystal panel 70, and the retardation plate 16 and the 2 nd optical compensation plate 18 are disposed on the other side, so that the value of the phase difference Rz in the Z direction can be made sufficiently large, and the viewing angle dependence of the contrast can be sufficiently compensated.
(embodiment 5)
The liquid crystal display element of the present invention can be applied to a transflective liquid crystal display element by further disposing a retardation plate between the pair of polarizing plates 8 and 9 in embodiment 1. Embodiment 5 applied to such a transflective liquid crystal display element will be described with reference to fig. 9 and 10.
As shown in fig. 9 and 10, the transflective liquid crystal display device of this embodiment includes: a transflective liquid crystal panel 71 having a reflective area and a transmissive area in each pixel; a pair of polarizing plates 8, 9 disposed on the outer sides of the pair of substrates 1, 2 of the liquid crystal panel 71 so as to sandwich the substrates; two 1 st optical compensation layers 12, 13 respectively disposed between the pair of polarizing plates 8, 9 on both sides of the liquid crystal panel 71; and another optical compensation layer (phase difference plates 19, 20) disposed between the 1 st optical compensation layer 12, 13 and the polarizing plates 8, 9, respectively. The liquid crystal display element of embodiment 5 has the same configuration as that of embodiment 1 except that the liquid crystal panel is a transflective liquid crystal panel 71, and that phase difference plates 18 and 19 are disposed between the 1 st optical compensation layers 12 and 13 and the polarizing plates 8 and 9, respectively, and therefore the same reference numerals are assigned to the same members, and the description thereof is omitted.
The liquid crystal panel 71 of the reflection transmission type includes: a pair of substrates 1, 2; a pixel electrode 3 and a counter electrode 4 formed on inner surfaces of the substrates facing each other; alignment films 5 and 6 formed on the surfaces of these electrodes; and a liquid crystal layer 7 sealed between the pair of substrates 1 and 2. An active element 3a for supplying a driving voltage is connected to the pixel electrode 3, and a pixel is formed by a region facing each of the counter electrodes 4, and a gap adjusting film 31 made of a transparent insulating film and a reflective film 32 formed thereon are formed in a part of each pixel.
The pixel electrode 3 is formed so as to cover the substrate surface of the substrate 2 and the reflective film 32 on the gap adjusting film 31, and in the pixel region facing the counter electrode 4, a transmissive display region is formed in a portion covering the transparent electrode on the substrate surface, and a reflective display region is formed in a portion covering the transparent electrode on the reflective film 32. That is, one pixel region is constituted by a reflective display region in which the reflective film faces the 1 st electrode and a transmissive region other than the reflective display region. In the reflective display region, the gap between the opposing substrates is formed to be narrow by the gap adjusting film 31, and is set to be approximately 1/2 of the substrate interval of the transmissive display region. In the liquid crystal layer 7, the product of the birefringence Δ n and the gap d in the transmissive display region is substantially λ/2, i.e., Δ nd has a value in the range of 250nm to 450nm, for example, 350nm, and the value of Δ nd in the reflective display region is substantially λ/4, i.e., Δ nd has a value in the range of 75nm to 275nm, for example, 175 nm.
On the outer sides of the pair of substrates 1, 2 of the liquid crystal panel 71, there are disposed optical compensation plates 12, 13 in which the refractive index Nx, Ny, and Nz values have the same relationship of Nx > Ny > Nz as in embodiment 1, the in-plane retardation R represented by (Nx-Ny) d is set in the range of 120nm to 160nm, and the retardation Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300nm, respectively, and further, there are disposed a pair of polarizing plates 8, 9 on the outer sides thereof.
In embodiment 5, another optical compensation plate (hereinafter, referred to as phase difference plates 19 and 20) composed of a phase difference plate in which the values of refractive indices Nx, Ny, and Nz have a relationship of Nx > Ny ≈ Nz and the value of in-plane retardation R expressed by (Nx-Ny) × d is set in the range of 240nm to 300nm is disposed between the two optical compensation plates 12 and 13 and the pair of polarizing plates 8 and 9, respectively.
The optical axes of the 1 st optical compensation plates 12 and 13 disposed on both sides of the liquid crystal panel 71, the retardation plates 19 and 20 disposed on the outer sides thereof, and the pair of polarizing plates 8 and 9 disposed so as to sandwich them are disposed as follows with reference to the horizontal direction when the liquid crystal display element is observed, as shown in fig. 10. The transmission axis 9a of the polarizing plate 9 located on the lower inner side on the drawing on the side opposite to the observation side is arranged to face 90 °, that is, to face the vertical direction, the retardation axis 20a of the retardation plate 20 located on the inner side closer to the observation side is arranged to face 105 °, the in-plane retardation axis 13a of the 1 st optical compensation plate 13 located on the inner side closer to the observation side is arranged to face 165 °, the in-plane retardation axis 12a of the 1 st optical compensation plate 12 located on the observation side with the liquid crystal panel 71 interposed therebetween is arranged to face 75 °, the retardation axis 19a of the retardation plate 19 located closer to the observation side is arranged to face 15 °, and the transmission axis 8a of the polarizing plate 8 closest to the observation side is arranged to face 0 °, that is, to face the horizontal direction.
That is, the transmission axes 8a and 9a of the pair of polarizing plates 8 and 9 are arranged orthogonal to each other, the retardation axes 19a and 20a of the two retardation plates 19 and 20 are arranged orthogonal to each other and intersect the transmission axes 8a and 9a of the adjacent polarizing plates 8 and 9 at 15 °, respectively, and the in-plane retardation axes 12a and 13a of the two 1 st optical compensation plates 12 and 13 are arranged orthogonal to each other and intersect the retardation axes 19a and 20a of the adjacent retardation plates 19 and 20 at 60 °. Further, the 1 st optical compensation plate 13 and the phase difference plate 20 disposed on the side opposite to the observation side of the liquid crystal panel 71 act as a broad band λ/4 plate substantially having a phase retardation axis oriented in the direction of 135 ° with respect to light transmitted in the normal direction of the liquid crystal panel 71, and the 1 st optical compensation plate 12 and the phase difference plate 19 disposed on the observation side of the liquid crystal panel 71 act as a broad band λ/4 plate having a phase retardation axis oriented in the direction of 45 ° with respect to light transmitted in the normal direction of the liquid crystal panel 71.
In the liquid crystal display element of embodiment 5, transmissive display is performed as follows with respect to light incident in the normal direction of the liquid crystal display element.
In a no-voltage state where no voltage is applied to the pixel electrode 3 and the counter electrode 4 facing each other, the linearly polarized light transmitted through the inner polarizing plate 9 is converted into circularly polarized light rotating in one direction by the inner phase difference plate 20 and the 1 st optical compensation plate 13, and is incident on the liquid crystal panel. Light incident from the inside of the liquid crystal panel 70 passes through the transmissive display region of each pixel of the liquid crystal panel 71, and at this time, since the liquid crystal molecules 7a of the liquid crystal layer 7 are vertically aligned and have no retardation, the light passes through the liquid crystal panel 71 in circularly polarized light as it is, and enters the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side. Since the optical axes 12a, 19a of the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side are arranged orthogonal to the optical axes 13a, 20a of the 1 st optical compensation plate 13 and the retardation plate 20 on the inner side, respectively, the circularly polarized light incident on the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side becomes linearly polarized light having a polarization plane parallel to the polarization plane of the linearly polarized light incident on the retardation plate 20 on the inner side and is incident on the polarizing plate 8 on the observation side, and the linearly polarized light is absorbed by the linearly polarized light having a polarization plane parallel to the absorption axis of the linearly polarized light incident on the polarizing plate 8 on the observation side, and black (dark) display is performed.
In a voltage applied state in which a sufficiently high voltage is applied to the pixel electrode 3 and the counter electrode 4 facing each other and the liquid crystal molecules 7a are aligned substantially parallel to the substrate surface, the linearly polarized light transmitted through the inner polarizer 9 is converted into circularly polarized light rotating in one direction by the inner retardation plate 20 and the 1 st optical compensation plate 13, and is incident on the liquid crystal panel 71. Light incident from the inside of the liquid crystal panel 71 passes through the transmissive display region of each pixel of the liquid crystal panel 71, and in this case, liquid crystal molecules 7a in the liquid crystal layer 7 in the transmissive display region are aligned parallel to the substrate surface and have a retardation (retardation) of λ/2, and therefore, the light becomes circularly polarized light rotating opposite to the incident circularly polarized light, and is emitted out of the liquid crystal panel 71, and enters the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side. Since the optical axes 12a, 19a of the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side are arranged orthogonal to the optical axes 13a, 20a of the 1 st optical compensation plate 13 and the retardation plate 20 on the inner side, respectively, circular polarization incident to the 1 st optical compensation plate 12 and the retardation plate 20 on the observation side becomes linearly polarized light having a polarization plane orthogonal to the polarization plane of linearly polarized light incident to the retardation plate 20 on the inner side and is incident to the polarizing plate 8 on the observation side, and linearly polarized light incident to the polarizing plate 8 on the observation side becomes linearly polarized light having a polarization plane parallel to the transmission axis thereof, and thus, white (bright) display is achieved.
In the liquid crystal display device of embodiment 5, light incident from the observation side is reflected by the liquid crystal panel 71 with respect to light incident in the normal direction of the liquid crystal display device, and reflection display is performed as follows for observation of the reflected light.
In the no-voltage state in which no voltage is applied to the pixel electrode 3 and the counter electrode 4 facing each other, the linearly polarized light transmitted through the polarizing plate 8 on the observation side is converted into circularly polarized light rotated in one direction by the phase difference plate 19 on the observation side and the 1 st optical compensation plate 12, and is incident on the liquid crystal panel 71. In this case, since the liquid crystal molecules 7a of the liquid crystal layer 7 are vertically oriented and have no phase difference, the circularly polarized light incident on the reflective display region of each pixel of the liquid crystal panel 71 from the observation side passes through the liquid crystal layer 7 as it is, is reflected by the reflective film 3 of each pixel, becomes circularly polarized light rotating in the opposite direction, returns to the liquid crystal layer 7, and enters the 1 st optical compensation plate 12 and the phase difference plate 19 on the observation side. Since the optical axes 12a, 19a of the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side are arranged orthogonal to the optical axes 13a, 20a of the 1 st optical compensation plate 13 and the retardation plate 20 on the inner side, respectively, the circularly polarized light incident on the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side becomes linearly polarized light having a polarization plane parallel to the absorption axis of the polarizing plate 8 on the observation side and is incident on the polarizing plate 8 on the observation side, and the linearly polarized light is absorbed and black (dark) display is performed.
In a voltage applied state in which a sufficiently high voltage is applied to the pixel electrode 3 and the counter electrode 4 facing each other and the liquid crystal molecules 7a are aligned substantially parallel to the substrate surface, the linearly polarized light transmitted through the polarizing plate 8 on the observation side is converted into circularly polarized light rotating in one direction by the retardation plate 19 on the observation side and the 1 st optical compensation plate 12, and is incident on the liquid crystal panel 71. At this time, since the liquid crystal molecules 7a of the liquid crystal layer 7 are aligned substantially horizontally with respect to the substrate surface and have a phase difference of λ/4, when circularly polarized light incident on the reflective display region of each pixel of the liquid crystal panel 71 from the observation side passes through the liquid crystal layer 7 and reaches the reflective film 32 of each pixel, the circularly polarized light becomes linearly polarized light having a polarization plane parallel to the polarization plane of the linearly polarized light having passed through the polarizing plate 8 on the observation side, is reflected by the reflective film 32 and returns to the liquid crystal layer 7, and in the process of this return, the phase difference of λ/4 is again given, and the circularly polarized light is rotated in the same direction as the circularly polarized light rotated in the one direction, is emitted from the liquid crystal layer 7 and is incident on the optical compensation plate 12 and the phase difference plate 19 on the observation side. The circularly polarized light incident on the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side becomes linearly polarized light having a polarization plane parallel to the transmission axis 8a of the polarizing plate 8 on the observation side, and transmits through the polarizing plate 8 on the observation side, thereby displaying white (bright).
Further, since the phase difference between the 1 st optical compensation plates 12 and 13 is increased by changing the inclination angle of the light incident from the oblique direction with respect to the normal line of the liquid crystal display element, the change in the phase difference caused by the oblique incidence to the liquid crystal layer 7 can be compensated by the change in the phase difference between the 1 st optical compensation plates 12 and 13, and the range of the viewing angle is expanded.
Fig. 11 shows a contrast distribution with respect to an angle (viewing angle) in an observation direction with respect to a substrate normal direction in the transflective liquid crystal display element according to embodiment 5. As shown in the drawing, in the case of the liquid crystal display element of the present embodiment in which the 1 st optical compensation layers 12 and 13 and the retardation plates 19 and 20 are provided, the region having a contrast of 10 or more is enlarged to approximately 135 ° in the vertical and horizontal directions as shown by the solid lines.
As described above, in embodiment 5, the 1 st optical compensation plates 12 and 13 having an in-plane retardation of substantially λ/4 and the retardation plates 19 and 20 having a retardation of λ/2 are disposed on both sides of the transflective liquid crystal panel 71, and the 1 st optical compensation plates 12 and 13 and the retardation plates 19 and 20 function as wide-band λ/4 retardation plates, thereby improving the transmittance and preventing the reflected light from being colored. Therefore, the viewing angle characteristics are improved by the phase difference Rz in the Z direction of the optical compensation plate.
(embodiment mode 6)
In embodiment 5, the liquid crystal display element in which one first optical compensation layer 12, 13 and one retardation plate 19, 20 are disposed on each of the viewing side and the opposite side of the liquid crystal panel is shown, but as shown in fig. 12 and 13, one second optical compensation plate 22, 23 may be additionally disposed on each of the outer sides of the 1 st optical compensation layer 12, 13 and the retardation plate 19, 20 disposed on each of the two sides of the liquid crystal panel 71. By disposing two additional 2 nd optical compensation plates 22 and 23 on both sides of the liquid crystal panel 71 in this manner, the value of the phase difference Rz in the Z direction can be made sufficiently large, and the viewing angle dependence of the contrast can be sufficiently compensated. The liquid crystal display device according to embodiment 6 is similar to that of embodiment 5 except that the liquid crystal display devices of fig. 9 and 10 are provided with the additional second 2 nd optical compensation layers 22 and 23 on both sides of the liquid crystal panel 71, and therefore the same members are given the same reference numerals and the description thereof is omitted.
As shown in fig. 12 and 13, the liquid crystal display device of this embodiment includes: a liquid crystal panel 71; a 1 st optical compensation layer 12 disposed on the viewing side of the liquid crystal panel 71; a phase difference plate 19 disposed on the observation side; and a 2 nd optical compensation plate 22 disposed between the polarizing plate 8 and the outside thereof, further comprising: a 1 st optical compensation plate 13 disposed on an inner side opposite to the observation side of the liquid crystal panel 71; a phase difference plate 20 disposed inside thereof; and a 2 nd optical compensation layer 23 disposed between the polarizing plate 9 inside thereof.
The 2 nd optical compensation layers 22 and 23 are optical compensation plates (hereinafter, referred to as 2 nd optical compensation plates 22 and 23) in which the values of refractive indices Nx, Ny, and Nz have a relationship of Nx > Ny > Nz, the value of in-plane retardation R represented by (Nx-Ny) d is set in the range of 120nm to 160nm, and the value of in-plane retardation Rz in the Z direction is set in the range of 50nm to 300nm, and the in-plane retardation R may be absent or present, and may have any value.
That is, as shown in fig. 13, on the observation side of the liquid crystal panel 71, the 1 st optical compensation plate 12 on the observation side as in embodiment 5 is disposed such that the in-plane retardation axis 12a thereof is oriented in a direction of 75 ° with respect to the horizontal direction (horizontal direction) when the liquid crystal display element is observed, on the observation side, the retardation plate 19 is disposed such that the retardation axis 19a thereof is oriented in a direction of 15 ° with respect to the horizontal direction, the polarizing plate 8 closest to the observation side is disposed such that the transmission axis 8a thereof is parallel to the horizontal direction, and between the retardation plate 19 closer to the observation side and the polarizing plate 8 on the observation side, the 2 nd optical compensation plate 22 is disposed such that the in-plane retardation axis 22a thereof is parallel to the transmission axis 8a of the polarizing plate 8 on the observation side. That is, the two sheets of the 1 st optical compensation plates are arranged so that the respective in-plane phase retardation axes are orthogonal to each other, and are arranged toward a direction intersecting with the transmission axis of the adjacent polarizing plate in a range of 5 ° to 25 ° or 65 ° to 85 °.
On the side opposite to the viewing side of the liquid crystal panel 71, the inner 1 st optical compensation plate 13 similar to embodiment 5 is disposed such that the in-plane optical axis 13a thereof is oriented in a direction 165 ° with respect to the horizontal direction, on the inner side thereof, the phase difference plate 20 is disposed such that the in-plane retardation axis 20a thereof is oriented in a direction 105 ° with respect to the horizontal direction of the liquid crystal display element, the transmission axis 9a thereof is orthogonal to the horizontal direction with respect to the innermost polarizing plate 9, and further, between the inner phase difference plate 20 and the inner polarizing plate 9, the inner 2 nd optical compensation plate 23 is disposed such that the in-plane retardation axis 23a thereof is orthogonal to the transmission axis 9a of the inner polarizing plate 9.
In this way, the 2 nd optical compensation plates 22 and 23 are disposed so that the in-plane retardation axes 22a and 23a thereof are parallel to or orthogonal to the transmission axes 8a and 9a of the adjacent polarizing plates 8 and 9, respectively, and the arrangement of these optical axes does not cause an optical effect on linear polarization having a polarization plane parallel to the transmission axes 8a and 9a or the absorption axes of the respective polarizing plates 8 and 9, and therefore, the 1 st optical compensation plates 12 and 13 and the 2 nd optical compensation plates 22 and 23 disposed on both sides of the liquid crystal panel 71 function as one optical compensation plate that adds up the value of the phase difference Rz in the Z direction, respectively.
Therefore, in the liquid crystal display device of embodiment 6, similarly to embodiment 5, in the transmissive display, in the no-voltage-applied state in which no voltage is applied to the pixel electrode 3 and the counter electrode 4, the linearly polarized light transmitted through the inner polarizing plate 9 is transmitted through the inner 2 nd optical compensation plate 23 without being optically acted and is incident on the phase difference plate 20 and the 1 st optical compensation plate 13, the circularly polarized light is converted into circularly polarized light by the phase difference plate 20 and the 1 st optical compensation plate 13 and is incident on the liquid crystal layer 7 of the liquid crystal panel 71, the circularly polarized light is transmitted through the liquid crystal layer 7 as it is, then returned to the original linearly polarized light by the 1 st optical compensation plate 12 and the phase difference plate 19 on the observation side again, and the circularly polarized light is transmitted without being optically acted through the 2 nd optical compensation plate 22, then absorbed by the polarizing plate 8 on the observation side arranged on the cross prism, and is displayed as black (dark.
In a state where a sufficiently high voltage is applied between the pixel electrode 3 and the counter electrode 4, linearly polarized light of the inner polarizing plate 9 is transmitted, the inner 2 nd optical compensation plate 23 is transmitted without being optically affected and then enters the phase difference plate 20 and the 1 st optical compensation plate 13, is converted into circular polarization by the inner phase difference plate 20 and the 1 st optical compensation plate 13 and enters the liquid crystal layer 7 of the liquid crystal panel 71, is converted into circular polarization rotated in the opposite direction by the liquid crystal layer 7 having a phase difference orientation of λ/2, is converted into linear polarization having a polarization plane rotated by 90 ° with respect to the polarization plane of the linear polarization transmitted through the inner polarizing plate 9 by the 1 st optical compensation plate 12 and the phase difference plate 20 on the observation side and enters the 2 nd optical compensation plate 22, the 2 nd optical compensation plate 22 is not optically transmitted, and then, transmits through the polarizing plate 8 on the observation side arranged on the cross prism, thereby displaying white (bright).
In the reflective display, in the no-voltage state in which no voltage is applied to the pixel electrode 3 and the counter electrode 4 facing each other, the linearly polarized light transmitted through the polarizing plate 8 on the observation side enters the phase difference plate 19 on the observation side without being subjected to the optical action of the 2 nd optical compensation plate 22 on the observation side, and is converted into circularly polarized light rotating in one direction by the phase difference plate 19 and the 1 st optical compensation plate 12 and enters the liquid crystal panel 7. The circularly polarized light incident on the reflective display region of each pixel of the liquid crystal panel 7 from the observation side of the liquid crystal panel 7 transmits the liquid crystal layer 7 as it is, is reflected by the reflective film 32 of each pixel to become circularly polarized light rotating in the reverse direction, returns to the liquid crystal layer 7, enters the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side, enters the circularly polarized light incident on the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side, becomes linearly polarized light having a polarization plane parallel to the absorption axis on the observation side, enters the 2 nd optical compensation plate 22 on the observation side and the polarizing plate 18 on the observation side, and is absorbed to become black (dark) display.
In the applied voltage state in which a sufficiently high voltage is applied to the pixel electrode 3 and the counter electrode 4 facing each other, the linearly polarized light transmitted through the polarizing plate 8 on the observation side enters the phase difference plate 19 on the observation side without being subjected to the optical action of the 2 nd optical compensation plate 122 on the observation side, and the circularly polarized light rotated in one direction by the phase difference plate 19 on the observation side and the 1 st optical compensation plate 12 enters the liquid crystal panel 7. The circularly polarized light entering the reflective display region of each pixel of the liquid crystal panel 7 from the observation side of the liquid crystal panel 7 becomes linearly polarized light having a polarization plane parallel to the polarization plane of the linearly polarized light transmitted through the polarizing plate 8 on the observation side, is reflected by the reflective film 2 and returns to the liquid crystal layer 7, becomes circularly polarized light rotating in the same direction as the circularly polarized light rotating in the one direction, exits the liquid crystal layer 7 and enters the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side, the circularly polarized light entering the 1 st optical compensation plate 12 and the retardation plate 19 on the observation side becomes linearly polarized light having a transmission plane parallel to the transmission axis on the observation side, enters the 2 nd optical compensation plate 22 on the observation side, passes through the polarizing plate 8 on the observation side without being subjected to the optical action of the 2 nd optical compensation plate 22 on the observation side, and becomes white (bright) display.
Further, since the phase difference between the 1 st optical compensation plates 12, 13 and the 2 nd optical compensation plates 22, 23 is increased by changing the inclination angle of light entering obliquely with respect to the normal line of the liquid crystal display element, the change in the phase difference caused by oblique incidence to the liquid crystal layer 7 can be compensated by the change in the phase difference between the 1 st and 2 nd optical compensation plates 12, 13, 22, 23, and the range of the viewing angle is expanded.
As described above, in embodiment 6, the 1 st optical compensation plates 12 and 13 and the 2 nd optical compensation plates 22 and 23 are disposed on both sides of the liquid crystal panel 7, so that the value of the phase difference Rz in the Z direction can be made sufficiently large, and the viewing angle dependence of the contrast can be sufficiently compensated for.
The present invention is not limited to the examples shown in the above embodiments, and various modifications and applications are possible. For example, as the 1 st and 2 nd optical compensation layers, optical compensation plates are used which are constituted by biaxial retardation plates having a relationship of Nx > Ny > Nz, in which the value of the in-plane retardation R represented by (Nx-Ny) d is set in the range of 120nm to 160nm, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300nm, but the present invention is not limited thereto, and one optical compensation plate may be constituted by combining a uniaxial retardation plate having a phase difference value in the range of 120nm to 160nm and a retardation plate having a value of the phase difference Rz in the Z direction in the range of 50nm to 300 nm. That is, as shown in fig. 14, the 1/4-wavelength plate 12a and the retardation plate 12b arranged such that the refractive index in the normal direction of the principal surface of the substrate is smaller than the refractive index in the direction parallel to the principal surface of the substrate may be stacked to form one optical compensation plate having the above characteristics.
In the above-described embodiment, the protrusions are formed in the alignment film on the opposite electrode side in order to radially align the liquid crystal toward the center of the pixel, but a method of forming such radial alignment itself is arbitrary. For example, a method of forming a recess on the lower pixel electrode substrate side, or a method of forming a slit in the pixel electrode and dividing one pixel into a plurality of alignment regions may be used.

Claims (20)

1. A liquid crystal display element, comprising:
a substrate provided with a 1 st electrode;
another substrate arranged to face the first substrate, and having a 2 nd electrode provided on a surface facing the first substrate, the 2 nd electrode forming a pixel region through a region facing the 1 st electrode;
a vertical alignment film formed on the surfaces of the 1 st electrode and the 2 nd electrode facing each other;
a liquid crystal layer sealed between the substrates and having negative dielectric anisotropy;
a pair of polarizing plates disposed on outer surfaces of the one and the other substrates opposite to the surfaces thereof facing each other, respectively; and
two optical compensation layers respectively disposed between the pair of substrates and the pair of polarizing plates and giving a phase difference of a value substantially 1/4 of a wavelength lambda to a visible light transmitted therethrough,
one of the two optical compensation layers is constituted by a 1 st optical compensation plate, and when a refractive index of the 1 st optical compensation plate in a 1 st axis direction parallel to the main surfaces of the pair of substrates is Nx, a refractive index of the 2 nd axis direction parallel to the main surfaces of the substrates and perpendicular to the 1 st axis direction is Ny, and a refractive index of the 3 rd axis direction perpendicular to the main surfaces of the substrates is Nz, values of Nx, Ny, and Nz have a relationship of Nx > Ny > Nz, and an in-plane phase difference in a plane parallel to the main surfaces of the substrates has a value of 1/4 of a visible light wavelength λ.
2. The liquid crystal display element according to claim 1,
the other of the two optical compensation layers is also constituted by the 1 st optical compensation plate.
3. The liquid crystal display element according to claim 1 or 2,
the optical compensation layer is composed of a 1 st optical compensation plate, wherein when the thickness of the optical compensation layer is d, the values of Nx, Ny and Nz have a relationship of Nx > Ny > Nz, the value of the in-plane phase difference R represented by (Nx-Ny) d is set in the range of 120nm to 160nm, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300 nm.
4. The liquid crystal display element according to claim 2,
the two pieces of the 1 st optical compensation plates provided on both outer surfaces of the pair of substrates are arranged so that an in-plane phase retardation axis in a direction in which a refractive index is maximum or an in-plane phase advancing axis in a direction in which the refractive index is minimum in a plane parallel to the principal surfaces of the substrates are orthogonal to each other,
a pair of polarizing plates are arranged so that transmission axes thereof are orthogonal to each other, and the transmission axis of any one polarizing plate crosses the in-plane phase retardation axis or the in-plane phase advance axis of the adjacent optical compensation plate at an angle of 35 DEG to 55 deg.
5. The liquid crystal display element according to claim 2,
phase difference plates are also respectively arranged between the two pieces of the 1 st optical compensation plates arranged on the two outer sides of the pair of substrates and the polarizing plates arranged on the outer sides of the two pieces of substrates, the values of Nx, Ny and Nz of the phase difference plates have a relationship of Nx > Ny ≈ Nz, and the phase difference R in a plane parallel to the main surface of the substrate has a value in the range of 240nm to 300 nm.
6. The liquid crystal display element according to claim 5,
the transmission axes of a pair of polarizing plates are orthogonal to each other,
two pieces of the 1 st optical compensation plates arranged on both outer surfaces of the pair of substrates are respectively arranged so that the in-plane phase delay axes in the direction in which the refractive index is maximum or the in-plane phase advance axes in the direction in which the refractive index is minimum in the plane parallel to the main surfaces of the substrates are orthogonal to each other, and the 1 st optical compensation plates are arranged in the direction intersecting the transmission axes of the adjacent polarizing plates in the range of 5 DEG to 25 DEG or 65 DEG to 85 DEG,
the two phase difference plates provided outside the two 1 st optical compensation plates are arranged such that the respective phase retardation axes in the direction of the maximum refractive index or the respective phase advancing axes in the direction of the minimum refractive index are orthogonal to each other in a plane parallel to the principal surface of the substrate, and the phase difference plates are arranged in directions intersecting the transmission axes of the adjacent polarizing plates at 15 degrees.
7. The liquid crystal display element according to claim 6,
a reflective film corresponding to a part of either one of the 1 st electrode and the 2 nd electrode is formed, and a transmissive display region for controlling light transmitted through a pair of substrates facing each other and a reflective display region for controlling light reflected by the reflective film are formed in one pixel region formed by a region facing each of the electrodes.
8. The liquid crystal display element according to claim 5,
between a pair of polarizing plates, another 2 nd optical compensation plate is disposed, and the values of Nx, Ny and Nz of the 2 nd optical compensation plate have a relationship of Nx > Ny > Nz, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300 nm.
9. The liquid crystal display element according to claim 8,
the transmission axes of a pair of polarizing plates are orthogonal to each other,
the 2 nd optical compensation plates are respectively arranged between the two phase difference plates and the polarizing plates arranged outside the two phase difference plates, and are arranged so that the in-plane phase retardation axes or the in-plane phase advance axes of the 2 nd optical compensation plates are parallel or orthogonal to each other and are parallel or orthogonal to the transmission axes of the adjacent polarizing plates,
two pieces of the 1 st optical compensation plates disposed on both outer surfaces of the pair of substrates are disposed so that respective in-plane phase retardation axes in a direction in which a refractive index is maximum or respective in-plane phase advancing axes in a direction in which a refractive index is minimum in a plane parallel to the main surfaces of the substrates are orthogonal to each other, and the 1 st optical compensation plate is disposed in a direction intersecting with a transmission axis of an adjacent polarizing plate in a range of 5 ° to 25 ° or 65 ° to 85 °,
the two phase difference plates provided outside the two 1 st optical compensation plates are arranged so that the in-plane phase delay axes in the direction of the maximum refractive index or the in-plane phase advance axes in the direction of the minimum refractive index are orthogonal to each other in a plane parallel to the main surface of the substrate, and the phase difference plates are arranged in directions intersecting the transmission axes of the adjacent polarizing plates at 15 °.
10. The liquid crystal display element according to claim 2,
between a pair of polarizing plates, a 2 nd optical compensation plate is disposed which is different from the 1 st optical compensation plate, and the values of Nx, Ny and Nz of the 2 nd optical compensation plate have a relationship of Nx > Ny > Nz, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300 nm.
11. The liquid crystal display element according to claim 10,
the transmission axes of a pair of polarizing plates are orthogonal to each other,
two pieces of the 1 st optical compensation plates disposed on both outer surfaces of the pair of substrates are disposed so that the in-plane phase retardation axes in the direction of the maximum refractive index or the in-plane phase advancing axes in the direction of the minimum refractive index in a plane parallel to the main surfaces of the substrates are orthogonal to each other, and the 1 st optical compensation plate is disposed so as to intersect with the transmission axes of the adjacent polarizing plates in a range of 35 ° to 55 °,
the two 2 nd optical compensation plates provided outside the two 1 st optical compensation plates are arranged so that the in-plane phase retardation axes in the direction of the maximum refractive index or the in-plane phase advance axes in the direction of the minimum refractive index in a plane parallel to the principal surface of the substrate are parallel to or orthogonal to each other and the transmission axes of the adjacent polarizing plates are parallel to or orthogonal to each other.
12. The liquid crystal display element according to claim 1,
one of the two optical compensation layers is a 1 st optical compensation plate whose Nx, Ny, and Nz values have a relationship of Nx > Ny > Nz and whose phase difference in a plane parallel to the principal surface of the substrate has a value of 1/4 of the visible light wavelength λ, and the other is a phase difference plate whose Nx, Ny, and Nz values have a relationship of Nx > Ny ≈ Nz and whose in-plane phase difference R in a plane parallel to the principal surface of the substrate has a value in a range of 120nm to 160 nm.
13. The liquid crystal display element according to claim 12,
the 1 st optical compensation plate and the retardation plate are arranged so that in-plane phase retardation axes in a direction in which the refractive index is the largest or in-plane phase advance axes in a direction in which the refractive index is the smallest in a plane parallel to the main surface of the substrate are orthogonal to each other,
the pair of polarizing plates are arranged so that transmission axes thereof are orthogonal to each other, and are arranged in a direction in which the transmission axis of each polarizing plate crosses an in-plane phase retardation axis or an in-plane phase advance axis of the 1 st optical compensation plate and the phase difference plate adjacent thereto at 35 ° to 55 °.
14. The liquid crystal display element according to claim 12,
another 2 nd optical compensation plate different from the 1 st optical compensation plate is disposed between the pair of polarizing plates, and the values of Nx, Ny and Nz of the other 2 nd optical compensation plate have a relationship of Nx > Ny > Nz, and the value of the phase difference Rz in the Z direction represented by { (Nx + Ny)/2-Nz } is set in the range of 50nm to 300 nm.
15. The liquid crystal display element according to claim 14,
the 2 nd optical compensation plate is respectively arranged between the 1 st optical compensation plate and one polarizing plate and between the phase difference plate and the other polarizing plate and is parallel to or orthogonal to the transmission axis of the adjacent polarizing plate,
the 1 st optical compensation plate and the retardation plate are arranged so that in-plane phase retardation axes in a direction in which the refractive index is the largest or in-plane phase advance axes in a direction in which the refractive index is the smallest in a plane parallel to the main surface of the substrate are orthogonal to each other,
the pair of polarizing plates are arranged so that transmission axes thereof are orthogonal to each other, and are arranged in a direction in which the transmission axis of each polarizing plate crosses an in-plane phase retardation axis or an in-plane phase advance axis of the 1 st optical compensation plate and the phase difference plate adjacent thereto at 35 ° to 55 °.
16. The liquid crystal display element according to any one of claims 1 to 15,
the liquid crystal display device further includes a member for aligning liquid crystals constituting the liquid crystal layer so that the director is directed in a plurality of directions by applying the electric field.
17. A liquid crystal display element, comprising:
a substrate provided with a transparent 1 st electrode;
another substrate which is arranged to face the first substrate and has a transparent 2 nd electrode formed on a surface thereof facing the first substrate, the transparent 2 nd electrode forming a pixel region for transmission type display through a region facing the 1 st electrode;
a vertical alignment film formed on the surfaces of the 1 st electrode and the 2 nd electrode facing each other;
a liquid crystal layer sealed between the substrates and having negative dielectric anisotropy;
a pair of polarizing plates disposed on outer surfaces of the one and the other substrates opposite to the surfaces thereof facing each other, respectively;
two pieces of 1 st optical compensation plates which are respectively arranged between the pair of substrates and the pair of polarizing plates, and which have a relationship that when a refractive index in a 1 st axis direction parallel to main surfaces of the pair of substrates is Nx, a refractive index in a 2 nd axis direction parallel to the main surfaces of the substrates and perpendicular to the 1 st axis direction is Ny, and a refractive index in a 3 rd axis direction perpendicular to the main surfaces of the substrates is Nz, values of Nx, Ny, and Nz have a relationship of Nx > Ny > Nz, and which give a phase difference of a value of 1/4 at a wavelength λ to transmitted light; and
two 2 nd optical compensation plates disposed between the two 1 st optical compensation plates and the polarizing plates disposed outside the two optical compensation plates, respectively, wherein the values of Nx, Ny and Nz have a relationship of Nx > Ny > Nz, and the direction of an in-plane phase retardation axis having a maximum refractive index in a plane parallel to the main surface of the substrate is orthogonal or parallel to the transmission axis of the adjacent polarizing plate.
18. The liquid crystal display element according to claim 17,
the transmission axes of the pair of polarizing plates are orthogonal to each other,
the two 1 st optical compensation plates are arranged so that the in-plane retardation in a plane parallel to the main surface of the substrate has a value of 1/4 which is the wavelength λ of visible light, and the direction of the in-plane retardation axis having the largest refractive index in a plane parallel to the main surface of the substrate is at an angle of substantially 45 ° to the transmission axis of the adjacent polarizing plate.
19. A liquid crystal display element, comprising:
a substrate provided with a transparent 1 st electrode;
a second substrate provided with a reflective film facing a part of the first electrode 1 on a surface facing the first substrate, and a second electrode 2 disposed in a region including the reflective film and forming a pixel region including a reflective display region corresponding to the reflective film and a transmissive region other than the reflective display region by a region facing the first electrode;
a vertical alignment film formed on the surfaces of the 1 st electrode and the 2 nd electrode facing each other;
a liquid crystal layer sealed between the substrates, having negative dielectric anisotropy, giving a phase difference of substantially 1/2 of a wavelength of light transmitted through a transmissive display region of the pixel region, and having a layer thickness of substantially 1/2 of a layer thickness corresponding to a reflective region of the pixel region;
a pair of polarizing plates disposed on outer surfaces of the one and the other substrates opposite to the surfaces thereof facing each other, respectively;
two pieces of 1 st optical compensation plates, respectively arranged between the pair of substrates and the pair of polarizing plates, wherein when a refractive index in a 1 st axis direction parallel to main surfaces of the pair of substrates is Nx, a refractive index in a 2 nd axis direction parallel to the main surfaces of the substrates and perpendicular to the 1 st axis direction is Ny, and a refractive index in a 3 rd axis direction perpendicular to the main surfaces of the substrates is Nz, values of Nx, Ny, and Nz have a relationship of Nx > Ny > Nz; and
two phase difference plates respectively arranged between the two 1 st optical compensation plates and the polarizing plates respectively arranged outside, the in-plane phase retardation axes of the 1 st optical compensation plate and the phase difference plate adjacent to each other, which have the maximum in-plane refractive index in a plane parallel to the main surface of the substrate, are substantially oriented to 45 DEG to each other, the values of Nx, Ny and Nz have a relationship of Nx > Ny ≈ Nz, and the value of the in-plane phase difference synthesized by the optical compensation plates and the phase difference plates adjacent to each other has a value of 1/4 in-plane phase difference which is substantially the wavelength of transmitted light.
20. The liquid crystal display element according to claim 19,
the transmission axes of a pair of polarizing plates are orthogonal to each other,
two pieces of the 1 st optical compensation plates disposed on both outer surfaces of the pair of substrates are disposed so that in-plane phase retardation axes in a direction in which a refractive index is maximum in a plane parallel to the main surfaces of the substrates are orthogonal to each other, and the 1 st optical compensation plates are disposed in a direction intersecting with a transmission axis of an adjacent polarizing plate in a range of 5 ° to 25 ° or 65 ° to 85 °,
the two retardation plates provided on the outer sides of the two 1 st optical compensation plates are arranged so that in-plane retardation axes in a direction in which the in-plane refractive index is maximum in a plane parallel to the principal surface of the substrate are orthogonal to each other.
HK07103106.8A 2005-03-30 2007-03-22 Liquid crystal display device of vertical alignment HK1096160B (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP100063/2005 2005-03-30
JP2005100063 2005-03-30
JP2005176971A JP2006309105A (en) 2005-03-30 2005-06-16 Liquid crystal display element
JP176971/2005 2005-06-16

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Publication Number Publication Date
HK1096160A1 HK1096160A1 (en) 2007-05-25
HK1096160B true HK1096160B (en) 2009-08-28

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