WO2012133141A1

WO2012133141A1 - Liquid crystal display device

Info

Publication number: WO2012133141A1
Application number: PCT/JP2012/057439
Authority: WO
Inventors: 彰坂井
Original assignee: シャープ株式会社
Priority date: 2011-03-31
Filing date: 2012-03-23
Publication date: 2012-10-04
Also published as: TW201243449A

Abstract

The present invention provides a liquid crystal display device with a circularly polarized VA mode, which can reduce costs and has excellent productivity, as well as an excellent gradation viewing angle from an intermediate gradation to a high gradation at a 45° heading. According to the present invention, the liquid crystal display device is provided, in the following order, with: a first polarizer; a first λ/4 plate, a liquid crystal cell; a second λ/4 plate having an Nz coefficient different from that of the first λ/4 plate, and a second polarizer. If the heading of the absorption axis of the second polarizer is defined as 0°, then with respect to the absorption axis of the second polarizer, the in-plane slow axis of the second λ/4 plate forms a substantially 45° angle, the in-plane slow axis of the first λ/4 plate forms a substantially 135° angle, and the absorption axis of the first polarizer forms a substantially 90° angle. The display brightness is changed by changing the liquid crystal molecules in a liquid crystal layer from a substantially vertical alignment to a tilted alignment with respect to a substrate surface. The liquid crystal layer has four domains in which the liquid crystal molecules have a tilted alignment at a heading of 12.5° to 32.5°, 102.5° to 122.5°, 192.5° to 212.5°, and 282.5° to 302.5°, respectively.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a VA (vertical alignment) mode liquid crystal display device using a circularly polarizing plate.

Liquid crystal display devices are widely used as display devices for various information processing devices such as computers and televisions. In particular, TFT-type liquid crystal display devices (hereinafter also referred to as “TFT-LCDs”) are widely spread, and further expansion of the market is expected. Along with this, further improvement in image quality is demanded. Hereinafter, the TFT-LCD will be described as an example. However, the present invention is not limited to the TFT-LCD and can be applied to all liquid crystal display devices. For example, a liquid crystal display device of a simple matrix method, a plasma address method, or the like. It is also applicable to.

To date, the most widely used method for TFT-LCD is a so-called TN (twisted nematic) mode in which liquid crystals having positive dielectric anisotropy are horizontally aligned between mutually opposing substrates. It was. The TN mode liquid crystal display device is characterized in that the alignment direction of liquid crystal molecules adjacent to one substrate is twisted by 90 ° with respect to the alignment direction of liquid crystal molecules adjacent to the other substrate. In such a TN mode liquid crystal display device, an inexpensive manufacturing technique has been established and industrially matured, but it has been difficult to achieve a high contrast ratio.

On the other hand, a so-called VA mode liquid crystal display device is known in which liquid crystals having negative dielectric anisotropy are vertically aligned between mutually opposing substrates. In the VA mode liquid crystal display device, when no voltage is applied, the liquid crystal molecules are aligned in a direction substantially perpendicular to the substrate surface, so that the liquid crystal cell hardly exhibits birefringence and optical rotation, and light is not It passes through the liquid crystal cell with almost no change in the polarization state. Therefore, by arranging a pair of polarizers (linear polarizers) on the top and bottom of the liquid crystal cell so that their absorption axes are orthogonal to each other (hereinafter also referred to as “crossed Nicols polarizer”), substantially no voltage is applied when no voltage is applied. Can achieve a black display. When a voltage equal to or higher than the threshold voltage is applied (hereinafter simply referred to as voltage application), the liquid crystal molecules are tilted to be substantially parallel to the substrate, exhibiting high birefringence and realizing white display. Therefore, such a VA mode liquid crystal display device can easily achieve a very high contrast ratio.

In such a VA mode liquid crystal display device, if the tilt direction of the liquid crystal molecules when a voltage is applied is one direction, asymmetry occurs in the viewing angle characteristics of the liquid crystal display device. Therefore, the alignment division type VA mode in which the tilt direction of the liquid crystal molecules is divided into a plurality of pixels in the pixel is widely used. Note that regions having different liquid crystal molecule tilt directions are also referred to as domains, and the alignment-divided VA mode is also referred to as an MVA mode (multi-domain VA mode).

In the MVA mode, from the viewpoint of maximizing the transmittance in the white display state, the axis direction of the polarizer and the tilt direction of the liquid crystal molecules when a voltage is applied are usually set to form an angle of 45 °. The transmittance when the birefringent medium is sandwiched between crossed Nicol polarizers is sin2 (2α), where α (unit: rad) is the angle between the polarizer axis and the slow axis of the birefringent medium. This is because it is proportional. In a typical MVA mode, the tilt direction of liquid crystal molecules can be divided into four domains of 45 °, 135 °, 225 °, and 315 °. Even in such an MVA mode divided into four domains, Schliere orientation and orientation in an unintended direction are often observed in the vicinity of the boundary between domains and the orientation control means, resulting in loss of transmittance. Cause.

In order to solve such a problem, a VA mode liquid crystal display device using a circularly polarizing plate has been studied (for example, see Patent Document 1). According to such a liquid crystal display device, the transmittance when the birefringent medium is sandwiched between the right and left circularly polarizing plates orthogonal to each other does not depend on the angle formed by the axis of the polarizer and the slow axis of the birefringent medium. Therefore, even if the tilt direction of the liquid crystal molecules is other than 45 °, 135 °, 225 °, and 315 °, the desired transmittance can be secured if the tilt of the liquid crystal molecules can be controlled. Therefore, for example, a circular protrusion may be arranged at the center of the pixel and the liquid crystal molecules may be tilted in all directions, or tilted in a random direction without controlling the tilt direction at all. May be. Note that in this specification, a VA mode using a circularly polarizing plate is also referred to as a circularly polarized VA mode or a circularly polarized mode. In contrast, a VA mode using a linear polarizing plate is also referred to as a linearly polarized VA mode or a linearly polarized mode. As is well known, the circularly polarizing plate is typically composed of a combination of a linearly polarizing plate and a λ / 4 plate.

Furthermore, since circularly polarized light has the property that the right and left palms are interchanged when reflected by a mirror or the like, for example, when a left circularly polarizing plate is placed on the mirror and light is incident, it passes through the circularly polarizing plate and passes through the left circle. The light converted into polarized light is reflected by a mirror to be converted into right circularly polarized light, and the right circularly polarized light cannot pass through the left circularly polarizing plate, so that the circularly polarizing plate eventually has an antireflection optical function. It is known that there is. Such an optical function of preventing reflection of the circularly polarizing plate can prevent unnecessary reflection when the display device is observed in a bright environment such as outdoors. Therefore, display devices such as a VA mode liquid crystal display device can be used. It is known to have an effect of improving the contrast ratio in a bright environment. Here, it is considered that the unnecessary reflection is mainly caused by a transparent electrode existing inside the display device, a metal wiring of the TFT element, or the like. If this unnecessary reflection is not prevented, even if the display device achieves substantially complete black display in a dark room environment, the amount of light during black display on the display device increases when observed in a bright environment. As a result, the contrast ratio is lowered.

As described above, the circularly polarized light VA mode using a circularly polarizing plate can obtain a transmittance improvement effect and an unnecessary antireflection effect, but a conventional circularly polarized light VA mode liquid crystal display device has a contrast ratio at an oblique viewing angle. There is room for improvement in that it is low and sufficient viewing angle characteristics cannot be obtained. For this, various techniques for improving viewing angle characteristics using a birefringent layer (retardation film) have been proposed. For example, Patent Document 1 discloses the following method (A), Patent Document 2 includes the following method (B), Patent Document 3 includes the following method (C), and Patent Document 4 includes the following method (D). Non-Patent Document 1 discloses the following method (E).

(A) A method of using two λ / 4 plates satisfying the relationship of nx>ny> nz.
(B) A method of using two λ / 4 plates satisfying the relationship of nx>ny> nz and one or two second-type birefringent layers satisfying the relationship of nx <ny ≦ nz.
(C) A method in which two λ / 4 plates satisfying the relationship of nx>nz> ny and a birefringent layer satisfying the relationship of nx = ny> nz are used in combination.
(D) A method of using one or two λ / 2 plates satisfying the relationship of nx>nz> ny in the method of (C).
(E) Two uniaxial λ / 4 plates (so-called A plates satisfying the relationship of nx> ny = nz), a birefringent layer satisfying the relationship of nx = ny> nz, and the relationship of nx>nz> ny A method in which birefringent layers satisfying the above are used in combination.

However, the methods (A), (B), and (C) still have room for improvement in viewing angle characteristics. In the methods (C), (D), and (E), a biaxial retardation film satisfying the relationship of nx> nz> ny (satisfying the relationship of 0 <Nz <1) that is difficult and expensive to manufacture. There was room for improvement in that it was necessary.

Therefore, the present inventor has made various studies in order to solve the above-described problems, and proposed the following method (F) (see Patent Document 5).

(F) two λ / 4 plates, a third birefringent layer satisfying a relationship of nx = ny> nz, a first birefringent layer satisfying a relationship of nx> ny ≧ nz, and nx < A method in which a second birefringent layer satisfying the relationship of ny ≦ nz is used in combination.

However, in the method (F), the viewing angle characteristics can be improved by optimally designing the Nz coefficient (a parameter representing biaxiality) of the two λ / 4 plates, but nx> ny ≧ nz ( (Nz ≧ 1.0) Under the design conditions using two general-purpose biaxial λ / 4 plates, there is room for improvement in viewing angle characteristics.

Therefore, as a result of further examination by the inventor, the two λ / 4 plates (first and second λ / 4 plates) were changed to biaxial λ / 4 plates satisfying the relationship of nx> ny ≧ nz. The Nz coefficient is adjusted to be substantially the same, and at least one of the first λ / 4 plate and the first polarizer and the second λ / 4 plate and the second polarizer In addition, it has been found that by arranging a birefringent layer satisfying the relationship of nx <ny ≦ nz, it is possible to easily manufacture a circularly polarized VA mode liquid crystal display device capable of obtaining a high contrast ratio in a wide viewing angle range. Have previously filed patent applications (see Patent Documents 6 and 7).

As described above, the present inventor has made various studies on improving the viewing angle characteristics in the circularly polarized VA mode. However, each of the above-described measures has been described in order to suppress the viewing angle dependence of the contrast ratio. This is to reduce the amount of light leaked at the time of display, in other words, to suppress the viewing angle dependency at a low gradation (low luminance). Therefore, as a result of further studies, the present inventor has determined that the azimuth of the absorption axis of the polarizer arranged in the crossed Nicol direction is defined as azimuth 0 ° and azimuth 90 ° in the circularly polarized light VA mode, particularly azimuth 45 °. It has been found that the viewing angle characteristics from intermediate gradation (medium brightness) to high gradation (high brightness) are inferior to those of the linearly polarized light VA mode. That is, at an azimuth of 45 °, not only a viewing angle characteristic at a low gradation (hereinafter also referred to as “contrast viewing angle”) but also a viewing angle characteristic from an intermediate gradation to a high gradation (hereinafter referred to as “gradation viewing angle”). It was found that it was not enough. Note that the gradation viewing angle is an input gradation and output luminance obtained by measurement in a specific direction in a graph in which the horizontal axis is the input gradation and the vertical axis is the normalized output luminance (transmittance). Pass / fail can be judged by the degree of coincidence between the gamma curve obtained by measurement in another direction and the line (also called “gamma (γ) curve”) that shows the correlation with the value of the normal value, In addition, it is desirable that the γ curve in the front direction (normal direction with respect to the display screen) matches the γ curve in other directions as much as possible.

Furthermore, the present inventor has found that the decrease in the contrast viewing angle and the decrease in the gradation viewing angle occur in the same direction, so that the front direction and the other direction are in a wide gradation range from a low gradation to a high gradation. Since the gamma curves are inconsistent, it is perceived by the observer of the liquid crystal display device that the display quality at the azimuth angle of 45 ° is extremely inferior, while the azimuth and gradation viewing angle at which the contrast viewing angle decreases. It was found that the overall display quality level can be improved if the direction in which the drop occurs does not match.

Then, the present inventor has a domain in which liquid crystal molecules are tilted and oriented in a 12.5 ° to 32.5 ° direction, a domain in which liquid crystal molecules are tilted and oriented in a direction of 102.5 ° to 122.5 °, By providing a domain in which the liquid crystal molecules are tilted and aligned in the 212.5 ° azimuth and a domain in which the liquid crystal molecules are tilted and aligned in the 282.5 ° to 302.5 ° azimuth, an intermediate at 45 ° in the circularly polarized VA mode is provided. It has been found that the gradation viewing angle from gradation to high gradation can be improved, and a patent application has already been filed (see Patent Document 8).

In addition, regarding a method for producing a circularly polarizing plate, there is a method for producing a polarizing plate by a roll-to-roll technique using a λ / 4 plate having an in-plane slow axis in an oblique direction with respect to a flow direction (machine direction). (For example, refer nonpatent literature 2). According to this method, the Nz coefficient of the λ / 4 plate can be controlled between 1.1 and 2.0.

Japanese Patent Laid-Open No. 2002-40428 JP 2009-37049 A JP 2003-207782 A JP 2003-186017 A International Publication No. 2009/125515 International Publication No. 2010/087058 International Publication No. 2010/137372 International Publication No. 2011-013399 JP 2008-146003 A

As described above, the circularly polarizing plate is typically a combination of a linear polarizing plate and a λ / 4 plate. In that case, the angle formed by the absorption axis of the linearly polarizing plate and the in-plane slow axis of the λ / 4 plate needs to be set to about 45 °. Therefore, in recent years, from the viewpoint of improving productivity, as a method for producing a circularly polarizing plate, an obliquely stretched λ / 4 plate, a uniaxially stretched polarizer, and a protective film (for example, a TAC film) are rolled. Methods have been developed to bond each other using roll technology. A λ / 4 plate having an Nz coefficient of approximately 1.6 and a circularly polarizing plate including the λ / 4 plate are commercially available.

However, when the Nz coefficient of the λ / 4 plate is large, it may be difficult to manufacture a circularly polarizing plate by a roll-to-roll technique. For example, even with the technique described in Non-Patent Document 2, it is difficult to produce a circularly polarizing plate including a λ / 4 plate having an Nz coefficient greater than 2.0. Therefore, when the Nz coefficient of the λ / 4 plate is large, the productivity of the circularly polarizing plate is lowered and the manufacturing cost may be increased. In addition, when a circularly polarizing plate including a λ / 4 plate having a large Nz coefficient is produced using a roll-to-roll technique, the quality may be deteriorated.

Also in the technique of Patent Document 8, the first and second λ / 4 plates depend on conditions such as the phase difference of the liquid crystal layer, the presence / absence of the third birefringent layer, the phase difference of the third birefringent layer, and the like. The Nz coefficient may be set large. In such a case, if the Nz coefficients of the first and second λ / 4 plates are substantially the same, the lower and upper circular polarizing plates have lower productivity, higher manufacturing cost, and lower quality. May occur. For example, when two upper and lower circularly polarizing plates are produced by batch processing (single-wafer processing), productivity is significantly reduced. In addition, the deterioration of the quality of the circularly polarizing plate leads to the deterioration of the viewing angle characteristics of the circularly polarized VA mode liquid crystal display device.

In the technique of Patent Document 8, when the third type birefringent layer is not provided, it is necessary to compensate the liquid crystal layer by adjusting the Nz coefficient of the first and second λ / 4 plates. is there. Further, various surface treatment layers are usually provided on the circularly polarizing plate on the observation surface side of the liquid crystal cell. Therefore, when the phase difference of the liquid crystal layer is changed, the upper and lower circular polarizing plates must be remade according to the phase difference value of the liquid crystal layer and the type of the surface treatment layer. This is not convenient in terms of both cost and productivity because small varieties and mass production are not possible. It can also be a cause of hindering mass production. Therefore, the technique of Patent Document 8 has room for improvement in terms of realizing cost reduction and productivity improvement. In this specification, the circularly polarizing plate provided on the observation surface side of the liquid crystal cell is also referred to as an observation surface side circularly polarizing plate, and the circularly polarizing plate provided on the back surface side of the liquid crystal cell is also referred to as a back side circularly polarizing plate. .

The present invention has been made in view of the above-described present situation, and is capable of reducing costs, is excellent in productivity, and is a circularly polarized VA mode that is excellent in gradation viewing angle from an intermediate gradation at an azimuth of 45 ° to a high gradation. An object of the present invention is to provide a liquid crystal display device.

The inventor conducted various studies on a circularly polarized VA mode liquid crystal display device capable of reducing cost, excellent in productivity, and excellent in gradation viewing angle at an azimuth of 45 °. Attention was paid to the retardation condition of the birefringent layer disposed between the polarizers (first and second polarizers). Two λ / 4 plates (first and second λ / 4 plates) necessary for the circularly polarized VA mode satisfy the relationship of nx> ny ≧ nz (in this specification, “nx> ny ≧ nz The birefringent layer satisfying the above relationship is defined as a first type birefringent layer), and the Nz coefficients thereof are made different from each other, and further, 12.5 ° to 32.5 A domain in which liquid crystal molecules are tilted in the direction of 10 °, a domain in which liquid crystal molecules are tilted in the direction of 102.5 ° to 122.5 °, a domain in which the liquid crystal molecules are tilted in the direction of 192.5 ° to 212.5 °, and By providing a domain in which liquid crystal molecules are tilted and oriented in the 282.5 ° to 302.5 ° azimuth, the grayscale viewing angle from the intermediate grayscale at the azimuth 45 ° in the circularly polarized VA mode to the high grayscale can be improved. I found what I can do. The birefringent layer of the first type is different from the biaxial retardation film controlled to nx> nz> ny (0 <Nz <1) by using a material having an appropriate intrinsic birefringence. It can be produced by a simple method. Further, even when the total of the Nz coefficients of the first and second λ / 4 plates is set to be large, a circularly polarizing plate including a λ / 4 plate having a smaller Nz coefficient is a highly productive method. It has been found that it can be produced using (for example, a method using roll-to-roll technology). Further, as a circularly polarizing plate including a λ / 4 plate having a smaller Nz coefficient, a commercially available circularly polarizing plate can be used. And since the Nz coefficient of the first and second λ / 4 plates can be adjusted separately, it is possible to respond very flexibly to design changes such as a change in the phase difference of the liquid crystal layer and a change in the type of the surface treatment layer. I found. More specifically, for example, when the phase difference of the liquid crystal layer is changed, the liquid crystal layer can be compensated by adjusting only the Nz coefficient of one λ / 4 plate. In such a case, only the Nz coefficient of one λ / 4 plate is adjusted, and a third type birefringent layer having an appropriate phase difference is provided on the circularly polarizing plate including the λ / 4 plate. Thus, compensation of the liquid crystal layer can also be performed. That is, it is possible to cope with a change in the phase difference of the liquid crystal layer only by changing the design of one circularly polarizing plate. As a result of the above, the inventors have conceived that the above problems can be solved brilliantly and have reached the present invention.

That is, according to one aspect of the present invention, when a birefringent layer satisfying a relationship of nx> ny ≧ nz is defined as a first type birefringent layer, the first polarizer has an in-plane retardation of λ / 4. An adjusted first λ / 4 plate, a liquid crystal cell having a pair of substrates facing each other and a liquid crystal layer sandwiched between the pair of substrates, having an Nz coefficient different from the first λ / 4, A second λ / 4 plate having an in-plane phase difference adjusted to λ / 4, and a second polarizer are provided in this order, and the first and second λ / 4 plates are a first type of composite. When it is a refractive layer and the orientation of the absorption axis of the second polarizer is defined as 0 °, the in-plane slow axis of the second λ / 4 plate forms an angle of approximately 45 °, and the first The in-plane slow axis of the λ / 4 plate is approximately 135 °, the absorption axis of the first polarizer is approximately 90 °, and the liquid crystal molecules in the liquid crystal layer are on the substrate surface. Is it in a state of being substantially vertically oriented? The display brightness is changed by changing the tilted state, and the liquid crystal layer has a domain in which liquid crystal molecules are tilted and oriented in the direction of 12.5 ° to 32.5 °, and 102.5 ° to 122.122. A domain in which liquid crystal molecules are tilted in the 5 ° azimuth, a domain in which liquid crystal molecules are tilted in the 192.5 ° to 212.5 ° azimuth, and a liquid crystal molecule is tilted in the 282.5 ° to 302.5 ° azimuth. A liquid crystal display device having a domain (hereinafter also referred to as a liquid crystal display device of the present invention).

In the present specification, the “azimuth” represents an orientation in a direction parallel to the substrate surface of the liquid crystal cell, takes an angle of 0 ° to 360 °, and an inclination angle from the normal direction of the substrate surface of the liquid crystal cell. Is not considered. The tilt angle from the normal direction of the substrate surface of the liquid crystal cell is called “polar angle”. The polar angle ranges from 0 ° to 90 °. In FIG. 1, the orientation of the absorption axis of the second polarizer is the X axis, the axis orthogonal to the X axis in the in-plane direction is the Y axis, and the axis orthogonal to the X axis in the out-of-plane direction is Z The azimuth angle φ and polar angle θ with respect to the orientation A ₀ of the tilted orientation of the liquid crystal molecules when using the axes are illustrated.

The liquid crystal display device of the present invention performs display in a so-called MVA mode (multi-domain VA mode). In the MVA mode, for example, alignment control means such as a pixel electrode used for applying a voltage to the liquid crystal layer and / or a slit (electrode notch) formed in the common electrode, a dielectric protrusion formed in the pixel, and the like are provided. Thus, the tilt direction of the liquid crystal molecules at the time of voltage application is divided into a plurality of portions within the pixel. Thereby, the symmetry of the tilt direction of the liquid crystal molecules can be enhanced, and the viewing angle characteristics of the liquid crystal display device can be improved. Further, the liquid crystal display device of the present invention performs display by so-called circularly polarized VA mode. Therefore, in order to maximize the transmittance in the white display state, the axis orientation of the polarizer and the tilt orientation of the liquid crystal molecules when a voltage is applied are 45 °, as in the MVA mode using a typical linear polarizing plate. There is no need to set the angle. For this reason, domains in which liquid crystal molecules are tilted and aligned in the direction of 12.5 ° to 32.5 °, domains in which liquid crystal molecules are tilted and aligned in the direction of 102.5 ° to 122.5 °, and 192.5 ° to 212.5 ° Even when a domain in which liquid crystal molecules are tilted in the azimuth and a domain in which liquid crystal molecules are tilted in the 282.5 ° to 302.5 ° azimuth is formed, as in the case of displaying in the linear polarization mode in principle. The transmittance in the white display state does not decrease.

In the liquid crystal display device of the present invention, a domain means a region in a pixel in which the tilt directions of liquid crystal molecules accompanying voltage application to the liquid crystal layer are substantially the same. Regions containing liquid crystal molecules having different polar angles are also included in the same domain if the tilt directions are substantially the same.

The liquid crystal display device of the present invention includes the first polarizer, the first λ / 4 plate, the liquid crystal cell, the second λ / 4 plate, and the second polarizer described above as constituent elements. As long as it is not particularly limited by other members, from the viewpoint of realizing a high contrast ratio in a wide viewing angle range, (1) between the first λ / 4 plate and the first polarizer. A second birefringent layer, wherein the in-plane fast axis of the second birefringent layer is substantially orthogonal to the absorption axis of the first polarizer, (2) A first birefringent layer of the first kind between the first λ / 4 plate and the first polarizer, and between the second λ / 4 plate and the second polarizer. A second birefringent layer of the second type, the in-plane fast axis of the first birefringent layer of the first type being substantially orthogonal to the absorption axis of the first polarizer, Second second The in-plane fast axis of the two types of birefringent layers is preferably used in a form that is substantially orthogonal to the absorption axis of the second polarizer.

In this specification, the term “polarizer” refers to an element having a function of converting natural light (non-polarized light), partially polarized light or polarized light into linearly polarized light, ie, taking out linearly polarized light from natural light (non-polarized light), partially polarized light or polarized light. That is, it is synonymous with a polarizing film. Note that in this specification, the contrast of a polarizing plate including a polarizer is not necessarily infinite, and may be 5000 or more (preferably 10,000 or more). The “birefringent layer” is a layer having optical anisotropy and is synonymous with a retardation film, a retardation plate, an optically anisotropic layer, a birefringent medium, and the like. In the present specification, the “birefringent layer” is such that at least one of an in-plane retardation R and an absolute value of the thickness direction retardation Rth described later is 10 nm from the viewpoint of sufficiently achieving the effects of the liquid crystal display device of the present invention. It means what has the above value, Preferably, it means what has a value of 20 nm or more. Further, as described above, in the present specification, the “first type birefringent layer” means a birefringent layer satisfying a relationship of nx> ny ≧ nz, and “second type birefringent layer” Means a birefringent layer satisfying the relationship of nx <ny ≦ nz. nx and ny represent the main refractive index in the in-plane direction for light having a wavelength of 550 nm, and nz represents the main refractive index in the out-of-plane direction (thickness direction) for light having a wavelength of 550 nm. Furthermore, the isotropic film means that both the in-plane retardation R and the absolute value of the thickness direction retardation Rth have a value of 10 nm or less, preferably 5 nm or less. Means.

In this specification, “in-plane retardation R” is defined as the main refractive index in the in-plane direction of a birefringent layer (including a liquid crystal cell and a λ / 4 plate) as nx and ny. When the main refractive index in the direction (thickness direction) is defined as nz and the thickness of the birefringent layer is defined as d, an in-plane retardation (unit: nm, absolute value) defined by R = | nx−ny | × d is there. On the other hand, the “thickness direction retardation Rth” is an out-of-plane (thickness direction) phase difference (unit: nm) defined by Rth = (nz− (nx + ny) / 2) × d. “Λ / 4 plate (this includes a λ / 4 plate whose in-plane phase difference is adjusted to λ / 4)” means at least about a quarter wavelength (accurately) for light having a wavelength of 550 nm. Is a layer having optical anisotropy of 137.5 nm, but larger than 115 nm and smaller than 160 nm), a λ / 4 retardation film, a λ / 4 retardation plate, It is synonymous.

The “in-plane slow axis (fast axis)” corresponds to the main refractive index ns (nf) when the larger one of the in-plane main refractive indexes nx and ny is redefined as ns and the smaller one as nf. This is the direction of the main dielectric axis (x-axis or y-axis direction). Further, the “Nz coefficient” is a parameter representing the degree of biaxiality of the birefringent layer defined by Nz = (ns−nz) / (ns−nf). Unless otherwise specified, the measurement wavelength of the main refractive index and the phase difference is 550 nm in this specification. Even in the case of a birefringent layer having the same Nz coefficient, if the average refractive index of the birefringent layer = (nx + ny + nz) / 3 is different, the effective position of the birefringent layer with respect to incidence from an oblique direction is affected by the refraction angle. The phase difference is different and the design guideline becomes complicated. In order to avoid this problem, the Nz coefficient is calculated in this specification by unifying the average refractive index of each birefringent layer to 1.5 unless otherwise specified. Birefringent layers having an actual average refractive index different from 1.5 are also converted assuming an average refractive index of 1.5. The same treatment is applied to the thickness direction retardation Rth.

In the form (2), the Nz coefficient of the first second birefringent layer and the Nz coefficient of the second second birefringent layer can each be set as appropriate. The Nz coefficient of the first second type birefringent layer and the Nz coefficient of the second second type birefringent layer are preferably substantially the same. The in-plane retardation of the first second birefringent layer and the in-plane retardation of the second second birefringent layer can each be set as appropriate. It is preferable that the in-plane retardation of one second-type birefringent layer and the in-plane retardation of the second second-type birefringent layer are substantially the same. Hereinafter, in this specification, the Nz coefficient and the in-plane retardation of the second second-type birefringent layer are substantially the same as the Nz coefficient and the in-plane retardation of the first second-type birefringent layer, respectively. Mention only the form.

In this specification, “the Nz coefficient of the first λ / 4 plate is different from the Nz coefficient of the second λ / 4 plate” represents a case where the difference between the Nz coefficients is 0.1 or more. It is preferably 3 or more. “The Nz coefficient of the first second-type birefringent layer and the Nz coefficient of the second second-type birefringent layer are substantially the same” means that the difference between the Nz coefficients is less than 0.1. Preferably less than 0.05. “The in-plane retardation of the first second-type birefringent layer and the in-plane retardation of the second second-type birefringent layer are substantially the same” means that the in-plane retardation is 20 nm. Represents a case of less than 10 nm, and preferably less than 10 nm.

“The in-plane slow axis of the second λ / 4 plate forms an angle of about 45 °” means that the in-plane slow axis of the second λ / 4 plate and the absorption axis of the second polarizer are The angle formed may be 40 to 50 °, particularly preferably 45 °. Even if the relative angle between the in-plane slow axis of the second λ / 4 plate and the absorption axis of the second polarizer is not completely 45 °, the in-plane slow of the first λ / 4 plate Since the phase axis and the in-plane slow axis of the second λ / 4 plate are substantially orthogonal to each other, a sufficient prevention effect can be obtained with respect to light leakage in the normal direction with respect to the substrate surface. On the other hand, in terms of the antireflection function and the improvement in transmittance, a remarkable effect is obtained when the relative angle is 45 °. “The in-plane slow axis of the first λ / 4 plate forms an angle of about 135 °” means that the in-plane slow axis of the second λ / 4 plate in the direction of about 45 ° and the first The angle formed with the in-plane slow axis of the λ / 4 plate may be 88 to 92 °, and particularly preferably 90 °. “The absorption axis of the first polarizer forms an angle of approximately 90 °” means that the angle between the absorption axis of the second polarizer and the absorption axis of the first polarizer is 88 to 92 °. Well, particularly preferably 90 °. “The in-plane fast axis of the (first or second) birefringent layer is substantially perpendicular to the absorption axis of the (first or second) polarizer” means that the second kind The angle formed between the in-plane fast axis of the birefringent layer and the absorption axis of the polarizer may be 88 to 92 °, particularly preferably 90 °.

As will be described later, from the viewpoint of realizing a high contrast ratio by controlling the change in the polarization state of the display light using the second birefringent layer and reducing the light leakage in the black display state in a wide viewing angle range. In the case of (1), the second birefringent layer, the first λ / 4 plate (first type birefringent layer), the liquid crystal cell, and the second λ / 4 plate (first In addition to a kind of birefringent layer, a form that does not include a birefringent medium between the first polarizer and the second polarizer is preferable. From the viewpoint of reducing the cost by reducing the number of birefringent layers used in the liquid crystal display device, the first polarizer, the second kind of birefringent layer, the first λ / 4 plate (the first kind of birefringence) Layer), the liquid crystal cell, the second λ / 4 plate (the first kind of birefringent layer), and the second polarizer, the liquid crystal display device does not include a birefringent medium. is there. On the other hand, the first polarizer, the second type birefringent layer, the first λ / 4 plate (first type birefringent layer), the liquid crystal cell, the second λ / 4 plate (first type birefringent layer). In addition to the second polarizer and the second polarizer, a birefringent medium may be added in the liquid crystal display device. For example, in order to adjust the wavelength dispersion of the birefringent layer, the in-plane retardation is A λ / 2 plate adjusted to λ / 2 may be added to the liquid crystal display device. Moreover, if it is the form of said (2), a 1st 2nd type birefringent layer, a 1st (lambda) / 4 board (1st type birefringent layer), a liquid crystal cell, a 2nd (lambda) / 4 board In addition to the (first type birefringent layer) and the second second type birefringent layer, a form that does not include a birefringent medium between the first polarizer and the second polarizer is suitable. It is. From the viewpoint of reducing the cost by reducing the number of birefringent layers used in the liquid crystal display device, the first polarizer, the first second type birefringent layer, the first λ / 4 plate (first type Liquid crystal cell, liquid crystal cell, second λ / 4 plate (first type birefringent layer), second second type birefringent layer, and second polarizer. A form that does not include a birefringent medium in the apparatus is more preferable. In the same manner as in the above (1), the first polarizer, the first second birefringent layer, the first λ / 4 plate (first birefringent layer), the liquid crystal cell, the second In addition to the λ / 4 plate (first birefringent layer), the second birefringent layer, and the second polarizer, a birefringent medium may be added in the liquid crystal display device. In order to adjust the wavelength dispersion of the birefringent layer or the like, a λ / 2 plate having an in-plane retardation adjusted to λ / 2 may be added to the liquid crystal display device.

Further, the present inventor has found that factors that prevent complete black display are different depending on the orientation, and a birefringent layer (this book) satisfying the relationship of nx≈ny> nz between the first and second λ / 4 plates. In the specification, it is found that phase difference compensation for a plurality of directions can be performed by arranging “a birefringent layer satisfying the relationship of nx≈ny> nz” as a third type of birefringent layer. It was. In the embodiment in which the third birefringent layer is provided, first, by adjusting the retardation value of the third birefringent layer, the condition for phase difference compensation at an azimuth of 0 ° can be optimized. Next, by appropriately arranging the phase difference values of the second birefringent layer, the conditions for phase difference compensation at 45 ° are optimized without changing the optimization conditions for phase difference compensation at 0 °. Thus, light leakage in a black display state in an oblique direction in a wider direction can be reduced. As a result, a high contrast ratio in a wide viewing angle range can be realized on both the azimuth and polar angles. Further, the birefringent layer of the third type is different from the biaxial retardation film controlled to nx> nz> ny (0 <Nz <1), by using a material having an appropriate intrinsic birefringence, It can be manufactured by a simple method.

In other words, the liquid crystal display device of the present invention has at least one layer between at least one of the first λ / 4 plate and the liquid crystal cell and between the liquid crystal cell and the second λ / 4 plate. The third birefringent layer may be further provided. The third birefringent layer is particularly preferably used when the average value of the Nz coefficient of the first λ / 4 plate and the second λ / 4 plate is less than 2.00. The third birefringent layer is preferably disposed adjacent to the liquid crystal cell. Here, “adjacent arrangement” means that a birefringent medium is not provided between the third birefringent layer and the liquid crystal cell. For example, the third birefringent layer and the liquid crystal cell A form in which an isotropic film is disposed therebetween is also included. When a plurality of third birefringent layers are provided, at least one of the plurality of third birefringent layers is disposed adjacent to the liquid crystal cell, and the third birefringent layers are arranged between each other. A form in which they are arranged adjacent to each other is preferable.

Note that nx≈ny in the third type of birefringent layer can also be expressed as | nx−ny | ≈0. Specifically, the case where the in-plane retardation R = | nx−ny | × d is less than 20 nm. It is preferably less than 10 nm. Accordingly, the third birefringent layer includes a birefringent layer that satisfies the relationship of nx = ny> nz. The third birefringent layer may be composed of multiple layers or only one layer, and may be located on the inner side of the first λ / 4 plate and the second λ / 4 plate ( As long as it is arranged on the liquid crystal cell side) and the sum of the thickness direction retardations is the same, the transmitted light intensity characteristics of the liquid crystal display device are in principle completely the same. Further, even when the liquid crystal display device does not actually have the third birefringent layer, it is considered that the liquid crystal display device has the third birefringent layer virtually having a thickness direction retardation of zero. There is no problem. Therefore, hereinafter, unless otherwise specified, in the present specification, as the liquid crystal display device of the present invention, a third birefringent layer is disposed between the first λ / 4 plate and the liquid crystal cell. The description will be simplified by referring only to the liquid crystal display device.

Examples of the polarizer typically include a polyvinyl alcohol (PVA) film adsorbed and oriented with an anisotropic material such as an iodine complex having dichroism. Usually, in order to ensure mechanical strength and heat-and-moisture resistance, a protective film such as a triacetyl cellulose (TAC) film is laminated on both sides of the PVA film, and this specification is used unless otherwise specified. Among them, the term “polarizer” refers only to an element having a polarizing function without including a protective film. Note that the first and second polarizers, in principle, have no characteristic of transmitted light intensity of the liquid crystal display device, regardless of which is a polarizer (a polarizer on the back surface side) or an analyzer (a polarizer on the observation surface side). It will be the same. That is, any of the first and second first-type birefringent layers may be provided on the observation surface side of the liquid crystal cell.

However, in general, the observation-side circular polarizing plate is more productive than the rear-side circular polarizing plate because it is necessary to manufacture multiple varieties that differ only in the surface treatment layer, depending on the application and user's request. It is desirable to have a simple configuration with high. On the other hand, since a surface treatment is generally unnecessary for the back side circularly polarizing plate, only one type needs to be manufactured. Therefore, even if the configuration of the back side circularly polarizing plate is somewhat complicated, the influence on mass production is relatively small. In view of this situation, a λ / 4 plate having a larger Nz coefficient (= λ / 4 plate that is more difficult to manufacture by a high-productivity manufacturing method) on the back side of the liquid crystal cell, and a λ / 4 plate having a smaller Nz coefficient. / 4 plate (= λ / 4 plate that is easier to manufacture by a highly productive manufacturing method) is preferably arranged on the observation surface side of the liquid crystal cell. From the same viewpoint, the second birefringent layer is preferably disposed on the back side of the liquid crystal cell together with the λ / 4 plate having the larger Nz coefficient. The third birefringent layer is more preferably disposed only on the back side of the liquid crystal cell.

When the phase difference (Δnd) of the liquid crystal layer is changed in the configuration including the third type birefringent layer, the phase difference of the third type birefringent layer is usually adjusted to cope with it. However, when the third birefringent layer is provided on the observation-surface-side circularly polarizing plate, it is further combined with the problem of increasing the variety due to the difference in surface treatment as described above, thereby further promoting the problem of increasing the variety. Therefore, it is particularly preferable that the third birefringent layer is disposed on the back side circularly polarizing plate. For example, in the case of corresponding to five types of surface treatment and four types of retardation of the liquid crystal layer, if the third birefringent layer is arranged on the observation surface side circularly polarizing plate, the observation surface side circularly polarizing plate has 5 × 4 = Since there are 20 types and the back side circularly polarizing plate is 1 type, a total of 21 types of circularly polarizing plates are required. On the other hand, if the third type birefringent layer is arranged on the back side circularly polarizing plate, there are 5 types of observation side side circularly polarizing plates and 4 types of back side circularly polarizing plates. All you have to do is prepare it.

From such a viewpoint, it is preferable that the larger Nz coefficient of the first and second λ / 4 plates is disposed on the back side of the liquid crystal cell. When the Nz coefficient of the first λ / 4 plate is larger than the Nz coefficient of the second λ / 4 plate, the liquid crystal display device according to the present invention has a surface on the observation surface side of the second polarizer. It is preferable to further include a treatment layer. In the form (1), the second birefringent layer is preferably disposed on the back side of the liquid crystal cell. At this time, the Nz coefficient of the first λ / 4 plate is the first More preferably, the second birefringent layer and the first λ / 4 plate are larger than the Nz coefficient of the second λ / 4 plate, and are arranged on the back side of the liquid crystal cell. In the form of (1), the at least one third-type birefringent layer is preferably disposed on the back side of the liquid crystal cell. At this time, the Nz of the first λ / 4 plate The coefficient is greater than the Nz coefficient of the second λ / 4 plate, and the second birefringent layer, the first λ / 4 plate, and the at least one third birefringent layer are More preferably, it is arranged on the back side of the liquid crystal cell. In the form (2), the at least one third birefringent layer is preferably disposed on the back side of the liquid crystal cell. At this time, the Nz coefficient of the first λ / 4 plate is The first λ / 4 plate and the at least one third birefringent layer are disposed on the back side of the liquid crystal cell. The Nz coefficient of the second λ / 4 plate is larger than the Nz coefficient. It is more preferable.

Hereinafter, unless otherwise specified, in this specification, only the liquid crystal display device in which the first polarizer is a polarizer will be referred to, and the description will be simplified.

The liquid crystal cell includes a pair of substrates facing each other and a liquid crystal layer sandwiched between the pair of substrates. The liquid crystal cell according to the present invention is a multi-domain VA (MVA) mode which is a type of vertical alignment (VA) mode in which black is displayed by aligning liquid crystal molecules in a liquid crystal layer substantially perpendicularly to a substrate surface. This is a liquid crystal cell. MVA mode can be combined with Continuous Pinwheel Alignment (CPA) mode, Patterned VA (PVA) mode, Biased VA (BVA) mode, Reverse TN (RTN) mode, In-Plane Switching-VA (IPS-VA) mode, etc. Good. In this specification, “alignment of liquid crystal molecules substantially perpendicularly to the substrate surface” is sufficient if the average pretilt angle of the liquid crystal molecules is 80 ° or more.

The liquid crystal display device of the present invention includes a first first-type birefringent layer (first-phase layer) in which an in-plane retardation is adjusted to λ / 4 between a first polarizer and a second polarizer. λ / 4 plate) and a second first-type birefringent layer (second λ / 4 plate) in which the in-plane retardation is adjusted to λ / 4. Although it may have a refractive layer and / or a third birefringent layer, from the viewpoint of realizing further cost reduction, the second polarizer is provided between the first polarizer and the second polarizer. The three birefringent layers are preferably not provided. When the phase difference (Δnd) of the liquid crystal layer is changed in a form not including the third type birefringent layer, it is preferable to adjust the Nz coefficient of the λ / 4 plate having the larger Nz coefficient. As a result, a circularly polarizing plate including a λ / 4 plate having a smaller Nz coefficient (= λ / 4 plate that is easier to manufacture by a high-productivity manufacturing method) is used as a plurality of types of liquid crystals having different liquid crystal layer retardations. Can be shared for cells.

The Nz coefficient of the first λ / 4 plate and the Nz coefficient of the second λ / 4 plate can be appropriately set, but are preferably larger than 1. The Nz coefficient of one of the first λ / 4 plate and the second λ / 4 plate is 2 or more, and the first λ / 4 plate and the second λ / 4 plate The other Nz coefficient of the four plates is more preferably 1 or more and less than 2. Thereby, the λ / 4 plate having a smaller Nz coefficient can be produced using a technique that is particularly excellent in productivity (for example, the technique described in Non-Patent Document 2). Further, as the λ / 4 plate having the smaller Nz coefficient, a commercially available λ / 4 plate (general-purpose product) having an Nz coefficient of approximately 1.6 can be used. In this form, a commercially available circularly polarizing plate can be used as a circularly polarizing plate including a λ / 4 plate having a smaller Nz coefficient. A plurality of types of circularly polarizing plates having different surface treatments are commercially available. In this way, by setting the Nz coefficient of one λ / 4 plate to 1 or more and less than 2, the cost of the circularly polarizing plate including this λ / 4 plate can be greatly reduced and its productivity is remarkably improved. can do. Also, by setting the Nz coefficient of one λ / 4 plate to 1 or more and less than 2 and setting the Nz coefficient of the other λ / 4 plate to 2 or more, the first and second λ / 4 plates The average value Nzq of Nz coefficients can be easily set within a preferable range described later. Note that a highly productive manufacturing technique such as a roll-to-roll technique may not be used for manufacturing a circularly polarizing plate including a λ / 4 plate having a larger Nz coefficient. However, the effect only affects the circular polarizing plate on the observation surface side or the back surface side, and is considerably smaller than the case where the circular polarizing plate on both sides is affected.

In the above form (1), the combination of the first λ / 4 plate and the second birefringent layer may be a laminated body that is laminated without an adhesive (via an adhesive). The laminate is preferably laminated via an adhesive. As described above, as a preferred embodiment of the liquid crystal display device of the present invention, the first λ / 4 plate and the second type birefringent layer are provided on the back side of the liquid crystal cell, and the first λ / 4 plate is provided. The Nz coefficient is larger than the Nz coefficient of the second λ / 4 plate. In this form, it may be difficult to manufacture the first λ / 4 plate using an oblique stretching method suitable for the roll-to-roll technique. Therefore, from the viewpoint of minimizing the influence, this form is preferably produced by the following method. That is, the second type birefringent layer is attached to the first polarizer using an adhesive by a roll-to-roll technique. The first λ / 4 plate is produced using a method other than the oblique stretching method (for example, a tenter lateral uniaxial stretching method, a longitudinal lateral biaxial stretching method, or the like). Then, the first λ / 4 plate is attached to the second birefringent layer on the first polarizer using an adhesive. This pasting process may be performed by a batch process. In addition, when batch processing is adopted, there is a concern that productivity is reduced. However, in the liquid crystal display device of the present invention, for example, a commercially available circularly polarizing plate can be diverted to a circularly polarizing plate including the second λ / 4 plate. Because there are many other advantages such as being able to do so, the disadvantages of batch processing can be fully compensated. Furthermore, assuming that batch processing is adopted for manufacturing a circularly polarizing plate including a λ / 4 plate having a larger Nz coefficient (= λ / 4 plate that is more difficult to manufacture by a high-productivity manufacturing method), There is also an advantage that the λ / 4 plate can be easily manufactured by using a method other than the oblique stretching method.

In the above configuration (2), a λ / 4 plate having a larger Nz coefficient (hereinafter also referred to as a high Nz λ / 4 plate) and a second type of compound closer to the high Nz λ / 4 plate. The combination with the refractive layer (hereinafter also referred to as a high Nz side birefringent layer) may be a laminated body laminated without an adhesive (via an adhesive), but via an adhesive. It is preferable that it is a laminated body. As described above, a preferred form of the liquid crystal display device of the present invention includes a form in which a high Nz λ / 4 plate is disposed on the back side of the liquid crystal cell. In this form, it may be difficult to produce a high Nz λ / 4 plate using an oblique stretching method suitable for roll-to-roll technology. Therefore, from the viewpoint of minimizing the influence, this form is preferably produced by the following method. That is, the high Nz side birefringent layer is attached to the first or second polarizer using an adhesive by a roll-to-roll technique. The high Nz λ / 4 plate is produced using a method other than the oblique stretching method (for example, a tenter transverse uniaxial stretching method, a longitudinal transverse biaxial stretching method, or the like). Then, a high Nz λ / 4 plate is attached to the high Nz side birefringent layer on the first or second polarizer using an adhesive. This pasting process may be performed by a batch process.

In the aspect (2), from the viewpoint of further improving productivity, a λ / 4 plate having a smaller Nz coefficient (hereinafter also referred to as a low Nz λ / 4 plate) is reduced by the following method. It is preferably laminated on the second type birefringent layer (hereinafter also referred to as a low Nz side birefringent layer) closer to the Nz λ / 4 plate. That is, the low Nz-side birefringent layer is attached to the first or second polarizer using an adhesive by a roll-to-roll technique. The low Nz λ / 4 plate is produced using an oblique stretching method. Then, using a roll-to-roll technique, a low Nz λ / 4 plate is attached to the low Nz side birefringent layer on the first or second polarizer. For attaching the low Nz λ / 4 plate, an adhesive or an adhesive may be used.

The combination of the first λ / 4 plate and / or the second λ / 4 plate and the third birefringent layer is preferably a laminated body laminated without an adhesive. Such a laminate can be formed by, for example, a method of laminating with an adhesive simultaneously with extrusion film formation such as a co-extrusion method, or by forming one birefringent layer in the laminate from a polymer film, and liquid crystallinity on the polymer film. The other birefringent layer formed of a material or a non-liquid crystal material can be formed by coating or by lamination by transfer. In the latter method using coating or transfer, the third birefringent layer is often produced by a method of applying a non-liquid crystalline material such as polyimide or a liquid crystalline material such as cholesteric liquid crystal. The λ / 4 plate and / or the second λ / 4 plate and the third birefringent layer can be suitably used.

Hereinafter, the function of the second and third birefringent layers in the liquid crystal display device of the present invention will be described. As an example, a first polarizer, a second birefringent layer, a first λ / 4 plate (first type birefringent layer), a third birefringent layer, a liquid crystal cell, a second λ / Consider a circularly polarized VA mode liquid crystal display device (A) according to the present invention corresponding to the above-described form (1), in which four plates (first birefringent layer) and a second polarizer are laminated in this order. .
In the liquid crystal display device (A), light incident from the front direction on the first polarizer is converted into linearly polarized light by the first polarizer, and the polarization state of the second birefringent layer is maintained. The first λ / 4 plate is converted from linearly polarized light to circularly polarized light, transmitted through the third birefringent layer and the liquid crystal cell while maintaining the polarization state, and the first λ / 4 plate By the second λ / 4 plate having an orthogonal relationship, the circularly polarized light is reconverted to linearly polarized light having the same polarization state as that immediately after passing through the first polarizer, and is orthogonally crossed with the first polarizer. A good black display can be obtained by blocking linearly polarized light by the polarizer. That is, the second and third birefringent layers are not intended to change the polarization state of light incident from the front direction.

In addition, although the said description demonstrated that the black display was obtained by tracking the polarization state which changes whenever it permeate | transmits each layer, it understands also by the following description more intuitively. That is, in the front direction, the liquid crystal display device (A) has (1) the first and second λ / 4 plates included between the first and second polarizers are substantially orthogonal to each other, and Since the phase difference is substantially the same (λ / 4), it is substantially invalidated by mutually canceling the phase difference. (2) The second type included between the first and second polarizers The birefringent layer is substantially invalidated because its fast axis is substantially perpendicular to the absorption axis of the first polarizer, and (3) between the first and second polarizers. The third birefringent layer and the liquid crystal cell included are substantially invalidated because the phase difference is substantially zero in the front direction, and (4) the first and second polarizers are substantially Since a so-called crossed Nicol polarizer is formed orthogonally, a good black display of the crossed Nicol polarizer (complete black display may be used) .) Is obtained.

On the other hand, assuming that there is no conversion of the polarization state by the second and third birefringent layers in the oblique direction, the liquid crystal display device (A) is the first polarizer for the following three reasons. On the other hand, light incident from an oblique direction is not blocked by the second polarizer, so that a complete black display cannot be obtained. That is, the second and third birefringent layers mainly convert the polarization state of light incident from an oblique direction (only the polarization state of light incident from an oblique direction may be converted), and the field of view. The purpose is to perform angle compensation.

As described above, the second and third birefringent layers in the liquid crystal display device of the present invention maintain a good black display in the front direction and obtain a good black display in an oblique direction. This makes it possible to improve the contrast ratio in the oblique direction. In other words, the second and third birefringent layers in the liquid crystal display device of the present invention can improve the gradation viewing angle at low gradation. Therefore, in the liquid crystal display device of the present invention, the orientation in which the liquid crystal molecules are tilted is adjusted to improve the gradation viewing angle from the intermediate gradation to the high gradation at the azimuth of 45 °, and the second type and / or the second kind. By providing three types of birefringent layers and improving the gradation viewing angle at low gradations, a liquid crystal display device having excellent viewing angle characteristics can be realized.

Next, three reasons why the polarization state is converted by the second and third birefringent layers and the viewing angle is compensated for light incident from an oblique direction will be described in detail. Here, as shown in FIG. 2, the first polarizer (absorption axis orientation 90 °) 110, the first λ / 4 plate (slow axis orientation 135 °) 120, the VA mode liquid crystal cell 130, the second λ / 4 plate (slow axis azimuth 45 °) 140 and second polarizer (absorption axis azimuth 0 °) 150 are laminated in this order, and does not include the second and third birefringent layers. Consider the circularly polarized VA mode liquid crystal display device 100 having the configuration. In FIG. 2, the arrows drawn on the first and

second polarizers

110 and 150 indicate the directions of the absorption axes, and the arrows drawn on the first and second λ / 4

plates

120 and 140. Represents the orientation of the slow axis, and the ellipsoid drawn in the VA mode liquid crystal cell 130 represents the shape of the refractive index ellipsoid.

First, considering the black display in the front direction, light incident on the first polarizer 110 from the front direction is converted into linearly polarized light by the first polarizer 110 and linearly polarized by the first λ / 4 plate 120. From the circularly polarized light by the second λ / 4 plate 140 which is orthogonal to the first λ / 4 plate 120 and is transmitted through the liquid crystal cell 130 while maintaining the polarization state. The light is converted back to linearly polarized light in the same polarization state as that immediately after passing through the polarizer 110, and a good black display is obtained by blocking the linearly polarized light by the second polarizer 150 orthogonal to the first polarizer 110. . In other words, the liquid crystal display device 100 includes (1) first and second λ / 4

plates

120 and 140 included between the first and

second polarizers

110 and 150 in the front direction. Since they are orthogonal to each other and have the same phase difference (λ / 4), they are invalidated by canceling each other's phase difference, and (2) the first and

second polarizers

110, 110, The liquid crystal cell 130 included in the gap 150 is substantially invalidated because the phase difference is zero in the front direction, and (3) the first and

second polarizers

110 and 150 are orthogonal to each other. Since a so-called crossed Nicol polarizer is formed, a complete black display can be obtained.

Next, considering black display in an oblique direction, complete black display cannot be obtained due to the following viewing angle obstruction factors (1) to (3).
(1) The first and second λ / 4

plates

120 and 140 are not invalidated because they are not orthogonal to each other or their phase differences are not the same.
(2) Since the phase difference of the liquid crystal cell 130 is not zero, it is not invalidated.
(3) Since the first and

second polarizers

110 and 150 are not orthogonal to each other, a crossed Nicol polarizer is not configured.

The viewing angle inhibition factors (1) to (3) will be described in more detail with reference to FIG. As schematically shown in FIG. 3A, in the front direction (normal direction to the substrate surface), the slow axis 121 of the first λ / 4 plate 120 and the second λ / 4 plate 140 While the slow axis 141 is orthogonal to each other, in the oblique direction at the azimuth of 0 °, the slow axis 121 of the first λ / 4 plate 120 and the slow axis 141 of the second λ / 4 plate 140 are Are not orthogonal to each other, so that the phase difference is not canceled and invalidated. As schematically shown in FIG. 3B, in the front direction, the slow axis 121 of the first λ / 4 plate 120 and the slow axis 141 of the second λ / 4 plate 140 are orthogonal to each other. In contrast, in the oblique direction at the azimuth of 45 °, the first and second λ / 4

plates

120 and 140 have the same phase difference although the slow axis 121 and the slow axis 141 are orthogonal to each other. Therefore, the mutual phase difference is not canceled. The phase difference is determined by birefringence (refractive index difference) × thickness, but the reason is that the effective birefringence differs between the front direction and the oblique direction, and also depends on the orientation. For the same reason, the phase difference of the VA mode liquid crystal cell 130 which is zero in the front direction is not zero in any oblique direction. Effective birefringence is zero only in the front direction, and the phase difference is zero. Further, as schematically shown in FIG. 3C, in the front direction, the absorption axis 111 of the first polarizer 110 and the absorption axis 151 of the second polarizer 150 are orthogonal to each other, while In the oblique direction at 45 °, the absorption axis 111 of the first polarizer 110 and the absorption axis 151 of the second polarizer 150 are not orthogonal to each other.

As described above, the circularly polarized VA mode liquid crystal display device 100 with the minimum configuration cannot obtain a complete black display in an oblique direction due to the above three viewing angle obstruction factors (1) to (3). In other words, a better black display can be obtained even in an oblique direction if treatment for these obstruction factors, that is, optical compensation can be performed. In many cases, the viewing angle inhibition factors (1) and (2) are observed in a combined manner. Therefore, when optically compensating them, a technique for optimizing the viewing angle inhibition factors (1) and (2) as a whole may be used instead of individual optimization.

The liquid crystal display device (A) is designed so as to simultaneously optically compensate for the viewing angle inhibiting factors (1) to (3) based on a design guideline described in detail below. Specifically, first, the first and second λ / 4 plates are biaxial λ / 4 plates (first type birefringent layer) satisfying the relationship of nx> ny ≧ nz, Different Nz coefficients from each other, and second, a birefringent layer satisfying the relationship of nx <ny ≦ nz (second birefringent layer) between the first λ / 4 plate and the first polarizer. And third, if necessary, a birefringent layer (third birefringent layer) satisfying the relationship of nx≈ny> nz is disposed between the first and second λ / 4 plates. Thus, optical compensation is realized.

Here, a design guideline for the birefringent layer will be described. The present inventor has made various studies in order to simply and effectively perform the optical compensation of the viewing angle inhibition factor, and has focused on the fact that the factors that require optical compensation differ depending on the orientation. Then, as shown in Table 1 below, it was found that the optical compensation of the polarizer for the viewing angle inhibition factor (3) is unnecessary at the azimuth of 0 °, and the λ / 4 plate for the viewing angle inhibition factor (1) at this orientation. It was found that only the optical compensation of the liquid crystal cell with respect to the optical compensation and the viewing angle inhibiting factor (2) should be performed.

Furthermore, the present inventor optimally calculates the average value Nzq of the Nz coefficient of the first and second λ / 4 plates and the thickness direction retardation Rlc of the liquid crystal cell by means of a polarization state diagram using a Poincare sphere and computer simulation. By adjusting, if necessary, a third birefringent layer satisfying the relationship of nx = ny> nz is arranged between the first and second λ / 4 plates, and the thickness direction retardation R3 is set. It was also conceived that the viewing angle inhibiting factors (1) and (2) can be simultaneously and effectively optically compensated at the azimuth of 0 ° by optimal adjustment. In the present specification, for the purpose of optical compensation at an azimuth of 0 ° as described above, the average value Nzq of the Nz coefficients of the first and second λ / 4 plates, the thickness direction retardation Rlc of the liquid crystal cell, and the third The process of selecting the optimum value of the thickness direction retardation R3 of the seed birefringent layer is called a 1st step.

Then, after this 1st step, the inventor forms a second birefringent layer satisfying the relationship of nx <ny ≦ nz between the first λ / 4 plate and the first polarizer in the plane. By arranging the fast axis to be substantially orthogonal to the absorption axis of the first polarizer and optimally adjusting the Nz coefficient Nz2 and the in-plane retardation R2, the field of view can be obtained at an azimuth of 45 °. It has been conceived that the angle inhibition factors (1), (2) and (3) can be optically compensated simultaneously and effectively. In the present specification, after the 1st step as described above, the process of selecting the optimum values of the Nz coefficient Nz2 and the in-plane retardation R2 of the second birefringent layer for the purpose of optical compensation at an azimuth of 45 ° is 2nd. This is called a step.

The in-plane fast axis of the second birefringent layer added in 2nd step is arranged so as to be substantially orthogonal to the absorption axis of the adjacent first polarizer. Absorption axis azimuth, that is, optical characteristics in the azimuth 0 ° direction are not substantially changed (it is not necessary to change them at all). That is, the characteristic of the optical compensation process in the liquid crystal display device of the present invention is that the optimized state obtained in the 1st step is still preserved after the 2nd step. Thus, the design of the birefringent layer is facilitated because the 1st step and the 2nd step can be studied completely independently.

The details of the optical compensation principle by the above-mentioned 1st step and 2nd step will be explained as follows in the illustration using the Poincare sphere. The concept based on the Poincare sphere is widely known in the field of crystal optics or the like as a technique useful for tracking the polarization state changing through the birefringent layer (see, for example, Non-Patent Document 3).

In the Poincare sphere, right-handed polarized light is represented in the upper hemisphere, left-handed polarized light is represented in the lower hemisphere, linearly polarized light is represented in the equator, and right circularly polarized light and left circularly polarized light are represented in the upper and lower poles. The two polarization states that are symmetric with respect to the center of the sphere form a pair of orthogonal polarization because the absolute values of the ellipticity angles are equal and the polarities are opposite.

Also, the effect of the birefringent layer on the Poincare sphere is that the polarization state immediately before passing through the birefringent layer is expressed by the slow axis on the Poincare sphere (more precisely, the two natural oscillations of the birefringent layer). Of the mode, the position of the point on the Poincare sphere representing the slower polarization state.) Counterclockwise by an angle determined by (2π) × (phase difference) / (wavelength) (unit: rad) The point is converted to a point that has been rotated and moved to the same point (the same is true if the point is rotated clockwise around the fast axis).

The rotation center and rotation angle when observed from an oblique direction are determined by the slow axis (or fast axis) and the phase difference at the observation angle. Although detailed explanation is omitted, these can be calculated by, for example, solving Fresnel's wavefront normal equation and knowing the vibration direction and wave number vector of the natural vibration mode in the birefringent layer. The slow axis when observed from the oblique direction depends on the observation angle and the Nz coefficient, and the phase difference when observed from the oblique direction is the observation angle, the Nz coefficient and the in-plane retardation R (or the thickness direction retardation Rth). ).

(1st step compensation principle)
First, the polarization state when the circularly polarized VA mode liquid crystal display device 100 of FIG. 2 is observed from the front direction will be considered. Under this condition, the light emitted from the backlight (not shown in FIG. 2, but below the first polarizer) is the

polarizers

110 and 150, the

birefringent layers

120 and 140, the liquid crystal cell. FIG. 4 shows the polarization state for each transmission through 130 on the S1-S2 plane of the Poincare sphere. Although the points representing the respective polarization states are actually on the Poincare sphere, they are projected onto the S1-S2 plane for illustration. A point representing the polarization state is indicated by ◯, and a point representing the slow (advance) phase axis of the birefringent layer is indicated by ×.

First, the polarization state immediately after passing through the first polarizer 110 is located at the point P0 on the Poincare sphere and can be absorbed by the second polarizer 150 represented by the point E, that is, the second polarizer. This coincides with the 150 extinction position (absorption axis direction). Then, by passing through the first λ / 4 plate 120, the polarization state at the point P0 is specified around the slow axis of the first λ / 4 plate 120 represented by the point Q1 on the Poincare sphere. Receiving the rotation conversion of the angle, the point P1 is reached. The rotation direction at this time is counterclockwise when viewed from the point Q1 to the origin O (the center point of the Poincare sphere).

Next, the light passes through the VA mode liquid crystal cell 130, but since the phase difference of the VA mode liquid crystal cell 130 is zero in the front direction, the polarization state does not change. Finally, by passing through the second λ / 4 plate 140, the second λ / 4 plate 140 represented by the point Q 2 is subjected to rotational conversion at a specific angle around the slow axis, and reaches the point P 2. This point P2 coincides with the extinction position E of the second polarizer 150. In this way, when the liquid crystal display device 100 of FIG. 2 is observed from the front direction, the light from the backlight can be blocked and a good black display can be obtained.

Further, the circularly polarized VA mode liquid crystal display device 100 of FIG. 2 is inclined by 60 ° from the normal direction at the absorption axis azimuth of the second polarizer 150 at 0 ° (hereinafter also referred to as a pole of 60 °). Let us consider the polarization state when observed from above. Under this condition, the polarization state every time the light emitted from the backlight passes through the

polarizers

110 and 150, the

birefringent layers

120 and 140, and the liquid crystal cell 130 is illustrated on the S1-S2 plane of the Poincare sphere as shown in FIG. It becomes like this.

First, the polarization state immediately after passing through the first polarizer 110 is located at the point P0 on the Poincare sphere and can be absorbed by the second polarizer 150 represented by the point E, that is, the second polarizer. This coincides with the 150 extinction position (absorption axis direction). Then, by passing through the first λ / 4 plate 120, the polarization state at the point P0 is specified around the slow axis of the first λ / 4 plate 120 represented by the point Q1 on the Poincare sphere. Receiving the rotation conversion of the angle, the point P1 is reached. The rotation direction at this time is counterclockwise when viewed from the point Q1 toward the origin O.

Next, by passing through the VA mode liquid crystal cell 130, it undergoes rotational conversion at a specific angle around the slow axis of the liquid crystal cell 130 represented by the point L on the Poincare sphere, and reaches the point P2. The rotation direction at this time is counterclockwise when viewed from the point L toward the origin O. Finally, by passing through the second λ / 4 plate 140, it undergoes rotational transformation at a specific angle around the slow axis of the second λ / 4 plate 140 represented by the point Q2, and reaches the point P3. The point P3 does not coincide with the extinction position E of the second polarizer 150. In this manner, the liquid crystal display device 100 of FIG. 2 cannot block light from the backlight when observed from the azimuth 0 ° pole 60 °.

4 and 5, the positions of the points P1 to P3 are the Nz coefficient Nzq1 of the first λ / 4 plate 120, the Nz coefficient Nzq2 of the second λ / 4 plate 140, and the thickness direction position of the liquid crystal cell 130. Although depending on the phase difference Rlc, FIGS. 4 and 5 show an example where Nzq1 = Nzq2 = 2.0 and Rlc = 320 nm. In order to make the conversion of the polarization state easy to understand, the position of each point is roughly shown, and some are not strictly accurate. Further, for the sake of clarity, the arrows representing the locus are not shown for the conversion of the points P1 to P3. Note that Rlc of the VA mode liquid crystal cell 130 is typically about 320 nm, but is generally adjusted within a range of 270 to 400 nm. For example, Rlc may be larger than 320 nm for the purpose of increasing the transmittance. Nzq1 and Nzq2 of the first and second λ / 4

plates

120 and 140 are generally adjusted within a range of 1.0 to 2.9. For example, in the case where a VA mode liquid crystal cell in which Rlc is set to around 400 nm is used and the third birefringent layer is not provided, the average value of the Nz coefficients is adjusted to 2.9. Two λ / 4 plates are preferably used.

Next, as shown in FIG. 6, a first polarizer (absorption axis orientation 90 °) 210, a first λ / 4 plate (slow axis orientation 135 °) 220, a third birefringent layer 235, A third birefringent layer in which a VA mode liquid crystal cell 230, a second λ / 4 plate (slow axis orientation 45 °) 240, and a second polarizer (absorption axis orientation 0 °) 250 are laminated in this order. Consider a circularly polarized VA mode liquid crystal display device 200 including: In FIG. 6, the arrows drawn on the first and

second polarizers

210 and 250 indicate the directions of the absorption axes, and the arrows drawn on the first and second λ / 4

plates

220 and 240. Represents the orientation of the slow axis, and the ellipsoid drawn on the VA mode liquid crystal cell 230 and the third birefringent layer 235 represents the shape of the refractive index ellipsoid.

First, the polarization state when the circularly polarized VA mode liquid crystal display device 200 of FIG. 6 is observed from the front direction will be considered. Under this condition, light emitted from the backlight (not shown in FIG. 6 but below the first polarizer 210) is emitted from each

polarizer

210, 250 and each

birefringent layer

220, 240, 235. FIG. 7 shows the polarization state for each transmission through the liquid crystal cell 230 on the S1-S2 plane of the Poincare sphere.

First, the polarization state immediately after passing through the first polarizer 210 is located at the point P0 on the Poincare sphere and can be absorbed by the second polarizer 250 represented by the point E, that is, the second polarizer. It corresponds to the extinction position (absorption axis direction) of 250. Then, by passing through the first λ / 4 plate 220, the polarization state at the point P0 is specified around the slow axis of the first λ / 4 plate 220 represented by the point Q1 on the Poincare sphere. Receiving the rotation conversion of the angle, the point P1 is reached. The rotation direction at this time is counterclockwise when viewed from the point Q1 toward the origin O.

Next, the light passes through the third birefringent layer 235 and the VA mode liquid crystal cell 230, but the third birefringent layer 235 and the VA mode liquid crystal cell 230 both have zero phase difference in the front direction. Does not change. Finally, by passing through the second λ / 4 plate 240, it undergoes rotational transformation of a specific angle around the slow axis of the second λ / 4 plate 240 represented by the point Q2, and reaches the point P2. The point P2 coincides with the extinction position E of the second polarizer 250. In this way, when the liquid crystal display device 200 of FIG. 6 is observed from the front direction, it is possible to block the light from the backlight as in the liquid crystal display device 100 of FIG. 2, and a good black display is obtained. .

Further, the polarization state when the circularly polarized VA mode liquid crystal display device 200 of FIG. 6 is observed from a direction inclined by 60 ° with respect to the absorption axis direction 0 ° of the second polarizer 210 will be considered. Under this condition, when the light emitted from the backlight is transmitted through the

polarizers

210 and 250, the

birefringent layers

220, 240 and 235, and the liquid crystal cell 230, the polarization state is illustrated on the S1-S2 plane of the Poincare sphere. It becomes like 8-1.

Next, by passing through the third birefringent layer 235, the third birefringent layer 235 on the Poincare sphere is subjected to rotational conversion at a specific angle around the slow axis of the third birefringent layer 235 represented by the point R 3. P2 is reached. The rotation direction at this time is counterclockwise when viewed from the point R3 toward the origin O. Next, by passing through the VA mode liquid crystal cell 230, it undergoes rotational transformation at a specific angle around the slow axis of the liquid crystal cell 230 represented by the point L on the Poincare sphere, and reaches the point P3. The rotation direction at this time is counterclockwise when viewed from the point L toward the origin O. Finally, by passing through the second λ / 4 plate 240, it undergoes a rotational transformation of a specific angle around the slow axis of the second λ / 4 plate 240 represented by the point Q2, and reaches the point P4. This point P4 coincides with the extinction position E of the second polarizer 250. In this way, the liquid crystal display device 200 of FIG. 6 can block light from the backlight even when observed from an oblique direction with an azimuth of 0 ° and a pole of 60 °, as in the case of observation from the front direction. it can.

7 and 8-1, the positions of the points P1 to P4 are the Nz coefficient Nzq1 of the first λ / 4 plate 220, the Nz coefficient Nzq2 of the second λ / 4 plate 240, and the third type birefringent layer. Although it depends on the thickness direction retardation R3 of 235 and the thickness direction retardation Rlc of the liquid crystal cell 230, in FIGS. 7 and 8-1, as an example, Nzq1 = Nzq2 = 2.0, R3 = −61 nm, Rlc = 320 nm. The form of is shown. In order to make the conversion of the polarization state easy to understand, the position of each point is roughly shown, and some are not strictly accurate. Further, for the sake of clarity, the arrows representing the locus are not shown for the conversion of the points P1 to P4.

As a result of investigation by the present inventor, according to the Nz coefficient Nzq1 of the first λ / 4 plate 220 and the Nz coefficient Nzq2 of the second λ / 4 plate 240, the third type birefringent layer 235 It has been found that there is an optimum phase difference value R3.

Here, by computer simulation, the Nz coefficient Nzq1 of the first λ / 4 plate 220, the Nz coefficient Nzq2 of the second λ / 4 plate 240, and the thickness direction retardation R3 of the third birefringent layer 235 are calculated. The results of investigating the relationship with the optimum value are shown in Table 2 and FIG. In the illustration using the Poincare sphere in FIG. 8A, the polarization state conversion of the point P 1 → P 3 is changed from the P 1 → P 2 conversion by the thickness direction retardation R 3 of the third birefringent layer 235 to the VA mode liquid crystal cell 230. The illustration is divided into P1 → P2 conversion by the thickness direction retardation Rlc. However, these two conversions have the same center of rotation and are only opposite in rotation direction. The rotation direction is determined by the sign of the thickness direction phase difference, and the rotation angle is determined by the absolute value of the thickness direction phase difference. Therefore, the above two conversions are the same even if considered as direct P1 → P3 conversion by “total thickness direction phase difference R3 + Rlc” of “third type birefringent layer 235 + VA mode liquid crystal cell 230”. In other words, as long as R3 + Rlc is the same, the optical characteristics of the liquid crystal display device are the same regardless of the thickness direction retardation Rlc of the VA mode liquid crystal cell 230. Therefore, in Table 2, the result of having calculated the optimal value of R3 + Rlc by computer simulation was shown. Further, for the sake of simplicity, it is assumed here that the Nz coefficient Nzq1 of the first λ / 4 plate 220 is the same as the Nz coefficient Nzq2 of the second λ / 4 plate 240 (Nzq1 = Nzq2 = Nzq). However, as will be described later, when the Nz coefficient Nzq1 of the first λ / 4 plate 220 and the Nz coefficient Nzq2 of the second λ / 4 plate 240 are different from each other, each of Nzq1 and Nzq2 Is equal to the average value Nzq, the optimal retardation value R3 of the third birefringent layer 235 can be calculated according to the Nzq, and the results of Table 2 and FIG. 8 can be referred to as they are. Found by the inventor. As can be seen from Table 2 and FIG. 9, the relationship between the average value Nzq and the optimum Rlc + R3 provides a sufficiently good approximation in the range of 1.0 ≦ Nzq ≦ 2.9. The solid line shown in FIG. 9 represents the following formula (A).
Rlc + R3 = 169 nm × Nzq−81 nm (A)

From the viewpoint of realizing a liquid crystal display with a high contrast ratio in a wide viewing angle range, the thickness direction retardation R3 of the third birefringent layer 235 and the VA mode liquid crystal cell 230 during black display (no voltage applied to the liquid crystal layer). R3 + Rlc, which is the sum of the thickness direction retardation Rlc at the time), is most preferably the optimum value shown in Table 2 and FIG. It may be slightly deviated from the value. From the viewpoint of sufficiently achieving the operational effects of the liquid crystal display device of the present invention, an optimal value in the range of ± 50 nm is preferable.

Here, even when the Nz coefficient Nzq1 of the first λ / 4 plate 220 and the Nz coefficient Nzq2 of the second λ / 4 plate 240 are different from each other, each of Nzq1 and Nzq2 is equal to the average value Nzq. By using the optimal retardation value R3 of the third birefringent layer 235 calculated on the assumption, light leakage is cut off when observed from an oblique direction of azimuth 0 ° and pole 60 °, and excellent viewing angle characteristics Explain why it is possible to obtain.

FIG. 8A illustrates a configuration in which Nzq1 = Nzq2 = 2.0, R3 = −61 nm, and Rlc = 320 nm as described above. FIG. 8-2 shows the form of Nzq1 = 3.0, Nzq2 = 1.0, R3 = −61 nm, Rlc = 320 nm, and FIG. 8-3 shows the form of Nzq1 = 2.5, Nzq2 = 1.5, R3 = -61 nm, Rlc = 320 nm, FIG. 8-4 shows Nzq1 = 1.0, Nzq2 = 3.0, R3 = -61 nm, Rlc = 320 nm, FIG. 8-5 shows Nzq1 = 1.5, Nzq2 = 2.5, R3 = −61 nm, and Rlc = 320 nm. The average value Nzq of Nzq1 and Nzq2 is 2.0 as in FIG. As can be seen from the figure, in any form, the point P4 coincides with the extinction position E of the second polarizer 250, and these liquid crystal display devices are viewed from an oblique direction with an azimuth of 0 ° and a pole of 60 °. When observed, the light from the backlight can be blocked as in the case of observation from the front direction.

As collectively shown in FIG. 8-6, the slow axis Q1 of the first λ / 4 plate 220 can be smaller than 2.0 with reference to the case where Nzq1 is 2.0. The closer to the S2 axis side, the closer to 2.0, the closer to the S1 axis side. Then, the slow axis Q2 of the second λ / 4 plate 240 is closer to the S1 axis side when Nzq2 is larger than 2.0 with reference to the case where Nzq2 is 2.0. If it becomes smaller, it will be closer to the S2 axis side. Therefore, when Nzq1 is set to be smaller by ΔNzq with reference to the design of Nzq1 = Nzq2 = Nzq = 2.0, by setting Nzq2 to be larger by ΔNzq, the rotation center of P0 → P1 conversion and P3 → P4 It is possible to appropriately shift the rotation center of the conversion in the same direction and keep ∠P1P0P3 substantially the same. As a result, as in the case of Nzq1 = Nzq2 = Nzq = 2.0, the point P4 is shifted to the polarizer 250. It is possible to match the extinction position E. On the contrary, when Nzq1 is set larger by ΔNzq based on the design of Nzq1 = Nzq2 = Nzq = 2.0, the rotation center of P0 → P1 conversion is set by setting Nzq2 smaller by ΔNzq. Then, the rotation center of the P3 → P4 conversion is appropriately shifted in the same direction, so that the point P4 coincides with the extinction position E of the polarizer 250 as in the case of Nzq1 = Nzq2 = Nzq = 2.0. Is possible.

From the above, even when the Nz coefficient Nzq1 of the first λ / 4 plate 220 and the Nz coefficient Nzq2 of the second λ / 4 plate 240 are different from each other, each of Nzq1 and Nzq2 is equal to the average value Nzq. By using the optimal retardation value R3 of the third birefringent layer 235 calculated on the assumption, light leakage is cut off when observed from an oblique direction of azimuth 0 ° and pole 60 °, and excellent viewing angle characteristics Can be obtained. If the Nz coefficient Nzq1 and the Nz coefficient Nzq2 are handled separately, the design of the phase difference condition becomes very complicated. Therefore, it is very significant that the optimum phase difference value R3 can be calculated using the average value Nzq.

(Compensation principle of 2nd step)
First, the liquid crystal display device 200 of FIG. 6 that has finished the 1st step is divided into an azimuth (azimuth) that bisects the absorption axis azimuth 90 ° of the first polarizer 210 and the absorption axis azimuth 0 ° of the second polarizer 250. Consider the case of observation from a direction inclined at 60 ° at 45 °. As described above, in the 1st step, the liquid crystal display device 200 determines the thickness direction of the liquid crystal cell 230 according to the Nz coefficient Nzq1 of the first λ / 4 plate 220 and the Nz coefficient Nzq2 of the second λ / 4 plate 240. Optimum values of the retardation Rlc and the thickness direction retardation R3 of the third birefringent layer 235 are selected, and optical compensation is performed at an azimuth of 0 °. Under these conditions, when the light emitted from the backlight passes through the

polarizers

210 and 250, the

birefringent layers

220, 240 and 235, and the liquid crystal cell 230, the polarization state is illustrated on the S1-S2 plane of the Poincare sphere. 10 and so on.

First, the polarization state immediately after passing through the first polarizer 210 is located at the point P0 on the Poincare sphere and can be absorbed by the second polarizer 250 represented by the point E, that is, the second polarizer. It does not coincide with the extinction position (absorption axis direction) of 250. In the oblique direction of 45 ° azimuth, the first and

second polarizers

210 and 250 are not orthogonal to each other, suggesting that optical compensation is necessary. Then, by passing through the first λ / 4 plate 220, the polarization state at the point P0 is specified around the slow axis of the first λ / 4 plate 220 represented by the point Q1 on the Poincare sphere. Receiving the rotation conversion of the angle, the point P1 is reached. The rotation direction at this time is counterclockwise when viewed from the point Q1 toward the origin O.

Next, by passing through the third birefringent layer 235, the third birefringent layer 235 on the Poincare sphere is subjected to rotational conversion at a specific angle around the slow axis of the third birefringent layer 235 represented by the point R 3. P2 is reached. The rotation direction at this time is counterclockwise when viewed from the point R3 toward the origin O. Next, by passing through the VA mode liquid crystal cell 230, it undergoes rotational transformation at a specific angle around the slow axis of the liquid crystal cell 230 represented by the point L on the Poincare sphere, and reaches the point P3. The rotation direction at this time is counterclockwise when viewed from the point L toward the origin O. Finally, by passing through the second λ / 4 plate 240, it undergoes a rotational transformation of a specific angle around the slow axis of the second λ / 4 plate 240 represented by the point Q2, and reaches the point P4. This point P4 does not coincide with the extinction position E of the second polarizer 250. In this manner, the liquid crystal display device 200 of FIG. 6 cannot block light from the backlight when observed from an oblique direction of azimuth 45 ° and pole 60 °. That is, the liquid crystal display device 200 that has just finished the 1st step is not optically compensated at the azimuth of 45 °.

In FIG. 10, the positions of the points P1 to P4 are the Nz coefficient Nzq1 of the first λ / 4 plate 220, the Nz coefficient Nzq2 of the second λ / 4 plate 240, and the thickness direction position of the third birefringent layer 235. Although depending on the phase difference R3 and the thickness direction retardation Rlc of the liquid crystal cell 230, FIG. 10 shows an example of Nzq1 = Nzq = 2.0, R3 = −61 nm, and Rlc = 320 nm. In order to make the conversion of the polarization state easy to understand, the position of each point is roughly shown, and some are not strictly accurate. Further, for the sake of clarity, the arrows representing the locus are not shown for the conversion of the points P1 to P4.

Next, as shown in FIG. 11, the first polarizer (absorption axis orientation 90 °) 310, the second birefringent layer (fast axis orientation 0 °) 315, the first λ / 4 plate (slow Phase axis orientation 135 °) 320, third birefringent layer 335, VA mode liquid crystal cell 330, second λ / 4 plate (slow axis orientation 45 °) 340, and second polarizer (absorption axis orientation 0). Consider a circularly polarized VA mode liquid crystal display device 300 including a second type birefringent layer in which 350) 350 are stacked in this order. The second type birefringent layer is added to the configuration of FIG. 6 in order to perform optical compensation at an azimuth of 45 °. In FIG. 11, the arrows drawn on the first and

second polarizers

310 and 350 represent the directions of the absorption axes, and the arrows drawn on the first and second λ / 4

plates

320 and 340. Represents the direction of the slow axis, and the arrow drawn on the second type birefringent layer 315 represents the direction of the fast axis, and the VA mode liquid crystal cell 330 and the third type birefringent layer 335 The drawn ellipsoid represents the shape of the refractive index ellipsoid.

First, the polarization state when the circularly polarized VA mode liquid crystal display device 300 of FIG. 11 is observed from the front direction will be considered. Light emitted from a backlight (not shown in FIG. 11, but below the first polarizer 310) is emitted from each

polarizer

310, 350, each

birefringent layer

320, 340, 335, 315, liquid crystal. The polarization state for each transmission through the cell 330 is illustrated on the S1-S2 plane of the Poincare sphere as shown in FIG.

First, the polarization state immediately after passing through the first polarizer 310 is located at the point P0 on the Poincare sphere and can be absorbed by the second polarizer 350 represented by the point E, that is, the second polarizer. It coincides with the extinction position (absorption axis direction) of 350. Then, the second birefringent layer 315 is transmitted, but the polarization state at the point P0 is a specific angle around the fast axis of the second birefringent layer 315 represented by the point R2 on the Poincare sphere. The polarization state does not change from the point P0 even when subjected to the rotational transformation of. Next, by passing through the first λ / 4 plate 320, the polarization state at the point P0 is centered on the slow axis of the first λ / 4 plate 320 represented by the point Q1 on the Poincare sphere. A point P1 is reached after undergoing rotational transformation at a specific angle. The rotation direction at this time is counterclockwise when viewed from the point Q1 toward the origin O.

Next, the light passes through the third birefringent layer 335 and the VA mode liquid crystal cell 330. Since the third birefringent layer 335 and the VA mode liquid crystal cell 330 have zero phase difference in the front direction, the polarization state Does not change. Finally, by passing through the second λ / 4 plate 340, it undergoes rotational transformation at a specific angle around the slow axis of the second λ / 4 plate 340 represented by the point Q2, and reaches the point P2. . This point P2 coincides with the extinction position E of the second polarizer 350. In this way, when the liquid crystal display device 300 of FIG. 11 is observed from the front direction, the light from the backlight can be blocked and a good black display can be obtained in the same manner as the liquid crystal display device 100 of FIG. .

Next, let us consider the polarization state when the circularly polarized VA mode liquid crystal display device 300 of FIG. 11 is observed from a direction inclined by 60 ° at an azimuth of 45 °. Under this condition, the polarization state every time the light emitted from the backlight passes through the

polarizers

310 and 350, the

birefringent layers

320, 340, 335, and 315 and the liquid crystal cell 330 is illustrated on the S1-S2 plane of the Poincare sphere. Then, as shown in FIG.

First, the polarization state immediately after passing through the first polarizer 310 is located at the point P0 on the Poincare sphere and can be absorbed by the second polarizer 350 represented by the point E, that is, the second polarizer. It does not coincide with the extinction position (absorption axis direction) of 350. Then, by passing through the second type birefringent layer 315, the second type birefringent layer 315 represented by the point R2 on the Poincare sphere is subjected to rotational conversion at a specific angle around the fast axis, and the point P1 To reach. The rotation direction at this time is clockwise as viewed from the point R2 toward the origin O. Note that the point P1 exists on the southern hemisphere of the Poincare sphere (S3 <0), but is illustrated in the same manner as other points (points on the northern hemisphere or the equator) in FIG. . Next, by passing through the first λ / 4 plate 320, the polarization state at the point P1 is centered on the slow axis of the first λ / 4 plate 320 represented by the point Q1 on the Poincare sphere. A point P2 is reached after a rotational transformation of a specific angle. The rotation direction at this time is counterclockwise when viewed from the point Q1 toward the origin O.

Next, by passing through the third birefringent layer 335, the third birefringent layer 335 on the Poincare sphere is subjected to rotational conversion at a specific angle around the slow axis of the third birefringent layer 335 represented by the point R 3. P3 is reached. The rotation direction at this time is counterclockwise when viewed from the point R3 toward the origin O. Next, by passing through the VA mode liquid crystal cell 330, it undergoes rotational conversion at a specific angle around the slow axis of the liquid crystal cell 330 represented by the point L on the Poincare sphere, and reaches the point P4. The rotation direction at this time is counterclockwise when viewed from the point L toward the origin O. Finally, by passing through the second λ / 4 plate 340, the rotational transformation of a specific angle is performed around the slow axis of the second λ / 4 plate 340 represented by the point Q2, and the point P5 is reached. . This point P5 coincides with the extinction position E of the second polarizer 350. In this manner, the liquid crystal display device 300 of FIG. 11 can block light from the backlight even when observed from an oblique direction with an azimuth of 45 ° and a pole of 60 °, as in the case of observation from the front direction. it can.

Finally, the polarization state when the circularly polarized VA mode liquid crystal display device 300 of FIG. 11 is observed from a direction inclined by 60 ° at an azimuth of 0 ° will be considered. Under this condition, the polarization state every time the light emitted from the backlight passes through the

polarizers

310 and 350, the

birefringent layers

Next, by passing through the third birefringent layer 335, the third birefringent layer 335 on the Poincare sphere is subjected to rotational conversion at a specific angle around the slow axis of the third birefringent layer 335 represented by the point R 3. P2 is reached. The rotation direction at this time is counterclockwise when viewed from the point R3 toward the origin O. Next, by passing through the VA mode liquid crystal cell 330, it undergoes rotational conversion at a specific angle around the slow axis of the liquid crystal cell 330 represented by the point L on the Poincare sphere, and reaches the point P 3. The rotation direction at this time is counterclockwise when viewed from the point L toward the origin O. Finally, by passing through the second λ / 4 plate 340, it undergoes rotational transformation at a specific angle around the slow axis of the second λ / 4 plate 340 represented by the point Q2, and reaches the point P4. . This point P4 coincides with the extinction position E of the second polarizer 350. In this manner, the liquid crystal display device 300 of FIG. 11 can block light from the backlight even when observed from an oblique direction with an orientation of 0 ° and a pole of 60 °, as in the case of observation from the front direction. And a good black display can be obtained.

In this way, the liquid crystal display device 300 of FIG. 11 that has finished the 2nd step blocks light from the backlight in all of the front direction, the oblique direction with the azimuth of 0 °, and the oblique direction with the azimuth of 45 °. And a good black display can be obtained.

In FIGS. 12, 13, and 14, the positions of the points P1 to P5 are the Nz coefficient Nzq1 of the first λ / 4 plate 320, the Nz coefficient Nzq2 of the second λ / 4 plate 340, and the third type of birefringence. Depending on the thickness direction retardation R3 of the layer 335, the thickness direction retardation Rlc of the liquid crystal cell 330, and the Nz coefficient Nz2 and the in-plane retardation R2 of the second type birefringent layer 315, FIG. FIG. 14 shows an example in which Nzq1 = Nzq2 = 2.0, R3 = −61 nm, Rlc = 320 nm, Nz2 = −0.30, and R2 = 118 nm. In order to make the conversion of the polarization state easy to understand, the position of each point is roughly shown, and some are not strictly accurate. Also, for the sake of clarity, the arrows representing the locus are not shown for the conversion of the points P1 to P5.

As a result of investigation by the present inventor, the optimum of the birefringent layer 315 of the second type is determined according to the Nz coefficient Nzq1 of the first λ / 4 plate 320 and the Nz coefficient Nzq2 of the second λ / 4 plate 340. It was found that there are Nz coefficient Nz2 and phase difference value R2.

Here, by computer simulation, the Nz coefficient Nzq1 of the first λ / 4 plate 320, the Nz coefficient Nzq2 of the second λ / 4 plate 340, the Nz coefficient Nz2 of the second birefringent layer 315, and the in-plane The results of examining the relationship with the optimum value of the phase difference R2 are shown in Table 3, FIG. 15 and FIG. Further, for the sake of simplicity, it is assumed here that the Nz coefficient Nzq1 of the first λ / 4 plate 320 is the same as the Nz coefficient Nzq2 of the second λ / 4 plate 340 (Nzq1 = Nzq2 = Nzq). In the case where the Nz coefficient Nzq1 of the first λ / 4 plate 320 and the Nz coefficient Nzq2 of the second λ / 4 plate 340 are different from each other, each of Nzq1 and Nzq2 is equal to the average value Nzq. Therefore, the optimum values of the Nz coefficient Nz2 and the in-plane retardation R2 of the second type birefringent layer 315 can be calculated according to the Nzq, and the results in Table 3, FIG. 15 and FIG. 16 are referred to as they are. It has been found by the inventor that this can be done. The reason is the same as that described with reference to FIG. As can be seen from Table 3, FIG. 15 and FIG. 16, the relationship between the average value Nzq and the optimum Nz2 and R2 is generally not simple, but in the range of 1.0 ≦ Nzq ≦ 2.9, the following formula (B ) And (C) give a sufficiently good approximation. The solid line shown in FIGS. 15 and 16 represents this.
Nz2 = −0.63 × Nzq ² + 0.56 × Nzq + 0.40 (B)
R2 = 43 nm × Nzq ² −226 nm × Nzq + 370 nm (C)

From the viewpoint of realizing a liquid crystal display with a high contrast ratio in a wide viewing angle range, Nz2 and R2 of the second birefringent layer 315 are most preferably the optimum values shown in Table 3, FIG. 15 and FIG. However, as long as the contrast ratio at an oblique viewing angle is not greatly reduced, it may be slightly deviated from the optimum value. From the viewpoint of sufficiently achieving the effects of the liquid crystal display device of the present invention, Nz2 is preferably in the range of the optimum value ± 0.80. R2 is preferably within an optimum value ± 50 nm. If the Nz coefficient Nzq1 and the Nz coefficient Nzq2 are handled separately, the design of the phase difference condition becomes very complicated. Therefore, it is very significant that the optimum Nz2 and R2 of the second birefringent layer 315 can be calculated using the average value Nzq.

Further, according to Table 3 and FIG. 15, the optimum value of Nz2 is in the range of 0 <Nz2 <1 in the range of Nzq <1.40. The birefringent layer exhibiting an Nz coefficient within this range is a biaxial retardation film that satisfies the relationship of nx> nz> ny, and therefore does not correspond to the second type birefringent layer, and the second type birefringent layer. It is a more expensive film that is more difficult to manufacture than layers. Note that it is preferable that 1.40 ≦ Nzq is satisfied in that this point is solved. The inventor examined a method for realizing a liquid crystal display with a high contrast ratio in a wide viewing angle range at a lower cost and in a simple manner in a range of Nzq <1.40. As a result, in the range of Nzq <1.40, instead of the birefringent layer satisfying the optimum Nz2 and R2 shown in Table 3, FIG. 15 and FIG. 16, the second type of compound having Nz2 = 0 and R2 = 138 nm is used. It has been found that if the refractive layer is used, the same effect can be sufficiently obtained. For example, in each example of Nzq = 1.00, 1.10, 1.20, 1.30, when calculating the optimum R2 with Nz2 = 0 fixed, all are 138 nm regardless of Nzq. became. From the viewpoint of sufficiently exhibiting the operational effects of the liquid crystal display device of the present invention, −0.80 ≦ Nz2 ≦ 0 (range of optimal value −0.80 or more and 0 (= optimum value) or less) and 88 nm ≦ It is preferable to satisfy R2 ≦ 188 nm (optimum value of 138 nm ± 50 nm).

The inventor of the present invention also examined the form of (2) above, that is, the form in which the second type birefringent layer is disposed on both sides of the liquid crystal cell, and as a result, the Nz coefficient of the first and second λ / 4 plates. It has been found that there are optimum Nz coefficient Nz2 and retardation value R2 of the first and second birefringent layers according to the average value Nzq.

Here, by computer simulation, the Nz coefficient Nzq1 of the first λ / 4 plate, the Nz coefficient Nzq2 of the second λ / 4 plate, and the Nz coefficient Nz2 of the first and second second-type birefringent layers. The results of examining the relationship with the optimum value of the in-plane retardation R2 are shown in Table 4, FIG. 17 and FIG. Further, for the sake of simplicity, here, the computer simulation is performed assuming that the Nz coefficient Nzq1 of the first λ / 4 plate and the Nz coefficient Nzq2 of the second λ / 4 plate are the same (Nzq1 = Nzq2 = Nzq). However, even when the Nz coefficient Nzq1 of the first λ / 4 plate and the Nz coefficient Nzq2 of the second λ / 4 plate are different from each other, it is considered that each of Nzq1 and Nzq2 is equal to the average value Nzq. According to the Nzq, the optimum values of the Nz coefficient Nz2 and the in-plane retardation R2 of the first and second birefringent layers of the second type can be calculated, and the results of Table 4, FIG. 17 and FIG. It has been found by the inventor that reference can be made. The reason is the same as that described with reference to FIG. As can be seen from Table 4, FIG. 17 and FIG. 18, the relationship between the average value Nzq and the optimum Nz2 and R2 is generally not simple, but in the range of 1.0 ≦ Nzq ≦ 2.9, the following formula (D ) And (E) give a sufficiently good approximation. The solid line shown in FIGS. 17 and 18 represents this.
Nz2 = −0.87 × Nzq ² + 2.15 × Nzq−0.76 (D)
R2 = 25 nm × Nzq ² −159 nm × Nzq + 311 nm (E)

From the viewpoint of realizing a liquid crystal display with a high contrast ratio in a wide viewing angle range, Nz2 and R2 of each of the first and second birefringent layers of the second type are optimum values shown in Table 4, FIG. 17 and FIG. Although it is most preferable, it may be slightly deviated from the optimum value as long as the contrast ratio at an oblique viewing angle is not greatly reduced. From the viewpoint of sufficiently achieving the effects of the liquid crystal display device of the present invention, Nz2 is preferably in the range of the optimum value ± 0.80. R2 is preferably in the range of an optimum value ± 40 nm. It should be noted that Nz2 of the first second birefringent layer and Nz2 of the second second birefringent layer are independent of each other as long as the difference between them is less than 0.1. Can be met. Further, R2 of the first second-type birefringent layer and R2 of the second second-type birefringent layer satisfy the above ranges independently of each other as long as the difference between them is less than 20 nm. be able to. In addition, if the Nz coefficient Nzq1 and the Nz coefficient Nzq2 are handled separately, the design of the phase difference condition becomes very complicated. Therefore, it is very significant that the optimum Nz2 and R2 of the first and second birefringent layers can be calculated using the average value Nzq.

Further, according to Table 4 and FIG. 17, the optimum value of Nz2 is in the range of 0 <Nz2 <1 in the range of Nzq <2.00. The birefringent layer exhibiting an Nz coefficient within this range is a biaxial retardation film that satisfies the relationship of nx> nz> ny, and therefore does not correspond to the second type birefringent layer, and the second type birefringent layer. It is a more expensive film that is more difficult to manufacture than layers. Note that it is preferable that 2.00 ≦ Nzq is satisfied in that this point is solved. The inventor studied a method for realizing a liquid crystal display with a high contrast ratio in a wide viewing angle range at a lower cost and in a simple manner in a range of Nzq <2.00. As a result, when Nzq <2.00, a second type birefringent layer with Nz2 = 0 is used instead of the birefringent layer satisfying the optimum Nz2 and R2 shown in Table 4, FIG. 17 and FIG. It has been found that the viewing angle characteristics can be effectively improved within the range where the biaxial retardation film controlled to nx> nz> ny (0 <Nz <1) is not used. The optimum R2 corresponding to each Nzq is shown in Table 4 and FIG. 19 as R2 ′. From the viewpoint of sufficiently achieving the operational effects of the liquid crystal display device of the present invention, −0.80 ≦ Nz2 ≦ 0 (range of optimal value −0.80 or more and 0 (= optimum value) or less) and 5 nm ≦ It is preferable to satisfy R2 ′ ≦ 133 nm (optimum value ± 40 nm range).

The liquid crystal display device of the present invention and typical examples of preferred embodiments of the liquid crystal display device of the present invention are shown below.

(Appendix 1)
When the birefringent layer satisfying the relationship of nx> ny ≧ nz is defined as the first type birefringent layer, the first polarizer, the first λ / 4 whose in-plane retardation is adjusted to λ / 4 A liquid crystal cell having a plate, a pair of substrates facing each other and a liquid crystal layer sandwiched between the pair of substrates, an Nz coefficient different from the first λ / 4, and an in-plane retardation of λ / 4 An adjusted second λ / 4 plate and a second polarizer are provided in this order, and the first and second λ / 4 plates are first-type birefringent layers, and the second polarization When the orientation of the absorption axis of the child is defined as 0 °, the in-plane slow axis of the second λ / 4 plate forms an angle of about 45 °, and the in-plane retardation of the first λ / 4 plate The phase axis forms an angle of about 135 °, the absorption axis of the first polarizer forms an angle of about 90 °, and the liquid crystal molecules in the liquid crystal layer are aligned substantially perpendicularly to the substrate surface. Change to tilted orientation The liquid crystal layer is a domain in which liquid crystal molecules are tilted in the direction of 12.5 ° to 32.5 °, and the liquid crystal molecules are tilted in the direction of 102.5 ° to 122.5 °. A liquid crystal display device having a domain in which liquid crystal molecules are tilted and oriented in a 192.5 ° to 212.5 ° direction, and a domain in which liquid crystal molecules are tilted and oriented in a 282.5 ° to 302.5 ° direction.

(Appendix 2)
The Nz coefficient of one of the first λ / 4 plate and the second λ / 4 plate is 2 or more, and the first λ / 4 plate and the second λ / 4 plate 2. The liquid crystal display device according to appendix 1, wherein the other Nz coefficient is 1 or more and less than 2.

(Appendix 3)
The liquid crystal display device according to

appendix

1 or 2, wherein the one having the larger Nz coefficient among the first and second λ / 4 plates is disposed on the back side of the liquid crystal cell.

(Appendix 4)
The Nz coefficient of the first λ / 4 plate is larger than the Nz coefficient of the second λ / 4 plate, and further includes a surface treatment layer on the observation surface side of the second polarizer. The liquid crystal display device according to any one of the above.

(Appendix 5)
When a birefringent layer satisfying the relationship of nx <ny ≦ nz is defined as a second type birefringent layer, a second type birefringent layer is interposed between the first λ / 4 plate and the first polarizer. The liquid crystal display device according to any one of supplementary notes 1 to 4, further comprising a refractive layer, wherein an in-plane fast axis of the second birefringent layer is substantially orthogonal to an absorption axis of the first polarizer. .

(Appendix 6)
The liquid crystal display device according to appendix 5, wherein the second birefringent layer is disposed on the back side of the liquid crystal cell.

(Appendix 7)
The Nz coefficient of the first λ / 4 plate is larger than the Nz coefficient of the second λ / 4 plate, and the second birefringent layer and the first λ / 4 plate are The liquid crystal display device according to appendix 6, which is disposed on the back side of the liquid crystal cell.

(Appendix 8)
When a birefringent layer satisfying the relationship of nx≈ny ≧ nz is defined as a third type birefringent layer, it is between the first λ / 4 plate and the liquid crystal cell, and between the liquid crystal cell and the second liquid crystal cell. The liquid crystal display device according to any one of appendices 5 to 7, further comprising at least one third-type birefringent layer on at least one of the two λ / 4 plates.

(Appendix 9)
The liquid crystal display device according to appendix 8, wherein the at least one third-type birefringent layer is disposed on the back side of the liquid crystal cell.

(Appendix 10)
The Nz coefficient of the first λ / 4 plate is greater than the Nz coefficient of the second λ / 4 plate, the second birefringent layer, the first λ / 4 plate, and the at least The liquid crystal display device according to appendix 8, wherein the third birefringent layer of one layer is disposed on the back side of the liquid crystal cell.

(Appendix 11)
The average value of the Nz coefficients of the first and second λ / 4 plates is Nzq, the thickness direction retardation of the liquid crystal cell during black display is Rlc, and the thickness direction position of the at least one third birefringent layer 11. The liquid crystal display device according to any one of supplementary notes 8 to 10, which satisfies the following formulas (1) to (3) when the sum of the phase differences is defined as R3.
1.0 ≦ Nzq ≦ 2.9 (1)
(169 nm × Nzq−81 nm) −50 nm ≦ Rlc + R3 (2)
Rlc + R3 ≦ (169 nm × Nzq−81 nm) +50 nm (3)

(Appendix 12)
Item 12. The liquid crystal display device according to item 11, wherein when the Nz coefficient of the second birefringent layer is defined as Nz2 and the in-plane retardation is defined as R2, the following formulas (4) to (7) are satisfied.
(−0.63 × Nzq ² + 0.56 × Nzq + 0.40) −0.80 ≦ Nz2 (4)
Nz2 ≦ (−0.63 × Nzq ² + 0.56 × Nzq + 0.40) +0.80 (5)
(43 nm × Nzq ² −226 nm × Nzq + 370 nm) −50 nm ≦ R2 (6)
R2 ≦ (43 nm × Nzq ² −226 nm × Nzq + 370 nm) +50 nm (7)

(Appendix 13)
The liquid crystal display device according to appendix 12, wherein 1.40 ≦ Nzq is satisfied.

(Appendix 14)
When the average value of the Nz coefficients of the first and second λ / 4 plates is defined as Nzq, the Nz coefficient of the second birefringent layer is defined as Nz2, and the in-plane retardation is defined as R2, Nzq <1. 12. The liquid crystal display device according to any one of appendices 8 to 11, which satisfies 40, satisfies −0.80 ≦ Nz2 ≦ 0, and satisfies 88 nm ≦ R2 ≦ 188 nm.

(Appendix 15)
When a birefringent layer satisfying the relationship of nx≈ny ≧ nz is defined as a third type birefringent layer, it is between the first λ / 4 plate and the liquid crystal cell, and between the liquid crystal cell and the second liquid crystal cell. 8. The liquid crystal display device according to any one of appendices 5 to 7, wherein the third birefringent layer is not provided between the second λ / 4 plate.

(Appendix 16)
When the average value of the Nz coefficients of the first and second λ / 4 plates is defined as Nzq, and the thickness direction retardation at the time of black display of the liquid crystal cell is defined as Rlc, the following formulas (1), (8) and Item 15. The liquid crystal display device according to appendix 15, which satisfies (9).
1.0 ≦ Nzq ≦ 2.9 (1)
(169 nm × Nzq−81 nm) −50 nm ≦ Rlc (8)
Rlc ≦ (169 nm × Nzq−81 nm) +50 nm (9)

(Appendix 17)
Item 17. The liquid crystal display device according to item 16, wherein when the Nz coefficient of the second birefringent layer is defined as Nz2 and the in-plane retardation is defined as R2, the following formulas (4) to (7) are satisfied.
(−0.63 × Nzq ² + 0.56 × Nzq + 0.40) −0.80 ≦ Nz2 (4)
Nz2 ≦ (−0.63 × Nzq ² + 0.56 × Nzq + 0.40) +0.80 (5)
(43 nm × Nzq ² −226 nm × Nzq + 370 nm) −50 nm ≦ R2 (6)
R2 ≦ (43 nm × Nzq ² −226 nm × Nzq + 370 nm) +50 nm (7)

(Appendix 18)
18. The liquid crystal display device according to appendix 17, wherein 1.40 ≦ Nzq is satisfied.

(Appendix 19)
When the average value of the Nz coefficients of the first and second λ / 4 plates is defined as Nzq, the Nz coefficient of the second birefringent layer is defined as Nz2, and the in-plane retardation is defined as R2, Nzq <1. 18. The liquid crystal display device according to appendix 15 or 16, wherein 40 is satisfied, −0.80 ≦ Nz2 ≦ 0 is satisfied, and 88 nm ≦ R2 ≦ 188 nm is satisfied.

(Appendix 20)
15. The liquid crystal display device according to any one of appendices 8 to 14, wherein Nzq <2.00 when an average value of Nz coefficients of the first and second λ / 4 plates is defined as Nzq.

(Appendix 21)
20. The liquid crystal display device according to any one of supplementary notes 15 to 19, wherein an average value of Nz coefficients of the first and second λ / 4 plates is defined as Nzq, and satisfies 2.00 ≦ Nzq.

(Appendix 22)
When the birefringent layer satisfying the relationship of nx <ny ≦ nz is defined as the second birefringent layer, the first second type between the first λ / 4 plate and the first polarizer. And a second birefringent layer of the second kind between the second λ / 4 plate and the second polarizer, and the first birefringent layer of the second kind. The in-plane fast axis of the second polarizer is substantially orthogonal to the absorption axis of the first polarizer, and the in-plane fast axis of the second second-type birefringent layer is that of the second polarizer. 5. The liquid crystal display device according to any one of appendices 1 to 4, which is substantially orthogonal to the absorption axis.

(Appendix 23)
The Nz coefficient and the in-plane retardation of the second second-type birefringent layer are substantially the same as the Nz coefficient and the in-plane retardation of the first second-type birefringent layer, respectively. Liquid crystal display device.

(Appendix 24)
When a birefringent layer satisfying the relationship of nx≈ny ≧ nz is defined as a third type birefringent layer, it is between the first λ / 4 plate and the liquid crystal cell, and between the liquid crystal cell and the second liquid crystal cell. 24. The liquid crystal display device according to appendix 22 or 23, further comprising at least one third-type birefringent layer on at least one of the two λ / 4 plates.

(Appendix 25)
25. The liquid crystal display device according to appendix 24, wherein the at least one third-type birefringent layer is disposed on the back side of the liquid crystal cell.

(Appendix 26)
The Nz coefficient of the first λ / 4 plate is larger than the Nz coefficient of the second λ / 4 plate, and the first λ / 4 plate and the at least one third-type birefringent layer 26. The liquid crystal display device according to appendix 25, which is disposed on the back side of the liquid crystal cell.

(Appendix 27)
The average value of the Nz coefficients of the first and second λ / 4 plates is Nzq, the thickness direction retardation of the liquid crystal cell during black display is Rlc, and the thickness direction position of the at least one third birefringent layer 27. The liquid crystal display device according to any one of supplementary notes 24 to 26, which satisfies the following formulas (1) to (3) when the sum of the phase differences is defined as R3.
1.0 ≦ Nzq ≦ 2.9 (1)
(169 nm × Nzq−81 nm) −50 nm ≦ Rlc + R3 (2)
Rlc + R3 ≦ (169 nm × Nzq−81 nm) +50 nm (3)

(Appendix 28)
The Nz coefficient and the in-plane retardation of the second second birefringent layer are substantially the same as the Nz coefficient and the in-plane retardation of the first second birefringent layer, respectively. 28. The liquid crystal display device according to supplementary note 27, wherein Nz coefficient of the second birefringent layer of the second type is defined as Nz2 and in-plane retardation is defined as R2, which satisfies the following expressions (10) to (13).
(−0.87 × Nzq ² + 2.15 × Nzq−0.76) −0.80 ≦ Nz2 (10)
Nz2 ≦ (−0.87 × Nzq ² + 2.15 × Nzq−0.76) +0.80 (11)
(25 nm × Nzq ² −159 nm × Nzq + 311 nm) −40 nm ≦ R2 (12)
R2 ≦ (25 nm × Nzq ² −159 nm × Nzq + 311 nm) +40 nm (13)

(Appendix 29)
The Nz coefficient and the in-plane retardation of the second second birefringent layer are substantially the same as the Nz coefficient and the in-plane retardation of the first second birefringent layer, respectively. When the average value of the Nz coefficient of the second λ / 4 plate is defined as Nzq, the Nz coefficient of the first and second birefringent layers of the second type is defined as Nz2, and the in-plane retardation is defined as R2, Nzq 28. The liquid crystal display device according to any one of appendices 24 to 27, which satisfies <2.00, satisfies −0.80 ≦ Nz2 ≦ 0, and satisfies 5 nm ≦ R2 ≦ 133 nm.

(Appendix 30)
When a birefringent layer satisfying the relationship of nx≈ny ≧ nz is defined as a third type birefringent layer, it is between the first λ / 4 plate and the liquid crystal cell, and between the liquid crystal cell and the second liquid crystal cell. 24. The liquid crystal display device according to appendix 22 or 23, wherein the third birefringent layer is not provided between the two λ / 4 plates.

(Appendix 31)
When the average value of the Nz coefficients of the first and second λ / 4 plates is defined as Nzq, and the thickness direction retardation of the liquid crystal cell during black display is defined as Rlc, the following formulas (1), (8) and The liquid crystal display device according to appendix 30, which satisfies (9).
1.0 ≦ Nzq ≦ 2.9 (1)
(169 nm × Nzq−81 nm) −50 nm ≦ Rlc (8)
Rlc ≦ (169 nm × Nzq−81 nm) +50 nm (9)

(Appendix 32)
The Nz coefficient and the in-plane retardation of the second second birefringent layer are substantially the same as the Nz coefficient and the in-plane retardation of the first second birefringent layer, respectively. 32. The liquid crystal display device according to appendix 31, which satisfies the following formulas (10) to (13) when the Nz coefficient of the second birefringent layer of the second type is defined as Nz2 and the in-plane retardation is defined as R2.
(−0.87 × Nzq ² + 2.15 × Nzq−0.76) −0.80 ≦ Nz2 (10)
Nz2 ≦ (−0.87 × Nzq ² + 2.15 × Nzq−0.76) +0.80 (11)
(25 nm × Nzq ² −159 nm × Nzq + 311 nm) −40 nm ≦ R2 (12)
R2 ≦ (25 nm × Nzq ² −159 nm × Nzq + 311 nm) +40 nm (13)

(Appendix 33)
The Nz coefficient and the in-plane retardation of the second second birefringent layer are substantially the same as the Nz coefficient and the in-plane retardation of the first second birefringent layer, respectively. When the average value of the Nz coefficient of the second λ / 4 plate is defined as Nzq, the Nz coefficient of the first and second birefringent layers of the second type is defined as Nz2, and the in-plane retardation is defined as R2, Nzq 32. The liquid crystal display device according to appendix 30 or 31, wherein <2.00, −0.80 ≦ Nz2 ≦ 0, and 5 nm ≦ R2 ≦ 133 nm are satisfied.

(Appendix 34)
The liquid crystal display device according to any one of appendices 24 to 29, wherein Nzq <2.00 when an average value of Nz coefficients of the first and second λ / 4 plates is defined as Nzq.

(Appendix 35)
The liquid crystal display device according to any one of supplementary notes 30 to 33, wherein an average value of Nz coefficients of the first and second λ / 4 plates is defined as Nzq, wherein 2.00 ≦ Nzq is satisfied.

Each form mentioned above may be combined suitably in the range which does not deviate from the gist of the present invention. Furthermore, a form in which two or more preferred forms are combined with each other is also one of the preferred forms.

According to the present invention, it is possible to provide a circularly polarized VA mode liquid crystal display device that can reduce costs, has excellent productivity, and has an excellent gradation viewing angle from an intermediate gradation at a 45 ° azimuth to a high gradation. it can. This liquid crystal display device can be suitably used for a display device such as an outdoor signage display.

It is a diagram illustrating an azimuth angle φ and polar angle θ with respect to the direction A ₀ of the inclined orientation of the liquid crystal molecules. It is a perspective exploded view which shows the structure of the circularly polarized light VA mode liquid crystal display device which consists of the simplest structure which does not contain a 2nd type and a 3rd type birefringent layer. (A) is a schematic diagram (upper) of the slow axis of the first λ / 4 plate and the slow axis of the second λ / 4 plate orthogonal to each other in the front direction when viewed from the front direction, and the orientation It is a schematic diagram (lower) when it sees from the diagonal direction of 0 degree. (B) is a schematic diagram (top) of the slow axis of the first λ / 4 plate and the slow axis of the second λ / 4 plate orthogonal to each other in the front direction when viewed from the front direction, and the orientation It is a schematic diagram (lower) when it sees from a 45 degrees diagonal direction. (C) is a schematic diagram (upper) when viewed from the front direction and an oblique direction of 45 ° azimuth with respect to the absorption axis of the first polarizer and the absorption axis of the second polarizer orthogonal to each other in the front direction. It is a schematic diagram (bottom) when viewed. The circularly polarized VA mode liquid crystal display device of FIG. 2 is shown projected on the S1-S2 plane of the Poincare sphere when the polarization state of the transmitted light changes as it passes through each member when viewed from the front. FIG. With respect to the circularly polarized VA mode liquid crystal display device of FIG. 2, when the polarization state of transmitted light changes as it passes through each member when observed from an oblique direction with an azimuth of 0 ° and a pole of 60 °, S1 of the Poincare sphere It is the figure projected and shown on S2 plane. It is a perspective exploded view which shows the structure of the circularly polarized light VA mode liquid crystal display device containing a 3rd type birefringent layer. With respect to the circularly polarized VA mode liquid crystal display device (Nzq1 = Nzq2 = 2.0, R3 = −61 nm, Rlc = 320 nm form) of FIG. 6, the polarization state of transmitted light passes through each member when observed from the front direction. It is the figure which projected and showed on a S1-S2 plane of a Poincare sphere how it changed every time. Transmitted light when the circularly polarized VA mode liquid crystal display device of FIG. 6 (Nzq1 = Nzq2 = 2.0, R3 = −61 nm, Rlc = 320 nm) is observed from an oblique direction with 0 ° orientation and 60 ° pole. It is the figure which projected and showed on a S1-S2 plane of a Poincare sphere that a polarization state of each changes, whenever it passes each member. When the circularly polarized VA mode liquid crystal display device of FIG. 6 (Nzq1 = 3.0, Nzq2 = 1.0, R3 = −61 nm, Rlc = 320 nm) is observed from an oblique direction with an orientation of 0 ° and a pole of 60 °. FIG. 6 is a diagram showing a state in which the polarization state of transmitted light changes each time it passes through each member, projected onto the S1-S2 plane of the Poincare sphere. When the circularly polarized VA mode liquid crystal display device of FIG. 6 (Nzq1 = 2.5, Nzq2 = 1.5, R3 = −61 nm, Rlc = 320 nm) is observed from an oblique direction with an orientation of 0 ° and a pole of 60 °. FIG. 6 is a diagram showing a state in which the polarization state of transmitted light changes each time it passes through each member, projected onto the S1-S2 plane of the Poincare sphere. When the circularly polarized VA mode liquid crystal display device of FIG. 6 (Nzq1 = 1.0, Nzq2 = 3.0, R3 = −61 nm, Rlc = 320 nm) is observed from an oblique direction with an azimuth of 0 ° and a pole of 60 °. FIG. 6 is a diagram showing a state in which the polarization state of transmitted light changes each time it passes through each member, projected onto the S1-S2 plane of the Poincare sphere. When the circularly polarized VA mode liquid crystal display device of FIG. 6 (Nzq1 = 1.5, Nzq2 = 2.5, R3 = −61 nm, Rlc = 320 nm) is observed from an oblique direction with an azimuth of 0 ° and a pole of 60 °. FIG. 6 is a diagram showing a state in which the polarization state of transmitted light changes each time it passes through each member, projected onto the S1-S2 plane of the Poincare sphere. For the circularly polarized VA mode liquid crystal display device of FIG. 6, the slow axes of the first and second λ / 4 plates change depending on the Nz coefficient when observed from an oblique direction with an orientation of 0 ° and a pole of 60 °. It is the figure which projected and showed on the S1-S2 plane of a Poincare sphere. Regarding the circularly polarized VA mode liquid crystal display device of FIG. 6, the relationship between the average value Nzq of the Nz coefficients of the first and second λ / 4 plates and the optimum value of the thickness direction retardation R3 of the third birefringent layer It is the graph which showed. With respect to the circularly polarized VA mode liquid crystal display device of FIG. 6, when the polarization state of transmitted light changes when passing through each member when observed from an oblique direction of azimuth 45 ° and pole 60 °, S1 of the Poincare sphere It is the figure projected and shown on S2 plane. It is a perspective exploded view which shows the structure of the circularly polarized light VA mode liquid crystal display device containing a 2nd type and a 3rd type birefringent layer. When the circularly polarized VA mode liquid crystal display device of FIG. 11 (Nzq1 = Nzq2 = 2.0, R3 = −61 nm, Rlc = 320 nm, Nz2 = −0.30, R2 = 118 nm) is observed from the front direction. FIG. 7 is a diagram showing a state in which the polarization state of transmitted light changes each time it passes through each member, projected onto the S1-S2 plane of the Poincare sphere. The circularly polarized VA mode liquid crystal display device of FIG. 11 (Nzq1 = Nzq2 = 2.0, R3 = −61 nm, Rlc = 320 nm, Nz2 = −0.30, R2 = 118 nm form) has an azimuth of 45 ° and a pole of 60 °. It is the figure which projected and showed on a S1-S2 plane of a Poincare sphere that the polarization state of the transmitted light would change every time it passed through each member when observed from the oblique direction. For the circularly polarized VA mode liquid crystal display device of FIG. 11 (in the form of Nzq1 = Nzq2 = 2.0, R3 = −61 nm, Rlc = 320 nm, Nz2 = −0.30, R2 = 118 nm), the azimuth is 0 ° and the pole is 60 °. It is the figure which projected and showed on a S1-S2 plane of a Poincare sphere that the polarization state of the transmitted light would change every time it passed through each member when observed from the oblique direction. 11 shows the relationship between the average value Nzq of the Nz coefficient of the first and second λ / 4 plates and the optimum value of the Nz coefficient Nz2 of the second birefringent layer for the circularly polarized VA mode liquid crystal display device of FIG. It is a graph. Regarding the circularly polarized VA mode liquid crystal display device of FIG. 11, the relationship between the average value Nzq of the Nz coefficient of the first and second λ / 4 plates and the optimum value of the in-plane retardation R2 of the second birefringent layer. It is the graph which showed. It is the graph which showed the relationship between the average value Nzq of the Nz coefficient of a 1st and 2nd (lambda) / 4 board, and the optimal value of Nz coefficient Nz2 of a 1st and 2nd 2nd type birefringent layer. It is the graph which showed the relationship between the average value Nzq of the Nz coefficient of the 1st and 2nd (lambda) / 4 board, and the optimal value of the in-plane phase difference R2 of a 1st and 2nd 2nd type birefringent layer. . The average value Nzq of the Nz coefficient of the first and second λ / 4 plates when the second birefringent layer of Nz2 = 0 is used in the range of Nzq <2.00, and the first and second It is the graph which showed the relationship with the optimal value of in-plane phase difference R2 of the 2nd kind of birefringent layer. It is a perspective exploded view showing the configuration of a circularly polarized VA mode liquid crystal display device that includes a second type of birefringent layer and does not include a third type of birefringent layer. 4 is a schematic diagram illustrating an example of domains formed in the liquid crystal cell of Example 1. FIG. 4 is a schematic diagram illustrating an example of domains formed in the liquid crystal cell of Example 1. FIG. 4 is a schematic diagram illustrating an example of domains formed in the liquid crystal cell of Example 1. FIG. It is a perspective exploded view showing a configuration of a circularly polarized VA mode liquid crystal display device including two second-type birefringent layers. It is a perspective exploded view showing the configuration of a circularly polarized VA mode liquid crystal display device including one second type birefringent layer. It is a perspective exploded view showing a configuration of a circularly polarized VA mode liquid crystal display device including two second-type birefringent layers. 4 is a graph showing a gamma curve obtained by measuring the liquid crystal display device of Example 1. It is a graph which shows the gamma curve obtained by measuring the liquid crystal display device of Example 2. 6 is a graph showing a gamma curve obtained by measuring the liquid crystal display device of Example 3. It is a graph which shows the gamma curve obtained by measuring the liquid crystal display device of Example 4. 10 is a graph showing a gamma curve obtained by measuring the liquid crystal display device of Example 5. It is a graph which shows the gamma curve obtained by measuring the liquid crystal display device of Example 6. It is a graph which shows the gamma curve obtained by measuring the liquid crystal display device of Example 7. 6 is a graph showing a gamma curve obtained by measuring the liquid crystal display device of Comparative Example 1. 10 is a graph showing a gamma curve obtained by measuring the liquid crystal display device of Comparative Example 2. It is a graph which shows the gamma curve obtained by measuring the liquid crystal display device of the comparative example 3. (A) shows the enlarged schematic diagram of the cross section of a moth-eye film, (b) is explanatory drawing which shows the change of the refractive index in the interface of a moth-eye film and an air layer. FIG. 12 is an exploded perspective view showing a configuration in which a moth-eye film is added to the circularly polarized VA mode liquid crystal display device of FIG. 11.

(Birefringent layer)
The birefringent layer used in the present invention is not particularly limited in terms of materials and optical performance, and includes, for example, a stretched polymer film, a fixed liquid crystal material orientation, a thin plate composed of an inorganic material, and the like. Can be used. The method for forming the birefringent layer is not particularly limited, and the most productive method can be appropriately selected according to the design conditions. In the case of a birefringent layer formed from a polymer film, for example, a solvent cast method, a melt extrusion method, or the like can be used. A method of simultaneously forming a plurality of birefringent layers by a coextrusion method may be used. As long as the desired phase difference is expressed, the film may be unstretched or may be stretched. The stretching method is not particularly limited, and stretching is performed under the action of the shrinkage force of the heat-shrinkable film, in addition to the inter-roll tensile stretching method, the inter-roll compression stretching method, the tenter transverse uniaxial stretching method, the oblique stretching method, the longitudinal and transverse biaxial stretching method. A special stretching method or the like can be used. In the case of a birefringent layer formed of a liquid crystalline material, for example, a method of applying a liquid crystalline material on an orientation-treated base film and fixing the orientation can be used. As long as a desired phase difference is developed, a method of not performing a special orientation treatment on the base film, a method of removing the base film from the base film and transferring it to another film may be used. . Further, a method that does not fix the alignment of the liquid crystal material may be used. In the case of a birefringent layer formed from a non-liquid crystalline material, the same formation method as that for a birefringent layer formed from a liquid crystalline material may be used. The first and second λ / 4 plates are laminated at a relative angle of approximately 45 ° with the polarizer to form a circularly polarizing plate, so that they are stretched obliquely with respect to the flow direction of the roll film. It is preferable to use an oblique stretching method for orientation. In particular, for the λ / 4 plate having a smaller Nz coefficient, it is preferable to adopt the oblique stretching method. On the other hand, for the λ / 4 plate having a larger Nz coefficient, it is preferable to adopt the oblique stretching method if possible, but if it cannot be adopted, the above-mentioned other methods can be appropriately selected. Hereinafter, more specific description will be given for each type of birefringent layer.

(First birefringent layer: first and second λ / 4 plates)
As the first kind of birefringent layer, a film obtained by stretching a film containing a material having a positive intrinsic birefringence as a component can be appropriately used. Examples of the material having a positive intrinsic birefringence include polycarbonate, polysulfone, polyethersulfone, polyethylene terephthalate, polyethylene, polyvinyl alcohol, norbornene, triacetylcellulose, and diacylcellulose.

(Second birefringent layer)
The second kind of birefringent layer is a stretched film containing a material having a negative intrinsic birefringence as a component, and a film containing a material having a positive intrinsic birefringence as a component is acting on the shrinkage force of the heat shrinkable film. What extended | stretched and processed below can be used suitably. Among these, from the viewpoint of simplifying the production method, a film obtained by stretching a film containing a material having a negative intrinsic birefringence as a component is preferable. Examples of the material having a negative intrinsic birefringence include a resin composition containing an acrylic resin and a styrene resin, polystyrene, polyvinyl naphthalene, polyvinyl biphenyl, polyvinyl pyridine, polymethyl methacrylate, polymethyl acrylate, and an N-substituted maleimide copolymer. , Polycarbonate having a fluorene skeleton, and triacetyl cellulose (particularly those having a low degree of acetylation). Among these, from the viewpoint of optical properties, productivity, and heat resistance, a resin composition containing an acrylic resin and a styrene resin is preferable. About the manufacturing method of the film which contains such a resin composition as a component, patent document 9 has an indication, for example.

(Third kind of birefringent layer)
As the third birefringent layer, a film containing a material having a positive intrinsic birefringence as a component is subjected to a longitudinal and lateral biaxial stretching process, and a liquid crystal material such as a cholesteric (chiral nematic) liquid crystal or a discotic liquid crystal is applied. In addition, a material coated with a non-liquid crystalline material containing polyimide, polyamide, or the like can be used as appropriate.

(Polarizer)
As the polarizer, for example, a material obtained by adsorbing and orienting an anisotropic material such as an iodine complex having dichroism on a polyvinyl alcohol (PVA) film can be appropriately used.

(Liquid crystal cell)
The liquid crystal cell is an alignment-divided VA mode in which the tilt direction of liquid crystal molecules is divided into a plurality of pixels in a pixel, so-called MVA mode (Multi-domain VA mode), and the liquid crystal molecules in the liquid crystal layer are formed on the substrate. Black display is performed by orienting perpendicularly to the surface. In addition to the TFT method (active matrix method), the liquid crystal cell may be driven by a simple matrix method (passive matrix method), a plasma address method, or the like. As a configuration of the liquid crystal cell, for example, a liquid crystal layer is sandwiched between a pair of substrates on which electrodes are formed, and display is performed by applying a voltage between the electrodes.

(Surface treatment layer)
As the surface treatment layer, there are mainly the following three layers. The first is a hard coat layer for preventing scratches, the second is an AG (Anti Glare) layer for imparting antiglare properties, and the third is an antireflection layer for reducing surface reflection. Examples of the antireflection layer include an AR (Anti Reflection) layer having a low reflectance, an LR (Low Reflection) layer having a higher reflectance than the AR layer, and a moth-eye layer having a very low reflectance. In addition, a surface treatment layer is normally formed on a transparent protective film (for example, TAC film). A plurality of surface treatment layers may be laminated. Examples of such a laminate include an AGLR layer in which an AG layer is laminated on an LR layer, an AGAR layer in which an AG layer is laminated on an AR layer, and the like. Is mentioned. The observation surface side circularly polarizing plate is preferably a roll-to-roller using a protective film with a surface treatment layer, a polarizer, and one having a smaller Nz coefficient among the first and second λ / 4 plates.・ Made by roll technology.

(Measurement method of R, Rth, Nz coefficient, nx, ny, nz)
The measurement was performed using a dual retarder rotation type polarimeter (manufactured by Axometrics, trade name: Axo-scan). The in-plane retardation R was measured from the normal direction of the birefringent layer. The main refractive indexes nx, ny, nz, thickness direction retardation Rth and Nz coefficient are measured by measuring the phase difference from the normal direction of the birefringent layer and each oblique direction inclined by −50 ° to 50 ° from the normal direction. The refractive index ellipsoidal curve fitting was used. The tilt direction was set to be perpendicular to the in-plane slow axis. Nx, ny, nz, Rxz and Nz depend on the average refractive index = (nx + ny + nz) / 3 given as the curve fitting calculation condition, but the average refractive index of each birefringent layer is unified to 1.5. Calculated. The birefringent layer having an actual average refractive index different from 1.5 was also converted assuming an average refractive index of 1.5.

(Measurement method of contrast ratio-viewing angle characteristics of liquid crystal display devices)
It measured using the viewing angle measuring apparatus (ELDIM company make, brand name: EZContrast160). A backlight mounted on a liquid crystal television (trade name: LC37-GH1) manufactured by Sharp Corporation was used as the light source. The luminance of white display and black display in an oblique direction with an azimuth of 45 ° and a pole of 60 ° was measured, and the ratio was defined as CR (45, 60). Further, the luminance of white display and black display in an oblique direction with an azimuth of 0 ° and a pole of 60 ° was measured, and the ratio was set to CR (0, 60).

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Examples 1 to 3, 7 and Comparative Example 3
As shown in FIG. 20, the liquid crystal display devices of Examples 1 to 3, 7 and Comparative Example 3 according to the present invention include a backlight (not shown), a first polarizer 410, and a second type. The birefringent layer 415, the first λ / 4 plate (first type birefringent layer) 420, the VA mode liquid crystal cell 430, the second λ / 4 plate 440, and the second polarizer 450 are laminated in this order. The circularly polarized VA mode liquid crystal display device 400 obtained in this manner. That is, the liquid crystal display device 400 of FIG. 20 differs from the liquid crystal display device 300 of FIG. 11 in that it does not include the third birefringent layer. In Examples 1 to 3 and 7, the Nz coefficient of the first λ / 4 plate 420 and the Nz coefficient of the second λ / 4 plate 440 are different from each other. However, in Comparative Example 3, the first λ The Nz coefficient of the / 4 plate 420 and the Nz coefficient of the second λ / 4 plate 440 are set to be the same. In FIG. 20, the arrows drawn on the first and

second polarizers

410 and 450 represent the directions of the absorption axes, and the arrows drawn on the first and second λ / 4

plates

420 and 440. Represents the orientation of the slow axis, the arrow drawn on the second type birefringent layer 415 represents the orientation of the fast axis, and the ellipsoid drawn on the VA mode liquid crystal cell 430 represents the refraction. It represents the shape of a rate ellipsoid.

The liquid crystal cell 430 includes a thin film transistor (TFT) substrate, a color filter (CF) substrate, and a liquid crystal layer sandwiched therebetween. A vertical alignment film is provided on the surface of the TFT substrate and the color filter substrate on the liquid crystal layer side, and an electrode is provided on the lower layer (substrate side) of each vertical alignment film. A desired voltage is applied to the liquid crystal layer by the electrode of the TFT substrate and the electrode of the color filter substrate, and the alignment of the liquid crystal molecules is controlled. The liquid crystal layer includes liquid crystal molecules having negative dielectric anisotropy. Therefore, in a state where no voltage is applied to the liquid crystal layer (off state), the liquid crystal molecules are aligned substantially perpendicular to the surface of the vertical alignment film, and a voltage higher than the threshold voltage is applied to the liquid crystal layer (on state). In this case, the liquid crystal molecules are tilted in the horizontal direction with respect to the surface of the vertical alignment film. Since the absorption axes of the first polarizer 410 and the second polarizer 450 are arranged so as to be orthogonal to each other (crossed Nicols arrangement), the liquid crystal display device 400 performs black display in the off state.

The liquid crystal cell 430 is a so-called MVA mode (multi-domain VA mode) liquid crystal cell, and has four domains in a pixel. When the tilt directions in the four domains are substantially orthogonal to each other when the display surface is viewed from the front, the asymmetry of the tilt directions can be effectively eliminated. In the circularly polarized light VA mode, since circularly polarized light is incident on the liquid crystal cell 430 for display, the tilt direction of the liquid crystal molecules does not affect the transmittance of the liquid crystal cell in the front direction (normal direction to the display screen). However, in the oblique direction, the tilt orientation of the liquid crystal molecules affects the transmittance of the liquid crystal cell. Therefore, the gradation viewing angle in the oblique direction can be improved by controlling the inclination directions in the four domains.

In the liquid crystal cell 430, as shown in FIG. 21, the domain D1 in which the liquid crystal molecules are tilted and oriented in the 22.5 ° direction, the domain D2 in which the liquid crystal molecules are tilted and oriented in the 112.5 ° direction, and the liquid crystal molecules in the 202.5 ° direction. Four domains are formed in each pixel, consisting of a domain D3 in which the liquid crystal molecules are tilted and a domain D4 in which the liquid crystal molecules are tilted in the 292.5 ° azimuth. In order to improve the viewing angle characteristics, as shown in FIG. 22, the four domains may be divided into two regions to which different voltages can be applied. In FIG. 22, a total of eight regions are formed in the pixel, but regions including liquid crystal molecules having different polar angles are included in the same domain if the tilt directions are substantially the same. There are four. That is, the regions D1-1 and D1-2 have the same tilt orientation of 22.5 ° although the polar angles of the liquid crystal molecules are different, and the regions D2-1 and D2-2 have the tilt orientations of the different polar angles of the liquid crystal molecules. 112.5 ° is common, regions D3-1 and D3-2 are different in polar angle of liquid crystal molecules, but the tilt direction is common at 202.5 °, and regions D4-1 and D4-2 are polar angles of liquid crystal molecules. However, they have a common inclination of 292.5 °.

The number of pixel domains may be increased to 4 or more. For example, in the liquid crystal cell 430, one pixel may be composed of a plurality of subpixels, and in that case, the above-described four types of domains may be provided in each subpixel.

In the liquid crystal cell 430, the tilt direction of the liquid crystal molecules is controlled by an alignment control unit formed on at least one of the TFT substrate and the CF substrate. The alignment control means is not particularly limited. For example, a combination of a slit formed in the electrode of the TFT substrate and a dielectric protrusion extending linearly formed in the lower layer (substrate side) of the vertical alignment film of the CF substrate. Is mentioned. At this time, the tilt direction of the liquid crystal molecules in each domain can be controlled by adjusting the stretch direction of the slit and the stretch direction of the dielectric protrusion, and can be attached to another member such as the first polarizer 410. It can also be controlled by adjusting the direction of alignment.

The tilt direction of the liquid crystal molecules deviates from the intended direction due to the electric field generated by the influence of the electrodes and wirings provided on the TFT substrate and the CF substrate, the surface shape of the TFT substrate and the CF substrate on the liquid crystal layer side, and the like. It may end up. In the liquid crystal display device of the present invention, the domain D1 in which the liquid crystal molecules are tilted and aligned in the 22.5 ° direction, the domain D2 in which the liquid crystal molecules are tilted and aligned in the 112.5 ° direction, and the liquid crystal molecules are tilted and aligned in the 202.5 ° direction. If four domains comprising a domain D3 to be aligned and a domain D4 in which liquid crystal molecules are tilted and oriented in a 292.5 ° azimuth are formed in a pixel, as shown in FIG. D5, D6, and D7 may also be included in the pixel.

Examples 4-6
As shown in FIG. 24, the liquid crystal display devices of Examples 4 to 6 according to the present invention include a backlight (not shown), a first polarizer 510, a first second-type birefringent layer 515, a first One λ / 4 plate (first-type birefringent layer) 520, third-type birefringent layer 535, MVA mode liquid crystal cell 530, second λ / 4 plate 540, second second-type birefringent layer This is a circularly polarized VA mode liquid crystal display device 500 obtained by laminating a refractive layer 545 and a second polarizer 550 in this order. That is, the liquid crystal display device 500 of FIG. 24 is different from the liquid crystal display device 300 of FIG. 11 in that it includes two second-type birefringent layers. In Examples 4 to 6, the Nz coefficient of the first λ / 4 plate 520 and the Nz coefficient of the second λ / 4 plate 540 are different from each other. The liquid crystal cell 530 has the same configuration as the liquid crystal cell 430 of Example 1, a domain in which liquid crystal molecules are tilted and aligned in the 22.5 ° azimuth, a domain in which liquid crystal molecules are tilted and aligned in the 112.5 ° azimuth, 202. Four domains are formed in each pixel, which are composed of domains in which liquid crystal molecules are tilted and aligned in the 5 ° direction and domains in which liquid crystal molecules are tilted and aligned in the 292.5 ° direction. In FIG. 24, the arrows drawn on the first and

second polarizers

510 and 550 indicate the directions of the absorption axes, and the arrows drawn on the first and second λ / 4

plates

520 and 540. Represents the orientation of the slow axis, and the arrows drawn on the first and second

birefringent layers

515 and 545 represent the orientation of the fast axis, and the liquid crystal cell 530 and the third kind The ellipsoid drawn on the birefringent layer 535 represents the shape of the refractive index ellipsoid.

Comparative Example 1
As shown in FIG. 25, the liquid crystal display device of Comparative Example 1 includes a backlight (not shown), a first polarizer 610, a first λ / 4 plate (first type birefringent layer) 620, MVA. This is a circularly polarized VA mode liquid crystal display device 600 obtained by laminating a mode liquid crystal cell 630, a second λ / 4 plate 640, a second birefringent layer 645, and a second polarizer 650 in this order. . In Comparative Example 1, the Nz coefficient of the first λ / 4 plate 620 and the Nz coefficient of the second λ / 4 plate 640 are set to be the same. The liquid crystal cell 630 has the same configuration as that of the liquid crystal cell 430 of Example 1, a domain in which liquid crystal molecules are tilted and aligned in the 22.5 ° azimuth, a domain in which liquid crystal molecules are tilted and aligned in the 112.5 ° azimuth, 202. Four domains are formed in each pixel, which are composed of domains in which liquid crystal molecules are tilted and aligned in the 5 ° direction and domains in which liquid crystal molecules are tilted and aligned in the 292.5 ° direction. In FIG. 25, the arrows drawn on the first and

second polarizers

610 and 650 indicate the directions of the absorption axes, and the arrows drawn on the first and second λ / 4

plates

620 and 640. Represents the orientation of the slow axis, the arrow drawn on the second type birefringent layer 645 represents the orientation of the fast axis, and the ellipsoid drawn on the liquid crystal cell 630 represents the refractive index ellipse. Represents the shape of the body.

Comparative Example 2
As shown in FIG. 26, the liquid crystal display device of Comparative Example 2 includes a backlight (not shown), a first polarizer 710, a first second-type birefringent layer 715, and a first λ / 4 plate. (First birefringent layer) 720, MVA mode liquid crystal cell 730, third birefringent layer 735, second λ / 4 plate 740, second second birefringent layer 745 and second This is a circularly polarized VA mode liquid crystal display device 700 obtained by laminating the polarizers 750 in this order. In Comparative Example 2, the Nz coefficient of the first λ / 4 plate 720 and the Nz coefficient of the second λ / 4 plate 740 are set to be the same. The liquid crystal cell 730 has the same configuration as the liquid crystal cell 430 of Example 1, a domain in which liquid crystal molecules are tilted and aligned in the 22.5 ° azimuth, a domain in which liquid crystal molecules are tilted and aligned in the 112.5 ° azimuth, 202. Four domains are formed in each pixel, which are composed of domains in which liquid crystal molecules are tilted and aligned in the 5 ° direction and domains in which liquid crystal molecules are tilted and aligned in the 292.5 ° direction. In FIG. 26, the arrows drawn on the first and

second polarizers

710 and 750 indicate the directions of the absorption axes, and the arrows drawn on the first and second λ / 4

plates

720 and 740. Represents the orientation of the slow axis, and the arrows drawn on the first and second

birefringent layers

715 and 745 of the second kind represent the orientation of the fast axis, and the liquid crystal cell 730 and the third kind The ellipsoid drawn on the birefringent layer 735 represents the shape of the refractive index ellipsoid.

Regarding the polarizer, birefringent layer, and liquid crystal cell of each example, the material name, axial angle, in-plane retardation R, thickness direction retardation Rth or Rlc, and Nz coefficient are as shown in Tables 5 and 6 below. It is. In the table, the axis of each birefringent layer is defined by the azimuth angle of the in-plane slow axis, and the axis of the polarizer is defined by the azimuth angle of the absorption axis. For the second type birefringent layer, the in-plane fast axis is important in design, but in the table, the axis of the second type birefringent layer is the in-plane retardation, as with the other birefringent layers. It is defined by the azimuth angle of the phase axis. The in-plane fast axis of the second birefringent layer is orthogonal to the in-plane slow axis of the second birefringent layer. In the table, the material names of the birefringent layers are indicated using the following abbreviations.
NB: Norbornene PI: Polyimide TAC: Triacetyl cellulose A: Resin composition containing acrylic resin and styrene resin Further, in the table, the average Nz coefficient is the Nz coefficient of the first λ / 4 plate, and the second It is defined as the average value of the Nz coefficient of the λ / 4 plate.

(Evaluation results)
The contrast ratio-viewing angle characteristics of the liquid crystal display device of each example were measured, and the contrast ratio [CR (0, 60)] at an azimuth of 0 ° and a polar angle of 60 °, and an azimuth of 45 ° and a polar angle of 60 ° The contrast ratio [CR (45, 60)] is shown in Tables 5 and 6 below. The “contrast ratio at azimuth X ° and polar angle Y °” is a contrast ratio measured in a direction in which the viewing angle is tilted by Y ° from the normal direction in the X ° azimuth. That is, the polar angle represents the angle formed by the front direction and the viewing angle direction. For each example, (1) azimuth 0 °, polar angle 0 °, (2) azimuth 0 °, polar angle 60 °, and (3) gamma curves at azimuth 45 °, polar angle 60 ° are shown in FIGS. It was shown to. The gamma curve shows the change in transmittance with respect to the voltage applied to the liquid crystal layer, with the gradation value on the horizontal axis and the normalized luminance on the vertical axis. Since the display mode of the liquid crystal display device of each example is normally black, the black display corresponds to the gradation value 0, the white display corresponds to the gradation value 256, and the liquid crystal layer increases as the gradation value increases. The voltage applied to is large. The standardization of the luminance is performed for each measurement direction with the luminance at the gradation value 256 being 1.0. Comparing multiple gamma curves obtained from different measurement directions is generally used as an indicator of how much the display screen looks different depending on the viewing direction of the liquid crystal display device. The closer to each other, the more consistent the appearance of the display screen.

CR (0, 60) and CR (45, 60) of the liquid crystal display devices of Examples 1 to 7 according to the present invention are both CR (0, 60) and CR (45, 60) of Comparative Examples 1 to 3. It was equivalent. The gamma curves of the liquid crystal display devices of Examples 1 to 7 were the same as the gamma curves of the liquid crystal display devices of Comparative Examples 1 to 3. The liquid crystal display devices of Examples 1 to 7 were excellent in display quality at an oblique viewing angle even in visual evaluation.

In Examples 1 to 7, since the Nz coefficient of the first λ / 4 plate and the Nz coefficient of the second λ / 4 plate are different from each other, the first λ / The productivity of the circularly polarizing plate including four plates is excellent, and the cost can be reduced. In particular, as a λ / 4 plate whose Nz coefficient is adjusted to approximately 1.6, a general-purpose λ / 4 plate manufactured by oblique stretching can be used, so the Nz coefficient is adjusted to approximately 1.6. The production merit of the embodiment including the λ / 4 plate is very large.

Further, in Examples 1 to 7, since the first λ / 4 plate having the smaller Nz coefficient is arranged on the observation surface side of the liquid crystal cell, the number of varieties tends to increase in order to meet the demand for the difference in surface treatment. Productivity of the polarizing plate on the observation surface side (second polarizer side) can be improved.

In Examples 1 to 3 and 7, the second birefringent layer is disposed on the back side (backlight side) of the liquid crystal cell, and Examples 1 to 3 and 7 are different from Examples 4 to 6. In comparison, since the configuration of the polarizing plate on the observation surface side (second polarizer side) is simpler, the productivity is higher.

In Examples 4 to 6, the third-type birefringent layer is disposed on the back side (backlight side) of the liquid crystal cell, and Examples 4 to 6 are compared with Comparative Example 2 on the observation surface side (first side). Since the configuration of the polarizing plate on the second polarizer side is simpler, the productivity is higher.

In the liquid crystal display devices of Comparative Examples 1 to 3, both the Nz coefficients of the first and second λ / 4 plates are relatively large, and it may be difficult to manufacture the first and second λ / 4 plates.

As described above, according to the liquid crystal display device of the present invention, it is possible to obtain various merits in manufacturing while ensuring a very excellent display quality at an oblique viewing angle.

In addition, since the liquid crystal display device of each Example is equipped with the circularly-polarizing plate which consists of a combination of a linearly polarizing plate (polarizer) and (lambda) / 4 board on both sides of a liquid crystal cell, all display by a circularly-polarized light VA mode. Is going. The circularly polarized VA mode is effective in improving the contrast ratio because it can obtain an antireflection effect in addition to the transmittance improving effect. The antireflection function based on the circularly polarized light VA mode is a liquid crystal display device in which light that is once incident on the liquid crystal display device from the periphery of the liquid crystal display device and reflected in the liquid crystal display device, that is, reflected light by so-called internal reflection is operated by the circularly polarizing plate. The light is not emitted to the outside. Therefore, according to the circularly polarized light VA mode, the light reflected by the surface of the black matrix, wiring, electrodes, etc. in the liquid crystal cell is less likely to be emitted outside the liquid crystal display device, particularly in a bright environment (bright environment). It can prevent that the contrast ratio of a liquid crystal display device falls.

On the other hand, the reflected light that reduces the contrast ratio of the liquid crystal display device in a bright environment includes the surface of the liquid crystal display device without entering the liquid crystal display device from the periphery of the liquid crystal display device in addition to the reflected light due to the internal reflection described above. The light reflected by the so-called surface reflected light. In the circularly polarized VA mode liquid crystal display device, the amount of reflected light due to surface reflection significantly affects the visibility of the display screen as a result of the suppression of reflected light due to internal reflection. Therefore, by taking measures to reduce the reflected light due to surface reflection on the circularly polarized VA mode liquid crystal display device, a very high contrast ratio can be obtained in a bright environment, and those who view the display screen have a remarkable display quality. I can feel the improvement.

Examples of the antireflection film (layer) used for suppressing surface reflection include an antireflection film formed by laminating a plurality of films having different refractive indexes, and an antireflection film having fine protrusions and depressions formed on the surface. . Among these, the “moth-eye film”, which is a type of the latter antireflection film, has a structure in which many protrusions smaller than the wavelength of visible light (380 to 780 nm) are provided on the surface. It is possible to achieve a very excellent effect in suppressing the above. As shown in FIG. 37 (a), the light incident on the moth-eye film reaches the film base portion 362 through the fine protrusions 361 provided on the surface, and therefore, between the air layer and the film base portion. A region where a certain protrusion and an air layer coexist (region between A and B in the figure) has a refractive index of the material constituting the film (about 1.5 in the case of a resin film) and a refractive index of air (1.0). ) And an intermediate refractive index. That is, as shown in FIG. 37 (b), the refractive index of this region corresponds to the change in the volume ratio of the protrusions and the air layer, and the refractive index of the material constituting the film from the refractive index of the air in contact with the film surface. Up to the refractive index, it gradually increases continuously within a distance shorter than the wavelength of visible light. As a result, the light incident on the moth-eye film does not recognize the air-film interface as an interface having a different refractive index, and the reflection of light generated at the interface can be greatly suppressed. According to the moth-eye film, for example, the surface reflectance of visible light can be reduced to about 0.15%.

If the moth-eye film is arranged at an interface having a different refractive index, the effect of reducing the reflectance can be achieved. For example, in the configuration shown in FIG. 11, the internal reflection generated inside the second polarizer 350 is as follows. It can be suppressed by a circularly polarizing plate comprising a combination of the second polarizer 350 and the second λ / 4 plate 340. Therefore, for example, when a moth-eye film is added to the configuration of FIG. 11, the moth-eye film 360 is arranged on the display surface side (observation surface side) with respect to the second polarizer 350 as shown in FIG. 38. When a member such as a protective plate is disposed on the display surface side of the second polarizer 350 and there are a plurality of interfaces, a moth-eye film may be provided for each interface, and at least exposed to the outside of the liquid crystal display device. It is preferable to arrange on the surface to be processed.

As a specific example of the moth-eye film, there is a resin film in which approximately cone-shaped protrusions having a height of about 200 nm are formed on the surface with a distance of about 200 nm between vertices.

As a method for producing a moth-eye film, there is a so-called nanoimprint technique, in which nanometer-sized irregularities (1 to 1000 nm) engraved in a mold are pressed against a resin material applied on a substrate to transfer the shape. Examples of the method for curing the resin material in the nanoimprint technique include a thermal nanoimprint technique and a UV nanoimprint technique. In UV nanoimprint technology, a thin film of ultraviolet curable resin is formed on a transparent substrate, a mold is pressed onto the thin film, and then irradiated with ultraviolet rays, thereby reversing the mold on the transparent substrate. The thin film which has this is formed.

In order to manufacture a thin film having a moth-eye structure at a low price by nanoimprint technology, it is preferable to use roll-to-roll processing rather than batch processing. According to the roll-to-roll process, a thin film having a moth-eye structure can be continuously produced using a mold roll. An example of such a mold roll is one in which a nanometer-sized depression is formed on the outer peripheral surface of a polished columnar or cylindrical aluminum tube by an anodic oxidation method. According to the anodic oxidation method, it is possible to form nanometer-sized depressions randomly and almost uniformly on the surface, and the surface of the mold roll has a seamless (seamless) moth eye suitable for continuous production. A structure can be formed.

Each form in embodiment mentioned above may be combined suitably in the range which does not deviate from the summary of this invention. Furthermore, a form in which two or more preferred forms are combined with each other is also one of the preferred forms.

This application claims priority based on the Paris Convention or the laws and regulations in the country of transition based on Japanese Patent Application No. 2011-080128 filed on Mar. 31, 2011. The contents of the application are hereby incorporated by reference in their entirety.

100 circularly polarized VA mode liquid crystal display device 110 first polarizer 111 first polarizer absorption axis 120 first λ / 4 plate 121 first λ / 4 plate slow axis 130 VA mode liquid crystal cell 140 first Second λ / 4 plate 141 Slow axis 150 of second λ / 4 plate Second polarizer 151 Absorption axis 200 of second polarizer Circularly polarized VA mode liquid crystal display device 210 First polarizer 220 First Λ / 4 plate 230 VA mode liquid crystal cell 235 Third birefringent layer 240 Second λ / 4 plate 250 Second polarizer 300 Circularly polarized VA mode liquid crystal display device 310 First polarizer 315 Second type Birefringent layer 320 first λ / 4 plate 330 VA mode liquid crystal cell 335 third type birefringent layer 340 second λ / 4 plate 350 second polarizer 360 moth-eye film 361 projection 362 film substrate 400 Circularly polarized VA mode liquid Display device 410 First polarizer 415 Second birefringent layer 420 First λ / 4 plate 430 VA mode liquid crystal cell 440 Second λ / 4 plate 450 Second polarizer 500 Circularly polarized VA mode liquid crystal display Device 510 first polarizer 515 first second type birefringent layer 520 first λ / 4 plate 530 VA mode liquid crystal cell 535 third type birefringent layer 540 second λ / 4 plate 545 second The second type of birefringent layer 550 Second polarizer 600 Circularly polarized VA mode liquid crystal display device 610 First polarizer 620 First λ / 4 plate 630 VA mode liquid crystal cell 640 Second λ / 4 plate 645 Second birefringent layer 650 Second polarizer 700 Circularly polarized VA mode liquid crystal display 710 First polarizer 715 First second birefringent layer 720 First λ / 4 plate 730 VA mode liquid crystal Cell 735 Third Birefringent Layer 740 Second lambda / 4 plate 745 second second birefringent layer 750 second polarizer

Claims

When defining a birefringent layer satisfying the relationship of nx> ny ≧ nz as a first type birefringent layer,
The first polarizer,
A first λ / 4 plate having an in-plane retardation adjusted to λ / 4,
A liquid crystal cell having a pair of substrates facing each other and a liquid crystal layer sandwiched between the pair of substrates;
A second λ / 4 plate having an Nz coefficient different from the first λ / 4 and having an in-plane retardation adjusted to λ / 4, and
With a second polarizer in this order,
The first and second λ / 4 plates are first-type birefringent layers,
When defining the orientation of the absorption axis of the second polarizer as 0 °,
The in-plane slow axis of the second λ / 4 plate forms an angle of approximately 45 °,
The in-plane slow axis of the first λ / 4 plate has an angle of approximately 135 °,
The absorption axis of the first polarizer forms an angle of approximately 90 °,
The display brightness is changed by changing the liquid crystal molecules in the liquid crystal layer from a state of being substantially vertically aligned with respect to the substrate surface to a state of being inclined and aligned,
The liquid crystal layer includes domains in which liquid crystal molecules are tilted and aligned in the direction of 12.5 ° to 32.5 °, domains in which liquid crystal molecules are tilted and aligned in the direction of 102.5 ° to 122.5 °, and 192.5 ° to 212. A liquid crystal display device having a domain in which liquid crystal molecules are tilted and aligned in a 5 ° azimuth and a domain in which liquid crystal molecules are tilted and aligned in a 282.5 ° to 302.5 ° azimuth.
The Nz coefficient of one of the first λ / 4 plate and the second λ / 4 plate is 2 or more,
2. The liquid crystal display device according to claim 1, wherein an Nz coefficient of the other of the first λ / 4 plate and the second λ / 4 plate is 1 or more and less than 2. 3.
3. The liquid crystal display device according to claim 1, wherein one of the first and second λ / 4 plates having a larger Nz coefficient is disposed on the back side of the liquid crystal cell.
The Nz coefficient of the first λ / 4 plate is larger than the Nz coefficient of the second λ / 4 plate,
The liquid crystal display device according to any one of claims 1 to 3, further comprising a surface treatment layer on an observation surface side of the second polarizer.
When defining a birefringent layer satisfying the relationship of nx <ny ≦ nz as a second birefringent layer,
A second birefringent layer is further provided between the first λ / 4 plate and the first polarizer,
The liquid crystal display device according to any one of claims 1 to 4, wherein an in-plane fast axis of the second birefringent layer is substantially orthogonal to an absorption axis of the first polarizer.
The liquid crystal display device according to claim 5, wherein the second birefringent layer is disposed on a back side of the liquid crystal cell.
The Nz coefficient of the first λ / 4 plate is larger than the Nz coefficient of the second λ / 4 plate,
The liquid crystal display device according to claim 6, wherein the second birefringent layer and the first λ / 4 plate are disposed on a back side of the liquid crystal cell.
When defining a birefringent layer satisfying the relationship of nx≈ny ≧ nz as a third birefringent layer,
At least one third-type birefringent layer is further provided between at least one of the first λ / 4 plate and the liquid crystal cell and between the liquid crystal cell and the second λ / 4 plate. The liquid crystal display device according to any one of claims 5 to 7.
The liquid crystal display device according to claim 8, wherein the at least one third-type birefringent layer is disposed on a back side of the liquid crystal cell.
The Nz coefficient of the first λ / 4 plate is larger than the Nz coefficient of the second λ / 4 plate,
9. The liquid crystal according to claim 8, wherein the second birefringent layer, the first λ / 4 plate, and the at least one third birefringent layer are disposed on a back side of the liquid crystal cell. Display device.
The average value of the Nz coefficients of the first and second λ / 4 plates is Nzq,
The thickness direction retardation at the time of black display of the liquid crystal cell is Rlc,
When the total sum of the thickness direction retardations of the third birefringent layer of the at least one layer is defined as R3,
The liquid crystal display device according to any one of claims 8 to 10, which satisfies the following formulas (1) to (3):
1.0 ≦ Nzq ≦ 2.9 (1)
(169 nm × Nzq−81 nm) −50 nm ≦ Rlc + R3 (2)
Rlc + R3 ≦ (169 nm × Nzq−81 nm) +50 nm (3)
When the Nz coefficient of the second birefringent layer is defined as Nz2 and the in-plane retardation is defined as R2,
The liquid crystal display device according to claim 11, which satisfies the following formulas (4) to (7):
(−0.63 × Nzq 2 + 0.56 × Nzq + 0.40) −0.80 ≦ Nz2 (4)
Nz2 ≦ (−0.63 × Nzq 2 + 0.56 × Nzq + 0.40) +0.80 (5)
(43 nm × Nzq 2 −226 nm × Nzq + 370 nm) −50 nm ≦ R2 (6)
R2 ≦ (43 nm × Nzq 2 −226 nm × Nzq + 370 nm) +50 nm (7)
The liquid crystal display device according to claim 12, wherein 1.40 ≦ Nzq is satisfied.
The average value of the Nz coefficients of the first and second λ / 4 plates is Nzq,
When the Nz coefficient of the second birefringent layer is defined as Nz2 and the in-plane retardation is defined as R2,
12. The liquid crystal display device according to claim 8, wherein Nzq <1.40 is satisfied, −0.80 ≦ Nz2 ≦ 0 is satisfied, and 88 nm ≦ R2 ≦ 188 nm is satisfied.
When defining a birefringent layer satisfying the relationship of nx≈ny ≧ nz as a third birefringent layer,
The third birefringent layer is not provided between the first λ / 4 plate and the liquid crystal cell and between the liquid crystal cell and the second λ / 4 plate. A liquid crystal display device according to any one of the above.