KR101217945B1 - Transflective ips liquid crystal display - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to a transparent in-plane switching (TIPS) liquid crystal display (LCD) comprising a patterned retardation film.

Description

Transflective IPS Liquid Crystal Display {TRANSFLECTIVE IPS LIQUID CRYSTAL DISPLAY}

1 shows a TIPS-LCD according to the present invention.

2 and 3 show the arrangement of optical layers in a TIPS-LCD according to a preferred embodiment of the present invention.

4A-9B show angular luminance, bright state chromaticity and angular contrast calculated for TIPS-LCDs according to Examples 1 and 2 in the transmissive scheme (a) and the reflective scheme (b). Shows.

Field of technology

The present invention relates to an in-plane switching (IPS) type of transparent liquid crystal display (LCD) comprising a patterned retardation film.

Prior art

The demand for portable electronic devices has increased interest in transflective LCDs. Transflective LCD devices use a backlight to light up the display, but can reduce power consumption by using ambient light in bright conditions. Therefore they can be seen in all ambient conditions.

A transverse display in which each pixel is divided into reflective and transmissive subpixels has been proposed for twisted and non-twisted switching cell structures (Kubo et al., IDW 1999, page 183-187; Baek et al., IDW 2000, page 41-44; WO 03/019276; Roosendaal et al., Proc. SID 2003, page 78-81). The transmissive subpixels have transmissive front and back electrodes, while the reflective subpixels have transmissive front electrodes and reflective back electrodes, such as patterned, which is achieved by a "hole-in-mirror" technique. It requires an electrode structure. Since the transmissive method uses half wavelength (λ / 2) light modulation (λ = wavelength of incident light) and the reflective method uses quarter wavelength (λ / 4) light modulation, different cell gaps ( Or LC layer thickness), it has been suggested that the reflective subpixels have about one half of the cell gap of the transparent subpixels.

In order to make the reflective subpixel work with the transmissive subpixel, an achromatic (or “wide-band”) quarter wave foil (AQWF) is required for the production of circularly polarized light [AQWF is a wide wavelength band (Preferably including the entire visible spectrum) showing an optical delay of λ / 4, for example formed by combining a QWF with a half wavelength foil (HWF) having an optical delay of λ / 2. Also, since the AQWF can cover the transmissive pixels, an even AQWF needs to be located on the backlight side of the cell.

Translucent displays typically require a total of four delays: two on the front (one QWF and one HWF) and two on the back (one QWF and one HWF). To reduce the number of films, Baek et al., IDW 2000, p. 41-44, prepared untwisted LC cells that are part of the AQWF, so that the cells are QWFs, requiring only two HWFs. Suggest that As a result, the cell is effectively switched from AQWF to a simple half-wave plate. This idea reduces the number of films and still allows the reflective state to work in association with the transmissive state, but still has the disadvantages of reduced contrast, reduced viewing angle and poor chromaticity.

WO 03/019276 and Van der Zande et al., SID 2003, p. 194-197, describe a transparent TN cell structure comprising a patterned retarder with different delays for reflective and transmissive subpixels. do. The use of patterned retarders allows for different degrees of freedom in the design of the transparent cell, and can also reduce the number of films needed to improve display quality. However, contrast, viewing angle and chromaticity are still unsatisfactory in the transmissive state.

In particular, due to the difficulty of narrow viewing cones, there has been little interest in the use of transflective displays in larger screen display devices for public places or even outdoor televisions.

It is an object of the present invention to produce a transmissive display which does not have the above-mentioned disadvantages, exhibits high contrast, brightness and low color shift over a wide viewing angle range and can be easily manufactured in a time and cost effective manner. To provide. Other objects of the present invention will immediately become apparent to those skilled in the art from the detailed description that follows.

The inventors of the present invention have found that these objects can be achieved by providing a transitive in-plane switching (IPS) type display (TIPS) claimed in the present invention.

Compared with conventional display schemes, such as the TN or VA scheme, in which the electric field is applied substantially perpendicular to the plane of the LC layer, the IPS scheme is characterized by the fact that the electric field is applied substantially parallel to the plane of the LC layer. Typical IPS displays are described, for example, in DE-A-40 00 451 and EP-A-0 588 568. In conventional displays, the IPS scheme is generally reported to have advantages in many areas (eg, as compared to the VA and TN schemes) (Endoh et al., IDW 1999, p. 187-190). In addition, suitable compensators (Kim, et al., IMID 2003, p. 1-4) or multi-domain constructs (Klausmann et al., J. Appl. Phys., 1998. 83 (4), p. 1854-1862 It has been reported that the IPS method provides a very good LCD viewing experience. In particular, the IPS technique is seen as a useful design for LC-TV, which can meet strict limits on viewing angle and color transition in transmissive devices. However, the above mentioned document does not disclose the transmissive IPS display claimed in the present invention.

The current technology of transmissive devices places limitations on the use of the IPS mode because of the need to use circularly polarized light in the reflective state. The nature of the IPS method in which the LC medium redirects its director in the plane of the display upon application of the electric field requires that circularly polarized light be equally affected, whether or not the LC cell is switched. This does not cause contrast between states.

The inventors have further discovered that these limitations can be overcome by proper design of the IPS display. For example, fabricating an IPS LC cell into the switchable QW portion of an AQW retarder and combining it with a non-switchable HWF opens up the possibility of using IPS in a translucent device because the current IPS cell is a prototype. Although no attempt is made to operate on polarized light, it is possible to take linearly polarized light and convert it to circular or leave it linear. In addition, to improve contrast, viewing angle, and chromaticity, HWFs with HWF regions covering reflective subpixels and non-delay regions covering transmissive subpixels are applied as patterned in cell retarders. In addition to improving optical performance, this also reduces the number of films, resulting in reduced thickness, higher brightness and easier and cheaper manufacturing processes.

Definition of Terms

As used herein, the term 'film' refers to a rigid or flexible self-supporting or free-standing film having mechanical stability, as well as a coating or layer on or between the supporting substrates. Include.

The term 'liquid crystal or mesogenic material' or 'liquid crystal or mesogenic compound' refers to a substance comprising one or more rod, board or disc mesogenic groups, ie groups having the ability to induce liquid crystalline phase properties or Point to a compound. In addition, liquid crystal (LC) compounds having rod or board groups are known in the art as 'calamitic' liquid crystals. In addition, liquid crystal (LC) compounds having a disk-like group are known in the art as 'discotic' liquid crystals. Compounds or materials comprising mesogenic groups do not necessarily have to show a liquid crystalline phase by themselves, they show a liquid crystalline phase only in a mixture with other compounds, or a mesogenic compound or material, or a mixture thereof can be polymerized. In this case, a liquid crystal phase may be shown.

For brevity, the term 'liquid crystal material' is hereafter used for both mesogenic and liquid crystal materials.

In addition, a polymerizable compound having one polymerizable group is referred to as a 'mono-reactive' compound, a polymerizable compound having two polymerizable groups is called a 'direactive' compound, and a polymerizable compound having more than two polymerizable groups It is referred to as a 'polyreactive' compound. Compounds without polymerizable groups are also referred to as 'non-reactive' compounds.

The term 'reactive mesogen (RM)' means a polymerizable mesogenic or liquid crystalline compound.

The term 'director' is known in the art and means the preferred orientation direction of the long molecular axis (for calamitic compounds) or the short molecular axis (for discotic compounds) of the mesogenic groups of the LC material.

In films comprising uniaxial positive birefringent LC materials, the optical axis is given by the director.

The term 'homeotropic structure' or 'homeotropic orientation' means a film whose optical axis is substantially perpendicular to the film plane (ie, substantially parallel to the film normal).

The term 'planar structure' or 'planar orientation' means a film whose optical axis is substantially parallel to the film plane.

The term 'A plate' means an optical retarder using a layer of uniaxial birefringent material having a special axis oriented parallel to the plane of the layer.

The term 'C plate' means an optical retarder using a layer of uniaxial birefringent material having a special axis oriented perpendicular to the plane of the layer.

In A- and C-plates comprising optically uniaxial birefringent liquid crystal materials with uniform orientation, the optical axis of the film is given by the direction of the special axis.

In addition, A- and C-plates comprising optically uniaxial birefringent materials with positive birefringence are referred to as '+ A / C plates' or 'positive A / C plates'. In addition, A- and C-plates comprising optically uniaxial birefringent materials having negative birefringence are referred to as '-A / C plates' or 'negative A / C plates'.

"E-way" means a twisted nematic liquid crystal display (TN-LCD) whose input polarization direction upon introduction into a display cell is substantially parallel to the director of LC molecules, ie according to extraordinary (E) refractive index. do. "O-way" means a TN-LCD whose input polarization upon introduction into a display cell is substantially perpendicular to the director, i.e. according to an ordinary (O) refractive index.

Unless stated otherwise, the term "polarization direction" of a linear polarizer means the polarizer extinction axis. In the case of stretched plastic polarizer films, for example comprising dichroic iodine based dyes, the extinction axis usually corresponds to the stretching axis.

Summary of the Invention

The present invention relates to an LC in an in-plane switching (IPS) scheme comprising an LC layer and an electrode layer switchable between different orientations upon application of an electric field having a principal component parallel to the plane of the LC layer. A cell (the electrode layer is preferably provided inside the transparent substrate); Optional front and rear polarizers which sandwich the LC cell and have front and rear polarization directions; And at least one retardation film positioned between the front polarizer and the LC layer, having a pattern of regions with defined delays and regions with substantially no delays, wherein the delay regions are arranged to essentially cover only reflective subpixels. A transflective liquid crystal display (LCD) comprising one or more pixels divided into reflective and transmissive subpixels.

The invention also provides a patterning with a pattern of regions with half wavelength (λ / 2) delay and regions substantially free of delay, for use in TIPS-LCDs comprising transmissive and reflective subpixels. Is about HWF.

As mentioned above, one problem when using IPS in a transmissive device is that circularly polarized light is affected by birefringent material regardless of its orientation so that the IPS cell is right circular in one position. In the case of switching to the left circular, when switching to another position in the plane, it behaves the same, so that no contrast occurs.

To solve this problem, an IPS cell according to the invention is made of part of a device that produces circularly polarized light. When considering standard AQWF consisting of oriented HWF and QWF to produce achromatic QWF doublet, it is possible to replace QWF with switchable LC cells, which allows the use of IPS schemes while simultaneously requiring film Can be reduced. This is ideal in a reflective state because the LC cell can be switched to produce circularly polarized light in the dark state and linearly polarized light in the bright state.

Another problem relates to display designs for transmissive states. Since light in the reflective subpixel passes through the LC layer twice, its cell gap is preferably about 0.5 times the cell gap of the transmissive subpixel, which provides the same delay. Thus, the transparent LC cell now effectively corresponds to two QWFs applied back to back. This means that the use of crossed polarizers produces high chromaticity or low contrast, all of which are not allowed. To solve this problem, a patterned retarder is used to make the reflector and the transmission work together. For example, patterned retarders are fabricated from patterned reactive mesogen materials to provide HWF delay over reflective subpixels and to provide optically isotropic regions over transmissive subpixels.

In this way, the benefits of IPS transmissive optics in combination with the desired reflective optics can be used to produce excellent transmissive displays in all respects.

In the reflective subpixel, preferably the LC layer has a quarter wavelength delay and thus has the function of a switchable quarter wavelength retarder. The delay of the LC layer in the reflective subpixel is preferably 0.25 times the incident light wavelength. The retardation value is particularly preferably 90 to 200 nm, very preferably 130 to 145 nm.

The delay of the LC layer in the transparent subpixel is preferably 0.5 times the incident light wavelength or twice the delay of the LC layer in the reflective subpixel. The retardation value is particularly preferably 180 to 400 nm, very preferably 260 to 290 nm.

The appropriate cell gap can be selected depending on the birefringence of the LC medium used. Suitable cell gaps are, for example, in the range from 0.5 to 5 μm.

Unless stated otherwise, the aforementioned delay values refer to a center wavelength of 550 nm.

Preferred TIPS-LCDs according to the invention include liquid crystal (LC) cells; A first linear polarizer on the first side of the LC cell; A second linear polarizer on the second side of the LC cell; And at least one patterned retardation film positioned between the first and second substrates of the LC cell, having a pattern of regions with different retardations and / or orientations. The orientation direction of the retardation film and the LC layer is as defined above and below, wherein the liquid crystal cell

First and second substrate planes parallel to one another, at least one of which is transparent to incident light;

An array of nonlinear electrical elements on one of the substrates, which can be used to switch each pixel of the LC cell respectively, wherein the element is preferably an active element such as a transistor, and a TFT is very preferred;

Array of color filters provided with one of the substrates, having a pattern of different pixels transmitting one of the primary red, green and blue (R, G, B) (color filters are optionally covered by the planarization layer) ;

An electrode layer provided inside of the first or second substrate, designed to apply an electric field having a main component parallel to the plane of the LC layer;

An alignment layer optionally provided on the electrode; And

LC medium switchable between two or more different orientations by electric field application
.

In order to provide an electric field substantially parallel to the plane of the LC layer, suitable IPS electrode designs, such as interdigited electrodes, are known in the art and described in the literature.

The patterned retardation film comprises an area with a defined axial-phase delay (having a value less than or greater than zero) and an area free of an axial delay. In the retarded region of the film, the optical axis is preferably parallel to the film plane (A-plate symmetry). In the non-delay region of the film, the film comprises, for example, an optically isotropic material, or the optical axis is eg perpendicular to the film plane (C-plate symmetry).

In the transmissive LCD according to the invention, a patterned retarder forms a switchable LC cell and is provided between the substrates containing the switchable LC medium ("incell" application). In comparison to conventional displays where the optical retarder is usually located between the LC cell and the polarizer, the in-cell application of the optical retarder has several advantages. For example, displays having optical retarders attached to the outside of the glass substrates that form the LC cells usually have parallax problems that can seriously impair viewing angle characteristics. If the retarder is fabricated inside the LC display cell, these parallax problems can be reduced or even eliminated.

Preferably, the patterned retarder is positioned in front of the display, preferably between the color filter and the LC medium, or between the color filter and the polarizing layer, if present.

The thickness of the patterned retarder is preferably 0.5 to 3.5 microns, very preferably 0.6 to 3 microns, most preferably 0.7 to 2.5 microns.

Preferably the patterned retarder is a half wavelength retardation film (HWF) with an axial-phase retardation (ie, viewing angle at 0 °) of 180 to 400 nm, most preferably 200 to 350 nm.

If the patterned retarder is a quarter wavelength retardation film (QWF), it preferably has an axial phase retardation of 90 to 200 nm, most preferably 100 to 175 nm.

An assembly of an LCD according to a preferred embodiment of the invention is shown schematically in FIG. 1. The top of FIG. 1 corresponds to the front portion of the display (ie, viewer surface). The lower part of FIG. 1 corresponds to the back portion (ie, backlight side) of the display. 1 shows a switchable LC medium 12 defined between two transparent planar parallel substrates 11a / b (eg glass substrates) and two polarizers 13a / b having crossed polarization directions sandwiching the substrate. Illustratively illustrates one pixel 10 of an LCD comprising a layer of.

The display further includes a pattern of reflective electrodes 14a and transparent electrodes 14b on the back side of the LC layer to form two sets of reflective subpixels 10a and transparent subpixels 10b. The transparent electrode 14b is, for example, a layer of indium tin oxide (ITO). The reflective electrode includes, for example, an ITO layer 14a1 and a reflective layer 14a2 which causes the light transmitted through the LC medium to be returned to the viewer (indicated by the curved arrow). The reflective layer 14a2 can be formed, for example, as a metal layer (eg Al) or as a mirror with holes (mirror regions are in the reflective subpixels and holes are in the transmissive subpixels). The electrode layer 14a1 and the mirror 14a2 may be adjacent layers or may be spatially separated as shown in FIG. 1.

The display further includes a color filter 15 having red, green and blue pixels and a patterned in-cell retardation film 16. In-cell delay 16 has a pattern of regions with a finite delay (has a value less than zero or greater than zero) and regions 16b having no on-axis delay. Delay region 16a covers reflective subpixel 10a and non-delay region 16b covers transmissive subpixel 10b.

If the display is of an active-matrix type as shown in Fig. 1, it is preferable that an array of nonlinear electrical elements 17 (e.g., TFTs) used to switch each pixel, respectively, on the side proximate to the electrode 14, preferably. It is also included on the side facing the side of the color filter 15.

Preferably the reflective and transmissive subpixels 10a / b have different cell gaps as indicated by the double arrows in FIG. 1. Preferably, the cell gap of the transparent subpixel 10b is twice the cell gap of the reflective subpixel 10a.

In order to achieve different cell gaps, the reflective subpixels include step 18, which may be formed, for example, from a transparent resin (eg, photoresist). Step 18 may be at the front or back of the LC cell.

The electrodes 14a / b may also be covered by an alignment layer (not shown) to induce or enhance the desired surface alignment in the LC medium 12. Optionally, there is also an alignment layer (not shown) provided between the color filter 15 and the patterned in-cell retardation film 16. In addition, the display may include a backlight (not shown) at the rear.

In TIPS-LCDs according to the invention, preferably, the optical layers comprising polarizers, LC cells, in-cell retardation films and optional additional retardation films are arranged such that their optical axes have a specific orientation direction with respect to each other.

Operation of a TIPS-LCD according to a preferred embodiment of the present invention is exemplarily described below.

The TIPS-LCD according to the first preferred embodiment of the present invention has a stack of optical layers exemplarily shown in FIG. 2 in the cross section, which is divided into a reflective subpixel 12a and a transparent subpixel 12b. A half wavelength region 16a covering the reflective subpixels and an optically isotropic region covering the reflective subpixels, including a layer, a reflector 14a, front and rear polarizers 13a / b, and a patterned in-cell HWF 16; 16b).

The transmission axis of the polarizer 13a / b is oriented at + 45 ° and -45 °, respectively, and the optical axis 16a of the HWF region is oriented at + 22.5 °.

The thickness d / 2 of the LC layer of the reflective transmissive subpixel is substantially 0.5 times the thickness of the transmissive subpixel d. The delay Δn? D of the LC layer, where Δn is the birefringence of the LC medium, is selected such that the transmissive subpixel has a substantially half-wave delay with respect to incident light and the reflective subpixel has a substantially quarter wavelength delay. .

Transmissive subpixels work in the same way as a normal IPS cell. The LC layer has a substantially planar alignment in the selected or bright (white) state (field applied) and in the unselected or dark (black) state (field not applied). In the dark state, the LC director orientation, for example given by the rubbing direction of the cell surface, is preferably parallel and perpendicular to the front and rear polarizer directions, respectively. In the bright state, most of the LC layer in the cell is preferably switched to a director orientation (in mono-domain IPS LCD) of ± 45 ° with respect to the front and rear polarizer directions (generally, one field). When applied to this IPS display, some LC molecules (such as LC molecules on the substrate) are not rearranged according to the field, so the average director must be estimated to calculate the switching]. Light entering the display from the backlight side is linearly polarized by the back polarizer. In the dark state, the polarization orientation of the light is not affected, so the light is blocked by the crossed front polarizers. In the bright state, the direction of polarization of light is rotated by the LC layer (having an average orientation of ± 45 ° and half wavelength delay), so that light can pass through the front polarizer.

In another preferred embodiment, the TIPS-LCDs are subdivided into multiple (e.g., two) domains with different orientation directions of the LC director in the white state where the transmissive subpixels 10b have improved viewing angle characteristics. Coming is a multi-domain display. This can be accomplished, for example, by providing a multi-domain alignment layer comprising different orientation directions as desired or by a specific electrode design. In a preferred TIPS-LCD, the transmissive subpixel comprises two domains with LC director orientation directions (in white state) of both + 45 ° and -45 ° relative to the front and rear polarizer directions. This creates a very wide viewing angle and very low chromaticity problems. Since reflective subpixels are self-compensating, they do not necessarily have to have a multi-domain structure, but may be multi-domain.

The reflective state is practically formed as the switchable QW portion of the AQW retarder using the reflective subpixel of the LC cell 10a (the AQW retarder is a combination of the QW and HW retarders). The HWF portion rotates the polarization plane of light (transmitted by the front polarizer) by 45 ° because the optical axis is formed by the patterned retarder 16a, which is oriented at 22.5 ° with respect to the extinction axis of the front polarizer.

In the dark state, when light interacts with the IPS cell, the light is polarized 45 ° in plane from the slow axis of the IPS cell. The LC orientation direction in the unselected state is preferably the same in the reflective and transmissive subpixels. Since the IPS cell has only a quarter wavelength delay due to the reduced thickness, this converts linearly polarized light into circularly polarized light. The combination of HWF and QW-IPS cells (forming the AQW retarder) means that the light is circularly polarized over the entire visible spectrum. When light encounters the reflector, it is converted into circularly polarized light of opposite handedness. When regressing through a combination of QW-IPS and HWF, the light is blocked by being converted to linearly polarized light oriented in the plane of the extinction axis of the front polarizer.

Switching the QW-IPS cell to + 45 ° or -45 ° (because it is self-compensating, there is no need for a dual-domain in the reflective cell) creates a bright state. HWF now rotates the light to be parallel or perpendicular to the slow axis of the cell. The light is not converted into a circularly polarized light, but is encountered by the reflector as linearly polarized light. Linearly polarized light passes back through the switched IPS cell. When passing through the HWF, the polarization direction is rotated again in the direction of the transmission axis of the front polarizer, so that light can pass through the front polarizer.

The manner described above is a preferred way to enable the TIPS-LCDs to operate without damaging any of the other states. Generating achromatic circularly polarized light using only one retardation film makes the design very attractive and also allows additional compensation of the transmissive state. For example, by the use of an A-plate and + C plate retarder at the back of the display, it is possible to compensate for light leakage of the polarizer at positions 45, 135, 225 and 315 degrees off the axis.

Thus, a TIPS-LCD according to another preferred embodiment of the present invention has a stack of optical layers comprising the optical component shown in FIG. 2, as exemplarily shown in FIG. 3. The display further comprises a rear + C plate retarder 19 having an optical axis perpendicular to the film plane and a rear + A plate retarder 20 having an optical axis parallel to the film plane. The transmission axis of the polarizer 13a / b is oriented at + 45 ° and -45 °, respectively, the optical axis of the in-cell HWF region 16a is oriented at + 112.5 °, and the optical axis of the + A-plate 20 is + 45 °. Is oriented.

The addition of the + A- and + C-plates improves the contrast at the wide viewing angle. Thus, a contrast ratio of up to 100: 1 or more can be achieved for viewing angles up to 80 ° or more, which is ideal for transflective televisions.

The in-cell retarder further shows a pattern of R-, G- and B-pixels with three different delays, covering the reflective subpixels, where the delay in the R-, G- and B-pixels of the film The efficiency of converting linearly polarized light into circularly polarized light is selected to be optimized for color red (R), green (G) or blue (B), respectively. The retarder is positioned so that the R-, G- and B-pixels cover the corresponding reflective R-, G- and B-subpixels of the display.

In R, G, B-pixelized QWF, the delay values at R-, G- and B- are preferably selected as follows:

In red light with a wavelength of 600 nm, the retardation is 140 to 190 nm, preferably 145 to 180 nm, very preferably 145 to 160 nm, most preferably 150 nm.

In red light with a wavelength of 550 nm, the retardation is 122 to 152 nm, preferably 127 to 147 nm, very preferably 132 to 142 nm and most preferably 137 nm.

In blue light with a wavelength of 450 nm, the retardation is 85 to 120 nm, preferably 90 to 115 nm, very preferably 100 to 115 nm and most preferably 112 nm.

In R, G, B-pixelized HWF, the delay value in R-, G- and B-pixels is preferably twice the desired value of QWF as given above.

In the LCD according to the invention, the linear polarizer is a standard light absorbing polarizer comprising, for example, a stretched dye-doped plastic film. In addition, as described in EP-A-0 397 263, a linear polarizer comprising a polymerized LC material having a uniform planar orientation and dichroic dye absorbing visible light can be used.

A-plates are elongated plastic films as disclosed in WO 98/04651 or films of polymerized LC materials having a planar structure. C-plates are films of polymerized LC materials having a homeotropic structure as disclosed, for example, in WO 98/00475. It is also possible to use other A-plate and C-plate retarders known from the prior art, for example as described in US Pat. No. 5,619,352.

Polarizers and external retarders such as A-plates and C-plates may be attached to the substrate by an adhesive layer, such as a commercially available PSA film (pressure sensitive adhesive).

Preferably the incell retarder is a film comprising a polymerized LC material optionally having a retardation and / or orientation pattern. They can be applied in-cell (ie, inside the substrate forming the LC) to eliminate parallax problems and patterned using UV light to form isotropic regions over the transmissive portion of the display. In principle, any in-cell applicable patterned retarder can be used.

Unpatterned QWFs and HWFs comprising polymerized LC materials are known in the art and are described, for example, in EP-A-1363144.

Patterned retarders suitable for use in LCDs according to the present invention have been described in the prior art. See, eg, WO 03/019276 and Van der Zande et al., Proceedings of the SID 2003, p. 194-197 may be used.

Particular preference is given to the patterned optical retardation film described in WO 2004/090025 A1. Preferably, the patterned film comprises a) providing a layer of polymerizable LC material comprising at least one photoisomerizable compound on a substrate; b) aligning the layer of LC material in a planar orientation; c) exposing the LC material in the layer or in selected areas of the layer to light irradiation (preferably UV radiation) causing isomerization of the isomerizable compound; d) polymerizing the LC material in at least a portion of the exposed area of the material to fix the orientation; And e) optionally, removing the polymerized film from the substrate, wherein the retardation and / or orientation of the LC material is varied by varying the amount and / or type of the photoisomerizable compound. And / or by varying the intensity and / or exposure time of light irradiation.

Preferably, the LC material is exposed to irradiation causing photoisomerization and photopolymerization, wherein the steps of photoisomerization and photopolymerization are carried out under different conditions, in particular under different gas atmospheres, particularly preferably photoisomerization In the presence of oxygen, photopolymerization is carried out in the absence of oxygen.

Particular preference is given to polymerized liquid crystal (LC) materials having two or more regions with different retardations and two or more regions with different orientations of the LC material, wherein the regions with different retardations may also differ in orientation, or they may be different regions. Can be. Thus, for example, the film has a pattern of first and second regions where the first and second regions differ in both retardation and orientation. In other embodiments, the film may comprise a first, second, wherein the first and second regions differ in one of retardation and orientation, and the third region differs in at least one of the first and second regions and at least one of retardation and orientation. It has a 2nd and 3rd area. In other embodiments, the film has a first, second, third, and fourth region, each of which has a different delay than the other regions, two of which have the same orientation. Other combinations are also possible.

In addition to the specific conditions and materials described herein, steps a) to e) can be carried out according to standard procedures known to those skilled in the art and described in the literature.

The polymerizable LC material comprises a photoisomerizable compound, preferably a photoisomerizable mesogenic compound or an LC compound, very preferably also a polymerizable and photoisomerizable compound. Isomerizable compounds change in shape, for example by E-Z-isomerization, upon irradiation of a particular wavelength, such as UV-irradiation. This results in a break in the uniform planar orientation of the LC material, resulting in a decrease in birefringence. Since the optical retardation of the oriented LC layer is given as the product of the layer thickness d and the birefringence Δn of the LC material, d? Δn, the decrease in the birefringence also causes a decrease in the delay in the irradiated portion of the LC material. Thereafter, the orientation and retardation of the LC is fixed by in-situ polymerization of the irradiated regions of the entire film.

Polymerization of the LC material is achieved for example by thermal or photopolymerization. If photopolymerization is used, the type of irradiation used for photoisomerization and photopolymerization of the LC material may be the same or different. In the case of irradiation, for example, UV-irradiation of wavelengths that can cause both photoisomerization and photopolymerization of LC materials is used, and the steps of photoisomerization and photopolymerization are preferably carried out under different conditions, in particular under different gas atmospheres. . In this case, photoisomerization is preferably carried out in the presence of oxygen, for example in air, and photopolymerization is carried out in the absence of oxygen, particularly preferably in an inert gas atmosphere, such as a noble gas such as nitrogen or argon. do. If the isomerization step is carried out in the presence of oxygen or in air, the oxygen removes the free radicals generated from the photoinitiators present in the material and thus prevents polymerization. In the next step, oxygen or air is removed and replaced by an inert gas such as nitrogen or argon, causing the polymerization to occur. This allows for better control of the process steps.

The degree of isomerization and thus the change in birefringence in the layer of LC material can be controlled, for example, by varying the dosage, ie intensity, exposure time and / or irradiation output. Further, by applying a photomask between the irradiation source and the LC layer, it is possible to produce a film having a pattern of regions or pixels, each having a specific retardation value different from each other. For example, a film consisting of two different retardation values can be produced using a simple monochrome mask. More complex films showing multiple regions of different delays can be created using grey-scale masks. After the desired delay value is achieved, the LC layer is polymerized. In this way it is possible to produce a polymer retardation film having a retardation value ranging from the retardation value of the initial LC layer to zero. The retardation value for the initial LC material layer is controlled by the appropriate choice of layer thickness and the type and amount of the individual components of the LC material.

The polymerizable LC material is a nematic or smectic LC material, in particular a nematic material and preferably comprises at least one direactive or polyreactive achiral RM and optionally at least one monoreactive achiral RM. Include. By the use of direactive or polyreactive RMs, crosslinked films are obtained which have a permanently fixed structure and exhibit high mechanical stability and stability of high optical properties to external environments such as temperature or solvent. Particular preference is thus given to films comprising crosslinked LC materials.

The polymerizable mesogenic mono-, di- and polyreactive compounds used in the present invention are described in standard methods of known methods and organic chemistry, such as Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. It can be produced by the method.

Examples of suitable polymerizable mesogenic compounds that can be used as monomers or comonomers in the polymerizable LC mixture are described, for example, in WO 93/22397, EP 0 261 712, DE 195 04 224, WO 95/22586, WO 97/00600 and GB 2 351 734. However, the compounds disclosed in these documents should only be considered as examples which do not limit the scope of the invention.

Examples of particularly useful polymeric mesogenic compounds (reactive mesogens) are listed below, which are taken as examples only and are not intended to limit the invention in any way and to illustrate the invention:

Wherein P is a polymerizable group, preferably an acrylic, methacryl, vinyl, vinyloxy, propenyl ether, epoxy, oxetane or styryl group, x and y being the same or different integers from 1 to 12 , A is 1,4-phenylene or 1,4-cyclohexylene optionally mono-, di- or trisubstituted by L ¹ , u and v are each independently 0 or 1, and Z ⁰ is -COO-, -OCO-, -CH ₂ CH _2- , -CH = CH-, -C≡C- or a single bond, R ⁰ is a polar group or a nonpolar group, L, L ¹ and L ² are each other Each independently is H, F, Cl, CN or an alkyl, alkoxy, alkylcarbonyl, alkylcarbonyloxy, alkoxycarbonyl or alkoxycarbonyloxy group having 1 to 7 carbon atoms optionally halogenated, r is 0 , 1, 2, 3 or 4. In the above formula, the phenyl ring is optionally substituted by 1, 2, 3 or 4 L groups.

In this relationship the term 'polar group' refers to F, Cl, CN, NO ₂ , OH, OCH ₃ , OCN, SCN, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy having up to 4 carbon atoms optionally halogenated Or an alkoxycarbonyloxy group or a group selected from mono-, oligo- or polyfluorinated alkyl or alkoxy groups having 1 to 4 carbon atoms. The term 'non-polar group' refers to optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbon having one or more, preferably 1 to 12, carbon atoms not covered by the definition of 'polar group' It refers to a silyloxy or alkoxycarbonyloxy group.

Particular preference is given to mixtures comprising at least one polymerizable compound (such as a compound of formula (Ig) above) comprising an acetylene or tolaine group having a high birefringence. Suitable polymerizable tolanes are described, for example, in GB 2,351,734.

Suitable photoisomerizable compounds are known in the art. Examples of photoisomerizable compounds include azobenzene, benzaldoxime, azomethine, stilbene, spiropyran, spiroxadine, fulgide, diarylethene, cinamate. Further examples are 2-methyleneinin-1-one as described in EP 1 247 796 and (bis-) benzylidenecycloalkanones as described in EP 1 247 797, for example.

Particularly preferably, the LC material comprises at least one cinnamate, in particular for example cinnamate reactive mesogen (RM) described in US Pat. No. 5,770,107 (P0095421) and EP 02008230.1. Very preferably, the LC material comprises at least one cinnamate RM selected from compounds of the formula:

Where

P, A and v have the meanings described above, L has ^one of the meanings of L ¹ defined above, and Sp is an alkylene or alkyleneoxy having a spacer group such as 1 to 12 carbon atoms, or a single bond R is Y or R ^{0 as} defined above, or P-Sp.

Particular preference is given to cinamate RMs containing the polar terminal groups Y defined above. Very preferred are cinamate RMs in which R is Y in formulas 3a and 4a.

The irradiation used to cause photoisomerization in the LC material depends on the type of photoisomerizable compound and can be readily selected by one skilled in the art. In general, compounds which exhibit photoisomerization induced by UV-irradiation are preferred. For example, for cinnamate compounds such as the compounds of Formulas 3a, 4a and 5a, UV-radiation having a wavelength in the UV-A range (320-400 nm) or a wavelength of 365 nm is typically used.

Polymerizable LC materials containing large amounts of photoisomerizable compounds have been found to be particularly useful for the purposes of the present invention because they allow for ease of control and adjustment of the delay of the optical retardation film. For example, oriented layers of LC mixtures containing large amounts of photoisomerizable compounds, treated with radiation to induce photoisomerization, show a large delay reduction as the irradiation time increases. In such materials, the delay can be changed within a wider range of values and more accurately controlled by varying the irradiation time when compared to a material showing only a slight delay change.

Thus, according to a preferred embodiment of the invention, the polymerizable component of the polymerizable LC material is at least 12 mole% of the photoisomerizable compounds, preferably cinnamate RM, most preferably in the compounds of formulas 3a, 4a and 5a It includes the compound selected.

The term 'polymerizable component' includes polymerizable mesogenic and non-mesogenic compounds in the total polymerizable mixture and does not include other nonpolymerizable components and additives such as initiators, surfactants, stabilizer solvents and the like.

Preferably, the polymerizable component of the LC material is 12 to 100 mol%, very preferably 40 to 100 mol%, in particular 60 to 100 mol%, most preferably 80 to 100 mol% of the photoisomerizable compounds, Preferably cinnamate RM, most preferably compounds selected from compounds of the formulas 3a, 4a and 5a.

In another preferred embodiment, the polymerizable component of the LC material is from 20 to 99 mole percent, very preferably from 30 to 80 mole percent, most preferably from 40 to 65 mole percent of photoisomerizable compounds, preferably cinnamates. RM, most preferably compounds selected from compounds of formulas 3a, 4a and 5a.

In another preferred embodiment, the polymerizable component of the LC material comprises 100 mole% of photoisomerizable RM, preferably cinnamate RM, most preferably a compound selected from compounds of formulas 3a, 4a and 5a.

The tilt angle θ of the LC-molecule (director) in the polymerized film can be measured from the delay measurement. These measurements indicate that the original planar orientation changes to tilt or splayed orientation when the LC material is exposed to light irradiation used for photoisomerization for longer periods of time or when exposed to higher irradiation intensities. Shows. Note that such splayed films do not show reverse tilt defects, which are usually associated with splayed LC films formed on low pretilt substrates. Therefore, the method according to the present invention provides an excellent method of obtaining a uniform splay type retardation film.

Thus, according to another preferred embodiment of the invention, the orientation of the LC material in the film is controlled by varying the irradiation time and / or the intensity of the light irradiation used to cause isomerization in the LC material. In addition, this preferred embodiment has a splay-like structure and exhibits a reduced number of inverse tilt defects by varying the orientation in the layer of polymerizable LC material with planar orientation as described above in steps a) to e). Or even tilt free of polymerized LC film.

This embodiment also relates to a splayed film obtained by the above method, preferably having a thickness of less than 3 μm, very preferably 0.5 to 2.5 μm.

Optimum irradiation time and irradiation intensity depend on the type of LC material used, in particular the type and amount of photoisomerizable compounds in the LC material.

As mentioned above, for example, the delay reduction of the polymerizable LC material containing cinnamate RM is greater in mixtures with high concentrations of cinnamate RM. On the other hand, irradiating the polymerizable LC material with high UV-light irradiation results in the formation of a splay type film.

Thus, another method of controlling the change in retardation and orientation in the LC layer is to reduce the maximum delay achieved by photoisomerization as a function of the concentration of the photoisomerizable compound while still maintaining the planar orientation in the LC layer. By limiting

In the case where no change in orientation from planar orientation to splay type orientation is required, in the polymerizable LC mixture used in the method for producing the film according to the invention, the polymerizable component is preferably 40 to 90 mol%, very preferably 50 to 70% of the photoisomerizable cinnamate compounds of Formulas 3a, 4a and / or 5a.

If a change in orientation from planar orientation to splayed orientation is desired, in the polymerizable LC mixture used in the process for producing the film according to the invention, the polymerizable component is preferably 100% of the formulas 3a, 4a and / or 5a. Photoisomerizable cinamate compounds.

In addition, when a change in orientation from a planar orientation to a splay type orientation is desired, the polymerizable LC mixture used in the method for producing a film according to the present invention may be prepared by using a photoisomerizable cinnamate compound of formula 3a or 4a wherein R is an alkyl group. do not include.

Using photomask techniques, a method according to this second preferred embodiment can be used for the production of a patterned film comprising regions with different orientations and / or different retardations.

Particular preference is given to films comprising at least one region having a planar orientation and at least one region having a splayed orientation.

Preference is also given to films comprising at least one region with a zero delay.

The method described above is also used to produce a multilayer comprising a plurality of polymerized LC films, each having a LC material in a different orientation, by a method comprising the following steps:

A) providing a first layer of a polymerizable LC material comprising at least one photoisomerizable compound on a substrate;

B) aligning the first layer of LC material in a planar orientation and polymerizing the material to fix the orientation; And

C) providing a second layer of LC material as described in steps A) and B), wherein the first layer serves as a substrate, wherein at or at one or more of said first and second layers The LC material in the selected area is exposed to light irradiation, preferably UV radiation, which causes isomerization of the isomerizable compound prior to polymerization.

Particular preference is given to multilayers comprising at least two, very preferably two, three or four polymerized LC films.

For example, a first polymerized planar LC film is prepared as described above. This film is used as the substrate and then coated with a second layer of the same LC mixture. The second layer is then aligned in a planar orientation. As such, a stack comprising two polymerized planar LC films can be produced. The second layer exhibits a splayed structure prior to polymerization, for example when irradiated with a sufficient dose of UV-light. Thus, stacks comprising planar and splayed polymerized LC films can be made.

If the LC mixture in the first layer is irradiated with a sufficient dose of UV-light prior to polymerization, the first layer shows a splayed LC film. If a second layer of the same LC mixture is coated on such a splayed film and irradiated prior to polymerization, the second layer forms a homeotropically aligned layer, thus stacking a splayed homeotropic film Can be prepared.

Particular preference is given to multilayers comprising at least one layer having a planar orientation and at least one layer having a splayed orientation.

Preference is also given to a multilayer comprising at least one layer having a splayed orientation and at least one layer having a homeotropic orientation.

It is also possible to combine the above methods to produce a film having a pattern of regions with different orientations and regions with different retardations.

Combining the above methods, it is also possible to produce multilayers comprising two or more layers, one or more of which have a pattern of regions with different orientations and / or different delays.

To prepare the polymer film, preferably the polymerizable LC mixture is coated onto a substrate, preferably aligned in a planar orientation, and isomerized to produce a pattern of the desired retardation or orientation, for example heat or actinic radiation ( actinic) to polymerize in situ by exposure to irradiation to fix the orientation of the LC molecules. Alignment and curing take place in the LC phase of the mixture.

In the display and optical device according to the invention, preferably polymerizable and isomerizable LC materials are applied on the color filter serving as the substrate or on the alignment layer applied to the color filter.

The polymerizable LC material may be applied onto the substrate by conventional coating techniques such as spin-coating or blade coating. In addition, conventional printing techniques known to those skilled in the art, such as screen printing, offset printing, reel-to-reel printing, letter press printing, gravure printing, rotogravure printing, flexographic printing, intaglio printing, It can be applied to the substrate by pad printing, heat-sealed printing, ink-jet printing or printing by stamp or printing plate.

It is also possible to dissolve the polymerizable mesogenic material in a suitable solvent. This solution is then coated or printed onto the substrate, for example by spin-coating or other known techniques, and the solvent is evaporated prior to polymerization. In most cases, heating is suitable to facilitate evaporation of the solvent. As the solvent, for example, standard organic solvents can be used. Solvents are, for example, ketones such as acetone, methyl ethyl ketone, methyl propyl ketone or cyclohexanone; Acetates such as methyl, ethyl or butyl acetate or methyl acetoacetate; Alcohols such as methanol, ethanol or isopropyl alcohol; Aromatic solvents such as toluene or xylene; Halogenated hydrocarbons such as di- or trichloromethane, glycols or esters thereof such as PGMEA (propyl glycol monomethyl ether acetate), γ-butyrolactone and the like. It may also be a binary, ternary or more mixture of the solvents.

Initial alignment (eg, planar alignment) of the polymerizable LC material can be achieved by coating a magnetic or electric field, for example by rubbing treatment of a substrate coated with the material, by shearing the material during or after coating, by applying an alignment layer By applying to the prepared material, it can be achieved by adding the surface-active compound to the LC material. Review of the alignment technique is described, for example, in I. Sage in "Thermotropic liquid Crystals" edited by G. W. Gray, John Wiley & Sons, 1987, pages 75-77 and T. Uchida and H. Seki in "Liquid Crystals-Applications and Uses Vol. 3" edited by B. Bahadur, World Scientific Publishing, Singapore 1992, pages 1-63. Review of alignment materials and techniques is described in J. Chem. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1 (1981), 1-77.

In another preferred embodiment, the polymerizable LC material comprises an additive that induces or enhances the planar alignment of the liquid crystal material on the substrate. Preferably the additive comprises at least one surfactant. Suitable surfactants are described, for example, in J. Cognard, Mol. Cryst. Liq. Cryst. 78 , Supplement 1, 1-77 (1981). Nonionic surfactants, in particular fluorocarbon surfactants, such as the commercially available fluorocarbon surfactant Fluorad FC-171® (3M Corporation) or Zonyl FSN® (Dupont) and GB Particular preference is given to the surfactants described in 0227108.8.

In another preferred embodiment, an alignment layer is applied on the substrate and a polymerizable LC material is applied on the alignment layer to form a retardation film. The alignment layer leads to the desired initial orientation, such as planar orientation, in the LC material. The LC material is then isomerized and cured as described above. Suitable alignment layers are known in the art and are, for example, rubbed polyimides prepared by photoalignment or alignment layers described in US 5,602,661, US 5,389,698 or US 6,717,644.

Polymerization is accomplished, for example, by exposure to heat or actinic radiation. Actinic radiation means light irradiation, such as UV light, IR light or visible light, X-rays or gamma radiation, or high energy particles such as ionic or electron radiation. Preferably, the polymerization is carried out by UV irradiation at non-absorbing wavelengths. As a light source of actinic irradiation, for example, a single UV lamp or a set of UV lamps can be used. Curing time can be shortened when using high lamp power. Other possible light sources for light irradiation are lasers such as UV lasers, IR lasers or visible light lasers.

The polymerization is carried out in the presence of an initiator which absorbs at the wavelength of actinic radiation. For example, in the case of polymerization by UV light, photoinitiators can be used which generate free radicals or ions which decompose under UV radiation to initiate the polymerization reaction. When curing the polymerizable material having an acrylate or methacrylate group, a radical photoinitiator is preferably used, and when curing the polymerizable material having vinyl, epoxide and oxetane groups, a cationic photoinitiator is preferably used. . Moreover, you may use the polymerization initiator which produces | generates the free radical or ion which decomposes at the time of a heating, and starts superposition | polymerization. As standard photoinitiators in radical polymerization, for example, commercially available Irgacure 651, Irgacure 184, Darocure 1173 or Darocure 4205 (all of which are available from Ciba-Geige AG) can be used, while cationic photopolymerization In the case of commercially available UVI 6974 (union carbide) can be used.

The curing time depends inter alia on the polymerizable material, the thickness of the coated layer, the type of polymerization initiator and the output of the UV lamp. The curing time according to the invention is preferably not longer than 10 minutes, particularly preferably not longer than 5 minutes and very particularly preferably shorter than 2 minutes. For mass production, short curing times of 3 minutes or less, very preferably 1 minute or less, in particular 30 seconds or less, are preferred.

The mixture can also contain one or more dyes, in particular UV dyes, such as 4,4'-axicinazole or commercially available Tinubin (Switzerland Vaselle), having an absorption maximum adjusted for the wavelength of the radiation used in the polymerization. Siva AG products of the material).

In another preferred embodiment, the mixture of polymerizable materials comprises at least 70%, preferably 1 to 50%, of at least one monoreactive non-mesogenic compound having one polymerizable functional group. Typical examples are alkyl acrylates or alkyl methacrylates.

In order to increase the crosslinking of the polymer, up to 20% of at least one non-mesogenic compound having at least two polymerizable functional groups in the polymerizable LC material is selected from the group consisting of di- or polyfunctional polymerizable mesogenic compounds for increasing the crosslinking of the polymer. In addition to or in addition to one or more of these may be added. Typical examples for direactive non-mesogenic monomers are alkyl diacrylates or alkyl dimethacrylates having alkyl groups of 1 to 20 carbon atoms. Typical examples for multifunctional non-mesogenic monomers are trimethylpropane trimethacrylate or pentaerythritol tetraacrylate.

It is also possible to add one or more chain transfer agents to the polymerizable material to modify the physical properties of the polymer film. Particularly preferably a thiol compound, such as a monofunctional thiol compound such as dodecane thiol, or a polyfunctional thiol compound such as trimethylpropane tri (3), as disclosed, for example, in WO 96/12209, WO 96/25470 or US 6,420,001 Mercaptopropionate), very preferably a mesogenic or liquid crystalline thiol compound. When a chain transfer agent is added, the length of the free polymer chains in the polymer film of the invention and / or the length of the polymer chains between the two crosslinks can be controlled. When the amount of chain transfer agent increases, the polymer length in the polymer film obtained decreases.

The polymerizable LC material may further comprise one or more monomers and / or one or more dispersing aids capable of forming a polymeric binder or polymeric binder. Suitable binders and dispersing aids are disclosed for example in WO 96/02597. However, LC materials that do not contain binders or dispersion aids are particularly preferred.

The polymerizable LC material may include one or more suitable components such as catalysts, photosensitizers, stabilizers, inhibitors, chain-trasfer agents, co-reacting monomers, surface-active compounds, lubricants, wetting agents, dispersants , Hydrophobizing agents, adhesives, flow improvers, antifoams, degassers, diluents, reactive diluents, adjuvants, colorants, dyes or pigments.

Unlike the patterned layer as described above, it is also patterned by polymerizing different regions at different temperatures with different birefringence and different retardation, for example using a polymerizable LC material layer that does not need to contain an isomerizable compound. Films can be produced.

The following examples serve to illustrate the invention without limiting the invention. In this example, all temperatures are given in degrees Celsius and all percentages are given in weight percent unless otherwise noted. Simulation of optical performance such as luminance, chromaticity and contrast plots is carried out using the Berreman 4x4 matrix calculation.

Example

Example 1 Preparation of Patterned HWF

The following polymerizable LC mixture is blended:

Compound 14.4%

Compound 18.0%

Compound 17.0%

Compound 17.0%

Compound 22.0%

Irgacure 651 1.0%

Fluoride FC 171 0.6%

Compounds of formulas 1-5 are described in the prior art. Irgacure 651 is a commercially available photoinitiator (Ciba AG, Vassel, Switzerland). Fluoride FC 171 is a commercially available nonionic surfactant (3M).

The mixture was dissolved to yield a 50 wt% solution in xylene. This solution was filtered (0.2 μm PTFE membrane) and spin coated onto a glass / rubbed polyimide slide (low pretilt polyimide JSR AL1054 from Japan Synthetic Rubber). The coated film was exposed to 20 mWcm ^-2 365 nm radiation through a grey-scale (0: 50: 100% T) mask in air.

The film was then photopolymerized using 20 mWcm ^-2 UV-A irradiation for 60 seconds under a nitrogen atmosphere to obtain a patterned film having a pattern of regions with different delays.

Example 2-TIPS-Display

The optical performance of the TIPS-LCD with the stack of optical layers shown in FIG. 2 was calculated. The parameters of the components are as follows:

Front polarizer direction: + 45 °

Rear polarizer orientation: -45 °

LC director orientation (transparent subpixel, dark): + 135 °

LC director orientation (transparent subpixel, bright): + 90/180 ° (dual-domain)

LC retardation (transparent subpixel): 275 nm

LC director orientation (reflective subpixel, dark): 135 °

LC director orientation (reflective subpixel, bright): 90 or 180 °

LC retardation (reflective subpixel): 138 nm

Optical axis of incell HWF (reflective subpixel): + 22.5 °

In-cell HWF delay (reflective subpixels): 275 nm

Patterned in-cell HWF can be prepared for the example described in Example 1.

Angular luminance of the transmissive and reflective subpixels is shown in FIG. 4. Axial-phase luminance is 45.4% (transparent) and 47.1% (reflective).

The bright state chromaticity plot of the transmissive and reflective subpixels is shown in FIG. 5. Chromaticity is 1.1% (transparent) and 0.9% (reflective).

On-axis contrast of the transmissive and reflective subpixels is shown in FIG. 6. The average angles of contrast greater than 10: 1 (> 10: 1) are 79.4 ° (transparent) and 49.0 ° (reflective). The average angles of contrast greater than 100: 1 (> 100: 1) are 52.2 ° (permeable) and 21.7 ° (reflective).

Example 3-TIPS-Display

The optical performance of the TIPS-LCD with the stack of optical layers shown in FIG. 3 was calculated.

The parameters of the components are as follows:

Front polarizer direction: + 45 °

Rear polarizer orientation: -45 °

LC director orientation (transparent subpixel, dark): + 45 °

LC director orientation (transparent subpixel, bright): + 0/90 ° (dual-domain)

LC retardation (transparent subpixel): 275 nm

LC director orientation (reflective subpixels, dark): 45 °

LC director orientation (reflective subpixel, bright): 0 or 90 °

LC retardation (reflective subpixel): 138 nm

In-axis HWF optical axis (reflective subpixel): + 112.5 °

In-cell HWF delay (reflective subpixels): 275 nm

+ C-plate delay: 90 nm

+ A-plate optical axis: + 45 °

+ A-plate delay: 138nm

Patterned in-cell HWF can be prepared for the example described in Example 1.

Angular luminance of the transmissive and reflective subpixels is shown in FIG. 7. The on-axis brightness is 46.3% (transparent) and 47.3% (reflective).

The bright state chromaticity plot of the transmissive and reflective subpixels is shown in FIG. 8. Chromaticity is 1.1% (transparent) and 1.5% (reflective).

On-axis contrast of the transmissive and reflective subpixels is shown in FIG. 6. Average angles of contrast greater than 10: 1 are 80 ° (transparent) and 41.8 ° (reflective). Average angles of contrast greater than 100: 1 are 80 ° (transparent) and 17.7 ° (reflective).

The simulated results clearly show that the introduction of a patterned retarder allows the design of a transactive IPS with good optical performance. Thus, standard viewing angle performance equivalent to the viewing angle required in the television industry can be combined with reflective LCD techniques to produce displays that can be viewed in all light conditions.

According to the present invention, it is possible to provide a transmissive display which shows high contrast and brightness over a viewing angle range, shows low color transition, and can be easily manufactured in a time and cost effective manner.

Claims (31)

A transflective liquid crystal display (LCD) comprising one or more pixels divided into reflective and transmissive subpixels, An LC cell in an in-plane switching (IPS) scheme comprising an LC layer switchable between different orientations and an electrode layer upon application of an electric field having a principal component parallel to the plane of the LC layer; A front polarizer and a rear polarizer, sandwiching the LC cell and having front and rear polarization directions; And Positioned between the front polarizer and the LC layer and having a pattern of regions with defined on-axis delays and regions with no delays, the delay regions arranged to essentially cover only reflective subpixels One or more retardation film Wherein the LC layer in the patterned retardation film and the reflective subpixel together form an achromatic quarter-wave retarder (AQWF). The method of claim 1, The LCD Liquid crystal (LC) cells; A first linear polarizer on the first side of the LC cell; A second linear polarizer on the second side of the LC cell; And At least one patterned retardation film as defined in claim 1 ≪ / RTI > The LC cell First and second substrate planes parallel to one another, at least one of which is transparent to incident light; An array of nonlinear electrical elements on one of the substrates, which may be used to switch each pixel of the LC cell respectively; A color filter array provided on one of the substrates, the pattern of different pixels transmitting one of primary red, green and blue (R, G, B) and optionally covered by a planarization layer; An electrode layer provided on the inside of the first or second substrate and designed such that an electric field having a main component parallel to the plane of the LC layer can be applied; Optionally, an alignment layer provided on the electrode; And LC medium switchable between two or more different orientations by electric field application Including, a transparent LCD. 3. The method according to claim 1 or 2, And the LC layer in said reflective subpixel has a quarter wavelength delay. 3. The method according to claim 1 or 2, And wherein the patterned retardation film in said retardation region has a half wavelength (λ / 2) retardation. delete The method of claim 1, And the LCD further comprises at least one + A-plate and / or at least one + C-plate delay. The method of claim 1, The LCD comprises a color filter having a pattern of R, G, B-pixels, The patterned retardation film additionally has an R, G, B-pixel pattern with different retardations where the efficiency of converting linearly polarized light into circularly polarized light is adjusted to optimize for red, green and blue, respectively. Indicates, Wherein the retardation film is arranged such that each R, G, B-pixel covers the corresponding R, G, B-pixel of the color filter. delete The method according to any one of claims 1, 6 and 7, And a retardation in the retarded region of the patterned retardation film at a 0 ° viewing angle of 180 to 400 nm. The method according to any one of claims 1, 6 and 7, Wherein said transmissive subpixel has a half wavelength delay and said reflective subpixel has a quarter wavelength delay. The method according to any one of claims 1, 6 and 7, And the LC layer thickness of the reflective subpixel is 0.5 times the LC layer thickness of the transmissive subpixel. The method according to any one of claims 1, 6 and 7, The delay of the LC layer in the reflective subpixel is between 90 and 200 nm. The method according to any one of claims 1, 6 and 7, The delay of the LC layer in the transmissive subpixel is 180-400 nm. The method according to any one of claims 1, 6 and 7, And wherein the transmission axes of the front polarizer and the rear polarizer are oriented at + 45 ° and -45 °, respectively, and the optical axis in the half wavelength region of the patterned retardation film is oriented at + 22.5 °. The method according to any one of claims 1, 6 and 7, The display comprises a + A-plate, wherein the transmission axes of the front polarizer and the rear polarizer are oriented at + 45 ° and -45 °, respectively, and the optical axis in the retardation area of the patterned retardation film is oriented at + 112.5 °. Wherein the optical axis of the + A-plate is oriented at + 45 °. The method according to any one of claims 1, 6 and 7, In the retarded region of the patterned retardation film, the optical axis exhibits A-plate symmetry parallel to the film plane. The method according to any one of claims 1, 6 and 7, In the non-delay region of the patterned retardation film, the optical axis exhibits C-plate symmetry perpendicular to the film plane. The method according to any one of claims 1, 6 and 7, In the non-delay region of the patterned retardation film, the patterned retardation film comprises an optically isotropic material The method according to any one of claims 1, 6 and 7, Wherein the patterned retardation film is provided between substrates forming a switchable LC cell. The method according to any one of claims 1, 6 and 7, And the patterned retardation film is located at the front of the display. The method according to any one of claims 1, 6 and 7, And the patterned retardation film is positioned between the color filter and the LC medium, or between the color filter and the polarization layer, if present. The method according to any one of claims 1, 6 and 7, And the patterned retardation film has a thickness of 0.5 to 3.5 microns. The method according to any one of claims 1, 6 and 7, The patterned retardation film is patterned responsive to provide an area with A plate symmetry with ½ wavelength retardation on the reflective subpixel and an area with optical isotropic or C plate symmetry over the transmissive subpixel. A transparent LCD made from mesogen material. The method according to any one of claims 1, 6 and 7, The patterned retardation film, a) providing a layer of a polymerizable LC material comprising at least one photoisomerizable compound on a substrate; b) aligning the layer of LC material in a planar orientation; c) exposing the LC material in the layer or in selected regions of the layer to light irradiation causing isomerization of the isomerizable compound; d) polymerizing the LC material in at least a portion of the exposed area of the material to fix the orientation; And e) optionally, removing the polymerized film from the substrate Wherein the retardation or orientation of the LC material is controlled by varying the amount, type or both of the photoisomerizable compounds, or by varying the intensity, exposure time or both of the irradiation. , Transparent LCD. 25. The method of claim 24, Wherein the polymerizable LC material comprises a photoisomerizable mesogenic compound or LC compound that is also polymerizable. 25. The method of claim 24, Wherein said photoisomerizable compound changes its shape by E-Z-isomerization upon exposure to UV-irradiation. 25. The method of claim 24, The photoisomerizable compounds are azobenzene, benzaldoxime, azomethine, stilbene, spiropyran, spiroxadine, fulgide, diarylethene, cinamate, 2-methyleneinden-1-one and Transflexive LCD, selected from (bis-) benzylidenecycloalkanones. 25. The method of claim 24, Wherein said photoisomerizable compound is selected from cinamate reactive mesogens. 25. The method of claim 24, Wherein the polymerizable LC material is exposed to irradiation causing photoisomerization and photopolymerization, wherein the steps of photoisomerization and photopolymerization are carried out under different conditions. 30. The method of claim 29, Wherein said step of photoisomerization and photopolymerization is carried out under a different gas atmosphere. 30. The method of claim 29, Wherein said photoisomerization is carried out in the presence of oxygen and said photopolymerization is carried out in the absence of oxygen.

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