WO2011028018A2 - Broadband reflective liquid crystal film, method for manufacturing same, light source assembly comprising the broadband reflective liquid crystal film, and liquid crystal display device - Google Patents

Abstract

Provided are a broadband reflective liquid crystal film and a method for manufacturing same. The broadband reflective liquid crystal film comprises a cholesteric liquid crystal layer in which the pitch of the liquid crystals varies from a first surface toward a second surface. The cholesteric liquid crystal layer has a first liquid crystal pitch in a first region adjacent to the first surface, a second liquid crystal pitch smaller than the first liquid crystal pitch in a second region adjacent to the second surface, and a third liquid crystal pitch larger than the first liquid crystal pitch in a third region formed between the first region and the second region.

Description

Broadband reflective liquid crystal film, light source assembly and liquid crystal display device including the manufacturing method and broadband reflective liquid crystal film

The present invention relates to a broadband reflective liquid crystal film, a manufacturing method thereof, and a light source assembly and a liquid crystal display device including the broadband reflective liquid crystal film.

A liquid crystal display (LCD) is a device that displays an image by injecting a liquid crystal between two glass plates and applying power to the upper and lower glass plate electrodes to change the liquid crystal molecular array in each pixel. Unlike a cathode ray tube (CRT), a plasma display panel (PDP), and the like, a display by a liquid crystal display is not light-emitting because it is non-luminous in itself. To compensate for this disadvantage, a lighting device such as a light source assembly that is uniformly irradiated onto the information display surface is mounted for the purpose of enabling use in a dark place.

The light source assembly used in the liquid crystal display device is largely classified into two types. The first is an edge type light source assembly that provides light at the side of the liquid crystal display, and the second is a direct type light source assembly that provides light directly at the rear of the liquid crystal display. In the case of the edge type light source assembly, a light guide plate is provided to allow the light emitted from the light source to be irradiated upward, and at least one optical film is disposed above the light guide plate to adjust optical characteristics of light passing through the light guide plate. In the case of the direct type light source assembly, a diffuser plate is provided to reduce bright lines of light emitted from the light source, and at least one optical film is provided to adjust optical characteristics of light passing through the diffuser plate. Some liquid crystal display devices include a reflective liquid crystal film as one of the optical films to improve the brightness.

In general, cholesteric liquid crystals do not have a wide bandwidth of reflected light, and it is difficult to cover visible light waves with a single cholesteric liquid crystal. Therefore, in order to cover the visible light electric wave field, a plurality of liquid crystal layers are stacked.

However, when a large number of liquid crystal layers are laminated, the thickness itself becomes thick and the light transmittance is not only disadvantageous, but also the adhesive is interposed between the liquid crystal layers. In addition, the adhesive generates light distortion. As a result, the brightness, light quality, and image quality of the light source assembly and the liquid crystal display device employing such a reflective liquid crystal film are reduced.

The present invention has been conceived based on these points, and the problem to be solved by the present invention is to provide a broadband reflective liquid crystal film which can have a predetermined reflectance for the full-wavelength range of visible light while using only one liquid crystal layer. will be.

Another object of the present invention is to provide an illumination device including the broadband reflective liquid crystal film described above.

Another object of the present invention is to provide a liquid crystal display device including the broadband reflective liquid crystal film described above.

Another problem to be solved by the present invention is to provide a method for manufacturing a broadband reflective liquid crystal film which can have a predetermined reflectance with respect to the wavelength range of visible light while using only one liquid crystal layer.

The objects of the present invention are not limited to the above-mentioned objects, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

The broadband reflective liquid crystal film according to an embodiment of the present invention for solving the above problems includes a cholesteric liquid crystal layer in which the liquid crystal pitch is changed from the first surface to the second surface direction, wherein the cholesteric liquid crystal layer is A first liquid crystal pitch in a first region adjacent to the first surface, a second liquid crystal pitch smaller than the first liquid crystal pitch in a second region adjacent to the second surface, and between the first and second regions And having a third liquid crystal pitch greater than the first liquid crystal pitch in a third region.

The broadband reflective liquid crystal film according to another embodiment of the present invention for solving the above problems is a liquid crystal layer including a first gradation region and a second gradation region, wherein the first gradation region has a liquid crystal pitch in a first direction. A liquid crystal layer increasing on the first gradation region to increase the liquid crystal pitch in a second direction opposite to the first direction, wherein the liquid crystal pitch of the first gradation region is increased; And a liquid crystal pitch reduction rate of the second gradation region is different from each other.

In the broadband reflective liquid crystal film according to another embodiment of the present invention for solving the above problems, the first to m (divided sequentially from the first surface to the second surface direction using each liquid crystal pitch as a unit) Wherein m is a natural number) and includes a cholesteric liquid crystal layer including a liquid crystal pitch period, wherein the cholesteric liquid crystal layer is formed in the first to nth (where n is a natural number of n <m) liquid crystal pitch intervals. With respect to k (where k is a natural number of 1 < k ≤ n), the ratio when the liquid crystal pitch of the liquid crystal pitch section is larger than the liquid crystal pitch of the k-1 liquid crystal pitch section is 70% or more, and the n + 1th The ratio of the liquid crystal pitch of the h th liquid crystal pitch section to the m th liquid crystal pitch section (where h is a natural number of n + 1 <h ≦ m) is smaller than the liquid crystal pitch of the h-1 liquid crystal pitch section. 70% or more, and the liquid crystal pitch of at least one of the nth and nth + 1th liquid crystal pitch periods is a maximum value Have, includes the m-th liquid crystal pitch of the liquid crystal region has a pitch has a minimum value, when the first liquid crystal pitch of the liquid crystal region has a pitch between the value of the maximum value and the minimum value.

The broadband reflective liquid crystal film according to another embodiment of the present invention for solving the above problems is a liquid crystal layer including a first gradation region and a second gradation region, the first gradation region is a liquid crystal pitch in a first direction Is increased, and the second gradation region is formed on the first gradation region, and includes a liquid crystal layer in which a liquid crystal pitch increases in a second direction opposite to the first direction, wherein the first relative to the liquid crystal layer The ratio of the gradation region and the ratio of the second gradation region to the liquid crystal layer may be different from each other.

The broadband reflective liquid crystal film according to another embodiment of the present invention for solving the above problems is a liquid crystal layer including a first gradation region and a second gradation region, the first gradation region is a liquid crystal pitch in a first direction Is reduced, and the second gradation region includes a liquid crystal layer formed on the first gradation region to reduce the liquid crystal pitch in a second direction opposite to the first direction, wherein the liquid crystal pitch of the first gradation region is reduced. The increase rate and the liquid crystal pitch decrease rate of the second gradation region may be different from each other.

The light source assembly according to an embodiment of the present invention for solving the other problem includes a broadband reflective liquid crystal film as described above.

The liquid crystal display according to the exemplary embodiment of the present invention for solving the another problem includes the broadband reflective liquid crystal film as described above.

In the method for manufacturing a broadband reflective liquid crystal film according to an embodiment of the present invention for solving the above another problem, by applying a liquid cholesteric liquid crystal coating liquid on a substrate, to form a liquid crystal coating layer on one surface of the substrate And drying the liquid crystal coating layer at a first temperature, performing a first curing on the dried liquid crystal coating layer with first energy, and performing a first curing on the first cured liquid crystal coating layer at a second temperature lower than the first temperature. Heat treatment is performed, and the second heat treatment is performed on the first heat-treated liquid crystal coating layer at a third temperature and a second heat treatment higher than the second temperature, and the second curing is performed at a second energy greater than the first energy, and the second heat treatment is performed. Performing a third heat treatment on the second main cured liquid crystal coating layer at a fourth temperature higher than the third temperature and performing a third curing at a third energy larger than the second energy. Include.

Specific details of other embodiments are included in the detailed description and drawings.

1 is a cross-sectional view of a broadband reflective liquid crystal film according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating each liquid crystal pitch in the first to third regions of FIG. 1.

FIG. 3 is a schematic diagram illustrating a traveling direction of light in a broadband reflective liquid crystal film according to an exemplary embodiment of the present invention.

4 to 6 are graphs showing transmittances according to wavelengths of light incident on respective regions of the broadband reflective liquid crystal film according to the exemplary embodiment of the present invention.

7 is a graph showing transmittance according to the wavelength of light incident on the broadband reflective liquid crystal film according to the exemplary embodiment of the present invention.

8 and 9 are graphs illustrating a change in pitch according to a thickness position of a cholesteric liquid crystal layer according to some embodiments of the present invention.

10 and 11 are graphs showing changes in the size of the liquid crystal pitch and the size of the reflection wavelength with respect to the thickness of the broadband reflective liquid crystal film according to some embodiments of the present invention.

12 and 13 are photographs showing the results of measuring the OAC of the broadband reflective liquid crystal film according to some embodiments of the present invention.

14 is a graph illustrating a change in luminance with respect to a viewing angle with respect to comparative examples and examples.

15 and 16 are graphs showing a change in pitch according to a thickness position of a cholesteric liquid crystal layer according to some other embodiments of the present invention.

17 and 18 are cross-sectional views of a broadband reflective liquid crystal film according to some other embodiments of the present invention.

19 to 23 are cross-sectional views illustrating process steps of a method of manufacturing a broadband reflective liquid crystal film according to embodiments of the present invention.

24 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims.

References to elements or layers "on" other elements or layers include all instances where another layer or other element is directly over or in the middle of another element. On the other hand, when a device is referred to as "directly on", it means that it does not intervene with another device or layer in between. Like reference numerals refer to like elements throughout. "And / or" includes each and all combinations of one or more of the items mentioned.

The spatially relative terms " below ", " beneath ", " lower ", " above ", " upper " It may be used to easily describe the correlation of a device or components with other devices or components. Spatially relative terms are to be understood as terms that include different directions of the device in use or operation in addition to the directions shown in the figures. For example, when flipping a device shown in the figure, a device described as "below" or "beneath" of another device may be placed "above" of another device. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device can also be oriented in other directions, so that spatially relative terms can be interpreted according to orientation.

As used herein, the term "film" may be used to mean "~ sheet" and "~ plate".

As used herein, the term "broadband reflective liquid crystal film" means a film including a liquid crystal layer, and does not exclude a case in which another layer or film is further included. For example, a composite film in which a liquid crystal layer is formed on a film, and a retardation film is laminated on or behind it may be referred to as a broadband reflective liquid crystal film as long as it is a film including a liquid crystal layer. .

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention.

1 is a cross-sectional view of a broadband reflective liquid crystal film according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating each liquid crystal pitch in the first to third regions of FIG. 1.

Referring to FIG. 1, the broadband reflective liquid crystal film 100 according to an embodiment of the present invention includes a cholesteric liquid crystal layer 110 including cholesteric liquid crystals (or chiral nematic liquid crystals). The cholesteric liquid crystal may include a nematic liquid crystal and a chiral dopant. Cholesteric liquid crystals have a constant pitch and have a spiral structure twisted repeatedly. Repeated twisted helical structure induces Bragg reflection of light.

The cholesteric liquid crystal layer 110 may be formed as a single layer. In some embodiments, the cholesteric liquid crystal molecules included in the single layer may be the same material.

Cholesteric liquid crystals are classified into right-handed cholesteric liquid crystals and left-handed cholesteric liquid crystals according to the twisted direction of the helical structure. Preferred cholesteric liquid crystals reflect right polarized light but transmit left polarized light. In contrast, the left cholesteric liquid crystal transmits right polarized light but reflects left circular polarized light. Therefore, in theory, the cholesteric liquid crystal transmits 50% of the light included in the wavelength range reflected by the cholesteric liquid crystal and reflects the remaining 50%.

That is, when light including first and second circularly polarized light is incident from the outside, the cholesteric liquid crystal layer 110 reflects light having a wavelength corresponding to the liquid crystal pitch of each region among the first or second circularly polarized light. Let's do it. For example, when the cholesteric liquid crystal layer 110 includes the preferential cholesteric liquid crystal, when the light including the first and second circularly polarized light is incident from the outside, the cholesteric liquid crystal layer 110 Reflects unidirectional polarized light, but reflects light having a wavelength corresponding to the liquid crystal pitch of each region among unipolar polarized light.

The pitch (liquid crystal pitch) of the cholesteric liquid crystal is related to the wavelength of the reflected light. The central wavelength of the reflected light reflected by the cholesteric liquid crystal is generally proportional to the liquid crystal pitch. Here, when the reflected light reflected by the cholesteric liquid crystal has a predetermined band width, the center wavelength of the reflected light may mean a wavelength that is maximum reflected within the band width or an average wavelength of the band width. Here, the bandwidth of the reflected light may mean a range of wavelengths capable of reflecting about 30% to about 70% of the incident light, preferably reflecting about 40% to about 60% of the incident light The range of wavelengths that can be used may mean a range of wavelengths that can more preferably reflect about 50% of incident light.

The cholesteric liquid crystal layer 110 includes a first surface 110_1 and a second surface 110_2. The first surface 110_1 is a surface on which light is incident, and the second surface 110_2 is a surface opposite to the first surface 110_1 and may be a surface on which light is transmitted and emitted. However, of course, the first surface 110_1 and the second surface 110_2 may be reversed.

The cholesteric liquid crystal layer 110 includes two or more different liquid crystal pitches. For example, the cholesteric liquid crystal layer 110 may have a liquid crystal pitch in a direction from the first surface 110_1 to the second surface 110_2, that is, in the thickness direction of the liquid crystal layer 110. In some embodiments, cholesteric liquid crystal layer 110 includes a plurality of regions, each liquid crystal region comprising a plurality of oriented cholesteric liquid crystal molecules, each liquid crystal region formed by cholesteric liquid crystal molecules. Can be classified according to the liquid crystal pitch.

As shown in FIG. 1, the cholesteric liquid crystal layer 110 includes a first region 111 adjacent to the first surface 110_1, a second region 112 adjacent to the second surface 110_2, and a first region. The third region 113 is formed between the region 111 and the second region 112. In this case, the first region 111 includes a cholesteric liquid crystal having a first liquid crystal pitch P1, and the second region 112 includes a cholesteric liquid crystal having a second liquid crystal pitch P2. The third region 113 includes a cholesteric liquid crystal having a third liquid crystal pitch P3. At this time, the second liquid crystal pitch P2 is smaller than the first liquid crystal pitch P1, and the third liquid crystal pitch P3 is larger than the first liquid crystal pitch P1. That is, the magnitude relationship of the first to third liquid crystal pitches P1 to P3 is expressed as P2 <P1 <P3.

Referring to FIG. 2, the first region 111 includes a cholesteric liquid crystal having a first liquid crystal pitch P1 and having a spiral structure twisted repeatedly. When the oriented cholesteric liquid crystal in the first region 111 includes two or more cholesteric liquid crystal molecules, the cholesteric liquid crystal molecules in the first region 111 have a first liquid crystal pitch P1 and are repeatedly It may have a twisted spiral structure. Similarly, the second region 112 includes a cholesteric liquid crystal having a second liquid crystal pitch P2 and a spirally twisted spiral structure, and the third liquid crystal pitch P3 is disposed in the third region 113. And a cholesteric liquid crystal having a spiral structure twisted repeatedly. Here, the second liquid crystal pitch P2 is smaller than the first liquid crystal pitch P1, and the third liquid crystal pitch P3 is larger than the first liquid crystal pitch P1.

As described above, since the center wavelength of the reflected light with respect to the liquid crystal is proportional to the liquid crystal pitch, the liquid crystal pitches P1, P2, When P3) is formed differently from each other, the wavelength of the light reflected by each region (the central wavelength of the reflected light) is also different. For example, when the first to third regions 111, 112, and 113 have the first to third liquid crystal pitches having a size relationship of P2 <P1 <P3, the first region 111 may have a first wavelength. The light may be reflected, and the second region 112 may reflect light having a second wavelength smaller than the first wavelength, and the third region 113 may reflect light having a third wavelength larger than the first wavelength. With reference to Figure 3 will be described in more detail.

FIG. 3 is a schematic diagram illustrating a traveling direction of light in a broadband reflective liquid crystal film according to an exemplary embodiment of the present invention. In FIG. 3, the first light includes the left circularly polarized light of the first wavelength λ1 and the right circularly polarized light of the first wavelength λ1, and the second light includes the second wavelength λ2. The left circularly polarized light of (L) and the right polarized light (R) of the second wavelength (λ2) of the light, and the third light is the left circularly polarized light (L) of the third wavelength (λ3) and the third wavelength ( It is assumed to contain unidirectional polarized light R of [lambda] 3).

The first wavelength λ1 is assumed to be the center light of the reflected light of the first region 111 but is not included in the bandwidth of the reflected light of the second and third regions 112 and 113. Similarly, the second wavelength λ2 is the center light of the reflected light of the second region 112, but is not included in the bandwidth of the reflected light of the first and third regions 111 and 113, and the third wavelength λ3. Is assumed to be the center light of the reflected light of the third region 113, but is not included in the bandwidth of the reflected light of the first and second regions 111 and 112.

In addition, it is assumed that all of the first to third regions 111, 112, and 113 are made of a preferential cholesteric liquid crystal for convenience of description. Of course, this is only one exemplary assumption, and each region may be made of a left cholesteric liquid crystal or a combination of priority and left cholesteric liquid crystal.

Referring to FIG. 3, under the assumption, the first light incident on the cholesteric liquid crystal layer 110 reaches the first region 111 to transmit the left circle polarized light, but the right circle polarized light R. Light is reflected. The cholesteric liquid crystals of the second region 112 and the third region 113 not only take priority, but if not, the first wavelength λ1 in the assumption is that the second region 112 and the third region ( Since it is not included in the bandwidth of the reflected light of 113, the left circularly polarized light L of the first wavelength λ1 passes through the second region 112 and the third region 113 as it is.

Similarly, since the second light of the second wavelength λ2 is not included in the bandwidth of the reflected light of the first region 111, the first region 111 is transmitted as it is and reaches the second region 112 to the left circle. The polarized light is transmitted and the right polarized light is reflected. The left circularly polarized light L having the second wavelength λ 2 transmitted through the second region 112 passes through the third region 113 as it is. Similarly, since the third light of the third wavelength λ3 is not included in the bandwidth of the reflected light of the first region 111 and the second region 112, the first region 111 and the second region 112. ) Is transmitted as it is, the light of left circularly polarized light (L) is transmitted through the third region 113, the light of right circularly polarized light (R) is reflected.

Therefore, while the first light, the second light, and the third light pass through the first region 111, the second region 112, and the third region 113, all of the left circularly polarized light L is transmitted. , All of the right polarized light is reflected. Assuming that light is classified into left polarized light (L) and right circularly polarized light (R), and that they are the same, in conclusion, the first light, the second light, and the incident light into the cholesteric liquid crystal layer 110 Only about 50% of the third light is transmitted and the remaining about 50% is reflected.

From this point of view, if the bandwidth of the reflected light in the first region 111, the bandwidth of the reflected light in the second region 112, and the bandwidth of the reflected light in the third region 113 cover the full-wavelength of the visible light, It will be possible to exhibit a specific reflectance for all light within the range of the field. 4 to 6 and 7 are referred to for more detailed description.

4 to 6 are graphs showing transmittances according to wavelengths of light incident on respective regions of the broadband reflective liquid crystal film according to the exemplary embodiment of the present invention.

Specifically, FIG. 4 is a graph showing transmittance according to the wavelength of light incident on the first region 111, where the first region 111 has a reflectance of about 50% within a wavelength range of about 510 nm to about 640 nm. Illustrated as having. 5 is a graph showing transmittance according to the wavelength of light incident on the second region 112, where the second region 112 has a reflectance of about 50% within a wavelength range of about 640 nm to about 780 nm. It is. 6 is a graph showing transmittance according to the wavelength of light incident on the third region 113, where the third region 113 has a reflectance of about 50% within a wavelength range of about 380 nm to about 510 nm. It is. As described above, the first region 111, the second region 112, and the third region 113 having different reflected light bandwidths can be adjusted by adjusting the liquid crystal pitch of the cholesteric liquid crystal present therein. Of course it can.

7 is a graph showing transmittance according to the wavelength of light incident on the broadband reflective liquid crystal film according to the exemplary embodiment of the present invention.

If the light passes through the first region 111, the second region 112, and the third region 113 having the reflected light bandwidth and reflectivity illustrated in FIGS. 4 to 6, the transmittance according to the wavelength is shown in FIG. 7. It may be represented as. That is, it has a reflectance of 50% with respect to the electric field of visible light (about 380 nm to about 780 nm).

In general, cholesteric liquid crystals do not have a wide bandwidth of reflected light, so it is difficult to cover the visible light field with a single cholesteric liquid crystal. Even if the cholesteric liquid crystal layer 110 is formed of a kind of cholesteric liquid crystal, a predetermined reflectance with respect to the visible light radio wave field can be realized.

If the reflected light bandwidth of each region is too narrow, more regions of different pitches are formed in the cholesteric liquid crystal layer 110, so that a predetermined reflectance for the visible light field may be realized. For example, if regions having hundreds of thousands of different pitches are formed in the cholesteric liquid crystal layer 110, even if the reflected light bandwidth of each region is only about 1 nm, a predetermined reflectance is provided for the visible light field. You have a very high chance of having it.

Although the reflectance implemented by the cholesteric liquid crystal layer 110 including a plurality of regions varies depending on the number of regions, the distribution of regions, the reflectance of each region, the reflected light bandwidth of each region, the type of cholesteric liquid crystal, etc. For example, it may have a reflectance of about 30% to about 70% of the full range of visible light. Preferably it can be adjusted to have a reflectance of about 40% to about 60% for the full range of visible light, more preferably about 50% for the full range of visible light.

Referring back to FIG. 1, the first to third regions 111, 112, and 113 may have a layered structure, for example. In this case, the incident light may pass through all of the first to third regions 111, 112, and 113 once regardless of the incident direction. In this structure, the reflectance of the cholesteric liquid crystal layer 110 may be more reliable.

In some other embodiments, a region having the same liquid crystal pitch as any of the first to third regions 111, 112, and 113, for example, a fourth region having the same liquid crystal pitch as the second liquid crystal pitch P2 may be formed. It may further include. For example, the first liquid crystal pitch and the second liquid crystal are disposed in the order of the first region, the fourth region, the third region, and the second region in the direction of the first surface 110_1 to the second surface 110_2. And a cholesteric liquid crystal having a pitch, a third liquid crystal pitch, and a second liquid crystal pitch. In this case, while passing through the same region, for example, the second region 112 several times, the reflectance of light having a corresponding wavelength may be further increased.

In addition, the broadband reflective liquid crystal film according to the embodiments of the present invention may include P2 in each of a first region adjacent to the first surface, a second region adjacent to the second surface, and a third region between the first region and the second region. By including the cholesteric liquid crystal layers having the first to third liquid crystal pitches P1, P2, and P3 having a size relationship of <P1 <P3, the reflectance can be further improved.

In addition, when a region having a relatively long wavelength light, for example, a region having a red light reflection band is exposed on the incident surface, a phenomenon in which the red light is shown off sideways occurs. However, according to the exemplary embodiment of the present invention, since the red light reflection region, that is, the second region 112 is positioned at the center, the liquid crystal reflects red light regardless of the incident direction of light in the first surface or the second surface. The region is not exposed to the surface of the cholesteric liquid crystal layer. Therefore, it is possible to prevent the phenomenon in which red light is shown off from the side. In addition, since the side surface visibility of the red light can be prevented even if the liquid crystal layer is changed up and down, the applicability is excellent.

In addition, in the broadband reflective liquid crystal film according to the exemplary embodiment of the present invention, the central portion of the liquid crystal layer is responsible for the reflection of red light, while one side of the light has a shorter wavelength, for example, green light, and the other side of the liquid crystal layer has Areas for reflecting light with shorter wavelengths, such as blue light, are arranged. Therefore, it is easy to configure the reflection band for the entire area of visible light.

In some other embodiments, the cholesteric liquid crystal layer 110 gradually increases from the first liquid crystal pitch P1 to the third liquid crystal pitch P3 along the direction of the first surface 110_1 to the second surface 110_2. The liquid crystal pitch may gradually change from the third liquid crystal pitch P3 to the second liquid crystal pitch P2. As described above, the first liquid crystal pitch P1 and the third liquid crystal between the first region 111 having the first liquid crystal pitch P1 and the third region 113 having the third liquid crystal pitch P3. A cholesteric liquid crystal having a value between the pitches P3 can be formed. It will be described in more detail with reference to Figs.

8 and 9 are graphs illustrating a change in pitch according to a thickness position of a cholesteric liquid crystal layer according to some embodiments of the present invention. In the graphs shown in FIGS. 8 and 9, the horizontal axis represents the thickness position of the cholesteric liquid crystal layer 110, and the vertical axis represents the size of the liquid crystal pitch of the cholesteric liquid crystal in the cholesteric liquid crystal layer 110. .

Here, the thickness position of the cholesteric liquid crystal layer 110 may be defined as, for example, the distance from the first surface 110_1 to the cholesteric liquid crystal when viewed based on the first surface 110_1. . Similarly, when referring to the second surface 110_2, the distance from the second surface 110_2 to the cholesteric liquid crystal may be defined. That is, when the leftmost side of the horizontal axis is called the first surface 110_1, it means the size of the liquid crystal pitch of the cholesteric liquid crystal corresponding to the region adjacent to the second surface 110_2 toward the right side. Similarly, when the leftmost side is referred to as the second surface 110_2, it means the size of the liquid crystal pitch of the cholesteric liquid crystal corresponding to the region adjacent to the first surface 110_1 toward the right side.

Hereinafter, a case where the thickness position of the cholesteric liquid crystal layer 110 is viewed based on the first surface 110_1 will be described as an example. That is, it is assumed that the first surface 110_1 of the cholesteric liquid crystal layer 110 corresponds to "0" in the graph. In some embodiments, the surface on which "0" in the graph is written, for example first surface 110_1, may be in contact with an air layer (not shown). Of course, the same applies to the second surface 110_2 as a reference. In addition, the vertical axis indicates that the size of the liquid crystal pitch increases as it goes up.

As shown in FIGS. 8 and 9, in some other embodiments, the cholesteric liquid crystal layer 110 is formed at the first liquid crystal pitch P1 along the direction of the second surface 110_2 at the first surface 110_1. The liquid crystal pitch profile may gradually increase to the third liquid crystal pitch P3 and gradually decrease from the third liquid crystal pitch P3 to the second liquid crystal pitch P2. In this case, the third liquid crystal pitch P3 has a maximum value among the liquid crystal pitches of the cholesteric liquid crystal layer 110.

In other words, the cholesteric liquid crystal layer 110 includes a first gradation region GR1 and a second gradation region GR2, wherein the first gradation region GR1 increases in the liquid crystal pitch in the first direction, and The liquid crystal pitch increases in the second gradation region GR2 in the second direction. The second gradation region GR2 is formed on the first gradation region GR1, and the second direction means a direction opposite to the first direction. At this time, the liquid crystal pitch increase rate α1 of the first gradation region GR1 and the liquid crystal pitch decrease rate α2 of the second gradation region GR2 are different from each other.

More specifically, when the first gradation region GR1 includes the first surface 110_1 of the cholesteric liquid crystal layer 110, the second gradation region GR2 is the cholesteric liquid crystal layer 110. The second surface 110_2, and the cholesteric liquid crystal layer 110 has a maximum value at the second surface 110_2 at a region where the first gradation region GR1 and the second gradation region GR2 are in contact with each other. The value has a liquid crystal pitch of a value between the maximum value and the minimum value at the first surface 110_1.

Further, the liquid crystal pitch increase rate α1 of the first gradation region GR1 is a change in the liquid crystal pitch with respect to the thickness d1 of the first gradation region GR1, that is, the first liquid crystal pitch P1 and the third liquid crystal pitch ( It can be defined as the value of the difference (P3-P1) of P3). Similarly, the liquid crystal pitch reduction rate α2 of the second gradation region GR2 is a change in the liquid crystal pitch with respect to the thickness D-d1 of the second gradation region GR2, that is, the third liquid crystal pitch P3 and the second liquid crystal. It may be defined as the value of the difference P3-P2 of the pitch P2.

As illustrated in FIG. 8, the first gradation region GR1 and the second gradation region GR2 may be formed to have the same thickness. Or, it may be formed of a different thickness of course. The liquid crystal pitch increase rate α1 of the first gradation region GR1 and the liquid crystal pitch decrease rate α2 of the second gradation region GR2 may have various values due to the thickness of each gradation region and the change of the liquid crystal pitch. However, the change in the liquid crystal pitch of the first gradation region GR1 and the second gradation region GR2 is formed asymmetrically with respect to the region where the first gradation region GR1 and the second gradation region GR2 are in contact. Therefore, the increase / decrease rates α1 and α2 of the liquid crystal pitch of each gradation region have different values.

In some other embodiments, as shown in the graph of FIG. 9, the cholesteric liquid crystal layer 110 may include a first gradation region GR1 in which the liquid crystal pitch increases in the first direction, and a liquid crystal pitch in the second direction. Including an increasing second gradation region GR2, the ratio of the first gradation region GR1 to the cholesteric liquid crystal layer 110 and the second gradation region GR2 with respect to the cholesteric liquid crystal layer 110 The ratios are different.

More specifically, since the maximum value D of the thickness position of the horizontal axis of the graph illustrated in FIG. 9 corresponds to the thickness of the cholesteric liquid crystal layer 110, the first gradient region with respect to the cholesteric liquid crystal layer 110. The ratio of GR1 corresponds to the ratio of the thickness of the first gradation region GR1 to the total thickness of the cholesteric liquid crystal layer 110. Similarly, the ratio of the second gradation region GR2 to the cholesteric liquid crystal layer 110 corresponds to the ratio of the thickness of the second gradation region GR2 to the total thickness of the cholesteric liquid crystal layer 110.

As a result, the ratio of the thickness d2 of the first gradation region GR1 to the overall thickness D of the cholesteric liquid crystal layer 110 is equal to that of the second gradation region GR2 with respect to the overall thickness D. It is different from the ratio of the thickness D-d2. Therefore, the ratio of the first gradation region GR1 to the cholesteric liquid crystal layer 110 and the ratio of the second gradation region GR2 to the cholesteric liquid crystal layer 110 are different from each other. It can be said that the thickness of GR1) and the thickness of the second gradation region GR2 are different from each other.

Therefore, in this case, the region having the maximum value among the liquid crystal pitches of the cholesteric liquid crystal layer 110 may be formed to be biased toward one side from the center of the thickness of the cholesteric liquid crystal layer 110. In other words, the region where the liquid crystal pitch has the maximum value is not at the same distance from the first surface 110_1 and the second surface 110_2, but rather in the region close to the first surface 110_1 or the second surface 110_2. Can be formed.

10 and 11 are graphs showing changes in the size of the liquid crystal pitch and the size of the reflection wavelength with respect to the thickness of the broadband reflective liquid crystal film according to some embodiments of the present invention.

In the graphs shown in Figs. 10 and 11, the horizontal axis represents the film thickness of the broadband reflective liquid crystal film, the left vertical axis represents the size of the liquid crystal pitch, and the right vertical axis represents the wavelength of reflection. Indicates the size.

As shown in the graphs of FIGS. 10 and 11, the broadband reflective liquid crystal film according to the exemplary embodiments includes a first gradation region GR1 and a second gradation region GR2. In the first gradation region GR1, the liquid crystal pitch increases from the interval Pa to the maximum value Pmax in the right direction in which the film thickness increases from zero. In the second gradation region GR2, the liquid crystal pitch increases from the minimum value Pmin to the maximum value Pmax in the left direction in which the film thickness decreases to zero.

Referring to FIG. 10, the minimum value Pmin of the liquid crystal pitch is about 180 nm, the maximum value Pmax is about 580 nm, and the inter-value Pa is about 320 nm. In addition, the thickness of the first gradation region GR1 is about 3.2 um, and the thickness of the second gradation region GR2 is about 3 um. As such, the broadband reflective liquid crystal film according to some embodiments may have a thickness substantially equal to a region of the first gradation GR1 and the second gradation GR2. In this case, the substantially same thickness includes not only the case where the numbers are exactly the same, but also the case where the error in the manufacturing process is taken into consideration.

In addition, the liquid crystal pitch increase rate of the first gradation region GR1 is (580-320) /3200=0.08, and the liquid crystal pitch reduction rate of the second gradation region GR2 is (580-180) /3000=0.13, The liquid crystal pitch increase rate of the gradation region GR1 may be greater than the liquid crystal pitch decrease rate of the second gradation region GR2.

Referring to FIG. 11, in the broadband reflective liquid crystal film according to another exemplary embodiment, the thickness of the first gradation region GR1 may be thicker than that of the second gradation region GR2. For example, the ratio of the thickness of the cholesteric liquid crystal layer to the thickness of the first gradation region GR1 may be about 1: 0.05 to about 1: 0.4.

In the broadband reflective liquid crystal film shown in FIG. 11, the minimum value Pmin of the liquid crystal pitch is about 200 nm, the maximum value Pmax is about 500 nm, and the inter-value Pa is about 395 nm. In addition, the thickness of the first gradation region GR1 is about 0.5 um, and the thickness of the second gradation region GR2 is about 3.5 um. That is, the thickness ratio of the thickness of the cholesteric liquid crystal layer to the first gradation region GR1 may have a value of about 1: 0.25.

For example, when the thickness of the cholesteric liquid crystal layer is about 5 μm or less, as illustrated in FIG. 11, the thickness of the second gradation region GR2 may be greater than the thickness of the first gradation region GR1. . However, this is merely an example and does not exclude a case in which the broadband reflective liquid crystal film including the liquid crystal layer having a thickness of about 5 μm or less has a liquid crystal pitch corresponding to the graph of FIG. 10.

As the ratio of the first gradation region GR1, that is, the ratio of the first gradation region GR1 to the thickness of the liquid crystal layer increases, the luminance of the emission surface side of the liquid crystal film increases, and the first gradation region GR1 As the ratio of is decreased, the Off Axis Color (OAC) characteristic of the emission surface side of the liquid crystal film may be improved. Therefore, by adjusting the ratio of the first gradation region GR1, it is possible to determine the optimization region of the luminance and OAC characteristics on the emission surface side of the liquid crystal film.

When the liquid crystal pitch of the broadband reflective liquid crystal film increases linearly in one direction, as shown in FIG. 12, the OAC change is very large, whereas the broadband according to the embodiment of the present invention has the liquid crystal pitch according to FIG. 11. In the case of the reflective liquid crystal film, it can be seen that the change of OAC is relatively small in FIG. 13. That is, the display quality can be expected to be improved.

14 shows a viewing angle with respect to the case where the liquid crystal pitch of the broadband reflective liquid crystal film increases linearly in one direction (comparative example) and the case where the liquid crystal pitch of the broadband reflective liquid crystal film has the liquid crystal pitch according to FIG. 11 (example). It is a graph showing a change in luminance (view angle) with respect to (view angle).

The horizontal axis of the graph illustrated in FIG. 14 represents a viewing angle, and the vertical axis represents luminance corresponding to each viewing angle. As shown in the graph, the luminance change according to the viewing angle in the case of the embodiment is smaller than that of the comparative example. More specifically, the luminance difference between the luminance at the front side where the viewing angle is near zero degrees and the luminance at the side where the viewing angle is close to ± 80 degrees is smaller in the case of the embodiment than in the case of the comparative example. That is, it can be seen that the luminance uniformity with respect to the viewing angle is improved in the case of the embodiment.

Referring back to FIGS. 10 and 11, in some other embodiments of the present invention, the first to mths are sequentially divided from the first surface to the second surface direction by using each liquid crystal pitch as a unit. m is a natural number) a cholesteric liquid crystal layer comprising a liquid crystal pitch period, wherein the cholesteric liquid crystal layer is the first to the nth (where n is a natural number of n <m) liquid crystal pitch interval, k (Where k is a natural number of 1 < k? N) The ratio when the liquid crystal pitch in the liquid crystal pitch section is larger than the liquid crystal pitch in the k-1 liquid crystal pitch section is 70% or more, and the n + 1 th to mth liquid crystals With respect to the pitch section, the ratio of the liquid crystal pitch of the h th liquid crystal pitch section (where h is a natural number of n + 1 <h ≦ m) is smaller than the liquid crystal pitch of the h-1 liquid crystal pitch section may be 70% or more. .

In this case, at least one liquid crystal pitch of the n-th and n-th liquid crystal pitch periods has a maximum value, the liquid crystal pitch of the m-th liquid crystal pitch period has a minimum value, and the liquid crystal pitch of the first liquid crystal pitch period has a maximum value. It has a value between the value and the minimum value.

As shown in the graphs of FIGS. 10 and 11, a liquid crystal pitch section including a point where the liquid crystal pitch has a maximum value is, for example, an nth liquid crystal pitch section. The ratio at which the kth liquid crystal pitch section has a larger value than the liquid crystal pitch of the k-1th liquid crystal pitch section is 70% or more. That is, any k-th liquid crystal pitch interval of the first to nth liquid crystal pitch intervals has a liquid crystal pitch larger than the k-1th liquid crystal pitch interval, and the first to n-th liquid crystal pitch intervals generally tend to increase the liquid crystal pitch. Has In this case, the first to n-th liquid crystal pitch periods correspond to the first gradation region described above.

When the liquid crystal pitch section including the point where the liquid crystal pitch has the maximum value is, for example, the n + 1 liquid crystal pitch section, any h-th liquid crystal pitch section of the n + 1 to m-th liquid crystal pitch sections is h- The ratio which has a value smaller than the liquid crystal pitch of 1 liquid crystal pitch area is 70% or more. That is, any h-th liquid crystal pitch interval of the n + 1th to mth liquid crystal pitch intervals has a liquid crystal pitch smaller than the h-1th liquid crystal pitch interval, and the n + 1th to mth liquid crystal pitch intervals generally have a liquid crystal pitch. Tends to decrease. In this case, the n + 1 th to m th liquid crystal pitch periods correspond to the second gradation region described above.

In addition, in some other embodiments of the present invention, the cholesteric liquid crystal layer may include 25 to 60 liquid crystal pitches. The thickness of the cholesteric liquid crystal layer at this time is, for example, 6.0 to 6.5 um.

15 and 16 are graphs showing a change in pitch according to a thickness position of a cholesteric liquid crystal layer according to some other embodiments of the present invention.

As shown in FIG. 15, in some other embodiments, the cholesteric liquid crystal layer 110 includes a first gradation region GR1 and a second gradation region GR2, and the first gradation region GR1 is The liquid crystal pitch decreases in the first direction, and the liquid crystal pitch decreases in the second direction in the second gradation region GR2. At this time, the liquid crystal pitch reduction rate α1 of the first gradation region GR1 and the liquid crystal pitch increase rate α2 of the second gradation region GR2 are different from each other.

Similarly, as shown in FIG. 16, in some other embodiments, the cholesteric liquid crystal layer 110 may include a first gradation region GR1 in which the liquid crystal pitch decreases in the first direction, and a liquid crystal pitch in the second direction. A second gradient region GR2 that decreases, wherein a ratio of the first gradient region GR1 to the cholesteric liquid crystal layer 110 and a second gradient region GR2 to the cholesteric liquid crystal layer 110 are included. Ratios have different values.

In the broadband reflective liquid crystal film including the cholesteric liquid crystal layer corresponding to the graphs shown in FIGS. 15 and 16, the liquid crystal pitch has a maximum value in a region adjacent to either one of the first surface and the second surface. In that the liquid crystal pitch has a minimum value in the region between the first and second surfaces, and in the region adjacent to the other one of the first and second surfaces, the liquid crystal pitch has a value between the maximum value and the minimum value. It is distinguished from the above-described embodiments. Other components are substantially the same as the above-described embodiments.

In the above embodiments, a broadband reflective liquid crystal film having a reflectance of about 30% to about 70% with respect to the wavelength range of visible light is discussed, but the present invention is not limited thereto, and some wavelengths or other wavelengths of visible light are not limited thereto. Of light, for example, infrared, ultraviolet, X-rays, or the like, or may be adjusted to have a reflectance for high frequency, medium frequency, low frequency electromagnetic waves, and the like. In addition, the reflectance is not limited to the above range, and it is apparent that other various reflectances may be employed.

As described above, according to the broadband reflective liquid crystal film according to the embodiments of the present invention, even if the liquid crystal layer is not laminated in multiple layers, it is possible to reflect the entire wavelength range of visible light. Therefore, the thickness of the broadband reflective liquid crystal film is reduced, and the light transmittance can be improved. In addition, unlike the case of laminating in a multilayer, since there is no need to use an adhesive at all, it is possible to prevent the distortion of light and the decrease in light transmittance due to the interposition of the adhesive.

In addition, according to the broadband reflective liquid crystal film according to some other embodiments of the present invention, in the cholesteric liquid crystal layer, the liquid crystal pitch increases from a value to a maximum value and then decreases to a minimum value or decreases from the value to a minimum value. The light reflectance can be further improved by forming a profile of the liquid crystal pitch which is increased to the maximum value.

17 and 18 are cross-sectional views of a broadband reflective liquid crystal film according to some other embodiments of the present invention.

17 and 18, the broadband reflective liquid crystal films 101 and 102 according to some other embodiments of the present invention may include a first surface 110_1 and a second surface of the cholesteric liquid crystal layer 110. 110_2) further comprises a retardation film 120 formed on one surface of the substrate, and the substrate 105 formed on the other surface.

As shown in FIG. 17, the broadband reflective liquid crystal film 101 according to another embodiment of the present invention includes a substrate 105 and a collet formed on the first surface 110_1 of the cholesteric liquid crystal layer 110. The phase difference film 120 formed on the second surface 110_2 of the steric liquid crystal layer 110 may be further included. In this case, the first surface 110_1 of the cholesteric liquid crystal layer 110 is an incident surface on which light is incident, and the second surface 110_2 is an exit surface on which light is emitted.

In addition, as shown in FIG. 18, the broadband reflective liquid crystal film 102 according to another embodiment of the present invention is a substrate 105 formed on the second surface 110_2 of the cholesteric liquid crystal layer 110. And a retardation film 120 formed on the first surface 110_1 of the cholesteric liquid crystal layer 110. In this case, the second surface 110_2 of the cholesteric liquid crystal layer 110 is the entrance face and the first surface 110_1 is the exit face.

Substrate 105 is a material capable of supporting the cholesteric liquid crystal layer 110, for example, a transparent material capable of transmitting light, for example, polycarbonate (poly carbonate), poly sulfone (poly sulfone), poly Acrylate (poly acrylate), poly styrene (poly styrene), poly vinyl chloride (poly vinyl chloride), poly vinyl alcohol (poly vinyl alcohol), poly norbornene (polyester), polyester (poly ester) It can comprise a series of materials. For example, the substrate may be made of polyethylene terephtalate or polyethylene naphthalate.

The retardation film 120 is formed on the cholesteric liquid crystal layer 110 to linearly polarize light passing through the cholesteric liquid crystal layer 110. The retardation film 120 may be a λ / 4 retardation film for retarding the phase of light by λ / 4.

In the drawing, the substrate 105 and the retardation film 120 are formed on both surfaces of the cholesteric liquid crystal layer 110, but some embodiments may omit either. For example, in some embodiments, a retardation film made of polycarbonate or the like may be applied to the substrate 105. In this case, the retardation film is integrally formed on the broadband reflective liquid crystal film to act as a composite film. In particular, when the cholesteric liquid crystal layer 110 is formed directly on one surface of the retardation film as the base material 105, the interposition of the adhesive can be omitted, so that the thickness of the broadband reflective liquid crystal films 101 and 102 can be reduced. In addition to reducing, it is possible to prevent the distortion of light due to the interposition of the adhesive.

Hereinafter, exemplary methods of manufacturing the broadband reflective liquid crystal film as described above will be described. In the following embodiments, a description of the configuration overlapping with the above-described embodiment will be omitted or simplified.

19 to 23 are cross-sectional views illustrating process steps of a method of manufacturing a broadband reflective liquid crystal film according to embodiments of the present invention.

Referring to FIG. 19, after preparing the substrate 105, the cholesteric liquid crystal coating layer 110a is formed by coating a liquid cholesteric liquid crystal coating solution on the substrate 105.

The cholesteric liquid crystal coating liquid may include a nematic liquid crystal and a chiral dopant, a UV curable material, and a photoinitiator.

The blending ratio of the nematic liquid crystal and the chiral dopant changes the reflected light wavelength of the cholesteric liquid crystal. The higher the blending ratio of the nematic liquid crystal, the longer the wavelength of the reflected light, while the higher the blending ratio of the chiral dopant, the shorter the wavelength of the reflected light. In view of this, the ratio of the nematic liquid crystal to the chiral dopant may be adjusted within the range of, for example, about 96: 4 to about 94: 6. However, it is a matter of course that the nematic liquid crystal and the chiral dopant may have different mixing ratios.

UV curable materials and photoinitiators are added to perform the subsequent curing process.

Examples of UV curable materials include reactive oligomers such as acrylic, urethane, polyester, silicone, ester, and the like, and monofunctional (meth) acrylate monomers or polyfunctional (di, tri) (meth) acrylate monomers. As said monofunctional (meth) acrylate or polyfunctional (meth) acrylate monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, tetrahydrofurfuryl (meth), for example Acrylate, butoxy ethyl (meth) acrylate, ethyl diethylene glycol (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, phenoxyethyl (meth) acrylate, di Cyclopentadiene (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methyl triethylene diglycol (meth) acrylate, isobornyl (meth) acrylate, N-vinylpyrroli Don, N-vinyl caprolactam, diacetone acrylamide, isobutoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, t-octyl (meth) acrylamide, di Methylaminoethyl (meth) acrylate, acryloylmorpholine, dicyclopentenyl (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) ) Acrylate, ethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,4-butanedioldi (meth) acrylate, 1,6-hexanediol Di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane trioxyethyl (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, dicyclodecane dimethanol di (meth) Acrylate, tripropylene glycol di (meth) acrylate, dicyclopentanedi (meth) acrylate, dicyclopentadienedi (meth) acrylate, and the like, It may be used alone or in mixture of the listed substances.

The photoinitiator is one or more free radical initiators selected from benzyl ketals, benzoin ethers, acetophenone derivatives, ketoxime ethers, benzophenones, benzo or thioxanthone compounds, onium salts, ferrocenium salts ( ferrocenium salts, and one or more cationic initiators selected from diazonium salts, or mixtures thereof.

Coating of the cholesteric liquid crystal coating liquid may be performed by various known coating methods for coating a solution on a substrate 105, for example, roll coating, dip coating, spin coating, slit coating, air knife coating, gravure coating, and three roll reverse. reverse) coating, comma coating and the like.

Subsequently, the liquid crystal coating layer 110a is dried. The drying process is performed to reduce the fluidity of the liquid crystal coating layer 110a to enhance process convenience and to facilitate the subsequent curing process. The said drying process can mount a drying object, for example in a heat processing apparatus or an oven. During the drying step, the cholesteric liquid crystal molecules in the liquid crystal coating layer 110a may be aligned with the first liquid crystal pitch. At this time, each of the cholesteric liquid crystal molecules may have the same liquid crystal pitch, but may be aligned with a partially different liquid crystal pitch depending on the process conditions.

Next, referring to FIG. 20, the dried cholesteric liquid crystal coating layer (see 110a of FIG. 19) is first cured, for example, at a temperature of about 20 to 100 ° C. FIG.

The first curing 910 uses less energy than the subsequent second and third curing to form a cholesteric liquid crystal coating layer 110b comprising a partially cured film. For example, when the curing process is performed through UV irradiation, the first curing may be performed with a first energy, for example, an ultraviolet irradiation dose of about 10 mJ / cm 2 to 200 mJ / cm 2.

Next, referring to FIG. 21, a first heat treatment 810 is performed.

The first heat treatment 810 may proceed to the second temperature. The second temperature may proceed to a temperature lower than the first temperature at the time of the coating and drying described above. For example, the first heat treatment 810 may be performed for a few seconds to several minutes at a temperature of about 4 to 80 ℃. Proceeding with the first heat treatment, the liquid crystal pitch of the liquid crystal molecules that are already oriented is at least partially varied. For example, the liquid crystal pitch of some liquid crystal molecules generated when performing the first curing may increase. Some liquid crystal molecules can maintain the existing liquid crystal pitch. This phenomenon can be understood to be due to the energy by the first heat treatment.

If the liquid crystal molecules located in the adjacent space are almost similar to the conditions exposed to the first curing or the heat treatment, they are likely to exhibit the same reactivity, thereby forming a region having the same liquid crystal. If it is assumed that each region is formed in a layered structure as shown in FIG. 1, it can be understood that the liquid crystal molecules in the first region have almost similar conditions exposed to the first curing or heat treatment. The same understanding is possible about the second region and the third region.

Subsequently, with reference to FIG. 22, a second curing 920 is performed simultaneously with the second heat treatment 820.

The second heat treatment 820 may be performed at a third temperature. The third temperature may be performed at a temperature higher than the second temperature of the first heat treatment 810, for example, about 50 ° C to about 150 ° C. The second curing may be performed at a second energy. That is, it can travel with energy higher than the 1st energy of the 1st hardening. When the second curing is performed through UV irradiation, the second curing 920 may be performed at, for example, an ultraviolet irradiation amount of about 70 mJ / cm 2 to 700 mJ / cm 2.

Next, referring to FIG. 23, a third curing 930 is performed along with the third heat treatment 830.

The third heat treatment 830 may be performed at a fourth temperature. The fourth temperature may be performed at a temperature similar to the third temperature of the second heat treatment 820, for example, about 50 ° C. to about 150 ° C. The third hardening 930 may be performed with the third energy. The third energy is similar to or higher than the second energy of the second curing 920, and when UV irradiation is used, the third curing 930 is performed with an ultraviolet radiation dose of, for example, about 70 mJ / cm 2 to about 1200 mJ / cm 2. can do.

If necessary, the third heat treatment and the third curing may be repeatedly performed at least once or more.

Moreover, it can also process combining the Example demonstrated above and combining the process of heat processing and pre-cure, and the heat processing individual process.

According to the method of manufacturing the broadband reflective liquid crystal film according to the embodiments of the present invention, since only one lamination of the liquid crystal coating layer may have a reflectance in the entire wavelength range of visible light, a manufacturing process is performed rather than forming a multilayer liquid crystal layer. This is much simpler and the process efficiency can be improved.

The broadband reflective liquid crystal film described above may be used to improve light efficiency by being employed in a light source assembly or a liquid crystal display device including the same. The light source assembly is classified into a direct type light source assembly in which the lamp is located at the bottom, and an edge type light source assembly in which the lamp is located at the side, and the like. It is possible. The present invention is also applicable to a back light assembly disposed below the liquid crystal panel or a front light assembly disposed above the liquid crystal panel. Hereinafter, as an example of various applications, a case in which a broadband reflective liquid crystal film according to an embodiment of the present invention is applied to a liquid crystal display device including a direct backlight assembly is described.

24 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 24, the liquid crystal display 500 may include a backlight assembly 200, a liquid crystal panel assembly 300, and a top chassis 400.

The backlight assembly 200 includes a lamp 210, a reflective film 235 for reflecting light emitted from the lamp 210, and a diffuser plate 220 and optical films 230 for adjusting optical characteristics of the emitted light. It includes.

The lamp 210 may be, for example, a Cold Cathode Fluorescent Lamp (CCFL), a Hot Cathode Fluorescent Lamp (HCFL), an External Electrode Fluorescent Lamp (EEFL), or the like.

A reflective film 235 is disposed below the lamp 210 to reflect light emitted downward from the lamp 210 upward.

The diffusion plate 220 and the optical films 230 are disposed on the lamp 210. The diffuser plate 220 diffuses the light incident from the lamp 210. The optical films 230 include a diffusion film for diffusing incident light, a prism sheet for collecting incident light, a broadband reflective liquid crystal film partially reflecting incident circular polarization, and a retardation film for converting circularly polarized light into linearly polarized light. , And / or a protective film. Here, when the broadband reflective liquid crystal film according to the embodiments of the present invention is applied to at least the broadband reflective liquid crystal film, 50% of circularly polarized light is transmitted and 50% is reflected to all wavelengths of incident visible light. Light utilization can be maximized. Furthermore, in particular, since the broadband reflective liquid crystal film according to the embodiment of the present invention is made of a cholesteric liquid crystal layer, the thickness is thinner than that of the multilayered layer, and thus the light efficiency is excellent. In addition, the adhesive does not need to be interposed so that light distortion can be minimized.

The lamp 210, the reflective film 235, the diffuser plate 220, and the optical films 230 are received by the bottom chassis 240 and the mold frame 250. The bottom chassis 240 forms the bottom surface of the backlight assembly 200, and a mold frame 250 having a window frame shape is disposed on the bottom chassis 240, and the light diffuser plate is disposed at a seating end of the mold frame 250. 220, optical films 230 and liquid crystal panel 310 are seated.

The liquid crystal panel assembly 300 includes a liquid crystal panel 310, a first display panel 311, and a second liquid crystal panel 310 including a first display panel 311, a second display panel 312, and a liquid crystal layer interposed therebetween. A polarizing plate (not shown) attached to the surface of the display panel 312, a data TCP (Tape Carrier Package) 330 attached to one side of the liquid crystal panel 310, and a printed circuit board attached to the data TCP 330 ( 340). A data driver integrated circuit (IC) 331 is mounted on the data TCP 330. A gate TCP (not shown) is attached to the other side of the liquid crystal panel 310 adjacent to the attachment side of the data TCP 330, and a gate driver IC (not shown) is mounted on the gate TCP.

The top chassis 400 covers an edge of the liquid crystal panel 310 and surrounds side surfaces of the liquid crystal panel 310 and the backlight assembly 200. The data TCP 330, the printed circuit board 340, and the like are bent and received in a space between the side wall of the bottom chassis 240 and the side wall of the top chassis 400.

In the backlight assembly described above, the broadband reflective liquid crystal film according to the exemplary embodiments of the present invention is applied, whereby the thickness is reduced, the luminance is improved, and the optical interference effect can be suppressed. Accordingly, the image quality of the liquid crystal display including the backlight assembly may be improved.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims (20)

1. A cholesteric liquid crystal layer in which the liquid crystal pitch is changed in a direction from the first surface to the second surface,

   The cholesteric liquid crystal layer has a first liquid crystal pitch in a first region adjacent to the first surface, and has a second liquid crystal pitch smaller than the first liquid crystal pitch in a second region adjacent to the second surface. A broadband reflective liquid crystal film having a third liquid crystal pitch greater than the first liquid crystal pitch in a third region between the first and second regions.
2. According to claim 1,

   The cholesteric liquid crystal layer gradually increases from the first liquid crystal pitch to the third liquid crystal pitch along the second surface direction at the first surface, and then from the third liquid crystal pitch to the second liquid crystal pitch. A broadband reflective liquid crystal film having a gradually decreasing liquid crystal pitch change.
3. According to claim 1,

   The first surface of the cholesteric liquid crystal layer is an incident surface to which light provided from the outside is incident, and the second surface of the cholesteric liquid crystal layer is an exit surface from which the light is transmitted through the liquid crystal layer. Broadband reflective liquid crystal film.
4. According to claim 1,

   The cholesteric liquid crystal layer is a broadband reflective liquid crystal film.
5. The method of claim 4, wherein

   The cholesteric liquid crystal layer is a broadband reflective liquid crystal film containing the same kind of cholesteric liquid crystal molecules.
6. According to claim 1,

   The cholesteric liquid crystal layer is formed of a single film, and the broadband reflective liquid crystal film further comprises a substrate formed directly on either surface of the first surface or the second surface of the cholesteric liquid crystal layer.
7. According to claim 1,

   And said third liquid crystal pitch is a maximum value among liquid crystal pitches of the cholesteric liquid crystal layer.
8. A liquid crystal layer comprising a first gradation region and a second gradation region,

   The liquid crystal pitch of the first gradation region increases in a first direction,

   The second gradation region includes a liquid crystal layer formed on the first gradation region, the liquid crystal pitch is increased in a second direction opposite to the first direction,

   A broadband reflective liquid crystal film having a liquid crystal pitch increase rate in the first gradation region and a liquid crystal pitch decrease rate in the second gradation region.
9. The method of claim 8,

   And the liquid crystal layer has a maximum liquid crystal pitch in a region where the first gradation region and the second gradation region are in contact with each other.
10. The method of claim 9,

    The first gradation region includes a first surface of the liquid crystal layer, the second gradation region includes a second surface of the liquid crystal layer, the liquid crystal layer having a minimum value at the second surface, and the first The broadband reflective liquid crystal film which has a liquid crystal pitch of the value between the minimum value and the said maximum value at the surface.
11. The method of claim 8,

    The broadband reflective liquid crystal film having a thickness of the first gradation region is smaller than that of the second gradation region.
12. The method of claim 11, wherein

    Thickness of the liquid crystal layer including the first and second gradation regions: The thickness of the first gradation region is 1: 0.05 to 1: 0.4 broadband reflective liquid crystal film.
13. Including a cholesteric liquid crystal layer comprising a liquid crystal pitch period of the first to m (where m is a natural number) divided by the liquid crystal pitch in one unit in a direction from the first surface to the second surface direction,

    The cholesteric liquid crystal layer has a k-th (where k is a natural number of 1 <k≤n) liquid crystal pitch period with respect to the first to nth (where n is a natural number of n <m) liquid crystal pitch period. The ratio when the liquid crystal pitch is larger than the liquid crystal pitch of the k-1th liquid crystal pitch section is 70% or more,

    For the nth + 1th to mth liquid crystal pitch periods, the liquid crystal pitch of the hth liquid crystal pitch period (h is a natural number of n + 1 <h≤m) is greater than the liquid crystal pitch of the h-1th liquid crystal pitch period Small percentage is over 70%,

    At least one liquid crystal pitch of the nth and nth + 1th liquid crystal pitch intervals has a maximum value, a liquid crystal pitch of the mth liquid crystal pitch interval has a minimum value, and a liquid crystal pitch of the first liquid crystal pitch interval is the maximum value A broadband reflective liquid crystal film having a value between the value and the minimum value.
14. A liquid crystal layer comprising a first gradation region and a second gradation region,

    The liquid crystal pitch of the first gradation region increases in a first direction,

    The second gradation region includes a liquid crystal layer formed on the first gradation region, the liquid crystal pitch is increased in a second direction opposite to the first direction,

    And a ratio of the first gradation region to the liquid crystal layer and the ratio of the second gradation region to the liquid crystal layer is different from each other.
15. A liquid crystal layer comprising a first gradation region and a second gradation region,

    The first gradation region is reduced in the liquid crystal pitch in the first direction,

    The second gradation region includes a liquid crystal layer formed on the first gradation region, the liquid crystal pitch is reduced in a second direction opposite to the first direction,

    A broadband reflective liquid crystal film having a liquid crystal pitch increase rate in the first gradation region and a liquid crystal pitch decrease rate in the second gradation region.
16. A light source assembly comprising a broadband reflective polarizing film according to any one of claims 1 to 15.
17. A liquid crystal display device comprising the broadband reflective polarizing film according to any one of claims 1 to 15.
18. Applying a liquid cholesteric liquid crystal coating liquid on the substrate to form a liquid crystal coating layer on one side of the substrate,

    The liquid crystal coating layer is dried at a first temperature,

    First curing is performed on the dried liquid crystal coating layer with first energy,

    Performing a first heat treatment on the first cured liquid crystal coating layer at a second temperature lower than the first temperature,

    The second heat treatment is performed on the first heat-treated liquid crystal coating layer at a third temperature higher than the second temperature, and the second hardening is performed at a second energy greater than the first energy.

    Performing a third heat treatment on the second heat treatment and the second main hardened liquid crystal coating layer at a fourth temperature higher than the third temperature, and simultaneously performing a third hardening at a third energy greater than the second energy. The manufacturing method of the broadband reflective liquid crystal film.
19. The method of claim 18,

    And said fourth temperature is lower than said first temperature.
20. The method of claim 19,

    And after performing the third heat treatment and the third curing, performing a fourth heat treatment at the same time as the fourth heat treatment at the fourth temperature. .

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