JP2003043460A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element, wherein display characteristic of a liquid crystal display can be improved. SOLUTION: In the liquid crystal display element provided with a backlight, a parallelizing means to parallelize light from the backlight, a liquid crystal cell with a plurality of pixels, color filters disposed on the respective pixels and a diffusing means to diffuse light emitted from the liquid crystal cell, the liquid crystal display element is characterized in that the parallelizing means contains a film material with selective reflection characteristics in wavelength region including no peak wavelength of bright lines in the emission spectrum of the backlight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a collimating means capable of improving the display characteristics of a liquid crystal display.

[0002]

2. Description of the Related Art OA for word processors and personal computers
As a display means used in equipment, a CRT display is being replaced with a liquid crystal display.

However, the liquid crystal display is inferior to the CRT display in the viewing angle characteristics of the display contrast and the display color due to the birefringence and the optical rotatory power due to the orientation of the liquid crystal. Therefore, for example, an attempt to improve the viewing angle by incorporating a retardation plate (Japanese Patent No. 2565644) and an attempt to reduce the birefringence of the liquid crystal by controlling the alignment of the liquid crystal have been proposed. At present, the display characteristics of CRT displays are still inferior.

[0004]

By the way, in a liquid crystal display, one of the causes of deterioration in display characteristics is that the light incident on the liquid crystal cell is not parallel light but diffused light. Is mentioned. Light incident on the liquid crystal cell at various angles other than the vertical direction may cause inconvenience such as deterioration of display quality due to coloring. Therefore, if perfect parallel light can be incident on the liquid crystal cell, the display characteristics can be improved without deterioration of the display characteristics due to the birefringence of the liquid crystal. In this case, there is no conventional member for collimating diffused light, that is, a collimator used in a liquid crystal display, and a prism sheet or the like for collecting diffused light is only partially used.

Further, the prism sheet is a member having a low parallelism, a complicated manufacturing process, and an expensive member, a member which is difficult to be thinned, and a member which may impair the brightness. However, none of them was sufficiently satisfactory for practical use.

The present invention has been made in view of the above problems, and is capable of irradiating parallel light, and particularly when applied to a liquid crystal display, improves display characteristics such as display contrast and viewing angle dependency. An object of the present invention is to provide a high quality liquid crystal display device capable of achieving the above.

[0007]

In order to solve the above problems, the present invention provides the following liquid crystal display device.

According to a first aspect of the invention, a backlight, a collimating means for collimating the light from the backlight, a liquid crystal cell having a plurality of pixels, a color filter provided for each pixel, In a liquid crystal display element having a diffusing means for diffusing light emitted from a liquid crystal cell,
The liquid crystal display element is characterized in that the collimating means includes a film material having a selective reflection characteristic in a wavelength band not including a peak wavelength of a bright line of an emission spectrum of a backlight.

[0009] The second aspect of the present invention, the parallel means consists cholesteric liquid crystal layer exhibiting a selective reflection wavelength band with respect to the vertical incident light on the wavelength _{λ 1 ~λ 2 (λ 1 <} λ 2), set if The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed of a film material satisfying λ ₀ <λ ₁ with respect to the maximum wavelength λ ₀ of the emission spectrum of the backlight that is used.

According to a third aspect of the present invention, two cholesteric liquid crystal layers are laminated, the spiral pitch, the average refractive index and the birefringence index of each cholesteric liquid crystal layer are substantially equal to each other, and the spiral rotation direction is The liquid crystal display elements according to claim 2, which are different from each other.

A fourth aspect of the present invention is the liquid crystal display element according to the second or third aspect, wherein the cholesteric liquid crystal layer has a thickness of 0.5 to 50 μm.

[0012] The invention of claim 5, wherein the collimating means, a dielectric multilayer film showing a selective reflection wavelength band in the wavelength _{λ 1 ~λ 2 (λ 1 <} λ 2) with respect to normally incident light, set The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed of a film material satisfying λ ₀ <λ ₁ with respect to the maximum wavelength λ ₀ of the emission spectrum of the backlights used in combination.

According to a sixth aspect of the present invention, the dielectric multilayer film comprises:
The optical film thickness is (λ ₁ + λ ₂ ) / 2 (where λ ₁ ,
lambda ₂ denotes the wavelength at 50% of the reflectivity of the maximum reflectance) the lambda _M and the time lambda _{M /} 4 high-refractive-index film and the low refractive index film and lambda / 4 which was deposited alternately which is The liquid crystal display element according to claim 5, which is an alternating multilayer film.

The invention of claim 7 is (λ ₂ −λ ₁ ) ≧ 50
The liquid crystal display element according to claim 2, wherein the liquid crystal display element has a thickness of nm.

The invention of claim 8 is (λ ₁ −λ ₀ ) ≦ 20
The liquid crystal display device according to claim 2, wherein the liquid crystal display device has a thickness of nm.

The invention of claim 9 is (λ ₁ −λ ₀ ) ≦ 10
The liquid crystal display device according to claim 2, wherein the liquid crystal display device has a thickness of nm.

[0017] The invention of claim 10 comprises a first collimating means for indicating a selective reflection wavelength band with respect to the vertical incident light on the wavelength _{λ 11 ~λ 12 (λ 11 <} λ 1 2), to the vertical incident light Wavelengths λ ₂₁ to λ ₂₂ (λ ₂₁ <λ
₂₂ ) second collimating means showing the selective reflection wavelength band, and wavelengths λ ₃₁ to λ ₃₂ (λ ₃₁ <λ for vertically incident light).
₃₂ ) is laminated with a third collimating means showing a selective reflection wavelength band, and is used in combination with a backlight having maximum light emission at wavelengths λ _B , λ _G and λ _R , and satisfies the following relational expression. The liquid crystal display device according to any one of claims 1 to 9. 420 nm ≦ λ _B ≦ 480 nm 520 nm ≦ λ _G ≦ 580 nm 585 nm ≦ λ _R ≦ 685 nm λ _B <λ ₁₁ <λ ₁₂ <λ _G <λ ₂₁ <λ ₂₂ <λ _R <
λ ₃₁ <λ ₃₂ <1000 nm

The eleventh aspect of the present invention is the liquid crystal display element according to any one of the first to tenth aspects, wherein the half width of the backlight is 20 nm or less.

A twelfth aspect of the present invention is the liquid crystal display element according to any one of the first to eleventh aspects, wherein the backlight has a half value width of 15 nm or less.

According to the present invention, the backlight, the collimating means for collimating the light from the backlight, the liquid crystal cell having a plurality of pixels, the color filter provided for each pixel, and the liquid crystal A film material having a selective reflection characteristic in a wavelength band that does not include the peak wavelength of the bright line of the emission spectrum of the backlight as a collimating means for a liquid crystal display element having a diffusing means for diffusing light emitted from the cell ( (Preferably cholesteric liquid crystal layer or dielectric multilayer film)
, The wavelengths λ ₁ to λ ₂ (λ
_{Even when} light of ₁ <λ ₂ ) is incident, the wavelengths λ _{1 to} λ ₂ (λ ₁ <λ ₂ ) are generated due to the selective reflection effect of the cholesteric liquid crystal layer or the dielectric multilayer film that constitutes the collimating means. Light is reflected. On the other hand, when the light of the maximum wavelength λ ₀ of the backlight, which is not included in the selective reflection wavelength band, is vertically incident on the cholesteric liquid crystal layer or the dielectric multilayer film, the light is emitted from the collimating means as parallel light. However, the selective reflection wavelength band of the cholesteric liquid crystal layer or the dielectric multilayer film shifts by a short wavelength depending on the incident angle α of light. As a result, the wavelength λ ₀ is included in the selective reflection wavelength band shifted by the short wavelength, and the light of the wavelength λ ₀ is incident on the incident angle α (α> 0).
When incident on the cholesteric liquid crystal layer or the dielectric multilayer film, the light is reflected by the selective reflection effect of the cholesteric liquid crystal layer or the dielectric multilayer film. Therefore, only the light of wavelength λ ₀ which is vertically incident on the cholesteric liquid crystal layer or the dielectric multilayer film from the backlight can pass through the cholesteric liquid crystal layer or the dielectric multilayer film, and only parallel light is emitted.

Since the optical characteristics such as the selective reflection wavelength band of the cholesteric liquid crystal layer or the dielectric multilayer film can be easily adjusted by controlling the selection and orientation of the material, the parallelizing means is easy to manufacture. Further, by selecting the material and controlling the orientation, the above function can be exhibited even if the thickness of the cholesteric liquid crystal layer or the dielectric multilayer film is reduced, and the demand for thinning can be met.

In the present invention, the term "normal incidence" means that light is incident perpendicularly to the collimating means. The incident angle α is the incident angle of light with respect to the spiral axis, and is defined as α in FIG. 3, for example. Further, in the present invention, the term “cholesteric liquid crystal layer” means a Grandjean-oriented cholesteric liquid crystal layer having a spiral axis in a direction substantially normal to the cholesteric liquid crystal layer.

In the collimating means constituting the liquid crystal display device of the present invention, the light reflected by the cholesteric liquid crystal layer or the dielectric multi-layer film is disturbed in its traveling direction by the light diffusing layer, and the light is again reflected. It is incident on the cholesteric liquid crystal layer or the dielectric multilayer film. Alternatively, after being reflected by the light reflection layer, it is incident on the cholesteric liquid crystal layer or the dielectric multilayer film again. By repeating this, the light from the backlight is collimated by the collimating means of the present invention. Therefore, according to the liquid crystal display element of the present invention, it is possible to irradiate parallel light, and by spreading the light that has passed through the liquid crystal panel by the diffusing means, it is possible to contribute to the improvement of display contrast and the expansion of the viewing angle.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a liquid crystal display device according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic sectional view showing an example of the liquid crystal display element of the present invention. The liquid crystal display element 10 includes a backlight 12
A collimating means 14 for collimating the backlight light from the backlight 12, a liquid crystal cell 16 having a plurality of pixels, and a color filter 18 provided for each pixel.
And a diffusing means 19 for diffusing the light emitted from the liquid crystal cell are arranged in this order.

The backlight 12 is a planar light emitting body,
The emission spectrum has an emission peak at the wavelength λ ₀ . The collimating means 14 includes a film material having a selective reflection characteristic in a wavelength band that does not include the peak wavelength of the bright line of the emission spectrum of the backlight, and is preferably a cholesteric liquid crystal layer or a dielectric multilayer film, as described later. Can be used for. The liquid crystal cell 16 is a TFT-LC.
Not only active matrix type LCD such as D,
It is applicable to LCDs of all display modes such as STN type LCDs. As the color filter 18, when the transmitted brightness is controlled by the liquid crystal layer to display in color, red,
It is common to use color filters of three primary colors of blue and green. The color filter may be arranged at any place on the optical path through which light passes, and may be arranged in the diffusing means or the collimating means, or in both the diffusing means and the collimating means. . The diffusing means 19 is not particularly limited, and one having a function of converting parallel light into diffused light can be used.

Here, in the liquid crystal display element of the present invention, as shown in FIG. 2, the light diffusing layer 13, the backlight 12, and the light reflecting layer 11 are arranged in this order below the collimating means 14. It is preferable to use a structured backlight system. A light diffusion layer 13 is arranged on the opposite side of the backlight 12 from the light reflection layer 11. The light diffusion layer 13 is a polymer sheet or film in which white inorganic powder or the like is dispersed to impart light diffusivity, and has a function of diffusing incident light. The light reflection layer 11 is formed of a metal thin film such as aluminum, and has a backlight 12
It has a function of reflecting the incident light in the direction of the collimating means 14 and returning it.

The case where a cholesteric liquid crystal layer or a dielectric multilayer film is used as the film material of the collimating means constituting the liquid crystal display device of the present invention will be described in detail below.

<Cholesteric Liquid Crystal Layer> FIG. 3 shows an enlarged sectional view when a cholesteric liquid crystal layer is used as the film material of the collimating means constituting the liquid crystal display device of the present invention. The collimating means 14 is configured by laminating a cholesteric liquid crystal layer 14R having a right-handed spiral alignment and a cholesteric liquid crystal layer 14L having a left-handed spiral alignment. The cholesteric liquid crystal layers 14R and 14L have substantially the same spiral pitch, average refractive index, and birefringence Δn. Here, the selective reflection center wavelength of the cholesteric liquid crystal layers 14R and 14L is determined by the product of the spiral pitch and the average refractive index, and the selective reflection wavelength band is the spiral pitch and the birefringence Δ.
It is determined by the product of n. Since the spiral pitch, the average refractive index, and the birefringence Δn of the cholesteric liquid crystal layers 14R and 14L are substantially the same, the selective reflection center wavelength and the selective reflection wavelength band are substantially the same.

FIG. 5 shows the emission spectrum of the backlight 12, the selective reflection wavelength band of the cholesteric liquid crystal layer 14R (or 14L), and its incident angle dependence. The backlight 12 exhibits an emission spectrum S ₀ having an emission peak at a wavelength λ ₀ (435 nm). On the other hand, the cholesteric liquid crystal layer 14R (or 14L) has a wavelength _{λ 1 ~λ 2 (λ 1 <} λ 2) in the selective reflection wavelength range _{R 0} with respect to the vertical incident light. When the light is incident on the cholesteric liquid crystal layer 14R (or 14L) at an angle other than vertical, the selective reflection wavelength band R ₀ is shifted by a short wavelength according to the incident angle. As shown in FIG. 5, the cholesteric liquid crystal layer 14R
(Or 14L) is the angle α ₁ , α ₂ and α ₃ (α ₁ <α
₂ <α ₃ ; for example α ₁ = 10 °, α ₂ = 20 ° and α ₃
= 40 °), the selective reflection wavelength bands R ₁ , R ₂ and R ₃ are shifted by a wavelength shorter than R ₀ . That is, the wavelength λ ₀ is the selective reflection wavelength band R ₁ , R ₂
And R ₃ and included in the angles α ₁ , α ₂ and α _3.
The circularly polarized light component of wavelength λ ₀ incident on the cholesteric liquid crystal layer 14R (or 14L) (the cholesteric liquid crystal layer 14R
Then, the clockwise circularly polarized light component and the cholesteric liquid crystal layer 14
In L, the counterclockwise circularly polarized light component) is reflected.

When light enters at an angle α (see FIG. 3) with respect to the spiral axis of the cholesteric liquid crystal layer, the selective reflection center wavelength λ (α) indicated by the cholesteric liquid crystal layer (average refractive index n) is When the central wavelength of selective reflection when light is vertically incident is λ, it is expressed by the following formula 1. <Formula 1> λ (α) = λ cos {sin ⁻¹ (sin α / n)}

In FIG. 2 again, the light (wavelength λ ₀ ) emitted from the backlight 12 is incident on the light diffusion layer 13 (directly or reflected by the light reflection layer 11) and its traveling direction is diffused. And enters the collimating means 14. First, the parallelization of the clockwise circularly polarized light component by the parallelization means 14 will be described. Of the right-handed circularly polarized light components incident on the collimating means 14, the light vertically incident on the cholesteric liquid crystal layer 14R forming the collimating means 14 satisfies λ ₀ <λ ₁ and therefore is not selectively reflected. To the cholesteric liquid crystal layer 14R, and is vertically incident on the cholesteric liquid crystal layer 14L. Since the incident right-handed circularly polarized light component is in the opposite direction to the spiral rotation direction of the cholesteric liquid crystal layer 14L, it is directly emitted from the collimating means 14 as parallel light.

On the other hand, the right-handed circularly polarized light components incident on the cholesteric liquid crystal layer 14R at angles α ₁ , α ₂ and α ₃ have a selective reflection wavelength band indicated by the cholesteric liquid crystal layer 14R according to the respective incident angles. Is shifted by a short wavelength, so that the wavelength λ ₀ is in any of the selective reflection wavelength bands R ₁ and R ₂
And R ₃ are also included and reflected. The traveling direction of the reflected light is diffused again by the light diffusion layer 13, and the backlight 12
And the reflected light from the light reflection layer 11 again enter the cholesteric liquid crystal layer 14R. Among them, only the light vertically incident on the cholesteric liquid crystal layer 14R is emitted from the collimating means 14 as parallel light by the same operation as described above. Then, by repeatedly passing through this optical path, the right-handed circularly polarized light component is almost completely collimated and emitted from the collimating means 14. In addition,
Of the clockwise circularly polarized light component reflected by the cholesteric liquid crystal layer 14R and incident on the light diffusion layer 13, the light reflection layer 11
The right-handed circularly polarized light component traveling in the direction is reflected by the light reflection layer 11, is converted into the left-handed circularly polarized light component, and is incident on the collimating means 14 again.

Next, parallelization of the counterclockwise circularly polarized light component incident on the collimating means 14 will be described. The left-handed circularly polarized light component is counterclockwise to the spiral rotation direction of the cholesteric liquid crystal layer 14R, and therefore passes through as it is, and the cholesteric liquid crystal layer 1
It is incident on 4L. Of the incident left-handed circularly polarized light component, the light vertically incident on the cholesteric liquid crystal layer 14L is
Since λ ₀ <λ ₁ is satisfied, the light passes through the cholesteric liquid crystal layer 14L as it is without being selectively reflected and is emitted as parallel light. On the other hand, the right-handed circularly polarized light components incident on the cholesteric liquid crystal layer 14L at angles α ₁ , α ₂ and α ₃ are:
Since the selective reflection wavelength band indicated by the cholesteric liquid crystal layer 14L is shifted by a short wavelength depending on the incident angle, the wavelength λ
₀ is included in any of the selective reflection wavelength bands R ₁ , R ₂ and R ₃ and is reflected. The reflected light repeatedly passes through the same optical path as the above-mentioned right-handed circularly polarized light component, is almost completely collimated, and is emitted from the collimating means 14. In this way, the collimating means 14 can almost completely collimate both circularly polarized light components and emit them.

FIG. 6 is a schematic sectional view showing an example of a backlight system constituting the liquid crystal display element of the present invention.
This backlight system is an example applied to a backlight system for a full-color display. In FIG. 6, the same members as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

This backlight system includes a light reflection layer 1
1, a backlight 12 ', a light diffusing layer 13 and a collimating means 14' are arranged in this order. The backlight 12 ′ is a three-wavelength type cold cathode fluorescent lamp, and has λ _B (420 nm to 480 nm, preferably 431 nm to 439 nm) and λ _G (520 nm to 58) corresponding to blue, green and red, respectively.
0 nm, preferably 539 nm to 551 nm), and λ
_R (585 nm to 685 nm, preferably 604 nm to
The emission spectrum has a peak wavelength of (616 nm). In this case, the surface of the light reflection layer 11 may be a curved surface having a predetermined curvature so that the light from the backlight 12 'can be efficiently reflected.

FIG. 7 shows an enlarged sectional view of the collimating means 14 'constituting the liquid crystal display element of the present invention. This parallelizing means 1
Reference numeral 4'denotes a cholesteric liquid crystal layer 114R having a clockwise spiral orientation, a cholesteric liquid crystal layer 114L having a counterclockwise spiral orientation, a cholesteric liquid crystal layer 214R having a clockwise spiral orientation, and a cholesteric liquid crystal having a counterclockwise spiral orientation. The layer 214L, a cholesteric liquid crystal layer 314R having a clockwise spiral alignment, and a cholesteric liquid crystal layer 314L having a counterclockwise spiral alignment are stacked. The cholesteric liquid crystal layers 114R and 114L are
The spiral pitch, the average refractive index and the birefringence Δn are substantially the same. In addition, the cholesteric liquid crystal layer 21
4R and 214L have substantially the same spiral pitch, average refractive index, and birefringence Δn. Further, the cholesteric liquid crystal layers 314R and 314L have substantially the same spiral pitch, average refractive index and birefringence Δn. Therefore, the cholesteric liquid crystal layers 114R and 1
14L selective reflection wavelength band, cholesteric liquid crystal layer 2
The selective reflection wavelength bands of 14R and 214L and the selective reflection wavelength bands of cholesteric liquid crystal layers 314R and 314L are substantially the same.

FIG. 9 shows the emission spectrum of the backlight 12 '.
Tol and cholesteric liquid crystal layer 114R (or 114
L), 214R (or 214L) and 314R (or 3)
14L) shows the selective reflection wavelength band. Backlight 1
2'is the wavelength λ_B, Λ_GAnd λ_RHas an emission peak at
Emission spectrum S₀’ On the other hand, cholesteric liquid
The crystal layer 114R (and 114L) is for vertically incident light.
Wavelength λ₁₁~ Λ₁₂(Λ₁₁<Λ₁₂) Selective reflection wavelength
Band R₀₁The cholesteric liquid crystal layer 214R (and 2
14L) has a wavelength λ for vertically incident light.₂₁~ Λ
₂₂(Λ₂₁<Λ₂₂) Selective reflection wavelength band R₀₂To
The cholesteric liquid crystal layer 314R (and 314L) is
Wavelength λ for directly incident light ₃₁~ Λ₃₂(Λ₃₁<
λ₃₂) Selective reflection wavelength band R₀₃Have the following functions
It meets the formula. λ_B<Λ₁₁<Λ₁₂<Λ_G<Λ₂₁<Λ₂₂<Λ_R<
λ₃₁<Λ₃₂<1000 nm

Selective reflection wavelength band R₀₁, R₀₂And R
₀₃The light is cholesteric liquid crystal layer 114R (and 11
4L), 214R (and 214L) and 314R (and
314L) when incident at an angle other than vertical.
Shifts by a short wavelength depending on the incident angle. For example,
Selective reflection wave of cholesteric liquid crystal layer 14R shown in FIG.
Cholesteric liquid crystals as well as long-range incident angle dependence
The layers 114R (and 114L) have an angle α₁, Α_TwoAnd α_Three
(Α₁<Α_Two<Α_Three; For example α₁= 10 °, α_Two= 20
° and α_Three= 40 °), R for each of the incident light
₀₁Selective reflection wavelength band R shifted by a shorter wavelength than₁₁，
R₁₂And R_Thirteen(Not shown). wavelength
λ_BIs R₁₁, R₁₂And R_ThirteenIncluded in any of the
Angle α₁, Α _TwoAnd α_ThreeAnd the cholesteric liquid crystal layer 114
Wavelength λ incident on R (and 114L) _BCircularly polarized component of
(In the cholesteric liquid crystal layer 114R, right-handed circularly polarized light is formed.
The left-handed circularly polarized light component) is reflected at
It

Similarly, the cholesteric liquid crystal layer 214R
(And 214L) and 314R (and 314L) are R ₀₂ and R ₀₃ for light incident at an angle other than vertical.
Each of them has a selective reflection wavelength band shifted by a shorter wavelength. Each of the short-wavelength-shifted selective reflection wavelength bands includes a wavelength λ _G and a wavelength λ _R , and the cholesteric liquid crystal layer 214R (and 214) at an incident angle other than vertical.
L) and 314R (and 314L) incident wavelength λ
Light of _G and wavelength λ _R is reflected.

Again referring to FIG. 6, the backlight 12 '.
The light (wavelengths λ _B , λ _G, and λ _R ) emitted from the laser beam is incident on the light diffusion layer 13 (directly or reflected by the light reflection layer 11), its traveling direction is diffused, and the parallelization means 14 is used. Incident on. The right-handed and left-handed circularly polarized light components of the wavelength λ _B are collimated by the cholesteric liquid crystal layers 114R and 114L, and the right-handed and left-handed circularly polarized components of the wavelength λ _G are collimated by the cholesteric liquid crystal layers 214R and 214L. Is
The right-handed and left-handed circularly polarized light components of the wavelength λ _R are collimated by the cholesteric liquid crystal layers 314R and 314L. As a result, the collimating means 14 'emits parallel light of three wavelengths corresponding to blue, green and red.

The collimating means of the present invention may be equipped with a light guide plate, a polarization separation plate, etc., if desired, depending on the application.

Next, the cholesteric liquid crystal layer constituting the parallelizing means of the liquid crystal display device of the present invention will be described in more detail. The collimating means of the present invention has at least one cholesteric liquid crystal layer, preferably three layers. This cholesteric liquid crystal layer has a wavelength λ ₁ to normal incident light.
λ ₂ (λ ₁ <λ ₂ ) shows a selective reflection wavelength band, and satisfies λ ₀ <λ ₁ with respect to the maximum wavelength λ ₀ of the emission spectrum of the backlight used in combination. In this case, the central wavelength of the selective reflection wavelength band is determined by the spiral pitch and the average refractive index of the cholesteric liquid crystal layer, and the selective reflection wavelength band is determined by the spiral pitch and the birefringence Δn of the cholesteric liquid crystal layer. Therefore,
By selecting a material forming the cholesteric liquid crystal layer and controlling the orientation thereof, it is possible to obtain a cholesteric liquid crystal layer satisfying the above relation with respect to the emission peak wavelength λ _{0 of the} backlight to be combined.

In this case, the cholesteric liquid crystal layer is shown.
Maximum wavelength of selective reflection wavelength band λ _TwoAnd minimum wavelength λ₁
Is preferably 50 nm or more, and the difference is
It is more preferably 70 nm or more. Maximum wavelength λ
_TwoAnd minimum wavelength λ₁Is less than 50 nm,
This oblique light is cut off, but when the incident angle becomes large
There is a possibility that light may pass again.

The cholesteric liquid crystal layer is (λ ₁ -λ
₀ ) ≦ 20 nm is preferable. If this relationship is satisfied, the full width at half maximum of the emission spectrum is 20n.
Even when used in combination with a backlight having a sharp emission spectrum of m or less, it is possible to obtain outgoing light that diffuses only within a range of ± 10 ° from perfect parallel light, and practically sufficient characteristics are obtained. A collimating means having is obtained.
Further, even when used in combination with a backlight showing a sharper emission spectrum having a full width at half maximum of 15 nm or less in the emission spectrum, if (λ ₁ −λ ₀ ) ≦ 10 nm is satisfied, perfect parallel light is obtained. It is possible to obtain outgoing light that diffuses only within a range of ± 10 °, and it is possible to obtain a collimating means having practically sufficient characteristics.

When the diffused light containing both the right-handed circularly polarized light component and the left-handed circularly polarized light component is collimated, at least two cholesteric liquid crystal layers having mutually different spiral rotation directions are laminated to constitute a collimating means. Preferably. There is no particular limitation on the stacking order of the cholesteric liquid crystal layer.
When the spiral pitch, the average refractive index and the birefringence Δn of each cholesteric liquid crystal layer are made to coincide with each other, the selective reflection wavelength bands and their incident angle dependencies become equal to each other, so that the clockwise and counterclockwise circularly polarized light components are This is preferable because the degree of parallelization can be made equal. Here,
“Match” means “substantially match”, and as described above, the degree of collimation is equal in both circularly polarized light components,
Even when applied to a liquid crystal display element, a liquid crystal display device, or the like, it is a degree of coincidence in which both of the circle changing components do not cause a significant parallel light imbalance.

Emission spectrum having two or more emission peaks
When used in combination with a backlight that indicates
The collimating means of the present invention is characterized by each emission peak wavelength (λ₀₁
<Λ ₀₂<…… <λ_0n) For λ₀₁<Λ₁₁,
λ₀₂<Λ₂₁, …… and λ _0n<Λ_n1Selection to meet
Minimum value of reflection wavelength band λ₁₁, Λ₂₁, …… and λ_{n 1}
Is formed by stacking cholesteric liquid crystal layers each having
Preferably. In this case, regarding the stacking order
There is no particular limitation. Also, it corresponds to each emission peak
The selective reflection wavelength band of the cholesteric liquid crystal layer is
Each cholesteric liquid crystal layer so as not to include the peak wavelength
The maximum value of the selective reflection wavelength band (λ₁₂, Λ₂₂, ... and
And λ_n2) Preferably satisfies the following relational expression:
Good λ₀₁<Λ₁₁<Λ₁₂<Λ₀₂<Λ₂₁<Λ
₂₂<Λ₀₃<…… <λ_0n<Λ_n1<Λ_n2

When the collimating means of the present invention is a laminate of two or more cholesteric liquid crystal layers, the laminate can be prepared by a conventionally known method such as laminating treatment and superposition coating treatment. Moreover, in order to improve the adhesiveness of each cholesteric liquid crystal layer, an adhesive layer may be interposed between the cholesteric liquid crystal layers.

The cholesteric liquid crystal layer may be composed of one kind of liquid crystalline material or may be composed of two or more kinds of liquid crystalline materials. When it is composed of two or more kinds of liquid crystalline materials, it may contain a material which cannot form the cholesteric liquid crystal layer by one kind alone. Further, in the cholesteric liquid crystal layer, the liquid crystalline material is preferably fixed in a desired orientation (a desired spiral pitch).

As a liquid crystalline material which can be used for the cholesteric liquid crystal layer of the present invention, a composition of a liquid crystalline polyester described in JP-A No. 11-124492 and an optically active liquid crystalline polyester ([0020] in the above publication) is used. ~ [00
72]). In addition, JP-A-10-31
The liquid crystal polymers described in columns [0023] to [0029] of 9235 can be used.

In the case of forming a cholesteric liquid crystal layer from the above-exemplified liquid crystal material, a coating solution containing the above liquid crystalline material is prepared, and the coating solution is optionally applied onto an alignment film to form a layer. The layer can be heated above the glass transition temperature but below the isotropic phase transition temperature to form the liquid crystalline polymer in the desired helical pitch orientation. In this case, the spiral pitch can be controlled by heating conditions, material mixing conditions, and the like.

The cholesteric liquid crystal layer is obtained by copolymerizing an optically active monomer having a polymerizable group such as an acrylic group, a mesogenic group and asymmetric carbon in its structure with a monomer having a polymerizable group and a mesogenic group. Can be formed by Specifically, it can be formed by coating a substrate with a coating liquid containing a mixture of the above monomers (optionally containing a photopolymerization initiator), and irradiating the substrate with light to polymerize it. The cholesteric liquid crystal layer formed by this method can be peeled off from the substrate and can be handled alone. After that, when it is incorporated in a liquid crystal display device or when laminated with another cholesteric liquid crystal layer, the operation becomes easy. . Further, when a cholesteric liquid crystal layer is formed by copolymerizing a monomer having two or more polymerizable groups, the copolymer is reliably fixed in a desired orientation due to a crosslinked structure. In particular, it is preferable because the optical characteristics are not impaired. For the method of forming the monomer and cholesteric liquid crystal layer, see JP-A-6-2818.
The details are described in Japanese Patent No. 14 publication.

The thickness of the cholesteric liquid crystal layer is 0.5.
The thickness is preferably ˜50 μm, more preferably 2 to 10 μm. When the thickness of the cholesteric liquid crystal layer is within the above range, it is easy to control the orientation of the desired spiral pitch and it is possible to meet the demand for thinning, which is preferable. When the collimating means of the liquid crystal display device of the present invention is composed of two or more laminates of the cholesteric liquid crystal layer, the thickness of the collimating means is preferably 1 to 100 μm, and preferably 4 to 20 μm. More preferable.

<Dielectric Multilayer Film> FIG. 4 is an enlarged cross-sectional view showing an example of the dielectric multilayer film which constitutes the parallelizing means of the liquid crystal display device of the present invention. This dielectric multilayer film is a multilayer film formed by alternately depositing several layers or several tens layers of two dielectric thin films having a thickness of λ / 4 and different in refractive index on a transparent substrate. The light wave propagating in this dielectric multilayer film is
Physically, some of the light waves are multiple-reflected for each film, and the light waves interfere with each other. As a result, only the wavelength determined by the product of the thickness of the dielectric thin film and the effective refractive index of the film with respect to the guided light is selectively transmitted. Further, the center transmission wavelength of this filter has an angle dependence with respect to the incident beam. Therefore, the transmission wavelength can be changed by changing the incident angle.

Specifically, the dielectric multi-layer film has an optical film thickness of λ _M / 4 (where λ _M is (λ ₁ + λ ₂ ) / 2) on a transparent substrate such as plastics and quartz glass. And
λ ₁ and λ ₂ mean the wavelength at a reflectance of 50% of the maximum reflectance), and the high refractive index film 14H and the low refractive index film 14
It is composed of alternating layers (usually 10 layers or more) with S and is formed by a vacuum deposition method or the like to a total thickness of about 0.2 to 20 μm.

This dielectric multilayer film has a certain width Δλ around λ _M which is larger than the maximum wavelength λ ₀ of the light emission spectrum of the light source.
It has a high reflectance band (selective reflection wavelength band) and shows high transmittance in the wavelength region on both sides of it. When the refractive index of the high refractive index film 14H is n _H , the refractive index of the low refractive index film 14S is n _S , and the refractive index of the substrate is n _B , the alternating multilayer films 14H (14S14
H) ^m G (where m represents the number of repetitions and G represents the substrate), the high reflectance band Δλ and the reflectance R are obtained from the following equation 2. <Formula 2> Δλ = λ _M / 45 · sin ⁻¹ (n _H −n _S ) / (n _H
+ _N S) R = ^{_{[(n B · n S 2m -n}} H 2 (m + 1) / (n B ·
n _S ^2m + n _H ^{2 (m +1)} )) ²

FIG. 5 shows the emission spectrum of the backlight 12, the selective reflection wavelength band of the dielectric multilayer film, and its incident angle dependence. The backlight 12 has a wavelength of λ ₀ (435
(nm) shows an emission spectrum S ₀ having an emission peak. On the other hand, the dielectric multilayer film has a wavelength λ for vertically incident light.
_{1 to} λ ₂ (λ ₁ <λ ₂ ) has a selective reflection wavelength band R ₀ . When the light is incident on the dielectric multilayer film at an angle other than vertical, the selective reflection wavelength band R ₀ is shifted by a short wavelength according to the incident angle. As shown in FIG. 5, the dielectric multilayer film has angles α ₁ , α ₂ and α ₃ (α ₁ <α ₂ <α ₃ ;
For example, α ₁ = 10 °, α ₂ = 20 ° and α ₃ = 40 °)
It has selective reflection wavelength bands R ₁ , R ₂ and R ₃ that are shifted by a wavelength shorter than R ₀ for each of the lights incident on. That is, the wavelength λ ₀ is included in any of the selective reflection wavelength bands R ₁ , R ₂ and R ₃ , and the light component of the wavelength λ ₀ incident on the dielectric multilayer film at the angles α ₁ , α ₂ and α ₃ is reflected. To be done.

In FIG. 2 again, the light (wavelength λ ₀ ) emitted from the backlight 12 enters the light diffusion layer 13 (directly or reflected by the light reflection layer 11) and its traveling direction is diffused. And enters the collimating means 14. First, light vertically incident on the dielectric multi-layered film forming the collimating means 14 satisfies λ ₀ <λ ₁ , so that the light is directly transmitted through the dielectric multi-layered film without being selectively reflected. The light is vertically incident on the film and is emitted as it is from the collimating means 14 as parallel light.

On the other hand, with respect to the dielectric multilayer film, the angles α ₁ ,
Lights incident at α ₂ and α ₃ have a short wavelength shift in the selective reflection wavelength band indicated by the dielectric multilayer film according to the respective incident angles. Therefore, the wavelength λ ₀ indicates which selective reflection wavelength band R ₁ , R ₂ and R ₃ are also included and reflected. The traveling direction of the reflected light is diffused again by the light diffusing layer 13, and the light again enters the dielectric multilayer film together with the light from the backlight 12 and the reflected light from the light reflecting layer 11. Among them, only the light vertically incident on the dielectric multilayer film is emitted from the collimating means 14 as parallel light by the same operation as described above. Then, by repeatedly passing through this optical path, the light is almost completely collimated and emitted from the collimator 14.

Next, FIG. 6 is a schematic sectional view showing an example of a backlight system which constitutes the liquid crystal display element of the present invention. This backlight system is an example applied to a backlight system for a full-color display. In the backlight system of FIG. 6, the same members as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

This backlight system includes a light reflection layer 1
1, a backlight 12 ', a light diffusing layer 13 and a collimating means 14' are arranged in this order. The backlight 12 ′ is a three-wavelength type cold cathode fluorescent lamp, and has λ _B (420 nm to 480 nm, preferably 431 nm to 439 nm) and λ _G (520 nm to 58) corresponding to blue, green and red, respectively.
0 nm, preferably 539 nm to 551 nm), and λ
_R (585 nm to 685 nm, preferably 604 nm to
The emission spectrum has a peak wavelength of (616 nm). In this case, the surface of the light reflection layer 11 may be a curved surface having a predetermined curvature so that the light from the backlight 12 'can be efficiently reflected.

FIG. 8 is a plan view showing the liquid crystal display device of the present invention.
The expanded sectional view of the line conversion means 14 'is shown. This parallelizing means 1
4'is a high refractive index film 114H and a low refractive index film 11 on the substrate.
First dielectric multilayer film formed by forming alternating layers with 4S
And a high refractive index film 214H and a low refractive index film 214S on the substrate.
A second dielectric multilayer film in which alternating layers of
The high refractive index film 314H and the low refractive index film 314S are formed on the plate.
By laminating a third dielectric multilayer film in which alternating layers are formed,
It is configured. The first dielectric multilayer film is
For wavelength λ₁₁~ Λ₁₂(Λ₁₁<Λ ₁₂) Selected against
The emission wavelength band is shown. The second dielectric multi-layered film is
For wavelength λ₂₁~ Λ₂₂(Λ₂₁<Λ ₂₂) To
The reflection wavelength band is shown. The third dielectric multilayer film has a normal incidence
Wavelength λ for light₃₁~ Λ₃₂(Λ₃₁<Λ ₃₂)
The selective reflection wavelength band is shown.

FIG. 9 shows the emission spectrum of the backlight 12 'and the selective reflection wavelength band of the first to third dielectric multilayer films. The backlight 12 ', the emission spectrum _{S 0} having an emission peak at a wavelength lambda _B, lambda _G and lambda _R' indicates a. On the other hand, the first dielectric multilayer film, a selective reflection wavelength band _{R 01} to the wavelength _{λ 11 ~λ 12 (λ 11 <} λ 12) to the vertical incident light, a second dielectric multilayer film, normally incident The selective reflection wavelength band R ₀₂ is set to the wavelengths λ ₂₁ to λ ₂₂ (λ ₂₁ <λ ₂₂ ) with respect to the light, and the third dielectric multilayer film has the wavelengths λ ₃₁ to λ ₃₂ (λ ₃₁ to the vertically incident light. Each has a selective reflection wavelength band R ₀₃ in <λ ₃₂ ) and satisfies the following relational expression. λ _B <λ ₁₁ <λ ₁₂ <λ _G <λ ₂₁ <λ ₂₂ <λ _R <
λ ₃₁ <λ ₃₂ <1000 nm

Here, the first dielectric multilayer film is an optical film.
Any thickness is (λ₁₁+ Λ₁₂) / 2 (however, λ₁₁，
λ₁₂Means the wavelength at the reflectance of 50% of the maximum reflectance.
Taste) λ_M1Then λ_M1High refractive index of / 4
Λ / 4 alternating multi-layers in which films of 1 and films of low refractive index are deposited alternately
It is a film. The optical thickness of the second dielectric multilayer film is
Also (λ₂₁+ Λ₂₂) / 2 (however, λ₂₁, Λ₂₂Is the most
(Meaning the wavelength at a reflectance of 50% of the large reflectance)
λ _M2Then λ_M2/ 4 film with high refractive index and low bending
It is a λ / 4 alternating multilayer film in which a film having a folding rate is alternately deposited.
The third dielectric multilayer film has an optical film thickness of (λ₃₁
+ Λ₃₂) / 2 (however, λ₃₁, Λ₃₂Is the maximum reflectance
Means the wavelength at 50% reflectance) _M3age
When λ_M3/ 4 high refractive index film and low refractive index film
Is a λ / 4 alternating multilayer film formed by alternately depositing

Selective reflection wavelength bands R ₀₁ , R ₀₂ and R
₀₃ , when light is incident on the first to third dielectric multilayer films at an angle other than vertical, a short wavelength shift occurs according to the incident angle. For example, similar to the incident angle dependence of the selective reflection wavelength band of the dielectric multilayer film shown in FIG. 5, the dielectric multilayer film has angles α ₁ , α ₂ and α ₃ (α ₁ <α ₂ <α ₃ ; α ₁ = 10 °, α ₂ = 20 ° and α ₃ = 40 °) for each of the incident lights, the selective reflection wavelength bands R ₁ , R ₂ and R ₃ are shifted by a wavelength shorter than R _0. . Wavelength λ
_B is included in any of R ₁₁ , R ₁₂ and R ₁₃ , and the light component of wavelength λ _B incident on the first dielectric multilayer film at angles α ₁ , α ₂ and α ₃ is reflected.

Similarly, the second and third dielectric multilayer films R ₀₂ and R ₀₃ are applied to light incident at an angle other than normal.
Each of them has a selective reflection wavelength band shifted by a shorter wavelength. The selective reflection wavelength band of each that these blue shifts, wavelength lambda _G and wavelength lambda _R is included each second at an incident angle other than vertical, the wavelength lambda _G incident on the third dielectric multilayer film
And light of wavelength λ _R is reflected.

Again referring to FIG. 6, the backlight 12 '.
The light (wavelengths λ _B , λ _G, and λ _R ) emitted from the laser beam is incident on the light diffusion layer 13 (directly or reflected by the light reflection layer 11), its traveling direction is diffused, and the parallelization means 14 is used. Incident on. The light component of wavelength λ _B is collimated by the first dielectric multilayer film, the light component of wavelength λ _G is collimated by the second dielectric multilayer film, and the light component of wavelength λ _R is The light is collimated by the third dielectric multilayer film. As a result, the collimating means 14 'emits parallel light of three wavelengths corresponding to blue, green and red.

Next, the dielectric multilayer film constituting the parallelizing means of the present invention will be described in more detail. The parallelizing means of the present invention has at least one dielectric multilayer film, preferably three layers. The dielectric multilayer film showed each selective reflection wavelength band in the wavelength _{λ 1 ~λ 2 (λ 1 <} λ 2) with respect to normally incident light, and combined with maximum wavelength of emission spectrum of the backlight used and satisfies the λ ₀ <λ ₁ with respect to lambda _0. In this case, the central wavelength of the selective reflection wavelength band is determined by the optical thickness of the dielectric multilayer film, and the selective reflection wavelength band is the refractive index of the low refractive index film and the high refractive index film of the dielectric multilayer film. It is determined by the refractive index. Therefore, by selecting the material used for the dielectric multilayer film and controlling the orientation thereof, it is possible to obtain a dielectric multilayer film satisfying the above relation with respect to the emission peak wavelength λ ₀ of the combined backlight. .

In this case, the difference between the maximum value wavelength λ ₂ and the minimum value wavelength λ ₁ of the selective reflection wavelength band shown by the dielectric multilayer film is preferably 50 nm or more, and the difference is 70 nm.
The above is more preferable. When the difference between the maximum value wavelength λ ₂ and the minimum value wavelength λ ₁ is 50 nm or less, the oblique light is cut off moderately, but when the incident angle becomes large, the light may pass again.

The dielectric multilayer film has (λ ₁ −λ ₀ ) ≦ 2
It is preferable to satisfy 0 nm. If this relationship is satisfied, even when used in combination with a backlight having a sharp emission spectrum with a full width at half maximum of 20 nm or less, ± 10 ° from perfect parallel light.
The emitted light that diffuses only within the range can be obtained, and the collimating means having practically sufficient characteristics can be obtained. Further, even when used in combination with a backlight showing a sharper emission spectrum having a full width at half maximum of 15 nm or less in the emission spectrum, if (λ ₁ −λ ₀ ) ≦ 10 nm is satisfied, perfect parallel light is obtained. It is possible to obtain outgoing light that diffuses only within a range of ± 10 °, and it is possible to obtain a collimating means having practically sufficient characteristics.

Emission spectrum having two or more emission peaks
When used in combination with a backlight that indicates
The collimating means of the present invention is characterized by each emission peak wavelength (λ₀₁
<Λ ₀₂<…… <λ_0n) For λ₀₁<Λ₁₁,
λ₀₂<Λ₂₁, …… and λ _0n<Λ_n1Selection to meet
Minimum value of reflection wavelength band λ₁₁, Λ₂₁, …… and λ_{n 1}
Are formed by laminating dielectric multilayer films each having
It is preferable. In this case, the order of stacking each dielectric multilayer film
It is not particularly limited. Also, for each emission peak
The selective reflection wavelength band of each corresponding dielectric multilayer film is
Selection of each dielectric multilayer so as not to include the optical peak wavelength
Maximum value of reflection wavelength band (λ₁₂, Λ₂₂, …… and λ
_n2) Preferably satisfies the following relational expression:
Yes. λ₀₁<Λ₁₁<Λ₁₂<Λ₀₂<Λ₂₁<Λ₂₂<Λ
₀₃<…… <λ_0n<Λ_n1<Λ_n2 Where λ₁₁, Λ₁₂, Λ₂₁, Λ₂₂...... is the maximum reflection
It means the wavelength in reflectance at 50% of the index.

As a material of such a dielectric multilayer film,
It is not particularly limited as long as it has the above characteristics, and it is suitable for the purpose.
It can be selected as appropriate, for example, TiO_Two, CeO
_Two, Ta_TwoO₅, ZrO_Two, Sb_TwoO_Three, HfO_Two, L
a_TwoO_Three, MgO, Al_TwoO _Three, SiO_Two, In
_TwoO_Three, ZnO, SnO_Two, Cd_TwoSnO_Four, CdIn
_TwoO _Four, Zn_TwoSnO_Four, ZnSnO_Three, MgIn_TwoO
_Four, Zn_TwoIn_TwoO₅, In _ThreeSn_ThreeO₁₂And so on
Among these, TiO is used as a high refractive index film._Two, Low
SiO as a refractive index film_TwoIs preferably used.

The method for producing the dielectric multilayer film is not particularly limited, and vacuum deposition methods such as ion plating and ion beam deposition, physical vapor deposition methods (PVD) such as sputtering, and chemical vapor deposition. A method (CVD) or the like can be appropriately adopted depending on the purpose.

The collimating means constituting the liquid crystal display element of the present invention may be provided with a substrate, a light distribution film, etc., if desired, in addition to the cholesteric liquid crystal layer or the dielectric multilayer film.

The liquid crystal display device of the present invention can be used not only for various liquid crystal displays such as watches, calculators, Japanese word processors, computer terminals, etc., but also for illumination signboards, various illuminations and the like.

Although the liquid crystal display element of the present invention has been described in detail above, the present invention is not limited to the above-mentioned embodiment,
Various changes may be made without departing from the scope of the present invention.

[0076]

As described above, according to the present invention,
It is possible to provide a high-quality liquid crystal display element capable of irradiating parallel light and capable of improving display characteristics such as display contrast and viewing angle dependency particularly when applied to a liquid crystal display.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an example of a liquid crystal display element of the present invention.

FIG. 2 is a sectional view schematically showing an example of the backlight system of the present invention.

FIG. 3 is a cross-sectional view schematically showing an example of parallelizing means of the present invention.

FIG. 4 is a sectional view schematically showing an example of another parallelizing means.

FIG. 5 is a graph showing an emission spectrum of a backlight and a selective reflection wavelength band of a cholesteric liquid crystal layer (or a dielectric multilayer film) which can be used in the present invention.

FIG. 6 is a cross-sectional view schematically showing an example of the backlight system of the present invention.

FIG. 7 is a cross-sectional view schematically showing an example of parallelizing means of the present invention.

FIG. 8 is a cross-sectional view schematically showing an example of parallelizing means of the present invention.

FIG. 9 is a graph showing an emission spectrum of a backlight and a selective reflection wavelength band of a cholesteric liquid crystal layer (or a dielectric multilayer film) which can be used in the present invention.

[Explanation of symbols]

10, 10 'Liquid crystal display element 11 Light reflecting layer 12, 12' Backlight 13 Light diffusing layer 14, 14 'Parallelizing means 16 Liquid crystal cell 18 Color filter 19 Diffusing means 18R, 118R, 218R, 318R Clockwise cholesteric liquid crystal layer 18L , 118L, 218L, 318L counterclockwise cholesteric liquid crystal layers 18H, 118H, 218H, 318H high refractive index films 18S, 118S, 218S, 318S low refractive index films

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02B 5/30 G02B 5/30 G02F 1/13357 G02F 1/13357 F term (reference) 2H048 FA04 FA09 FA15 FA22 FA24 GA15 GA33 GA61 2H049 BA03 BA05 BA43 BB03 BC22 2H091 FA01Z FA02Y FA14Z FA31Z FA41Z FB06 FB08 KA10 LA17 LA19

Claims (12)

[Claims] 1. A backlight, a collimating unit for collimating light from the backlight, a liquid crystal cell having a plurality of pixels, and a color filter provided for each pixel,
In a liquid crystal display device including a diffusing unit that diffuses light emitted from the liquid crystal cell, the collimating unit has a selective reflection characteristic in a wavelength band that does not include a peak wavelength of a bright line of an emission spectrum of a backlight. A liquid crystal display device comprising a film material having 2. The collimating means for vertically incident light
Wavelength λ₁~ Λ_Two(Λ ₁<Λ_Two) Indicates the selective reflection wavelength band
It consists of a cholesteric liquid crystal layer and is used in combination.
Maximum wavelength λ of the emission spectrum of the backlight₀Against
Then λ₀<Λ ₁Formed from a film material that satisfies
The liquid crystal display element according to claim 1. 3. The two cholesteric liquid crystal layers are laminated, the spiral pitch, the average refractive index, and the birefringence index of each cholesteric liquid crystal layer are substantially equal to each other, and the rotation directions of the spirals are different from each other. The liquid crystal display element described. 4. The thickness of the cholesteric liquid crystal layer is 0.
The liquid crystal display device according to claim 2, which has a thickness of 5 to 50 μm. 5. The collimating means for vertically incident light
Wavelength λ₁~ Λ_Two(Λ ₁<Λ_Two) Indicates the selective reflection wavelength band
It consists of a dielectric multilayer film and is used in combination.
The maximum wavelength λ of the emission spectrum of Klite₀Against λ₀
<Λ₁It is formed from a film material that satisfies
1. The liquid crystal display element according to 1. 6. The dielectric multilayer film has an optical film thickness of (λ ₁ + λ ₂ ) / 2 (where λ ₁ and λ ₂ mean a wavelength at a reflectance of 50% of the maximum reflectance). the liquid crystal display device according to claim 5, wherein the a high refractive index film and a low refractive index of the film lambda / 4 was deposited alternately and alternate multilayer film which is a lambda _{M /} 4 when the lambda _M. 7. The liquid crystal display device according to claim _{2, wherein} (λ ₂ −λ ₁ ) ≧ 50 nm. 8. The liquid crystal display element according to claim 2, wherein (λ ₁ −λ ₀ ) ≦ 20 nm. 9. The liquid crystal display device according to claim 2, wherein (λ ₁ −λ ₀ ) ≦ 10 nm. 10. Wavelengths λ ₁₁ to λ for vertically incident light
₁₂ (λ ₁₁ <λ ₁₂ ) indicates the first selective reflection wavelength band
And the wavelengths λ ₂₁ to λ ₂₂ (λ ₂₁ <λ for vertically incident light).
₂₂ ) second collimating means showing the selective reflection wavelength band, and wavelengths λ ₃₁ to λ ₃₂ (λ ₃₁ <λ for vertically incident light).
₃₂ ) is laminated with a third collimating means showing a selective reflection wavelength band, and is used in combination with a backlight having maximum light emission at wavelengths λ _B , λ _G and λ _R , and satisfies the following relational expression. The liquid crystal display element according to claim 1. 420 nm ≦ λ _B ≦ 480 nm 520 nm ≦ λ _G ≦ 580 nm 585 nm ≦ λ _R ≦ 685 nm λ _B <λ ₁₁ <λ ₁₂ <λ _G <λ ₂₁ <λ ₂₂ <λ _R <
λ ₃₁ <λ ₃₂ <1000 nm 11. The full width at half maximum of the backlight is 20 nm.
The liquid crystal display device according to claim 1, wherein: 12. The full width at half maximum of the backlight is 15 nm.
The liquid crystal display element according to any one of claims 1 to 11, which is as follows.