WO2004088366A1

WO2004088366A1 - Process for producing wideband cholesteric liquid crystal film, circular polarization plate, linear polarizer, lighting apparatus and liquid crystal display

Info

Publication number: WO2004088366A1
Application number: PCT/JP2004/003718
Authority: WO
Inventors: Takahiro Fukuoka; Kazutaka Hara; Miki Shiraogawa; Naoki Takahashi; Kentarou Takeda
Original assignee: Nitto Denko Corporation
Priority date: 2003-03-31
Filing date: 2004-03-19
Publication date: 2004-10-14
Also published as: JP4293882B2; TW200428041A; TWI341928B; JP2004318062A

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 20°C or higher by means of 20 to 200 mW/cm2 ultraviolet irradiator for 0.2 to 5 sec; subsequently the step (2) of exposing the alignment substrate side of the liquid crystal layer while in contact with an oxygenic gas to ultraviolet radiation of intensity lower than in the step (1) for 10 sec or longer while increasing temperature to a final temperature that is higher than in the step (1) and not lower than 60°C at a rate of 2°C/sec or greater; and the step (3) 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

Manufacturing method of broadband cholesteric liquid crystal film, circularly polarizing plate, linearly polarizing element, lighting 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. Light

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 the 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 largest factor that lowers the efficiency of liquid crystal displays. Also, due to this absorbed light, when the output of the light source is increased to a certain degree or more, the liquid crystal display device destroys the polarizer due to the heat generated by the heat conversion of the absorbed light, or the thermal effect on the liquid crystal layer inside the cell. This has caused 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 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. is there. 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 is reflected and reused, so that 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 λ Ζ 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. That is, when a cholesteric liquid crystal film is used as a linear polarizing element in combination with an L / 4 wavelength plate, there is theoretically no loss of light, so that a conventional absorption type polarizing light absorbing 50% light is used. In theory, it is possible to obtain twice the brightness improvement compared to the case of using a single element.

However, the selective reflection characteristics of the cholesteric liquid crystal are limited to a specific wavelength band, and it has been difficult to cover the entire visible light range. The selective reflection wavelength range width コ of the cholesteric liquid crystal is

Δ Χ = 2 1-(n e — no) / (ne + no)

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

n e: refractive index of cholesteric liquid crystal molecules for 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, if ne-no is increased, the selective reflection wavelength region width λ λ is widened, but ne-η ο 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 selective reflection wavelength region width 領域 λ was at most about 150 nm. Most of the cholesteric liquid crystals that can be practically used 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 of the liquid crystal molecules and the pitch length. Therefore, in order to cover the entire visible light range, a plurality of layers having different selective reflection center wavelengths are laminated, or the pitch distribution is continuously changed in the thickness direction to form the existence distribution of the selective reflection center wavelength itself. 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. 6-28184, Japanese Patent No. 3272686, 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 exposed surface and the exit surface 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 Zm 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, the exposure time required was about 1 to 60 minutes, 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 quick pitch change due to the theoretical problem of controlling the cholesteric pitch by changing the composition ratio due to mass transfer. In Japanese Patent Application Laid-Open No. 6-281814, the pitch ratio on the short pitch side and the long pitch side differs by about 100 nm, so it is necessary to greatly change the composition ratio. Liquid crystal thickness, weak UV irradiation, and long exposure time are required. In Japanese Patent Application Laid-Open No. Hei 11-248, 943, the mobility of the substance causing the pitch change is better than the material example used in Japanese Patent Application Laid-Open No. 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 In the specification, the temperature conditions of the primary exposure and the secondary exposure are changed, and the time required for the composition ratio to change in the thickness direction is separately provided in a dark place, 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 technique of continuously changing the pitch length as disclosed in Japanese Patent Application Laid-Open No. 2002-2866935.

Three 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 of Example 1 of Japanese Patent Application Laid-Open No. 2002-2866935, although the selective reflection wavelength is broadened, the slope of the transmittance curve on the short wavelength end side and on 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 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 emission 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, the wavelength band of about 400 to 700 nm is covered. These wavelength bands cover 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

L = npco S '{sin— ¹ s ι n θ / n)}

n = average refractive index of liquid crystal

ρ-cholesteric pitch length

入射 Incident angle

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 for 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 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 substrate, and a step of polymerizing and curing the liquid crystal mixture by irradiating the liquid crystal mixture with ultraviolet light. A method for producing a broadband cholesteric liquid crystal film having a bandwidth of 200 nm or more,

The ultraviolet polymerization step,

In the 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, when the liquid crystal layer is in contact with a gas containing oxygen, the pressure is higher than in step (1). Until the temperature reaches 60 ° C or more, the heating rate is 2 ° C / second or more, and the UV irradiation intensity is lower than that in step (1), and the intensity is 10 seconds or more from the alignment substrate side. UV irradiation process (2),

Next, there is provided a method for producing a broadband cholesteric liquid crystal film, which comprises a step of irradiating ultraviolet rays in the absence of oxygen (3).

2. The method for producing a broadband cholesteric liquid crystal film according to the above item 1, wherein a pitch length of the cholesteric liquid crystal film is changed so as to be continuously narrowed 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. Manufacturing method of cholesteric liquid crystal film.

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

) Has a molar extinction coefficient of

0.l ^ S O O d mSm o l -ic m S e S nm

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

4. The method for producing a broadband cholesteric liquid crystal film according to any one of the above items 1 to 3, wherein the thickness is 100 to 100 000 dm ³ mol ^ cm ^ SlA nm.

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

(Wherein, R _t to R ₁₂ may be the same or different and represent 1 F, 1 H, 1 CH ₃ , -C ₂ H ₅ or 1 CH ₃ , and R ₁₃ represents 1 H or _CH ₃ And the general formula (2)

:-(CH ₂ CH ₂ 0) _a- (CH ₂ ) _b- (O) _c- , and X ₂ represents one CN or one F. However, in the general formula (2), a is an integer of 0 to 3, b is 0 to: an integer of L2, c is 0 or 1, and when a = l to 3, b = 0 and c = 0, and when a = 0, b = l to 12 and c = 0 to l. ) 5. The method for producing a broadband cholesteric liquid crystal film according to any one of the above items 1 to 4.

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 selective reflection wavelength bands of polarized light overlap each other.

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

Reflective polarizer (a) Power Polarizing element characterized by being a circularly polarizing plate as described in 6 above

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

9. The retardation layer (b), in which the cholesteric liquid crystal phase having a selective reflection wavelength region other than the visible light region has a fixed planar alignment,

The fixed state of the home-pic pick alignment of the rod-shaped liquid crystal,

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

1 1. The linear polarizing element according to 10 above, obtained by laminating a cholesteric liquid crystal film, which is a circular polarizing plate, on a λΖ4 plate so that the pitch length is continuously narrowed.

12. The linearly polarized light as described in 10 or 11 above, wherein the 14 plate is a retardation plate having an improved viewing angle by biaxially stretching and performing phase difference correction of obliquely incident light. element 1 3. The linearly polarizing element according to 10 or 11, wherein the e / 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. If the / 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

The linear polarizing element according to any one of the above 10 to 13, which satisfies the following conditions: 5 to 2.5.

1 5. A linear polarizing element, characterized in that a Z 2 plate is further laminated on the quarter plate of the linear polarizing element according to any one of the above 10 to 14.

16. The absorption polarizer whose transmission axis and transmission axis of the linear polarizing element according to any of the above 10 to 15 are aligned on the λ / 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.

1 8. 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.

1 9. A viewing angle widening liquid crystal display device as described in 18 above, 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, the irradiance and irradiation temperature of ultraviolet irradiation from the alignment substrate side are as follows. Different conditions are used in the first exposure step (1) and the second exposure step (2). This makes it possible to realize more precise control of the reaction behavior of the polymerizable liquid crystal mixture and to obtain a broadband cholesteric liquid crystal film with a higher production rate than before. That is, the ultraviolet irradiation condition is that the first irradiation intensity is greater than the second irradiation intensity, and that the first irradiation time is shorter than the second irradiation time. In the second UV irradiation, the temperature rises rapidly to a predetermined set temperature (achieved temperature). 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 the radical distribution has a large gradient in the thickness direction 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 cholesteric pitch is short on the surface where the polymerizable chiral agent (B) is rich, and long on the opposite surface. As a result, a cholesteric liquid crystal film having a broadband reflection wavelength as a whole can be obtained.

The broadband cholesteric liquid crystal film obtained in this manner functions as a broadband circularly polarizing reflector, and has the same optical characteristics as those of Japanese Patent Application Laid-Open Nos. In addition to having the same properties, the thickness can be reduced by reducing the number of layers compared to the conventional manufacturing method, and the manufacturing can be performed easily and in a short time. Conversion 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.

The fact that a circularly polarized light reflector has a broadband reflection band even in a long wavelength region is an important issue for obtaining good viewing angle characteristics 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 production method of the present invention, a broadband cholesteric liquid crystal film having a reflection band even in such a long wavelength region can be obtained. Such a broadband collection The Steric liquid crystal film is used not only as a reflective polarizer for obtaining high brightness, but also in the case of a polarizing element made in combination with other optical elements such as a retardation plate, except for the front. Stable optical characteristics are required for obliquely incident light

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a conceptual diagram of a viewing angle widening liquid crystal display device using the polarizing plate integrated polarizing element of Examples 1, 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 film produced in Example 1.

FIG. 5 is a reflection spectrum of the cholesteric liquid crystal film produced in Example 2.

FIG. 6 shows the reflection spectrum of the cholesteric liquid crystal film produced in Example 3.

FIG. 7 is a reflection spectrum of the cholesteric liquid crystal film produced in Example 4.

FIG. 8 is a reflection spectrum of the cholesteric liquid crystal film produced in Comparative Example 1.

FIG. 9 is a reflection spectrum of the cholesteric liquid crystal film produced in Comparative Example 2.

FIG. 10 is a reflection spectrum of the cholesteric liquid crystal film produced in Comparative Example 3. BEST MODE FOR CARRYING OUT THE INVENTION

The broadband cholesteric liquid crystal film of the present invention comprises a polymerizable mesogen compound (A) And a liquid crystal mixture containing 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. . Further, by using a compound having two or more polymerizable functional groups, a crosslinked structure can be introduced to improve the durability. Examples of the cyclic unit to be a mesogen group include biphenyl-based, phenylbenzoate-based, phenylcyclohexane-based, azoxybenzene-based, azomethine-based, azobenzene-based, phenylpyrimidine-based, and diphenyl-based. Examples include acetylene, diphenylbenzoate, bicyclohexane, cyclohexylbenzene, and terphenyl. In addition, the terminal of these cyclic units may have a substituent such as a cyano group, an alkyl group, an alkoxy group, and 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 0 to 10; preferably 1 to 3.

The molar extinction coefficient of the polymerizable mesogen compound (A) is 0.1 to 500 dm ³ mo 1

An SSA nm, force one 1 0 0 0~ 1 0 0 0 0 0 dm 3 mo 1 one ^{^{1 c m- 1 @ 3 1 4}} nm Dearuko and are preferred. Those having the molar extinction coefficient have an ultraviolet absorbing ability. The molar extinction coefficient is 0.1 to 50 dm ³ mol — ¹ c ni- ¹ @ 365 nin, and 50 to: ¹⁰⁰ 000 dm ³ mo 1 — ic m- ^ SS nm and a, 1 0 0 0 0~ 5 0 0 0 0 dm 3 mo 1 -.. 1 cm "1 ® 3 1 4 nm Gayo Ri is suitable molar absorption ^{coefficient, 0 1 ~ 1 0 dm 3} mo 1 ^_1 cm ^_1 @ ³⁶⁵ nm, 1 0 0 0 ~ 4 0 0 dm ³ mo 1 — ¹ cm— ^L @ 3 3 4 nm, 3 0 0 0 0 ~ 4 0 0 0 dm ³ mo 1 ^_1 cm " ¹ ® 3 14 nm is more preferable. Molar extinction coefficient is 0. I dm ³ mo 1 ^_1 cm " ¹ ® ³⁶⁵ nm, 10 dm ³ mol ^ cm ^ OS 34 nm 100 dm ³ mol ^_1 cm ^-1 @ 3 1 If it is smaller than 4 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 "^ ¹ cm" ¹ ® ³⁶⁵ nm, ³⁰⁰ ⁰⁰⁰ dm ³ mo 1 ^_1 cm ^_1 @ ³³⁴ nm, 100 ⁰⁰⁰ dm ³ mo 1 ^_1 cm " ¹ ® 3 14 nm, the polymerization may not completely proceed and the curing may not be completed. The molar extinction coefficient was obtained by measuring the spectrophotometric spectrum of each material. It is a value measured from the absorbance at 65 nm, 334 nm, and 314 nm.

The polymerizable mesogen compound (A) having one polymerizable functional group has, for example, the following general formula:

(Wherein 1 ^ to 1 ₁₂ may be the same or different and represent 1 F, 1 H, 1 CH ₃ , 1 C ₂ H ₅ or 1 CH ₃ , and R ₁₃ represents 1 H or 1 CH ₃ are shown, the general formula (2): -. (CH 2 CH 2 0) a - (CH 2) b - (O) c -, indicates, X ₂ represents an CN or a F, however, the general formula A in (2) is an integer of 0 to 3, b is an integer of 0 to: 12 is an integer of 2, c is 0 or 1, and when a = l to 3, b = 0 and c = 0; When a = 0, b = l to 12 and c = 0 to l.). Table 1 shows specific examples of the polymerizable mesogen compound (A) represented by the general formula (1).

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 amount of the polymerizable chiral agent (B) to be mixed with 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 region.

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 Ciba Specialty Chemicals Inc. 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 may 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 in preparing the solution are usually forms of chloroform, dichloromethane, dichloromethane, tetrachlorethane, trichloroethylene, tetrachloroethylene, and chloroform. Halogenated hydrocarbons such as benzene, phenols such as phenol and parachlorophenol, benzene, tonolen, xylene, methoxybenzene, aromatic hydrocarbons such as 1,2-dimethoxybenzene, etc. Ton, methylethyl ketone, ethyl acetate, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol ^, ethylene glycol, monomethyl methinooleate, diethylene glycol dimethyl ether, ethylcellosolve, butylcellosolve, 2 — Pyrrolidone, N-methyl I 2-pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitril, butyronitrile, carbon disulfide, cyclopentanoic And cyclohexane can be used. The solvent to be used is not particularly limited, but is preferably methylethyl ketone, cyclohexanone, cyclopentanone, or the like. The concentration of the solution cannot be specified unconditionally because it depends on the solubility of the thermotropic liquid crystal compound and the final thickness of the target cholesteric liquid crystal film, but it is usually about 3 to 50% by weight. Is preferred.

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 with a photocrosslinking 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, it can be oriented 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 substrate, 2 0 0 ₁ 1 1 ₁ 1 or more 4 0 0 11 m or less, good Ri desirably 3 0 0 nm or more 4 0 0 nm transmittance of 1 0% or more in the ultraviolet region, preferably Is required to be 20% or more. Specifically, it is preferable that the plastic film has a transmittance of 10% or more to ultraviolet light having a wavelength of 365 nm, more preferably 20% or more. The transmittance is a value measured by an 11 1 OOS spectrophotometer.

Examples of the substrate include polyethylene terephthalate, triacetyl cellulose, norbornene resin, polyvinyl alcohol, polyimide, polyacrylate, polycarbonate, polysulfone, and polyethersulfone. A plastic film or glass plate is used. Examples include Triacetyl cellulose manufactured by Fudo Photo Film Company, ARTON manufactured by JSR, and ZONEX manufactured by Zeon Corporation.

Further, a polymer film described in Japanese Patent Application Laid-Open Publication No. 2001-334535 (WO01Z37007), for example, (A) a side chain substituted and / or unsubstituted And (B) a thermoplastic resin having a substituted or unsubstituted phenyl in the side chain and a thermoplastic resin having a ditolyl group. Specific examples And a resin composition film containing an alternating copolymer of isobutylene 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 incorporating a light stabilizer or the like into the aforementioned 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 (the coating thickness after drying the solvent in the case of a solution) is preferably about 1 to 20 im. If the coating thickness is thinner than 1 μm, 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 / im or more, more preferably 3 µm or more. On the other hand, when the coating thickness is larger than 20 / zm, no remarkable improvement is seen in both the reflection bandwidth and the degree of polarization, and the cost is simply increased, which is not preferable. The coating thickness is preferably 15 / im or less, and more preferably 10 / m 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 per coating method, or the like can be employed. 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 base material to be used-although it cannot be generally specified, it is usually selected in the range of 10 seconds to 2 hours, preferably in the range of 20 seconds to 30 minutes. Is done. The step of applying the liquid crystal mixture to the alignment base material and irradiating the liquid crystal mixture with ultraviolet rays includes the above three steps (1) to (3).

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 (oxygen In the thickness direction (at the interface side), there is a difference in the reaction rate due to oxygen inhibition and the difference in the amount of radicals generated due to ultraviolet absorption of the liquid crystal composition, forming a layer in which the amount of polymer z oligomers is continuously distributed in the thickness direction Let it.

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, 2 5~ 2 0 0 mW / cm 2 is laid favored, 4 0~; 1 5 0 mWZ cm 2 Gayo Ri preferred arbitrariness. If the UV irradiation intensity is lower than ²⁰ mWZ cm ² , the 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. Further, 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 is not broadened.

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 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 one that can utilize oxygen polymerization inhibition, 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. Note that the required amount of the photopolymerization initiator (C) tends to increase under an air atmosphere. The desired purpose can be achieved with an addition amount of about 1 to 5 parts by weight based on a total of 100 parts by weight 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 speed becomes too high. Care must therefore be taken to ensure that uncontrolled diffusion rates do not even out the polymer / oligomer concentration gradient. It is necessary not only to form a large change in the cholesteric pitch length in the thickness direction of the liquid crystal layer 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 / oligomer is formed in a weight average molecular weight of about 1,000 to 5,000. The weight average molecular weight of the polymer / oligomer is preferably between 1000 and 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 HLC—8 120 GPC, power ram: Tosoh Supper AWM-H + Supper AWM-H + Supper AW 300 0 (each 6 mni (i) X 15) cm, total 45 cm), Column temperature: 40 ° C, Eluent: 10 mM—LiBr ZNMP, Flow rate: 0. A ml Zmin, 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 Can obtain only the same level of reflection wavelength band as in JP-A-2002-2866935, etc.

Therefore, in the step (2), in a state where the liquid crystal layer is in contact with the gas containing oxygen, the heating rate is higher than that of the step (1) and the heating rate is increased until the temperature reaches 60 ° C or more. UV irradiation is performed from the alignment substrate side for 10 seconds or more at a UV irradiation intensity lower than that in step (1) for at least CZ seconds. By the second ultraviolet irradiation in the step (2), the effective depth of polymerization inhibition by oxygen penetrating from the oxygen interface side can be made deeper than in the step (1). Since the gomers are formed with a concentration gradient in the thickness direction, the concentration gradient of the unpolymerized monomer component formed conversely can be made uniform. At the same time, by allowing the reaction to 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 of the liquid crystal composition layer and the decrease in the diffusion rate are significantly different from those during the first ultraviolet irradiation in step (1), the amount of radicals generated per unit time should be reduced, and the progress rate of polymerization should be reduced. Further broadening of the bandwidth is possible.

In the specification of Japanese Patent No. 3,272,668, the temperature conditions for the first ultraviolet irradiation and the second ultraviolet irradiation are changed, and the time required for the composition ratio to change in the thickness direction is separately determined in a place. It is set up. However, in order to cover substantially the entire visible light region using this method, it is necessary to wait about 120 minutes for mass transfer due to this temperature change. On the other hand, the manufacturing method of the present invention does not require a dark place. Furthermore, the process can be completed in a short time of less than one minute, so that a practical and efficient production speed can be produced.

In the step (2), the second ultraviolet irradiation is performed while increasing the temperature to a predetermined temperature. In the step (2), the starting temperature at the time of the irradiation of the second ultraviolet ray is the same as that in the step (1). That is, it is at least 20 ° C. If the onset 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. Further, the attained temperature is set higher than that of the step (1) and at a temperature of 60 ° C. or more. If the reached temperature is lower than 60 ° C, the diffusion of the polymerizable mesogen compound (a) does not sufficiently occur, and the band is not sufficiently widened. The upper limit of the attained temperature is not particularly limited, but is preferably 140 ° C. or lower. Furthermore, the ultimate temperature is 80 ° C ~ 120 ° C is preferred. If the ultimate temperature is higher than 140 ° C, the diffusion rate is too fast to control.

At the time of the second ultraviolet irradiation, the temperature is rapidly increased from the end of the first ultraviolet irradiation to the ultimate temperature at a heating rate of 2 ° C / sec or more. If the heating rate is lower than 2 ° CZ seconds, the diffusion of the polymerizable mesogen compound (a) will not occur sufficiently, and the band will not be sufficiently widened. The heating rate is preferably between 2 and 20 ° C / sec. After reaching the predetermined attained temperature, the second ultraviolet irradiation can be usually performed while maintaining the attained temperature. In addition, if the temperature is within a range of 140 ° C. or less, the temperature can be gradually increased after reaching a predetermined temperature. 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 hardly changes. It is possible to broaden the long wavelength band on the substrate side. The second ultraviolet irradiation intensity is preferably 1 to 50 mW / cm ² in a range lower than the first ultraviolet irradiation intensity.

The second ultraviolet irradiation time depends on the illuminance, but is generally preferably 10 seconds or more. The second UV irradiation time is the sum of the irradiation time until the temperature is rapidly increased to the reached temperature and the irradiation time after the reached the reached temperature. The ultraviolet irradiation time is preferably 120 seconds or less, more preferably 60 seconds or less from the point of working time. As described above, the bandwidth can be broadened by the step (2) as described in the following embodiment, and the viewing angle at which the obliquely incident light is colored and decolored by the blue shift becomes extremely large. Coloring can be significantly reduced.

Next, in step (3), ultraviolet irradiation is performed in the absence of oxygen. By the third ultraviolet ray irradiation, the cholesteric reflection band extended in the steps (1) and (2) 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 preferable. Further, by bonding a transparent base material to the cholesteric liquid crystal layer, it is possible to eliminate the presence of oxygen.

In step (3), the ultraviolet irradiation may be performed from any of the alignment substrate side and 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 and 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 utilize oxygen inhibition positively in the first ultraviolet irradiation in the step (1) and the second ultraviolet irradiation in the step (2). For this reason, it is possible to form a large gradient in the reaction direction in the thickness direction. There is a possibility that problems such as lack of sex may occur. For this reason, in step (3), third ultraviolet irradiation is performed in an oxygen-free atmosphere to complete the polymerization of the remaining monomers and enhance the 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. This is because irradiation from the liquid crystal layer side is desirable, but the reaction on the surface proceeds sufficiently even from the substrate side in a nitrogen atmosphere.

The cholesteric liquid crystal film thus obtained can be used without peeling from the substrate, 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. Four circular plates can be stacked on the circularly polarizing plate to form a linearly polarizing element. The cholesteric liquid crystal film, which is a circularly polarizing plate, is preferably laminated on four plates so that the pitch length is continuously narrowed.

The λ4 plate is not particularly limited, but may be formed by stretching such as polycarbonate, polyethylene terephthalate, polystyrene, polysulfone, polybutyl alcohol, polymethyl methacrylate, or the like. Generating transparent resin fill Mupol A norpolene-based resin film such as ARTON film manufactured by JSR is preferably 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, a λ / 4 plate obtained by fixing a four-layer obtained by, for example, aligning a liquid crystal other than the expression of a retardation by stretching a resin may be used. In this case, the thickness of the e / 4 plate can be significantly reduced. The thickness of the λ / 4 wavelength plate is usually preferably from 0.5 to 200 m, and particularly preferably from 1 to 100 zm.

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 four-wavelength plate for light-color 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. It is used with the transmission axis direction aligned.

The polarizer is not particularly limited, and various types can be used. Polarizers include, for example, hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene / vinyl acetate copolymer-based partially saponified films; Examples thereof include a uniaxially stretched film obtained by adsorbing a dichroic substance such as a dichroic dye, a dehydrated product of polyvinyl alcohol, and a dehydrochlorinated product of polychlorinated 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 / Xm.

A uniaxially stretched polarizer obtained by dyeing a polybutyl alcohol-based film with iodine is dyed, for example, by immersing the polybutyl alcohol in an aqueous solution of iodine, and stretching the original length 3 to 7 times. It can be manufactured by the following. 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 washed by water In addition to being able to clean surface stains 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. Stretching can be performed 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. Examples of the transparent protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, and cellulose polymers such as diacetinoresenorelose and triacetinoresenorelose. Examples include films made of transparent polymers such as polycarbonate polymers and acrylic polymers such as polymethyl methacrylate. Styrene polymers such as polystyrene, acrylonitrile and styrene copolymers; and polyolefins such as polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, and ethylene propylene copolymers. 1. Films made of transparent polymers such as amide polymers such as vinyl chloride polymers and nylon-aromatic polyamides are also included. In addition, imid-based polymers, sulfone-based polymers, polyether-sulfone-based polymers, polyether-ether-ketone-based polymers, polyphenylene-sulfide-based polymers, vinyl alcohol-based polymers, vinylidene chloride-based polymers, and vinyl 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 may also be used. In particular, those having low optical birefringence are preferably used. From the viewpoint of a protective film for a polarizing plate, triacetyl cellulose, polycarbonate, an acrylic polymer, a cycloolefin resin, a polyolefin having a norbornene structure, and the like are preferable.

Further, a polymer film described in Japanese Patent Application Laid-Open No. 2001-334529 (WO 01/37007), for example, (A) a side chain substituted and / or unsubstituted imide Resin compositions containing a thermoplastic resin having a group, and (B) a thermoplastic resin having a substituted or unsubstituted phenyl and a ditolyl group in a side chain. Specific examples For example, a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleide and an acrylonitrile / styrene copolymer may be used. As the film, a film made 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 μm in view of strength, workability and other workability, and thinness. In particular, it is preferably from 20 to 300 / zm, more preferably from 30 to 200 μηι.

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 plane of the film plane, nz is the refractive index in the film thickness direction, and d is the film refractive index. The retardation value in the film thickness direction represented by) is-9 0 η π! A protective film having a thickness of up to +75 nm is preferably used. By using such a retardation value (Rth) in the thickness direction of 190 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film is almost eliminated. be able to. The thickness direction retardation value (R th) is more preferably 180 η π! To +60 nm, particularly preferably from 70 nm to +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 antireflection treatment, a treatment for preventing sticking, or a treatment for diffusion or antiglare.

The hard coat 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 an appropriate 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 for the purpose of preventing adhesion to the adjacent layer. W 200 The anti-glare treatment is performed for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering the visibility of light transmitted through the polarizing plate, and is, for example, a sand-plasting method or an embossing method. It can be formed by imparting a fine uneven structure to the surface of the transparent protective film by an appropriate method such as a surface roughening method or a method of blending transparent fine particles. Examples of the fine particles to be included in the formation of the surface fine unevenness include silica, alumina, titania, zircoair, tin oxide, indium oxide, cadmium oxide having an average particle size of 0.5 to 50 μηι. Transparent fine particles such as inorganic fine particles which may be made of antimony oxide or the like and organic fine particles made of a crosslinked or uncrosslinked polymer or the like are used. When forming the fine surface uneven structure, the amount of the fine particles used is generally about 2 to 50 parts by weight with respect to 100 parts by weight of the transparent resin forming the fine surface uneven structure, and 5 to 25 parts by weight. Parts by weight are preferred. The anti-glare layer may also serve as a diffusion layer (such as a viewing angle expansion function) for diffusing light transmitted through the polarizing plate to increase the viewing angle.

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-described 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.For example, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer may be used as a base 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, natural or synthetic resins, in particular, tackifying resin, glass, It may contain fillers such as fibers, glass beads, metal powders, and other inorganic powders, and additives such as pigments, colorants, and antioxidants that are added to the 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 a base polymer or a composition thereof dissolved or dispersed in a solvent consisting of a single substance 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 according to the purpose of use, adhesive strength, and the like, and is generally 1 to 500, preferably 5 to 200 / im, and particularly preferably 10 to 100. μπι is preferred.

A separator is temporarily attached to the exposed surface of the adhesive layer for the purpose of preventing contamination, etc., until it is put to practical use. This can prevent the adhesive layer from coming into contact with the adhesive layer in a normal handling state. Except for the above thickness conditions, suitable thin sheets such as plastic films, rubber sheets, paper, cloth, non-woven fabrics, nets, foamed sheets, metal foils, and laminates thereof are used as the separator. If necessary, use an appropriate material similar to the conventional one, such as a material treated with a suitable release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

Each layer such as an adhesive layer is treated with an ultraviolet absorber such as a salicylate compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. It may be a method having a function of absorbing ultraviolet rays by a method such as a method.

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 and an optical element and, if necessary, an illumination system and incorporating a drive circuit. There is no particular limitation except that an element is used, and the conventional method is followed. As for the liquid crystal cell, any type such as セ -type, STN-type, and π-type can be used. sell.

Appropriate liquid crystal display devices 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, and 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, for example, appropriate components such as a diffusion plate, an antiglare layer, an antireflection film, a protection plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight are appropriately positioned. One or two or more layers can be arranged.

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 retardation (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 arranged. Used in polarizing element systems. In the cholesteric liquid crystal film, either the maximum pitch or the minimum pitch of the spiral twisted molecular structure may be the side of the retardation layer (b), but the viewing angle (the viewing angle is good and the coloring is small) From the point of view, if the reflection polarizer (a) is expressed as (maximum pitch / minimum pitch), it is preferable to arrange the polarizers as maximum pitch / minimum pitch Z phase difference layer (b) / maximum pitch / minimum pitch. Further, in the case of combining / 4 plates, it is preferable to arrange the reflective polarizer (a) such that the minimum pitch side of the reflective polarizer (a) is the four plate side.

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

The retardation layer (b) has a phase difference of almost zero in the front direction, and has a phase difference of 8 or more with respect to incident light at an angle of 30 ° from the normal direction. The front phase difference is desirably ぇ 10 or less since the purpose is to maintain the vertically incident 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 at the time of measurement at is about 1/2. 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. In this case, the phase difference may be smaller than E2. Since the phase difference of the C-plate increases monotonically as the incident light tilts, the effective total reflection occurs when the light is tilted at an angle of 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, the cholesteric liquid crystal having a selective reflection wavelength other than in the visible light region (380 ηπ! ~ 780 nm) is fixed in the planar state, or the rod-shaped liquid crystal is fixed in the homeotropic aperture. And those utilizing columnar orientation and nematic orientation of discotic liquid crystals, those in which negative uniaxial crystals are oriented in-plane, and 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 of a cholesteric liquid crystal. It is desirable that the wavelength is not colored in the visible light region. 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 350 nm or less due to the effects of optical rotation, etc., causing 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 are easy to control and easy to form a mono domain. From the viewpoint of the above, it is desirable that the liquid crystal is a thermo-pic pickable liquid crystal. The homeotropic alignment can be obtained, for example, by coating the above-mentioned birefringent material on a film on which a vertical alignment film (such as a long-chain alkylsilane) has been formed, and developing and fixing a liquid crystal state. As a C-plate using discotic liquid crystal, the liquid crystal material has a negative uniaxial property like a phthalocyanine or triphenylene compound having a molecular spread in the plane as a liquid crystal material. It is a discotic liquid crystal material that is fixed by developing a nematic phase or 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 utilizing the biaxial orientation of polymer films include a method of biaxially stretching a polymer film having a positive refractive index anisotropy, a method of pressing a thermoplastic resin, and a crystal with 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 this case, the adhesive or pressure-sensitive adhesive is transparent, has no absorption in the visible light region, and the refractive index is preferably as close as possible to the refractive index of each layer from the viewpoint of suppressing surface reflection. From this viewpoint, for example, an acrylic pressure-sensitive adhesive is preferably used. Each layer separately forms a monodomain in the form of an alignment film, and is sequentially laminated on a translucent substrate by a method such as transfer, or without an adhesive layer, etc. It is also possible to form each layer appropriately and to sequentially 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 a leveling property. Although the polarizing element (cholesteric liquid crystal laminate) of the present invention has a function of reflecting and transmitting circularly polarized light, it can be used as a linear polarizing element for converting transmitted light into linearly polarized light by combining four plates. it can. Examples of the plate include those similar to the above.

Although the λ / plate functions well only for a specific wavelength in a single layer made of a single material, there is a problem that the λ / plate has a reduced function as a λ4 plate due to wavelength dispersion characteristics for other wavelengths. Therefore, if lamination is performed with the λ / 2 plate and the axis angle specified, there is a practical difference over the entire visible light range. It can be used as a broadband / 4 board that functions within a range that does not hurt. In this case, the L4 plate and the λ / 2 plate may be the same material, or may be a combination of different materials obtained by the same method as the above-described E / 4 plate.

For example, a / 4 plate (140 nm) is laminated on a broadband circularly polarizing plate, and a 1/2 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 ぇ 4 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 pack light direction. Here, if the rear-side reflector has high specular reflectivity, the reflection angle is preserved, and light cannot be emitted in the front direction, resulting in lost light. 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 enhanced 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 pack light, Newton rings may occur in the gap between the film surface and the pack light. By arranging a diffusion plate having surface irregularities on the side surface, the generation of Newton rings can be suppressed. In addition, the surface itself of the collimating film in the present invention has an uneven structure and a light diffusion structure. A layer that also serves as a layer may be formed.

(Placement of viewing angle expansion film)

The viewing angle expansion in the liquid crystal display device of the present invention is achieved by diffusing light beams having good display characteristics near the front obtained from the liquid crystal display device, which are combined with the parallel-packed pack light, so as to be uniform within the entire viewing angle. It is obtained by obtaining good display characteristics. For 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 the 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 JP-A-2000-347706 and JP-A-2007-40707 is preferably used.

When the viewing angle widening film is located outside the polarizing plate, the parallelized light passes through the liquid crystal layer and one polarizing plate.Therefore, in the case of a TN liquid crystal cell, a viewing angle compensating phase plate must be used. Is also good. 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. On the other hand, when a viewing angle widening film is inserted between the polarizing plate and the liquid crystal layer, the light is diffused at the stage of passing through the polarizing plate. In the case of a TN liquid crystal, it is necessary to compensate for the viewing angle characteristics of the polarizer itself. 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 the STN liquid crystal, it is necessary to insert a retardation plate for compensating 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 viewing angle widening film that has a regular structure inside, such as a microlens array film or hologram film that has existed in the past, the liquid crystal display device's black matrix ゃ parallel light from the conventional backlight It interfered with the microstructure of the system such as micro lens array / prism array / looper / micro mirror array etc. and easily caused moire. However, the collimated film in the present invention is in-plane. Since the regular structure is not visible at all, and there is no regular modulation in the emitted light, there is no need to consider the compatibility with the viewing angle expansion film and the arrangement order. Therefore, the viewing angle widening film has no particular limitation 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 main Sogen compound (polymerizable nematic liquid crystal monomer, compounds 2 0 of Table 1, the molar extinction coefficient, ld mSm ol ^ cm ^ S e S nm 2 1 0 0 dm 3 mo 1 _1 cm _1 @ 3 3 4 nm, 3 6 0 0 0 dm 3 mol. 1 c m. 1 @ 3 1 4 nm. purity> 99% of was used.) 9 4.8 parts by weight Contact Yopi polymerizable chiral agent (BASF LC756) 5.2 parts by weight and a solvent (cyclopentanone) adjusted and blended so that the selective reflection center wavelength becomes 550 nm, and the photopolymerization initiator ( A coating liquid (solid content: 30% by weight) was prepared by adding 3% by weight of Irgacure 907) manufactured by Chipa Specialty Chemicals. The coating liquid is applied on a stretched polyethylene terephthalate film (oriented substrate) using a wire par so that the thickness after drying is 7 μηι, and the solvent is applied at 100 ° C. Dried for minutes. The obtained film was irradiated with first ultraviolet rays at 40 mW / cm ² for 1.2 seconds in an air atmosphere at 40 from the alignment substrate side. Continue at 90 ° C with a heating rate of 3 ° CZ seconds The second UV irradiation was carried out in an air atmosphere at 4 mWZ cm ² for 60 seconds while the temperature was raised up to 90 ° C. (after reaching 90 ° C.). Next, in a nitrogen atmosphere at 50 ° C, third ultraviolet irradiation was performed from the alignment substrate side at 60 mWZ cm ² for 10 seconds, and the selected wavelength was 425 to 90 nm broadband cholesteric. 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, 93 parts by weight of a photopolymerizable nematic liquid crystal monomer (manufactured by BASF, LC224), and 30 parts by weight of 7 parts by weight of a polymerizable chiral agent (LC755, manufactured by BASF). / ₀ as a by Uni solvent to a concentration Kisano down the added cyclohexane and was compounded adjusted power sale by selective reflection center wavelength is 3 5 0 nm, and a photopolymerization initiator for the solid content of the above A coating solution containing 5% by weight of irgacure 907 was prepared, and the above solution was applied to a stretched polyethylene terephthalate substrate using a wire bar so that the thickness after drying was 4 / zm. Then, the solvent was dried at 100 ° C. for 2 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. The obtained layer was obtained by fixing the alignment state by performing 50 mWZcm for 5 seconds on the obtained layer. When the phase difference of this negative biaxial retardation plate was measured, it was 2 nm and 30 in the front direction with respect to light having a wavelength of 55 O nm. The phase difference measured at an inclination was 120 nm. The measurement of the phase difference was performed by KOBRA-121 ADH manufactured by Oji Scientific Instruments.

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 I4 plate (front retardation: 140 nm) was adhered 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, and a polarizing plate integrated polarizing element was obtained.

The coating liquid prepared in Example 1 was applied to a stretched polyethylene terephthalate film The substrate was coated with a wire par so as to have a thickness after drying, and the solvent was dried at 100 ° C. for 2 minutes. The obtained film was subjected to first ultraviolet irradiation at 40 mW / cm ² for 1.2 seconds in an air atmosphere at 40 ° C. from the alignment substrate side. Then, while raising the temperature to 90 ° C at a temperature rising rate of 1 ° CZ second (while maintaining the temperature at 90 ° C after reaching the temperature), the second UV irradiation was performed in an air atmosphere at 4 mW. 60 cm / cm ² . Then, at 5 0 ° 6 0 the third ultraviolet radiation from the alignment substrate side under a nitrogen atmosphere at C m W / cm ^2, 1 performs 0 seconds, broadband co Leste selected wavelength is 4 3 0 to 9 0 0 nm A liquid crystal film was obtained. Figure 5 shows the reflection spectrum of the broadband cholesteric liquid crystal film.

Using a translucent adhesive, a negative biaxial retardation plate similar to that of Example 1 was transferred onto the obtained broadband cholesteric liquid crystal film (circularly polarizing reflector). 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 λ / 4 plate (front retardation: 140 nm) obtained by uniaxially stretching a polycarbonate film was adhered to the obtained polarizing element to obtain a linear polarizing element. Further, a polycarbonate film was uniaxially stretched on an I-4 plate; and an I2 plate (front retardation: 270 nm) was adhered to obtain a linearly polarizing element. A polarizing plate (manufactured by TOKYO ELECTRIC CO., LTD., TEG1465DU) was bonded to the linear polarizing element so that the direction of the transmission axis was aligned to obtain a polarizing element integrated with the polarizing plate. The lamination was performed as shown in FIG. 3 in which the angle between the stretching axis (slow axis) of the four or two plates and the stretching axis (absorption axis) of the polarizing plate was set. In FIG. 3, P L denotes an absorption type polarizing plate, C 1 denotes a λ / 4 plate (front retardation: 140 nm), and C 2 denotes a λΖ2 plate (front retardation: 2700 nm). The arrow of PL indicates the stretching axis (long side direction), where 0 is 17.5 ° and 02 is 80 °.

Example 3

Photopolymerizable mesogen compound (Polymerizable nematic liquid crystal monomer, compound 20 in Table 1 above, monolith extinction coefficient is ld mSol -icm— ¹ @ 365 nm, 2100 dm ³ mo 1 ^_1 cm ^_1 @ 3 3 4 nm, 3 6 0 0 0 dm 3 mol- one ^{1 @ 3 1 4 nm.)} 9 4. 8 parts by weight of the polymerizable chiral agent (BASF Corp. LC 7 5 6) 5. 2 parts by weight Contact And solvent (cyclopentanone) are adjusted so that the central reflection wavelength is 550 nm. The formulation solution, the solid content with respect to a photopolymerization initiator (Ciba Specialty Chemicals Luz Co., Irugakyua 3 6 9) 0 .. 3 wt% added with the coating solution (solid content 3 0 wt ⁰ / ₀ ) was prepared. The coating liquid is applied on a stretched polyethylene terephthalate film (alignment substrate) using a wire par so that the thickness after drying is 7 μm, and the solvent is heated at 100 ° C. Dry for 2 minutes. The obtained film was subjected to first ultraviolet irradiation at 40 mW / cm ² for 1.2 seconds in an air atmosphere at 40 ° C. from the alignment substrate side. Then, while raising the temperature to 90 ° C at a heating rate of 3 ° C / sec (while maintaining the temperature at 90 ° C after reaching the temperature), the second ultraviolet irradiation was performed in an air atmosphere at 4, mWZ cm ² For 30 seconds. Then, 5 from 0 ° oriented substrate side under a nitrogen atmosphere at C the third ultraviolet irradiation at 6 0 mW / cm ^2, 1 performs 0 seconds, selected wavelengths 4 2 0~ 9 2 5 nm broadband co Leste Li A liquid crystal film was obtained. Figure 6 shows the reflection spectrum of a broadband cholesteric liquid crystal film.

Using a translucent adhesive, a negative biaxial retardation plate similar to that of Example 1 was transferred onto the obtained broadband cholesteric liquid crystal film (circularly polarizing reflector). 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 λ-no. 4 plate (front retardation: 125 nm, Nz coefficient: 11.0) obtained by biaxially stretching the polycarbonate film was adhered to the obtained polarizing element to obtain a linear polarizing element. Was. A polarizing plate (manufactured by Nitto Denko Corporation, TEG1465DU) was bonded to the linear polarizing element so that the transmission axis directions coincided with each other to obtain a polarizing plate-integrated polarizing element.

Example 4

Photopolymerizable mesogen compound (Polymerizable nematic liquid crystal monomer, Compound 3 in Table 1 above, molar extinction coefficient is 0.1 ld mSmol -icm— ¹ @ 365 nm, 220 nm dm ³ mol ¹ cm ¹ @ 3 334 nm, ³⁷⁰⁰ dm ³ mol ^_1 cm ^_1 @ 314 nm.) 94.8 parts by weight of polymerizable chiral agent (LC756 manufactured by BASF) 5. 2 parts by weight and a solvent (cyclopentanone) were adjusted and blended so that the central wavelength of selective reflection was 550 nm. The solid content of the solution was adjusted with a photopolymerization initiator (Chipa Specialty Chemicals Co., Ltd. A coating liquid (solid content 30 wt. ⁰ /.) Was prepared by adding 3 wt. Apply the coating solution to a stretched polyethylene terephthalate film Using a wire bar, a coating was applied on a substrate (alignment substrate) so that the thickness after drying was 7 μΐη, and the solvent was dried at 100 ° C for 2 minutes. The obtained film was subjected to first ultraviolet irradiation at 50 mW / cm ² for 2.2 seconds in an air atmosphere at 40 ° C. from the alignment substrate side. Then, while raising the temperature to 90 ° C at a heating rate of 3 ° CZ seconds (while maintaining the temperature at 90 ° C after reaching the temperature), the second ultraviolet irradiation was performed in an air atmosphere at 4 mWZ cm ² , Performed for 60 seconds. Then, at 5 0 ° the third ultraviolet radiation from the alignment substrate side under a nitrogen atmosphere at ^{C 6 0 mW / cm 2,} 1 performs 0 seconds, broadband Collector Steri selected wavelength is 4 5 5~ 9 3 O nm A liquid crystal film was obtained. FIG. 7 shows the reflection spectrum of the broadband cholesteric liquid crystal film.

Comparative Example 1

The coating solution prepared in Example 1 was applied on a stretched polyethylene terephthalate film (directing substrate) using a wire bar so as to have a thickness after drying, and the solvent was added to the solution. Dried at ° C for 2 minutes. The obtained film was irradiated with first ultraviolet rays at 50 mW / cm ² for 10 seconds in an air atmosphere at 60 ° C. from the alignment substrate side. Then, at 5 0 ° UV irradiating 6 0 mW / cm ² from the alignment substrate side under a nitrogen atmosphere at C, 1 performs 0 seconds, broadband co Leste click selection wavelengths 4 3 5~ 8 3 5 nm A liquid crystal film was obtained. Figure 8 shows the reflection spectrum of a broadband cholesteric liquid crystal film. Using a translucent adhesive, a negative biaxial retardation plate similar to that of Example 1 was transferred onto the obtained broadband cholesteric liquid crystal film (circularly polarizing reflector). 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 λ4 plate (front retardation: 14 O nm) obtained by uniaxially stretching a polycarbonate film was adhered to the obtained polarizing element 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 plate integrated polarizing element.

Comparative Example 2

The coating solution prepared in Example 1 was applied on a stretched polyethylene terephthalate film (directing substrate) using a wire par so that the thickness after drying was 7 μπι, and the solvent was added to the solution. Dry at 0 ° C for 2 minutes. The obtained film was subjected to first ultraviolet irradiation at 40 mW / cm ² for 1.2 seconds in an air atmosphere at 40 ° C. from the alignment substrate side. Continue Then, the temperature was raised to 90 ° C. at a rate of 3 ° C./second, and after reaching 90 ° C., treatment was performed at 90 ° C. in an air atmosphere for 20 seconds. Next, UV irradiation from the alignment substrate side was performed at 60 mWZ cm ² for 10 seconds in a nitrogen atmosphere at 50 ° C, and the selected wavelength was 415-710 nm, a broadband cholesteric liquid crystal film. Got. Figure 9 shows the reflection spectrum of a broadband cholesteric liquid crystal film.

Using a translucent adhesive, a negative biaxial retardation plate similar to that of Example 1 was transferred onto the obtained broadband cholesteric liquid crystal film (circularly polarizing reflector). 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; an I / 4 plate (front retardation: 140 nm) was adhered 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 coincided with each other to obtain a polarizing plate integrated polarizing element.

Comparative Example 3

The coating solution prepared in Example 1 was applied on a stretched polyethylene terephthalate film (directing substrate) using a wire par so that the thickness after drying was 7 m, and the solvent was removed. Dry at 100 ° C. for 2 ′ minutes. The obtained film was subjected to first ultraviolet irradiation at 40 mW / cm ² for 1.2 seconds in an air atmosphere at 40 ° C. from the alignment substrate side. Then, while increasing the temperature to 90 ° C at a rate of 3 ° C / sec (while maintaining the temperature at 90 ° C after reaching the temperature), ultraviolet irradiation was performed in an air atmosphere at 4 mW / cm ^2. For 60 seconds to obtain a broadband cholesteric liquid crystal film having a selected wavelength of 425 to 90 O nm. Figure 10 shows the reflection spectrum of the broadband cholesteric liquid crystal film.

Using a translucent adhesive, a negative biaxial retardation plate similar to that in Example 1 was transferred onto the obtained broadband cholesteric liquid crystal film (circularly polarizing reflector). 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. The obtained polarizing element was bonded with a quarter plate (front retardation: 14 Onm) obtained by uniaxially stretching a polycarbonate film to obtain a linear polarizing element. A polarizing plate (manufactured by Nitto Denko Corporation, TEG1465DU) was attached to this linear polarizing element so that the transmission axis directions coincided with each other to obtain a polarizing plate integrated polarizing element.

(Liquid crystal display) The polarizing plate integrated with the polarizing plate obtained in each example was used as the lower plate of the TFΤ-LCD, while the upper plate side was made of an acrylic adhesive (thickness 25 / im, refractive index 1.4). 7) A polarizing plate (manufactured by Nitto Denko Corporation) using a light scattering adhesive (haze 80%) in which spherical silica particles (refractive index: 1.44, diameter: 4 / m) are embedded at 20% by weight. , TEG 1465 DU).

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 the light source holder was made of a silver-evaporated polyethylene terephthalate film. A silver-evaporated polyethylene terephthalate film reflection plate was disposed 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 disposed 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 Figures 1 and 2, PL is an absorption polarizer, D is a viewing angle widening film (diffusion adhesive), LC is a liquid crystal cell, C1 is 4 plates, C2 is 2 plates, and A is reflection. Polarizer (a): Circular polarizer, B: retarder (b): C-plate, S: thyroid type light guide plate, R: diffusion reflector. X indicates a polarization element, Y indicates a linear polarization element, and Z indicates a polarization-integrated linear polarization element. In Example 4, only the selective reflection wavelength band and the change in the bandwidth pitch were evaluated.

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 comparative examples.

(Selective reflection wavelength band and bandwidth (Δλ))

The reflection spectrum of the broadband cholesteric liquid crystal film was measured with a spectrophotometer (Otsuka Electronics Co., Ltd., Instantaneous Multi-System MC PD 2000), and the selective reflection wavelength band was approximately half-value width λλ. I asked. The half-value width Δλ was set as the reflection band at half the reflectance of the maximum reflectance. (Pitch change)

Cross-sectional TEM photographs measure the pitch near the UV-irradiated surface of the broadband cholesteric liquid crystal film (1 μππ below the UV-irradiated surface), near the air interface (1 m below the air interface), and the intermediate pitch. did.

(reliability)

When a wideband cholesteric liquid crystal film is put into a reliability test of 90% RH at 80 ° C and 60 ° C for 500 hours each, does powdery substance precipitate 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-printing 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- i) ² + (Y o- 7 i) ₂ ) °. ⁵

Front chromaticity (x., Y.), Oblique. Chromaticity from ± 60 ° ( _Xl , _yi )

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 the gas containing oxygen, the temperature is higher than in the step (1) and the heating rate is 2 ° CZ seconds or more until the temperature reaches 60 ° C or more. A step (2) of irradiating ultraviolet rays from the alignment substrate side for 10 seconds or more with a lower ultraviolet irradiation intensity than the step (1);

Next, there is provided a method for producing a broadband cholesteric liquid crystal film, which comprises a step (3) of irradiating ultraviolet rays in the absence of oxygen.

2. The broadband cholesteric liquid crystal film according to claim 1, wherein the pitch length of the cholesteric liquid crystal film changes so as to continuously narrow from the alignment substrate side. Manufacturing method.

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.:! Is a ^{^{~ 5 0 0 dm 3 mo 1}} cm _1 @ 3 6 5 nm,

10 to 3 0 0 0 0 dm ³ mo I ^-1 cm— ¹ @ 3 3 4 nm, and

1 0 0 0~ 1 0 0 0 0 0 dm 3 mo 1 _1 cm "1 ® 3 1 4 nm Dearuko wideband co according to any one of claims 1 through Section third term, characterized in Resuteri Manufacturing method of backlit liquid crystal film.

(In the formula, 1 ^ to 1 ₁₂ 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 1 ₁₃ is-: << or 1 ( "^ indicates, the general formula (2): -. (CH 2 CH 2 0) a - (CH 2) b - (O) c one, indicates, X ₂ represents an CN or a F, however, In the general 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, b = l to 12 and c = 0 to l.) The compound according to any one of claims 1 to 4, characterized in that: Method for manufacturing wideband cholesteric 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.

A phase difference layer (b) having a phase difference of I / 8 or more is disposed for incident light that has almost zero front phase difference (normal direction) and is inclined at an angle of 30 ° or more with respect to the normal direction. Polarizing element,

7. A reflective polarizer (a) power A polarizing element, which is the circularly polarizing plate according to claim 6.

8. The polarized light according to claim 7, wherein the selective reflection wavelengths of at least two layers of the reflective polarizer (a) overlap each other in a wavelength range of 550 nm ± 10 nm. 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 planar orientation,

Fixed homeotropic alignment state of rod-shaped liquid crystal,

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 polarized light element that can obtain polarized light.

1 1. 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 44 plate so that the pitch length is continuously narrowed. Polarizing element.

12. The λΖ4 plate is a retardation plate having a viewing angle improved by performing biaxial stretching to correct a phase difference of obliquely incident light beams, wherein the λ Ζ 4 plate is a retardation plate having an improved viewing angle. Linear polarizing element described in section.

13. The straight line according to claim 10 or 11, wherein the four-plate is a liquid crystal polymer type retardation plate obtained by applying and fixing a nematic liquid crystal or a smectic liquid crystal. Polarizing element.

1 4. If the λΖ4 plate has a principal refractive index in the plane of nx and ny and a principal refractive index in the thickness direction as nz, N defined by the formula: (nx—nz) / (nX-ny) The linear polarizing element according to any one of claims 10 to 13, wherein the z coefficient satisfies 0.5 to 12.5.

1 5. A straight line, characterized in that the linear polarizing element according to any one of claims 10 to 14 further comprises an I 2 plate laminated on a λ 4 plate. Polarizing element.

1 6. An absorption polarizer whose transmission axis is aligned with the transmission axis of the linear polarizing element according to any one of claims 10 to 15 is the λ / 4 plate side of the linear polarizing element. A linear polarizing element characterized by being laminated on a substrate.

1 7. A circularly polarizing plate according to claim 6, a polarizing element according to any one of claims 7 to 9, or a claim on a surface side of a surface light source having a reflective layer on a back surface side. 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 or depolarization is used as the viewing angle widening film. .