JP4683998B2 - Ultraviolet irradiation device, optical compensation sheet, and polarizing plate and liquid crystal display device using the same - Google Patents

Description

  The present invention relates to an ultraviolet irradiation device useful for producing various optical films such as an optical compensation sheet. In addition, the present invention relates to an optical compensation sheet, a polarizing plate, and a liquid crystal display device manufactured using the same.

  CRT (Cathode Ray Tube) has been mainly used as a display device used for OA devices such as word processors, notebook personal computers, personal computer monitors, portable terminals, and televisions. In recent years, liquid crystal display devices (LCDs) have been widely used instead of CRTs because of their thinness, light weight, and low power consumption. The liquid crystal display device has a liquid crystal cell and a polarizing plate. The polarizing plate is composed of a protective film and a polarizing film, and is obtained by dyeing a polarizing film made of a polyvinyl alcohol film with iodine, stretching, and laminating both surfaces with a protective film. For example, in a transmissive liquid crystal display device, the polarizing plate is attached to both sides of the liquid crystal cell, and one or more optical compensation sheets may be disposed. On the other hand, in a reflective liquid crystal display device, a reflector, a liquid crystal cell, one or more optical compensation sheets, and a polarizing plate are arranged in this order. The liquid crystal cell includes a liquid crystal molecule, two substrates for encapsulating the liquid crystal molecule, and an electrode layer for applying a voltage to the liquid crystal molecule. A liquid crystal cell performs ON / OFF display depending on the alignment state of liquid crystal molecules, and can be applied to any of a transmission type, a reflection type, and a semi-transmission type, such as TN (Twisted Nematic), IPS (In-Plane Switching), Display modes such as OCB (Optically Compensatory Bend), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), and STN (Super Twisted Nematic) are proposed. However, the color and contrast that can be displayed by a conventional liquid crystal display device vary depending on the angle at which the LCD is viewed. For this reason, the viewing angle characteristics of liquid crystal display devices have not yet exceeded the performance of CRT.

  In recent years, as an LCD method for improving the viewing angle characteristics, nematic liquid crystal molecules having negative dielectric anisotropy are used, and the major axis of the liquid crystal molecules is aligned in a direction substantially perpendicular to the substrate without applying a voltage. A vertical alignment nematic liquid crystal display device (hereinafter referred to as VA mode) in which this is driven by a thin film transistor has been proposed (see Patent Document 1). This VA mode not only has excellent display characteristics when viewed from the front, but also exhibits a wide viewing angle characteristic by applying a viewing angle compensation phase difference plate (optical compensation sheet). . In the VA mode, a wider viewing angle characteristic can be obtained by using a negative uniaxial retardation plate (negative c-plate) having an optical axis in a direction perpendicular to the film surface. It is also known that a wider viewing angle characteristic can be realized by using a uniaxially oriented retardation plate (positive a-plate) having a positive refractive index anisotropy having a retardation value of 50 nm ( Non-patent document 1).

  However, when the number of retardation plates is increased in this way, the production cost increases. In addition, since a large number of films are bonded together, it tends to cause not only a decrease in yield but also a deterioration in display quality due to a shift in the bonding angle. Furthermore, since a plurality of films are used, the thickness increases, which may be disadvantageous for thinning the display device.

  Moreover, although a stretched film is normally used for positive a-plate, when using the longitudinally stretched film in a continuous conveyance process, the slow axis of a-plate turns into the film conveyance (MD) direction. However, in the VA mode viewing angle compensation, the slow axis of the a-plate must be orthogonal to the MD direction which is the absorption axis of the polarizing plate. Rises significantly. As a method for solving this, it is possible to use a so-called laterally stretched film that is stretched in a direction orthogonal to MD (TD direction). However, the transversely stretched film is apt to cause distortion of a slow axis called bowing, and the yield is high. The cost increases because it does not increase. Furthermore, since an adhesive layer is used for lamination of stretched films, the adhesive layer contracts due to temperature and humidity changes, and defects such as peeling and warping between films may occur. As a method for improving these, a method of producing a-plate by applying a rod-like liquid crystal is known (see Patent Document 2).

  Furthermore, in recent years, a method using a biaxial retardation plate in place of the combination of c-plate and a-plate has been proposed (Non-Patent Document 2). By using a biaxial retardation plate, there is an advantage that not only the contrast viewing angle but also the color can be improved. However, the biaxial stretching usually used to produce a biaxial retardation plate is a lateral Similar to stretching, uniform axis control over the entire region of the film is difficult, and the yield does not increase, resulting in an increase in cost.

  Therefore, a biaxial retardation plate is produced without using stretching by a method of irradiating polarized violet light to a special cholesteric liquid crystal (Patent Document 3) or a method of irradiating a special disk-shaped liquid crystal to polarized ultraviolet light (Patent Document 4). A way to do it was proposed. By this method, various problems caused by stretching can be solved.

Japanese Patent Laid-Open No. 2-176625 JP 2000-304930 A EP1389199 A1 Japanese Patent Laid-Open No. 2002-6138 SID 97 DIGEST Pages 845-848 SID 2003 DIGEST, pages 1208-1211

  In order to irradiate such polarized ultraviolet rays, it is necessary to use a polarizing filter having a polarization separation characteristic in an ultraviolet region of 380 nm or less, but at least half of the polarizing component cannot be used due to the principle problem of the polarizing filter. Compared with non-polarized light irradiation, the irradiation amount is small. However, in order to maintain high productivity in the continuous conveyance process, it is necessary to increase the conveyance speed, and the irradiation amount of polarized ultraviolet rays becomes small in inverse proportion to the conveyance speed. Thus, in the biaxial retardation plate by irradiation with polarized ultraviolet rays, means for producing the biaxial retardation plate at a high transport speed without impairing the biaxial expression is demanded.

  As a feature of the irradiated light required in the ultraviolet curing process, the irradiation amount and irradiation intensity are important parameters in the hardening phenomenon that reacts via radicals generated by ultraviolet irradiation. Irradiation intensity is an effective parameter for generating radicals instantaneously. By installing an optical system that collects light with a reflector placed behind the light source in the irradiation direction, the illuminance peak is near the focal position. Get higher. In order to continue the chain reaction due to the generation of radicals, it is effective to increase the irradiation amount. In order to lengthen the irradiation time, it can be considered that the conveyance speed of the irradiated object at the time of irradiation is slowed, but the productivity is lowered. Therefore, increasing the irradiation intensity is necessary to improve productivity in the ultraviolet curing process.

  In order to improve productivity in this way, high irradiation intensity is required, but an ordinary ultraviolet irradiation device is provided with an elliptical reflector, and the irradiation intensity increases as it approaches the focal point of the elliptical surface. It is designed so that it can be used at any irradiation intensity below the irradiation intensity at the focal length. On the other hand, polarizers using the reflection of a transparent body and polarizers using obliquely incident light using birefringence need to make the incident light ideally parallel light and collect the emitted ultraviolet light. Therefore, when the light source having the same irradiation intensity is used, the irradiation intensity becomes low.

  For this reason, a high intensity of UV irradiation of the condensing light source can be obtained, so a combination with a reflective or absorptive polarizing element is conceivable. In that case, the total length of the light source is perpendicular to the transport direction. The number of polarizing elements covering the minute is necessary. However, there are few choices for a polarizer in the ultraviolet region, and it is generally difficult to produce a large-area filter. Thus, polarized light irradiation can be performed by arranging polarizing elements having a small area in the longitudinal direction of the light emitting element, but light rays passing through the boundary between the polarizing elements are not strictly polarized. Furthermore, in the case of curing with an irradiation intensity in the vicinity of the focal point in order to increase the irradiation intensity with a condensing system light beam, it is easily affected by the boundary of the element arrangement. If ultraviolet irradiation can be carried out uniformly without being affected by the boundary between a plurality of polarizers, an optical compensation sheet having desired optical characteristics, for example, desired optical compensation capability, can be stably produced.

  It is an object of the present invention to provide an ultraviolet irradiation apparatus suitable for use in an ultraviolet curing process that has high irradiation intensity and can perform uniform ultraviolet irradiation. Moreover, this invention makes it a subject to provide the novel ultraviolet irradiation device which contributes to the improvement of productivity of the ultraviolet curable film which shows desired optical characteristics, such as an optical compensation sheet. Furthermore, it is an object of the present invention to provide an optical compensation sheet that has an optical compensation capability for a liquid crystal cell and is excellent in productivity, a polarizing plate using the same, and a liquid crystal display device. In particular, it is an object to provide a device used for a VA mode liquid crystal display device.

  As a result of intensive studies in order to solve the above problems, the present inventor has found that when arranging optical filters, for example, polarizing elements, so that the boundaries between the filters intersect with the conveyance direction, the hardness during conveyance is reduced. It was found that it is possible to substantially reduce the influence of light rays passing near the boundary in the membrane process. If the optical filters are arranged so that the length of the irradiation window in the conveyance direction is the same in the irradiation window width direction, and the integrated irradiation dose in the width direction is substantially the same, it is affected by the boundary between the optical filters. I got no knowledge. Based on these findings, further studies have been made and the present invention has been completed.

Means for solving the above problems are as follows.
[1] An ultraviolet irradiation device used for irradiating ultraviolet rays to a continuously conveyed ultraviolet curable layer, comprising a light source and a plurality of optical filters arranged in front of the irradiation direction of light from the light source. The ultraviolet irradiation apparatus, wherein the plurality of optical filters are arranged with their boundaries intersecting with the transport direction.
[2] The ultraviolet irradiation device according to [1], wherein the plurality of optical filters are arranged so that the length of the effective irradiation distance in the conveyance direction is substantially uniform in the irradiation window width direction.
[3] The ultraviolet irradiation device according to [1] or [2], wherein the light source is a light source capable of irradiating at least 200 nm to 400 nm of emitted light.
[4] The ultraviolet irradiation device according to any one of [1] to [3], in which the irradiation light from the light source has a spectral characteristic controlled by a bandpass filter.
[5] The ultraviolet irradiation device according to any one of [1] to [4], wherein the optical filter is a polarizer.
[6] The ultraviolet irradiation device according to [5], wherein the polarizer is a wire grid polarizer.
[7] An optical compensation sheet having at least one layer formed by ultraviolet irradiation by the ultraviolet irradiation device according to any one of [1] to [6].
[8] A polarizing plate having at least one optical compensation sheet of [7] and a polarizing layer.
[9] A liquid crystal display device having the optical compensation sheet according to [7] or the polarizing plate according to [8].
[10] The liquid crystal display device according to [9], wherein the display mode is a VA mode.

[11] A layer made of a composition containing at least one liquid crystalline compound is irradiated with polarized ultraviolet rays by the ultraviolet irradiation device according to [5] or [6] to change at least the optical characteristics of the layer before and after irradiation. An optical compensation sheet manufacturing method including a first irradiation step.
[12] The method according to [10], including a second irradiation step of forming an optically anisotropic layer by irradiating polarized ultraviolet rays or non-polarized ultraviolet rays to at least cure the layer after the first irradiation step. .

  Since the ultraviolet irradiation apparatus of the present invention has an optical filter (for example, a polarizer) whose arrangement is optimized, a part or all of the high irradiation intensity is polarized by combining it with a light source with high irradiation intensity. Irradiation of ultraviolet rays can be performed, and when used for the dura process in the continuous conveyance manufacturing process, the productivity of the ultraviolet irradiation process can be remarkably improved. By producing an optical compensation sheet using the ultraviolet irradiation device of the present invention, an optical compensation sheet having a desired optical compensation capability can be produced with high productivity. By using such an optical compensation sheet, a liquid crystal cell can be optically compensated with the same configuration as a conventional liquid crystal display device, and a liquid crystal display device with improved viewing angle as well as display quality is provided. can do. In addition, the ultraviolet irradiation apparatus of the present invention can meet the needs of production capacity enhancement accompanying the increase in the supply amount of the optical compensation sheet, and the polarized ultraviolet irradiation process that governs the optical characteristics of the optical compensation sheet, A continuous process of polarized / non-polarized ultraviolet irradiation that dominates the hardening process, which is an essential process, is possible, and as a result, an optical compensation sheet having excellent optical compensation characteristics and excellent productivity can be produced.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  In the present invention, Re and Rth each represent a front retardation and a retardation in the thickness direction at a wavelength λ. Re is measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) by making light having a wavelength of λ nm incident in the normal direction of the film. Rth is Re and the slow axis in the plane (determined by KOBRA 21ADH) is used as the tilt axis (rotation axis), and the angle is changed with respect to the normal direction of the film. KOBRA 21ADH is calculated based on a plurality of retardation values measured in this manner. At this time, it is necessary to input an assumed value of average refractive index and a film thickness. KOBRA 21ADH calculates nx, ny, and nz in addition to Rth. The average refractive index of 1.48 is used for cellulose acetate, but values of polymer films for typical optical applications other than cellulose acetate include cycloolefin polymer (1.52), polycarbonate (1.59), poly Values such as methyl methacrylate (1.49) and polystyrene (1.59) can be used. As the average refractive index value of other existing polymer materials, the polymer handbook (John Wiley & Sons, Inc.) and the catalog values of polymer films can be used. Further, in the case of a material whose average refractive index is unknown, it can be measured using an Abbe refractometer. In this specification, λ refers to 545 ± 5 nm or 590 ± 5 nm unless otherwise specified.

  In this specification, “substantially” for the angle means that the error from the exact angle is within a range of less than ± 5 °. Furthermore, the error from the exact angle is preferably less than 4 °, more preferably less than 3 °. With regard to retardation, “substantially” means that the retardation is within ± 5%. Furthermore, “Re is not 0” means that Re is 5 nm or more. In addition, the measurement wavelength of the refractive index indicates an arbitrary wavelength in the visible light region unless otherwise specified. Further, in the present specification, “ultraviolet light” refers to light having a wavelength of 200 to 780 nm.

[Ultraviolet irradiation equipment]
Hereinafter, embodiments of the ultraviolet irradiation device of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram of an example of an ultraviolet irradiation device of the present invention. The ultraviolet irradiation device shown in FIG. 1 is formed on the surface of an ultraviolet lamp 1 that is a light source, a reflector 2 that reflects and collects ultraviolet rays emitted from the ultraviolet lamp 1, and a substrate 4 on which the collected ultraviolet rays are incident. A plurality of optical filters 3. The reflector 2 may be omitted, and in this case, the light from the ultraviolet lamp 1 is directly incident on the optical filter 3. The substrate 4 is preferably made of quartz, but may be glass that transmits ultraviolet rays. In FIG. 1, the optical filter 3 is disposed below the substrate 4, but may be disposed above the substrate 4. When the sample having the ultraviolet curable layer irradiated with ultraviolet rays is conveyed under the substrate 4, the ultraviolet rays from the light source 1 that has passed through the optical filter 3 (for example, when the optical filter 3 is a polarizer, a predetermined polarized light is used). UV light).

  The ultraviolet curable layer, which is an ultraviolet irradiation target, is continuously conveyed under the optical filter 3, for example, in a state of being disposed on the surface of a long support. The ultraviolet curable composition may be continuously applied to a long support (for example, a long plastic film) and then continuously conveyed to pass under the optical filter 3.

  In the ultraviolet irradiation device of the present invention, the plurality of optical filters are arranged such that the boundaries between the optical filters intersect the transport direction. In the present specification, “crossing” means crossing at an angle exceeding 0 °. The conveyance direction and the boundary line of the optical filter preferably cross each other at 1 to 45 °, more preferably 5 to 30 °. By installing a plurality of optical filters so that their boundary lines intersect the transport direction, the joints of the optical filters can be made invisible. It is desirable that no light is emitted from the joint portion. Further, it is preferable to determine the arrangement so that the total amount of irradiation light depending on the position in the width direction of the support body does not change depending on the joint portion. In other words, the arrangement of the optical filters is preferably determined so that the length of the effective irradiation distance in the transport direction is substantially uniform in the irradiation window width direction. An example of the arrangement of the optical filters is shown in FIG. In FIG. 2A, a plurality of trapezoidal optical filters 3 are arranged on the surface of the substrate 4 in the width direction b so that the upper and lower bases are staggered and parallel. In the transport direction a, adjacent optical filters 3 are arranged so as to be shifted up and down by a width 6. In this arrangement, it is possible to intentionally form a gap 6 that is shifted by the same amount as the width 5 of the joint at the joint position 5 of the optical filter. As a result, the length of the effective irradiation distance (direction a) Can be made substantially uniform in the irradiation window width direction (b). On the other hand, as shown in FIG. 2D, when a plurality of rectangular optical filters are arranged in the width direction b with each side parallel, the boundary line between the transport direction and the optical filter does not intersect, and the effective irradiation distance Becomes non-uniform in the width direction.

  FIG. 2A shows an example using a trapezoidal optical filter. However, the shape of the optical filter is not particularly limited as long as the boundary line of each filter and the transport direction intersect each other when a plurality of optical filters are arranged. Although not shown, a parallelogram-shaped optical filter may be used, or a triangular optical filter shown in FIG. 2B may be used. Further, as shown in FIG. 2C, rectangular or square optical filters are arranged with their sides parallel to each other to form a rectangular region, and an ultraviolet curable layer is formed in the diagonal direction c of the region. It is also effective to carry.

  The ultraviolet irradiation device of the present invention is particularly effective when placed in a polarized ultraviolet irradiation device using a polarizer as an optical filter. As described above, the polarized ultraviolet irradiation device is particularly important in the production of an optical compensation sheet. Polarizers in the ultraviolet region have few options, and it is generally difficult to produce a large area filter. In the production of an optical compensation sheet, since a width of 1 m or more is required at the time of ultraviolet irradiation, it is a common method to use a filter array. However, film nonuniformity due to the presence of joints is particularly ultraviolet irradiation. This is a problem in the case of a material that is highly dependent on intensity and dose.

  A polarizer is mentioned as an example of the optical filter which the ultraviolet irradiation device of this invention has. The polarizer that can be used as an optical filter in the present invention is not particularly limited as long as it has polarization separation characteristics with respect to the necessary ultraviolet wavelength, and the absorption polarizer is doped with iodine or a dichroic dye. Examples include polarizers made by stretching polyvinyl alcohol and polarizers in which dichroic needle-like crystals are arranged. Non-absorbing polarizers include Brewster angle polarizers and dielectric multilayer polarizers. , Wire grid polarizers, scattering polarizers, and the like. Non-absorptive polarizers are preferred, and wire grid polarizers having high polarization separation ability over a wide wavelength range and high workability are particularly preferred.

  Wire grid polarizers are conventionally used in fields such as radar using radio waves, astronomical observation devices using infrared rays, and recently, have begun to be used in fields using visible light such as liquid crystal projector systems. The wire grid polarizer is composed of a plurality of parallel conductive electrodes supported by a substrate. Characterized by the pitch or period of the conductors, the width of the individual conductors, and the thickness of the conductors. For the electric conductor of the wire grid polarizer, for example, a metal wire such as silver, chromium, and aluminum can be used.

  The light beam generated by the light source is incident on the polarizer at an angle θ with respect to the normal, and the incident surface is orthogonal to the conductive element. The wire grid polarizer splits this beam into a specular reflection component and a non-diffracting transmission component. If the wavelength is shorter than the longest resonance wavelength, there will also be at least one higher order diffraction component. Using the usual definitions of S-polarization and P-polarization, light in the S-polarization state has a polarization vector that is orthogonal to the plane of incidence and is therefore parallel to the conductive element. Conversely, light in the P-polarized state has a polarization vector parallel to the plane of incidence and is therefore orthogonal to the conductive element. The wire grid polarizer reflects light having an electric field vector parallel to the grid wires and transmits light having an electric field vector perpendicular to the grid wires.

  The wire grid polarizer has less dependency on the incident angle of the extinction ratio (the angle of light incident on the polarizer) than a polarizing element using the Brewster angle, so the incident angle on the wire grid polarizer is If it is in a range of about ± 45 ° with respect to normal incidence, it has a feature that polarized light having a large extinction ratio can be obtained. Ideally, the wire grid polarizer functions as a perfect mirror for the polarization of one light, such as polarized S-polarized light, and is completely transparent for other polarizations, such as polarized P-polarized light. In reality, however, even the most reflective metal used as a mirror absorbs part of the incident light, only 90% to 95% is reflected, and even the plate glass has a reflection on the surface. It is not transparent.

  The linear electric conductor of the wire grid polarizer is created using a lithography technique or an etching technique. The cross-sectional shape of the electric conductor is defined by the pitch, the width of the electric conductor, the height of the electric conductor, and the length of the electric conductor, and can be manufactured by lithography and etching techniques used to create a linear electric conductor. Range. For the structure of the wire grid polarizer, the size and configuration of the electric conductor are determined by the wavelength used, and the length of the electric conductor can be applied as long as the shape is longer than the polarization wavelength within a possible range, and is longer than 100 nm. An electric conductor can be applied, and the pitch of the electric conductor is not more than the wavelength of the polarization wavelength, desirably not more than 1/3 of the wavelength, preferably 1.5 to 0.06 μm, and the width of the electric conductor is the wavelength of the polarization wavelength. Hereinafter, it is desirable that the wavelength is 1/3 or less, and it is preferable to have a width ranging from 10% to 90% of the pitch, and the height of the electric conductor is 0.005 to 0.5 μm. preferable. In the wire grid polarizer, the wavelength of light that can be polarized depends on the pitch of the electrical conductor. Specifically, ultraviolet rays can be polarized without reducing the extinction ratio within a range of about ± 50 to ± 100 nm with respect to the wavelength of light to be polarized. Decreases the extinction ratio.

  Moreover, the ultraviolet irradiation apparatus of this invention may have an edge filter and a band pass filter as an optical filter, for example, may be used together with a polarizer. When used in combination with a polarizer, it is preferable to dispose the polarizer in front of the bandpass filter light irradiation direction (that is, at a position closer to the irradiated sample). The characteristics of the edge filter and the band pass filter are generally defined by the wavelength dependency of the transmittance. The wavelength (λa) when the transmittance is 0.005 and the transmittance when the transmittance is 0.5. It is indicated by the wavelength (λc) and the wavelength (λp) at which the transmittance is 0.95 or more. For example, when it is desired to excite radical generation by near-ultraviolet light of 350 nm to 400 nm, it is desirable to set λa to about 340 nm and λp to about 370 nm. The wavelength selectivity of the optical filter is improved by keeping λa and λp in a narrow wavelength range, and the degree of curing of the coating layer can be adjusted by the characteristics of such edge filters and bandpass filters, or unnecessary light irradiation can be performed. In some cases, such effects as preventing the material from changing can be obtained.

Edge filters and bandpass filters utilize light interference in which substances having different refractive indexes are stacked and light reflected between layers cancels incident light by changing the phase by 1/2 of the wavelength. As a typical example of an edge filter or a band pass filter, there is one in which a thin film of an inorganic material is formed on a base. Examples of the inorganic material include fluorides such as AlF ₃ , BaF ₂ , CaF ₂ , Na ₃ AlF ₆ , DyF ₃ , GdF ₃ , LaF ₃ , MgF ₂ , NdF ₂ , TdF ₃ , YbF ₃ and YF ₃ , SiO _2. SiO, Al ₂ O ₃ , HfO ₂ , ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , TiO ₂ , In ₂ O ₃ , oxides such as WO ₃ , nitrides such as SiON, Si ₃ N ₄ , Carbides such as SiC and B ₄ C, and SiO ₂ / Al ₂ O ₃ , Al ₂ O ₃ / Pr ₆ O ₁₁ , Al ₂ O ₃ / La ₂ O ₃ , ZrO ₂ / Ta ₂ O ₅ , ZrO ₂ / MgO A mixture of oxides such as ZrO ₂ / Al ₂ O ₃ , TiO ₂ / Pr ₆ O ₁₁ , TiO ₂ / Al ₂ O ₃ , TiO ₂ / La ₂ O ₃ is used. These inorganic materials are formed into a thin film on a substrate by vacuum deposition, electron beam deposition, ion beam deposition, plasma deposition, or sputtering. As the substrate, ozoneless quartz glass, synthetic quartz glass, or natural quartz glass, which has excellent UV transmittance and is stable against heat from a UV light source, is preferable.

  There is no restriction | limiting in particular about the light source which the ultraviolet irradiation device of this invention has, Any may be sufficient if it is a light source which can irradiate an ultraviolet-ray. Preferably, the light source is capable of irradiating at least 200 nm to 400 nm of emitted light. For example, an ultraviolet lamp, a laser light source, etc. are mentioned.

  The ultraviolet irradiation device of the present invention is not limited to the configuration shown in FIG. 1 and may include other members. For example, the ultraviolet irradiation device of the present invention preferably has a mechanism for cooling the optical filter with a liquid refrigerant. The cooling mechanism includes, for example, an inlet formed on the side surface of the substrate 4 in FIG. 1 into which liquid refrigerant is injected, an outlet through which liquid refrigerant is discharged, and a cavity formed inside the substrate through which the refrigerant can be circulated. Or a flow path. With such a cooling mechanism, it is possible to reduce the deterioration of the optical filter that is excessively heated by the ultraviolet irradiation. As a result, the film forming process can be performed more stably, and the productivity is further improved. The shape of the flow path of the liquid refrigerant inside the substrate part is not particularly limited, and the plurality of optical filters 3 can be cooled more efficiently even when the shape is a linear shape penetrating from the inlet to the outlet. Furthermore, you may have a bending part and a branch part. Moreover, the whole inside of the board | substrate part 4a may be a cavity.

The material used is not particularly limited as long as it is liquid at room temperature. Moreover, when the optical filter is arrange | positioned under the cooling unit, it is preferable that the refractive index of the liquid refrigerant to be used is 1.30-1.60. Similarly, in order to prevent the liquid refrigerant from absorbing the ultraviolet rays from the light source and reducing the irradiation efficiency, the refrigerant is preferably selected from materials that do not absorb at least the wavelength of the irradiated ultraviolet rays. More preferably, it is selected from materials that do not substantially absorb at 780 nm, preferably 300-700 nm, more preferably 330-600 nm. Examples of the refrigerant having a refractive index in the above range and having no absorption in the wavelength region include pure water, alcohols (for example, ethylene glycol, propylene glycol, glycerin, methanol, ethanol, isopropyl alcohol), and silicon oil. A mixed solution of pure water and alcohols is also preferable.
The temperature of the liquid refrigerant is preferably 10 to 70 ° C, more preferably 15 to 60 ° C, and further preferably 20 to 50 ° C.

  Moreover, the ultraviolet irradiation device of the present invention can be used, for example, without using a conveying means for conveying a long support (for example, a polymer film) having an ultraviolet curable layer irradiated with ultraviolet rays or an optical filter. In order to enable the sample to be irradiated with ultraviolet rays, the sample may have a support member that movably supports the substrate 4 on which the optical filter 3 is disposed, and the sample is irradiated with ultraviolet rays or the like without passing through the optical filter. Other possible light sources may be arranged upstream or downstream of the sample transport direction.

  The ultraviolet irradiation apparatus of the present invention can be used for production of various optical films including a hardening process by ultraviolet irradiation. Hereinafter, although the optical compensation sheet produced using the ultraviolet irradiation device of the present invention will be described, the use of the ultraviolet irradiation device of the present invention is not limited to the production of the optical compensation sheet.

[Optical compensation sheet]
FIG. 3 is a schematic cross-sectional view of an example of the optical compensation sheet of the present invention. The optical compensation sheet shown in FIG. 3 has an optically anisotropic layer 12 on a transparent support 11. Between the transparent support 11 and the optically anisotropic layer 12, an alignment layer 13 for controlling the alignment of liquid crystalline molecules in the optically anisotropic layer 12 is disposed. The optically anisotropic layer 12 is a layer formed by ultraviolet irradiation by the ultraviolet irradiation apparatus of the present invention. For example, a solution of an ultraviolet curable composition containing at least one liquid crystal compound is applied and dried on the alignment layer 13 provided on the transparent support while transporting the transparent support to form a coating layer. Then, the coating layer is irradiated with polarized ultraviolet rays at least once by the ultraviolet irradiation device of the present invention, and then further irradiated with non-polarized ultraviolet rays or polarized ultraviolet rays having no polarization plane at least once to cure the coating layer. Can be formed.

  The alignment layer 13 can be formed from a polymer having a reactive group in the side chain, or a monomer or oligomer having a reactive group. In particular, if the reactive group of the alignment layer can react with the reactive group of the liquid crystalline compound used in the optically anisotropic layer, the adhesion between the optically anisotropic layer and the alignment layer is high, Peeling and the like hardly occur at the time of washing treatment such as water washing and chemical treatment such as saponification treatment, and the handleability is good.

  The optical characteristics of the optically anisotropic layer 12 are determined according to its use. For example, when used for optical compensation of a liquid crystal cell, particularly a VA mode liquid crystal cell, the front retardation (Re) is not 0, and the normal line of the optical compensation sheet has the in-plane slow axis as the tilt axis (rotation axis). The retardation value measured by making light of wavelength λ nm incident from a direction inclined + 40 ° with respect to the direction, and the normal axis direction of the optical compensation sheet with the in-plane slow axis as the tilt axis (rotation axis) − It is preferable that the retardation values measured by making light having a wavelength λ nm incident from a direction inclined by 40 ° are adjusted to be substantially equal.

[Polarizer]
4A to 4D are schematic cross-sectional views of a polarizing plate having the optical compensation sheet of the present invention. In general, the polarizing plate can be prepared by dyeing a polarizing film made of a polyvinyl alcohol film with iodine and performing stretching to obtain the polarizing film 21, and laminating protective films 22 and 23 on both sides thereof. it can. Since the optical compensation sheet of the present invention has a support made of a polymer film or the like that supports the optically anisotropic layer, this support can be used as it is for at least one of the protective films 22 and 23. At this time, even if the optically anisotropic layer 12 is disposed on the polarizing layer 21 side (that is, the optically anisotropic layer 12 is closer to the polarizing layer 21 than the support 11), the optically anisotropic layer 12 is on the opposite side of the polarizing layer 21 ( That is, the optically anisotropic layer 12 may be disposed farther from the support 11 than the polarizing layer 21, but as shown in FIG. 4A, the optically anisotropic layer 12 includes the polarizing layer 21. It is preferable that it exists in the other side. Moreover, as shown in FIG.4 (b), it is also possible to paste on the outer side of one protective film 22 of the polarizing layer 21 via an adhesive.

  FIGS. 4C and 4D are configuration examples of a polarizing plate in which another functional layer 24 is arranged on the polarizing plate having the configuration shown in FIG. FIG. 4C is a configuration example in which another functional layer 24 is disposed on the protective film 23 disposed on the opposite side with the optical compensation sheet of the present invention and the polarizing layer 21 in between. d) is a configuration example in which another functional layer 24 is disposed on the optical compensation sheet of the present invention. Examples of other functional layers are not particularly limited, and examples thereof include functional layers that impart various characteristics, such as λ / 4 layers, antireflection layers, and hard coat layers. These layers may be bonded together with, for example, an adhesive as a member such as a λ / 4 plate, an antireflection film, or a hard coat film. In the configuration example of FIG. 4D, the optical compensation of the present invention is used. Another functional layer 24 may be formed on the sheet (the optically anisotropic layer 12) and then bonded to the polarizing layer 21. Further, the protective film 23 itself on the side opposite to the optical compensation sheet of the present invention can be made into other functional films such as a λ / 4 plate, an antireflection film, and a hard coat film.

  When producing a polarizing plate by laminating a polarizing film and a protective film, a total of three films of a pair of protective film and polarizing film are bonded together in a roll-to-roll manner. This roll-to-roll is a preferable method as a manufacturing process of a polarizing plate because it is difficult to cause dimensional change and curling of the polarizing plate as well as productivity, and can impart high mechanical stability.

[Liquid Crystal Display]
FIG. 5 shows an example of the liquid crystal display device of the present invention. The liquid crystal display device includes a liquid crystal cell 35 having a nematic liquid crystal sandwiched between upper and lower electrode substrates, and a pair of polarizing plates 36 and 37 disposed on both sides of the liquid crystal cell, and at least one of the polarizing plates. Uses the polarizing plate of the present invention shown in FIG. When using the polarizing plate of this invention, it can arrange | position so that an optically anisotropic layer may exist between a polarizing layer and the electrode substrate of a liquid crystal cell. Nematic liquid crystal molecules are controlled so as to be in a predetermined alignment state by providing an alignment layer applied on the electrode substrate and a structure such as a rubbing treatment or a rib on the surface thereof.

  One or more light control films 34 such as a brightness enhancement film and a diffusion film may be provided below the liquid crystal cell sandwiched between the polarizing plates. Furthermore, the light control film has a reflection plate 32 and a light guide plate 33 for irradiating light emitted from the cold cathode tubes 31 to the front. Instead of a backlight unit comprising a cold cathode tube and a light guide plate, recently, a direct type backlight in which several cold cathode tubes are arranged under a liquid crystal cell, an LED backlight using an LED as a light source, or an organic EL A backlight that emits light using inorganic EL or the like is also used, but the optical compensation sheet of the present invention is effective in any backlight.

  Furthermore, although not shown in the drawing, in the aspect of the reflective liquid crystal display device, only one polarizing plate needs to be disposed on the observation side, and a reflective film is provided on the back surface of the liquid crystal cell or on the inner surface of the lower substrate of the liquid crystal cell. . Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side. Further, a transflective type in which a transmissive portion and a reflective portion are provided in one pixel of the display device is also possible.

Next, materials used for manufacturing the optical compensation sheet and polarizing plate of the present invention, a manufacturing method, and the like will be described in detail.
One embodiment of the optical compensation sheet of the present invention has a transparent support, an alignment layer, and an optically anisotropic layer. The optically anisotropic layer contributes to increase the contrast viewing angle of the liquid crystal display device and to eliminate image coloring of the liquid crystal display device. In the optical compensation sheet of the present embodiment, the support of the optically anisotropic layer also serves as a protective film for the polarizing plate, or the optically anisotropic layer also serves as the protective film for the polarizing plate, The components of the device can be reduced. In other words, such an embodiment contributes to the thinning of the liquid crystal display device. Hereinafter, although this aspect demonstrates in detail about the material used for preparation, a preparation method, etc., this invention is not limited to this aspect. Other embodiments can also be produced with reference to the following description and conventionally known methods. However, the present invention is not limited to the embodiments described below.

  In the present invention, an optically anisotropic layer containing a liquid crystalline compound is formed on an optically uniaxial or biaxial transparent support made of a high molecular polymer, thereby significantly improving the optical characteristics of the liquid crystal display device. be able to.

[Optically anisotropic layer]
In the present invention, the optically anisotropic layer contributes to optically compensate the liquid crystal cell. Of course, the optically anisotropic layer alone may have sufficient optical compensation ability, or may be an aspect satisfying the optical characteristics required for optical compensation in combination with other layers (for example, a support). The optically anisotropic layer is, for example, an alignment layer provided on the transparent support with an ultraviolet curable coating solution containing at least one liquid crystalline compound while transporting the transparent support using a continuous transport process. After the coating layer is applied and dried to form the coating layer, the coating layer is irradiated with polarized ultraviolet rays at least once by the ultraviolet irradiation device of the present invention while transporting the transparent support having the coating layer, and further, The coating layer is formed by irradiating at least once with non-polarized ultraviolet light or polarized ultraviolet light having no polarization plane.

  In general, liquid crystal compounds can be classified into a rod-shaped type and a disk-shaped type based on their shapes. In addition, there are low and high molecular types, respectively. Polymer generally refers to a polymer having a degree of polymerization of 100 or more (Polymer Physics / Phase Transition Dynamics, Masao Doi, 2 pages, Iwanami Shoten, 1992). In the present invention, any liquid crystalline compound can be used, but a rod-like liquid crystalline compound is preferably used from the viewpoint that in-plane retardation can be efficiently generated by irradiation with polarized ultraviolet rays. Two or more kinds of rod-like liquid crystalline compounds, two or more kinds of disc-like liquid crystalline compounds, or a mixture of a rod-like liquid crystalline compound and a disk-like liquid crystalline compound may be used. It is more preferable to use a rod-like liquid crystal compound or a disk-like liquid crystal compound having a reactive group, because at least one of the reactive groups in one liquid crystal molecule can be formed. Is more preferably 2 or more. The liquid crystalline compound may be a mixture of two or more, and in that case, at least one preferably has two or more reactive groups. The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, and more preferably 0.5 to 10 μm.

  The discotic liquid crystalline compound used for forming the optically anisotropic layer is not particularly limited, and a known one can be used. Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Not only the above low-molecular liquid crystalline compounds but also high-molecular liquid crystalline compounds can be used. The polymer liquid crystalline compound is a polymer compound obtained by polymerizing a rod-like liquid crystalline compound having a low molecular reactive group. As the rod-like liquid crystalline compound having a low-molecular reactive group that is particularly preferably used, a rod-like liquid crystalline compound represented by the following general formula (I) can be exemplified.

Formula (I): Q ¹ -L ¹ -A ¹ -L ³ -ML ⁴ -A ² -L ² -Q ²
Wherein, Q ¹ and Q ² respectively represent a reactive group, the L ^1, L ^2, L ³ and L ⁴ respectively represent a single bond or a divalent linking group, L ³ and At least one of L ⁴ is preferably —O—CO—O—. A ¹ and A ² each independently represent a spacer group having 2 to 20 carbon atoms. M represents a mesogenic group.

Hereinafter, the rod-like liquid crystal compound having a reactive group represented by the general formula (I) will be described in more detail. In the formula, Q ¹ and Q ² are each independently a reactive group. The polymerization reaction of the reactive group is preferably addition polymerization (including ring-opening polymerization) or condensation polymerization. In other words, the reactive group is preferably a reactive group capable of an addition polymerization reaction or a condensation polymerization reaction. Examples of reactive groups are shown below.

Examples of the divalent linking group represented by L ¹ , L ² , L ³ and L ⁴ include —O—, —S—, —CO—, —NR ² —, —CO—O—, and —O—CO. —O—, —CO—NR ² —, —NR ² —CO—, —O—CO—, —O—CO—NR ² —, —NR ² —CO—O—, and NR ² —CO—NR ^2. A divalent linking group selected from the group consisting of-is preferred. R ² is an alkyl group having 1 to 7 carbon atoms or a hydrogen atom. In this case, at least one of L ³ and L ⁴ is —O—CO—O— (carbonate group). In the formula (I), Q ¹ -L ¹ and Q ² -L ² -are CH ₂ ═CH—CO—O—, CH ₂ ═C (CH ₃ ) —CO—O—, and CH ₂ ═C ( Cl) -CO-O-CO- O- are _{preferable, CH 2 = CH-CO-} O- is most preferable.

A ¹ and A ² represent a spacer group having 2 to 20 carbon atoms. An aliphatic group having 2 to 12 carbon atoms is preferable, and an alkylene group is particularly preferable. The spacer group is preferably chain-like and may contain oxygen atoms or sulfur atoms that are not adjacent to each other. The spacer group may have a substituent and may be substituted with a halogen atom (fluorine, chlorine, bromine), a cyano group, a methyl group, or an ethyl group.

Examples of the mesogenic group represented by M include all known mesogenic groups. In particular, a group represented by the following general formula (II) is preferable.
Formula (II): - (- W 1 -L 5) n -W 2 -
In the formula, W ¹ and W ² each independently represent a divalent cycloaliphatic group, a divalent aromatic group or a divalent heterocyclic group, L5 represents a single bond or a linking group, and a linking group Specific examples of these include specific examples of groups represented by L ^{1 to} L ⁴ in the formula (I), —CH ₂ —O—, and O—CH ₂ —. n represents 1, 2 or 3.

W ¹ and W ² include 1,4-cyclohexanediyl, 1,4-phenylene, pyrimidine-2,5-diyl, pyridine-2,5diyl, 1,3,4-thiadiazole-2,5-diyl, 1,3,4-oxadiazole-2,5-diyl, naphthalene-2,6-diyl, naphthalene-1,5-diyl, thiophene-2,5-diyl, pyridazine-3,6-diyl . In the case of 1,4-cyclohexanediyl, there are trans isomers and cis isomers, but either isomer may be used, and a mixture in any proportion may be used. More preferably, it is a trans form. W ¹ and W ² may each have a substituent. Examples of the substituent include a halogen atom (fluorine, chlorine, bromine, iodine), a cyano group, an alkyl group having 1 to 10 carbon atoms (methyl group, ethyl group, propyl group, etc.), and an alkoxy group having 1 to 10 carbon atoms. (Methoxy group, ethoxy group, etc.), C1-10 acyl group (formyl group, acetyl group, etc.), C1-10 alkoxycarbonyl group (methoxycarbonyl group, ethoxycarbonyl group, etc.), carbon atom Examples thereof include an acyloxy group having 1 to 10 (acetyloxy group, propionyloxy group, etc.), nitro group, trifluoromethyl group, difluoromethyl group and the like.

  Preferred examples of the basic skeleton of the mesogenic group represented by the general formula (II) are shown below. These may be substituted with the above substituents.

  Examples of the compound represented by the general formula (I) are shown below, but the present invention is not limited thereto. The compound represented by the general formula (I) can be synthesized by the method described in JP-T-11-513019.

  The optically anisotropic layer is preferably formed using an alignment layer and a gas-liquid interface. Specifically, it can be produced by providing an alignment layer directly on the transparent support and then forming an optically anisotropic layer directly on the alignment layer.

  In the present invention, the optically anisotropic layer allows light having a wavelength of λ nm to be incident from a direction inclined by + 40 ° with respect to the normal direction of the optical compensation sheet with an in-plane slow axis as an inclination axis (rotation axis). The measured retardation value and the retardation measured by injecting light of wavelength λ nm from the direction inclined by −40 ° with respect to the normal direction of the optical compensation sheet with the in-plane slow axis as the tilt axis (rotation axis) It is preferable to have optical properties that the values are substantially equal. When using a rod-like liquid crystalline compound having a reactive group, in order to develop biaxiality, the cholesteric alignment or the hybrid cholesteric alignment that is twisted while the inclination angle gradually changes in the thickness direction may be distorted by polarized light irradiation. is necessary. As a method of distorting the alignment by irradiation with polarized light, a method using a dichroic liquid crystalline polymerization initiator (WO03 / 054111 A1) or a method using a rod-like liquid crystalline compound having a photoalignable functional group such as a cinnamoyl group in the molecule (Japanese Patent Laid-Open No. 2002-6138). Any of them can be used in the present invention.

  The Re of the optically anisotropic layer is preferably 5 to 250 nm, more preferably 10 to 100 nm, and most preferably 20 to 80 nm. Rth is preferably 30 to 500 nm in total with Rth of the transparent support, more preferably 40 to 400 nm, and most preferably 100 to 350 nm.

  In the case of laminating two or more optically anisotropic layers, the combination of liquid crystalline compounds is not particularly limited, and is a laminate of layers composed of all discotic liquid crystalline compounds, a laminate of layers composed of all rod-like liquid crystalline compounds, It may be a laminate of a layer made of a discotic liquid crystalline compound and a layer made of a rod-like liquid crystalline compound. It is preferable that at least one layer consists of a rod-like liquid crystalline compound. The combination of the alignment states of the layers is not particularly limited, and optically anisotropic layers having the same alignment state may be stacked, or optically anisotropic layers having different alignment states may be stacked. In particular, the optically anisotropic layer preferably exhibits a cholesteric phase before irradiation with polarized ultraviolet rays.

  The optically anisotropic layer is formed by coating and drying a coating liquid containing a liquid crystalline compound and the following polymerization initiator and other additives directly on the alignment layer, for example, using a continuous conveyance process, and curing. Can be formed. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. Application | coating of a coating liquid can be implemented by a well-known method (For example, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method), for example using a continuous conveyance process.

  Examples of the photopolymerization initiator used in the solution for forming an optically anisotropic layer in the present invention include α-carbonyl compounds (described in the specifications of US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (US Pat. 2448828 description), α-hydrocarbon-substituted aromatic acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), triarylimidazole dimers, Combination with p-aminophenyl ketone (described in U.S. Pat. No. 3,549,367), acridine and phenazine compounds (described in JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970) Description).

  The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. In polarized ultraviolet irradiation and / or non-polarized ultraviolet irradiation, the surface temperature of the optically anisotropic layer is preferably maintained at 70 ° C. or higher and 160 ° C. or lower.

[Horizontal alignment agent]
In the present invention, the liquid crystal compound molecule is obtained by containing at least one of the compounds (horizontal alignment agents) represented by the following general formulas (1) to (3) in the optical anisotropic layer forming solution. Can be substantially horizontally oriented. In the present invention, “horizontal alignment” means that in the case of a rod-like liquid crystal, the molecular long axis is parallel to the horizontal plane of the transparent support. In the case of a disc-like liquid crystal, the disc surface of the core of the disc-like liquid crystal compound. And the horizontal plane of the transparent support is parallel, but it is not required to be strictly parallel, and in this specification, an inclination angle with the horizontal plane is less than 10 degrees. To do. The inclination angle is preferably 0 to 5 degrees, more preferably 0 to 3 degrees, further preferably 0 to 2 degrees, and most preferably 0 to 1 degree.
Hereinafter, the following general formulas (1) to (3) will be described in order.

In the formula, R ¹ , R ² and R ³ each independently represent a hydrogen atom or a substituent, and X ¹ , X ² and X ^{3 each} represent a single bond or a divalent linking group. The substituent represented by each of R ^{1 to} R ³ is preferably a substituted or unsubstituted alkyl group (more preferably an unsubstituted alkyl group or a fluorine-substituted alkyl group), an aryl group (particularly a fluorine-substituted alkyl). An aryl group having a group is preferred), a substituted or unsubstituted amino group, an alkoxy group, an alkylthio group, and a halogen atom. The divalent linking groups represented by X ¹ , X ² and X ³ are each an alkylene group, an alkenylene group, a divalent aromatic group, a divalent heterocyclic residue, —CO—, —NR ^a — ( R ^a is ^a divalent linking group selected from the group consisting of an alkyl group having 1 to 5 carbon atoms or a hydrogen atom), —O—, —S—, —SO—, —SO ₂ —, and combinations thereof. Preferably there is. The divalent linking group is selected from the group consisting of an alkylene group, a phenylene group, —CO—, —NR ^a —, —O—, —S—, and —SO ₂ —. It is more preferable that the divalent linking group is a combination of at least two groups. The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The number of carbon atoms of the divalent aromatic group is preferably 6-10.

In the formula, R represents a substituent, and m represents an integer of 0 to 5. When m represents an integer greater than or equal to 2, several R may be same or different. Preferred substituents for R are the same as those recited as preferred ranges for the substituents represented by R ¹ , R ² , and R ³ . m preferably represents an integer of 1 to 3, particularly preferably 2 or 3.

In the formula, R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a hydrogen atom or a substituent. The substituents represented by R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are each preferably a substituent represented by R ¹ , R ² and R ³ in the general formula (I). It is listed as a thing. As the horizontal alignment agent used in the present invention, compounds described in Japanese Patent Application No. 2003-331269 can be used, and the synthesis method of these compounds is also described in the specification.

  The amount of the compound represented by the general formulas (1) to (3) is preferably 0.01 to 20% by mass, and 0.01 to 10% by mass based on the mass of the liquid crystal compound. Is more preferable, and 0.02 to 1% by mass is particularly preferable. In addition, the compounds represented by the general formulas (1) to (3) may be used alone or in combination of two or more.

[Optical alignment by polarized irradiation]
The optically anisotropic layer is a layer formed by being irradiated with ultraviolet rays at least once by the ultraviolet irradiation device of the present invention. A layer formed by irradiation with polarized ultraviolet rays is preferable, and an optically anisotropic layer formed by generating in-plane retardation by photo-alignment by irradiation with polarized ultraviolet rays is preferable. In order to obtain a large in-plane retardation, it is necessary to perform irradiation with polarized ultraviolet rays first after coating and drying the liquid crystal compound layer. The polarized light irradiation is preferably performed in an inert gas atmosphere having an oxygen concentration of 0.5% or less. The irradiation energy is preferably ^{20mJ / cm 2 ~10J / cm 2} , further preferably 20~800mJ / cm ^2. The illuminance is preferably 20~1200mW / cm ^2, more preferably 50~1000mW / cm ^2, further preferably 100~800mW / cm ^2. Although there is no restriction | limiting in particular about the kind of liquid crystalline compound hardened | cured by polarized irradiation, The liquid crystalline compound (more preferably rod-shaped liquid crystalline compound) which has an ethylenically unsaturated group as a reactive group is preferable. The irradiation wavelength preferably has a peak at 300 to 450 nm, and more preferably has a peak at 350 to 400 nm.
Note that the optically anisotropic layer exhibiting in-plane retardation generated by photo-alignment due to polarized light irradiation is particularly excellent in optically compensating a VA mode liquid crystal display device.

  Conventionally, when a plurality of polarizing elements are arranged and irradiated with ultraviolet rays through the polarizing elements, the light passing through the boundary between the polarizing elements is not strictly polarized, and the irradiation intensity is increased by the light from the condensing system In order to cure at an irradiation intensity in the vicinity of the focal point, there is a problem that it is easily affected by the boundary of the element arrangement. Therefore, in the present invention, by using an ultraviolet irradiation device in which a polarizing element is arranged so that the boundary between the polarizing elements and the transport direction intersect, the influence of light passing through the vicinity of the boundary between the polarizing elements in the dura process at the time of transport. Is substantially reduced, and the optically anisotropic layer is stably formed. Further, as described above, when the ultraviolet irradiation device of the present invention in which the polarizers are arranged so that the length of the irradiation window in the conveyance direction length is the same in the irradiation window width direction, the integrated irradiation dose is substantially the same in the width direction. And the influence of the boundary of the polarizing element can be further reduced.

[Post-curing by UV irradiation after polarized irradiation]
In order to form the optically anisotropic layer, a second light irradiation step of further irradiating polarized or non-polarized ultraviolet rays is performed after the first polarized ultraviolet irradiation step using the ultraviolet irradiation device of the present invention. It may be formed. By carrying out the second light irradiation step, it is possible to increase the reaction rate of the reactive group of the polymerizable component contained in the layer (post-curing), improve adhesion, etc., and produce at a high transport speed. It becomes possible. The ultraviolet rays used for post-curing in the present invention may be polarized or non-polarized, but are preferably polarized. Further, it is preferable to carry out the post-curing step twice or more, and it is preferable to irradiate the polarized light before the non-polarized light. .

At the time of ultraviolet irradiation in the post-curing step, inert gas substitution may or may not be performed, but it is preferably performed in an inert gas atmosphere having an oxygen concentration of 0.5% or less. UV irradiation energy in the post-curing is preferably ^{20mJ / cm 2 ~10J / cm 2} , further preferably 20~300mJ / cm ^2. The illuminance is preferably 20~1200mW / cm ^2, more preferably 50~1000mW / cm ^2, further preferably 100~800mW / cm ^2. In the case of polarized light irradiation, the irradiation wavelength preferably has a peak at 300 to 450 nm, and more preferably 350 to 400 nm. In the case of non-polarized light irradiation, it preferably has a peak at 200 to 450 nm, and more preferably has a peak at 250 to 400 nm.

  Biaxiality can be developed even at high transport speeds by performing a continuous process of polarized UV irradiation that controls optical characteristics and polarized / non-polarized UV irradiation that controls the dura of the liquid crystal layer of the optical compensation sheet. it can. If a continuous process is carried out, for example, biaxiality can be efficiently expressed by irradiation with polarized ultraviolet rays at a film conveyance speed of 5 to 50 m / min, preferably 10 to 40 m / min, and an optical product with excellent productivity. Compensation sheets can be manufactured.

[Alignment layer]
The optical compensation sheet of the present invention may have an alignment layer between the transparent support and the optically anisotropic layer. The alignment layer can be formed by applying and drying an alignment layer forming solution on a transparent support or an undercoat layer coated on the transparent support. The alignment layer is used for defining the alignment direction of the liquid crystal compound contained in the optically anisotropic layer provided thereon. The orientation layer may be any layer as long as it can impart orientation to the optically anisotropic layer. Preferable examples of the alignment layer include a layer subjected to a rubbing treatment of an organic compound (preferably a polymer), an oblique deposition layer of an inorganic compound, and a layer having a microgroove, ω-tricosanoic acid, dioctadecylmethylammonium chloride and stearyl. Examples thereof include a cumulative film formed by Langmuir-Blodgett method (LB film) such as methyl acid, or a layer in which a dielectric is oriented by applying an electric field or a magnetic field.

  Examples of organic compounds for the alignment layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol, poly (N-methylolacrylamide), styrene / vinyltoluene copolymer. , Polymers such as chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene and polycarbonate, and Examples of the compound include a silane coupling agent. Examples of preferred polymers include polyimide, polystyrene, polymers of styrene derivatives, gelatin, polyvinyl alcohol, and alkyl-modified polyvinyl alcohol having an alkyl group (preferably having 6 or more carbon atoms).

  For forming the alignment layer, it is preferable to use a polymer. The type of polymer that can be used can be determined according to the orientation (particularly the average tilt angle) of the liquid crystal compound. For example, in order to align the liquid crystalline compound horizontally, a polymer that does not decrease the surface energy of the alignment film (ordinary alignment polymer) can be used. Specific types of polymers are described in various documents about liquid crystal cells or optical compensation sheets. For example, polyvinyl alcohol or modified polyvinyl alcohol, a copolymer with polyacrylic acid or polyacrylate, polyvinyl pyrrolidone, cellulose, or modified cellulose are preferably used. Any of the alignment films preferably has a polymerizable group for the purpose of improving the adhesion between the liquid crystal compound and the transparent support. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group. It is more preferable to use an alignment film that forms a chemical bond with a liquid crystal compound at the interface. Such an alignment film is described in JP-A-9-152509, and acid chloride or Karenz MOI (manufactured by Showa Denko KK). The modified polyvinyl alcohol in which an acrylic group is introduced into the side chain by using The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

  A polyimide film (preferably fluorine atom-containing polyimide) widely used as an alignment layer for LCD is also preferable as the organic alignment layer. For this, polyamic acid (for example, LQ / LX series manufactured by Hitachi Chemical Co., Ltd., SE series manufactured by Nissan Chemical Co., Ltd., etc.) was applied to the support surface and baked at 100 to 300 ° C. for 0.5 to 1 hour. Thereafter, it is obtained by rubbing. Furthermore, the alignment layer used in the present invention can be obtained by introducing a reactive group into the polymer or by using the polymer together with a crosslinking agent such as an isocyanate compound and an epoxy compound to cure these polymers. It is preferable that it is a cured film obtained.

  Moreover, the rubbing process can utilize a processing method widely adopted as a liquid crystal alignment process of LCD. That is, a method of obtaining the orientation by rubbing the surface of the orientation layer in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are flocked on average. In this invention, after apply | coating and drying the solution for alignment layer formation, it is preferable to carry out the rubbing process of the alignment layer, conveying the transparent support body which provided the alignment layer, for example using a continuous conveyance process.

Further, as a vapor deposition material for the inorganic oblique vapor deposition film, SiO is representative, metal oxides such as TiO ₂ and ZnO ₂ , fluorides such as MgF ₂ , and metals such as Au and Al. The metal oxide can be used as an oblique deposition material as long as it has a high dielectric constant, and is not limited to the above. The inorganic oblique deposition film can be formed using a deposition apparatus. An inorganic oblique vapor deposition film can be formed by fixing the film (support) and performing vapor deposition, or moving the long film and performing continuous vapor deposition.

  The alignment layer forming solution preferably contains a polymer having a reactive group in the side chain, or a monomer or oligomer having a reactive group, specifically, a modified polyvinyl alcohol having a reactive group in the side chain. Examples of the reactive group include the reactive groups described above. Moreover, it is preferable that a reactive group can react directly with the reactive group which the liquid crystalline compound used for an optically anisotropic layer has. When the compound of the alignment layer and the optically anisotropic layer undergoes a direct crosslinking reaction, the adhesion of the completed film can be imparted.

  The optically anisotropic layer of the optical compensation sheet of the present invention may be transferred by, for example, using a pressure-sensitive adhesive on the transparent support after aligning the liquid crystalline compound on the temporary alignment layer and fixing the alignment. However, it is preferable to form the optical compensation sheet directly without transfer from the viewpoint of productivity.

  Each of the optically anisotropic layer and the alignment layer is formed by a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, or an extrusion coating method (US Pat. No. 2,681,294). Can be applied. Two or more layers may be applied simultaneously. The method of simultaneous application is described in US Pat. Nos. 2,761,791, 2,941,898, 3,508,947, and 3,526,528 and Yuji Harasaki, Coating Engineering, page 253, Asakura Shoten (1973).

[Transparent support]
The optical compensation sheet of the present embodiment has a transparent support that supports the optically anisotropic layer. As the transparent support, it is preferable to use a polymer film having a light transmittance of 80% or more. The thickness of the transparent support is preferably 10 to 500 μm, more preferably 20 to 200 μm, and most preferably 35 to 110 μm.

  The glass transition temperature (Tg) of the transparent support is appropriately determined according to the purpose of use. The glass transition temperature of the resin is preferably 70 ° C. or higher, more preferably 75 ° C. to 200 ° C., and particularly preferably 80 ° C. to 180 ° C. When a resin having a glass transition temperature in this range is employed, heat resistance and molding processability are highly balanced, which is preferable.

  The Re of the transparent support is preferably adjusted to a range of −200 to 100 nm, and Rth is preferably adjusted to a range of −100 to 100 nm. Re is more preferably −50 to 30 nm, and most preferably −30 to 20 nm. In this specification, negative Re means that the in-plane slow axis of the transparent support is in the direction (TD direction) perpendicular to the film transport direction, and negative Rth is the in-plane average refractive index in the thickness direction. It is larger than the rate. In order to improve the color, it is preferable that the in-plane slow axis of the transparent support is in the TD direction.

  As the polymer constituting the transparent support, for example, cellulose polymers and cycloolefin polymers can be used. Specifically, cellulose esters (eg, cellulose acetate, cellulose propionate, cellulose butyrate), Polyolefin (eg, norbornene-based polymer), poly (meth) acrylic acid ester (eg, polymethyl methacrylate), polycarbonate, polyester and polysulfone, and norbornene-based polymer can be used. From the viewpoint of low birefringence, cellulose esters and norbornene-based polymers are preferable, and as commercially available norbornene-based polymers, Arton (manufactured by JSR Corporation), Zeonex, Zeonore (above, Nippon Zeon Corporation) and the like are used. Can do.

  In particular, when used as a protective film for a polarizing plate, cellulose ester is preferable, and cellulose lower fatty acid ester is more preferable. Lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. Of the lower fatty acid esters of cellulose, cellulose acetate is most preferred. The acyl group substitution degree of the cellulose ester is preferably 2.50 to 3.00, more preferably 2.75 to 2.95, and most preferably 2.80 to 2.90.

  The viscosity average polymerization degree (DP) of the cellulose ester is preferably 250 or more, and more preferably 290 or more. In addition, the cellulose ester preferably has a narrow molecular weight distribution of Mm / Mn (Mm is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The value of Mm / Mn is preferably 1.0 to 5.0, more preferably 1.3 to 3.0, and most preferably 1.4 to 2.0.

  In the cellulose ester, the hydroxyl groups at the 2-position, 3-position and 6-position of cellulose are not evenly substituted but the degree of substitution at the 6-position tends to be small. In the present invention, the 6-position substitution degree of the cellulose ester is preferably about the same as or higher than the 2-position and 3-position. The ratio of the 6-position substitution degree to the total of the 2-position, 3-position and 6-position substitution degrees is preferably 30 to 40%. The ratio of the 6-position substitution degree is preferably 31% or more, particularly preferably 32% or more. The substitution degree at the 6-position is preferably 0.88 or more. The 6-position of cellulose may be substituted with an acyl group having 3 or more carbon atoms (eg, propionyl, butyryl, valeroyl, benzoyl, acryloyl) in addition to acetyl. The degree of substitution at each position can be measured by NMR. Cellulose esters having a high degree of substitution at the 6-position are described in Synthesis Example 1 described in Paragraph Nos. 0043 to 0044, Synthesis Example 2 described in Paragraph Nos. 0048 to 0049, and Paragraph Nos. 0051 to 0052. It can synthesize | combine with reference to the synthesis example 3 of these.

  A plasticizer can be added to the cellulose ester film in order to improve mechanical properties or increase the drying speed. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP), biphenyl diphenyl phosphate and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The addition amount of the plasticizer is preferably 0.1 to 25% by mass of the amount of cellulose ester, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass.

  A degradation inhibitor (eg, antioxidant, peroxide decomposer, radical inhibitor, metal deactivator, acid scavenger, amine) may be added to the cellulose ester film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by mass of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by mass. When the addition amount is less than 0.01% by mass, the effect of the deterioration preventing agent is hardly recognized. When the addition amount exceeds 1% by mass, bleed-out (bleeding) of the deterioration preventing agent to the film surface may be observed. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA). Furthermore, a very small amount of dye may be added to prevent light piping. From the viewpoint of transmittance, it is preferable to adjust the type and amount so that the transmittance of light having a wavelength of 420 nm is 50% or more. The added amount of the dye is preferably 0.01 ppm to 1 ppm.

  A retardation control agent can be added to the cellulose ester film in order to control Re and Rth. The retardation control agent is preferably used in the range of 0.01 to 20 parts by mass, more preferably 0.05 to 15 parts by mass, with respect to 100 parts by mass of the cellulose ester. Most preferably, it is used in the range of 1 to 10 parts by mass. Two or more retardation control agents may be used in combination. The retardation control agent is described in pamphlets of WO01 / 88574 and WO00 / 2619, and JP-A 2000-1111914 and 2000-275434.

  The cellulose ester film can be produced by a solvent cast method using a solution containing cellulose ester and other components as a dope. The dope can be cast on a drum or band and the solvent evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 10 to 40% by mass. The solid content is more preferably 18 to 35% by mass. Two or more dopes can be cast. The surface of the drum or band is preferably finished in a mirror state. Regarding casting and drying methods in the solvent cast method, U.S. Pat. Nos. 2,336,310, 2,367,603, 2,429,078, 2,429,297, 2,429,978, 2,607,704, 2,37,069, 2,273,070, British Patent 6,407,331, No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.

  The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. Then, the method can be employed in which the obtained film is peeled off from the drum or the band and further dried with high-temperature air at different temperatures of 100 to 160 ° C. to evaporate the residual solvent (described in Japanese Patent Publication No. 5-17844). . According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting. When casting a plurality of cellulose ester solutions, a solution is prepared by casting a solution containing cellulose ester from a plurality of casting openings provided at intervals in the traveling direction of the support, and laminating them. (Japanese Unexamined Patent Publication Nos. 61-158414, 1-122419, and 11-198285). A film can also be produced by casting a cellulose ester solution from two casting ports (Japanese Patent Publication Nos. 60-27562, 61-94724, 61-947245, 61-104413, 61-158413 and JP-A-6-134933). Employs a method of casting a cellulose ester film (described in JP-A-56-162617) by wrapping a flow of a high-viscosity cellulose ester solution with a low-viscosity cellulose ester solution and extruding a high-viscosity and low-viscosity cellulose ester solution simultaneously. May be.

  The retardation of the cellulose ester film can be further adjusted by a stretching treatment. The draw ratio is preferably in the range of 3 to 100%. Tenter stretching is preferred. In order to control the slow axis with high accuracy, it is preferable to make the difference between the left and right tenter clip speeds and the separation timing as small as possible. The stretching process is described on page 37, line 8 to page 38, line 8 of the pamphlet of WO 01/88574.

  The cellulose ester film can be subjected to a surface treatment. Examples of the surface treatment include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose ester film in the surface treatment is preferably Tg (glass transition temperature) or lower, specifically 150 ° C. or lower.

  The thickness of the cellulose ester film can be adjusted by lip flow rate and line speed, or stretching or compression when it is produced by film formation. Since the moisture permeability varies depending on the main material to be used, it is possible to obtain a preferable moisture permeability range as a protective film for the polarizing plate by adjusting the thickness. Moreover, the free volume of the said cellulose-ester film can be adjusted with drying temperature and time, when producing by film forming. Also in this case, since the moisture permeability varies depending on the main material used, it is possible to make the moisture permeability range preferable as a protective film by adjusting the free volume. The hydrophilicity / hydrophobicity of the cellulose ester film can be adjusted by an additive. Moisture permeability is increased by adding a hydrophilic additive in the free volume, and conversely, moisture permeability can be lowered by adding a hydrophobic additive. Thus, by adjusting the moisture permeability of the cellulose ester film by various methods, it is possible to obtain a range of moisture permeability preferable as a protective film for the polarizing plate, and the support for the optically anisotropic layer is protected for the polarizing plate. A polarizing plate that can also serve as a film and has optical compensation ability can be manufactured at low cost with high productivity.

[Polarizer]
The polarizing plate of the present invention has the above-described optical compensation sheet of the present invention and a polarizing film. The polarizing plate is composed of a polarizing film and a pair of protective films that sandwich the polarizing film. Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. The kind of protective film is not particularly limited, and cellulose esters such as cellulose acetate, cellulose acetate butyrate, and cellulose propionate, polycarbonate, polyolefin, polystyrene, polyester, and the like can be used. The transparent protective film is usually supplied in a roll form, and it is preferable that the transparent protective film is continuously bonded to the long polarizing film so that the longitudinal (MD) direction is coincident. Here, the orientation axis (slow axis) of the protective film may be any direction. Further, the angle between the slow axis (alignment axis) of the protective film and the absorption axis (stretching axis) of the polarizing film is not particularly limited, and can be appropriately set according to the purpose of the polarizing plate.

The polarizing film and the protective film may be bonded together with an aqueous adhesive. The adhesive solvent in the water-based adhesive is dried by diffusing in the protective film. The higher the moisture permeability of the protective film, the faster the drying and the higher the productivity. However, if the protective film is too high, the moisture will enter the polarizing film due to the usage environment (high humidity) of the liquid crystal display device. The performance drops. The moisture permeability of the optical compensation sheet is determined by the thickness, free volume, hydrophilicity / hydrophobicity, etc. of the polymer film (and polymerizable liquid crystal compound). The moisture permeability of the protective film for the polarizing plate is preferably in the range of 100 to 1000 (g / m ² ) / 24 hrs, and more preferably in the range of 300 to 700 (g / m ² ) / 24 hrs.

  In the present invention, for the purpose of reducing the thickness, one of the protective films of the polarizing film may also serve as the support for the optically anisotropic layer, or may be the optical compensation sheet itself. The optical compensation sheet and the polarizing film are preferably subjected to a fixing treatment from the viewpoint of preventing the optical axis from shifting and preventing foreign matters such as dust from entering. An appropriate method such as an adhesive method through a transparent adhesive layer can be applied to the fixed lamination. There is no particular limitation on the type of the adhesive and the like, and from the viewpoint of preventing changes in the optical properties of the constituent members, those that do not require a high-temperature process during curing or drying are preferable, and a long-time curing And those that do not require drying time. From such a viewpoint, a hydrophilic polymer adhesive or a pressure-sensitive adhesive layer is preferably used.

  Appropriate functional layers such as a protective film for various purposes such as water resistance according to the above protective film, an antireflection layer and / or an antiglare treatment layer for the purpose of preventing surface reflection, etc. on one or both sides of the polarizing film You may use the polarizing plate which formed. The antireflection layer can be suitably formed, for example, as a light interference film such as a fluorine polymer coating layer or a multilayer metal vapor deposition film. The antiglare layer is also formed by an appropriate method that diffuses the surface reflected light, for example, by providing a fine uneven structure on the surface by an appropriate method such as a resin coating layer containing fine particles, embossing, sandblasting or etching. can do.

  In addition, as said microparticles | fine-particles, inorganic type which may have electroconductivity, such as silica, calcium oxide with an average particle diameter of 0.5-20 micrometers, an alumina, a titania, a zirconia, a tin oxide, an indium oxide, a cadmium oxide, an antimony oxide, for example One kind or two or more kinds of fine particles, cross-linked or non-cross-linked organic fine particles made of a suitable polymer such as polymethyl methacrylate and polyurethane can be used. The above-mentioned adhesive layer or pressure-sensitive adhesive layer may contain such fine particles and exhibit light diffusibility.

  The polarizing plate of the present invention preferably has optical properties and durability (storability in the short term and long term) equivalent to or better than those of a commercially available super high contrast product (for example, HLC2-5618 manufactured by Sanlitz Co., Ltd.). . Specifically, the visible light transmittance is 42.5% or more, and the degree of polarization √ ({(Tp−Tc) / (Tp + Tc)} ≧ 0.9995 (where Tp is parallel transmittance and Tc is orthogonal transmittance) ), The change rate of the light transmittance before and after being left for 500 hours in a 60 ° C., 90% humidity RH atmosphere and at 80 ° C. for 500 hours in a dry atmosphere is 3% or less based on the absolute value, Further, it is preferably 1% or less, and the rate of change in polarization degree is preferably 1% or less, more preferably 0.1% or less, based on the absolute value.

[Liquid Crystal Display]
The liquid crystal display device of the present invention is a liquid crystal display device having the above-described optical compensation sheet or polarizing plate of the present invention. The display mode of the liquid crystal display device of the present invention is not particularly limited, but the VA mode is preferable. The liquid crystal display device of the present invention is effective not only in the display mode but also in an aspect applied to the STN mode, TN mode, and OCB mode.

[VA mode liquid crystal cell]
In the present invention, the liquid crystal cell is preferably in a vertically aligned mode (VA mode). The VA mode liquid crystal cell is formed by sealing liquid crystal molecules having negative dielectric anisotropy between upper and lower substrates whose opposite surfaces are rubbed. For example, by using liquid crystal molecules having Δn = 0.0813 and Δε = −4.6, a director indicating the alignment direction of the liquid crystal molecules, that is, a liquid crystal cell having a so-called tilt angle of about 89 ° can be manufactured. At this time, the thickness d of the liquid crystal layer can be about 3.5 μm. The brightness at the time of white display changes depending on the magnitude of the product Δn · d of the thickness d (nm) of the liquid crystal layer and the refractive index anisotropy Δn. In order to obtain the maximum brightness, the thickness d of the liquid crystal layer is preferably in the range of 2 to 5 μm (2000 to 5000 nm), and Δn is in the range of 0.060 to 0.085.

  As shown in FIG. 5, transparent electrodes are formed inside the upper and lower substrates of the liquid crystal cell 35, but in a non-driving state in which no driving voltage is applied to the electrodes, the liquid crystal molecules in the liquid crystal layer are roughly with respect to the substrate surface. As a result, the polarization state of light passing through the liquid crystal panel is hardly changed. Since the absorption axis of the upper polarizing plate 37 of the liquid crystal cell and the absorption axis of the lower polarizing plate 36 are substantially orthogonal, light does not pass through the polarizing plate. In other words, in the VA mode liquid crystal display device, an ideal black display can be realized in the non-driven state. On the other hand, in the driving state, the liquid crystal molecules are inclined in a direction parallel to the substrate surface, and the light passing through the liquid crystal panel changes the polarization state by the inclined liquid crystal molecules and passes through the polarizing plate.

  Up to this point, since an electric field is applied between the upper and lower substrates, an example using a liquid crystal material having a negative dielectric anisotropy in which liquid crystal molecules respond perpendicularly to the electric field direction has been shown. In the case where the liquid crystal material is disposed on the substrate and an electric field is applied in a lateral direction parallel to the substrate surface, a liquid crystal material having a positive dielectric anisotropy can be used.

  The characteristics of the VA mode are high-speed response and high contrast. However, there is a problem that the contrast is high in the front but decreases in the oblique direction. Since the liquid crystal molecules are aligned perpendicular to the substrate surface during black display, when viewed from the front, there is almost no birefringence of the liquid crystal molecules, so the transmittance is low and high contrast can be obtained. However, when observed obliquely, birefringence occurs in the liquid crystalline molecules. Furthermore, the crossing angle of the upper and lower polarizing plate absorption axes is 90 ° perpendicular to the front, but is greater than 90 ° when viewed from an oblique direction. Due to these two factors, leakage light tends to occur in the oblique direction, and the contrast tends to decrease. In the present invention, this problem can be solved by providing at least one optically anisotropic layer on a transparent support having predetermined optical properties.

  In the VA mode, liquid crystal molecules are tilted during white display, but the birefringence of the liquid crystal molecules when viewed from an oblique direction is different between the tilt direction and the opposite direction, resulting in differences in luminance and color tone. . In order to solve this, the liquid crystal cell is preferably multi-domain. Multi-domain refers to a structure in which a plurality of regions having different alignment states are formed in one pixel. For example, in a multi-domain VA mode liquid crystal cell, a plurality of regions in which tilt angles of liquid crystal molecules are different from each other when an electric field is applied exist in one pixel. In a multi-domain VA mode liquid crystal cell, the tilt angle of liquid crystal molecules due to application of an electric field can be averaged for each pixel, whereby the viewing angle characteristics can be averaged. Dividing the orientation within one pixel can be achieved by providing a slit in the electrode, providing a protrusion, changing the direction of the electric field, or biasing the electric field density. In order to obtain a uniform viewing angle in all directions, the number of divisions may be increased. However, since the transmittance during white display is reduced, four divisions are preferable.

  In a VA mode liquid crystal display device, the addition of a chiral agent generally used in a Twisted Nematic mode (TN mode) liquid crystal display device is rarely used to degrade the dynamic response characteristics. Sometimes added to reduce. At the boundary of the alignment division, the liquid crystal molecules are difficult to respond. For this reason, in normally black display, since black display is maintained, a reduction in luminance becomes a problem. Adding a chiral agent to the liquid crystal material contributes to reducing the boundary region.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

(Preparation of transparent support S-1)
A roll film (width 180 mm) of Fujitac TD80UF (Fuji Photo Film Co., Ltd., Re = 3 nm, Rth = 50 nm), which is a commercially available cellulose acetate film, was used as the transparent support S-1.

(Preparation of coating liquid AL-1 for alignment layer)
The following composition was prepared, filtered through a polypropylene filter having a pore size of 30 μm, and used as an alignment layer coating liquid AL-1. As the modified polyvinyl alcohol, one described in JP-A-9-152509 was used.
───────────────────────────────────
Coating liquid composition for alignment layer (mass%)
─────────────────────────────────――
Modified polyvinyl alcohol AL-1-1 4.01
Water 72.89
Methanol 22.83
Glutaraldehyde (crosslinking agent) 0.20
Citric acid 0.008
Citric acid monoethyl ester 0.029
Citric acid diethyl ester 0.027
Citric acid triethyl ester 0.006
───────────────────────────────────

(Preparation of coating liquid LC-1 for optically anisotropic layer)
After the following composition was prepared, it was filtered through a polypropylene filter having a pore size of 0.2 μm and used as a coating liquid LC-1 for an optically anisotropic layer. LC-1-1 was synthesized by the method described on page 21 of EP 1388538 A1.
───────────────────────────────────
Coating liquid composition for optically anisotropic layer (mass%)
─────────────────────────────────――
Bar-shaped liquid crystal (Paliocolor LC242, BASF Japan) 26.66
Chiral agent (Paliocolor LC756, BASF Japan) 3.10
Photopolymerization initiator (LC-1-1) 1.24
Methyl ethyl ketone 69.00
───────────────────────────────────

(Polarized UV irradiation device POLUV-1)
Using a microwave emission type ultraviolet irradiation device (Light Hammer 10, 240 W / cm, manufactured by Fusion UV Systems) equipped with D-Bulb having a strong emission spectrum at 350 to 400 nm as a UV light source, 2.5 cm from the irradiation surface. A bandpass filter (made by USHIO INC., 340 nm or less wavelength cut specification 150 * 200 mm (t = 3.0)) is installed at a remote position, and a wire grid polarizing filter (ProFlux is 3 cm away from the irradiation surface). Three pieces of PPL02 (high transmittance type), manufactured by Motekk) were installed to produce a polarized UV irradiation apparatus. The wire grid polarizing filter consists of four polarizing filters obtained by cutting a 90mm * 90mm (0.7mm thick) single plate with a scriber into a trapezoid with an upper base of 30mm and a lower base of 90mm when the transmission axis is set in the light source direction. Prepared. As shown in FIG. 2A, the four sheets were arranged so as to be parallel to the light source axis direction so that the upper base and the lower base were alternated. The maximum illuminance of this device was 400 mW / cm ² .

(Polarized UV irradiation device POLUV-2)
Using a microwave emission type ultraviolet irradiation device (Light Hammer 10, 240 W / cm, manufactured by Fusion UV Systems) equipped with D-Bulb having a strong emission spectrum at 350 to 400 nm as a UV light source, 2.5 cm from the irradiation surface. A bandpass filter (made by USHIO INC., 340 nm or less wavelength cut specification 150 * 200 mm (t = 3.0)) is installed at a remote position, and a wire grid polarizing filter (ProFlux is 3 cm away from the irradiation surface). Three pieces of PPL02 (high transmittance type), manufactured by Motekk) were installed to produce a polarized UV irradiation apparatus. As shown in FIG. 2D, three wire grid polarizing filters were arranged as shown in FIG. 2D so that the transmission plate was parallel to the light source axis direction as it was as a single plate of 90 mm * 90 mm (thickness 0.7 mm). The maximum illuminance of this device was 400 mW / cm ² .

(Polarized UV irradiation device POLUV-3)
A microwave emission type ultraviolet irradiation device (Light Hammer 10, 240 W / cm, manufactured by Fusion UV Systems) equipped with D-Bulb having a strong emission spectrum at 350 to 400 nm as a UV light source was separated from the irradiation surface by 3 cm. At the position, three wire grid polarizing filters (ProFlux PPL02 (high transmittance type), manufactured by Moxtek) were installed to produce a polarized UV irradiation device. The wire grid polarizing filter consists of four polarizing filters obtained by cutting a 90mm * 90mm (0.7mm thick) single plate with a scriber into a trapezoid with an upper base of 30mm and a lower base of 90mm when the transmission axis is set in the light source direction. Prepared. As shown in FIG. 2 (a), it was arranged so that the upper base and the lower base were alternated so as to be parallel to the light source axis direction. The maximum illuminance of this device was 400 mW / cm ² . A bandpass filter was not used.

(One-side saponification treatment of cellulose ester film)
The cellulose ester film was passed through a dielectric heating roll having a temperature of 60 ° C. and the film surface temperature was raised to 40 ° C., and then an alkali solution having the composition shown below was applied at 14 ml / m ² using a bar coater. Then, after retaining for 10 seconds under a steam far infrared heater (manufactured by Noritake Co., Ltd.) heated to 110 ° C., 3 ml / m ^{2 of} pure water was applied using the same bar coater. The film temperature at this time was 40 degreeC. Next, washing with a fountain coater and draining with an air knife were repeated three times, and then the sample was retained in a drying zone at 70 ° C. for 2 seconds and dried.
─────────────────────────────
Alkaline solution composition
─────────────────────────────
Potassium hydroxide 4.7
Water 14.7
Isopropanol 64.8
Propylene glycol 14.8
Surfactant (SF-1) 1.0
─────────────────────────────

[Example 1, Example 2, Comparative Example 1, Comparative Example 2]
After saponifying one side of the transparent support S-1 using the above-described one-side saponification method, the coating liquid AL-1 for alignment layer is applied thereon with a # 14 wire bar coater, and warm air at 60 ° C. For 60 seconds and then with warm air at 90 ° C. for 150 seconds to form an alignment layer having a thickness of 1.0 μm. Subsequently, after rubbing the formed alignment layer in the transport direction (MD direction) of the transparent support, the coating liquid LC-1 for optically anisotropic layer was applied thereon with a # 8 wire bar coater. Then, the film surface temperature was 95 ° C. for 2 minutes by heat drying to form an optically anisotropic layer having a uniform liquid crystal phase. Further, immediately after aging, the optically anisotropic layer is irradiated with ultraviolet rays in the pattern shown in Table 2 using the irradiation conditions shown in Table 1 in a nitrogen atmosphere with an oxygen concentration of 0.3% or less by continuous conveyance. The optically anisotropic layer was fixed (cured) to prepare optical compensation sheets of Examples 1 and 2 and Comparative Examples 1 and 2. The optically anisotropic layer did not show a liquid crystal phase even when heated after fixing. The thickness of the optically anisotropic layer was 3.4 μm.

  In Table 1, when there was no polarization, the POLUV-1 wire grid polarization filter was removed and used as an unpolarized UV light source.

(Dry adhesion)
The presence or absence of peeling was visually observed by a cross-cut method, and the following three-stage evaluation was performed.
◯: No peeling was observed
Δ: 10% or more peeling was observed
X: 50% peeled off

(Wet adhesion)
A 24 × 36 mm sample was immersed in hot water of 60 ° C. for 5 minutes, and the presence or absence of peeling was visually observed, and the following three-stage evaluation was performed.
◯: No peeling was observed
Δ: 10% or more peeling was observed
X: 50% peeled off

(Phase difference measurement)
Retardation Re (40) and Re (−40) when a sample is tilted ± 40 degrees with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) and front retardation Re at 589 nm and the slow axis as the rotation axis. It was measured. The retardation of the optically anisotropic layer was determined by subtracting the retardation of the support at each angle from the retardation of the entire optical compensation sheet at each angle.

  Table 3 shows adhesion evaluation results and phase difference measurement results of Examples 1 and 2 and Comparative Example 1. In Comparative Example 2, yellow discoloration, which was considered to be discoloration of the transparent support, was observed, which was inappropriate as a viewing angle compensation film.

(Preparation of polarizing plate with optical compensation sheet)
Each of the optical compensation sheets of Example 1 and Comparative Example 1 of the present invention and commercially available Fujitac TD80UF (Fuji Photo Film Co., Ltd., Re = 3 nm, Rth = 50 nm) were hydroxylated at 1.5 mol / L. It was immersed in an aqueous sodium solution at 55 ° C. for 2 minutes. Subsequently, it was washed in a water bath at room temperature and neutralized at 30 ° C. with 0.05 mol / L sulfuric acid. This was washed again in a room temperature water bath and further dried with hot air at 100 ° C. After this, washing with water and neutralization treatment were performed, and the two saponified films were attached to both sides of the polarizing film with a roll-to-roll using a polyvinyl alcohol adhesive as a protective film for the polarizing plate. The polarizing plate with an optical compensation sheet of Example 1 and the polarizing plate with an optical compensation sheet of Comparative Example 1 were produced.

[Example 3 and Comparative Example 3]
(Production of VA-LCD liquid crystal display device)
The upper and lower polarizing plates of a commercially available VA-LCD (SyncMaster 173P, manufactured by Samsung Electronics Co., Ltd.) are removed, the upper polarizing plate is the upper polarizing plate, and the lower polarizing plate with the optical compensation sheet of Example 1 prepared above is used. The liquid crystal display device of the present invention was prepared as Example 3 by pasting with an adhesive such that the optically anisotropic layer was on the liquid crystal cell substrate glass surface. Similarly, the polarizing plate with an optical compensation sheet of Comparative Example 1 prepared above was bonded with an adhesive so that the optically anisotropic layer became the glass surface of the liquid crystal cell substrate, to produce a liquid crystal display device, and Comparative Example 3 It was. FIG. 6 shows a schematic cross-sectional view of the manufactured liquid crystal display device together with the angular relationship of the optical axes of the respective layers. In FIG. 6, 41 is a polarizing layer, 42 is a transparent support, 43 is an orientation layer, 44 is an optically anisotropic layer (41 to 44 constitute an optical compensation sheet), 45 is a polarizing plate protective film, 46 is A glass substrate for a liquid crystal cell, 47 is a liquid crystal cell, and 48 is an adhesive layer. Further, the arrow in the polarizing layer 41 indicates the direction of the absorption axis, the arrow in the optically anisotropic layer 44 or its support 44 and the protective film 45 indicates the direction of the slow axis, and the circle indicates the direction of the arrow relative to the paper surface. Indicates the line direction.

(Evaluation of VA-LCD liquid crystal display device)
The viewing angle characteristics of the manufactured liquid crystal display device were measured with a viewing angle measuring device (EZ Contrast 160D, manufactured by ELDIM). Furthermore, it evaluated also visually about 45 degree | times diagonally especially. The contrast characteristics by EZ Contrast of Example 6 are shown in FIG. 7, and the visual evaluation results are shown in the following table.

  ADVANTAGE OF THE INVENTION According to this invention, the optical compensation sheet and polarizing plate which contribute to the improvement of the viewing angle characteristic of a VA mode liquid crystal display device which has the outstanding viewing angle characteristic, and a liquid crystal display device can be provided. Moreover, according to this invention, the ultraviolet irradiation device used for the ultraviolet curing process of various optical fills, such as an optical compensation sheet, can be provided.

It is the schematic of an example of the ultraviolet irradiation device of this invention. It is a figure which shows the example of arrangement | positioning of an optical filter. It is a schematic sectional drawing of an example of the optical compensation sheet | seat of this invention. It is a schematic sectional drawing of an example of the polarizing plate of this invention. It is a schematic sectional drawing of an example of the liquid crystal display device of this invention. It is the schematic sectional drawing which showed the layer structure of the liquid crystal display device produced in Example 3 with the direction of the optical axis in a layer. 6 is a diagram showing contrast characteristics of a liquid crystal display device manufactured in Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultraviolet lamp 2 Reflector 3 Optical filter 4 Substrate 5 Optical filter arrangement boundary width 6 Adjustment gap a Transport direction b Width direction (irradiation window width direction)
DESCRIPTION OF SYMBOLS 11 Transparent support 12 Optically anisotropic layer 13 which consists of liquid crystalline compound Orientation layer 21 Polarizing layers 22, 23 Protective film 24 Functional layer 31, such as (lambda) / 4 board, anti-reflective film, Cold cathode tube 32 Reflective sheet 33 Light guide plate 34 Light control film 35 such as brightness enhancement film, diffusion film, etc. Liquid crystal cell 36 Lower polarizing plate 37 Upper polarizing plate 41 Polarizing layer 42 Transparent support 43 Orientation layer 44 Optical anisotropic layer 45 Polarizing plate protective film 46 Glass for liquid crystal cell Substrate 47 Liquid crystal cell 48 Adhesive 51 Uniaxially stretched optical compensation sheet

Claims (7)

An ultraviolet irradiation device used for irradiating ultraviolet rays to a continuously conveyed ultraviolet curable layer, comprising a light source and a plurality of trapezoidal optical filters arranged on the same plane in front of the light irradiation direction from the light source And the plurality of trapezoidal optical filters are arranged with their boundaries intersecting the transport direction,
A plurality of the trapezoidal optical filters are arranged in the width direction so that the upper and lower bases are staggered and parallel, and adjacent trapezoidal optical filters are shifted up and down by a predetermined width in the transport direction. An ultraviolet irradiation device characterized by being arranged. The ultraviolet irradiation device according to claim 1, wherein the plurality of optical filters are arranged so that the length of the effective irradiation distance in the transport direction is substantially uniform in the irradiation window width direction. The ultraviolet irradiation device according to claim 1, wherein the ultraviolet curable layer contains a polymerization initiator and a polymerizable liquid crystal. The ultraviolet light irradiation apparatus according to any one of claims 1 to 3, wherein the light source is a light source capable of irradiating at least a light emitting beam having a wavelength of 200 nm to 400 nm. The ultraviolet irradiation device according to any one of claims 1 to 4, wherein the spectral characteristics of the irradiation light from the light source are controlled by a band-pass filter. The ultraviolet irradiation device according to claim 1, wherein the optical filter is a polarizer. The ultraviolet irradiation device according to claim 6, wherein the polarizer is a wire grid polarizer.

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