KR20040069493A - Reflection and penetration type optical film and liquid crystal display having the same - Google Patents

Abstract

A reflective-transmissive optical film having the same optical properties while reducing the number of optical sheets and a liquid crystal display device having the same are disclosed. The first retardation film is outputted by first retarding the phase of incident light when operating in the first mode, and the second retardation film is outputted by retarding the phase of incident light when operating in the first and second modes. The reflecting portion is formed in a partial region between the first retardation film and the second retardation film. The liquid crystal layer has a characteristic of a normally black mode, and when operating in the first mode, changes the characteristics of the first delayed light to provide it to the second retardation film, and when operating in the second mode, changes the characteristics of the second delayed light It outputs to a reflection part, changes the characteristic of the light reflected by the reflection part, and provides it to a 2nd phase difference film. Accordingly, by designing a liquid crystal layer operating in a normally black mode, and employing one retardation film on each of the upper and lower sides of the liquid crystal layer, it is possible to reduce the number of optical sheets while maintaining the optical characteristics, thereby reducing the manufacturing cost.

Description

REFLECTION AND PENETRATION TYPE OPTICAL FILM AND LIQUID CRYSTAL DISPLAY HAVING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective-transmissive optical film and a reflective-transmissive liquid crystal display device having the same, and more particularly, to a reflective-transmissive optical film having the same optical properties while reducing the number of optical sheets and a reflective-transmissive liquid crystal display device having the same. It is about.

In general, since a reflection type LCD uses light incident from the outside, the display becomes dark due to a decrease in the amount of light in a dark place, so that the displayed image cannot be properly viewed.

In addition, since a transmission type LCD uses a light source inside a device such as a backlight, it is possible to recognize an image displayed regardless of a bright or dark place, but the power consumption is increased by the amount of the light source. There is a disadvantage that it is not suitable for a portable display device or the like operated by a battery.

In order to solve these shortcomings, the recent development of a reflection-transmission liquid crystal display (Reflection and Penetration type LCD) using the above-described reflective liquid crystal display and the transmissive liquid crystal display is emerging.

FIG. 1A is a diagram schematically illustrating a general reflection-transmissive liquid crystal display, and FIG. 1B is a diagram for explaining the VT characteristic (transmittance vs. voltage characteristic) of FIG. 1A.

Referring to FIG. 1A, a general reflection-transmissive liquid crystal display device 10 includes a first polarizing plate 11, a first λ / 2 retardation film 12, and a first λ / 4 that are sequentially arranged from a surface on which artificial light is incident. The retardation film 13, the reflector 14, the liquid crystal layer 15, the color filter 16, the second lambda / 4 phase difference film 17, the second lambda / 2 phase difference film 18 and the second polarizing plate ( 19). Here, retardation films are typically used to change linearly polarized light into elliptical polarization or circularly polarized light, to change elliptical polarization or circularly polarized light into linearly polarized light, or to change the polarization direction of linearly polarized light, in particular, the first and second The λ / 2 retardation films 12 and 18 are used to change the polarization direction of linearly polarized light, and the first and second λ / 4 retardation films 13 and 17 change the linearly polarized light into circularly polarized light, It is used when changing polarized light into linearly polarized light.

When operating in the transmission mode, the artificial light provided from the backlight assembly (not shown) receives the first polarizing plate 11, the first λ / 2 retardation film 12, the first λ / 4 retardation film 13, and the liquid crystal layer 15. ), A color filter 16, a second lambda / 4 phase difference film 17, a second lambda / 2 phase difference film 18 and a second polarizing plate 19 to transmit through to display an image.

On the other hand, when operating in the reflection mode, via the second polarizing plate 19, the second lambda / 2 phase difference film 18, the second lambda / 4 phase difference film 17, the color filter 16 and the liquid crystal layer 15 Incident light is reflected using the reflector 14, the liquid crystal layer 15, the color filter 16, the second lambda / 4 phase difference film 17, the second lambda / 2 phase difference film 18 and The image is displayed by being transmitted through the second polarizing plate 19.

Here, the liquid crystal layer 15 is made of liquid crystal molecules operating in a normally white mode. That is, as shown in FIG. 1B, when the low voltage is applied, the white level is maintained, and when the high voltage is applied, the screen is displayed by changing to the black level. Of course, you can see that the VT curves coincide almost similarly, whether in transmissive or reflective mode.

However, in the above-mentioned reflection-transmissive liquid crystal display device shown in FIG. 1A, two retardation films are used under the array substrate, two retardation films are used on the color filter substrate, and a total of four retardation films are used. There is.

FIG. 2A is a diagram schematically illustrating a general reflection-transmissive liquid crystal display, and FIG. 2B is a diagram for explaining the VT characteristic of FIG. 2A.

Referring to FIG. 2A, the general reflection-transmissive liquid crystal display device 20 includes a first polarizing plate 21, a first reverse dispersion film 22, a reflecting unit 23, and a liquid crystal that are sequentially disposed from a surface on which artificial light is incident. A layer 24, a color filter 25, a second anti-dispersion film 26 and a second polarizer 27.

When operating in the transmissive mode, the artificial light provided from the backlight assembly (not shown) receives the first polarizing plate 21, the first reverse dispersion film 22, the liquid crystal layer 24, the color filter 25, and the second reverse dispersion film. The image is displayed by transmitting it through the 26 and the second polarizing plate 27.

On the other hand, when operating in the reflective mode, the natural light incident through the second polarizing plate 27, the second reverse dispersion film 26, the color filter 25 and the liquid crystal layer 24 by using the reflector 23. The light is reflected and transmitted through the liquid crystal layer 24, the color filter 25, the second reverse dispersion film 26, and the second polarizing plate 27 to display an image.

Here, the liquid crystal layer 24 is made of liquid crystal molecules operating in a normally white mode. That is, as shown in FIG. 2B, when the low voltage is applied, the white state is maintained, and when the high voltage is applied, the screen is displayed by changing to the black state. Of course, you can see that the VT curves coincide almost similarly, whether in transmissive or reflective mode.

However, in the case of using the two anti-dispersion films described above, not only color shift is severely generated depending on the direction of the light source, but also the manufacturing cost increases because a special material having anti-dispersion characteristics must be used. Due to this problem, the above-described structure shown in Fig. 2A does not employ a high-cost anti-dispersion film in the reflection-transmissive liquid crystal display device, but employs four retardation films as the structure shown in Fig. 1A. to be.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a reflection-transmissive optical film having optical characteristics similar to those of conventional optical characteristics even when two phase difference films are used for cost reduction. .

Another object of the present invention is to provide a reflection-transmissive liquid crystal display device using the above-mentioned reflection-transmissive optical film.

FIG. 1A is a diagram schematically illustrating a general reflection-transmissive liquid crystal display, and FIG. 1B is a diagram for explaining the VT characteristic.

FIG. 2A is a diagram schematically illustrating a general reflection-transmissive liquid crystal display, and FIG. 2B is a diagram for explaining the VT characteristic.

FIG. 3 is a diagram for schematically illustrating a reflection-transmissive liquid crystal display device according to the present invention, in particular showing a side view.

4 is a view for explaining an optical axis polarized by the liquid crystal display of FIG. 3 described above.

5A to 5E are diagrams illustrating an implementation principle of a dark state on a spherical curry sphere in the reflective mode operation according to the present invention, and FIG. 5E is a view for explaining dispersion characteristics of a dark state.

FIG. 6 is a diagram for describing dispersion characteristics of a dark state in a reflection mode operation according to a comparative example. FIG.

Fig. 7a shows a poangare representation of the bright state in the reflective mode according to the invention, and Fig. 7b shows the dispersion characteristics.

FIG. 8A shows a poangare representation of the bright state in the reflection mode according to the comparative example, and FIG. 8B shows the dispersion characteristics.

9a to 9d show a pore curry representation of the gray state of the reflection mode according to the invention, and FIGS. 9e to 9h show the dispersion characteristics corresponding to each of the above FIGS. 9a to 9d.

10A to 10D show the pore curry representation of the gray state in the reflection mode according to the comparative example, and FIGS. 10E to 10H show the dispersion characteristics corresponding to each of the above FIGS. 10A to 10D.

11 is a diagram schematically illustrating a transmission mode of the reflection-transmissive liquid crystal display device according to the present invention.

FIG. 12A shows the Poangcurry representation in the dark state of the transmission mode according to the comparative example, and FIG. 12B shows the VT characteristics.

FIG. 13A shows the Poang Karre representation of the dark state in transmission mode according to the invention, and FIG. 13B shows the VT characteristics.

14 is a view for comprehensively describing optical characteristics of the reflection-transmissive liquid crystal display device according to the present invention.

<Description of the symbols for the main parts of the drawings>

11, 21, 110: 1st polarizing plate 12, 120: 1st (lambda) / 2 phase difference film

13: first lambda / 4 phase difference film 14, 23, 130: reflecting portion

15, 24, 140: liquid crystal layer 16, 25, 150: color filter

17: second lambda / 4 phase difference film 18, 160: second lambda / 2 phase difference film

19, 27, 170: 2nd polarizing plate

According to one aspect of the present invention, a reflection-transmitting optical film includes a liquid crystal layer and a reflection portion formed in a portion of the liquid crystal layer, and defines an area in which the reflection portion is not formed as a transmission portion. And a liquid crystal layer corresponding to the reflecting portion reflects the phase of natural light by λ / 4 delay, and a liquid crystal layer corresponding to the transmitting portion reflects the phase of artificial light by λ / 2 delay and transmits the reflection-transmissive optics. In the film, a first polarizing plate disposed under the liquid crystal panel, the first polarizing plate to emit the artificial light by the first polarization; A first λ / 2 phase difference film disposed on the first polarizing plate and outputting the transmissive part by retarding the phase difference of the first polarized artificial light by λ / 2; A second λ / 2 retardation film disposed on the liquid crystal panel and outputting the incident artificial light or natural light by delaying λ / 2; And a second polarizing plate disposed on the second λ / 2 retardation film to emit incident artificial light or natural light by second polarization.

In addition, a reflection-transmissive liquid crystal display device according to one feature for achieving the above object of the present invention, when operating in the first mode, the first phase difference film for outputting the first delayed phase of the incident light; A second retardation film outputting by second delaying the phase of the incident light when operating in the first and second modes; A reflector formed in a partial region between the first retardation film and the second retardation film; And change the characteristics of the first delayed light to provide to the second retardation film when operating in the first mode, and change the characteristics of the second delayed light to output to the reflector when operating in the second mode. And a liquid crystal layer provided to the second retardation film by changing the characteristics of the light reflected by the reflector. Here, it is preferable that the said 1st phase difference film is a (lambda) / 4 phase (s) difference film, and the said 2nd phase difference film is a (lambda) / 4 phase (s) difference film. In addition, the liquid crystal layer is preferably made of liquid crystal molecules operating in a normally black mode.

According to such a reflection-transmissive optical film and a reflection-transmission liquid crystal display device using the same, an optical characteristic is achieved by designing a liquid crystal layer operating in a normally black mode, and employing one retardation film on each of the upper and lower sides of the liquid crystal layer. The manufacturing cost can be reduced by reducing the number of optical sheets while maintaining.

Hereinafter, with reference to the accompanying drawings, it will be described in detail the present invention.

3 is a diagram schematically illustrating a reflection-transmissive liquid crystal display device according to the present invention, and FIG. 4 is a view for explaining an optical axis polarized by the liquid crystal display device of FIG. 3.

3 and 4, the reflective-transmissive liquid crystal display device 100 according to the present invention includes a first polarizing plate 110 and a first λ / 2 phase difference film 120 sequentially arranged from a surface on which artificial light is incident. And a reflector 130, a liquid crystal layer 140, a color filter 150, a second λ / 2 retardation film 160, and a second polarizing plate 170 to display an image in response to artificial light or to react with natural light. In response to displaying an image.

The first polarizing plate 110 has a transmission axis of −8 degrees, converts incident artificial light into first polarized light and converts the linearly polarized light into light, and provides the first polarized artificial light to the first λ / 2 retardation film 120. In general, since the incident light has the same probability in all directions, the first polarizer 110 transmits only the light that vibrates in the same direction as the polarization axis of the first polarizer 110, and the rest of the other light. The light vibrating in the direction is absorbed or reflected by using a certain medium to make light vibrating only in one specific direction. That is, the first polarizing plate 110 passes only a predetermined linearly polarized light component in the incident light and provides the first polarizing plate 110 to the first λ / 2 retardation film 120.

The first λ / 2 retardation film 120 has a slow axis of 13 degrees and is provided between the partially formed reflector 130 and the liquid crystal layer 140 and the first polarizing plate 110, and thus the first polarizing plate 110. The first polarized light of the linearly polarized light component is incident to the light of the circularly polarized light component to be provided to the liquid crystal layer 140. Here, the first λ / 2 retardation film 120 is emitted by delaying the phase of the incident light λ / 2, it is preferable that λ / 2 has a value in the range of 220 to 300 [nm].

The retardation film has a structure in which a first layer made of a resin having a positive intrinsic birefringence value and a second layer made of a resin having a negative intrinsic birefringence value are laminated. The first layer and the second layer are birefringent, and the phase retardation axes are laminated at right angles to each other. It is. Since the retardation of the retardation film is the sum of the respective retardations of the first layer and the second layer, the phase retardation axes of the first layer and the second layer are laminated orthogonally to each other to form the phase plate. The retardation on the short wavelength side is small, and the retardation on the long wavelength side can be made large. As a result, the ratio Re (λ) / λ between the retardation Re (λ) at the wavelength λ of the retardation film and the wavelength can be maintained substantially constant in the visible light region.

The reflector 130 is formed on an array substrate (not shown) in which a plurality of TFT switching elements are arranged to invert the path of the light incident through the liquid crystal layer 140 to re-inject the light into the liquid crystal layer 140. Perform. On the other hand, a transmission window (not shown) is formed in a part of the plane on which the reflector plate 130 is formed, and the TFT array substrate (not shown) provided with light incident through the liquid crystal layer 140 through the transmission window. ) To the first λ / 2 retardation film 120 and the first polarizing plate 110. Of course, the light incident on the first polarizing plate 110 via the transmission window is reflected by a reflecting member (not shown) disposed below and is reincident to the first polarizing plate 110.

The liquid crystal layer 140 has a slow axis of 75 degrees, is formed between the first λ / 2 retardation film 120 and the partially formed reflector 130 and the color filter 150 and arranged by an electric field. The angle changes, and the light transmittance changes according to this arrangement angle to obtain a desired image. In particular, the liquid crystal layer 140 converts circularly polarized light into incident linearly polarized light, and converts the linearly polarized light into circularly polarized light when incident. Here, a reflector 130 is formed in a portion of the lower portion of the liquid crystal layer 140, and the transmission window is formed in the remaining region. The liquid crystal layer corresponding to the reflector has a phase delay of λ / 4 phase relative to incident light. In addition, the liquid crystal layer corresponding to the transmission window demonstrates the phase of the outgoing light relative to the incident light by lambda / 2 phase. In this case, it is preferable that the λ / 2 has a value in the range of 220 to 300 [nm], and the λ / 2 preferably has a value in the range of 120 to 150 [nm].

Here, the liquid crystal layer 140 is composed of liquid crystal molecules in a normally black mode that maintains a black state when the voltage for the screen display is not applied and gradually changes to a white state according to the applied voltage.

Next, the parameters and optical parameters representing the physical properties of the liquid crystal required to implement the normally black mode liquid crystal according to the present invention will be briefly described.

The liquid crystal parameter has a first elastic modulus K11, which is a coefficient of splay, 8.9, a second elastic modulus K22, which is a coefficient of twist, is 5.1, and a third elastic modulus, which is a coefficient of bend. K33) is 13.5, the horizontal dielectric constant (ε _∥ ), which is the dielectric constant for the electric field in the long axis direction of the liquid crystal molecules, is 15.7, the vertical dielectric constant (ε _⊥ ) is 4.5, and the pitch is 124.0 The pretilt angle [deg] is 5.0.

In addition, the optical parameters are shown in Table 1 below, and the optical parameters preferably satisfy the Cauchy formular of Equation 1 below.

n _∞ A (nm ^-2 ) zsm5342 liquid crystal n _e Distributed data n _o Distributed data λ / 2 retardation film n _e 1.55817 11296 n _o 1.55464 11110

Here, n _e is the major axis transmissivity of the liquid crystal molecules, and n _o is the minor axis transmissivity of the liquid crystal molecules.

On the other hand, the color filter 150 is formed on the transparent substrate by a thin film process, and is any one of the color pixels of RGB in which a predetermined color is expressed as light passes, and the liquid crystal layer 140 and the second lambda / 2 phase difference It arrange | positions with the film 160, and emits the incident light as it is.

The second λ / 2 retardation film 160 has a slow axis of 16 degrees and is formed between the color filter 150 and the second polarizing plate 170 to convert circularly polarized light passing through the color filter 150 into linearly polarized light, thereby forming the second polarizing plate. The linear polarized light provided from the second polarizing plate 170 is converted into circularly polarized light and provided to the color filter 150. Here, the second λ / 2 retardation film 160 is emitted by delaying the phase of incident light by λ / 2, and the λ / 2 preferably has a value in the range of 220 to 300 [nm].

The second polarizing plate 170 has a transmission axis of 0 degrees, polarizes incident natural light, and provides polarized artificial light to the second λ / 2 retardation film 160. That is, since generally the incident light has the same probability in all directions, only the light vibrating in the same direction as the polarization axis is transmitted, and the light vibrating in the other direction is absorbed using a certain medium. Or it reflects and serves to create light that vibrates only in one particular direction. That is, the second polarizing plate 170 passes only a predetermined linearly polarized light component in the incident light and provides the second polarizing plate 170 to the second λ / 2 retardation film 160.

In addition, the second polarizing plate 170 passes through a predetermined linearly polarized light component of the light provided from the second λ / 2 retardation film 160 and exits to the outside.

As described above, when the reflection-transmissive liquid crystal display device operates in the reflection mode, the optical arrangement is almost mirror symmetric with respect to the reflecting portion provided in the liquid crystal layer, and when the liquid crystal layer is operated in the transmission mode, It can be seen that the optical arrangement is almost mirror symmetric with respect to the transmission window provided in the. At this time, the angle deviation of the mirror symmetry is within ± 15 degrees, and Δnd deviation (where Δn is the anisotropic refractive index and d is the cell gap) according to the type of the liquid crystal layer and the retardation film has a ± 30nm or less.

Then, the operation of the reflection-transmissive liquid crystal display device according to the present invention is separated into a reflection mode and a transmission mode, respectively, and a brief description will be given of the characteristics of light being changed according to the dark state, the bright state, and the gray state in the corresponding mode.

First, in reflection mode operation, the implementation of the dark state is as follows. That is, natural light incident on the second polarizing plate 170 is changed to linearly polarized light of approximately 0 degrees, and is changed to linearly polarized light of approximately 30 degrees by the second λ / 2 retardation film 160. The linearly polarized light having approximately 30 degrees is passed through the color filter 150 as it is, is changed into circularly polarized light by the liquid crystal layer 140 and then applied to the reflector 130, and is reflected by the reflector 130. Circularly polarized light is changed into linearly polarized light of approximately 120 degrees by the liquid crystal layer 140. The linearly polarized light of about 120 degrees is changed into linearly polarized light of approximately 90 degrees by the second λ / 2 retardation film 160 after passing through the color filter 150 as it is, and is almost blocked by the second polarizing plate 170 to be black. The state is implemented.

Meanwhile, in the reflective mode operation, the bright state is implemented as follows. That is, natural light incident on the second polarizing plate 170 is changed to linearly polarized light of approximately 0 degrees, and is changed to linearly polarized light of approximately 30 degrees by the second λ / 2 retardation film 160. The linearly polarized light of approximately 30 degrees is passed through the color filter 150 as it is, is changed to the linearly polarized light of approximately 30 degrees by the liquid crystal layer 140 is applied to the reflector 130, reflected by the reflector 130 About 30 degrees of linearly polarized light passes through the liquid crystal layer 140 as it is. The linearly polarized light of approximately 30 degrees passes through the color filter 150 as it is, is changed into linearly polarized light of approximately 0 degrees by the second λ / 2 retardation film 160, and then passes through the second polarizing plate 170 as it is, thereby giving a bright state. Is implemented.

Meanwhile, in the reflection mode operation, the implementation of the gray state is as follows. That is, natural light incident on the second polarizing plate 170 is changed to linearly polarized light of approximately 0 degrees, and is changed to linearly polarized light of approximately 30 degrees by the second λ / 2 retardation film 160. The linearly polarized light of approximately 30 degrees is passed through the color filter 150 as it is, and is changed to light from approximately 30 degrees linearly polarized light to circularly polarized light by the liquid crystal layer 140, and then is applied to the reflector 130. The light from the linearly polarized light of approximately 30 degrees to the circularly polarized light reflected by 130 is changed from the linearly polarized light of approximately 120 degrees to the elliptical polarization and the linearly polarized light of approximately 30 degrees by the liquid crystal layer 140. The light from the linearly polarized light of approximately 120 degrees to the elliptical polarization and the linearly polarized light of approximately 30 degrees passes through the color filter 150 as it is, and is then approximately 90 degrees linearly polarized light, elliptical polarization and The light is changed to light up to approximately 0 degrees of linearly polarized light, and then applied to the second polarizing plate 170. The second polarizing plate 170 is converted into linearly polarized light from 0 to 90 degrees according to the incident light, and is emitted. Is implemented.

On the other hand, in the transmission mode of operation, the implementation of the dark state is as follows. That is, the artificial light applied to the first polarizing plate 110 is changed into linearly polarized light of 0 degrees by the first polarizing plate 110, and is changed to linearly polarized light of approximately 30 degrees while passing through the first λ / 2 retardation film 120. It is applied to the liquid crystal layer 140 and is changed to linearly polarized light of approximately 120 degrees. The light changed to the linearly polarized light of about 120 degrees is passed through the color filter 150 as it is, is applied to the second lambda / 2 phase difference film 160 is changed to a linearly polarized light of approximately 90 degrees, the linearly polarized light of approximately 90 degrees is the second The dark state is realized by being blocked by the polarizer 170.

Meanwhile, in the transmission mode operation, the implementation of the bright state is as follows. That is, the artificial light applied to the first polarizing plate 110 is changed into linearly polarized light of 0 degrees by the first polarizing plate 110, and is changed to linearly polarized light of approximately 30 degrees while passing through the first λ / 2 retardation film 120. It is applied to the liquid crystal layer 140 and is changed to linearly polarized light of approximately 30 degrees. The light changed to the linearly polarized light of approximately 30 degrees is passed through the color filter 150 as it is and is applied to the second λ / 2 retardation film 160 to be changed to the linearly polarized light of approximately 0 degrees, the linearly polarized light of approximately 0 degrees is the second The bright state is implemented while passing through the polarizing plate 170 as it is.

Meanwhile, in the transmission mode operation, the gray state is implemented, that is, the artificial light applied to the first polarizing plate 110 is changed to linearly polarized light of 0 degrees by the first polarizing plate 110, and the first λ / 2 retardation film 120 After passing through), it is changed into linearly polarized light of approximately 30 degrees and then applied to the liquid crystal layer 140 to be changed into linearly polarized light from approximately 120 degrees to 30 degrees. The light changed to the linearly polarized light from about 120 degrees to 30 degrees is passed through the color filter 150 as it is, and then applied to the second λ / 2 retardation film 160 to be changed to the linearly polarized light from approximately 90 degrees to 0 degrees. It is applied to the second polarizing plate 170. The second polarizing plate 170 is converted into a linearly polarized light from 0 degrees to 90 degrees according to the incident light and is emitted, thereby implementing a gray state.

Then, hereinafter, for convenience of description, an area in which the reflector 130 is formed is defined as a reflection area, and an area in which the reflector 130 is not formed, that is, an area in which a transmission window (not shown) is formed, is defined as a transmission area. In addition, a description will be given using a simulation waveform separately attached to the reflection mode and the transmission mode of the reflection-transmission liquid crystal display according to the present invention.

<Reflex Mode>

5A to 5D are diagrams illustrating an implementation principle of a dark state on a spherical curry sphere in the reflective mode operation according to the present invention, FIG. 5E is a diagram for explaining dispersion characteristics of a dark state, and FIG. 6 is a comparative example. It is a figure for demonstrating the dispersion | distribution characteristic of the dark state of the reflection mode in accordance with this.

In general, as an example for intuitively grasping the polarization transmission characteristics of light, the light is geometrically formed using a Poangcare sphere composed of points having Cartesian coordinates of an equation with a radius of 1 in three-dimensional space. Interpret the characteristics. That is, all the points on the equator line in the Poangcurry spherical body correspond to linearly polarized light, and the north pole corresponds to the right hand circularly polarized light and the south pole corresponds to the left hand circularly polarized light. All points in the northern hemisphere correspond to right-hand elliptical polarization, and all points in the southern hemisphere correspond to left-hand elliptical polarization.

When the light linearly polarized by the second polarizing plate 170 passes through the second λ / 2 retardation film 160, it has a dispersion characteristic of wavelengths as shown in FIG. 5A. That is, 400 [nm] light is converted into a right-hand elliptical polarization component, 550 [nm] light is converted into a linearly polarized light component, and 700 [nm] light is converted into a left-hand elliptical polarization component.

When the light dispersed by the second λ / 2 retardation film 160 is compensated with the λ / 4 designed liquid crystal layer 140, the light dispersed at the south pole is collected again as shown in FIG. 5B. That is, the light of 400 [nm], the light of 550 [nm], and the light of 700 [nm] are converted into the light of the left hand circularly polarized light component by the liquid crystal layer 140.

The light compensated by the liquid crystal layer 140 is reflected by the reflector 130 and is re-entered into the λ / 4 designed liquid crystal layer 140. . That is, 400 [nm] light is converted into a right-hand elliptical polarization component, 550 [nm] light is converted into a linearly polarized light component, and 700 [nm] light is converted into a left-hand elliptical polarization component.

This dispersed light passes through the second λ / 2 retardation film 160, and as shown in FIG. 5D, polarized light is rotated by 90 degrees with the incident light at all wavelengths, thereby achieving a good dark state. At this time, it can be confirmed that the dispersion result is similar to the dispersion characteristic according to the comparative example shown in FIG. 6. As described above with reference to FIG. 1, the comparative example may be a reflection-transmissive liquid crystal display device employing four retardation films, or the reflection-transmission liquid crystal display employing two anti-dispersion films described in FIG. 2. It may be a device.

FIG. 7A shows the poangare representation of the bright state of the reflective mode according to the invention, FIG. 7B shows the dispersion characteristic, and FIG. 8A shows the poangare representation of the bright state of the reflective mode according to the comparative example described above. 8b shows the dispersion characteristics.

As shown in FIG. 7A, light of 400 [nm] is converted into a left-hand elliptical polarization component, light of 550 [nm] is converted into a left-hand elliptical polarization and linearly polarized light component, and light of 700 [nm] is right-handed elliptical polarization. It can be confirmed that the conversion to the component.

In particular, in the design of the reflection-transmissive liquid crystal display device according to the present invention, the implementation of the bright state is dispersion for lambda modulation, whereas the design according to the comparative example is considered to be dispersion for lambda / 2 modulation, so that the dispersion characteristics are deteriorated. However, the design according to the comparative example described above has a reference axis in the bright state of 45 degrees, while the design according to the present invention has a reference axis in the bright state of 15 degrees, so as shown in FIGS. 7b and 8b, almost similar dispersion characteristics. It can be confirmed that having.

9a to 9d show a pore curry representation of the gray state of the reflection mode according to the invention, FIGS. 9e to 9h show the dispersion characteristics corresponding to each of the above FIGS. 9a to 9d and FIGS. 10a to 10d Fig. 10 shows Poangcurry representation of the gray state in the reflection mode according to the comparative example, and Figs. 10E to 10H show dispersion characteristics corresponding to each of Figs. 10A to 10D described above.

In the designs according to the comparative examples shown in FIGS. 10A to 10D, color shift occurs badly because only the liquid crystal cell exhibits dispersion characteristics in the gray state. In addition, there is a problem in that a compensation film must be added separately to compensate for the color shift.

However, in the design according to the present invention, dispersion occurs in the film, which can improve color shift because the liquid crystal cell compensates for color shift in a gray state, as shown in FIGS. 9A to 9D. Of course, the design according to the present invention does not have to provide a separate compensation film for compensating the color shift.

<Transmission mode>

On the other hand, since the transmission mode of the reflection-transmissive liquid crystal display according to the present invention is a method of designing the reflection mode to be mirror symmetric, the operation principle is the same as the reflection mode.

That is, when the reflection mode is operated, natural light is incident on the reflector 130 through the second polarizing plate 170, the second λ / 2 retardation film 160, the color filter 150, and the liquid crystal layer 140. The light incident on the reflecting unit 130 is reflected and emitted through the liquid crystal layer 140, the color filter 150, the second λ / 2 retardation film 160, and the second polarizing plate 170.

On the other hand, when operating in the transmission mode, artificial light is the first polarizing plate 110, the first λ / 2 phase difference film 120, the liquid crystal layer 140, the color filter 150, the second λ / as shown in FIG. Since it exits via the second retardation film 160 and the second polarizing plate 170, the same operation principle as the reflection mode.

However, in the reflection mode described above, once the arrangement of the incidence paths is determined, the arrangement on the reflection path cannot be changed. In the transmission mode, as shown in FIG. 11, under the mirror symmetry, that is, under the liquid crystal layer 140. Since the arrangement of the first polarizing plate 110 and the first λ / 2 retardation film 120 arranged can be varied, fine tuning can provide better optical characteristics than the reflection mode. Of course, here, the optimum conditions of the transmission mode using the two lambda / 2 phase difference film 120, 160 and the zsm5342 liquid crystal having a normally black mode are as described above with reference to FIGS. 3 and 4. same.

Then, the dispersion characteristics of the operation in the transmission mode according to the comparative example and the dispersion characteristics of the operation in the transmission mode according to the comparative example are compared with reference to the accompanying drawings. Of course, the above-described comparative example may also be a reflection-transmissive liquid crystal display device employing four retardation films, as described above with reference to FIG. 1, or the reflection-adopting two anti-dispersion films described with reference to FIG. It may be a transmissive liquid crystal display device.

FIG. 12A shows the Poang Karre representation of the dark state of the transmission mode according to the comparative example described above, FIG. 12B shows the VT characteristics, and FIG. 13A shows the Poang Karre representation of the dark state of the transmission mode according to the present invention. 13B shows the VT characteristic.

12A and 12B, since the transmission mode according to the comparative example is designed to shift the optical axis and the polarizing plate of the upper and lower films by 90 degrees with respect to the liquid crystal layer, which is a mirror symmetry point, optical and dispersion characteristics of the long axis and the short axis are optically improved. It is perfectly compensated for good dark conditions, and the contrast ratio (or CR) is above about 1000.

However, when the ECB mode is used, since it is a normally white mode, it is difficult to realize the excellent dark state unless a high voltage is applied as shown in FIG. 12B. Of course, there is a method to solve this problem by increasing the cell gap, but there is a problem in that a dark state is realized by setting a voltage, and a large step difference occurs at the boundary between the reflecting part and the transmitting part because of a large gap between the reflecting part and the transmitting part. There is a problem. As a result, if a liquid crystal layer having a normally white mode which is widely adopted at present is used as it is, it is difficult to secure a theoretically obtainable CR in the design according to the comparative example.

On the other hand, in the transmissive mode operation of the reflective-transmissive liquid crystal display according to the present invention, the dark state is only about 120 because CR cannot completely compensate the dispersion characteristics as shown in Fig. 13a. However, because of the optically normally black mode, we can obtain a CR that is almost similar to the simulated waveform shown in Figure 13b. As described above, according to the present invention, since it is not necessary to apply a high voltage in order to realize an excellent dark state, it is excellent in terms of power consumption, and does not have to increase the cell gap between the reflecting unit and the transmitting unit, thereby meeting the tendency of light and thinning of the liquid crystal display device. The level difference between the boundary portion between the reflecting portion and the transmitting portion can also be reduced.

14 is a view for comprehensively describing optical characteristics of the reflection-transmissive liquid crystal display device according to the present invention.

As shown in FIG. 14, the reflection-transmissive liquid crystal display according to the present invention maintains a perfectly dark state in the transmission mode or the reflection mode when the driving power is not applied, and at the level to which the driving power is applied. As a result, the luminance gradually increases to maintain a perfect white state from around 3 volts. In particular, in the case of the VT curve of the reflection-transmissive liquid crystal display device employing the four retardation films shown in FIG. 1B described above, or the reflection-transmissive liquid crystal employing the two reverse dispersion films shown in FIG. 2 described above. Compared with the VT curve of the display device, only the bright state and the dark state are reversed with each other, and thus, similar optical characteristics are obtained. In particular, the general reflection-transmissive liquid crystal display device has a disadvantage in that a high voltage is applied in order to implement an excellent dark state, but according to the present invention, it can be confirmed that it is excellent in power consumption because it can implement an excellent dark state even at a high voltage.

As described above, according to the present invention, even if two retardation films are employed in the reflection-transmissive liquid crystal display device, it can be confirmed that they are similar to the optical characteristics of the reflection-transmission liquid crystal display device employing four retardation films. The number of films can be reduced.

In addition, since it is similar to the optical characteristics of the reflection-transmissive liquid crystal display device employing a high-dispersion reverse dispersion film, the manufacturing cost can be reduced.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

As described above, according to the present invention, by designing a liquid crystal panel, that is, a liquid crystal layer operating in a normally black mode, even if one phase difference film is adopted on both sides of the liquid crystal layer, a general reflection-transmissive liquid crystal Compared with the optical characteristics of the display device, it can be similarly secured, thereby reducing manufacturing costs.

In addition, color shift occurring in the gray state can be improved.

In addition, in the present invention, since the liquid crystal layer operating in the normally black mode is adopted, it is advantageous not only in terms of contrast ratio, but also in the excellent dark state even when a low voltage is applied.

Claims (9)

A liquid crystal layer and a reflecting portion formed in a portion of the liquid crystal layer, and a region in which the reflecting portion is not formed is defined as a transmission portion, and the liquid crystal layer corresponding to the reflecting portion reflects the phase of natural light by? / 4 delay, The liquid crystal layer corresponding to the transmission portion is a reflection-transmissive optical film employed in the liquid crystal panel that transmits by delaying the phase of the artificial light λ / 2, A first polarizing plate disposed under the liquid crystal panel to emit artificial light with first polarization; A first λ / 2 phase difference film disposed on the first polarizing plate and outputting the transmissive part by retarding the phase difference of the first polarized artificial light by λ / 2; A second λ / 2 retardation film disposed on the liquid crystal panel and outputting the incident artificial light or natural light by delaying λ / 2; And And a second polarizing plate disposed on the second λ / 2 retardation film to emit incident artificial light or natural light by second polarization. The reflective-transmissive optical film of claim 1, wherein the optical arrangement is approximately mirror symmetrical with respect to either the reflective or transmissive portion. The reflective-transmissive optical film of claim 2, wherein the angular deviation of the mirror symmetry is within ± 15 degrees, and the Δnd deviation has ± 30 nm or less. The reflective-transmissive optical film of claim 1, wherein λ / 2 has a range of 200 to 300 nm, and λ / 4 has a range of 120 to 150 nm. A first retardation film which emits light by first retarding a phase of incident light when operating in the first mode; A second retardation film outputting by second delaying the phase of the incident light when operating in the first and second modes; A reflector formed in a partial region between the first retardation film and the second retardation film; And When operating in the first mode, the characteristics of the first delayed light is changed to provide to the second retardation film, when operating in the second mode, the characteristics of the second delayed light is changed and output to the reflector, the reflection A reflection-transmissive liquid crystal display device comprising a liquid crystal layer provided with the second retardation film by changing the characteristics of the light reflected by the negative. The method of claim 5, A first polarizing plate which firstly polarizes incident light and exits the first retardation film; And And a second polarizing plate which emits the second delayed light from the second retardation film by second polarization. The method of claim 6, wherein the first mode transmits artificial light to the first polarizing plate and transmits light emitted through the first path of the first retardation film, the liquid crystal layer, the second retardation film, and the second polarizing plate. In the second mode, light emitted through the second path of the second retardation film, the liquid crystal layer, the reflector, the liquid crystal layer, the second retardation film, and the second polarizing plate by applying natural light to the second polarizing plate. Reflection-transmissive liquid crystal display device characterized in that the reflection mode using. The reflection-transmissive liquid crystal display device according to claim 5, wherein the first retardation film is a λ / 2 retardation film, and the second retardation film is a λ / 2 retardation film. The reflection-transmissive liquid crystal display device according to claim 5, wherein the liquid crystal layer is formed of liquid crystal molecules operating in a normally black mode.