WO2004088367A1

WO2004088367A1 - Process for producing wideband cholesteric liquid crystal film, circular polarization plate, linear polarizer, lighting apparatus and liquid crystal display

Info

Publication number: WO2004088367A1
Application number: PCT/JP2004/003791
Authority: WO
Inventors: Takahiro Fukuoka; Miki Shiraogawa; Kentarou Takeda; Naoki Takahashi; Kazutaka Hara
Original assignee: Nitto Deno Corporation
Priority date: 2003-03-31
Filing date: 2004-03-19
Publication date: 2004-10-14
Also published as: JP2004318066A; TWI383181B; JP4293888B2; TW200502595A

Abstract

A process for producing a wideband cholesteric liquid crystal film, comprising the step of coating an alignment substrate with a liquid crystal mixture containing a polymerizable mesogen compound (A) and a polymerizable chiral agent (B) and the step of exposing the liquid crystal mixture to ultraviolet radiation so as to effect polymerization and hardening, wherein the ultraviolet polymerization step comprises the step (1) of exposing the alignment substrate side of the liquid crystal mixture while in contact with an oxygenic gas to ultraviolet radiation at an ultraviolet irradiation intensity of 20 to 200 mW/cm2 at 20°C or higher for 0.2 to 5 sec; the step (2) of heating at 70 to 120°C for 2 sec or longer; the step (3) of exposing the alignment substrate side of the liquid crystal layer to ultraviolet radiation at an ultraviolet irradiation intensity lower than in the step (1) at 20°C or higher for 10 sec or longer; and the step (4) of effecting ultraviolet irradiation in the absence of oxygen. Through this process, there can be obtained a wideband cholesteric liquid crystal film having a wide reflection band in even long wavelength region.

Description

Description Manufacturing method of broadband cholesteric liquid crystal film, circularly polarizing plate, linearly polarizing element, illumination device and liquid crystal display device

The present invention relates to a method for producing a broadband cholesteric liquid crystal film. The broadband cholesteric liquid crystal film of the present invention is useful as a circularly polarizing plate (reflective polarizer).

. Further, the present invention relates to a linearly polarizing element, an illuminating device and a liquid crystal display device using the circularly polarizing plate. Background art

Generally, a liquid crystal display has a structure in which liquid crystal is injected between glass plates on which transparent electrodes are formed, and polarizers are arranged before and after the glass plates. A polarizer used for such a liquid crystal display is manufactured by adsorbing iodine or a dichroic dye on a polyvinyl alcohol film and stretching it in a certain direction. The polarizer thus manufactured itself absorbs light that oscillates in one direction, and passes only light that oscillates in the other direction to produce linearly polarized light. As a result, the efficiency of the polarizer cannot theoretically exceed 50%, which is the biggest factor that lowers the efficiency of liquid crystal displays. Also, due to this absorbed light, if the output of the light source is increased to a certain level or more, the liquid crystal display device may destroy the polarizer due to heat generated by the heat conversion of the absorbed light, or may have a negative effect on the liquid crystal layer inside the cell. This causes adverse effects such as deterioration of display quality.

Cholesteric liquid crystals with a function of separating circularly polarized light have a selective reflection characteristic that reflects only the circularly polarized light whose wavelength is the helical pitch of the liquid crystal, with the direction of rotation of the liquid crystal helix and the direction of circular polarization being the same. There is. By using this selective reflection characteristic, only specific circularly polarized light of natural light in a certain wavelength band is transmitted and separated, and the remaining light is reflected and reused, whereby a highly efficient polarizing film can be manufactured. At this time, the transmitted circularly polarized light is converted into linearly polarized light by passing through a ぇ / 4 wavelength plate, and the direction of the linearly polarized light is transmitted to the liquid crystal display. A liquid crystal display device with high transmittance can be obtained by adjusting the transmission direction of the absorption polarizer used. In other words, when a cholesteric liquid crystal film is used as a linear polarizing element in combination with a four-wavelength plate, there is theoretically no loss of light, so a conventional absorption polarizer that absorbs 50% of light In theory, it is possible to obtain twice the brightness improvement as compared with the case where is used alone.

However, the selective reflection characteristic of the cholesteric liquid crystal is limited only to a specific wavelength band, and it has been difficult to perform the power analysis over the entire visible light range. The selective reflection wavelength region width Δλ of the cholesteric liquid crystal is

A λ = 2 λ * (ne-no) / (ne + no)

n o: Refractive index of cholesteric liquid crystal molecules for normal light

ne: Refractive index of cholesteric liquid crystal molecules to extraordinary light

λ: center wavelength of selective reflection

It depends on the molecular structure of the cholesteric liquid crystal itself. According to the above equation, the width of the selective reflection wavelength region 波長 λ can be increased by increasing ne−no, but ne−ηο is usually 0.3 or less. If this value is increased, other functions (alignment characteristics, liquid crystal temperature, etc.) of the liquid crystal become insufficient, and practical use was difficult. Therefore, in practice, the width of the selective reflection wavelength region was at most about 150 nm. Most of the practically usable cholesteric liquid crystals are only about 30 to 100 nm. Also, the selective reflection center wavelength is

λ = (ne + no) P / 2

P: Spiral pitch length required for one turn of cholesteric liquid crystal

If the pitch is constant, it depends on the average refractive index and pitch length of the liquid crystal molecules. Therefore, in order to improve the power of the entire visible light region, a plurality of layers having different selective reflection center wavelengths are laminated, or the pitch length is continuously changed in the thickness direction to form an existence distribution of the selective reflection center wavelength itself. I was

For example, there is a method of continuously changing the pitch length in the thickness direction. For example, Japanese Unexamined Patent Application Publication No. Hei 6-218184, Japanese Patent No. 3272686, Japanese Unexamined Patent Application Publication No. Hei 11-248943, Japanese Unexamined Patent Application Publication No. See Japanese Patent Publication No. 86953/86. In this method, when the cholesteric liquid crystal composition is cured by exposure to ultraviolet light, the exposure side and the exit side are exposed. By making a difference in light intensity and making a difference in polymerization rate, the composition ratio of liquid crystal compositions having different reaction rates is changed in the thickness direction.

The point of this method is to take a large difference in exposure intensity between the exposure surface side and the emission surface side. For this reason, in many of the above-mentioned prior art examples, a method is employed in which an ultraviolet absorber is mixed with a liquid crystal composition to cause absorption in a thickness direction to amplify a difference in exposure amount due to an optical path length. Was.

However, the method of continuously changing the pitch length as disclosed in Japanese Patent Application Laid-Open No. 6-281814 requires a liquid crystal layer thickness of about 15 to 20 μm necessary for realizing the function. In addition to the problem of precision coating of the liquid crystal layer, cost was inevitable due to the need for expensive liquid crystals. In addition, an exposure time of about 1 to 60 minutes was required, and a long production line with an exposure line length of 10 to 60 Om was required to obtain a line speed of 10 mZ. If the line speed is reduced, the line length can be reduced, but a reduction in production speed is inevitable.

This is due to the difference in UV exposure intensity in the thickness direction to change the pitch length in the thickness direction and the resulting polymerization speed difference, as described in JP-A-6-281814. This is because it is difficult to form a rapid change in pitch due to the theoretical problem of controlling the cholesteric pitch by changing the composition ratio due to mass transfer. In Japanese Patent Laid-Open Publication No. 6-281814, the pitch ratio differs by about 100 nm between the short pitch side and the long pitch side, so that it is necessary to greatly change the composition ratio. Liquid crystal thickness, weak UV irradiation, and long exposure time are required. In Japanese Unexamined Patent Publication No. Hei 11-248 943, since the mobility of the substance that changes the pitch is better than the material example used in Japanese Unexamined Patent Publication No. Hei 6 A film can be formed with an exposure amount of about a minute. However, even in this case, a thickness of 15 / m is required.

Patent No. 3 2 7 2 6 6 8 changes the temperature conditions of the primary exposure and the secondary exposure, and separately provides the time required for the composition ratio to change in the thickness direction, In order to cover substantially the entire visible light region by this method, it is necessary to wait about 120 minutes for mass transfer due to this temperature change.

A method of continuously changing the pitch length as disclosed in Japanese Patent Application Laid-Open No. 2002-286935. Requires a liquid crystal layer thickness of about 15 to 20 μm to exhibit its functions, and in addition to the problem of precise coating of the liquid crystal layer, it also requires a large amount of expensive liquid crystal, which saves cost. I couldn't. In Japanese Patent Application Laid-Open No. 2002-2866935, when the cholesteric liquid crystal composition is cured by ultraviolet exposure from the side opposite to the substrate (air interface side), the cholesteric liquid crystal composition is inhibited by oxygen. The composition ratio change is changed in the thickness direction by making a difference between the exposure intensity on the exposure surface side and the exposure intensity on the emission surface side.

However, in FIG. 4 in Example 1 of Japanese Patent Application Laid-Open No. 2000-286935, although the selective reflection wavelength is broadened, the inclination of the transmittance curve on the short wavelength end side and the long wavelength side is reduced. However, they are both calm and do not cover virtually all visible light. Also, in FIG. 6 in Example 2 of the publication, the slope at both wavelength ends is steep, but the band itself is narrow.

In particular, when this type of polarizing element is used in a liquid crystal display, the transmission is sufficiently flat for the three emission wavelengths of the backlight source, namely, 355 nm, 545 nm, and 615 nm. It is necessary to ensure the reflectivity and Z-reflectance characteristics. The bandwidth broadening range obtained by the methods of Examples 1 and 2 described in Japanese Patent Application Laid-Open No. 2002-2866935 is 43.5 nm and 615 nm in each case. It was not enough to cover the bright line spectrum. In such a case, the color tone of the transmitted light is difficult to obtain white and cannot be used for a liquid crystal display device or the like. Disclosure of the invention

In response to the above problems, the present applicant has filed a Japanese Patent Application No. 2001-339396. In this application, the liquid crystal composition applied to the alignment substrate is irradiated with ultraviolet light from the alignment substrate. As a result, polymerization is started from the surface that is not easily affected by polymerization inhibition due to oxygen in contact with the alignment substrate, and an ultraviolet irradiation intensity distribution is formed in the thickness direction by utilizing absorption by the molar absorption coefficient of the liquid crystal layer. At the same time, the liquid crystal reaction rate gradient and the composition concentration distribution gradient are larger than before by reducing the effective UV radiation on the air surface side, which is greatly affected by oxygen inhibition. By making a difference between the exposure intensity on the exposure surface side and the exposure intensity on the emission surface side, we succeeded in forming a large change in the cholesteric pitch length in the thickness direction. In this application, a selective reflection wavelength bandwidth as wide as 296 nm was obtained. Had been.

In the case of the above-mentioned application, a wavelength band of about 400 to 70 nm is used. These wavelength bands power the light source spectrum. These provide good circularly polarized light reflection characteristics near normal incidence. On the other hand, at oblique incidence, the wavelength band was not sufficient. The selective reflection wavelength at oblique incidence is

λ = n p co s i s i in '(s ϊ η θ / η)}

n = average refractive index of liquid crystal

p = 3 resteric pitch length

Θ = angle of incidence

As a result, the selective reflection wavelength shifts to a shorter wavelength side when the light is obliquely incident than when it is perpendicularly incident. Therefore, in order to function effectively for oblique incident light, it is necessary to function in a long wavelength region.

An object of the present invention is to provide a method capable of manufacturing a broadband cholesteric liquid crystal film having a broadband reflection band even in a long wavelength region.

Another object of the present invention is to provide a circularly polarizing plate using a broadband cholesteric liquid crystal film obtained by the manufacturing method. It is another object of the present invention to provide a linear polarizing element, a lighting device, and a liquid crystal display device using the circular polarizing plate. The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that a broadband cholesteric liquid crystal film that can achieve the above object can be obtained by the following manufacturing method, and have completed the present invention. . That is, the present invention is as follows.

1. a step of applying a liquid crystal mixture containing a polymerizable mesogen compound (A) and a polymerizable chiral agent (B) to an alignment base material, and a step of irradiating the liquid crystal mixture with ultraviolet rays and polymerizing and curing the liquid crystal mixture. A method for producing a broadband cholesteric liquid crystal film having a bandwidth of 200 nm or more,

The ultraviolet polymerization step,

In a state where the liquid crystal mixture is in contact with a gas containing oxygen, at a temperature of 20 ° C. or more, at an ultraviolet irradiation intensity of ^{20 to} 200 mWZ cm ² for 0.2 to 5 seconds, the alignment group UV irradiation from the material side (1),

Next, with the liquid crystal layer in contact with a gas containing oxygen at 70 to 120 ° C. , Heating for more than 2 seconds (2),

Next, in a state where the liquid crystal layer is in contact with a gas containing oxygen, at a temperature of 20 ° C. or more, at a UV irradiation intensity lower than that in the step (1), for 10 seconds or more, the alignment substrate side UV irradiation process (3),

Next, a method for producing a broadband cholesteric liquid crystal film, comprising the step of irradiating ultraviolet rays in the absence of oxygen (4).

2. The method for producing a broadband cholesteric liquid crystal film as described in 1 above, wherein the pitch length of the cholesteric liquid crystal film is changed so as to continuously narrow from the alignment substrate side.

3. The broadband as described in 1 or 2 above, wherein the polymerizable mesogen compound (A) has one polymerizable functional group, and the polymerizable chiral agent (B) has two or more polymerizable functional groups. A method for manufacturing a cholesteric liquid crystal film.

4. The molar extinction coefficient of the polymerizable mesogen compound (A) is

0.1 to 500 dm ³ mo 1 ¹ cm— 丄 @ 365 nm,

1 0~ 3 0 0 0 0 dm 3 mo 1 _1 <; 111 ^-1 @ 3 3 4 1101 Deari, one force,

1 0 0 0~ 1 0 0 0 0 0 dm 3 mo 1- 1 cm -1 @ 3 1 4 characterized in that it is a nm according to any one of the above 1 to 3 broadband co Resuteri click crystal film Production method.

5. The polymerizable mesogen compound (A) has the following general formula (1):

(Wherein 1 ^ to 1 ₁₂ may be the same or different, one F, one H, One CH _3, shows an C ₂ H _s or a OCH _3, the R ₁₃ an H or a CH ₃ X _t represents the general formula (2): — (CH ₂ CH ₂₀ ) _a — (CH ₂ ) _b- (◦) _c —, and X ₂ represents one CN or one F. In the formula (2), a is an integer of 0 to 3, b is an integer of 0 to 12, c is 0 or 1, and when a = l to 3, b = 0 and c = 0; a = 0 Then b = l ~ 12 and c = 0 ~ l. 5. The method for producing a broadband cholesteric liquid crystal film according to any one of the above items 1 to 4, wherein the compound is a compound represented by the following formula:

6. A circularly polarizing plate using the broadband cholesteric liquid crystal film obtained by the production method according to any one of the above 1 to 5.

7. Between at least two layers of reflective polarizers (a) where the wavelength bands of polarized light selective reflection overlap each other,

A retardation layer (b) with almost zero front phase difference (normal direction) and a phase difference of λ 8 or more with respect to incident light that is incident at an angle of 30 ° or more with respect to the normal direction is arranged. A polarizing element,

A polarizing element, wherein the reflective polarizer (a) is the circularly polarizing plate according to the above item 6.

8. The polarizing element according to the above 7, wherein the selective reflection wavelengths of at least two layers of the reflective polarizers (a) overlap each other in a wavelength range of 550 nm ± 10 nm.

9. Retardation layer (b) Force Fixed cholesteric liquid crystal phase having a selective reflection wavelength range other than the visible light range, with fixed planar orientation,

A rod-shaped liquid crystal with a fixed home-mouth pick alignment state,

A discotic liquid crystal in which the nematic or columnar phase orientation is fixed,

Biaxially oriented polymer film, or

9. The polarizing element according to the above item 7 or 8, wherein an inorganic layered compound having a negative uniaxial property is fixed so as to have an optical axis in a direction normal to the surface.

10. A straight line characterized in that a λ / 4 plate is laminated on the circularly polarizing plate described in 6 above or the polarizing element described in any of 7 to 9 above, so that linearly polarized light can be obtained by transmission. Polarizing element.

11. The linearly polarizing element according to 10 above, obtained by laminating a cholesteric liquid crystal film as a circularly polarizing plate on an e / 4 plate so that the pitch length is continuously narrowed.

12. The linear polarizing element as described in 10 or 11, wherein the 2./4 plate is a retardation plate whose viewing angle has been improved by biaxially stretching and correcting the phase difference of obliquely incident light. 13. The linear polarizing element as described in 10 or 11, wherein the 3./4 plate is a liquid crystal polymer type retardation plate obtained by applying and fixing a nematic liquid crystal or a smectic liquid crystal.

1 4. When a λ / 4 plate has a principal refractive index in the plane of nx and ny and a principal refractive index in the thickness direction as nz, it is defined by the formula: (nx—nz) / (nx-ny). N z coefficient is 1 0

5. The linear polarizing element as described in any one of 10 to 13 above, which satisfies 52.5.

15. A linearly polarizing element characterized in that a λ / 2 plate is further laminated on the λ Z 4 plate of the linearly polarizing element according to any of the above 10 to 14.

16. The absorption polarizer whose transmission axis and transmission axis direction of the linear polarizing element according to any of the above 10 to 15 are aligned on the fourth / 4 plate side of the linear polarizing element. Features a linear polarization element.

1 7. On the front side of a surface light source having a reflective layer on the back side, the circularly polarizing plate described in 6 above, the polarizing element in any of 7 to 9 above, or the polarizing element in any of 10 to 16 above. An illumination device comprising a linear polarizing element.

18. A liquid crystal display device comprising a liquid crystal cell on the light emission side of the lighting device according to the above item 17.

19. The viewing angle widening liquid crystal display device according to the above item 18, wherein a viewing angle widening film for diffusing light on the viewing side transmitted through the liquid crystal cell is arranged on the viewing side with respect to the liquid crystal cell. .

20. The viewing angle widening liquid crystal display device according to the above item 19, characterized in that a spreading plate having substantially no backscattering or depolarization is used as the viewing angle widening film.

(The invention's effect)

As described above, in the present invention, in order to broaden the reflection band, in the state where the liquid crystal mixture is in contact with a gas containing oxygen, ultraviolet irradiation is performed from the alignment substrate side under ultraviolet irradiation. Different conditions are used for the first exposure step (1) and the second exposure step (3). As a result, more precise control of the reaction behavior of the polymerizable liquid crystal mixture can be realized, resulting in more efficient production than before. Depending on the speed, a broadband cholesteric liquid crystal film can be obtained.

That is, the ultraviolet irradiation condition is such that the first irradiation intensity> the second irradiation intensity, and the first irradiation time <the second irradiation time. A heating step (3) is provided between the first UV irradiation and the second UV irradiation. Due to the difference in irradiation intensity, the amount of radicals generated by the UV reaction of the photoreaction initiator in the liquid crystal composition per unit time is greatly changed between the first UV irradiation and the second UV irradiation. In the first UV irradiation, a large amount of radicals are instantaneously formed under monomer-rich conditions at the beginning of the reaction, and a large gradient in the thickness direction is formed in the radical existence distribution due to oxygen inhibition and absorption of the liquid crystal composition. As a result, a polymer / oligomer having an average molecular weight of about 1,000 to 5,000 is formed, and a concentration distribution is formed in the thickness direction. At this time, the polymerization ratio differs in the thickness direction because the reaction rates of the polymerizable mesogen compound (A) and the polymerizable chiral agent (B) in the liquid crystal composition are different. For this reason, the surface where the polymerizable chiral agent (B) is rich has a short cholesteric pitch and the surface in the opposite direction becomes long. As a result, a cholesteric liquid crystal film having a broad reflection wavelength as a whole can be obtained.

The broadband cholesteric liquid crystal film thus obtained functions as a broadband circularly polarizing reflector and has the same optical characteristics as the above-mentioned JP-A-6-218184. In addition to these properties, the thickness can be reduced by reducing the number of layers compared to the conventional manufacturing method, and furthermore, it can be manufactured easily and in a short time, and the cost is reduced by improving the production speed. Is possible.

The broadband cholesteric liquid crystal film obtained by the production method of the present invention has a wide reflection bandwidth of 200 nm or more in the selective reflection wavelength, and has a broadband reflection bandwidth. The reflection bandwidth is preferably at least 300 nm, more preferably at least 400 nm, and further preferably at least 450 nm. Further, it is preferable that the reflection band width of 200 nm or more is provided in a visible light region, particularly in a wavelength region of 400 to 900 nm.

It is an important problem that a circularly polarizing reflector has a wide reflection band even in a long wavelength region in order to obtain a good viewing angle characteristic of a liquid crystal display device. The long wavelength end of the selective reflection must reach 800 to 900 nm in order to prevent the transmitted light from being colored in a practical viewing angle range. According to the manufacturing method of the present invention, a reflection band is provided even in such a long wavelength region. A broadband cholesteric liquid crystal film can be obtained. Such a broadband cholesteric liquid crystal film is used not only when it is used as a reflective polarizer for obtaining high luminance but also when it is used for a polarizing element formed in combination with another optical element such as a retardation plate. Similarly, stable optical characteristics for obliquely incident light rays other than the front face are required. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a conceptual view of a viewing angle widening liquid crystal display device using the polarizing element integrated with a polarizing plate of Examples 1 and 3 and Comparative Examples 1 to 3.

FIG. 2 is a conceptual diagram of a viewing angle widening liquid crystal display device using the polarizing plate integrated polarizing element of the second embodiment.

FIG. 3 is a diagram illustrating an axis angle of each layer in the polarizing plate integrated polarizing element according to the second embodiment.

FIG. 4 is a reflection spectrum of the cholesteric liquid crystal finolem produced in Example 1, Comparative Example 1, and Comparative Example 2. BEST MODE FOR CARRYING OUT THE INVENTION

The broadband cholesteric liquid crystal film of the present invention is obtained by ultraviolet polymerization of a liquid crystal mixture containing a polymerizable mesogen compound (A) and a polymerizable chiral agent (B). As the polymerizable mesogen compound (A), a compound having at least one polymerizable functional group and having a mesogen group composed of a cyclic unit or the like is preferably used. Examples of the polymerizable functional group include an acryloyl group, a methacryloyl group, an epoxy group and a butyl ether group. Of these, an acryloyl group and a methacryloyl group are preferable. It is. Further, by using a compound having two or more polymerizable functional groups, a crosslinked structure can be introduced to improve durability. Examples of the cyclic unit to be a mesogen group include biphenyl-based, phenylbenzoate-based, phenylsilicone hexane-based, azoxybenzene-based, azomethine-based, azobenzene-based, phenylpyrimidine-based, and diphenyl-based. Ninoleacetylene, diphenylenobenzoate, bicyclohexane, cyclohexylbenzene, terphenyl and the like. Note that this Further, the terminal of the cyclic unit may have a substituent such as, for example, a cyano group, an alkyl group, an alkoxy group, or a halogen group. The mesogen group may be bonded via a spacer that imparts flexibility. Examples of the spacer include a polymethylene chain and a polymethylene chain. The number of repetitions of the structural unit forming the spacer portion is appropriately determined depending on the chemical structure of the mesogen portion, but the number of recurring units of the polymethylene chain is 0 to 20, preferably 2 to 12, The repeating unit of the methylene chain is from 0 to 10, preferably:! ~ 3.

The molar extinction coefficient of the polymerizable mesogen compound (A) is 0.1 to 500 dm ³ mol-L e na— [© 365 5 1101, and 10 to 300 dm ³ mo 1 ^_1 cm "is ¹ ® 3 3 4 nm, with a force one 1 0 0 0~ 1 0 0 0 0 0 dm 3 mol -1 cm one ¹ @ 3 ¹ 4 nm Dearuko and are preferred. the molar extinction coefficient Molar absorption coefficient is 0.1 ~ 50 dm ³ mol- ¹ cm- ¹ @ 365 nm, 50 ~ 100 000 dm ³ mol ^-1 cm — '②, ¹⁰⁰ 000 to 500 000 dm ³ mo 1 ¹ cm— ¹ ® 3 14 nm is more preferred The molar extinction coefficient is 0.1 to 10 dm ³ mo 1 ^_1 cm ^{_ 1} @ ³⁶⁵ nm, 100 0 0 ~ 400 m dm ³ mo I- ¹ cm-1 ¹ @ 3 34 nm, 300 0 0 0 ~ 400 0 0 dm ³ mo 1 cm "'@ 314 nm is more preferable. Molar extinction coefficient is 0. I dm ³ mo 1 ^_1 cm ^ l® 365 nm, 10 dm ³ mo 1 ^_1 cm ^_1 @ ³³⁴ nm, 100 dm ³ mo 1 ^-1 cm " ¹ ® If it is smaller than 3 14 nm, there is no sufficient difference in polymerization rate, and it is difficult to broaden the band.—On the other hand, 500 dm ³ mo ¹ cm— ^l @ 365 nm, 300 dm ³ mo 1 — ¹ cm ¹ @ 3 3 4 nm, 1 0 0 0 0 0 dm ³ mo 1 ^_1 cm "If it is larger than ¹ ® 3 14 nm, polymerization may not proceed completely and curing may not be completed. is there. The molar extinction coefficient is a value obtained by measuring the spectrophotometric spectrum of each material and measuring the resulting absorbance at 365 nm, 334 nm, and 314 nm. The polymerizable mesogen compound (A) having one polymerizable functional group has, for example, the following general formula: (1)

(In the formula,! ^ ~ _{May be the same} or different and represents 1 F, 1 H, —CH ₃ , —C ₂ H ₅ or 1 OCH ₃ , R ₁₃ represents 1 H or 1 CH ₃ , Is the general formula (2)

:-(CH ₂ CH ₂ 0) _a- (CH ₂ ) _b- (O) c-, and ₂ represents -〇 ^^ or 1F. However, in the general formula (2), a is an integer of 0 to 3, b is 0 to; 12 is an integer of 2, c is 0 or 1, and when a = l to 3, b = 0 and c = 0, and when a = 0, b = l to l2 and c = 0 to l. ). —Specific examples of the polymerizable mesogen compound (A) represented by the general formula (1) are shown in Table 1.

The polymerizable mesogen compound (A) is not limited to these exemplified compounds. Examples of the polymerizable chiral agent (B) include LC756 manufactured by BASF.

The compounding amount of the polymerizable chiral agent (B) is the same as that of the polymerizable mesogen compound (A). The amount is preferably about 1 to 20 parts by weight, more preferably 3 to 7 parts by weight, based on the total of 100 parts by weight of the sex chiral agent (B). The helical torsional force (HTP) is controlled by the ratio of the polymerizable mesogen compound (A) and the polymerizable chiral agent (B). By setting the ratio within the above range, the reflection band can be selected so that the reflection spectrum of the obtained cholesteric liquid crystal film can cover a long wavelength range.

The liquid crystal mixture usually contains a photopolymerization initiator (C). Various photopolymerization initiators (C) can be used without particular limitation. For example, irgacure 184, irgacure 907, irgacure 369, and irgacure 651 manufactured by Chipa Specialty Chemicals Co., Ltd. may be mentioned. The amount of the photopolymerization initiator is preferably about 0.01 to 10 parts by weight based on 100 parts by weight of the total of the polymerizable mesogen compound (A) and the polymerizable chiral agent (B). 0.05-5 parts by weight is more preferred.

In order to widen the bandwidth of the obtained cholesteric liquid crystal film, the mixture can be mixed with an ultraviolet absorber to increase the difference in ultraviolet exposure intensity in the thickness direction. A similar effect can be obtained by using a photoinitiator having a large molar extinction coefficient.

The mixture can be used as a solution. Solvents used for preparing the solution are usually chloroform, dichloromethane, dichloromethane, tetrachlorethane, trichloroethylene, tetrachloroethylene, and tetrachloroethylene. Halogenated hydrocarbons such as benzene, phenols such as phenol and parachlorophenol, and aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene and 1,2-dimethoxybenzene And others, such as acetone, methylethyl ketone, ethyl acetate, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol, monomethylinoleate, diethyleneglycorereginette, Ethylsilenosolve, butyl cellosolve, 2-pyrrolidone, N-Methyl-1-2-pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitril, ptyronitrile, disulfide Carbon, cyclopentanone, cyclohexanone, and the like can be used. The solvent used is not particularly limited, but methyl ethyl ketone, cyclohexanone, cyclopentanone, and the like are preferred. The concentration of the solution cannot be determined unconditionally because it depends on the solubility of the thermopick liquid crystal compound and the final thickness of the target cholesteric liquid crystal film, but it is usually about 3 to 50% by weight. It is preferred that '

The production of the broadband cholesteric liquid crystal film of the present invention includes a step of applying the liquid crystal mixture to an alignment substrate, and a step of irradiating the liquid crystal mixture with ultraviolet rays and polymerizing and curing.

As the alignment base material, a conventionally known one can be used. For example, a polymer having a photo-crosslinking group such as a rubbing film, obliquely deposited film, or cinnamate diazobenzene, which is formed by forming a thin film made of polyimide or polyvinyl alcohol on a substrate and rubbing it with rayon cloth or the like Alternatively, a light directing film or a stretched film obtained by irradiating a polyimide with polarized ultraviolet light is used. In addition, orientation can be performed by magnetic field, electric field orientation, and shear stress operation.

The type of the base material is not particularly limited, but a material having a high transmittance is desirable in view of the method of irradiating irradiation light (ultraviolet rays) from the base material side. For example, the base material has a transmittance of at least 10%, preferably at least 2%, in the ultraviolet region of from 200 nm to 400 nm, more preferably from 300 nm to 400 nm. It is required to be 0% or more. Specifically, it is preferable that the plastic film has a transmittance of 10% or more, more preferably 20% or more, for ultraviolet light having a wavelength of 365 nm. The transmittance is directly measured by U-410 Spectr ο ρ hh ο ο ο m te ter manufactured by HITACHI. The substrate may be a plastic material such as polyethylene terephthalate, triacetyl cellulose, norbornene resin, polyvinyl alcohol, polyimide, polyarylate, polycarbonate, polysulfone or polyethersulfone. A film or a glass plate is used. For example, Triacetyl cellulose manufactured by Fudo Photographic Film Co., Ltd., ARTON manufactured by JSR, and ZONEX manufactured by Zeon Corporation can be mentioned.

Further, a polymer film described in Japanese Patent Application Laid-Open No. 2001-334529 (WO 01/37007), for example, (A) Substituted or unsubstituted side chain Examples of the resin composition include a thermoplastic resin having an imido group and (B) a thermoplastic resin having a substituted and / or unsubstituted fuunyl and a ditolyl group in a side chain. Specific examples Examples of such a film include a resin composition film containing an alternating copolymer of isoptylene and N-methylmaleimide and an acrylonitrile'styrene copolymer. As the film, a film made of a mixed extruded product of a resin composition or the like can be used. The base material may be used while being bonded to the cholesteric liquid crystal layer, or may be peeled off. When using it as it is, use a material whose retardation value is sufficiently small for practical use.

When the base material is used while being bonded, it is desirable that the base material does not decompose, deteriorate or yellow even when irradiated with ultraviolet rays. For example, the desired purpose can be achieved by adding a light stabilizer or the like to the above-mentioned base material. As the light stabilizer, Tinuvin 120 and 144, manufactured by Chipa Specialty Chemicals, etc., are preferably used. By increasing the wavelength from the exposure light to a wavelength of 300 nm or less, coloring, deterioration, and yellowing can be reduced.

The coating thickness of the liquid crystal mixture (in the case of a solution, the coating thickness after drying the solvent) is preferably about 1 to 20 / ζηι. If the coating thickness is thinner than 1 m, the reflection bandwidth can be secured, but the degree of polarization itself tends to decrease, which is not preferable. The coating thickness is preferably 2 / Z1T1 or more, and more preferably 3 / 1m or more. On the other hand, when the coating thickness is larger than 20 / im, no remarkable improvement is seen in both the reflection bandwidth and the degree of polarization, and the cost is simply high, which is not preferable. The coating thickness is preferably 15 m or less, more preferably 10 πι or less.

As a method of applying the mixed solution to the alignment substrate, for example, a roll coating method, a gravure coating method, a spin coating method, a bar coating method, or the like can be adopted. After the application of the mixed solution, the solvent is removed, and a liquid crystal layer is formed on the substrate. The conditions for removing the solvent are not particularly limited, and it is sufficient that the solvent can be substantially removed, and the liquid crystal layer does not flow or drop. Usually, the solvent is removed by drying at room temperature, drying in a drying oven, or heating on a hot plate.

Next, the liquid crystal layer formed on the alignment base material is brought into a liquid crystal state, and cholesteric alignment is performed. For example, heat treatment is performed so that the liquid crystal layer has a liquid crystal temperature range. The heat treatment can be performed by the same method as the above-mentioned drying method. The heat treatment temperature varies depending on the type of liquid crystal material and alignment substrate, and cannot be unconditionally determined. To 300 ° C., preferably 70 to 200 ° C. The heat treatment time varies depending on the heat treatment temperature and the type of liquid crystal material or alignment substrate used, but cannot be generally specified, but is usually in the range of 10 seconds to 2 hours, preferably in the range of 20 seconds to 30 minutes. Selected.

The step of applying to the alignment base material and irradiating the liquid crystal mixture with ultraviolet rays includes the above steps (1) to (4).

In the step (1), in a state where the liquid crystal mixture is in contact with a gas containing oxygen, at a temperature of 20 ° C. or more, an ultraviolet irradiation intensity of ^{20 to 200} mW / cm ² is used. UV irradiation from the alignment substrate side for ~ 5 seconds. As a result, the liquid crystal mixture is polymerized to form a polymer oligomer having an average molecular weight of about 1,000 to 500,000, and the alignment base material side and its opposite side (the oxygen interface side) In the thickness direction, a difference in the reaction rate due to oxygen inhibition and a difference in the amount of generated radicals due to the absorption of ultraviolet light by the liquid crystal composition occur.

In the step (1), the temperature at the time of the first ultraviolet irradiation is set to 20 ° C. or higher in order to polymerize and cure the liquid crystal mixture in a favorable alignment state. On the other hand, the upper limit of the temperature is not particularly limited, but is preferably 100 ° C. or lower. If the temperature is higher than 100 ° C

However, diffusion may occur during irradiation, making management difficult. From these points, the temperature is preferably from 20 ° C to 50 ° C. The first ultraviolet irradiation intensity is 2 0~ 2 0 0 mW / cm 2, preferably 2 5~ 2 0 0 mW / cm 2, 4 0~: I 5 0 mWZ cm 2 Gayo more preferable. If the UV irradiation intensity is lower than ²⁰ mW / cm ² , polymerization will not be performed to the extent that a monomer distribution is formed in the thickness direction, so that the band will not be broadened. On the other hand, if the UV irradiation intensity is higher than ²⁰⁰ mW / cm ² , the polymerization reaction rate becomes higher than the diffusion rate, so that the band cannot be broadened, which is not preferable.

The first ultraviolet irradiation time in the step (1) is 0.2 to 5 seconds, and preferably 0.3 to 3 seconds. More preferably, it is 0.5 to 1.5 seconds. If the time is shorter than 0.2 seconds, the polymerization is not carried out to such an extent that the monomer is distributed in the thickness direction, so that the band is not broadened. If the time is longer than 5 seconds, the change in the pitch of the cholesteric liquid crystal layer is not a continuous change from large to small from the alignment substrate side to the oxygen interface side, but is a discontinuous change. Discontinuous pitch changes cause severe coloring when viewed from an angle Become.

The exposure environment for ultraviolet irradiation is performed in a state where the liquid crystal mixture applied to the alignment base material is in contact with a gas containing oxygen. Preferably, the gas containing oxygen contains 0.5% or more of oxygen. Such an environment may be any as long as oxygen polymerization inhibition can be used, and can be performed under a general atmospheric atmosphere. The oxygen concentration may be increased or decreased in view of the wavelength width for controlling the pitch in the thickness direction and the speed required for polymerization. In the atmosphere, the required amount of the photopolymerization initiator (C) tends to increase. However, if irgacure 184 and irgacure 907 (both manufactured by Ciba Specialty Chemicals) are used, the polymerizable mesogen can be used. The desired purpose can be achieved with an addition amount of about 1 to 5 parts by weight based on 100 parts by weight of the total of the compound (A) and the polymerizable chiral agent (B).

In the irradiation of the first ultraviolet ray, if the weight average molecular weight of the formed polymer / oligomer is too small, the diffusion rate becomes too high. Care should therefore be taken to ensure that uncontrolled diffusion rates do not even out the concentration gradient of the polymer Z oligomer. It is necessary not only to form a large change in the cholesteric pitch length in the liquid crystal layer thickness direction but also to maintain this. If the polymer / oligomer is too low in molecular weight, the formed gradient cannot be maintained, and the structure is lost due to molecular diffusion. In order to satisfy the conditions for controlling the diffusion rate under industrial conditions, the polymer Z oligomer is formed in a weight-average molecular weight of about 1,000 to 5,000. It is preferred that the weight average molecular weight of the polymer / oligomers is from 1000 to 3000. The weight average molecular weight of the polymer oligomer is a value measured by the GPC method. The weight average molecular weight was calculated using polyethylene oxide as a standard sample. Main unit: Tosoh's HLC—8 120 GPC, Power Ram: Tosoh's Super AWM- H + S Super AWM—H + Super AW 300 (0 mm each (i> X 15 c ni, total 45 cm), column temperature: 40 ° C, eluent: 10 mM—LiBr / NMP, flow rate: 0.4 ml_min, inlet pressure: 8.5 MPa, sample concentration : 0.1% NMP solution, Detector: Differential refractometer (RI).

When fixing the concentration distribution formed by the first ultraviolet irradiation in step (1) as it is JP 2 0 0 2 2 8 6 9 3 5 discloses such a Rere reflection wavelength band only such obtained the same level to ₀

Therefore, in the step (2), the liquid crystal layer is heated at 70 to 120 ° C. for 2 seconds or more while being in contact with the gas containing oxygen. In the step (2), in the step (1), the polymer / oligomer is formed with a concentration gradient in the thickness direction, so that the unpolymerized monomer component formed in the reverse direction remains in the thickness direction. The concentration gradient distribution is made uniform in the thickness direction, and this is used to further increase the pitch length.

The heating temperature is preferably from 70 ° C to 100 ° C. If the temperature is lower than 70 ° C, the diffusion speed is very slow and it takes a long time to broaden the band. Also, it is not preferable because the orientation gradually deteriorates. On the other hand, if the temperature exceeds 120 ° C, the diffusion rate is too far to be controlled. The heating time is at least 2 seconds, and further at least 10 seconds. However, since the liquid crystal layer supported on one side of the alignment substrate has an oxygen interface, if the heating time is prolonged, volatilization loss of liquid crystal composition components and photopolymerization initiator, deterioration of the film surface flatness, and adhesion of foreign matter Etc. tend to occur. Practically, the time is preferably 5 minutes or less, and more preferably 2 minutes or less.

As described above, the homogenization step by heating is performed for several seconds to several minutes, and it is not always necessary to perform heating in some places. On the other hand, in the specification of Japanese Patent No. 3,272,668, extending the selective reflection band of the cholesteric liquid crystal to more than twice that of a single pitch requires an annealing time of 4 minutes or more, and the visible light It took about 2 hours of annealing to create a selective reflection band of 300 nm or more covering the optical region.

According to the specification of Japanese Patent No. 3,272,668, it is necessary to maintain the diffusion speed of molecules in the liquid crystal layer because a remarkably long time is required to extend the pitch length of the cholesteric liquid crystal by diffusion. . Therefore, unless light irradiation during heating is avoided as much as possible, photopolymerization proceeds during heating, and pitch expansion cannot be obtained due to an increase in molecular weight or progress of crosslinking. This is because, in the specification of Patent No. 3,272,668, a polymer component having a low diffusion rate is formed upon irradiation with the first ultraviolet ray because both sides are held by substrates and is not subject to oxygen inhibition, resulting in a low degree of polymerization. However, this is an inevitable disadvantage because the mobility of the molecule is reduced. On the other hand, in the present invention, since the decrease in the degree of polymerization due to oxygen inhibition is reversely utilized in the step (1), the molecular weight of the reactant produced under the same reaction rate condition is low, Spreading speed is ensured. The conditions for securing the diffusion rate have been greatly relaxed, and the pitch length has been sufficiently extended even in the short-time heating process in the light. As a result, not only is the time significantly shortened, but also the film quality control, inspection, and measurement during in-line exposure are remarkably superior. If the speed of the production line is 10 m / min, patent specification No. 3,272,668 requires an annealing treatment at a place for as long as 120 minutes. Is a process that is virtually impossible inline. The present invention can be implemented in a short time as described above, and there are few practical problems.

Next, in the step (3), the liquid crystal layer is in contact with a gas containing oxygen, at a temperature of 20 ° C. or more, at a UV irradiation intensity lower than that of the step (1) for 10 seconds or more. Irradiate ultraviolet rays from the alignment substrate side. By the second ultraviolet irradiation in step (3), the effective depth of polymerization inhibition by oxygen penetrating from the oxygen interface side can be made deeper than in step (1), and the pitch of the short pitch region on the oxygen interface side can be reduced. The length is not substantially changed, and the reaction proceeds only in the long pitch region on the alignment substrate side, thereby further increasing the pitch on the alignment substrate side.

As mentioned above, broadband castles are not satisfactory with only the first UV irradiation. Therefore, in step (2), the remaining unreacted monomer is homogenized while maintaining the gradient structure of the polymer of the polymer / oligomer, that is, the structure of changing the pitch length, and then the second ultraviolet irradiation in step (3) is performed. As a result, the residual monomer is polymerized, and a pitch gradient is formed. As a result, the effective depth of polymerization inhibition due to oxygen penetrating from the oxygen interface side can be made deeper than in step (1), and the pitch length of the short pitch region on the oxygen interface side does not substantially change. By making the reaction proceed only in the long pitch region on the alignment substrate side, the pitch on the alignment substrate side can be further increased.

Since the increase in the molecular weight and the decrease in the diffusion rate of the liquid crystal composition layer are significantly different from those during the first ultraviolet irradiation in step (1), the amount of radicals generated per unit time is reduced, and the progress rate of polymerization is reduced. This allows for a wider bandwidth.

In the step (3), the temperature at the time of the irradiation of the second ultraviolet ray is 20 ° C. or more. The upper limit of the temperature is not particularly limited, but is preferably 140 ° C. or lower. More preferably, the temperature is from 60 ° C to 140 ° C, more preferably from 80 ° C to 120 ° C. If the temperature is lower than 20 ° C, the diffusion rate of the polymerizable mesogen compound (a) is extremely slow, and it takes a long time to broaden the band. It will take some time.

Irradiation is performed at a second UV irradiation intensity lower than the first UV irradiation intensity. By making the illuminance lower than when irradiating the first ultraviolet ray, the oxygen inhibition depth becomes deeper than the oxygen inhibition depth when irradiating the first ultraviolet ray, and the short-wavelength band formed on the air interface side is almost changed. Instead, the long wavelength band on the substrate side can be broadened. The second UV irradiation intensity is preferably 1 to 50 mW / c in ² in a range lower than the first UV irradiation intensity.

The second ultraviolet irradiation time depends on the illuminance, but is generally preferably 10 seconds or more, and more preferably 30 seconds or more. The ultraviolet irradiation time is preferably not more than 120 seconds, more preferably not more than 60 seconds from the viewpoint of working time.

As a comparison, referring to the examples of the specification of Japanese Patent No. 3272680, the irradiation intensity of the first ultraviolet irradiation and the second ultraviolet irradiation is described in the specification of Japanese Patent No. 3272680. Are the same. In this manufacturing method, pitch expansion at the time of the irradiation of the second ultraviolet ray cannot be expected, and it has to rely on diffusion at the time of annealing. Therefore, it is understood that Patent Document 3 272 668 requires a long annealing time, which has a serious problem in practical use.

Further, if the process (3) has a defect such as a discontinuous change in the pitch length in the process (1), it can be made continuous. If the change in pitch length is discontinuous, only specific wavelengths will be cut or the transmittance will be high, resulting in unnecessary characteristics in the selective reflection wavelength band. In such a case, problems such as uneven color tone in the plane or uneven coloring of the color tone occur. Furthermore, as described above, the wavelength characteristic shifts to a short wavelength at oblique incidence, so that when the emission line spectrum of the light source is applied to the extraordinary wavelength region where the transmittance is high or low, the sharp color tone * brightness This will cause a change and significantly degrade the visibility. Such defects should be eliminated as much as possible, and the selective reflection wavelength band 內 should be flat with little change in reflectivity / transmittance. Since the band broadening process in step (3) is different from the band broadening in step (1) under the condition of ultraviolet irradiation, even if a discontinuity in pitch length change occurs, it differs from the wavelength range formed in step (1). Since they occur in the area, the superposition effect as a whole complements each other's shortcomings, resulting in a continuous change. This step (3) If not, for example, in the case of Example 2 of Japanese Patent Application Laid-Open No. 2002-286935, a step occurs in the extended band, but in the present invention, As shown in the figure, it has continuous and smooth characteristics. This is very advantageous in actual use. As described above, the broadening of the band by the step (3) enables the broadening of the band as described in the later-described embodiment, and coloring and color omission by oblique incident light due to blue shift occur. The viewing angle becomes extremely large, and coloring due to the viewing angle can be significantly reduced. Next, in step (4), ultraviolet irradiation is performed in the absence of oxygen. By the third ultraviolet ray irradiation, the cholesteric reflection band extended in steps (1) to (3) is cured without deteriorating. As a result, the pitch change structure is fixed without deterioration.

The absence of oxygen can be, for example, an inert gas atmosphere. The inert gas is not particularly limited as long as it does not affect the ultraviolet polymerization of the liquid crystal mixture. Examples of such an inert gas include nitrogen, argon, helium, neon, xenon, and krypton. Of these, nitrogen is the most versatile and preferred. Further, by bonding a transparent base material to the cholesteric liquid crystal layer, it is possible to eliminate the presence of oxygen.

In step (4), the ultraviolet irradiation may be performed from either the alignment substrate side or the applied liquid crystal mixture side.

The ultraviolet irradiation condition is not particularly limited as long as the liquid crystal mixture is cured. Usually, it is preferable to irradiate at an irradiation intensity of about 40 to 300 mWZ cm ^{2 for} about 1 to 60 seconds. The irradiation temperature is about 20 to 100 ° C.

As a result, the crosslink density of the liquid crystal layer is improved. The reliability is significantly improved due to the increase in the molecular weight. In the present invention, ultraviolet irradiation is performed from the alignment substrate surface side in order to positively utilize oxygen inhibition in the first ultraviolet irradiation in the step (1) and the second ultraviolet irradiation in the step (3). For this reason, it is possible to form a large gradient in the reaction rate in the thickness direction, but the problem is that the polymerization rate on the air interface side is low, and the hardness and strength of the film surface are insufficient, or long-term reliability is a problem. There is a possibility that problems such as lack of sex may occur. For this reason, in step (4), third ultraviolet irradiation is performed in an oxygen-free atmosphere to complete polymerization of the remaining monomer, Enhancing film quality. In this case, the reaction rate of the surface does not improve sufficiently in an air atmosphere (in the presence of oxygen), and it is difficult for the reaction rate to exceed 90%. Therefore, in order to obtain sufficient reliability, it is desired to perform ultraviolet irradiation in the absence of oxygen. The direction of the irradiation surface is not particularly limited. Irradiation from the liquid crystal layer side is desirable, but the reaction on the surface proceeds sufficiently even under irradiation from the substrate side under a nitrogen atmosphere.The cholesteric liquid crystal film obtained in this way peels off from the substrate It may be used without being used, or may be peeled off from the substrate.

The broadband cholesteric liquid crystal film of the present invention is used as a circularly polarizing plate. A linear polarizing element can be obtained by laminating a λ / 4 plate on the circularly polarizing plate. It is preferable that the cholesteric liquid crystal film, which is a circularly polarizing plate, is laminated on the λ / 4 plate so that the pitch length is continuously narrowed.

A / 4 plate is not particularly limited, but a phase difference is generated by stretching such as polycarbonate, polyethylene terephthalate, polystyrene, polysnoreon, polyvinyl alcohol, polymethyl methacrylate, etc. General-purpose transparent resin film Norbornene resin film such as ARTON film manufactured by JSR is suitably used. Further, it is preferable to perform biaxial stretching and use a retardation plate that compensates for a change in retardation value due to the incident angle, since the viewing angle characteristics can be improved. Further, other than the expression of the retardation by stretching the resin, for example, a quarter plate obtained by fixing liquid crystal by fixing a quarter layer may be used. In this case, the thickness of the 4 plate can be significantly reduced. The thickness of the λ4 wave plate is usually preferably from 0.5 to 200 / im, especially: It is preferably up to 100 μm.

A retardation plate that functions as a λ / 4 wavelength plate in a wide wavelength range such as a visible light castle is, for example, a retardation layer that functions as a / 4 wavelength plate for light-colored light having a wavelength of 550 nm. It can be obtained by a method in which a phase difference layer exhibiting other phase difference characteristics, for example, a phase difference layer functioning as a two-wavelength plate is superimposed. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or two or more retardation layers. Paste along the transmission axis direction Used together.

The polarizer is not particularly limited, and various types can be used. Examples of polarizers include iodine and two-color polarizers, such as hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and polyethylene / butyl acetate copolymer-based partially saponified films. Uniaxially stretched by adsorbing a dichroic substance such as a chromatic dye; a dehydrated product of polyvinyl alcohol; a dehydrochlorination product of polyvinyl chloride; and a polyene-based oriented film. Among these, a polarizer made of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μπι.

A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching is dyed, for example, by immersing polyvinyl alcohol in an aqueous solution of iodine, and stretching it to 3 to 7 times its original length. Can be made. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. If necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. Polyvinyl alcohol-based film is obtained by washing the polyvinyl alcohol-based film with water. In addition to being able to clean surface dirt and anti-blocking agents, it also has the effect of preventing unevenness such as uneven dyeing by swelling the polyvinyl alcohol-based film. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or calcium iodide or in a water bath.

The polarizer is usually provided with a transparent protective film on one or both sides and used as a polarizing plate. It is preferable that the transparent protective film is excellent in transparency, mechanical strength, heat stability, moisture shielding property, isotropy and the like. Transparent protective films include, for example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, senorellose polymers such as diacetinose / relose, triacetinoresenorelose, etc., and polymers. Examples include films made of transparent polymers such as acrylic polymers such as carbonate polymers and polymethylmethacrylate. Styrene polymers such as polystyrene, acrylonitrile and styrene copolymer, polyethylene, polypropylene, polyolefin having cyclic or norbornene structure, and ethylene. 'Films made of transparent polymers such as olefin-based polymers such as propylene copolymers, vinyl chloride-based polymers, and amide-based polymers such as vinyl-aromatic polyamides can also be used. Furthermore, imid polymer, sulfone polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, BULL A film made of a transparent polymer such as a butyral-based polymer, an arylate-based polymer, a polyoxymethylene-based polymer, an epoxy-based polymer, or a blend of the above polymers is also included. In particular, those having low optical birefringence are preferably used. From the viewpoint of the protective film of the polarizing plate, triacetyl cellulose, polycarbonate, acrylic polymer, cycloolefin resin, polyolefin having a norbornene structure, and the like are preferable.

Further, a polymer film described in Japanese Patent Application Laid-Open Publication No. 2001-334529 (WO01Z37007), for example, (A) substituted or unsubstituted And (B) a thermoplastic resin having a substituted and / or unsubstituted phenyl in the side chain and a thermoplastic resin having a ditolyl group. As a specific example, there is a film of a resin composition containing an alternating copolymer of isobutylene and N-methylmaleide and an acrylonitrile / styrene copolymer. As the film, a film composed of a mixed extruded product of a resin composition or the like can be used. A transparent substrate that can be particularly preferably used in view of polarization characteristics and durability is a triacetyl cellulose film whose surface is saponified with alkali or the like. The thickness of the transparent protective film can be determined as appropriate, but is generally about 10 to 500 / x m from the viewpoint of workability such as strength and handleability and thinness. In particular, it is preferably from 20 to 300 m, more preferably from 30 to 200 μπι.

Further, it is preferable that the transparent protective film has as little coloring as possible. Therefore, R th = [(nx + ny) / 2-nz] d (where nx and ny are the main refractive indices in the finolem plane, nz is the refractive index in the film thickness direction, and d is the film thickness. A protective film having a retardation value in the thickness direction of the film represented by) of _90 nm to +75 nm is preferably used. By using such a retardation value (Rth) in the thickness direction of -90 nm to 1775 nm, the polarizing plate caused by the protective film can be used. Coloring (optical coloring) can be almost completely eliminated. The thickness direction retardation value (R th) is more preferably 180 nm + 60 nm, particularly preferably 170 nm + 45 nm.

As the transparent protective film, a transparent protective film made of the same polymer material on both sides may be used, or a transparent protective film made of a different polymer material or the like may be used.

The surface of the transparent protective film on which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, a treatment for preventing sticking, and a treatment for diffusion or antiglare.

The coating treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having an excellent hardness and a sliding property by a suitable ultraviolet curable resin such as an acrylic or silicone resin is used. It can be formed by a method of adding to the surface of the protective film. The anti-reflection treatment is performed for the purpose of preventing reflection of external light on the polarizing plate surface, and can be achieved by forming an anti-reflection film or the like according to the related art. The anti-stating treatment is performed to prevent adhesion to the adjacent layer. The anti-glare treatment is performed to prevent external light from being reflected on the surface of the polarizing plate and hindering the visibility of light transmitted through the polarizing plate. The surface of the transparent protective film is provided with a fine uneven structure by an appropriate method such as a sandblasting method, a roughening method using an embossing method, or a compounding method of transparent fine particles. Can be formed. Examples of the fine particles to be included in the formation of the surface fine unevenness include silica having an average particle diameter of 0 to 550 μπι, alumina, titania, zirconia, tin oxide, indium oxide, and oxidizing power. Transparent fine particles such as conductive inorganic fine particles made of antimony oxide or the like, and organic fine particles made of a crosslinked or uncrosslinked polymer or the like are used. In the case of forming a surface fine DA convex structure, the amount of fine particles used is generally about 250 parts by weight with respect to 100 parts by weight of the transparent resin forming the fine surface unevenness structure, and Parts are preferred. The anti-glare layer may also serve as a diffusion layer (such as a viewing angle expanding function) for diffusing light transmitted through the polarizing plate to increase the viewing angle and the like. The anti-reflection layer, anti-sticking layer, diffusion layer, anti-glare layer and the like can be provided on the transparent protective film itself, or separately provided as an optical layer separately from the transparent protective layer. You can also.

The above-mentioned linear polarizing element may be provided with an adhesive layer for bonding to another member such as a liquid crystal cell. The pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer is not particularly limited, but is, for example, based on polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, and fluorine and rubber polymers. A polymer can be appropriately selected and used. In particular, those having excellent optical transparency such as an acrylic adhesive, exhibiting appropriate wettability, cohesiveness and adhesive adhesive properties, and having excellent weather resistance and heat resistance are preferably used.

In addition to the above, it is also necessary to prevent foaming and peeling phenomena due to moisture absorption, prevent optical characteristics from deteriorating due to differences in thermal expansion, prevent liquid crystal cells from warping, and form the liquid crystal display device with high quality and excellent durability. Therefore, an adhesive layer with low moisture absorption and excellent heat resistance is preferred.

The adhesive layer is made of, for example, a natural or synthetic resin, particularly a tackifying resin, a filler, a pigment, a colorant, an antioxidant, and the like made of glass fiber, glass beads, metal powder, and other inorganic powders. May be added to the pressure-sensitive adhesive layer. In addition, an adhesive layer containing fine particles and exhibiting light diffusibility may be used.

The attachment of the adhesive layer may be performed by an appropriate method. For example, about 10 to 40% by weight of an adhesive obtained by dissolving or dispersing a base polymer or a composition thereof in a solvent composed of a single solvent or a mixture of appropriate solvents such as toluene and ethyl acetate. An adhesive solution is prepared and applied directly on the polarizer by an appropriate developing method such as a casting method or a coating method, or an adhesive layer is formed on a separator according to the method described above, and then the optical element is formed. There is a method to transfer to the top. The adhesive layer may be provided as a superimposed layer of different compositions or types of layers. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use, adhesive strength, and the like, and is generally 1 to 500 / m, preferably 5 to 200 μm, and more preferably 10 to 1 / m. 0 Ο μ πι is preferred.

A separator is temporarily attached to the exposed surface of the adhesive layer to prevent contamination, etc., until it is practically used, and is covered. This allows the adhesive layer to be used in normal handling conditions. Contact can be prevented. Except for the above thickness conditions, the separator may be any suitable thin leaf such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet or metal foil, or a laminate thereof. If necessary, use an appropriate material similar to the conventional one, such as one coated with an appropriate release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

Each layer such as the adhesive layer is treated with an ultraviolet absorber such as a salicylate compound, a benzofurnol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. For example, a material having an ultraviolet ray absorbing ability according to such a method may be used.

The linear polarizing element of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The formation of the liquid crystal display device can be performed according to a conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an optical element, and, if necessary, an illumination system and incorporating a drive circuit. There is no particular limitation except that a polarizing element is used, and the conventional method is used. As for the liquid crystal cell, any type such as TN type, STN type, and π type may be used.

An appropriate liquid crystal display device such as a liquid crystal display device in which the linear polarizing element is arranged on one side or both sides of a liquid crystal cell, or a lighting system using a backlight or a reflector can be formed. In that case, the linear polarizing element according to the present invention can be installed on one side or both sides of the liquid crystal cell. When linear polarizing elements are provided on both sides, they may be the same or different. In addition, when forming a liquid crystal display device, appropriate components such as a diffusion plate, an anti-glare layer, an anti-reflection film, a protection plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight are appropriately positioned. One layer or two or more layers can be arranged in one layer.

Further, the circular polarizer (reflective polarizer) using the cholesteric liquid crystal film is provided between at least two reflective polarizers (a) in which the wavelength bands of selective reflection of polarized light overlap each other. A retardation layer (b) having a front phase difference (normal direction) of almost zero and having a phase difference of / 8 or more with respect to incident light incident at an angle of 30 ° or more with respect to the normal direction is arranged. Used in polarizing element systems. The cholesteric liquid crystal film is Either the maximum pitch or the minimum pitch of the helical twisted molecular structure may be the side of the retardation layer (b), but from the viewpoint (the viewing angle is good, the coloring is small), the reflection polarizer (a) is used. If it is displayed as (maximum pitch / minimum pitch), it is preferable to arrange them in such a way that the maximum pitch / minimum pitch phase difference layer (b) Z maximum pitch / min pitch When four λ-plates are combined, it is preferable to arrange the reflective polarizer (a) so that the minimum pitch side is the IZ-four plate side.

The polarizing element system, that is, the cholesteric liquid crystal laminate having a wide-band selective reflection function has a circularly-polarized reflection / transmission function in the front direction, and is used in a liquid crystal display device as a wide-band circularly polarizing plate. Can be. In this case, it can be used as a circularly polarizing plate by disposing it on the light source side of a circularly polarized mode liquid crystal cell, for example, a transmissive VA mode liquid crystal cell having multiple domains.

The phase difference layer (b) has a phase difference of almost zero in the front direction and has a phase difference of λ / 8 or more with respect to incident light at an angle of 30 ° from the normal direction. The front phase difference is desirably LZ10 or less because the purpose is to maintain the vertically polarized light.

The incident light from the oblique direction is appropriately determined by the angle of total reflection so as to be efficiently converted in polarization. For example, 60 to completely reflect at an angle of about 60 ° from the normal. What is necessary is just to determine so that the phase difference when measured at is about λ / 2. However, since the transmitted light by the reflective polarizer (a) changes its polarization state due to the C-plate birefringence of the reflective polarizer itself, it is measured at that angle of the normally inserted C-plate. The phase difference at this time can be a value smaller than 1/2. Since the phase difference of the C-plate increases monotonically as the incident light is inclined, the effective total reflection occurs when the angle of inclination is 30 ° or more. And L / 8 or more.

The material of the retardation layer (b) is not particularly limited as long as it has the above-mentioned optical characteristics. For example, a fixed cholesteric liquid crystal having a selective reflection wavelength outside the visible light region (380 nm to 780 nm), or a fixed liquid crystal with a homeotropic aperture of a rod-shaped liquid crystal Columnar orientation of discotic liquid crystal, nematic orientation, negative uniaxial crystal in-plane orientation, Examples include biaxially oriented polymer films.

In the present invention, the C plate in which the cholesteric liquid crystal having a selective reflection wavelength other than the visible light region (380 nm to 780 nm) has a fixed planar state is a selective reflection wavelength of the cholesteric liquid crystal. It is desirable that the visible light region has no coloring or the like. Therefore, it is necessary that the selective reflection light is not in the visible region. The selective reflection is uniquely determined by the chiral pitch of the cholesteric and the refractive index of the liquid crystal. The value of the central wavelength of selective reflection may be in the near-infrared region, but it may be in the ultraviolet region of 35 O nm or less because it is affected by optical rotation and causes a somewhat complicated phenomenon. More desirable. The formation of the cholesteric liquid crystal layer is performed in the same manner as the formation of the cholesteric layer in the reflective polarizer described above.

In the present invention, the C-plate having a fixed homeotropic orbital alignment state is a liquid crystalline thermoplastic resin or a liquid crystal monomer exhibiting nematic liquid crystallinity at a high temperature, and an alignment aid as required, and ionizing radiation such as an electron beam or ultraviolet light. Polymerizable liquid crystal polymerized by irradiation or heat, or a mixture thereof is used. The liquid crystal properties may be either lyotropic or thermotropic, but from the viewpoint of easy control and easy formation of a monodomain, it is desirable that the liquid crystal be a thermostatically-picking liquid crystal. The homeotropic alignment can be obtained, for example, by applying the above-mentioned birefringent material on a film on which a vertical alignment film (such as long-chain alkylsilane) is formed, and developing and fixing a liquid crystal state. As a C-plate using a discotic liquid crystal, as a liquid crystal material, a negative uniaxial compound such as a phthalocyanine compound or a triphenylene compound having an in-plane molecular spread is used. It is a discotic liquid crystal material that has properties and is fixed by developing a nematic phase and a columnar phase. Negative uniaxial inorganic layered compounds are described in detail in, for example, Japanese Patent Application Laid-Open Publication No. Hei 6—8277777.

C-plates using biaxial orientation of polymer film are a method of biaxially stretching a polymer film having positive refractive index anisotropy, a method of pressing a thermoplastic resin, and a crystal in parallel orientation. It can be obtained by the method of cutting out from the.

The layers may be stacked only, but it is preferable that the layers be stacked using an adhesive or a pressure-sensitive adhesive from the viewpoint of workability and light use efficiency. In that case, the adhesive or adhesive is transparent, has no absorption in the visible light range, and the refractive index is as high as the refractive index of each layer. Closer to each other is desirable from the viewpoint of suppressing surface reflection. From this viewpoint, for example, an acrylic adhesive is preferably used. For each layer, a monodomain is separately formed in the form of an alignment film and then sequentially laminated by a method such as transfer to a translucent grave material, or an alignment film is provided for alignment without providing an adhesive layer. It is also possible to form such layers appropriately and to directly form each layer sequentially.

Particles may be added to each layer and the (viscosity) adhesive layer to adjust the degree of diffusion, if necessary, to provide isotropic scattering, or to use an ultraviolet absorber, an antioxidant, A surfactant or the like can be appropriately added for the purpose of imparting leveling properties. Although the polarizing element (cholesteric liquid crystal laminate) of the present invention has a function of reflecting / transmitting circularly polarized light, it can be used as a linearly polarizing element that converts transmitted light into linearly polarized light by combining four plates. Can be. Examples of the λ / 4 plate include the same as those described above.

For example, a / 4 plate has a single layer made of a single material that works well only for a specific wavelength, but there is a problem that the function of the / 4 plate is reduced for other wavelengths due to wavelength dispersion characteristics . Therefore, by laminating the λ2 plate with the specified axis angle, the λ2 plate can be used as a broadband / 4 plate that functions within a practically acceptable range over the entire visible light range. In this case, each of the four plates and the two λ plates may be made of the same material, or a combination of materials manufactured using different materials obtained by the same method as the λΖ plate described above may be used.

For example, a quarter-wave plate (140 nm) is laminated on a broadband circularly polarizing plate, and a λΖ2 plate (270 nm) is arranged at 17.5 degrees with respect to this axis angle. In this case, the transmission polarization axis is 10 degrees with respect to the axis of the λ / plate. Since the bonding angle varies depending on the phase difference value of each phase difference plate, the bonding angle is not limited to the above bonding angle.

An absorptive polarizer is attached to the transmission axis of the linearly polarizing element so that its transmission axis direction is aligned.

(Arrangement of diffuse reflector)

It is desirable to arrange a diffuse reflection plate below the light guide plate as the light source (on the side opposite to the liquid crystal cell arrangement surface). The main component of the light beam reflected by the collimating film is an oblique incident component, which is specularly reflected by the collimating film and returned to the backlight direction. Here, when the back side reflector has high specularity, the reflection angle is preserved, and Light is lost due to scratches. Therefore, it is desirable to dispose a diffuse reflector in order to increase the diffuse reflection component in the front direction without preserving the reflection angle of the reflected return light beam.

(Arrangement of diffusion plate)

It is also desirable to provide a suitable diffuser between the collimating film and the backlight light source in the present invention. This is because the light reuse efficiency is increased by scattering the light beam obliquely incident and reflected near the backlight light guide and scattering a part of the light beam in the vertical incidence direction.

The diffusion plate used can be obtained by embedding fine particles having different refractive indices in a resin, etc., in addition to the one having the uneven surface shape. This diffusion plate may be sandwiched between the collimating film and the pack light, or may be bonded to the collimating film.

If the liquid crystal cell with the collimated film attached is placed in close proximity to the backlight, a U-ton ring may occur in the gap between the film surface and the backlight. By arranging a diffusion plate having surface irregularities on the light plate side surface, the generation of Newton rings can be suppressed. Further, a layer having both the concavo-convex structure and the light diffusion structure may be formed on the surface of the parallel light conversion film in the present invention.

(Placement of viewing angle expansion film)

The viewing angle expansion in the liquid crystal display device of the present invention is achieved by diffusing the light beams having good display characteristics near the front obtained from the liquid crystal display device combined with the parallelized backlight, so as to be uniform within the entire viewing angle. It is obtained by obtaining good display characteristics. As the viewing angle widening film used here, a diffusion plate having substantially no back scattering is used. The diffusion plate can be provided as a diffusion adhesive. The placement location is on the viewing side of the liquid crystal display device, but it can be used either above or below the polarizing plate. However, in order to prevent the effects of pixel bleeding and the like, and a decrease in contrast due to slightly remaining back scattering, it is desirable to provide the layer as close to the cell as possible, such as between the polarizing plate and the liquid crystal cell. In this case, a film that does not substantially eliminate polarized light is desirable. For example, a fine particle-dispersed diffusion plate as disclosed in Japanese Patent Application Laid-Open No. 2000-347706 and Japanese Patent Application Laid-Open No. 2000-34707 is preferably used.

When the viewing angle widening film is located outside the polarizing plate, the liquid crystal layer and the polarizing plate In the case of a TN liquid crystal cell, it is not particularly necessary to use a viewing angle compensating phase difference plate because the collimated light beam is transmitted. In the case of an STN liquid crystal cell, it is only necessary to use a retardation film in which only the front characteristics are well compensated. In this case, since the viewing angle widening film has an air surface, it is possible to adopt a type using a refraction effect due to the surface shape. When a viewing angle-enhancing film is inserted between the polarizing plate and the liquid crystal layer on the negative side, the light is diffused when the film passes through the polarizing plate. In the case of TN liquid crystal, the viewing angle characteristics of the polarizer itself must be compensated. In this case, it is necessary to insert a retardation plate for compensating the viewing angle characteristics of the polarizer between the polarizer and the viewing angle widening film. In the case of STN liquid crystal, it is necessary to introduce a retardation plate that compensates for the viewing angle characteristics of the polarizer in addition to the front phase difference compensation of the STN liquid crystal.

In the case of a film with a wide viewing angle that has a regular structure inside, such as a microphone array lens array film or hologram film that has existed in the past, the liquid crystal display device's platform matrix ゃ parallel light from the conventional backlight It interfered with the microstructures of the system such as micro lens array / prism array / louver / micro mirror array, and easily caused moire. However, in the collimating film of the present invention, the regular structure is not visually recognized in the plane, and there is no regular modulation in the emitted light. Therefore, it is not necessary to consider the compatibility with the viewing angle expansion film and the arrangement order. Therefore, the viewing angle widening film is not particularly limited as long as it does not cause interference / moire with the pixel black matrix of the liquid crystal display device, and there are a wide range of options.

In the present invention, the viewing angle widening film has substantially no backscattering and does not eliminate polarization, and is disclosed in Japanese Patent Application Laid-Open Publication No. 2000-34067 and Japanese Patent Publication No. A light-scattering plate as described in JP-A-347077, which has a haze of 80% to 90%, is suitably used. In addition, even if it has a regular structure inside, such as a hologram sheet, microprism array, microphone opening lens array, etc., it can be used without forming interference / moire with the pixel black matrix of the liquid crystal display device.

In addition, the liquid crystal display device is manufactured by appropriately using various optical layers and the like according to an ordinary method. Example

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1

Photopolymerizable mesogen compound (polymerizable nematic liquid crystal monomer, compound 20 in Table 1 above, molar extinction coefficient is 1 dm ³ mo 1 ^_1 cm " ¹ ® 365 nm, 2 100 dm ³ mo 1 ^{^{_1 cm "1 ® 3 3 4}} nm, 3 6 0 0 0 dm 3 mol one ¹ c m- ^ S lnm purity> 99% of was used.) 9 4.8 parts by weight of a polymerizable chiral agent ( BASF LC750) 5.2 parts by weight of a solvent (cyclohexanone) adjusted to have a selective reflection center wavelength of 550 nm A coating solution (solid content: 30% by weight) was prepared by adding 3% by weight of a polymerization initiator (Irgacure 907, manufactured by Chipa Specialty Chemicals). The coating solution is applied on a stretched polyethylene terephthalate film (oriented substrate) using a wire bar so that the thickness after drying becomes 6 μm, and the solvent is applied at 100 ° C. Dry for 2 minutes. The obtained film was irradiated with a first ultraviolet ray at 50 mW / cm ² for 1 second in an air atmosphere at 40 ° C. from the alignment substrate side. Thereafter, heating was performed at 90 ° C for 1 minute without irradiation with ultraviolet rays (the selective reflection wavelength band at this time was 420 to 650 nm). Then, in an air atmosphere of the second ultraviolet irradiation of 9 0 ° C, at 5 mW / cm ^2, for 6 0 seconds (met this and Kino selective reflection wavelength band 4 2 0 to 9 0 0 nm T). Then, at 5 0 ° 8 a third ultraviolet radiation from the alignment substrate side under a nitrogen atmosphere at C 0 mW / cm ^2, 3 performs 0 seconds, broadband co Resuteri Tsu selected wavelength is 4 2 0 to 9 0 0 nm A liquid crystal film was obtained. Figure 4 shows the reflection spectrum of the broadband cholesteric liquid crystal film. Using a translucent adhesive, a negative biaxial retardation plate was transferred onto the upper part of the obtained broadband cholesteric liquid crystal film (circularly polarizing reflector). This negative biaxial retardation plate was obtained by the following method. That is, the concentration is 30% by weight in 93 parts by weight of the photopolymerizable nematic liquid crystal monomer (BASF, LC224) and 7 parts by weight of the polymerizable chiral agent (BASF, LC756). After adding cyclohexanone as a solvent and adjusting the blend so that the central wavelength of selective reflection becomes 350 nm, irgacure 907 is used as a photopolymerization initiator for the solid content described above. Prepare coating liquid with weight% added Then, the above solution was applied to a stretched polyethylene terephthalate material using a wireper so that the thickness after drying was 4 / m, and the solvent was dried for 100 minutes for 100 minutes. Thereafter, the temperature was once raised to the isotropic transition temperature of the liquid crystal monomer, and then gradually cooled to form a layer having a uniform alignment state. To the resulting eyebrows, it was obtained by fixing 5 0 mW / _C m 5 seconds performs alignment state. When the phase difference of this negative biaxial retardation plate was measured, the phase difference when the light with a wavelength of 550 nm was measured at an angle of 2 rim in the front direction and at an angle of 30 ° was 12 0 It was lira. The measurement of the phase difference is performed using K〇 BRA—21 ADH manufactured by jiji S centific Instruments.

Further, a circularly-polarized light reflecting plate similar to that described above was transferred onto the upper portion using the same translucent adhesive to form a ridge layer, thereby obtaining a solid optical device. A linear polarizing element was obtained by adhering a Peno 4 plate (front retardation: 140 II m) obtained by uniaxially stretching the polycarbonate film to the obtained optical element. This linearly polarizing element, a polarizing plate (day bundle Denko Co., TEG 1 ⁴ 6 5 DU) bonded to the transmission axis direction coincides, to obtain a polarizing plate integrated僞光element ₀

Example 2

In Example 1, a polarizing element; a linear polarizing element obtained by laminating an I-no. 4 plate, and a: λ / 2 plate obtained by uniaxially stretching a polycarbonate film on the A front phase difference of 270 nm) was adhered to obtain a straight line 镉 ko Hatako. A polarizing plate (TEG1465DU, manufactured by Nitto Dye Co., Ltd.) was bonded to the linear polarizing element so that the transmission axis directions were aligned, to obtain a polarizing plate integrated polarizing element. In these layers, the angle between the stretching axis (slow axis) of the λΖ4 plate and the λ / 2 plate and the stretching axis (absorption axis) of the polarizing plate was set as shown in FIG. In Fig. 3, PL indicates an absorption-type polarizing plate, (1 indicates a No. 4 plate (front phase difference I 40 nni), and C2 indicates a λ / 2 plate (front phase difference 2700 nm). The mark indicates the stretching axis (long side direction), where 01 is 17.5 and 02 is 80.

Example 3

A polycarbonate film was biaxially stretched on the photon obtained in Example 1; a four plate (front retardation: 125 nm, Nz coefficient: 11.0) was adhered. A linear polarization cord was obtained. A polarizing plate (Nitto Denko Corporation, TEG 1 4 6 5 (DU) were bonded together so that the transmission axis directions coincided to obtain a polarizing element integrated with a polarizing plate.Comparative Example 1

A coating solution containing the liquid crystal mixture prepared in Example 1 was applied on a stretched polyethylene terephthalate film (alignment substrate) using a wire bar so that the thickness after drying was 6 μm. The solvent was dried at 1000C for 2 minutes. The obtained film was irradiated with ultraviolet rays at 50 mW / cm ² for 10 seconds in an air atmosphere at 40 ° C. from the orientation substrate side. At this time, the selective reflection wavelength band was approximately 420 to 800 nm. Then, 5 0 ° UV irradiation to 8 0 mW / cm ² from the alignment substrate side under a nitrogen atmosphere for C, 3 do 0 seconds, broadband cholesteric click liquid crystal film of the selected wavelengths 4 2 0 to 8 0 0 nm Got. Fig. 4 shows the reflection spectrum of the broadband cholesteric liquid crystal film. In the same manner as in Example 1, a negative biaxial retardation similar to that of Example 1 was applied to the upper part of the obtained broadband cholesteric liquid crystal film (circularly-polarized light reflecting plate) using a translucent adhesive. The board was transferred.

Further, a circularly-polarized light reflecting plate similar to that described above was transferred and laminated on the upper portion using the same translucent adhesive to obtain a polarizing element. A linear polarizing element was obtained by adhering a four-layer plate (front retardation: 140 nm) obtained by uniaxially stretching the polycarbonate film to the obtained polarizing element. This linearly polarizing element, a polarizing plate (manufactured by Nitto Denko Corporation, TEG 1 4 6 5 DU) bonded to the earthenware pots by the transmission axis direction coincides, to obtain a polarizing plate integrated polarizing element ₀

Comparative Example 2

A coating liquid containing the liquid crystal mixture prepared in Example 1 was applied on a stretched polyethylene terephthalate film (alignment substrate) using a wire par so as to have a thickness after drying of 6 μm. The solvent was dried at 1000C for 2 minutes. The obtained film was irradiated with ultraviolet rays at 50 mW / cm ² for 1 second in an air atmosphere at 40 ° C. from the orientation substrate side. Thereafter, heating was performed at 90 ° C for 1 minute without irradiation with ultraviolet rays (the selective reflection wavelength band at this time was 420 to 650 nm). Then, at 5 0 ° C 8 0 ultraviolet radiation from the alignment substrate side under nitrogen Kiri囲vapor of mW / cm ^2, 3 performs 0 seconds, broadband co Leste selection wave length of 4 2 0~6 5 0 nm A liquid crystal film was obtained. Wideband Fig. 4 shows the reflection spectrum of the resteric liquid crystal film.

In the same manner as in Example 1, a negative biaxial retardation similar to that of Example 1 was applied to the upper part of the obtained broadband cholesteric liquid crystal film (circularly-polarized light reflecting plate) using a translucent adhesive. The board was transferred.

Further, a circularly polarized light reflecting plate similar to that described above was transferred and laminated on the upper portion using the same light-transmitting adhesive to obtain a polarizing element. A polycarbonate film was uniaxially stretched to the obtained polarizing element. An YZ4 plate (front retardation: 140 nm) was adhered to obtain a linear polarizing element. A polarizing plate (TEG1465DU, manufactured by Nitto Denko Corporation) was adhered to the linear polarizing element so that the transmission axis directions coincided with each other to obtain a polarizing plate integrated polarizing element.

Comparative Example 3

The coating liquid containing the liquid crystal mixture prepared in Example 1 was applied on a stretched polyethylene terephthalate film (alignment substrate) using a wire bar so that the thickness after drying was 6 m, and the solvent was applied. Was dried at 100 ° C. for 2 minutes. The obtained film was irradiated with ultraviolet rays at 50 mW / cm ² for 1 second in an air atmosphere at 40 ° C. from the orientation substrate side. Thereafter, heating was performed at 90 ° C for 1 minute without irradiation with ultraviolet light (the selective reflection wavelength band at this time was 420 to 650 nm). Then, in an air atmosphere of the ultraviolet irradiation 9 0 ° C, in 5 mWZ cm ^2, 6 0 seconds KoTsuta (selective reflection wave Nagataijo at this time Atsuta at 4 2 0~ 9 0 0 nm) .

The same negative biaxial phase as in Example 1 was applied to the top of the obtained broadband cholesteric liquid crystal film (circularly polarized light reflecting plate) in the same manner as in Example 1 using a translucent adhesive. The difference plate was transferred.

Further, a circularly polarized light reflecting plate similar to the above was transferred and laminated on the upper portion using the same translucent adhesive to obtain a polarizing element. A polycarbonate film was uniaxially stretched to the obtained polarizing element; a LZ 4 plate (front retardation: 140 nm) was bonded to obtain a linear polarizing element. A polarizing plate (manufactured by Nitto Denko Corporation, TEG1465DU) was attached to the linear polarizing element so that the transmission axis directions were aligned, to obtain a polarizing element integrated with the polarizing plate. (Liquid crystal display)

The polarizing plate integrated with the polarizing plate obtained in each example was used as the lower plate of the TFT-LCD, while an acrylic adhesive (thickness 25 / zm, refractive index 1.47) was used on the upper plate side. ) 20 weight spherical silica particles (refractive index: 1.44, diameter: 4 / m). A polarizing plate (TEG1465 DU, manufactured by Nitto Denko Corporation) was laminated using a light-scattering adhesive (haze 80%) embedded in / ₀ .

In addition, a cold cathode tube with a diameter of about 3 mm was placed on the side of a light guide having a fine prism structure on the lower surface, and covered with a light source holder made of silver-deposited polyethylene terephthalate film. A silver-evaporated polyethylene terephthalate film reflector was arranged on the lower surface of the light guide plate, and a polyethylene terephthalate film having a scattering layer made of styrene beads formed on the surface was arranged on the upper surface of the light guide plate. This was disposed as a light source below the polarizing plate integrated with the polarizing element.

FIG. 1 shows a case in which the polarizing plate integrated type polarizing elements of Examples 1 and 3 and Comparative Examples 1 to 3 are used, and FIG. 2 shows a case in which the polarizing plate integrated type polarizing element of Example 2 is used.

In FIGS. 1 and 2, PL is an absorption polarizer, D is a viewing angle widening film (diffusion adhesive), LC is a liquid crystal cell, C 1 is a λ / 4 plate, C 2 is a λ'2 plate, and Α is Reflective polarizer (a): Circular polarizer, B is retarder (b): C-plate, S is thyroid type light guide plate

, R indicates a diffuse reflection plate. X indicates a polarization element, Y indicates a linear polarization element, and Z indicates a polarization-integrated linear polarization element.

The broadband cholesteric liquid crystal film (circularly polarizing reflector) and the polarizing plate integrated polarizing element obtained above were evaluated as follows. Table 2 shows the results. Table 2 also shows the conditions of each step in the examples and the comparative examples.

(Selective reflection wavelength band and bandwidth (Δ))

The reflection spectrum of the broadband cholesteric liquid crystal film is measured with a spectrophotometer (Otsuka Electronics Co., Ltd., Instant Multi-System MC PD 2000), and the selective reflection wavelength band is about half bandwidth. λ was determined. The half bandwidth was defined as the reflection bandwidth at half the maximum reflectance. (Pitch change)

Cross-sectional TEM images of the broadband cholesteric liquid crystal film near the UV-irradiated surface (1 m below the UV-irradiated surface), near the air interface (1 μm below the air interface), and the pitch in between did.

(reliability)

When a broadband cholesteric liquid crystal film was put into a reliability test of 90% RH at 80 ° C and 60 ° C for 500 hours each, whether or not powdery substances were observed on the surface Was evaluated.

〇: No precipitate.

X: There is a precipitate.

(Front brightness)

The polarizing plate integrated polarizing element was placed on a dot-printed backlight with the polarizing plate side facing up, and evaluated with a luminance meter (TOPCON, BM-7).

(Slanted color change)

The oblique change in color tone of the liquid crystal display device was evaluated by a viewing angle measuring instrument EZ-CONTRAST manufactured by ELDIM, according to the following criteria.

Δ X y = ((x o- X!) 2 + (y 0- Y i) 2). · ⁵

Front chromaticity (x., Y _0), diagonal. Chromaticity from ± 60 ° (X or y!)

Good: Color tone change ΔXy at a viewing angle of 60 ° is less than 0.04.

Poor: Color tone change ΔXy at a viewing angle of 60 ° is 0.04 or more.

Table 2

In the examples, a cholesteric liquid crystal film having a selective reflection wavelength in a wide band including a long wavelength region is obtained. The cholesteric liquid crystal film has high reliability, and a polarizing element using the cholesteric liquid crystal film as a circularly polarizing plate is also excellent in luminance enhancement characteristics. In addition, in the liquid crystal display device using the polarizing element, the display information in the region where the gradation is not inverted is distributed by light diffusion in the oblique direction. A display device can be obtained. Industrial applicability

The broadband cholesteric liquid crystal film obtained by the production method of the present invention is useful as a circularly polarizing plate (reflection type polarizer), and the circularly polarizing plate is used for a linear polarizing element, an illumination device, a liquid crystal display device, and the like. Applicable.

Claims

The scope of the claims

1. a step of applying a liquid crystal mixture containing a polymerizable mesogen compound (A) and a polymerizable chiral agent (B) to an alignment substrate, and a step of irradiating the liquid crystal mixture with ultraviolet rays to polymerize and cure. A method for producing a broadband cholesteric liquid crystal film having a bandwidth of 200 nm or more,

The ultraviolet polymerization step,

In a state where the liquid crystal mixture is in contact with a gas containing oxygen, at a temperature of 20 ° C. or more, at an ultraviolet irradiation intensity of ^{20 to 200} mW / cm ² , the alignment is performed for 0.2 to 5 seconds. UV irradiation from the substrate side (1),

Next, in a state where the liquid crystal layer is in contact with a gas containing oxygen, a step of heating at 70 to 120 ° C. for 2 seconds or more (2),

2. The broadband castle collesteric according to claim 1, wherein the pitch length of the colesteric liquid crystal film changes so as to be continuously narrower from the side of the oriented grave material. Manufacturing method of liquid crystal film.

3. The polymerizable mesogen compound (A) has one polymerizable functional group, and the polymerizable chiral agent (B) has two or more polymerizable functional groups. Or the method for producing a broadband cholesteric liquid crystal film according to item 2.

0.:! ~ S O O d mSm o l ^ c m— Β δ δ η πι,

10 ~ 3 0 0 0 0 dm ³ mo 1 ^_1 cm ^_1 @ 3 3 4 nm

The broadband cholesterol according to any one of claims 1 to 3, characterized in that the diameter is 1 000 to 100 000 dm ³ mo 1 ^_1 cm " ¹ 3 14 nm. Manufacturing method of liquid crystal film.

(In the formula,! ^ ~ Scales may be the same or different, and represent 1 F, 1 H, 1 CH ₃ , 1 C ₂ H ₅ or 1 OCH ₃ , and R ₁₃ represents 1 H or 1 CH ₃ , Represents the general formula (2):-(CH ₂ CH ₂ 0) _a — (CH ₂ ) _b — (〇) _c- , X ₂ represents one CN or one F. However, the general formula (2) A) is an integer from 0 to 3, b is an integer from 0 to 12, c is 0 or 1, and when a = l to 3, b = 0, c = 0, and a = 0 Wherein b = l to 12 and c = 0 to l.) A broadband cholesterol according to any one of claims 1 to 4, characterized in that: Manufacturing method of backlit liquid crystal film.

6. A circularly polarizing plate using a broadband cholesteric liquid crystal film obtained by the production method according to any one of claims 1 to 5.

7. Between at least two layers of reflective polarizers (a) where the selective reflection wavelength bands of polarized light overlap each other.

A retardation layer (b) having a front phase difference (normal direction) of almost zero and having a phase difference of λ / 8 or more with respect to incident light incident at an angle of 30 ° or more with respect to the normal direction is provided. A polarizing element,

A polarizing element, characterized in that the reflective polarizer (a) is the circularly polarizing plate according to claim 6.

8. The method according to claim 7, wherein the selective reflection wavelengths of at least two reflective polarizers (a) overlap each other in a wavelength range of 550 nm ± 10 nm. Polarizing element.

9. Retardation layer (b) Force Fixed cholesteric liquid crystal phase having a selective reflection wavelength range other than the visible light range, with fixed Blanar orientation,

A rod-shaped liquid crystal with a fixed home-mouth pick alignment state,

The alignment state of the nematic or columnar phase of discotic liquid crystal is fixed. of,

Biaxially oriented polymer film, or

9. The polarizing element according to claim 7, wherein an inorganic layered compound having a negative uniaxial property is fixed so as to have an optical axis in a direction normal to the surface. .

10. A λ / 4 plate is laminated on the circularly polarizing plate according to claim 6 or the polarizing element according to any one of claims 7 to 9, and the transmission is linear. A linearly polarizing element, which can obtain polarized light.

11. The straight line according to claim 10, which is obtained by laminating a cholesteric liquid crystal film, which is a circularly polarizing plate, on a λΖ4 plate so that the pitch length is continuously narrowed. Linear polarizing element.

12. The plate according to claim 10 or 11, wherein the plate is a retardation plate having an improved viewing angle by biaxially stretching and performing phase difference correction of obliquely incident light beams. The linear polarizing element described.

13. The f / 4 plate is a liquid crystal polymer type retardation plate obtained by applying and fixing a nematic liquid crystal or a smectic liquid crystal, according to claim 10 or 11, wherein Linear polarizing element.

14. Λ 4 plate is defined by the formula: (nx— nz) / (n X-ny), where η X and ny are the in-plane principal refractive index and nz is the principal refractive index in the thickness direction. Wherein the Nz coefficient satisfies 0.5.2.5.

13. The linear polarizing element according to any one of the above items 13.

15. A linearly polarizing element, characterized in that a λΖ2 plate is further laminated on a / 4 plate of the linearly polarizing element according to any one of claims 10 to 14. .

16. An absorption polarizer whose transmission axis and transmission axis direction of the linear polarizing element according to any one of claims 10 to 15 are aligned with each other, and the fourth polarizing plate side of the linear polarizing element. A linear polarizing element characterized by being laminated on a substrate.

17. The circularly polarizing plate according to claim 6 on the front side of a surface light source having a reflective layer on the back side, the polarizing element according to any one of claims 7 to 9, or the claim. Characterized by having the linear polarizing element according to any one of Items 10 to 16 Lighting equipment.

18. A liquid crystal display device having a liquid crystal cell on the light emission side of the lighting device according to claim 17.

19. The viewing field according to claim 18, wherein a viewing angle magnifying film for diffusing the light beam on the viewing side transmitted through the liquid crystal cell is disposed on the viewing side with respect to the liquid crystal cell. Angle enlarged liquid crystal display.

20. The viewing angle widening liquid crystal display device according to claim 19, wherein a spreading plate having substantially no backscattering and no depolarization is used as the viewing angle widening film. .