CN1858641A - Fully-coated high-transmission brightness-enhancing optical components for LCDs - Google Patents

Abstract

The present invention discloses a high-transmittance brightness enhancement optical component, comprising a cholesterol phase liquid crystal film and a quarter wavelength retardation film sequentially formed on a substrate, and preferably further comprising a polarizing film formed on the quarter wavelength retardation film. The cholesterol phase liquid crystal film and the quarter wavelength retardation film are formed by coating, and the polarizing film can be formed by coating or by laminating a pre-formed polarizing film on the quarter wavelength retardation film. The high-transmittance brightness enhancement optical component of the present invention having the polarizing film is combined with a backlight module of a liquid crystal display to form a brightness enhancement polarized light source of the liquid crystal display.

Description

Fully-coated high-transmission brightness-enhancing optical components for LCDs

technical field

The invention is mainly applied to a high-transmission brightness-increasing optical component of a backlight LCD, in particular to a high-transmission brightness-enhancing optical component integrated with a polarizing film on a backlight LCD.

Background technique

Among all flat panel displays, liquid crystal displays are the only ones that use linearly polarized light to create bright, dark, and gray scales. First of all, the light from the backlight module is processed by the polarizer assembly to produce linearly polarized light; as the liquid crystal molecules are arranged and twisted, bright and dark changes occur, which enriches the display content.

However, the total brightness of the current liquid crystal display is only 4-6% of that provided by its backlight source, and the dichroic polarizer assembly that absorbs half of the incident light is one of the main reasons for the loss. Therefore, if the incident light can be processed first, so that it can be completely converted into linearly polarized light that can completely pass through the polarizer assembly before entering the polarizer assembly, the efficiency of the incident light can be greatly improved, and the current LCD can be improved. Problem with poor brightness.

A reflective polarizer assembly that does not absorb light itself is used as an LCD brightening optical assembly, one of which is a cholesteric liquid crystal reflective polarizer assembly that processes circularly polarized light. The principle of the so-called cholesteric liquid crystal reflective polarizer assembly is to use the separation characteristics of the special circularly polarized light of the cholesteric liquid crystal layer, which can separate an incident unpolarized white light into left and right circularly polarized light, one of which can penetrate the cholesteric liquid crystal layer, while circularly polarized light in the other direction of rotation is reflected. The circularly polarized light originally reflected by the cholesteric liquid crystal layer can be easily reversed into a penetrable circularly polarized light by using a simple reflective surface (usually LCD backlight modules contain such a reflection mechanism), and then the cholesteric liquid crystal can pass through layer, forming circularly polarized light with double the light intensity and a single rotation direction. At this time, if a 1/4 wavelength retarder is pasted on the cholesteric liquid crystal layer, the incident unpolarized white light can be completely converted into linearly polarized light with twice the light intensity, and its light wave polarization plane is exactly the same as that of the linear polarizing film. The light transmission axis is consistent to achieve the effect of brightening. A similar cholesteric liquid crystal reflective polarizer assembly is disclosed in US Patent No. 5,506,704, the content of which is incorporated herein by reference.

U.S. Patent No. 5,506,704 is a reflective polarizer assembly made of cholesteric liquid crystal with a 1/4 wavelength retarder and a polarizer. The 1/4 wavelength retarder used is extruded (extrude) or solvent The solvent casting method first forms the film and then stretches it precisely. In order to assemble the above-mentioned reflective polarizer assembly, the 1/4 wavelength retarder needs to be covered with an optical glue to ensure that it can be successfully pasted on the cholesteric liquid crystal. In order to ensure the integrity of the 1/4 wavelength retarder before use, it is pasted with a protective film. Therefore, the outer protective film must be removed before the lamination step can be carried out before the lamination of the optical adhesive. Such an operation not only consumes Additional materials, increasing the complexity of the manufacturing process, and increasing the interface between several layers lead to light loss at the interface. The polarizer is usually manufactured through a more complex stretching process, and is covered with two layers of substrate (TAC film) and a layer of optical glue, which has more interface problems than 1/4 wavelength retarder and is thicker Thick, material and process costs are not easy to reduce. The most important thing is that the interface between layers will cause a decrease in light transmittance, which has a negative impact on the function of the optical component.

Another example is U.S. Patent No. 5,601,884 and No. 5,743,980, which disclose a method of using glass as a substrate and using a birefringent liquid crystal material to prepare a phase retarder by coating; in addition, U.S. Patent No. 6,262,788 B1 discloses a The method of coating a liquid crystal material on a TAC film to prepare a phase retarder, none of the objects of these prior art is used for optical conversion after the cholesteric liquid crystal film splits light, nor does it deal with the interface required for direct coating on the cholesteric liquid crystal film superficial problem. In terms of the preparation of polarizers, U.S. Patent 6,049,428 discloses a technology to complete a new type of E-type polarizer by coating disc columnar polymer molecules (supermolecular). The penetration axis is parallel to the molecular optical axis and the traditional vertical molecular optical axis. The O-type polarizer of the axis is different, but basically it is still a light-absorbing polarizing film, which does not have the functions of light polarization state conversion, light recycling mechanism and resulting brightness enhancement.

Contents of the invention

A main purpose of the present invention is to provide a high-transmittance brightness-enhancing optical component, which includes a cholesteric phase liquid crystal film and a 1/4 wavelength retardation film sequentially formed on a substrate, preferably further comprising a film formed on the substrate A polarizing film of 1/4 wavelength retardation film. The cholesteric liquid crystal film and the 1/4 wavelength retardation film are formed by coating, and the polarizing film can be formed by coating or pasting a pre-formed polarizing film on the 1/4 wavelength retardation film Forming, preferably by coating. The combination of the high-transmittance brightness-enhancing optical component with the polarizing film of the present invention and the backlight module of the liquid crystal display can be used as a brightness-enhancing polarized light source for the liquid crystal display.

According to the technology of the present invention, an ultra-thin, integrated polarizing optical film can be provided, and there are no substrate/layer/layer bonding interfaces and optical glue between the optical function layers, and it can be placed on the backlight of the LCD. Reducing the absorption or scattering of light also makes the light transmittance relatively increase. At the same time, one of the methods according to the technology of the present invention is to provide a low-cost direct coating method to manufacture the integrated polarizing optical film of the present invention, which can complete the cholesteric phase liquid crystal film, 1/4 wavelength retardation film on a single coating machine. The coating of thin film and polarizing film requires a small amount of coating raw materials, and only a single substrate is required, so it can save material costs and lamination procedures, which has a significant impact on the reduction of costs and the reduction of resources required for production. help.

Implementation

The present invention discloses an optical component comprising a cholesteric phase liquid crystal film, a 1/4 wavelength retardation film and a polarizing film on a single substrate in the order of coating by direct coating, and is applied to a general backlight LCD as a brightness enhancement mechanism.

The coating method can be directly carried out on a single substrate of an optical grade transparent substrate by means of extrusion die or doctor blade coating, and the optical grade transparent substrate can be such as TAC, PET, PS or polyacrylate. At the same time, the coating sequence of the cholesteric liquid crystal film, the 1/4 wavelength retardation film and the polarizing film cannot be changed (unique), and the brightness enhancement mechanism cannot be produced by arbitrarily changing or reducing one item. First of all, in the coating process, it is necessary to give each film in the component a specific optical axis: such as a cholesteric liquid crystal film, it is necessary to make its optical axis perpendicular to the coating surface, that is, the molecular arrangement direction of the uppermost layer and the lowermost layer must be The alignment direction is parallel to the substrate, and the molecules in between are helically arranged, so that it has the function of separating the unpolarized incident light into circularly polarized light. The cholesteric liquid crystal film can generally have a single-layer or multi-layer structure. In order to achieve the effect of brightening in the entire light range of visible light, the cholesteric liquid crystal film of the present invention needs to have different pitches in the layer thickness direction, and the pitch size has a continuous or discontinuous change from large to small or from small to large. .

Another example is the 1/4 wavelength retardation film of the component, which needs to make its optical axis parallel to the coating surface, that is, the molecular arrangement direction must be parallel to the alignment direction of the substrate, which has the function of delaying the incident wavelength by 0.25 times; coating on the cholesterol phase The liquid crystal film has the function of converting the circularly polarized light converted by the cholesteric liquid crystal film into linearly polarized light.

The optical axis of the polarizing film of the optical component of the present invention is parallel to the coating surface, and has a transmission axis and an absorption axis perpendicular to each other, and can convert unpolarized incident light into linearly polarized light; when matched with the above two films , pay special attention to the fact that the angle between the optical axis and the 1/4 wavelength retardation film needs to be different from each other by 45 degrees to achieve their respective optical functions. The polarizing film can optionally adopt an O-type polarizer whose transmission axis is perpendicular to the molecular optical axis, or an E-type polarizer whose transmission axis is parallel to the molecular optical axis. The polarizing film is preferably formed by a coating method, but it can also be formed by pasting a pre-formed polarizing film on the 1/4 wavelength retardation film.

To achieve the above specified optical axis, except for the cholesteric liquid crystal film, all film materials used in the present invention are compounds or mixtures containing liquid crystal properties, especially polymerizable nematic liquid crystals. Among them, dichroic dyes with liquid crystal properties can be selected for the polarizing film or dichroic dye raw materials can be used as formula components.

Description of drawings

FIG. 1 shows the light-splitting effect of a brightness-enhancing optical component and a polarizer that are parallel and perpendicular to each other according to Embodiment 1 of the present invention, wherein the horizontal axis is the wavelength, and the vertical axis is the transmittance (T%).

Fig. 2 shows the comparison of the transmittance (T%) of a kind of brightness-enhancing optical assembly completed according to Embodiment 1 of the present invention and the brightness-enhancing optical assembly of the prior art, wherein the thick line is Embodiment 1 of the present invention, and the thinner Lines represent prior art brightening optical components.

Detailed ways

Example 1

Polymerizable cholesteric liquid crystals SLM 90032 and SLM 90034 were formulated into a 25wt% solution with SLM 90032:SLM 90034=70:30 ratio and toluene (Toluene), and at the same time, 1wt% of UV light-generating agent Irgacure 907(R) (Ciba Geigy) was added , and then coated on the aligned PET film with a thickness of 50 μm, dried at 80°C for 2 minutes, and then irradiated with a 100W/cm ² UV lamp for 20 seconds to form a film, and finally a cholesteric phase liquid crystal film with a film thickness of about 5 μm was obtained.

The polymerizable liquid crystal SLM 90519 and toluene (Toluene) were formulated into a 10wt% solution, and 1wt% of UV light initiator Irgacure 907(R) was added at the same time. Apply this solution on the above-mentioned cholesteric liquid crystal film, dry it at 80°C for 1 minute, and then irradiate it with a 100W/ ^cm2 UV lamp for 20 seconds to form a film with a thickness of 2 μm, thus completing 1/2 of the brightness-enhancing optical component. 4-wavelength retarder part.

The thickness of the brightness-enhancing optical component manufactured in the above-mentioned manner is only about 57 μm. FIG. 1 shows the parallel and perpendicular spectral diagrams of a brightness enhancing optical component and a polarizer completed according to Embodiment 1 of the present invention, wherein the horizontal axis is the wavelength, and the vertical axis is the transmittance (T%).

comparative example

The 5 μm thick cholesteric phase liquid crystal film completed in Example 1 was directly bonded to a commercially available 100 μm 1/4 wavelength retarder, and the brightness-enhancing optical component made in the above-mentioned manner had a thickness of about 155 μm. Figure 2 is a comparison of the transmission spectra of the two. The thick line represents Example 1 of the present invention, and the thinner line represents the brightness enhancement optical component prepared in the comparative example of the prior art. Obviously, it can be seen from FIG. 2 that the brightness enhancement optical component of the present invention has a high transmittance.

Example 2

A brightness-enhancing optical assembly integrated with a polarizing film was prepared by using the brightness-enhancing optical assembly prepared in Example 1. First confirm the optical axis direction of the above-mentioned 1/4 wavelength retarder, and apply the following solution in the direction of its optical axis at an angle of 45 degrees: make a 20wt% solution of polymerizable liquid crystal SLM 90519 and toluene (Toluene), and add 1 wt% UV light initiator Irgacure 907(R) and 3 wt% black dichroic dye. After drying at 80°C for 2 minutes and irradiating with 100W/cm ² UV lamp for 1 minute, a film with a thickness of 2 μm is formed, which is the polarizer part of the brightness-enhancing optical component.

The brightness-enhancing optical component manufactured in the above-mentioned way has a thickness of only about 59 μm, and it has the characteristics of brightness enhancement and high penetration when placed on a backlight LCD.

Claims (11)

1. full coated high pentration type brightening optical module that is applicable to LCD, comprise the cholesteric liquid crystal phase film and the 1/4 wavelength retardation films that are formed in regular turn on the base material, wherein this base material is directly to contact with this cholesteric liquid crystal phase film, and does not have an applying glue in fact therebetween; Reaching this cholesteric liquid crystal phase film is directly to contact with this 1/4 wavelength retardation films, and does not have an applying glue in fact therebetween; Wherein this cholesteric liquid crystal phase film adds a unpolarized incident light and gives circular polarization, and this 1/4 wavelength retardation films has 0.25 times of circular polarization light wavelength that an optical delay equals the reflection of this cholesteric liquid crystal phase film in fact, so, can convert this unpolarized incident light to linearly polarized light when the circularly polarized light of this reflection is reflected when entering this cholesteric liquid crystal phase film.

2. optical module as claimed in claim 1, it further comprises a light polarizing film that is formed on this 1/4 wavelength retardation films.

3. optical module as claimed in claim 2, wherein this 1/4 wavelength retardation films is directly to contact with this light polarizing film, and does not have an applying glue in fact therebetween.

4. optical module as claimed in claim 2 wherein has an applying glue between this 1/4 wavelength retardation films and this light polarizing film, this applying glue is fitted in this light polarizing film on this 1/4 wavelength retardation films.

5. optical module as claimed in claim 1, wherein this base material is a transparent optical classes and grades in school base material.

6. as claim 1,2 or 3 described optical modules, this cholesteric liquid crystal phase film wherein, the cholesteric liquid crystal phase of this cholesteric liquid crystal phase film has a part spiral, the optical axis of this molecular spiral is perpendicular to this cholesteric liquid crystal phase film, its the superiors and undermost molecules align direction are parallel to the alignment direction of base material, give circular polarization so a unpolarized incident light can be added, wherein this cholesteric liquid crystal phase film can be the cholesteric liquid crystal phase macromolecule of single or multiple lift.

7. optical module as claimed in claim 6, wherein this 1/4 wavelength retardation films comprises a liquid-crystal compounds, and this liquid-crystal compounds has a part spiral, and the optical axis of this molecular spiral is parallel to this 1/4 wavelength retardation films.

8. optical module as claimed in claim 7, wherein this light polarizing film comprises a liquid-crystal compounds, and this liquid-crystal compounds has a part spiral, and wherein the optical axis of the molecular spiral of the liquid-crystal compounds of this 1/4 wavelength retardation films and light polarizing film differs from 45 degree in fact mutually.

9. optical module as claimed in claim 6, wherein the molecular spiral of this cholesteric liquid crystal phase has the pitch that varies in size, and the pitch size has by big and little or by little and big continuous or discrete variation.

10. optical module as claimed in claim 8, wherein this light polarizing film its be to have the O-type light polarizing film of a penetrating shaft perpendicular to the optical axis of this molecular spiral, or for having an E-type light polarizing film that a penetrating shaft is parallel to the optical axis of this molecular spiral.

11. optical module as claimed in claim 4, wherein this light polarizing film is that iodine system or dichroic dye are light polarizing film.

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