【jQuery】チェックボックスにチェックを入れるとボタンが活性化する

HTML

<section>

  <div class="notes_required">
    <div class="checkBtn_area">
      <label for="checkBtn" class="checkBtn"><input id="checkBtn" type="checkbox"><span class="label_inner">同意する</span></label>
    </div>
    <p class="check_text_b">チェックを入れると「ボタン」が有効となります。</p>
  </div>

  <div class="btnArea">
    <input type="submit" value="">
    <a href="https://125naroom.com/web/3191" target="_blank" class="btn_one _a">ボタン</a>
  </div>

  <div class="btnArea">
    <input type="submit" value="">
    <a href="https://125naroom.com/web/3191" target="_blank" class="btn_one _b">ボタン</a>
  </div>

</section>

JavaScript

//チェックが入ったら、ボタンを押せる
$(function() {
  $(".label_inner").click(function(){
    $(".notes_required").toggleClass("_check");
    $(".btnArea").toggleClass("_check");
  });
});

CSS

/*------------------------------------------------------------
.notes_required
------------------------------------------------------------*/

.notes_required {
	text-align: center;
	background: #fff;
	border: 2px solid #ffb97c;
	padding: 30px 20px;
}
.notes_required .check_text_b {
	font-size: 16px;
}
.notes_required .checkBtn_area {
	max-width: 400px;
	margin: 15px auto 10px;
	border-radius: 12px;
	background: #ffd6b3;
	padding: 20px 0;
	transition-duration: 0.2s;
}
.notes_required._check .checkBtn_area {
	background: #ffb97c;
}
.notes_required label {
	color: #333;
	font-size: 20px;
	border-bottom: 1px solid rgba(255, 255, 255, 0);
	cursor: pointer;
	transition-duration: 0.3s;
	position: relative;
}
.notes_required label .label_inner {
	padding-left: 22px;
}
.notes_required label .label_inner:before {
	content: "";
	width: 24px;
	height: 24px;
	background: #fff;
	border: 4px solid #737373;
	box-sizing: border-box;
	position: absolute;
	top: 50%;
	left: 0;
	margin-top: -13px;
}
.notes_required._check label .label_inner:after {
	content: '';
	width: 20px;
	height: 12px;
	border-top: 6px solid #d6042e;
	border-right: 6px solid #d6042e;
	-webkit-transform: rotate(130deg);
	transform: rotate(130deg);
	position: absolute;
	top: 50%;
	left: 0;
	margin-top: -.9em;
}
.notes_required label input {
	position: relative;
	z-index: -1;
}
@media screen and (min-width: 768px) {
	.notes_required label:hover {
		border-bottom: 2px solid #ff7600;
	}
}
@media screen and (max-width: 1024px) {
	.notes_required label {
		font-size: 18px;
	}
	.notes_required .check_text_b {
		font-size: 14px;
	}
	.notes_required label .label_inner {
		padding-left: 10px;
	}
	.notes_required label .label_inner:before {
		width: 20px;
		height: 20px;
		margin-top: -10px;
	}
	.notes_required._check label .label_inner:after {
		width: 16px;
		height: 8px;
		margin-top: -0.8em;
	}
}
@media screen and (max-width: 767px) {
	.notes_required {
		padding: 20px 15px;
	}
	.notes_required .check_text_b {
		font-size: 13px;
	}
	.notes_required._check label .label_inner:after {
		width: 16px;
		height: 8px;
		margin-top: -0.8em;
	}
}

/*------------------------------------------------------------
.btnArea
------------------------------------------------------------*/

.btnArea {
	max-width: 400px;
	margin: 30px auto 0;
	position: relative;
}
.btnArea input[type="submit"] {
	position: absolute;
	top: 0;
	left: 0;
	right: 0;
	margin: 0 auto;
	width: 100%;
	height: 100%;
	border: none;
	border-radius: 0;
	background: rgba(255, 255, 255, 0);
	padding: 0;
	z-index: -1;
	transition-duration: 0.3s;
	box-sizing: border-box;
	-webkit-appearance: none;
}
.btnArea input[type="submit"] {
	cursor: default;
	z-index: +1;
	outline: none;
}
.btnArea._check input[type="submit"] {
	z-index: -1;
}
a.btn_one {
	display: flex;
	justify-content: center;
	align-items: center;
	background: #969696;
	border-radius: 12px;
	box-sizing: border-box;
	box-shadow: 0px 0px 0px 0px #00407b;
	width: 100%;
	height: 80px;
	padding: 0 10% 0 6%;
	color: #ffffff;
	font-size: 24px;
	font-weight: bold;
	text-align: left;
	text-decoration: none;
	position: relative;
	transition-duration: 0.2s;
}
a.btn_one:before {
	content: "";
	display: inline-block;
	width: 0;
	height: 0;
	border-style: solid;
	border-width: 10px 0 10px 12px;
	border-color: transparent transparent transparent #ffffff;
	position: absolute;
	top: 50%;
	right: 8%;
	margin-top: -11px;
}
._check a.btn_one._a {
	background: #3475b1;
	box-shadow: 0px 5px 0px 0px #104575;
}
a.btn_one._a:hover {
	background: #228bc8;
	opacity: 1;
}
._check a.btn_one._b {
	background: #459d3c;
	box-shadow: 0px 5px 0px 0px #255720;
}
a.btn_one._b:hover {
	background: #63b559;
	opacity: 1;
}
@media screen and (max-width: 1024px) {
	a.btn_one {
		height: 60px;
		font-size: 20px;
	}
}
@media screen and (max-width: 767px) {
	a.btn_one {
		font-size: 16px;
	}
}