JP3369715B2 - Optical compensation sheet and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical compensation sheet, and more particularly to an optical compensation sheet useful for improving the viewing angle characteristics of display contrast and display color, and a method for producing the same.

[0002]

2. Description of the Related Art CRTs, which are the mainstream display devices for office automation equipment such as Japanese word processors and desktop personal computers
Have been converted into liquid crystal display elements which have the great advantages of thinness, light weight, and low power consumption. Most of the liquid crystal display elements (hereinafter, referred to as LCDs) which are currently popular use twisted nematic liquid crystals. The display method using such a liquid crystal can be roughly classified into a birefringence mode and an optical rotation mode.

An LCD using a birefringence mode has a twisted angle of 90 ° or more in the alignment of liquid crystal molecules and has steep electro-optical characteristics. Therefore, a simple matrix is provided without active elements (thin film transistors or diodes). A large-capacity display can be obtained by time-divisional driving with the electrode structure. But,
An LCD using this birefringence mode has a drawback that the response speed is slow (several hundreds of milliseconds) and gradation display is difficult. Therefore, a liquid crystal display element (TFT-LCD, MIM-LCD, etc.) using an active element is used. The display performance of) is exceeded.

For the TFT-LCD and MIM-LCD, a display system (TN type liquid crystal display element) of optical rotation mode in which the alignment state of liquid crystal molecules is twisted by 90 ° is used. This display method is the most effective method for high image quality compared with other LCDs because it has a fast response speed (tens of milliseconds), white display is easily obtained, and high display contrast is exhibited. is there. However, since the twisted nematic liquid crystal is used, there is a problem in the viewing angle characteristics that the display color and the display contrast change depending on the viewing direction due to the principle of the display system, and the display performance of the CRT cannot be exceeded.

Japanese Unexamined Patent Publication No. 4-229828 and Japanese Unexamined Patent Publication No. 4-2
As disclosed in Japanese Patent No. 58923, a method has been proposed in which a viewing angle is increased by disposing a retardation film between a pair of polarizing plates and a TN type liquid crystal cell. The retardation film proposed in the above-mentioned patent publication has a retardation of almost zero in the direction perpendicular to the liquid crystal cell, and does not exert any optical action from the front.
A phase difference appears when tilted, and the phase difference that appears in the liquid crystal cell is compensated. However, even with these methods, the viewing angle of LCD is still insufficient, and further improvement is desired. In particular, when considered as a vehicle-mounted type or as a substitute for a CRT, the current viewing angle cannot cope with the situation.

Further, in JP-A-4-366808 and JP-A-4-366809, a viewing angle is improved by using a liquid crystal cell containing a chiral nematic liquid crystal having an inclined optical axis as a retardation film. It is a two-layer liquid crystal system, which is expensive and very heavy. Further, Japanese Patent Application Laid-Open No. 5-80323 proposes a method of using a retardation film having an optical axis inclined with respect to a liquid crystal cell. However, since uniaxial polycarbonate is sliced and used, a large area is obtained. However, there is a problem in that it is difficult to obtain the retardation film (1) at low cost. Furthermore, Japanese Patent Application No. 5-5823
The specification describes a method of using a retardation film in which an optical axis is tilted by using a photoisomerizable substance. According to this method, a liquid crystal display device having a wide viewing angle characteristic, a light weight, and a low cost can be realized. However, the drawback of this method is that the retardation film is not sufficiently stable against heat and light.

Further, in Japanese Patent Laid-Open No. 215921/1993, there is proposed a plan for optically compensating an LCD with a birefringent plate in which a rod-shaped compound exhibiting liquid crystal properties at the time of curing is sandwiched between a pair of aligned substrates. However, this plan is no different from the so-called double-cell type compensator that has been proposed in the past, and it causes a great increase in cost and is practically unsuitable for mass production. Further, as long as a rod-shaped compound is used, the birefringent plate is TN for the optical reason described later.
It is impossible to improve the omnidirectional viewing angle of the type LCD. Further, in Japanese Patent Laid-Open Nos. 3-9326 and 3-291601, there is described a plan to apply a polymer liquid crystal to a film-shaped substrate on which an alignment film is provided to form an optical compensator for LCD. However, since it is impossible to orient molecules obliquely with this method, TN-type LCDs are also used.
It is impossible to improve the omnidirectional viewing angle.

Therefore, the inventor of the present invention has filed Japanese Patent Application No. 5-23653.
No. 9 invented an optical compensation sheet in which a discotic liquid crystal is aligned by an alignment film. Then, when the correspondence between the alignment state and the optical characteristics was studied in more detail, when the layer containing the discotic liquid crystal was applied to the isotropic film and then heated for alignment ripening, the layer formed a discotic nematic phase. The one prepared by the method of putting it in a constant temperature bath set to the temperature for forming and then taking it out after a while has a capability of improving the viewing angle, but the contrast is lowered due to the presence of microscopic orientation disorder. Therefore, it was found that the display quality from the front slightly deteriorates as compared with the case without the optical compensation sheet.

[0009]

Therefore, the object of the present invention is to achieve a state in which there is no microscopic alignment disorder in an optical compensation sheet using a discotic liquid crystal, so that all of the display quality including the display quality from the front can be achieved. An object of the present invention is to provide an optical compensation sheet that can improve the display quality from the viewing angle.

[0010]

SUMMARY OF THE INVENTION The present invention is an optical isotropic method.
A low molecular weight discotic liquid crystal is displayed on the film.
Solidified with the formation of the scotic nematic phase
The optical compensation sheet is provided with a layer formed from light
An alignment film is provided between the biologically isotropic film and the layer.
Preferably. The optical compensation sheet of the present invention is a table
Optically isotropic film whose surface is rubbed, or
Rubbed or not rubbed
Of an optically isotropic film having a surface having an alignment film,
A layer containing low molecular weight discotic liquid crystal is applied on the surface
Then, the layer containing the discotic nematic liquid crystal was
Temperature rise to the temperature at which the discotic nematic phase is formed
The layer containing the discotic liquid crystal,
Solidification while maintaining discotic nematic phase
It can be advantageously produced by the method of cooling under the conditions
it can.

The usefulness of the present invention will be described below. First,
The optical utility will be described with reference to the drawings using a TN LCD as an example. 1 and 2 show polarization states of light propagating in a liquid crystal cell when a sufficient voltage equal to or higher than a threshold voltage is applied to the liquid crystal cell. Since the transmittance characteristic of light particularly when a voltage is applied greatly contributes to the viewing angle characteristic of the contrast, a case where a voltage is applied will be described as an example. FIG. 1 is a diagram showing a polarization state of light when light is vertically incident on a liquid crystal cell. When the natural light L0 is vertically incident on the polarizing plate A having the polarization axis PA, the light transmitted through the polarizing plate PA becomes the linearly polarized light L1.

When a sufficient voltage is applied to the TN type liquid crystal cell, the alignment state of the liquid crystal molecules is schematically shown as a model with one liquid crystal molecule, which is represented by LC in the schematic diagram. Modeling the liquid crystal molecules in a liquid crystal cell, when the LC major axis in the schematic diagram is parallel to the light path, a difference in refractive index occurs on the incident surface (in the plane perpendicular to the light path). Since it does not exist, linearly polarized light propagates even when it passes through the liquid crystal cell. Polarization axis P of polarizing plate B
When B is set to be perpendicular to the polarization axis PA of the polarizing plate A, the linearly polarized light L2 that has passed through the liquid crystal cell cannot pass through the polarizing plate B and is in a dark state.

FIG. 2 is a diagram showing a polarization state of light when the light obliquely enters the liquid crystal cell. Natural light of incident light L
When 0 is obliquely incident, the polarized light L1 transmitted through the polarizing plate A becomes almost linearly polarized light. (In the actual case, it becomes elliptically polarized due to the characteristics of the polarizing plate). In this case, the refractive index anisotropy of the liquid crystal causes a difference in the refractive index on the incident surface of the liquid crystal cell, and the light L2 transmitted through the liquid crystal cell is elliptically polarized light and is not completely blocked by the polarizing plate B. As described above, in the case of oblique incidence, blocking of light in a dark state becomes insufficient, which causes a large reduction in contrast, which is not preferable.

An object of the present invention is to provide an optical compensator capable of preventing such a decrease in contrast due to oblique incidence and improving the viewing angle characteristics, and at the same time, not deteriorating the display quality from the front. FIG. 3 shows an example of using the optical compensation sheet manufactured by the present invention. An optical anisotropic element RF1 having an optical axis inclined from the normal line direction of the liquid crystal cell is arranged between the polarizing plate A and the liquid crystal cell TNC. The optically anisotropic element RF1 is a birefringent body in which the phase difference increases as the angle of light incident on the optical axis increases. An optical anisotropic element RF2 having an optical axis inclined from the normal line direction of the liquid crystal cell is arranged between the polarizing plate B and the liquid crystal cell TNC. The optically anisotropic element RF2 is a birefringent body having the same optical characteristics as RF1. When the natural light L0 is obliquely incident on the liquid crystal display device having such a structure as in the case of FIG. 2, the optical modulation described below occurs. First, it is converted into linearly polarized light L1 by the polarizing plate A, and is modulated into elliptically polarized light L3 by the phase delay action when passing through the optically anisotropic element RF1. Next, when passing through the liquid crystal cell TNC, the elliptically polarized light L4 having the opposite phase is obtained.
When the light is further modulated by the optical anisotropic element RF2 and is further transmitted through the optical anisotropic element RF2, it is returned to the original linearly polarized light L5 by the phase delay action. With such an effect, the natural light L0 can obtain the same transmittance even under various oblique incidences, and it is possible to obtain a liquid crystal display element capable of high-quality display without viewing angle dependence.

It is presumed as follows that the viewing angle of the liquid crystal display device can be greatly improved by the optical compensation sheet manufactured according to the present invention. Most TN-LCDs adopt a normally white mode.
In this mode, the transmittance of light from the black display portion is significantly increased as the viewing angle is increased, resulting in a sharp drop in contrast. The black display is the state when a voltage is applied, but at this time, the TN type liquid crystal cell should be regarded as a laminate of two positive uniaxial optical anisotropic bodies with the optical axis slightly tilted from the direction normal to the cell surface. You can In the case of halftone, the optical axis is
It is considered that two optical anisotropically laminated bodies tilted from the normal direction of the LC cell will be formed.

When the optical axis of the liquid crystal cell is tilted from the direction normal to the surface of the liquid crystal cell, it is expected that the optical anisotropic body having the optical axis in the normal direction will be insufficiently compensated. Further, if the liquid crystal cell can be regarded as a laminate of two positive uniaxial optical anisotropic bodies, it is preferable to use two negative uniaxial optical anisotropic bodies in order to compensate for it. For these reasons, it is presumed that the negative uniaxial optical anisotropic body in which the optical axis is tilted from the normal direction in the present invention significantly improves the viewing angle characteristics.

As a matter of course, it is preferable that the negative uniaxial optically anisotropic substance is a homogeneous film-like substance whose optical axes are aligned in one direction. The inventor of the present invention is Japanese Patent Application No. 5-236.
Although the optical compensation sheet was prepared by the method as shown in No. 539 and the details were packed, it is not necessary to simply put the sheet in and out of the constant temperature bath heated to the discotic liquid crystal phase temperature in the heat treatment for orientation ripening. , It was found that the sheet would have microscopic orientation disorder. Due to this disordered orientation, the optical axis of the sheet is slightly deviated depending on the microscopic location, and microscopic unevenness occurs in optical compensation. As a result, the naked eye perceives a decrease in contrast.

This micro-orientation is caused by C.I. DESTR
ADE, et al; Molecular Cryst
al and Liquid Crystal, 198
1, Vol. 71, 111-135, and D.I. Gold
farb, et al; Israel Journal
of Chemistry, Vol. 23, 198
Analysis by the present inventors with reference to Nos. 3,341-352 and the like revealed that the smectic-like columnar phase temperature range existing on the low temperature side of the liquid crystal phase temperature range was for 5 seconds or more during heating and cooling. It was found that the property of the columnar phase is caused by the exposure of the liquid crystal layer. That is, random polycrystals are generated when the columnar phase enters from the non-oriented state at the time of temperature rise, and the polycrystals are extinguished when the temperature further rises to enter the discotic nematic phase, and the orientation regulation of the alignment film, magnetic field, etc. The force of uniaxial orientation works according to the force, but the history of the polycrystal cannot be completely erased, and alignment unevenness remains. In addition, when the temperature falls, when entering the columnar phase from the discotic nematic phase, the columnar phase is maintained with the uniaxial orientation, and when the temperature is lowered above the discotic liquid crystal phase / solid phase transition temperature, the multi-domain characteristic of the columnar phase is formed. Will be formed. This multi-domain is recognized as a minute unit of alignment spots. It is presumed that microscopic alignment unevenness is formed by the mechanism as described above.

Therefore, it was thought that a uniform alignment phase could be obtained if the columnar phase, which is the root cause of the microscopic alignment unevenness, was not taken, and as a result of the study, the present invention was reached. That is, the discotic nematic phase is used as it is, and it is used as an optical compensation sheet. As a manufacturing method, a thin film of discotic liquid crystal is formed by coating on a substrate, and the glass state of the discotic nematic phase is formed by rapidly heating to a discotic nematic phase temperature and then rapidly cooling. A uniformly oriented solid is obtained.

The term "rapid heating / quenching" as used herein means a heating / cooling means in which the staying time in the columnar phase temperature range is within 5 seconds in both heating and cooling. As a specific method, after applying a discotic liquid crystal to a film-like substrate, the substrate is brought into contact with a heating roller set to a temperature at which the discotic liquid crystal takes a discotic nematic phase, and immediately after that, the solid state of the discotic liquid crystal is fixed. A method of bringing the material into contact with a cooling roller set to a temperature below the phase / liquid crystal phase transition temperature is mentioned, but the method is not limited to this method as long as it is a means of satisfying the conditions of rapid heating / quenching defined above.

The discotic liquid crystal used in the present invention itself has an optically negative uniaxial property, and includes this discotic liquid crystal, and its optical axis is obliquely inclined from the normal direction. Is effective for improving the viewing angle characteristics of the TN type liquid crystal cell. In a particular discotic liquid crystal, if the discotic liquid crystal phase is solidified in the aligned state, the structure is kept stable below the discotic liquid crystal phase / solid phase transition temperature. Is also stable.

The discotic liquid crystals in the present invention are those listed below, but the molecules themselves have negative uniaxiality and the optical axis is aligned obliquely with respect to the substrate surface by the oblique alignment film. If it is, it is not particularly limited to the following substances.

[0023]

[Chemical 1]

[0024]

[Chemical 2]

[0025]

[Chemical 3]

Negative uniaxiality in the present invention means that n ₁ <n ₂ when the triaxial refractive index of a sheet having optical anisotropy is n ₁ , n ₂ and n _{3 in the} order of decreasing values. = and has a relationship of n _3. Therefore, it has a characteristic that the refractive index in the optical axis direction is the smallest. However, n ₂ and n ₃
The values of do not have to be exactly equal, they need to be approximately equal. Specifically, if | n ₂ −n ₃ | / | n ₂ −n ₁ | ≦ 0.2, there is no practical problem. In addition, as a condition for significantly improving the viewing angle characteristics of the TFT or TN type liquid crystal cell, the inclination β of the optical axis from the normal line direction of the sheet surface is preferably 5 ° to 50 °, and 10 ° to 40 °. The degree is more preferable.
Further, when the thickness of the sheet is d, it is preferable to satisfy the condition of 50 ≦ Δn · d ≦ 400 (nm). However, Δn = n ₂ −
n ₁

There are various methods for the alignment treatment that can be used in the present invention. There is a discotic liquid crystal in which effective alignment can be obtained simply by rubbing the surface of the substrate and coating it on it, but the most versatile method is to use an alignment film. As the alignment film, an inorganic oblique vapor deposition film,
Alternatively, this is an alignment film obtained by rubbing a specific organic polymer film.

A typical example of the inorganic oblique vapor deposition film is SiO 2.
It is an oblique deposition film. A roll-shaped sheet can be manufactured by using a continuous oblique vapor deposition machine as shown in FIG. The minimum vapor deposition angle θ shown in FIG. 4 is in the range of 10 ° <θ <88 °. Note that rod-shaped vapor deposition particles grow from the substrate surface toward the vapor deposition source by this oblique vapor deposition, but the vapor deposition angle θ is about 65 to 88.
The liquid crystal is oriented in the direction of the vapor-deposited particle column and the optical axis of the discotic liquid crystal are substantially perpendicular to each other at the angle of 0 °, and when the vapor deposition angle θ is approximately 20 ° to 65 °, the direction of the vapor-deposition column and the discotic liquid crystal are Are oriented so that their optical axes substantially coincide with each other.

A polyimide film is a typical organic alignment film. The discotic liquid crystal can be obliquely aligned by applying a polyamic acid (for example, SE-7210 manufactured by Nissan Kagaku Co., Ltd.) to the surface of the substrate, baking at 100 ° C. to 300 ° C., and rubbing.

It is preferable that the substrate material used for the optical compensation sheet of the present invention has good optical transmissivity and also has good optical isotropy. Therefore, a substrate formed of a material having a small intrinsic birefringence value, which is sold under the trade name of Zeonex (Nippon Zeon), ARTON (Nippon Synthetic Rubber), Fujitac (Fuji Photo Film Co., Ltd.) is preferable. However, it is possible to form an optically isotropic substrate by controlling the molecular orientation during film formation, even for materials with large intrinsic birefringence values such as polycarbonate, polyarylate, polysulfone, and polyethersulfone. Yes, they can also be suitably used.

Magnetic field orientation and electric field orientation are available as methods other than the above in which the discotic liquid crystal coated on the substrate is oriented obliquely. In this method, after the discotic liquid crystal is applied to the substrate, a zone for applying a magnetic field or an electric field at a desired angle is required, but it is necessary to adjust the zone itself to a temperature at which a discotic nematic phase is formed. is there.

[0032]

EXAMPLES The present invention will be described in detail below based on examples. 100μ thick film of polyether sulfone (FS-1300 manufactured by Sumitomo Bakelite Co., Ltd., size 2)
50 mm × 250 mm) as a substrate, and a polyamic acid (SE-721 manufactured by Nissan Chemical Industries, Ltd.) as an alignment film on the substrate.
0) is applied and baked at 180 ° C. to form a polyimide film.
This polyimide film is rubbed by a rubbing machine to give orientation ability. On top of that, dissolve the above-mentioned discotic liquid crystal TE-8 in a methyl ethyl ketone solution to
3000 wt by a spin coater
m to form a discotic liquid crystal non-alignment layer having a thickness of 1 μm. This is referred to as a film-like material A.

A 100 μ thick film of polyether sulfone (FS-1300 manufactured by Sumitomo Bakelite Co., Ltd., size 250 mm × 250 mm) is used as a substrate, and an alignment film is formed thereon by using the continuous vapor deposition machine as shown in FIG. A 0.1 μm thick SiO oblique deposition film was formed at an angle x = 40 °. In addition, the above-mentioned discotic liquid crystal TE-9
Was dissolved in a methyl ethyl ketone solution to a concentration of 10 wt% and was applied by a spin coater at 3000 rpm to form a discotic liquid crystal non-alignment layer having a thickness of 1 μm. This is referred to as a film-like material B.

Example 1 According to a microscopic observation, the discotic liquid crystal TE-8 takes a columnar phase at about 149 to 167 ° C. and about 167 to 167 ° C.
It takes a discotic nematic phase at 245 ° C. Therefore, the orientation aging temperature of the liquid crystal is set to 180 ° C. That is,
The film-like material A was pressed against a metal roller heated to a surface temperature of 180 ° C. for 10 seconds, and immediately thereafter, the film-shaped material A was pressed against a metal roller adjusted to a surface temperature of 20 ° C. for 10 seconds to obtain an optical compensation sheet. . Microscopic observation of this sheet confirmed that it had a uniaxial orientation of the monodomain, that is, it had a nematic phase.

Example 2 According to microscopic observation, the discotic liquid crystal TE-9 takes a columnar phase at about 120 to 130 ° C.
It takes a discotic nematic phase at 210 ° C. Therefore, the alignment aging temperature of the liquid crystal is set to 150 ° C. That is,
The film-like material B was pressed against a metal roller heated to a surface temperature of 150 ° C. for 10 seconds, and immediately thereafter, the film-shaped material B was pressed against a metal roller adjusted to a surface temperature of 20 ° C. for 10 seconds to obtain an optical compensation sheet. . Microscopic observation of this sheet confirmed that it had a uniaxial orientation of the monodomain, that is, it had a nematic phase.

Comparative Example 1 Film-like material A was pressed against a metal roller heated to a surface temperature of 180 ° C. for 10 seconds, and then placed in a thermostatic chamber adjusted to 180 ° C., and the temperature of the thermostatic chamber was set to 20 ° C./min. The temperature was lowered to 40 ° C. to obtain an optical compensation sheet. When the sheet was observed under a microscope, it was confirmed that the sheet was in a multi-domain state in which it was divided into domains of several μm, and the orientation directions were almost uniaxial, that is, it had a columnar phase.

Comparative Example 2 The film-like material A was placed in a constant temperature bath adjusted to 40 ° C., and 2
After the temperature was raised to 180 ° C. at a rate of 0 ° C./min, the film-like material A was taken out and immediately pressed against a metal roller whose surface temperature was adjusted to 20 ° C. to obtain an optical compensation sheet. When this sheet was observed under a microscope, it was several μm.
It was confirmed that, in a multi-domain state in which the domains were divided into unit domains, the orientation directions were substantially uniaxial, that is, they had a columnar phase.

Comparative Example 3 The film-like material A was placed in a constant temperature bath adjusted to 40 ° C., and 2
After heating up to 180 ° C. at a rate of 0 ° C./min, the temperature of the constant temperature bath was lowered to 40 ° C. at a rate of 20 ° C./min to obtain an optical compensation sheet. When the sheet was observed under a microscope, it was confirmed that the sheet was in a multi-domain state in which it was divided into domains of several μm, and the orientation directions were almost uniaxial, that is, it had a columnar phase.

Optical axis angle β of Example 1 and Comparative Examples 1, 2 and 3
And .DELTA.n.d were measured by ellipsometry and found to be approximately uniform at .beta. = 40 (.degree.) And .DELTA.n.d = 100 (nm). Further, when the optical axis angles β and Δn · d of Example 2 were measured by ellipsometry, β = 30 (°) and Δn · d = 120 (nm) were obtained.

For the measurement, the Shimadzu ellipsometer (AEP-100) was used as the transmission mode to determine the angle dependence of the retardation, and the optimum triaxial refractive index and optical axis direction were calculated from the values. It was

The product of the difference in refractive index between the extraordinary light and the ordinary light of the liquid crystal and the gap size of the liquid crystal cell is 490 nm, and the twist angle is 90.
TN type liquid crystal cell of Example 1.2 and Comparative Example 1.2.
The optical compensation sheet obtained in 3 was mounted as shown in FIG. 5, and the angle dependence of the contrast in a 30 Hz rectangular wave of 0 V to 5 V was measured with respect to a liquid crystal cell by LCD-5000 manufactured by Otsuka Electronics. The position with a contrast ratio of 10 was defined as the viewing angle, and the viewing angles in the vertical and horizontal directions were obtained. Also, the contrast ratio when viewed from the front was measured. Here, the measurement of only the TN type liquid crystal cell with no optical compensation sheet attached,
It was set as Comparative Example 4. The results are shown in Table 1. In FIG. 5, arrows indicate the rubbing direction in the optical compensation sheet, the flying direction of vapor deposition particles, and the rubbing direction in the liquid crystal cell. In FIG. 5, the discotic liquid crystal layer side of the optical compensation sheet is the upper side.

[0042]

[Table 1]

[0043]

As is apparent from Table 1, the optical compensation sheet of the present invention obtained by rapid heating / cooling can significantly widen the viewing angle of a TN type liquid crystal cell without deteriorating the front contrast. . On the other hand, the optical compensatory sheets obtained in Comparative Example 1 of rapid heating / slow cooling, Comparative Example 2 of slow heating / quenching, and Comparative Example 3 of slow heating / slow cooling have a viewing angle improving effect but a front contrast. Make it worse. Therefore,
By using the optical compensation sheet of the present invention, the viewing angle of the TN type liquid crystal cell can be extremely widened.

[Brief description of drawings]

FIG. 1 is a diagram showing a polarization state of light when light is vertically incident on a liquid crystal cell.

FIG. 2 is a diagram showing a polarization state of light when light obliquely enters a liquid crystal cell.

FIG. 3 is a diagram showing an example of use of an optical compensation sheet.

FIG. 4 is a diagram showing a continuous inorganic oblique vapor deposition method.

FIG. 5 is a diagram showing a relationship among a polarization axis of a polarizing plate, a rubbing direction of a liquid crystal cell, and a rubbing direction of an optical compensation sheet alignment film when measuring viewing angle characteristics in Examples and Comparative Examples.

[Explanation of symbols]

TNC: TN type liquid crystal cell A, B: Polarizing plate PA, PB: Polarization axis L0: Natural light L1, L5: Linearly polarized light L2: Modulated light after passing through the liquid crystal cell L3, L4: Elliptical polarized light LC: TN type liquid crystal cell State of liquid crystal molecules when sufficient voltage is applied to the electrodes RF1, RF2: Optical compensation sheet x: Minimum vapor deposition angle T in continuous inorganic oblique vapor deposition method T: Crucible BL containing vapor deposition material: Backlight

Claims (3)

(57) [Claims] To 1. A on the optically isotropic film, it has a layer discotic liquid of low molecular weight formed by solidified while forming a discotic nematic phase is provided
That the optical compensation sheet. 2. The optical compensation sheet according to claim 1, wherein an alignment film is provided between the optically isotropic film and the layer . 3. An optically isotropic film whose surface is rubbed , or which has been rubbed, or Rabin.
Optical, etc. having a surface with an alignment film that has not been treated
A low molecular weight discotic liquid is applied to the surface of the anisotropic film.
After applying a layer containing crystals, the discotic nematic
Layer containing liquid crystal forms discotic nematic phase
Up to the temperature, and then the discotic liquid
A layer containing crystals to maintain the discotic nematic phase.
A contract consisting of cooling under conditions that solidify while holding
The method for producing an optical compensation sheet according to claim 1 .